Get ready: It's loud.
Amateur radio astronomer Thomas Ashcraft doesn't like to just look at space: He also listens to it. Last weekend, he picked up the radio emissions resulting from a relatively small (C 2.9) solar flare, and shared the recording with Discover Magazine.
Over email, Aschcraft described to Discover's Breanna Draxler how he got the recording:
DISCOVER: What exactly are we hearing on this recording?
Ashcraft: 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.
What kind of equipment do you use to record the activity of a solar flare?
I have a complex array of instruments and observe at multiple frequencies. This particular solar burst was recorded using two simple shortwave radios connected to a three element yagi antenna. The Sun radiates across the full spectrum but, serendipitously, it can be very strong and hot at common shortwave radio frequencies. I audio record into a digital recorder.