Influence of deeply trapped energetic ions on tearing modes

Abstract

The effects of deeply trapped energetic ions (DTEIs) on the stability of tearing modes through stability criterion Δ ′ are studied. In contrast to the stabilizing adiabatic effect of background plasma pressure, the adiabatic contribution of the DTEI destabilizes due to the direct coupling between the bad curvature and asymmetrical pressure of energetic ions. When the orbit width is much larger than the island width, the nonadiabatic effect of the DTEI stabilizes, which counteracts the major destabilizing adiabatic contribution. DTEIs are shown to have a net destabilizing effect on the tearing mode. The main physics of destabilization of Δ ′ comes from the modification of the Mercier index.