The Bermuda Triangle of space, also known as the South Atlantic Anomaly (SAA), is a geomagnetic intensity minimum where the inner Van Allen Belt dips dangerously close to the Earth’s surface.
As this area expands and moves westward, satellites and spacecraft are increasingly at risk from intense solar particle bombardment, resulting in catastrophic spacecraft hardware failures and ‘single-event upsets’ of onboard electronics. The SAA covers a geographic footprint extending from the Southern Cone of South America to the tip of Southern Africa. To mitigate these risks to sensitive instruments such as the Hubble Space Telescope, mission controllers have to power down sensitive instruments during transit through the SAA.
What is the Southern Atlantic Anomaly, the ‘Bermuda Triangle of space’, and why is it dangerous
In the Southern Atlantic Anomaly (SAA), the intensity of Earth’s magnetic field is much less than what is expected for the Earth. The data provided by NASA OSDR (Open Science Data Repository) shows that during SAA, there is a large amount of proton energy, which enables these particles to penetrate deeper into the atmosphere to altitudes as low as 200 kilometres. The high-energy particle events can flip memory bits within computers or induce destructive Single-Event Latch-ups (SELs); therefore, these events caused the failure of several missions, like the Japanese Hitomi satellite.
Currently, the SAA is being observed to have separated into two distinct lobes, thus making it more challenging to fly assets in Low Earth Orbit (LEO).
How the Southern Atlantic Anomaly affects astronauts and space telescopes
The International Space Station (ISS) has extensive shielding to protect astronauts against ionising radiation when they fly through SAA. According to a National Institute of Health (NIH) study, many astronauts experience radiation phosphenes when passing through SAA due to cosmic rays impacting their retinas.
Additionally, the Hubble Space Telescope cannot perform observations for 15 per cent of its orbit due to the required shutdown of HST detectors (overwhelmed by radiation noise) while in SAA.
Why the Southern Atlantic Anomaly is a natural part of Earth’s geodynamo
Geophysicists have examined paleomagnetic data in order to find historical trends of the South Atlantic Anomaly (SAA). This has led researchers to suggest that the SAA was created from a ‘Large Low-Shear Velocity Province’ deep within the African continent, which means there may be some correlation between the SAA and these geologically deep-seated structures at the core-mantle boundary that are having a direct effect on the flow patterns of liquid iron, thereby creating ‘reverse flux patches’ at the surface and providing a weaker magnetic field through these patches of reverse flux, according to research published by the University of Rochester.
Therefore, the SAA is likely not a developing anomaly but rather something that has previously existed as a part of the Earth’s geodynamo system.
How ESA’s swarm mission tracks the weakening field
As the SAA continues to drift westward at a rate of approximately 20 kilometres per year, the various space agencies are now required to develop enhanced radiation-hardening protection for future solid-state semiconductor electronic components. The European Space Agency (ESA) states that the current rate of growth for the anomaly is an excellent way to assess the declining dipole strength of the Earth’s magnetic dipole field.
This information may not indicate an imminent pole reversal; however, as conditions change (e.g., continue to evolve), it becomes critical for ESA (and other agencies) to monitor these changes continually. One way to accomplish this will be through missions such as Swarm (satellite constellation) to provide adequate levels of communication and navigation services.
