Instability of twisted magnetic tubes with axial mass flows

Zaqarashvili, T. V.; Díaz, Antonio; Oliver, R.; Ballester, J. L.

doi:10.1051/0004-6361/200913874

Cited by 53 publications

(70 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, a twist in the magnetic field of the flux tube or its environment may have the effect of lowering the instability threshold (see Bennett et al 1999;Zaqarashvili et al 2010) and eventually lead to the triggering of the Kelvin-Helmholtz instability. According to Antolin & Shibata (2010), a promising way to ensure spicules'/coronal heating is by means of the mode conversion and parametric decay of Alfvén waves generated by magnetic reconnection or driven by the magnetoconvection at the photosphere.…”

Section: Resultsmentioning

confidence: 99%

Magnetohydrodynamic waves and their stability status in solar spicules

Zhelyazkov

2012

A&A

View full text Add to dashboard Cite

Aims. We investigate conditions under which magnetohydrodynamic waves propagating along spicules become unstable because of the Kelvin-Helmholtz instability. Methods. We employ the dispersion relations of normal modes (kink and sausage waves) derived from the linearised magnetohydrodynamic equations. We assume real wave numbers and complex angular wave frequencies, namely complex wave phase velocities. The dispersion relations are solved numerically at fixed input parameters and various flow velocities. Results. It is shown that the stability of the waves depends upon three parameters, the density contrast between spicules and their environment, the ratio of the background magnetic field outside to that inside spicules, and the value of the Alfvén-Mach number (the ratio of the jet velocity to Alfvén speed inside the spicules). At certain densities and magnetic fields, an instability of the Kelvin-Helmholtz type can arise if the Alfvén-Mach number exceeds a critical value -in our case it is equal to 12.6, which means that for an Alfvén speed inside the spicules of 70 km s −1 the jet velocity should be larger than 882 km s −1 . Conclusions. It is found that only kink waves can become unstable, while the sausage ones are always unaffected by the Kelvin-Helmholtz instability.

show abstract

Section: Resultsmentioning

confidence: 99%

Magnetohydrodynamic waves and their stability status in solar spicules

Zhelyazkov

2012

A&A

View full text Add to dashboard Cite

show abstract

“…1a) and so there are no resonant flow instabilities for slow flows. Although instabilities due to longitudinal flows are unlikely to occur in coronal loops, other kinds of instabilities, for example produced by the azimuthal shear of the kink mode are possible (see Terradas et al 2008a;Terradas 2009;Clack & Ballai 2009;Soler et al 2010;Zaqarashvili et al 2010).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

The effect of longitudinal flow on resonantly damped kink oscillations

Terradas

Goossens

Ballai³

2010

A&A

View full text Add to dashboard Cite

Context. The most promising mechanism acting towards damping the kink oscillations of coronal loops is resonant absorption. In this context most of previous studies neglected the effect of the obvious equilibrium flow along magnetic field lines. The flows are in general sub-Alfvénic and hence comparatively slow. Aims. Here we investigate the effect of an equilibrium flow on the resonant absorption of linear kink MHD waves in a cylindrical magnetic flux tube with the aim of determining the changes in the frequency of the forward and backward propagating waves and in the modification of the damping times due to the flow. Methods. A loop model with both the density and the longitudinal flow changing in the radial direction is considered. We use the thin tube thin boundary (TTTB) approximation in order to calculate the damping rates. The full resistive eigenvalue problem is also solved without assuming the TTTB approximation. Results. Using the low ratio of flow and Alfvén speeds we derive simple analytical expressions to the damping rate. The analytical expressions are in good agreement with the resistive eigenmode calculations. Conclusions. Under typical coronal conditions the effect of the flow on the damped kink oscillations is weak when the characteristic scale of the density layer is similar or lower than the characteristic width of the velocity layer. However, in the opposite situation the damping rates can be significantly altered, specially for the backward propagating wave which is undamped while the forward wave is overdamped.

show abstract

“…It turns out that the flow may decrease the threshold for the kink instability, as was tested experimentally in a laboratory twisted plasma column (Furno et al 2007). This observation was theoretically confirmed by Zaqarashvili et al (2010). The authors studied the influence of axial mass flows on the stability of an isolated twisted magnetic tube of incompressible plasma embedded in a perfectly conducting unmagnetized plasma.…”

Section: Waves and Instabilities In Twisted Solar Magnetic Structuresmentioning

confidence: 71%

On Modeling the Kelvin–Helmholtz Instability in Solar Atmosphere

Zhelyazkov

2015

J Astrophys Astron

View full text Add to dashboard Cite

Abstract.In the present review article, we discuss the recent developments in studying the Kelvin-Helmholtz (KH) instability of magnetohydrodynamic (MHD) waves propagating in various solar magnetic structures. The main description is on the modeling of KH instability developing in the coronal mass ejections (CMEs), and contributes to the triggering of wave turbulence subsequently leading to the coronal heating. KH instability of MHD waves in coronal active regions recently observed and imaged in unprecedented detail in EUV high cadence, highresolution observations by SDO /AIA, and spectroscopic observations by Hinode/EIS instrument, is posing now challenge for its realistic modeling. It is shown that considering the solar mass flows of CMEs as moving cylindrical twisted magnetic flux tubes, the observed instability can be explained in terms of unstable m = −3 MHD mode. We also describe the occurrence of the KH instability in solar jets. The obtained critical jet speeds for the instability onset as well as the linear wave growth rates are in good agreement with the observational data of solar jets.

show abstract

Instability of twisted magnetic tubes with axial mass flows

Cited by 53 publications

References 49 publications

Magnetohydrodynamic waves and their stability status in solar spicules

Magnetohydrodynamic waves and their stability status in solar spicules

The effect of longitudinal flow on resonantly damped kink oscillations

On Modeling the Kelvin–Helmholtz Instability in Solar Atmosphere

Contact Info

Product

Resources

About