National Geographic News
Magnetic forces draw out loops and strands of hot plasma from the sun's surface.

An illustration of what it might look like if magnetic forces draw out loops and strands of hot plasma from the sun's surface.

Image courtesy SDO/NASA

Ker Than

for National Geographic

Published August 7, 2013

The sun's magnetic field, which spans the solar system, is just months away from flipping, observatory measurements show.

"This change will have ripple effects throughout the solar system," solar physicist Todd Hoeksema of Stanford University said in a statement.

Hoeksema is the director of Stanford's Wilcox Solar Observatory, one of just a few observatories around the world that monitors the sun's polar magnetic fields.

The sun's magnetic field changes polarity approximately every 11 years during the peak of each solar cycle as the sun's inner dynamo reorganizes itself.

This next reversal—which will be only the fourth observed since tracking began in 1976—will mark the midpoint of Solar Cycle 24.

During a magnetic field reversal, "the sun's polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity," explained solar physicist Phil Scherrer, also at Stanford, in the statement.

Scientists are already seeing signs of the reversal happening, and this time there's a twist: Data from Wilcox show that the sun's two hemispheres are oddly out of sync, with the North Pole already beginning to change and the South Pole racing to catch up. That means that for now, at least, the sun effectively has two South Poles.

Soon both poles should be completely reversed. "It looks like we're no more than three to four months away from a complete field reversal," Hoeksema said.

The Wilcox Solar Observatory has been observing the sun's magnetic field since 1975, and its scientists have been converting those numerical measurements into a map that can now be viewed online.

"What we're really happy about is we've never changed or upgraded [the observatory]," Scherrer said in an interview Wednesday. "It's the only instrument in the world where you can look back over 40 years and know you're measuring the same thing. That allows us to compare fields from one cycle to the next."

What Does a Reversal Mean?

A reversal of the sun's magnetic field will have consequences throughout the solar system since the domain of the sun's magnetic influence—called the heliosphere—extends far beyond Pluto. Changes to the field's polarity ripple all the way out to the Voyager probes, which are racing toward interstellar space.

Playing a central role in solar field reversals is the "current sheet," a sprawling surface that juts out of the sun's equator where the sun's slowly rotating magnetic field induces an electric current.

The current itself is small—only one ten-billionth of an amp per square meter—but there's a lot of it, and the entire heliosphere is organized around it.

During field reversals, the current sheet becomes very wavy. Scherrer likens the undulations to the seams on a baseball.

As the Earth orbits the sun, our planet dips in and out of the wavy current sheet, and the transitions can stir up stormy space weather around us.

The geometry of the current sheet can also affect Earth's exposure to cosmic rays, which are high-energy particles accelerated to the speed of light by supernova explosions and other violent events in the galaxy.

Cosmic rays pose a threat to astronauts and space probes, and some researchers say they might also affect the cloudiness and climate of Earth.

The sun's current sheet functions as a barrier to cosmic rays, preventing them from penetrating into the inner solar system. And a wavy, crinkly current sheet appears to create a better shield against these energetic particles.

Earth's Flip-Flop Coming

The sun isn't the only body in the solar system with a magnetic field that reverses. Earth has a magnetic field as well, and it has flipped many times over the last billion years.

This isn't surprising, Scherrer said, because the magnetic fields of both the sun and the Earth are thought to be generated by similar "dynamo" processes that involve rotating and convecting electrically conducting fluids—molten iron in the case of the Earth and hot, ionized gases for the sun.

The difference, however, is that Earth's magnetic field reversals happen much less frequently—only once every 200,000 to 300,000 years on average, although the actual time can vary widely—and over much longer timescales.

An analysis of centuries-old ship logs performed in 2006, for example, found that the Earth's magnetic field weakens in staggered steps, and that its strength has declined by a few percentage points since 1840.

If this decline is continuous, scientists predict the Earth's magnetic field could reverse sometime in the next 2,000 years.

