Every 11 Years, the Sun's magnetic field reverses polarity, an event whose effects reach throughout the solar system, and is closely being monitored by solar physicists. While the internal mechanisms that drive the polarity shift are not entirely understood, scientists at Stanford's Solar Observatory have observed the Sun's magnetic field closely since the 1970's and can identify the initiation of the shift as it occurs on the surface of the Sun. This will be the fourth polarity shift the observatory has monitored.
Where does it come from? Well, new polarity, or the development of magnetic charge, builds up throughout the 11 year cycle as sunspots, cooler areas of the surface in which there is intense magnetic activity. These sunspots appear as dark spots near the equator of the Sun's surface; over the course of a month, the sunspot spreads and causes the magnetic field to migrate from the equator to one of the poles of the sun. As the magnetic field moves towards the pole, it erodes the existing opposite polarity, until the field reduces towards zero and rebounds with the opposite polarity. The process repetitively occurs with the sunspots until a full shift of polarity happens.
Not only is the activity noticeable by the increase in sunspots, but also a surge in solar activity, such as solar flares and emissions. These changes can interact with Earth's magnetic field, as well as extend beyond NASA's Voyager probes which remain near the edge of interstellar space. So we'll be watching closely as the poles switch.