Fluid analysis of the collisionless magnetohydrodynamic ballooning mode branch in tokamaks

Abstract

The stability of electromagnetic ballooning modes is investigated using a toroidal two‐fluid model allowing for arbitrary Ln/LB (the characteristic scale lengths of density and magnetic‐field inhomogeneities). The ballooning mode equation is solved numerically and the two‐fluid and magnetohydrodynamic stability properties are discussed and compared. The perpendicular compressibility strongly reduces the growth rate and for Ln/LB∼Ln/LT∼1, the mode is completely stabilized.