How to Analyse the Data

Joachim Köppen DF3GJ Kiel/Strasbourg/Illkirch Summer 2004

Schematic dynamic spectra of the various types of solar radio bursts. Type II and III burst are relatively narrow-band and sweep from high frequency to low frequencies, rapidly or more slowly; Type IV and V are more broadband, resembling even more a broadband noise.

In a different orientation, such a spectrum is shown below, as observed with the Spectrograph at the University of Florida's Radio Observatory, built by Richard Flagg. The observations are from March 31, 2004, and more data can be found in the Radio Jove Data Archive.

One notes as horizontal red lines the strong emissions by the 13 m broadcast band near 21.6 MHz, also some strong signal around 27 MHz (CB radio) and other terestial emissions. The solar bursts are weaker (light blue), and show up as almost vertical structures, sweeping rapidly from high frequencies down. At a single frequency, such as 20 MHz, the amplitude of the two strong bursts would resemble the 'shark's fin' shape of rapid rise - slow fall. Below is a similar view, in yet another orientation, from the Nançay Decametric Array

So what we can do with our single-frequency data:

• Compare with other's observations: Radio Jove Data Archive at NASA's GSFC
• Check solar radio bursts with NOAA's Lists of Edited Solar Events for of the day. Archived data are found here (from june 2015 onwards) Please note that these lists take a few days to be in the final form. Also, they are not complete; you might come across a radio burst the professional stations might have missed. However, make sure that such an event is not a man-made signal or interference...
• check with the Dynamic Spectra from the Nançay Decametric Radiotelescope
• Compare noise temperatures with typical observations of other people ... radio communications that might come up on the frequency could be much more intense than a normal solar noise storm. Likewise, strong local interference from a passing poorly kept car might cause unnatural high signals ...
• Listen to the signals as much as you can: train yourself a bit to distinguish the rushing noise of thermal noise from the computer noise which may sound like a whine with several tones superposed. Operation of faulty electric apparatus becomes obvious when you hear it switched on and off. Recently, I heard a gargling/throbbing sound becoming louder in almost a rythmic way, leaving a trace on the plot a bit similar to some complex solar radio bursts. From its sound, I recognized it as a kind of data transmission one often hears on the short waves. Since the sound persisted independent of the tuning of the receiver, it became obvious: It was that kind of data transmission, on a nearby frequency, but so strong that it caused overload of the receiver's mixer. Its strength varied because of fading due to the short waves reflected by the ionosphere. If I had seen only the plot, I would have thought of having observed an interesting radio burst...
• some solar radio bursts have a characteristic shape: noise rising fast but decaying more slowly. In the chart they look like shark fins. Also they have a characteristic duration of a few tens seconds. When you look through the data, it helps to set the time interval displayed on the screen to a suitable value, to make it easier to spot them. You can train your eyes on the data stored in the Radio Jove Data Archive