Research explains why ozone layer in the mesosphere is depleting

The findings were published in Scientific Reports, which is published by the journal Nature

NEW DELHI Depletion of the mesospheric ozone layer is caused by the same process that generates aurorae, the beautiful curtains of green light visible from the Earth’s polar regions. Because this depletion might have ramifications for global climate change, it’s critical to comprehend it.

Prof. Yoshizumi Miyoshi of Nagoya University in Japan has headed a group of experts who have observed, analysed, and offered more understanding into this phenomenon.

The findings were published in Nature’s Scientific Reports journal.

Ozone layer depletion in mesosphere

Electrons from the sun are caught in the magnetosphere, which is the area of the magnetic field that surrounds the Earth. Electron-plasma wave interactions can allow trapped electrons to escape and reach the Earth’s upper atmosphere (thermosphere).

Aurorae are caused by a process known as electron precipitation. However, new research suggests that this is also responsible for local ozone layer depletion in the mesosphere (lower than the thermosphere), which might have an effect on our climate.

Furthermore, ozone depletion in the mesosphere may occur especially during aurorae. While scientists have examined electron precipitation in connection to aurorae, none have been able to fully explain how it leads to ozone depletion in the mesosphere.

The concept of ‘pulsating aurorae’ (PsA)

During a moderate geomagnetic storm over the Scandinavian Peninsula in 2017, Prof. Miyoshi and his colleagues used the chance to modify this perception.

They were looking for “pulsating aurorae” (PsA), which are a form of weak aurora.

Coordinated tests with the European Incoherent Scatter (EISCAT) radar (at an altitude between 60 and 120 km, where the PsA occurs), the Japanese spacecraft Arase, and the all-sky camera network allowed them to make their observations.

The trapped electrons in the Earth’s magnetosphere have a wide energy range, according to Arase data. Chorus waves, a form of electromagnetic plasma wave, were also detected in that region of space.

‘Electrons deplete ozone layer in mesosphere’

Computer models revealed that Arase had seen plasma waves causing these electrons to precipitate across a wide energy range, which is compatible with EISCAT findings in the Earth’s thermosphere.

Electrons with energies ranging from a few keV (kilo electron volts) to MeV (mega electron volts) precipitate to generate PsA, according to EISCAT data. These electrons have enough energy to enter our atmosphere to depths of less than 100 kilometres, up to a height of 60 kilometres, where mesospheric ozone is found.

In fact, simulations based on EISCAT data revealed that when these electrons enter the mesosphere, they promptly deplete the local ozone (by more than 10%).

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