[CHyLmxDr]

Could the Earth lose its magnetic field?

Is our magnetic field already in decay?

The infamous South Atlantic Anomaly region exists in a weakened part of our magnetic field...Is this a forerunner of things to come?
When are we due for the next pole flip?
Will this contribute to a decay in our magnetic field?


Do any of the above present a greater danger to our fart arse little blue orb then say getting slammed by a large Asteroid, .....or human induced global warming?.
Would rapid decay of our magnetic field contribute to global warming....

Our magnetic field is thought to be caused by the differential spin rate, of the Earth's molten core and crust and mantle and convection currents created due to temperature differentials with depth.

What would need to change with these physical aspects to affect the magnetic field to any great extent......

Are we aware of when any of the situations I have mentioned are due?
If not what sort of warning would we get [if we havn't got it already]

Are we confident of changes affecting our magnetic field to be a couple of billion years away?
A few hundred thousand years?
A few hundred years?

[st01en_lox]

The Earth's magnetic field has reversed several times over the last few hundred million years.

[Bwvapays]

The Earth's magnetic field has reversed several times over the last few hundred million years.

Yes I mentioned that...But during and/or before and after these pole flips, is their any decaying of the magnetic field?

[xquFzpNw]

I do remember reading something also, re decay of the magnetic field is already taking place to a certain extent....Can't recollect how much, as it was a couple of years ago now.

[Romobencience]

Hey molly......Any comments. thoughts. errors or corrections?

[aceriscoolon]

> Could the Earth lose its magnetic field?

Not in the near future. A magnetic flip only affects the dipole component of the magnetic field. Higher order components such as quadrupole would still be around, and that would still give us plenty of protection against external radiation.

> Is our magnetic field already in decay?

Yes.

> The infamous South Atlantic Anomaly region exists in a weakened part of our magnetic field...Is this a forerunner of things to come?

Yes.

> When are we due for the next pole flip?

Nobody knows for sure. The pole positions have been constant for 780,000 years whereas the average time between flips over the past 5 million years is only 210,000 years. Also, that 780,000 years is longer than any other interval between pole flips in the past 5 million years, so in that sense we're overdue for a flip.

On the other hand, look at this image of the strength of the earth's magnetic field over the past 800,000 years. A value of "0" represents a flip. The Earth's magnetic field is actually stronger now (in the past 5,000 years) than it has been over any other time in the past 800,000 years so a flip looks unlikely in the near future. It looks as if at least another 20,000 years will occur before the next flip.



NASA’s Radiation Belt Storm Probes (RBSP) mission will probe the rate of weakening in detail and sort out differences between magnetic effects due to Earth's core and those due to the solar sunspot cycle.

> Will this contribute to a decay in our magnetic field?

Other way around. The decay in the magnetic field may or may not lead to a flip.

> Do any of the above present a greater danger to our fart arse little blue orb then say getting slammed by a large Asteroid, .....or human induced global warming?.

My preferred high risk danger is flood basalt. One is due about now and that would be about a million times as deadly as a magnetic reversal. Flood basalt is about 5 to 10 times the risk from an asteroid/comet impact. A star passing through the solar system (eg. Gliese 710 is due in 1.4 million years) and a nearby supernova are other dangers to watch out for. Global warming is more deadly than a magnetic reversal, but nowhere near as deadly as an asteroid/comet impact or flood-basalt/supervolcano event.

Of course, mass deaths due to economic collapse are just around the corner, unless nuclear war gets us first.

> Would rapid decay of our magnetic field contribute to global warming....

Not much - or would it? No, it wouldn't.

> Our magnetic field is thought to be caused by the differential spin rate, of the Earth's molten core and crust and mantle and convection currents created due to temperature differentials with depth. What would need to change with these physical aspects to affect the magnetic field to any great extent......

Time. The Earth's liquid outer core is slowly shrinking and freezing solid as the radioactive elements uranium and thorium decay. It is only the radioactivity of these elements that are keeping the outer core molten.

> Are we aware of when any of the situations I have mentioned are due?

Not that I know of.

> If not what sort of warning would we get [if we havn't got it already]

There are geomagnetic observatories set up all around the world to measure the long term variation in the Earth's magnetic field. Many of these were set up hundreds of years ago at about the same time as the first meteorological observatories. A website http://www.intermagnet.org/Welcom_e.php. The following is a map of magnetic observatories around the world.



> Are we confident of changes affecting our magnetic field to be a couple of billion years away?

For complete freezing of the Earth's outer core leading to permanent and almost total loss of the magnetic field. Yes.

> A few hundred thousand years?

For the next polar reversal at roughly that time.

> A few hundred years?

Some predictions for the next reversal are on that timescale, based on the strengthening of the South Antarctic Anomaly.

[AssinHT]

Wow!!!...What a great comprehensive answer molly...Thanks..

[HonestSean]

Should we be worried about Earth's magnetic poles reversing?
What will happen when north-pointing compasses make a 180-degree turn toward Antarctica? Will the continents tear themselves apart, or are we in store for much more mundane changes?



