Multi-Fluid Extensions of MHD and Their Implications on Waves and Instabilities

Khomenko, E.

doi:10.1007/978-3-030-16343-3_3

Cited by 5 publications

(11 citation statements)

References 56 publications

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“…whether the fluid feels the Lorentz force or not), one sensible way to model this system is to look at a two-fluid system where the charged species are modelled as a charge-neutral plasma and the neutral species as a separate fluid with the two fluids coupled through collisions and ionisation/recombination (e.g. Khomenko, 2020). The equations for this approximation of the system (assuming a purely hydrogen plasma and including only the collisional coupling terms) are given as…”

Section: Dynamics In Partially Ionised Plasmasmentioning

confidence: 99%

“…where v CM is the centre-of-mass velocity of the two fluids (e.g. Khomenko, 2020). This allows the mass, momentum and energy equations to be summed and solved as a single fluid approximation (e.g.…”

Section: Connecting Between the Two-fluid And Single Fluid Approximat...mentioning

confidence: 99%

“…This is known as the strong coupling limit of the velocity drift, and is applied (often in simplified forms, e.g. Braginskii, 1965;Khomenko, 2020) as a correction to the induction equation giving…”

Section: Connecting Between the Two-fluid And Single Fluid Approximat...mentioning

confidence: 99%

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Shocks and instabilities in the partially ionised solar atmosphere

Hillier

Snow

2023

Advances in Space Research

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Section: Dynamics In Partially Ionised Plasmasmentioning

confidence: 99%

Section: Connecting Between the Two-fluid And Single Fluid Approximat...mentioning

confidence: 99%

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Shocks and instabilities in the partially ionised solar atmosphere

Hillier

Snow

2023

Advances in Space Research

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“…Studies of two-fluid waves in a stratified atmosphere show that the two-fluid effects lead to additional damping (Popescu Braileanu et al 2019). Reviews of partial ionisation can be found in Khomenko (2017); Ballester et al (2018); Khomenko (2020).…”

Section: Introductionmentioning

confidence: 99%

Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere

Snow

Hillier

2020

A&A

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Context. The plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfvén speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. How the energy is distributed between the two modes depends on the angle of magnetic field. Aims. The separation of neutral and ionised species in a gravitationally stratified atmosphere is investigated. The role of two-fluid effects on the structure of the shocks post-mode-conversion and the frictional heating is quantified for different levels of collisional coupling. Methods. Two-fluid numerical simulations are performed using the (PIP) code of a wave steepening into a shock in an isothermal, partially-ionised atmosphere. The collisional coefficient is varied to investigate the regimes where the plasma and neutral species are weakly, strongly and finitely coupled. Results. The propagation speeds of the compressional waves hosted by neutral and ionised species vary, therefore velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fast-mode shock. We find that the collisional coefficient drastically changes the features present in the system, specifically the mode conversion height, type of shocks present, and the finite shock widths created by the two-fluid effects. In the finitely-coupled regime fast-mode shock widths can exceed the pressure scale height leading to a new potential observable of two-fluid effects in the lower solar atmosphere.

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“…treating the two fluids separately, but coupling them 5215 through collisions) [130], and nonlinear simulations of the magnetic Rayleigh-Taylor instability including ambipolar diffusion which show that the neutral and ion flows can have large (order of a few km s −1 ) differences in the velocities between them [272]. Details of the formulation behind ambipolar diffusion and multi-fluid modeling can be found in [271].…”

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confidence: 99%