Estimation of Coronal Magnetic Field Using Multiple Type II Radio Bursts

The magnetic fields in the corona is determined using multiple type II radio bursts observed on 20 January 2004 with the Culgoora solar radio spectrograph. Using the relation between the relative bandwidth of the band-split and the density in the upstream and the downstream of the shock the Alfven Mach number is estimated. From the observed drift rates of the multiple type II bursts the Alfven speed and the magnetic field is estimated. The relative bandwidths for the first and second type II bursts respectively are 0.28 and 0.20. The Alfven Mach numbers for the first and second bursts respectively are 1.64 and 1.44. The mean frequency of the first type II burst is 73 MHz and the same for the second burst is 49 MHz. The derived magnetic field varies from 1.30 to 2.24 Gauss for the first burst and 1.32 to 2.46 Gauss for the second burst for Newkirk’s density with density enhancement factors 1 to 5. The associated activities show a single flare and a Coronal Mass Ejection (CME). The results are discussed in the frame work of the single flare/CME.