Tomaschitz, R.
(2016). The stationary non-equilibrium plasma of cosmic-ray electrons and
positrons, *Physica A* **451**, 456-464, DOI:
10.1016/j.physa.2016.01.091

**Abstract (**ScienceDirect**, **SAO/NASA ADS**)**

The statistical properties of the two-component plasma of cosmic-ray electrons and positrons measured by the AMS-02 experiment on the International Space Station and the HESS array of imaging atmospheric Cherenkov telescopes are analyzed. Stationary non-equilibrium distributions defining the relativistic electron-positron plasma are derived semi-empirically by performing spectral fits to the flux data and reconstructing the spectral number densities of the electronic and positronic components in phase space. These distributions are relativistic power-law densities with exponential cutoff, admitting an extensive entropy variable and converging to the Maxwell-Boltzmann or Fermi-Dirac distributions in the non-relativistic limit. Cosmic-ray electrons and positrons constitute a classical (low-density high-temperature) plasma due to the low fugacity in the quantized partition function. The positron fraction is assembled from the flux densities inferred from least-squares fits to the electron and positron spectra and is subjected to test by comparing with the AMS-02 flux ratio measured in the GeV interval. The calculated positron fraction extends to TeV energies, predicting a broad spectral peak at about 1 TeV followed by exponential decay.

05.20.Gg Classical ensemble theory

05.30.Fk Fermion systems and electron gas

52.27.Ny Relativistic plasmas

52.27.Ep Electron-positron plasmas

52.25.Kn Thermodynamics of plasmas

98.70.Sa Cosmic rays

description: Roman
Tomaschitz (2016) The stationary non-equilibrium plasma of cosmic-ray electrons
and positrons, *Physica *A **451**, 456.

**Keywords:** Stationary non-equilibrium distributions; Cosmic-ray
electron-positron plasma; Relativistic statistical ensembles; Power-law
densities with exponential cutoff; Nonthermal ensemble averaging; Classical
& quantum partitions with extensive entropy

**Highlights**

The thermodynamic variables of the cosmic-ray electron-positron plasma are calculated.

Spectral fits to the AMS-02 and HESS GeV-TeV electron and positron fluxes are performed.

A semi-empirical phase-space reconstruction of the partial probability densities is carried out.

Partition function & entropy of a relativistic plasma in stationary non-equilibrium are derived.

The positron fraction extrapolated to TeV energies shows a broad spectral peak & exponential decay.

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