Science development study for the Atacama Large Aperture Submillimeter Telescope (AtLAST): Solar and stellar observations.

Observations at (sub-)millimeter wavelengths offer a complementary perspective on our Sun and other stars, offering significant insights into both the thermal and magnetic composition of their chromospheres. Despite the fundamental progress in (sub-)millimeter observations of the Sun, some important aspects require diagnostic capabilities that are not offered by existing observatories. In particular, simultaneously observations of the radiation continuum across an extended frequency range would facilitate the mapping of different layers and thus ultimately the 3D structure of the solar atmosphere.

Partial ionization of plasma in solar prominences.

The plasma in cool cores of solar prominences is partially ionized and its ionization degree, in general, depends on the actual kinetic temperature and density of the plasma and the ions considered. However, we demonstrate that under typical prominence conditions, the dominant mechanism contributing to partial ionization is photoionization by radiation diffusing through the plasma. This mechanism strongly depends on the radiation illuminating prominences from the surrounding solar atmosphere.