Alfvénic Fluctuations Associated With Jupiter's Auroral Emissions

Abstract The Alfvén wave mode transmits field‐aligned currents and large‐scale turbulence throughout Jupiter's magnetosphere. Magnetometer data from the Juno spacecraft have provided the first observations of Alfvénic fluctuations along the polar magnetic flux tubes connected to Jupiter's main auroral oval and the Jovian satellites. Transverse magnetic field perturbations associated with Io are observed up to ~90° away from main Io footprint, supporting the presence of extended Alfvénic wave activity throughout the Io footprint tail. Additional broadband fluctuations measured equatorward of the statistical auroral oval are composed of incompressible magnetic turbulence that maps to Jupiter's equatorial plasma sheet at radial distances within ~20 R J. These fluctuations exhibit a k || power spectrum consistent with strong magnetohydrodynamic turbulence. This turbulence can generate up to ~100 mW/m 2 of Poynting flux to power the Jovian aurora in regions connected to the inner magnetosphere's central plasma sheet.