Powerful solar flares in September 2017. Comparison with the largest flares in cycle 24

TL;DR

This study analyzes the most powerful solar flares of cycle 24, comparing their timing and energy outputs across different wavelengths, and relates these energies to previous large flares in 2011-2012.

Contribution

It provides a detailed comparison of the timing and energy release of the largest flares in cycle 24 with earlier significant flares, using satellite data from GOES-15 and SDO/EVE.

Findings

Flare energies in different spectral lines are closely correlated.

Timing of flux increases varies among different flare classes.

Energy calculations from different instruments show strong interrelation.

Abstract

Solar flare activity in cycle 24 is studied. Satellite observations of x-ray fluxes from GOES-15 and UV emission lines from the SDO/EVE experiment are used. The most powerful flares of cycle 24 in classes X9.3 and X8.2 in September 2017 are compared with powerful flares in classes M5-X6.9. The times at which the fluxes in the 30.4 and 9.4 nm lines and in the 0.1-0.8 nm x-ray range begin to increase are compared for 21 of the large flares. The total energies arriving at the earth from flares in the 30.4 and 9.4 nm lines and in the 0.1-0.9 nm x-ray range, $E_{30.4}$, $E_{9.4}$, and $E_{0.1-0.8}$, from 25 flares during 2011 and 2012 are calculated. It is shown that the calculated energies of the flares in the analyzed lines from SDO/EVE and in the x-ray range from GOES-15 are closely interrelated.