Magnetic reconnection fluxes in solar flares and their implications for solar and stellar superflares
Abstract
We study the energy release process of a set of 51 solar flares which span almost four orders of magnitude in flare energy, from GOES class B3 to X17. 19 events of our sample are eruptive, i.e. have a CME associated, and 32 are confined (no CME associated). We use Hα filtergrams from Kanzelhöhe Observatory together with SDO HMI and SOHO MDI magnetograms to derive magnetic reconnection fluxes and reconnection rates. We find that the flare reconnection flux is strongly correlated with the peak of the GOES 1-8 Å soft X-ray flux (r=0.9, in log-log space), both for confined and eruptive flares. In the largest events, up to ≈50% of the total magnetic flux of the host active region (AR) is involved in the flare magnetic reconnection. Based on these findings, we extrapolate the properties of the largest flares that may be launched from our present day's Sun. A complex solar AR that hosts a magnetic flux of 2\cdot 10^{23} {Mx}, which is supported by the largest active-region magnetic fluxes directly measured, is capable of producing an X80 flare (corresponding to a bolometric energy of about 7 \cdot 10^{32} ergs). Using a magnetic flux estimate of 6\cdot 10^{23} {Mx} for the largest solar AR observed, we find that flares of GOES class ≈X500 could be produced (E_{bol} ≈ 3 \cdot 10^{33} ergs). Our results lie on the lower end of the energies of superflares on solar-type stars recently detected in Kepler data. Furthermore, they suggest that the present day's Sun is capable of producing flares and related space weather events more than an order of magnitude stronger than observed in the past.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E3538V