  With strong gradients in the pedestal of high confinement mode (H-mode)
fusion plasmas, gyrokinetic simulations are carried out for the trapped
electron and ion temperature gradient modes. A broad class of unconventional
mode structures is found to localize at arbitrary poloidal positions or with
multiple peaks. It is found that these unconventional ballooning structures are
associated with different eigen states for the most unstable mode. At weak
gradient (low confinement mode or L-mode), the most unstable mode is usually in
the ground eigen state, which corresponds to a conventional ballooning mode
structure peaking in the outboard mid-plane of tokamaks. However, at strong
gradient (H-mode), the most unstable mode is usually not the ground eigen state
and the ballooning mode structure becomes unconventional. This result implies
that the pedestal of H-mode could have better confinement than L-mode.
