The convection electric field in auroral substorms
The convection electric field in auroral substorms
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极光亚暴中的对流电场
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
R. Hoffman
中科院分区：
文献类型：
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作者：
J. Gjerloev;R. Hoffman
利用动力学探测器2（DE 2）的电场和离子漂移资料，对膨胀型极光亚暴的电离层对流电场进行了统计研究。31个单独的DE 2亚暴过境仔细选择和组织使用全球极光图像获得的DE 1。所选的过程，发生在亚暴扩展阶段，最大，或早期恢复阶段，覆盖整个夜间亚暴。数据的组织使用了Fujii等人[1994]开发的方法，该方法将数据分为六个当地时间扇区，覆盖夜间亚暴区域。按照Gjerloev和霍夫曼[2000 b]论文中采用的程序，然后调整每个极光椭圆交叉的纬度宽度和位置，以适应扇区平均值。除了详细研究每个扇区内的电场特征外，该数据库还使我们能够编制电离层对流电场模型。午夜前对流反转的特征表现出明显的当地时间依赖性。在浪涌的西面，是一个相当明确的点反转或对流切变。接近浪涌和浪涌内是一个弱电场的区域，其宽度在午夜增加，将赤道和极向电场区域分开。因此，我们采用Harang区域而不是Harang间断来描述午夜前的对流反转。一个相对较窄的对流通道是一致的最高电导位于极向哈朗地区。这条通道驱动了向西电急流中的亚暴电流楔分量。它存在于所有午夜前的通道，因此是三维亚暴电流楔系统的一个组成部分。
Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained by DE 1. The selected passes, which occurred during substorm expansion phase, maximum, or early recovery phase, cover the entire nighttime substorm. The organization of the data used the method developed by Fujii et al. [1994], which divided the data into six local time sectors covering the nighttime substorm region. Following the procedures employed in the paper by Gjerloev and Hoffman [2000b], the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average. In addition to the detailed study of the characteristics of the field within each sector this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection channel is coincident with the highest conductances located just poleward of the Harang region. This channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors. It is present in all premidnight passes and consequently is an integral part of the three-dimensional substorm current wedge system.