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Martin Uman of the University of Florida asked these questions
yesterday at the opening of the International Conference for
Atmospheric Electricity. While most of the scientists will share
what they have learned in their specific areas of study, Uman
instead decided to ask a few general questions about atmospheric
electricity. Uman hopes to motivate discussion among all the
conference scientists so they will work together to solve these
atmospheric mysteries. |
Increasing concentrations of nitric oxide and other chemicals in the Earth's atmosphere contribute to the ozone hole over Antarctica. Although most of this nitric oxide is produced by human activity, lightning also produces a small but significant amount. Still, estimates vary about exactly how much nitric oxide is produced by lightning. "The literature about NO production is confusing,"
said Uman. "Everyone cites different production levels,
so it's still an unsolved mystery." Also, scientists don't really know what sort of electrical discharges produce nitric oxide. Although it is well established that lightning produces some nitric oxide, other electrical discharges such as sprites could also be a source. |
According to current models, only the most powerful lightning strikes generate enough energy to produce sprites. Uman questioned whether these models are accurate representations of the energy needed to generate sprites. "The models don't agree with the all the measurements,
so there's a big debate over which is wrong," said Uman.
"Are the models wrong, or do we need to get better measurements?" "The transmission line model is a case of a model that works, but probably shouldn't," Uman said. |
The transmission line model for lightning shows a smooth upward curve of current. Lightning, however, is not a smooth and steady phenomena. "Lightning is a mess," said Uman. "The transmission line model is the oldest and simplest model about lightning, so it shouldn't work. Lightning is much more complicated than that." Lightning does not follow a simple path across the sky. For
instance, downward lightning can meet upward lighting
in the middle of a cloud. Despite the 'messiness' of lightning,
it somehow still obeys the simple current curve of the transmission
line model. |
Web Links |
Human
Voltage (June 18, 1999) Scientists discuss biology, safety,
and statistics of lightning strikes. News shorts from Atmospheric Electricity Conference (June 16, 1999) Poster papers on hurricanes and tornadoes summarized. Soaking in atmospheric electricity (June 15, 1999) 'Fair weather' measurements important to understanding thunderstorms. Lightning position in storm may circle strongest updrafts (June 11, 1999) New finding could help in predicting hail, tornadoes Lightning follows the Sun (June 10, 1999) Space imaging team discovers unexpected preferences Spirits of another sort (June 10, 1999) Thunderstorms generate elusive and mysterious sprites. Getting a solid view of lightning (June 9, 1999): New Mexico team develops system to depict lightning in three dimensions. Learning how to diagnose bad flying weather (June 8, 1999): Scientists discuss what they know about lightning's effects on spacecraft and aircraft. Three bolts from the blue (June 8, 1999): Fundamental questions about atmospheric electricity posed at conference this week. Lightning Leaders Converge in Alabama (May 24, 1999): Preview of the 11th International Conference on Atmospheric Electricity. What Comes Out of the Top of a Thunderstorm? (May 26, 1999): Gamma-rays (sometimes). Lightning research at NASA/Marshall and the Global Hydrology and Climate Center. |
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