The Monthly Media kicking off the holiday season for 2021 is from PhD student Jishnu N. Thekkeppattu from Curtin University. Jishnu is following up on this year’s January Monthly Media, which was on the deployment tests of the SITARA telescope at the Australian Space Academy in Meckering.

After undergoing further tests and making sure it doesn’t interfere with other telescopes at the Murchison Radio-astronomy Observatory (MRO), SITARA was deployed at the MRO in March 2021. SITARA has been observing the radio sky ever since – practically 24×7.

While SITARA’s main purpose is to test new methods to detect signals from the first stars, during daytime SITARA detects activity from our own star – the Sun!

The Sun is a strong source of constant electromagnetic radiation (aka light); from radio waves to X-rays. Solar activity follows an 11-year cycle and is starting to ramp up in activity again. You may have been hearing about increases in aurora sightings because of it!

We are currently in the rising phase of cycle 25, and witnessing increased activity from the Sun such as coronal mass ejections (CMEs; plasma material from the Sun gets blasted into space) and flares (bright flashes from spots on the Sun), among other events.

Solar activity also gives rise to strong radio emissions, and they are generally classified into various types, such as Types I, II, III and IV. We are interested in Type II bursts here.

Type II bursts are typically associated with shocks related to CMEs (plasma blasting into space). The plasma emits radio waves with a frequency dependant on how thick the plasma is. As the shock wave moves away from the Sun, it encounters thinner plasma and emits radio waves at a lower frequency. Here on Earth we see the radio signal drift down in frequency over time as the shock wave encounters ever thinner plasma further from the Sun.

The video shown below shows a Type II burst that was detected on the 17th of July, 2021 at the MRO, around local noontime.

Artificially generated white noise has been “modulated” in order to get what you hear in this video. The constant tone is an internal clock signal arising from the digitisers. The main Solar activity can be heard within the 2-5 minute marks.

While the data collected by SITARA are radio spectra, they can be converted to audio using some digital signal processing (DSP). It may be noted that the SITARA data span frequencies of 0-250 MHz, well beyond the range of human hearing of 20 Hz – 20 kHz. This process of converting data into audio is called sonification.

We find the resulting video quite interesting, what do you think?