FIP Bias Evolution in an Emerging Active Region as observed in SPICE Synoptic Observations

TL;DR

FIP bias evolution in an emerging active region is probed with SPICE SPROUTS, spanning from the upper chromosphere to the low corona. The study employs differential emission measure analysis and three line-ratio proxies to quantify relative abundances and compares the results to a ponderomotive-force (Alfvén-wave) fractionation model. Findings show the AR core preserving photospheric composition while fan loops, footpoints, and boundaries exhibit coronal abundances, with Mg/Ne FIP bias rising from approximately $1.5$ to around $2.25$ over two days; S/O behavior supports resonant-wave fractionation in transition-region structures, and model predictions align best with boundary regions. The work supports a chromospheric origin for FIP fractionation and underscores resonant Alfvén waves as a primary driver, with implications for linking surface magnetic topology to coronal composition and solar wind sources; future multi-instrument campaigns are recommended to refine constraints.

Abstract

We investigate the time evolution of relative elemental abundances in the context of the first ionization potential effect focusing on an active region. Our aim is to characterize this evolution in different types of solar active region structures as well as in different atmospheric layers. We wish to assert how the measured changes relate to different magnetic topologies by computing abundance enhancement in different conditions using the ponderomotive force model. Leveraging spectroscopic observations from the Spectral Imaging of the Coronal Environment instrument on board Solar Orbiter, we use extreme ultraviolet lines from ions formed across a broad temperature range--from the upper chromosphere to the low corona--and we perform relative abundance ratios following differential emission measure analysis. This methodology yields relative abundance maps from low, intermediate, and high first ionization potential elements. We obtain the temporal evolution of a number of abundance ratios for different structures on the Sun. We compare these results with the outcomes of the ponderomotive force model. We find good correlation between the model and our results, suggesting an Alfvén-wave driven fractionation of the plasma. Fan loops, loop footpoints and active region boundaries exhibit coronal abundances, while the active region core shows more photospheric-like composition. A slow and steady increase in the magnesium to neon relative first ionization potential bias values is observed, starting around 1.5 and increasing by about 50\% after two days. The sulfur to oxygen evolution coupled with the model brings evidence of resonant waves fractionating the plasma in transition region structures.

Figures (8)

• Figure 1: Contribution functions for the SPICE lines of interest computed with the CHIANTI database version 11 Dufresne2024. The solid lines are computed with a density of $n_e = 1 \times 10^8$ cm$^{-3}$, dotted lines of $n_e = 1 \times 10^9$ cm$^{-3}$ and dashed lines of $n_e = 1 \times 10^{10}$ cm$^{-3}$.
• Figure 2: Evolution of AR 13169 in terms of sunspot number (blue curve) and sunspot area (orange curve). Data is the courtesy of https://www.spaceweatherlive.com. During this period, 3 M-class flares and 61 C-class flares have been recorded. The time of the observations studied here is highlighted in gray.
• Figure 3: Evolution of AR 13169 (situated in the top left on the first raster) from 2022 December 20 to 2022 December 22. Left: SPICE's Ne VIII 770 Å rasters overlayed on SDO/AIA 171 Å. Right: corresponding SDO/HMI magnetograms with C III 977 Å rasters. On the magnetograms, green/yellow areas represent positive/negative polarity. Note: the dark horizontal lines ("dumbbells") are square alignment apertures, located at each end of the slits .
• Figure 4: DEM estimation (left panel), EM loci (middle panel, providing an estimation of the upper limit of the DEM) and corresponding zone on the Ne VIII 770 Å map. The DEM estimation indicates a rather multithermal emission. The gray dotted lines indicate the range of temperature where the DEM estimation is reliable, and different line styles represent different densities. Note: the scale for the DEM is linear.
• Figure 5: Evolution of AR 13169 with time progressing downwards. Left column: SPICE radiance maps seen in the Ne VIII 770 line ($\log_{10}\frac{T}{1\, \text{K}}$=5.8). Middle column: corresponding FIP bias maps seen in the Mg IX / Ne VIII ratio. Right column: Evolution of the FIP bias values, tracking different zones. Note: time progresses from left to right in this column's plots, and the offset is to show error bars with more clarity. The black dotted line represents the photospheric / quiet Sun reference. Bottom right plot: ratio of contribution functions for the lines presented. The solid lines are computed with a density of $n_e= 10^8$ cm$^{-3}$, dotted with $n_e= 10^9$ cm$^{-3}$ and dashed $n_e= 10^{10}$ cm$^{-3}$.