Emergence of small-scale magnetic flux in the quiet Sun, observed from the photosphere to the corona

by Ioannis Kontogiannis

Hosted by Leibniz-Institut für Astrophysik Potsdam (AIP) on June 20, 2019


We study the emergence and evolution of new magnetic flux in the vicinity of a quiet Sun network. We employ high-resolution spectropolarimetric, spectroscopic and spectral imaging observations from ground-based (Dutch Open Telescope) and space-born instruments (TRACE, Hinode, SoHO), which provided a multi-wavelength, tomographic view of the region from the photosphere up to the corona. Throughout its evolution, the region exhibited many of the phenomena revealed by recent simulations. The event starts with a series of granular-scale events, which follow the photospheric flow field and merge to form a small-scale magnetic flux system of the order of 1018 Mx. Spectropolarimetric inversions reveal an evolving, complicated pattern of horizontal and vertical magnetic field patches at the region between the main polarities. As the magnetic flux accumulates and the region expands, Doppler-shifted H-alpha absorption features appear above and at the crests of the structure, indicating an immediate interaction with the pre-existing, overlying magnetic field. Roughly 60 min after the region first emerged at the photosphere, a jet-like feature appeared in the chromosphere and a small soft X-ray bright point formed in the corona. The coronal brightening exhibited intense spatial and temporal variations and had a lifetime that exceeded one hour. EUV spectroscopy and DEM analysis revealed temperatures up to 106 K and densities up to 1010 cm-3. Even in the absence of a strong ambient magnetic field, small-scale magnetic flux emergence affects dramatically the dynamics and shape of the quiet Sun.