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Global-scale consequences of magnetic-helicity injection and condensation on the sun

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mackay2014astrophysicalj164.pdf (2.636Mb)
Date
01/04/2014
Author
Mackay, Duncan Hendry
DeVore, Rick
Antiochos, Spiro
Funder
Science & Technology Facilities Council
The Leverhulme Trust
Grant ID
ST/K000950/1
RPG-305
Keywords
Magnetic fields
Sun: activity
Sun: corona
QC Physics
BDC
Metadata
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Abstract
In the recent paper of Antiochos, a new concept for the injection of magnetic helicity into the solar corona by small-scale convective motions and its condensation onto polarity inversion lines (PILs) was been developed. We investigate this concept through global simulations of the Sun’s photospheric and coronal magnetic fields, and compare the results with the hemispheric pattern of solar filaments. Assuming that the vorticity of the cells is predominately counterclockwise/clockwise in the northern/southern hemisphere, the convective motions inject negative/positive helicity into each hemisphere. The simulations show that: (1) on a north–south oriented PIL, both differential rotation and convective motions inject the same sign of helicity, which matches that required to reproduce the hemispheric pattern of filaments. (2) On a high-latitude east–west oriented polar crown or subpolar crown PIL, the vorticity of the cells has to be approximately 2–3 times greater than the local differential-rotation gradient in order to overcome the incorrect sign of helicity injection from differential rotation. (3) In the declining phase of the cycle, as a bipole interacts with the polar field, in some cases, helicity condensation can reverse the effect of differential rotation along the east–west lead arm but not in all cases. The results show that this newly developed concept of magnetic helicity injection and condensation, in conjunction with the mechanisms used in Yeates et al., is a viable explanation for the hemispheric pattern of filaments. Future observational studies should focus on examining the vorticity component within convective motions to determine both its magnitude and latitudinal variation relative to the differential-rotation gradient on the Sun.
Citation
Mackay , D H , DeVore , R & Antiochos , S 2014 , ' Global-scale consequences of magnetic-helicity injection and condensation on the sun ' , Astrophysical Journal , vol. 784 , no. 2 , 164 . https://doi.org/10.1088/0004-637X/784/2/164
Publication
Astrophysical Journal
Status
Peer reviewed
DOI
https://doi.org/10.1088/0004-637X/784/2/164
ISSN
0004-637X
Type
Journal article
Rights
(C) Copyright 2014. The American Astronomical Society. All rights reserved.
Collections
  • University of St Andrews Research
URI
http://hdl.handle.net/10023/4735

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