Asymmetric Interaction of a Solar Wind Reconnecting Current Sheet and Its Magnetic Hole With Earth’s Bow Shock and Magnetopause

Abstract

We report results of our multi-spacecraft analysis of a solar wind reconnecting current sheet (RCS) and its solar wind magnetic hole (SWMH) observed on November 20, 2018. In the solar wind, the normal vector to the current sheet plane makes an angle of 32° with the Sun-Earth line. A combination of tilted current sheet plane and foreshock effects cause an asymmetric interaction with the bow shock, in which the structure arrives at the quasi-perpendicular side of the bow shock before the quasi-parallel side. The magnetic field strength inside the magnetic hole decreases by ∼69 percent in the solar wind, with a similar depression rate observed inside the magnetosheath due to this structure. The solar wind flow slowdown and deflection during the bow shock crossing significantly disrupt the reconnection exhausts within the RCS. The interaction of the RCS and SWMH with the bow shock creates enhanced fluxes of accelerated electrons and ions. Plasma flow deflection in the magnetosheath also increases with the passage of the RCS. The ion density and temperature both increase within the current sheet to form a roughly pressure balanced structure. Field rotation and change in the dynamic pressure during this event modify the reconnection zones at the magnetopause and cause asymmetric inward motions in portions of the bow shock and the magnetopause boundaries (i.e., deformation). Unlike localized magnetosheath jets, an RCS and its associated SWMH in the solar wind have a global impact on the bow shock and the magnetopause.Plain Language SummarySpace Weather is the study of effects of solar inputs on the space environment surrounding Earth. A source of solar input is through the solar wind, a stream of charged particles from the Sun carrying the interplanetary magnetic field. In this study, we analyze effects of a particular type of solar wind anomaly on Earth. The structure is initially observed by solar wind monitors far upstream of Earth, and later appears in the data of several near Earth spacecraft. We show that the structure can pass through the outer most boundary around Earth, the bow shock, and propagate closer to Earth. This study has significance in shaping our understanding of space weather as it describes near-Earth effects of a commonly observed solar wind phenomenon.Key PointsAsymmetric interaction is caused by the current sheet plane orientation in the solar wind and foreshock effectsFlux of accelerated electrons and ions increase in the magnetosheath due to current sheet and magnetic hole interactions at the bow shockThe structure causes deformation of the bow shock and magnetopause boundaries and modulates the reconnection process at the magnetopause