Observations of Type III and Type IV Solar Radio Bursts at 26.3 Mc/s

Abstract

A source of Type III bursts in the solar corona was observed at 26.3 Mc/s (11.4 meters) with the Clark Lake antenna during the period July 31-August 12, 1963. The height of the source was found to be 2.4 + 0.2 R0 from the center of the sun which presumably is the height of the plasma level for 26.3 Mc/s, corresponding to an electron density of 8.5 X 100 . This height refers to the density in a coronal streamer over an active region and, together with determinations at frequencies of 1.5-201 Mc/s, corresponds to the density distribution with height of the van de Huist model of the equatorial maximum corona, with all the densities multiplied by a factor of 10. No evidence was found for refraction in the corona. A moving Type IV burst arising from a west-limb flare in the same active region on August 11 was observed to travel out through the corona at an angle of 32 north of the radial direction to about 6.3 R0 from the center of the disk with a velocity of about 1400 km/s. After reaching this height, the source moved inward with a velocity of 380 km/s to an altitude of 5.4 R0, where it remained until the end of the burst. The brightness distribution found for the source agrees with the "core and halo" model of Weiss and Sheridan for various types of bursts and the results of Erickson for Type III bursts. The observed properties of the burst are in reasonably good agreement with those found by other workers for moving Type IV bursts at frequencies of Mc/s.