When it does happen, Scherrer thinks that the flip will happen gradually—as is the case with the sun—and won't be marked by any kind of calamitous drop of the Earth's magnetic field strength to zero.

"It won't just disappear and come back again," Scherrer said.

Follow Ker Than on Twitter.

26 comments
Time Lord
Time Lord

It will be the end of all binary systems.

Peachy Oneplm
Peachy Oneplm

With the Polar Ice Cap melting, would the Earth expect any concern, with the Magnetic Field Change - as these appear in diagram to be related to the two Poles?

Phil Rickard
Phil Rickard

makes sense really.. not so sure that it happens regularly enough to know precisely what will happen. In my mind I wonder if the earth changes poles, do we change poles to.  Everything has a ripple effect the Weather changing and having severe storms, more earthquakes and tidal waves around the world, volcanoes have been getting more active.  However if we look back 200,000 years ago or whatever it has been since the last shift, the days of perhaps cavemen. in those tales I remember the earth moving majorly, volcanoes erupting etc. yet man survived through this... Of course they are only stories, how could we know for sure... when did the Mayans disappear?... was there some story about some perfect pyramids under the sea 2000feet or so near cuba.. not sure if that would match up with this story.. but my thoughts when i read this...

cyril deons vithali
cyril deons vithali

anyway it is only a routine process.then we shall wait and see what happens to the Voyager.nothing to panic i guess.

cyril 

DanielleandJack Pootiecakes
DanielleandJack Pootiecakes

So since we revolve around the sun and the suns magnetic field is flipping and ours is not flipping right along with it does'nt that mean that the suns north will now be at our south and vice versa? and would'nt that inturn result in our planet being magnetically attracted to the sun? 

Ali oztoprak
Ali oztoprak

i have read an article about affects of reversal of sun's magnetic field that will be gold age for humans in the world.

S. S.
S. S.

Since it happens so frequently I'm guessing (hoping) it won't have too large of an effect on us humans.

jonty kilpatrick
jonty kilpatrick

I am intrigued... The google snippet features the notion that it "will have ripple effects throughout the solar system," On reading the article there's not much to say beyond the possibility of "slightly increased cloudiness?" Is this a non news piece or did I miss an earth-shattering inference somewhere?

Linda Nemiroff
Linda Nemiroff

Very interesting and thought provoking article. 

 Opinions, be them acceptable or not,  are only opinions/comments.   If one wishes to speak out against another's opinion than that is their opinion. 

 On to the amazing  and ever changing world and universes we are part of with many thank you(s) to the people teaching us their observations.



Rahmat Julyanto
Rahmat Julyanto

wow... scientifically proven that the end of our galaxy is imminent... albeit in some 2000 years... :)

Avani Swami
Avani Swami

Wow! Though I wonder what will happen if the change is sudden not gradual.

Daniel Rost
Daniel Rost

So does anyone know how this will effect the travel of comet ISON that is supposed to make a very close approach to the sun on November 28??

Rob Slater
Rob Slater

No. It doesn't work like that. If NatGeo isn't crapping their pants,neither should you.

Giles O'Dell
Giles O'Dell

@Ali oztoprakExactly, just as 1992 - 2003 was the previous golden age of humanity. And who can forget the paradise on Earth from 1970 - 1981?

Rob Slater
Rob Slater

That sounds like unscientific new-age nonsense.

DanielleandJack Pootiecakes
DanielleandJack Pootiecakes

@Babu Ranganathan religion is nothing but an organization built to attempt to control the masses, it will never have full control.  The only true faith is individual faith which is created by a common bond that every living thing in this universe has.  Religion, Government and Education are no more than human built structures that claim to help us and keep us in track while at the same time ripping us apart at the roots.  The onlly thing we have that keeps us together is conciousness and a conscious bond, the hydrogen bond.  Big deal, you are in book that is published and sold for monetary gain.  woohoo hope you enjoy the money cuz when you leave this earth it is not going with you. Only your energy and its hydrogen bond will be going.

