Sun May Weaken Mercury's Magnetic Field

After a long time studying why Mercury's magnetic field is so weak, researchers were finally able to determine that the planet's magnetism is stifled by the solar wind. The effects are so intense because the planet is very close to the star.

Studying magnetism at Mercury is so critically important to scientists because the innermost planet is the only body in the solar system, other than Earth, to have a magnetosphere and global magnetic fields. Understanding how it functions could help us better understand our planet as well.

When Mercury's magnetism was studied for the first time, scientists were surprised to learn that it is very flimsy. However, they could not identify an immediately-obvious reason for this. The new proposal, while simple, was not thought of seriously until now.

In fact, theoretical calculations predicted that Mercury should have a magnetic field about 30 times stronger than what the NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) space probe can detect from orbit.

These calculations were based on the fact that the planet contains vast amounts of iron, and a core that makes up about 67 percent of its entire mass. Such much iron would produce impressive magnetic fields, the thinking went, but nothing of this sort was discovered.

The new study was carried out as a computer model, where researchers included all the processes taking place inside and outside the planet. At the same time, they included the huge flow of solar particles hitting the world.

It was discovered that the dynamo effect present on Earth – which was supposed to amplify Mercury's magnetic field – is continuously hindered by solar winds. This is done by deflecting charged particles in the planet's magnetosphere.

“The magnetic coupling between the magnetosphere and the dynamo in the planetary interior yields a weakened dynamo that can explain the enigmatic weakness of the magnetic field of Mercury,” expert Daniel Heyner explains, quoted by Space.

The scientist – who holds an appointment as a physicist at the Technical University in Braunschweig, Germany – was also the lead author of the new study. Details of the research were published in the December 23 issue of the top journal Science.