arXiv subjects

Roberto Soler

Publications and source records attributed to Roberto Soler.

At least 19 recordsLinked to original sources

arXiv2026

The role of ambipolar heating in the energy balance of solar prominences

Solar prominence threads are typically located around magnetic dips, where cold and dense plasma is suspended against gravity in the hot corona thanks to the upward magnetic force. Because prominences are partially ionized, ambipolar diffusion can deposit part of the energy of their non-force-free magnetic field into the plasma. This ambipolar heating may therefore play a role in the energy balance of prominences. In this proof-of-concept work, we explore the effect of ambipolar diffusion in one-dimensional models that satisfy both mechanical equilibrium and energy balance. The magnetic configuration is based on the classic Kippenhahn-Schl\"uter model, incorporating a sheared magnetic field. The temperature profile along the magnetic field is computed numerically by balancing radiative losses, thermal conduction, and ambipolar heating. The resulting models consistently consist of a cold, dense, partially ionized thread with prominence core conditions, a very thin prominence-corona transition region, and an extended, hot, fully ionized region with coronal conditions. In addition to providing heating that partly compensates for radiative losses, ambipolar diffusion also gives rise to stationary flows associated with the gravitational drainage of neutrals in the partially ionized region. We investigate how the length of the cold threads depends on the central temperature, central pressure, magnetic field strength, and shear angle, and show that thread lengths compatible with observations are obtained for realistic values of these parameters. Therefore, we demonstrate that ambipolar diffusion plays a relevant role in this simple configuration, indicating that this effect should be incorporated into more elaborate multi-dimensional models and simulations.

astro-ph.SR↗

arXiv2026

Alfv\'en wave propagation in the partially ionized lower solar atmosphere: a test of the single-fluid approximation

Alfv\'en waves are widely believed to play an important role in the transport of energy from the solar photosphere to the corona through the partially ionized chromosphere. In previous work, the properties of torsional Alfv\'en waves were theoretically studied using a multi-fluid model. Here, we compare those multi-fluid results with those obtained using the single-fluid magnetohydrodynamic approximation, as a way to assess the performance of the latter in the context of Alfv\'enic waves in the lower solar atmosphere. We consider a broadband photospheric driver that excites torsional Alfv\'en waves with frequencies ranging from 0.1 mHz to 300 mHz. These waves propagate upwards to the corona along a magnetic flux tube expanding with height. For both models, we compare the energy flux, chromospheric reflection, transmission and absorption coefficients, and the associated heating rates. In general, the results are almost identical in the two models, with the exception of two minor differences: (1) the net energy flux reaching the corona is approximately 5% larger in the single-fluid model, mainly owing to the higher reflectivity found in the multi-fluid model for wave frequencies exceeding 10 mHz; and (2) in a narrow region around 500 km above the photosphere, the single-fluid model underestimates the plasma heating rate due to ion-neutral damping by about a factor of two compared with the multi-fluid model. Both discrepancies arise from the approximate treatment of the ion-neutral drift in the single-fluid model and are expected to have a very limited impact on practical applications.

astro-ph.SR↗

arXiv2025

MHD waves with mixed properties / Alfv\'{e}n waves with pressure variations: a review

Non-uniformity plays an important role for MHD waves. For a uniform plasma of infinite extent the MHD waves can be subdivided in two classes with distinct properties. The first class contains the Alfv\'en waves. The Alfv\'en waves are incompressible and propagate parallel vorticity. They do not have a parallel component of displacement, they do not cause variations in pressure and are driven by magnetic tension only. The second class contains the magneto-sonic waves. They are compressible and have a parallel component of displacement. They do not propagate parallel vorticity and are driven by pressure and magnetic tension. In non-uniform plasmas the situation can be very different. The clear division between Alfv\'en waves and magneto-sonic waves is no longer present. In a given part of the equilibrium an MHD wave can strongly resemble a magneto-sonic wave with little or no resemblance to Alfv\'en waves; while in another part of the equilibrium the MHD wave is practically an Alfv\'en wave, which has the amazing property of being accompanied by variations in pressure.

astro-ph.SR↗

arXiv2025

Alfven wave propagation from the photosphere to the corona: temporal evolution against stationary results

