Escaping particle fluxes in the atmospheres of close-in exoplanets. ii. reduced mass loss rates and anisotropic winds

Abstract

We constructed a multi-fluid two-dimensional hydrodynamic model with detailed radiative transfer to depict the escape of particles. We found that the tidal forces supply significant accelerations and result in anisotropic winds. An important effect of the tidal forces is that it severely depresses the outflow of particles near the polar regions. As a consequence, most particles escape the surface of the planet from the regions of low-latitude. Comparing the tidal and non-tidal locking cases, we found that their optical depths are very different so that the flows also emerge with a different pattern. In the case of the non-tidal locking, the radial velocities at the base of the wind are higher than the meridional velocities. However, in the case of tidal locking, the meridional velocities dominate the flow at the base of the wind, and they can transfer effectively mass and energy from the day sides to the night sides. Further, we also found that the differences of the winds show middle extent at large radii. It expresses that the structure of the wind at the base can be changed by the two-dimensional radiative transfer due to large optical depths, but the extent is reduced with an increase in radius. Because the escape is depressed in the polar regions, the mass loss rate predicted by the non-tidal locking model, in the order of magnitude of $10^{10}$ g s${}^{-1}$, is a factor of 2 lower than that predicted by one-dimensional hydrodynamic model. The results of tidal locking show that the mass loss rate is decreased a order of magnitude, only 4.3$\times$ $10^9$ g s${}^{-1}$, due to large optical depths on the night side. We also found that the distributions of hydrogen atoms show clear variations from the day side to night side, thus the origin of the excess absorption in Ly $\alpha$ should be reexamined by using multi-dimensional hydrodynamic models.

41 pages, 13figures,accepted by ApJ

References in corpus (6)

• Atmospheric Escape from Hot Jupiters
• Detection of Thermal Emission from an Extrasolar Planet
• Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b
• Strong Infrared Emission from the Extrasolar Planet HD189733b
• Energetic neutral atoms as the explanation for the high velocity hydrogen around HD 209458b
• Escaping Particle fluxes in the atmospheres of close-in exoplanets: I. model of hydrogen

Cited by in corpus (21)

• Lyman-$\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
• Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet
• 3D model of hydrogen atmospheric escape from HD209458b and HD189733b: radiative blow-out and stellar wind interactions
• Partially Ionized Plasmas in Astrophysics
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) III. Atmospheric structure of the misaligned ultra-hot Jupiter WASP-121b
• Atmosphere Expansion and Mass Loss of Close-Orbit Giant Exoplanets heated by Stellar XUV. II. Effects of Planetary Magnetic Field, Structuring of inner Magnetosphere
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Atmosphere expansion and mass loss of close-orbit giant exoplanets heated by stellar XUV: I. Modeling of hydrodynamic escape of upper atmospheric material
• Re-visit of HST FUV observations of hot-Jupiter system HD 209458: No Si III detection and the need for COS transit observations
• Modeling magnesium escape from HD209458b atmosphere
• The influence of the Extreme Ultraviolet spectral energy distribution on the structure and composition of the upper atmosphere of exoplanets
• High-resolution detection of neutral oxygen and non-LTE effects in the atmosphere of KELT-9b
• A hydrodynamic study of the escape of metal species and excited hydrogen from the atmosphere of the hot Jupiter WASP-121b
• Modeling the Ly$\alpha$ transit absorption of the hot Jupiter HD 189733b
• Modelling atmospheric escape and MgII near-ultraviolet absorption of the highly irradiated hot Jupiter WASP-12b
• Atmosphere escape inferred from modelling the H$\alpha$ transmission spectrum of WASP-121b
• Using the helium triplet as a tracer of the physics of giant planet outflows
• Orbital Evolution of Close-in Super-Earths Driven by Atmospheric Escape
• The escape of hydrogen-rich atmosphere of exoplanet: Mass loss rates and the absorptions of stellar Lyman $\alpha$
• Molecular formation along the atmospheric mass loss of HD 209458 b and similar Hot Jupiters
• Mass loss by atmospheric escape from extremely close-in planets