NASA is actively monitoring a mysterious anomaly in Earth's magnetic field: a giant region of lower magnetic intensity that
stretches between South America and southwestern Africa.
This vast unfolding phenomenon, called
the South Atlantic Anomaly
intrigued and concerned scientists
for years, and perhaps none more so than NASA researchers.
Space agency satellites and spacecraft are particularly vulnerable to the strength of the
weakened magnetic field within the anomaly
and the resulting exposure to charged particles from the Sun.
Likened by NASA to a "dent" in Earth's magnetic field, or a kind of "bump in space," the South Atlantic Anomaly (SAA) generally does not
affect life on Earth
, but cannot be The same can be said of orbiting spacecraft (including the International Space Station), which pass directly through the anomaly as they circle the planet.
During these encounters, the reduced strength of the magnetic field within the anomaly means that technological systems aboard the satellites
and malfunction if hit by high-energy protons emanating from the Sun.
These random hits can usually only produce low-level failures, but they carry the risk of causing significant data loss, or even permanent damage to key components, threats that force satellite operators to routinely shut down spacecraft systems early
. before the spacecraft enters the anomaly zone.
Mitigating those 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 occurrence.
"The magnetic field is actually
a superposition of fields
from many current sources," explained geophysicist Terry Sabaka of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The primary source is believed to be
a swirling ocean of molten iron
within the Earth's outer core, thousands of miles below ground.
The movement of that mass generates electrical currents that create the Earth's magnetic field, but not necessarily uniformly, it seems.
A huge reservoir of dense rock called the African High Low Shear Rate Province, located some 2,900 kilometers below the African continent,
disturbs the field generation
, resulting in a dramatic weakening effect.
"The observed SAA can also be interpreted as
a consequence of weakening
dipole field dominance in the region," said NASA Goddard geophysicist and mathematician Weijia Kuang.
"More specifically, a localized field
with reversed polarity grows strong
in the SAA region, making the field strength very weak, weaker than that of the surrounding regions."
While there is much that scientists still do not fully understand about the anomaly and its implications
, new insights are
continually 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.
NASA Explores Earth's Magnetic 'Dent'
However, it is not just about moving.
Even more remarkable, the phenomenon appears to be in the process of splitting in two, and researchers in 2020 found that the SAA appeared
to be splitting into two distinct cells,
each representing a separate center of minimal magnetic intensity within the larger anomaly.
What that means for
the future of SAA remains unknown,
but in any case, there is evidence to suggest that the anomaly is not a new occurrence.
A study published in July 2020 suggested that the phenomenon
is not a freak event of recent times
, but rather a recurring magnetic event that may have affected Earth as far back as 11 million years.
If so, that could indicate that the South Atlantic Anomaly is not a trigger or precursor to the reversal of the entire planet's magnetic field, which is something that actually happens, if not over hundreds of thousands of years at a time
"Although the SAA is moving slowly,
it is undergoing some changes
in morphology, so it is also important that we continue to observe it through continuous missions," Sabaka concluded.
Source: Science Alert
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