Relationship between Polytropic Index and Temperature Anisotropy in Space Plasmas

Abstract The paper develops a theoretical relationship between the polytropic index and temperature anisotropy that may characterize space plasmas. derivation is based on correlation among kinetic energies of particles with velocities described by anisotropic kappa distributions. coefficient depends effective dimensionality velocity distribution, which determined caused ambient magnetic field; other hand, directly dependent index. This analysis leads to connection coefficient, space, index, anisotropy. Moreover, data statistical performed test developed model in solar wind proton plasma near 1 au. derived good agreement observations, showing lowest classical value adiabatic occurs isotropic case, while higher values more Finally, possible extensions theory considering (i) nonadiabatic behavior (ii) general distributions, are further discussed.