List of Figures

View Image Figure 1:
Two ribbons of a flare observed in Hα (I – V) and EUV (VI – X). Hα data are taken at Kwasan Observatory of Kyoto University, and EUV data are taken with EUV telescope aboard TRACE (from Asai et al., 2003).
View Image Figure 2:
Phenomenological models for flares based on magnetic reconnection. Lines with arrows on them indicate magnetic field lines. (a) Carmichael (1964), (b) Sturrock (1966), (c) Hirayama (1974), (d) Kopp and Pneuman (1976).
View Image Figure 3:
(a) Soft X-ray image of a long-durational-event (LDE) flare (see Section 2) observed by Yohkoh. (b) Schematic picture of a modified version of the CSHKP model, incorporating the new features discovered by Yohkoh (from Shibata et al., 1995).
View Image Figure 4:
A soft X-ray image of an LDE flare with cusp shaped-loop structure, observed on Feb. 21, 1992 (Tsuneta et al., 1992a; Tsuneta, 1996). Shown in reversed contrast.
View Image Figure 5:
Soft X-ray images of plasmoid ejection associated with the flare on Oct. 5, 1992 (from Ohyama and Shibata, 1998). Shown in reversed contrast.
View Image Figure 6:
A giant arcade observed in soft X-ray on April 14, 1994 (from McAllister et al., 1996). Shown in reversed contrast.
View Image Figure 7:
Helmet streamer observed in soft X-ray on January 24, 1992 (modified from Hiei et al., 1993).
View Image Figure 8:
Hard X-ray loop-top source (contours) of an impulsive flare observed on January 13, 1992 (from Masuda, 1994). Colors represent soft X-ray intensity.
View Image Figure 9:
(Left) X-ray jet observed in soft X-rays (from Shibata et al., 1992a). Shown in reversed contrast. (Right) Longitudinal magnetic field distribution in the same field of view as in the left panel. The contour shows the soft X-ray intensity, revealing that the footpoint of the X-ray jet correspond to the mixed polarity region (from Shibata, 1999).
View Image Figure 10:
Two types of X-ray jets. (a) Two sided-loop jet. (b) Anemone-type jet. (c) Typical configuration for the two sided-loop jet at left panel and anemone-type jet at right panel (modified from Yokoyama and Shibata, 1996).
View Image Figure 11:
Unified model for solar eruptions (Shibata et al., 1995; Shibata, 1999). Top: Pre-eruption (left) and post-eruption (right) states of a large-scale eruption. Bottom: Pre-eruption (left) and post-eruption (right) states of a small-scale eruption.
View Image Figure 12:
Evolution of an active region, showing the development of magnetic shear. The left panels are Hα images and the right panels are white-light images (from Kurokawa, 1989).
View Image Figure 13:
Top: Two-dimensional simulations of flux emergence in a flux-sheet configuration. Contours represent magnetic field lines. Bottom: Distributions of rising velocity (vz), Alfvén velocity (v A), density (ρ), and horizontal magnetic field (B x) with height during the expansion of emerging magnetic field. The dashed curves in the graphs (c) and (d) at the bottom panel represent the analytic curves of the self-similar solution (from Shibata et al., 1989b).
View Image Figure 14:
(a) A rising flux tube becomes flattened when it approaches the surface. (b) A developed magnetic sheet and its horizontal extent (λ) (from Magara, 2001). (c) Histogram of the observed horizontal extent of emerging magnetic field (from Pariat et al., 2004).
View Image Figure 15:
A magnetic structure formed by the emergence of a twisted flux tube. Two field lines (outer and inner) composing the flux tube are presented. The arrows on these field lines represent flow velocity. The outer field line forms an expanding loop, below which the inner field line forms a sheared loop which is less dynamic (from Magara and Longcope, 2003).
View Image Figure 16:
Difference in evolution between the outer and inner field lines composing a twisted flux tube (from Magara and Longcope, 2003).
View Image Figure 17:
Magnetic structure of a filament (from Low and Hundhausen, 1995) (top-left panel), DeVore and Antiochos (2000) (top-right panel) and van Ballegooijen and Martens (1989) (bottom panel).
