Speaker
Description
Planets and comets offer unique laboratories for studying the complex interactions between space plasmas and the solar wind. Mercury, the only telluric planet besides Earth with an intrinsic magnetic field, provides a critical case study for examining a dynamic and compact airless magnetosphere. Comets provide invaluable insights into the interactions between the solar wind and outgassing objects, which are governed by mass loading processes.
Space missions such as BepiColombo for Mercury, and Rosetta and Comet Interceptor for comets, play a pivotal role in exploring these space plasma environments and providing essential observational constraints. The structure and dynamics of these environments, as well as their complex interactions with the solar wind, are governed by nonlinear, multi-scale processes spanning from electron kinetic to ion kinetic to fluid scales.
To model these interactions, we utilize the iPIC3D numerical code, which semi-implicit scheme makes a powerful tool for global kinetic simulations. Our simulations of the interaction between the solar wind and outgassing comets reveal the structure of cometary magnetospheres and their complex plasma dynamics. These dynamics lead to both collisionless electron heating, which boosts plasma generation in the induced magnetosphere, and collisional electron cooling enhanced by collisionless trapping, which controls plasma pressure in the inner coma. This explains the anomalous plasma generation observed by the Rosetta space mission.
For Mercury, our global kinetic simulations demonstrate how the magnetospheric engine accelerates and heats electrons to energies of a few keVs in the magnetotail through magnetic reconnection when the interplanetary magnetic field is southward. These high-energy electrons, traveling planetward, lead to strong particle precipitation on the nightside of Mercury, even down to the planet's surface, explaining the origin of X-ray emissions observed by the MESSENGER space mission. Additionally, our simulations show that energetic electrons are partially trapped in the planet's dipolar magnetic field, mainly on the nightside, forming a partial electron belt.
This overview underscores the critical role of iPIC3D in advancing our understanding of planetary and cometary magnetospheres. Our findings support the interpretation of past observations from MESSENGER and Rosetta and prepare the ground for future observations by BepiColombo and Comet Interceptor missions, ultimately enhancing our comprehension of space plasma interactions in the solar system.