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Magnetic Helicity Reversal in the Corona at Small Plasma Beta
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
2018 (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
Institute of Physics Publishing , 2018. Vol. 869, no 1, article id 2
Keywords [en]
dynamo, magnetohydrodynamics (MHD), methods: numerical, solar wind, Sun: corona, Sun: magnetic fields
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-246997DOI: 10.3847/1538-4357/aae97aISI: 000452440000002Scopus ID: 2-s2.0-85058436979OAI: oai:DiVA.org:kth-246997DiVA, id: diva2:1330966
Note

QC 20190626

Available from: 2019-06-26 Created: 2019-06-26 Last updated: 2019-06-26Bibliographically approved

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Singh, Nishant K.Brandenburg, Axel

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