Do Statistical Models Capture the Dynamics of the Magnetopause During Sudden Magnetospheric Compressions?
Do Statistical Models Capture the Dynamics of the Magnetopause During Sudden Magnetospheric Compressions?
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DOI：
10.1029/2019ja027289
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发表时间：
2020-04
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影响因子：
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通讯作者：
F. Staples;I. J. Rae;Colin Forsyth;A. Smith;K. Murphy;Katie Raymer;F. Plaschke;Nathan Case
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文献类型：
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作者：
F. Staples;I. J. Rae;Colin Forsyth;A. Smith;K. Murphy;Katie Raymer;F. Plaschke;Nathan Case
在强烈的太阳风驱动下，磁层顶可能会被压缩，在从外部辐射带吸收电子方面发挥重要作用。也被称为“磁层顶遮蔽”，这种损失过程传统上被归因于磁层压缩和电子向外径向扩散的结合。然而，相对论性电子的漂移路径和磁层顶的位置通常是从统计模型中计算出来的，因此可能无法代表这种高度动态过程的时变性质。在这项研究中，我们建立了一个数据库，记录了20，000个航天器穿越向阳面磁层顶的数据，以量化常用的Shue等人（1998，https：//doi.org/10.1029/98JA01103）模型的准确性。我们发现，对于大多数事件（74%），磁层顶模型可以用来估计磁层顶的位置在±1 RE。然而，如果磁层顶被压缩到8 RE以下，则观测到的磁层顶平均在模型位置内部大于1 RE。观测到的磁层顶也显着位移从模型的位置在风暴突然开始，当测量平均接近辐射带的6%，最大的42%。我们发现，磁层顶很少足够接近的外辐射带，导致直接的磁层顶阴影，因此快速向外径向传输的电子也是必需的。我们的结论是，统计磁层顶参数化可能是不适当的动态压缩。我们建议，统计模型只应在静止的太阳风条件下使用，并尽可能补充磁层顶观测。
Under periods of strong solar wind driving, the magnetopause can become compressed, playing a significant role in draining electrons from the outer radiation belt. Also termed “magnetopause shadowing,” this loss process has traditionally been attributed to a combination of magnetospheric compression and outward radial diffusion of electrons. However, the drift paths of relativistic electrons and the location of the magnetopause are usually calculated from statistical models and, as such, may not represent the time‐varying nature of this highly dynamic process. In this study, we construct a database ∼20,000 spacecraft crossings of the dayside magnetopause to quantify the accuracy of the commonly used Shue et al. (1998, https://doi.org/10.1029/98JA01103) model. We find that, for the majority of events (74%), the magnetopause model can be used to estimate magnetopause location to within ±1 RE. However, if the magnetopause is compressed below 8 RE, the observed magnetopause is greater than 1 RE inside of the model location on average. The observed magnetopause is also significantly displaced from the model location during storm sudden commencements, when measurements are on average 6% closer to the radiation belts, with a maximum of 42%. We find that the magnetopause is rarely close enough to the outer radiation belt to cause direct magnetopause shadowing, and hence rapid outward radial transport of electrons is also required. We conclude that statistical magnetopause parameterizations may not be appropriate during dynamic compressions. We suggest that statistical models should only be used during quiescent solar wind conditions and supplemented by magnetopause observations wherever possible.