Deformation of Ionospheric Potential Pattern by Ionospheric Hall Polarization
Deformation of Ionospheric Potential Pattern by Ionospheric Hall Polarization
复制标题
电离层霍尔极化引起的电离层势图变形
DOI：
10.1029/2018ja026013
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
A. Yoshikawa
中科院分区：
文献类型：
--
作者：
A. Nakamizo;A. Yoshikawa
研究表明，电离层霍尔极化可以使高纬度电离层对流场发生变形，这被广泛认为是磁层对流场的一种表现形式。我们用电势解器实现霍尔极化分离，将电导分布从均匀分布逐步改变为更接近实际的分布。我们采用黎明-黄昏和南北对称的电导分布和区域1(R1)场向电流(FAC)。R1系统的主场和电导张量(霍尔电导)的每个非对角分量的梯度对产生霍尔极化场，从而引起如下电势形变。(A)向赤道方向的梯度引起顺时针旋转。(B)横跨终结点的梯度，加上向赤道方向梯度的影响，造成了黎明-黄昏的不对称。(C)极光区的高电导带引起扭结形变。特别是，午夜扇区中频带赤道向外边缘的嵌套结构与Harang反转非常相似。结果(A)可以解释IMF无法解释的顺时针偏倚--单独通过效应，(A)和(B)的组合可以解释黎明-黄昏细胞圆形或新月形的清晰和不清晰，这取决于IMF-by极性；(C)表明电离层可能不需要向上的FAC来形成Harang反转。我们认为，电离层电势的最终结构是由磁层需求(外部原因)和电离层极化(内部效应)共同作用的结果。
The present study shows that the ionospheric Hall polarization can deform the high‐latitude ionospheric convection field, which is widely considered to be a manifestation of the convection field in the magnetosphere. We perform the Hall polarization field separation with a potential solver by changing the conductance distribution step by step from a uniform one to a more realistic one. We adopt dawn‐dusk and north‐south symmetric distributions of conductance and region 1 (R1) field‐aligned current (FAC). The pair of the primary field of the R1 system and each gradient of off‐diagonal component of conductance tensor (Hall conductance) generates the Hall polarization field and consequently causes potential deformations as follows. (a) The equatorward gradient causes clockwise rotation. (b) The gradient across the terminator, together with the effect of the equatorward gradient, causes the dawn‐dusk asymmetry. (c) The high conductance band in the auroral region causes kink‐type deformations. In particular, a nested structure at the equatorward edge of the band in the midnight sector well resembles the Harang Reversal. Result (a) can explain the clockwise bias inexplicable by the IMF‐By effect alone, the combination of (a) and (b) can explain the clearness and unclearness in the round or crescent shapes of the dawn‐dusk cells depending on the IMF‐By polarity, and (c) suggests that the ionosphere may not need the upward‐FAC for the formation of the Harang Reversal. We suggest that the final structure of the ionospheric potential is established by the combined effects of the magnetospheric requirements (external causes) and ionospheric polarization (internal effect).