Inner Magnetospheric Convection impacted by Magnetopause Kelvin–Helmholtz Vortices Following an IMF Southward Turning: Global MHD Simulations

Following a southward turning of the interplanetary magnetic field (IMF), dayside magnetic reconnection rapidly re-establishes sunward convection on closed field lines, modifying plasma flow near the magnetopause. How magnetopause Kelvin–Helmholtz (KH) vortices develop and inflxuence magnetospheric convection under southward IMF conditions remains unclear. Here, we use global magnetohydrodynamic (MHD) simulations to investigate the formation, evolution, and convection impact of KH vortices under fast (800 km/s) and slow (400 km/s) solar-wind conditions.After the IMF turns southward, KH vortices form along the magnetopause and extend across the low-latitude boundary layer (LLBL) into the closed-field-line convection region, locally distorting the global convection pattern. Regardless of solar-wind speed, the azimuthal region of distorted convection near magnetic local time 06 exhibits a characteristic thickness of approximately 3–4 RE (~3° in magnetic latitude). These vortices and associated convection perturbations propagate antisunward. Compared with slow solar-wind cases, fast solar-wind conditions lead to more rapid earthward propagation and deeper penetration of the distorted convection into the inner magnetosphere. These results demonstrate that inner magnetospheric convection can be shaped by LLBL instabilities in the southward IMF.