Living Reviews in Solar Physics A peer-refereed, solely online journal publishing invited reviews covering all areas of solar and heliospheric physics research. Reviews are kept up to date by their authors. All reference information is collected into a searchable database. http://solarphysics.livingreviews.org/ is a free resource to the scientific community. Published by the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany. Copyright Max-Planck-Gesellschaft. physics, solar physics, heliospheric physics, physics research, electronic journal, electronic publishing, physics information sources http://solarphysics.livingreviews.org/ 1614-4961 en Max Planck Institute for Solar System Research copyright Max Planck Society journal 2013-03-21 Borrero borrero.juan Juan M. Borrero Juan M. Kiepenheuer-Institut für Sonnenphysik (KIS), Schöneckstr.6, D-79104 Freiburg, Germany author sun-earth-connection Sun-Earth Connection subjectField My main interest is magnetohydrodynamics (MHD), particularly the structure and evolution of the Sun's magnetic field. I focus on problems which are nonlinear, three-dimensional, time-dependent, or all three. I apply a mixture of numerical and analytical modelling. yeates.anthony Anthony Yeates Anthony Yeates Department of Mathematical Sciences, Durham University, Science Laboratories, South Road, Durham DH1 3LE, UK author This paper reviews our attempts to understand the transport of magnetic flux on the Sun from the Babcock and Leighton models to the recent revisions that are being used to simulate the field over many sunspot cycles. In these models, the flux originates in sunspot groups and spreads outward on the surface via supergranular diffusion; the expanding patterns become sheared by differential rotation, and the remnants are carried poleward by meridional flow. The net result of all of the flux eruptions during a sunspot cycle is to replace the initial polar fields with new fields of opposite polarity. A central issue in this process is the role of meridional flow, whose relatively low speed is near the limit of detection with Doppler techniques. A compelling feature of Leighton’s original model was that it reversed the polar fields without the need for meridional flow. Now, we think that meridional flow is central to the reversal and to the dynamo itself. Surface Evolution of the Sun's Magnetic Field: A Historical Review of the Flux-Transport Mechanism 2 2005-10-04 2005LRSP....2....5S 5 2005-10-18 2005-09-16 lrsp-2005-5 Solar magnetic fields publication Coronal mass ejections (CMEs) are the largest-scale eruptive phenomenon in the solar system, expanding from active region-sized nonpotential magnetic structure to a much larger size. The bulk of plasma with a mass of ∼10^11 – 10^13 kg is hauled up all the way out to the interplanetary space with a typical velocity of several hundred or even more than 1000 km s^-1, with a chance to impact our Earth, resulting in hazardous space weather conditions. They involve many other much smaller-sized solar eruptive phenomena, such as X-ray sigmoids, filament/prominence eruptions, solar flares, plasma heating and radiation, particle acceleration, EIT waves, EUV dimmings, Moreton waves, solar radio bursts, and so on. It is believed that, by shedding the accumulating magnetic energy and helicity, they complete the last link in the chain of the cycling of the solar magnetic field. In this review, I try to explicate our understanding on each stage of the fantastic phenomenon, including their pre-eruption structure, their triggering mechanisms and the precursors indicating the initiation process, their acceleration and propagation. Particular attention is paid to clarify some hot debates, e.g., whether magnetic reconnection is necessary for the eruption, whether there are two types of CMEs, how the CME frontal loop is formed, and whether halo CMEs are special. Coronal Mass Ejections: Models and Their Observational Basis 8 2011-03-03 2011LRSP....8....1C 1 2011-04-08 2009-10-13 lrsp-2011-1 Magnetic field Models Magnetic reconnection Coronal mass ejections (CMEs) Solar activity publication lrsp-2012-3-webb.david 1 authorOrder The past few decades have seen dramatic progress in our understanding of solar interior dynamics, prompted by the relatively new science of helioseismology and increasingly sophisticated numerical models. As the ultimate driver of solar variability and space weather, global-scale convective motions are of particular interest from a practical as well as a theoretical perspective. Turbulent convection under the influence of rotation and stratification redistributes momentum and energy, generating differential rotation, meridional circulation, and magnetic fields through hydromagnetic dynamo processes. In the solar tachocline near the base of the convection zone, strong angular velocity shear further amplifies fields which subsequently rise to the surface to form active regions. Penetrative convection, instabilities, stratified turbulence, and waves all add to the dynamical richness of the tachocline region and pose particular modeling challenges. In this article we review observational, theoretical, and computational investigations of global-scale dynamics in the solar interior. Particular emphasis is placed on high-resolution global simulations of solar convection, highlighting what we have learned from them and how they may be improved. Large-Scale Dynamics of the Convection Zone and Tachocline 2 lrsp-2005-1 2005LRSP....2....1M 1 2005-04-22 2005-03-18 Solar convection, Tachocline, Differential rotation, Meridional circulation, Turbulence, Shear, Dynamo theory publication Variations in solar activity, at least as observed in numbers of sunspots, have been apparent since ancient times but to what extent solar variability may affect global climate has been far more controversial. The subject had been in and out of fashion for at least two centuries but the current need to distinguish between natural and anthropogenic causes of climate change has brought it again to the forefront of meteorological research. The absolute radiometers carried by satellites since the late 1970s have produced indisputable evidence that total solar irradiance varies systematically over the 11-year sunspot cycle, relegating to history the term “solar constant”, but it is difficult to explain how the apparent response to the Sun, seen in many climate records, can be brought about by these rather small changes in radiation. This article reviews some of the evidence for a solar influence on the lower atmosphere and discusses some of the mechanisms whereby the Sun may produce more significant impacts than might be surmised from a consideration only of variations in total solar irradiance. The Sun and the Earth's Climate 4 2007-09-18 2007LRSP....4....2H 2 2007-10-02 2007-08-13 lrsp-2007-2 Solar activity, Climate, Solar-terrestrial relations publication 2012-12-13 Corrected Solwind values in Table 1 and added the references Dere et al. (1997), Hudson et al. (1995), and Vourlidas et al. (2012). lrsp-2012-3-u1 2012-12-28 update Christensen-Dalsgaard christensen-dalsgaard christensen-dalsgaard J. Christensen-Dalsgaard J. University of Aarhus, Denmark ebMember Rosner rosner rosner Robert Rosner Robert University of Chicago, U.S.A. ebMember lrsp-2012-2-arregui.inigo 1 authorOrder lrsp-2009-2-nordlund.ake 1 authorOrder Theory and observations of magnetohydrodynamic wave phenomena in the solar corona and the determination of physical coronal plasma parameters from observations of MHD wave characteristics. Application of image-analysis techniques to solar image data. verwichte.erwin Erwin Verwichte Erwin Verwichte Physics Department, University of Warwick, Coventry CV4 7AL, U.K. author Solar and stellar astrophysics; acceleration of stellar winds; heating of stellar coronae and chromospheres; plasma physics and kinetic theory of waves and turbulence; rotating hot (O, B, Wolf-Rayet) stars; circumstellar fluid dynamics; radiative transfer and spectroscopy. cranmer.steven Steven R. Cranmer Steven R. Cranmer Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Mail Stop 50, Cambridge, MA 02138, U.S.A. author Kinetic plasma physics of the solar corona and solar wind are reviewed with emphasis on the theoretical understanding of the in situ measurements of solar wind particles and waves, as well as on the remote-sensing observations of the solar corona made by means of ultraviolet spectroscopy and imaging. In order to explain coronal and interplanetary heating, the microphysics of the dissipation of various forms of mechanical, electric and magnetic energy at small scales (e.g., contained in plasma waves, turbulences or non-uniform flows) must be addressed. We therefore scrutinise the basic assumptions underlying the classical transport theory and the related collisional heating rates, and also describe alternatives associated with wave-particle interactions. We elucidate the kinetic aspects of heating the solar corona and interplanetary plasma through Landau- and cyclotron-resonant damping of plasma waves, and analyse in detail wave absorption and micro instabilities. Important aspects (virtues and limitations) of fluid models, either single- and multi-species or magnetohydrodynamic and multi-moment models, for coronal heating and solar wind acceleration