PSP Observations of a Slow Shock Pair Bounding a Large‐Scale Plasmoid/Macro Magnetic Hole. Issue 6 (25th March 2022)

• Record Type: Journal Article
• Authors: Zhou, Zilu; Xu, Xiaojun; Zuo, Pingbing; Wang, Yi; Wang, Ludi; Ye, Yudong; Wang, Ming; Chang, Qing; Wang, Xing; Luo, Lei
• Is Part Of: Geophysical research letters. Volume 49:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-25
• Subjects: slow shocks -- magnetic reconnection -- solar wind -- magnetic hole; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL097564
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Slow shocks are introduced to be the main dissipation sites in Petschek reconnection model, but they are seldom observed in interplanetary space. We report a slow shock pair bounding a plasmoid/macro magnetic hole observed by Parker Solar Probe. The jump conditions across the shocks are examined and confirmed to satisfy the Rankine‐Hugoniot relations. The flow speed in the preshock and postshock regions of both shocks match up with the characteristics of slow shocks. The slow shock pair is suggested to be a part of a curved slow shock bounding the plasmoid produced by magnetic reconnection. Our findings append a new dissipation site to the picture of energy conversion through solar wind magnetic reconnection. In addition, the results suggest that plasmoids emitted by local magnetic reconnections could be a possible origin of macro magnetic holes in the solar wind. Plain Language Summary: There are two basic types of magnetohydrodynamic shocks: Fast shocks and slow shocks. Slow shocks, across which the magnetic field strength decreases from the upstream to the downstream, are suggested to be the main sites of energy conversion at the boundary of outflow jets in Petschek reconnection model. Slow shocks are seldom observed in the solar wind. Based on the magnetic field and plasma measurements by Parker Solar Probe, we report a slow shock pair bounding a macro magnetic hole in the solar wind. Surprisingly, the observed slow shock pair are not located at the boundary of reconnection outflow jets, but at the boundary of a dense and hot plasmoid. These two slow shocks are suggested to be parts of a curved slow shock bounding the plasmoid produced by magnetic reconnection, which is in agreement with previous numerical studies of fast magnetic reconnection, confirming that slow shocks could be formed at the boundaries of giant plasmoids downstream the Petschek reconnection exhausts. This finding updates the picture of dissipation sites in solar wind magnetic reconnection. In addition, plasmoids emitted by local magnetic reconnections might be a possible origin of macro magnetic holes in the solar wind. Key Points: We report a slow shock pair bounding a plasmoid/macro magnetic hole observed by Parker Solar Probe in the inner heliosphere The two slow shocks are probably parts of a curved slow shock bounding a plasmoid produced by magnetic reconnection The plasmoids emitted by magnetic reconnection could be a possible origin of macro magnetic holes in the solar wind