The sun’s magnetic field may originate near its surface, shows study


The sun’s surface is a mesmerizing display of sunspots and flares, all driven by its magnetic field.

Traditionally, scientists believed this magnetic field was generated deep within the sun through a process called dynamo action.

However, a recent study by researchers from MIT, the University of Edinburgh, and others suggests that this activity might actually stem from a much shallower process.

Published in Nature, the study reveals that the sun’s magnetic field could arise from instabilities within its outermost layers.

The research team created a detailed model of the sun’s surface and found that small changes in the flow of plasma (ionized gas) within the top 5 to 10 percent of the sun could generate realistic magnetic field patterns.

These patterns matched the sunspots and flares observed by astronomers. In contrast, simulations involving deeper layers produced less accurate results.

The sun’s outer layer, known as the “convection zone,” is where the plasma boils and flows.

This zone makes up the top one-third of the sun’s radius, extending about 200,000 kilometers below the surface.

Scientists have long believed that the sun’s magnetic field originates from the bottom of this convection zone.

However, this new study challenges that assumption.

The team used data from helioseismology, which studies vibrations on the sun’s surface to understand the structure and flow of plasma beneath it.

By observing these vibrations, scientists can infer the sun’s internal structure, similar to how studying a drum’s vibrations can reveal its shape and stiffness.

Using the Dedalus Project, a numerical framework developed by study author Keaton Burns, the team simulated the sun’s surface flows.

They discovered that small changes in the flow of plasma near the surface could grow and produce the magnetic structures observed on the sun. These findings suggest that the sun’s magnetic field may be generated by processes occurring in its outer layers, rather than deep within.

Sunspots, which appear as dark spots on the sun’s surface, are thought to be shaped by the sun’s magnetic field. These spots follow a cyclical pattern, growing and receding every 11 years and typically appearing near the sun’s equator.

The team’s simulations showed that surface-level changes could generate magnetic structures in the same regions and timescales as observed sunspots. In contrast, changes in deeper layers resulted in magnetic fields concentrated near the poles, which is inconsistent with observations.

This new perspective on the sun’s magnetic field generation could improve our ability to forecast solar flares and geomagnetic storms, which can damage satellites and communication systems.

Co-author Geoffrey Vasil from the University of Edinburgh emphasized the importance of understanding the solar dynamo: “This new idea of how the solar dynamo starts is essential to understanding and predicting it.”

The researchers are continuing to explore whether these surface field patterns can generate individual sunspots and the full 11-year solar cycle.

While this study provides a fresh and promising approach, it is not the final word on the subject. Steven Balbus, a professor of astronomy at Oxford University, praised the innovative approach and suggested it could lead to further discoveries.

Supported in part by NASA, this research opens up new possibilities for understanding the sun’s magnetic field and its impact on our solar system.