Density structure in a multicomponent coronal loop

We investigate the variation of species densities and electric held along a static model coronal loop consisting of electrons, protons, and heavier io ns in a gravitationally stratified stellar atmosphere in an attempt to rela te photospheric and coronal loop abundances. The loop plasma is assumed to be confined along a strong magnetic field line, so all forces transverse to the magnetic field are taken to be in balance and the loop can be modeled as a one-dimensional structure. Differential gravitational stratification o f the ion species induces a polarization electric field E along the loop. B y invoking charge quasineutrality, we devise an iteration scheme to compute numerical solutions for the species densities and E to prescribed accuracy ; we also derive approximate analytic solutions. For confined coronal plasm a loops that are sufficiently long lived for gravitational settling to occu r (e.g., greater than or similar to 1 day), severe reduction in coronal ion densities would be expected. Our self-consistent, multicomponent treatment predicts higher loop densities than those predicted by a model that neglec ts the effect of the heavy ions on the electric held, the density enhanceme nt is an increasing function of the distance along the loop and of the ion charge and ranges from 4% for twice-ionized species to 33% for 14 times-ion ized species at the top of an isothermal loop with T = 3 x 10(6) K and a ra dius of 10(9) cm.