video version here

http://www.nasa.gov/mpg/297403main_THEMIS_svsLG.mpg

Dec. 16, 2008: NASA's five THEMIS spacecraft have discovered a breach in Earth's magnetic field ten times larger than anything previously thought to exist. Solar wind can flow in through the opening to "load up" the magnetosphere for powerful geomagnetic storms. But the breach itself is not the biggest surprise. Researchers are even more amazed at the strange and unexpected way it forms, overturning long-held ideas of space physics.

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"At first I didn't believe it," says THEMIS project scientist David Sibeck of the Goddard Space Flight Center. "This finding fundamentally alters our understanding of the solar wind-magnetosphere interaction."

The magnetosphere is a bubble of magnetism that surrounds Earth and protects us from solar wind. Exploring the bubble is a key goal of the THEMIS mission, launched in February 2007. The big discovery came on June 3, 2007, when the five probes serendipitously flew through the breach just as it was opening. Onboard sensors recorded a torrent of solar wind particles streaming into the magnetosphere, signaling an event of unexpected size and importance.

One of the THEMIS probes exploring the space around Earth, an artist's concept:

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"The opening was huge—four times wider than Earth itself," says Wenhui Li, a space physicist at the University of New Hampshire who has been analyzing the data. Li's colleague Jimmy Raeder, also of New Hampshire, says "1027 particles per second were flowing into the magnetosphere—that's a 1 followed by 27 zeros. This kind of influx is an order of magnitude greater than what we thought was possible."

The event began with little warning when a gentle gust of solar wind delivered a bundle of magnetic fields from the Sun to Earth. Like an octopus wrapping its tentacles around a big clam, solar magnetic fields draped themselves around the magnetosphere and cracked it open. The cracking was accomplished by means of a process called "magnetic reconnection." High above Earth's poles, solar and terrestrial magnetic fields linked up (reconnected) to form conduits for solar wind. Conduits over the Arctic and Antarctic quickly expanded; within minutes they overlapped over Earth's equator to create the biggest magnetic breach ever recorded by Earth-orbiting spacecraft.




Above: A computer model of solar wind flowing around Earth's magnetic field on June 3, 2007. Background colors represent solar wind density; red is high density, blue is low. Solid black lines trace the outer boundaries of Earth's magnetic field. Note the layer of relatively dense material beneath the tips of the white arrows; that is solar wind entering Earth's magnetic field through the breach. Credit: Jimmy Raeder/UNH.

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The size of the breach took researchers by surprise. "We've seen things like this before," says Raeder, "but never on such a large scale. The entire day-side of the magnetosphere was open to the solar wind."

The circumstances were even more surprising. Space physicists have long believed that holes in Earth's magnetosphere open only in response to solar magnetic fields that point south. The great breach of June 2007, however, opened in response to a solar magnetic field that pointed north.

"To the lay person, this may sound like a quibble, but to a space physicist, it is almost seismic," says Sibeck. "When I tell my colleagues, most react with skepticism, as if I'm trying to convince them that the sun rises in the west."

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Here is why they can't believe their ears: The solar wind presses against Earth's magnetosphere almost directly above the equator where our planet's magnetic field points north. Suppose a bundle of solar magnetism comes along, and it points north, too. The two fields should reinforce one another, strengthening Earth's magnetic defenses and slamming the door shut on the solar wind. In the language of space physics, a north-pointing solar magnetic field is called a "northern IMF" and it is synonymous with shields up!

"So, you can imagine our surprise when a northern IMF came along and shields went down instead," says Sibeck. "This completely overturns our understanding of things."

Northern IMF events don't actually trigger geomagnetic storms, notes Raeder, but they do set the stage for storms by loading the magnetosphere with plasma. A loaded magnetosphere is primed for auroras, power outages, and other disturbances that can result when, say, a CME (coronal mass ejection) hits.

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The years ahead could be especially lively. Raeder explains: "We're entering Solar Cycle 24. For reasons not fully understood, CMEs in even-numbered solar cycles (like 24) tend to hit Earth with a leading edge that is magnetized north. Such a CME should open a breach and load the magnetosphere with plasma just before the storm gets underway. It's the perfect sequence for a really big event."

