Ionospheric Response to Electric Fields - The Earth's Ionosphere: Plasma Physics and Electrodynamics - page 457

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Figure 9.19 Plot of wind vectors from 50 ◦ latitude to the pole at 120-km altitude during
a simulated substorm. The plot shown is at a time of 1 h 40min after the substorm onset.
Scale: an arrow the same length as 2 ◦ in latitude corresponds to 40m/s. [After Fuller-
Rowell and Rees (1981). Reproduced with permission of Pergamon Press.]

With computing power increasing quickly and becoming more readily avail-
able, a number of the three-dimensional models now exist. Models such as those
discussed here will prove quite valuable in developing further insights into the
electrodynamic forcing of the neutral atmosphere.

9.4 Particle Acceleration in the Topside Ionosphere

Remarkably, the earth's topside ionosphere is a powerful particle accelerator.
This is manifested most obviously by one of nature's most spectacular phenom-
ena: the aurora. We can only hope to scratch the surface of ion and electron
acceleration phenomena in this text but at least some introduction is possible.

9.4.1 Parallel Electric Fields in the Upper Ionosphere
Low-altitude rocket experiments gave the first evidence for the existence of large
parallel electric fields via observations of anticorrelated electron and ion fluxes
(Mozer and Bruston, 1966) and mono-energetic electron spectra peaked at 6 keV
(Evans, 1968). The first definitive detection came from observation of upward
barium ion acceleration using shaped, charged injections (Haerendel et al., 1976)
and from in situ parallel electric field observations from a satellite (Mozer et al.,
1977). Figure 9.20 shows the altitude of the tip of a barium-shaped charge