Magnetic Structures at the Boundary of the Closed Corona: Interpretation of S-Web Arcs

Scott, Roger B.; Pontin, David I.; Yeates, Anthony R.; Wyper, Peter F.; Higginson, Aleida K.

Abstract

The topology of coronal magnetic fields near the open-closed magnetic flux boundary is important to the the process of interchange reconnection, whereby plasma is exchanged between open and closed flux domains. Maps of the magnetic squashing factor in coronal field models reveal the presence of the Separatrix-Web (S-Web), a network of separatrix surfaces and quasi-separatrix layers, along which interchange reconnection is highly likely. Under certain configurations, interchange reconnection within the S-Web could potentially release coronal material from the closed magnetic field regions to high-latitude regions far from the heliospheric current sheet, where it is observed as slow solar wind. It has also been suggested that transport along the S-Web may be a possible cause for the observed large longitudinal spreads of some impulsive, 3He-rich solar energetic particle events. Here, we demonstrate that certain features of the S-Web reveal structural aspects of the underlying magnetic field, specifically regarding the arcing bands of highly squashed magnetic flux observed at the outer boundary of global magnetic field models. In order for these S-Web arcs to terminate or intersect away from the helmet streamer apex, there must be a null spine line that maps a finite segment of the photospheric open-closed boundary up to a singular point in the open flux domain. We propose that this association between null spine lines and arc termination points may be used to identify locations in the heliosphere that are preferential for the appearance of solar energetic particles and plasma from the closed corona, with characteristics that may inform our understanding of interchange reconnection and the acceleration of the slow solar wind.

Citation

Scott, R. B., Pontin, D. I., Yeates, A. R., Wyper, P. F., & Higginson, A. K. (2018). Magnetic Structures at the Boundary of the Closed Corona: Interpretation of S-Web Arcs. Astrophysical Journal, 869(1), Article 60. https://doi.org/10.3847/1538-4357/aaed2b

• Journal Article Type: Article
• Acceptance Date: Oct 23, 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
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 869
• Issue: 1
• Article Number: 60
• DOI: https://doi.org/10.3847/1538-4357/aaed2b
• Public URL: https://durham-repository.worktribe.com/output/1306818