  In this study we propose a new generic model for QPOs based on oscillation
modes of neutron star magnetospheres. We argue that the interaction of the
accretion disk with the magnetosphere can excite resonant shear Alfven waves in
a region of enhanced density gradients. We demonstrate that depending on the
distance of this enhanced density region from the star and the magnetic field
strength, the frequency of the field line resonance can range from several Hz
(weaker field, farther from star), to approximately kHz frequencies (stronger
field, ~ 2-10 star radii from the star). We show that such oscillations are
able to significantly modulate inflow of matter from the high density region
toward the star surface, and possibly produce the observed X-ray spectrum. In
addition, we show that the observed 2:3 frequency ratio of QPOs is a natural
result of our model.
