Sunward Flows in the Dayside Magnetosheath.
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| Title: | Sunward Flows in the Dayside Magnetosheath. |
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| Authors: | Sibeck, D. G.1 (AUTHOR) david.g.sibeck@nasa.gov, Rastätter, L.1 (AUTHOR) |
| Source: | Journal of Geophysical Research. Space Physics. Mar2026, Vol. 131 Issue 3, p1-13. 13p. |
| Subject Terms: | Plasma flow, Plasma boundary layers, Solar wind, Magnetopause, Shock waves, Magnetohydrodynamics, Magnetosphere |
| Abstract: | Solar wind densities and dynamic pressures can fall abruptly upon the arrival of a magnetic cloud. Results from the SWMF BATS‐R‐US global magnetohydrodynamic (MHD) simulation indicate that the arrival of a factor of 10 decrease in the solar wind density associated with a tangential discontinuity moving antisunward with the solar wind immediately causes the subsolar bow shock to move outward at a velocity half that of the solar wind. Shortly thereafter, the subsolar magnetopause moves outward and the magnetic field strengths within the dayside magnetosphere fall. The sudden drops in solar wind densities and dynamic pressure reverse flows within the pre‐existing magnetosheath, resulting in cold dense inner magnetosheath plasma moving sunward and away from the Sun‐Earth line. Meanwhile, the newly arriving magnetosheath plasma comes to a halt, resulting in a stagnant hot tenuous plasma in the outer subsolar magnetosheath. Transient sunward plasma velocities peak at velocities half those in the solar wind in the outer magnetosphere at and/or just inside the subsolar magnetopause. The magnetopause overshoots its final position and begins to move antisunward, indicating the start of an oscillation, while the speed of the outward bow shock motion diminishes. Plasma flows antisunward and away from the Sun‐Earth line throughout the magnetosheath. Plain Language Summary: A sharp drop in the solar wind density and dynamic pressure results in transient sunward plasma flows throughout the dayside magnetosheath and outer dayside magnetosphere. A transient two‐layer magnetosheath forms with a hot tenuous outer magnetosheath and a cold dense inner magnetosheath. The magnetopause and bow shock move sunward, overshooting their final positions. Key Points: An abrupt decrease in the solar wind density and dynamic pressure results in steady rapid outward bow shock and magnetopause motionLarge transient sunward flows appear throughout the magnetosheath and outer magnetosphere but peak just inside the magnetopauseThe interaction produces a transient cool dense inner magnetosheath bounded by a hot tenuous outer magnetosheath [ABSTRACT FROM AUTHOR] |
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| Database: | GreenFILE |
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