New insights into how matter behaves in the extreme conditions of the Sun’s atmosphere have been discovered by a team of Irish and French scientists.
They used large radio telescopes and ultraviolet cameras on a Nasa spacecraft to better understand the exotic "fourth state of matter" known as plasma.
It could hold the key to developing safe, clean and efficient nuclear-energy generators on Earth, according to researchers who are based in Trinity College Dublin (TCD) and Dublin Institute of Advanced Studies (DIAS) who led the project.
"Most of the matter we encounter in our everyday lives comes in the form of solid, liquid or gas, but the majority of the Universe is composed of plasma – a highly unstable and electrically charged fluid," explained Dr Eoin Carley, a researcher at TCD and DIAS; the Sun is also made up of this plasma.
Despite being the most common form of matter in the Universe, plasma remains a mystery, mainly due to its scarcity in natural conditions on Earth, which makes it difficult to study.
“Special laboratories on Earth recreate the extreme conditions of space for this purpose, but the Sun represents an all-natural laboratory to study how plasma behaves in conditions that are often too extreme for the manually constructed Earth-based laboratories,” added Dr Carley, who led the international collaboration.
The solar atmosphere is a hotbed of extreme activity, with plasma temperatures in excess of 1 million degrees and particles that travel close to light-speed. “The light-speed particles shine bright at radio wavelengths, so we’re able to monitor exactly how plasmas behave with large radio telescopes.”
The team worked closely with scientists at the Paris Observatory and availed of a radio telescope located at Nançay in central France. "We combined the radio observations with UV cameras on Nasa's space-based Solar Dynamics Observatory spacecraft to show that plasma on the Sun can often emit radio light that pulses like a light-house."
Nuclear fusion
This activity has been known about for decades, but the use of space and ground-based equipment allowed them to image the radio pulses for the first time and see exactly how plasmas become unstable in the solar atmosphere.
Studying the behaviour of plasmas on the Sun allows for a comparison of how they behave on Earth, where much effort is now under way to build “magnetic confinement fusion reactors” that are much safer, cleaner and more efficient than fission reactors currently used today.
Nuclear fusion is a different type of nuclear energy generation that fuses plasma atoms together, as opposed to breaking them apart like fission does, said Prof Peter Gallagher of DIAS, a collaborator on the project. "Fusion is more stable and safer, and it doesn't require highly radioactive fuel; in fact, much of the waste material from fusion is inert helium."
But nuclear fusion plasmas are highly unstable. As soon as the plasma starts generating energy, some natural process switches off the reaction; an inherent safety switch – fusion reactors cannot form runaway reactions. “It also means the plasma is difficult to maintain in a stable state for energy generation. By studying how plasmas become unstable on the Sun, we can learn about how to control them on Earth,” he said.
Dr Carley continues to work closely with his French colleagues, and hopes to soon study the same phenomena using both French instruments and a newly built radio telescope at Birr Castle.
“We’re already making progress with newly built radio telescopes, such as the Irish Low Frequency Array. [It] can be used to uncover new plasma physics on the Sun in far greater detail than before, teaching us about how matter behaves in both plasmas on the Sun, here on Earth and throughout the Universe in general.”
The research was funded by the Irish Research Council, while their latest findings have been published in Nature Communications.
