Does Nearby Open Flux Affect the Eruptivity of Solar Active Regions?

The most energetic solar flares are typically associated with the ejection of a cloud of coronal material into the heliosphere in the form of a coronal mass ejection (CME). However, large flares exist that are not accompanied by a CME. The existence of these noneruptive flares raises the question of whether such flares suffer from a lack of access to nearby open fields in the vicinity above the flare (reconnection) site. In this study, we use a sample of 56 flares from sunspot Cycles. 23 and. 24 to test whether active regions that produce eruptive X-class flares are preferentially located near coronal magnetic field domains that are open to the heliosphere, as inferred from a potential field source-surface model. The study shows that X-class flares with access to open fields are eruptive at a higher rate than those for which access is lacking. The significance of this result should be moderated due to the small number of noneruptive X-class flares in the sample, based on the associated Bayes factor.