In a new paper published by researchers from Queen Mary University of London(QMUL) and others, scientists reveal that the Earth’s magnetic field booms like a drum when hit by solar radiation.
Magnetic Field Vibrates Like a Drum
According to the study, published in Nature Communications, when plasma from the solar wind strikes the magnetopause—the outermost boundary of the magnetic field—the impact sends a rippling wave along the surface of the field, which gets reflected back as it approaches the magnetic poles.
The interaction between the original wave and the reflected wave creates what’s known as a standing wave pattern, where certain points along the wave seem to stand still while the area around it vibrates. This is exactly the way a drum resonates when struck in a similar manner.
Such a vibration in the magnetopause had been theorized 45 years ago but hasn’t been heard until now. “There had been speculation that these drum-like vibrations might not occur at all, given the lack of evidence over the 45 years since they were proposed,” said Dr. Martin Archer, a space physicist at QMUL and the paper’s lead author.
“Another possibility was that they are just very hard to definitively detect.”
Detecting the Sound of the Magnetic Field
The problem, according to Archer, is that the magnetic field is being constantly hit by the solar wind, charged particles cast out from the sun in a form of plasma, making it difficult to detect isolated impacts.
“Earth's magnetic shield is continuously buffeted with turbulence so we thought that clear evidence for the proposed booming vibrations might require a single sharp hit from an impulse. You would also need lots of satellites in just the right places during this event so that other known sounds or resonances could be ruled out.”
The researchers lucked out, however, when five NASA THEMIS satellites were perfectly positioned to detect this oscillation just when a massive, isolated jet of plasma slammed into the magnetopause. The satellites were able to record the “sound” made by the impact, which showed the original theory to be correct.
“The event in the paper ticked all those quite strict boxes and at last we've shown the boundary's natural response,” said Archer.
The Earth’s Magnetic Shield
The Earth’s magnetic field is crucial for our survival. Without it, life on Earth would not be possible as the radiation from the sun would have made Earth inhospitable to life.
It is theorized that Mars suffered just such a fate when its underdeveloped magnetic field was insufficient to protect it from the solar wind, which slowly tore away its atmosphere like a sand-blaster.
In fact, it’s now been suggested that Earth was on its way to suffering just such a fate when we caught a lucky break: Earth’s iron core solidified, jump-starting our magnetic field just in time to shield the atmosphere from the solar wind about 565 million years ago.