Ohmic dissipation as a mechanism for hot Jupiter inflation?

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Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Sirius_Alpha on 21st February 2010, 10:31 pm

Inflating Hot Jupiters With Ohmic Dissipation
http://arxiv.org/abs/1002.3650

Abstract wrote:We present a new, magnetohydrodynamic mechanism for inflation of close-in giant extrasolar planets. The idea behind the mechanism is that current, which is induced through interaction of atmospheric winds and the planetary magnetic field, results in significant Ohmic dissipation of energy in the interior. We develop an analytical model for computation of interior Ohmic dissipation, with a simplified treatment of the atmosphere. We apply our model to HD209458b, Tres-4b and HD189733b. With conservative assumptions for wind speed and field strength, our model predicts a generated power that appears to be large enough to maintain the transit radii, opening an unexplored avenue towards solving a decade-old puzzle of extrasolar gas giant radius anomalies.

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Re: Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Lazarus on 8th May 2010, 2:55 pm

There's a talk about this mechanism up at the Kavli Institute website.
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Re: Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Sirius_Alpha on 9th May 2010, 4:47 am

Interesting, I think I understand the whole idea better now.

If this is dependent on zonal jets, could we expect hot Jupiters with efficient heat redistribution to be the planets that are more likely to be inflated?

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Re: Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Sirius_Alpha on 20th January 2011, 9:11 pm

Hot Jupiter Radius Anomalies Explained
http://arxiv.org/abs/1101.3800

We present calculations of thermal evolution of Hot Jupiters with various masses and effective temperatures under Ohmic dissipation. The resulting evolutionary sequences show a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of alkali metals in the atmosphere, compatible with the trend of the data. The degree of inflation shows that Ohmic dissipation, along with the likely variability in heavy element content can universally explain all of the currently detected radius anomalies. Furthermore, we find that in absence of a massive core, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores.

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Re: Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Lazarus on 31st January 2011, 2:45 pm

More on this from Greg Laughlin at the systemic blog. Seems to be looking good for this idea.
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Re: Ohmic dissipation as a mechanism for hot Jupiter inflation?

Post by Sirius_Alpha on 2nd February 2012, 12:06 am

Ohmic Heating Suspends, not Reverses, the Cooling Contraction of Hot Jupiters
http://arxiv.org/abs/1202.0026

We study the radius evolution of close-in extra-solar jupiters under Ohmic heating, a mechanism that was recently proposed to explain the large observed sizes of many of these planets. Planets are born with high entropy and they subsequently cool and contract. We focus on two cases: first, that ohmic heating commences when the planet is hot (high entropy); and second, that it commences after the planet has cooled. In the former case, we use analytical scalings and numerical experiments to confirm that Ohmic heating is capable of suspending the cooling as long as a few percent of the stellar irradiation is converted into Ohmic heating, and the planet has a surface wind that extends to pressures of ~10 bar or deeper. For these parameters, the radii at which cooling is stalled are consistent with (or larger than) the observed radii of most planets. The only two exceptions are WASP-17b and HAT-P-32b. In contrast to the high entropy case, we show that Ohmic heating cannot significantly re-inflate planets after they have already cooled. This leads us to suggest that the diversity of radii observed in hot jupiters may be partially explained by the different epochs at which they are migrated to their current locations.

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