@techreport{oai:nifs-repository.repo.nii.ac.jp:00010253,
 author = {"Sugama,  H. and Watanabe,  T.-H."},
 month = {Jan},
 note = {"Theory for describing collisionless long-time behavior of zonal flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of zonal flows to a given source becomes weaker for longer radial wave numbers and deeper helical ripples while a high-level zonal-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance zonal flows which lower anomalous transport."},
 title = {Dynamics of Zonal Flows in Helical Systems},
 year = {2005}
}