NASA scientists have for the first time detected a vast electric field surrounding Earth that pushes part of the atmosphere into space.
Called the dipole electric field, the field was discovered by NASA’s Endurance suborbital rocket more than 60 years after researchers first hypothesized it plays a key role on Earth, just like magnetic fields and gravity. By studying the dipole electric field, scientists hope to better understand how the planet’s atmosphere evolved and how it functions today. The team published their findings on August 28 in the journal Nature.
“Any planet with an atmosphere should have a dipole electric field,” said Glyn Collinson, lead investigator on the Endurance mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Now that we’ve measured it, we can begin to understand how it shapes the Earth over time.”
In the layer of Earth’s atmosphere called the ionosphere (located 60–300 km above the ground), ultraviolet radiation from the Sun interacts with atoms, causing them to lose electrons and become ions. In theory, this process creates a weak electric field that surrounds the planet. Clues to the existence of such an electric field were first detected in 1968 by spacecraft orbiting the North and South Poles, in the form of “polar winds,” or streams of particles that flow from Earth’s atmosphere into space.
Scientists predict that some of Earth’s atmosphere is lost to space, especially after it is heated by sunlight. But polar winds are made more mysterious by the fact that they contain cold particles, meaning they are not heated, but still travel at speeds that break the sound barrier. “Something must be pulling these particles out of the atmosphere,” Collinson says. But detecting the electric field is difficult because it is quite weak and the noticeable fluctuations only occur over hundreds of kilometers.
In an attempt to understand the source of polar winds, researchers launched the Endurance rocket from a launch site in Svalbard near the North Pole, taking it to an altitude of 768.03 km above the ground before landing in the Greenland Sea 19 minutes later.
Over the 518 kilometers that Endurance collected data, it detected a change of 0.55 volts, about the strength of a watch battery. But that voltage difference pushes hydrogen ions, the most abundant particles in the solar wind, with 10.6 times the force of gravity. That’s strong enough to propel atmospheric particles into space at hypersonic speeds, says study co-author Alex Glocer, Endurance project scientist at Goddard. It’s like a conveyor belt that lifts the atmosphere into space.
After discovering the Earth’s electric field, scientists hope to find similar electric fields in the atmospheres of planets like Venus and Mars.
An Khang (Theo Live Science)