Sunspots

- Describe the appearance and explain the nature of sunspots
- Interpret data (for example a Butterfly Diagram) in order to describe the long-term latitude drift of sunspots, determine the length of the solar cycle and predict the year of the next solar maximum

Sunspots are areas on the photosphere of the Sun that are cooler than the surrounding area and so appear darker.

Typically they travel around the Sun's disc in groups roughly 1/3 of the surface from 40 north to 40 south of the Equator.

They consist of a central region called an umbra and a surrounding area called a penumbra. Note that these terms are similar to those used in the eclipse section but mean different things.

Temperatures of the umbra are typicaly 4,000k. The penumbra is usually around 5,600k.

Sunspots are caused by local changes in the Sun's magnetic field. When this field is stronger in one region, the convention abilities (the way heat rises) are diminished and so the hotter gases from below do not affect that region temporarily.Their duration may vary from several hours to months.

Typically they vary from a few thousand miles to 50,000km. Exceptionally large sunspots have been observed around 200,000km.

Solar Flares emanate from sunspots producing more solar particles.

The rotation of the Sun can be observed because of the movement of sunspots across its disc.

Sunspots are good evidence of a solar cycle which the Sun goes through every 11 years.

The more sunspots occur, the more heat the Sun produces and vice versa. More sunspots mean the Sun is active, less mean the Sun is quiet.

The next period of maximum activity will be in 2011/2012.

 

Animation New Window

Sunspot Cycle Animation Sunspots

Image New Window








Summary

Darker part of sunspot = Umbra
Lighter part of sunspot = Penumbra
Sunspot cycle = 11 years


Links New Window

Exploratorium Introduction to sunspots

Earth Observatory Sunspot information

Space Weather Up to date solar activity information including a sunspot number

Solar Max Sunspot Cycle Information

SOHO Sunspots

Questions

  • Why does a sunspot look darker than the rest of the Sun?
  • Describe the long term drift of sunspots.
  • Describe the sunspot Cycle.

Did you know?

A period of very low sunspot activity in the 17th century called the Maunder Minimum coincides with a cold period in northern Europe.