are critically discussed. Also, kinetic model results which were recently obtained by numerically solving the Vlasov–Boltzmann equation in a coronal funnel and hole are presented. Promising areas and perspectives for future research are outlined finally. Kinetic Physics of the Solar Corona and Solar Wind 3 2006-06-27 2006LRSP....3....1M 1 2006-07-27 2006-06-19 lrsp-2006-1 Kinetic theory, Fluid equations, Transport theory, Solar wind, Solar corona, Ion and electron velocity distributions, Plasma waves and instabilities, Wave-particle interactions publication Adaptive optics (AO) has become an indispensable tool at ground-based solar telescopes. AO enables the ground-based observer to overcome the adverse effects of atmospheric seeing and obtain diffraction limited observations. Over the last decade adaptive optics systems have been deployed at major ground-based solar telescopes and revitalized ground-based solar astronomy. The relatively small aperture of solar telescopes and the bright source make solar AO possible for visible wavelengths where the majority of solar observations are still performed. Solar AO systems enable diffraction limited observations of the Sun for a significant fraction of the available observing time at ground-based solar telescopes, which often have a larger aperture than equivalent space based observatories, such as HINODE. New ground breaking scientific results have been achieved with solar adaptive optics and this trend continues. New large aperture telescopes are currently being deployed or are under construction. With the aid of solar AO these telescopes will obtain observations of the highly structured and dynamic solar atmosphere with unprecedented resolution. This paper reviews solar adaptive optics techniques and summarizes the recent progress in the field of solar adaptive optics. An outlook to future solar AO developments, including a discussion of Multi-Conjugate AO (MCAO) and Ground-Layer AO (GLAO) will be given. Solar Adaptive Optics 8 2011-06-05 2011LRSP....8....2R 2 2011-06-10 2010-09-09 lrsp-2011-2 Imaging systems Wavefront sensor Solar observations Ground-layer adaptive optics Sun Deformable mirrors Adaptive optics Multi-conjugate adaptive optics Atmospheric turbulence Solar telescopes publication Observational study of the solar magnetohydrodynamics by means of spectroscopy mainly in visible light. Instrumentation for Hinode/SOT, ground telescopes at Hida and Norikura. ichimoto.kiyoshi Kiyoshi Ichimoto Kiyoshi Ichimoto Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan author 2012-03-29 Removed Figure 7 post-publication due to copyright restrictions. Springer did not grant permission to reuse material "in a work to be published on an Open Access Website". lrsp-2012-1-u1 2012-03-29 update The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundary conditions must be obtained from measurements of the magnetic field vector in the solar photosphere. This approach is currently of large interests, as accurate measurements of the photospheric field become available from ground-based (for example SOLIS) and space-born (for example Hinode and SDO) instruments. If we can obtain accurate force-free coronal magnetic field models we can calculate the free magnetic energy in the corona, a quantity which is important for the prediction of flares and coronal mass ejections. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma. Solar Force-free Magnetic Fields 9 2012-08-20 2012LRSP....9....5W 5 2012-09-20 2012-06-22 lrsp-2012-5 solar corona magnetic fields publication Helioseismology, solar rotation and the solar cycle, solar cycle changes in local and global helioseismic parameters. howe.rachel Rachel Howe Rachel Howe National Solar Observatory, 950 N. Cherry Ave., Tucson AZ 85719, U.S.A. author The acceleration and heating of the solar wind have been studied for decades using satellite observations and models. However, the exact mechanism that leads to solar wind heating and acceleration is poorly understood. In order to improve the understanding of the physical mechanisms that are involved in these processes a combination of modeling and observational analysis is required. Recent models constrained by satellite observations show that wave heating in the low-frequency (MHD), and high-frequency (ion-cyclotron) range may provide the necessary momentum and heat input to coronal plasma and produce the solar wind. This review is focused on the results of several recent solar modeling studies that include waves explicitly in the MHD and the kinetic regime. The current status of the understanding of the solar wind acceleration and heating by waves is reviewed. Wave Modeling of the Solar Wind 7 2010-09-09 2010LRSP....7....4O 4 2010-10-15 2010-01-25 lrsp-2010-4 Solar wind Multi-fluid models Hybrid models MHD models Waves publication solar-interior Solar Interior subjectField MHD waves in the solar atmosphere, Magnetic structure of the solar corona, Magnetic and thermodynamic equilibrium of solar prominences, Temporal behaviour of solar activity ballester.jose-luis José Luis Ballester José Luis Ballester Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain) author This article surveys the development of observational understanding of the interior rotation of the Sun and its temporal variation over approximately forty years, starting with the 1960s attempts to determine the solar core rotation from oblateness and proceeding through the development of helioseismology to the detailed modern picture of the internal rotation deduced from continuous helioseismic observations during solar cycle 23. After introducing some basic helioseismic concepts, it covers, in turn, the rotation of the core and radiative interior, the “tachocline” shear layer at the base of the convection zone, the differential rotation in the convection zone, the near-surface shear, the pattern of migrating zonal flows known as the torsional oscillation, and the possible temporal variations at the bottom of the convection zone. For each area, the article also briefly explores the relationship between observations and models. Solar Interior Rotation and its Variation 6 2009-02-10 2009LRSP....6....1H 1 2009-02-23 2009-01-30 lrsp-2009-1 Sun, Solar interior, Helioseismology, Solar convection, Solar cycle publication Hudson hudson hudson Hugh S. Hudson Hugh S. University of California, Berkeley, U.S.A. and University of Glasgow, U.K. ebMember The solar coronal magnetic field is anchored to a complex distribution of photospheric flux consisting of sunspots and magnetic elements. Coronal activity such as flares, eruptions and general heating is often attributed to the manner in which the coronal field responds to photospheric motions. A number of powerful techniques have been developed to characterize the response of the coronal field by describing its topology. According to such analyses, activity will be concentrated around topological features in the coronal field such as separatrices, null points or bald patches. Such topological properties are insensitive to the detailed geometry of the magnetic field and thereby create an analytic tool powerful and robust enough to be useful on complex observations with limited resolution. This article reviews those topological techniques, their developments and applications to observations. Topological Methods for the Analysis of Solar Magnetic Fields 2 2005-06-28 2005LRSP....2....7L 7 2005-11-29 2005-06-13 lrsp-2005-7 Solar magnetic fields publication The Sun’s magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun. The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment. The emphasis is on the phenomenology related to the production of high-energy photons and particles. Apart from the activity on the young Sun, systematic trends applicable to the entire main-sequence life of a solar analog are discussed. The Sun in Time: Activity and Environment 4 2007-10-11 2007LRSP....4....3G 3 2007-12-20 2007-08-29 lrsp-2007-3 Active stars, Climate, Cool stars, Solar corona, Circumstellar disks, Solar dynamo, Solar flares, High-energy radiation, Magnetic activity, Solar magnetic fields, Planetary atmospheres, Solar analogs, Solar evolution publication lrsp-2004-2-u1 This revision includes 23 new references, two new Figures 11 and 13, and two revised Figures 14 and 15, which replace former Figures 12 and 13 of the original publication. Changes have been made to Sections 2.1, 2.3, 4.2, 5.2, 5.3 and 5.4. The most substantial revisions have taken place in Sections 4.3 and 5.1. Section 6, Conclusions, has been added. See below for more details on the changes. 2007-07-13 2007-07-09 update physical-foundations Physical Foundations subjectField Star formation, accretion, circumstellar disks, outflows; The "Young Sun" and its environment; Magnetic activity in young stars and stellar environments, coronal heating; Plasma astrophysics and magnetohydrodynamics in stellar plasmas; Radio interferometry, infrared-/mm-/sub-mm astronomy, X-ray spectroscopy guedel.manuel Manuel Güdel Manuel Güdel University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, A-1180 Vienna, Austria and ETH Zurich, Department of Physics, Wolfgang-Pauli-Str. 27, CH-8093 Zürich, Switzerland author solar-surface-and-atmosphere Solar Surface and Atmosphere subjectField Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number. Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxies, such as the cosmogenic isotopes 14C and 10Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene. A separate section is devoted to reconstructions of strong solar energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. Finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed. A History of Solar Activity over Millennia 10 2013-03-07 The review has been thoroughly revised and updated. Added Sections 3.8 and 5.1 and 8 new figures (3 were removed). 55 new references have been included (4 were removed). 2013LRSP...10....1U 1 2013-03-21 2012-09-10 lrsp-2013-1 cosmogenic isotopes solar dynamo solar activity paleo-astrophysics long-term reconstructions solar physics solar-terrestrial relations publication Coronal mass ejections howard.timothy Timothy A. Howard Timothy A. Howard Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302, USA author My research interests are in the solar physics, astrophysics and nonlinear wave theory. The key word in all my work is a wave (for me, it is something which can propagate somewhere). Particularly, I deal with magnetohydrodynamic (MHD) waves, which are believed to be responsible for a number of astrophysical phenomena and are observed in the atmosphere of the Sun, solar wind and magnetosphere of the Earth (However, it seems that they can be found everywhere in the Universe, where there is a plasma penetrated by the magnetic field). Propagating through an inhomogeneous, non-stationary, nonlinear and sometimes active medium, such as the space plasma, MHD waves gain extremally interesting new properties leading to a number of amazing physical phenomena, like the existence of solitons, negative energy effects, self-organisation and many others. nakariakov.valery Valery M. Nakariakov Valery M. Nakariakov Physics Department, University of Warwick, Coventry CV4 7AL, U.K. author Atmospheric radiative transfer; Climate modelling; Radiation codes for numerical models; Interaction of radiation, dynamics and photochemistry in the middle atmosphere; Satellite remote sensing of cloud, aerosol and ocean colour; Radiative forcing of climate change; Solar irradiance variability and its influence on the structure of the lower and middle atmosphere; 3D radiative transfer in inhomogeneous cloud. haigh.joanna Joanna D. Haigh Joanna D. Haigh Imperial College, London SW7 2AZ, U.K. author Oliver oliver.ramon Ramón Oliver Ramón Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain) author Schwenn schwenn Former Editor schwenn Rainer Schwenn Rainer MPI for Solar System Research, Germany (emeritus) ebMember lrsp-2005-6-gizon.laurent 1 authorOrder lrsp-2012-2-oliver.ramon 2 authorOrder Astrophysical turbulence and MHD; Solar physics petrovay.kristof Kristóf Petrovay Kristóf Petrovay Eötvös Loránd University, Department of Astronomy, H-1518 Budapest, Pf. 32., Hungary author Wave and oscillatory activity of the solar corona is confidently observed with modern imaging and spectral instruments in the visible light, EUV, X-ray and radio bands, and interpreted in terms of magnetohydrodynamic (MHD) wave theory. The review reflects the current trends in the observational study of coronal waves and oscillations (standing kink, sausage and longitudinal modes, propagating slow waves and fast wave trains, the search for torsional waves), theoretical modelling of interaction of MHD waves with plasma structures, and implementation of the theoretical results for the mode identification. Also the use of MHD waves for remote diagnostics of coronal plasma - MHD coronal seismology - is discussed and the applicability of this method for the estimation of coronal magnetic field, transport coefficients, fine structuring and heating function is demonstrated. Coronal Waves and Oscillations 2 2005-03-22 2005LRSP....2....3N 3 2005-07-05 2004-12-16 lrsp-2005-3 Solar corona, Magnetohydrodynamics publication My professional interests include solar coronal physics, coronal mass ejections (CMEs) and space weather, which includes a heavy dose of halo CMEs and their heliospheric characteristics and geoeffectiveness. webb.david David F. Webb David F. Webb Institute for Scientific Research, Boston College, Kenny Cottle, 885 Centre Street, Newton, MA 02459, USA author solar-wind-and-heliosphere Solar Wind and Heliosphere subjectField My primary research interests involve observational studies of the outer atmosphere of cool stars using UV, EUV, X-ray, and radio emissions from these stars. I am also interested in the local interstellar medium and its interactions with the winds of late-type stars. The Sun certainly falls within my purview, as I have analyzed observations of the Sun and heliosphere, in addition to my work on cool stars in general. wood.brian Brian E. Wood Brian E. Wood Naval Research Laboratory, Space Science Division, Washington, DC 20375, U.S.A. author Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind. It is still unknown to what extent the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wave-like fluctuations), and to what extent much of the mass and energy is input intermittently from closed loops into the open-field regions. Evidence for both paradigms is summarized in this paper. Special emphasis is also given to spectroscopic and coronagraphic measurements that allow the highly dynamic non-equilibrium evolution of the plasma to be followed as the asymptotic conditions in interplanetary space are established in the extended corona. For example, the importance of kinetic plasma physics and turbulence in coronal holes has been affirmed by surprising measurements from the UVCS instrument on SOHO that heavy ions are heated to hundreds of times the temperatures of protons and electrons. These observations point to specific kinds of collisionless Alfvén wave damping (i.e., ion cyclotron resonance), but complete theoretical models do not yet exist. Despite our incomplete knowledge of the complex multi-scale plasma physics, however, much progress has been made toward the goal of understanding the mechanisms ultimately responsible for producing the observed properties of coronal holes. Coronal Holes 6 2009-09-15 2009LRSP....6....3C 3 2009-09-29 2009-06-30 lrsp-2009-3 Kinetic and MHD theory Wave-particle interactions Magnetohydrodynamics UV radiation Space plasmas Corona Alfv\'{e}n waves Magnetohydrodynamic waves Turbulence Coronal heating Stellar winds Sun Coronal holes Solar wind plasma Plasma heating Cyclotron resonance Solar wind Solar wind turbulence Waves and instabilities Solar cycle publication We review the properties of solar magneto-convection in the top half of the convection zones scale heights (from 20 Mm below the visible surface to the surface, and then through the photosphere to the temperature minimum). Convection is a highly non-linear and non-local process, so it is best studied by numerical simulations. We focus on simulations that include sufficient detailed physics so that their results can be quantitatively compared with observations. The solar surface is covered with magnetic features with spatial sizes ranging from unobservably small to hundreds of megameters. Three orders of magnitude more magnetic flux emerges in the quiet Sun than emerges in active regions. In this review we focus mainly on the properties of the quiet Sun magnetic field. The Sun’s magnetic field is produced by dynamo action throughout the convection zone, primarily by stretching and twisting in the turbulent downflows. Diverging convective upflows and magnetic buoyancy carry magnetic flux toward the surface and sweep the field into the surrounding downflow lanes where the field is dragged downward. The result is a hierarchy of undulating magnetic Ω- and U-loops of different sizes. New magnetic flux first appears at the surface in a mixed polarity random pattern and then collects into isolated unipolar regions due to underlying larger scale magnetic structures. Rising magnetic structures are not coherent, but develop a filamentary structure. Emerging magnetic flux alters the convection properties, producing larger, darker granules. Strong field concentrations inhibit transverse plasma motions and, as a result, reduce convective heat transport toward the surface which cools. Being cooler, these magnetic field concentrations have a shorter scale height and become evacuated. The field becomes further compressed and can reach strengths in balance with the surrounding gas pressure. Because of their small internal density, photons escape from deeper in the atmosphere. Narrow evacuated field concentrations get heated from their hot sidewalls and become brighter than their surroundings. Wider magnetic concentrations are not heated so they become darker, forming pores and sunspots. Solar Surface Magneto-Convection 9 2012-05-31 2012LRSP....9....4S 4 2012-07-19 2012-03-26 lrsp-2012-4 magnetic fields dynamo flux emergence sunspots solar physics convection pores publication The term space weather refers to conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems and that can affect human life and health. Our modern hi-tech society has become increasingly vulnerable to disturbances from outside the Earth system, in particular to those initiated by explosive events on the Sun: Flares release flashes of radiation that can heat up the