Preacceleration in collapsing magnetic neutral sheets and anomalous abundances of solar flare particles

Levine's (1974) concept of a collapsing magnetic neutral sheet which can accelerate ambient protons to several times the mean thermal speed, provided that the collapse time scale is shorter than the proton Coulomb loss time, is applied to heavier elements in an investigation of the composition of the particles which can be accelerated by such a sheet. Tables of ionization equilibrium are combined with the thermal structure of a constant pressure loop in order to calculate phi sub x (the fraction of an element x which is accelerated) of 18 heavy elements, from carbon to nickel which satisfy a maximum-ionization criterion. Normalizing phi sub x to oxygen, it is found that relative to the composition of the ambient materials, C and N can be depleted by factors of up to 2-10, while other heavy elements, along with hydrogen, are enhanced. The numerical results obtained are qualitatively similar to anomalous abundances reported among solar flare particles.