Lightning can generate energy waves that travel vast distances into space.

This overlooked mechanism could allow lightning energy to reach the top of the atmosphere, threatening the safety of satellites and astronauts.

When lightning strikes, the energy it carries can create special electromagnetic waves called whistlers, so named because they can be converted into sound signals. For decades, researchers thought that the whistlers produced by lightning remained confined to altitudes relatively close to the Earth's surface, below about 1,000 kilometers.

now Vikas Sonwalkar and Amani Lady Researchers at the University of Alaska Fairbanks discovered that some whistlers bounce off a layer of the atmosphere filled with charged particles called the ionosphere, which allows whistler waves and the energy they carry to travel up to 20,000 kilometers above Earth's surface—all the way into the magnetosphere, the region of space governed by Earth's magnetic field.

Researchers found evidence of these reflective whistlers in data from the Van Allen Probes, twin robotic spacecraft that measured the magnetosphere between 2012 and 2019. They also found hints of the phenomenon in studies published in the 1960s. Both the old and new data indicate that the phenomenon is very frequent and happens all the time, Reddy said.

In fact, the lightning may be depositing twice as much energy into this region as previously estimated, the researchers say, and this energy charges and accelerates nearby particles, creating electromagnetic radiation that can damage satellites and endanger the health of astronauts.

“Lightning has always been considered a bit of a smaller player. Until 10 years ago, this data wasn't available and we'd never looked at it at this level of detail.” Jacob Bortnick researcher at the University of California, Los Angeles. He says the new study is a call for others to develop a more accurate picture of the magnetosphere.

Establishing the connection between lightning and the magnetosphere is also important because changes in Earth's climate could make lightning storms more frequent, Sonwalker said.

The research team now hopes to analyze data from more satellites to learn more about how lightning-based whistlers are distributed in the magnetosphere and how they are affected by space weather.