terrestrial atmosphere such that satellites are slowed down and drop into lower orbits, solar energetic particles accelerated to near-relativistic energies may endanger astronauts traveling through interplanetary space, and coronal mass ejections are gigantic clouds of ionized gas ejected into interplanetary space that after a few hours or days may hit the Earth and cause geomagnetic storms. In this review, I describe the several chains of actions originating in our parent star, the Sun, that affect Earth, with particular attention to the solar phenomena and the subsequent effects in interplanetary space. Space Weather: The Solar Perspective 3 2006-07-10 2006LRSP....3....2S 2 2006-08-09 2006-06-21 lrsp-2006-2 Solar flares Solar wind Space weather Sun, Space weather, Solar wind, Solar flares Sun publication Star formation, Plasma astrophysics, Heating of solar and stellar coronae, Particle acceleration in flares, Millimeter and sub-millimeter astronomy, Very Long Baseline Interferometry of stars benz.arnold Arnold O. Benz Arnold O. Benz ETHZ Institut für Astronomie, ETH Hönggerberg, HIT J 23.1, CH-8093 Zürich, Switzerland author Dr. Longcope conducts theoretical research into the basic physics of magnetic fields in ionized plasmas and the application of these concepts to magnetic fields on the Sun. He has studied the storage and release of magnetic energy in the Sun's corona through a process known as reconnection. He has also studied the rise of slender strands of magnetic field from deep within the Sun up to the solar surface. longcope.dana Dana W. Longcope Dana W. Longcope Department of Physics, Montana State University, Bozeman, Montana 59717, U.S.A. author Magnetic activity from stars to planets, Search for M dwarfs with Exoearths with near-infrared spectrographs reiners.ansgar Ansgar Reiners Ansgar Reiners Georg-August-Universität, Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany author We review the properties of solar convection that are directly observable at the solar surface, and discuss the relevant underlying physics, concentrating mostly on a range of depths from the temperature minimum down to about 20 Mm below the visible solar surface. The properties of convection at the main energy carrying (granular) scales are tightly constrained by observations, in particular by the detailed shapes of photospheric spectral lines and the topology (time- and length-scales, flow velocities, etc.) of the up- and downflows. Current supercomputer models match these constraints very closely, which lends credence to the models, and allows robust conclusions to be drawn from analysis of the model properties. At larger scales the properties of the convective velocity field at the solar surface are strongly influenced by constraints from mass conservation, with amplitudes of larger scale horizontal motions decreasing roughly in inverse proportion to the scale of the motion. To a large extent, the apparent presence of distinct (meso- and supergranulation) scales is a result of the folding of this spectrum with the effective "filters" corresponding to various observational techniques. Convective motions on successively larger scales advect patterns created by convection on smaller scales; this includes patterns of magnetic field, which thus have an approximately self-similar structure at scales larger than granulation. Radiative-hydrodynamical simulations of solar surface convection can be used as 2D/3D time-dependent models of the solar atmosphere to predict the emergent spectrum. In general, the resulting detailed spectral line profiles agree spectacularly well with observations without invoking any micro- and macroturbulence parameters due to the presence of convective velocities and atmosphere inhomogeneities. One of the most noteworthy results has been a significant reduction in recent years in the derived solar C, N, and O abundances with far-reaching consequences, not the least for helioseismology. Convection in the solar surface layers is also of great importance for helioseismology in other ways; excitation of the wave spectrum occurs primarily in these layers, and convection influences the size of global wave cavity and, hence, the mode frequencies. On local scales convection modulates wave propagation, and supercomputer convection simulations may thus be used to test and calibrate local helioseismic methods. We also discuss the importance of near solar surface convection for the structure and evolution of magnetic patterns: faculae, pores, and sunspots, and briefly address the question of the importance or not of local dynamo action near the solar surface. Finally, we discuss the importance of near solar surface convection as a driver for chromospheric and coronal heating. Solar Surface Convection 6 2009-02-24 2009LRSP....6....2N 2 2009-04-04 2009-02-07 lrsp-2009-2 Solar convection, Granulation, Mesogranulation, Supergranulation publication Active regions on the solar surface are generally thought to originate from a strong toroidal magnetic field generated by a deep seated solar dynamo mechanism operating at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. Understanding this process of active region flux emergence is therefore a crucial component for the study of the solar cycle dynamo. This article reviews studies with regard to the formation and rise of active region scale magnetic flux tubes in the solar convection zone and their emergence into the solar atmosphere as active regions. Magnetic Fields in the Solar Convection Zone 6 lrsp-2009-4 Substantially revised and updated the previous version. Added 15 figures and new Sections 4.3, 5.1.5, 5.2, 5.5, and 5.7.3. 55 new references are added. 2009LRSP....6....4F 4 2009-12-14 2009-06-30 2009-12-09 Solar activity Sunspots Solar magnetic fields Magnetohydrodynamics Solar interior publication Prominences are intriguing, but poorly understood, magnetic structures of the solar corona. The dynamics of solar prominences has been the subject of a large number of studies, and of particular interest is the study of prominence oscillations. Ground- and space-based observations have confirmed the presence of oscillatory motions in prominences and they have been interpreted in terms of magnetohydrodynamic (MHD) waves. This interpretation opens the door to perform prominence seismology, whose main aim is to determine physical parameters in magnetic and plasma structures (prominences) that are difficult to measure by direct means. Here, we review the observational information gathered about prominence oscillations as well as the theoretical models developed to interpret small amplitude oscillations and their temporal and spatial attenuation. Finally, several prominence seismology applications are presented. Prominence Oscillations 9 2012-02-10 2012LRSP....9....2A 2 2012-04-05 2011-07-25 lrsp-2012-2 Seismology Oscillations Prominences publication We review our current understanding of sunspots from the scales of their fine structure to their large scale (global) structure including the processes of their formation and decay. Recently, sunspot models have undergone a dramatic change. In the past, several aspects of sunspot structure have been addressed by static MHD models with parametrized energy transport. Models of sunspot fine structure have been relying heavily on strong assumptions about flow and field geometry (e.g., flux-tubes, "gaps", convective rolls), which were motivated in part by the observed filamentary structure of penumbrae or the necessity of explaining the substantial energy transport required to maintain the penumbral brightness. However, none of these models could self-consistently explain all aspects of penumbral structure (energy transport, filamentation, Evershed flow). In recent years, 3D radiative MHD simulations have been advanced dramatically to the point at which models of complete sunspots with sufficient resolution to capture sunspot fine structure are feasible. Here overturning convection is the central element responsible for energy transport, filamentation leading to fine-structure and the driving of strong outflows. On the larger scale these models are also in the progress of addressing the subsurface structure of sunspots as well as sunspot formation. With this shift in modeling capabilities and the recent advances in high resolution observations, the future research will be guided by comparing observation and theory. Sunspot Modeling: From Simplified Models to Radiative MHD Simulations 8 2011-07-29 2011LRSP....8....3R 3 2011-09-07 2011-06-07 lrsp-2011-3 Sunspots Magnetohydrodynamics (MHD) publication Modeling of magnetic structure producing flares (sigmoid), convective motions interacting with magnetic field, prominence in dynamic state, solar wind; Evolution of active region, Activity in sunspot magara.tetsuya Tetsuya Magara Tetsuya Magara Dept. of Astronomy and Space Science, Kyung Hee University, Yongin, 446-701, Korea author Schüssler schuessler schuessler Manfred Schüssler Manfred MPI for Solar System Research, Germany ebMember lrsp-2011-2-rimmelethomas 1 authorOrder lrsp-2009-2-asplundmartin 3 authorOrder lrsp-2011-6-magara.tetsuya 2 authorOrder Solar eruptive phenomena embrace a variety of eruptions, including flares, solar energetic particles, and radio bursts. Since the vast majority of these are