The Sun, our closest star, provides us with the light and heat that is needed to sustain life on our planet. On a nice, bright day, the Sun might seem friendly and harmless, but in reality, this gigantic ball of intensely hot, electrically charged, gas is the source of violent storms that can destroy satellites and disrupt communication, navigation and power grids on Earth. As our society relies more and more on resources placed in space, understanding the influence of the Sun and its activity is more important then ever before.

Although the Sun might look serene to us, it is in fact, literally, bursting with activity. Part of the Sun's outer atmosphere constantly flows into space. This stream of hot particles, which can travel at speeds in excess of 1 million miles per hour, is called the solar wind. When the solar wind arrives at the Earth, it interacts with our magnetic field, and just like the wind on Earth, the solar wind can sometimes cause `magnetic' storms in the upper layers of the Earth's atmosphere. Occasionally, the Sun also ejects huge clouds of material far into space, known as coronal mass ejections (or CMEs for short). If such a CME is directed toward us, the result is likely to be a serious magnetic storm. Together, the disturbances in the solar wind and CMEs from the Sun are called `space weather'.

So what has space weather to do with us? To start with, magnetic storms can interfere with all kinds of signals, most importantly, satellite signals. Our society depends heavily on satellites, for example to provide navigation information for airplanes and ships or to transmit radio, television and telephone signals (think about all those mobile phones!). During a magnetic storm, huge electric currents are generated, which can disrupt power distribution on Earth and cause blackouts in an instant. Additionally, oil and gas pipes corrode faster due to the large currents travelling along them, induced by solar storms. In space, there are even more problems. A large CME will bombard satellites with tons of particles, which could cause severe damage, or even disable them altogether. Astronauts may be exposed to dangerous amounts of particle radiation from explosions on the Sun. Finally, disturbances in the Earth's magnetic field caused by solar storms, can trigger a beautiful display of coloured curtains of light, making the sky glow in this hemisphere with the Northern Lights, or the Aurora Borealis.

Using a fleet of spacecraft and satellites, scientists all over the world are observing the Sun and the solar wind. For example, in 1995, the Solar and Heliospheric Observatory (SOHO) was launched. This project is a joint, international space mission, supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA). One of SOHO's main goals is to help scientists understand the interactions between the Sun and the Earth's environment, which will hopefully, one day, enable them to predict the Sun's activity and space weather conditions.

To celebrate `International Sun-Earth Day 2003', Dr. Clare Parnell, Prof. Alan Hood, and Dr. Thomas Neukirch from the Solar Theory Group in the School of Mathematics and Statistics at St Andrews will give a series of three 20-minute talks for the general public. Using stunning images and the latest observations from satellites, they will give an informal, "virtual" tour of the Sun. They will discuss its various different types of activity and its impact and influence on the Earth. Afterwards, along with some refreshments, there will be an opportunity to take part in an interactive, internet session, finding out how you can view close-up, real-time, images of the Sun from home and discover more about the Sun and its effects on our lives. This event will take place on Tuesday 18th March, from 7.30 pm onwards, in Lecture Theatre A (School of Physics & Astronomy, North Haugh, St Andrews) and is suitable for a general audience.

Written by Dr. Ineke De Moortel