Positron annihilation radiation from the 1991 Novermber 15 flare

Details Positron annihilation radiation from the 1991 Novermber 15 flare Positron annihilation radiation from the 1991 Novermber 15 flare

Feb 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apjs...90..701k&link_type=abstract

Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 90, no. 2, p. 701-705

Astronomy and Astrophysics

Astrophysics

6

Coronal Loops, Nuclear Fusion, Pair Production, Positron Annihilation, Solar Flares, Abundance, Angular Distribution, Bremsstrahlung, Decay Rates, Gamma Ray Spectrometers, Temperature Effects

Scientific paper

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.

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