Ion Pressure in Different Regions of the Dayside Auroral Precipitation
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Pressure in Different Regions of the Dayside Auroral Precipitation V. G. Vorobjeva, *, O. I. Yagodkinaa, and E. E. Antonovab, c aPolar
b
Geophysical Institute, Apatity, Russia Research Institute of Nuclear Physics, Moscow State University, Moscow, Russia c Institute of Space Research, Russian Academy of Sciences, Moscow, Russia *e-mail: [email protected] Received April 19, 2020; revised April 22, 2020; accepted May 21, 2020
Abstract—The ion pressure in the regions of ionospheric projections of the plasma mantle, polar cusp, lowlatitude boundary layer, and the region of structured precipitation of the auroral oval during magnetic calm is studied based on data from the DMSP F6 and F7 low-altitude spacecraft. It is shown that the level of ion pressure in all of these regions does not depend on either the polarity or the value of the Bz component of the IMF. The ion pressure in the mantle varies from 0.02 to 0.06 nPa and does not depend on the magnitude of the solar wind dynamic pressure. The average pressure level is Pm = 0.03 ± 0.01 nPa. In the cusp area at IMF Bz > 0, the ion pressure (Pc) does not depend on the solar wind dynamic pressure (Psw), while the pressure at IMF Bz < 0 increases significantly with the increasing in Psw. The average pressure level is Pc = 1.0 ± 0.3 nPa, which is almost two orders of magnitude higher than that in the mantle. The ion pressure also increases with the solar wind dynamic pressure in both the LLBL and the auroral oval precipitation (AOP). The average pressure in the LLBL is PL = 0.27 ± 0.07 nPa, while in the AOP region its average value is two times lower. The MLT pressure pattern in LLBL shows a pronounced increase in the noon sector (~11–14 MLT), the value of which increases with increasing in the solar wind dynamic pressure. In the AOP region the pressure is distributed over MLT fairly evenly, which results in a significant pressure difference (ΔP = PL – PA) in the noon sector between the low-latitude boundary layer and the auroral oval. DOI: 10.1134/S0016793220060146
1. INTRODUCTION Plasma pressure is one of the main parameters that determine the state of the Earth’s magnetosphere and the dynamic processes occurring in the magnetosphere-ionosphere system. Suffice it to say that the azimuthal pressure gradients in the plasma sheet are able to maintain longitudinal currents connecting the magnetosphere and the ionosphere (Antonova and Ganushkina, 1997; Troshichev, 2004; Xing et al. 2009). Plasma pressure is determined either in situ with satellites in the magnetospheric plasma or from observations of polar-orbiting, low-altitude satellites. The use of low-altitude satellites, the orbits of which cover virtually the entire high-latitude ionosphere with high spatial and temporal resolutions, is based on the fact that the plasma pressure, temperature, and density remain constant along the geomagnetic field lines (Goertz and Baumjohann, 1991). Thus, the characteristics of the magnetospheric plasma can be obtained via the projecting of ionospheric data into the equatorial plane of
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