Abstract
The set of semicollisional layer equations derived by Fitzpatrick [Phys. Fluids B 1, 2381 (1989)] is used to investigate the effect of trapped particles on the linear stability of long wavelength resistive modes in a large‐aspect‐ratio tokamak. At O(1) shear, destabilization by trapped particles is found to significantly modify previous cylindrical results for the drift‐tearing mode. At low shear, a fairly weak trapped particle‐driven interchange (g mode) instability is found, in addition to the usual drift‐tearing mode instability, which, in this limit, is virtually unaffected by trapped particles.