Sunspots - Sunspots are magnetic regions on the sun with magnetic field strengths thousands of times stronger than the Earth's magnetic field. Plasma flows in the sun's magnetic field lines and sunspots appear as dark spots on its surface. Temperatures in the dark centers of sunspots, the "umbra", drop to about 3700 K, compared to 5700 K for the surrounding photosphere. It's this difference in temperatures that makes the spots appear darker than elsewhere.      Sunspots usually form in groups containing two sets of spots. One set will have a positive or north magnetic field while the other set will have a negative or south magnetic field. The magnetic field is strongest in the darker parts of the sunspot; the field is weaker and more horizontal in the lighter part, the "penumbra". [Quoted from Tomas Hood NW7US, from Popular Communications, Nov. 2009, pp. 63-4] show images of sunspots

Sunspot Number - In 1848, the Swiss astronomer Johann Rudolph Wolf introduced a daily measurement of sunspot number. His method, which is still used today, counts the total number of spots visible on the face of the sun and the number of groups into which they cluster, because neither the quantity alone satisfactorily measures sunspot activity. 

     The sunspot number is calculated by first counting the number of sunspot groups and then the number of individual sunspots. The "sunspot number" is then given by the sum of the number of individual sunspots and ten times the number of groups. Since most sunspot groups have on average, about 10 spots, this formula for counting sunspots gives reliable numbers, even when the observing conditions are less than ideal and small spots are hard to see. 

     Because one observer may have difficulty in accurately counting the day's sunspot number (it might be a cloudy day, after all), observations are made at various locations around the world. In addition, images are taken by spacecraft far above our atmosphere. 

     To compensate for the many limitations of observing the sun at various places, each daily international number is computed as a weighted average of measurements made from a network of cooperating observatories. [Quoted from Tomas Hood NW7US, from Popular Communications, Nov. 2009, pp. 64-5]

Sunspot Cycles -  Since the time of Galileo Galilea, who made the first European observations of sunspots in 1610, observers and scientists have discovered a great deal about the sun and its influence on the Earth and our atmosphere. The Chinese and many other early civilizations were the first to discover sunspots. Daily sunspot observations were started at the Zurich Observatory n 1749, and by 1849 continuous sunspot observations were recorded. Over time, cycles in solar activity were revealed. The sun's sunspot activity has a cycle that lasts for an approximate 11-year period. The cycle starts with very quiet solar activity with very few sunspots, then peaks about three to five years later with a very high number of daily sunspots, and then decreases in sunspot activity until the end of the solar cycle. show image or link for current sunspot cycle

Solar Flares/ CME's (Coronal Mass Ejections) show image of solar flare

Explanation of SFI (Solar Flux Index), A & K indices