Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagnetic sudden commencements
Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagnetic sudden commencements
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DOI：
10.1002/2015ja022166
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发表时间：
2016-02
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影响因子：
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通讯作者：
T. Kikuchi;K. Hashimoto;I. Tomizawa;Y. Ebihara;Y. Nishimura;T. Araki;A. Shinbori;B. Veenadhari;T. Tanaka;T. Nagatsuma
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文献类型：
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作者：
T. Kikuchi;K. Hashimoto;I. Tomizawa;Y. Ebihara;Y. Nishimura;T. Araki;A. Shinbori;B. Veenadhari;T. Tanaka;T. Nagatsuma
在地磁突然开始期间，中纬度电离层等离子体向上/向下移动，导致高频多普勒频率的变化;除了菊池等人（1985）发现的晚上的SCF（+ −）之外，在昼侧和夜侧分别为SCF（+ −）和（− +）。虽然SCF的初始和主要频率偏差（PFD，MFD）已被归因于黄昏到黎明和黎明到黄昏的电位电场，但仍然存在问题，如果正PFD可以由压缩磁流体动力学（MHD）波引起，以及是什么导致SCF的夜间异常。利用高频多普勒探测器，我们发现，在SC的主脉冲（MI）期间，当压缩波被认为是向下推动电离层时，向阳侧电离层向上朝着太阳移动。电离层的运动被证明是与赤道电射流，匹配的潜在电场传输的电离层电流从极地电离层。我们证实了压缩波的电场是严重抑制的导电电离层和复制SC电场使用全球MHD模拟中采用的电位求解器。模型计算很好地再现了初始脉冲和MI电场及其晚间异常。这表明电势是通过地球电离层波导中的零阶横磁（TM 0）模波从极地电离层传输到赤道的。电势的近瞬时传输导致不可压缩电离层的瞬时全局响应。
The ionospheric plasma in midlatitude moves upward/downward during the geomagnetic sudden commencement causing the HF Doppler frequency changes; SCF (+ −) and (− +) on the dayside and nightside, respectively, except for the SCF (+ −) in the evening as found by Kikuchi et al. (1985). Although the preliminary and main frequency deviations (PFD, MFD) of the SCF have been attributed to the dusk‐to‐dawn and dawn‐to‐dusk potential electric fields, there still remain questions if the positive PFD can be caused by the compressional magnetohydrodynamic (MHD) wave and what causes the evening anomaly of the SCF. With the HF Doppler sounder, we show that the dayside ionosphere moves upward toward the Sun during the main impulse (MI) of the SC, when the compressional wave is supposed to push the ionosphere downward. The motion of the ionosphere is shown to be correlated with the equatorial electrojet, matching the potential electric field transmitted with the ionospheric currents from the polar ionosphere. We confirmed that the electric field of the compressional wave is severely suppressed by the conducting ionosphere and reproduced the SC electric fields using the global MHD simulation in which the potential solver is employed. The model calculations well reproduced the preliminary impulse and MI electric fields and their evening anomaly. It is suggested that the electric potential is transmitted from the polar ionosphere to the equator by the zeroth‐order transverse magnetic (TM0) mode waves in the Earth‐ionosphere waveguide. The near‐instantaneous transmission of the electric potential leads to instantaneous global response of the incompressible ionosphere.