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Title: Planet-Disk Interaction / Migration
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Authors:
Wilhelm Kley
& Geoffrey Bryden
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Abstract:
After its
formation a planetary embryo of a few earth masses is still
surrounded by the protoplanetary
disk material. Gravitational
interaction of
such an embedded protoplanet with the disk matter will
lead to a
change of the orbital elements of the planet, most notably
its semi-major
axis (the change of which is referred to as migration)
and
eccentricity. In this contribution we review the main
aspects of
this process and
discuss modern developments and remaining problems.
Depending on the
mass of the planet and on the properties of the disk
it is possible
to classify into different types of migration. In the
first
case, for low planetary masses, the interaction is linear
and
can be
treated by semi-analytical methods. This leads
to a simple
estimate
for the migration rate, so called Type I migration, studied
long before
the discovery of the first extra-solar planet.
In the
second case, for large planetary masses, the interaction is
non-linear, the
planet wake becomes a shock in the vicinity of
the
planet location
and opens an annular gap at the planet orbit. In this
regime numerical
methods are used to analyse the torques acting on the
planet, yielding
the so called Type II migration. A possible new type
of migration
(Type III) has been found for planets partially depleting
their
co-orbital region in massive disks. In this
case a positive
feedback between the planet
migration rate and the so-called
corotation
torque (the latter increasing with the former) may lead to
runaway
migration. We present an analysis
of these 3 Types of
migration.
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