NASA scientists believe sunspots form when the sun's magnetic pressure increases, whereas the surrounding atmospheric temperature decreases, due to the magnetic field suppressing hot gases. Strong magnetic points prevent hotter temperatures from reaching the sun's surface. Sunspots usually occur in pairs because the magnetic field points in opposite directions at that area of the sun. These phenomena last anywhere from days up to several weeks, according to Stanford University.
Sunspots are cooler regions of the sun's surface because hot gases are kept away. The average temperature in the middle of a sunspot is 6,300 degrees Fahrenheit, while the edges of the dark area reach 10,000 degrees Fahrenheit. NASA explains these regions are the size of Earth or larger.
Sunspots affect conditions on Earth because solar flares also occur near points of strong magnetic fields. Massive solar flares, called coronal mass ejections, interact with the Earth's magnetic field and cause the aurora borealis. These Northern or Southern Lights are geomagnetic storms that burn up in thinner layers of the atmosphere. NASA reveals solar flares disrupt global communications by interfering with satellite transmissions. Sunspots are also associated with increased ultraviolet radiation and tree ring growth.
Sunspots increase and decrease in 11-year cycles. This phenomena occurs as the sun's magnetic field, which is 2,500 times stronger than Earth's, moves across the sun in regular patterns. NASA states humans have observed sunspots since 1749, and scientists are currently watching the 24th sunspot cycle since that time.