The interaction between stellar winds and planetary magnetospheres has been a focus of research for decades. Within the heliospheric context, star-planet interactions similar to that between the Sun and the Earth reshapes the planet’s local magnetic environment leading to the formation of magnetospheres. Magnetic reconnection within these magnetospheres gives rise to helical magnetic flux ropes known as flux transfer events (FTEs). We developed a two-way coupled magnetosphere-ionosphere model to investigate the impact of FTEs on the planet’s ionosphere. For a specific case of an Earth like planet, the field aligned currents generated by these FTEs closely resemble observations of discrete dayside auroral arcs, suggesting FTEs to be a probable cause. In the context of exoplanetary systems, star-planet interactions vary depending on the planet's orbital location. For close-in orbits located in the sub-Alfvénic stellar wind, the Poynting flux generated by star-planet interactions can propagate toward the star, giving rise to stellar chromospheric hotspots. Our current work characterises and quantifies the efficiency of this energy transfer between the planet and the star, revealing that a significant portion of the energy never reaches the star and is reflected by the stellar transition region back toward the planet. The firm detection and characterisation of such magnetic interactions from observations of chromospheric hotspots would also lead to constraints on the amplitude of the magnetic field of exoplanets, to which we are blind so far. Future research, utilising the previously developed magnetosphere-ionosphere model, will also explore how the presence or absence of a planetary ionosphere influences the Poynting flux generated by the planet.
Local contact: Thierry FOGLIZZO
Organization: Frédéric GALLIANO
