Two-fluid reconnection jets in a gravitationally stratified atmosphere

Abstract

The density decreases exponentially with height in the solar gravitationally stratified atmosphere, therefore the collisional coupling between the ionized plasma and the neutrals also decreases. Here, we investigate the role of collisions between ions and neutrals on the reconnection process occurring at various heights in the atmosphere. We perform simulations of magnetic reconnection induced by a localized resistivity in a gravitationally stratified atmosphere, where we vary the height of the initial reconnection X-point. We compare a magnetohydrodynamic (MHD) model and two two-fluid configurations: one where the collisional coupling is calculated from local plasma parameters and another where the coupling is decreased, so that collisional effects are enhanced. Simulations in a stratified atmosphere show similar structures in MHD and two-fluid simulations with strong coupling. However, when collisional effects are increased to attain representative parameter regimes, we find a nonlinear runaway instability, which separates the plasma-neutral densities across the current sheet (CS). With increased collisional effects, the initial decoupling in velocity heats the neutrals and this sets up a nonlinear feedback where neutrals migrate outside the CS, replacing charged particles which accumulate towards the center of the CS. The reconnection rate has a maximum value around 0.1, similar for both reconnection heights, and is consistent with the use of a localized enhanced resistivity used in all three models. The initial stages of plasmoid formation, observed near the end of our simulations, is influenced by the outflow from the primary reconnection point, rather than by collisions. We synthesize optically thin emission for both MHD and two-fluid models, which can show a very different evolution when the charged particle density is used instead of the total density.

References in corpus (14)

• Instability of current sheets and formation of plasmoid chains
• MPI-AMRVAC 3.0: updates to an open-source simulation framework
• Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere
• Magnetohydrodynamic shocks in and above post-flare loops: two-dimensional simulation and a simplified model
• A fully self-consistent model for solar flares
• MHD turbulence formation in solar flares: 3D simulation and synthetic observations
• Plasmoids, Flows, and Jets During Magnetic Reconnection in a Failed Solar Eruption
• Solar jets observed with the Interface Region Imaging Spectrograph (IRIS)
• Intermediate shock substructures within a slow-mode shock occurring in partially ionised plasma
• Three-dimensional MHD wave propagation near a coronal null point: a new wave mode decomposition approach
• Annihilation of Magnetic Islands at the Top of Solar Flare Loops
• Coalescence Instability in Chromospheric Partially Ionised Plasmas
• Magnetic field amplification and structure formation by the Rayleigh-Taylor instability
• Two-fluid implementation in MPI-AMRVAC, with applications in the solar chromosphere

Cited by in corpus (3)

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