Coronal Elemental Abundances in Solar Emerging Flux Regions

Deborah Baker,David M Long,Harry P Warren,David H Brooks,Alexander W James,David R Williams,Lidia Van Driel-Gesztelyi,Pascal Démoulin

doi:10.3847/1538-4357/aaadb0

Abstract

Abstract The chemical composition of solar and stellar atmospheres differs from the composition of their photospheres. Abundances of elements with low first ionization potential (FIP) are enhanced in the corona relative to high-FIP elements with respect to the photosphere. This is known as the FIP effect and it is important for understanding the flow of mass and energy through solar and stellar atmospheres. We used spectroscopic observations from the Extreme-ultraviolet Imaging Spectrometer on board the Hinode observatory to investigate the spatial distribution and temporal evolution of coronal plasma composition within solar emerging flux regions inside a coronal hole. Plasma evolved to values exceeding those of the quiet-Sun corona during the emergence/early-decay phase at a similar rate for two orders of magnitude in magnetic flux, a rate comparable to that observed in large active regions (ARs) containing an order of magnitude more flux. During the late-decay phase, the rate of change was significantly faster than what is observed in large, decaying ARs. Our results suggest that the rate of increase during the emergence/early-decay phase is linked to the fractionation mechanism that leads to the FIP effect, whereas the rate of decrease during the later decay phase depends on the rate of reconnection with the surrounding magnetic field and its plasma composition.

Highlights

Element abundance patterns have long been used as tracers of physical processes throughout astrophysics
The emergence/decay phases are of nearly comparable duration, an important difference compared to active regions (ARs) where the decay phase is much longer than the emergence phase
We analyzed the temporal evolution and spatial distribution of coronal plasma composition within flux regions of varying sizes located inside an equatorial coronal hole using observations from Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS)

Summary

Introduction

Element abundance patterns have long been used as tracers of physical processes throughout astrophysics. The observed variation in coronal solar and stellar abundances depends on the first ionization potential (FIP) of the main elements found in the solar atmosphere. Those elements with FIP values greater than 10 eV (high-FIP elements) maintain their photospheric abundances in the corona, whereas elements with lower FIP have enhanced abundances (low-FIP elements), i.e., the so-called solar/stellar FIP effect. The inverse FIP (IFIP) effect refers to the enhancement/depletion of high-/low-FIP elements in solar and stellar coronae. FIP bias is the factor by which low-FIP elements such as Si, Mg, and Fe are enhanced or depleted in the corona relative to their photospheric abundances

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Discussion

Conclusion