THE INFLUENCE OF DISSIPATION RANGE POWER SPECTRA AND PLASMA-WAVE POLARIZATION ON COSMIC-RAY SCATTERING MEAN FREE PATH

The influence of the polarization state and the dissipation range spectral steepening of slab plasma waves on the scattering mean free path of single-charged cosmic-ray particles is investigated in a turbulence model, where the crucial scattering of cosmic-ray particles with small pitch-angle cosines is caused by resonant cyclotron interactions with slab plasma waves. Analytical expressions for the mean free path of protons, antiprotons, negatrons, and positrons are derived for the case of constant frequency-independent magnetic helicity values sigma and different values of the dissipation range spectral index k for characteristic interplanetary and interstellar plasma conditions. The positron mean free path is not affected by the dissipation range spectral index k as these particles can only cyclotron-resonate for rigidity values larger than R-0 = m(p)c = 938 MV. Proton and antiproton mean free paths are only slightly affected by the dissipation range spectral index k at small rigidities R < R-0. The negatron mean free path is severely affected by the dissipation range spectral index k at rigidities smaller than R-0. At high rigidities R >> R-0, all particle species approach the same power-law dependence alpha R2-s determined by the inertial range spectral index s = 5/3. The magnetic helicity value sigma affects the value of the mean free path. At all rigidities, the ratio of the antiproton to proton mean free paths equals the constant (1 + sigma)/(1 - sigma), which also agrees with the ratio of the negatron to the proton and positron mean free paths at relativistic rigidities. At relativistic rigidities the positron and proton mean free paths agree, as do the negatron and antiproton mean free paths.