Lightning is more powerful than we thought

Florida, for some reason, has more lightning strikes then any other US state. When lightning strikes sand, it creates rock formations that Matthew Pasek, Associate Professor of Geosciences, University of South Florida has used to measure the energy in  lightning bolts. One discovery from examining these fulgurites was that there are mega bolts. A big lightning strike might be 20 times as large as the average one. Professor Pasek writes:

 … how close does Hollywood come, with estimates like in Back to the Future of 1.21 gigawatts of power in lightning?
Power is energy per time, and our measurements of fulgurites suggest that megajoules of energy make rock in thousandths to millionths of seconds. So a gigawatt is actually on the low side – lightning power may be a thousand times that, reaching into the terawatts, though the average is probably tens of gigawatts.

That’s enough energy to power about a billion houses, albeit only for a few millionths of a second. Unfortunately, given its sporadic and unpredictable nature, no power grid will ever be able to harness lightning effectively.

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If you’ve been following this site for a while, you may recall that lightning is thought by some to be generated by cosmic rays which trigger a cascade of events. Other research casts doubt on this theory:

Over the past few decades, researchers have gained a better understanding of how the charges become separated in thunderclouds. Data and simulations show that charge separation occurs when small hail-like particles called “graupel” and ice crystals collide with one another in a cloud. The charges are separated as the heavier graupel particles fall, while the lighter ice crystals are carried upward by updrafts in the turbulent thundercloud. This process is somewhat like how rubbing your feet on carpet separates charges in your body, causing you to produce static electricity when you touch a metal doorknob.

Since the 1990s, one of the leading proposals for lightning formation is that the initial spark comes from relativistic electrons that come from either high-energy cosmic rays or a process called relativistic runaway electron avalanche. However…

“If relativistic electron showers were the initiating events for lightning flashes, then the motion of the breakdown would be initially upward for intracloud flashes between the mid-level negative and upper positive charges,” Rison explained. “Using a recently developed broadband interferometer to observe the propagation of electrical breakdown in lightning, we found that the propagation direction of narrow bipolar events is downward rather than upward, showing they are caused by downward-developing positive rather than upward-developing negative breakdown.”

Both negative breakdown and positive breakdown can move charges, which can intensify the fields at both ends of the cloud. But the data here shows that all flashes for which the interferometer could determine the motion exhibited an initial breakdown that was fast and positive.

The next step is to investigate how fast positive breakdown develops physically. Fast positive streamers have been observed in sprites, a type of electrical breakdown that occurs in the upper atmosphere where the pressure is several orders of magnitude lower than in thunderclouds. The discharge observed here move at the same fast propagation speeds but at lower altitudes and higher pressures.

Could it be that mega bolts and regular bolts are the result of different process, that both methods of lightning creation are in play? 

Why is Florida, the Himalayas and central Africa so popular with lightning?

Dec. 5, 2001: Lightning. It avoids the ocean, but likes Florida. It’s attracted to the Himalayas and even more so to central Africa. And lightning almost never strikes the north or south poles. These are just a few of the things NASA scientists have learned using satellites to monitor worldwide lightning.

“For the first time, we’ve been able to map the global distribution of lightning, noting its variation as a function of latitude, longitude and time of year,” says Hugh Christian, project leader for the National Space Science and Technology Center’s (NSSTC’s) lightning team at NASA’s Marshall Space Flight Center.

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If you find theories about why this is, post the link in a comment. 

Stay tuned as science learns more. 

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