1. AGU Web Site: EiS. How Are Geomagnetic Reversals Related to Field Intensity?
For the past 2000 years Earth's magnetic field has been weakening. At the going rate of decay, the north-south magnetic dipole—generated within the convecting metallic fluid of Earth's outer core—would totally vanish, perhaps reversing polarity in the next 2000 years. This scenario of a coming attempt by Earth's magnetic field to reverse its polarity is suggested by direct observation of the field since the 19th century and laboratory investigation of historic lavas and other fired materials that record the ambient field while cooling. The ongoing weakening of the field does not ensure that a reversal will occur. After all, Earth's dipole reverses direction only on occasion, currently at a rate of a few times each million years. How a change in polarity is actually approached and, moreover, the degree to which such a process can be predicted, are unclear. Nonetheless, a significant step toward such an understanding may have been made through investigations of the ancient, or paleomagnetic field recorded in Ocean Drilling Project (ODP) marine sediment cores.

2. BEHIND MAGNETIC FLIP-FLOPS
The earth's magnetic field frequently reverses its polarity. Such flips can of-ten be correlated with climate changes, global ice volumes, sea-floor spreading rates, and deposition of black shales, tektite falls, biological extinctions, etc. The frustrating thing is the lack of clear-cut cause and effect; that is, how these phenomena are linked physically to the geomagnetic field. Part of the problem is that we can only guess at how the geomagnetic field is generated. Let us assume that the earth's magnetic field is created by dynamo action in the planet's fluid core. P. Olson finds analytically that the core dynamo may reverse sign due to fluctuations in core turbulence caused by two competing energy sources: heat loss at the mantle-core boundary and progressive growth of the inner core. In concept, the heat lost at the core-mantle boundary might be linked to climate changes and sea-floor spreading.

3. Magnetic flip heralds solar max: Science News Online, March 3, 2001
Scientists have found another indicator that the sun has reached the maximum of its current activity cycle: The polarity of its magnetic field has reversed.1.

4. Magnetic Flip-Flops
Sun's magnetic flip affects cosmic ray penetration ! By Dan Vergano, USA TODAY. Increasing evidence suggests that the direction of the sun's magnetic field appears to affect how cosmic rays penetrate our solar system, scientists say. Since 1954, solar scientists have known that the sun's magnetic field, or heliosphere, shields the solar system from the full effects of cosmic rays, energetic atomic particles from space. Cosmic rays are thought to play a role in initiating changes in the upper atmosphere that affect Earth's weather, sparking increased interest in their occurrence among scientists.

5. New Scientist - Magnetic Flip Explained
Anomalies hint at magnetic pole flip The Earth's magnetic poles might be starting to flip say researchers who have seen strange anomalies in our planet's magnetic field. The magnetic field is created by the flow of molten iron inside the Earth's core. These circulation patterns are affected by the planet's rotation, so the field normally aligns with the Earth's axis - forming the north and south poles. But the way minerals are aligned in ancient rock shows that the planet's magnetic dipole occasionally disappears altogether, leaving a much more complicated field with many poles all over the planet. When the dipole comes back into force, the north and south poles can swap places. The last reversal happened about 780,000 years ago, over a period of several thousand years. Now Gauthier Hulot from the Institute of Earth Sciences in Paris and his colleagues think they have spotted early signs of another reversal.

6. USATODAY.com - Sun s magnetic flip affects cosmic ray penetration
Suns magnetic flip affects cosmic ray penetration By Dan Vergano, USA TODAY Increasing evidence suggests that the direction of the suns magnetic field appears to affect how cosmic rays penetrate our solar system, scientists say.

7. WHEN NORTH GOES SOUTH: Three-Dimensional Simulation of Geomagnetic Field Reversal
Magnetic Flip-Flops Considering that ships, planes and Boy Scouts steer by it, Earth's magnetic field is less reliable than you'd think. Rocks in an ancient lava flow in Oregon suggest that for a brief erratic span about 16 million years ago magnetic north shifted as much as 6 degrees per day. After little more than a week, a compass needle would have pointed toward Mexico City. The lava catches Earth's magnetic field in the act of reversing itself. Magnetic north heads south, and -- over about 1,000 years -- the field does a complete flip-flop. While the Oregon data is controversial, Earth scientists agree that the geological evidence as a whole -- the "paleomagnetic" record -- proves such reversals happened many times over the past billion years. "Some reversals occurred within a few 10,000 years of each other," says Los Alamos scientist Gary Glatzmaier, "and there are other periods where no reversals occurred for tens of millions of years." How do these flip-flops happen, and why at such irregular intervals? The geological data, invaluable to show what happened, registers only a mute shrug when it comes to the deeper questions.

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