Dynamics of plasma sheet and dayside polar cusp according to solar proton measurements in polar regions

Displacements of the polar and low-latitude boundaries of auroral regions of 1-MeV solar-proton penetration were studied on the basis of Cosmos-480 data for the flare of Apr. 18, 1972, when a North-South asymmetry of protons in polar caps was observed. The nightside polar boundary of the proton-penetration auroral region during the substorm expansion phase shifts to lower latitudes. The recovery-phase polar boundary shifts polewards. In this case, the width of the proton-penetration region varies from 7 to 14 degrees. Such variations are assumed to relate to variations of the plasma-sheet depth during substorms. The OGO-4 data are used to similarly measure the events of Nov. 2, 1967. A comparison between the data on solar-proton fluxes beyond the polar penetration boundary at 1000-1500 MLT indicates the possibility of longitude shifts of the cusp toward afternoon hours during magnetic disturbances.