Skew-kappa Distribution Functions and Whistler Heat Flux Instability in the Solar Wind: The Core-strahlo Model

Electron velocity distributions in the solar wind are known to have field-aligned skewness, which has been characterized by the presence of secondary populations such as the halo and strahl. Skewness may provide energy for the excitation of electromagnetic instabilities, such as the whistler heat flux instability (WHFI), which may play an important role in regulating the electron heat flux in the solar wind. Here we use kinetic theory to analyze the stability of the WHFI in a solar-wind-like plasma where solar wind core, halo, and strahl electrons are described as a superposition of two distributions: a Maxwellian core, and another population modeled by a Kappa distribution to which an asymmetry term has been added, representing the halo and also the strahl. Considering distributions with small skewness, we solve the dispersion relation for the parallel-propagating whistler mode and study its linear stability for different plasma parameters. Our results show that the WHFI can develop in this system and provide stability thresholds for this instability, as a function of the electron beta and the parallel electron heat flux, to be compared with observational data. However, since different plasma states, with different stability level to the WHFI, can have the same moment heat flux value, it is the skewness (i.e., the asymmetry of the distribution along the magnetic field), and not the heat flux, that is the best indicator of instabilities. Thus, systems with high heat flux can be stable enough to WHFI, so that it is not clear whether the instability can effectively regulate the heat flux values through wave–particle interactions.

Multi-component dense plasma with ion and super-thermal electrons with kappa distribution

The soliton waves are one of the nonlinear phenomena which can propagate in the different types of plasma such as multiple particles of plasma, nonthermal plasma, and space plasma. Using the Sagdeev potential technique, the stability conditions of the soliton waves in the nonthermal plasma have been theoretically studied. One of the significant factors that can affect the propagation of the soliton waves is the distribution function such as nonMaxwellian distribution function or Kappa distribution function. In this paper, we try to investigate the soliton wave in the unmagnetized multi-component plasma consisting of the nonthermal electron and the nonthermal ion, positron and dust with Kappa distribution function. Then by using the Sagdeev potential, the nonlinear equation for the potential is obtained and then the compression and rarefaction soliton waves are computed with the numerical method for this nonlinear wave. Finally, by imposing the Sagdeev potential condition, we discuss the stability of these soliton waves.

Olbert’s Kappa Fermi and Bose Distributions

The quantum version of Olbert’s kappa distribution applicable to fermions is obtained. Its construction is straightforward but requires recognition of the differences in the nature of states separated by Fermi momenta. Its complement, the bosonic version of the kappa distribution is also given, as is the procedure of how to construct a hypothetical kappa-anyon distribution. At very low temperature the degenerate kappa Fermi distribution yields a kappa-modified version of the ordinary degenerate Fermi energy and momentum. We provide the Olbert-generalized expressions of the Olbert-Fermi partition function and entropy which may serve determining all relevant statistical mechanical quantities. Possible applications are envisaged to condensed matter physics, possibly quantum plasmas, and dense astrophysical objects like the interior state of terrestrial planets, neutron stars, magnetars where quantum effects come into play and dominate the microscopic scale but may have macroscopic consequences.