Bombs and flares at the Surface and Lower Atmosphere of the Sun

A spectacular manifestation of solar activity, is the appearance of transient brightenings in the far wings of the H(alpha) line, originally known as "Hydrogen bombs” but now as "Ellerman bombs" (EBs) after their discoverer. Recent observations obtained by the Interface Region Imaging Spectrograph (IRIS) have revealed another type of plasma ``bombs'' (UV bursts) with high temperatures of perhaps up to 80 000 K within the cooler lower solar atmosphere. Realistic numerical modeling showing such events is needed to explain their nature. Here, we report on 3D radiative magneto-hydrodynamic simulations of magnetic flux emergence in the solar atmosphere. We find that ubiquitous reconnection between emerging bipolar magnetic fields can trigger EBs in the photosphere, UV bursts in the mid/low chromosphere and small (nano-/micro-) flares (1 MK) in the upper chromosphere. These results provide new insights on the emergence and build up of the coronal magnetic field, the formation of coronal loops, and the dynamics and heating of the solar surface and lower atmosphere.

18/05/2017 - 12:30
Prof. Viggo Hansteen
Institute for Theoretical Astrophysics, University of Oslo & IAA-CSIC