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. – 150 с.

Pig. 5. A mapping of points 1 and 2 (corresponding to 1 and 2 in Pig.2) in the ionosphere to their equatorial crossing points. An exaggerated wave is shown at the LLBL/PS interface. Conv is the statistical location of the plasma convection reversal in the ionosphere. from HILAT were taken in about 50 seconds, it is reasonable to assume time independence for the observed pattern of Birkeland currents, electric fields and auroral arcs shown hare. Prom the Kp > 2, model of the geomagnetic field (Mead and Pairfield, 1975) and field line mapping model computed by Pairfield and Head /1975/, we have determined that the locus of equatorial crossing points of the field lines beginning at 70° MLAT and extending to 68° MLAT, 5:00 MLT is nearly parallel to the LLBL/PS interface and spans from about -10 Rg to -0 in GSM Y coordinates and from about -9 Rg to -2 Rfi in GSM X coordinates. Thus, the equatorial crossing points of the region of arcs observed by HILAT would map along the interface a distance of about 7 RE , which is sufficient to cross the number of wavelengths required to include the observed low altitude area. The equatorial mapping of these field lines may have extended to even greater distances along the flank of the magnetosphere due to the more disturbed magnetic conditions .existing at the time of our observations. The component of plasma drift associated with the wavelike motion is directed normal to the LLBL, generating a polarization - 7 X S’ electric field directed alternatively sunward and tailward, over each half wavelength in the instability region. The polarization current flow is directed opposite to the electric field (Ж • 7 < 0). Therefore, the electric field and the resulting charge separation represent a generator for small-scale Birkeland currents observed at low altitudes. This mechanism has recently been suggested by Lundin and Evans /1985/ to explain arcs in the early afternoon sector. A quantitative comparison between an idealized perturbation electric field and potential drop that one might expect from the wave-like structure, and their observed counterparts in the ionosphere is shown in Pig.6. The measured ionospheric electric field is depicted ideally as a sine wave. This 54