Sun-to-Earth Propagation of the 2015 June 21 Coronal Mass Ejection Revealed by Optical, EUV, and Radio Observations

TL;DR

This study tracks the Sun-to-Earth journey of the 2015 June 21 CME-driven shock using multi-wavelength observations, revealing its propagation, deflection, and impact on geomagnetic activity and SEP events.

Contribution

It provides a comprehensive analysis of the CME's propagation from the Sun to Earth, integrating optical, EUV, and radio data to understand its evolution and geomagnetic effects.

Findings

CME was deflected by an equatorial coronal hole.

Interplanetary type II burst was intense and visible from corona to Wind spacecraft.

Shock speed evolution matched coronagraph and in-situ observations.

Abstract

We investigate the propagation of the 2015 June 21 CME-driven shock as revealed by the type II bursts at metric and longer wavelengths and coronagraph observations. The CME was associated with the second largest geomagnetic storm of solar cycle 24 and a large solar energetic particle (SEP) event. The eruption consisted of two M-class flares, with the first one being confined, with no metric or interplanetary radio bursts. However, there was intense microwave burst, indicating accelerated particles injected toward the Sun. The second flare was eruptive that resulted in a halo CME. The CME was deflected primarily by an equatorial coronal hole that resulted in the modification of the intensity profile of the associated SEP event and the duration of the CME at Earth. The interplanetary type II burst was particularly intense and was visible from the corona all the way to the vicinity of the Wind spacecraft with fundamental-harmonic structure. We computed the shock speed using the type II drift rates at various heliocentric distances and obtained information on the evolution of the shock that matched coronagraph observations near the Sun and in-situ observations near Earth. The depth of the geomagnetic storm is consistent with the 1-AU speed of the CME and the magnitude of the southward component.