Influence of photoelectrons on the structure and dynamics of the upper atmosphere of a hot Jupiter

Abstract

A self-consistent, aeronomic model of the upper atmosphere of a "hot Jupiter" including reactions involving suprathermal photoelectrons is presented. This model is used to compute the height profiles of the gas density, velocity, and temperature in the atmosphere of the exoplanet HD 209458b. It is shown that including suprathermal electrons when computing the heating and cooling functions reduces the mass loss rate of the atmosphere by a factor of five.

Atmospheric Mass Loss from Hot Jupiters Irradiated by Stellar Superflares

“…Our model provides a slightly lower thermosphric temperature comparing with the previous aeronomic models (Yelle 2004;Koskinen et al 2013). Details of such comparison can be found in (Ionov et al, 2017). Once the flare reaches the planet, the temperature maximum increases to 9000 K and the position of the peak slightly shifts to a higher altitude relative to the initial position.…”

“…We model the planetary atmosphere employing the code of Ionov et al (2017Ionov et al ( , 2018. This is a self-consistent 1D code taking into account both atmospheric heating caused by atmospheric absorption of stellar XUV radiation and the contribution of reactions involving suprathermal photoelectrons.…”

Atmospheric Escape and the Evolution of Close-In Exoplanets

“…The key results of these works are that atmospheric escape for giant planets is unlikely to have an evolutionary impact, while it will be significant for close-in low-mass planets with Hydrogen-rich atmospheres. Recently, this style of calculations has been improved where the adopted constant local heating efficiencies are determined from Monte-Carlo calculations of the deposition of a photoelectron's energy (Shematovich et al 2014;Ionov & Shematovich 2015;Ionov et al 2017Ionov et al , 2018, indicating the heating efficiency never exceeds ∼ 20%.…”

The Influence of a Stellar Flare on the Dynamical State of the Atmosphere of the Exoplanet HD 209458b

“…Depending on the upper atmosphere composition and heating efficiency, the atmospheric escape regime can vary from hydrostatic to hydrodynamic. In order to study this problem, a onedimensional self-consistent model of the hot Jupiter was developed [9]. It includes three main modules: a Monte Carlo module, a module of chemical kinetics and a gas-dynamic.…”

“…The gravitational potential was set equal to the three-dimensional Roche potential along the line connecting the planetary and the stellar centers. This aeronomic model made it possible to study the dynamic state of HD 209458b's atmosphere and to estimate the effect of reactions with suprathermal photoelectrons on the atmospheric dynamics, chemical composition, and outflow rate [9]. In the present study, this model is used to calculate the dynamic response of the planetary atmosphere to the impact of the host star's flare.…”