Dr Gareth Dorrian is a research fellow in the Space Environment and Radio Engineering (SERENE) group. His research looks at the small-scale fluctuations in the ionosphere, which impact satellite communication and navigation systems. In order to understand the ionosphere, he uses a network of radio telescopes all across Europe.

What is the ionosphere, and where is it?

The Earth’s atmosphere is layered, and the process of ionisation begins around 65 km in altitude. Solar UV radiation causes the gas in the atmosphere to separate into positive and negative charges, forming a region of plasma. The ionosphere varies by latitude - stronger ionisation occurs at the equator due to the increased UV and at the poles due to auroral activities.

Why do aurora appear in different colours?

When the sun emits a burst of radiation during a solar storm, the Earth’s magnetic field is compressed. This causes a buildup of a lot
of energy, so when particles are funnelled down the Earth’s magnetic poles, the gas is energised and causes ionisation. This plasma is not stable, and when it recombines, it releases energy in the form of light. The type of molecule it is determines the colour of light that is emitted.

What tools do we have to monitor the ionosphere?

The delay in the GPS signals from satellites
to the Earth is one method to measure the density of the plasma. But I work mostly with the Low Frequency Array (LOFAR), which consists of many astronomical radio tele- scopes spread all across Europe. They work together to make one big observatory. Unfor- tunately for the astronomers, but fortunately for us, the frequencies used to look into the depths of the universe are very sensitive to the ionosphere. It’s very sensitive to changes in the plasma density at scales we haven’t been able to observe before, which is really exciting.

Can we predict these changes?

Ionosphere research has been going on actively since the early 20th century. So we understand the basic structure and how it behaves at various scales quite well. But that doesn’t give us the ability to predict it. It’s a complex system with many interacting parts. The 2022 Tonga volcanic eruption caused such a powerful pressure wave that it propagated up into even the ionosphere.

How might the Ionosphere be affected by a big change in the Earth’s magnetic field?

We know from Venus and Mars that you can still have an ionosphere without a planetary magnetic field. However, the behaviour of the aurora will change. Without the magnetic poles funnelling the particles, the aurora will become diffuse and distributed globally. In the case of the magnetic poles flipping, there might be a weakening in the magnetic field, which would cause increases in radiation at higher altitudes and more auroras.