Estimation of Strength of the Solar Coronal Magnetic Field using Contemporaneous Radio and Whitelight Observations


Estimation of the magnetic field strength (B) in the solar corona is one of the widely pursued areas of research in observational solar physics. We estimated the coronal magnetic field strength during the 23 July 2016 coronal mass ejection (CME) event using i) the flux rope structure of the CME in the whitelight coronagraph images and ii) the band splitting in the associated type II burst. No models were assumed for the coronal electron density (N (r)) used in the estimation. The results obtained using the above two independent methods correspond to different heliocentric distances (r) in the range ≈ 2.5 – 4.5Ro, but they show excellent consistency and could be fitted with a single power-law distribution of the type B(r) = 5.7r^{−2.6} G, which is applicable in the aforementioned distance range. The power law index (i.e. −2.6) is in good agreement with the results obtained in previous studies by different methods, for example, using Faraday rotation observations of the linearly polarized carrier signals of the HELIOS spacecraft and using observations of similar signals from extragalactic radio sources occulted by the solar corona.

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