Goldstone Apple Valley Radio Telescope (GAVRT) Observations of the 2023 Solar Eclipse: Tracing Gyroresonance Layers above Active Region 13465 and Magnetic Field Extrapolations in the Inner Corona

We present results from the Goldstone Apple Valley Radio Telescope (GAVRT) observations of active region (AR) 13465 during the 2023 October 14 eclipse. GAVRT is a 34 m radio dish located in Goldstone, CA, that produced near-daily maps of the Sun between 2023 September and 2025 January, at four simultaneous GHz-frequency bands, spanning 3.5–13 GHz. GAVRT tracked AR 13465 during the eclipse, which provided high (∼arcsec) angular-resolution structural information on coronal magnetic fields in the direction perpendicular to the Moon’s limb, independent of wavelength. GAVRT GHz-frequency observations are ideally suited for probing the solar corona above sunspots via gyroresonance emission, in which thermal electrons gyrating along strong magnetic field lines fully reveal the layer-by-layer density, temperature, and magnetic field structure up to heights of 20,000 km in the inner corona. For comparison against the observational data, we simulate the AR 13465 iso-Gauss intensity profiles using the Solar Dynamics Observatory (SDO) Helioseismic Magnetic Imager (HMI) photospheric magnetic field maps as input to the pyAMPP tool. We find broad consistency between the observed brightness temperature profiles across AR 13465 and the extrapolated magnetic field iso-Gauss intensity profiles. We show that harmonic s = 3 is consistent with both the magnetic field extrapolation data and the eclipse observations at all GHz frequencies. The magnetic field extrapolation validates the presence of magnetic field intensities in the inner corona at heights matching those required for the gyrofrequency harmonics for the GHz-frequency bands observed by GAVRT.