Electron-only Magnetic Reconnection: Observations and Simulations

ORAL  · Invited

Abstract

Magnetic reconnection dissipates magnetic energy by breaking and reconnecting magnetic fields and efficiently energizes particles. Reconnection usually involves both electrons and ions. A special case of reconnection where ions did not couple to the reconnection process was discovered in the turbulent magnetosheath region downstream of Earth's quasi-parallel shock. In such events, the reconnection occurs primarily in electron-scale current sheets and are postulated to exist in turbulence where the magnetic field structures are spatially confined by the eddies generated by turbulence. In collisionless turbulence, reconnection has been suggested to drive the energy dissipation at kinetic scales and many electron-scale reconnecting current sheets are generated. The reconnection processes in these environments are limited to few ion skin depths (di) leading solely to the formation of the electron diffusion region (EDR), without the ion diffusion region (IDR). Hence, this type of reconnection was dubbed ‘electron-only reconnection’. Given that the scale-size of turbulent magnetic structure in the magnetosheath can be quite small, exhibiting correlation scales on the order of 1-10 di, electron-only reconnection may be the dominant form of reconnection in the turbulent magnetosheath and bow shock. Below ion kinetic length scales, theoretical models also suggest that electron scale reconnection may dominantly release the magnetic energy further steepening the energy spectrum.

In this talk I aim to provide the current state of electron-only reconnection starting from its discovery at the magnetosheath to the latest works in both observations and simulations.

*NSF grants No. AGS-2024198, No. PHY2109083 and NASA grants Nos. 80NSSC21K1481, 80NSSC20K1781, 80NSSC22K0352, 80NSSC20K1813 and NASA contract NNG04EB99C (at SWRI). We acknowledge high-performance computing support from Cheyenne provided by NCAR's CISL, sponsored by the NSF. This research also used NERSC resources; a U.S. DOE office of Science User Facility operated under Contract No. DE-AC02-05CH11231.

–

Publication: Pyakurel, P. S., Shay, M. A., Phan, T. D., Matthaeus, W. H., Drake, J. F., TenBarge, J. M., Haggerty, C. C., K. Klein, and Cassak, P. A., Parashar, T. N., Swisdak, M., and Chasapis, A. (2019). Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence. Physics of Plasmas.

Pyakurel, P. S., Shay, M. A., Drake, J. F., Phan, T. D., Cassak, P. A., & Verniero, J. L. (2021), Phys. Rev. Lett., Faster Form of Electron Magnetic Reconnection with a Finite Length X-Line, 127, 155101.

Pyakurel, P. S., Phan, T. D., Drake, J. F., Shay, M. A., Øieroset, M., Haggerty, C. C., Stawarz, J., Burch, J. L., Ergun, R. E., Gershman, D. J., Giles, B. L., Torbert, R. B., Strangeway, R. J., & Russell, C. T. (2023), The Astrophysical Journal, On the Short-scale Spatial Variability of Electron Inflows in Electron-only Magnetic Reconnection in the Turbulent Magnetosheath Observed by MMS, 948, 20.

Presenters

  • Prayash Sharma Pyakurel

    • University of California, Berkeley
    • University of California Berkeley

Authors

  • Prayash Sharma Pyakurel

    • University of California, Berkeley
    • University of California Berkeley

  • Tai Phan

    • Space Sciences Laboratory, University of California, Berkeley
    • Space Sciences Laboratory, U.C. Berkeley
    • University of California Berkeley
    • University of California, Berkeley,

  • James F Drake

    • University of Maryland, College Park

  • Michael A Shay

    • University of Delaware

  • Marit Oieroset

    • University of California, Berkeley