Spectral morphology of the X‐ray emission from Jupiter's aurorae

Abstract

Simultaneous Chandra X‐ray and Hubble Space Telescope FUV observations of Jupiter's aurorae carried out in February 2003 have been re‐examined to investigate the spatial morphology of the X‐ray events in different energy bands. The data clearly show that in the Northern auroral region (in the main auroral oval and the polar cap) events with energy > 2 keV are located at the periphery of those with energy < 2 keV and coincide with FUV bright features. In addition, X‐ray spectra extracted from the areas where the two event distributions are concentrated possess different shapes. We associate the > 2 keV events (∼45 MW emitted power) with the electron bremsstrahlung component recently revealed by XMM‐Newton in the spectra of Jupiter's aurorae, and the < 2 keV emission (∼230 MW) with the product of ion charge exchange, now established as the likely mechanism responsible for the soft X‐ray Jovian aurora. We suggest that the same population of energetic electrons may be responsible for both, the X‐ray bremsstrahlung and the FUV emission of Jupiter's aurorae. Comparison of the > 2 keV X‐ray and FUV (340 GW) powers measured during the observations shows that they are broadly consistent with the predicted emissions from a population of energetic electrons precipitating in the planet's atmosphere, thus supporting our interpretation.