Observations of the hard X-ray spectrum of the impulsive phase of solar flares

Abstract

view Abstract Citations (35) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of the hard X-ray spectrum of the impulsive phase of solar flares. Elcan, M. J. Abstract The impulsive solar hard X-ray spectrum provides a direct diagnostic on the impulsive energy release of the flare. The data from the hard X-ray (14-342 keV) spectrometer on OSO 7 have been examined for events covering a wide energy range to determine the photon spectrum more precisely. This resulted in a sample of 38 events. The data have been fitted with either single- or double-power laws, and with an exponential spectrum, as from thermal bremsstrahlung. The chi-squared statistic between two-parameter fits strongly favors the exponential fit, particularly at peak intensity when the widest energy range is sampled. This result supports a single-temperature thermal source of the impulsive solar hard X-rays with temperatures in the range 4.7-31 keV and emission measures in the range from 8.4 x 10 to the 43rd to 6.0 x 10 to the 46th per cu cm. The temperature reaches a single maximum and then rapidly decays, but the emission measure usually increases throughout, even after temperature maximum, for data with 10-s resolution. Publication: The Astrophysical Journal Pub Date: December 1978 DOI: 10.1086/182840 Bibcode: 1978ApJ...226L..99E Keywords: Solar Flares; Solar Temperature; Solar X-Rays; X Ray Spectra; Bremsstrahlung; Oso-7; Plasma Diagnostics; Thermal Energy; Solar Physics; Solar Flares:X-Ray Spectra full text sources ADS |