| Vol. 27, Issue 6 |
Jupiter has a large magnetosphere that can be divided into the inner, middle, and outer regions. Up to now, there has been evidence for ultra low frequency (ULF) waves in the middle magnetosphere only on the dayside. But Wilson and Doherty [835] report that the spacecraft Galileo, the first probe to spend long periods in the nightside regions of Jupiter, shows that the ULF waves are present also in the nightside magnetosphere, thereby suggesting that the waves are a global phenomenon within the Jovian middle magnetosphere. To identify the waves of 10–20 minute periods, the authors apply Fourier Analysis to sections of data that are of 120-minute duration. Sprites, a form of lightning discharge, develop at high altitudes and usually last no more than a few milliseconds. On account of their low surface brightness, sprites have been imaged only at night. Now Stanley et al. [871] report the first detection of daytime sprites by using the sprites' extremely low frequency signature. With the help of a sferic system located on a mountain ridge in New Mexico, the authors describe three daytime sprite events that occurred in August 1998. They find that the sprites contain the kind of unusually large charge moment changes that suggest that daytime sprites are considerably more energetic than their nighttime counterparts. |
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