  It is shown that the processes of neutrino oscillations in a magnetic field
can be consistently described in the framework of a new quantum
field-theoretical approach without use of the neutrino flavor states. It is
based on the Feynman diagram technique with a modified distance-dependent
propagator, which takes into account the geometry of neutrino oscillation
experiments. Processes of neutrino oscillations in a magnetic field, where the
neutrinos are detected through the weak charged- and neutral-current
interaction, have been studied and numerical calculations have been carried out
for some specific examples. Implications for the solar neutrinos are briefly
discussed, and formulas for the asymptotic values of the normalized probability
of solar neutrino oscillation processes are derived, which coincide with the
observable ratio of the measurable neutrino flux to that predicted by the
standard solar model.
