When magnetic fields move about in the vicinity of
a conductor such as a wire, an electric current is induced into the
conductor. This happens on a grand scale during geomagnetic storms.
Power companies transmit alternating current to their customers via
long transmission lines. The nearly direct currents induced in these
lines from geomagnetic storms are harmful to electrical transmission
equipment. On March 13, 1989, in Montreal, Quebec, 6 million people
were without commercial electric power for 9 hours as a result of
a huge geomagnetic storm. Some areas in the northeastern
U.S. and in Sweden also lost power. By receiving geomagnetic storm alerts and warnings, power companies can minimize damage and power outages.
The Sun is the heat engine that drives the circulation of our atmosphere. Although it has long been assumed to be a constant source of energy, recent measurements of this solar constant have shown that the base output of the Sun can have temporary decreases of up to one-half percent. Atmospheric scientists say that this variation is significant and that it can modify climate over time. Plant growth has been shown to vary over the 11-year sunspot and 22-year magnetic cycles of the Sun, as evidenced in tree-ring records.
While the solar cycle has been nearly regular during the last 300 years, there was a period of 70
years during the 17th and 18th centuries when very few sunspots were seen. This drop in sunspot number coincided with the timing of the Little Ice Age in Europe, implying a Sun-climate connection. Recently, a more direct link between climate and solar variability has been speculated. Stratospheric winds near the equator blow in different directions, depending on the time in the solar cycle. Studies are under way to determine how this wind reversal affects global circulation patterns and weather. During proton events, many more energetic particles reach the Earth’s middle atmosphere. There they cause molecular ionization, creating chemicals that destroy atmospheric ozone and allow increased amounts of harmful solar ultraviolet radiation to reach the surface of the Earth. A solar proton event in 1982 resulted in a temporary 70% decrease in ozone densities.
Possibly the most closely studied of the variable biological effects
of the Sun has been the
degradation of homing pigeons’ navigational abilities during geomagnetic storms. Pigeons and other migratory animals, such as dolphins and whales, have internal biological compasses composed of the mineral magnetite wrapped in bundles of nerve cells. While this probably is not their primarily method of navigation, there have been many pigeon race smashes during a geomagnetic storm. A smash is a term used when only a small percentage of birds return home from a release site. Because these losses have occurred during geomagnetic storms, pigeon handlers have learned to ask for geomagnetic alerts and warnings as an aid to scheduling races.
Better understanding and better forecasts are keys to providing better services. SWPC conducts research in solar-terrestrial physics, develops techniques for forecasting solar and geophysical disturbances, and provides real-time monitoring and forecasting of solar and geophysical events.
The SWPC is one of the nine National Centers for Environmental Prediction,
part of the NOAA National Weather Service.
