Chromospheric diagnostics with ALMA

Costas Alissandrakis, University of Ioannina

We are well in the ALMA era, as far a solar mm-λ astronomy is concerned. Arc-second resolution images, with a 1-2 sec cadence, as well as high quality, low resolution, full disk images are accumulating, starting with the commissioning period of December 2015 and extending over three cycles of solar observations so far. A variety of chromospheric structures, from spicules to sunspots, has been observed, as well as some dynamic phenomena. In this review I will focus on the information on the physical parameters of the solar chromosphere that ALMA images provide, exploiting the basic advantage of radio observations, that of simple diagnostics of thermal plasmas. I will summarize results obtained so far and will attempt an extrapolation to the future.