Seasons of the Sun - Solar Cycyle

The Sun's magnetic poles reverse at solar maxima. Starting at the equator, a slow flow at the surface drags the magnetic field toward the poles. Conversely, sunspots first appear in the mid-latitudes and then congregate toward the equator later in the solar cycle.

The extra ultraviolet (UV) and X-ray radiation created by the magnetic field around sunspots causes the Earth's atmosphere to heat up and expand. This creates added drag in the area where satellites and the Space Shuttle orbit. This drag could slowly pull such spacecraft out of orbit earlier than expected.

The extra UV produced by sun spot activity also increases the amount of ozone in the Earth's upper atmosphere.

Although sunspots are cooler areas on the solar surface, the Sun is actually hotter when sunspots appear and cooler when they are absent. Scientists believe that a long period of solar inactivity may correspond with colder temperatures on Earth. From 1645 to 1715, astronomers observed very little solar activity. This time period coincides with an era known as the Little Ice Age, when rivers and lakes throughout Europe (and perhaps the world) froze.

Although there are good records of solar activity since the invention of the telescope in 1610, scientists have to look toward other sources to determine if there were even earlier periods of low solar activity. Because it is believed that sun spot activity correlates to the amount of Carbon 14 and Beryllium 10 in the environment, scientists can use ice core samples on Earth to determine solar activity levels.

"We can go back in time, before telescopes, by looking at ice core samples," says Hathaway. "Based on these samples, there appears to have been other, earlier sunspot minima."

In 1843, the amateur astronomer Heinrich Schwabe found that sunspots come and go in a predictable 11-year cycle. Ever since that announcement, many have tried to correlate the Sun's cycle with all sorts of events on Earth - some have even believed the Sun influences the stock market! Although there is no evidence that solar activity affects economic trends, by predicting what the Sun will do in the future we can better prepare for the many other impacts solar activity has for life on Earth.