View Image Figure 18:
Possible magnetic structure of a filament formed via the emergence of a twisted flux tube of left handedness. The top panel shows pre- and post-emergence states. The flux tube undulates along the axis when it emerges. Field lines composing the twisted flux tube which are located away from tube axis (outer field lines) are displayed in red, while inner field lines close to tube axis are in white. Note that the inner field lines form the main body of a filament while the outer field lines overlie the main body by forming a coronal arcade and underlie the main body by forming barbs. The middle panels show top and side views of the main body formed by the inner field lines (blue) and barbs formed by the outer field lines (green and orange). The bottom panels schematically show the spatial relationship among the coronal arcade, main body and barbs of a dextral filament. The sinistral case is given by the mirror symmetry of the dextral case (flux tube has right handedness). From Magara (2007), except for the top panel, which is now given from a different viewing angle (same 3D plot), and the bottom-left panel, which is adapted from Martin (1998).
View Image Figure 19:
Double J-shaped structure formed inside an emerging flux tube. Colors of field lines represent the strength of current density measured at their chromospheric footpoints. Top, side and perspective views are presented at top-left, bottom-left, and bottom-right panels, respectively. The top-right panel shows the distribution of current density at a chromospheric plane (from Magara, 2004).
View Image Figure 20:
Magnetic structure formed by a (a) highly and (b) weakly twisted flux tube. The bottom panels (c, d) show an observed example in each case (from Magara, 2006).
View Image Figure 21:
(a) Sigmoid observed by the soft X-ray telescope on board Yohkoh (courtesy of the Yohkoh team members). (b) Two-dimensional map of gas density (color map) and the magnetic field (black arrows) projected onto the middle plane at y = 0, which is obtained by the emergence of a twisted flux tube (initially placed along the y-axis). The red, white, and orange dots represent the locations where red (above the axis), white (axis), and orange (below the axis) field lines cross this plane. (c) Three-dimensional viewgraph of these magnetic field lines. The bottom map at z = 0 shows horizontal velocity field (white arrows), vertical velocity (color map), and vertical magnetic field (contour lines). (d) Top view of (c), where a color map shows the absolute value of the current density measured at z = 3 (chromospheric level) (from Magara and Longcope, 2001).
View Image Figure 22:
Sigmoid formation by an emerging flux tube. Shown is the cross section of the flux tube.
View Image Figure 23:
Comparison between simulations (left and middle columns) and soft X-ray observations (right column). The left column shows the evolution of the isosurface of current density, the middle one shows the corresponding snapshots of the heating term, and the right column shows soft X-ray images at three different times during the evolution of the sigmoidal structure (from Archontis et al., 2009).
View Image Figure 24:
(a) Top-left panel: Temporal development of the height of three field lines which compose a twisted flux tube of left handedness (contains negative magnetic helicity). Top-right panel: Time variation of emerged magnetic flux. Middle-left panel: Time variation of magnetic energy injected to the atmosphere (z > 0). Middle-right panel: Time variation of magnetic energy flux. Bottom-left panel: Time variation of magnetic helicity injected to the atmosphere. Bottom-right panel: Time variation of magnetic helicity flux. (b) Snapshot of the emerging flux tube at the early (t = 12, left panel) and late (t = 40, right panel) phases (from Magara and Longcope, 2003).
View Image Figure 25:
(a) Emergence of a partially split flux tube (from Zwaan, 1985). (b) Simulation of the emergence of a partially flux tube. (c) – (d) Quadrupolar-like structure formed by this flux tube. Panels (b) – (d) from Magara (2008).
View Image Figure 26:
Magnetic reconnection in a current sheet.
View Image Figure 27:
Fractal current sheet (from Shibata and Tanuma, 2001).
View Image Figure 28:
Fractal current sheet in a flare (from Tajima and Shibata, 1997).
View Image Figure 29:
Formation of a current sheet via the interaction of emerging and preexisting magnetic fields.
View Image Figure 30:
Interaction of emerging and preexisting fields and resultant dynamic processes, reproduced by a two-dimensional MHD simulation. The upper panel shows the evolution of magnetic field (contours) and flow (velocity field), while the lower represents the enhancement of temperature (colors) (from Yokoyama and Shibata, 1996).
View Image Figure 31:
Interaction of emerging and preexisting magnetic fields in three-dimensional space. In the top panel, the color surfaces correspond to the isosurface of flow velocity, the arrows to the velocity field, and the white/pink lines to the field lines (from Isobe et al., 2005). In the bottom panel, the blue and pink surfaces represent j∕B and temperature, and the blue, orange, and green lines represent field lines in different connectivity domains (from Moreno-Insertis et al., 2008).
View Image Figure 32:
Interaction of emerging (red field lines) and preexisting magnetic fields (others) in three-dimensional space (from Archontis et al., 2004).
View Image Figure 33:
Interaction of emerging and preexisting magnetic fields in three-dimensional space. The light-blue isosurface represents a current sheet. The arrows show the direction of the magnetic field vector (from Galsgaard et al., 2007).
