On Modeling the Kelvin–Helmholtz Instability in Solar Atmosphere

Zhelyazkov, I.

doi:10.1007/s12036-015-9332-2

Cited by 22 publications

(19 citation statements)

References 151 publications

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“…It is well established that in magnetically structured solar atmosphere various jets with axial mass flow like spicules, surges, EUV and X-ray jets can become unstable against the so called Kelvin-Helmholtz instability (KHI)-for reviews see, e.g., Zhelyazkov (2015), Nakariakov et al (2016), Zhelyazkov et al (2017) and the references therein. Recall that the instability exhibits itself as a vortex sheet evolving near jet's boundary which (the vortex sheet) can become unstable to the spiral-like perturbations at small spatial scales provided that jet's axial velocity exceeds some critical/threshold value (Ryu et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Kelvin–Helmholtz instability in a twisting solar polar coronal hole jet observed by SDO/AIA

Zhelyazkov

Zaqarashvili

Ofman

et al. 2018

Advances in Space Research

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We investigate the conditions under which the fluting (m = 2), m = 3, and m = 12 magnetohydrodynamic (MHD) modes in a uniformly twisted flux tube moving along its axis become unstable in order to model the Kelvin-Helmholtz (KH) instability in a twisting solar coronal hole jet near the northern pole of the Sun. We employed the dispersion relations of MHD modes derived from the linearized MHD equations. We assumed real wavenumbers and complex angular wave frequencies, namely complex wave phse velocities. The dispersion relations were solved numerically at fixed input parameters (taken from observational data) and varying degrees of torsion of the internal magnetic field. It is shown that the stability of the modes depends upon five parameters: the density contrast between the flux tube and its environment, the ratio of the external and internal axial magnetic

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Section: Introductionmentioning

confidence: 99%

Kelvin–Helmholtz instability in a twisting solar polar coronal hole jet observed by SDO/AIA

Zhelyazkov

Zaqarashvili

Ofman

et al. 2018

Advances in Space Research

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“…The conclusion was that these speeds are too high to be registered in spicules. So KHI in cylindrical model of spicules can not happen (Zhelyazkov 2012). In this paper we study the possibility of KHI in spicules in a wider range of input parameters η and b and apply the actual conditions of spicules.…”

Section: Introductionmentioning

confidence: 99%

“…Spicules are considered straight cylindrical jets flowing in ambient plasma environment. The basic of our investigation is the dispersion equations of kink waves derived from linearized MHD equations (Zhelyazkov 2012;Edwin & Roberts 1983).…”

Section: Introductionmentioning

confidence: 99%

The possibility of Kelvin-Helmholtz instability in solar spicules

Ajabshirizadeh

Ebadi

Vekalati

et al. 2015

Astrophys Space Sci

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Transversal oscillations of spicules axes may be related to the propagation of magnetohydrodynamic waves along them. These waves may become unstable and the instability can be of the Kelvin-Helmholtz type. We use the dispersion relation of kink mode derived from linearized magnetohydrodynamic equations. The input parameters of the derived dispersion equation, namely, spicules and their ambient medium densities ratios as well as their corresponding magnetic fields ratios, are considered to be within the range 0 − 1. By solving the dispersion equation numerically, we show that for higher densities and lower magnetic fields ratios within the range mentioned, the KHI onset in type ii spicules conditions is possible. This possibility decreases with an increase in Alfvén velocity inside spicules. A rough criterion for appearing of Kelvin-Helmholtz instability is obtained. We also drive a more reliable and exact criterion for KHI onset of kink waves.

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“…By restricting ourselves to sub-Alfvénic flows, we are also discarding the triggering of the Kelvin-Helmholtz instability due to velocity shear at the boundary of the tube. The Kelvin-Helmholtz instability in flux tubes with longitudinal shear flows has been extensively investigated in the literature (e.g., Holzwarth et al 2007;Ryutova et al 2010;Zhelyazkov 2015) and is not the subject of the present study.…”

Section: Solution In the Internal And External Plasmasmentioning

confidence: 99%

Transverse waves in coronal flux tubes with thick boundaries: The effect of longitudinal flows

Soler

2019

A&A

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Observations show that transverse magnetohydrodynamic (MHD) waves and flows are often simultaneously present in magnetic loops of the solar corona. The waves are resonantly damped in the Alfvén continuum because of plasma and/or magnetic field nonuniformity across the loop. The resonant damping is relevant in the context of coronal heating, since it provides a mechanism to cascade energy down to the dissipative scales. It has been theoretically shown that the presence of flow affects the waves propagation and damping, but most of the studies rely on the unjustified assumption that the transverse nonuniformity is confined to a boundary layer much thinner than the radius of the loop. Here we present a semi-analytic technique to explore the effect of flow on resonant MHD waves in coronal flux tubes with thick nonuniform boundaries. We extend a published method, which was originally developed for a static plasma, in order to incorporate the effect of flow. We allowed the flow velocity to continuously vary within the nonuniform boundary from the internal velocity to the external velocity. The analytic part of the method is based on expressing the wave perturbations in the thick nonunform boundary of the loop as a Frobenius series that contains a singular term accounting for the Alfvén resonance, while the numerical part of the method consists of solving iteratively the transcendental dispersion relation together with the equation for the Alfvén resonance position. As an application of this method, we investigated the impact of flow on the phase velocity and resonant damping length of MHD kink waves. With the present method, we consistently recover results in the thin boundary approximation obtained in previous studies. We have extended those results to the case of thick boundaries. We also explored the error associated with the use of the thin boundary approximation beyond its regime of applicability.

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On Modeling the Kelvin–Helmholtz Instability in Solar Atmosphere

Cited by 22 publications

References 151 publications

Kelvin–Helmholtz instability in a twisting solar polar coronal hole jet observed by SDO/AIA

Kelvin–Helmholtz instability in a twisting solar polar coronal hole jet observed by SDO/AIA

The possibility of Kelvin-Helmholtz instability in solar spicules

Transverse waves in coronal flux tubes with thick boundaries: The effect of longitudinal flows

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