Nonlinear wave-particle interactions contribute to the acceleration and
precipitation of electrons in the outer radiation belt. Recent
simulations and spacecraft observations suggest that oblique
whistler-mode chorus can cause loss cone overfilling through nonlinear
Landau resonance and thus break the strong diffusion limit of
quasilinear theories. Here we show with test-particle simulations that a
single element of parallel-propagating chorus can also break the
diffusion limit through nonlinear cyclotron resonance, as long as its
amplitude remains high. This is due to the strong scattering at low
pitch angles caused by individual chorus subpackets. We further
demonstrate that the subpacket modulations create a discernible pattern
in the precipitating electron fluxes, with peaks correlated with the
largest subpackets. Such flux patterns may be connected to weak
micropulsations within diffuse auroras.