Theory for planetary exospheres: III. Radiation pressure effect on the Circular Restricted Three Body Problem and its implication on planetary atmospheres

TL;DR

This paper extends the Circular Restricted Three Body Problem to include stellar radiation pressure effects, analyzing their impact on planetary exospheres and escape mechanisms, especially for Hot Jupiters like HD 209458b.

Contribution

It provides an analytical framework for incorporating radiation pressure into the CR3BP and explores its effects on exosphere stability and escape, generalizing previous models.

Findings

Radiation pressure alters equipotential surfaces and Lagrange points.

The Hill sphere radius is modified by radiation effects.

HD 209458b exhibits a radiation-induced blow-off escape regime.

Abstract

The planetary exospheres are poorly known in their outer parts, since the neutral densities are low compared with the instruments detection capabilities. The exospheric models are thus often the main source of information at such high altitudes. We present a new way to take into account analytically the additional effect of the stellar radiation pressure on planetary exospheres. In a series of papers, we present with an Hamiltonian approach the effect of the radiation pressure on dynamical trajectories, density profiles and escaping thermal flux. Our work is a generalization of the study by Bishop and Chamberlain (1989). In this third paper, we investigate the effect of the stellar radiation pressure on the Circular Restricted Three Body Problem (CR3BP), called also the photogravitational CR3BP, and its implication on the escape and the stability of planetary exospheres, especially for Hot Jupiters. In particular, we describe the transformation of the equipotentials and the location of the Lagrange points, and we provide a modified equation for the Hill sphere radius that includes the influence of the radiation pressure. Finally, an application to the hot Jupiter HD 209458b reveals the existence of a blow-off escape regime induced by the stellar radiation pressure.