  The zodiacal emission, which is the thermal infrared (IR) emission from the
interplanetary dust (IPD) in our Solar System, has been studied for a long
time. Nevertheless, accurate modeling of the zodiacal emission has not been
successful to reproduce the all-sky spatial distribution of the zodiacal
emission, especially in the mid-IR where the zodiacal emission peaks. We
therefore aim to improve the IPD cloud model based on Kelsall et al. 1998,
using the AKARI 9 and 18 micron all-sky diffuse maps. By adopting a new fitting
method based on the total brightness, we have succeeded in reducing the
residual levels after subtraction of the zodiacal emission from the AKARI data
and thus in improving the modeling of the zodiacal emission. Comparing the
AKARI and the COBE data, we confirm that the changes from the previous model to
our new model are mostly due to model improvements, but not temporal variations
between the AKARI and the COBE epoch, except for the position of the
Earth-trailing blob. Our results suggest that the size of the smooth cloud, a
dominant component in the model, is by about 10% more compact than previously
thought, and that the dust sizes are not large enough to emit blackbody
radiation in the mid-IR. Furthermore we significantly detect an
isotropically-distributed IPD component, owing to accurate baseline measurement
with AKARI.
