The Formation of Magnetic Depletions and Flux Annihilation Due to Reconnection in the Heliosheath
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Drake-2017-The Formation of Magnetic Depletion.pdf
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Author(s)
Drake, J. F.
Swisdak, M.
Opher, M.
Richardson, John D.
Date Issued
March 2017
Journal
Astrophysical Journal
Publisher
IOP Publishing
Citation
Drake, J. F.; Swisdak, M.; Opher, M. and Richardson, J. D. “The Formation of Magnetic Depletions and Flux Annihilation Due to Reconnection in the Heliosheath.” The Astrophysical Journal 837, no. 2 (March 2017): 159 © 2017 The American Astronomical Society
Version
Final published version
Abstract
The misalignment of the solar rotation axis and the magnetic axis of the Sun produces a periodic reversal of the Parker spiral magnetic field and the sectored solar wind. The compression of the sectors is expected to lead to reconnection in the heliosheath (HS). We present particle-in-cell simulations of the sectored HS that reflect the plasma environment along the Voyager 1 and 2 trajectories, specifically including unequal positive and negative azimuthal magnetic flux as seen in the Voyager data. Reconnection proceeds on individual current sheets until islands on adjacent current layers merge. At late time, bands of the dominant flux survive, separated by bands of deep magnetic field depletion. The ambient plasma pressure supports the strong magnetic pressure variation so that pressure is anticorrelated with magnetic field strength. There is little variation in the magnetic field direction across the boundaries of the magnetic depressions. At irregular intervals within the magnetic depressions are long-lived pairs of magnetic islands where the magnetic field direction reverses so that spacecraft data would reveal sharp magnetic field depressions with only occasional crossings with jumps in magnetic field direction. This is typical of the magnetic field data from the Voyager spacecraft. Voyager 2 data reveal that fluctuations in the density and magnetic field strength are anticorrelated in the sector zone, as expected from reconnection, but not in unipolar regions. The consequence of the annihilation of subdominant flux is a sharp reduction in the number of sectors and a loss in magnetic flux, as documented from the Voyager 1 magnetic field and flow data.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/1538-4357/aa6304
