2003-12-05 | SCIENCE
Cracks in Earth's Magnetic Shield

The Earth's magnetosphere typically protects life on the planet from solar radiation. However, according to new observations from NASA's IMAGE spacecraft and the joint NASA/European Space Agency (ESA) Cluster satellites, immense cracks sometimes develop in Earth's magnetosphere and remain open for hours. This allows the solar wind to gush through, sometimes causing problems with satellites, radio communications and power systems.

The solar wind is a fast-moving stream of electrically charged particles (electrons and ions) blown constantly from the Sun. The wind can get gusty during violent solar events, like coronal mass ejections (CMEs), which can shoot a billion tons of electrified gas into space at millions of miles per hour. Fortunately, these cracks don't expose Earth's surface to the solar wind. Our atmosphere protects us, even when our magnetic field doesn't. However, astronauts in space are particularly vulnerable to such radiation and must take extra measures to reduce the risk of exposure. Passengers on commercial jets can also be exposed to radiation levels equivalent to those of a medical chest x-ray during large solar storms.

Understanding the connections between the Sun and Earth are important for determining the habitability of other planets. For instance, the Earth's magnetosphere protects Earth life from the solar wind's harmful radiation. After Mars lost its magnetosphere, the solar wind may have blown away much of Mars' atmosphere. The presence of a magnetosphere might be one of the factors that make a planet habitable. This connection is also important for determining how the Sun's behavior could affect environmental changes on Earth. Finally, knowing how solar radiation affects humans and how humans respond to such effects is especially important in making spaceflight safe for today's missions as well as future missions to distant locations like Mars.

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