associated with the eruption, development, and evolution of coronal mass ejections (CMEs), we focus on CME observations in this review. CMEs are a key aspect of coronal and interplanetary dynamics. They inject large quantities of mass and magnetic flux into the heliosphere, causing major transient disturbances. CMEs can drive interplanetary shocks, a key source of solar energetic particles and are known to be the major contributor to severe space weather at the Earth. Studies over the past decade using the data sets from (among others) the SOHO, TRACE, Wind, ACE, STEREO, and SDO spacecraft, along with ground-based instruments, have improved our knowledge of the origins and development of CMEs at the Sun and how they contribute to space weather at Earth. SOHO, launched in 1995, has provided us with almost continuous coverage of the solar corona over more than a complete solar cycle, and the heliospheric imagers SMEI (2003 – 2011) and the HIs (operating since early 2007) have provided us with the capability to image and track CMEs continually across the inner heliosphere. We review some key coronal properties of CMEs, their source regions and their propagation through the solar wind. The LASCO coronagraphs routinely observe CMEs launched along the Sun-Earth line as halo-like brightenings. STEREO also permits observing Earth-directed CMEs from three different viewpoints of increasing azimuthal separation, thereby enabling the estimation of their three-dimensional properties. These are important not only for space weather prediction purposes, but also for understanding the development and internal structure of CMEs since we view their source regions on the solar disk and can measure their in-situ characteristics along their axes. Included in our discussion of the recent developments in CME-related phenomena are the latest developments from the STEREO and LASCO coronagraphs and the SMEI and HI heliospheric imagers. Coronal Mass Ejections: Observations 9 2012-05-16 2012LRSP....9....3W 3 2012-06-29 2011-08-16 lrsp-2012-3 Coronal mass ejections Solar-terrestrial relations Solar wind plasma Magnetic field reconnection publication Sheeley, Jr. sheeley.neil Neil R. Sheeley, Jr. Neil R. E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC 20375-5352, U.S.A. author Space weather effects arise from the dynamic conditions in the Earth’s space environment driven by processes on the Sun. While some effects are influenced neither by the properties of nor the processes within the Earth’s magnetosphere, others are critically dependent on the interaction of the impinging solar wind with the terrestrial magnetic field and plasma environment. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent on technological systems vulnerable to space weather influences, understanding and predicting hazards posed by the active solar events has grown in importance. This review introduces key dynamic processes within the magnetosphere and discusses their relationship to space weather hazards. Space Weather: Terrestrial Perspective 4 2007-05-10 2007LRSP....4....1P 1 2007-05-23 2007-04-24 lrsp-2007-1 Magnetosphere, Solar wind, Ionosphere, Plasma, Space weather publication We review stereoscopic and tomographic methods used in the solar corona, including ground-based and space-based measurements, using solar rotation or multiple spacecraft vantage points, in particular from the STEREO mission during 2007--2010. Stereoscopic and tomographic observations in the solar corona include large-scale structures, streamers, active regions, coronal loops, loop oscillations, acoustic waves in loops, erupting filaments and prominences, bright points, jets, plumes, flares, CME source regions, and CME-triggered global coronal waves. Applications in the solar interior (helioseismic tomography) and reconstruction and tracking of CMEs from the outer corona and into the heliosphere (interplanetary CMEs) are not included. Solar Stereoscopy and Tomography 8 2011-08-30 2011LRSP....8....5A 5 2011-10-10 2011-04-22 lrsp-2011-5 corona stereoscopy tomography Sun publication Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays at 100 MeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio waves. Space missions such as RHESSI, Yohkoh, TRACE, and SOHO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections (CMEs), electrons, and ions may be accelerated at different sites, there are at least 3 different magnetic topologies, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s) of energy release, tests of energy release scenarios and particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting reconnection of magnetic field lines as the basic cause. While this process has become generally accepted as the trigger, it is still controversial how it converts a considerable fraction of the energy into non-thermal particles. Flare-like processes may be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth’s lower ionosphere. While flare scenarios have slowly converged over the past decades, every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain a complex problem of astrophysics including major unsolved questions. Flare Observations 5 2008-02-22 2008LRSP....5....1B 1 2008-02-26 2007-12-13 lrsp-2008-1 Sun, Solar corona, Solar flares, Particle acceleration, Solar magnetic fields publication X-ray and UV astronomy. Solar and stellar coronal physics: dynamic phenomena in confined structures; data analysis and modeling of structuring and dynamics of the solar corona; modeling and diagnostics of stellar flares and coronae; study of the Sun as an X-ray star. Astrophysics of binary systems and interstellar medium: variability of extragalactic X-ray binary systems; thermal stability of stratified atmospheres; interaction of supernova remnants with interstellar clouds; circumstellar matter in star forming regions. Numerical astrophysics: hydrodynamic and MHD codes; parallel high performance computing. reale.fabio Fabio Reale Fabio Reale Dipartimento di Scienze Fisiche & Astronomiche, Università di Palermo, Sezione di Astronomia, Piazza Parlamento 1, 90134 Palermo, Italy author Solar plasma physics; Magnetohydrodynamics; Fluid waves and instabilities; Kinetic waves and instabilities; Numerical MHD; Numerical hybrid kinetic models; Solar active regions; Coronal Mass Ejections; Coronal heating; Solar wind; Analysis of satellite EUV observations ofman.leon Leon Ofman Leon Ofman Catholic University of America, NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771, U.S.A. author Carbone carbone.vincenzo Vincenzo Carbone Vincenzo Dipartimento di Fisica, Università della Calabria, Ponte P. Bucci, Cubo 31C 87036 Rende (CS), Italy author lrsp-2006-2-u1 Updated this review on status of planned and launched missions. Added references to three related Living Reviews articles and to the LASCO CME catalog (Robbrecht et al., 2009). 2010-06-16 2010-05-28 update Fleck fleck fleck Bernhard Fleck Bernhard NASA Goddard Space Flight Center, U.S.A. ebMember 2011-10-18 Corrected two references. lrsp-2011-3-u1 2011-10-20 update Sunspots, Magnetohydrodynamics, Spectroscopy and spectropolarimetry schlichenmaier.rolf Rolf Schlichenmaier Rolf Schlichenmaier Kiepenheuer-Institut für Sonnenphysik, Schöneckstr.6, D-79104 Freiburg, Germany author solar observation and theoretical research, specializing in studying magnetic fields on the Sun's surface sakurai.takashi Takashi Sakurai Takashi Sakurai Solar and Plasma Astrophysics Division, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan author lrsp-2004-1-u1 Sections 5.2 and 8.2 have been significantly rewritten to add new studies and results. Two new figures are added. Section 8.3 has been updated with recent calculations. 18 new references are included. 2007-02-09 2007-02-06 update Origin of the elements, Formation and evolution of the Galaxy asplund.martin Martin Asplund Martin Asplund Max Planck Institute for Astrophysics, Postfach 1317, D-85741 Garching, Germany author Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number. Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxy, such as the cosmogenic isotopes 14C and 10Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene. A separate section is devoted to reconstructions of strong solar–energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. Finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed. A History of Solar Activity over Millennia 5 lrsp-2008-3 2008LRSP....5....3U 3 2008-10-21 2008-07-30 2008-09-05 Solar activity Long-term reconstructions Solar activity, Paleo-astrophysics, Cosmogenic isotopes, Solar-terrestrial relations, Long-term reconstructions, Solar dynamo Solar-terrestrial relations Solar dynamo Paleo-astrophysics Cosmogenic isotopes publication lrsp-2011-2-marino.jose 2 authorOrder Berdyugina berdyugina.svetlana Svetlana V. Berdyugina Svetlana V. Kiepenheuer Institut fuer Sonnenphysik, Schoeneckstrasse 6, 79104 Freiburg, Germany author I'm interested in astrophysical fluid dynamics and magnetohydrodymanics, particularly as it applies to the interior of the sun and other stars. Most of my recent work focuses on high-resolution numerical simulations of convection, turbulence, and shear in the solar interior and the implications all this has for solar dynamo theory and for detectable surface flows such as differential rotation and solar sub-surface weather. I've also done some work on turbulence and waves in interstellar molecular clouds. miesch.mark Mark S. Miesch Mark S. Miesch High Altitude Observatory, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301, U.S.A. author solar-stellar-connection Solar-Stellar Connection subjectField Stellar analogs for the solar wind have proven to be frustratingly difficult to detect directly. However, these stellar winds can be studied indirectly by observing the interaction regions carved out by the collisions between these winds and the interstellar medium (ISM). These interaction regions are called ``astrospheres'', analogous to the ``heliosphere'' surrounding the Sun. The heliosphere and astrospheres contain a population of hydrogen heated by charge exchange processes that can produce enough H I Ly alpha absorption to be detectable in UV spectra of nearby stars from the Hubble Space Telescope (HST). The amount of astrospheric absorption is a diagnostic for the strength of the stellar wind, so these observations have provided the first measurements of solar-like stellar winds. Results from these stellar wind studies and their implications for our understanding of the solar wind are reviewed here. Of particular interest are results concerning the past history of the solar wind and its impact on planetary atmospheres. Astrospheres and Solar-like Stellar Winds 1 2004-06-30 2004LRSP....1....2W 2 2004-07-29 2004-03-29 lrsp-2004-2 Solar wind, Stellar winds, Heliosphere, Astrosphere publication lrsp-2008-3-u1 The review has been updated by an overview of recent relevant papers (19 new references), published between 2008 and March 2010, and their role in advancing the topic of long-term solar activity. 2010-04-22 2010-04-21 update Rotating fluids, Rotating stars rieutord.michel Michel Rieutord Michel Rieutord Laboratoire d’Astrophysique de Toulouse-Tarbes, Universitéde Toulouse, CNRS 14 Avenue Edouard Belin, 31400 Toulouse, France author lrsp-2011-6-shibata.kazunari 1 authorOrder Bruno bruno.roberto Roberto Bruno Roberto Istituto Fisica Spazio Interplanetario - INAF, Via Fosso del Cavaliere 100, 00133 Rome, Italy author This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10^32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare. Solar Flares: Magnetohydrodynamic Processes 8 2011-09-21 2011LRSP....8....6S 6 2011-12-15 2010-09-13 lrsp-2011-6 Flares CMEs current sheet particle acceleration space weather MHD, flux emergence radiation magnetic reconnection waves plasmoid ejection publication Cosmical Magnetohydrodynamics / Plasma Astrophysics (Solar MHD, Solar Flares/Jets, Magnetic Reconnection, AGN, Astrophysical Jet, Accretion Disk MHD, Galactic and Intergalactic MHD) shibata.kazunari Kazunari Shibata Kazunari Shibata Kwasan and Hida Observatories, Kyoto University, Kyoto, 607-8471, Japan author The Solar Cycle is reviewed. The 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. We examine a number of other solar activity indicators including the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores that vary in association with the sunspots. We examine the characteristics of individual solar cycles including their maxima and minima, cycle periods and amplitudes, cycle shape, and the nature of active latitudes, hemispheres, and longitudes. We examine long-term variability including the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev–Ohl Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double peaked maxima. We conclude with an examination of prediction techniques for the solar cycle. The Solar Cycle 7 2010-02-21 2010LRSP....7....1H 1 2010-03-02 2009-11-17 lrsp-2010-1 Solar activity Sunspots Solar cycle prediction Solar cycle publication Aznar Cuadrado cuadrado Scientific Copy Editor c Regina Aznar Cuadrado Regina MPI for Solar System Research, Germany teamMember Active regions, Coronal holes, Magnetic fields, Coronal heating, Solar image processing, Tomography, Stereoscopy, Magnetic Reconnection, Helmet streamer, Solar Wind, Coronal Mass Ejections (CMEs), Basic Plasmaphysics (MHD, Kinetics), Optimization methods wiegelmann.thomas Thomas Wiegelmann Thomas Wiegelmann Max Planck Institute for Solar System Research, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau, Germany author instruments-methods-and-techniques Instruments, Methods and Techniques subjectField His research covers the physics of the solar corona and solar wind, and generally of space plasmas. He has been active in data analysis as well as theory and modelling. He has been co investigator of many experiments, among them the EUV spectrometer SUMER on SOHO and the SECCHI instrument on STEREO. He proposed the Solar Orbiter mission, which was selected by ESA to fly around 2014. marsch.eckart Eckart Marsch Eckart Marsch Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau, Germany; now at Institute for Experimental and Applied Physics, Christian Albrechts University Kiel, Germany author lrsp-2009-2-steinrobert 2 authorOrder My main research interests are three-dimensional simulations of convection and magneto-convection in the Sun, and one-dimensional radiation-hydrodynamics of waves and non-equilibrium radiation in the solar atmosphere. stein.robert Robert F. Stein Robert F. Stein Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824, U.S.A. author Recent studies of the dynamic evolution of magnetic flux tubes in the solar convection zone are reviewed with focus on emerging flux tubes responsible for the formation of solar active regions. The current prevailing picture is that active regions on the solar surface originate from strong toroidal magnetic fields generated by the solar dynamo mechanism at the thin tachocline layer at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. This review discusses results with regard to the following major topics: 1. the equilibrium properties of the toroidal magnetic fields stored in the stable overshoot region at the base of the convection zone, 2. the buoyancy instability associated with the toroidal magnetic fields and the formation of buoyant magnetic flux tubes, 3. the rise of emerging flux loops through the solar convective envelope as modeled by the thin flux tube calculations which infer that the field strength of the toroidal magnetic fields at the base of the solar convection zone is significantly higher than the value in equipartition with convection, 4. the minimum twist needed for maintaining cohesion of the rising flux tubes, 5. the rise of highly twisted kink unstable flux tubes as a possible origin of -sunspots, 6. the evolution of buoyant magnetic flux tubes in 3D stratified convection, 7. turbulent pumping of magnetic flux by penetrative compressible convection, 8. an alternative mechanism for intensifying toroidal magnetic fields to significantly super-equipartition field strengths by conversion of the potential energy associated with the superadiabatic stratification of the solar convection zone, and finally 9. a brief overview of our current understanding of flux emergence at the surface and post-emergence evolution of the subsurface magnetic fields. Magnetic Fields in the Solar Convection Zone 1 2004-06-30 2004LRSP....1....1F 1 2004-07-29 lrsp-2004-1 Magnetohydrodynamics, Solar interior, Solar convection publication Computational MHD and code development, Solar Prominences, Coronal Heating, Magnetic Flux Transport and Magnetofrictional Relaxation Simulations, Stellar Magnetic Fields, Sun's Open Magnetic Flux and Solar Terrestrial mackay.duncan Duncan Mackay Duncan Mackay University of St Andrews, School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK author Schwenn schwenn.rainer Rainer Schwenn Rainer Max-Planck-Institut für Sonnenystemforschung, D-37191 Katlenburg-Lindau, Germany author Solar and astrophysical magnetohydrodynamics; dynamics of rising magnetic flux tubes in the solar interior; physics of solar active region formation; interaction of solar p-modes with active region magnetic flux tubes; helioseismology. fan.yuhong Yuhong Fan Yuhong Fan HAO, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301, U.S.A. author Seismology of the Sun and stars gizon.laurent Laurent Gizon Laurent Gizon Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau, Germany author lrsp-2012-2-ballesterjoseluis 3 authorOrder Cosmic rays usoskin.ilya Ilya G. Usoskin Ilya G. Usoskin Sodankylä Geophysical Observatory (Oulu unit), FIN-90014 University of Oulu, Finland author He focuses his research on modeling of MHD processes in the solar interior, coupled models of the differential rotation, meridional flow, and large-scale dynamo, addressing non-kinematic effects and cycle variations of the solar differential rotation (torsional oscillations). rempel.matthias Matthias Rempel Matthias Rempel High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307, USA author We review the current status of local helioseismology, covering both theoretical and observational results. After a brief introduction to solar oscillations and wave propagation through inhomogeneous media, we describe the main techniques of local helioseismology: Fourier-Hankel decomposition, ring-diagram analysis, time-distance helioseismology, helioseismic holography, and direct modeling. We discuss local helioseismology of large-scale flows, the solar-cycle dependence of these flows, perturbations