NASA discovers planet-wide field that is "as important as gravity"
Using observations from a NASA suborbital rocket, an international team of scientists has, for the first time, successfully measured a planet-wide electric field that is as fundamental to Earth as gravity and magnetic fields.
This electric field, known as the ambipolar electric field, was first hypothesized over 60 years ago as a driving force behind the way our planet’s atmosphere escapes above the North and South Poles.
Confirmation of the electric field
The measurements from the rocket, part of NASA’s Endurance mission, have now confirmed the existence of the ambipolar field, quantified its strength, and revealed its role in driving atmospheric escape and shaping the ionosphere — a crucial layer of the upper atmosphere.
Understanding the intricate movements and evolution of Earth’s atmosphere not only sheds light on our planet’s history but also provides valuable insights into the characteristics of other planets, helping to determine which might be capable of supporting life.
Understanding the ionosphere
The ionosphere is a layer in Earth’s upper atmosphere, sitting about 30 miles (48 kilometers) to 600 miles (965 kilometers) above the surface. It’s filled with a bunch of ionized particles, mainly electrons and ions, created when ultraviolet and X-ray radiation from the Sun zaps atmospheric gases.
This ionization forms charged layers that are super important for reflecting and transmitting radio waves, which we rely on for long-distance radio communication and navigation systems.
Instead of being a uniform layer, the ionosphere is a dynamic and complex structure, with varying levels of ionization that shift with solar activity and the time of day.
During the day, solar radiation ramps up ionization, creating stronger and more reflective layers, while at night, with less solar activity, it becomes less ionized and weaker.
These changes can affect the quality and range of radio signals, impacting everything from satellite communications to GPS systems.
Understanding how the ionosphere behaves is key to improving communication technologies and predicting space weather events that can mess with electronic systems.
Mysterious polar wind
Since the late 1960s, spacecraft flying over Earth’s poles have detected streams of particles flowing from our atmosphere into space, a phenomenon known as “polar wind.” This outflow had been predicted by theorists, prompting further research to understand its underlying causes.
Some atmospheric outflow was expected; intense, unfiltered sunlight can cause particles in the atmosphere to escape into space, much like steam rising from boiling water.
However, the observed polar wind was puzzling because many of the particles within it were cold and showed no signs of heating – yet they were traveling at supersonic speeds.
“Something had to be drawing these particles out of the atmosphere,” explained Glyn Collinson, principal investigator of the Endurance mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the paper. Scientists suspected that an undiscovered electric field might be responsible.
The Endurance mission
This hypothetical electric field, generated at the subatomic scale, was believed to be incredibly weak, with effects that could only be detected over vast distances.
For decades, detecting it was beyond the capabilities of existing technology. In 2016, Collinson and his team began developing a new instrument designed to measure Earth’s ambipolar field.
The team determined that their instruments and experimental design were best suited for a suborbital rocket flight launched from the Arctic.
In homage to the ship that carried Ernest Shackleton on his famous 1914 Antarctic expedition, the team named their mission Endurance.
Flying through the polar wind
The rocket headed to Svalbard, a Norwegian archipelago just a few hundred miles from the North Pole, which houses the world’s northernmost rocket range.
“Svalbard is the only rocket range in the world where you can fly through the polar wind and make the measurements we needed,” said Suzie Imber, a space physicist at the University of Leicester, UK, and co-author of the paper.
On May 11, 2022, the Endurance mission launched, reaching an altitude of 477.23 miles (768.03 kilometers) before splashing down 19 minutes later in the Greenland Sea.
Throughout its 322-mile altitude range, Endurance measured a change in electric potential of just 0.55 volts.
“A half a volt is almost nothing — it’s only about as strong as a watch battery,” Collinson said. “But that’s just the right amount to explain the polar wind.”
Outward force of the electric field
The most abundant particles in the polar wind, hydrogen ions, experience an outward force from this electric field that is 10.6 times stronger than gravity.
“That’s more than enough to counter gravity – in fact, it’s enough to launch them upwards into space at supersonic speeds,” added Alex Glocer, Endurance project scientist at NASA Goddard and co-author of the paper.
Heavier particles also receive a boost. For instance, oxygen ions at that altitude, when exposed to this half-a-volt field, effectively weigh half as much.
Overall, the team found that the ambipolar field increases the “scale height” of the ionosphere by 271%, meaning the ionosphere remains denser at greater heights than it would without the field. “It’s like this conveyor belt, lifting the atmosphere up into space,” Collinson explained.
Broader implications of the study
The discovery by the Endurance mission has opened numerous new avenues for research. As a fundamental energy field of our planet, alongside gravity and magnetism, the ambipolar field may have continuously influenced the evolution of our atmosphere in ways that can now be explored.
Because this field is generated by the internal dynamics of an atmosphere, similar electric fields are likely to exist on other planets, such as Venus and Mars.
“Any planet with an atmosphere should have an ambipolar field. Now that we’ve finally measured it, we can begin learning how it’s shaped our planet as well as others over time,” Collinson concluded.
The study is published in the journal Nature.
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