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

摘要

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 and B_y > 0 on 11 August 2000, (2) B_z < 0 and B_y < 0 on 8 May 2001, and (3) 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° magnetic latitude (MLAT) for all magnetic local times; when B_y is positive, the duskside aurora can even reach beyond 80° 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 Pdyn can increase the ionospheric transpolar potential and the corresponding field-aligned currents, leading to the observed auroral brightening.