Plasma composition measurements in an active region from Solar Orbiter/SPICE and Hinode/EIS

TL;DR

This study combines Solar Orbiter/SPICE and Hinode/EIS observations to measure and analyze the elemental composition of an active region, providing insights into solar wind sources and coronal abundance variations.

Contribution

It demonstrates the capability of SPICE to differentiate between photospheric and coronal abundances and benchmarks its measurements against EIS data for the first time.

Findings

SPICE can distinguish between photospheric and coronal Mg/Ne abundances.

Combined SPICE and EIS data reveal the atmospheric composition of a fan loop.

Challenges remain in resolving elemental fractionation without detailed temperature constraints.

Abstract

A key goal of the Solar Orbiter mission is to connect elemental abundance measurements of the solar wind enveloping the spacecraft with EUV spectroscopic observations of their solar sources, but this is not an easy exercise. Observations from previous missions have revealed a highly complex picture of spatial and temporal variations of elemental abundances in the solar corona. We have used coordinated observations from Hinode and Solar Orbiter to attempt new abundance measurements with the SPICE (Spectral Imaging of the Coronal Environment) instrument, and benchmark them against standard analyses from EIS (EUV Imaging Spectrometer). We use observations of several solar features in AR 12781 taken from an Earth-facing view by EIS on 2020 November 10, and SPICE data obtained one week later on 2020 November 17; when the AR had rotated into the Solar Orbiter field-of-view. We identify a range of spectral lines that are useful for determining the transition region and low coronal temperature structure with SPICE, and demonstrate that SPICE measurements are able to differentiate between photospheric and coronal Mg/Ne abundances. The combination of SPICE and EIS is able to establish the atmospheric composition structure of a fan loop/outflow area at the active region edge. We also discuss the problem of resolving the degree of elemental fractionation with SPICE, which is more challenging without further constraints on the temperature structure, and comment on what that can tell us about the sources of the solar wind and solar energetic particles.