ORIGINAL RESEARCH article
Front. Astron. Space Sci.
Sec. Space Physics
Volume 12 - 2025 | doi: 10.3389/fspas.2025.1574577
This article is part of the Research TopicVariability in the Solar Wind and its Impact on the Coupled Magnetosphere-Ionosphere-Thermosphere SystemView all 13 articles
Sunward Flows in the Magnetosheath Associated with Magnetic Pressure Gradient and Magnetosheath Expansion
Provisionally accepted
Hadi Madanian1,2*
Yann Pfau-Kempf3
Rachel Rice2,4
Terry Zixu Liu5
Tomas Karlsson6
Savvas Raptis7
Drew Turner7
Jason Beedle8- 1The Catholic University of America, Washington, D.C., United States
- 2Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, United States
- 3University of Helsinki, Helsinki, Uusimaa, Finland
- 4University of Maryland, College Park, College Park, Maryland, United States
- 5University of California, Los Angeles, Los Angeles, California, United States
- 6Royal Institute of Technology, Stockholm, Stockholm, Sweden
- 7Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, United States
- 8University of New Hampshire, Durham, North Carolina, United States
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A density structure within the magnetic cloud of an interplanetary coronal mass ejection impacted Earth and caused significant perturbations in plasma boundaries. We describe the effects of this structure on the magnetosheath plasma downstream of the bow shock using spacecraft observations. During this event, the bow shock breathing motion is evident due to the changes in the upstream dynamic pressure. A magnetic enhancement forms in the inner magnetosheath and ahead of a plasma compression region. The structure has the characteristics of a fast magnetosonic shock wave, propagating earthward and perpendicular to the background magnetic field further accelerating the already heated magnetosheath plasma. Following these events, a sunward motion of the magnetosheath plasma is observed. Ion distributions show that both the high density core population as well as the high energy tail of the distribution have a sunward directed flow indicating that the sunward flows are caused by magnetic field line expansion in the very low $\beta$ magnetosheath plasma. Rarefaction effects and enhancement of the magnetic pressure in the magnetosheath result in magnetic pressure gradient forcing that drives the expansion of magnetosheath magnetic field lines. This picture is supported by a reasonable agreement between the estimated plasma accelerations and the magnetic pressure gradient force.
Keywords: Shocks, magnetosheath, Space weather, Solar wind, Space plasmas, bow shock, Interplanetary coronal mass ejection (ICME)
Received: 11 Feb 2025; Accepted: 16 Apr 2025.
Copyright: © 2025 Madanian, Pfau-Kempf, Rice, Liu, Karlsson, Raptis, Turner and Beedle. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Hadi Madanian, The Catholic University of America, Washington, D.C., United States
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