Ultimately, the sun drives our weather. Its uneven heating of the earth creates temperature differences, which trigger pressure differences that set the air in motion. So, indirectly, the sun prompts the wind to blow.

But there's also a very different category of wind that comes directly from the sun. While solar wind constantly bombards the earth, it isn't anything like the wind we know. Solar wind is a stream of high-energy particles ejected from the corona, the sun's extremely hot outer atmosphere. The solar wind streams from the sun in all directions, at varying intensities. It sometimes disrupts communications on earth and even presents a hazard to astronauts.

So the solar wind must be monitored, and one satellite doing this is called the Advanced Composition Explorer, or ACE. ACE sits about a million miles from Earth in the direction of the sun, and since the average speed of the solar wind is about 1 million mph, ACE can give about one hour's advance warning of potentially disruptive solar wind activity. You can get real-time information from ACE on the web at, appropriately, spaceweather.com.