New research from Ā鶹Ćā·Ń°ęĻĀŌŲBoulder could help scientists better understand the phenomena behind āsunspotsāĢż
The sun has long intrigued scientists. However, this sphere of super-heated plasmaāthe closest star to Earthāis also notoriously difficult to study, leaving many unanswered questions.
Now, researchers have one possible answer to a long-perplexing solar phenomenon called āthe convective conundrum.ā The findings, , offer a new window into the sunās mysterious inner workings and may have future implications for understanding space weather, which affects everything from satellites to the electrical grid.
At the top of the page:ĢżA corona mass ejection erupts from our sun on August 31, 2012. Photo by NASA. “”²ś“Ē±¹±š:ĢżKeith Julien
The sun has several distinct regions. One of them, the convective zone, spans roughly 200,000 kilometers (200 megameters) and makes up the outer 30% of the sun. Energy generated by nuclear fusion in the sunās core moves outward toward the surface. When it reaches the convective zone, the energy causes fluid to swirl in eddies and spirals called convective flows.
Scientists believed that the largest of these eddies should be about the same size as the convective zone itselfā200,000 kilometersāand began looking for these so-called āgiant cells.ā Despite searching for many years, though, researchers havenāt been able to observe convective flows that are this large, hence the conundrum.
āWhy are classic giant cells not observed? And why and how do observations seem to contradict numerical models?ā said Keith Julien, Ā鶹Ćā·Ń°ęĻĀŌŲ professor and department chair of applied mathematics and one of the studyās co-authors.
New research from University of Sydneyās Geoffrey Vasil (PhDAstroPhys/Atmosā08), Southwest Research Instituteās Nicholas Featherstone (PhDAstroPhysā10) and Julien suggests that the sunās rotation is more important than researchers previously thought. Strong rotation creates elongated, oval-shaped convective flows that are actually 30,000 kilometers (30 megameters) in size, not 200,000.Ģż
They made this theoretical prediction by drawing on multi-disciplinary equations and theories used in the fields of physics, mathematics, meteorology and oceanography.Ģż
āIn essence, there are no giant cells,ā said Julien. āThis long-held belief or hunt for them may have been a bit of a red herring. Rotation gives a different fluid flow structure, maxing out at these scales of 30 megameters.ā
These findings are significant because they offer a solution to a scientific problem thatās existed for decades, Julien said.Ģż
But beyond that, learning more about the sunās convection zone may help scientists better understand the sunās magnetic field, a phenomenon called the global solar dynamo.Ģż
āThe sunās global dynamo magnetic field is responsible for space weather, and thatās a really big deal,ā said Julien. āWe wonāt be able to say much about space weather without understanding more about how the dynamo works.ā
The sunās magnetic field is of particular interest to researchers, governments and companies because it affects the drag on satellites and the International Space Station.Ģż
It also has the potential to cause catastrophic damage. The sunās magnetic fields emerge onto its surface in the form of sunspots, which sometimes erupt and fling radioactive plasma at Earth.
The sunās global dynamo magnetic field is responsible for space weather, and thatās a really big deal."
āA big solar event could easily wipe out $10 trillion of global infrastructure in a matter of days,ā said Vasil. āAnd we would only have a few hours to do something about it. It could make the pandemic that currently has a stranglehold on the globe look small by comparison. A big solar event could mean no communication or electricity globally. It's a huge risk, and almost no one knows about it.ā
These findings donāt directly answer our questions about the sunās magnetic field, but they are an important step in the journey to understanding the global solar dynamo that other researchers can build upon.Ģż
In the near term, these findings offer a new constraint for researchers doing numerical simulations of the sun, who can now better understand the challenges for simulating rotation.
āUp to this point, dynamo models havenāt taken rotation properly into account,ā said Vasil.
The researchers hope that they or other scientists can confirm their predictions mathematically and eventually actually observe the convective flows in the sun.Ģż
āFor many reasons, it's difficult to measure the kinds of flows we predict in the interior,ā said Vasil. āPart of the reason is there is a lot of noise at the surface that happens to be roughly the same size as what we expect deeper down. We believe this is only a coincidence. But it means observers are going to need much more data to see what's going on.āĢż
More broadly, the findings get us one step closer to demystifying the sun, which sustains our existence and holds many clues about the evolution of the universe itself.
āThe sun is the giver of life, but it also has many curiosities as well,ā said Julien. āOur universe is built up of stars, and we know that stars are also associated with planetary systems, so understanding our nearest planetary system and our nearest star is quite important from a general scientific perspectiveāWhere do we come from? How did we get here?āĢż
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