A Unified Picture of the FIP and Inverse FIP Effects

TL;DR

This paper presents a unified model explaining both FIP and Inverse FIP effects in stellar coronae by analyzing wave-induced ponderomotive forces at loop footpoints, accounting for observed abundance anomalies.

Contribution

It introduces a comprehensive model based on wave ponderomotive forces that explains both FIP and Inverse FIP effects in the coronae of the sun and other stars.

Findings

Model reproduces observed abundance anomalies.

Both positive and negative abundance changes are possible.

Variations in parameters match stellar observations.

Abstract

We discuss models for coronal abundance anomalies observed in the coronae of the sun and other late-type stars following a scenario first introduced by Schwadron, Fisk & Zurbuchen of the interaction of waves at loop footpoints with the partially neutral gas. Instead of considering wave heating of ions in this location, we explore the effects on the upper chromospheric plasma of the wave ponderomotive forces. These can arise as upward propagating waves from the chromosphere transmit or reflect upon reaching the chromosphere-corona boundary, and are in large part determined by the properties of the coronal loop above. Our scenario has the advantage that for realistic wave energy densities, both positive and negative changes in the abundance of ionized species compared to neutrals can result, allowing both FIP and Inverse FIP effects to come out of the model. We discuss how variations in model parameters can account for essentially all of the abundance anomalies observed in solar spectra. Expected variations with stellar spectral type are also qualitatively consistent with observations of the FIP effect in stellar coronae.