associated with regions of magnetic activity, and solar supergranulation. Local Helioseismology 2 2005-05-13 2005LRSP....2....6G 6 2005-11-15 2004-10-18 lrsp-2005-6 Helioseismology publication Adaptive optics and multi-conjugate adaptive optics applied to solar observations, solar point spread function estimation, post-processing techniques. marino.jose Jose Marino Jose Marino National Solar Observatory, PO Box 62, Sunspot, NM 88340, U.S.A. author Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered, and therefore topics such as loop oscillations and flaring loops (except for non-solar ones which provide information on stellar loops) are not specifically addressed here. The observational section discusses loop classification and populations, and then describes the morphology of coronal loops, its relationship with the magnetic field, and the concept of loops as multi-stranded structures. The following part of this section is devoted to the characteristics of the loop plasma and of its thermal structure in particular, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics and flows are illustrated. In the modeling section some basics of loop physics are provided, supplying some fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are distinguished between those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. Then, more specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC) and impulsive (DC) heating. Finally, a brief discussion about stellar X-ray emitting structures related to coronal loops is included and followed by conclusions and open questions. Coronal Loops: Observations and Modeling of Confined Plasma 7 2010-10-28 2010LRSP....7....5R 5 2010-11-08 2009-10-26 lrsp-2010-5 Coronal loops Solar corona publication Adaptive optics, Small-scale magnetic fields, Active region dynamics, Helioseismology rimmele.thomas Thomas R. Rimmele Thomas R. Rimmele National Solar Observatory, PO Box 62, Sunspot, NM 88340, U.S.A. author Marsch marsch marsch Eckart Marsch Eckart Christian Albrechts University Kiel, Germany ebMember solar-activity Solar Activity subjectField lrsp-2012-5-wiegelmann.thomas 1 authorOrder In this review we will focus on a topic of fundamental importance for both plasma physics and astrophysics, namely the occurrence of large-amplitude low-frequency fluctuations of the fields that describe the plasma state. This subject will be treated within the context of the expanding solar wind and the most meaningful advances in this research field will be reported emphasizing the results obtained in the past decade or so. As a matter of fact, Ulysses’ high latitude observations and new numerical approaches to the problem, based on the dynamics of complex systems, brought new important insights which helped to better understand how turbulent fluctuations behave in the solar wind. In particular, numerical simulations within the realm of magnetohydrodynamic (MHD) turbulence theory unraveled what kind of physical mechanisms are at the basis of turbulence generation and energy transfer across the spectral domain of the fluctuations. In other words, the advances reached in these past years in the investigation of solar wind turbulence now offer a rather complete picture of the phenomenological aspect of the problem to be tentatively presented in a rather organic way. The Solar Wind as a Turbulence Laboratory 2 2005-04-09 2005LRSP....2....4B 4 2005-09-20 2005-03-22 lrsp-2005-4 Solar wind, Turbulence, Interplanetary space, Dynamical systems, Magnetohydrodynamics, Nonlinear phenomena publication My research focuses on astrophysical fluid and plasma dynamics, notably solar physics, turbulent convection, MHD and dynamo theory, accretion disk turbulence, microinstabilities in magnetized plasmas, and pulsations of magnetized stars. rincon.francois François Rincon François Rincon Laboratoire d’Astrophysique de Toulouse-Tarbes, Universitéde Toulouse, CNRS 14 Avenue Edouard Belin, 31400 Toulouse, France author A review of solar cycle prediction methods and their performance is given, including forecasts for cycle 24. The review focuses on those aspects of the solar cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming solar maximum no later than right after the start of the given cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of solar activity or magnetism at a specified time to predict the amplitude of the following solar maximum. Their implicit assumption is that each numbered solar cycle is a consistent unit in itself, while solar activity seems to consist of a series of much less tightly intercorrelated individual cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time and, therefore, it lends itself to analysis and forecasting by time series methods. Finally, instead of an analysis of observational data alone, model based predictions use physically (more or less) consistent dynamo models in their attempts to predict solar activity. In their overall performance during the course of the last few solar cycles, precursor methods have clearly been superior to extrapolation methods. Nevertheless, most precursor methods overpredicted cycle 23, while some extrapolation methods may still be worth further study. Model based forecasts have not yet had a chance to prove their skills. One method that has yielded predictions consistently in the right range during the past few solar cycles is that of K. Schatten et al., whose approach is mainly based on the polar field precursor. The incipient cycle 24 will probably mark the end of the Modern Maximum, with the Sun switching to a state of less strong activity. It will therefore be an important testbed for cycle prediction methods and, by inference, for our understanding of the solar dynamo. Solar Cycle Prediction 7 2010-12-21 2010LRSP....7....6P 6 2010-12-27 2010-08-26 lrsp-2010-6 Solar cycle Solar dynamo publication Magnetospheric dynamics, Geomagnetic storms and substorms, Large-scale magnetospheric modeling, Auroral electrodynamics pulkkinen.tuija Tuija Pulkkinen Tuija Pulkkinen Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland author lrsp-2012-3-howard.timothy 2 authorOrder Schulz schulz Manager BackOffice a Frank Schulz Frank MPI for Gravitational Physics, Germany teamMember In this review, our present day understanding of the Sun's global photospheric and coronal magnetic fields is discussed from both observational and theoretical viewpoints. Firstly, the large-scale properties of photospheric magnetic fields are described, along with recent advances in photospheric magnetic flux transport models. Following this, the wide variety of theoretical models used to simulate global coronal magnetic fields are described. From this, the combined application of both magnetic flux transport simulations and coronal modeling techniques to describe the phenomena of coronal holes, the Sun's open magnetic flux and the hemispheric pattern of solar filaments is discussed. Finally, recent advances in non-eruptive global MHD models are described. While the review focuses mainly on solar magnetic fields, recent advances in measuring and modeling stellar magnetic fields are described where appropriate. In the final section key areas of future research are identified. The Sun's Global Photospheric and Coronal Magnetic Fields: Observations and Models 9 2012-09-28 2012LRSP....9....6M 6 2012-11-26 2012-06-15 lrsp-2012-6 Magnetic fields Photosphere Modelling Corona Observations publication Hall hall.jeffrey Jeffrey C. Hall Jeffrey C. Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, U.S.A. author Weyher weyher Manager Research & Development (1997-2011) d Christina Weyher Christina teamMember Arregui arregui.inigo Iñigo Arregui Iñigo Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain) author Sakurai sakurai sakurai Takashi Sakurai Takashi National Astronomical Observatory of Japan ebMember Hathaway hathaway.david David H. Hathaway David H. Mail Code VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812, U.S.A. author Charbonneau charbonneau.paul Paul Charbonneau Paul Département de Physique, Université de Montréal, CP 6128 Centre-Ville, Montréal (Qc), H3C-3J7, Canada author MHD numerical simulations of solar and space plasmas, Multi-wavelength observations of solar activities, Space weather, Planetary science, Application of magnetic reconnection in astrophysics chen.pf P. F. Chen P. F. Chen Department of Astronomy, Nanjing University, Nanjing 210093, China author Magnetic activity similar to that of the Sun is observed on a variety of cool stars with external convection envelopes. Stellar rotation coupled with convective motions generate strong magnetic fields in the stellar interior and produce a multitude of magnetic phenomena including starspots in the photosphere, chromospheric plages, coronal loops, UV, X-ray, and radio emission and flares. Here I review the phenomenon of starspots on different types of cool stars, observational tools and diagnostic techniques for studying starspots as well as starspot properties including their temperatures, areas, magnetic field strengths, lifetimes, active latitudes and longitudes, etc. Evolution of starspots on various time scales allows us to investigate stellar differential rotation, activity cycles, and global magnetic fields. Together these constitute the basis for our understanding of stellar and