Astronomers Solve Puzzle of Mysterious Streaks In Radio Images of the Sky

KentuckyFC (1144503) writes 'Back in 2012, astronomers constructed an array of 256 radio antennas in the high deserts of New Mexico designed to listen for radio waves produced by gamma ray bursts, one of the most energetic phenomena in universe and thought to be associated with the collapse of a rapidly rotating stars to form neutron stars and black holes. The array generates all sky images of signals produced in the 25 MHz to 75 MHz region of the spectrum. But when researchers switched it on, they began to observe puzzling streaks across the sky that couldn't possibly be generated by gamma ray bursts. One source left a trail covering more than 90 degrees of the sky in less than 10 seconds. This trail then slowly receded to an endpoint which glowed for around 90 seconds. Now the first study of these transient radio signals has discovered that they are almost certainly produced by fireballs as they burn up after entering the Earth's atmosphere. The conclusion comes after the researchers were able to match several of the radio images with visible light images of fireballs gathered by NASA's All Sky Fireball Network. That solves the mystery but not without introducing another to keep astrophysicists busy in future. The question they're scratching their heads over now is how the plasma trails left by meteors can emit radio waves at this frequency.'

Cyclotron Radiation?

[bosef1]

What about cyclotron radiation from the ions in the meteor plasma trails? Could charge carriers be orbiting in the plasma trail under the influence of the Earth's magnetic field, and radiating RF in the megahertz band?

Is this not the same as grass noise?

[zoid.com]

I've heard reports of people laying on the ground and "hearing" meteors. What baffled scientist about this was people were hearing them realtime and not delayed due to the speed of sound. They finally realized that it was radio waves emitted by the meteors causing the grass to vibrate and they were hearing the vibrations.

Maybe I dreamed it...

Re:Cyclotron Radiation?

[xfade551]

Let's see, meteor generates a plasma trail... that would be moving charged particles (both positive and negative). Moving charge means a changing electric field. A changing electric field causes a changing magnetic field, so we have a changing electro-magnetic field... i.e. radiowaves. The ions in the plasma trail don't stay that way, the electrons get recaptured at some point, which means a photon will be discharged, i.e. a radio wave-packet. As to frequency, just put a couple grad students to write a program to calculate photon emission frequencies of a couple million different ion configurations, and they'll probably find the correct correspondence somewhere in there.

Re:That's odd

[Anonymous Coward]

Except that they have reasons to thick it is not an echo, but being radiated by the trail itself. They explicitly discuss this. The ability of a plasma trail to radiate in the RF is not too surprising considering there are all sorts of frequencies and signals you can get from the vast zoo of waves in a magnetized plasma. Although figuring out exactly what type and source of waves you have in plasmas can be difficult, even on a table top plasma experiment where you have a lot more diagnostic access.