November 1999 General Meeting
Space Weather Impacts on Earth.
Professor Peter L. Dyson
Department of Physics, La Trobe University

Astronomers are a bit like farmers. Both are inordinately preoccupied with the weather. Perhaps it’s because the effectiveness of their work and their productivity is closely linked to clouds, wind and rain. They talk much about apparitions, the seasons, activity of the sun and the phases of the moon. But whereas the farmer’s weather stops with the troposphere, the elements of the astronomer also include the stratosphere, the ionosphere, the magnetosphere and the solar wind. Professor Peter Dyson calls the Ionosphere the TV screen of the astronomer. It makes “Space-weather” visible, he says. Its colour pixels are the ions of hydrogen (red) and oxygen (green), and in the southern hemisphere the show is called the “southern dawn”, the aurora australis.
How does one become a space-meteorologist? You get involved in “over the horizon radar”, upper atmosphere backscatter, you take some measurements, and in no time at all space weather will play havoc with your results. Then you need to know why, and that’s how it starts.

Meteorology, the study of things “beyond air” is very old. Aristotle already wrote a book called Meteorologia, but little science was done until the seventeenth century, when that man of many talents, Galileo, constructed the first practical thermometer, and Torricelli discovered the principle of the barometer. Now, in attempting to quantify this celestial interference, you collect data on this so-called space weather, and - meet serendipity - you find a ready made demand for such information. It so happens most of the man-made satellites are affected by changes in space weather, and accurate data is valuable to owners and users of these facilities alike. Power utilities, Communications, GPS systems, basically everything electrical is susceptible to magnetic disturbances. It is fascinating. In time you become hooked on the phenomena. Your timely warnings allow precautionary measures to be taken. Radiation and solar wind carry energy that may damage delicate equipment. Increases in heat makes the Earth atmosphere expand and invade the rarefied space where the satellites circle, and that perturbs their orbits.

Two powerful radar transmitters are now used to give accurate three dimensional aurora tracking over the whole Antarctic area. While monitoring of sunspot activity and solar flares can signal a coming disturbance, only auroras are actual indicators to the degree of disturbance. Consisting of clouds of electrically charged particles following the Earth’s magnetic field lines, these awe-inspiring phantom curtains provide a direct measure of the severity and duration of solar storms. With the original transmitter in Tasmania, and the new station across the Tasman in New Zealand, the acronym for the system has to be TIGER.

There used to be an old saying that weather and politics are the only safe conversation topics. There you can say whatever you want, for no one can prove you wrong. Maybe one of the topics has just become somewhat delicate? (No one can predict politics yet).

In the end it did not matter that the computer hook up cable to the projector could not be found. An improvised white-board together with Professor Dyson’s expertise with felt-pens and graphic presentations made the evening so entertaining it went into overtime, and questions had to be cut short. In closing Barry Adcock thanked Peter Dyson and presented him with a memento, a bottle of ASV port. The Professor had the last word when he said: “I have been here before, you know, eleven years ago, and I still have the souvenir you gave me then. But I can assure you this bottle of port won’t last eleven years.”
Alfred Klink

Thank you, Andrew, for your kind Christmas Greeting. Compliments of the Season to you, too.