Recent observations have confirmed that a significant fraction of the coronal Alfvenic wave spectrum originates in the photosphere. These waves travel from the photosphere to the corona, overcoming the barriers of reflection and dissipation posed by the chromosphere. Previous studies have theoretically calculated the chromospheric reflection, transmission, and absorption coefficients for pure Alfven waves under the assumption of stationary propagation. Here, we relax that assumption and investigate the time-dependent propagation of Alfven waves driven at the photosphere. Using an idealized chromospheric background model, we compare the coefficients obtained from time-dependent simulations with those derived under the stationary approximation. Additionally, we examine the impact of the spatial resolution in the numerical simulations. Considering a spatial resolution of 250 m, we find that the time-dependent transmission coefficient converges to the stationary value across the entire frequency range after only a few chromospheric Alfven crossing times, while the reflectivity displays a good convergence for frequencies lower than 30 mHz. The absorption coefficient also converges for wave frequencies above 1 mHz, for which chromospheric dissipation is significant. In contrast, at lower frequencies, wave energy dissipation is weak and the time-dependent simulations typically overestimate the absorption. Inadequate spatial resolution artificially enhances the chromospheric reflectivity, reduces wave transmission to the corona, and poorly describes the wave energy absorption. Overall, the differences between the stationary and time-dependent approaches are only minor and gradually decrease as spatial resolution and simulation time increase, which reinforces the validity of the stationary approximation.

astro-ph.SR↗

arXiv2025

Wave coupling in partially ionized plasmas with shear flows I. Fast-to-Alfv\'en transformation

We theoretically investigate the interplay between magnetohydrodynamic (MHD) waves and shear flows in a partially ionized solar plasma, focusing on the energy exchange mediated by the flow and the transformation between wave modes. We consider a simple model composed of a uniform partially ionized plasma with a straight magnetic field. A shear flow is present in the direction of the magnetic field with a velocity that varies linearly across the magnetic field. The linearized MHD equations in the single-fluid approximation are used, which include the ambipolar diffusion term due to ion-neutral collisions. A nonmodal approach is adopted, in order to convert the flow spatial inhomogeneity into a temporal one, adding a temporal dependence into the component of the wavevector in the direction of the flow inhomogeneity. A system of three ordinary differential equations is derived, which generally governs the temporal evolution of the coupled MHD waves, their interaction with the shear flow, and their ambipolar damping. Numerical solutions are computed to study the coupling and mutual transformation between the fast magnetosonic wave and the Alfv\'en wave. A detailed parameter study is conducted, demonstrating how the energy transfer and mode transformation are affected. The role of ambipolar diffusion is investigated by comparing the results of the ideal case with those obtained when ambipolar diffusion is included. It is found that ambipolar diffusion can significantly affect the efficiency of the energy exchange between modes and introduces a new coupling mechanism. Additionally, a specific application to solar prominence threads is included, showing that wave coupling and energy exchange can occur within these and other similar structures in the solar atmosphere.

astro-ph.SR↗

arXiv2025

Linear analysis of shear-flow instabilities in a prominence-corona interface with ambipolar diffusion

Observations have shown the presence of the Kelvin-Helmholtz instability (KHi) in solar prominences. Effects due to partial ionization of the prominence plasma may influence the KHi onset. We study the triggering of the KHi in an interface model that consists of a partially ionized prominence region and a fully ionized coronal region, with a uniform magnetic field parallel to the interface. There is a longitudinal flow in the prominence region. The plasma is compressible and the role of ambipolar diffusion, which accounts for collisions between charges and neutrals, is taken into account in the prominence plasma. We derive the dispersion relation of linear perturbations on the interface and analyze some limit cases analytically. Numerical results are obtained for realistic prominence parameters. We find that compressibility and gas pressure are important in determining the unstable flow velocities, specially in the range of sub-Alfv\'enic flows that are consistent with the observations. The ambipolar diffusion has a generally destabilizing influence and reduces the threshold flow velocity for the KHi onset.

