  In the absence of efficient collisions, deviations from thermal equilibrium
of plasma particle distributions are controlled by the self-generated
instabilities. The whistler instability is a notorious example, usually
responsible for the regulation of electron temperature anisotropy $A =
T_{\perp}/T_\parallel>$ (with $\perp, \parallel$ respective to the magnetic
field direction) observed in space plasmas, e.g., solar wind and planetary
magnetospheres. Suprathermal electrons present in these environments change the
plasma dispersion and stability properties, with expected consequences on the
kinetic instabilities and the resulting fluctuations, which, in turn, scatter
the electrons and reduce their anisotropy. In order to capture these mutual
effects we use a quasilinear kinetic approach and PIC simulations, which
provide a comprehensive characterization of the whistler instability under the
influence of suprathermal electrons. Analysis is performed for a large variety
of plasma conditions, ranging from low-beta plasmas encountered in outer corona
or planetary magnetospheres to a high-beta solar wind characteristic to large
heliospheric distances. Enhanced by the suprathermal electrons, whistler
fluctuations stimulate the relaxation of temperature anisotropy, and this
influence of suprathermals increases with plasma beta parameter.
