Energy distributions of precipitating electrons in Jupiter's auroral regions from combined Juno/JADE and Juno/JEDI measurements

Jupiter's auroras are produced by magnetospheric electrons precipitating into its atmosphere. The Juno/JADE and Juno/JEDI instruments together measure these electrons over the energy range 100, However, their spectra in Jupiter's auroral regions cannot be accurately reproduced by the widely used kappa distribution, hereafter referred to as the classical single-kappa distribution. We aim to statistically characterize the energy flux distributions of precipitating electrons in Jupiter's auroral regions and to derive a new phenomenological energy distribution, referred to as the 4-kappa distribution, better suited to reproduce the combined JADE+JEDI data. We builT mean electron energy flux distributions in six auroral subregions (the polar, the main, and the outer emission regions, for both hemispheres), combining JADE and JEDI data from PJ3 to PJ35. These data were mapped to the Jovian SIII reference frame using the JRM33 magnetic field model, which accounts for the contribution of the current sheet. We fitted these distributions using MCMC in logarithmic space, testing both the classical single-kappa distribution and the 4-kappa distribution. The mean distributions show an overall monotonic power-law decay, with an energy cutoff visible beyond ∼ 500, in most subregions, although a fraction of the individual spectra depart from this behavior at intermediate energies. Mean energies range from ∼ 21 to ∼ 119, , and total energy fluxes range from ∼ 9.5 to ∼ 28.7, ^2 depending on the subregion. Fitting with the classical single-kappa distribution fails in all subregions, with ąppa parameter systematically converging to the lower bound of the assumed prior range in the MCMC fit. We therefore introduced the 4-kappa distribution, defined as a linear combination of four classical single-kappa distributions modulated by an exponential high-energy cutoff. This distribution accurately fits the spectra in all six auroral subregions. At equal total energy flux and mean energy, electron transport simulations show that the 4-kappa distribution deposits its energy at lower altitude than the classical single-kappa distribution, and distributes it differently along the vertical, with direct implications for the UV color ratio, for the atmospheric chemical composition and thermal structure, and for ionospheric conductances. keV keV mW/m The 4-kappa distribution provides a physically motivated analytical framework for future realistic modeling of electron precipitation and UV auroral emissions at Jupiter.