magnetic field
Researchers have identified a way to simulate the sun’s magnetic field on many scales at high resolution. This image is the result of their new simulation model. Hideyuki Hotta, Chiba University

A new simulation of the sun's magnetic field, which represents both large-scale and small-scale magnetic cycles, has been created by Japanese scientists. They hope this model will help them better understand the complex solar magnetic cycles that occur every 11 years.

The sun is not a stable, unchanging disk, high up in space. Made out of ionized gas plasma, it constantly changes, and goes through magnetic cycles of varying intensity, every decade. These cycles are responsible for a range of phenomenons in space and Earth, from solar explosions which cause auroras, to interplanetary magnetic field and radiation driving any spacecraft journeying in the solar system.

Simulations and digital imagery are crucial to help scientists pinpoint the different effects of solar cycles. Though important efforts have been made in recent years to create useful representations of solar magnetic fields, interrogations remain on how to best represent the processes at stake.

One of the mysteries is how the sun's large-scale magnetic field is maintained in the presence of chaotic small-scale fields. Simulating a magnetic cycle has proved hard for scientists, because they were not able represent small-scale magnetic fields with the large-scale magnetic field, all in the same reproduction.

In this latest study, published in Science, the team led by Hideyuki Hotta reveal a way of combining both processes in a single simulation. By reducing the small-scale magnetic diffusivities in the simulation (rate at which particles or heat or fluids spread), the scientists first diminish the magnetic dynamo effect at large scales. However, by lowering diffusivities even more, they are able to also reproduce a large magnetic field. Their simulations, which play around with diffusivity rates, can thus reproduce both the large and small scale physics involved in the sun magnetic field, at the same time.