Single-dish solar imaging at high radio frequencies: SunDish &amp; Solaris Projects
Authors: Mulas Sara ,   SunDish and Solaris
Published: March 2024

The SunDish and Solaris projects are devoted to solar radio imaging and monitoring up to 100 GHz using existing INAF large radio telescopes in Italy, and smaller and flexible radio telescopes in development for polar regions. This powerful network can complement other existing ground-based and space-based facilities aimed at the direct monitoring of the solar atmosphere both for Heliophysics science and Space Weather awareness.The SunDish Project aims to map the brightness temperature of the solar atmosphere in the radio band to reveals plasma processes mostly originating from free-free emission in the local thermodynamic equilibrium, providing a probe of physical conditions in a wide range of atmospheric layers. In particular, long-term diachronic observations of the solar disk at high radio frequencies represents an effective tool to characterise the vertical structure and physical conditions of the solar chromosphere both for quiet and active regions during their evolution at different phases of the solar cycle. Within this context, the Medicina 32-m and SRT 64-m radiotescopes could have an important role in the international solar radio science panorama. After a first test campaign aimed at defining and optimising solar imaging requirements for the radio telescopes, the system is ready for systematic monitoring of the Sun to provide: (1) accurate measurement of the brightness temperature of the radio quiet Sun component, that has been poorly explored in the 20-26 GHz range to date, and representing a significant constraint for atmospheric models; (2) characterisation of the flux density, spectral properties and long-term evolution of dynamical features (active regions, coronal holes, loop systems, streamers and the coronal plateau). One of our future scientific goals is the comparison of our results with recently updated flare catalogs, based on GOES and AGILE data, in order to correlate our active regions data with the flares detections. The prediction of powerful flares through the detection of peculiar spectral variations in the active regions is a valuable forecasting probe for the Space Weather hazard network. For more information and early science results see: https://sites.google.com/inaf.it/sundishThe Solaris Project is a scientific and technological project aimed at the development of a smart Solar monitoring system at high radio frequencies based on innovative single-dish imaging techniques, recently approved as a permanent observatory in Antarctica. It combines the implementation of dedicated and interchangeable high-frequency receivers on existing small single-dish radio telescope systems (1.5/2.6-m class) available in our laboratories and in Antarctica, to be adapted for Solar observations. Operations in Antarctica will offer unique observing conditions (very low sky opacity and long Solar exposures) and unprecedented Solar monitoring in radio W-band (70-120 GHz). This opens for the identification and spectral analysis of active regions before, after and during the occurrence of Solar flares. For more information see: https://sites.google.com/inaf.it/solaris