SPACE WEATHER - MSSL SPACE PLASMA GROUP
The Changing Sun: X-ray images showing the sun changing from
solar maximum in 1991 (left) to solar minimum in 1995 (right). Courtesy
is space weather?
The Sun does not only emit heat and light. Every
second a million tonnes of hot plasma, electrons and ions, escape the Sun?s
gravity. This solar wind buffets any obstacles, including Earth?s magnetic
shield, but even this is leaky and lets electrons and ions through to cause
the aurora and problems for satellites. Without solar wind the Earth would
be like a bar magnet in space. With solar wind, the magnetic field is compressed
like a balloon on the Sun side and dragged out into an invisible comet-like
tail behind. Conditions depend on the 11-year solar activity cycle, the
27-day solar rotation and the interplanetary conditions. Near solar maximum,
as in 2000, there are more ?coronal mass? ejections from the Sun, tens
of billions of tonnes at a time, which disrupt the constant flow of the
solar wind. Also there are more flares which hurl faster particles Earthwards.
Space weather is about all these effects - and their influence on the Earth
and mankind?s technological systems.
The Sun Earth Connection: Huge eruptions from the sun, can send
billions of tonnes of plasma towards the Earth.
What are we doing about space weather?
group are active in several areas of the application of space plasma physics.
These include helping to define ESA's future space weather monitoring programme
as part of a contract led by satellite industry. In addition it has just
been announced that MSSL are starting two studies funded by the satellite
insurance industry, as part of the Tsunami initiative, to examine the effects
of space weather on satellites. The first involves the development of a
"black box" detector to be carried by future commercial satellites. This
will add much needed data to what are currently sparse records of the radiation
environment near the Earth. The second study will involve the categorisation
of the magnetospheric environment at times of satellite anomalies. This
will pave the way for early work on predicting periods that may be hazardous
We are studying the science
behind space weather in our main stream research, using data from Polar,
- and the exciting Cluster satellite quartet will reveal the underlying
small scale processes for the first time.
The Aurora: The visible sign that solar activity is affecting
Satellites in Danger: The GPS satellites orbit brings them through
the heart of the radiation belts, modelled in this figure.
Coming Our Way: The LASCO chronograph on the SOHO spacecraft
uses an occulting disc to from an artificial eclipse allowing the suns
atmosphere to be seen. (the white circle shows the size of the sun). The
coronal mass ejection seen here headed straight towards the Earth on June
6th 2000, causing a huge geomagnetic storm.
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