Light Isotope Abundances in Solar Energetic Particles Measured by the Space Instrument NINA

This article reports nine Solar Energetic Particle events detected by theinstrument NINA between October 1998 and April 1999. NINA is a silicon-basedparticle detector mounted on-board the Russian satellite Resurs-01-N4, whichhas flown at an altitude of about 800 km in polar inclination since July 1998.For every solar event the power-law He4 spectrum across the energy interval10--50 MeV/n was reconstructed, and spectral indexes, gamma, from 1.8 to 6.8extracted. Data of He3 and He4 were used to determine the He3/He4 ratio, thatfor some SEP events indicated an enrichment in He3. For the 1998 November 7event the ratio reached a maximum value of 0.33+- 0.06, with spectral indexesof gamma = 2.5 +- 0.6 and gamma = 3.7 +- 0.3 for He3 and He4, respectively. TheHe3/He4 ratio averaged over the remaining events was 0.011 +- 0.004. For allevents the deuterium-to-proton ratio was determined. The average value over allevents was (3.9+-1.4) 10^{-5} across the energy interval 9--12 MeV/n. For oneevent (1998 November 24) this ratio yielded approximately 10 times higher thannormal coronal values. Upper limits on the H3/H1 counting ratio for all eventswere determined. For the 1998 November 14 SEP event the high flux of heavyparticles detected made it possible to reconstruct the carbon and oxygen flux.Comment: 42 pages, 14 figures, submitted to Journal of Geophysical Researc