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- Title
Solar Wind Ion Entry Into the Magnetosphere During Northward IMF.
- Authors
Sorathia, K. A.; Merkin, V. G.; Ukhorskiy, A. Y.; Allen, R. C.; Nykyri, K.; Wing, S.
- Abstract
Extended periods of northward interplanetary magnetic field (IMF) lead to the formation of a cold, dense plasma sheet due to the entry of solar wind plasma into the magnetosphere. Identifying the paths that the solar wind takes to enter the magnetosphere, and their relative importance has remained elusive. Any theoretical model of entry must satisfy observational constraints, such as the overall entry rate and the dawn‐dusk asymmetry observed in the cold, dense plasma sheet. We model, using a combination of global magnetohydrodynamic and test particle simulations, solar wind ion entry into the magnetosphere during northward IMF and compare entry facilitated by the Kelvin‐Helmholtz instability to cusp reconnection. For Kelvin‐Helmholtz entry we reproduce transport rates inferred from observation and kinetic modeling and find that intravortex reconnection creates buoyant flux tubes, which provides, through interchange instability, a mechanism of filling the central plasma sheet with cold magnetosheath plasma. For cusp entry we show that an intrinsic dawn‐dusk asymmetry is created during entry that is the result of alignment of the westward ion drift with the dawnward electric field typically observed during northward IMF. We show that both entry mechanisms provide comparable mass but affect entering plasma differently. The flank‐entering plasma is cold and dawn‐dusk symmetric, whereas the cusp‐entering plasma is accelerated and preferentially deflected toward dawn. The combined effect of these entry mechanisms results in a plasma sheet population that exhibits dawn‐dusk asymmetry in the manner that is seen in nature: a two‐component (hot and cold) dusk flank and hotter, broadly peaked dawn population. Key Points: Global MHD model with kinetic test particles shows comparable solar wind entry from KH vortices and cusp reconnection under northward IMFSolar wind entry exhibits intrinsic dawn‐dusk asymmetry due to the preferential energization and dawnward deflection of cusp‐entering ionsCombined flank‐ and cusp‐entering solar wind ions recreates observed two‐component (hot and cold) dusk and broad‐peaked dawn population
- Subjects
SOLAR wind; MAGNETOSPHERE; DENSE plasmas; MAGNETOHYDRODYNAMICS; INTERPLANETARY magnetic fields
- Publication
Journal of Geophysical Research. Space Physics, 2019, Vol 124, Issue 7, p5461
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2019JA026728