TEMPORAL AND SPATIAL VARIATIONS OF PLASMA AND NEUTRAL VELOCITIES DURING SUBSTORM PERIODS

Abstract

AbstractThis study statistically investigates the temporal and spatial variations of plasma convection velocity (Vy) and thermospheric zonal wind velocity (Uy) in the range of –4 hour (h) and +2 h MLT relative to substorm onsets (MLT onset) with both CHAMP and DMSP (F13, F15) satellites observations from 2001 to 2005. It shows that Vy increase significantly in all MLT sectors and the latitudes of the peak values move equatorward in 1.5 h after substorm onsets. In the subsequent 1.5 h Vy decrease in intensity and the peaks retreat poleward, which shows that the onsets of substorm can enhance the plasma convection velocity dramatically. The relative increase of Vy is largest from –2 h to MLT onset, which indicates that the substorm mainly affects the thermosphere in the westward 0∼2 h MLT sector. Uy increases steadily in 3 hours after substorm onsets, with a 1.5 h delay relative to Vy in response to the substorm onsets.