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Context. Recent studies on Kappa distribution functions invoked in spaceplasma applications have emphasized two alternative approaches which may assumethe temperature parameter either dependent or independent of the power-index$\kappa$. Each of them can obtain justification in different scenariosinvolving Kappa-distributed plasmas, but direct evidences supporting any ofthese two alternatives with measurements from laboratory or natural plasmas arenot available yet. Aims. This paper aims to provide more facts on thisintriguing issue from direct fitting measurements of suprathermal electronpopulations present in the solar wind, as well as from their destabilizingeffects predicted by these two alternating approaches. Methods. Two fittingmodels are contrasted, namely, the global Kappa and the dual Maxwellian-Kappamodels, which are currently invoked in theory and observations. Thedestabilizing effects of suprathermal electrons are characterized on the basisof a kinetic approach which accounts for the microscopic details of thevelocity distribution. Results. In order to be relevant, the model is chosen toaccurately reproduce the observed distributions and this is achieved by a dualMaxwellian-Kappa distribution function. A statistical survey indicates a$\kappa$-dependent temperature of the suprathermal (halo) electrons for anyheliocentric distance. Only for this approach the instabilities driven by thetemperature anisotropy are found to be systematically stimulated by theabundance of suprathermal populations, i.e., lowering the values of$\kappa$-index.

Dual Maxwellian-Kappa modelling of the solar wind electrons: new clues on the temperature of Kappa populations