Scientists Discover Long-Sought Global Electric Field on Earth

Using observations from a NASA suborbital rocket, an international team of scientists has succeeded, for the first time, in measuring a planetary electric field considered as fundamental to Earth as its gravity and magnetic fields.

More than 60 years ago, scientists hypothesized that this ambipolar electric field was behind the leakage of Earth’s atmosphere over the North and South Poles. Measurements by NASA’s Endurance rocket confirmed the ambipolar field’s existence and quantified its strength, revealing its role in atmospheric leakage and in shaping our ionosphere (a layer of the upper atmosphere) more broadly.

Understanding the complex motions and evolution of our planet’s atmosphere not only provides clues to Earth’s history, but also helps us better understand the mysteries of other planets and determine which ones might be suitable for life. A research paper on this topic is published in the journal Nature.

An electric field that attracts particles into space

Since the late 1960s, space probes flying over Earth’s poles have detected a stream of particles flowing from our atmosphere into space. Theorists predicted this flow, which they dubbed “polar wind,” prompting researchers to understand its causes.

Some leakage from our atmosphere was expected. The intense, unfiltered light from the Sun should cause some particles in our air to escape into space, like steam evaporating from a pot of water. But the observed polar wind was more mysterious. Many of the particles in it were cold, with no signs of warming, but they were traveling at supersonic speeds.

“Something had to be pulling these particles out of the atmosphere,” said Glyn Collinson, principal investigator for the Endurance study at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. Scientists suspected that a yet-to-be-discovered electric field might be at work.

The hypothetical electric field, generated at the subatomic scale, was thought to be incredibly weak and its effects felt only hundreds of miles away. For decades, its detection was beyond the limits of existing technology. In 2016, Collinson and his team set to work inventing a new instrument that they believed could measure Earth’s ambipolar field.

Rocket launch from the Arctic

The team’s instruments and ideas were particularly suited to a suborbital rocket flight launched from the Arctic. In homage to the ship that carried Ernest Shackleton on his famous 1914 voyage to Antarctica, the team named their mission Endurance. The scientists set sail for Svalbard, a Norwegian archipelago a few hundred miles from the North Pole and home to the world’s northernmost rocket launch site.

“Svalbard is the only rocket launch site in the world where we can fly through the polar wind and make the measurements we need,” said Suzie Imber, a space physicist at the University of Leicester in the United Kingdom and co-author of the study.

On May 11, 2022, Endurance took off and reached an altitude of 768.03 kilometers (477.23 miles), before splashing down 19 minutes later in the Greenland Sea. Over the 322-mile altitude range where it collected data, Endurance measured an electrical potential change of just 0.55 volts.

“Half a volt is almost nothing, it’s about as powerful as a watch battery,” Collinson said. “But it’s just enough to explain the polar wind.”

Hydrogen ions, the most abundant type of particle in the polar wind, experience an outward force from this field 10.6 times stronger than gravity.

“That’s more than enough to counteract gravity — in fact, it’s enough to launch them upward into space at supersonic speeds,” said Alex Glocer, Endurance project scientist at NASA Goddard and co-author of the paper.

Heavier particles also get a boost. Oxygen ions at the same altitude, immersed in this half-volt field, weigh half as much. Overall, the team found, the ambipolar field increases what’s called the “scale height” of the ionosphere by 271 percent, meaning the ionosphere remains denser at higher heights than it would be without it.

“It’s like a conveyor belt that lifts the atmosphere into space,” Collinson added.

The discovery of Endurance has opened up many new avenues of exploration. The ambipolar field, as a fundamental energy field on our planet alongside gravity and magnetism, may have continually shaped the evolution of our atmosphere in ways we can now begin to explore. Because it is created by the internal dynamics of an atmosphere, similar electric fields should exist on other planets, including Venus and Mars.

“Any planet with an atmosphere should have an ambipolar field,” Collinson said. “Now that we’ve finally measured it, we can begin to understand how it’s shaped our planet and others over time.”