On the Stability of Incompressible MHD Modes in Magnetic Cylinder with Twisted Magnetic Field and Flow

Cheremnykh, O. K.; Fedun, V.; Ladikov-Roev, Yu.P.; Verth, G.

doi:10.3847/1538-4357/aadb9f

Cited by 18 publications

(10 citation statements)

References 53 publications

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“…Hence, it looks like a viable assumption that the plasma flows along the magnetic field lines. In accordance with this, we now make the same assumption as in Cheremnykh et al (2018) and Bahari (2018), namely that the velocity is parallel to the magnetic field, U B. This assumption implies that…”

Section: Problem Formulation and Unperturbed Statementioning

confidence: 97%

Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes

Bahari

Petrukhin

2020

Monthly Notices of the Royal Astronomical Society

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We study the propagation and stability of kink waves in a twisted magnetic tube with the flow. The flow velocity is assumed to be parallel to the magnetic field, and the magnetic field lines are straight outside the tube. The density is constant inside and outside of the tube, and it monotonically decreases from its value inside the tube to that outside in the transitional or boundary layer. The flow speed and magnetic twist monotonically decrease in the transitional layer from their values inside the tube to zero outside. Using the thin tube and thin boundary layer (TTTB) approximation, we derived the dispersion equation determining the dependence of the wave frequency and decrement/increment on the wavenumber. When the kink wave frequency coincides with the local Alfvén frequency at a resonant surface inside the transitional layer, the kink wave is subjected to either resonant damping or resonant instability. We study the properties of kink waves in a particular unperturbed state where there is no flow and magnetic twist in the transitional layer. It is shown that in a tube with flow, the kink waves can propagate without damping for particular values of the flow speed. Kink waves propagating in the flow direction either damp or propagate without damping. Waves propagating in the opposite direction can either propagate without damping, or damp, or become unstable. The theoretical results are applied to the problem of excitation of kink waves in spicules and filaments in the solar atmosphere.

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Section: Problem Formulation and Unperturbed Statementioning

confidence: 97%

Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes

Bahari

Petrukhin

2020

Monthly Notices of the Royal Astronomical Society

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“…where 1  and 2  are the densities on both sides of the boundary. The procedure for deriving equality (29) is exactly the same as in the papers by Cheremnykh et al (2018a) and Cheremnykh et al (2018b). In the barometric atmosphere we…”

Section: T T mentioning

confidence: 99%

Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization, applications to the earth's and solar atmospheres

Cheremnykh¹,

Fedorenko²,

Kryuchkov³

et al. 2019

Preprint

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Abstract. The objects of research in this work are evanescent wave modes in a gravitationally stratified atmosphere and their associated pseudo-modes. Whereas the former, according to the dispersion relation, rapidly decrease with distance from a certain surface, the latter, having the same dispersion law, differ from the first by the form of polarization and the character of its decreasing away from the surface. Within a linear hydrodynamic model, the propagation features of evanescent wave modes in an isothermal atmosphere are studied. Research carried out for different assumptions about the properties of the medium. On this way, a new wave mode – anelastic evanescent wave mode – was discovered. Also, the possibility of the existence of a pseudo-mode related to it is indicated. The case of two isothermal media differing in temperature at the interface is studied in detail. It is shown that a non-divergent pseudo-mode with the dispersion of solar f-mode type can be realized on the interface for the specified horizontal scale. The newly discovered dispersion relation, at the interface of two media, is satisfied by the wave mode, which has different types of amplitude versus height dependencies at different horizontal scales. The applicability of the obtained results to clarify the properties of f-mode observed on the Sun is analyzed.

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“…A dispersion relation for the propagation of high-mode (m 2) MHD waves in a magnetized axially moving and rotating twisted jet was derived by Zaqarashvili, Zhelyazkov, and Ofman (2015) and Cheremnykh et al (2018b). That equation was obtained, however, under the assumption that both media (the jet and its environment) are incompressible plasmas.…”

Section: Wave Dispersion Relationmentioning

confidence: 99%

“…In particular, they found that rotation has a stabilizing effect on the current driven mode only for rotation velocities of the order on the Alfvén speed. The more general case, when both the magnetic field and jet flow velocity are twisted, was studied by Zaqarashvili, Zhelyazkov, and Ofman (2015) and Cheremnykh et al (2018b), whose dispersion equations for modes with m 2, represented in different ways, yield practically identical results.…”

Section: Introductionmentioning

confidence: 99%

How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

Zhelyazkov

Chandra

Joshi

2019

Front. Astron. Space Sci.

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Recent observations support the propagation of a number of magnetohydrodynamic (MHD) modes which, under some conditions, can become unstable and the developing instability is the Kelvin-Helmholtz instability (KHI). In its nonlinear stage the KHI can trigger the occurrence of wave turbulence which is considered as a candidate mechanism for coronal heating. We review the modeling of tornado-like phenomena in the solar chromosphere and corona as moving weakly twisted and spinning cylindrical flux tubes, showing that the KHI rises at the excitation of high-mode MHD waves. The instability occurs within a wavenumber range whose width depends on the MHD mode number m, the plasma density contrast between the rotating jet and its environment, and also on the twists of the internal magnetic field and the jet velocity. We have studied KHI in two twisted spinning solar polar coronal hole jets, in a twisted rotating jet emerging from a filament eruption, and in a rotating macrospicule. The theoretically calculated KHI development times of a few minutes for wavelengths comparable to the half-widths of the jets are in good agreement with the observationally determined growth times only for high order (10 m 65) MHD modes. Therefore, we expect that the observed KHI in these cases is due to unstable high-order MHD modes.

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On the Stability of Incompressible MHD Modes in Magnetic Cylinder with Twisted Magnetic Field and Flow

Cited by 18 publications

References 53 publications

Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes

Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes

Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization, applications to the earth's and solar atmospheres

How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

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