Simulations of observed auroral brightening caused by solar wind dynamic pressure enhancements under different interplanetary magnetic field conditions

Abstract

Solar wind dynamic pressure (P(dyn)) enhancements have been observed to cause large-scale auroral brightening. The mechanism for this kind of auroral brightening is still a topic of current space research. Using the global piecewise parabolic method Lagrangian remap (PPMLR)-MHD simulation model, we investigate three auroral brightening events caused by dynamic pressure enhancement under different interplanetary magnetic field (IMF) conditions: (1) B(z) 0 on 11 August 2000, (2) B(z) = 0 on 21 January 2005. We show that the auroral location depends on the IMF conditions. Under southward IMF conditions, when B(y) is negative, the duskside aurora is located more equatorward at around 70 degrees magnetic latitude (MLAT) for all magnetic local times; when B(y) is positive, the duskside aurora can even reach beyond 80 degrees MLAT. A smaller and more localized response is seen when the IMF B(z) is nearly zero or northward, as shown in previous studies. Our simulation results are consistent with these observations, indicating that the observed aurora activities could be caused by solar wind dynamic pressure enhancements. The simulation results suggest that the enhancement of P(dyn) can increase the ionospheric transpolar potential and the corresponding field-aligned currents, leading to the observed auroral brightening.