Torsional Alfvén waves in solar partially ionized plasma: effects of neutral helium and stratification
arXiv:1211.1348 · doi:10.1051/0004-6361/201220272
Abstract
Ion-neutral collisions may lead to the damping of Alfven waves in chromospheric and prominence plasmas. Neutral helium atoms enhance the damping in certain temperature interval, where the ratio of neutral helium and neutral hydrogen atoms is increased. Therefore, the height-dependence of ionization degrees of hydrogen and helium may influence the damping rate of Alfven waves. We aim to study the effect of neutral helium in the damping of Alfven waves in stratified partially ionized plasma of the solar chromosphere. We consider a magnetic flux tube, which is expanded up to 1000 km height and then becomes vertical due to merging with neighboring tubes, and study the dynamics of linear torsional Alfven waves in the presence of neutral hydrogen and neutral helium atoms. We start with three-fluid description of plasma and consequently derive single-fluid magnetohydrodynamic (MHD) equations for torsional Alfven waves. Thin flux tube approximation allows to obtain the dispersion relation of the waves in the lower part of tubes, while the spatial dependence of steady-state Alfven waves is governed by Bessel type equation in the upper part of tubes. Consecutive derivation of single-fluid MHD equations results in a new Cowling diffusion coefficient in the presence of neutral helium which is different from previously used one. We found that shorter-period (< 5 s) torsional Alfven waves damp quickly in the chromospheric network due to ion-neutral collision. On the other hand, longer-period (> 5 s) waves do not reach the transition region as they become evanescent at lower heights in the network cores. Propagation of torsional Alfven waves through the chromosphere into the solar corona should be considered with caution: low-frequency waves are evanescent due to the stratification, while high-frequency waves are damped due to ion neutral collisions.
9 pages, 7 figures (accepted in A&A)
References in corpus (8)
- Alfven Waves in the Lower Solar Atmosphere
- Ubiquitous torsional motions in type II spicules
- Three Dimensional MHD Wave Propagation and Conversion to Alfven Waves near the Solar Surface. I. Direct Numerical Solution
- Observation of kink waves in solar spicules
- Doppler shift oscillations in solar spicules
- Energy flux of Alfven waves in weakly ionized plasma
- Cut-off wavenumber of Alfven waves in partially ionized plasmas of the solar atmosphere
- Two-wave interaction in ideal magnetohydrodynamics
Cited by in corpus (28)
- Partially Ionized Plasmas in Astrophysics
- Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun
- Fluid description of multi-component solar partially ionized plasma
- Alfven waves in a partially ionized two-fluid plasma
- Two-fluid simulations of waves in the solar chromosphere I: numerical code verification
- Magnetoacoustic waves in a partially ionized two-fluid plasma
- Overdamped Alfven waves due to ion-neutral collisions in the solar chromosphere
- On the spatial scales of wave heating in the solar chromosphere
- Two-fluid simulations of waves in the solar chromosphere II. Propagation and damping of fast magneto-acoustic waves and shocks
- On the effects of ion-neutral interactions in solar plasmas
- Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media
- Waves in weakly ionised solar plasmas
- Solar chromosphere heating and generation of plasma outflows by impulsively generated two fluid Alfven waves
- Chromospheric heating and generation of plasma outflows by impulsively generated two-fluid magnetoacoustic waves
- Torsional Alfvénic Oscillations Discovered in the Magnetic Free Energy During Solar Flares
- Two-fluid implementation in MPI-AMRVAC, with applications in the solar chromosphere
- 3D numerical simulations of propagating two-fluid, torsional Alfvén waves and heating of a partially-ionized solar chromosphere
- Alfven wave heating in partially ionized thin threads of solar prominences
- The non-ideal finite Larmor radius effect in the solar atmosphere
- Structure of the solar photosphere studied from the radiation hydrodynamics code ANTARES
- Generation of solar chromosphere heating and coronal outflows by two-fluid waves
- SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network
- Viscous Heating and Instabilities in the Partially Ionized Solar Atmosphere
- Observation of the period ratio P_1/P_2 of transversal oscillations in solar macro-spicules
- Fast magneto-acoustic waves in the solar chromosphere: Comparison of single-fluid and two-fluid approximations
- Alfvén wave propagation in the partially ionized lower solar atmosphere: a test of the single-fluid approximation
- MHD waves in the partially ionized plasma: from single to multi-fluid approach
- The role of ambipolar heating in the energy balance of solar prominences