Flippin’ incredible – the story of the sun’s magnetic field reversal

We’re on the verge of a once in an eleven year solar event that sounds as impossible as it does fascinating, if not a little menacing – a solar field reversal. More specifically, a complete reversal of the sun’s polar magnetic field which means that its magnetic north and south poles will change places entirely.

Solar physicists have been monitoring these 11-year events since the 1970s and assure us that there is nothing to worry about, so we can sit back, observe and marvel at the wonders of our solar system.


Why does the sun’s magnetic field reverse?

The sun’s activity is monitored at various observatories across the globe and for nearly 100 years scientists have understood that sunspots have their own strong magnetic fields. Although the physical mechanism that starts the process of reversing the sun’s polar magnetic field is not yet entirely understood it has been observed that throughout the 11-year cycle new sunspots build up, each with their own magnetic field and polarity. These areas of intense magnetic activity then disintegrate over a period of time and the strong magnetic field migrates from the sun’s equator to one of the sun’s poles and as it does so, it erodes the existing opposite polarity until there is zero magnetic field. The magnetic field then rebounds with the opposite polarity.


When will the sun’s magnetic field flip?

The switch has already begun, solar physicists say. In fact, the northern hemisphere of the sun has already changed with the southern hemisphere expected to change imminently. The fact that the hemispheres have switched at different rates is surprising in itself.

Normally, a star like our sun, or a planet like the Earth has a north and a south magnetic pole but right now the sun has effectively two south poles, which goes against a fundamental law of magnetism that every magnet must have a north and a south pole.

The Earth has a dipole magnetic field, like an internal bar magnet with a north pole at one end and a south pole at the other. During its stable periods, the sun’s magnetic field is dipolar too but as a reversal approaches there can be as many as eight poles jumbled together; as a reversal occurs they rearrange themselves with strange temporary effects, like a double south or north pole.


How will the solar field reversal effect Earth?

When the flip is complete, the ripple will be felt throughout our solar system and beyond due to increased solar activity such as sunspots and flares around the time of the flip. Activity on the surface of the sun effects the Earth’s own magnetic field as well as intergalactic weather, which has the potential to affect technology such as power grids and global positioning systems (GPS).

Northern lights (aurora borealis) in Canada.

Northern Lights (Aurora Borealis) in Canada.

Mass ejection of particles from the Sun during this period also increases the frequency of auroras such as the northern lights. These beautiful spectacles are created as electrically charged particles ejected by the Sun enter the Earth’s atmosphere and collide with gaseous particles.

The sun’s influence, known as the heliosphere, stretches mind-blowingly far, beyond Pluto to the edge of interstellar space and when the sun’s magnetic field is reversed the effects are felt right at the very edge of the heliosphere.  For example, Jupiter gets more storms while Saturn is blessed with auroras.


Does the Earth’s magnetic field flip?

Surprising as it sounds the Earth’s magnetic field has flipped, and pretty recently too when you consider the life of our planet, just 800,000 years ago. Scientists can tell by studying rock formations that the Earth’s magnetic field flips somewhere between every 100,000 and 1,000,000 years.


Find our more about this fascinating phenomenon by watching the videos below.

Published by Stanford University


Published by NASA

Image courtesy of NASA.

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