Formation of current sheets in magnetohydrostatic atmospheres (MHS)

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It is demonstrated that a 2-D magnetic field configuration in a magnetohydrostatic equilibrium without any null point can be deformed into a configuration with current sheets, i.e., tangential discontinuities, either by temperature change or by footpoint displacement. The magnetohydrostatic solutions by Low, which have a quadrupolar field geometry, are chosen as our initial configurations. When the whole atmosphere is uniformly heated, the expansion of plasma is more effective in the outer flux tubes than in the inner ones. The expanding plasma pushes out the field lines in each bipolar region so that a current sheet of a finite length is ... continued below

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Choe, G.S. & Cheng, C.Z. December 31, 1996.

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It is demonstrated that a 2-D magnetic field configuration in a magnetohydrostatic equilibrium without any null point can be deformed into a configuration with current sheets, i.e., tangential discontinuities, either by temperature change or by footpoint displacement. The magnetohydrostatic solutions by Low, which have a quadrupolar field geometry, are chosen as our initial configurations. When the whole atmosphere is uniformly heated, the expansion of plasma is more effective in the outer flux tubes than in the inner ones. The expanding plasma pushes out the field lines in each bipolar region so that a current sheet of a finite length is formed where the lines from each region come into contact. The resulting pressure profile at the base has pressure maxima at the center of each bipolar regions. The smooth equilibrium solution with the same pressure distribution contains and X-point. If the pressure is initially higher in the outer tubes than in the inner ones, cooling of the atmosphere can also lead to current sheet formation. As the pressure scale height decreases by cooling, the magnetic field pressure dominates the plasma pressure in the upper part of the flux tubes. The subsequent expansion of field lines creates a tangential discontinuity. If resistivity is considered in this weak equilibrium state, magnetic reconnection results in a new Kippenhahn-Sch{umlt u}ITER type field configuration with a magnetic island. It is expected that a prominence can stably reside within the magnetic island. When the field footpoints undergo a shearing motion with a continuous shearing profile, a current sheet can be reformed beyond a critical amount of shear. Our results suggest that the formation of a current sheet and the subsequent magnetic reconnection can be ubiquitous in the solar atmosphere. The resulting field configurations are quite favorable for prominence formation.

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25 p.

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OSTI as DE97005292

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  • Fall meeting of the American Geophysical Union, San Francisco, CA (United States), 9-13 Dec 1996

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  • Other: DE97005292
  • Report No.: CONF-961203--1
  • Grant Number: AC02-76CH03073
  • Office of Scientific & Technical Information Report Number: 468501
  • Archival Resource Key: ark:/67531/metadc674232

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  • December 31, 1996

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  • July 25, 2015, 2:21 a.m.

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  • April 15, 2016, 5:32 p.m.

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Choe, G.S. & Cheng, C.Z. Formation of current sheets in magnetohydrostatic atmospheres (MHS), article, December 31, 1996; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc674232/: accessed June 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.