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.

the interface between the LLBL or BPS and CPS. We suggest that the high average energy (5 keV) in the region between 10:21:40 UT and 10:23:00 UT may be the result of mixing hot plasma sheet and coolei" boundary layer plasma in the stagnation region of the LLBL (Williams et al.,1985). DISCUSSION. On July 17, 1983 instruments onboard HILAT recorded a aeries of auroral emission features, electron precipitation enhancements and "inverted V's" at an altitude of about 800 km in the post-midnight/early morning sector. These features are about 80 km wide and are separated by а few minutes in MLT and about 0.8 degrees in the invariant latitude. Large scale undulations located along the poleward edge of the auroral emission region appear to narrow into the arc-like features seen in the VUV image. The relationship between the measured electron energy and flux, the Region 1 ourrent and embedded small-scale currents, and the corresponding ion drift are consistent with a mapping of those features to the Low Latitude Boundary Layer in the equatorial plane of the magnetosphere near the interface between the LLBL and the Plasma Sheet. The LLBL is one site of momentum, mass and energy transfer from the solar wind into the magnetosphere (Eastman et al.,1976). Its outer boundary is roughly defined by the magnetopause while its inner surface is marked by the onset of the plasma sheet. Within the LLBL, bulk plasma flow is directed predominantly anti-sunward. The strong velocity shear and nearly parallel orientation of magnetic field lines in the LLBL to those of the inner magneto sphere at the interface of these tv/o regions presents an ideal site for gener ation of a Kelvin-Helmholtz instability (Sonnerup 1980, Lee et al.,1981). Sckopke et al. /1981/ have shown that indeed, the thickness of the LLBL under goes quasi-periodic temporal variations. These variations in thickness may be as large as 1 Rg and occur over a period of 2-5 mine, which corresponds to a distance of 3 to 8 Rg along the interface of the boundary layer and the plasma sheet. Sckopke et al. attribute this periodic variation to the Kelvin- Helmholtz instability acting on the layer's inner edge, although Cowley et al. (1983) have suggested that these variations can result from flux transfer events traveling along the magnetopause boundary layer. Hones et al. /1978, 1981/ have reported the presence of plasma vortices within the plasma sheet that they attribute to the action of this same Kelvin-Helmholtz mechanism. Since the field lines that thread the inner edge of the LLBL map to a portion of the Region 1 current system and to a characteristic particle boundary in the ionosphere, some evidence of this activity should be detect able at low altitudes. In Fig,5, we show a conceptual mapping from the iono spheric footprints of the poleward portion of the HILAT pass to the equator ial plane. Fig,5a is an adaptation of Fig.8 from Heelis et al./1980/ showing on an invariant latitude, magnetic local time dial, the portion of HILAT's trajectory through the ionosphere that encountered the multiple arc-like structure (shown by small arcs) discussed in the previous section. The trajectory is superimposed on the statistical pattern of the plasma convection reversal and the ionospheric BPS/CPS eleotron population. Points 1 and 2 marked in Fig.5a correspond to Points 1 and 2 in Fig.2 and are mapped to an exaggerated instability region near the LLBL in Fig,5b. The observations at the LLBL by ISEE 1 and 2 require that these variations extend to between 6 and 10 earth radii along the boundary (Schopke et al.,1981). Since the period of waves on the inner surface of the LLBL observed by Schopke et al./1981/ is on the order of two to five minutes and the low altitude measurements made 53