Understanding the invisible but powerful particles in Earth’s radiation belts – sciencedaily


Tiny charged electrons and protons that can damage satellites and alter ozone have revealed some of their mysteries to scientists at the University of Otago.

In a study published in Geophysical research letters, the group looked at charged particles interacting with a type of radio wave called “EMIC” – a wave generated in Earth’s radiation belts (invisible rings of charged particles orbiting the Earth).

Lead author Dr Aaron Hendry of the Department of Physics says it’s important to understand how these waves affect the belts – which are filled with expensive and important satellites – and the Earth’s climate.

“Like the Earth’s atmosphere, the Earth’s magnetosphere – the region around the Earth where our magnetic field is stronger than that of the Sun – sometimes experiences strong ‘storms’ or periods of high activity. These storms can cause significant changes in the number of particles in radiation belts and can accelerate some of them to very high speeds, making them a danger to our satellites. It is very important for us to know the number of these particles and the speed at which they are moving, so that we can make sure that our satellites continue to operate.

“Activity within radiation belts can sometimes cause the orbits of these particles to change. If these changes bring the particles low enough to reach Earth’s upper atmosphere, they can strike the dense air, lose all of their energy, and fall out of orbit.

“EMIC waves are known to be able to induce these changes and cause particle loss from radiation belts. In addition to causing beautiful bright displays that we call auroras, this shower of particles can also cause complex chemical changes in the upper atmosphere. can in turn cause minor, but significant, changes in the amount of ozone in the atmosphere.

“Although these changes are small, understanding them is very important in order to fully understand how the chemistry of the atmosphere works, how it changes over time and its impact on the climate,” says Dr. Hendry.

For their latest study, the researchers used data from GPS satellites to see how many electrons EMIC waves can strike in Earth’s atmosphere.

A general rule of thumb in radiation belts is that at slower speeds you have a lot more electrons. So if the minimum speed of the EMIC wave interaction is lowered, there are many more electrons around to interact with the waves.

By examining data from satellites that monitor how many electrons are in radiation belts and how fast they go, the researchers were able to show that you can see the number of electrons in radiation belts decrease dramatically as the radiation belts decrease. EMIC waves are around the corner.

“Interestingly, we have also seen changes in the number of electrons at speeds significantly lower than the current ‘accepted’ minimum speed. This means that EMIC can affect a much larger number of electrons than we do. thought possible before. It is clear that we need to rethink how we model this interaction and its impact on radiation belts There are a lot of electrons in radiation belts, so being able to project enough of them into the atmosphere to make a noticeable change is quite remarkable.

“It showed that we need to take these EMIC waves into account when we think about how radiation belts change over time and how these changes in the radiation belt affect the climate on Earth.”

Dr Hendry says the impact of EMIC-driven electrons on atmospheric chemistry is currently not included in major climate models, which attempt to predict how Earth’s climate will change over time, so ensure that this process is understood and included in these models is very important.

“The changes are very small compared to things like the human impact on the climate, but we have to understand the big picture in order to fully understand how it all fits together.”

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