THE STORAGE AND DISSIPATION OF MAGNETIC ENERGY IN THE QUIET SUN CORONA DETERMINED FROM SDO /HMI MAGNETOGRAMS

Abstract

In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona.

Energy and helicity budgets of solar quiet regions

“…Free magnetic energy, released in the network mainly by reconnection, can fuel the dynamics of several smallscale structures, such as mottles/spicules, which reside there and are governed by the dynamics and physics of the network magnetic field (see the review by Tsiropoula et al 2012, for further details). Free magnetic energy release from nonpotential magnetic configurations in the quiet Sun has also been reported to result in small-scale structures, such as bright points (Zhao et al 2009), blinkers (Woodard & Chae 1999) and quiet-Sun corona nanoflares (Meyer et al 2013). There are no reports in the literature concerning the accumulation and expulsion of relative magnetic helicity in the magnetic network and quiet-Sun regions in general and this mechanism's role in quiet-Sun dynamics; only Zhao et al (2009) have investigated current helicity budgets in A&A 564, A86 (2014) network bright points.…”

The emergence of braided magnetic fields

“…This pattern appears across a range of scales, from the 'salt and pepper' fields of the quiet Sun (e.g. Meyer et al 2013) to full active regions that can be hundreds of megametres in length. Despite a certain amount of self-similarity across the length scales, including the eruptive capabilities of smaller ephemeral regions (Schrijver 2010), it is generally believed that the processes which create large active regions are different to those of smaller regions.…”

Dynamic Flaring Non-Potential Fields on Quiet Sun Network Scales

“…It is even plausable to extend the notion of self-similar non-potentiality as a possible driving force behind nanoflares. If the free magnetic energy of the currently unresolved magnetic environment in QS conditions is sufficient for flaring non-potential fields, as seen here by AIA, then it may also be able to explain small-scale, impulsive nanoflare events (Meyer et al 2013). As such, an important implication of the identification of these events could be the ability of these QS-like, supergranular network-scale flaring non-potential fields to help constrain the power-law distribution of solar energetic events at lower temperatures (Aschwanden 2008).…”

“…The local magnetic field environment is a fundamental driver of plasma dynamics in the solar atmosphere (Meyer et al 2013). Thus, it is important to consider the evolution of the photospheric magnetic field underlying these transient flaring QS-like non-potential fields.…”