Magnetic heating in the solar atmosphere takes many forms, from large-scale flares to small-scale bursts. A post written by Dr. Smitha Narayanamurthy, from Max-Planck Institute for Solar System Research (Germany).
The solar chromosphere is the thin layer appearing reddish in color during a total solar eclipse. This layer lies in between the cool photosphere and the million degree corona. The chromosphere loses energy through radiation, thus it needs to be continually replenished. Observations of the chromosphere reveal a variety of dynamic events such as slender fibrils, compact ultra-violet (UV) bursts showing up as intense brightenings and jets of plasma releasing bursts of energy. All these events can be associated with chromospheric heating. Realistic computer simulations reveal that these events are likely triggered by the reconnection of magnetic field.
To gain more insight into the physical processes driving these bursts of energy, we require observations with high spatial and temporal resolutions. In 2013, the balloon-borne telescope SUNRISE recorded images of the solar chromosphere at a resolution of 0.1" which corresponds to a spatial scale of roughly 70 km on the Sun with a cadence of 7s. The observations were carried out in the Ca II H spectral line at a wavelength of 397 nm. During this flight, SUNRISE captured the fine details of the UV burst shown in the movie. The burst is composed of an extended ribbon-like feature and rapidly evolving thin loop-like strands. Similar features are often observed in large-scale flares on the Sun. This hints at a unified picture of magnetic heating in the solar atmosphere from large-scale flares to small-scale bursts.
The European Solar Telescope with its high spatio-temporal resolution will be able to resolve many more bursts like this to help us probe deeper into their fine structure, understand the role of the magnetic field, and to build up statistics for the unified picture.
More details about this topic can be found in Smitha et al. 2018, A&A, 617, A128.