The Sun life and death

Our Sun has a magnetic field which is strong and changeable and which varies year by year reversing direction every 11 years or so.  Due to the fact that the Sun is made up of gas and plasma, it rotates faster at the equator than at the poles. This difference in the rotation means the magnetic field lines of the Sun can become mixed up and twisted resulting in the formation of several phenomena:

• Sunspots are dark spots on the Sun caused by the magnetic activity reducing convection and causing a fall in surface temperature.
• Solar flares are large explosions in the Sun’s atmosphere powered by the magnetic field of the Sun.
• A coronal mass ejection is a massive burst of solar wind, a stream of charged particles and radiation from the Sun.

All three phenomena increase during the active phase of the solar cycle which we are now entering. Indeed direct evidence of the changing of the solar cycle came on August 4, 2010, when significant auroras caused by a coronal mass ejection were seen in many areas of the planet.

Sunspots and flares do not directly affect the Earth; however coronal mass ejections could possibly have negative consequences for life on Earth. The radiation emitted by coronal mass ejections can cause long-lasting radiation storms in the Earth’s ionosphere, the uppermost part of the planet’s atmosphere, and trigger radio blackouts around the world. A particularly large coronal mass ejection could potentially destroy satellites and wreck power and communications grids around the globe for a sustained period of time.

If this were to happen our modern way of life, based on electricity and computer technology would be seriously affected. The evidence suggests that every 100 years there is a large coronal mass ejection and we are currently overdue with the last such event happening in 1859.

Such an event, however, may not cause any problems. Space-based satellites have a large tolerance margin to extreme conditions as it is difficult and costly to go into space to repair them. Our ground-based systems are probably more vulnerable but there are ways of protecting these systems being worked on and as some people point out there have been periods of increased solar activity before where our modern systems have had no problems.

There are also efforts underway to better predict and detect solar events giving us more warning of possible large events. The NASA Stereo (Solar TErrestrial RElations Observatory) has produced three-dimensional images of coronal mass ejections and other solar activity helping out understanding of the way the Sun behaves.

Inspec covers many of the aspects of solar physics discussed. Listed below are thesaurus terms and classification codes that would be useful when searching within this area.

Thesaurus Terms:

aerospace instrumentation, artificial satellites, astronomical telescopes, solar activity, solar atmosphere, solar flares, solar magnetism, solar prominences, solar rotation, solar wind, Sun and sunspots.

Classification Terms: