  Recent observations reveal that magnetic turbulence in the nearly
colisionless solar wind plasma extends to scales smaller than the plasma
microscales, such as ion gyroradius and ion inertial length. Measured breaks in
the spectra of magnetic and density fluctuations at high frequencies are
thought to be related to the transition from large-scale hydromagnetic to
small-scale kinetic turbulence. The scales of such transitions and the
responsible physical mechanisms are not well understood however. In the present
work we emphasize the crucial role of the plasma parameters in the transition
to kinetic turbulence, such as the ion and electron plasma beta, the electron
to ion temperature ratio, the degree of obliquity of turbulent fluctuations. We
then propose an explanation for the spectral breaks reported in recent
observations.
