Thinkshop12

Correlation of Hard X-Ray and White Light Emission in Solar Flares

Matej Kuhar (FHNW, Windisch, Switzerland)

Abstract. We present a statistical study of the correlation between hard X-ray and white light emission in solar flares, which was performed in order to search for a link between flare-accelerated electrons and white light formation. We analyzed 43 white light flares spanning GOES classes M and X using the observations from RHESSI and HMI. We calculated X-ray fluxes at different energies and white light fluxes at 617.3 nm summed over the hard X-ray ribbons, with an integration time of 45 seconds around the peak time of hard-X ray emission. We find a best correlation for photons with energy of 30 keV, with the correlation coefficient in that case of 0.68 between the logarithmic values of hard-X ray and white light fluxes. Assuming the thick-target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above 50 keV. We observed a gradual decrease of the correlation coefficient towards higher energies, while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy around 50 keV are the main source for WL emission.

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