Sunspots are large dark spots that appear on the sun’s surface due to reduced temperature in that area. They move across the surface of the sun and appear near the equator. High magnetic activity present temporarily in an area on the sun’s surface inhibits convective motion which reduces the temperature resulting in sunspots. The convective motion brings hot matter up from the interior of the sun forming areas of reduced temperature.
Sunspots expand and contract as they move. The sunspots have two main parts- the umbra and the penumbra. The center of the sunspot is called the umbra which is darker and the outer area is called penumbra which is lighter. The magnetic field in the sunspot is 2500 times stronger than the earth’s magnetic field. Sunspots increase and decrease through an average cycle of 11 years.
Sunspots were recorded in ancient China around 28 B.C. They were first observed with the telescope by the English astronomer Thomas Harriot and Frisian astronomer Johannes and David Fabricius. Galileo also reported and studied these sunspots.
There are many effects caused by sunspots on earth.
During 1645 – 1715, reduced sunspot activity was recorded. This period was also called as the ‘Little ice age’ as it was unusually cold on earth. This led to the speculation that the sunspot activity affected the earth’s temperature. This period of reduced solar activity was recorded by E.W Maunder and is now called as the Maunder Minimum.
Research is still being carried on to prove this because the earth’s climate is highly complex. Increased volcanic activity, burning of fossil fuels and cutting down forests also result in drastic temperature changes.
During high sunspot activity ultraviolet radiation increases which can effect on earth’s atmosphere.
Northern and southern lights
The magnetic field in the sunspot comes to the surface and expands beyond the surface. Plasma which is the hot matter interacts with this magnetic field, resulting in the burst of plasma outside the sun in flares, otherwise called the solar flare. These flares contain x-rays, energetic particles and magnetic fields which bombard the earth as geometric storms.
The geometric storms produce heightened spectacular display, which is the Northern and southern lights.
The geomagnetic storms also disrupt radio transmissions and power grids on the earth. Power surges are produced.
This storm also affects the satellites. They produce electric fields and when the satellites pass through these electric fields they change the polarity in satellites resulting in severe damage.
Studies are still going on learn about the effects of sunspots on the earth.