Reconnection and interchange instability in the near magnetotail

Journal Article · Thu Jul 16 00:00:00 EDT 2015 · Earth, Planets and Space (Online)

DOI:https://doi.org/10.1186/s40623-015-0282-3· OSTI ID:1212698

Birn, Joachim ^[1]; Liu, Yi -Hsin ^[2]; Daughton, William ^[3]; Hesse, Michael ^[2]; Schindler, Karl ^[4]

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1. Space Science Institute, Boulder, CO (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. NASA/Goddard Space Flight Center, Greenbelt, MD (United States)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
4. Ruhr Univ., Bochum (Germany)

This paper provides insights into the possible coupling between reconnection and interchange/ballooning in the magnetotail related to substorms and flow bursts. The results presented are largely based on recent simulations of magnetotail dynamics, exploring onset and progression of reconnection. 2.5-dimensional particle-in-cell (PIC) simulations with different tail deformation demonstrate a clear boundary between stable and unstable cases depending on the amount of deformation, explored up to the real proton/electron mass ratio. The evolution prior to onset, as well as the evolution of stable cases, are governed by the conservation of integral flux tube entropy S as imposed in ideal MHD, maintaining a monotonic increase with distance downtail. This suggests that ballooning instability in the tail should not be expected prior to the onset of tearing and reconnection. 3-D MHD simulations confirm this conclusion, showing no indication of ballooning prior to reconnection, if the initial state is ballooning stable. The simulation also shows that, after imposing resistivity necessary to initiate reconnection, the reconnection rate and energy release initially remain slow. However, when S becomes reduced from plasmoid ejection and lobe reconnection, forming a negative slope in S as a function of distance from Earth, the reconnection rate and energy release increase drastically. The latter condition has been shown to be necessary for ballooning/interchange instability, and the cross-tail structures that develop subsequently in the MHD simulation are consistent with such modes. The simulations support a concept in which tail activity is initiated by tearing instability but significantly enhanced by the interaction with ballooning/interchange enabled by plasmoid loss and lobe reconnection.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1212698
• Journal Information: Earth, Planets and Space (Online), Journal Name: Earth, Planets and Space (Online) Journal Issue: 1 Vol. 67; ISSN 1880-5981
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
interchange
magnetotail dynamics
reconnection
substorms