Intermediate shock substructures within a slow-mode shock occurring in partially ionised plasma

Abstract

Slow-mode shocks are important in understanding fast magnetic reconnection, jet formation and heating in the solar atmosphere, and other astrophysical systems. The atmospheric conditions in the solar chromosphere allow both ionised and neutral particles to exist and interact. Under such conditions, fine substructures exist within slow-mode shocks due to the decoupling and recoupling of the plasma and neutral species. We study numerically the fine substructure within slow-mode shocks in a partially ionised plasma, in particular, analysing the formation of an intermediate transition within the slow-mode shock. High-resolution 1D numerical simulations are performed using the (P\underline{I}P) code using a two-fluid approach. We discover that long-lived intermediate (Alfven) shocks can form within the slow-mode shock, where there is a shock transition from above to below the Alfven speed and a reversal of the magnetic field across the shock front. The collisional coupling provides frictional heating to the neutral fluid, resulting in a Sedov-Taylor-like expansion with overshoots in the neutral velocity and neutral density. The increase in density results in a decrease of the Alfven speed and with this the plasma inflow is accelerated to above the Alfven speed within the finite width of the shock leading to the intermediate transition. This process occurs for a wide range of physical parameters and an intermediate shock is present for all investigated values of plasma-$\beta$, neutral fraction, and magnetic angle. As time advances the magnitude of the magnetic field reversal decreases since the neutral pressure cannot balance the Lorentz force. The intermediate shock is long-lived enough to be considered a physical structure, independent of the initial conditions.

Accepted for A&A

References in corpus (9)

• Three-dimensional magnetic reconnection regimes: A review
• A Review of the 0.1 Reconnection Rate Problem
• The structure of the magnetic reconnection exhaust boundary
• Ellerman Bombs - Evidence for Magnetic Reconnection in the Lower Solar Atmosphere
• The formation and evolution of reconnection-driven slow-mode shocks in a partially ionised plasma
• The Magnetic Response of the Solar Atmosphere to Umbral Flashes
• On the effects of ion-neutral interactions in solar plasmas
• Differences between Doppler velocities of ions and neutral atoms in a solar prominence
• Diagnosis of Magnetic and Electric Fields of Chromospheric Jets through Spectropolarimetric Observations of HI Paschen Lines

Cited by in corpus (15)

• Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
• Two-fluid simulations of waves in the solar chromosphere II. Propagation and damping of fast magneto-acoustic waves and shocks
• Magnetohydrodynamic Non-linearities in Sunspot Atmospheres: Chromospheric Detections of Intermediate Shocks
• Joint action of Hall and ambipolar effects in 3D magneto-convection simulations of the quiet Sun. I. Dissipation and generation of waves
• Collisional ionisation, recombination and ionisation potential in two-fluid slow-mode shocks: analytical and numerical results
• Coalescence Instability in Chromospheric Partially Ionised Plasmas
• Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy
• Stability of two-fluid partially-ionised slow-mode shock fronts
• Two-fluid implementation in MPI-AMRVAC, with applications in the solar chromosphere
• Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere
• Characterisation of shock wave signatures at millimetre wavelengths from Bifrost simulations
• Two-fluid reconnection jets in a gravitationally stratified atmosphere
• Shock identification and classification in 2D MHD compressible turbulence -- Orszag-Tang vortex
• Shocks and instabilities in the partially ionised solar atmosphere
• MHD waves in the partially ionized plasma: from single to multi-fluid approach