Positron annihilation radiation from the 1991 Novermber 15 flare

Abstract

view Abstract Citations (7) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Positron Annihilation Radiation from the 1991 November 15 Flare Kawabata, K. ; Yoshimori, M. ; Suga, K. ; Morimoto, K. ; Hiraoka, T. ; Sato, J. ; Ohki, K. Abstract The gamma-ray spectrometer on Yohkoh has detected the positron annihilation line at 511 keV produced during the 1991 November 15 flare (X1.0/3B). The 511 keV line fluence, integrated over the time interval of 22:37:50-22:38:14 UT, is (6.7 +/- 2.2) photons cm/sq cm. The time profile of 511 keV line exhibited long decay time compared with the electron bremsstrahlung and prompt gamma-ray line components. From the analysis of time profile of the 511 keV line, we come to the following conclusions: (1) the main source of positrons is deexcitation of (16)O*6.052 by e(+)-e(-) pair emission. (2) Beta(+) -emitting nuclei of S-31, P-29, Si-27, Al-26m, Al-25, Mg-23, Ne-19, and Na-21 are also important sources of positrons in the decay phase. (3) The density of the positron annihilation region in the photosphere is 1016/cu cm. (4) Most likely interpretation of the time profile is that at least 50% of positrons annihilate in coronal flare loops with a density of 1012 to 1013/cu cm and with a temperature of 106 - 3 x 106 K. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1994 DOI: 10.1086/191893 Bibcode: 1994ApJS...90..701K Keywords: Coronal Loops; Nuclear Fusion; Pair Production; Positron Annihilation; Solar Flares; Abundance; Angular Distribution; Bremsstrahlung; Decay Rates; Gamma Ray Spectrometers; Temperature Effects; Solar Physics; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; ABUNDANCES; SUN: FLARES; SUN: X-RAYS; GAMMA RAYS full text sources ADS |