Analytical and numerical studies of collisionless tearing modes that are wider than the "current channel" are presented. The $m=1\mathrm{}$ type of inertial mode is shown to be strongly unstable for typical tokamak shear and ${\beta }_e$. Large spatial extension and large growth rate make it a possible candidate for explaining plasma disruption.

• Received 7 August 1978

DOI:https://doi.org/10.1103/PhysRevLett.41.1375