Authors: Adriana V R Silva G H Share R J Murphy J E R Costa C G Giménez de Castro JP Raulin P Kaufmann
Publish Date: 2007/11/08
Volume: 245, Issue: 2, Pages: 311-326
Abstract
We investigate the origin of the increasing spectra observed at submillimeter wavelengths detected in the flare on 2 November 2003 starting at 1717 UT This flare classified as an X83 and 2B event was simultaneously detected by RHESSI and the Solar Submillimeter Telescope SST at 212 and 405 GHz Comparison of the time profiles at various wavelengths shows that the submillimeter emission resembles that of the highenergy X rays observed by RHESSI whereas the microwaves observed by the Owens Valley Solar Array OVSA resemble that of ∼50 keV X rays Moreover the centroid position of the submillimeter radiation is seen to originate within the same flaring loops of the ultraviolet and Xray sources Nevertheless the submillimeter spectra are distinct from the usual microwave spectra appearing to be a distinct spectral component with peak frequency in the THz range Three possibilities to explain this increasing radio spectra are discussed 1 gyrosynchrotron radiation from accelerated electrons 2 bremsstrahlung from thermal electrons and 3 gyrosynchrotron emission from the positrons produced by pion or radioactive decay after nuclear interactions The latter possibility is ruled out on the grounds that to explain the submillimeter observations requires 3000 to 2×105 more positrons than what is inferred from Xray and γray observations It is possible to model the emission as thermal however such sources would produce too much flux in the ultraviolet and soft Xray wavelengths Nevertheless we are able to explain both spectral components at microwave and submillimeter wavelengths by gyrosynchrotron emission from the same population of accelerated electrons that emit hard X rays and γ rays We find that the same 5×1035 electrons inferred from RHESSI observations are responsible for the compact submillimeter source 05 arcsec in radius in a region of 4500 G low in the atmosphere and for the traditional microwave spectral component by a more extended source 50 arcsec in a 480 G magnetic field located higher up in the loops The extreme values in magnetic field and source size required to account for the submillimeter emission can be relaxed if anisotropy and transport of the electrons are taken into account
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