by New research has shown that the secrets of the sun’s magnetic field, shrouded in secrecy for four centuries, may lie close to its surface.
The sun’s magnetic field is responsible for generating dark patches called sunspots, erupting solar flares, and even explosive ejections of matter called coronal mass ejections (CMEs). But, ever since astronomers began investigating the sun’s magnetic fields, their point of origin remains uncertain. Now, an international team of researchers may be closer to solving the 400-year-old mystery that baffled even Galileo Galilei.
The discovery means that sunspots and flares are likely the product of a shallow magnetic field rather than one that originates deeper within the sun, as previously theorized. The team’s findings could help solar scientists better predict solar flares and geomagnetic storms that threaten Earth’s satellites, communications systems and power infrastructure while providing a curious link between the sun’s outer layers and holes to feed blacks.
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Using NASA’s supercomputer, the team behind this research performed a series of complex calculations that showed that the sun’s magnetic field is generated about 40,000 miles (64,000 kilometers) below the surface of its surface, the photosphere. This may seem extremely deep, but the radius of the sun is about 433,000 miles (697,000 km), which means that the magnetic fields are generated in the outer 10% of the superheated plasma of the sun.
“The features we see when we look at the sun, like the corona that many people saw during the recent solar eclipse, sunspots, and solar flares, are all related to the sun’s magnetic field,” team member Keaton Burns, a research scientist at the. Massachusetts Institute of Technology (MIT), said in a statement. “We show that remote perturbations near the surface of the sun, far from the deeper layers, can grow over time that could produce the magnetic structures we see.”
Sunspots are cool, dark patches on the sun’s surface that scientists think are created when magnetic field lines collide. Solar scientists have discovered an increase in the number of sunspots during the solar maximum period of the sun’s 11-year solar cycle. Observations have shown that sunspots are usually found closer to the sun’s equator rather than at the poles of our star.
The solar dynamic is not that deep
The sun generates its magnetic field through a physical process scientists call solar dynamics. Previous models of this dynamic have suggested that it begins in a turbulent region of the sun known as the convective zone. Here, hot plasma rises away from the sun’s core, where most of its energy is generated, carrying heat and energy to the sun’s surface, the photosphere.
After depositing the energy, the plasma cools and falls back through the convection zone, which has a depth of about 124,000 miles (200,000 km) and is about 30% of the Sun’s volume, over the first Another “batch” of heated plasma rising. .
“One of the basic ideas of how to start a dynamo is that you need a region where there is a lot of plasma moving over other plasma and that shear motion converts kinetic energy into magnetic energy,” Burns explained. “People thought that the solar magnetic field is created by the 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 throughout its various layers and thus determine where its magnetic field originates. The team argues that these simulations failed to find the true starting point of solar dynamics because they failed to capture the true picture of how chaotic and turbulent the sun really is.
Burns and his team took a different approach. Instead of modeling the plasma flow throughout all the layers in the interior of the sun, they focused on the stability of plasma at the surface of the sun. They wanted to determine if changes in this surface region would be enough to start solar dynamics.
How the sun’s magnetic fields go with the flow
To get started, Burns and his colleagues used a process called “helioseismology” that measures trapped sound waves as they rip through the sun and cause oscillations called “starquakes” at the sun’s surface to determine inside the sun. This allowed them to determine the structure and flow of plasma just below the surface of the sun.
“If you take a video of a drum and watch how it vibrates in slow motion, you can work out the shape of the drum and stiffness from the modes of vibration,” said Burns. “Similarly, we can use vibrations we see on the surface of the sun to infer the average structure in the interior. These average flows are like an onion, with different layers of plasma rotating over each other.”
The team turned to Project Dedalus, a framework developed by Burns that can simulate fluid flows with high accuracy, to look at this solar plasma flow and then see if any small changes or “perturbations” could be introduced into the possible regular structure. grow and cause the solar dynamo.
Their algorithm discovered new patterns in the plasma flow that can grow and create a picture of real solar activity. These patterns were consistent with the locations of sunspots that astronomers have seen since 1612 and with Galileo’s observations.
Sunspots are cool, dark patches on the sun’s surface that scientists think are created when magnetic field lines collide. Solar scientists have discovered an increase in the number of sunspots during the solar maximum period of the sun’s 11-year solar cycle. Observations have shown that sunspots are usually found closer to the sun’s equator rather than at the poles of our star.
Project Dedalus simulations showed that changes in plasma flows in the upper 5% to 10% of the sun were sufficient enough to generate magnetic structures that can account for observed sunspot activity. When they modeled deeper regions of our star as the source of the magnetic fields, this caused sunspots to converge at the sun’s poles rather than its equator, the opposite of what astronomers see.
Looking more closely at how plasma flows on the sun’s surface, Burns and his colleagues also found a surprising similarity to the immediate environments of black holes.
A strange connection between the sun and feeding black holes
When stars get too close to black holes, they can be destroyed by massive gravitational forces that squash them horizontally and push them vertically, “splashing” them in an event called a tidal disruption event (TDE). .
In addition, in cases where a black hole star orbits in a binary system and is too close, or its outer layers are “puffed out,” the black hole’s gravitational influence can remove stellar material.
In both stellar cannibalism and the less extreme cases of black holes in regions of gas and dust, this superheated plasma has angular momentum (or spin), which means it cannot collapse into the black hole.
Instead, this plasma forms a flattened cloud around the black hole that gradually feeds it and is subjected to enormous frictional forces due to the black hole’s gravity that heats it up, causing it to burn. This plasma plate is called an accretion disk. Accretion discs are turbulent and give birth to black holes due to a so-called “magnetic instability” in their plasma flow. This turbulence is created when it is magnetized material closer to the edge of an accretion disk moves more slowly than material closer to its center.
Burns and team think that a similar phenomenon is occurring in the sun’s magnetic field, and this magnetorotational instability in the sun’s outermost layers is the first step in generating the sun’s magnetic field.
“I think this result could be controversial,” Burns added. “Most of the community has focused on finding dynamo activity deep in the sun. Now we’re showing that there’s another mechanism that seems to better match observations.”
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The team will now continue their investigation by studying the surface magnetic field patterns and trying to see if they can create individual sunspots in their simulations and find out how they connect to the overall 11 year cycle of Sun.
“We know that the dynamo acts like a giant clock with many complex interacting parts,” said Geoffrey Vasil, a team member and researcher at the University of Edinburgh. “But we don’t know many of the pieces or how they fit together. This new idea of ​​how the solar dynamo starts is essential to understanding and predicting it.”
The team’s research was published on Wednesday (May 22) in the journal Nature.
