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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. 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, themore » 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:
;  [1];  [2];  [3];  [4];  [5]
  1. Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States)
  2. Department of Physics and the Institute for Physical Science and Technology and the Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States)
  3. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO 80303 (United States)
  4. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
  5. Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
Publication Date:
OSTI Identifier:
22679751
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOUNDARY CONDITIONS; FORECASTING; MAGNETIC FIELDS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; SIMULATION; SOLAR WIND; SPACE VEHICLES; SUN; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Shepherd, L. S., Cassak, P. A., Drake, J. F., Gosling, J. T., Phan, T.-D., and Shay, M. A. Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA9066.
Shepherd, L. S., Cassak, P. A., Drake, J. F., Gosling, J. T., Phan, T.-D., & Shay, M. A. Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent. United States. doi:10.3847/1538-4357/AA9066.
Shepherd, L. S., Cassak, P. A., Drake, J. F., Gosling, J. T., Phan, T.-D., and Shay, M. A. Fri . "Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent". United States. doi:10.3847/1538-4357/AA9066.
@article{osti_22679751,
title = {Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent},
author = {Shepherd, L. S. and Cassak, P. A. and Drake, J. F. and Gosling, J. T. and Phan, T.-D. and Shay, M. A.},
abstractNote = {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. 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, 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.},
doi = {10.3847/1538-4357/AA9066},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 848,
place = {United States},
year = {2017},
month = {10}
}