A bright impulsive solar burst detected at 30 THz

TL;DR

This paper reports the first detection of a solar flare burst at 30 THz, revealing new insights into flare emissions at infrared wavelengths and their relation to other spectral observations.

Contribution

It introduces a new imaging system capable of detecting impulsive solar bursts at 30 THz, expanding the observational wavelength range for solar flare studies.

Findings

30 THz emission coincides with peaks at other wavelengths

Emission location matches a weak white-light feature

Peak flux at 30 THz exceeds microwave peak near 9 GHz

Abstract

Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies.