They say that in the cosmos no one can hear you cry, but it seems you can hear the bumps of the Earth's magnetic shield when it is hit by jets of plasma thrown out of the Sun, a new study found.
NASA's five-year decade data analysis has provided the first direct evidence that the edge of the magnetosphere vibrates like a drum, according to a study published in Nature Communications.
"This study basically shows that we can add some percussion instruments to this multi-instrumental magnetic instrument we live in," said lead author Martin Archer of the University of London, Queen Mary.
While we have long known that the protective magnet bubble in which we live resonates in a similar way to string and wooden instruments, proving that it also oscillates like a drum, it is much harder.
"The first book that really discusses the idea was 45 years ago … but we did not have the evidence from observations to prove it was happening," said Dr. Archer.
The idea is that when the jet of plasma strikes the magnitosphere boundary (called magnetopause), the waves move on the surface to the magnetic poles where they return to the center.
When the original and reflected waves collide with each other, they create a pattern that causes the magnetopause to vibrate, just like a drum wave.
But finding a real-life event that coincides with the theoretical patterns of this phenomenon requires very special circumstances.
"This gave us the idea that what you want is at least four or five satellites in a row [to measure the movement of the magnetosphere]"said Dr. Archer.
In 2007, the five NASA satellites were perfectly arranged in a pearl configuration.
Dr. Archer and an international team of colleagues snatched the data and discovered an isolated stream of plasma that travels 400 kilometers per second – four times faster than the surrounding solar wind.
Although the jet was far less vigorous than massive mass ejection (CME) – a massive explosion of high energy particles that create solar storms – the outer edge of the magnetosphere oscillates.
"Sounds" of space
Four of the five THEMIS satellites have discovered waves known as magneto waves when the edge of the magnetosphere overturns them.
Magnetic waves are pressure waves like sound waves. But instead of moving through gas or solids, the magneto waves pass through the plasma, an electrically charged soup.
"In plasma, not only do you have pressure because you are moving around charged particles, but you also have electromagnetism … which has its own pressure associated with it," said Dr. Archer.
These ultra-low frequency waves are impossible for people to hear without some fancy (see the video below).
"They are absolutely small – even the pressure changes, not the magnetic, could not move the eardrum – so you will not be able to hear them because they are too weak and too low-frequency."
Although waves do not pack the same type of impact as CME, they could still affect space time on a large scale, Dr. Archer said.
– It could damage [satellites] and to influence the technology we rely on. "
Does the evidence "unambiguous"?
The team said the observations had given "unambiguous" evidence of a drum-like effect.
"For the first time, we had an event where observation coincided almost exactly with the theoretical model," said Dr. Archer.
But Colin Waters, an Australian physicist at Newcastle University, said there are still some doubts.
"It's pretty close, but we'll need more observations and we need to improve our modeling," said Professor Waters, adding that the team had only been able to check the results with one ground station.
"All observation says you have this oscillating movement, but then there are limitations in what the spacecraft." [satellites] can actually find out. "
He said it is still possible that the open wave model is the result of vibrations moving up and down through the magnetosphere rather than through it.
Another alternative, which Dr. Archer said, that exceptions to exceptions are that fluctuations are caused by the action of solar wind on waves producing magnetopause in plasma.
This effect, known as the Kelvin-Helmholtz wave – which we also see when the wind blows over the ocean or in certain cloud formations – is the preferred mechanism proposed to explain the oscillations in the magnetosphere over the past 40 years.
Last year, for example, a team of Japanese scientists presented evidence of these waves in the queue of the magnetosphere.
"It's more than likely a mixture of all these options," said Professor Waters.