New research has revealed that the secrets of the Sun’s magnetic field, which has remained a mystery for four centuries, may be close to its surface.
The sun’s magnetic field is responsible for producing dark spots called sunspots, explosive solar flares, and even explosive eruptions called coronal mass ejections (CMEs). However, since astronomers began investigating the sun’s magnetic fields, their origin has not been determined. Now an international team of researchers may be closer to solving this 400-year-old mystery that baffled even Galileo Galilei.
The discovery means that sunspots and outbursts may be the product of a shallow magnetic field rather than a field originating deeper within the sun, as previously theorized. The team’s findings could help solar scientists better predict solar flares and geomagnetic storms that pose risks to Earth’s satellites, communications systems and energy infrastructure, while also providing a strange connection between the sun’s outer layers and what fuels black holes.
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The team behind this research used a NASA supercomputer to perform a series of complex calculations showing that the sun’s magnetic field is generated approximately 40,000 miles (64,000 kilometers) below the surface of the photosphere. This may seem incredibly deep, but the sun has a radius of approximately 433,000 miles (697,000 km), which means that magnetic fields are produced in the outer 10% of the sun’s superheated plasma.
“The features we see when we look at the sun, such as the corona, sunspots, and solar flares that many people saw during the last solar eclipse, are all related to the sun’s magnetic field,” said team member Keaton Burns, a research scientist. Massachusetts Institute of Technology (MIT) said in a statement. “We show that isolated perturbations near the Sun’s surface, away from deeper layers, can grow over time and potentially produce the magnetic structures we see.”
Sunspots are cool, dark spots on the sun’s surface that scientists think are caused by the interference of magnetic field lines. Solar scientists have found that the number of sunspots increases during the solar maximum period of the Sun’s 11-year solar cycle. Observations have shown that sunspots tend to be found closer to the sun’s equator rather than our star’s poles.
The solar dynamo is not that deep
The Sun produces its magnetic field through a physical process that scientists call the solar dynamo. Previous models of this dynamo suggested that it was operated in a turbulent and turbulent region of the sun called the convection zone. Here, the hot plasma moves away from the sun’s core, where most of its energy is produced, and carries heat and energy to the sun’s surface, the photosphere.
Once the energy is stored, the plasma cools and falls back, passing the next “batch” of heated plasma, which rises through the convection zone, which is about 124,000 miles (200,000 km) deep and accounts for about 30% of the sun’s volume. .
“One of the basic ideas of how to start a dynamo is that you need a region where there is a lot of plasma passing next to other plasma, and the shearing motion converts kinetic energy into magnetic energy,” Burns explained. “People thought that the sun’s magnetic field was created by movements at the bottom of the convection zone.”
Other teams of researchers have previously created three-dimensional simulations of the sun to model the flow of plasma through various layers of the sun and thereby determine where the magnetic field originates. The team argues that these simulations fail to determine the true origin of the solar dynamo because they fail to capture the true picture of how chaotic and turbulent the sun actually is.
Burns and his team took a different approach. Instead of modeling plasma flow through all layers of the sun’s interior, they focused on the stability of plasma at the solar surface. They wanted to determine whether changes in this surface region would be sufficient to initiate the solar dynamo.
How do the sun’s magnetic fields flow?
To start, Burns and his colleagues used a process called “helioseismology,” which measures trapped sound waves that ripple through the sun and cause oscillations on the solar surface called “starquakes” to determine the sun’s interior. This allowed them to determine the structure and flow of plasma just below the sun’s surface.
“If you take a video of a drum and watch how it vibrates in slow motion, you can calculate the shape and stiffness of the drum head from the vibration modes,” Burns said. “Similarly, we can use the vibrations we see at the sun’s surface to infer the average structure inside. These average fluxes kind of look like an onion, with different layers of plasma orbiting next to each other.”
Turning to Project Dedalus, a framework developed by Burns that can simulate fluid flows with high precision, the team looked at this flow of solar plasma and then saw if any small changes, or “perturbations,” could be introduced into the ordered structure. grows and causes solar dynamo.
Their algorithms discovered new patterns that can grow in the plasma flow and create a picture of actual solar activity. These patterns matched the positions of sunspots that astronomers had been seeing since 1612 and Galileo’s observations.
Sunspots are cool, dark spots on the sun’s surface that scientists think are caused by the interference of magnetic field lines. Solar scientists have found that the number of sunspots increases during the solar maximum period of the Sun’s 11-year solar cycle. Observations have shown that sunspots tend to be found closer to the sun’s equator rather than our star’s poles.
Project Dedalus simulations revealed that changes in plasma flows in the upper 5% to 10% of the sun are sufficient to create magnetic structures that could explain the observed sunspot activity. When they modeled deeper regions of our star as the source of magnetic fields, this caused sunspots to cluster at the sun’s poles rather than its equator, the opposite of what was actually seen by astronomers.
By taking a closer look at how plasma flows across the sun’s surface, Burns and his colleagues also found a surprising similarity to the immediate surroundings of black holes.
A strange connection between sun-fed black holes
When stars get too close to black holes, they can be destroyed by the massive gravitational forces that crush them horizontally and compress them vertically, turning them into “spaghetti” in an event called a tidal disruption event (TDE).
Moreover, in cases where a star orbits a black hole in a binary system and is very close to it, or its outer layers are “inflated”, the gravitational influence of the black hole can strip away the star’s material.
In both stellar cannibalization and less extreme cases where black holes are in regions of gas and dust, this superheated plasma has angular momentum (or spin) meaning it cannot fall into the black hole.
Instead, this plasma forms a flattened cloud around the black hole that gradually feeds into it and is subjected to tremendous frictional forces due to the black hole’s gravity, which heats it and causes it to glow. This ‘sheet’ of plasma is called an accretion disk. Accretion disks are turbulent and fuel black holes due to so-called “magnetorotational instability” in their plasma flows. This turbulence is created when magnetized Material near the edge of the accretion disk moves slower than material closer to the center.
Burns and his team think a similar phenomenon occurs in the sun’s magnetic field, and the first step in creating the sun’s magnetic field is this magneto-spinal instability in the sun’s outermost layers.
“I think this conclusion may be controversial,” Burns added. “Most of the community has focused on finding dynamo action deep within the sun. Now we show that there is a different mechanism that matches the observations better.”
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The team will now continue their research by examining surface magnetic field patterns and trying to determine whether they can form individual sunspots in their simulations and how they relate to the sun’s overall 11-year cycle.
“We know that the dynamo behaves like a giant clock with many complex interacting parts,” said team member and researcher Geoffrey Vasil from the University of Edinburgh. “But we don’t know most of the parts or how they fit together. This new idea of how the solar dynamo got started is crucial to understanding and predicting it.”
The team’s research was published in the journal Nature on Wednesday, May 22.