Thunderstorms play cosmic pinball with space weather

When lightning strikes, electrons pour out in masses. In a new study, researchers at the University of Colorado Boulder, led by an undergraduate student, have discovered a new link between weather on Earth and space weather. The team used satellite data to reveal that storms on our planet can dislodge particularly energetic, or “very hot,” electrons from the inner radiation belt, a region of space enveloped by charged particles that surround the Earth like an inner tube.

The team’s findings could help satellites and even astronauts avoid dangerous radiation in space. That’s a type of downpour you don’t want to find yourself in, said lead author and undergraduate student Max Feinland.

“These particles are scary or what some call ‘killer electrons,’” ​​said Feinland, who earned his bachelor of science in aerospace engineering from the University of Boulder in spring 2024. “They can penetrate metal satellites, hit circuit boards, and can be carcinogenic if they hit a person in space.

The study was published on October 8 in the journal Natural communication.

The results relate to the radiation belts generated by the Earth’s magnetic field. Lauren Blum, co-author of the paper and assistant professor in the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder, explained that two of these regions encircle our planet: although they move a lot over time, the inner belt tends to begin more than 600 miles above the surface. The outer belt begins about 12,000 miles from Earth. These pool floats in space trap charged particles coming from the sun to our planet, forming a sort of barrier between Earth’s atmosphere and the rest of the solar system.

But they are not really airtight. Scientists, for example, have long known that high-energy electrons can fall toward Earth from the outer radiation belt. Blum and his colleagues, however, are the first to spot similar rain coming from the inner belt.

In other words, Earth and space may not be as separate as they seem.

“Space weather really depends on both the top and bottom,” Blum said.

Thunderclap

It is a testament to the power of lightning.

When lightning flashes in Earth’s sky, this burst of energy can also send radio waves spiraling into the depths of space. If these waves hit the electrons in the radiation belts, they can jostle them, a bit like shaking your umbrella to make the water fall. In some cases, such “lightning-induced electron precipitation” can even influence the chemistry of Earth’s atmosphere.

Until now, researchers had only collected direct measurements of lower-energy, or “colder,” electrons falling from the inner radiation belt.

“In general, we think the inner belt is pretty boring,” Blum said. “It’s stable. It’s still there.”

His team’s new discovery happened almost by chance. Feinland was analyzing data from NASA’s now-decommissioned Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite when he saw something strange: clusters of what appeared to be high-energy electrons colliding. moving through the inner belt.

“I showed Lauren some of my events and she said, ‘That’s not where they’re supposed to be,’” Feinland said. “Some publications suggest that there are no high-energy electrons in the inner belt.”

The team decided to dig deeper.

In total, Feinland counted 45 high-energy electron surges in the inner belt between 1996 and 2006. He compared these events to records of lightning strikes in North America. Sure enough, some electron spikes appeared to occur less than a second after lightning struck the ground.

Electronic pinball machine

Here’s what the team thinks is happening: Following a lightning strike, radio waves from Earth trigger a kind of manic pinball game in space. They hit electrons in the inner belt, which then begin bouncing between Earth’s northern and southern hemispheres, traveling back and forth in just 0.2 seconds.

And every time the electrons bounce around, some of them move out of the belt and into our atmosphere.

“You have a big blob of electrons that bounces around, then comes back and bounces again,” Blum said. “You will see this initial signal, and it will disappear.”

Blum isn’t sure how often such events occur. They can occur mainly during periods of high solar activity, when the sun spits out lots of high-energy electrons, thereby storing the inner belt of these particles.

Researchers want to better understand these events so they can predict when they might occur, potentially helping to ensure the safety of people and electronic devices in orbit.

Feinland, for his part, is grateful for the chance to study these magnificent storms.

“I didn’t even realize how much I loved research until I took on this project,” he said.

Other co-authors of the new study included Robert Marshall, associate professor in the Ann and HJ Smead Department of Aerospace Engineering Sciences at CU Boulder, Longzhi Gan of Boston University, Mykhaylo Shumko of the Applied Physics Laboratory of Johns Hopkins University and Mark Looper of The Aerospace Society.