Forecasting Solar Storms

Dr. Sten Odenwald (Raytheon STX, NASA Goddard Space Flight Center)

Solar storms are a problem. A big problem. Chances are you have never heard of them at all because unlike the conventional storms that produce rain and thunder, solar storms are remote and distant. It really all depends on where you are and who you are. If you are an astronaut walking on the moon, a solar storm could give you a lethal dose of radiation in a matter of a few minutes. If you happened to be in Quebec on March 13, 1989, your entire province would have been blacked-out by a solar storm-induced power outage. If you were dialing '911' from a cellphone, the solar storm would have prevented your call from going through.

Scientists have spent a lot of time trying to predict solar storms so that, like hurricane warnings, we can have at least some forewarning of their approach. When solar storms buffet the earth's magnetic field they can, and often do, raise havoc with radio communication, power transmission, and even satellite functions. Nothing in our high-tech world seems to be entirely immune from the outfall from solar storms.

The sun and the wind from the sun are under around the clock survelance by a network of ground-based, and satellite-based observatories such as SOHO, the Solar Heliospheric Observatory, and ACE, the Advanced Composition Experiment to name a few. Other spacecraft orbiting the earth measure the changes in the earth's magnetic field and the populations of high-energy trapped particles which circulate within this vast magnetic bottle. Our sun has only recently begun to emerge from its lowest point in the famous 'sunspot cycle'. This ebb and flow of solar activity lasts an average of 11 years from peak to peak, with the current cycle, Number 23, destined to reach maximum in the summer of 2000.

Even though near its low point in the cycle, the sun has treated scientists to many spectacular storms which have reached earth and, in so doing, demonstrated that space weather forecasting is not an idle activity. On January 7th, 1997 a region of intense activity on the sun's eastern sector launched a billion-ton gas cloud called a coronal mass ejection (CME) which, 3 3/4 days later reached earth. Its transit and arrival was monitored by 20 scientific research satellites as part of the International Solar-terrestrial Physics program (ISTP). According to NASA astronomer Dr. Stephen Maran, "This is the first time a solar event has been captured from cradle to grave".

A small part of the million mile-wide cloud brushed by the earth, and shook the magnetic field of the earth for over 24 hours like a flame flickering in a breeze. This geomagnetic storm and the particles comprising it allegedly affected the operation of a $200 million Telstar 401 communications satellite which had to be taken out of commission on January 17th according to articles published in Sky and Telescope magazine ( July, 1997 page 20) and Aviation Week and Space Technology ( January 27, 1997 page 61-62).

With the upcoming 'solar maximum' approaching, and with our rapidly escalating dependence on satellite communication technology in the 21st century, additional space weather forecasting satellites will be launched so that as the older satellites reach the ends of their operating lifetimes, new generations of early-warning satellites will be on the scene to give scientists the data they need to make accurate forecasts in the next century.