A prolific solar flare factory. Nearly continuous monitoring of an active region nest with Solar Orbiter

Abstract

The properties of active region nests, which are locations on the Sun with recurring flux emergence, are poorly constrained by observations from Earth alone. ESA's Solar Orbiter now monitors the far side of the Sun for extended periods of time. This facilitates observations of the entire Sun. We combined observations from near-Earth satellites and Solar Orbiter to evaluate the contribution of a long-lived active region nest to the global flaring activity of the Sun. We identified a location in Carrington coordinates with episodic bursts of flux emergence throughout 2022. The combined observations allowed a nearly continuous monitoring of this region from April to October, that is, during its most active period. GOES and Solar Orbiter/STIX were used to compare its flaring activity to that of the entire Sun. The region morphology was extracted from SDO/AIA and Solar Orbiter/EUI extreme-ultraviolet images and was combined with magnetic field measurements from SDO/HMI and Solar Orbiter/PHI to assess its unsigned magnetic flux. The active region nest grew in complexity from January to May due to repeated flux emergence events. The peak unsigned magnetic flux was $5\times 10^{22}$Mx. The region caused 40% of the observed solar flares in 2022, including five months in which it produced 50-70% of all flares over the entire Sun (in the nearly continuous monitoring window). Of the 17 complex flaring NOAA active regions in 2022, this region contained 10, but they occupied less than 20% of the area in the active latitudes. Active region nests can maintain a high rate of flaring activity for several solar rotations and are more likely to produce complex active regions that can trigger X-class solar flares. Improving the identification and monitoring of long-lived active region nests would benefit space weather forecasts in the short to medium term.

Accepted to A&A. 12 Pages + Appendix. 11 Figures + 5 Appendix Figures

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