Kinetic corrections to a previous ideal MHD ballooning stability study of the TJ-II heliac standard configuration are numerically calculated using a criterion derived from the gyrokinetic Maxwell equations for modes with perpendicular wavelengths on the scale of the ion gyroradius in a general magnetic geometry. In this criterion, finite ion gyroradius and trapped particle effects are retained at first order. The existence of temperature gradients and different ion and electron temperatures are accounted for. The relevant kinetic regime for TJ-II is found to be the intermediate frequency regime, with ωbi, ωti < γ < ωbe, ωte across all the relevant region whenever electron cyclotron resonance heating (ECRH) plasmas are considered. Therefore, only trapped electrons are included in the calculations. The threshold poloidal wavenumber mu for diamagnetic stabilization of unstable ballooning modes is obtained, and a reduction of about 30% of the instability region radial width has been found. The trapped electron contribution to the growth rate is shown to be destabilizing for all modes with poloidal wavenumber below this threshold and is evaluated perturbatively, showing that an important part of it is due to those electrons trapped in the ripple of the magnetic field.
Electromagnetic and kinetic effects on the ion temperature gradient mode