Sibeck agrees. "This could result in stronger geomagnetic storms than we have seen in many years."

For more information about the THEMIS mission, visit http://nasa.gov/themis

Author: Dr. Tony Phillips | Credit: Science@NASA

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What happened to conventional wisdom? Researchers at the University of New Hampshire are using computer models to unravel the basic physics of the great breach. They're finding that reconnection at the poles is key. Conventional wisdom held that equatorial reconnection was more important, which is why the giant breaches were not anticipated until THEMIS flew through one.

THEMIS, short for Time History of Events and Macroscale Interactions during Substorms, is the fifth medium-class mission under NASA's Explorer Program. The program, managed by The Explorers Program Office at Goddard Space Flight Center, Greenbelt, Md., provides frequent flight opportunities for world-class space investigations in Heliophysics and Astrophysics. The University of California, Berkeley's Space Sciences Laboratory managed the project development and is currently operating the THEMIS mission. Swales Aerospace, Beltsville, Md., built the THEMIS satellites.

Cactus, the video link is messed up; it's easily fixed.

This reminds me of the idea that the Earth's magnetism can reverse itself -- flip from north to south -- just like the Sun can do. I'm not well up on these matters of physics; can anyone elaborate on it? How quickly can the Earth's magnetism flip, and what would the effects be?

Fixed video link!

and again here -

http://www.nasa.gov/mpg/297403main_THEMIS_svsLG.mpg

The magnetic field can flip in an instant and if it did we would have to worry about neither global warming or economic collapse.

Scientists claim it has done so in the past with mass extictions. Believe them if you like as there is nothing to be done anyway

Respectfully, I don't think that's entirely true Young Dan.
The geological record shows the magnetic field switching between 5,000 years and 50 million years with no apparent reasoning behind it.

I don't think there are any mass extinctions on record concurring with magnetic field changes. Certainly birds and other animals who seem to navigate like this could have trouble. And Ibis' political compass wouldn't work very well. Scientists don't really know what would happen.

The real problems for us would begin if the actual magnetic field strength dies away. If it did hit 0 gauss, the atmosphere if it didn't actually float off into space it would be much thinner at sea level and we would not be protected by solar winds and stuff like that.

The only part we disagree on is the extinctions and indeed who knows. I have heard it said that should it switch we would have winds of 300 mph for days. If it hit 0 gauss(great word from the memory bank) then our goose was cooked.

A more likely disastor is the yellowstone caldara. They reckon everything within 600 miles would be dead immediatly with most evetrything else to follow later.

studiorat wrote:

Respectfully, I don't think that's entirely true Young Dan.
The geological record shows the magnetic field switching between 5,000 years and 50 million years with no apparent reasoning behind it.

I don't think there are any mass extinctions on record concurring with magnetic field changes. Certainly birds and other animals who seem to navigate like this could have trouble. And Ibis' political compass wouldn't work very well. Scientists don't really know what would happen.

The real problems for us would begin if the actual magnetic field strength dies away. If it did hit 0 gauss, the atmosphere if it didn't actually float off into space it would be much thinner at sea level and we would not be protected by solar winds and stuff like that.

The Earth's magnetic field reverses regularly. One of the proofs of sea-floor spreading was the symmetrical pattern of magnetic polarity stripes in the ocean floor basalt:

ibis wrote:

The Earth's magnetic field reverses regularly.

So, when is the next reversal due?

(I believe the Yellowstone caldera supervolcano could blow any time now. It will be curtains for the U.S., but I think Europeans and some others could survive... Time to head back to the ould sod, Youngdan?)

soubresauts wrote:

ibis wrote:

The Earth's magnetic field reverses regularly.

So, when is the next reversal due?

(I believe the Yellowstone caldera supervolcano could blow any time now. It will be curtains for the U.S., but I think Europeans and some others could survive... Time to head back to the ould sod, Youngdan?)

Nobody knows, I'm afraid. It reverses roughly every 500,000 years, and the last reversal was 700,000 years ago.