The end of the world as we know it could come in any number of ways, depending on who you ask. Some people believe global cataclysm will occur when Earth's magnetic poles reverse. When north goes south, they say, the continents will lurch in one direction or the other, triggering massive earthquakes, rapid climate change and species extinctions.

The geologic record shows that hundreds of pole reversals have occurred throughout Earth's history; they happen when patches of iron atoms in Earth's liquid outer core become reverse-aligned, like tiny magnets oriented in the opposite direction from those around them. When the reversed patches grow to the point that they dominate the rest of the core, Earth's overall magnetic field flips. The last reversal happened 780,000 years ago during the Stone Age, and indeed there's evidence to suggest the planet may be in the early stages of a pole reversal right now.

But should we really fear this event? What will actually happen when north-pointing compasses make a 180-degree turn toward Antarctica? Will the continents tear themselves apart, or are we in store for much more mundane changes?

Weak field
"The most dramatic changes that occur when the poles reverse is a very large decrease of the total field intensity," said Jean-Pierre Valet, who conducts research on geomagnetic reversals at the Institute of Earth Physics of Paris. [5 Ways the World Will Change Dramatically this Century]

Earth's magnetic field takes between 1,000 and 10,000 years to reverse, and in the process, it greatly diminishes before it re-aligns. "It's not a sudden flip, but a slow process, during which the field strength becomes weak, very probably the field becomes more complex and might show more than two poles for a while, and then builds up in strength and [aligns] in the opposite direction," said Monika Korte, the scientific director of the Niemegk Geomagnetic Observatory at GFZ Potsdam in Germany.

The scientists say it's the weak in-between phase that would be roughest on Earthlings.

According to John Tarduno, professor of geophysics at the University of Rochester, a strong magnetic field helps protect Earth from blasts of radiation from the sun. "Coronal mass ejections (CMEs) occasionally occur on the Sun, and sometimes hurtle directly toward Earth," Tarduno said. "Some of the particles associated with CMEs can be blocked by Earth's magnetic field. With a weak field, this shielding is less efficient."

The charged particles bombarding Earth's atmosphere during solar storms would punch holes in Earth's atmosphere, and this could hurt humans. "Ozone holes, like that over Antarctica (which today are due to an entirely different cause related to man) could form as solar particles interact with the atmosphere in a cascade of chemical reactions. These 'holes' would not be permanent, but might be present on one- to 10-year timescales — arguably important enough to be a concern in terms of skin cancer rates," Tarduno said. [Will Sunscreen Protect You from the Upcoming Solar Flares?]

Valet agrees that a weak magnetic field could lead to the formation of ozone holes. He wrote a paper last year proposing a direct link between the demise of Neanderthals, our evolutionary cousins, and a significant decrease of the geomagnetic field intensity that occurred exactly at the same period. (That time, the lead-up to a geomagnetic reversal appears to have been "aborted"; the field weakened but didn't end up flipping.)

Other scientists aren't convinced that there's a connection between pole reversals and species extinctions. "Even if the field becomes very weak, at the Earth's surface we are shielded from radiation by the atmosphere. Similarly as we cannot see or feel the presence of the geomagnetic field now, we most likely would not notice any significant change from a reversal," Korte said.

Our technology definitely would be in danger, however. Even now, solar storms can damage satellites, cause power outages and interrupt radio communications. "These kinds of negative influences clearly will increase if the magnetic field and thus its shielding function became significantly weaker, e.g. during a reversal, and it will be important to find mitigation strategies," she told Life's Little Mysteries.

One additional worry is that a weakening and eventual reversal in the field would disorient all those species that rely on geomagnetism for navigation, including bees, salmon, turtles, whales, bacteria and pigeons. There is no scientific consensus on how those creatures would cope.

Continental shifts?
Many of the disaster scenarios associated with geomagnetic pole reversals in popular imagination are pure fantasy, the scientists said. There definitely won't be any break-up or shift of the continents.

The first proof is the geologic record. When the last pole switch happened, "no worldwide shifting of continents or other planet-wide disasters occurred, as geoscientists can testify to from fossil and other records," said Alan Thompson, head of geomagnetism at the British Geological Survey.

The scientists explained that changes in the Earth's liquid core happen on a completely different distance and timescale than convection in the Earth's mantle (which causes Earth's tectonic plates to shift, moving the continents). The liquid core does indeed touch the bottom of the mantle, but it would take tens of millions of years for changes in the core to propagate up through the mantle and influence the motion of the tectonic plates. In short, "there is no evidence from the geological past and in my opinion also no conceivable method that magnetic reversals could trigger Earthquakes," Korte said.

Sooner or later
The geomagnetic field is currently weakening, possibly because of a growing patch of reverse-alignment in the liquid core deep beneath Brazil and the South Atlantic. According to Tarduno, the strength of Earth's magnetic field "has been decreasing for at least 160 years at an alarming rate, leading some to speculate that we are heading toward a reversal."

The reversal might happen, or it might be aborted — Earth is too complex a system for scientists to know which outcome to expect. Either way, the process will drag on over the next few thousand years, giving us time to adjust to the changes.





http://www.mnn.com/earth-matters/spa...oles-reversing