Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence

P. Sharma Pyakurel; M. A. Shay; T. D. Phan; W. H. Matthaeus; J. F. Drake; J. M. TenBarge; C. C. Haggerty; K. G. Klein; P. A. Cassak; T. N. Parashar; M. Swisdak; A. Chasapis; Univ. of California, Oakland, CA (United States)

doi:10.1063/1.5090403

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Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence

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Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence

P. Sharma Pyakurel, M. A. Shay, T. D. Phan, W. H. Matthaeus, J. F. Drake, J. M. TenBarge, C. C. Haggerty, K. G. Klein, P. A. Cassak, T. N. Parashar, …

Physics of plasmas, Vol.26(8), 082307

08/01/2019

DOI: 10.1063/1.5090403

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Abstract

Using 2.5 dimensional kinetic particle-in-cell simulations, we simulate reconnection conditions appropriate for the magnetosheath and solar wind, i.e., plasma beta (ratio of gas pressure to magnetic pressure) greater than 1 and low magnetic shear (strong guide field). Changing the simulation domain size, we find that the ion response varies greatly. For reconnecting regions with scales comparable to the ion inertial length, the ions do not respond to the reconnection dynamics leading to electron-only reconnection with very large quasisteady reconnection rates. Note that in these simulations, the ion Larmor radius is comparable to the ion inertial length. The transition to a more traditional ion-coupled reconnection is gradual as the reconnection domain size increases, with the ions becoming frozen-in in the exhaust when the magnetic island width in the normal direction reaches many ion inertial lengths. During this transition, the quasisteady reconnection rate decreases until the ions are fully coupled, ultimately reaching an asymptotic value. The scaling of the ion outflow velocity with the exhaust width during this electron-only to ion-coupled transition is found to be consistent with a theoretical model of a newly reconnected field line. In order to have a fully frozen-in ion exhaust with ion flows comparable to the reconnection Alfven speed, an exhaust width of at least several ion inertial lengths is needed. In turbulent systems with reconnection occurring between magnetic bubbles associated with fluctuations, using geometric arguments, we estimate that fully ion-coupled reconnection requires magnetic bubble length scales of at least several tens of ion inertial lengths.

Physical Sciences

Physics

Physics, Fluids & Plasmas

Science & Technology

Details

Title: Subtitle: Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence
Creators: P. Sharma Pyakurel - University of Delaware
M. A. Shay - University of Delaware
T. D. Phan - University of California, Berkeley
W. H. Matthaeus - University of Delaware
J. F. Drake - University of Maryland, College Park
J. M. TenBarge - Princeton University
C. C. Haggerty - University of Chicago
K. G. Klein - University of Arizona
P. A. Cassak - West Virginia University
T. N. Parashar - University of Delaware
M. Swisdak - University of Maryland, College Park
A. Chasapis - University of Delaware
Univ. of California, Oakland, CA (United States)
Resource Type: Journal article
Publication Details: Physics of plasmas, Vol.26(8), 082307
DOI: 10.1063/1.5090403
ISSN: 1070-664X
eISSN: 1089-7674
Publisher: AIP Publishing
Number of pages: 14
Grant note: 80NSSC18K015; NNX17AI25G; NNX14AC78G; NNX08A083G-MMS IDS / NASA; National Aeronautics & Space Administration (NASA) DE-AC02-05CH11231 / National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility National Science Foundation; National Science Foundation (NSF) AGS-1219382; AGS-1602769; AGS-1338944; AGS-1622306 / NSF; National Science Foundation (NSF)
Language: English
Date published: 08/01/2019
Academic Unit: Physics and Astronomy
Record Identifier: 9985224414402771

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