Whitepaper #124 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: solar physics.
Diagnostics of coronal and chromospheric magnetic fields have recently been developed that must be exploited in the next decade, including ultra-broadband radio imaging spectropolarimetry. To capitalize on these developments requires the superior broadband microwave imaging for which the Frequency Agile Solar Radiotelescope (FASR) has been strongly endorsed by several past decadal surveys.