  We study neutrino spin-flavor oscillations in presence of rapidly varying
external fields. The general formalism for the description of neutrino
oscillations in arbitrary rapidly varying external fields is elaborated. We
obtain the effective Hamiltonian which determines the evolution of the averaged
neutrino wave function. We apply the general technique to neutrino oscillations
in rapidly varying magnetic fields. The special case of the constant
transversal and twisting magnetic fields is studied. We evaluate the effect of
neutrino spin-flavor oscillations in rapidly varying magnetic fields of the
Sun. The numerical solutions of the Schroedinger equation with the Hamiltonian
accounting for the constant transversal and twisting magnetic fields are
presented. We compare them with our approximate analytical transition
probability formula and reveal good agreement at high frequencies of the
twisting magnetic field.
