Bow shock transients caused by solar wind dynamic pressure depletions

Abstract

The bow shock and the dayside magnetopause are the principle boundaries that determine the interaction of the magnetosphere with the solar wind. Specifically, the bow shock determines the properties of the shocked solar wind plasma that interacts with the magnetosphere. In addition to the shocked solar wind plasma, a number of transient events associated with the bow shock and foreshock regions can have a major impact on the magnetosphere. Among these transients, specifically so-called hot flow anomalies (HFAs) can play a significant role for magnetospheric physics including auroral and ionospheric perturbations, ultra low frequency waves, and strong deformations of the magnetospheric boundaries. This paper first reviews the properties and types of bow shock transients with a focus on HFAs, and than investigates the response of oblique fast shocks with upstream transient density depleted regions. It is demonstrated that a density depleted flux tube can cause all of the typical properties associated with HFAs. The results are discussed in the context of observations and simulation.