New upper limits on Jovian X rays

The paper presents results of a comprehensive search for X-ray emission from the Jovian magnetosphere, using data obtained with an X-ray telescope aboard OSO 3. This satellite scanned Jupiter for 33 days from a distance of 4.4 AU during a maximum phase of solar activity. No transient X-ray fluxes were observed to accompany decameter-wave radio bursts, but upper limits on the steady X-ray emission over the energy range from 7.7 to 210 keV are estimated. These limits are shown to be consistent with the fluxes measured by Pioneer 10 as well as with the trapped-particle fluxes predicted by recent precise modeling of the Jovian trapped radiation. Upper limits are determined for the energy dissipated on Jupiter in bremsstrahlung-producing collisions and also for the electron loss rate. The energy limit is found to be approximately equal to the total solar radiant energy intercepted by the Jovian disk. It is concluded that Jovian X-rays are unlikely to be detected by near-earth observations with sensitivities currently conceivable.