In 2013, the European Space Agency (ESA) launched three “Swarm” satellites on a highly experimental mission to observe and analyze the Earth’s magnetic field. So far, their mission has been mostly successful: earlier this year, the ESA released data that showed the Earth’s magnetic field was mysteriously weakening for unknown reasons and even found a strange relationship between ocean tides and magnetic fluctuations. To add more mystery to the satellites’ discoveries, ESA scientists have been puzzled since launch by a strange anomaly that has eluded explanation throughout the Swarm mission.
For years, scientists have noticed that the three satellites experience unexplained but regularly occurring blackouts as they cross over certain points above the Earth’s equator. This mysterious “Bermuda Triangle of space” caused the satellites to lose GPS signal on all of their eight receiver channels 166 times in their first two years in orbit. A variety of solutions and theories were tested unsuccessfully, but now a team of atmospheric researchers believe they have identified the cause: powerful ion storms high in the upper atmosphere.
According to their data published in the journal Space Weather, researchers believe so-called equatorial plasma irregularities (EPIs) cause rapid ionization of the ionosphere, Earth’s electrical field:
Our result shows that the Swarm satellites encountered most of the total loss of GPS signal at the ionization anomaly crests, between ±5° and ±20° magnetic latitude, forming two bands along the magnetic equator, and these low-latitude events mainly appear around post-sunset hours from 19:00 to 22:00 local time. By further checking the in situ electron density measurements of Swarm, we found that practically, all the total loss of GPS signal events at low latitudes are related to equatorial plasma irregularities (EPIs).
These equatorial plasma irregularities disturb the density of electrons in the outer atmosphere, wreaking havoc upon sensitive electronics aboard the satellites. The ionosphere is created by the Sun’s ultraviolet radiation, so these ionic disturbances are thought to naturally occur immediately after sunset once this radiation dissipates.
Once again, the data gathered by the Swarm satellites continues to demonstrate that science has only begun to scratch the surface of what surprising discoveries lie in store for us in this mysterious universe.