行星际磁场（IMF）B_y分量对磁正午前后区极光嘶声发生率的调制

THE EFFECT OF IMF By ON THE MLT DISTRIBUTION OF THE OCCURRENCE OF VLF HISS

利用南极极点站（磁纬约７５°）１９８６年３１—３８ｋＨｚ频率的ＶＬＦ波数据和卫星观测的ＩＭＦＢｙ分量数据，分析研究了ＩＭＦ晨昏分量Ｂｙ对高纬ＶＬＦ极光嘶声统计发生率周日分布的影响．结果发现，马对极光嘶声的统计发生率的磁地方对（ＭＬＴ）分布有明显的调制作用．磁正午前后的ＶＬＦ统计发生率不对称，Ｂｙ为正，午后发生率大于午前；Ｂｙ为负，午前发生率大于午后．Ｂｙ极性对夜侧ＶＬＦ发生频次的磁地方时分布也有明显影响．

The effect of the interplanetary magnetic field dawn-dusk component (IMF By) on the MLT distribution of VLF hiss occurrence is analysed in this paper by using 31-38kHz VLF data observed at the south pole station (invarent latitude about 75°). It is foUnd that IMF By influnces the distribution of the VLF occurrence stronly, especially at the day side. The asymmytry of VLF occurrence at pre-noon MLT region and at post-noon MLT region at cusp latitude exists.The peak of the VLF occurrence is much more higher at post-noon sector than at pre-noon sector when positive By but the peak of VLF occurrence at postnoon becomes bigger when is negative By. This By control is related to the By control of magnetospheric plasma convection patterns and the distribution of electrons precipitation.