Abstract
Abstract Interchange reconnection is thought to play an important role in driving the dynamics of the slow solar wind. To understand the details of this process, it is important to catalog the various magnetic structures that are present at the boundary between open and closed magnetic flux. To this end we have developed a numerical method for partitioning the coronal volume into individual flux domains using volume segmentation along layers of high magnetic squashing degree (Q). Our publicly available implementation of this method is able to identify the different magnetic structures within a coronal magnetic field model that define the open-closed boundary and comprise the so-called Separatrix-Web (S-Web). With this we test previous predictions of how different configurations of high-Q arcs within the S-Web are related to coronal magnetic field structures. Here we present our findings from a survey of 11 different potential field source surface models, spanning from 2008 to 2017, which offer a representative sample of the coronal magnetic field across nearly a complete solar cycle. Two key findings of our analysis are that (i) “vertex” structures—where arcs of the S-Web meet away from the heliospheric current sheet—are associated with underlying magnetic dome structures, and (ii) that any given arc of the S-Web is almost equally as likely to be formed by a narrow corridor of open flux (corresponding to a hyperbolic flux tube) as by the separatrix surface of a magnetic null. Together, these findings highlight the importance of a variety of topological configurations for future studies of interchange reconnection and the acceleration of the solar wind.
Highlights
Variations in the velocity, density, and composition of the Sun’s “slow” solar wind (SSW) suggest that it is formed by the release of plasma from the magnetically closed corona onto open field lines via interchange reconnection (Crooker et al 2002; Fisk 2003; Antiochos et al 2011; Abbo et al 2016)
The 10 remaining models are depicted in Figure 4, which shows the shape of the heliospheric current sheet (HCS) and myriad HQAs in each case
The method that we have developed for identifying structures within the magnetic field is heavily reliant on our ability to accurately resolve the shape of individual magnetic flux domains
Summary
Variations in the velocity, density, and composition of the Sun’s “slow” solar wind (SSW) suggest that it is formed by the release of plasma from the magnetically closed corona onto open field lines via interchange reconnection (Crooker et al 2002; Fisk 2003; Antiochos et al 2011; Abbo et al 2016) The viability of this mechanism has been explored in numerical experiments, which have yielded insights into both the latitudinal variation in wind speed (Higginson et al 2017) and the topological stability of structures at the boundary between closed flux domains and open field regions (Edmondson et al 2010), where the “fast” solar wind is thought to originate (Habbal et al 1997). The magnetic skeleton is useful for predicting sites of null point and separator reconnection; it is of limited use for predicting 3D reconnection in general, as 3D reconnection can occur in QSLs, away from null points and separators (Galsgaard et al.2003; Titov et al 2003; Aulanier et al 2005; Pontin et al 2005; Démoulin 2006; Janvier et al 2013)
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