A study of long-term strong dawn-dusk asymmetry of the earth's magnetosphere in 1991

A study of dawn-dusk asymmetry of the Earth's magnetosphere was made by the indirect way using data from a middle-energy-range (E: ∼ 80/1000 keV) electron semiconductor spectrometer onboard the geosynchronous satellite Gorizont from July, 1991 to April, 1992. In July-September, 1991 the diurnal variation of the examined fluxes had a number of unusual features. The most interesting feature was existence of local maxima on the diurnal distribution of electron flux intensity in dawn and dusk sectors. Observed features of the flux distributions could be explained as appeared due to the particle drift in the strong dawn-dusk asymmetry of the magnetospheric magnetic field. In the presented case, probably, the intrinsic factor was the main cause stabilising the dawn-dusk asymmetric geomagnetic field.