A nonpotential model for the Sun's open magnetic flux

Yeates, A.R.; Mackay, D.H.; van Ballegooijen, A.A.; Constable, J.A.

Abstract

[1] Measurements of the interplanetary magnetic field (IMF) over several solar cycles do not agree with computed values of open magnetic flux from potential field extrapolations. The discrepancy becomes greater around solar maximum in each cycle when the IMF can be twice as strong as predicted by the potential field model. Here we demonstrate that this discrepancy may be resolved by allowing for electric currents in the low corona (below 2.5R⊙). We present a quasi-static numerical model of the large-scale coronal magnetic evolution, which systematically produces these currents through flux emergence and shearing by surface motions. The open flux is increased by 75%–85% at solar maximum, but only 25% at solar minimum, bringing it in line with estimates from IMF measurements. The additional open flux in the nonpotential model arises through inflation of the magnetic field by electric currents, with superimposed fluctuations due to coronal mass ejections. The latter are modeled by the self-consistent ejection of twisted magnetic flux ropes.

Citation

Yeates, A., Mackay, D., van Ballegooijen, A., & Constable, J. (2010). A nonpotential model for the Sun's open magnetic flux. Journal of Geophysical Research: Space Physics, 115(A9), https://doi.org/10.1029/2010ja015611

• Journal Article Type: Article
• Acceptance Date: Jun 23, 2010
• Publication Date: Sep 29, 2010
• Deposit Date: Oct 17, 2011
• Publicly Available Date: Apr 29, 2015
• Journal: Journal of Geophysical Research: Space Physics
• Print ISSN: 2169-9402
• Electronic ISSN: 2169-9402
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 115
• Issue: A9
• DOI: https://doi.org/10.1029/2010ja015611
• Keywords: Open flux, Solar magnetic field, Solar activity cycle, Interplanetary magnetic field, Electric currents.
• Public URL: https://durham-repository.worktribe.com/output/1504678