Evolution of a foreshock bubble from dayside to nightside and its impact on the magnetosheath/magnetopause: 3D global hybrid simulation

Abstract:

Our current understanding of foreshock transients and its impact on the magnetosphere have been limited to the dayside. In this study, we present three-dimensional global hybrid simulation results to show how a foreshock bubble (FB) evolves as it propagates from the dayside (X = 15 R_E) to nightside (X = –50 R_E) and how it affects the magnetosheath and magnetopause. In the simulation, the foreshock region extends from the dayside to nightside, and the FB is driven by an IMF rotational discontinuity. The FB is initially formed on the dayside foreshock. As it propagates tailward, its spatial size grows to > 10 R_E, and its density and dynamic pressure perturbations are enhanced by > 50% of the solar wind values. As the FB interacts with the bow shock, the bow shock is temporarily eroded, and the corresponding dynamic pressure perturbations in the magnetosheath penetrate deep to the magnetopause, causing localized distortion of the magnetopause shape. As the FB moves from dayside to nightside, it continuously generates new perturbations in the magnetosheath and magnetopause following FB’s propagation. The results indicate that foreshock transients can have significant impact on both the dayside and nightside magnetosphere.