Earth's Magnetic Field Shook by Spacequakes

A new study suggests that auroras are actually generated by temblors of the Earth's magnetic field. These spacequakes are caused by the plasma flying off the sun and even though they are stronger in orbit, they can reach the Earth's surface as well.

Spacequakes' precursors were discovered in 2007 by THEMIS. The Earth's magnetic tail is stretched by the extremely powerful solar wind and can sometimes snap back like a rubber band. Then, the solar wind plasma that is trapped inside the tail is projected toward Earth.

THEMIS spacecraft was in front of these jets several times and managed to finally see what was going on once the plasma jets had hit the planet. THEMIS project scientist David Sibeck of NASA's Goddard Space Flight Center in Greenbelt, Md. Says that this results in spacequakes. Scientists explain that plasma jets crash into the geomagnetic field at approximately 30,000 km above the Equator. After the first impact, a rebound process appears and makes the incoming plasma to bounce up and down on the magnetic field, and bounces get less intense as the energy spreads.

“We've long suspected that something like this was happening,” said Sibeck. “By observing the process in situ, however, THEMIS has discovered something new and surprising.”
this surprise is actually plasma vortices. They are huge whirls of magnetized gas, wide as the planet itself, that spin on the verge of the quaking magnetic field. Researchers believe that vortices' tails are actually causing the Aurora Borealis phenomenon.

Vassilis Angelopoulos of UCLA said that “Magnetic reverberations have been detected at ground stations all around the globe, much like seismic detectors measure a large earthquake.”

The first author of a paper reporting the results of a study on spacequakes, published in the April 2010 issue of Geophysical Research Letters, Evgeny Panov of the Space Research Institute in Austria, said that “The total energy in a spacequake can rival that of a magnitude 5 or 6 earthquake.”

Besides spacequakes, scientists also discovered starquakes, moonquakes and asteroid quakes, according to SPACE.com.