Astrophysicists have pinpointed the origins of the sun’s magnetic field much closer to its surface than previously thought. This revelation could alter our understanding of solar activity and improve predictions of potentially disruptive solar storms, the most powerful of which could be so strong they could knock out power grids and even the entire internet.
For decades, astronomers believed that the sun’s magnetic field was generated deep within its core. That’s certainly the way it works for Earth’s magnetic field, which is produced by the motion of molten iron inside our planet’s core, like a planetary dynamo.
However, recent simulations suggest that the Sun’s magnetic field arises from instabilities in the plasma in the sun’s outer layers.
The Sun — which is essentially a massive ball of plasma — has a dynamic magnetic field created by swirling charged ions moving past each other. The Sun’s surface (which is a bit of a misnomer since it’s all plasma gas) is known as the convection zone. It extends from the outmost layer to roughly 124,000 miles (200,000 kilometers) beneath. For reference, the Sun’s radius is 432,000 miles (696,000 kilometers) Scientists used to think that the dynamo effect, deep within this zone, was responsible for the sun’s magnetism. But the new study challenges this view.
Researchers from MIT and Northwestern University developed a sophisticated computer model using data from helioseismology, which observes vibrations on the sun’s surface to determine the average structure and flow of plasma in the convection zone. Their results showed that the magnetic field most closely matches the behavior of plasma in the sun’s outermost layers, specifically within the top 5% to 10% of the surface.
Implications for Solar Forecasting
The implications of this discovery are significant. If confirmed, it could lead to better predictions of solar storms, which are known to cause power outages, disrupt communications, and damage satellites.
Keaton Burns, a research scientist at MIT, stated, “This result may be controversial. Most of the community has been focused on finding dynamo action deep in the sun. Now we’re showing there’s a different mechanism that seems to be a better match to observations.”
Sunspots, which appear as dark spots on the sun’s surface, are linked to these magnetic fields and are the starting points for solar flares and coronal mass ejections (CMEs). These events release massive amounts of energy and charged particles into space. When aimed at Earth, they can trigger geomagnetic storms that affect our technology. On the upside, they also produce spectacular auroras. The recent solar storm, which caused auroras as far south as Pennsylvania, Iowa, and Oregon in the US, or Germany in Europe, serves as a reminder of this constant threat, although disguised in a beautiful light show.
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Daniel Lecoanet, a co-author of the study from Northwestern University, highlighted the importance of these findings for understanding the 11-year solar cycle. “The previous models have not been able to make accurate forecasts of whether the next solar cycle will be strong or weak,” he said. The new model could provide more reliable predictions.
Future Prospects
The quest to understand the sun’s magnetic field dates back to Galileo Galilei, who first observed sunspots in the early 1600s. Galileo noted how these spots varied over time, laying the foundation for centuries of solar observation. Since then, scientists have developed increasingly sophisticated tools and models to study the sun, yet many mysteries remain.
By using helioseismology data and advanced computer simulations, researchers have now provided a more accurate depiction of how the sun’s magnetic field behaves. Previous models were often too simplistic and failed to capture the true complexity of the sun’s plasma dynamics.
To create their model, the researchers employed sophisticated algorithms to analyze surface vibrations on the sun. These algorithms simulated how changes in the flow of plasma across the sun’s top layers could produce the observed magnetic fields. When they incorporated possible effects from the sun’s deeper layers into their simulations, the results became muddled and did not match the observed magnetic field as closely.
The features we see when looking at the sun, like the corona that many people saw during the recent solar eclipse, sunspots, and solar flares, are all associated with the sun’s magnetic field,” Burns explained. “We show that isolated perturbations near the sun’s surface, far from the deeper layers, can grow over time to potentially produce the magnetic structures we see.”
Future research will focus on refining these models and testing their predictions against solar observations. For instance, Burns and colleagues plan to generate new simulations to see if they can replicate individual sunspots and even the full 11-year solar cycle through these new surface field patterns.
As solar activity peaks in its current cycle, this new understanding of the sun’s magnetic origins could be crucial in mitigating the impacts of solar storms on modern technology and infrastructure. Overall, the findings mark a significant step forward in our ongoing efforts to comprehend and predict the behavior of our closest star.
The findings appeared in the journal Nature.
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