A team of scientists in India have uncovered a truly shocking secret about the actual energy contained in thunderclouds—and it could change the way we look at storms.
By studying muons—the negatively charged particles that are 200 times heavier than electrons—researchers were able to gauge the electrical voltage of a 2014 storm.
Their measurement? 1.3 billion volts, about 10 times more energy than any previous storm in history.
To put that number in perspective, a single thundercloud in that storm could power all of New York City for half an hour, with subway tracks containing less than 1,000 volts and lightning bolts containing about 100 million volts between their ends.
The study, published this month in the journal Physical Review Letters, not only sheds light on the connection between events in outer space and those on Earth, but it also could unwrap a mystery that has beguiled physicists for decades.
While most studies of lightning have relied on simple balloons, drones or airplanes, physicists in India have been using the Gamma Ray Astronomy PeV EnergieS phase-3, or GRAPES-3, telescope since 2001 to monitor the sub-atomic particles called muons. These naturally occurring high-energy cosmic particles hit the planet whenever cosmic rays from across the universe arrive in our upper atmosphere.
While the researchers were measuring muon showers, which carry a negative charge, they began noticing the correlation with the electrical effects of thunderstorms. When the storms struck, the muon flux detected by the GRAPES-3 telescope slowed down as it interacted with the electrical field of storm clouds.
After the scientists modeled a thundercloud as a huge parallel plate capacitator containing both positively- and negatively-charged clouds layered with gaps of several kilometers, the team was able to estimate the electrical potential of the cloud.
During the 2014 storm, the telescope was able to detect a 2 percent drop in muons, which the researchers calculated would determine the storm’s potential at 1.3 billion volts with a total power of 2 billion watts—about the equivalent energy contained in two medium-sized nuclear reactors.
Study coauthor Balakrishnan Hariharan noted:
“To achieve such high voltages on the ground is almost impossible … But nature seems to know how to do it almost effortlessly.”
Sunil Gupta, a coauthor of the study and high-energy physicist at the Tata Institute of Fundamental Research in Mumbai, India, told National Geographic:
“This was more of an amusing episode for us than anything serious … We were studying high-energy cosmic rays and interplanetary space, and not so much the thunderstorms.”
What makes the high-voltage storm especially impressive is that it may explain the origin of enigmatic high-energy gamma-ray flashes which have been detected on cloud tops during thunderstorms. Bolts of gamma rays had previously been assumed to be caused by simple storms, but in this case it appears that the 1.3 billion volts of the mammoth 2014 storm were capable of doing the job.
This also means that ultra-powerful rays emanating from the cosmos can be affected by standard lightning—which is, it turns out, a supremely powerful natural particle accelerator.
As Michael Cherry, physics professor at Louisiana State University in Baton Rouge, explains:
“These high-energy processes don’t have to be studied in an exotic source like a distant black hole or supernova … We can study them by looking up close and personal at nearby lightning.”
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