Curvature drift is a mode of motion of charged particles in a curved magnetic field. In contrast to the motion of charged particles in a uniform magnetic field, where the charged particles gyrate around the magnetic fields, in curvature drift the particles move mostly parallel to the magnetic field.
Consider a toroidal magnetic field of uniform intensity . A charge particle in such a field can also move in a helical trajectory, with constant speed. The equations of motion are
The velocity is assumed to be of the form , where and are constants. Substituting into the equation of motion, keeping in mind that , where is the distance from the axis, yields
In contrast to the helical motion in a uniform magnetic field, where the two components of the velocity are independent.