Toroidal global eigenmodes in ion-ion hybrid range of frequencies

As it is known, Alfven wave forms a continuum spectrum in nonuniform plasma. In a tokamak plasma this continuum has gaps in which specific global modes - Toroidal Alfven Eigenmodes (TAE) - have been found. These modes are localized near a magnetic surface and weakly damped. Therefore, they can be responsible for the instabilities, driven by alpha particles in a fusion reactor. The characteristic frequencies of TAE are much lower than ion cyclotron frequencies. For higher frequencies, near the ICRF, gaps in continuum spectrum become very thin and TAE do not exist. However, in a plasma with two ion species (for example, deuterium and tritium) in Ion-Ion Hybrid Range of Frequencies (IIHRF, ωC1 < ω < ωC2) continuum spectrum has other properties. Examining the dispersion relation for IIHRF continuum spectrum one can find large gaps and suggest the existence of localized global TAE-like modes. The problem of existence of such modes is studied in the present report. In order to solve this problem, a general equation describing continuum and global eigenmodes as well in the whole frequency range in appropriate magnetic trap having magnetic surfaces has been derived. Using this equation global modes of two types have been found in IIHRF: TLE - TAE-like mode and OHE - original hybrid eigenmode. (author) 3 refs