Effect of superthermal electrons on Alfvén wave propagation in the dusty plasmas of solar and stellar winds

Abstract

[1] The dispersive characteristics and absorption coefficient of Alfvén waves propagating parallel to the ambient magnetic field are discussed, taking into account the effects of both the charged dust particles present in the interplanetary medium and the superthermal character of the electron distribution function, using physical parameters relevant for solar and stellar winds. The solar wind electrons are described by an isotropic distribution and the protons are described by a Maxwellian. The results are valid for a frequency regime well above the dust-plasma and dust-cyclotron frequencies. However, the theoretical formulation is fully kinetic and the dust charge variation is taken into account. The charging process of the dust is assumed to be associated with the capture of electrons and ions by the dust particles during inelastic collisions with the plasma particles. The dispersion relation for parallel-propagating Alfvén waves is numerically solved and the solutions are compared with particular situations where either the dust particles are absent or the electrons are described by a Maxwellian. It is shown that the presence of both the charged dust particles and the superthermal character of the electron distribution function sensibly modify the dispersion relation of low-frequency and long-wavelength Alfvén waves and significantly increase the absorption coefficient, strongly suggesting that both effects are equally important for a realistic description of the physical processes that occur in solar and stellar winds and that are influenced by the Alfvén waves, such as the energization of particles and the turbulent cascade of magnetic fluctuations.Citation: Gaelzer, R., M. C. de Juli, and L. F. Ziebell (2010), Effect of superthermal electrons on Alfvén wave propagation in the dusty plasmas of solar and stellar winds,

Alfvén waves in space and astrophysical dusty plasmas

“…where Gaelzer et al (2010) focused on high-frequency regimes with superthermal character of electrons and reported a significant modification of the dispersive and absorption characteristics. The absorption coefficient increases due to kappa-distributed electrons, which in turn have a large effect on the Whistler mode.…”

Alfvén waves in dusty plasmas with plasma particles described by anisotropic kappa distributions

“…We make the convenient choice, (11) was considered, both j ? and j k variables are restricted to the intervals 37,44 1 < j ? < 1, 1=2 < j k < 1.…”

“…More recently, we have explored the combined effect of the non-Maxwellian features of kappa distributions and the presence of dust, combination which originate considerable modifications in the dispersion relation for Alfv en waves. 37 In the present work, we develop further the investigation by exploring the anisotropic features which have been observed in the solar wind, by considering a magnetized dusty plasma in which the electrons and ions are described by anisotropic kappa distributions. In Sec.…”

The Dielectric Tensor for Magnetized Dusty Plasmas with Superthermal Plasma Populations and Dust Particles of Different Sizes

“…Some examples are an early paper by Rosenberg [36], which contains a study of instabilities of ion-acoustic waves produced by current in a fully ionized collisionless dusty plasma, without taking into account the effect of variations of the dust charge, a more recent investigation of the effect of dust-charge variation on high-frequency electrostatic plasma waves [37], and several studies on low-frequency electromagnetic waves [38][39][40][41][42][43] and on electrostatic waves in dusty plasmas [44][45][46] in which some of us have been engaged, which also take into account the effect of dust-charge variation, incorporating the dependence on the frequency of inelastic collisions of plasma electrons and ions with the dust particles into the components of the dielectric tensor. It may be added that the kinetic formulation employed in Refs.…”

“…The resulting formulation can be therefore very useful for the investigation of waves and instabilities in dusty plasmas featuring a variety of non-thermal distributions. In fact, a preliminary investigation on nonthermal features coupled with the presence of dust particles, considering a single population of dust particles, was recently conducted for the case of isotropic kappa distribution for electrons and Maxwellian distribution for ions [43].…”