The sun’s magnetic cycles last 22 years. For the first half, the magnetic north end is located in the sun’s northern hemisphere with the magnetic south in the southern hemisphere, as would seem to make sense. At the 11 year mark, however, the sun’s magnetic orientation flips, leaving the magnetic north in the southern hemisphere and vice versa; this is known as a Solar Cycle. At the end of that 11 years, the sun “flips” back and marks the beginning of the next magnetic cycle. NASA has released a video giving a visual representation of this phenomenon.
Recently, the sun reached the midpoint of Solar Cycle 24 and the magnetic north pole shifted into the southern hemisphere. Aside from the predictable time scale of the event, astronomers knew the flip was about to happen due to an increase in solar activity in the form of sunspots, coronal mass ejections, and flares. Magnetic fields in the sun’s atmosphere trap hot gas, and leading up to a magnetic flip, these pockets are released and result in huge bursts, called coronal mass ejections (CMEs). When this solar activity peaks, known as the solar maximum, the magnetic orientation flips. Once the magnetic north returns to the northern hemisphere, the former solar cycle ends and the next one begins.
Though sunspots had been observed since prehistoric time, they had not been investigated with a telescope until 1610 by Thomas Harriot. Regular investigation of the sunspots began in the 18th century, with the first recorded solar cycle beginning in March of 1755. Though the cycles are roughly 11 years, the shortest cycle lasted only 9 years and the longest lasted 14 years.
This video shows the magnetic orientation of the sun, with the green denoting the magnetic north and purple representing the magnetic south. The video begins in the spring of 1997, and shows the beginning of Solar Cycle 24 in 2002. The video ends in October of 2013, just before the orientation flipped.