Estimating the coronal supra-arcade downflows radio emission: from centimetre through submillimetre wavelengths

ZURBRIGGEN, E., GIMENEZ DE CASTRO, G., C.COSTA, A., CÉCERE, M., SELHORST,

frontiers in astronomy and space science

KARGER

Lugar: Basel; Año: 2022

Supra-arcade downflows (SADs) are infrequent, wiggly opaque structures observed to descendthrough the solar corona, mostly in EUV and soft X-ray frequencies. From their physicalcharacteristics, SADs have been interpreted as voided (subdense) bubbles and are relatedto magnetic reconnection processes during long-term erupting flares. In this work we usenumerical MHD simulations to compute flux density maps, which are convolved with telescopebeams to synthesise images with the aim to assess the expected SADs emission at radiowavelengths and propose observing strategies, including the instruments that can be used. Weassume that the emission is thermal bremsstrahlung from a fully ionised plasma without anyappreciable gyroresonance contribution since magnetic fields are of the order of ∼10 G. Wefind that SADs emission should be optically thin in the frequency [10 ? 1000] GHz range, and thespatially integrated flux should be larger than 1 Jy. We conclude, therefore, that observing SADsin radio frequencies between [0.5 ? 1000] GHz is feasible with present instrumentation. Moreover,since the emission is for the most part optically thin, the flux density is proportional to temperature,density and line-of-sight depth, and when combined with EUV and soft X-ray images, may allowa better density and temperature determination of SADs.