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Murray-Clay paper

Authors seek to numerically determine validity of hypothesis that hot Jupiters could be evaporated down to their rocky cores over the planetary lifetime. They use a one-dimensional model that includes heating/cooling terms, tidal gravity, and the effects of ionization on the mass-loss rate, and focus on the substellar point, at which tidal gravity and UV flux are greatest, thereby putting an upper limit on the possible mass-loss rate of the planet (by extending the one-dimensional result over the surface of the planet). They assume a planet of 1.4 R_J and 0.7 M_J and ignore the Coriolis force, under the assumption that the Lyman-alpha radiation from excited H is the only significant cooling term. Numerically, they use a relaxation solver, and find solutions iteratively by removing simplifying conditions one at a time.

They find that, for main-sequence stars, about 20% of H is still neutral at the sonic point, and place an upper bound of ~3.3*10¹⁰ g/s on the mass loss rate. For hotter (T Tauri) stars, they find an upper bound of ~6.4*10¹² g/s. At low flux, the mass loss is energy-limited, while for higher flux, the mass loss is radiation/recombination-limited. The assumption of a hydrodynamic wind is shown to be self-consistent, and they estimate that, due to the directionality of the tidal gravity and the UV irradiation, the maximum rate is an overestimate by ~4x. By reducing the wind speed to subsonic values and including a stellar wind, the day-side wind may be reduced or completely suppressed - they hypothesize that this may lead to night-side outflows, due to circulation of hot gases from the day-side.

They compare observations to estimates from their model, and note that the disagreement in Lyman-alpha lines could be due to a variety of factors, including some missing physics or a cause unrelated to absorption by the planetary wind. A promising candidate is cited as acceleration of neutral hydrogen due to charge exchange. They note that modelled spectrally-unresolved measurements appear to be in agreement with observation.

Stone-Proga paper

Paper is a comparison of 2D simulations (of close-in hot Jupiters) to spherically symmetric simulations run by others. They characterize escape from the planet with the hydrodynamic escape parameter (lambda), ratio of gravitational potential to thermal potential - a small lambda suggests a thermal wind. They use no magnetism (hydrodynamic rather than MHD), and ignore heating and small-scale effects at the base of the wind. The wind is made self-consistent by fixing the density and energy at the base.

In models with no stellar wind and an isothermal outflow, they find that the sonic surface of the wind is closer to the planet, with a slower radial velocity on the night side of the planet, and a very evident shock in the |v|/v_s plot at various angles. For larger values of gamma, this shock produces a delta T, and the sonic surface is farther from the planet (but still nearer than in the spherically symmetric models). Introducing a stellar wind creates a back-swept profile, but has little effect on the sonic surfaces or mass-loss rate.

Experimenting with AstroBEAR

Ran OutflowWind simulations with varying parameters. Thickness and wind velocity don't appear to have any effect - perhaps an effect of rescaling? Velocity speeds up the simulation as a whole. The rest are as follows:

Reference (default parameters, 100 frames, 2 units computational time (conversion?)):

Radius increases size of wind, but otherwise has little effect, at least at small values (expected).

Radius of 2:

Increasing density appears to decrease relative density at the center of the front of the outflow (slightly counter-intuitive, but makes sense).

Density of 5: Density of 10: Density of 20:

Increasing temp. creates a more diffuse cloud at the end (predictably). Temp = 0 appears to cause buggy behavior.

Temp = 0: Temp = 1: Temp = 5:

Also tried a run at 1000 frames, but definitely overkill for time.