astro-ph.SR↗

arXiv2025

The energy content of Alfven waves in the stratified solar atmosphere

Alfven waves propagating in a vertically stratified plasma, such as those travelling from the solar photosphere to the corona, are partially reflected due to the gradient in the Alfven speed. Wave reflection naturally results in the superposition of upward- and downward-propagating waves. A simple analytic model demonstrates that this superposition leads to the non-equipartition of kinetic and magnetic energies in the Alfven wave perturbations and slows down the net energy transport. A numerical model of Alfven wave propagation in the lower solar atmosphere reveals significant wave reflection below the transition region, leading to highly variable kinetic and magnetic energy content in the lower chromosphere. At higher altitudes, the kinetic energy eventually dominates, depending on the wave frequency. The velocity at which net energy propagates upward is significantly smaller than the local Alfven speed throughout the chromosphere. Consequently, the commonly used expression for unidirectional Alfven waves in a uniform plasma, which relates the energy flux to the kinetic energy density, is not generally applicable in the stratified lower solar atmosphere and cannot be reliably used to estimate the energy content of observed waves. A generalized expression is given, incorporating correction factors that account for wave reflection and energy non-equipartition. The applicability of the expression is discussed.

astro-ph.SR↗

arXiv2024

Nonlinear evolution of fluting oscillations in coronal flux tubes

Magnetic flux tubes in the solar corona support a rich variety of transverse oscillations, which are theoretically interpreted as magnetohydrodynamic (MHD) modes with a fast and/or Alfv\'enic character. In the standard flux tube model made of a straight cylindrical tube, these modes can be classified according to their azimuthal wavenumber, $m$. Sausage $m=0$ modes produce periodic expansion and contraction of the tube cross section and are observed during solar flares. Kink $m=1$ modes laterally displace the tube axis and are related to, for example, post-flare global transverse oscillations of coronal loops. Fluting $m \geq 2$ modes produce disturbances that are mainly confined to the tube boundary, but their observation remains elusive to date. We use 3D ideal MHD numerical simulations to investigate the nonlinear evolution of fluting modes in coronal flux tubes with transversely nonuniform boundaries. The simulations show that fluting modes are short-lived as coherent, collective motions of the flux tube. Owing to the process of resonant absorption, fluting oscillations become overdamped modes in tubes with wide enough nonuniform boundaries. During the nonlinear evolution, shear flows drive the Kelvin-Helmholtz instability at the tube boundary, which further disrupts the coherent fluting oscillation. For large-enough oscillation amplitudes, baroclinic instabilities of Rayleigh-Taylor type are also present at locations in the boundary where the plasma acceleration is normal to the boundary. The evolution of the instabilities drives turbulence in the flux tube, which may inhibit the resonant damping. However, the oscillations remain strongly damped even in this case. As a result of the combination of the strong damping and the induced instabilities, it is unlikely that coronal flux tubes can support fluting modes as sufficiently enduring coherent oscillations.

astro-ph.SR↗

arXiv2024

Numerical simulations of turbulence in prominence threads induced by torsional oscillations

Threads are the main constituents of prominences and are subjected to oscillations that might be interpreted as MHD waves. Moreover, the Kelvin-Helmholtz instability (KHI) has been reported in prominences. Both waves and KHI may affect the thermodynamic state of the threads. We investigate the triggering of turbulence in a thread caused by the nonlinear evolution of standing torsional Alfv\'en waves as well as possible observational signatures of this dynamics and the plasma heating. We modeled the thread as a radially and longitudinally nonuniform cylindrical flux tube with a uniform axial magnetic field embedded in a coronal environment. We perturbed the flux tube with the longitudinally fundamental mode of standing torsional Alfv\'en waves and numerically solved the 3D MHD equations to study the temporal evolution in both ideal and dissipative scenarios. We also performed forward modeling to calculate the synthetic H{\alpha} imaging. Standing torsional Alfv\'en waves undergo phase-mixing owing to the radially nonuniform density. The phase-mixing generates azimuthal shear flows that eventually trigger the KHI and, later, turbulence. If nonideal effects are included, plasma heating is localized in an annulus region at the thread boundary and does not increase the temperature in the cool core. Instead, the average temperature in the thread decreases owing to the mixing of internal and external plasmas. In the synthetic observations, first we find periodic pulsations in the H{\alpha} intensity caused by the integration of the phase-mixing flows along the line of sight. Later, we find fine strands that may be associated with the KHI vortices. Turbulence can be generated by standing torsional Alfv\'en waves in a thread after the onset of KHI, but this mechanism is not enough to heat globally the structure. The dynamics could be seen in high-resolution H{\alpha} observations.

astro-ph.SR↗

arXiv2023

Self-consistent equilibrium models of prominence thin threads heated by Alfv\'en waves propagating from the photosphere

