Equatorward diffuse auroral emissions at Jupiter: Simultaneous HST and Galileo observations

We study the auroral emissions equatorward of the main oval based on Hubble Space Telescope (HST) observations of both Jovian hemispheres on September 20, 1997. On the same day, Galileo observed changes in the electron pitch angle distribution between the inner and middle magnetosphere (PAD boundary), indicative of electron diffusion. This region, magnetically maps to the equatorward diffuse emissions on both hemispheres. Whistler mode waves, observed simultaneously, can scatter electrons into the loss cone and lead to electron precipitation in the ionosphere. Based on simultaneous HST FUV and Galileo wave and electron data we test the conditions for electron scattering by whistler mode waves and derive the energy flux precipitated in the ionosphere. The comparison of the derived precipitation energy flux with the observed auroral brightness indicates that the energy contained in the PAD boundary can account for the auroral emissions. Citation: Radioti, A., A. T. Tomas, D. Grodent, J.-C. Gerard, J. Gustin, B. Bonfond, N. Krupp, J. Woch, and J. D. Menietti (2009), Equatorward diffuse auroral emissions at Jupiter: Simultaneous HST and Galileo observations, Geophys. Res. Lett., 36, L07101, doi:10.1029/2009GL037857.