EQUATORIAL X-RAY EMISSIONS - IMPLICATIONS FOR JUPITER HIGH EXOSPHERICTEMPERATURES

Observations with the High Resolution Imager on the Rontgensatellit re veal x-ray emissions from Jupiter's equatorial latitudes. The observed emissions probably result from the precipitation of energetic (>300 k iloelectron volts per atomic mass unit) sulfur and oxygen ions out of Jupiter's inner radiation belt, Model calculations of the energy depos ition by such heavy ion precipitation and of the resulting atmospheric heating rates indicate that this energy source can contribute to the high exospheric temperatures (>800 kelvin at 0.01 microbar) measured b y the Galileo probe's Atmospheric Structure Instrument. Low-latitude e nergetic particle precipitation must therefore be considered, in addit ion to other proposed mechanisms such as gravity waves and soft electr on precipitation, as an important source of heat for Jupiter's thermos phere.