By Mark Prigg
It is known as the ‘bermuda triangle of space’ and is one of the most dangerous areas of radiation ever encountered.
European researchers today revealed a glimpse into the bizarre radiation zone a few hundred kilometres above the coast of Brazil.
Known as the South Atlantic Anomaly (SAA), it is the point where the Van Allen radiation belts – rings of charged particles that surround Earth – come closest to the planet’s surface.
The South Atlantic Anomaly (SAA) is an area which exposes orbiting satellites to higher-than-usual levels of radiation.
WHAT IS THE SAA
This anomaly is part of a radiation belt, which is a ring of trapped solar radiation between 1000 and 6000 kilometres above the Earth’s surface.
This exists due to weak points in the planet’s magnetic field, with one of these weak points sitting right where the Bermuda Triangle of Space is located.
The South Atlantic Anomaly is of great significance to astronomical satellites and other spacecraft which orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation.
When the belts were discovered in the 1950s, scientists suspected the SAA could pose some risk.
Astronauts’ on the space shuttle complained laptop computers would sometimes crash when they passed through the anomaly.
Some spacecraft, such as the Hubble Space Telescope, are even programmed to switch off their delicate instruments as they fly through the area to avoid damage.
The International Space Station has also been given extra shielding to deal with this problem.
Astronauts are also affected by this region, which is said to be the cause of peculiar ‘shooting stars’ (phosphenes) seen in the visual field of astronauts.
Passing through the South Atlantic Anomaly is also thought to be the reason for the early failures of the Globalstar network’s satellites.
Image of the South Atlantic Anomaly (SAA) taken by the ROSAT satellite. Image reflects the SAA at approximately 560Km.
Riccardo Campana at the National Institute for Astrophysics in Bologna, Italy, has analysed radiation data from an X-ray-monitoring satellite called BeppoSAX, which was active from 1996 to 2003.
They found that radiation levels in the lower layer of the SAA were much less than in the upper layers.
They also saw that the anomaly is slowly moving westwards.
The team is now designing a space telescope that will orbit through the lower part of the danger zone, which is not well studied.
‘Most radiation models used in planning space missions are based on extrapolations from high-latitude, high-inclination observations,’ Campana told New Scientist.
‘Low-inclination, low altitude Earth orbits (LEO) are of increasing importance for astrophysical satellites, due to their low background environment, the team wrote.
‘We study the radiation environment in a LEO (500-600 km altitude, 4 degrees inclination) through the particle background measured by the Particle Monitor (PM) experiment onboard the BeppoSAX satellite, between 1996 and 2002.
‘The low-latitude SAA regions are found to have an intensity strongly decreasing with altitude and dependent on the magnetic rigidity. The SAA extent, westward drift and strength vs altitude is shown.’