The Sun is nearing the pinnacle of its 11-year cycle of solar activity, which means things have been pretty wild on the surface of our resident star. As the cycle approaches peak activity (scheduled to climax this year), solar flares like the double eruption observed just this morning are expected to increase in both frequency and activity. But while most of us have probably seen footage of a solar flare, we're willing to be there's a fair number of you who've never heard one. Now's your chance to do exactly that.
The recording below was made last Saturday by Thomas Ashcraft. The amateur radio astronomer operates his own observatory in New Mexico, complete with a multi-frequency radiotelescope that's been modified for binaural audio recording. Featured here is a recording of the effect that last weekend's solar eruption had on radio waves here on Earth — what Ashcraft calls a solar Type III radio burst. For "the most intricate pulsation experience," he recommends listening with headphones, or speakers with good stereo separation:
Over at DISCOVER, Ashcraft shares the details of his methodology, and explains what you're hearing in this recording:
We are hearing a solar Type III radio burst that was generated by a solar flare as recorded at 28 MHz and 21 MHz. Although the flare was relatively small, this particular radio burst was quite strong. Type III solar radio emissions are produced by electrons accelerated to high energies by solar flares. As the electrons stream outward from the sun, they excite plasma oscillations in the sun's atmosphere. The plasma oscillations in turn generate radio emissions that sweep out into space.
On one stereo channel there was a voice transmission in progress, likely a ham radio operator, and as the solar radio wave passed through the voice gets thoroughly overpowered and then returns as the blast passes through. Type III solar bursts are also called "fast drift bursts" because they drift down in frequency. It is a little hard to hear in this recording but the burst actually hits one channel at 28 MHz first and then can be heard at 21 MHz a second later on the other stereo channel. Listen close to hear this.