Chromospheric heating by flux emergence (1/2)

Swedish 1-m Solar Telescope

Observations reveal that the solar chromosphere radiates more energy than it absorbs in areas where the magnetic field is strong. The origin of this surplus energy must be in the photosphere or below. Physical processes involved in transporting this energy to the chromosphere, and the dissipation there, are made more efficient by the presence of magnetic fields. However, the precise role of the various processes is not known. 

The image shows the lower part of the chromosphere observed in the wing of the Ca II K line at the highest spatial resolution available today. The target is an active region where new magnetic flux is emerging into the surface of the Sun. One can see many small scale (bright) reconnection events at the foot-points of magnetic loops and long threaded features where the magnetic field is more horizontal.

The observations were acquired by the Institute for Solar Physics (Stockholm University) at the Swedish 1-m Solar Telescope on La Palma (Spain) with the CHROMIS and CRISP imaging spectropolarimeters. They allowed us to conclude that the heating of this active region primarily is from locations with large scale horizontal magnetic field in the chromosphere, and not at locations of the brightest magnetic reconnection events where the magnetic field is more vertical.

Image credit: Jaime de la Cruz Rodríguez (ISP/Stockholm)

Publication: Leenaarts et al., 2018, A&A, 612, A28