Microwave radio emissions as a proxy for coronal mass ejection speed in arrival predictions of interplanetary coronal mass ejections at 1 AU

Abstract

The propagation of a coronal mass ejection (CME) to the Earth takes between about 15 h and several days. We explore whether observations of non-thermal microwave bursts, produced by near-relativistic electons via the gyrosynchrotron process, can be used to predict travel times of interplanetary coronal mass ejections (ICMEs) from the Sun to the Earth. In a first step, a relationship is established between the CME speed measured by the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph (SoHO/LASCO) near the solar limb and the fluence of the microwave burst. This relationship is then employed to estimate speeds in the corona of earthward-propagating CMEs. These speeds are fed into a simple empirical interplanetary acceleration model to predict the speed and arrival time of the ICMEs at Earth. The predictions are compared with observed arrival times and with the predictions based on other proxies, including soft X-rays (SXR) and coronographic measurements. We found that CME speeds estimated from microwaves and SXR predict the ICME arrival at the Earth with absolute errors of 11 ± 7 and 9 ± 7 h, respectively. A trend to underestimate the interplanetary travel times of ICMEs was noted for both techniques. This is consistent with the fact that in most cases of our test sample, ICMEs are detected on their flanks. Although this preliminary validation was carried out on a rather small sample of events (11), we conclude that microwave proxies can provide early estimates of ICME arrivals and ICME speeds in the interplanetary space. This method is limited by the fact that not all CMEs are accompanied by non-thermal microwave bursts. But its usefulness is enhanced by the relatively simple observational setup and the observation from ground, which makes the instrumentation less vulnerable to space weather hazards.

Solar Observations with Single-Dish INAF Radio Telescopes: Continuum Imaging in the 18 – 26 GHz Range

“…This could reflect the presence of ARs generated by faint magnetic fields or spotless regions, which are a considerable fraction of the counted ARs. It is thus important that such observations continue for the decades to come (see, e.g., Zucca, Núñez, and Klein, 2017;Matamoros, Klein, and Trottet, 2017).…”

Validation of the SMOS Mission for Space Weather Operations: The Potential of Near Real‐Time Solar Observation at 1.4 GHz

“…Salas Matamoros et al. (2017) showed the potential of 9 GHz SRBs fluences as a tool to predict the arrival of interplanetary coronal mass ejections (ICMEs) at 1 AU. They found a relationship between the SRBs fluence and the speed of limb CMEs that they then applied to Earth‐directed CMEs.…”

Radio Observations of Coronal Mass Ejections: Space Weather Aspects

“…To circumvent these problems, several authors have searched for emission signatures concurrent to CMEs, such as EUV dimmings (Mason et al, 2016), soft X-ray light curves and more recently high frequency (GHz) fluence measurements, to use as proxies by relating their evolution to the CME speed via empirical relationships. Focusing on the radio proxies, Matamoros et al (2017) have recently demonstrated a correlation between microwave fluence at 9 GHz and CME arrival time at the Earth, using limb CME observations to construct the empirical (linear in this case) relationship. The performance of the method is average and has only been demonstrated with a very small event sample (11 events) so it is unclear if it holds SpWx potential.…”