Percival Andrews of Tokyo, Japan has a nice project that you can work on to beat the heat, even though it involves the Sun! I would like to thank Percival for writing this months Classroom Session article, Space Weather. He takes FM Radio astronomy one step further using Very Low Frequency (VLF) technology to listen to the calls of the Sun! Read the Classroom Session article and follow the included link to his web-site to learn more about building your own, low cost, Solar Storm Radio Telescope (SSRT).
by Percival Andrews
percival.andrews@gmail.com
July, 2007
Storms on the Sun
Even in these days of changing climate, it's easy to think of the Sun as if it were the Earth's forever stable and benevolent great uncle: shining constantly to give us the warmth and light we need for our lives. In fact, our "great uncle", the Sun, is anything but constant or peaceful. The surface of the sun boils and rages with storms, and sometimes here on Earth we take the fallout!
Let's take a closer look at the Sun's surface. Through a specially equipped solar telescope, sunspots become visible. Sunspots are dark blotches on the surface of the sun that are cooler than their surroundings. (By the way, please never ever look directly at the sun with binoculars or an ordinary telescope. Doing so will likely cause permanent eye damage and blindness because of the heat concentrated into your eye. It's happened before unfortunately). What can't been seen directly are the curious magnetic fields around a sunspot. The Sun, like the Earth, has a magnetic field that flows smoothly between it's north and south poles. Except that is, around a sunspot. Around a sunspot the magnetic field become twisted and distorted, storing up huge amounts of energy in an unstable situation, rather like an overstretched elastic band.
When the stress becomes too much, the magnetic fields around a sunspot suddenly snap and then reconnect. In the process, the huge amount of excess energy that was stored up is released in an explosion. The temperature on the Sun's surface reaches several million degrees, and a burst of X-rays is shot out into space at the speed of light. These are solar flares. They are the most powerful explosions in the solar systems.
Solar Storms and the Earth
Luckily for us, the Earth is a relatively small target! The X-rays fired by solar flares usually go shooting past in some other direction. Once in a while though, the Earth is in the line of fire. It takes about 8 minutes for the X-rays from a solar flare to cross the 93 million miles between us and the Sun and reach the Earth. When they do, the effects are surprising. Here is the Japanese weather satellite Midori 2. On October 29Th, 2003 this $450 million piece of technology was burnt out completely by a solar flare. At ground level, electricity blackouts have been caused by overloads in the distribution network also caused by solar flares. Sensitive modern electronics doesn't cope well with large doses of X-rays from the sun!
With plenty at stake you'd think that astronomers would have perfected the art of forecasting these damaging solar storms by now, so that precautions can be taken in advance. Unfortunately, forecasting, "space weather" as it's known, is not much more reliable than forecasting storms here on Earth. The first problem is that while sunspots are easily visible in suitable telescopes, there is no easy way of predicting when a solar flare will erupt from a particular sunspot. The second problem is that once a solar flare does occur, the Earth-bound X-rays are traveling at the speed of light, so we don't know they are coming until they actually arrive!
Monitoring Space Weather
Monitoring space weather with your own radio telescope can be a cool hobby. Amateur radio telescopes, like the one pictured, alert the arrival of incoming solar storms in real time. A network of enthusiasts around the world operate their own receiving stations and share their discoveries through the Internet. Modern designs that rely on simple electronics and a personal computer are feasible to build for less than $150. For those who are interested I have published an eBook, "How To Build Your Own Radio Telescope". There is also more information, including a free download of a longer PDF article, here: http://www.radiotelescopebuilder.com
Keep a lookout for those solar storms!