At any given time, there are trillions of charged particles – protons and electrons, basic blocks of basic matter – tremble above your head. These high-energy particles can travel at speeds close to the speed of light, usually thousands of kilometers away from the earth, trapped by the shape of the earth’s magnetic field.
Sometimes, though, an event that disengages them from position and causes electrons to rain into the Earth’s atmosphere. These high-energy particles in space form the so-called Van Allen radiation belt, and their discovery was the first in the space age. A new study by my research team found that electromagnetic waves generated by lightning trigger these electronic showers.
A brief history lesson
At the beginning of the space race in the 1950s, Professor James Van Allen and his research team at the University of Iowa were tasked with establishing an experiment to fly the first satellite of the United States, Explorer 1. They designed sensors to study cosmic radiation, which are made from high-energy particles derived from the sun, are silvery Galaxy or Beyond.
However, after the launch of Explorer 1, they noticed that their instruments detected significantly higher levels of radiation than expected. They do not seem to measure distant sources of radiation outside our solar system, but rather local and extremely strong sources.
This measurement led to the discovery of the Van Allen radiation belt, the dough-shaped region of two high-energy electrons and the ions surrounding the planet.
Scientists believe that the internal radiation belt about 1,000 kilometers away from the Earth is composed of electrons and high-energy protons and is relatively stable over time.
The external radiation band is about three times farther away and is composed of high-energy electrons. The belt can be highly dynamic. Its location, density, and energy content may vary greatly in response to the hours due to solar activity.
The discoveries in these highly radiant areas are not only interesting stories about the early stages of the space race. This also reminds people that many scientific discoveries are caused by happy accidents.
It is a lesson for me (including myself) to be open to the point of analyzing and evaluating data. If the data do not match our theories or expectations, it may be necessary to revisit these theories.
Our strange observation
When I teach the history of the space race in my Space Policy course at Boulder, I rarely associate it with scientists who study Earth’s radiation belts. Or, at least I didn’t until recently.
In a study led by Max Feinland, an undergraduate student in my research group, we stumbled upon some of our own accidental observations of the Earth’s radiation belt. Our findings have led us to rethink our understanding of the radiation belts inside the Earth and their impact processes.
Initially, we set out to look for very fast high-energy electron bursts, entering the atmosphere from external radiation belts, and they are often observed.
Many scientists believe that an electromagnetic wave called a “chorus” can eliminate these electrons from position and send them into the atmosphere. Because they are called chorus waves when listening on a broadcast receiver.
Feinland has developed an algorithm to search for these events over the decades of the Sampex satellite. When he showed me a location with the location of all the events he discovered, we noticed that many of them were not what we expected. Some events map to the internal radiation band, not the takeaway band.
This discovery is curious for two reasons. First, chorus waves are not common in this area, so these electrons must be shaken loose.
Another surprise is the discovery of electrons in the internal radiation band. NASA’s measurement of Van Allen probe task has prompted interest in internal radiation bands. Observations from the Van Allen probe show that high-energy electrons are not usually present in this internal radiation band, at least in the first few years of the task, from 2012 to 2014.
Now, our observations show that in fact, sometimes the inner band contains high-energy electrons. This is a real frequency under which conditions remains open to explore the question. These high-energy particles can damage spacecraft and harm humans in space, so researchers need to know when and where they exist in space to better design spacecraft.
Determine the culprit
In fact, the way to interfere with electrons in the internal radiation belt and kick them into the Earth’s atmosphere actually starts from the atmosphere itself.
Lightning is a large electromagnetic emission that illuminates the sky during a thunderstorm, which can actually produce electromagnetic waves that blow whistle-blowing, called lightning.
These waves can then enter space through the atmosphere, where they interact with electrons in the internal radiation band—when the chorus waves interact with electrons in the external radiation band.
To test whether lightning is behind our internal radiation band detection, we reviewed the electron bursts and compared them with thunderstorm data. Some lightning activities seem to be related to our electronic events, but most of them are not. Specifically, only lightning that occurs in so-called geomagnetic storms leads to the electron bursts we find.
Geomagnetic storms are interferences in near-Earth space environments, usually caused by eruptions on the surface of the sun. This solar activity, if it faces the Earth, can produce researchers deem it as space weather. The weather in space can lead to amazing aurora, but it can also damage satellite and grid operations.
We found that the combination of weather and space weather on Earth produced the unique electronic signatures we observed in our study. Solar activity disturbs the Earth’s radiation band and fills the inner band with very high electrons, which then lightning interacts with these electrons and produces the rapid burst we observe.
These results are a good reminder of the interconnection between the earth and space. This is also a welcome reminder to my often nonlinear scientific discovery process.
Lauren Blum is an assistant professor of atmospheric and space physics at the University of Colorado Boulder. This article is from dialogue.
publishing – February 28, 2025, 4:58 pm IST
