Search for continuum solar flare radiation in the terahertz range

A new solar burst emission spectral component has been found showing sub-THz fluxes increasing with frequency, spectrally separated from the well known microwave component bringing serious constraints for the interpretation. The THz spectral component might be the evidence of synchrotron emission from high energy electrons peaking somewhere in the far IR range. The knowledge of THz continuum spectral shape is therefore essential to investigate the nature of the emission mechanisms involved. Sub-THz solar flare flux data are available from observations carried out at El Leoncito high altitude observatory, at two atmosphere transmission windows (0.2 and 0.4 THz). We describe the results from developments addressed to the construction of solar flare radiometers at two frequencies to operate outside the terrestrial atmosphere (i.e. at 3 and 7 THz). The system has been planned as part of the SOLAR-T mission on a stratosphere long-duration balloon flight over Russia sometime in 2013–2016.