AUTHOR=Loukitcheva Maria , Reardon Kevin P. 

TITLE=First looks at solar active regions with ALMA

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2022.1025368

DOI=10.3389/fspas.2022.1025368

ISSN=2296-987X

ABSTRACT=During the first few years of observing the Sun with the Atacama Large Millimeter/submillimeter
4 Array (ALMA), the scientific community has acquired a number of observational datasets targeting
5 various structures in active regions, including sunspot umbra and penumbra, active region pores,
6 and plages. In this paper we review the results obtained from the extensive analysis of these
7 interferometric millimeter data, together with the coordinated observations from IRIS, SDO, IBIS,
8 and Hinode, that reveal information on the chromospheric thermal structure above active regions
9 and properties of small-scale heating events near magnetic field concentrations. We discuss the
10 properties of waves (especially the three-minute oscillations) in sunspots, plage, and network. We
11 speculate how high-resolution millimeter data can supplement spectral line observations in the
12 visible and UV and can improve chromospheric spectroscopic inversions. We identify challenges
13 in the interpretation of the millimeter continuum emission due to the complex, non-local and
14 time-dependent processes that determine the electron density through the chromosphere. Finally
15 we overview the prospects for future active regions observations with ALMA during the ascending
16 phase of the solar cycle.