Formation of the 0. 511 MeV line in solar flares

Journal Article · Wed Dec 01 04:00:00 EST 1976 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/154863· OSTI ID:7338084

Crannell, C J; Joyce, G; Ramaty, R; Werntz, C

The ..gamma..-ray line produced at 0.51 MeV in solar flares is the result of either the free annihilation of positrons with electrons or the formation and decay of positronium by two-photon emission. Positron annihilation from the bound state of positronium may also proceed by three-photon emission, resulting in a continuum with energies up to 0.51 MeV. The temperature, density, and state of ionization of the plasma in which the positrons annihilate determine the width of the 0.51 MeV line and the ratio of three-photon to two-photon emission. The widths and ratios are obtained for three representative sets of physical conditions: a completely ionized plasma, a partially ionized plasma, and a weakly ionized plasma that is essentially an atomic gas. When the relative abundance of free electrons to neutral atoms in the annihilation region is of the order of unity or greater, the width of the 0.51 MeV line is determined by thermal broadening. Whenever atomic hydrogen is present in any significant amount, annihilation proceeds via positronium formation, and the ratio of 3..gamma.. to 2..gamma.. annihilation depends primarily on the density. (AIP)

• Research Organization: NASA/Goddard Space Flight Center
• OSTI ID: 7338084
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 210:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
ATMOSPHERES
BASIC INTERACTIONS
COLLISIONS
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EQUATIONS
FERMIONS
FOKKER-PLANCK EQUATION
GAMMA RADIATION
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
LINE WIDTHS
MATHEMATICAL MODELS
MONTE CARLO METHOD
PLASMA
POSITRON COLLISIONS
POSITRONIUM
POSITRONS
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR FLARES
STAR MODELS