How the Suns 11 Year Solar Cycle Works

The Sun´s magnetic activity cycle takes place around a period of 11 years. The Sun´s magnetic field causes tremendous solar activity, including solar flares, sunspots and solar wind reaching the entire solar system. Every 11 years the Sun´s magnetic poles flip over, producing periods of great solar activity (solar maximum) followed by periods of least solar activity (solar minimum). The following outlines how the Sun´s 11-year solar cycle works.

The solar cycle takes approximately 11 years to go from one solar maximum to the next with an intermediate period of solar calmness; however, variations of 9-14 year cycles have been observed. During a solar maximum, the Sun´s activity increases with a quantitative number of sunspots on its surface, including solar flares blowing out into space and billions of tons of electrified gases blasted into space, as well.

The solar cycle has been observed since the invention of the telescope, and the cycle has been continuously observed at the Zurich observatory since 1849. The number of sunspots in the Sun is calculated by first counting the number of sunspot groups followed by the counting of individual sunspots. The sum of individual sunspots multiplied by the number of groups is the result of the total number of sunspots. Monthly updated averages of the number of sunspots on the Sun indicate that the number of sunspots increases and decreases with a fairly accurate 11-year cycle.

Early records show that the Sun has gone through periods of inactivity. The time period from 1645-1766 was a time during which very few sunspots were observed. His period is known as the Maunder minimum. Observations of the sizes, positions and numbers of sunspots have been obtained from the Royal Greenwich Observatory since 1874. A butterfly diagram shows how sunspots appear at mid-latitudes on either side of the equator, and eventually, displace toward the equator, signaling the beginning of a new cycle.

Sunspots may remain visible anywhere from a few days to a couple of months; however, they eventually fade away, releasing strong magnetic flux in the solar photosphere, generating the Sun´s magnetic field. The polarity of sunspots in one hemisphere is opposite to that of the sunspots of the other hemisphere, and the polarities interchange from one cycle to the next. The dipolar component of the Sun´s magnetic field reverses the polarity just about the time of the solar maximum.

Magnetic fields are stretched out and wrap around the Sun by the change in rotation rate (differential rotation). The Sun´s differential rotation can make a north-south oriented magnetic field wrap around the Sun in approximately 8 months. This twisting of the magnetic field lines is produced by the Sun´s rotation. The Sun rotates every 24 hours at the equator, and takes 35 days to rotate at the poles. The twist makes the magnetic field reverse from one sunspot cycle to the next.

The flow of material along meridian lines from the equator to the both sides of the poles through the surface and from both poles to the equator below the surface are thought to play an important role in the Sun´s magnetic dynamo. At the surface the flow is slow; however, below the surface, the flow is slower due to a higher density. This slow flow would transport material from the mid-latitudes to the poles in approximately 11 years, suggesting that the variations observed in the meridional circulation are the cause of variations in sunspot cycle.

The latest prediction for the Sun´s 11 year cycle 24 is a solar maximum of about 96 sunspots for late 2013.  We are over three years into cycle 24. One of the most reliable techniques for predicting the behavior of the Sun´s cycle is the one that utilizes the changes observed in the Earth´s magnetic field at and before sunspot minimum. These changes are known to be produced by solar storms.