List of Figures

View Image Figure 1:
Periodicities in solar and geomagnetic activity. The left panels show time series of the monthly values of the sunspot number and the geomagentic Ap index. The top right panel shows the solar cycle variation present both in the geomagnetic and solar records, showing peak geomagnetic activity during the declining phase of the solar cycle. The bottom right panel shows the semiannual variation in the geomagnetic data not visible in the solar records. The data were obtained from External Linkftp://ftp.ngdc.noaa.gov/STP/.
View Image Figure 2:
Basic structure of the magnetosphere. The faint blue arrows show the magnetic field direction toward the Earth in the northern tail lobe, away from the Earth in the southern lobe, and northward at the dayside magnetosphere. The red regions in the inner magnetosphere contain both the ring current and the outer van Allen belt, where the ions and electrons are trapped on closed drift paths. Direction of the Sun is to the left (courtesy ESA).
View Image Figure 3:
Large-scale current systems in the magnetosphere. An enlargement of the Earth showing the auroral oval, auroral electrojet currents, and the large-scale Region 1 (more poleward) and Region 2 (more equatorward) currents bounding the high-latitude polar cap is shown in the background (Figure: Teemu Makinen/Finnish Meteorological Institute).
View Image Figure 4:
Inner magnetosphere plasma populations. The outer van Allen belt, the ring current, and the plasmasphere are colocated within the inner magnetosphere trapping region. The plasma sheet in the closed field line region extends to the dayside magnetopause and to the distant nightside tail.
View Image Figure 5:
A schematic of the magnetospheric substorm. After the onset of dayside reconnection, energy is loaded into the magnetotail, which leads to the formation of a large-scale thin (ion gyroradius scale) current sheet. Magnetic reconnection at a near-Earth neutral line is associated with the bursty energy release, followed by ejection of plasma in the form of a plasmoid back to interplanetary space.
View Image Figure 6:
Ring current evolution during a magnetic storm on August 12, 2000. Top panel: Geomagnetic SYM-H (proxy for ring current intensity) and ASY-H (proxy for ring current asymmetry) indices. Bottom panel: Observations made by the HENA energetic neutral atom imager onboard the IMAGE satellite. The polar plots show the equatorial ion fluxes in units of 1 keVssrcm2 averaged over pitch-angle in the energy range 27 – 39 keV. The direction to the Sun is to the left and dawn is up. (From Fok et al., 2003).
View Image Figure 7:
Magnetic storm on April 6 – 7, 2000. Left, from top to bottom: interplanetary magnetic field Bx and By, Bz, solar wind density and pressure, speed, and motional electric field. Right, from top to bottom: 𝜖-parameter giving a measure of the energy input to the system; AU and AL indices giving a proxy of the ionospheric electrojet current activity; AL-index-based proxies for ionospheric Joule heating and particle precipitation power; Dst index and its pressure-corrected variant Dst, Dst and its prediction using Equation 7View Equation that provide an estimate of the ring current intensity.
View Image Figure 8:
Schematic of the structure of a global MHD simulation. Measured solar wind and IMF values are used as input at the Sunward boundary of the MHD simulation box. The MHD part solves the temporal evolution of the plasmas and electromagnetic fields, and feeds the field-aligned currents and electron precipitation to the ionospheric simulation. The ionospheric part solves the potential equation using the magnetospheric input as well as the solar EUV values to compute the ionospheric current and potential pattern and feeds the electric potential pattern back to the MHD simulation.
View Image Figure 9:
Magnetic storm on April 6 – 7, 2000. Left, from top to bottom: 𝜖 parameter characterizing energy input, Bz component of the magnetic field at GOES-10 and GOES-8 (negative Bz is an indication of the satellite being outside the magnetosphere), empirical Shue et al. model for the subsolar magnetopause position (blue) and two measures of the subsolar magnetopause position from the GUMICS-4 MHD simulation (current maximum, upper black curve, and open-closed field line boundary, lower black curve), and Bz from the Geotail spacecraft (blue) and from the GUMICS-4 MHD simulation (black). Right: Two equatorial plane cuts of plasma density from the GUMICS-4 MHD simulation. The direction of the Sun is to the left, and the black sphere at the center marks the inner boundary of the MHD simulation at 3.7 RE. The large black dot shows the Geotail satellite position inside the magnetosheath at 16:00 UT and outside in the solar wind at 21:00 UT as the magnetosphere is compressed during the storm main phase.
