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17 Jun 2002
A new device detects lightning by observing changes in the transmission of laser light through an optical cell during a thunderstorm.
This latest lightning sensor was developed, in the US, by William Koshak, of NASA Marshall Flight Center, and Richard Solakiewicz, of Chicago State University. It relies on the fact that lightning changes the electric field in the atmosphere at the sensor.
The main component of the sensor is a crystal of potassium dihydrogen phosphate. A change in the atmospheric electric field drives a current through the crystal, producing a change in the voltage across the crystal. The voltage affects the optical transmission of the crystal and so changes the amount of laser light that can be detected coming out of the crystal. The change in light output is related to the strength of the lightning.
Apart from lightning research, possible uses include hazard warning systems for aircraft, space vehicles or for recreational activities such as golf. A network of about thirty sensors placed several kilometres apart would enable people to determine the amount and location of charge deposited by a lightning event. Koshak says that the knowledge of these parameters is fundamental both to lightning research and to lightning hazard warning.
Although the sensor cannot predict when and where lightning will strike, it can detect approaching storms tens of kilometres away that a person might not be able to see or hear.
In the future the researchers plan to scale down the size of the device to fit into a tube a few inches long. Koshak says that the sensors can be built for about USD 5000 from off-the-shelf components but he expects that this cost will be reduced dramatically once the device is miniturized and some components are customized.
This research was published in the 20 July 1999 issue of the journal Applied Optics.
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