Solar observations in the infrared domain can bring important clues on the response of the low solar atmosphere to primary energy released during flares. At present the infrared continuum has been detected at 30 THz (10 µm) in only a few flares. SOL2012-03-13 , which is one of these flares, has been presented and discussed in Kaufmann et al. (2013). No firm conclusions were drawn on the origin of the mid-infrared radiation. In this work we present a detailed multi-frequency analysis of the SOL2012-03-13 event, including observations at radio millimeter and sub-millimeter wavelengths, in hard X-rays (HXR), gamma-rays (GR), Hα, and white-light. HXR/GR spectral analysis shows that SOL2012-03-13 is a GR line flare and allows estimating the numbers of and energy contents in electrons, protons and α particles produced during the flare. The energy spectrum of the electrons producing the HXR/GR continuum is consistent with a broken power-law with an energy break at ∼ 800 keV. It is shown that the high-energy part (above ∼ 800 keV) of this distribution is responsible for the high-frequency radio emission (> 20 GHz) time-independent models of the quiet and flare atmospheres, we find that most (∼80%) of the observed 30 THz radiation can be attributed to thermal freefree emission of an optically-thin source. Using the F2 flare atmospheric model (Machado et al., 1980) this thin source is found to be at temperatures T ∼ 8000 K and is located well above the minimum temperature region. We argue that the chromospheric heating, which results in 80 % of the 30 THz excess radiation, can be due to energy deposition by non-thermal flare accelerated electrons, protons and α particles. The remaining 20% of the 30 THz excess emission is found to be radiated from an optically-thick atmospheric layer at T ∼ 5000 K, below the temperature minimum region, where direct heating by non-thermal particles is insufficient to account for the observed infrared radiation.

This paper describes a new "SMART/SDDI Filament Disappearance Catalogue," in which we listed almost all the filament disappearance events that the Solar Dynamics Doppler Imager (SDDI) has observed since its installation on the Solar Magnetic Activity Research Telescope (SMART) in May 2016. Our aim is to build a database that can help predict the occurrence and severity of coronal mass ejections (CMEs). The catalogue contains miscellaneous information associated with filament disappearance such as flare, CME, active region, three-dimensional trajectory of erupting filaments, detection in Interplanetary Scintillation (IPS), occurrence of interplanetary CME (ICME) and Dst index. We also provide statistical information on the catalogue data. The catalogue is available from the following website: https://www.kwasan.kyoto-u.ac.jp/observation/event/sddi-catalogue/.

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Impulsive 30 THz continuum bursts have been recently observed in solar flares, utilizing small telescopes with a unique and relatively simple optical setup concept. The most intense burst was observed together with a GOES X2 class event on 27 October 2014, also detected at two subterahertz (sub‐THz) frequencies, Reuven Ramaty High Energy Solar Spectroscopic Imager X‐rays and Solar Dynamics Observatory/Helioseismic and Magnetic Imager and EUV. It exhibits strikingly good correlation in time and in space with white‐light flare emission. It is likely that this association may prove to be very common. All three 30 THz events recently observed exhibited intense fluxes in the range of 104 solar flux units, considerably larger than those measured for the same events at microwave and submillimeter wavelengths. The 30 THz burst emission might be part of the same spectral burst component found at sub‐THz frequencies. The 30 THz solar bursts open a promising new window for the study of flares at their origin.

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