Mark Megahan
The signal coming in from near-Earth space sounds like chirping birds. Chorus waves don’t only annoy radio astronomers, they “produce high-energy electrons capable of scrambling satellite communications.” It would be nice if we could figure out what causes them. Then, there’s another mystery.
Chirping birds from space
Long ago, back in the 1960’s, researchers “detected cosmic waves that sound like birds chirping.” Recently, they noticed the same signal coming from an “unexpected” place. The latest batch pinged out from more than 62,000 miles out.
That’s not far in the cosmic scheme of things but it’s a lot further away than normal. They’ve long been associated with the Earth’s individual magnetic field.
Termed “chorus waves,” they’re ordinary bursts of plasma. What made them noticeable is the fact they “ripple” at a frequency within the range of human hearing. “When converted to audio signals,” their sharp notes mimic the high-pitched calls of birds.
It was a team of scientists working at the south pole in the 1960’s who first picked up the signals. They didn’t have any fancy gear, only ordinary radio antennas.
Since the beginning, they’ve been associated with the magnetic field produced by the Earth’s core. It shields the planetary surface from harsh cosmic radiation by deflecting it around.
As expected, NASA’s twin Van Allen Probes detected the chirping birds and triangulated their origin to the radiation belts. All of that made sense, even though they don’t fully understand the phenomena. Now, the data threw them a twist.
Why there?
NASA’s Magnetospheric Multiscale satellites were “launched in 2015 to explore the Earth and sun’s magnetic fields.” Recently, they picked up the chirping birds signal. The problem was that they originated 62,000 miles away from Earth.
“That opens up a lot of new questions about the physics that could be possible in this area,” relates Allison Jaynes. She happens to be a space physicist at the University of Iowa but wasn’t “involved with the work.”
The same chirping birds signal has been detected “near other planets including Jupiter and Saturn.” That fits the original set of data.
It’s important to find out why these strange signals are coming from the middle of nowhere because they “produce high-energy electrons capable of scrambling satellite communications.”
Chorus waves, Chengming Liu of Beihang University relates, “are one of the strongest and most significant waves in space.” He was involved with the work and authored the recently published study about the new discovery.
He confirmed that the latest flock of chirping birds flew out from “a region where Earth’s magnetic field is stretched out, which scientists didn’t expect.” Ms. Jaynes is fascinated. “It’s very captivating, very compelling,” she observes. “We definitely need to find more of these events.“
