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ORIGINAL RESEARCH article

Front. Phys.
Sec. Space Physics
Volume 12 - 2024 | doi: 10.3389/fphy.2024.1503092
This article is part of the Research Topic Variability in the Solar Wind and its Impact on the Coupled Magnetosphere-Ionosphere-Thermosphere System View all 9 articles

Simultaneous Observations of MHD Hot Flow Anomaly and Kinetic Foreshock Bubble and Their Impacts

Provisionally accepted
Xi Lu Xi Lu 1*Terry Zixu Liu Terry Zixu Liu 2*Xingran Chen Xingran Chen 1Antonius Otto Antonius Otto 1Hui Zhang Hui Zhang 1
  • 1 University of Alaska Fairbanks, Fairbanks, United States
  • 2 University of California, Los Angeles, Los Angeles, California, United States

The final, formatted version of the article will be published soon.

    Hot flow anomalies (HFAs) and foreshock bubbles (FBs) are two types of transient phenomena characterized by flow deflected and hot cores bounded by one or two compressional boundaries in the foreshock. Using conjunction observations by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, we present an MHD HFA with a core filled with magnetosheath material around the bow shock and a typical kinetic FB associated with foreshock ions upstream of the bow shock, occurring simultaneously under the same solar wind/interplanetary magnetic field (IMF) conditions. The displacements of the bow shock moving back and forth along the sun-earth line are observed. Electron energy shows enhancements from ~50 keV in the FB to ~100 keV in the HFA core, suggesting additional acceleration process across the bow shock within the transient structure. The magnetosheath response of an HFA core-like structure with particle heating and electron acceleration is observed by the Magnetospheric Multiscale (MMS) mission. Ultralow frequency waves in the magnetosphere modulating cold ion energy are identified by THEMIS, driven by these transient structures. Our study improves our understanding of foreshock transients and suggests that single spacecraft observations are insufficient to reveal the whole picture of foreshock transients, leading to an underestimation of their impacts (e.g., particle acceleration energy and spatial scale of disturbances).

    Keywords: hot flow anomalies, foreshock bubbles, magnetohydrodynamics, bow shock, THEMIS

    Received: 28 Sep 2024; Accepted: 10 Dec 2024.

    Copyright: © 2024 Lu, Liu, Chen, Otto and Zhang. 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:
    Xi Lu, University of Alaska Fairbanks, Fairbanks, United States
    Terry Zixu Liu, University of California, Los Angeles, Los Angeles, 90095, California, United States

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