Wednesday 20 Jun 2018[Seminar] The Dynamics of Tidally and Non-Tidally Locked Atmospheres

James Penn - University of Exeter

4th Floor Physics 14:00-15:00

Close-in exoplanets discovered by transit methods are most commonly assumed to be tidally-locked to their host star; to date, most models of exoplanet atmospheric dynamics have focussed on this case. However, there are reasons why a planet may not be tidally-locked: gravitational interactions with other planets and satellites, thermal tides, and as our detection methods improve, we will discover more planets that lie outside the region of inescapable locking.

We will present recent studies we have performed using two dynamical models:

(a) a simple shallow water,
(b) a hydrostatic three-dimensional model.

Both models are forced by a thermal structure approximating the conditions found on tidally and non-tidally locked planets. We identify the key atmospheric parameters that determine when the circulation may transition from one regime e.g. globally divergent flow, to another e.g. superrotating jets.

We present this work in the context of observing exoplanets by understanding the phase curve offset as a function of both orbital and rotation rate.

Finally we touch upon a possible application of the theory - given that we have relaxed the assumption of tidal-locking, can information about rotation rate of the exoplanet be inferred from it's phase curve offset?

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