Hall instability of solar flux tubes in the presence of shear flows

Pandey, B. P.; Wardle, Mark

doi:10.1111/j.1365-2966.2012.21718.x

Cited by 20 publications

(24 citation statements)

References 58 publications

(85 reference statements)

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“…Not only the sub-Alfvénic flows were not considered in this limit but the other strong diffusion limit was completely ignored. Since it is well known that the Hall diffusion opens a new channel though which the free shear energy can flow to the waves (Wardle 1999;Pandey & Wardle 2012), we should anticipate similar outcome also in the present case when the plasma is highly diffusive.…”

Section: Dispersion Relationsupporting

confidence: 70%

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Pandey

2018

Monthly Notices of the Royal Astronomical Society

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In the Hall magnetohydrodynamics, the onset condition of the Kelvin-Helmholtz instability is solely determined by the Hall effect and is independent of the nature of shear flows. In addition, the physical mechanism behind the super and sub-Alfvénic flows becoming unstable is quite different: the high frequency right circularly polarized whistler becomes unstable in the super-Alfvénic flows whereas low frequency, left circularly polarized ion-cyclotron wave becomes unstable in the presence of sub-Alfvénic shear flows. The growth rate of the Kelvin-Helmholtz instability in the super-Alfvénic case is higher than the corresponding ideal magnetohydrodynamic rate. In the sub-Alfvénic case, the Hall effect opens up a new, hitherto inaccessible (to the magnetohydrodynamics) channel through which the partially or fully ionized fluid can become Kelvin-Helmholtz unstable. The instability growth rate in this case is smaller than the super-Alfvénic case owing to the smaller free shear energy content of the flow.When the Hall term is somewhat smaller than the advection term in the induction equation, the Hall effect is also responsible for the appearance of a new overstable mode whose growth rate is smaller than the purely growing Kelvin-Helmholtz mode. On the other hand, when the Hall diffusion dominates the advection term, the growth rate of the instability depends only on the Alfvén -Mach number and is independent of the Hall diffusion coefficient. Further, the growth rate in this case linearly increase with the Alfvén frequency with smaller slope for sub-Alfvénic flows.

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Section: Dispersion Relationsupporting

confidence: 70%

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Pandey

2018

Monthly Notices of the Royal Astronomical Society

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“…, 2010Goossens et al 2011;Khomenko & Collados 2012;Zaqarashvili et al 2012;Pandey 2013;Khomenko et al 2014). The drift of magnetic field through the matter in a partially ionized gas provides new pathways through which energy can be channelled to waves (Pandey & Wardle 2012, 2013.…”

Section: Introductionmentioning

confidence: 99%

Surface wave propagation in non-ideal plasmas

Pandey

Dwivedi²

2015

Monthly Notices of the Royal Astronomical Society

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The properties of surface waves in a partially ionized, compressible magnetized plasma slab are investigated in this work. The waves are affected by the non-ideal magnetohydrodynamic (MHD) effects which causes finite drift of the magnetic field in the medium. When the magnetic field drift is ignored, the characteristics of the wave propagation in a partially ionized plasma fluid is similar to the fully ionized ideal MHD except now the propagation properties depend on the fractional ionization as well as on the compressibility of the medium.The phase velocity of the sausage and kink waves increases marginally (by a few percent) due to the compressibility of the medium in both ideal as well as Halldiffusiondominated regimes. However, unlike ideal regime, only waves below certain cut-off frequency can propagate in the medium in Hall dominated regime. This cut-off for a thin slab has a weak dependence on the plasma beta whereas for thick slab no such dependence exists. More importantly, since the cut-off is introduced by the Hall diffusion, the fractional ionization of the medium is more important than the plasma compressibility in determining such a cutoff. Therefore, for both compressible as well incompressible medium, the surface modes of shorter wavelength are permitted with increasing ionization in the medium. We discuss the relevance of these results in the context of solar photosphere-chromosphere.

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“…In the upper chromosphere Alfvén waves may propagate although typically as very damped modes. So some efficient drivers are instabilities are required to have these and other waves present there in order to take part in the heating which still remains a puzzle (Vranjes & Poedts 2009a,b, 2010aVranjes 2011a,b;Pandey & Wardle 2012. In the corona the Alfvén wave is affected by viscosity for wavelengths roughly below the limit of around 30 km.…”

Section: Discussionmentioning

confidence: 99%

Viscosity effects on waves in partially and fully ionized plasma in magnetic field

Vranjes

2014

Monthly Notices of the Royal Astronomical Society

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Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on two very different waves (Alfvén and Langmuir) in solar atmosphere. A full set of viscosity coefficients is presented which includes coefficients for electrons, protons and hydrogen atoms. These are applied to layers with mostly magnetized protons in solar chromosphere where the Alfvén wave could in principle be expected. The viscosity coefficients are calculated and presented graphically for the altitudes between 700 and 2200 km, and required corresponding cross sections for various types of collisions are given in terms of altitude. It is shown that in chromosphere the viscosity plays no role for the Alfvén wave, which is only strongly affected by ion friction with neutrals. In corona, assuming the magnetic field of a few Gauss, the Alfvén wave is more affected by ion viscosity than by ion-electron friction only for wavelengths shorter that 1-30 km, dependent on parameters and assuming the perturbed magnetic field of one percent of its equilibrium value. For the Langmuir wave the viscosityfriction interplay in chromosphere is shown to be dependent on altitude and on wavelengths. In corona the viscosity is the main dissipative mechanism acting on the Langmuir mode.

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Hall instability of solar flux tubes in the presence of shear flows

Cited by 20 publications

References 58 publications

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Surface wave propagation in non-ideal plasmas

Viscosity effects on waves in partially and fully ionized plasma in magnetic field

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