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.

S /± Pig. 6. Schematic of the iono spheric electric field across an arc and the boundary wave giving rise to this field. VOAt -15L (E> * 10 mV/m Ф- (E)it Vsc it — 10secVj(; ~8 km/sec Фаге■ 0.8 kV PS. B.L. perturbation it * 180 sec B 2 - 207 <Vy>= 18.7 km/sec (tx) * 0.334mV/m Ф)j « 2.0kV АФ* 1.2kV » ■ Ionosphere field is superimposed on the baseline convection electric field that, in this case, v/as driving sunward plasma flow. The average electric field for 1/2 wavelength was determined from HILAT drift measurements to be about 10 raV/m and the width of an arc shown in Pig.2 was about 80 km. Thus, the potential drop across an arc like region was about 0.8 kV. At the interface between the boundary layer and the plasma sheet, we can estimate the perturbation electric field and potential drop from typical values of the period, wave-length, and amplitude of waves observed along this interface. From the mapping discussed above, we expect a wavelength of about 2 R^ with a typical period of 3 win and we assume a typical amplitude of 1/2 Rg. This wavelength and period is consistent with a phase velocity of about 70 km/sec., which is comparable to the plasma velocity near the inner edge of the LLBL. In Fig. 6, the dimensions were simplified to 3000 X 12000 km and I = 160 s, thus, requiring a component of plasma velocity in the Y direction of 16.7 km/sec. We aaaurae a value of 20 nT for the Z-component of the geomagnetic field re sulting in an average 7 X S’ perturbation electric field of 0.33 mV/m. The potential drop across 1/2 wavelength at the equatorial plane is then 2.0 kV. A potential difference of 1.2 kV exists between the ionosphere and the LLBL. If we assume that this is disturbed along the field lines, then the spectra of electrons flowing into the ionosphere should have a peak of 1.2 keV. In the case of the "inverted V" shown in Fig.4 at 37365 sec UT, there is a peak at about 1 keV. Thus, the sum of the computed ionospheric potential and the inferred field-aligned potential is consistent with the potential one could derive from wavelike motion of the LLBL/P3 interface. SUMMARY А1ШCOHCLUSIONS. The principal conclusions of this study are as follows: 1. Three pairs of small-scale Birkeland currents were observed to be embedded ia the Region 1 current system. Each outward directed current is oo-located with enhanoed electron precipitation and, for two of the enhance ments, a narrow band of increased auroral emission is observed. 2. The small-scale Birkeland currents map to the equatorial plane in a region from about -9 R^, to about -2 R^ in the GMS X direction and from about Kg to about -io Rg in the GSM Y direction. In this mapping, each pair of Birkeland currents extend for approximately 2 R^ in the tailward direction. 3. The periodic structure of these Birkeland currents, their location with respect to ionospheric electron populations, and the velocity shear coincident with the Region 1 current system lead us to conclude that wave 55