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  • G. Q. Wang, S. D. Xiao, M. Y. Wu, Y. Q. Chen, T. L. Zhang. 2024: Statistical study of magnetic holes in the upstream region of the Mercury’s bow shock. Earth and Planetary Physics. DOI: 10.26464/epp2024013
    Citation: G. Q. Wang, S. D. Xiao, M. Y. Wu, Y. Q. Chen, T. L. Zhang. 2024: Statistical study of magnetic holes in the upstream region of the Mercury’s bow shock. Earth and Planetary Physics. DOI: 10.26464/epp2024013
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Statistical study of magnetic holes in the upstream region of the Mercury’s bow shock

  • Magnetic holes are magnetic depression structures, and widely exist in many plasma environments. The magnetic holes with durations of > 1 s in the solar wind at Mercury’s orbit have drawn much attention, but the properties of the magnetic holes with shorter durations are still unclear. Here, we investigate the magnetic holes with durations of 0.1 – 100 s in the upstream region of the Mercury’s bow shock based on observations of the MESSENGER spacecraft. According to their durations’ distribution, they can be divided into two groups: small duration of magnetic holes (SDMHs, < 0.6 s) and large duration of magnetic holes (LDMHs, > 0.6 s). The durations of both groups approximately obey a log-normal distribution with a median of ~0.25 s and 3 s, respectively. About 1.7% (32.6%) of the SDMHs (LDMHs) reduce the magnetic field strength by more than 50%. For both groups, some structures are linear or quasi-linear polarization, while others are elliptical polarization. The magnetic hole events in both groups tend to have a higher occurrence rate during a weaker interplanetary magnetic field strength. Their occurrence rates are also affected by Mercury’s foreshock, which can increase (decrease) the occurrence rate of the SDMHs (LDMHs). This suggests that Mercury’s foreshock might be one source of the SDMHs, and can destroy some LDMHs. Our above observations suggest that a new group of magnetic holes with durations < 0.6 s exists in the upstream region of the Mercury’s bow shock.
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