NASA has been actively monitoring a strange anomaly in Earth’s magnetic field for two years: a giant region of low magnetic intensity in the skies above the planet, stretching between South America and southwestern Africa. The South Atlantic Anomaly (SAA) is a developing phenomenon that has intrigued and concerned scientists for years, perhaps none more so than NASA researchers.
The vulnerability of satellites and spacecraft
Space agency satellites and spacecraft are particularly vulnerable to decreased magnetic field strength within the anomaly, and the resulting exposure to charged particles from the Sun. During these encounters, decreased magnetic field strength within the anomaly means that technological systems aboard the satellites can short-circuit and fail if hit by high-energy protons emanating from the Sun. These random hits can produce low-level failures, but they can also cause significant data loss or even permanent damage to key components, forcing satellite operators to routinely shut down spacecraft systems before they enter the anomaly zone.
Investigating the phenomenon
Mitigating these hazards in space is one reason NASA is tracking SAA; another is that the mystery of the anomaly represents a great opportunity to investigate a complex and difficult-to-understand phenomenon, and NASA’s extensive resources and research groups are exceptionally well-equipped to study the phenomenon.
The magnetic field is actually a superposition of fields from many current sources, as NASA Goddard Space Flight Center geophysicist Terry Sabaka explained in 2020. The main source is considered to be a mass of molten iron moving inside the core. outside of the Earth, thousands of kilometers underground. The movement of that mass generates electrical currents that create the Earth’s magnetic field, but not uniformly, it seems.
An enormous deposit of dense rock, located some 2,900 kilometers below the African continent, disturbs the generation of the field, resulting in the dramatic weakening effect, which is aided by the tilt of the planet’s magnetic axis. The SAA can be interpreted as a consequence of the weak dominance of the dipole field in the region. That is, a localized field with reversed polarity grows strongly in the SAA region, making the field strength very weak, weaker than that of the surrounding regions.
New research and discoveries
While there is still much that scientists do not fully understand about the anomaly and its implications, new insights are shedding light on this strange phenomenon. For example, a study led by NASA heliophysicist Ashley Greeley in 2016 revealed that the SAA is moving slowly in a northwesterly direction.
It’s not just moving, though, the phenomenon appears to be in the process of splitting in two, with researchers finding in 2020 that the SAA appeared to be splitting into two distinct cells, each representing a separate center of minimum magnetic intensity within the biggest anomaly. Evidence suggests that the anomaly is not a new occurrence, but rather a recurring magnetic event that may have affected Earth from about 11 million years ago.
The importance of continuous observation
Although the SAA is moving slowly, it is undergoing changes in its morphology, so it is important that we continue to observe it through continuous missions, as noted by Sabaka. This is what helps us make models and predictions.
The study of the South Atlantic Anomaly is not only important for the understanding of the Earth and its magnetic field, but also for the future of space exploration and colonization. Findings from this research can help improve the safety of satellites and spacecraft in low-Earth orbit, allowing science and technology to advance.