Large‐scale current systems and ground magnetic disturbance during deep substorm injections
Large‐scale current systems and ground magnetic disturbance during deep substorm injections
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DOI：
10.1029/2011ja017415
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发表时间：
2012-04
影响因子：
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通讯作者：
J. Yang;F. Toffoletto;R. Wolf;S. Sazykin;P. Ontiveros;J. Weygand
中科院分区：
文献类型：
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作者：
J. Yang;F. Toffoletto;R. Wolf;S. Sazykin;P. Ontiveros;J. Weygand
[1]我们提出了一个详细的分析大尺度电流系统和它们对地面磁场扰动的一个理想的亚暴事件模拟与平衡版本的赖斯对流模型。本研究的目的是评估如何以及气泡注入图片可以占亚暴膨胀阶段的一些经典功能。气泡内部的熵消耗被故意设计得如此严重，以至于它可以深入地球同步轨道。结果如下：（1）区域1感测和区域2感测场向电流（FACs）均显著增强。前者类似于亚暴流楔，沿着气泡的东西边缘流动。后者与磁层中的增强部分环电流有关，磁层中的环电流与磁泡向地的偶极前沿有关。在电离层中，这两对FACs主要通过彼得森电流互连。(2)水平电离层电流显示出明显的向西电喷流，峰值位于气泡足迹的赤道边缘。估计的地面磁扰动是一致的，在不同的位置相对于向西电急流中心的典型特征。(3)在地面ΔH扰动和等离子体流型中均观察到一个明显的Harang反转边界，该边界出现在气泡足迹向赤道方向边缘的向西，其纬度范围为0.55 °，纵向范围为气泡的半宽。(4)气泡内部的戏剧性的偶极化导致内部等离子体片的电离层图呈现出隆起状结构，这可能与极光向极扩展有关。(5)当磁泡到达磁过渡区时，出现了明显的向西电喷流、类Harang反转边界和向极膨胀现象。我们还估计了水平和垂直电流使用磁记录在几十个地面站的深注入亚暴事件发生在2008年4月9日，导致在定性与模拟一致的图片。基于模拟和观测结果，得到了深磁泡注入过程中电离层动力学及其磁层驱动因素的整体图像。
[1] We present a detailed analysis of the large-scale current systems and their effects on the ground magnetic field disturbance for an idealized substorm event simulated with the equilibrium version of the Rice Convection Model. The objective of this study is to evaluate how well the bubble-injection picture can account for some classic features of the substorm expansion phase. The entropy depletion inside the bubble is intentionally designed to be so severe that it can penetrate deep into geosynchronous orbit. The results are summarized as follows: (1) Both the region-1-sense and region-2-sense field-aligned currents (FACs) intensify substantially. The former resembles the substorm current wedge and flows along the eastern and western edges of the bubble. The latter is connected to the enhanced partial ring current in the magnetosphere associated with a dipolarization front earthward of the bubble. In the ionosphere, these two pairs of FACs are mostly interconnected via Pedersen currents. (2) The horizontal ionospheric currents show a significant westward electrojet peaked at the equatorward edge of the footprint of the bubble. The estimated ground magnetic disturbance is consistent with the typical features at various locations relative to the center of the westward electrojet. (3) A prominent Harang-reversal-like boundary is seen in both ground ΔH disturbance and plasma flow pattern, appearing in the westward portion of the equatorward edge of the bubble footprint, with a latitudinal extent of ∼5° and a longitudinal extent of the half width of the bubble. (4) The dramatic dipolarization inside the bubble causes the ionospheric map of the inner plasma sheet to exhibit a bulge-like structure, which may be related to auroral poleward expansion. (5) The remarkable appearance of the westward electrojet, Harang-reversal-like boundary and poleward expansion starts when the bubble reaches the magnetic transition region from tail-like to dipole-like configuration. We also estimate the horizontal and vertical currents using magnetograms at tens of ground stations for a deep injection substorm event occurred on April 9, 2008, resulting in a picture that is qualitatively consistent with the simulation. Based on the simulations and the observations, an overall picture of the ionospheric dynamics and its magnetospheric drivers during deep bubble injections is obtained.