WEAKENING OF EARTH’S MAGNETIC FIELD

Context:

The Earth’s magnetic field is weakening between Africa and South America, causing issues for satellites and space craft.

Latest Observations

  • Using data gathered by the European Space Agency’s (ESA) Swarm constellation of satellites, researchers noted that the area of the anomaly dropped in strength by more than 8 per cent between 1970 and 2020.
  • Swarm satellites are designed to identify and precisely measure the different magnetic signals that makeup Earth’s magnetic field.
  • Between 1970 and 2020, the magnetic field of Earth has weakened considerably in the region stretching from Africa to South America, which is known as the ‘South Atlantic Anomaly’. This area has grown and moved westwards at a rate of around 20 km per year.
  • The North Magnetic Pole of the Earth has also shifted in recent years away from Canada at the rate of 50-60 km per year towards Siberia in Russia. The pole will continue to move towards Russia but will in time begin to slow, scientists say.

South Atlantic Anomaly (SAA)

The South Atlantic Anomaly (SAA) is an area where the Earth’s inner Van Allen radiation belt comes closest to the Earth’s surface, dipping down to an altitude of 200 kilometres (120 mi). This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.

  • The effect is caused by the non-concentricity of the Earth and its magnetic dipole.
  • The SAA is the near-Earth region where the Earth’s magnetic field is weakest relative to an idealized Earth-centered dipole field.
  • The area of the SAA is confined by the intensity of Earth’s magnetic field at less than 32,000 nanotesla at sea level, which corresponds to the dipolar magnetic field at ionospheric altitudes.
  • Over the past five years a second centre of minimum intensity has developed southwest of Africa, which researchers believe indicates the anomaly could split into two separate cells.
  • The South Atlantic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude as it causes issues with satellites orbiting Earth and spacecrafts flying in the area could also experience “technical malfunctions”.
  • The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem.
  • Astronauts are also affected by this region, which is said to be the cause of peculiar “shooting stars” (phosphenes) seen in the visual field of astronauts, an effect termed the cosmic ray visual phenomena.

Magnetic field of Earth

Earth’s magnetic field, or the geomagnetic field, is the magnetic field that extends from the Earth’s interior out into space exerting a force on the charged particles emanating from the Sun.

  • The magnetic field of the Earth is due to the metallic and liquid outer core of the planet, around 3,000 km below our feet.
  • It creates electric currents that generate and change our electromagnetic field. The outer core of the planet is like a giant dynamo.
  • The rotation of the Earth creates movements inside the liquid outer core which gives rise to the geomagnetic field.
  • Other sources of magnetism come from minerals in Earth’s mantle and crust, while the ionosphere, magnetosphere and oceans also play a role.
  • A Magnetosphere is that area of space, around a planet, that is controlled by the planet’s magnetic field.
  • The shape of the Earth’s magnetosphere is the direct result of being blasted by solar wind.
  • The solar wind compresses its sunward side to a distance of only 6 to 10 times the radius of the Earth. A supersonic shock wave is created sunward of Earth called the Bow Shock.
  • Most of the solar wind particles are heated and slowed at the bow shock and detour around the Earth in the

Significance of Earth’s Magnetic Field

Earth’s magnetic field is essential to life on our planet.

  • Protection: The Earth’s magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. This also protects our satellites from harmful solar winds.
  • Aurora borealis: The Northern Lights in the Polar Regions are also caused by the magnetic field of Earth – the energy particles emitted by the Sun are channeled by the Earth’s magnetic field towards the poles, where they interact with the atmosphere to create the aurora borealis.
  • Navigation: A compass works the way it does because of the Earth’s magnetic field.
  • Directional drilling: A specialist form of navigation is directional drilling in the petroleum industry which makes use of magnetic tools to identify oil fields.
  • Exploration geophysics: Magnetic field, usually total intensity, traverses and surveys over an area can aid understanding of the underlying geology and in the case of iron ore deposits, can indicate very clearly their locations.

Why is the magnetic field weakening?

Swarm constellation of satellites of the European Space Agency, which identify and measure the different magnetic signals that constitute Earth’s magnetic field, is studying the development of South Atlantic Anomaly. The challenge that lies ahead is to study the reason behind the change.

  • A team from Leeds University said the drift of the North Pole is explained by the competition of two magnetic “blobs” on the edge of the Earth’s outer core. Changes in the flow of molten material in the Earth’s interior have changed the strength of the negative magnetic flux.
  • This is why the North Pole has left its historic position over the Canadian Arctic and crossed over the International Date Line.
  • Another possible reason, as per the ESA, according to the ESA, is that the weakening field is a sign that the Earth’s magnetic field is about to reverse, whereby the North Pole and South Pole switch places.
  • Such geomagnetic reversals happen roughly every 2, 50,000 years and given the last one took place 7,80,000 years ago, it was long overdue.
  • The repercussions of such an event could be significant, as the Earth’s magnetic field plays an important role in protecting the planet from solar winds and harmful cosmic radiation.
  • However, a study published in the scientific journal Proceedings of the National Academy of Sciences in 2018 found that despite the weakening field, “Earth’s magnetic field is probably not reversing”.

Effects of weakening of Earth’s magnetic field

  • The magnetic field of Earth protects the life of Earth from the harmful cosmic radiation and charged particles emitted from the Sun.
  • Birds, turtles and other creatures also use the magnetic field of Earth to navigate.
  • The telecommunication and satellite systems also rely on the geomagnetic field.
  • Therefore, computers, mobile phones and other devices could also face difficulties.
  • South in the compass could point to Canada and North to Antarctica. The navigation systems and mapping functions in smartphones may be affected.
  • Between Africa and South America, the weakening of the Earth’s magnetic field is causing issues for satellites and spacecraft. Satellites and other spacecraft flying through the area usually experience technical malfunctions due to a weak magnetic field. Thus, charged particles can penetrate the altitudes of low-Earth orbit satellites.
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