  This letter presents the results of an advanced parametrization of the solar
wind electron temperature anisotropy and the instabilities resulting from the
interplay of the (bi-)Maxwellian core and (bi-)Kappa halo populations in the
slow solar wind. A large set of observational data (from the Ulysses, Helios
and Cluster missions) is used to parametrize these components and establish
their correlations. The instabilities are significantly stimulated in the
presence of suprathermals, and the instability thresholds shape the limits of
the temperature anisotropy for both the core and halo populations re-stating
the incontestable role that the selfgenerated instabilities can play in
constraining the electron anisotropy. These results confirm a particular
implication of the suprathermal electrons which are less dense but hotter than
thermal electrons.
