Northern lights phenomenon connected to Mesospheric ozone layer depletion, says study

In a development, recent studies have shown that the same phenomenon that causes aurorae, often referred to as northern lights or polar lights, is responsible for causing mesospheric ozone layer depletion. A group of scientists led by Prof. Yoshizumi Miyoshi from Nagoya University, Japan, have studied this phenomenon to understand the significance of the depletion in relation to global climate change. According to the study, scientists have found that the ozone layer depletion in the mesosphere could be occurring specifically during aurorae.

Study explains depletion in mesospheric ozone layer

The results of the study led by Prof. Yoshizumi Miyoshi are published in the journal Nature's Scientific Reports. According to this, electrons from the sun remain trapped in the Earth's magnetosphere i.ei; the region of the magnetic field around the Earth. Interactions between electrons and plasma waves could cause the trapped electrons to come up to the Earth's upper atmosphere (thermosphere). This very phenomenon, called electron precipitation, causes aurorae, which we enjoy watching from the Earth’s poles.

Now the recent study showed that the same phenomenon is responsible for local ozone layer depletion in the mesosphere (lower than thermosphere). This ozone layer depletion that could be occurring specifically during aurorae is adding to climate change. Although various scientists tried, none were able to fully understand how the electron precipitation is causing ozone depletion.

Prof. Miyoshi and the team, during a moderate geomagnetic storm over the Scandinavian Peninsula in 2017, changed the already existing narrative regarding the matter. The team studied observations at "pulsating aurorae" (PsA), a type of faint aurora through coordinated experiments 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.

Arase data studied by the team showed that the trapped electrons in the Earth's magnetosphere have a wide energy range and indicated the presence of chorus waves in regions of space. Computer simulations were then put to use, which showed that Arase had observed plasma waves causing precipitations of these electrons across the wide energy range. Meanwhile, analysis of EISCAT data showed that electrons, from a few keV (kilo electron volts) to MeV (mega electron volts), precipitate to cause PsA. These electrons were proven to carry enough energy to penetrate our atmosphere to lower than 100 km, up to the altitudes of the mesospheric ozone.

Further explaining the finding, Prof. Miyoshi said, "PsAs occur almost daily, are spread over large areas, and last for hours. Therefore, the ozone depletion from these events could be significant.". Stressing on the significance of these findings, Prof. Miyoshi added, "This is only a case study. Further statistical studies are needed to confirm how much ozone destruction occurs in the middle atmosphere because of electron precipitation. After all, the impact of this phenomenon on the climate could potentially impact modern life.".

IMAGE: UNSPLASH