Studies on solar hard x-rays and gamma-rays: Compton backscatter, anisotropy, polarization, and evidence for two phases of acceleration

Technical Report · Fri Apr 01 04:00:00 EST 1977

OSTI ID:7211764

Bai, T

Observations of solar X-rays and gamma-rays from large flares show that the hard X-ray spectrum extends into the gamma ray region, where a flattening in the spectrum of the continuum emission is observed above about 1 MeV. This emission is believed to be due to bremsstrahlung. In addition to electron-proton collisions, at energies greater than approximately 500 keV, bremsstrahlung due to electron-electron collisions becomes significant. Bremsstrahlung production was calculated for a variety of electron spectra extending from the nonrelativistic region to relativistic energies with electron-electron bremsstrahlung taken into account. By comparing these calculations with data, it is shown that the flattening in the spectrum of the continuum emission can be best explained by an electron spectrum consisting of two distinct components. This evidence, together with information on the X-ray and gamma ray time profiles, implied the existence of two phases of acceleration. The first phase accelerates electrons mainly up to about several hundred keV; the second phase accelerates a small fraction of the electrons accelerated in the first phase to relativistic energies and accelerates protons to tens and hundreds of MeV.

• Research Organization: National Aeronautics and Space Administration, Greenbelt, Md. (USA). Goddard Space Flight Center
• OSTI ID: 7211764
• Report Number(s): N-77-24048; NASA-TM-X-71309; X-660-77-85
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ANISOTROPY
BASIC INTERACTIONS
BREMSSTRAHLUNG
COMPTON EFFECT
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EMISSION SPECTRA
ENERGY RANGE
FERMIONS
GAMMA RADIATION
HARD X RADIATION
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
MEV RANGE
POLARIZATION
RADIATIONS
SCATTERING
SOLAR ACTIVITY
SOLAR FLARES
SOLAR X-RAY BURSTS
SPECTRA
STARS
SUN
X RADIATION
X-RAY SPECTRA