Solar Wind Structures Impacting the Plasma Stability and Ion Energy Distribution Downstream of the Terrestrial Bow Shock

Abstract

The plasma properties of the incoming solar wind undergo significant changes as they cross the terrestrial bow shock and traverse the magnetosheath. The solar wind itself can be categorized into different categories depending on their solar origin and linked to large-scale structures like coronal mass ejections (CMEs) or stream interaction regions (SIRs) detected in near-Earth space. Using measurements from THEMIS combined with OMNI data spanning from 2008 onward, we provide a statistical overview of temperature anisotropy-driven plasma instabilities in the dayside magnetosheath. This analysis is conducted under various upstream solar wind conditions and structures, which significantly impact the plasma environment in the magnetosheath. We extend this analysis to transient phenomena such as dynamic pressure enhancements in the magnetosheath (so-called jets) as well. As a consequence of collisionless shock physics, the shocked plasma is expected to display vastly different behaviours in terms of plasma properties and stability when sorted into quasi-parallel and quasi-perpendicular downstream magnetosheath regions. However, this categorization is complicated by the presence of fast solar wind streams originating in solar coronal holes due to the significantly increased ion energy flux of the plasma. Consequently, in our statistical analysis, we emphasize the importance of magnetosheath classification under different solar wind plasma origins and show how stable the magnetosheath plasma is in any given upstream solar wind condition. Combining knowledge of solar wind origins and structures with shock and magnetosheath research can contribute to an improved classification of quasi-perpendicular and quasi-parallel shock conditions across all solar wind origins.