Can High-Mode Magnetohydrodynamic Waves Propagating in a Spinning Macrospicule Be Unstable Due to the Kelvin–Helmholtz Instability?

Zhelyazkov, I.; Chandra, Ramesh

doi:10.1007/s11207-019-1408-8

Cited by 4 publications

(4 citation statements)

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“…The B cr iφ that suppresses the KHI onset, equals 0.57 G and was calculated with ε cr 1 = 0.202085 and M A = 1.2119. Our study (Zhelyazkov and Chandra, 2019) shows that a decrease in the background magnetic field to B e = 4.8 G would require the excitation of MHD wave with mode number m = 48, at which the KHI characteristics at the wavelengths of 3 and 5 Mm are very close to those obtained with m = 52.…”

Section: Kelvin-helmholtz Instability In a Spinning Macrospiculesupporting

confidence: 66%

“…According to the authors, the detected rotation assuredly plays an important role in the dynamics of the transition region. Using the basic observational parameters obtained by Pike and Mason (1998), Zhelyazkov and Chandra (2019) examined the conditions for KHI rising in the macrospicule. Let us discuss that study as follows.…”

Section: Kelvin-helmholtz Instability In a Spinning Macrospiculementioning

confidence: 99%

“…Our (Zhelyazkov and Chandra, 2019) choice for modeling namely the macrospicule observed on 1997 March 8 at 00:02 UT (see Table II in Pike and Mason, 1998) was made taking into account the fact that this macrospicule possesses the basic characteristics of the observed over the years tornado-like jets-the axial velocity of the jet was U z = 75 km s −1 , while its rotating speed, we evaluate to be U φ = 40 km s −1 . For the other characteristics of the macrospicule such as lifetime, maximum width, average flow velocity, and maximum length or height, we used some average values obtained from a huge number of observations and specified in Kiss, Gyenge, and Erdélyi, 2017 as 16.75 ± 4.5 min, 6.1 ± 4 Mm, 73.14 ± 25.92 km s −1 , and 28.05 ± 7.67 Mm, respectively.…”

Section: Kelvin-helmholtz Instability In a Spinning Macrospiculementioning

confidence: 99%

See 2 more Smart Citations

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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Section: Kelvin-helmholtz Instability In a Spinning Macrospiculesupporting

confidence: 66%

Section: Kelvin-helmholtz Instability In a Spinning Macrospiculementioning

confidence: 99%

Section: Kelvin-helmholtz Instability In a Spinning Macrospiculementioning

confidence: 99%

See 1 more Smart Citation

How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

Zhelyazkov

Chandra

Joshi

2019

Front. Astron. Space Sci.

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“…This is a rather realistic value not contradicting to the observations. Zhelyazkov, Zaqarashvili & Chandra (2015) and Zhelyazkov & Chandra (2019) studied the KH instability in spicules modelling them as tubes with twisted magnetic field. They showed that the tube can be KH unstable for realistic values of spicule parameters, however, only with respect to fluting wave modes, while the kink waves remain stable.…”

Section: Application To Spicules and Filaments In The Solar Atmospherementioning

confidence: 99%

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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Simulations of the Biermann battery mechanism in two-fluid partially ionised plasmas

Martínez‐Gómez

Braileanu

Khomenko

et al. 2021

A&A

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Context. In the absence of an initial seed, the Biermann battery term of a non-ideal induction equation acts as a source that generates weak magnetic fields. These fields are then amplified via a dynamo mechanism. The Kelvin-Helmholtz instability is a fluid phenomenon that takes place in many astrophysical scenarios and can trigger the action of the Biermann battery and dynamo processes. Aims. We aim to investigate the effect of the ionisation degree of the plasma and the interaction between the charged and neutral species on the generation and amplification of magnetic fields during the different stages of the instability. Methods. We use the two-fluid model implemented in the numerical code Mancha-2F. We perform 2D simulations starting from a configuration with no initial magnetic field and which is unstable due to a velocity shear. We vary the ionisation degree of the plasma and we analyse the role that the different collisional terms included in the equations of the model play on the evolution of the instability and the generation of magnetic field. Results. We find that when no collisional coupling is considered between the two fluids, the effect of the Biermann battery mechanism does not depend on the ionisation degree. However, when elastic collisions are taken into account, the generation of magnetic field is increased as the ionisation degree is reduced. This behaviour is slightly enhanced if the process of charge-exchange is also considered. We also find a dependence on the total density of the plasma related to the dependence on the coupling degree between the two fluids. As the total density is increased, the results from the two-fluid model converge to the predictions of single-fluid models. Conclusions. The charged-neutral interaction in a partially ionised plasmas has a non-negligible effect on the Biermann battery mechanism and it effectively enhances the generation of a magnetic field. In addition, single-fluid models, which assume a very strong coupling between the two species, may overestimate the contribution of this interaction in comparison with two-fluid models.

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Can High-Mode Magnetohydrodynamic Waves Propagating in a Spinning Macrospicule Be Unstable Due to the Kelvin–Helmholtz Instability?

Cited by 4 publications

References 42 publications

How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

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

Simulations of the Biermann battery mechanism in two-fluid partially ionised plasmas

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