S. S.
S. S.

@Babu Ranganathan You're lazy attempt to solicit people to your website needs to stop. I visit Scientific American daily and am sick of seeing you post the SAME thing repeatedly. Not only is it COMPLETELY off topic, it's getting extremely old.

Also - I'd love for you to state which college or university you have lectured at; I don't believe that at all. I took the time to visit that Marquis Who's Who thing....you're a retail service associate? A retail service associate who lectures at colleges and universities? Please, get over yourself and quit taking advantage of this educational site by trying to advertise yourself.

I could see if you took the time to acknowledge this article or write something relevant, but like I said you must just copy & paste THE SAME thing in every comments section possible on this website. Get a life. Quit wasting the time of people who are interested to learn and discuss specific article topics.

Nik Zanella
Nik Zanella

Come on. Leave us alone you stupid moron!

S. S.
S. S.

@S. S. @Babu Ranganathan......National Geographic - duh. That was moronic of me I'll admit, I read all my science mags at the same time and had scientific american in my mind. LOL.

You still need to quit posting the same crap - I'd embrace your opinion on the article topic. You seem like a very intelligent person, but doing stuff like this makes you come off the wrong way, or like you didn't even READ the article just saw another chance to freely try to advertise yourself.

cathy H.
cathy H.

@Nik Zanella National Geographic embraces the world as a whole. Please have respect for opinions that differ from your own. Speak only for yourself in a polite manner unless posting on a private level where no person other than whom you are addressing will see your remarks. Do not presume you speak for every member of the National Geographic Organization as evidenced in your remark, and I quote, "...leave us alone". The fact you described Mr. Ranganathan as a "moron" in response to his obvious educated invitation to his website only reveals your lack thereof, on all levels. Please be more circumspect in your remarks out of respect for others, if not for yourself as a fellow human being residing on this wonderful planet. Such vitriolic response to an opinion other than your own reveals a multitude of emotional layers of insecurity.

cathy H.
cathy H.

@sus grant I had hoped to be among tolerant people who would not expose people to childish remarks such as "stupid morons". National Geographic provides ways for the reader to report spam and even offers a delete button. That was the point of my response to Mr. Zanella's comment. Whether people believe one way or the other is immaterial to the subject at hand. This is a site for discussion of this beautiful world we live in. The only responses I have read that possess intolerance are those of yours and Mr. Zanellas. You are the only one who has brought up any subject "going to Hell" as you put it. The point I was trying to make was to emphasize that no matter the differences in opinions people have, that politeness and tolerance should be the adult response. Leave the childish remarks to the social media sites. National Geographic is not the place for it. Your sarcastic assumption that I am an amateur psychologist is exactly what I am talking about. I refuse to be a part of discussions such as this. National Geographic is not the place for emotional name throwing because one feels threatened by opinions different than their own, whether it is "spam" or not. Please feel free to delete my response to you and Mr. Zanellas, yes, vitriolic, comments. Rest assuredly, I will be deleting yours.

sus grant
sus grant

@cathy H.You call Babu's  comment an "obvious educated invitation to his website." I call it spam. 


sus grant
sus grant

@cathy H. @Nik ZanellaGee, Cathy, do you have to give Nik a lecture and tell him how to act? I appreciated his comment, as this is a scientific site, and hopefully one domain that we don't have to be bothered by the people that think everyone is going to hell besides those who believe exactly as they do. We are tired of being lectured by the likes of Babu. And then you have to jump in and lecture Nik as well. I appreciate Nik's outspokenness, as most of us just have to hush up and take it, lest we be thought of as intolerant or "vitriolic." And then you top it off by playing amateur psychologist and say he has "a multitude   of emotional layers of insecurity." Come on! Sounds like you are one of them as well. Nik has a right to his opinion, and I second it!

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