The fine structure of solar prominences is made by thin threads that outline the magnetic field lines. Observations show that transverse waves of Alfv\'enic nature are ubiquitous in prominence threads. These waves are driven at the photosphere and propagate to prominences suspended in the corona. Heating due to Alfv\'en wave dissipation could be a relevant mechanism in the cool and partially ionized prominence plasma. We explore the construction of 1D equilibrium models of prominence thin threads that satisfy energy balance between radiative losses, thermal conduction, and Alfv\'en wave heating. We assume the presence of a broadband driver at the photosphere that launches Alfv\'en waves towards the prominence. An iterative method is implemented, in which the energy balance equation and the Alfv\'en wave equation are consecutively solved. From the energy balance equation and considering no wave heating initially, we compute the equilibrium profiles along the thread of the temperature, density, ionisation fraction. We use the Alfv\'en wave equation to compute the wave heating rate, which is then put back in the energy balance equation to obtain new equilibrium profiles. The process is repeated until convergence to a self-consistent thread model heated by Alfv\'en waves is achieved. We have obtained equilibrium models composed of a cold and dense thread, a extremely thin PCTR, and an extended coronal region. The length of the cold thread decreases with the temperature at the prominence core and increases with the Alfv\'en wave energy flux. Equilibrium models are not possible for sufficiently large wave energy fluxes when the wave heating rate inside the cold thread becomes larger than radiative losses. The maximum value of the wave energy flux that allows an equilibrium depends on the prominence core temperature. This constrains the existence of equilibria in realistic conditions.

astro-ph.SR↗

arXiv2022

Transition to turbulence in nonuniform coronal loops driven by torsional Alfv\'en waves. II. Extended analysis and effect of magnetic twist

It has been shown in a previous work that torsional Alfv\'en waves can drive turbulence in nonuniform coronal loops with a purely axial magnetic field. Here we explore the role of the magnetic twist. We model a coronal loop as a transversely nonuniform straight flux tube, anchored in the photosphere, and embedded in a uniform coronal environment. We consider that the magnetic field is twisted and control the strength of magnetic twist by a free parameter of the model. We excite the longitudinally fundamental mode of standing torsional Alfv\'en waves, whose temporal evolution is obtained by means of high-resolution three-dimensional ideal magnetohydrodynamic numerical simulations. We find that phase mixing of torsional Alfv\'en waves creates velocity shear in the direction perpendicular to the magnetic field lines. The velocity shear eventually triggers the Kelvin-Helmholtz instability (KHi). In weakly twisted magnetic tubes, the KHi is able to grow nonlinearly and, subsequently, turbulence is driven in the coronal loop in a similar manner as in the untwisted case. Provided that magnetic twist remains weak, the effect of magnetic twist is to delay the onset of the KHi and to slow down the development of turbulence. In contrast, magnetic tension can suppress the nonlinear growth of the KHi when magnetic twist is strong enough, even if the KHi has locally been excited by the phase-mixing shear. Thus, turbulence is not generated in strongly twisted loops

astro-ph.SR↗

arXiv2022

Quasimodes in the cusp continuum in nonuniform magnetic flux tubes

The study of MHD waves is important both for understanding heating in the solar atmosphere and for solar atmospheric seismology. The analytical investigation of wave mode properties in a cylinder is of particular interest in this domain, as many atmospheric structures can be modeled as such in a first approximation. We use linearized ideal MHD to study quasimodes (global modes that are damped through resonant absorption) with a frequency in the cusp continuum, in a straight cylinder with a circular base and an inhomogeneous layer at its boundary which separates two homogeneous plasma regions inside and outside. We are in particular interested in the damping of these modes, and shall hence try to determine their frequency as a function of background parameters. After linearizing the ideal MHD equations, we find solutions to the second-order differential equation for the perturbed total pressure in the inhomogeneous layer in the form of Frobenius series around the regular singular points that are the Alfv\'en and cusp resonant positions, as well as power series around regular points. By connecting these solutions appropriately through the inhomogeneous layer and with the solutions of the homogeneous regions inside and outside the cylinder, we derive a dispersion relation for the frequency of the eigenmodes of the system. From the dispersion relation, it is also possible to find the frequency of quasimodes even though they are not eigenmodes. As an example, we find the frequency of the slow surface sausage quasimode as a function of the inhomogeneous layer's width, for values of the longitudinal wavenumber relevant for photospheric conditions. The results were found to match well the results found in another paper which studied the resistive slow surface sausage eigenmode. We also discuss the perturbation profiles of the quasimode and the eigenfunctions of continuum modes.

