亚暴期间高纬黄昏—子夜扇区极光弧增亮与衰减及其与IMF的关系

摘要

利用南极中山站极光全天空摄相、地磁、地磁脉动数据和Wind卫星的行星际磁场IMF观测数据，分析了7个亚暴期间高纬黄昏—子夜扇区极光弧的短暂增亮现象.极光弧特征是，短暂增亮随后很快衰减，历时10—20min，基本沿着日-地方向，有明显黄昏方向运动.这些事件大都发生在IMFBz南转之后，亚暴增长相或膨胀相期间，极光浪涌到达之前10—73min消失.相应的IMFBx＞0，IMFBy＜0.这种极光弧和亚暴极光不同，它们与地磁活动及Pi2脉动不相关.这7个极光弧的形态和IMF特征表明，极光弧的增亮很可能由尾瓣重联产生，很快衰减归因于IMFBz南向条件，而黄昏方向运动受IMFBy控制.%Observations of all-sky auroral imaging, geomagnetic field, Pi2pulsation from Zhongshan Station and IMF data from Wind satellite have been used to investigate 7 cases of nightside auroral arcs intensification and f ading in high latitudes. The characteristics of auroral arcs are as follows: All of arcs intensify briefly, and then fade lasting for 10—20min; the arcs nearly align along the Sun-Earth direction with pronounced duskward drift; most of the arcs occur after the interplanetary magnetic field (IMF) turns southward corres ponding to the substorm growth or expansion phase, and IMF Bx＞0, IMF B y＜0; the dawn-dusk drift of the arcs is in the opposite direction of IMF By; these arcs have no close relation to magnetic activities and Pi2 p ulsation. The present results suggest that the brief intensification of auroral arcs may be due to IMF Bx＞0 which favors magnetic reconnection in the sou thern lobe of the magnetotail, the arc fading may be attributed to southward IMF Bz, and the dawn-dusk motion of the arcs may be driven by the effect of the IMF By on the motion of the reconnection site.