There is much to be learned about lightning. Scientists are now a step closer, though, gaining the ability to measure intense electric fields within thunderclouds by monitoring electromagnetic bursts from cosmic rays.
Electric fields have normally been measured before by sounding balloons or rockets, but turning to cosmic rays is believed to offer better insight into where lightning comes from, as well as verifying if cosmic rays themselves have been triggering bolts. The method exploring electric fields through cosmic rays was detailed in a study published in the journal Physical Review Letters.
Heino Falcke leads the Low Frequency Array (LOFAR) at the Netherlands' Radboud University Nijmegen. LOFAR is a network of particle detectors and radio antennae spread across five countries in Europe, built as a multi-purpose tool for studying radio waves coming from cosmic phenomena at a distance. At the same time, LOFAR is also designed for observing cosmic rays that make their way to the Earth's atmosphere.
When highly energetic particles from a cosmic ray collides with air molecules, the interaction starts a chain reaction that showers millions of electrically charged particles down to the ground.
LOFAR antennae worked toward detecting radio waves emitted by falling charged particles, recording 762 high-energy showers from June 2011 to September 2014.
Pim Schellart, lead author of the study, noted that radio waves behave in an orderly manner when the weather is fair, with polarizations neatly aligned. The researchers observed that these radio-wave behaviors become erratic when thunderclouds are nearby.
Instead of doing away with this anomaly, the researchers redesigned their computer models to accommodate intense electric fields. When polarizations were recalculated, scrambled patterns were a match to the new simulations.
Measuring electric fields within clouds may aid in solving one of the biggest mysteries in atmospheric science. Lightning acts like an electrical conduction channel, briefly opening up the atmosphere and partially restoring electric charge balance. However, researchers do not know yet what triggers a bolt. While electric fields are strong, they are not enough to turn air into a conductor from being an insulator.
It is hoped that LOFAR will be able to test whether or not cosmic rays falling to the ground coincide with lightning strikes but there is a bit of hesitation using the network to do so as well because lightning hitting the delicate equipment could be destructive.
"Scientifically, you're hoping that one lightning strike would fall right in the middle of LOFAR, but then as a radio astronomer, you kind of hope it wouldn't," said Falcke.
Photo: Ian Boggs | Flickr
