We propose a polytropic-like index that depends on the concentration and number of
degrees of freedom of a gas of charged particles following a nonextensive distribution. An
equation of state of the gas is obtained and a dispersion relation describing Langmuir waves
is derived. Comparison of the acquired dispersion relation with a previous one, recently
deduced in the realm of the Kappa distribution, provides an adiabatic map of suprathermal
onto nonextensive parameters. In the isothermal limit, the map recovers a well-known …