Sulfur fractionation in coronal plumes as observed by Solar Orbiter/SPICE

Abstract

Coronal plumes are bright, narrow structures rooted in coronal holes that contribute to the solar wind. Their composition, particularly elemental fractionation as a function of first ionization potential (FIP), provides diagnostics of plasma properties and magnetic connectivity. Earlier plume studies of fractionation using low-FIP elements reached conflicting conclusions. Intermediate-FIP elements may provide additional diagnostic insight, since their fractionation is thought to involve processes beyond those affecting low-FIP species. We investigate sulfur (intermediate-FIP element) in plumes to assess the presence of fractionation, its evolution, and its relation to wave activity. We analyzed Solar Orbiter observations of two plumes in an equatorial coronal hole during March--April 2024, using Spectral Imaging of the Coronal Environment (SPICE) to derive the sulfur-to-nitrogen ratio. EUV imaging and magnetograms provided additional context. Data were processed with the open-source Python tool Spectral Analysis Fitting Framework and Reduction of Noise (SAFFRON). Both plumes showed sulfur fractionation that remained constant within uncertainties. The fractionated plasma was co-located with strong magnetic footpoints, in contrast with the surrounding interplume plasma. These results provide the evidence for sulfur fractionation in plumes and suggest, consistent with the ponderomotive force model, wave dynamics in the chromosphere as a driver.

26 pages, 10 figures

References in corpus (16)

• Array Programming with NumPy
• The Solar Orbiter mission -- Science overview
• Alfven Waves in the Lower Solar Atmosphere
• Element Abundances: A New Diagnostic for the Solar Wind
• Quasiperiodic Energy Release and Jets at the Base of Solar Coronal Plumes
• Plumelets: Dynamic Filamentary Structures in Solar Coronal Plumes
• Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun
• Directly comparing coronal and solar wind elemental fractionation
• Observation of Alfvén Wave Reflection in the Solar Chromosphere: Ponderomotive Force and First Ionization Potential Effect
• Imaging and spectroscopic observations of extreme-ultraviolet brightenings using EUI and SPICE on board Solar Orbiter
• Accuracy analysis of the on-board data reduction pipeline for the Polarimetric and Helioseismic Imager on the Solar Orbiter mission
• Magnetic fields inferred by Solar Orbiter: A comparison between SO/PHI-HRT and SDO/HMI
• Relative Abundance Measurements in Plumes and Interplumes
• Slow Solar Wind Connection Science during Solar Orbiter's First Close Perihelion Passage
• SPICE Connection Mosaics to link the Sun's surface and the heliosphere
• The Evolution of Heavy Ion Abundances with Solar Activity