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.

DISCUSSION. Ground-based observations show that the specific field, current, and precipitating particle structure is conserved during WTS westward movement and from case to case. It is reasonably to assume that the correspon ding structure exists at the equator region of the magnetosphere. If this is true, E-field and partial flux variations presented in Fig.1a may be considered as spatial ones. Therefore, it becomes possible to reconstruct the picture Of field-aligned currents and electric changes in the region of E^ sign reverse, as shown on top of Fig.1b. As was anticipated, the upward FAC J* is located at the western edge of WTS. Westward of the WTS, when the D-component grows on the Earth, in the magnetosphere there are observed simultaneous enhancements of the energetic proton fluxes and the eastern azimuthal component of the quasi' stationary E-field (-E^). Appearance of such a component can be explained by the d o w n w a r d FAC . Existence of this current in front of the WTS was discussed in /7/. On the other hand, increase (or decrease) of proton flux may be interpret ed as satellite entrance into the region of enhanced (or decreased) plasma pressure since energetic protons give the main contribution to the pressure P level (Fig.1b, bottom). Westward V P gives the upward field-aligned current and vice versa. Existence of azimuthal pressure gradients during substorms has been reported in several papers /1,4,8/. From Fig.1 one can see the sign of the charges predicted at the pressure boundary corresponds to the observed reversals of azimuthal E-field component. The obtained picture of the fields and particles behaviour in the magneto sphere during WTS drift throught the satellite’s meridian has much in common with the interchange plasma instability in the magnetic field. Application of this instability to the outer boundary of the ring current in the Earth's magnetosphere was discussed in /9/. Similar resulting E-field and current pic ture has been described recently by Roux /4/ for the case of the WTS with a smaller spatial scale ~ 100 km temporal scale of variation of the order of 1 min. The author supposed that as a result of Rayleigh-Taylor instability (which ie relative to interchange one) the surface wave is generated at the boundary between dipolar and tailward configuration of the magnetic field. Detailed analysis of the active phase dynamics during 5 substorms shows that the western edge of the WTS corresponds to some magnetospheric boundary dividing the regions with different magnetic field topology, westward of this boundary - the taillike field with the enhancement of the proton flux, east ward - the dipolar field with increasing electron fluxes /6/. This boundary is similar to the "fault-line" from the paper /10/. The discussed E-field and proton flux relation describe the processes near this boundary. It can be supposed that the variations discussed in /4/ may represent a fine structure of the large-scale WTS considered in this work. CONCLUSIONS. The analysis of the quasi-stationary component of the E- field at 6.6 R„ in the vicinity of the western edge of the substorm current tj wedge results in the following main conclusions: 1. The change of the direction of the azimuthal component of the quasi- stationary electric field is connected with the fronts of proton fluxes with energies > 20 keV. 2. Inside the active region where the magnetic field changes from tailward to a more dipolar configuration a decrease of proton fluxes is observed and the electric field is directed westward, whereas to the west of this region east ward direction is observed. 37