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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Statistical characteristics of plasma flows associated with magnetic dipolarizations in the near-tail region of r < 12 R_E
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Statistical characteristics of plasma flows associated with magnetic dipolarizations in the near-tail region of r < 12 R_E

机译：r <12 R_E的近尾区域中与磁双极化相关的等离子体流的统计特性

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The magnetic dipolarization in the tail close to Earth is often associated with plasma flows of some magnitude, and the flow direction can be critically related to the substorm triggering issue. In this work we identified 167 events of dipolarizations in the near-Earth tail (r 7-12 RE) using Time History of Events and Macroscale Interactions during Substorms (THEMIS) tail observations and examined plasma flow patterns associated with the dipolarizations. We first find that～50% of the dipolarizations in this near-tail region initiate with plasma flows of a significant magnitude (>100 km/s). Out of such fast flow events, —78% are earthward flows and～22% are tailward flows, which we interpret as rebound of the earthward flows. The overall occurrence rate of the fast flows (including both earthward and tailward flows) noticeably decreases earthward: It drops from ～47% at r≈ 8-9 RE to ～27% at r≈ 7-8 RE. This implies that the earthward flows can seldom penetrate inside of 7-8 RE, consistent with previous reports. Incidentally, we find that the flow directions often change during the course of the entire dipolarization process whether dipolarization begins with an earthward or tailward flow. Nevertheless, the net magnetic transport is earthward during the main duration of most of the dipolarizations, even if they initiate with dominantly tailward flows at the onset.
机译：靠近地球的尾巴中的磁偶极极化通常与某种程度的等离子体流相关，并且流向可能与亚暴触发问题至关重要。在这项工作中，我们使用事件的时间历史和亚暴期间的大尺度相互作用（THEMIS）尾部观测，确定了近地尾巴中的167个偶极极化事件（r 7-12 RE），并检查了与偶极极化相关的血浆流动模式。我们首先发现，在该近尾区域中约50％的双极化是由相当大的等离子流（> 100 km / s）引发的。在这种快速流动事件中，有-78％是向地流，而〜22％是向后流，我们将其解释为向地流的反弹。快速流（包括向地流和向后流）的整体发生率明显向地减小：从r≈8-9RE时的〜47％下降到r≈7-8RE时的〜27％。这意味着与先前的报告一致，向地球的流动很少能渗透到7-8 RE内部。顺便说一句，我们发现，无论双极化是从地流还是向尾流开始，在整个双极化过程中流向都经常改变。尽管如此，净磁传输在大多数双极化的主要持续时间内都是向地球移动的，即使它们在开始时主要是向后流动。

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