CORONAL ABUNDANCES OF NEON AND MAGNESIUM ISOTOPES FROM SOLAR ENERGETIC PARTICLES

The relative abundances of 22 to 70 MeV nucleon-1 Ne and Mg isotopes f rom two large flare-associated solar energetic particle (SEP) events i n 1992 October and November, are determined from data taken by the Mas s Spectrometer Telescope on the polar-orbiting SAMPEX satellite. After converting the measured abundances to coronal values, the average Ne- 22/Ne-20 ratio is 0.076 +/- 0.008, consistent with the solar wind valu e of 0.073 but significantly less than that of previous SEP measuremen ts, in which the abundance of Ne-22 was substantially enhanced. The av erage Mg-26/Mg-24 ratio is 0.152 +/- 0.012, consistent with both previ ous SEP and other solar system measurements.