MODELING IRON ABUNDANCE ENHANCEMENTS IN THE SLOW SOLAR WIND

We have studied the behavior of Fe ions in the slow solar wind, using a fluid model extending from the chromosphere to 1 AU. Emphasis is on elemental "pileup" in the corona, i.e., a region where the Fe density increases and has a local maximum. We study the behavior of individual Fe ions relative to each other in the pileup region, where Fe(+10) and Fe(+12) have been used as examples. We find that elemental pileups can occur for a variety of densities and temperatures in the corona. We also calculate the ion fractions and obtain estimates for the freezing-in distance of Fe in the slow solar wind. We find that the freezing-in distance for iron is high, between 3 and 11 R(circle dot), and that a high outflow velocity, of order 50-100 km s(-1), in the region above the temperature maximum is needed to obtain ion fractions for Fe(+10) and Fe(+12) that are consistent with observations.