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Abstract

Nanoflares, short bursts of energy release, provide a possible mechanism for heating the solar corona, particularly active region (AR) cores, to million-degree temperatures. The term "nanoflare" may refer to any impulsive release of energy (Klimchuk 2015), regardless of the underlying driver, whether that be reconnection, Alfvén waves, or some other mechanism. Several recent studies have shown that such bursty, time-dependent heating is consistent with observations of AR cores (e.g. Viall and Klimchuk, 2012; Brosius et al., 2014; Ishikawa et al., 2017). However, given the short timescales of these events and the difficulties of deriving observables from remote sensing data (e.g. uncertainties in atomic data, limited spectral coverage of instruments, line-of-sight integration) a conclusive detection of such events has proved difficult (see Winebarger et al., 2012).

While nanoflares have been studied primarily in coronal loops in closed-field ARs, they may also play a role in heating and accelerating the slow solar wind. Several workers (Liewer et al., 2004; Sakao et al., 2007) have shown that open field regions in or at the edges of ARs are a likely source of the slow solar wind, suggesting that these slow-wind streamers may be recently-opened field previously rooted in ARs and thus contain plasma heated in these ARs. Additionally, Baker et al. (2009) showed that AR outflows occur in the vicinity of quasi-separatrix layers, suggesting that reconnection at these sites is a possible driver for the slow solar wind. Furthermore, Bradshaw et al. (2011) modeled the plasma response to a rarefaction wave driven by interchange reconnection at the boundary between open and closed field in ARs. Their results were consistent with observations and suggested that such a mechanism could be responsible for driving the slow solar wind from ARs. This gives rise to two primary questions: 1. What role does the closed field in ARs (i.e. coronal loops) play in the source and acceleration of the slow solar wind? and 2. Do observable signatures of AR heating persist in the slow solar wind plasma?

One of the main goals of this session is to foster discussions between researchers focused on the low, closed-field corona and the solar wind/heliosphere community. In particular, we want to discuss how best to coordinate remote-sensing and in-situ observations in order to understand connections between closed-field coronal loops and solar wind streamers. Data from instruments like Wind and ACE could hold signatures of heating in AR cores not accessible via remote sensing observations. Similarly, remote sensing observations and modeling of time-dependent heating in AR cores could help in understanding slow solar wind variability.

This session will continue discussions began in the 2016 SHINE sessions "Outstanding Challenges in Understanding the Heating of the Solar Corona and Solar Wind" and "Why is the slow solar wind so variable?" with an emphasis on attracting speakers and participants outside of the typical solar wind/heliosphere community, e.g. those in the coronal loops community.