NASA's suborbital rocket confirms existence of global electric field
An international team of scientists has measured an Earth-wide electric field, known as the ambipolar electric field, using observations from NASA's suborbital rocket. This discovery confirms a hypothesis first proposed over 60 years ago, about the role of this field in driving atmospheric escape above Earth's North and South Poles. The measurements also revealed the strength of the ambipolar field and its influence on shaping our ionosphere, an upper layer of Earth's atmosphere.
Understanding Earth's atmosphere and beyond
The study of the ambipolar electric field provides valuable insights into the complex movements and evolution of Earth's atmosphere. This understanding is crucial not only for unraveling Earth's history, but also for exploring other planets and determining their potential habitability. The research findings have been published in the esteemed scientific journal, Nature. Since the late 1960s, spacecraft have detected a particle stream, known as the "polar wind," flowing from our atmosphere into space.
The mystery of the polar wind unveiled
The polar wind has been a subject of intrigue since its detection in the late 1960s. While some atmospheric outflow was anticipated due to intense sunlight, polar wind presented an enigma as many particles within it were cold and showed no signs of heating, yet they were moving at supersonic speeds. Glyn Collinson, principal investigator and lead author, stated, "something had to be drawing these particles out of the atmosphere."
The quest to measure Earth's ambipolar field
Scientists speculated that an undiscovered electric field could be responsible for the polar wind phenomenon. This hypothesized field, generated at the subatomic scale, was expected to be incredibly weak and its effects felt only over hundreds of miles. For decades, detecting it was beyond the capabilities of existing technology. However, in 2016, Collinson and his team began developing a new instrument capable of measuring Earth's ambipolar field.
The Endurance mission: A journey to the Arctic
The team's instruments were best suited for a suborbital rocket flight launched from the Arctic. In homage to Ernest Shackleton's famous 1914 voyage to Antarctica, they named their mission Endurance. The scientists chose Svalbard, a Norwegian archipelago near the North Pole, and home to the world's northernmost rocket range, as their launch site. Co-author Suzie Imber, stated, "Svalbard is the only rocket range in the world where you can fly through the polar wind and make the measurements we needed."
Endurance's successful launch and findings
On May 11, 2022, the Endurance mission was successfully launched, reaching an altitude of 768km before splashing down in the Greenland Sea 19 minutes later. During its flight, Endurance measured a change in electric potential of only 0.55 volts across a range of 518km. Collinson noted that "a half a volt is almost nothing—it's only about as strong as a watch battery," but it was just enough to explain the polar wind phenomenon.
The ambipolar field's impact on atmospheric particles
The ambipolar field exerts an outward force on hydrogen ions, the most abundant type of particle in the polar wind, that is 10.6 times stronger than gravity. Alex Glocer, Endurance project scientist at NASA Goddard and co-author, stated that this force is "more than enough to counter gravity—in fact, it's enough to launch them upwards into space at supersonic speeds." Heavier particles like oxygen ions also get a boost from this field, effectively halving their weight at the same altitude.
