Observation of standing kink waves in solar spicules

2013

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Interaction of Alfvén waves with plasma inhomogeneities generates phase mixing which can lead to dissipate Alfvén waves and to heat the solar plasma.Here we study the dissipation of Alfvén waves by phase mixing due to viscosity and resistivity variations with height. We also consider nonlinear magnetohydrodynamic (MHD) equations in our theoretical model. Nonlinear terms of MHD equations include perturbed velocity, magnetic field, and density. To investigate the damping of Alfvén waves in a stratified atmosphere of solar spicules, we solve the non-linear MHD equations in the x−z plane. Our simulations show that the damping is enhanced due to viscosity and resistivity gradients. Moreover, energy variations is influenced due to nonlinear terms in MHD equations.

Section: Numerical Results and Discussionsupporting

confidence: 90%

Non-linear damping of visco-resistive Alfvén waves in solar spicules

Fazel

2013

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“…This means that with an increase in height, amplitude of velocity oscillations is expanded due to significant decrease in density, which acts as inertia against oscillations. Similar results are observed by time-distance analysis of Solar spicule oscillations (Ebadi et al 2012). It is worth to note that the density stratification influence on the magnetic field is negligible, which is in agreement with Solar Optical Telescope observations of Solar spicules (Verth et al 2011).…”

Section: Numerical Results and Discussionsupporting

confidence: 88%

Phase mixing of propagating Alfvén waves in a stratified atmosphere: solar spicules

Hosseinpour

Altafi-Mehrabani

2012

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Alfvénic waves are thought to play an important role in coronal heating and solar wind acceleration. Recent observations by Hinode/SOT showed that the spicules mostly exhibit upward propagating high frequency waves.Here we investigate the dissipation of such waves due to phase mixing in stratified environment of solar spicules. Since they are highly dynamic structures with speeds at about significant fractions of the Alfvén phase speed, we take into account the effects of steady flows. Our numerical simulations show that in the presence of stratification due to gravity, damping takes place in space than in time. The exponential damping low, exp(− At 3 ), is valid under spicule conditions, however the calculated damping time is much longer than the reported spicule lifetimes from observations.

“…It is interesting that the oscillations amplitude are increasing towards higher heights. The same behavior was observed in spicules by He et al (2009);Ebadi et al (2012a); Ebadi & Khoshrang (2014). This means that with a little increase in height, amplitude of oscillations become expanded due to significant decrease in density, which acts as inertia against oscillations.…”

Section: Numerical Results and Discussionsupporting

confidence: 68%

Torsional Alfvén waves and the period ratio P 1/P 2 in spicules

Shahmorad

2014

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The effects of both density stratification and magnetic field expansion on torsional Alfvén waves in solar spicules are studied. Also, their eigenfrequencies, eigenfunctions, and the period ratio P 1 /P 2 are obtained with a novel mathematical method. We showed that under some circumstances this ratio can approach its observational value even though it departs from its canonical value of 2. Moreover, Eigenfunction height variations show that the oscillations amplitude are increasing towards higher heights which is in agreement with the observations. This means that with a little increase in height, amplitude of oscillations expands due to the significant decrease in the density.