What’s the common thing in all of our bucket lists? To travel to either of the Arctic or Antarctic circles, to look at the magnificent and dazzling Aurora borealis (northern lights) or Aurora australis (southern lights). Yet, unknown to most, these spectacular lighting displays in the polar sky are caused by the deflection of hazardous high energy cosmic rays by the Earth’s magnetic field.
With the ongoing SARS-CoV-2 outbreak across the world, we have experienced the Earth changing in bizarre ways. An unusually large ozone “hole” mysteriously “opened up” above the Arctic and “closed” itself in about a month. When people believed that things couldn’t get worse, the European Space Agency’s (ESA) Swarm constellation, has brought in some bad news regarding a “hole” in the magnetic field. The Swarm constellation consists of 3 satellites that collect data for the geophysical modelling of the Earth’s Magnetic field and help scientists study its interaction with other physical aspects of the Earth System. Although we have observed the Earth’s magnetic field gradually weakening over time, the satellites have probed that the weakest spots are expanding further. This change was observed in an area stretching from South America to Africa above the South Atlantic Ocean. Geophysicists across the world are using the data from ESA’s Swarm to understand better, this area known as the ‘South Atlantic Anomaly (SAA).’
The Earth’s Magnetic field is a dynamic field that is formed by the goings-on in the liquid outer core, which has molten iron at very high temperatures. The convection, coupled with the Earth’s rotation, allows the fluid to move with sufficient speed, creating the magnetic field in a self-excited dynamo-like mechanism. Apart from serving as the basis of navigation, it is essential for life to exist on Earth. It shields the Earth from the solar wind, a stream of energetic charged particles (plasma) that flows from the Sun’s corona at very high speeds (about 900 km/s) and temperatures (about 1 Million °C). A magnetic anomaly is an area where there is a weakness in the Earth’s magnetic field. In this zone, the Earth’s inner Van Allen radiation belt, a zone of energetic charged particles comes closest to the Earth’s surface almost into the atmosphere, thus increasing exposure.
Observations over the past 180 years by various monitoring organizations have shown that the magnetic north has drifted eastwards from the Canadian Arctic towards Siberia. What is surprising is that the rate of drifting has suddenly jumped from 0-15 Km/yr to 50-60 Km/yr during the '90s. It has also been observed that over the past 50 years from 1970 to 2020, the strength of the field over the South Atlantic has reduced from 24000 nT to 22000 nT. The area has grown significantly, and the anomaly minimum has drifted westwards at a considerable pace of 20 Km/yr. Further, scientists from the German Research Centre for Geosciences have observed the appearance of a new eastern anomaly minimum in the South Atlantic Anomaly over the past couple of decades. This minimum has experienced vigorous growth in the past 5 years, causing scientists to worry more.
Scientists have speculated that the weakening of this magnetic field might point out to the fact that the Earth is heading toward an imminent pole reversal. This is a phenomenon that generally occurs every 200,000 to 300,000 years, where the South and North magnetic poles switch places, the last one being the Brunhes–Matuyama reversal approximately 781,000 years ago. Although such an event is long past due, the observed magnitude of the dip in the magnetic field is well within the typical range of fluctuation. Scientists haven’t been able to solve the mysterious origin of this South Atlantic Anomaly yet. However, magnetic field observations by ESA’s Swarm constellation have provided exciting new insights into this poorly understood phenomenon.
The main concern regarding such a reversal event is that the magnetic field weakens drastically, increasing our exposure to harmful cosmic rays. Further, all the Earth-orbiting satellites depend on the Earth’s magnetic field for the protection of their electronic circuitry. Such an event would cause the burning of the electronics, and needless to say, wreak havoc on communication.
References:
https://phys.org/news/2020-05-swarm-probes-weakening-earth-magnetic.html
http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/3-what-is-solar-wind.html
https://www.esa.int/Applications/Observing_the_Earth/Swarm/Swarm_probes_weakening_of_Earth_s_magnetic_field
http://www.esa.int/Applications/Observing_the_Earth/Swarm/Magnetic_north_and_the_elongating_blob
Image references:
https://www.esa.int/Applications/Observing_the_Earth/Swarm/Swarm_probes_weakening_of_Earth_s_magnetic_field
http://www.esa.int/Applications/Observing_the_Earth/Swarm/Magnetic_north_and_the_elongating_blob