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The change, whenever it occurs, will be gradual and the field will not drop to zero in between--doing so would mean that the magnetic energy of the Earth was somehow converted or dissipated, and all processes we know for this tend to run on scales of thousands of year, if not more. Right now the main (dipole) field is getting weaker at a rate of about 7% per century, and if you draw a straight line through the points you find it reversing between 1000 and 2000 years from now. It might happen, although the trend may well change. The energy of the field, however, has hardly changed. What seems to have happened is that the more complicated parts of the field (equivalent to several magnets in different directions) have got stronger while the main two-pole ("dipole") field lost strength. The complex field is somewhat weaker (it drops off faster with distance from the source, which is the core of the Earth), but we should not expect the field to be ever greatly weakened.

What will not happen (because it is complete bollocks) is that the Earth's core will stop spinning. Nor will there be a massive influx of radiation:

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Some people worry that during magnetic reversals the Earth would receive a higher dosage of high-energy ions and electrons ("radiation" in common terms), which might affect us and any living creatures on Earth. This is not so. Even today, the magnetic shield is not effective near the magnetic poles, yet the radiation received there on the ground is only slightly higher than anywhere else. The reason is that our main shield against such particles is not the magnetic field of the Earth but the atmosphere, equivalent to some 10 feet of concrete.

In any case, during reversal the magnetic field does not go away, it only gets weaker and develops several more magnetic poles, at unpredictable locations.

Nor are magnetic reversals associated with mass extinctions. It won't even destroy navigation systems, which are based on GPS from satellites, not compasses.

After the freezing I suffered today at the Patriots/Arizona game maybe I should go home. I will bring my sun tan lotion. The caldara has risen by a few feet and some say it could blow at any time. A pole shift would be catastophic from what I have heard but I am not worried about it

youngdan wrote:

After the freezing I suffered today at the Patriots/Arizona game maybe I should go home. I will bring my sun tan lotion. The caldara has risen by a few feet and some say it could blow at any time. A pole shift would be catastophic from what I have heard but I am not worried about it

Interesting. How concerned about the caldera uplift are the seismologists, do you know?

Note how i got the word "uplift" Anyone see Supervolcano ? A great BBC docu-drama about what would happen when yellowstone blows. The webpage is pretty cool, too -

http://www.bbc.co.uk/sn/tvradio/programmes/supervolcano/


HAs a sim-game where you get to be head of disaster managment for an area, and see what effects your decisions have on the poplulation! (a lot of needless deaths in my case )

yehbut_nobut wrote:

youngdan wrote:

After the freezing I suffered today at the Patriots/Arizona game maybe I should go home. I will bring my sun tan lotion. The caldara has risen by a few feet and some say it could blow at any time. A pole shift would be catastophic from what I have heard but I am not worried about it

Interesting. How concerned about the caldera uplift are the seismologists, do you know?

Note how i got the word "uplift" Anyone see Supervolcano ? A great BBC docu-drama about what would happen when yellowstone blows. The webpage is pretty cool, too -

http://www.bbc.co.uk/sn/tvradio/programmes/supervolcano/


HAs a sim-game where you get to be head of disaster managment for an area, and see what effects your decisions have on the poplulation! (a lot of needless deaths in my case )

You reckon you'd get the "Great Job, Brownie" final screen?

I used to hear more about it but not recently. If it blows it blows. Even if the president was told there was a 90% chance of it going in a matter of days there would be nothing to be done anyway and the news could be suppressed

youngdan wrote:

I used to hear more about it but not recently. If it blows it blows. Even if the president was told there was a 90% chance of it going in a matter of days there would be nothing to be done anyway and the news could be suppressed

Sure we could all be hit by a meteor tomorrow and we would not know it was coming. Humanity and being part of it is great fun, what do you want, guarantees as well?

We can only do the best that we can with the knowledge that we have.

The Yellowstone supervolcano is not far from eruption but a big meteorite hit is a longshot that might be millions of years away

youngdan wrote:

The Yellowstone supervolcano is not far from eruption but a big meteorite hit is a longshot that might be millions of years away

Happy Christmas, youngdan. I have an asbestos umbrella in the post to you.