Characterization of coronal mass ejections using solar radio bursts

Abstract

Solar radio bursts (SRBs) are often early indicators of coronal mass ejections (CMEs). Since SRBs propagate much faster than CMEs, they can serve as advance warning of incoming solar event with ability to drive space weather. This study characterizes the CMEs using the associated SRBs with a special emphasis on high starting frequency type II bursts. The latter are important because, they indicate shock formation very close to the Sun, which is well suited for accelerating electrons and protons to very high energies, representing another aspect of space weather. In this study, we determined the properties of a sample of 40 high-startingfrequency (≥ 150 MHz) type II radio bursts and the characteristics of the associated CMEs such as width, location and speed during 2010–2016. Taking into account the radial variation of CME speeds from the inner corona to the interplanetary medium, we observed the deviations from the universal drift-rate spectrum of type II bursts and confirmed the previous results relating type II bursts to CMEs. We also used radio observations from the Compound Astronomical Low frequency Low cost Spectroscopy and Transportable Observatory (CALLISTO) instrument with those derived from multi-spacecraft CME observations from Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph (SOHO/LASCO) and Solar Terrestrial Relations Observatory (STEREO) coronagraphs whose upper-frequency cutoff lies in between 150 MHz-450 MHz during 2010–2019 to investigate the origin of high-frequency type II bursts. We found that 60% of the CMEs solar sources associated with the higher-startingfrequency (≥ 300 MHz) bursts are located in the latitude range of ±25◦, corresponding to the active region belt. The radial speed of a CME determines the shock-driving capability of a CME as indicated by the presence of a type II radio burst. Finally, the current study analyzed the shock driving capability of a CME inferred from multiwavelength observations. The April 18, 2014 CME was associated with a type II radio burst in the metric and interplanetary domains. We used the radio-burst data provided by the San Vito Solar Observatory of the Radio Solar Telescope Network and data from the Wind spacecraft. The CME is a full halo in SOHO/LASCO FOV. The CME was also observed by the STEREO. We determined the CME shock speed from metric and interplanetary radio observations and found them to be consistent with white-light observations, provided the metric type II burst and its continuation into the decameter-hectometric domain are produced at the shock flanks, where the speed is still high enough to accelerate electrons that produce the type II bursts. There was an interplanetary type II burst segment consistent with an origin at the shock nose suggesting that the curved shock was crossing plasma levels separated by a few solar radii. We conclude that the CME speed is high enough to produce the interplanetary Type II burst and a solar energetic particle (SEP) event. However, the speed is not high enough to produce a ground level enhancement (GLE) event, which requires the shock to form at a height of ∼ 1.5 Rs. This analysis agrees with previous similar studies that type II bursts can act as a proxy to estimate this eruption’s early kinematics and dynamics near the Sun. Notably, the present research study demonstrates the importance of using type II bursts observed from the ground to monitor space weather.