Re-ionization of a partially ionized plasma by an Alfvén wave of moderate amplitude (original) (raw)
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Study of effect of ion temperature on Magnetoacoustic Shock waves in plasma
Journal of Chemical and Pharmaceutical Sciences, 2018
In this search, it has been studied the properties of the magneto acoustic shock waves in ultra-dense quantum plasma and its including ions and electrons and positrons after taking effect of ion temperature on phase velocity of the magneto sonic wave and , this is by the ion pressure into momentum equation of ion fluid. Moreover, it has been studied that waves by using reductive perturbation method. The results have been compared to the shock waves ones with what others have reached in related references.
Astronomy & Astrophysics, 2011
Context. Chromospheric and prominence plasmas contain neutral atoms, which may change the plasma dynamics through collision with ions. Most of the atoms are neutral hydrogen, but a significant amount of neutral helium may also be present in the plasma with a particular temperature. Damping of MHD waves due to ion collision with neutral hydrogen is well studied, but the effects of neutral helium are largely unknown. Aims. We aim to study the effect of neutral helium in the damping of Alfvén waves in solar partially ionized plasmas. Methods. We consider three-fluid magnetohydrodynamic (MHD) approximation, where one component is electron-proton-singly ionized helium and other two components are the neutral hydrogen and neutral helium atoms. We derive the dispersion relation of linear Alfvén waves in isothermal and homogeneous plasma. Then we solve the dispersion relation and derive the damping rates of Alfvén waves for different plasma parameters. Results. The presence of neutral helium significantly enhances the damping of Alfvén waves compared to the damping due to neutral hydrogen at certain values of plasma temperature (10000 − 40000 K) and ionization. Damping rates have a peak near the ion-neutral collision frequency, but decrease for the higher part of wave spectrum. Conclusions. Collision of ions with neutral helium atoms can be of importance for the damping of Alfvén waves in chromospheric spicules and in prominence-corona transition regions.
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Magnetoacoustic oscillations in a Helium plasma are investigated. The plasma is strongly inhomogeneous. The average density is ne =4-1012 cm-3, but drops to an immeasurable value near the wall. The device, in which an r-/-discharge produces this profile, is described. The results of a theoretical calculation are given. This calculation is based on a three fluid cold plasma theory and the density and temperature profile as well as the finite length of the plasma column and the length of the exciting coil is taken into account. It is shown that the experiments can only be described by this calculation, if an effective collision rate is introduced. This veff might be justified by observed fluctuations at the boundary of the plasma.
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The properties of gas acoustic and ion acoustic modes are investigated in a collisional, weakly ionized plasma in the presence of unmagnetized ions and magnetized electrons. In such a plasma, an ion acoustic mode, driven by an electron flow along the magnetic field lines, can propagate almost at any angle with respect to the ambient field lines as long as the electrons are capable of participating in the perturbations by moving only along the field lines. Several effects, including the electron-ion collisions, the perturbations of the neutral gas, and the electromagnetic perturbations, are studied in the present work. The electron-ion collisions are shown to modify the previously obtained angle-dependent instability threshold for the driving electron flow. The inclusion of the neutral dynamics implies an additional neutral sound mode, which couples to the current driven ion acoustic mode, and these two modes can interchange their identities in certain parameter regimes. The electromagnetic effects, which in the present model imply a bending of the magnetic field lines, result in a further destabilization of an already unstable ion acoustic wave. The applicability of these results to the solar and/or space and laboratory plasmas is discussed.
Heating of ions by low-frequency Alfvén waves in partially ionized plasmas
Physics of Plasmas, 2011
In the solar atmosphere, the chromospheric and coronal plasmas are much hotter than the visible photosphere. The heating of the solar atmosphere, including the partially ionized chromosphere and corona, remains largely unknown. In this letter, we demonstrate that the ions can be substantially heated by Alfvén waves with very low frequencies in partially ionized low-beta plasmas. This differs from other Alfvén wave related heating mechanisms such as ion-neutral collisional damping of Alfvén waves and heating described by previous work on resonant Alfvén wave heating. We find that the nonresonant Alfvén wave heating is less efficient in partially ionized plasmas than when there are no ion-neutral collisions, and the heating efficiency depends on the ratio of the ion-neutral collision frequency to the ion gyrofrequency.
