Evolution of the Auroral Signatures of Jupiter's Magnetospheric Injections

Auroral emissions equatorward of the main emission at Jupiter are suggested to reflect the dynamics of the plasma in the middle magnetosphere. Here we examine the motion of the auroral signatures of magnetospheric injections appearing in Hubble Space Telescope (HST) images. Our results suggest that the injected plasma moves planetward and lags behind corotation. We then compare the characteristics of the observed signatures with simulations of the auroral precipitation related to injections due to pitch angle scattering. These results indicate that the lifetime of the auroral structures lies between a half and a full rotation of Jupiter. Ultraviolet spectrally resolved images acquired with HST are then used to highlight the energy-dependent drift of the electrons in auroral injection signatures. Comparison of these observations with simulations of the energy-dependent drift of injected particles suggests that these structures are similar to 3-hr old. Finally, we extend our investigations toward larger and less structured outer emissions possibly associated with younger plasma injections. The motion and evolution of these features are similar to those of the small and compact ones considered in the first part of the study.