Figure. Monthly sunspot numbers for solar cycle 24 (the current one), cycle 23, and cycle 21, the last one with one, normal peak.
2013 was supposed to be the year of “solar maximum,” the peak of the 11-year sunspot cycle. Yet 2013 has arrived and solar activity is relatively low. Sunspot numbers are well below their values from 2011, and strong solar flares have been infrequent. The quiet has led some observers to wonder if forecasters missed the mark.
Every 11 years on average the sun reaches a peak period of activity called “Solar Maximum” or “Solar Max” which is followed 5-6 years later, by a period of relative quiet called “Solar Minimum”. During Solar Max, there are many sunspots, prominences, and solar storms (solar flares, and coronal mass ejections), all of which can affect communications and technology on Earth. During solar max there can be hundreds of sunspots, formed when magnetic field lines just below the Sun’s surface become twisted and poke through the Solar Photosphere.
The next animation shows the Earth-facing side of the Sun during a full solar rotation from February 1-28, 2013. Images were collected by the Helioseismic and Magnetic Imager (HMI) on NASA’s Solar Dynamics Observatory. HMI observes the solar disk at 6173 Ångstroms, a wavelength designed to study oscillations and the magnetic field. HMI observed just a few small sunspots on an otherwise clean face, which is usually riddled with many spots during peak solar activity.