Michael A T, Sorathia K A, Merkin V G, Nykyri K, Burkholder B, Ma X, Ukhorskiy A Y, Garretson J
The Johns Hopkins University Applied Physics Laboratory Laurel MD USA.
Department of Physical Sciences and Center for Space and Atmospheric Research (CSAR) Embry-Riddle Aeronautical University Daytona Beach FL USA.
Geophys Res Lett. 2021 Oct 16;48(19):e2021GL094002. doi: 10.1029/2021GL094002. Epub 2021 Oct 7.
The Kelvin-Helmholtz instability at the magnetospheric boundary plays a crucial role in solar wind-magnetosphere-ionosphere coupling, particle entry, and energization. The full extent of its impact has remained an open question due, in part, to global models without sufficient resolution to capture waves at higher latitudes. Using global magnetohydrodynamic simulations, we investigate an event when the Magnetospheric Multiscale (MMS) mission observed periodic low-frequency waves at the dawn-flank, high-latitude boundary layer. We show the layer to be unstable, even though the slow solar wind with the draped interplanetary magnetic field is seemingly unfavorable for wave generation. The simulated velocity shear at the boundary is thin ( ) and requires commensurately high spatial resolution. These results, together with MMS observations, confirm for the first time in fully three-dimensional global geometry that KH waves can grow in this region and thus can be an important process for energetic particle acceleration, dynamics, and transport.
磁层边界处的开尔文 - 亥姆霍兹不稳定性在太阳风 - 磁层 - 电离层耦合、粒子进入和能量激发过程中起着至关重要的作用。其影响的全部范围一直是个悬而未决的问题，部分原因是全球模型的分辨率不足以捕捉高纬度地区的波动。利用全球磁流体动力学模拟，我们研究了磁层多尺度（MMS）任务在黎明侧高纬度边界层观测到周期性低频波的一个事件。我们发现该层是不稳定的，尽管具有被拖曳的行星际磁场的缓慢太阳风似乎不利于波的产生。边界处模拟的速度切变很薄（ ），需要相应的高空间分辨率。这些结果与MMS观测结果一起，首次在全三维全球几何结构中证实，开尔文 - 亥姆霍兹波可以在该区域增长，因此可能是高能粒子加速、动力学和输运的一个重要过程。
