Moving solar radio bursts and their association with coronal mass ejections

Abstract

Context. Solar eruptions, such as coronal mass ejections (CMEs), are often accompanied by accelerated electrons that can in turn emit radiation at radio wavelengths. This radiation is observed as solar radio bursts. The main types of bursts associated with CMEs are type II and type IV bursts that can sometimes show movement in the direction of the CME expansion, either radially or laterally. However, the propagation of radio bursts with respect to CMEs has only been studied for individual events. Aims. Here, we perform a statistical study of 64 moving bursts with the aim to determine how often CMEs are accompanied by moving radio bursts. This is done in order to ascertain the usefulness of using radio images in estimating the early CME expansion. Methods. Using radio imaging from the Nançay Radioheliograph (NRH), we constructed a list of moving radio bursts, defined as bursts that move across the plane of sky at a single frequency. We define their association with CMEs and the properties of associated CMEs using white-light coronagraph observations. We also determine their connection to classical type II and type IV radio burst categorisation. Results. We find that just over a quarter of type II and half of type IV bursts that occurred during the NRH observing windows in Solar Cycle 24 are accompanied by moving radio emission. All but one of the moving radio bursts are associated with white–light CMEs and the majority of moving bursts (90%) are associated with wide CMEs (> 60° in width). In particular, all but one of the moving bursts corresponding to type IIs are associated with wide CMEs; however, and unexpectedly, the majority of type II moving bursts are associated with slow white–light CMEs (< 500 km s−1). On the other hand, the majority of moving type IV bursts are associated with fast CMEs (> 500 km s−1). Conclusions. The observations presented here show that moving radio sources are almost exclusively associated with CMEs. The majority of events are also associated with wide CMEs, indicating that strong lateral expansion during the early stages of the eruption may play a key role in the occurrence of the radio emission observed.

Trends and characteristics of high-frequency type II bursts detected by CALLISTO spectrometers

“…They are believed to be plasma emission produced by a shock when it propagates through the solar corona (Mann et al, 1995;Zlotnik et al, 1998;Cliver et al, 2004;Schmidt et al, 2014). These bursts are often associated with the shock propagating ahead of a CME in the solar corona (e.g., Gopalswamy et al, 1998;Kumari et al, 2017a;Morosan et al, 2021;Majumdar et al, 2021). Type II bursts can sometimes occur without any CME, and are then associated with flares (Magdalenić et al, 2012;Su et al, 2015).…”

Type IV Radio Bursts and Associated Active Regions in Sunspot Cycle 24

“…The CME association of these radio bursts was checked using the CMEs detected with SOHO/LASCO-C2, STEREO-A and -B based on a temporal correlation (for details see Kumari, Morosan, and Kilpua, 2021). The first appearance of a CME in a coronagraph field of view (FOV) depends upon the speed, acceleration, and the propagation direction of the CME with respect to the Sun-Earth line (for LASCO) and the Sun-STEREO line (for STEREO).…”

“…Recently, Kumari, Morosan, and Kilpua (2021) studied the association of these bursts with CMEs in the previous solar cycle (Cycle 24) based on their spectral properties. Morosan et al (2021) studied the moving bursts in the rising phase of Solar Cycle 24 using radio images. However, due to the lack of radio-imaging instruments, locating the source region of these radio bursts in the corona becomes almost impossible.…”

Interferometric Imaging, and Beam-Formed Study of a Moving Type-IV Radio Burst with LOFAR

“…They are classified at meter wavelengths into five major types, Type I to Type V named after Roman numbers (Boischot, 1957 ). Solar radio bursts are generally related to coronal mass ejections (CMEs) and solar flares (Morosan et al., 2021 ). In this paper we focus on a Type-IV radio burst, which is a long-lasting broadband continuum emission in radio wavelengths that usually appears approximately 10 minutes after a solar flare (Pick, 1963 ).…”