The Sun is much more than a ball of fire suspended 150 million kilometres from the Earth. Its magnetic activity makes it the unruly neighbour in our celestial environment. An expert in numerical modelling, Paul Charbonneau attempts to understand what is brewing up there to better understand what is happening down here. “Sunspots are one of the most spectacular manifestations of the Sun’s magnetic activity,” remarks the new holder of the Canada Research Chair for Stellar Astrophysics. “When they erupt, several billion tons of plasma are ejected into space at incredible speeds. If the eruption is aimed at Earth, electrical currents in the upper atmosphere can be disrupted.” This results in a large number of aurora borealis and an elevated risk of overloading high tension lines. Telecommunication satellites can even be “toasted” as a result of these incidents.

This means the Sun does not always shine with the same brightness. “The Sun’s luminosity varies in phase with its magnetic activity: when the activity is high, the Sun is from 0.1 to 0.2% brighter. Conversely, lower magnetic activity darkens the Sun. Moreover, more than 400 years of observations have shown that the Sun’s magnetic activity follows a regular cycle: every 11 years, the number of sunspots increases. The last peak occurred between the end of 2000 and the beginning of 2001.” Since we are currently in a period when the Sun’s magnetic activity is average—neither too high nor too low—we do not feel the effects of the solar cycle on our climate. But this wasn’t always the case: “In the years 1645-1715, there was a drastic drop in temperature. Records from this period tell us that very few sunspots were seen, a sign of low levels of solar magnetic activity.”

In the past years, research on the Sun’s magnetic activity has received an unprecedented boost. “We have been making great progress thanks to the many satellites that observe the Sun and transmit thousands of images to scientists daily,” Paul Charbonneau explains. But to make some sense of these “astronomical” quantities of information, you need the right mathematical models. Mr. Charbonneau has developed a revolutionary method: genetic algorithms. Inspired by the laws of evolution, this method involves comparing a hundred completely arbitrary models with results obtained by observation. “A subset of the best solutions is then selected, and they are combined with one another in order to obtain a new population of solutions. Then we start the operation all over again, each time selecting the best results, until we get the model that corresponds to reality.” His software package, released in 1995, has been used in hundreds of research projects and can also be applied to other disciplines, such as engineering.”

After working for 12 years at the prestigious National Centre for Atmospheric Research in Colorado, this graduate of the Department of Physics at Université de Montréal looks forward to his homecoming. You might say he was born under a lucky star.

Researcher: Paul Charbonneau
Telephone: (514) 343-2300
Funding : National Science and Engineering Research Council. Canada Foundation for Innovation.