SolarWind Discontinuity Interaction with the Bow Shock: Current Density Growth and Dawn-Dusk Asymmetry

摘要

The solar wind is filled with various magnetic field fluctuations,and one of the most widespread types of such fluctuations is solar wind discontinuities.They are rapid highamplitude magnetic field rotations sharing properties of nonlinear Alfvén waves and plane plasma slabs.They are believed to play an important role in the interaction of the solar wind with the Earth's magnetosphere.Most studies of solar wind discontinuities are based on observations in pristine solar wind,often by solar wind monitors at L1.However,before interacting with the Earth's magnetosphere,solar wind discontinuities cross the bow shock and can change their properties.In this study,we investigate the transformation of discontinuities due to the bow shock crossing.We compiled a set of 100 high-amplitude (> 3 nT) discontinuities observed by ARTEMIS in the upstream of the bow shock and by THEMIS in the downstream from the bow shock crossing (in the Earth's magnetosheath).Comparison of discontinuity properties in the solar wind and magnetosheath demonstrates discontinuity thinning and current density increase in the magnetosheath.Although all considered solar wind discontinuities mostly resemble rotational discontinuities,in the magnetosheath they start having properties of tangential discontinuities.We reveal a clear dawn-dusk asymmetry of discontinuity properties that are likely related to the asymmetry of the ion foreshock. We discuss how solar wind discontinuity transformation at the bow shock crossing can alter their interaction with the Earth's magnetosphere.