Unveiling the Unexpected Role of Earth’s Geomagnetic Field

The importance of studying the Earth’s ionosphere, which is situated high within the atmosphere, is underscored by its influence on satellite operations, communication systems, and key atmospheric components such as the ozone layer.

Recently, a simulation-based study led by geophysicist Yuto Katoh from Tohoku University has provided new perspectives on the behavior of high-energy electrons.

This study has been published in the journal Earth, Planets, and Space.

Katoh asserts “Our results clarify the unexpected role of the geomagnetic field surrounding the Earth in protecting the atmosphere from high energy electrons.”

The ionosphere, a broad layer spanning from approximately 60 to over 600 kilometers above the Earth’s surface, is populated by a blend of ions and free electrons. These charged particles are produced through the interaction between the atmosphere and solar radiation.

In the ionosphere’s polar regions, an incessant and vigorous influx of electrons occurs, in a process known as electron precipitation. These ‘relativistic’ electrons, moving nearly at the speed of light, become significantly influenced by Einstein’s theory of relativity. As they collide with gas molecules, they induce various phenomena in the ionosphere, including the brilliant spectacle of auroras. The geomagnetic field notably impacts the behavior of these charged particles.

Katoh’s team, alongside colleagues from Germany and other Japanese institutions, developed a refined software code that zeroes in on the unexplored ‘mirror force’ effect on electron precipitation. This force arises from the magnetic influence on charged particles within the geomagnetic field.

The team’s simulations shed light on how the mirror force propels relativistic electrons back upward, an effect dependent on their arrival angles. This suggests that electron collisions with other charged particles occur higher in the ionosphere than previously assumed.

Illustrating an application of these findings, Katoh explains that “Precipitating electrons that manage to pass through the mirror force can reach the middle and lower atmosphere, contributing to chemical reactions related to variations in ozone levels.”

The decrease in ozone at the poles, a result of atmospheric pollution, compromises the protection ozone provides against harmful ultraviolet radiation.

The study’s key contribution lies in highlighting the unexpected importance of the geomagnetic field and the mirror force in safeguarding the lower atmosphere from electron precipitation by maintaining a distance.

Katoh states that a new project is underway to integrate the simulations utilized in this research with real observations of the polar ionosphere to foster a more comprehensive understanding of these vital geophysical processes.

Source: 10.1186/s40623-023-01871-y

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