The role of thermal plasma density gradient in the problem of Alfvén cascades in tokamaks

The localization effect of thermal plasma density gradient on the Alfvén cascades in tokamaks is studied. It is shown that this effect can be stronger than the toroidal magnetohydrodynamic effect considered by Breizman et al. [Phys. Plasmas 10, 3649 (2003)] as squared aspect ratio. Thus, the Alfvén cascade modes can be theoretically shown in cylindrical geometry approximation. Then the role of thermal plasma density gradient can be dominant if the localization effect of density gradient of large-orbit hot ions [Berk et al., Phys. Rev. Lett. 87, 185002 (2001)] is sufficiently weak.