astro-ph.SR↗

arXiv2021

Transverse kink oscillations of inhomogeneous prominence threads: numerical analysis and H$\alpha$ forward modelling

Prominence threads are very long and thin flux tubes which are partially filled with cold plasma. Observations have shown that transverse oscillations are frequent in these solar structures. The observations are usually interpreted as the fundamental kink mode, while the detection of the first harmonic remains elusive. Here, we aim to study how the density inhomogeneity in the longitudinal and radial directions modify the periods and damping times of kink oscillations, and how this effect would be reflected in observations. We solve the ideal magnetohydrodynamics equations through two different methods: a) performing 3D numerical simulations, and b) solving a 2D generalised eigenvalue problem. We study the dependence of the periods, damping times and amplitudes of transverse kink oscillations on the ratio between the densities at the centre and at the ends of the tube, and on the average density. We apply forward modelling on our 3D simulations to compute synthetic H$\alpha$ profiles. We confirm that the ratio of the period of the fundamental oscillation mode to the period of the first harmonic increases as the ratio of the central density to the footpoint density is increased or as the averaged density of the tube is decreased. We find that the damping times due to resonant absorption decrease as the central to footpoint density ratio increases. Contrary to the case of longitudinally homogeneous tubes, we find that the damping time to period ratio also increases as the density ratio is increased or the average density is reduced. We present snapshots and time-distance diagrams of the emission in the H$\alpha$ line. The results presented here have implications for the field of prominence seismology. While the H$\alpha$ emission can be used to detect the fundamental mode, the first harmonic is barely detectable in H$\alpha$. This may explain the lack of detections of the first harmonic.

astro-ph.SR↗

arXiv2021

Alfven wave heating in partially ionized thin threads of solar prominences

There is observational evidence of the presence of small-amplitude transverse magnetohydrodynamic (MHD) waves with a wide range of frequencies in the threads of solar prominences. It is believed that the waves are driven at the photosphere and propagate along the magnetic field lines up to prominences suspended in the corona. The dissipation of MHD wave energy in the partially ionized prominence plasma is a heating mechanism whose relevance needs to be explored. Here we consider a simple 1D model for a non-uniform thin thread and investigate the heating associated with dissipation of Alfven waves. The model assumes an ad hoc density profile and a uniform pressure, while the temperature and ionization degree are self-consistently computed considering either LTE or non-LTE approximations for the hydrogen ionization. A broadband driver for Alfven waves is placed at one end of the magnetic field line, representing photospheric excitation. The Alfvenic perturbations along the thread are obtained by solving the linearized MHD equations for a partially ionized plasma in the single-fluid approximation.We find that wave heating in the partially ionized part of the thread is significant enough to compensate for energy losses due to radiative cooling. A greater amount of heating is found in the LTE case because the ionization degree for core prominence temperatures is lower than that in the non-LTE approximation. This results in a greater level of dissipation due to ambipolar diffusion in the LTE case. Conversely, in the hot coronal part of the model, the plasma is fully ionized and wave heating is negligible. The results of this simple model suggest that MHD wave heating can be relevant for the energy balance in prominences. Further studies based on more elaborate models are required.

astro-ph.SR↗

arXiv2020

Phase Mixing of Kink MHD Waves in the Solar Corona: Viscous Dissipation and Heating

Magnetohydrodynamic (MHD) kink waves have been observed frequently in solar coronal flux tubes, which makes them a great tool for seismology of the solar corona. Here, the effect of viscosity is studied on the evolution of kink waves. To this aim, we solve the initial value problem for the incompressible linearized viscous MHD equations in a radially inhomogeneous flux tube in the limit of long wavelengths. Using a modal expansion technique the spatio-temporal behavior of the perturbations is obtained. We confirm that for large Reynolds numbers representative of the coronal plasma the decrement in the amplitude of the kink oscillations is due to the resonant absorption mechanism that converts the global transverse oscillation to rotational motions in the inhomogeneous layer of the flux tube. We show that viscosity suppresses the rate of phase mixing of the perturbations in the inhomogeneous region of the flux tube and prevents the continuous building up of small scales in the system once a sufficiently small scale is reached. The viscous dissipation function is calculated to investigate plasma heating by viscosity in the inhomogeneous layer of the flux tube. For Reynolds numbers of the order of 10^6-10^8, the energy of the kink wave is transformed into heat in two to eight periods of the kink oscillation. For larger and more realistic Reynolds numbers, heating happens, predominantly, after the global kink oscillation is damped, and no significant heating occurs during the observable transverse motion of the flux tube.

astro-ph.SR↗

arXiv2019

Transverse waves in coronal flux tubes with thick boundaries: The effect of longitudinal flows

Observations show that transverse magnetohydrodynamic (MHD) waves and flows are often simultaneously present in magnetic loops of the solar corona. The waves are resonantly damped in the Alfvén continuum because of plasma and/or magnetic field nonuniformity across the loop. The resonant damping is relevant in the context of coronal heating, since it provides a mechanism to cascade energy down to the dissipative scales. It has been theoretically shown that the presence of flow affects the waves propagation and damping, but most of the studies rely on the unjustified assumption that the transverse nonuniformity is confined to a boundary layer much thinner than the radius of the loop. Here we present a semi-analytic technique to explore the effect of flow on resonant MHD waves in coronal flux tubes with thick nonuniform boundaries. We extend a published method, which was originally developed for a static plasma, in order to incorporate the effect of flow. We allowed the flow velocity to continuously vary within the nonuniform boundary from the internal velocity to the external velocity. The analytic part of the method is based on expressing the wave perturbations in the thick nonuniform boundary of the loop as a Frobenius series that contains a singular term accounting for the Alfvén resonance, while the numerical part of the method consists of solving iteratively the transcendental dispersion relation together with the equation for the Alfvén resonance position. As an application of this method, we investigated the impact of flow on the phase velocity and resonant damping length of MHD kink waves. We consistently recover results in the thin boundary approximation obtained in previous studies. We have extended those results to the case of thick boundaries. We also explored the error associated with the use of the thin boundary approximation beyond its regime of applicability.

astro-ph.SR↗

arXiv2018

Energy transport and heating by torsional Alfvén waves propagating from the photosphere to the corona in the quiet Sun

In the solar atmosphere, Alfvén waves are believed to play an important role in the transfer of energy from the photosphere to the corona and solar wind, and in the heating of the chromosphere. We perform numerical computations to investigate energy transport and dissipation associated with torsional Alfvén waves propagating in magnetic flux tubes that expand from the photosphere to the corona in quiet-Sun conditions. We place a broadband driver at the photosphere that injects a wave energy flux of $10^7$ erg cm$^{-2}$ s$^{-1}$ and consider Ohm's magnetic diffusion and ion-neutral collisions as dissipation mechanisms. We find that only a small fraction of the driven flux, $\sim 10^5$ erg cm$^{-2}$ s$^{-1}$, is able to reach coronal heights, but it may be sufficient to partly compensate the total coronal energy loss. The frequency of maximal transmittance is $\sim 5$ mHz for a photospheric field strength of 1 kG and is shifted to smaller/larger frequencies for weaker/stronger fields. Lower frequencies are reflected at the transition region, while higher frequencies are dissipated producing enough heat to balance chromospheric radiative losses. Heating in the low and middle chromosphere is due to Ohmic dissipation, while ion-neutral friction dominates in the high chromosphere. Ohmic diffusion is enhanced by phase mixing because of the expansion of the magnetic field. This effect has the important consequence of increasing the chromospheric dissipation and, therefore, reducing the energy flux that reaches the corona. We provide empirical fits of the transmission coefficient that could be used as input for coronal models.

astro-ph.SR↗

arXiv2018

Multi-fluid approach to high-frequency waves in plasmas. III. Nonlinear regime and plasma heating

The multi-fluid modelling of high-frequency waves in partially ionized plasmas has shown that the behavior of magnetohydrodynamics waves in the linear regime is heavily influenced by the collisional interaction between the different species that form the plasma. Here, we go beyond linear theory and study large-amplitude waves in partially ionized plasmas using a nonlinear multi-fluid code. It is known that in fully ionized plasmas, nonlinear Alfvén waves generate density and pressure perturbations. Those nonlinear effects are more pronounced for standing oscillations than for propagating waves. By means of numerical simulations and analytical approximations, we examine how the collisional interaction between ions and neutrals affects the nonlinear evolution. The friction due to collisions dissipates a fraction of the wave energy, which is transformed into heat and consequently rises the temperature of the plasma. As an application, we investigate frictional heating in a plasma with physical conditions akin to those in a solar quiescent prominence.

astro-ph.SR↗