Combined Full Wave and Test Particle Simulations of the Io Footprint in the Jovian Aurora

Abstract

It is known that the perturbation of the co-rotating plasma of Jupiter by Io propagates as Alfvén waves along the magnetic field lines. These waves accelerate electrons, which leads to precipitation and the formation of an auroral footprint on the ionosphere. The Io footprint (IFP) has been observed in Infrared and ultraviolet emissions and known to have a complex morphology. Recently, Lysak et al. (2023, https://doi.org/10.1029/2022ja031180) modeled the propagation of the Alfvén waves in the Io-Jupiter system. This work will present test particle simulations based on these numerical models. By calculating the precipitating electron fluxes integrated with energy and solid angle in the ionosphere, and using it as a proxy for auroral emissions, we successfully reproduced many intricate features of the IFP. In particular, we replicate the main spot, leading spot, sub-dots, asymmetry between northern and southern ionosphere, and asymmetrically bifurcated tail. However, our simulations did not reproduce the stationarity of the sub-dots in the co-rotating frame, as observed by Moirano et al. (2021, https://doi.org/10.1029/2021ja029450). Additionally, we calculated the precipitating electron flux as functions of energy and pitch angle on the main spot, which could serve as input for models that calculate emissions from precipitating electron flux.