View Image Figure 34:
Shear-induced model for the formation of a current sheet. (a) From Mikić et al. (1988), (b) from Biskamp and Welter (1989), and (c) from Choe and Lee (1996) (bottom right).
View Image Figure 35:
Formation of a magnetic flux rope by sheared magnetic field emerging into a stratified atmosphere. The colors indicate shear angle (from Manchester IV, 2001).
View Image Figure 36:
Emergence of an U-loop with diverging flow on it (from Magara, 2011).
View Image Figure 37:
Models for the eruption of a flux rope. (a) Flux-cancellation model (from Linker et al., 2003). (b) Tether-cutting model (from Moore et al., 2001). (c) Kink instability (from Fan and Gibson, 2003). (d) Flux cancellation model (from Amari et al., 2000). (e) Loss-of-equilibrium model (from Forbes and Isenberg, 1991).
View Image Figure 38:
Destabilizing mechanism for the eruption of a flux rope, known as the breakout model presented in Antiochos et al. (1999a).
View Image Figure 39:
Destabilizing mechanism for the eruption of a flux rope, known as the emerging flux trigger mechanism presented in Chen and Shibata (2000). The solid lines correspond to the magnetic field, the arrows to the velocity, and the color map to the temperature. At the top panels, the emerging field appears just on the polarity inversion line of the preexisting field, while it appears at one side of the inversion line at the bottom panels.
View Image Figure 40:
Destabilizing mechanism for the eruption of a flux rope, known as the reversed magnetic-shear model developed in Kusano et al. (2004). Typical plasma flows are illustrated by thick arrows. The green surface in (b) represents an isosurface on which Vz = 0.1VA. The color maps on the side and bottom boundaries represent the flux density of sheared and vertical component of magnetic field.
View Image Figure 41:
Typical time variation of emissions observed in various wavelengths during a flare (from Kane, 1974).
View Image Figure 42:
Magnetic configurations in the impulsive (left panel) and gradual (right panel) phases of a flare. The source region of emissions observed in various wavelengths are also presented. These two kinds of configurations are applied to different types of flares such as impulsive flares and LDE flares (adapted from Magara et al., 1996). An observational example of these flares are displayed at the top left (Masuda, 1994) and top right (Tsuneta et al., 1992a), respectively.
View Image Figure 43:
(a) Hight-time relation of a magnetic island in a two-dimensional numerical simulation, which is supposed to be the two-dimensional counterpart of a plasmoid. Time variation of the conductive electric field defined by Equation (16View Equation) is also plotted (from Magara et al., 1997). (b) Time variations of the height of an observed plasmoid as well as hard X-ray intensity (modified from Ohyama and Shibata, 1997). (c) Multiple ejection of plasmoids (from Choe and Cheng, 2000).
View Image Figure 44:
Top panels show temperature (left) and pressure (right) distributions in the Petschek-type reconnection for the cases without and with conduction. The curves show magnetic field lines and the arrows show velocity vectors. Note that the adiabatic slow shocks dissociate into the conduction fronts and the isothermal slow shocks in the case with conduction (from Yokoyama and Shibata, 1997). Bottom panel shows the time evolution of the temperature and density distributions in the reconnection with thermal conduction and chromospheric evaporation as a model of solar flares. The curves show magnetic field lines and the arrows show velocity vectors. In this case, not only the conduction fronts and isothermal slow shocks but also dense chromospheric evaporation flow are clearly seen (from Yokoyama and Shibata, 1998).
View Image Figure 45:
Structure and evolution of a Moreton wave in soft X-rays and Hα observed on 1997 November 3. (a – f) Hα + 0.8 Å running difference images of a Moreton wave (black arrows). (g – j) Soft X-ray (middle panels) and running difference (bottom panels) images of an X-ray wave (white arrows). (k) Wave fronts of the Moreton wave at every minute (black lines) and the X-ray wave at every 48 seconds (white lines) overlaid on the photospheric magnetic field. Gray lines show the great circles through the flare site (gray arrow). The rectangle, circle, and lines shown in (l) are the field of view of (a – k), the limb of the Sun, and the great circles, respectively (from Narukage et al., 2002).
View Image Figure 46:
The universal correlation between emission measure and temperature of solar and stellar flares (Shibata and Yokoyama, 1999). The solid lines show the theoretical scaling law EM ∝ B − 5T 17∕2 (Equation (43View Equation)) for B = constant = 15, 50, 150 G, and the dash-dotted lines show EM-T relation for L = constant = 108, 1010, 1012 cm.
View Image Figure 47:
Physical processes responsible for flare and flare-associated phenomena.