亚暴期间等离子体对流速度及热层纬向风速度变化的统计学分析

本文利用2001年至2005年间CHAMP卫星及DMSP(F13,F15)卫星观测数据,对亚暴发生前后,亚暴初始位置所在磁地方时(Magnetic Local Time, MLT)东侧2 h(+2 h,MLT)至西侧4 h(-4 h,MLT)范围内等离子体对流速度(Vy)及热层纬向风速度(Uy)的变化进行了统计学分析.研究发现在亚暴发生后的1.5 h内,所有MLT区间的Vy均明显增大,且峰值位置的地磁纬度向赤道侧移动,1.5 h后,Vy减小,峰值的纬度向极区移动,表明亚暴的发生能显著增强等离子体对流速度;在亚暴发生位置的西侧0~2 h内,Vy增幅最大,这表明亚暴对热层的影响主要在西侧,影响最大的区域是西侧0~2 h MLT区间;Uy在亚暴发生后3 h持续增大,其对亚暴的响应相较于Vy有1.5 h的延迟.

Temporal and spatial variations of plasma and neutral velocities during substorm periods

This study statistically investigates the temporal and spatial variations of plasma convection velocity (V_y) and thermospheric zonal wind velocity (U_y) in the range of -4 hour (h) and +2 h MLT relative to substorm onsets (MLT onset) with both CHAMP and DMSP (F13, F15) satellite observations from 2001 to 2005. It shows that V_y increases 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 V_y decreases 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 V_y is the largest from -2h to MLT onset, which indicates that the substorm mainly affects the thermosphere in the westward 0~2 h MLT sector. U_y increases steadily in 3 hours after substorm onsets, with an 1.5 h delay relative to V_y in the response to the substorm onsets.