Observations made by NASA’s suborbital rocket have made it possible to successfully measure the planet’s electric field, which is as important as its magnetic and gravitational fields.
More than 60 years ago, scientists first hypothesized that this ambipolar electric field was responsible for allowing our planet’s atmosphere to escape above Earth’s north and south poles. Measurements from NASA’s Endurance rocket confirmed the existence of the ambipolar field and quantified its strength, revealing its role in escape from the atmosphere and in shaping our ionosphere (layer of the upper atmosphere) more generally.
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Understanding the complex motions and evolution of our planet’s atmosphere provides clues not only to Earth’s history, but also allows us to understand the mysteries of other planets and determine which ones might be suitable for life. A research paper on this topic was published in the journal Nature.
Since the late 1960s, spacecraft flying over Earth’s poles have detected a stream of particles flowing from our atmosphere into space. Theorists predicted this current, which they called the “polar wind”, which prompted research to understand its causes.
A certain amount of current was expected from our atmosphere. Intense, unfiltered sunlight 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 it contained were cool, showing no signs of heating, but moving at supersonic speeds.
“Something had to extract these particles from the atmosphereGlyn Collinson, principal investigator for Endurance at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the paper, said in a statement. Scientists suspected that an as-yet-undiscovered electric field might be at work.
The hypothetical electric field, generated on a subatomic scale, was expected to be incredibly weak and its effects felt only hundreds of kilometers 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 they believed could measure Earth’s ambipolar field.
The team’s tools and ideas were best suited for the flight of a suborbital rocket launched from the Arctic. In a nod to the ship that carried Ernest Shackleton on his famous voyage to Antarctica in 1914, the team named their mission Endurance. Scientists have set a course for Svalbard, the Norwegian archipelago just a few hundred kilometers from the North Pole, home to the world’s northernmost missile field.
“Svalbard is the only rocket field in the world where you can fly in the polar wind and make the measurements we neededsaid Suzie Imber, a space physicist at the University of Leicester in the UK and co-author of the paper.
On May 11, 2022, Endurance lifted off and reached an altitude of 768.03 kilometers before splashing up in the Greenland Sea 19 minutes later. At an altitude of 518 kilometers where it collected data, Endurance measured a change in electrical potential of just 0.55 volts.
“Half a volt is next to nothing; It is as strong as a watch batteryCollinson said. “But it is the right amount 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.
“This is more than enough to counteract gravity; in fact, just launch them into space at supersonic speedssaid Alex Glocer, Endurance Project Scientist at NASA’s Goddard Center and co-author of the paper.
Heavier particles also get a boost. Oxygen ions at the same height, immersed in this half-volt field, weigh half as much. Overall, the team found that the ambipolar field increases what is known as the “scale height” of the ionosphere by 271%, meaning the ionosphere remains denser at higher altitudes than it would be without it.
“It’s like a conveyor belt that lifts the atmosphere into space.Collinson added.
The discovery of Endurance opened up many new avenues for exploration. As our planet’s fundamental energy field, along with gravity and magnetism, the ambipolar field 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 the atmosphere, similar electric fields are expected to exist on other planets, including Venus and Mars.
“Any planet with an atmosphere should have an ambipolar fieldCollinson said. “Now that we’ve finally measured it, we can begin to figure out how it has shaped our planet and others over time.“.
