2. Kappa Plasmas
Workshop organized by: M. Lazar and V. Pierrard
Lorentzian (Kappa) distributions as an advanced tool of statistical modeling and analysis of the solar wind
The so-called Kappa distribution functions are generalized power-laws that provide valuable description for the particle energy spectra in space plasmas. In plasmas where collisions are rare, the independence of particles breaks down due to long-range correlations supplied by the fields and plasma instabilities, and classical statistics cannot reproduce the observed distributions of Kappa-type. Power-law distributions can instead result from a generalized statistics for the charged particles with long-range correlations, which contribute to a super-extensive entropy and implies generalization of the plasma temperature to non-thermal quasi-stationary states.
However, we are still far from a complete and rigorous understanding of these models, and significant issues are still to be addressed, covering all the fundamental and observational aspects:
- Generalized statistics for particle systems out of thermal equilibrium involving long-range interactions (Coulomb, gravitational, etc.) as providing fundamental explanation for Kappa distributions in natural plasmas systems
- Thermodynamical implications, moments of the Kappa distributions and limitations by the power-index
- Evidences of Kappa distributions in space plasmas: integrating and fitting observational data with advanced 3D or 2D (gyrotropic) Kappa models; temperature anisotropy; strahl (beaming) component
- Generation of Kappa distributions in theory and numerical simulations: particle acceleration and pitch-angle scattering by self-generated fields and wave instabilities (beams/counterstreams relaxation and wave decay from large to small scales)
- Origin of the Kappa distributions in the solar wind and terrestrial magnetosphere; coronal scenario and implications.
