The high Ne/C and Ne/O abundance ratios in the footpoints of solar flares

High chromospheric abundance ratios of Ne/C and Ne/O were deduced from the gamma-ray spectroscopy of the 1981 April 27 flare. A similar high Ne/O ratio was observed in energetic solar particles from $^3\text {He}$-rich flares. These high ratios are consistent neither with local galactic abundances, nor with the first ionization-potential (FIP) scenario (Meyer 1985a). The inconsistency is explained by temporal deviations from the quiet-chromosphere abundances in the nuclear (gamma-ray) line production region (the interaction region). During the flare soft X-ray radiation penetrates through the chromosphere and creates a slab-like region of non-thermal ionization ratios, i.e. ionized neon mixed with mostly neutral carbon and neutral oxygen below the interaction region. Charge-dependent mass transport upward from this slab causes an enhancement of Ne/C and Ne/O ratios at the interaction region. These considerations constrain the use of ‘gamma-ray’ abundances as indicators of quiet-chromosphere abundances.