solar dynamos and provide valuable constraints for theoretical models. Starspots: A Key to the Stellar Dynamo 2 2005-08-15 2005LRSP....2....8B 8 2005-12-13 2005-07-28 lrsp-2005-8 Starspots, Sunspots, Stellar magnetic fields, Stellar cycles, Dynamo models, Differential rotation, Doppler imaging publication I am involved in research projects in the general area of Computational Astrophysics. nordlund.ake Åke Nordlund Åke Nordlund JILA, University of Colorado, and Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 København Ø, Denmark author This paper reviews recent advances and current debates in modeling the solar cycle as a hydromagnetic dynamo process. Emphasis is placed on (relatively) simple dynamo models that are nonetheless detailed enough to be comparable to solar cycle observations. After a brief overview of the dynamo problem and of key observational constraints, we begin by reviewing the various magnetic field regeneration mechanisms that have been proposed in the solar context. We move on to a presentation and critical discussion of extant solar cycle models based on these mechanisms. We then turn to the origin of fluctuations in these models, including amplitude and parity modulation, chaotic behavior, and intermittency. The paper concludes with a discussion of our current state of ignorance regarding various key questions, the most pressing perhaps being the identification of the physical mechanism(s) responsible for the generation of the Sun’s poloidal magnetic field component. Dynamo Models of the Solar Cycle 2 lrsp-2005-2 2005LRSP....2....2C 2 2005-06-13 2005-03-31 2005-04-23 Dynamo models, Solar cycle publication lrsp-2012-5-sakurai.takashi 2 authorOrder Osswald osswald Database Management b Vera Osswald Vera MPI for Gravitational Physics, Germany teamMember The Sun’s supergranulation refers to a physical pattern covering the surface of the quiet Sun with a typical horizontal scale of approximately 30,000 km and a lifetime of around 1.8 d. Its most noticeable observable signature is as a fluctuating velocity field of 360 m s–1 rms whose components are mostly horizontal. Supergranulation was discovered more than fifty years ago, however explaining why and how it originates still represents one of the main challenges of modern solar physics. A lot of work has been devoted to the subject over the years, but observational constraints, conceptual difficulties and numerical limitations have all concurred to prevent a detailed understanding of the supergranulation phenomenon so far. With the advent of 21st century supercomputing resources and the availability of unprecedented high-resolution observations of the Sun, a stage at which key progress can be made has now been reached. A unifying strategy between observations and modelling is more than ever required for this to be possible. The primary aim of this review is therefore to provide readers with a detailed interdisciplinary description of past and current research on the problem, from the most elaborate observational strategies to recent theoretical and numerical modelling efforts that have all taken up the challenge of uncovering the origins of supergranulation. Throughout the text, we attempt to pick up the most robust findings so far, but we also outline the difficulties, limitations and open questions that the community has been confronted with over the years. In the light of the current understanding of the multiscale dynamics of the quiet photosphere, we finally suggest a tentative picture of supergranulation as a dynamical feature of turbulent magnetohydrodynamic convection in an extended spatial domain, with the aim of stimulating future research and discussions. The Sun’s Supergranulation 7 2010-05-28 2010LRSP....7....2R 2 2010-06-15 2010-01-25 lrsp-2010-2 Supergranulation Convection Turbulence MHD publication In this review we give an overview about the current state-of-knowledge of the magnetic field in sunspots from an observational point of view. We start by offering a brief description of tools that are most commonly employed to infer the magnetic field in the solar atmosphere with emphasis in the photosphere of sunspots. We then address separately the global and local magnetic structure of sunspots, focusing on the implications of the current observations for the different sunspots models, energy transport mechanisms, extrapolations of the magnetic field towards the Corona, and other issues. Magnetic Structure of Sunspots 8 2011-08-09 2011LRSP....8....4B 4 2011-09-09 2011-05-30 lrsp-2011-4 Sunspots Magnetic fields publication Birch birch.aaron Aaron C. Birch Aaron C. Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau, Germany author lrsp-2005-6-birch.aaron 2 authorOrder Cool stars like the Sun harbor convection zones capable of producing substantial surface magnetic fields leading to stellar magnetic activity. The influence of stellar parameters like rotation, radius, and age on cool-star magnetism, and the importance of the shear layer between a radiative core and the convective envelope for the generation of magnetic fields are keys for our understanding of low-mass stellar dynamos, the solar dynamo, and also for other large-scale and planetary dynamos. Our observational picture of cool-star magnetic fields has improved tremendously over the last years. Sophisticated methods were developed to search for the subtle effects of magnetism, which are difficult to detect particularly in cool stars. With an emphasis on the assumptions and capabilities of modern methods used to measure magnetism in cool stars, I review the different techniques available for magnetic field measurements. I collect the analyses on cool-star magnetic fields and try to compare results from different methods, and I review empirical evidence that led to our current picture of magnetic fields and their generation in cool stars and brown dwarfs. Observations of Cool-Star Magnetic Fields 9 2012-02-20 2012LRSP....9....1R 1 2012-02-29 2011-06-07 lrsp-2012-1 Magnetic fields Stellar activity publication Solanki solanki Editor in Chief solanki Sami Solanki Sami MPI for Solar System Research, Germany ebMember This paper reviews recent advances and current debates in modeling the solar cycle as a hydromagnetic dynamo process. Emphasis is placed on (relatively) simple dynamo models that are nonetheless detailed enough to be comparable to solar cycle observations. After a brief overview of the dynamo problem and of key observational constraints, we begin by reviewing the various magnetic field regeneration mechanisms that have been proposed in the solar context. We move on to a presentation and critical discussion of extant solar cycle models based on these mechanisms. We then turn to the origin and consequences of fluctuations in these models, including amplitude and parity modulation, chaotic behavior, intermittency, and predictability. The paper concludes with a discussion of our current state of ignorance regarding various key questions relating to the explanatory framework offered by dynamo models of the solar cycle. Dynamo Models of the Solar Cycle 7 lrsp-2010-3 Besides updates relating to the literature published in the past five years (added about 60 new references), and reworking a few sections of the 2005 version, main major novelties compared to the 2005 version are: 1. Material on turbulent pumping, and its effect in various types of dynamo models. 2. Expanded Section 4.9 on MHD numerical simulations of large-scale dynamo action. 3. Added Section 5.7 on dynamo model-based cycle prediction schemes. 4. Inclusion (and discussion of) animations directly in the text. By appropriate deletions elsewhere in the review, I have managed to retain its overall length at nearly the same as the 2005 version. 2010LRSP....7....3C 3 2010-09-04 2010-04-09 2010-08-26 Solar activity Magnetic fields Dynamo Solar cycle publication Aschwanden aschwanden.markus Markus J. Aschwanden Markus J. Solar and Astrophysics Laboratory, Lockheed Martin, Advanced Technology Center, Bldg. 252, Org. ADBS, 3251 Hanover St., Palo Alto, CA 94304, USA author Schrijver schrijver schrijver Karel Schrijver Karel Lockheed Martin Solar and Astrophysics Laboratory, U.S.A. ebMember The Sun, stars similar to it, and many rather dissimilar to it, have chromospheres, regions classically viewed as lying above the brilliant photosphere and characterized by a positive temperature gradient and a marked departure from radiative equilibrium. Stellar chromospheres exhibit a wide range of phenomena collectively called activity, stemming largely from the time evolution of their magnetic fields and the mass flux and transfer of radiation through the complex magnetic topology and the increasingly optically thin plasma of the outer stellar atmosphere. In this review, I will (1) outline the development of our understanding of chromospheric structure from 1960 to the present, (2) discuss the major observational programs and theoretical lines of inquiry, (3) review the origin and nature of both solar and stellar chromospheric activity and its relationship to, and effect on, stellar parameters including total energy output, and (4) summarize the outstanding problems today. Stellar Chromospheric Activity 5 2008-01-29 2008LRSP....5....2H 2 2008-03-10 2007-12-22 lrsp-2008-2 Sun, Stars, Chromospheres publication