麻豆影院

New research from CU 麻豆影院 could help scientists better understand the phenomena behind 鈥榮unspots鈥櫶�

The sun has long intrigued scientists. However, this sphere of super-heated plasma鈥攖he closest star to Earth鈥攊s also notoriously difficult to study, leaving many unanswered questions.

Now, researchers have one possible answer to a long-perplexing solar phenomenon called 鈥渢he convective conundrum.鈥� The findings, , offer a new window into the sun鈥檚 mysterious inner workings and may have future implications for understanding space weather, which affects everything from satellites to the electrical grid.

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 sun鈥檚 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 itself鈥�200,000 kilometers鈥攁nd began looking for these so-called 鈥済iant cells.鈥� Despite searching for many years, though, researchers haven鈥檛 been able to observe convective flows that are this large, hence the conundrum.

鈥淲hy are classic giant cells not observed? And why and how do observations seem to contradict numerical models?鈥� said Keith Julien, 麻豆影院 professor and department chair of applied mathematics and one of the study鈥檚 co-authors.

New research from University of Sydney鈥檚 Geoffrey Vasil (PhDAstroPhys/Atmos鈥�08), Southwest Research Institute鈥檚 Nicholas Featherstone (PhDAstroPhys鈥�10) and Julien suggests that the sun鈥檚 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.听

They made this theoretical prediction by drawing on multi-disciplinary equations and theories used in the fields of physics, mathematics, meteorology and oceanography.听

鈥淚n essence, there are no giant cells,鈥� said Julien. 鈥淭his 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.鈥�

These findings are significant because they offer a solution to a scientific problem that鈥檚 existed for decades, Julien said.听

But beyond that, learning more about the sun鈥檚 convection zone may help scientists better understand the sun鈥檚 magnetic field, a phenomenon called the global solar dynamo.听

鈥淭he sun鈥檚 global dynamo magnetic field is responsible for space weather, and that鈥檚 a really big deal,鈥� said Julien. 鈥淲e won鈥檛 be able to say much about space weather without understanding more about how the dynamo works.鈥�

The sun鈥檚 magnetic field is of particular interest to researchers, governments and companies because it affects the drag on satellites and the International Space Station.听

It also has the potential to cause catastrophic damage. The sun鈥檚 magnetic fields emerge onto its surface in the form of sunspots, which sometimes erupt and fling radioactive plasma at Earth.

鈥淎 big solar event could easily wipe out $10 trillion of global infrastructure in a matter of days,鈥� said Vasil. 鈥淎nd 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.鈥�

These findings don鈥檛 directly answer our questions about the sun鈥檚 magnetic field, but they are an important step in the journey to understanding the global solar dynamo that other researchers can build upon.听

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.

鈥淯p to this point, dynamo models haven鈥檛 taken rotation properly into account,鈥� 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.听

鈥淔or many reasons, it's difficult to measure the kinds of flows we predict in the interior,鈥� said Vasil. 鈥淧art 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.鈥澨�

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.

鈥淭he sun is the giver of life, but it also has many curiosities as well,鈥� said Julien. 鈥淥ur 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 perspective鈥擶here do we come from? How did we get here?鈥澨