swax06/periodicity_of_sunspots

Periodicity of Sunspots

The sun is very slightly pulsating star (a star that alternately increases and decreases in size usually with corresponding changes in brightness). During contracting phase there are many sunspots and at the expanding phase accompanies few sunspots. The sun’s interior pressure sometimes upsets the equilibrium of its forces and is responsible for the periodic cycles of sunspots.

The mechanical cause of the periodicity of sunspots can be explained as –

· The sun is a slightly pulsating star.

· After the expansion phase, the sun begins to contract again.

· When it contracts, it gets smaller and denser thereby increasing its inner pressure.

· The interior is compressed and heated to the point where its outward pressure is greater to the weight of outer layers pressing it down.

· And because of greater outward pressure, the sun’s interior expands, forcing heated gas to the surface to cool off and spread out, and turn into dark sunspots.

This process keeps on going like simple harmonic motion and hence is periodic in nature. Sunspots are cold areas on the sun's surface, though "cold" is a relative term. Sunspots average around 5,000 to 7,500 degrees Fahrenheit (2,760 to 4150 degrees Celsius), in contrast to the areas surrounding them, which average around 9,900 degrees F (5,480 C).

This period of pulsation can be found using sunspot numbers recorded over several decades from a website on sunspot data (Sunspot Index & Long-term Solar Observations (SILSO)). I am using the 13-month smoothed monthly total sunspot number [1/1749 - now] data set to find periodicity of sunspots.