View Image Figure 10:
Poynting flux enters through the magnetopause and focuses toward the inner magnetosphere. The left panel shows the noon-midnight meridian plane with direction of the Sun to the left and the right panel shows the equatorial plane with direction of the Sun to the top. The plots illustrate how the energy enters through the high-latitude boundary and is focussed toward the inner magnetotail and finally toward the ionosphere.
Watch/download Movie Figure 11: (avi-Movie; 12665 KB)
Movie Magnetic storm on April 6 – 7, 2000. Magnetopause shape and size and the energy transfer through the magentopause surface during three time instants from the GUMICS-4 global MHD simulation. The magnetospheric boundary is viewed from a direction upstream (Sunward) of the magnetosphere. Note that the energy entry shown in blue is concentrated at the nose of the magnetosphere as well as in two high-latitude regions which are in sectors roughly parallel to the interplanetary magnetic field direction.
View Image Figure 12:
Magnetic storm on April 6 – 7, 2000. Panels from top to bottom: Total power input through the magnetopause from the GUMICS-4 global MHD simulation (black) and 𝜖-parameter (blue, scale on the right). Note how the energy entry in the simulation continues after the IMF has turned northward even though the 𝜖-proxy would indicate very small energy input. Ionospheric Joule heating integrated over both hemispheres from GUMICS-4 (black) and AE-based proxy from Ahn et al. (1983) (blue, scale on the right). Note the large energy input associated with the solar wind pressure pulse seen in the simulation, but not in the observational proxies. Energy input rate from particle precipitation from GUMICS-4 (black) and from AE-based proxy from Østgaard et al. (2002) (blue, scale on the right).
Watch/download Movie Figure 13: (avi-Movie; 3099 KB)
Movie Magnetic storm on April 6 – 7, 2000. Northern hemisphere Joule heating during three instants from the GUMICS-4 global MHD simulation. The polar plots are drawn with Sun to the top and dusk to the left. Note how the auroral precipitation energy (shown in Figure 14) is concentrated in the auroral oval region and the dayside cusp where solar wind has direct access, while the Joule heating maximizes in the polar cap where the electric field is largest.
Watch/download Movie Figure 14: (mpeg-Movie; 3046 KB)
Movie Magnetic storm on April 6 – 7, 2000. Northern hemisphere auroral precipitation during three instants from the GUMICS-4 global MHD simulation. The polar plots are drawn with Sun to the top and dusk to the left. Note how the auroral precipitation energy is concentrated in the auroral oval region and the dayside cusp where solar wind has direct access, while the Joule heating (shown in Figure 13) maximizes in the polar cap where the electric field is largest.
View Image Figure 15:
Substorm on December 10, 1996. Left, from top to bottom: North-south component of the IMF. Magnetotail observations of the thinning and intensification of the tail current sheet. The period of energy storage is bracketed with the vertical lines. Increasing Bx in the magnetotail lobe recorded by Interball is a measure of increasing magnetic flux content in the tail. Decreasing Bz in the plasma sheet at geostationary orbit (recorded by GOES-9) and at about 25 RE distance (recorded by Geotail) reflects the increasing tail current intensity.
Watch/download Movie Figure 16: (mpg-Movie; 3926 KB)
Movie Substorm on December 10, 1996. Four snapshots of the LFM global MHD simulation. The color coding shows the plasma density in the noon-midnight meridian plane. The gray shading outlines the last closed flux surface indicating the large-scale magnetic topology of the system. The topological changes are consistent with those presented in the schematic picture in Section 3. The direction of the Sun is to the left.
