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Magnetic Helicity Reversal in the Corona at Small Plasma Beta
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Max-Planck-Institut für Sonnensystemforschung, Germany.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Astronomy. University of Colorado, USA.
Number of Authors: 32018 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 869, no 1, article id 2Article in journal (Refereed) Published
Abstract [en]

Solar and stellar dynamos shed small-scale and large-scale magnetic helicity of opposite signs. However, solar wind observations and simulations have shown that some distance above the dynamo both the small-scale and large-scale magnetic helicities have reversed signs. With realistic simulations of the solar corona above an active region now being available, we have access to the magnetic field and current density along coronal loops. We show that a sign reversal in the horizontal averages of the magnetic helicity occurs when the local maximum of the plasma beta drops below unity and the field becomes nearly fully force free. Hence, this reversal is expected to occur well within the solar corona and would not directly be accessible to in situ measurements with the Parker Solar Probe or SolarOrbiter. We also show that the reversal is associated with subtle changes in the relative dominance of structures with positive and negative magnetic helicity.

Place, publisher, year, edition, pages
2018. Vol. 869, no 1, article id 2
Keywords [en]
dynamo, magnetohydrodynamics (MHD), methods: numerical, Sun: corona, Sun: magnetic fields, solar wind
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-163693DOI: 10.3847/1538-4357/aae97aISI: 000452440000002OAI: oai:DiVA.org:su-163693DiVA, id: diva2:1280271
Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-18Bibliographically approved

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Singh, Nishant K.Brandenburg, Axel
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Nordic Institute for Theoretical Physics (Nordita)Department of Astronomy
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