NASA supercomputer solves 400-year-old solar magnetic puzzle

Researchers, including a team from Northwestern University, have made a breakthrough in understanding the solar magnetic field, discovering that it originates closer to the surface than previously thought. This information could improve forecasts of solar storms, which pose risks to Earth’s technological infrastructure. Credit:

A new study reveals that the sun’s magnetic field originates closer to the surface, solving a 400-year-old mystery first probed by Galileo and improving prediction of solar storms.

An international team of researchers, including Northwestern University engineers, is moving closer to solving a 400-year-old solar mystery that even baffled famed astronomer Galileo Galilei.

Since first observing the Sun’s magnetic activity, astronomers have struggled to determine the origin of this process. Now, after running a series of complex calculations on a NASA supercomputer, researchers discovered that the magnetic field is generated about 20,000 miles below the surface of the sun.

This discovery contradicts previous theories, which suggest the phenomenon has deep origins – starting more than 130,000 miles below the sun’s surface.

The research was published May 22 in the journal Nature.

Not only does this new discovery help us better understand the dynamic processes of our sun, but it could also help scientists more accurately predict powerful solar storms. Although this month’s strong solar storms have provided magnificent, expansive views of the Northern Lights, similar storms can cause intense destruction, damaging satellites orbiting Earth, power grids and radio communications.

This illustration shows a representation of the sun’s magnetic fields in an image captured by NASA’s Solar Dynamics Observatory. The complex superposition of lines can teach scientists about how the sun’s magnetism changes in response to constant movement on and within the sun. Credit: NASA/SDO/AIA/LMSAL

“Understanding the origin of the solar magnetic field has been an open question since Galileo and is important for predicting future solar activity, such as flares that could hit Earth,” said Daniel Lecoanet, co-author of the study. “This work proposes a new hypothesis for how the solar magnetic field is generated, which better matches solar observations and, we hope, could be used to make better predictions of solar activity. »

An expert in astrophysical fluid dynamics, Lecoanet is an assistant professor of engineering sciences and applied mathematics at Northwestern’s McCormick School of Engineering and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics. Geoffrey Vasil, a professor of mathematics at the University of Edinburgh in Scotland, led the study.

A confusing story

For centuries, astronomers have studied the telltale signs of the Sun’s magnetic activity. Among them was Galileo, who made the first detailed observations of sunspots in 1612. Using early telescopes and even his naked eye, Galileo documented the changing dark spots caused by the sun’s ever-changing magnetic field .

Over the years, astronomers have made significant progress in understanding the origins of the solar dynamo – the physical process that generates the magnetic field – but limitations remain. Theories suggesting the dynamo has a deep origin, for example, predict solar features that astronomers have never observed, such as powerful magnetic fields at high latitudes.

This image from June 20, 2013 at 11:15 p.m. EDT shows the bright light of a solar flare on the left side of the sun and a flare of solar material passing through the sun’s atmosphere, called a prominence flare. Credit: NASA/Goddard/SDO

Missing pieces

To solve this puzzle, the research team developed new cutting-edge numerical simulations to model the sun’s magnetic field. Unlike previous models, the new model takes into account torsional oscillations, a cyclic model of how gas and plasma circulate in and around the sun. Because the Sun is not solid like the Earth and the Moon, it does not rotate as a single body. Instead, its rotation varies with latitude. Like the 11-year solar magnetic cycle, torsional oscillations also experience an 11-year cycle.

“As the wave has the same period as the magnetic cycle, we thought these phenomena were linked,” Lecoanet said. “However, the traditional ‘deep theory’ of the solar magnetic field does not explain where these torsional oscillations come from. An intriguing clue is that torsional oscillations only occur near the sun’s surface. Our hypothesis is that the magnetic cycle and the torsional oscillations are different manifestations of the same physical process.

When Kyle Augustson, a postdoctoral researcher in Lecoanet’s lab at Northwestern, performed the numerical simulations, the researchers found that their new model provided a quantitative explanation for the properties observed in the torsional oscillations. The model also explains how sunspots follow patterns in the sun’s magnetic activity – another detail missing from the deep origin theory.

Improve forecasting

With a better understanding of the solar dynamo, researchers hope to improve solar storm forecasts. When solar flares and coronal mass ejections launch toward Earth, they can severely damage electrical and telecommunications infrastructure, including GPS navigation tools. Recent solar storms this month, for example, destroyed agricultural equipment’s navigation systems, right at the height of the planting season.

But researchers view an even more powerful solar storm that hit Canada in September 1859 as a warning. Dubbed the Carrington Event, the intense storm damaged the country’s fledgling telegraph system. If given enough warning, engineers could take steps to prevent catastrophic damage in the future.

“Even though recent solar storms have been powerful, we are concerned about even more powerful storms like the Carrington event,” Lecoanet said. “If a storm of similar intensity hit the United States today, it would cause between $1 trillion and $2 trillion in damage. Although many aspects of solar dynamics remain shrouded in mystery, our work makes enormous progress in solving one of the oldest unsolved problems in theoretical physics and opens the way to better predictions of solar activity. dangerous solar energy.

To find out more about this research:

  • Astrophysicists rethink solar magnetic fields

The study was supported by NASA (grant numbers 80NSSC20K1280, 80NSSC22K1738, and 80NSSC22M0162). The calculations were performed with support from NASA’s High-End Computing program through the NASA Advanced Supercomputing (NAS) Division at the Ames Research Center.



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