ИСТИНА

Extreme compression of the magnetosphere was found during magnetic storm on 21 January 2005. From 1712 to 2400 UT, the dayside magnetosphere was continuously located inside geosynchronous orbit due to strong solar wind dynamic pressure (Pd). The compression was found to be extremely strong from 1846 to 2035 UT when Pd peaked up to almost 200 nPa. The minimal size of the dayside magnetosphere was estimated to be less than 3 RE. Under the extreme compression, the outer magnetosphere at L > 5 was pushed inward such that particles from the radiation belts suffered fast radial transport toward the Earth and populated the forbidden zones at low latitudes. The polar cup expanded dramatically that allowed auroral precipitation and solar energetic particles penetrating to middle latitudes (<60 grad). Ionization by the precipitating particles and electrodynamic process disturbed whole the ionosphere and resulted in development of a great positive ionospheric storm from equator to middle latitudes both on the day and night sides.