Space weather means the state of the space environment and is usually expressed in terms of the behaviour of energetic particles, as well as in changes in electric and magnetic fields. We are mostly interested in conditions in near-Earth space, though space weather is important throughout the solar system.
The significance of space weather lies in its potential impact on man-made technologies on Earth and in space, for example, on satellites and spacecraft, electricity power grids, pipelines, radio and telephone communications and on geophysical exploration. Space weather also has implications for manned space flight, both in Earth orbit and further out into space.
Space weather arises as a result of various dynamic, but relatively short-lived, phenomena produced by the Sun, which are carried in the solar wind and which may interact with the Earth's magnetosphere (see our on-line glossary for other common terms). Long-term changes, that is, changes over decades to centuries, also occur in the near-Earth space environment. These changes are due to long period variations in solar magnetic activity and in variations in the strength of the Earth's magnetic field. However, for the most part we are concerned only with those space weather 'events' that happen on time scales of minutes to a few days. The implications of long-term variations in the Sun's magnetic field, for example on possible connections with climate change, is still being actively discussed by scientists.
Dynamic solar-terrestrial events and interactions can be seen in ground-based geomagnetic observations, for example those made by BGS at our UK observatories. Fast, high amplitude variations in geomagnetic measurements caused by space weather are therefore sometimes described as posing a 'geomagnetic hazard'. Space weather effects and the associated geomagnetic hazard can be recognised in observatory records dating back over 150 years.
One of the more spectacular space weather events was the 13th March 1989 solar and geomagnetic 'super storm'. This event caused a widespread electricity blackout for over nine hours, and affected 6 million people, in the region of Canada covered by the Hydro-Quebec power grid. As a result of this event, power companies worldwide are now much more aware of the risk posed by geomagnetic storms.
In all these activities, accurate and reliable real time data can be very important and therefore some BGS data products, such as our estimate of the Ap geomagnetic index, are updated every few minutes.