The Lyman-alpha bulge of Jupiter and the auroral-equatorial regions coupling

The Lyman-α bulge of Jupiter is a strong and enigmatic asymmetry in the Jovian H Ly-α emission simultaneously discovered by a sounding rocket and Voyager 1 during its encounter with the planet. Almost two decades of observations with IUE and recent observations made by Galileo have shown that this is a long-lived stable feature of the Jovian airglow, characterized by a significant enhancement of the Ly-α emission centered on the magnetic drift equator, and fixed in magnetic longitude (system III). By contrast, no corresponding asymmetry in the Jovian H₂ Lyman and Werner band emissions has been observed. We review the key observations that helped to better characterize this phenomenon and provide suggestions for the optimal use of future UV instruments (IUE archive, Galileo, STIS, FUSE) in order to improve our knowledge of the physics beyond.