feature ■ Basic radio astronomy with simple equipment by Whitham D Reeve

Following on from his recent article on listening Listening to the Sun’s to radio storms on Jupiter, Whitham D Reeve explains Radio Storms how easy it is to tune into

radio emissions from the frequencies and, if equipped with the makes catching them exciting but proper receiver and antenna, VHF and because they are not predictable, it is not Sun with a standard HF UHF frequencies. possible to preset RSP for timed audio When a solar radio storm occurs, the recording as we do with Jupiter. Some receiver and a simple piece Earth’s ionosphere is affected, which listeners set up RSP to record audio in turn affects signal propagation. This everyday for a certain amount of time, of software. means the Sun’s outbursts also can hoping to capture the Sun. If you use be detected indirectly by monitoring this technique, be sure to have a large manmade signals that propagate long hard drive for fi le storage. Each minute distances by ionospheric refraction. The of recording requires about 1 to 1.5MB, he strongest extraterrestrial signals to monitor are transmitted by depending on how your soundcard is radio source we experience high-power, very low frequency (VLF) set up. Other listeners use a VHS video T on Earth is our own Sun. Solar transmitters located around the world recorder with the record mode set to fl ares and other phenomena cause and listeners can use VLF receivers extended play to record the receiver powerful radio emissions and RadioUser to detect the Sudden Ionospheric audio output each day. readers equipped with an HF receiver Disturbance (SID). I will not cover this When unattended audio recordings are can easily listen to these outbursts. type of listening here – perhaps it might made, it can be quite time consuming to This article follows on from my be a good subject for a future article. go back and listen for bursts that might 2-part article Listening to Jupiter’s Some of the Sun’s radio bursts are so have occurred. However, an RSP chart Radio Storms, which appeared in the powerful that they drown out manmade can be quickly reviewed at the end of September and October 2009 issues interference but it is good practice to the day and the signature shape of a of RadioUser. If you set up a radio always tune to a quiet spot. When a solar burst is easy to spot. The chart telescope for listening to Jupiter as I burst occurs, the background noise trace will rise sharply and then fall slowly, described then, you already have one level will quickly increase and then the characteristic ‘shark fi n’ shape. It is suitable for listening to the Sun’s radio taper off slowly. Some listeners leave common to mistake a reverse shark fi n storms. Of course, it must be daylight at their receivers on as a solar burst. your location (although I have received all day with the A reverse shark solar bursts after sunset). volume low enough fi n is caused The Sun has an approximate 11-year so that the normal by manmade cycle of activity, which is measured by background noise is not annoying but interference; it rises slowly and ends the number of visible sunspots. The last high enough to hear the change. When it abruptly. cycle ended in the autumn of 2008. The sounds like a burst is occurring, you can Another way to determine if a solar current cycle is off to a slow start but as change the receiver tuning to confi rm its burst has occurred is to look at the it progresses, listeners will hear more wideband nature. Manmade interference Space Weather Prediction Center’s and more solar radio storms. The current disappears when the receiver tuning is (SWPC) daily solar event reports. cycle is predicted to peak between late changed but the burst noise will remain. However, these reports do not always 2012 and the middle of 2013. show all solar events that took place. The Recording Solar Storms SWPC also will send you e-mail alerts Listening Frequencies The Radio-Sky Publishing software, when solar events occur (select Email The Sun’s radio bursts cover a very Radio-SkyPipe (RSP), described in the Products in the left panel on the SWPC wide frequency range (from very low previous article, is also used for charting website). frequency radio waves to gamma and solar radio storms. A free version with www.swpc.noaa.gov x-rays) but, as I explained in my previous limited features is available and the PRO article, the Earth’s ionosphere blocks version is only $49.95 for home use. Results frequencies below around 15 MHz. Both can be downloaded from the Radio- I obtained my fi rst chart recording of Therefore, we must tune our receivers Sky website, where you’ll also fi nd a lot a solar burst on May 8th 2009 – see above this range. A good frequency of interesting information on monitoring Fig. 1. I had the receiver running in to start with is 20.1MHz, the same extraterrestrial signals. the background and heard the sudden frequency we use for Jupiter. However, www.radiosky.com/skypipeishere.html noise increase at 2107:44 UTC and listeners also should try higher HF The unpredictable nature solar bursts the relatively slow tapering off over

20 February 2010 radiouser the next almost one minute. By lucky coincidence, I had RSP running during a predicted daytime Jupiter radio storm but I caught the solar burst instead. The next day, I recorded another solar burst – see Fig. 2. By even luckier Fig. 1: The solar burst is the ‘shark-fi n’ shaped event in the centre. The spikes were caused by tuning coincidence, I not only had RSP set up to around the 20.1MHz centre frequency to verify the wideband nature of the burst. There were several chart but I also had it preset to record the stations in the tuning range and each one caused a spike as I tuned through it. audio in anticipation of another Jupiter radio storm. Again, I caught the Sun and not Jupiter. The audio recording can be heard on my website. www.reeve.com/solar.htm A useful way to fi nd out about solar events after-the-fact is to visit NASA’s Radio JOVE website data archives. http://jovearchive.gsfc.nasa.gov I was looking through the archive one day in August when I noticed two submissions for July 4th 2009 by Richard Flagg (a dedicated Jupiter and Sun observer in Hawaii). I went back to my RSP fi les for that date and found that I had also recorded two events at the same time, one of which is shown in Fig. 3.

Conclusions Fig. 2: The characteristic ‘shark-fi n shape is obvious in this May 9th 2009 RSP chart. The burst The radio telescope you set up for started at 0814:09 local time, almost 3 hours after sunrise. Jupiter can be used for listening to the Sun without any changes. The only setback is that solar radio storms are not predictable. However, as the sunspot cycle increases over the next several years, listeners will have numerous chances to catch something on their charts and even on audio. Good luck and happy listening! ●

Further Reading The British Astronomical Association Radio Astronomy Group www.britastro.org/radio The Stanford Solar Center http://solar-center.stanford.edu The Nancay Observatory in France www.obs-nancay.fr/a_index.htm A list of radio telescopes throughout the world can be found on Wikipedia. Fig. 3: The ‘shark fi n’ shape of this event is not obvious but I was able to match its time to charts from http://en.wikipedia.org/wiki/List_of_radio_ Hawaii in the NASA Radio JOVE data archive. If it had been manmade interference, there would be no telescopes time correlation between Alaska and Hawaii. Note the time duration of almost 11 minutes. radiouser February 2010 21