Slow Shock Formation Upstream of Reconnecting Current Sheets

Journal Article · 08 February 2022 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/ac423b · OSTI ID:1868291

Arnold, H.  ^[1]; Drake, J. F.  ^[1]; Swisdak, M.  ^[1]; Guo, F.  ^[2]; Dahlin, J. T.  ^[3]; Zhang, Q. ^[2]

---

1. Univ. of Maryland, College Park, MD (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)

The formation, development, and impact of slow shocks in the upstream regions of reconnecting current layers are explored. Slow shocks have been documented in the upstream regions of magnetohydrodynamic (MHD) simulations of magnetic reconnection as well as in similar simulations with the kglobal kinetic macroscale simulation model. They are therefore a candidate mechanism for preheating the plasma that is injected into the current layers that facilitate magnetic energy release in solar flares. Of particular interest is their potential role in producing the hot thermal component of electrons in flares. During multi-island reconnection, the formation and merging of flux ropes in the reconnecting current layer drives plasma flows and pressure disturbances in the upstream region. These pressure disturbances steepen into slow shocks that propagate along the reconnecting component of the magnetic field and satisfy the expected Rankine–Hugoniot jump conditions. Plasma heating arises from both compression across the shock and the parallel electric field that develops to maintain charge neutrality in a kinetic system. Shocks are weaker at lower plasma β, where shock steepening is slow. While these upstream slow shocks are intrinsic to the dynamics of multi-island reconnection, their contribution to electron heating remains relatively minor compared with that from Fermi reflection and the parallel electric fields that bound the reconnection outflow.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: LDRD; NSF; NASA; FINESST
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1868291
• Report Number(s): LA-UR-21-27254
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 926; ISSN 0004-637X
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English