SOLARNET Conference: The Many Scales of the Magnetic Sun

Solar flares sometimes lead to coronal mass ejections that directly affect the Earth's environment. However, a large fraction of flares, especially on solar-type stars, are confined flares. What are the differences in physical properties between confined and eruptive flares? For the first time, we quantify thermodynamic and magnetic properties of hundreds confined and eruptive flares of GOES class C5.0 and above, 480 flares total. We first analyze large flares of GOES class M1.0 and above observed by the SDO, 216 flares total, including 103 eruptive and 113 confined flares, from 2010 until 2016 April; we then look at the entire dataset above C5.0 of 480 flares. We compare GOES X-ray thermodynamic flare properties, including peak temperature and emission measure, and active-region and flare-ribbon magnetic field properties, including reconnected magnetic fluxes and peak reconnection rates. We find that confined and eruptive flares have similar distributions of reconnection flux. Confined flares, however, have larger peak magnetic reconnection rates, are more compact, and occur in larger active regions than eruptive flares. These findings suggest that confined flares are caused by reconnection within more compact, stronger, lower lying magnetic-field regions in larger ARs that reorganizes smaller fractions of ARs. This reconnection proceeds at faster rates and ends earlier, leading potentially to more efficient flare particle acceleration in confined flares.