 The regions within the main ovals emits most of auroral X-rays.The spectrum of the auroral X-ray radiation consists of spectral lines of highly ionized oxygen and sulfur, which probably appear when energetic (hundreds of kiloelectronvolts) S and O ions precipitate into the polar atmosphere of Jupiter.The source of this precipitation remains unknown but this is inconsistent with the theory that these magnetic field lines are open and connect to the solar wind.