Comparison of Emission Properties of two Homologous Flares in AR 11283

TL;DR

This study compares two homologous X-class solar flares in active region NOAA 11283, analyzing their white-light emission, correlations with X-ray data, and associated sunquake signals to understand their triggering and heating mechanisms.

Contribution

It provides a detailed comparison of homologous flares' emission properties and their different seismic responses, highlighting the role of particle bombardment in sunquake generation.

Findings

Both flares showed similar white-light and X-ray emission characteristics.

The second flare was associated with a sunquake, unlike the first.

Particle bombardment may not be the main driver of sunquakes.

Abstract

Large, complex, active regions may produce multiple flares within a certain period of one or two days. These flares could occur in the same location with similar morphologies, commonly referred to as homologous flares. In 2011 September, active region NOAA 11283 produced a pair of homologous flares on the 6th and 7th, respectively. Both of them were white-light (WL) flares, as captured by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory in visible continuum at 617.3 nm which is believed to originate from the deep solar atmosphere.We investigate the WL emission of these X-class flares with HMIs seeing-free imaging spectroscopy. The durations of impulsive peaks in the continuum are about 4 minutes. We compare the WL with hard X-ray (HXR) observations for the September 6 flare and find a good correlation between the continuum and HXR both spatially and temporally. In absence of RHESSI data during the second flare on September 7, the derivative of the GOES soft X-ray is used and also found to be well correlated temporally with the continuum. We measure the contrast enhancements, characteristic sizes, and HXR fluxes of the twin flares, which are similar for both flares, indicating analogous triggering and heating processes. However, the September 7 flare was associated with conspicuous sunquake signals whereas no seismic wave was detected during the flare on September 6. Therefore, this comparison suggests that the particle bombardment may not play a dominant role in producing the sunquake events studied in this paper.