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Numerical Simulations (HD and MHD) of outflows from photoevaporating Hot Jupiters interacting with stellar winds

Anselmo J. G. Falorca

A significant fraction of extrasolar giant planets orbit their host stars at less than 0.1 AU, leading to significant atmospheric blow-off which strongly influences key aspects of planetary evolution. Also known as hydrodynamic (HD) evaporation, atmospheric blow-off is the planet’s mass evaporation due to strong extreme-ultraviolet radiation from the host star. However, many open questions remain, requiring improved physical modelling to explain observations.
The aim of this work is to understand the physical processes that impact the wind structure and outflow rates of a Hot Jupiter (HJ), such as temperature anisotropy at the wind’s base and planetary magnetic fields.
To achieve this goal, we used the astrophysical code PLUTO to perform HD and MHD simulations, building a 3D grid to incorporate a star and a HJ which resemble the HD 209458 system.
We start by performing HD simulations of planetary winds and explore them in a local grid, with and without the effects of a stellar host. Subsequently, we explore the stellar and planetary winds by including the effects of a magnetic dipole field in both the planet and the host star.
Results show that temperature anisotropy creates an inflow of material from the planet’s day side to the night, driven by the high ram pressure of the day side. Additionally, since the HJ is orbiting at high speeds, the presence of rotational effects such as Coriolis and centrifugal forces affect deeply the outflow, enhancing asymmetries in the system.
The MHD simulations are quite rich in several features, being qualitatively discussed in a time-dependent framework and supported by theoretical predictions using characteristic standoff distances. Since the flow is magnetically controlled, the dipolar magnetic field will have important geometric implications in the vicinity of the HJ.
Overall, this investigation contributes to a better understanding of the major physical processes that govern the interacting winds morphology and the quantitative and qualitative behavior of outflows.

2023 October 26, 13:30

Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia