Lightning strikes on Earth make ‘killer electrons’ play scary pinball in space

Earth is surrounded by a scary invisible region, called the inner radiation belt. In this region, our planet’s magnetic field traps several high-energy electrons and protons. These particles are released by the Sun and cosmic rays in other galaxies.

The inner radiation belt captures these high-energy particles when they attempt to enter Earth’s atmosphere, preventing them from causing any damage to life on our planet. However, a new study reveals that radiowaves from lightning on Earth can knock high-energy electrons out of the inner radiation belt.

These knocked-out electrons cannot enter Earth but can give rise to harmful radiation, posing a serious threat to our satellites and astronauts.

“These particles are the scary ones or what some people call ‘killer electrons. They can penetrate metal on satellites, hit circuit boards, and can be carcinogenic if they hit a person in space,” Max Feinland, lead study author, and a student of the University of Colorado Boulder (CU Boulder), said .

High-energy electrons can escape the inner belt

The study authors were studying data from the Solar, Anomalous, and Magnetospheric Particle Explorer ( SAMPEX ), a decommissioned satellite of NASA that completed its mission in 2004 but continued to stay functional until 2012.

During their study, they accidentally potted some unusual events showing high-energy electrons coming out of the inner radiation belt . “I showed Lauren some of my events, and she said, ‘That’s not where these are supposed to be,’ ” Feinland said.

The inner radiation belt is located at a height of 370 to 3,700 miles above Earth’s surface. Until now, scientists were only aware of high-energy electrons falling from the outer radiation belt, a region that exists way beyond (12,000 miles and more) the inner belt.

Only lower energy, or “colder,” electrons have been reported to fall from the inner radiation belt. However, the events spotted by the researchers indicated that high-energy electrons can also escape the inner belt.

They identified 45 such events in total between 1996 and 2006. It surprised them, and now they wanted to know what was actually causing the electrons to leave the belt. So they examined the satellite data further and discovered that the events shared a connection with lightning strikes in North America.

Our findings suggest, “Following a lightning strike, radio waves from Earth kick off a kind of manic pinball game in space. They knock into electrons in the inner belt, which then begins to bounce between Earth’s northern and southern hemispheres—going back and forth in just 0.2 seconds.”

“You have a big blob of electrons that bounces, and then returns and bounces again. You’ll see this initial signal, and it will decay away,” Lauren Blum, study co-author and a professor at CU Boulder, added.

This discovery can save satellites and astronauts

For the first time, scientists have found evidence that harmful radiation containing clumps of extra-hot electrons can leave the inner belt. “Typically, the inner belt is thought to be kind of boring,” Blum said.

However, these findings show that this isn’t always the case. Also, since the occurrence of such high-energy electron events wasn’t known before, “Our results could help satellites and even astronauts avoid dangerous radiation in space,” Feinland said.

Moreover, it also suggests that space weather , i.e., the conditions in the space surrounding Earth, aren’t just a result of what’s happening outside our planet but also of what’s happening inside it.

Hopefully, further research will provide more insights into inner belt high-energy electrons, and allow scientists to accurately predict their behavior.

The study is published in the journal Nature Communications .