Drift-Modified Tearing Instabilities Due to Trapped Electrons

Abstract

It is shown that the collisional detrapping of magnetically trapped electrons in tokamaks can excite drift tearing modes with high azimuthal mode numbers. For normal temperature gradients ($\frac{d\mathrm{ln}{T}_{e}}{d\mathrm{ln}n}>0$), the modes are unstable in the collisional regime (${\ensuremath{\nu}}_{\mathrm{eff}}>{\ensuremath{\omega}}_{^{*}e}$), but stable in the collisionless regime (${\ensuremath{\nu}}_{\mathrm{eff}}<{\ensuremath{\omega}}_{^{*}e}$).