ИСТИНА

Observations from DMSP spacecraft were used to determine ion pressure in nighttime auroral zone during periods of magnetic quietness under extreme values of the solar wind dynamic pressure (Psw). It is found that at Psw < 0.4 nPa, the energy fluxes of both precipitating ions and electrons are at the level of the noise variations of the detectors, the zone of auroral precipitation is not identified, AL < 50 nT. The amplitude of the noise variations in the ion pressure is ~0.02 nPa. With an increase in Psw, the maximum ion pressure (Pmax) in the auroral zone increases significantly and can reach 5-6 nPa at Psw~20-22 nPa. The average latitudinal profiles of the ion pressure at =0.5, 2.1 and 16.3 nPa are plotted. The latitude of the ion pressure maximum (Φ' = 72.2°, 68.6° and 64.6° CGL, respectively) coincides well with the position of the isotropy boundary (IB). Auroral precipitation poleward of IB are isotropic, so the plasma pressure remains unchanged along the geomagnetic field line from the ionosphere to the equatorial plane in the Earth's magnetosphere. Thus, the latitudinal pressure profiles, when projected into the equatorial plane, make it possible to discuss the radial distribution of pressure in the magnetosphere.