Goldstone Apple Valley Radio Telescope Observations of 2012 Solar Eclipse: A Multi-wavelength Study of cm-λ Gyroresonance Emission from Active Regions

Abstract

Goldstone Apple Valley Radio Telescope (GAVRT) is a science education partnership among NASA, the Jet Propulsion Laboratory, and the Lewis Center for Educational Research, offering unique opportunities for K-12 students and their teachers. The GAVRT program operates a 34 m radio telescope with a wide-band, low noise receiver, which is tunable in four independent dual-polarization bands from 3 to 14 GHz. The annular eclipse of the Sun on 2012 May 20 was observed by GAVRT as part of education outreach. In this paper we present the results of this eclipse data and discuss the multi-wavelength strip scan brightness distribution across three active regions. We derive the source brightness temperatures and angular sizes as a function of frequency and interpret the results in terms of the gyroresonance mechanism. We show examples of the increasing brightness and widening of source size (isogauss surface) with wavelength as evidence for gyroresonance emission layers of broader (diverging) isogauss surfaces of the magnetic field geometry in the corona above solar surface. We present an example how the derived frequency-brightness temperature relationship is translated to a magnetic field-brightness temperature relationship under the frame-work of gyroresonance emission. Our results demonstrate the usefulness of GAVRT bands as excellent probes to study the layers of the corona above the active regions (Sun spots), in particular the prevalence of the gyroresonance mechanism. Our results provide a frame-work for multiwavelength cm-lambda eclipse observations and illustrate how the GAVRT program and K-12 student/teacher participation can produce science data useful to the scientific community and science missions.