Next-Generation Solar Radio Imaging Spectroscopy

Abstract:

Recent progress using instruments such as the Expanded Owens Valley Solar Array (EOVSA) and the Jansky Very Large Array (JVLA) have amply demonstrated the power of radio imaging spectroscopy at centimeter and decimeter wavelengths for quantitative diagnostics of both flaring and non-flaring solar plasma. For example, the unique sensitivity of radio emission to the flaring coronal magnetic field has been dramatically shown in a series of recent EOVSA papers, along with accelerated electron diagnostics in the same volume. JVLA observations have been used to probe particle acceleration in a termination shock during a flare. In addition, multi-frequency full-disk imaging of the non-flaring Sun with EOVSA is showing promise for quantitative diagnostics of electron-based emission measure and active region magnetic field and temperature structure. But EOVSA and the JVLA are mere demonstrators for a far more advanced solar radio instrument, the Frequency Agile Solar Radiotelescope (FASR), that is designed to address a much more comprehensive science program with much greater precision than is possible with EOVSA or non-solar-dedicated instruments like the JVLA. This includes direct imaging of Coronal Mass Ejections (CMEs) and their associated energetic particles both on and off the solar disk, routine coronal magnetic field measurements at high cadence, and continuous sampling of the full-Sun coronal temperature and emission measure. Here we use examples from EOVSA and the JVLA to envision what FASR's advanced design will be capable of. When paired with highly complementary new X-ray-based diagnostics from space, the remote sensing of high-energy particles through radio imaging spectroscopy from the ground provides a far more complete picture of the broad range of energetic phenomena that occur on the Sun than either alone. Scientists interested in high-energy solar phenomena have ample incentive to coordinate their efforts to ensure that space- and ground-based capabilities advance together.