Multi-Vantage Point Observations of a High-Frequency Type II Radio Burst Caused by A Far-Side Flare Blast Wave

Abstract

High-frequency (>500 MHz) solar Type II radio bursts are rare and are believed to be manifes-tations of coronal shocks produced by explosive solar surface phenomena, such as solar flares and coronal mass ejections (CME). However, the exact cause of high-frequency Type II bursts remains debatable. The high-frequency burst events, observed from the limb, present a sce-nario where a comprehensive multi-wavelength and multi-vantage point approach could help to pinpoint the exact cause. We present here one such high-frequency Type II radio burst (≈640 MHz), observed by the Nancay Radio Heliograph (NRH) at 13:26:56 UT on 11 February 2014, on the western limb of the Sun. Our analysis, using Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) (SDO/AIA), reveals the presence of an EUV wave and a slow CME during the Type II burst. It is found that the estimated speed of the Type II radio burst (663 km/s) is twice the speed of the CME (330 km/s). On the other hand, the EUV wave, spatio-cotemporal with the Type II burst, is traveling with a speed ∼705 km/s, suggesting that the Type II burst could be associated with the EUV wave. Multi-vantage point observations from EUVI on board Solar TErrestrial RElations Observatory (STEREO) show a co-temporal far-side solar flare with an EUV wave signature at the time of the Type II burst. The same EUV wave is also observed in the SDO/AIA field of view on the western limb of the Sun, spatio-cotemporal with the Type II burst. Our study thus presents a clear case of a high-frequency Type II radio burst caused by a flare bast wave, the origin of which could have remain undetected unless we used multi-vantage-point observations from STEREO.