arXiv subjects

Marian Lazar

Publications and source records attributed to Marian Lazar.

22 records · Page 2Linked to original sources

arXiv2019

Moments of the anisotropic regularized $κ$-distributions

For collisionless (or collision-poor) plasma populations which are well described by the $κ$-distribution functions (also known as the Kappa or Lorentzian power-laws) a macroscopic interpretation has remained largely questionable, especially because of the diverging moments of these distributions. Recently significant progress has been made by introducing a generic regularization for the isotropic $κ$-distribution, which resolves this critical limitation. Regularization is here applied to the anisotropic forms of $κ$-distributions, commonly used to describe temperature anisotropies, and skewed or drifting distributions of beam-plasma systems. These regularized distributions admit non-diverging moments which are provided for all positive $κ$, opening promising perspectives for a macroscopic (fluid-like) characterization of non-ideal plasmas.

physics.comp-ph↗

arXiv2019

On the applicability of $κ$-distributions

The standard (non-relativistic) $κ$-distribution is widely used to fit data and to describe macroscopic thermodynamical behavior, e.g.\ the pressure (temperature) as the second moment of the distribution function. By contrast to a Maxwellian distribution, for small relevant values $κ< 2$ there exists a significant, but unphysical contribution to the pressure from unrealistic, superluminal particles with speeds exceeding the speed of light. Similar concerns exist for the entropy. We demonstrate here that by using the recently introduced regularized $κ$-distribution one can avoid such unphysical behaviour.

physics.plasm-ph↗

arXiv2018

Uncertainties in the heliosheath ion temperatures

The Voyager plasma observations show that the physics of the heliosheath is rather complex, and especially that the temperature derived from observation differs from expectations. To explain this fact the temperature in the heliosheath should be based on $κ$ distributions instead of Maxwellians because the former allows for much higher temperature. Here we show an easy way to calculate the $κ$ temperatures when those estimated from the data are given as Maxwellian temperatures. We use the moments of the Maxwellian and $κ$ distributions to estimate the $κ$ temperature. Moreover, we show that the pressure (temperature) given by a truncated $κ$ distribution is similar to that given by a Maxwellian and only starts to increase for higher truncation velocities. We deduce a simple formula to convert the Maxwellian to $κ$ pressure or temperature. We apply this result to the Voyager-2 observations in the heliosheath.

physics.space-ph↗

arXiv2008

Macroscopic description for a quantum plasma micro-instability: the quantum Weibel solution

The Weibel instability in the quantum plasma case is treated by means of a fluid-like (moments) approach. Quantum modifications to the macroscopic equations are then identified as effects of first or second kind. Quantum effects of the first kind correspond to a dispersive term, similar to the Bohm potential in the quantum hydrodynamic equations for plasmas. Effects of the second kind are due to the Fermi statistics of the charge carriers and can become the dominant influence for strong degeneracy. The macroscopic dispersion relations are of higher order than those for the classical Weibel instability. This corresponds to the presence of a cutoff wave-number even for the strong temperature anisotropy case.

physics.plasm-ph↗