Response timescales of the magnetotail current sheet during a geomagnetic storm: Global MHD simulations
Response timescales of the magnetotail current sheet during a geomagnetic storm: Global MHD simulations
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DOI：
10.3389/fspas.2022.966164
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
J. Eggington;J. Coxon;R. Shore;R. Desai;L. Mejnertsen;J. Chittenden;J. Eastwood
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文献类型：
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作者：
J. Eggington;J. Coxon;R. Shore;R. Desai;L. Mejnertsen;J. Chittenden;J. Eastwood
地球磁尾电流片对外部太阳风驱动器的响应是高度依赖于时间和不对称的。例如，电流片响应行星际磁场（IMF）的B y分量的变化而扭曲，并且通过偶极倾斜铰接。了解这些不对称性表现的时间尺度是特别重要的，在磁暴时，尾部的动态控制亚暴活动。为了研究这一点，我们使用Gorgon MHD模型来模拟2014年5月3日开始的地磁风暴，并主持多次B y和B z反转和长时间的向南IMF驱动。我们发现，扭曲的电流片是相关的IMF B y在整个事件中，与旋转的角度线性增加的downtail的距离和更明显时，尾部包含较少的开放通量。在向南IMF期间的扭曲的中央电流片响应最强烈的时间滞后为100分钟的距离超过20 R E，一致的1-2小时的对流时间尺度中确定的开放通量的内容。在主要向北IMF的扭转的响应是双峰，与最强的相关性之间的15和40 R E下尾是在一个较短的时间尺度为1.30分钟一致的诱导B Y由于波传播的估计，相比，一个较长的时间尺度为1.30小时进一步下尾再次归因于对流。这表明，在磁尾的不对称性传达IMF B y的影响主要是由全球对流在强太阳风驱动，但更多的即时诱导B y效应可以占主导地位的近地尾巴，在较弱的驱动期间。这些结果提供了新的见解的特征时间尺度的太阳风磁层电离层耦合。
The response of the Earth’s magnetotail current sheet to the external solar wind driver is highly time-dependent and asymmetric. For example, the current sheet twists in response to variations in the B y component of the interplanetary magnetic field (IMF), and is hinged by the dipole tilt. Understanding the timescales over which these asymmetries manifest is of particular importance during geomagnetic storms when the dynamics of the tail control substorm activity. To investigate this, we use the Gorgon MHD model to simulate a geomagnetic storm which commenced on 3 May 2014, and was host to multiple B y and B z reversals and a prolonged period of southward IMF driving. We find that the twisting of the current sheet is well-correlated to IMF B y throughout the event, with the angle of rotation increasing linearly with downtail distance and being more pronounced when the tail contains less open flux. During periods of southward IMF the twisting of the central current sheet responds most strongly at a timelag of ∼ 100 min for distances beyond 20 R E , consistent with the 1–2 h convection timescale identified in the open flux content. Under predominantly northward IMF the response of the twisting is bimodal, with the strongest correlations between 15 and 40 R E downtail being at a shorter timescale of ∼ 30 min consistent with that estimated for induced B y due to wave propagation, compared to a longer timescale of ∼ 3 h further downtail again attributed to convection. This indicates that asymmetries in the magnetotail communicated by IMF B y are influenced mostly by global convection during strong solar wind driving, but that more prompt induced B y effects can dominate in the near-Earth tail and during periods of weaker driving. These results provide new insight into the characteristic timescales of solar wind-magnetosphere-ionosphere coupling.