Scientists have unraveled the mystery behind the disappearing act of high-energy electrons in Earth’s outer radiation belt, which may pave the way to predict space weather phenomena.
UCLA researchers showed that the missing electrons are swept away from the planet by a tide of solar wind particles during periods of heightened solar activity.
“This is an important milestone in understanding Earth's space environment,” said lead study author Drew Turner, an assistant researcher in the UCLA Department of Earth and Space Sciences and a member of UCLA''s Institute for Geophysics and Planetary Physics (IGPP). "We are one step closer towards understanding and predicting space weather phenomena."During powerful solar events such as coronal mass ejections, parts of the magnetized outer layers of sun’s atmosphere crash onto Earth’s magnetic field, triggering geomagnetic storms capable of damaging the electronics of orbiting spacecraft.
These cosmic squalls have a peculiar effect on Earth’s outer radiation belt, a doughnut-shaped region of space filled with electrons so energetic that they move at nearly the speed of light.
“During the onset of a geomagnetic storm, nearly all the electrons trapped within the radiation belt vanish, only to come back with a vengeance a few hours later,” said Vassilis Angelopoulos, a UCLA professor of Earth and space sciences and IGPP researcher.
The missing electrons surprised scientists when the trend was first measured in the 1960s by instruments onboard the earliest spacecraft sent into orbit, said study co-author Yuri Shprits, a research geophysicist with the IGPP and the departments of Earth and space sciences, and atmospheric and oceanic sciences.
“It’s a puzzling effect,” he said.
“Oceans on Earth do not suddenly lose most of their water, yet radiation belts filled with electrons can be rapidly depopulated.”
Even stranger, the electrons go missing during the peak of a geomagnetic storm, a time when one might expect the radiation belt to be filled with energetic particles because of the extreme bombardment by the solar wind.
Where do the electrons go? This question has remained unresolved since the early 1960s. Some believed the electrons were lost to Earth’s atmosphere, while others hypothesized that the electrons were not permanently lost at all but merely temporarily drained of energy so that they appeared absent.
To resolve the mystery, Turner and his team used data from three networks of orbiting spacecraft positioned at different distances from Earth to catch the escaping electrons in the act.
The data show that while a small amount of the missing energetic electrons did fall into the atmosphere, the vast majority was pushed away from the planet, stripped away from the radiation belt by the onslaught of solar wind particles during the heightened solar activity that generated the magnetic storm itself.
A greater understanding of Earth’s radiation belts is vital for protecting the satellites we rely on for global positioning, communications and weather monitoring, Turner said.
The study has been recently published in the journal Nature Physics.