EOVSA Full-Disk Imaging of the Sun at Microwave Frequencies: Techniques and Updates

Abstract:

The Expanded Owens Valley Solar Array (EOVSA), which consists of thirteen 2.1-meter antennas, is a recently commissioned radio interferometer dedicated to solar observing. It provides daily observations of the full solar disk in the microwave range 1–18 GHz, with up to 451 frequency channels at 1-s time cadence. Despite the small number of antennas, spectral imaging of the full solar disk can be achieved by taking advantage of the Earth-rotation synthesis technique to integrate the visibilities over an entire day (typically 8 hours) to improve the uv coverage. Here we discuss techniques and recent updates to our full-disk imaging pipeline, with a particular focus on the self-calibration techniques we developed to improve the image quality and fidelity. We present examples of the updated full-disk imaging results for both the cases when the disk is spotless and when it has sunspots/active regions present. These images reveal a rich variety of features of the quiescent Sun at different microwave frequencies, including active regions, filaments, coronal holes, and network structures, providing a unique dataset to the solar community.