The relation between cyclotron heating and energetic particles on open coronal field lines

Cyclotron resonance with high-frequency Alfven waves has been proposed as a n ion heating mechanism for producing high-speed winds and large ion temper atures in coronal holes. In the simplest version of the model (cyclotron sw eep model), the waves propagate without interacting until they hit a resona nce with the plasma ions at distance, where the ion cyclotron frequency bec omes comparable to the wave frequency. We calculate the energetic test-part icle mean free path lambda in solar corona heated by this mechanism. The pr imary result of our study is that energetic particles are efficiently coupl ed to the high-frequency MHD waves and may, thus, provide important feed ba ck to wave-heating models. Detailed calculations are presented for a solar- wind stream of intermediate speed driven by the cyclotron sweep mechanism a pplying an extended quasi-linear theory for the mean free path. A local max imum of lambda is located near r = 2 R., but lambda is very small at distan ces close to the Sun (r <1.3 R.) helping the acceleration of particles to h igh energies on open coronal field lines there. Another minimum for the mea n free path is obtained near r = 10 R. enabling ion acceleration beyond 10 MeV/n in streams of intermediate speeds by CME shock waves in the test-part icle approximation. However, the presence of high-frequency Alfven waves in amounts required for the cyclotron sweep heating has to be limited below < similar to>10 R. on field lines close to the ecliptic to avoid discrepancie s with the inferred arrival times of solar energetic particles. Non-linear effects are discussed as a possible mechanism for removing the wave excess from the plasma.