Watch/download Movie Figure 17: (mpg-Movie; 16561 KB)
Movie Substorm on December 10, 1996. LFM global MHD simulation results of the magnetotail flows in an equatorial plane projection. The direction of the Sun is to the left. The color coding shows the cross-tail electric field, with brighter colors showing higher electric field values indicative of a thin and intense current sheet at that location (highlighted by the white circle). The white arrows depict the flow velocity. Note a flow channel initiating from about 40 RE distance and focusing toward the thin current sheet region (outlined with the white dotted line). Such flow channels become larger and more frequent during substorm activity and finally lead to disruption of the intense inner-tail current sheet during the substorm expansion phase.
View Image Figure 18:
The top panel shows the inner belt proton flux in red and the sunspot number in black. The bottom panel shows the relativistic electron distribution in the inner magnetosphere. Color coding shows the inner magnetosphere relativistic electron flux intensity as a function of time and L shell giving the equatorial distance from the Earth. The black curve overlaid shows the daily averages of the Dst index (scale on the right), used here as a measure of the ring current energetic ion flux with more negative values indicating larger ring current (from Li et al., 2001).
View Image Figure 19:
Magnetic storm on May 2 – 4, 1998. Magnetotail electric current intensity variations during May 4, 1998. The color coding shows the perpendicular current intensity in the equatorial plane (top panels) and in the noon-midnight meridian plane (bottom panels). Note the strong enhancement of both the ring and tail currents during the storm main phase (from Ganushkina et al., 2005).
View Image Figure 20:
Magnetic storm on May 2 – 4, 1998. Ring current energy content as a function of time. Total energy content is shown in black, red shows the energy contribution from high-energy particles (80 – 200 keV), green shows the energy content in the medium energy particles (20 – 80 keV) and blue shows the contribution of the low-energy particles (1 – 20 keV). The left panels show observations from the Polar spacecraft. The observations indicate strong enhancement of the high-energy component during the later part of the storm (lowest panel shown in red). The three panels on the right show results from drift computations using different magnetic and electric field models, from top to bottom: dipole magnetic field and Volland–Stern convection electric field, T96 magnetic field model and Boyle et al. (1997) convection electric field, T96 magnetic field, Boyle et al. (1997) convection electric field, and substorm-associated electric field pulses. The bottom panel shows the Dst index during the storm. Only the model including the pulsed small-scale electric fields is able to reproduce the strong increase the high-energy component (after Ganushkina et al., 2005).
View Image Figure 21:
Magnetic storm on May 2 – 4, 1998. Relativistic electron distribution in the inner magnetosphere. Logarithmic color coding shows the daily values inner magnetosphere relativistic electron flux intensity (#/cm2-s-sr) as a function of time and L shell (in 0.1 bins) giving the equatorial distance from the Earth during April 1 – June 30, 1998. Note the dropout prior to the storm as well as the strong intensification and Earthward intrusion of the electron population after the storm onset (courtesy X. Li/University of Colorado).
View Image Figure 22:
Illustration of the chain of events from the Sun to the Earth related to ground-based space weather effects (courtesy Teemu Makinen/Finnish Meteorological Institute).
View Image Figure 23:
Measurements of the Lyman-α intensity of the entire sky during two days. The left and middle panels show the Lα intensity over the entire sky in two different look directions, while the right panels show images of the Sun. Left panels: SWAN full-sky Lα image showing the celestial hemisphere in the direction of the Sun. Middle panels: SWAN full-sky Lα image showing the celestial hemisphere in the direction away from the Sun. Right panels: EIT image in the EUV wavelength. The top row shows a time period when there was a bright activation on the solar surface. Consequently, the anti-sunward side hemisphere, which is illuminated by the Sun as viewed from EIT, shows a brightening. The bottom panel shows a day when there were no activations on the visible solar surface, and consequently the anti-sunward hemisphere is in darkness. On the other hand, the sunward hemisphere shows a brightening, which is taken as an indicator of a bright spot on the far side of the Sun. This was verified as the bright spot became visible a few days later (from Bertaux et al., 2000).