Non-WKB Models of the FIP Effect: The Role of Slow Mode Waves

TL;DR

This paper develops a non-WKB model for the FIP effect, incorporating slow mode waves generated by Alfven waves, to better understand element fractionation between the solar chromosphere and corona.

Contribution

It introduces a new physical model that includes slow mode wave effects and improved ionization balance, advancing the understanding of the FIP effect in solar physics.

Findings

Slow mode waves influence element fractionation.

Fractionation can become quasi-mass independent.

Alfven wave frequency affects element fractionation.

Abstract

A model for element abundance fractionation between the solar chromosphere and corona is further developed. The ponderomotive force due to Alfven waves propagating through, or reflecting from the chromosphere in solar conditions generally accelerates chromospheric ions, but not neutrals, into the corona. This gives rise to what has become known as the First Ionization Potential (FIP) Effect. We incorporate new physical processes into the model. The chromospheric ionization balance is improved, and the effect of different approximations is discussed. We also treat the parametric generation of slow mode waves by the parallel propagating Alfven waves. This is also an effect of the ponderomotive force, arising from the periodic variation of the magnetic pressure driving an acoustic mode, which adds to the background longitudinal pressure. This can have subtle effects on the fractionation, rendering it quasi-mass independent in the lower regions of the chromosphere. We also briefly discuss the change in the fractionation with Alfven wave frequency, relative to the frequency of the overlying coronal loop resonance.