Coronal Abundances in an Active Region: Evolution and Underlying Chromospheric and Transition Region Properties

TL;DR

This study investigates the spatial and temporal variations of coronal element abundances in an active solar region, revealing links between FIP bias, outflow regions, and chromospheric turbulence, with implications for understanding solar atmospheric processes.

Contribution

It provides new insights into the spatial distribution and variability of FIP bias in an active region, integrating spectroscopic data from Hinode/EIS and IRIS to connect coronal composition with chromospheric turbulence.

Findings

FIP bias varies significantly across the active region, highest at outflow boundaries.

Chromospheric turbulence is enhanced in regions with high FIP bias.

Temporal variability of FIP bias is modest, but some moss regions show increased variability.

Abstract

The element abundances in the solar corona and solar wind are often different from those of the solar photosphere, typically with a relative enrichment of elements with low first ionization potential (FIP effect). Here we study the spatial distribution and temporal evolution of the coronal chemical composition in an active region (AR) over about 10 days, using Hinode/EIS spectra, and we also analyze coordinated IRIS observations of the chromospheric and transition region emission to investigate any evidence of the footprints of the FIP effect in the lower atmosphere. To derive the coronal abundances we use a spectral inversion method recently developed for the MUSE investigation (Cheung et al. 2019, De Pontieu et al. 2020). We find that in the studied active region (AR 12738) the coronal FIP bias presents significant spatial variations, with its highest values (~ 2.5-3.5) in the outflow regions at the boundary of the AR, but typically modest temporal variability. Some moss regions and some regions around the AR sunspot show enhanced FIP (~ 2-2.5) with respect to the AR core, which has only a small FIP bias of ~1.5. The FIP bias appears most variable in some of these moss regions. The IRIS observations reveal that the chromospheric turbulence, as derived from IRIS2 inversions of the Mg II spectra, is enhanced in the outflow regions characterized by the high FIP bias, providing significant new constraints to both models aimed at explaining the formation of AR outflows and models of chemical fractionation.