Shock wave driven by CME evidenced by metric type II burst and EUV wave

Abstract

Solar type II radio bursts are produced by plasma oscillations in the solar corona as a result of shock waves. The relationship between type II bursts and coronal shocks is well evidenced by observations since the 1960s. However, the drivers of the shocks associated with type II events at metric wavelengths remain as a controversial issue among solar physicists. The flares and the coronal mass ejections (CMEs) are considered as potential drivers of these shocks. In this article, we present an analysis of a metric type II burst observed on May 17, 2013, using data provided by spectrometers from e-CALLISTO (extended-Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatories) and EUV images from the Extreme Ultraviolet Imager (EUVI), aboard the Solar Terrestrial Relations Observatory (STEREO). The event was associated with an M3.2 SXR flare and a halo CME. The EUV wave produced by the expansion of the CME was clear from the EUV images. The heights of the EUV wave fronts proved to be consistent with the heights of the radio source obtained with the 2–4×Newkirk density model, which provided a clue to an oblique propagation of the type-II-emitting shock segment. The results for the magnetic field in the regions of the shock also revealed to be consistent with the heights of the radio source obtained using the 2–4×Newkirk density model. Exponential fit on the intensity maxima of the harmonic emission provided a shock speed of ∼580–990kms−1, consistent with the average speed of the associated EUV wave front of 626kms−1.