Radio Observations of Coronal Holes

K. V. Sheridan, G. A. Dulk
1980 Symposium - International astronomical union  
Coronal holes have been observed on several occasions with the 80 and 160 MHz radioheliograph at Culgoora. At 160 MHz the holes invariably appear as areas of low brightness, either on the disk or at the limb. At 80 MHz holes on the limb always appear less bright than their surroundings but on the disk they frequently appear brighter.The simplest interpretation is that the coronal temperature in holes near the 80 MHz critical density (8 × 107cm−3) is higher than in normal quiet regions, but that
more » ... t regions, but that the density at this level is lower.
doi:10.1017/s0074180900067322 fatcat:l7auzqcipvfujdzzzmqqbnmvpu