Duncan H. Mackay
Magnetic Helicity Condensation and the Solar Cycle
Mackay, Duncan H.; DeVore, C. Richard; Antiochos, Spiro K.; Yeates, Anthony R.
Authors
Abstract
Solar filaments exhibit a global chirality pattern where dextral/sinistral filaments, corresponding to negative/positive magnetic helicity, are dominant in the northern/southern hemisphere. This pattern is opposite to the sign of magnetic helicity injected by differential rotation along east–west oriented polarity inversion lines, posing a major conundrum for solar physics. A resolution of this problem is offered by the magnetic helicity-condensation model of Antiochos. To investigate the global consequences of helicity condensation for the hemispheric chirality pattern, we apply a temporally and spatially averaged statistical approximation of helicity condensation. Realistic magnetic field configurations in both the rising and declining phases of the solar cycle are simulated. For the helicity-condensation process, we assume convective cells consisting of positive/negative vorticities in the northern/southern hemisphere that inject negative/positive helicity. The magnitude of the vorticity is varied as a free parameter, corresponding to different rates of helicity injection. To reproduce the observed percentages of dominant and minority filament chiralities, we find that a vorticity of magnitude 2.5 × 10−6 s−1 is required. This rate, however, is insufficient to produce the observed unimodal profile of chirality with latitude. To achieve this, a vorticity of at least 5 × 10−6 s−1 is needed. Our results place a lower limit on the small-scale helicity injection required to dominate differential rotation and reproduce the observed hemispheric pattern. Future studies should aim to establish whether the helicity injection rate due to convective flows and/or flux emergence across all latitudes of the Sun is consistent with our results.
Journal Article Type | Article |
---|---|
Acceptance Date | Oct 25, 2018 |
Online Publication Date | Dec 12, 2018 |
Publication Date | Dec 12, 2018 |
Deposit Date | Dec 14, 2018 |
Publicly Available Date | Jan 8, 2019 |
Journal | Astrophysical Journal |
Print ISSN | 0004-637X |
Publisher | American Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 869 |
Issue | 1 |
Article Number | 62 |
DOI | https://doi.org/10.3847/1538-4357/aaec7c |
Public URL | https://durham-repository.worktribe.com/output/1311685 |
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© 2018. The American Astronomical Society. All rights reserved
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