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Title: Helicity transformation under the collision and merging of two magnetic flux ropes

Magnetic helicity has become a useful tool in the analysis of astrophysical plasmas. Its conservation in the magnetohydrodynamic limit (and other fluid approaches) constrains the global behavior of large plasma structures. One such astrophysical structure is a magnetic flux rope: a tube-like, current-carrying plasma embedded in an external magnetic field. Bundles of these ropes are commonly observed in the near-earth environment and solar atmosphere. In this well-diagnosed experiment (three-dimensional measurements of n e, T e, V p, B, J, E, and u flow), two magnetic flux ropes are generated in the Large Plasma Device at UCLA. These ropes are driven kink-unstable to trigger complex motion. As they interact, helicity conservation is examined in regions of reconnection. We examine (1) the transport of helicity and (2) the dissipation of the helicity. As the ropes move and the topology of the field lines diverge, a quasi-separatrix layer (QSL) is formed. As the QSL forms, magnetic helicity is dissipated within this region. Here, at the same time, there is an influx of canonical helicity into the region such that the temporal derivative of magnetic helicity is zero
Authors:
 [1] ; ORCiD logo [1]
  1. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Grant/Contract Number:
FC02-07ER54918
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 7; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1474289
Alternate Identifier(s):
OSTI ID: 1367936

DeHaas, Timothy, and Gekelman, Walter. Helicity transformation under the collision and merging of two magnetic flux ropes. United States: N. p., Web. doi:10.1063/1.4991413.
DeHaas, Timothy, & Gekelman, Walter. Helicity transformation under the collision and merging of two magnetic flux ropes. United States. doi:10.1063/1.4991413.
DeHaas, Timothy, and Gekelman, Walter. 2017. "Helicity transformation under the collision and merging of two magnetic flux ropes". United States. doi:10.1063/1.4991413. https://www.osti.gov/servlets/purl/1474289.
@article{osti_1474289,
title = {Helicity transformation under the collision and merging of two magnetic flux ropes},
author = {DeHaas, Timothy and Gekelman, Walter},
abstractNote = {Magnetic helicity has become a useful tool in the analysis of astrophysical plasmas. Its conservation in the magnetohydrodynamic limit (and other fluid approaches) constrains the global behavior of large plasma structures. One such astrophysical structure is a magnetic flux rope: a tube-like, current-carrying plasma embedded in an external magnetic field. Bundles of these ropes are commonly observed in the near-earth environment and solar atmosphere. In this well-diagnosed experiment (three-dimensional measurements of ne, Te, Vp, B, J, E, and uflow), two magnetic flux ropes are generated in the Large Plasma Device at UCLA. These ropes are driven kink-unstable to trigger complex motion. As they interact, helicity conservation is examined in regions of reconnection. We examine (1) the transport of helicity and (2) the dissipation of the helicity. As the ropes move and the topology of the field lines diverge, a quasi-separatrix layer (QSL) is formed. As the QSL forms, magnetic helicity is dissipated within this region. Here, at the same time, there is an influx of canonical helicity into the region such that the temporal derivative of magnetic helicity is zero},
doi = {10.1063/1.4991413},
journal = {Physics of Plasmas},
number = 7,
volume = 24,
place = {United States},
year = {2017},
month = {7}
}