Magnetic Helicity Reversal in the Corona at Small Plasma Beta

Author
Keywords
Abstract
<p>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.</p>
Year of Publication
2018
Journal
The Astrophysical Journal
Volume
869
Number of Pages
2
Date Published
12/2018
URL
http://stacks.iop.org/0004-637X/869/i=1/a=2?key=crossref.90fa7f41d90e2c8b57f8248c0437cc6b
DOI
10.3847/1538-4357/aae97a