Current sheet
The Sun\'s current sheet becomes wavy during a magnetic flip (Nasa)

The sun's magnetic field is getting ready to flip over, an event that will have a ripple effect throughout the solar system and produce stormy weather on Earth.

Measurements from Nasa's observatories show that the sun's magnetic field is preparing to change polarity - a change that takes place once every 11 years. The last magnetic flip, or Solar Maxim, took place in 2000.

Todd Hoeksema, a solar physicist from Stanford University, said: "It looks like we're no more than three to four months away from a complete field reversal. This change will have ripple effects throughout the solar system."

Solar physicist Phil Scherrer, also from Stanford, described what happens: "The sun's polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity."

The flip takes place at the peak of each solar cycle, when the sun's inner magnetic dynamo re-organises itself. The reverse marks the midpoint of the cycle.

The sun's magnetic influence extends billions of kilometres beyond Pluto and changes to the field go all the way out to Voyager probes, "on the doorstep of interstellar space", Nasa said.

Scientists have been tracking the sun's polar magnetism since 1976. The forthcoming flip will be the fourth recorded since then, but historical weather events may be attributed to a Solar Maxim.

Stormy, cloudy weather

In 1859, a solar storm was recorded and saw solar flares appearing all over earth. It was so strong that the Northern Lights, a natural light display normally only visible in the Arctic and Antarctic regions, could be seen in Rome.

Solar physicians focus their attention on the 'current sheet', when speaking about solar field reversals. The current sheet is a surface jutting out from the sun's equator.

The sun's rotating magnetic field creates an electrical current, which itself is very small, at around one ten-billionth of an amp per square metre. However, there is a lot of current, and it flows through a region 10,000km thick and billions of kilometres wide.

During magnetic field reversals, the current sheet becomes wavy and as Earth orbits the sun, it dips in and out of the current sheet, resulting in stormy weather across the planet.

Cosmic rays will also be affected, creating a danger to astronauts and space probes - cosmic rays are high-energy particles accelerated to almost light speed by supernova explosions and other violent events.

Researchers believe these cosmic rays may also affect the cloudiness and climate of Earth.

Scherrer said: "The sun's north pole has already changed sign, while the south pole is racing to catch up. Soon, however, both poles will be reversed, and the second half of solar max will be underway."