Protons and electrons, the fundamental building elements of matter, are among the billions of charged particles that are constantly flying about over your head. The Earth’s magnetic field traps these high-energy particles, which can move at nearly the speed of light, thousands of kilometers away from the planet.
However, sometimes something happens that can knock them out of alignment and send electrons crashing into the atmosphere. One of the earliest discoveries of the space era was the identification of these high-energy particles in space, which are known as the Van Allen radiation belts. According to a recent study conducted by my research team, these electron showers can be triggered by electromagnetic waves produced by lightning.
A little lesson in history.
Professor James Van Allen and his research team at the University of Iowa were assigned to construct an experiment to fly on Explorer 1, the United States’ first satellite, at the beginning of the space race in the 1950s. In order to investigate cosmic radiation—which is brought on by high-energy particles that come from the Sun, the Milky Way galaxy, or beyond—they created sensors.
However, they discovered after the launch of Explorer 1 that their equipment was picking up much more radiation than they had anticipated. They seemed to be measuring a local, very powerful source of radiation rather than a far-off source beyond our solar system.
The Van Allen radiation belts, two doughnut-shaped areas of high-energy electrons and ions surrounding the planet, were found as a result of this observation.
According to scientists, the inner radiation belt, which peaks at a distance of roughly 621 miles (1000 kilometers) from Earth, is made up of high-energy protons and electrons and is rather stable over time.
High-energy electrons make up the outer radiation belt, which is located around three times farther away. This belt has a lot of dynamic potential. Its location, density and energy content may vary dramatically by the hour in reaction to solar activity.
In addition to providing an intriguing account of the early stages of the space race, the discovery of these high-radiation zones serves as a reminder that many scientific breakthroughs have been the result of fortunate accidents.
For experimental scientists like myself, it serves as a reminder to be open-minded while assessing and analyzing data. It might be necessary to reexamine our theories if the data does not support them.
Our intriguing findings
I rarely relate the history of the space race to my personal experiences as a scientist studying Earth’s radiation belts, even though I teach it in a space policy course at the University of Colorado, Boulder. I didn’t until recently, however.
My research group’s undergraduate student Max Feinland led a study in which we discovered some of our own surprising findings about the radiation belts of Earth. Our discoveries have caused us to reconsider how we perceive the inner radiation belt of Earth and the mechanisms that influence it.
Our initial goal was to search for extremely quick—sub-second—bursts of high-energy electrons that enter the atmosphere from the outer radiation belt, where they are usually seen.
Many scientists think that these electrons can be knocked out of place and sent toward the atmosphere by a kind of electromagnetic wave called “chorus.” Because of their characteristic chirping sound when heard on a radio receiver, they are known as chorus waves.
Feinland used an algorithm to look for these occurrences in SAMPEX satellite observations spanning decades. He gave me a graphic showing the locations of every event he had found, and we saw that several of them were not where we had anticipated. Instead of mapping to the outer radiation belt, some occurrences did so to the inner one.
Two factors made this finding intriguing. For starters, something else had to be jarring these electrons loose because chorus waves aren’t common in this area.
Finding electrons this energetic in the inner radiation belt at all was the other surprise. Measurements from NASA’s Van Allen Probes mission prompted renewed interest in the inner radiation belt. Observations from the Van Allen Probes suggested that high-energy electrons are often not present in this inner radiation belt, at least not during the first few years of that mission, from 2012 to 2014.
Our measurements now indicated that, in reality, there are instances that the inner belt includes high-energy electrons. It is yet unknown how frequently and under what circumstances this is true. In order to effectively construct spacecraft, researchers must determine when and where these high-energy particles are present in space. These particles have the potential to injure both humans and spacecraft.
Identifying the offender
In fact, the atmosphere itself is the starting point for one method of upsetting electrons in the inner radiation belt and launching them into Earth’s atmosphere.
Lightning-generated whistlers are electromagnetic waves that are genuinely produced by lightning, the massive electromagnetic discharges that illuminate the sky during thunderstorms.
Similar to how chorus waves interact with electrons in the outer radiation belt, these waves can then pass through the atmosphere and into space, where they interact with electrons in the inner radiation belt.
We matched the electron bursts with thunderstorm data to see if lightning was responsible for our inner radiation belt detections. While much of the lightning activity was unrelated to our electron occurrences, some of it appeared to be.
In particular, the electron bursts we observed were exclusively produced by lightning that happened immediately following so-called geomagnetic storms.
Large eruptions on the Sun’s surface are frequently the cause of geomagnetic storms, which are disruptions in the near-Earth space environment. If aimed toward Earth, this solar activity can create what scientists refer to as space weather. In addition to producing breathtaking auroras, space weather can interfere with satellite and electrical grid operations.
We found that the distinct electron signals we saw in our investigation are a result of both Earthly and space weather. Earth’s radiation belts are disturbed by solar activity, which also fills the inner belt with extremely high-energy electrons. Lightning then reacts with these electrons to produce the quick explosions we saw.
These findings serve as a pleasant reminder of how intertwined space and Earth are. Additionally, they served as a helpful reminder to me of the frequently nonlinear nature of scientific research.
ALSO READ:
Amid The Sino-US Tariff Battle And Growing US Crude Inventories, Oil Prices Decline.