XMM-Newton Observations of X-Ray Emission from Jupiter

XMM-Newton observations of Jupiter show prominent soft X-ray emission from the auroral spots and, albeit at a lower intensity, from the equatorial regions. While the spectra of the auroral X-rays can be modeled with a superposition of unresolved emission lines, including most prominently those of highly ionized oxygen, Jupiter's equatorial ‘disk’ emission has a spectrum consistent with that of solar X-rays scattered in the planet's upper atmosphere. Remarkably, a large solar X-ray flare, which took place on the Sun's Jupiter-facing side in November 2003, is found to be associated with a corresponding feature in the Jovian disk X-ray lightcurve. This suggests that the non-auroral X-ray emission from Jupiter is directly controlled by the Sun. However, the XMM-Newton results support the view that Jupiter's auroral emissions originate from the capture and acceleration of heavy ions, followed by X-ray production by charge exchange. They presently favor a solar wind scenario, although a magnetospheric origin for some of the ions cannot be excluded.