The geomagnetic field is generated by convective movements taking place in the Earth's core. This magnetic field envelops the Earth in a protective shield against cosmic rays, and in particular the fluxes of charged particles that are continuously projected by the Sun (solar winds). However, there is an area of weakness in this magnetic field, called the South Atlantic Anomaly (SAA), allowing solar particles to come very close to the planet in an area above South America. and the South Atlantic Ocean. So how do space agencies deal with this anomaly?
These particles can damage instruments in space. Space agency engineers therefore have no choice but to adapt to this "hiccup" of the magnetic field, by turning off the satellite instruments that pass through the SAA and accepting the loss of some data on the instruments at aboard the International Space Station (ISS). They also closely monitor the SAA.
“Even though the AAS is slow, it undergoes a change in morphology, so it is also important that we continue to observe it “, explains Terry Sabaka, geophysicist at NASA. Earth's magnetic field is the product of its iron-rich outer core, which creates the field as it swirls around the inner core. The field prevents the Earth's atmosphere from being slowly destroyed by the solar winds. It also protects electronic equipment on Earth from this same bombardment.
Normally, particles from the Sun are either deflected by the field or trapped in two areas called the Van Allen belts, which prevent particles from approaching within 644 kilometers of the Earth's surface. This provides plenty of space to protect the planet and its human-launched satellites. The ISS, for example, orbits about 350 km above the Earth's surface.
But the magnetic field is weakening, suggesting it may be about to reverse, swapping its north and south poles. Alternatively, it could go through a phase of weakness and then strengthen again, as has happened in the past.
Ground zero for this weakening appears to be the South Atlantic Anomaly, a strange place of particular weakness that stretches between South America and Africa. The area is changing, with recent research suggesting it is developing not one, but two separate anomalies.
Related topic:Earth's Magnetic Field; how does it withstand the most violent solar storms?
Satellites crossing the SAA must do so with many sensitive instruments turned off. When the ISS passes through it, some of the space station's instruments are vulnerable to magnetic bursts caused by solar particles. The Global Ecosystem Dynamics Investigation mission (GEDI), for example, experiences a power reset about once a month and loses a few hours of data each time. Fortunately, these events do not cause any damage to the GEDI, according to Bryan Blair.
Using data from SAMPEX (the Solar Anomalous and Magnetospheric Particle Explorer ), a satellite that was launched in 1992 and collected data until 2012, Goddard researchers learned that SAA is drifting slightly westward, findings published in the journal Space Weather in 2016. ESA launched a set of satellites known as Swarm in 2013 that provide detailed observations of the Earth's magnetic field and changes in the SAA.
It was data from the Swarm satellites that showed the development of two distinct points of minimum strength in the SAA, hinting that the anomaly could split into two distinct areas. Analyzing this data allows engineers to design their satellites to withstand the amount of solar radiation they are likely to encounter once in orbit. Researchers are also combining observational data with models of Earth's core dynamics to try to predict how the anomaly will evolve.
NASA video regarding SAA:
