Effect of partial ionization on wave propagation in solar magnetic flux tubes

Abstract

Observations show that waves are ubiquitous in the solar atmosphere and may play an important role for plasma heating. The study of waves in the solar corona is usually based on linear ideal magnetohydrodynamics (MHD) for a fully ionized plasma. However, the plasma in the photosphere and the chromosphere is only partially ionized. Here we investigate theoretically the impact of partial ionization on MHD wave propagation in cylindrical flux tubes in the two-fluid model. We derive the general dispersion relation that takes into account the effects of neutral-ion collisions and the neutral gas pressure. We take the neutral-ion collision frequency as an arbitrary parameter. Particular results for transverse kink modes and slow magnetoacoustic modes are shown. We find that the wave frequencies only depend on the properties of the ionized fluid when the neutral-ion collision frequency is much lower that the wave frequency. For high collision frequencies realistic of the solar atmosphere ions and neutrals behave as a single fluid with an effective density corresponding to the sum of densities of both fluids and an effective sound velocity computed as the average of the sound velocities of ions and neutrals. The MHD wave frequencies are modified accordingly. The neutral gas pressure can be neglected when studying transverse kink waves but it has to be taken into account for a consistent description of slow magnetoacoustic waves. The MHD waves are damped due to neutral-ion collisions. The damping is most efficient when the wave frequency and the collision frequency are of the same order of magnitude. For high collision frequencies slow magnetoacoustic waves are more efficiently damped than transverse kink waves. In addition, we find the presence of cut-offs for certain combinations of parameters that cause the waves to become non-propagating.

Accepted for publication in A&A

References in corpus (8)

• Alfven Waves in the Lower Solar Atmosphere
• Heating of the magnetized solar chromosphere by partial ionization effects
• Surface Alfven waves in solar flux tubes
• Observation of kink waves in solar spicules
• Doppler shift oscillations in solar spicules
• Non-adiabatic magnetohydrodynamic waves in a cylindrical prominence thread with mass flow
• Kelvin-Helmholtz instability in partially ionized compressible plasmas
• Cut-off wavenumber of Alfven waves in partially ionized plasmas of the solar atmosphere

Cited by in corpus (12)

• 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
• Two-fluid simulations of waves in the solar chromosphere II. Propagation and damping of fast magneto-acoustic waves and shocks
• Synthetic observations of wave propagation in a sunspot umbra
• Magnetoacoustic Waves in a Stratified Atmosphere with a Magnetic Null Point
• Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes
• Dissipative instability in partially ionised prominence plasmas
• Magneto-seismological insights into the penumbral chromosphere and evidence for wave damping in spicules
• Two-fluid implementation in MPI-AMRVAC, with applications in the solar chromosphere
• Surface Waves in the paritally ionized solar plasma slab
• Future Prospects for Partially Ionised Solar Plasmas: the Prominence Case