Why the sun's magnetic field is still a mystery

Scientists know a lot about the sun, but the forces behind the star's magnetic field remain a mystery.

First Look

A new model from NASA shows the strange, swirling lines of plasma being shot around the sun’s magnetic field. 

The images and videos are hypnotizing, showing superhot plasma looping and twirling around the giant star. The plasma lines, also called coronal loops, reach from the sun’s interior to the solar atmosphere, or the corona.  

And while scientists know the sun’s magnetic field exists, they are still clueless as to what drives the sun’s magnetic field. 

“We’re not sure exactly where in the sun the magnetic field is created,” Dean Pesnell, a space scientist at NASA’s Goddard Space Flight Center in Maryland, says in a press release. “It could be close to the solar surface or deep inside the sun – or over a wide range of depths.” 

And scientists are racing to understand the sun’s magnetic field because they do know that the magnetism is responsible for triggering plasma flows and coronal mass ejections, which can affect astronauts in space and even people on Earth.

“Getting a handle on what drives that magnetic system is crucial for understanding the nature of space throughout the solar system: The sun’s magnetic field is responsible for everything from the solar explosions that cause space weather on Earth – such as auroras – to the interplanetary magnetic field and radiation through which our spacecraft journeying around the solar system must travel,” says NASA in a press release. 

These side effects of magnetism are important to understand because they can damage radio signals among space satellites, causing power blackouts on the ground. 

Such a solar explosion happened on March 13, 1989, which caused a province-wide electrical blackout in Quebec, Canada. On March 10, magnetic forces on the sun released a storm cloud of gas that came rushing toward Earth at a million miles per hour. When the electric gas cloud struck Earth’s magnetic field, it created electrical currents underground, taking down Quebec’s power grid. 

But despite the potential powerful impacts from the sun’s magnetic field, scientists are still confused about the Earth’s host star.

“To understand the hows and whys behind the solar cycle, the energetic processes that drive powerful flares in the corona and their impacts on Earth, we must understand how the sun’s magnetism is generated in the first place,” Discovery News explains. “And as it turns out, our knowledge in this area is a little sketchy.”

And to further complicate scientists’ studies, the magnetic field is constantly changing. 

Scientists have recognized an 11-year cycle of the sun’s behavior. Pressure and chaos slowly builds within the sun’s interior over an 11-year period, with the end of the cycle – called a solar maximum – witnessing the most activity. Solar maximums include the greatest number of solar flares and eruptions.  

“At solar maximum, the magnetic field has a very complicated shape with lots of small structures throughout – these are the active regions we see,” said Dr. Pesnell. “At solar minimum, the field is weaker and concentrated at the poles. It’s a very smooth structure that doesn’t form sunspots.”

Understanding the sun's magnetic field at the solar maximum is especially important, say scientists, because these years render the powerful solar flares that can trigger Quebec-like blackouts.