Characteristics of Kelvin–Helmholtz Waves as Observed by the MMS From September 2015 to March 2020
Characteristics of Kelvin–Helmholtz Waves as Observed by the MMS From September 2015 to March 2020
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DOI：
10.1029/2021ja029685
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发表时间：
2021-06
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影响因子：
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通讯作者：
R. Rice;K. Nykyri;Xuanye Ma;B. Burkholder
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作者：
R. Rice;K. Nykyri;Xuanye Ma;B. Burkholder
磁层多尺度（MMS）使命为研究地球磁层的精细尺度结构和现象，包括与开尔文-亥姆霍兹不稳定性（KHI）相关的跨尺度过程提供了一个新的机会，但对KHI及其次级过程的此类研究将需要一个MMS与开尔文-亥姆霍兹波（KH）相遇的数据库。在这里，我们概述了2015年9月至2020年3月期间对KHI的45次MMS观测。使用一种新技术计算了45个事件中每个事件的增长率和不稳定立体角，以自动检测磁层顶边界两侧的等离子体区域。在KHI期间的太阳风条件与其增长率和不稳定的立体角之间没有明显的相关性，这并不奇怪，因为KH波在其源区下游观察到。我们注意到，所有的KHI观测到的太阳风流速在295和610 km/s之间，可能是由于不稳定性开始标准和等离子体压缩性的过滤效应。将二维磁流体动力学（2D MHD）模拟与观察到的两个MMS事件进行了比较。与二维MHD模拟结果的比较表明，新的区域排序方法是可靠和鲁棒的。自动检测移动边界两侧的单独等离子体区域并确定KHI生长速率的能力可能被证明对未来识别和研究与KHI相关的二次过程的工作有用。
The Magnetospheric Multiscale (MMS) mission has presented a new opportunity to study the fine scale structures and phenomena of the Earth’s magnetosphere, including cross scale processes associated with the Kelvin–Helmholtz Instability (KHI), but such studies of the KHI and its secondary processes will require a database of MMS encounters with Kelvin–Helmholtz (KH) waves. Here, we present an overview of 45 MMS observations of the KHI from September 2015 to March 2020. Growth rates and unstable solid angles for each of the 45 events were calculated using a new technique to automatically detect plasma regions on either side of the magnetopause boundary. There was no apparent correlation between solar wind conditions during the KHI and its growth rate and unstable solid angle, which is not surprising as KH waves were observed downstream of their source region. We note all KHI were observed for solar wind flow speeds between 295 and 610 km/s, possibly due to a filtering effect of the instability onset criteria and plasma compressibility. Two‐dimensional Magnetohydrodynamic (2D MHD) simulations were compared with two of the observed MMS events. Comparison of the observations with the 2D MHD simulations indicates that the new region sorting method is reliable and robust. The ability to automatically detect separate plasma regions on either side of a moving boundary and determine the KHI growth rate may prove useful for future work identifying and studying secondary processes associated with the KHI.