High Angular Resolution Radio Observations of a Coronal Mass Ejection Source Region at Low Frequencies during a Solar Eclipse

Abstract

We carried out radio observations of the solar corona in the frequency range 109-50 MHz during the annular eclipse of 2010 January 15 from the Gauribidanur Observatory, located about 100 km north of Bangalore in India. The radio emission in the above frequency range originates typically in the radial distance range ≈1.2-1.5 R ☉ in the "undisturbed" solar atmosphere. Our analysis indicates that (1) the angular size of the smallest observable radio source (associated with a coronal mass ejection in the present case) is ≈1' ± 0farcm3, (2) the source size does not vary with radial distance, (3) the peak brightness temperature of the source corresponding to the above size at a typical frequency like 77 MHz is ≈3 × 109 K, and (4) the coronal magnetic field near the source region is ≈70 mG.