基于T96模型的极尖区位形变化特性研究

Variation Characteristics of Cusp Configuration Based on T96 Model

基于T96模型,定义了极尖区的位形以及相关的描述参量(例如赤道向边界磁纬的最小值,纬向宽度,子午向和晨昏向的张角,倾斜度,扁平度,中心磁地方时等),讨论了太阳风动压(P_d)、行星际磁场(IMF)及磁暴强度对极尖区位形的影响.太阳风动压和磁暴强度越大,则极尖区的赤道向边界磁纬越小,纬向宽度越大,子午向和晨昏向的张角越大,倾斜度越大,扁平度越小;南向IMF B_z越强,则极尖区的赤道向边界磁纬越小,纬向宽度越小,子午向的张角越小,晨昏向的张角越大,倾斜度越大,扁平度越大;北向IMF B_z与南向IMF B_z的情况刚好相反;极尖区的中心磁地方时受IMF B_y控制,IMF B_y为正时,极尖区向昏侧移动,而IMF B_y为负时,极尖区则向晨侧移动,并且极尖区的中心磁地方时与IMF B_y之间有着良好的线性关系.将所得结果与前人的观测结果进行了简单比较,发现利用T96模型确定的极尖区位形与观测基本一致.

Based on the T96 model, we obtained the topology of the Earth＇s cusp and defined some parameters （e.g., minimum magnetic latitude of the equatorial boundary, latitudinal width, flare angels in the meridian and terminator plane, inclination, flatness, central magnetic local time） to describe its configuration. The influences of the solar wind dynamic pressure, the interplanetary magnetic field and storm intensity on the cusp＇s configuration are further studied. As the increasing of the solar wind dynamic pressure and storm intensity, the cusp＇s minimum magnetic latitude of the equatorial boundary, inclination, and the flatness all decrease, while the latitudinal width and flareangles in the midnight-noon and dawn-dusk directions increase. With the increasing of southward IMF, the equatorial boundary, latitudinal width, flare angle in the midnight-noon direction and inclination all decrease, while the flare angle in the dawn-dusk direction and flatness both increase. However, the situations of northward IMF are contrary. The magnetic local time of the cusp is controlled by IMF By. When By is positive/negative, the cusp moves toward dusk/dawn side. And there is a good linear correlation between the magnetic local time and IMF By. By comparing to some former observational results, the cusp obtained from the T96 model is nearly in accordance with the observations.