A hot mess: mathematically mapping the Sun's magnetic field


The Sun's magnetic field is a giant mess of loops on a small scale, with large-scale poles that flip every 11 years. Belinda Smith reports on work that, for the first time, simulates both at once.


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The Sun's magnetic field is a chaotic mess – but somehow the large-scale magnetic field isn't too perturbed by small-scale changes.
Hideyuki Hotta, Chiba University

There's no other way to phrase it: at first glance, the Sun's magnetic field is a mess.

Unlike Earth's relatively orderly north-south magnetic field, the Sun's loopy, seemingly chaotic fields extend millions of kilometres into space, dragging masses of hot material along for the ride. These coronal mass ejections can do serious damage to Earth.

But taking a step back, its overall magnetic field is generally oriented north-south. And every 11 years, it flips. This regular flipping happens even with the seemingly random smaller scale loops and eddies.

Scientists have tried to simulate those small-scale and overall fields together without success – until now.

A paper published in Science by physicists in Japan and the US, led by Chiba University's Hideyuki Hotta, calculated the Sun's magnetic fields at low and high resolution.

Researchers have found a way to simulate the Sun's magnetic field at high and low resolution. The yellow patches are moving in one direction; the dark blue parts are moving in the other. Red areas are stationary. – Hideyuki Hotta, Chiba University

The reason for the Sun's turbulent magnetic field is its gassy make-up. Various areas spin faster than others, and like a dynamo, some of that kinetic energy is transformed to magnetic energy.

Hotta and colleagues found that when small-scale eddies in the magnetic field are toned down, the overall magnetic dynamo effect also drops. But not completely – the Sun-wide magnetic field can still be produced.

Further reading:
An early warning system for solar flares
Tracking the violence in the Sun
The Sun flips out

  1. http://science.sciencemag.org/cgi/doi/10.1126/science.aad1893
  2. https://cosmosmagazine.com/technology/early-warning-system-solar-flares
  3. https://cosmosmagazine.com/space/tracking-violence-sun
  4. https://cosmosmagazine.com/physical-sciences/sun-flips-out
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