English: Here we see the Sun's mid-atmosphere, the Chromosphere, face on. These observations are targeting a region of moderate magnetic activity. The inner blue-wing of the Ca II K 393.4 nm line is imaged with a 13 nanometer bandpass using the CHROMIS double Fabry–Pérot instrument at the Swedish 1-meter Solar Telescope on the 25th of May, 2017.

The darker regions feature an hydrodynamic web-like pattern known as "reverse granulation" with a contribution from propagating bright shock-fronts. In between these areas, clusters of bright points can be seen where bright arching fibrils seem to be anchored on. These fibrils are elongated and very slender when imaged in this wavelength, as slender as 0.1 arcsec or less than 75 km wide in this image. This is how finely we can observe the chromosphere of the Sun as of early 2020.

Observations such as these help us understand the most complex region of the solar atmosphere and how mass and energy are transported between the surface of the Sun and the multi-million degree Corona.

Vasco Henriques and Ainar Drews (ITA, University of Oslo)