DEUTERIUM SYNTHESIS IN THE SOLAR-FLARE ON 24 MAY 1990 - OBSERVATIONS OF DELAYED EMISSION IN THE 2.2 MEV GAMMA-RAY LINE BY THE GRANAT SATELLITE

The PHEBUS instrument on the GRANAT observatory detected strong emissi on in the 2.2 MeV line during a bright solar flare on 24 May 1990. Thi s gamma-ray line occurs in the reaction H-1(n,gamma)H-2 which forms de uterium. The maximum in the gamma-emission was observed to be delayed by approximately 100 sec relative to the maxima at 4-6 MeV and 65-120 MeV. A declining flux was detected in the 2.2 MeV line for more than 8 minutes after the maximum in the emission at 4-6 MeV. Integrating ove r the entire flare, the number of photons in the 2.2 MeV line was 345/-6 photons/cm2. These observations imply that more than 3 tons of deu terium were synthesized at the surface of the sun.