Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

E.E. Antonova et al. Now we have only very limited information on plasma pressure distribution at the equatorial plane during magnetic storms. However, auroral oval motion to the equator during magnetic storms is a well known phenomena. Starkov [1993] determined the location of the equatorial boundary of the auroral oval in dependence o f the Dst index, which is in a rather good agreement with Tverskaya relation [Tverskaya, 2011]. This indicates the location o f equatorial boundary of the auroral oval at the geocentric distances of new outer radiation belt formation during storm recovery phase. 3. Magnetic field distortion and outer radiation belt High level of turbulent fluctuations of electric and magnetic fields at the latitudes of auroral oval in different frequency bands is practically constantly observed during magnetic storms, which made the theories o f outer belt electron acceleration due to wave-particle interactions very attractive. However, other phenomena changing energetic electron spectra are observed during storms. This is the decrease of magnetic field inside the magnetosphere by developed ring current and its restore during storm recovery phase. Tverskoy [1997] suggested, that injection o f seed population of electrons in the region o f depressed magnetic field can lead to considerable particle acceleration during storm recovery phase due to betatron acceleration (adiabatic effect). Tverskoy [1997] theory explains the dependence (1) and predicted the formation of sharp pressure peak at Lmax. Antonova [2006] shows, that it is possible to explain the value o f coefficient in relation (1). However, theoretical analysis of Tverskoy [1997] and Antonova [2006] considers the case of dipole magnetic field and does not analyze nonlinear effects connected with finite values of plasma parameter. Antonova and Stepanova [2015] using data of DMSP observations show the sharp ion peak formation at Lmaxfor the magnetic storm on October 8-9, 2012. They also show that the most equatorial position of equatorial boundary o f the westward electrojet for this storm coincides with Lmn. Such findings are in agreement with the first auroral arc brightening at the equatorial boundary of auroral oval as increase of electron flux leads to the increase of ionospheric conductivity and corresponding increase of ionospheric current. Large fluxes of downward accelerated electrons are accompanied by large fluxes of upward accelerated ions [Stepanova et al., 2002]. Relaxation of ion beams creates local increase of ion pressure at the equatorial plane and formation of the peak of plasma pressure. Formation o f pressure peak leads to local magnetic field decrease due to diamagnetic effect. Such local increases o f plasma pressure (pressure humps) and decreases of magnetic field (magnetic holes) are really observed at the equatorial plane (see Vovchenko and Antonova [2015]) and references in their paper. Magnetic hole can be effective local trap for energetic particles [Vovchenko and Antonova, 2012] in which injected electrons can be accelerated. The restore o f the magnetic field to undisturbed level will lead to betatron acceleration of electrons. Figure 3. a - results of RBSP measurements of electron fluxes with energy 1.8 and 2.1 MeV and simultaneous ground based and solar wind parameters, b - electron spectra for moments shown by vertical lines on (a). Local variations of magnetic field at the equatorial plane are not proper studied till now. Therefore, it is difficult to evaluate the contribution of large-scale magnetic field change in the formation of relativistic electron fluxes. Analysis of different mechanism contributions to the acceleration of outer belt electrons requires complex observations o f electromagnetic fields and evolution of particle spectra. That is why it will be rather interesting to evaluate the contribution o f adiabatic effect analyzing storms with clearly distinguished adiabatic effect. The main feature o f such storms is the restore of relativistic electron fluxes after storm to near the same level as before storm. Reeves et al. [2003] and Turner et al. [2013] show that relativistic electron fluxes restore to the same level as before storm in 25- 28% cases. Fluxes of relativistic electrons are increased in 53-58% storms and are decreased in 17-19% storms. Fig. 3a shows an example of variations o f electrons with energy 1.8 MeV and 2.1 Mev (second and third panels) during 8