Структура и динамика полярных токовых систем : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая, Суздаль, СССР / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : [б. и.], 1988.

current pair spans about 10 sec. or about 80 km along the orbit track. As expected, for earthward flowing currents, the observed Region 1 current is not associated with intense auroral emissions, but at least two of the embed ded current pairs appear to be co-located with arc-like emissions that protrude from the poleward edge of the diffuse aurora and cross the orbit track at about 10:22:20 and 10:22:45 UT. Proceeding equatorward along the orbit, HILAT encountered a positive (eastward) deflection of the disturbance magnetic field at about 10:23:05 UT signaling a reversal of the Birkeland current flow. The positive slope extends to about 10:23:30 UT indicating an average Region 2 current density out of the p ionosphere of approximately 2.0 jx A/m . Within this current, the gradient of the perturbation magnetic field showed a sharp increase at about 10:23:20 UT and remain steady to 10:23:25 UT. This portion of the Region 2 current has a p density of nearly 3.0 jjA/m , while the current density on either side of it is about 0.8 j j A/m2 . In the superimposed image, we can see that this intense current flowing out of the ionosphere spans the brightest emission features. Equatorward of the arc-like feature, the diffuse aurora extends for about 1.5° in magnetic latitude and there is another small-scale reversal of the Birkeland current but with no noticeable change in the emission structure or intensity. As one might expect, the signatures of both large and small- scale upward directed Birkeland currents are related to the brightest emission features. Throughout much of this pass the IDM indicated both eastward and west ward plasma drift, but near the brightest emission, the drift was generally in an eastward (sunward) direction. The ionospheric electric fields associated with these drifts are consistent with the inferred Birkeland currents and with a mapping to the inner edge of the LLBL. Shears in the ion drift velocity are associated with each pair of small-scale Birkeland currents and with the Region 2 current. 1 7 . 0 7 . 1 9 8 3 0 Ul" H:M:S CGLAT CGLT Pig. 3. The electron versus energy flux time spectrogram corresponding to the magnetic field and image data. The three electron flux enhancements (indicated by dashed lines) that are present between 10:22:20 or 10:22:50 UT correspond to the three pairs of Birkeland currents in Pig.2. The electron energy flux versus time spectrogram in Fig.3 covers the period from 10:21:40 UT, about the beginning of the imaging scan, to 10:24:20 UT, about one minute after the arc-like feature occured. This spectrogram was produces from data aquired by the zenith looking electron detector. A struc tured region of precipitation extends from 10:21:40 UT to 10:23:00 UT. The structured precipitation and inverted V's are indicative of the LLBL or BPS but the average electron energy is about 5 keV, hotter than typical LLBL electrons yet cooler than the CPS electron population observed equatorward of 10:23:22 UT. Three bursts (dashed lines) of enhanced electron flux at energies less than 5 keV are centered at 10:22:20. 10:22:32, and 10:22:45 UT. 51