期刊
ASTROPHYSICAL JOURNAL
卷 848, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aa9066
关键词
magnetic reconnection; magnetohydrodynamics (MHD); solar wind; Sun: flares
资金
- Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]
- NASA EPSCoR RID Augmentation grant program, NSF [PHY-0902479, AGS-0953463, AGS-1460037]
- NASA [NNX10AN08A, NNX16AF75G]
- NSF [AGS-1219382]
- International Space Science Institute, Bern
- Directorate For Geosciences [1460037] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences [1460037] Funding Source: National Science Foundation
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.
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