CME-driven Shock and Type II Solar Radio Burst Band Splitting

Chrysaphi, Nicolina, EduardĀ P. Kontar, GordonĀ D. Holman, and Manuela Temmer, CME-driven Shock and Type II Solar Radio Burst Band Splitting, ApJ, 868, 79 (2018) (ADS)

The cartoon

(click on the image for a larger version)

Solar metric type II bursts result from large-scale shock disturbances of the corona associated with CME occurrence, and their remarkable morphology sometimes includes distinct "band splitting" frequency patterns. New and very detailed LOFAR data show a clear spatial separation between the source of the two split bands in a well-observed event (SOL2015-06-25). This could in principle be due to physically distinct sources, but an interesting model proposed by Smerd long ago suggested that the split bands actually originate in the upstream and downstream regions of the shock - at the same point in space, essentially - is also consistent with the observations, if one allows for scattering effects within the perturbed corona, making use of the density jump at the shock.

      This seems to be a part of the renaissance in meter-wave solar radioastronomy made possible by wonderful new facilities. Interestingly in this case, the activity seems to have been at the flank of the shock, rather than at the nose of the bow wave (as shown in the cartoon and usually). The cartoon nicely represents the gross distortions of the meter-wave image structure that result from propagation and scattering near the plasma frequency.

Date: 2019 February 09

Update: 2019 December 28