Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

Diamagnetizm ofplasma andformation o flocal decreases o fthe magneticfields near the equatorialplane location of satellite orbit near to the equatorial plane till geocentric distances 8.8RE and helium and 0 + measurements which provide comparatively high accuracy of pressure determination. Hole/hump structures of magnetic field were not analyzed using AMPTE/CCE observations. In this paper we present the results of the analysis of the magnetic field measurements at the equatorial plane using data of AMPTE/CCE satellite. We select the quasistationary decreases of the magnetic field which can be considered as the magnetic holes and obtain their MLT distribution. We obtain AE and Dst dependence of the probability to observe such events. We produce the nonlinear modeling of the magnetic field distortion by plasma pressure hump observed 06 June 1985 near midnight and try to show that local increase of plasma pressure can be considered as the probable mechanism of hole/hump structure formation in the magnetic field. 2. Results of the analysis of AMPTE/CCE observations of magnetic holes The AMPTE/CCE spacecraft had a near-equatorial elliptical orbit with an inclination of 4.8°, an apogee of 8.8 R e and perigee altitude of -1000 km. The orbital period is 15.7 hour. We used for this study the results of AMPTE/CCE fluxgate magnetometer system. We also analyze the measurements of the ion population from -1 keV to 300 keV from the charge-energy-mass spectrometer (CHEM), and ion fluxes above 300 keV from the medium energy particle analyzer (МЕРА). We try to select hole/hump quasistationary regions of B: decrease accompanied by Bz increase. Fig. 1 sows such kind of event near to midnight, position of the hoie/hump event at the equatorial plane and corresponding geomagnetic parameters (SYM-H, AE, PC). Solar wind parameters were not available for this event. Vertical line shows the moment of structure registration. It is possible to see the formation of hole/hump structure at geocentric distance form 4.7 till 5.4Д£. The event 06 June 1985 can be identified as classical magnetic field decrease near midnight. However such kind of events can be observed not only near midnight. Fig. 2 show the results of hole/hump structure observed 10 December 1984 in the morning sector. This event demonstrates comparatively large azimuthal scale of hole/hump structure and its existence for more than five hours. We analyze all time of AMPTE/CCE operation when data were available and selected 102 hole/hump events. Their positions at the equatorial plane are shown on Fig. 3. It is possible to see analyzing Fig. 3 that hole/hump events are observed at all local times at geocentric distances larger than 5RE till the AMPTE/CCE apogee. Such feature shows that the most natural explanation for the appearance of the observed hole/hump events is the diamagnetic effect of the ring current plasma. Ring current in such a case is located at distances smaller than the AMPTE/CCE apogee but mainly larger than 5 RE. Figure 1. The event 06 June 1985 (near midnight) __Л , J t > • • 00 03 06 OS 12 IS 18 21 00 tlm » , h o u r Figure 2. The event 10 December 1984 (morning sector) Figure 3. Position of selected hole/hump events at the equatorial plane Fig. 4 and 5 show the numbers of observed events on Dst and AE. It is possible to see that the probabilities to observe analyzed phenomena practically do not depend on the geomagnetic activity. 45