How do we measure lightning?

Salutations,

The article I read on Monday was written by Matthew Pasek, an Associate Professor of Geosciences at the University of South Florida. I found it particularly interesting because it was such an unusual article but it did not fail to teach me a great deal about lightning.

Pasek describes just how difficult it is to measure how much energy there is in a bolt of lightning, and until now I had not considered that at all. He demonstrates how one usually records the power of a lightning strike by measuring the length of a strike and multiplying it by the energy per length required to heat the air up, which I am sure it related to specific heat capacity. Another method of measuring the energy of a strike is the voltage one contains. This method is very clever because it uses the inductive effect to calculate how much voltage has been induced on nearby powerlines. Using Ohm’s law, one can then multiply this number by the number of electrons that move during a strike to calculate the energy.  However, the percentage error of these methods is enormous and so they are not very accurate methods.

Consequently, Pasek has developed another, more accurate way of finding how much energy a strike of lightning contains. In Florida, lightning is very common and when it hits sand (of which there is a lot), a new rock type, named a fulgurite, is formed. This weird rock formation is actually a hollow glass tube which travels through the sand. And yes, this is a type of rock, metamorphic rock to be precise, because the sand was changed by heat and pressure to a new type of rock.

He details how his team collected many of these fulgurites which ranged in size from ‘a baby’s little finger to about the size of a man’s arm in thickness.’ After extensive calculations, he concluded that lightning strikes with more energy created larger fulgurites and that overall, lightning strikes can contain tens of gigawatts of energy. Furthermore, the fulgurites followed a lognormal trend which means that the graph was not bell shaped like most variables are, but instead was exponential in one part. Therefore, the energy from one lightning strike can be easily calculated if the graph is handy.

Finally, he describes how this method could be used in the future to show the maximum damage lightning could cause and could help form better protection systems, especially for those in LEDCs.

Keep your eyes peeled for my next post,

Lara

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