Scientists using the Chandra X-ray Observatory have discovered on Jupiter a particularly active region of x-ray emission near the planet's north magnetic pole. The identification of this hot spot, along with evidence that the x-rays radiate in pulses, appears to rule out a previous explanation for the source of the phenomenon. Reporting their findings in the current edition of the journal Nature, the researchers suggest that the pulsating x-rays could be the product of the interaction between solar winds and Jupiter's outer magnetic fields.

Prior to this finding, scientists thought that energetic ions originating from Jupiters moon Io produced the x-rays. In this scenario, Jupiter's inner magnetosphere accelerates oxygen and sulfur ions from Io, flinging some of them into the atmosphere. These heavy, energetic ions then collide with atmospheric hydrogen and helium ions, generating x-rays. According to team member Randy Gladstone of the Southwest Research Institute in San Antonio, Tex., the new data invalidates this theory. Specifically, that model fails to explain both the location of the hot spot at the higher latitude and the fact that the x-rays pulsate with periods of 45 minutes, rather than emanating steadily. Both of these factors imply that the heavy ions must be coming from much farther away than Io, Gladstone says. The researchers thus propose that the sun may instead be the source: solar winds could carry heavy ions to Jupiter and deposit them in the outer magnetosphere, they propose. Once trapped in this powerful magnetic field, the heavy ions oscillate between Jupiter's poles, producing the pulsating x-rays. Time will tell whether this theory holds water. But whatever the source of the newly identified hot spot x-rays, the team concludes, once pinpointed it should explain other emissions as well.