<LI><A NAME="tex2html1" HREF="node2.html#22">Selected portions of auroral spectra in the visible [Vallance Jones, 1974], 
showing the discrete nature of the auroral lines. </A>
<LI><A NAME="tex2html2" HREF="node2.html#28">Energy level diagram for atomic oxygen [Carlson and Egeland, 1995]. The 
radiative half-lives  <IMG WIDTH=7 HEIGHT=7 ALIGN=BOTTOM ALT="tex2html_wrap_inline301" SRC="img1.gif"  >  and wavelengths of the emitted photons are also shown. </A>
<LI><A NAME="tex2html3" HREF="node3.html#34">Schematic illustration of the patterns of particle precipitation into Earth's 
upper atmosphere and the different classes of auroral emissions [Hartz, 1971; Carlson and 
Egeland, 1995], as functions of local time and geomagnetic latitude. The direction to the Sun is at local 
noon (12 hours) while the center of the tail lies at local midnight (0 hours). The 
radial direction corresponds to geomagnetic latitude; the geomagnetic pole is at the 
cross symbol. The figure is described more in the text.  </A>
<LI><A NAME="tex2html4" HREF="node3.html#40">Variation in the size and location of the auroral oval with geomagnetic activity 
[Feldstein and Starkov, 1967; Carlson and Egeland, 1995]. The 
shaded areas show the spatial regions with maximum auroral activity, averaged over many episodes, 
in the northern hemisphere. The coordinate system is similar to that in Figure 17.3.</A>
<LI><A NAME="tex2html5" HREF="node4.html#45">Schematic pattern of an auroral substorm [Akasofu, 1968].</A>
<LI><A NAME="tex2html6" HREF="node4.html#49">An example of an auroral substorm [Frank and Craven, 1988].</A>
<LI><A NAME="tex2html7" HREF="node5.html#55">Flow of plasma and associated frozen-in field lines in the magnetosphere and across the 
polar cap as a result of magnetic reconnection at the magnetopause for southwards IMF [Hughes, 1995]. 
The return paths of the anti-sunwards plasma flow across the polar cap lead to the auroral electrojets.</A>
<LI><A NAME="tex2html8" HREF="node5.html#63">The different directions of plasma and current flow in the auroral electrojets during 
quiet times (``convection electrojets'') and substorms [Cravens, 1997].</A>
<LI><A NAME="tex2html9" HREF="node6.html#68">Pattern of field-aligned (Birkeland) currents for relatively quiet conditions 
[Iijima and Potemra, 1978].</A>
<LI><A NAME="tex2html10" HREF="node6.html#74">Observations from the S3-2 satellite during a dawn-to-dusk South Pole pass on 19 September 1976 
[Harel et al., 1981; Wolf, 1995]: electron energy flux in the downswards direction, the transverse 
magnetic field deflection, and the electric field.</A>
<LI><A NAME="tex2html11" HREF="node6.html#145">High resolution FAST observations of the near-midnight auroral zone [Ergun et al., 1998a]. 
The dashed line separates the downward and upward current regions. (a) DC electric field perpendicular 
to  <IMG WIDTH=12 HEIGHT=11 ALIGN=BOTTOM ALT="tex2html_wrap_inline303" SRC="img2.gif"  >  and along the satellite path, (b) Electric field in a 4 kHz bandwidth. (c) East-west 
component of  <IMG WIDTH=12 HEIGHT=11 ALIGN=BOTTOM ALT="tex2html_wrap_inline303" SRC="img2.gif"  > . (d)-(e) Electric field spectrograms of plasma waves. (f) Electron energy 
spectrogram. (g) Electron pitch-angles, with 180 degrees upgoing and 0 and 360 degrees downgoing. 
(h)-(i) Similar to (f) and (g) but for ions.</A>
<LI><A NAME="tex2html12" HREF="node6.html#147">(a) DC electric fields perpendicular to  <IMG WIDTH=12 HEIGHT=11 ALIGN=BOTTOM ALT="tex2html_wrap_inline303" SRC="img2.gif"  >  and (b) upgoing ion energy flux 
spectrogram with the parallel potential inferred from the observed electric field 
superimposed [Ergun et al., 1998a]. The data are consistent with acceleration by a parallel 
potential. </A>
<LI><A NAME="tex2html13" HREF="node6.html#149">A fast solitary wave at 0.5  <IMG WIDTH=8 HEIGHT=14 ALIGN=MIDDLE ALT="tex2html_wrap_inline311" SRC="img3.gif"  > s resolution, moving anti-Earthward at 
about 2000 km s <IMG WIDTH=14 HEIGHT=7 ALIGN=BOTTOM ALT="tex2html_wrap_inline313" SRC="img4.gif"  >  [Ergun et al., 1998b]. </A>
