author = "Elfimov, Artour G. and Galv{\~a}o, Ricardo Magnus Os{\'o}rio and 
                         Gorelenkov, N. N.",
          affiliation = "{Universidade de S{\~a}o Paulo (USP)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Princeton University}",
                title = "Geodesic modes driven by untrapped resonances of NB energetic ions 
                         in tokamaks",
              journal = "Physics of Plasmas",
                 year = "2019",
               volume = "26",
               number = "10",
                pages = "e102508",
                month = "Oct.",
             abstract = "Geodesic modes are typically excited by a minor concentration of 
                         energetic ions, but unstable mode frequencies are substantially 
                         different from Geodesic Acoustic Modes (GAMs) and are named EGAM 
                         (Energetic particle GAM). The EGAM instability driven by Neutral 
                         Beam Injection (NBI) has been observed in DIII-D tokamak 
                         experiments. The problem of the geodesic mode instability is 
                         analytically studied using a full drift kinetic equation. To 
                         analyze the instability condition, an ionization NBI location is 
                         assumed to be on the high field side of tokamaks. A minority NBI 
                         ion distribution is modeled by an energetic ion tail in the 
                         untrapped-passing region that remains between a magnetic axis and 
                         the trapped NBI boundary. The EGAM instability condition is 
                         defined by the parallel NBI ion velocity vjj 1:2 1:5xR0q0 that 
                         has to be above the effective EGAM phase velocity. In this case, 
                         the EGAM frequency is 50% below the standard stable GAM frequency, 
                         which is reduced by a small concentration of energetic NBI ions. 
                         Qualitative comparison of the developed geodesic mode theory with 
                         NBI heating experiments in the midregion of the tokamak plasma is 
                  doi = "10.1063/1.5110175",
                  url = "http://dx.doi.org/10.1063/1.5110175",
                 issn = "1070-664X",
             language = "en",
           targetfile = "elfimov_geodesic.pdf",
        urlaccessdate = "13 abr. 2021"