Magnetic local time and latitude dependence of amplitude of the main impulse (MI) of geomagnetic sudden commencements and its seasonal variation
Magnetic local time and latitude dependence of amplitude of the main impulse (MI) of geomagnetic sudden commencements and its seasonal variation
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DOI：
10.1029/2012ja018006
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发表时间：
2012-08
影响因子：
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通讯作者：
A. Shinbori;Y. Tsuji;T. Kikuchi;Tohru Araki;A. Ikeda;T. Uozumi;D. Baishev;Boris Shevtsov;T. Nagatsuma;K. Yumoto
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文献类型：
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作者：
A. Shinbori;Y. Tsuji;T. Kikuchi;Tohru Araki;A. Ikeda;T. Uozumi;D. Baishev;Boris Shevtsov;T. Nagatsuma;K. Yumoto
[1]利用1996-2010年高时间分辨率（1- 3s）地磁资料，研究了27-70 °纬度范围内地磁突发主脉冲幅度的地磁地方时纬依赖性及其季节变化。在亚极光区和中纬度（35-60度），SC-MI振幅的日间分布与DP-2型地磁变化相似，分别在上午和下午出现负变化和正变化。在磁纬63-65度附近，磁场变化是反向的。这表明，一对场向电流（FACs），类似于区域-1（R-1）FACs，位于磁纬度63-65度附近。夜间SC振幅在低纬和中纬（27-60度）显著增强。这种增强是由于SC-MI FAC产生的磁效应。在夜间极光纬度（63-65度），由于与磁层压缩有关的向西极光电急流的增强，SC振幅急剧下降。日变化的大小往往在夏季显着增加，在冬季相比。这种季节性变化表明，DP-2型电离层电流（IC）和FACs在SC-MI阶段期间产生的增强电离层电导率在夏季。结果表明，电离层和磁层中的大尺度MI电流系统是电压发生器。
[1] The magnetic local time and latitude dependence of amplitude of the main impulse (MI) of geomagnetic sudden commencements (SCs) and its seasonal variation have been investigated using high time resolution (1–3 sec) geomagnetic data in the latitudinal range 27–70 degrees for the period 1996–2010. The daytime distribution of the SC-MI amplitude in the sub-auroral and middle latitudes (35–60 degrees) is similar to the DP-2 type geomagnetic variation which shows negative and positive changes in the morning and afternoon, respectively. The magnetic field variation is reversed around the magnetic latitude of 63–65 degrees. This suggests that a pair of field-aligned currents (FACs), resembling the region-1 (R-1) FACs, is located near the magnetic latitude of 63–65 degrees. The nighttime SC amplitude is enhanced significantly in the low and middle latitudes (27–60 degrees). The enhancement is due to the magnetic effect produced by the SC-MI FACs. In the nighttime auroral latitude (63–65 degrees), the SC amplitude decreases steeply due to the enhanced westward auroral electrojet associated with the compression of the magnetosphere. The size of the diurnal variation tends to increase significantly during the summer, compared with that during the winter. This seasonal variation suggests that the DP-2 type ionospheric currents (ICs) and FACs generated during the SC-MI phase are intensified by increased ionospheric conductivities during the summer. It can be concluded that the large-scale MI current system in the ionosphere and magnetosphere is voltage generator.