On Possible Types of Magnetospheres of Hot Jupiters

Abstract

As a rule, the orbits of “hot Jupiter” exoplanets are located close to the Alfven point of the stellar wind of the host star. Many hot Jupiters could be in the sub-Alfven zone, where the magnetic pressure of the stellar wind exceeds the dynamical pressure. Therefore, the magnetic field in the wind should play an extremely important role in the process of stellar wind flowing around the atmosphere of a hot Jupiter. This must be taken into account when constructing theoretical models and interpreting observational data. Analyses show that many typical hot Jupiters should have shockless induced magnetospheres, which have no analogs in the solar system. Such magnetospheres are characterized first and foremost by the fact that there is no bow shock, and the magnetic barrier (ionopause) is formed by induced currents in upper layers of the ionosphere. This conclusion is confirmed here using three-dimensional numerical simulations of the flow of the stellar wind from the host star around the hot Jupiter HD 209458b, taking into account both the intrinsic magnetic field of the planet and the magnetic field in the wind.