Alfvén waves in the magnetosphere generated by shock wave / plasmapause interaction
Solnechno-Zemnaya Fizika, 2019
We study Alfvén waves generated in the magnetosphere during the passage of an interplanetary shock wave. After shock wave passage, the oscillations with typical Alfvén wave dispersion have been detected in spacecraft observations inside the magnetosphere. The most frequently observed oscillations are those with toroidal polarization; their spatial structure is described well by the field line resonance (FLR) theory. The oscillations with poloidal polarization are observed after shock wave passage as well. They cannot be generated by FLR and cannot result from instability of high-energy particle fluxes because no such fluxes were detected at that time. We discuss an alternative hypothesis suggesting that resonant Alfvén waves are excited by a secondary source: a highly localized pulse of fast magnetosonic waves, which is generated in the shock wave/plasmapause contact region. The spectrum of such a source contains oscillation harmonics capable of exciting both the toroidal and poloid...
Ionization waves in the medium pressure helium and neon plasma
1997
We present the experimental results obtained on the ionisation waves in the helium and neon plasmas, within the pressure range of 200 Pa to 2000 Pa (133 Pa = 1 Torr), and for discharge electric currents of 5 mA to 35 mA. The main characteristics of the ionization waves in the medium presure neon and helium discharge are a small amplitude and a high frequency. The amplitude of the waves is smaller than 1 V. In the case of the neon plasma, the frequency varies between approximately 700 Hz and 2250 Hz and increases with the discharge current. In the helium plasma, the frequency is in the range between approximately 1500 Hz and 4000 Hz and decreases with the discharge electric current.
Alfvén Waves in a Partially Ionized Two-Fluid Plasma
The Astrophysical Journal, 2013
Alfvén waves are a particular class of magnetohydrodynamic waves relevant in many astrophysical and laboratory plasmas. In partially ionized plasmas the dynamics of Alfvén waves is affected by the interaction between ionized and neutral species. Here we study Alfvén waves in a partially ionized plasma from the theoretical point of view using the two-fluid description. We consider that the plasma is composed of an ion-electron fluid and a neutral fluid, which interact by means of particle collisions. To keep our investigation as general as possible we take the neutral-ion collision frequency and the ionization degree as free parameters. First, we perform a normal mode analysis. We find the modification due to neutral-ion collisions of the wave frequencies and study the temporal and spatial attenuation of the waves. In addition, we discuss the presence of cutoff values of the wavelength that constrain the existence of oscillatory standing waves in weakly ionized plasmas. Later, we go beyond the normal mode approach and solve the initial-value problem in order to study the time-dependent evolution of the wave perturbations in the two fluids. An application to Alfvén waves in the low solar atmospheric plasma is performed and the implication of partial ionization for the energy flux is discussed.
Response to ``Comment on `Heating of ions by low-frequency Alfvén waves in partially ionized plasmas
Physics of Plasmas, 2011
The calculation of temperature in a plasma system that is not in thermal equilibrium remains a topic of debate. In our article [Dong and Paty, Phys. Plasmas 18, 030702 (2011)] we use the average kinetic energy to calculate the ``kinetic temperature'' in a non-equilibrium system to quantify the heating of ions by low-frequency Alfvén waves in a partially ionized plasma (i.e., where collisions with neutrals can not be ignored). We implement a method previously used by Wang, Wu and Yoon [Wang, Wu and Yoon, Phys. Rev. Lett. 96, 125001 (2006)] and several others studying the effects of low frequency Alfvén waves in collisionless plasmas. This method is appropriate for several reasons discussed in this response. Most notably, we implement it to investigate heating of the plasma population since the bulk velocity of the particle ensemble perpendicular to the ambient magnetic field remains zero during the numerical experiment.
Excitation of ion-acoustic perturbations by incoherent kinetic Alfvén waves in plasmas
Physics of Plasmas, 2007
The dispersion relation for ion-acoustic perturbations ͑IAPs͒ in the presence of incoherent kinetic Alfvén waves ͑KAWs͒ in plasmas is derived. The wave-kinetic-approach is used to study the nonlinear interactions between an ensemble of random phase KAWs and IAPs. It is found that incoherent KAW spectrum is unstable against IAPs. The instability growth rates for particular cases are obtained. The present instability offers the possibility of heating ions in a turbulent magnetoplasma composed of incoherent KAWs.