The Time-Extended Phase of Solar Flares at MM-SUBMM Wavelengths

RAULIN, J.P; TROTTET, G.; GIMÉNEZ DE CASTRO, C.G.; LUTHI, T.; CASPI, A.; MANDRINI, C.H.; LUONI, M.L.; KAUFMANN, P.

Congreso; American Astronomical Society, SPD meeting N 42; 2011

American Astronomical Society

We give a brief overview of the observations of the few flare which exhibit a slowly-varying and time-extended phase lasting for tens of minutes after the impulsive phase, and which are detected in radio up to submillimeter wavelengths. We present a detailed analysis of the 2003 October 27 event at 12:30 UT, which shows such a gradual phase. The radio, UV/EUV, X-ray and optical observations of the gradual phase are consistent with thermal bremsstrahlung from coronal material at two temperatures which is optically thick below 8 GHz and optically thin at higher frequencies. At 345 GHz there is a flux density excess with respect to the optically thin emission which arises from the chromosphere. We show that these findings constitute a challenge for the modeling of the chromospheric response to energy deposition during solar flares.