Search for High energy particle acceleration signatures in the submillimetre-visible solar flare emission spectrum

KAUFMANN, P.; MELO, A.M.; MARCON, R.; KUDAKA,A.S.; MARUN, A.; PEREYRA, P.; RAULIN, J.P.; LEVATO, H.

Praga

Workshop; Solar Active Regions and 3D Magnetic Structure; 2006

Recent results obtained at submm-waves indicated that key questions regarding physical mechanisms at the origin of solar flares are expected to become better understood with measurements in the far to mid IR range. A new spectral component discovered with fluxes increasing for shorter submillimeter wavelengths indicates emissions by particles accelerated to very high energies. The nature of emission is not known. The observed parameters rule out a thermal interpretation, and the first emission models recently suggested assume three different mechanisms which may become comparable in importance: (a) synchrotron radiation by beams of ultrarelativistic electrons; (b) synchrotron radiation by positrons produced by nuclear reactions arising from energetic beams interactions at dense regions close to the photosphere, and (c) Langmuir waves emission from deep photosphere excited by high energy electron beams. The spectral band where observed features would be critically defined is in the far infrared to visible range, where the terrestrial atmosphere is highly opaque. New experiments are being considered to observe solar flares from the ground in the remaining high frequency atmospheric "windows" at 670, 850 GHz and in mid- and near infrared. Space experiments are planned for discrete frequencies between 1-20 THz. We show the first results obtained with a new setup developed to measure solar activity at 10 ìm (or 30 THz), using a camera with a focal plane array of uncooled microbolometers coupled to a celostat by an adequate optical arrangement.