Global Coronal Equilibria with Solar Wind Outflow

Rice, Oliver E.K.; Yeates, Anthony R.

Abstract

Given a known radial magnetic field distribution on the Sun’s photospheric surface, there exist wellestablished methods for computing a potential magnetic field in the corona above. Such potential fields are routinely used as input to solar wind models, and to initialize magneto-frictional or full magnetohydrodynamic simulations of the coronal and heliospheric magnetic fields. We describe an improved magnetic field model which calculates a magneto-frictional equilibrium with an imposed solar wind profile (which can be Parker’s solar wind solution, or any reasonable equivalent). These ‘outflow fields’ appear to approximate the real coronal magnetic field more closely than a potential field, take a similar time to compute, and avoid the need to impose an artificial source surface. Thus they provide a practical alternative to the potential field model for initializing time-evolving simulations or modeling the heliospheric magnetic field. We give an open-source Python implementation in spherical coordinates and apply the model to data from Solar Cycle 24. The outflow tends to increase the open magnetic flux compared to the potential field model, reducing the well known discrepancy with in situ observations.

Citation

Rice, O. E., & Yeates, A. R. (2021). Global Coronal Equilibria with Solar Wind Outflow. Astrophysical Journal, 923(1), Article 57. https://doi.org/10.3847/1538-4357/ac2c71

• Journal Article Type: Article
• Acceptance Date: Sep 30, 2021
• Online Publication Date: Dec 10, 2021
• Publication Date: Dec 10, 2021
• Deposit Date: Oct 4, 2021
• Publicly Available Date: Jan 18, 2022
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 923
• Issue: 1
• Article Number: 57
• DOI: https://doi.org/10.3847/1538-4357/ac2c71
• Public URL: https://durham-repository.worktribe.com/output/1234523