ESTIMATION OF THE CORONAL MAGNETIC FIELD STRENGTH USING HIGH-FREQUENCY TYPE II RADIO BURST OBSERVATIONS

We report the estimation of the coronal magnetic field strength in the height range of 1.04-1.08 R☉ using radio observations of a high-frequency band-splitting type II radio burst associated with an X2.2 solar flare and a fast coronal mass ejection (CME) on 2024 December 8. The burst was recorded by the e-CALLISTO (Uzbekistan) radio spectrometer in the frequency range of 45-413 MHz. By analysing the band-splitting between the upper and lower frequency sub-bands of the split emission lane, we derived the upstream-to-downstream density jump X = 1.472-1.513 and the Alfvén Mach number Ma = 1.373-1.407, confirming a weakly super-Alfvenic shock. The coronal magnetic field strength is estimated to be 7.27-10.15 G, following a power-law B = 13.32 r⁻⁸·⁰² (in Gauss). The shock speed derived from height-time measurements (1192 km/s) exceeds the CME leading-edge speed (913 km/s), consistent with a CME-driven shock propagating through dense coronal loops in the inner corona. These results provide new observational constraints on the coronal magnetic field at very low heliocentric heights, demonstrating the scientific value of ground-based high-frequency radio monitoring.

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