For the first time scientists have detected and measured a previously hypothesized but elusive electric field surrounding Earth known as the ambipolar field. This discovery, more than 60 years in the making, promises to reshape our understanding of the dynamics of Earth’s atmosphere and its evolution over time.
The ambipolar field, first theorized in 1968, plays a crucial role in countering gravity and stripping particles off into space, particularly over Earth’s poles. This phenomenon, until now undetectable due to technological limitations, has been confirmed by a team of astronomers led by Glyn Collinson at NASA’s Goddard Space Flight Center.
“Any planet with an atmosphere should have an ambipolar field,” Collinson explains. “Now that we’ve finally measured it, we can begin learning how it’s shaped our planet as well as others over time.”
Understanding the Ambipolar Field
The ambipolar field emerges in the ionosphere, a layer of Earth’s atmosphere starting around 250 kilometers (155 miles) above the surface. Here, ultraviolet and solar radiation ionize atmospheric atoms, separating electrons and creating positively charged ions. The resulting imbalance leads to the formation of an electric field that attempts to tether the lighter electrons and heavier ions together.
This electric field, while incredibly weak—measured at just 0.55 volts, equivalent to the strength of a watch battery—plays a significant role in shaping Earth’s atmosphere. It “puffs up” the atmosphere, allowing some ions to escape into space, a phenomenon observable as the polar wind.
The Endurance mission, launched in May 2022, was specifically designed to detect this subtle force. It reached an altitude of 768 kilometers (477 miles) before returning with critical data, confirming the presence of the ambipolar field.
Implications for Earth’s Evolution
The discovery of the ambipolar field offers new insights into the behavior of Earth’s atmosphere, particularly in how it has evolved and interacted with solar radiation over billions of years. The field’s ability to launch hydrogen ions into space at supersonic speeds and elevate oxygen ions, thereby increasing the density of the ionosphere, highlights its significant influence on Earth’s atmospheric dynamics.
“This field is a fundamental part of the way Earth works,” says Collinson. “And now we’ve finally measured it, we can actually start to ask some of these bigger and exciting questions.”
The implications of this discovery extend beyond Earth, potentially offering clues about the atmospheres and evolutionary paths of other planets. As scientists delve deeper into the ambipolar field’s properties and effects, they may uncover new aspects of planetary science that have remained hidden until now.
The research detailing this groundbreaking discovery has been published in Nature.
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