astrobites | Daily Paper Summaries | 2019 Apr 29
Ellis Avallone wrote:
The coronal heating problem is one of the biggest unsolved mysteries in solar physics. The solar corona is the region of the Sun’s atmosphere that extends past the surface – or photosphere – of the Sun. It is a diffuse cloud of plasma that is heated to temperatures several hundred times that of the photosphere, which isn’t what you’d expect as you move further away from a hot object. The coronal heating problem has been hotly debated since the 1940s and is thought to be related to the Sun’s magnetic field. However, no theory has yet been able to explain why the corona is so much hotter than the photosphere, and the possibility remains that multiple processes may be at work.
To study coronal heating, solar physicists use various structures that operate on smaller scales. The authors of today’s paper focus on the heating processes of coronal loops, which occur when plasma in the corona flows along the solar magnetic field (Figure 2). Coronal loops are rooted in strong concentrations of magnetic field such as sunspots – dark patches in the solar photosphere. Sunspots are composed of two regions, a dark umbra and a surrounding penumbra (Figure 3), that are surrounded by a bright region called a plage. Understanding how coronal loops are linked to their sunspot footprints and the surrounding magnetic field is critical to determining the heating mechanisms at work. ...
New Evidence that Magnetoconvection Drives Solar–Stellar Coronal Heating ~ Sanjiv K. Tiwari et al