Title: The physical foundation of the reconnection electric field

Abstract

Magnetic reconnection is a key charged particle transport and energy conversion process in environments ranging from astrophysical systems to laboratory plasmas [Yamada et al., Rev. Mod. Phys. 82, 603–664 (2010)]. Magnetic reconnection facilitates plasma transport by establishing new connections of magnetic flux tubes, and it converts, often explosively, energy stored in the magnetic field to kinetic energy of charged particles [J. L. Burch and J. F. Drake, Am. Sci. 97, 392–299 (2009)]. The intensity of the magnetic reconnection process is measured by the reconnection electric field, which regulates the rate of flux tube connectivity changes. The change of magnetic connectivity occurs in the current layer of the diffusion zone, where the plasma transport is decoupled from the transport of magnetic flux. Here we report on computer simulations and analytic theory to provide a self-consistent understanding of the role of the reconnection electric field, which extends substantially beyond the simple change of magnetic connections. Rather, we find that the reconnection electric field is essential to maintain the current density in the diffusion region, which would otherwise be dissipated by a set of processes. Natural candidates for current dissipation are the average convection of current carriers away from the reconnection region bymore » the outflow of accelerated particles, or the average rotation of the current density by the magnetic field reversal in the vicinity. Instead, we show here that the current dissipation is the result of thermal effects, underlying the statistical interaction of current-carrying particles with the adjacent magnetic field. We find that this interaction serves to redirect the directed acceleration of the reconnection electric field to thermal motion. This thermalization manifests itself in form of quasi-viscous terms in the thermal energy balance of the current layer. This collisionless viscosity, found in the pressure evolution equation, dominates near the x-line. These quasi-viscous terms act to increase the average thermal energy. Our predictions regarding current and thermal energy balance are readily amenable to exploration in the laboratory or by satellite missions, in particular, by NASA's Magnetospheric Multiscale mission.« less

Authors:

Hesse, M.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0377-9673"

Liu, Y. -H. ^[2]; Chen, L. -J. ^[3]; Bessho, N. ^[3]; Wang, S. ^[3]; Burch, J. L. ^[4]; Moretto, T. ^[5]; Norgren, C. ^[5]; Genestreti, K. J.  ^[6];

• Search DOE PAGES for author "Genestreti, K. J."
• Search DOE PAGES for ORCID "0000-0001-6890-2973"

Phan, T. D. ^[7]; Tenfjord, P. ^[5]

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+ Show Author Affiliations

1. Bergen Univ. (Norway); Southwest Research Inst. (SwRI), San Antonio, TX (United States)
2. Dartmouth College, Hanover, NH (United States)
3. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
4. Southwest Research Inst. (SwRI), San Antonio, TX (United States)
5. Bergen Univ. (Norway)
6. Space Research Institute, Austrian Academy of Sciences, Graz (Austria)
7. Univ. of California, Berkeley, CA (United States)

Publication Date:

Thu Mar 01 00:00:00 EST 2018

Research Org.:

Univ. of Maryland, College Park, MD (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1499376

Grant/Contract Number:  

SC0016278

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 25; Journal Issue: 3; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY