A thermal/nonthermal model for solar microwave bursts

Abstract

view Abstract Citations (51) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Thermal/Nonthermal Model for Solar Microwave Bursts Benka, Stephen G. ; Holman, Gordon D. Abstract A theoretical framework is developed for modeling high-resolution spectra of microwave bursts from the Owens Valley Radio Observatory which can account for departures from expectations based on simple thermal or nonthermal models. Specifically, 80 percent of the events show more than one spectral peak; many bursts have a low-side spectral index steeper than the maximum expected slope; and the peak frequency stays relatively constant and changes intensity in concert with the secondary peaks throughout a given event's solution. It is shown that the observed spectral features can be explained through gyrosynchrotron radiation. The 'secondary' components seen on the LF side of many spectra are nonthermal enhancements superposed upon thermal radiation, occurring between the thermal harmonics. A steep optically thick slope is accounted for by the thermal absorption of nonthermal radiation. If the coexistence of thermal and nonthermal particles is interpreted in terms of electron heating and acceleration in current sheets, a changing electric field strength can account for the gross evolution of the microwave spectra. Publication: The Astrophysical Journal Pub Date: June 1992 DOI: 10.1086/171394 Bibcode: 1992ApJ...391..854B Keywords: Cyclotron Radiation; Microwaves; Solar Flares; Solar Radio Bursts; Synchrotron Radiation; Distribution Functions; Electric Fields; Solar Physics; RADIATION MECHANISMS: CYCLOTRON AND SYNCHROTRON; SUN: FLARES; SUN: RADIO RADIATION full text sources ADS |