A recent study published in the journal Nature Physics reveals that the moon has an unknown effect on Earth’s “plasma ocean” which surrounds the upper atmosphere. Scientists used data collected by satellites over 40 years to track the minute changes in the shape of the plasmasphere, the inner region of Earth’s magnetosphere. The researchers discovered that the moon’s gravitational pull can create fluctuations in the plasma ocean, similar to ocean tides.
Understanding the Plasma Tides
The moon’s tidal effect on Earth’s plasmasphere had not been tested until now. The researchers analyzed data from 50,000 crossings of the plasmasphere by satellites from 10 scientific missions, including NASA’s THEMIS mission. The satellites detected minute changes in plasma concentrations, which allowed the team to map the plasmapause boundary in greater detail. The fluctuations in the plasmapause followed daily and monthly patterns that were very similar to ocean tides, indicating that the moon was the likely cause.
The Cause of Plasma Tides
The team is unsure how the moon causes the plasma tides, but their current hypothesis is that the moon’s gravity perturbs Earth’s electromagnetic field. Further research is needed to confirm this. The researchers believe this interaction between Earth and the moon could help them understand other parts of the magnetosphere, such as the Van Allen radiation belts.
Implications for Other Celestial Systems
The researchers also want to see if plasma in the magnetospheres of other planets is influenced by their moons. “These findings may have implications for tidal interactions in other two-body celestial systems,” they wrote.