Before I produced this story, I had little idea that the Sun was capable of so much dynamic activity, let alone that its celestial vicissitudes could reverberate through the heliosphere all the way to our planetary doorstep, 93 million miles away. This highly variable ‘space weather’, emanating from the sun, is carried along the solar wind, a fast-moving stream of solar radiation which constantly rains upon our planet's protective magnetic shield.
I was also surprised to learn how the Sun drives terrestrial weather, the kind that has us grabbing our sunglasses or an umbrella before leaving the house. While producing this story, I interviewed David Dempsey, a Professor of Meteorology at San Francisco University, who illuminated for me the role the Sun plays in this process. According to him, "we wouldn’t have anything we would call weather without the Sun. It shines directly on the lower latitudes of the Earth and less directly at the high latitudes, and that creates a big difference in temperature between the tropics and the polar regions. That difference in temperature in turn creates differences in pressure within the atmosphere that then drives winds. Wherever the air is, it goes up, it cools and you can get condensation of water vapor in the air and clouds form. Clouds then produce rain and they also reflect sunlight back to space, which then modifies the heating of the sun and you have a very complex system taking place across the globe we call weather."
Although weather forecasting has been the subject of much derision, huge strides have been made in weather forecasting, driven by a steady technological progress that has revolutionized the science of meteorology. As Professor Dempsey told me, "we’re probably in the 5 to 7 or even 8-day range as far as making forecasts that have some value to them. Forty years ago, it would have been just a couple of days. Improvements in satellites, in ground-based observations, have all contributed to our better understanding of the state of the atmosphere at any one moment." Take for example COSMIC, six satellites which launched in 2006 and which ingeniously use GPS signals from other satellites to discern the temperature and moisture content of the atmosphere over oceans, which traditional weather balloons, launched from land, can't provide.
Astrophysicists who track space weather today are at a stage Earth weather forecasters were roughly three decades ago when increased computing capabilities allowed them to amass more atmospheric data and analyze the data faster and more accurately. Moreover, with a powerful new tool within their toolkit in the form of NASA's Solar Dynamics Observatory, a satellite that provides a constant, ultra-high resolution view of the sun, the space weather trackers should be able to make more reliable and more detailed forecasts. Phil Scherrer, one of the Principal Investigators on the SDO mission, told me that a reasonable target to aim for is a space weather forecast that would be accurate for roughly a week, which is about what you can expect for a fairly accurate terrestrial weather forecast today.
Today, the stakes couldn't be higher for increased vigilance as our satellites arc through the atmosphere, which for all their state-of-the art ruggedized construction, are still vulnerable to the radiative slings and blows volleying from the Sun. As Professor Dempsey put it, "Solar storms can interfere with our ability to get the data we need, the observations we need, from weather satellites.That can be really critical if you have a hurricane developing off the coast of Florida and you need to know in advance whether you’re going to have all the data you need to try to make your best forecast of the impact of that hurricane. And if you know that you’re going to have an interruption in observations from satellites because of variations in solar output, then you can try to compensate and warn people about it."