Development and effects of turbulence in connection with CIRs

We present an overview of the properties of magnetohydrodynamic turbulence within corotating interaction regions (CIRs) and its effects on energetic p articles. We stress the importance of both the population of fluctuations i n the inner heliosphere and the changing local environment in determining t heir properties at larger heliospheric distances. We present observations f rom two typical CIRs, one at 0.3 AU before compression regions have formed and the other well developed at 5.1 AU, and discuss the properties of fluct uations within them and show that it is possible to distinguish different r egions of the CIR on the basis of the turbulence itself. The strength of th e turbulence varies strongly within and close to the CIRs, explaining chang es in the mean free path of energetic particles of several orders of magnit ude with implications for the modulation of cosmic rays and for diffusive a cceleration of particles. The mechanisms by which turbulent fluctuations wi thin interaction regions scatter energetic particles are briefly discussed on a theoretical basis.