Ultraviolet observations of the preimpulsive phase in a solar flare - Enhanced turbulence and heating

view Abstract Citations (13) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultraviolet Observations of the Preimpulsive Phase in a Solar Flare: Enhanced Turbulence and Heating Cheng, Chung-Chieh Abstract The unique UV spectra of the January 21, 1974 flare obtained from Skylab before the onset of an impulsive hard X-ray burst are presented. The observations show that the UV emission lines were much enhanced and their line profiles much widened, indicating large nonthermal turbulence in the transition region plasmas before the impulsive phase. This excitation could be due to the dissipation of enhanced current in the preflare loop. This excitation continued until some parameters that characterized the current flow were exceeded and some plasma instabilities appeared that accelerated the electrons which produced the hard X-ray emission. The heating of the flaring plasmas to high temperatures started before the impulsive phase, as shown by the presence of Fe XXI emission. Publication: The Astrophysical Journal Pub Date: January 1990 DOI: 10.1086/168319 Bibcode: 1990ApJ...349..362C Keywords: Coronal Loops; Plasma Heating; Plasma Turbulence; Solar Flares; Ultraviolet Spectra; Energetic Particles; Gamma Ray Bursts; Skylab Program; Solar Spectra; Solar X-Rays; Solar Physics; SUN: FLARES; SUN: TRANSITION REGION; TURBULENCE; ULTRAVIOLET: SPECTRA full text sources ADS |