The electrostatic high-n ballooning mode equation is solved, preserving the radial structures of the electron and ion Z-functions. Two branches of ballooning instability are found. The Pearlstein-Berk mode remains stable in a torus with magnetic shear, while the ballooning mode is always unstable and is especially important for Te/Ti∼O(1). The instabilities are characterized by large growth rates and small real frequencies ω*∼γ>|ω|∼0.
All Science Journal Classification (ASJC) codes