In the ring current dynamics, various loss mechanisms contribute to
the ring current decay, including the loss to the upper atmosphere through
particle precipitation. This study implements the
field-line curvature (FLC) scattering mechanism in a kinetic ring
current model and investigates its role in precipitating ions into
the ionosphere. The newly included process is solved via a diffusion
equation in the model with associated pitch-angle dependent diffusion
coefficients. The simulation results indicate that (1) the FLC
scattering process exert mostly on energetic ions above 30 keV on the
nightside where the magnetospheric configuration is more
stretching. Such ion loss thereafter leads to a faster recovery of the
ring current. (2) The FLC-associated ion precipitation mainly occurs in
the outer region (L>5 for protons and L>4.5 for oxygen ions) on the
nightside, and the oxygen ion precipitation takes places in a wider
region than protons although its intensity is much lower. Comparisons
with POES observations suggest that more precipitation is needed in
the inner region, implying that other loss process is required
in the model. (3) We further found that the precipitating energy flux of
protons due to the FLC scattering can sometimes become comparable to the one from
the electrons on the nightside, although electrons usually dominate the
ionospheric energy deposit from the midnight eastward towards the
dayside. (4) Finally, the FLC scattering process seems to be capable of
explaining the formation of the isotropic boundary in the ionosphere.