Linear and non-linear MHD wave propagation in steady-state magnetic cylinders

Terra-Homem, M.; Erdélyi, R.; Ballai, I.

doi:10.1023/b:sola.0000006901.22169.59

Cited by 66 publications

(70 citation statements)

References 29 publications

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“…Oscillations of magnetic tubes with mass flows have been studied intensively (Roberts 1987;Goossens et al 1992;Terra-Homem et al 2003;Soler et al 2008Soler et al , 2009Soler et al , 2010Gruszecki et al 2008;Terradas et al 2008Terradas et al , 2010Vasheghani Farahani et al 2009). They show that including flow modifies the phase speeds and consequently the propagation properties of tube waves.…”

Section: Introductionmentioning

confidence: 99%

Instability of twisted magnetic tubes with axial mass flows

Zaqarashvili

Díaz

Oliver

et al. 2010

A&A

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Context. Recent observations of various kinds of jets in the solar atmosphere motivate studying the influence of mass flow on the stability of solar magnetic structures. Aims. We study the influence of axial mass flows on the stability of twisted magnetic flux tubes. Methods. We use the incompressible magnetohydrodynamic equations to get the dispersion relation governing the behaviour of normal modes in uniformly twisted magnetic tubes with sub-Alfvénic flows. The dispersion relation is then solved analytically and numerically to find stability criteria for twisted tubes with flow. Results. Two main important results are found. First, the axial mass flow reduces the threshold of kink instability in twisted magnetic tubes. Second, the twist of magnetic tubes leads to the Kelvin-Helmholtz instability of sub-Alfvénic flows for the harmonics with a large enough azimuthal wave number −m. Conclusions. The observed mass flow may trigger the kink instability in magnetic configurations that are near their stability threshold, leading to solar flares and coronal mass ejections. The effect is more significant for photospheric magnetic tubes than for coronal ones. Sub-Alfvénic flows undergo the Kelvin-Helmholtz instability in slightly twisted magnetic tubes if the azimuthal wavenumber is big enough.

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Section: Introductionmentioning

confidence: 99%

Instability of twisted magnetic tubes with axial mass flows

Zaqarashvili

Díaz

Oliver

et al. 2010

A&A

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“…The theoretical model of MHD waves guided by a plasma structure of steady flow was developed by Goossens et al (1992) and Terra-Homem et al (2003) for the cylindrical geometry and by Nakariakov & Roberts (1995) for the slab geometry. The main new feature introduced by the flow was the modification of the dispersion relations and wave-flow interaction effects associated with negative energy (Joarder et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Propagating transverse waves in soft X-ray coronal jets

Farahani¹,

Doorsselaere²,

Verwichte³

et al. 2009

A&A

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Aims. The theoretical model for magnetohydrodynamic (MHD) modes guided by a field-aligned plasma cylinder with a steady flow is adapted to interpret transverse waves observed in solar coronal hot jets, discovered with Hinode/XRT in terms of fast magnetoacoustic kink modes. Methods. Dispersion relations for linear magnetoacoustic perturbations of a plasma jet of constant cross-section surrounded by static magnetised plasma are used to determine the phase and group speeds of guided transverse waves and their relationship with the physical parameters of the jet and the background plasma. The structure of the perturbations in the macroscopic parameters of the plasma inside and outside the jet, and the phase relations between them are also established. Results. We obtained a convenient expansion for the long wave-length limit of the phase and group speeds and have shown that transverse waves observed in soft-X-ray solar coronal jets are adequately described in terms of fast magnetoacoustic kink modes by a magnetic cylinder model, which includes the effect of a steady flow. In the observationally determined range of parameters, the waves are not found to be subject to either the Kelvin-Helmholtz instability or the negative energy wave instability, and hence they are likely to be excited at the source of the jet.

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“…Here ω is a wave cyclic frequency and D represents the left-hand side of the dispersion relation, D(ω, k) = 0 with k denoting a wavenumber. In our case we have [12] …”

Section: Numerical Simulations Of Acoustic Waves With the Graphic Accmentioning

confidence: 70%

Numerical simulations of acoustic waves with the graphic acceleration GAMER code

Murawski¹,

Schive²

2012

Bulletin of the Polish Academy of Sciences: Technical Sciences

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Abstract. We present results of numerical simulations of acoustic waves with the use of the Graphics Processing Unit (GPU) acceleration GAMER code which implements a second-order Godunov-type numerical scheme and adaptive mesh refinement (AMR). The AMR implementation is based on constructing a hierarchy of grid patches with an octree data structure. In this code a hybrid model is adopted, in which the time-consuming solvers are dealt with GPUs and the complex AMR data structure is manipulated by Central Processing Units (CPUs). The code is highly parallelized with the Hilbert space-filling curve method. These implementations allow us to resolve well desperate spatial scales that are associated with acoustic waves. We show that a localized velocity (gas pressure) pulse that is initially launched within a uniform and still medium triggers acoustic waves simultaneously with a vortex (an entropy mode). In a flowing medium, acoustic waves experience amplitude growth or decay, a scenario which depends on a location of the flow and relative direction of wave propagation. The amplitude growth results from instabilities which are associated with negative energy waves.

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Linear and non-linear MHD wave propagation in steady-state magnetic cylinders

Cited by 66 publications

References 29 publications

Instability of twisted magnetic tubes with axial mass flows

Instability of twisted magnetic tubes with axial mass flows

Propagating transverse waves in soft X-ray coronal jets

Numerical simulations of acoustic waves with the graphic acceleration GAMER code

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