The Association of Solar Flares with Coronal Mass Ejections During the Extended Solar Minimum

TL;DR

This study investigates the relationship between solar flares and coronal mass ejections during a deep solar minimum, revealing that only the most energetic and fast CMEs are consistently associated with flares, with various low coronal signatures observed.

Contribution

It provides new insights into the conditions and signatures associated with CME-flare relationships during a solar minimum, highlighting factors beyond active region size.

Findings

Fast and wide CMEs are always associated with flares.

Most high-intensity flares during the minimum are not associated with CMEs.

Low coronal signatures are observed in a majority of CME-associated flares.

Abstract

We study the association of solar flares with coronal mass ejections (CMEs) during the deep, extended solar minimum of 2007-2009, using extreme-ultraviolet (EUV) and white-light (coronagraph) images from the {\it Solar Terrestrial Relations Observatory} (STEREO). Although all of the fast (v $>$ 900 km s$^{-1}$) {\it and} wide ($\theta >$ 100$\arcdeg$) CMEs are associated with a flare that is at least identified in GOES soft X-ray light curves, a majority of flares with relatively high X-ray intensity for the deep solar minimum (e.g. $\gtrsim$1 \times 10^{-6}$ W m$^{-2}$ or C1) are not associated with CMEs. Intense flares tend to occur in active regions with strong and complex photospheric magnetic field, but the active regions that produce CME-associated flares tend to be small, including those that have no sunspots and therefore no NOAA active-region numbers. Other factors on scales comparable to and larger than active regions seem to exist that contribute to the association of flares with CMEs. We find the possible low coronal signatures of CMEs, namely eruptions, dimmings, EUV waves, and Type III bursts, in 91%, 74%, 57%, and 74%, respectively, of the 35 flares that we associate with CMEs. None of these observables can fully replace direct observations of CMEs by coronagraphs.