The Tidal and Magnetic influence of Hot Jupiters
Evgenya Shkolnik (DTM)
The interacting processes taking place
between a giant planet orbiting its star within 10 stellar radii (also
known as a "hot Jupiter") have been getting increasing attention both
observationally and theoretically. Our work has shown that such a
short-period planet can induce activity on the upper atmosphere of its
host star through both tidal and magnetic star-planet interactions
(SPI).
Evidence
for magnetic SPI includes a diverse array of photometric, spectroscopic
and spectropolarimetric studies. Because of the small separation (<
0.1 AU), many of the hot Jupiters lie within the Alfven radius of their
host stars, allowing direct magnetic interaction with the stellar
surface. Models show both the stellar and planetary magnetic fields are
strongly affected, possibly influencing the magnetic activity of both
bodies, as well as modifying irradiation and non-thermal and dynamical
processes.
In
addition, a hot Jupiter’s tidal influence on its star may increase the
stellar rotation rate and thus also increase the global stellar
activity level. Our recent work has shown that stars with hot Jupiters
have twice the UV emission than stars with planets in wider orbits,
which is also anti-correlated with the stellar synchronization time
scales. Even though the stars with hot Jupiters are not fully
synchronized (full synchronization in most cases will take longer than
the age of the Universe), they have already undergone some increase in
rotation rate, provided that the planets migrated early on in the
system's history.
Studying
both tidal and magnetic star-planet interactions aids our understanding
of the formation, migration and evolution of hot Jupiters, and provides
the best-available probe of exoplanetary magnetic fields.