Title: Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent

Abstract

We present quantitative predictions of the structure of reconnection exhausts in three-dimensional magnetic reconnection with an X-line of finite extent in the out-of-plane direction. Sasunov et al. showed that they have a tilted ribbon-like shape bounded by rotational discontinuities and tangential discontinuities. We show analytically and numerically that this prediction is largely correct. When there is an out-of-plane (guide) magnetic field, the presence of the upstream field that does not reconnect acts as a boundary condition in the normal direction, which forces the normal magnetic field to be zero outside the exhaust. This condition constrains the normal magnetic field inside the exhaust to be small. Thus, rather than the ribbon tilting in the inflow direction, the exhaust remains collimated in the normal direction and is forced to expand nearly completely in the out-of-plane direction. This exhaust structure is in stark contrast to the two-dimensional picture of reconnection, where reconnected flux expands in the normal direction. We present analytical predictions for the structure of the exhausts in terms of upstream conditions. Here, the predictions are confirmed using three-dimensional resistive-magnetohydrodynamic simulations with a finite-length X-line achieved using a localized (anomalous) resistivity. Implications to reconnection in the solar wind are discussed. In particular,more » the results can be used to estimate a lower bound for the extent of the X-line in the out-of-plane direction solely using single-spacecraft data taken downstream in the exhausts.« less

Authors:

Shepherd, L. S. ^[1]; Cassak, P. A.  ^[1];

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Drake, J. F.  ^[2];

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Gosling, J. T.  ^[3];

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Phan, T. -D. ^[4]; Shay, M. A.  ^[5]

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• Search DOE PAGES for ORCID "0000-0003-1861-4767"
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+ Show Author Affiliations

1. West Virginia Univ., Morgantown, WV (United States)
2. Univ. of Maryland, College Park, MD (United States)
3. Univ. of Colorado, Boulder, CO (United States)
4. Univ. of California, Berkeley, CA (United States)
5. Univ. of Delaware, Newark, DE (United States)

Publication Date:

2017-10-17

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1544051

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

The Astrophysical Journal (Online)

Additional Journal Information:

Journal Name: The Astrophysical Journal (Online); Journal Volume: 848; Journal Issue: 2; Journal ID: ISSN 1538-4357

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics; magnetic reconnection; magnetohydrodynamics (MHD); solar wind; Sun: flares