Understanding Sunspots

Sunspots are dark patches that appear from time to time on the surface of the sun. Despite their distance from the Earth, they have a significant impact on daily life, influencing weather, disrupting air travel and even damaging orbiting satellites.  Scientists believe that if they could better model the processes that go on inside the sun it might be possible to predict the occurrence of sunspots, and so minimize the impact they can have on daily life.

Sunspots are understood to be regions of intense magnetic activity on the surface of the sun. Despite a darker appearance they actually put out more energy than the normal surface. This means that during periods of intense sunspot activity the Earth receives more solar energy than is typical, resulting in higher temperatures and changes in normal weather patterns. Sunspots can also throw out solar flares with more immediate impacts. A solar flare is a massive ejection of material from the sun that moves rapidly out into space. If directed towards Earth, a flare can disable satellites and even imperil aircraft flying over the poles.

Sunspot activity rises and falls over a cycle of about eleven years. Periods of intense sunspot activity are termed solar maxima and lulls are solar minima. The next maxima is due around the end of 2013, so sunspot activity should be increasing. However, the most recent solar minimum lasted much longer than is usual, and scientists are trying to get a better understanding of what controls this cycle.

Recent research suggests that sunspot activity is related to the way plasma (ionized gas) flows within the sun. Plasma tends to flow along the surface moving away from the equator and towards the north and south poles. Then it dives down deep inside and flows back towards the equator where it comes back to the surface. These “meridional plasma flows” as they are termed are thought to be the driving force for sunspot activity.

Computer modeling has shown that the speed with which these flows move influences the sun’s magnetic field, which in turn determines the level of sunspot activity. More specifically, it is thought that a weaker magnetic field corresponds to the solar minima, with field strength increasing as the sun approaches a maxima. However, there is disagreement in the scientific community as to the nature of the relationship between the speed of meridional plasma flow and the strength of the sun’s magnetic field.

The most recent research indicates that rapid flow early in a solar cycle (when moving from minimum to maximum,) followed by a slowing later in the cycle, corresponds to a weaker magnetic field. What’s causing intense debate among solar scientists is that this conflicts with previous work that suggested the exact opposite.

Such conflicts are not uncommon in science and are usually only resolved through further study. For now it is safe to say only that there appears to be a relationship between meridional plasma flows and sunspot activity. Research on this important issue will continue, and at some point in the future it may be possible to anticipate and prepare for the effects of sunspot activity. 

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