The solar cycle (or solar magnetic activity cycle) is the periodic change in the sun's activity (levels of solar radiation, ejection of solar material, auroras) and appearance ( number of sunspots, flares, etc.). Solar cycles have an average duration of about 11 years. They have been observed by humans for thousands of years, and recorded reliably for about for 250 years.
Solar variation causes changes in space weather and to some degree weather and climate on Earth. It causes a periodic change in the amount of irradiation from the Sun that is experienced on Earth.The part of the solar cycle with low sunspot activity is referred to as "solar minimum" while the portion of the cycle with high activity is known as "solar maximum" or "solar max." We reached the solar minimum about 3 years ago, and sunspot activity has been slowly increasing since then.The most recent solar minimum, solar cycle 23-24 minimum, was unusually long (266 spotless days in 2008, the most since 1913)."A sunspot is simply a region on the surface of the sun that is temporarily cool and dark compared to surrounding regions. Solar measurements reveal that the average surface temperature of the sun is 6000° Celsius and that sunspots are about 1500° Celsius cooler than the area surrounding them (still very hot), and can last anywhere from a few hours to a few months. Sunspots expand and contract as they move across the surface of the sun and can be as large as 80, 000 km in diameter."The Sun goes through 11-year cycles (actually I've calculated the average since 1749 to be 11.15892 years, lest any of you get the idea that they are EXACTLY 11 years). They are not, and have varied from 7.7 to 12.9 years.The current predicted and observed size of the current Solar Cycle 24 is the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February of 1906. The max for this cycle is predicted to peak in about 2014.As you can see from the chart below, the biggest solar max in recorded history was Solar Cycle 19, which peaked in about 1958.
Don't count the sun out just yet. There still could be some X-flares coming our way. Even wimpy solar cycles can be unpredictable. Above charts by MP from raw data.
Above: Cycle 24 Sunspot Number Prediction.
