The magnetic structure of a tearing perturbation is determined by the so-called cylindrical tearing mode equation, (3.35), which can be written in the form [4,14]
Cylindrical Tearing Mode Equation
is a dimensionless measure of the toroidal current density profile.
Note that Equation (3.60) is singular at the so-called rational magnetic flux-surface, radius , at which
At the rational surface,
, where is the equilibrium magnetic field, and
the wavevector of the tearing perturbation.