A magnetic field evolution scenario for brown dwarfs and giant planets

Details A magnetic field evolution scenario for brown dwarfs and giant planets A magnetic field evolution scenario for brown dwarfs and giant planets

2010-07-09

arxiv.org/abs/1007.1514v1

Astronomy and Astrophysics

Astrophysics

Earth and Planetary Astrophysics

7 pages, accepted by A&A

Scientific paper

Very little is known about magnetic fields of extrasolar planets and brown dwarfs. We use the energy flux scaling law presented by Christensen et al. (2009) to calculate the evolution of average magnetic fields in extrasolar planets and brown dwarfs under the assumption of fast rotation, which is probably the case for most of them. We find that massive brown dwarfs of about 70 M_Jup can have fields of a few kilo-Gauss during the first few hundred Million years. These fields can grow by a factor of two before they weaken after deuterium burning has stopped. Brown dwarfs with weak deuterium burning and extrasolar giant planets start with magnetic fields between ~100G and ~1kG at the age of a few Myr, depending on their mass. Their magnetic field weakens steadily until after 10Gyr it has shrunk by about a factor of 10. We use observed X-ray luminosities to estimate the age of the known extrasolar giant planets that are more massive than 0.3M_Jup and closer than 20pc. Taking into account the age estimate, and assuming sun-like wind-properties and radio emission processes similar to those at Jupiter, we calculate their radio flux and its frequency. The highest radio flux we predict comes out as 700mJy at a frequency around 150MHz for $\tau$Boob, but the flux is below 60mJy for the rest. Most planets are expected to emit radiation between a few Mhz and up to 100MHz, well above the ionospheric cutoff frequency.

Affiliated with

Also associated with

No associations

Rating

A magnetic field evolution scenario for brown dwarfs and giant planets does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A magnetic field evolution scenario for brown dwarfs and giant planets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A magnetic field evolution scenario for brown dwarfs and giant planets will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-644713