Dynamics of Coronal-Hole Boundaries

• Main Authors: Higginson, A. K, Antiochos, S. K, DeVore, C. R, Wyper, P. F, Zurbuchen, T. H
• Format: Journal Article
• Language: English
• Published: 24-05-2017
• Subjects: Physics - Solar and Stellar Astrophysics; Physics - Space Physics
• DOI: 10.48550/arxiv.1611.04968

The Astrophysical Journal. 837 (2017) 113 Remote and in-situ observations strongly imply that the slow solar wind
consists of plasma from the hot, closed-field corona that is released onto open
magnetic field lines. The Separatrix Web (S-Web) theory for the slow wind
proposes that photospheric motions, at the scale of supergranules, are
responsible for generating dynamics at coronal-hole boundaries, which result in
the closed plasma release. We use three-dimensional magnetohydrodynamic (3D
MHD) simulations to determine the effect of photospheric flows on the open and
closed magnetic flux of a model corona with a dipole magnetic field and an
isothermal solar wind. A rotational surface motion is used to approximate
photospheric supergranular driving and is applied at the boundary between the
coronal hole and helmet streamer. The resulting dynamics consist primarily of
prolific and efficient interchange reconnection between open and closed flux.
Magnetic flux near the coronal-hole boundary experiences multiple interchange
events, with some flux interchanging over fifty times in one day. Additionally,
we find that the interchange reconnection occurs all along the coronal-hole
boundary, even producing a lasting change in magnetic-field connectivity in
regions that were not driven by the applied motions. Our results show that
these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the
implications of our simulations for understanding the observed properties of
the slow solar wind, with particular focus on the global-scale consequences of
interchange reconnection.