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

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168319· OSTI ID:6956077

Cheng, Chungchieh ^[1]

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1. E. O. Hulburt Center for Space Research, Washington, DC (USA)

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. 21 refs.

• OSTI ID: 6956077
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 349; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
HEATING
INSTABILITY
LEPTONS
PLASMA HEATING
PLASMA INSTABILITY
RADIATIONS
SOLAR ACTIVITY
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR RADIATION
SOLAR X-RAY BURSTS
SPECTRA
STELLAR RADIATION
TURBULENCE
ULTRAVIOLET SPECTRA