1. His geomagnetic surveys showed that auroral activity was nearly uninterrupted. 2. Auroral activity is insignificant as compared to Jupiter and Saturn. 3. One surprise, Spann said, is how auroral activity at night is sometimes mysteriously echoed on the day side. 4. At this time of year the aurora borealis can occasionally be seen on the northern horizon during moderate auroral activity. 5. The auroral activity on Uranus is not as powerful as at Jupiter and Saturn and contributes little to the ionization. 6. Did the comet impacts trigger an unusual wave of auroral activity on Jupiter-- like the " Northern Lights " on Earth? 7. An auroral electrojet index ( measured in nanotesla ) is regularly derived from ground data and serves as a general measure of auroral activity. 8. It is also notable for the fact that it is the first time where the phenomena of auroral activity and electricity were unambiguously linked. 9. The heat sources necessary to sustain such high temperatures are not understood, since neither solar EUV radiation nor auroral activity can provide the necessary energy. 10. The phenomenon is essentially an anti-aurora, similar to a photographic negative, and is visible only when it is embedded in a region of faint auroral activity, Marklund said.