Superposition of Drive and Selection Fields. Superposition of selection and drive field at a spatial position x. The magnetization flips when the field H(x, t) = H
S(x) - H
D(t) crosses zero. The selection field offset H
S(x) causes a time shift of the magnetization flip. Harmonic (a) and triangular (b) drive fields with amplitude A are displayed. Note that for mathematical convenience, the harmonic drive field ranges from -A to A, whereas the triangular field varies between 0 and 2A.