Radio spectra fitting for solar events exhibiting the THz component

MANDRINI, C.H.; CRISTIANI, G.D.

San Juan

Workshop; Towards Future Research on Space Weather Drivers; 2019

Flares are one of the most energetic transient phenomena in the Sun. Since the Solar Submillimeter Telescope installation (SST, Kaufmann et al., 2000 (a)) regular observations of the Sun at 212 and 405 GHz were made throughout the present millennium. In addition to SST observations, the KOSMA/BEMRAK telescope was operative from 2004 (Luthi et al., 2004 (b)) at 210 and 230/340 GHz. During solar  flares the Sun can become very bright at the frequency range from 1 GHz to 100 GHz (microwaves). At these frequencies the burst emission is well explained by incoherent gyrosynchrotron radiation from mildly relativistic electrons moving through plasmas permeated by magnetic fields of 100-1000 G. Above 100 GHz some events exhibit an unexpected upturn towards the THz domain, during both impulsive and gradual phases, the so-called THzcomponent. A recent work (Kontar et al., 2018 (c)) shows that the spectral component rising with frequency can be explained by free-free emission from a plasma with temperatures between 104 and 106 K.Following Kontar et al., in this work we model the emission at 1-1000 GHz as gyrosynchrotron plus free-free emission due to inhomogeneous sources, trying to t the observed spectra corresponding to events where the THz component was present.(a) Kaufmann, P. et al., 2000, in High Energy Solar Physics Workshop Anticipating Hessi, ed.R. Ramaty, N. Mandzhavidze, 318, ASP Conf. Ser., 206.(b) Luthi, T. et al., 2004, A&A, 420, 361.(c) Kontar, E. et al., 2018, A&A, 620, 95.