Revealing the Local Time Structure of the Alfvén Radius in Jupiter's Magnetosphere Through High-Resolution Simulations

Abstract

In the context of planetary magnetospheres, the Alfvén radius plays a critical role as the demarcation line where the planet's magnetosphere and ionosphere effectively decouple. This boundary is pivotal in understanding the complex interactions between planetary magnetic fields and space plasma environments. This study presents a dynamic analysis of the Alfvén radius within Jupiter's magnetosphere using high-resolution simulations to capture its temporal variability. Our simulations reveal that the Alfvén radius presents a dynamic behavior, which is strongly modulated by planetary rotation. However, when averaged over one Jovian rotation period, the location of the Alfvén radius displays striking similarities to that described by the statistical models proposed by Jenkins et al. (2024, 10.17635/lancaster/researchdata/661). Specifically, our averaged results highlight a prominent outward bulge in the radius location toward ∼03 local time with a notable absence of the radius between the noon and dusk sectors. The absence of the Alfvén radius suggests the higher Alfvén velocities in the noon-to-dusk sector associated with strong magnetic fields. These results suggest that while short-term dynamics are present, the average position of the Alfvén radius over a rotation period roughly remains consistent with previous steady-state models, providing an enhanced understanding of the long-term behavior exhibited by the magnetospheric plasma environment in Jupiter's magnetosphere. Importantly, the dynamic location of the Alfvén radius and the observed asymmetry after averaging over one rotation period could demonstrate a significant correlation with the complex evolution of the auroral enhancement.