Evidence for collisionless conduction fronts in impulsive solar flares

Journal Article · Thu Aug 01 04:00:00 EDT 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163370· OSTI ID:5266230

Batchelor, D A; Crannell, C J; Wiehl, H J; Magun, A

Impulsive bursts of hard x-rays and microwaves are observed during most solar flares, and both emissions can be attributed to a common distribution of source electrons with energies from approximately 10 keV to several hundred keV. A detailed account of the evolution of the electron distribution is crucial to a complete description of the energy process in flares. In this paper, a new analysis is made of a thermal flare model proposed by Brown. Melrose, and Spicer; and Smith and Lilliequist. They argued that the source assumed in this model would not explain the simultaneous impulsive microwavve emissio. In contrast, the new results presented here show that this model leads to the development of a quasi-Maxwellian distribution of electrons that explains both the hard x-ray and microwave emissions. This implies that the source sizes can be determined from observations of the optically thick portios of microwave spectra and the temperatures obtained from associated hard x-ray observations. In this model, the burst emission would rise to a maximum in a time t/sub r/ approximately equal to L/c/sub s/, where L is the half-length of the arch, and c/sub s/ = (kT/sub e//m/sub i/)/sup 1/2/ is the ion-sound speed. New observations of these impulsive flare emissions are analyzed herein to test this prediction of the model.

• Research Organization: Laboratory for Astronomy and Solar Physics, NASA/Goddard Space Flight Center, Greenbelt, Maryland
• OSTI ID: 5266230
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 295:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DATA
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELECTRONS
ELEMENTARY PARTICLES
EXPERIMENTAL DATA
FERMIONS
HARD X RADIATION
INFORMATION
ION ACOUSTIC WAVES
ION WAVES
IONIZING RADIATIONS
LEPTONS
MAIN SEQUENCE STARS
MICROWAVE SPECTRA
NUMERICAL DATA
OPACITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLASMA
PLASMA WAVES
RADIATION FLUX
RADIATION SOURCES
RADIATIONS
RADIOWAVE RADIATION
SOLAR ACTIVITY
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR RADIATION
SOLAR X-RAY BURSTS
SPECTRA
STARS
STELLAR RADIATION
SUN
X RADIATION
X-RAY SPECTRA