A team of scientists has made a groundbreaking discovery, detecting a planet-wide electric field known as the ambipolar electric field, which is as fundamental to Earth as its gravity and magnetic fields. This field, first hypothesized over 60 years ago, plays a crucial role in driving the "polar wind," a steady outflow of charged particles into space that occurs above Earth's poles.
An animation showing newly discovered Earth's electrical field. Image credit: NASA/Goddard Space Flight Center
Using observations from NASA's Endurance suborbital rocket, the international team of scientists successfully measured the ambipolar electric field, confirming its existence and quantifying its strength. The field lifts charged particles in our upper atmosphere to greater heights than they would otherwise reach and may have shaped our planet's evolution in ways yet to be explored.
The ambipolar electric field is generated at the subatomic scale and is incredibly weak, with its effects felt only over hundreds of miles. It begins at around 150 miles altitude, where atoms in our atmosphere break apart into negatively charged electrons and positively charged ions. The field works in both directions, with ions pulling electrons down with them as they sink with gravity, while electrons lift ions to greater heights as they attempt to escape to space.
The team launched the Endurance rocket from the Arctic, reaching an altitude of 477.23 miles and collecting data across a 322-mile altitude range. The measurements revealed a change in electric potential of only 0.55 volts, which is almost nothing, but just 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. Heavier particles also get a boost, with oxygen ions
at that same altitude immersed in this half-a-volt field weighing half as much.
The Endurance rocket ship launches from Ny-Ålesund, Svalbard.
Credit: Andøya Space/Leif Jonny Eilertsen
In general, the team found that the ambipolar field increases what's known as the "scale height" of the ionosphere by 271%, meaning the ionosphere remains denser to greater heights than it would be without it. "It's like this conveyor belt, lifting the atmosphere up into space," said Glyn Collinson, principal investigator of Endurance.
The discovery of the ambipolar electric field has opened new paths for exploration, revealing a fundamental energy field of our planet that may have continuously shaped the evolution of our atmosphere. Similar electric fields are expected to exist on other planets, including Venus and Mars, making this discovery a significant step forward in understanding the mysteries of our planet and others.
"This is a major breakthrough in our understanding of the Earth's atmosphere and its interaction with space," said Suzie Imber, a space physicist at the University of Leicester and co-author of the paper. "The ambipolar electric field is a key driver of the polar wind, and its discovery will help us better understand the complex processes that shape our planet's upper atmosphere."
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