The Impact of Multifluid Effects in the Solar Chromosphere on the Ponderomotive Force under SE and NEQ Ionization Conditions

• Published in: The Astrophysical journal Vol. 949; no. 2; pp. 112 - 129
• Main Authors: Martínez-Sykora, Juan, De Pontieu, Bart, Hansteen, Viggo H., Testa, Paola, Wargnier, Q. M., Szydlarski, Mikolaj
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.06.2023; IOP Publishing
• Subjects: Alfven waves; Astrophysics; Atmosphere; Atmospheric models; Chromosphere; Corona; First ionization potential; Ionization; Ionization effects; Magnetohydrodynamic waves; Magnetohydrodynamics; Mathematical models; Modelling; Numerical models; Ponderomotive forces; Solar abundances; Solar atmosphere; Solar chromosphere; Solar corona; Solar magnetic fields; Solar spicules; Solar wind; Spicules; Stellar atmospheres; Stellar coronae; Stellar physics
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/acc465

Abstract The ponderomotive force has been suggested to be the main mechanism to produce the so-called first ionization potential (FIP) effect—the enrichment of low-FIP elements observed in the outer solar atmosphere, in the solar wind, and in solar energetic events. It is well known that the ionization of these elements occurs within the chromosphere. Therefore, this phenomenon is intimately tied to the plasma state in the chromosphere and the corona. For this study, we combine IRIS observations, a single-fluid 2.5D radiative magnetohydrodynamics (MHD) model of the solar atmosphere, including ion–neutral interaction effects and nonequilibrium (NEQ) ionization effects, and a novel multifluid multispecies numerical model (based on the Ebysus code). Nonthermal velocities of Si iv measured from IRIS spectra can provide an upper limit for the strength of any high-frequency Alfvén waves. With the single-fluid model, we investigate the possible impact of NEQ ionization within the region where the FIP may occur, as well as the plasma properties in those regions. These models suggest that regions with strongly enhanced network and type II spicules are possible sites of large ponderomotive forces. We use the plasma properties of the single-fluid MHD model and the IRIS observations to initialize our multifluid models to investigate the multifluid effects on the ponderomotive force associated with Alfvén waves. Our multifluid analysis reveals that collisions and NEQ ionization effects dramatically impact the behavior of the ponderomotive force in the chromosphere, and existing theories may need to be revisited.