Properties of Turbulent Alfvénic Fluctuations and Wave‐Particle Interaction Associated With Io's Footprint Tail

Abstract We investigate the small‐scale magnetic field fluctuations and their associated turbulent nature in the Io flux tube (IFT) connected to Io's footprint tail (IFPT). Our study is based on the recent magnetic field measurements by the Juno spacecraft during the PJ12 Juno flyby. Here, we are interested in understanding what type of turbulence is consistent with the fluctuations in the quasi‐dispersionless frequency range of 0.2–800 Hz as observed by Sulaiman et al. (2020), https://doi.org/10.1029/2020GL088432 . Knowledge of the turbulent fluctuations is important to constrain the acceleration mechanisms for ions and electrons in the IFT. In this work, we suggest that the observed temporal fluctuations in the spacecraft frame correspond to Doppler‐shifted spatial fluctuation structured perpendicular to the background magnetic field. This would imply an alternative reinterpretation of the spectral index of the observed magnetic power spectral density to be potentially the result of weak‐MHD and sub‐ion scale kinetic Alfvén wave turbulence in the low‐frequency regime. Our theoretical modelings show that turbulence can be driven both in the torus region and at high‐latitudes rendering results in agreement with the Juno measurements. Calculated turbulence heating rates are consistent with observed energy fluxes in the IFT and represent efficient drivers for particle acceleration. Moreover, a widening of the IFPT structure with respect to the IFT extent is consistent with propagating dispersive Alfvén waves modified by kinetic effects on their group velocities.