**DPS Pasadena Meeting 2000, 23-27 October 2000**

*Session 53. Solar System Origin Posters*

Displayed, 1:00pm, Monday - 1:00pm, Friday, Highlighted Tuesday and Thursday, 3:30-6:30pm, C101-C105, C211
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## [53.12] Gas Accretion Flows onto Giant Protoplanets: High-Resolution Two-Dimensional Local Simulation

*T. Tanigawa, S. Watanabe (Dept. of Earth and Planetary Sciences, Nagoya Univ.)*

We investigate the gas accretion flows onto the giant
protoplanets from protoplanetary disks in detail in order to
clarify the gas capturing process of the giant planets after
the onset of a gravitational instability of the
proto-atmosphere, using high-resolution two-dimensional
numerical simulations with local Cartesian coordinates. We
use ZEUS-2D code, which is a kind of finite-difference
time-marching methods, and obtain the steady gas-accretion
flows depending on normalized sound speed \tilde{c}
corresponding to the ratio of disk scale height to Hill
radius. Then we find that; (1) Accretion flow patterns:
There exist two types of steady shocks; a pair of bow shocks
around the planetary gravitational sphere and a pair of
spiral shocks in the sphere. And only gases in narrow bands
are able to flow into the planetary gravitational sphere.
The band location is about 2.5 Hill radius away from the
planetary orbit and the width is about 0.1 Hill radius. The
band width increases with decreasing \tilde{c} and the
band location approaches the planetary orbit with decreasing
\tilde{c}. (2) Gas accretion rates onto the giant
protoplanets: When the gas temperature is given by the
radiative equilibrium with central star and the ratio of
specific heats \gamma is chosen to unity (isothermal), we
get \dot{M} = 8.0 \times 10^{-3} M_{\rm E} (a/{\rm
5.2AU})^{-1.5} (M_{\rm p}/10M_{\rm E})^{1.3}
(f\Sigma_{0}/\Sigma_{\rm min}) {\rm yr}^{-1}, where f is
the depletion factor of the surface density at the flow-in
band caused by the formation of a gap, \Sigma_{0} is the
original surface density, which has no gap, and \Sigma_{\rm
min} is the surface density of minimum mass disk model. The
accretion rate decreases with increasing \gamma. (3)
Migration of giant planets: The circum-planetary
spiral-shock structures may strongly affect the torque about
a central star exerted on the planet by the gas.

The author(s) of this abstract have provided an email address
for comments about the abstract:
tanigawa@eps.nagoya-u.ac.jp

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