This site explains some of the background to our work and provides an overview of cosmogenic isotope research at the University of Washington.
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Gary Glatzmaier, now at the University of California, Santa Cruz, and Paul Roberts of the University of California, Los Angeles, began work on a computer model that simulates this interaction. By 1995, they had created a model that not only created a self-sustaining magnetic field (the first to do so), but after simulating the passage of 36,000 years, the field it generated spontaneously flipped.
The Earth is not alone in this fickleness: The sun's magnetic shield appears to reverse its polarity approximately every 11 years. Even our Milky Way galaxy is magnetized, and experts say it probably reverses its polarity as well. Moreover, while a severe weakening or disappearance of the magnetic field would lay us open to harmful radiation from the sun, there's little evidence to date that "flips" per se inflict any lasting damage.
� experts like Dennis Kent, the Rutgers University geologist who supplied NOVA with updated figures for the time line, are hard at work trying to answer them.
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Dr. Gary Glatzmaier of the University of California at Santa Cruz, one of the geomagnetism experts featured in the NOVA program "Magnetic Storm," maintains this informative Web page, where you can view animations and read accurate information on magnetic field reversals.
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The Great Magnet, the Earth, Dr. David P. Stern
I don't know about migrating animals (they may have magnetic organs, sort of built-in compasses), but there seem to exist no magnetic effects on DNA, resistance to antibiotics and so on; those changes seem more related to chemistry.
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Geological Survey of Canada Geomagnetism
Magnetic field reversals
� Although fast by geological standards, reversals are by no means quick on the human time scale. They take roughly 5,000 years, with estimates ranging from 1,000 years and 8,000 years.
� Both the total magnetic field and its dipole component decrease substantially during a reversal to values that range from 10% to 25% of the pre-reversal strength.
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The weakening -- if coupled with a subsequently large influx of radiation in the form of protons streaming from the sun -- can also affect the chemistry of the atmosphere, said Charles Jackman of NASA's Goddard Space Flight Center. That can lead to significant but temporary losses of atmospheric ozone, he said.
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Robert Felix's home page
I disagree with both of those contentions. I have evidence that there have been at least eleven magnetic reversals in the past 780,000 years - probably many more. I also have evidence that extinctions and reversals do in fact go hand-in-hand. And I have evidence (from Steens Mountain in Oregon) that magnetic reversals can take place in a mere 30 days.
(One of the methods Sharma used to determine historic magnetic activity on the Sun was through the study of berillium 10, which I thoroughly agree with. In fact, I mention berillium 10 production several times in my book.)
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Cosmogenic 10Be concentrations in Antarctic ice during the past 30,000 years Nature 292, 825 - 826 (27 August 1981); G. M. RAISBECK*, F. YIOU*, M. FRUNEAU�, J. M. LOISEAUX�, M. LIEUVIN�, J. C. RAVEL� & C. LORIUS�
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Evidence for an increase in cosmogenic 10Be during a geomagnetic reversal Nature 315, 315 - 317 (23 May 1985);G. M. RAISBECK, F. YIOU, D. BOURLES & D. V. KENT
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10Be evidence for the Matuyama�Brunhes geomagnetic reversal in the EPICA Dome C ice core Nature 444, 82-84 (2 November 2006) Received 10 February 2006; Accepted 18 September 2006 G. M. Raisbeck1, F. Yiou1, O. Cattani2 & J. Jouzel2
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Geomagnetic Modulation of the 36Cl Flux in the GRIP Ice Core, Greenland S. Baumgartner, J. Beer, * J. Masarik, G. Wagner, L. Meynadier, H.-A. Synal Science 27 February 1998: Vol. 279. no. 5355, pp. 1330 - 1332
REPORTS
Geomagnetic field strength is expected to affect the production rate of cosmogenic isotopes such as beryllium-10, carbon-14, or chlorine-36. Chlorine-36 data from the Greenland Ice Core Project (GRIP) ice core agree well with a production rate calculation based on a paleomagnetic reconstruction for the past 100,000 years over both long- and short-term variations.
A chlorine-36 peak at 38,000 years ago previously found in the beryllium-10 record from the Vostok ice core can be explained by a period of low geomagnetic field intensity.
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Factors Influencing the Earth's Magnetic Field Evolution Authors: A. Yu. Kurazhkovskii, N. A. Kurazhkovskaya, B. I. Klain (Submitted on 19 Jun 2008)
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Cosmic Rays and Climate Authors: Jasper Kirkby (Submitted on 11 Apr 2008)
2.3.2 Laschamp event If cosmic rays are indeed forcing the climate then there should be a climatic response to geomagnetic reversals or excursions (�failed reversal� events during which the geomagnetic field dips to a low value but returns with the same polarity). A relatively recent excursion was the Laschamp event, when the geomagnetic field fell briefly to around 10% of its present strength and the global 10Be production rate approximately doubled [81]. Based on several independent radioisotope measurements, the Laschamp event has been precisely dated at (40.4_2.0) ky ago (2_ error) [82].
Several climatic effects coincident with the Laschamp event were recorded elsewhere. 2.4.1
An alternative mechanism has been proposed to explain these apparently galactic-related periodicities. When passing through the spiral arms of the galaxy, as well as experiencing a higher cosmic ray flux, the solar system encounters giant molecular clouds [96]. These are the remnants of supernovae, and comprise 99% gas and 1% dust grains. In extreme cases the clouds may reach densities as high as 2000 H atoms cm��3. This may be compared with about 0.3 H atoms cm��3 in the present local interstellar cloud which, nevertheless, gives rise to about 40,000 tons of extraterrestrial matter falling on Earth�s surface each year. Passage through high density interstellar clouds would cause the heliosphere to collapse below 1 AU, exposing the stratosphere to large quantities of interstellar dust and potentially triggering a �snowball� glaciation on Earth by radiative forcing [97].
Collapse of the heliospheric shield would also lead to a large increase of GCR flux on Earth; the 10Be rate is estimated to increase up to 400% of the present value [98]. Thankfully, present estimates suggest that the frequency of encounter of the solar system with an interstellar cloud of >2000 H atoms cm��3 is rather low (of order one per Gy).
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Galactic bursts signature in Antarctica 10Be Authors: M. Omerbashich (Submitted on 19 Dec 2006 (v1), last revised 1 Jun 2007 (this version, v2))
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Reconstruction of solar activity for the last millennium using $^{10}$Be data Authors: I.G. Usoskin, K. Mursula, S. Solanki, M. Schuessler, K. Alanko (Submitted on 20 Sep 2003)
The geomagnetic field is known to change in time both in strength and orientation, which affects the 10Be production rate on time scales of centuries and longer (Baumgartner et al. 1998).
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On Deep-Ocean Fe-60 as a Fossil of a Near-Earth Supernova Authors: Brian D. Fields, John Ellis (Submitted on 29 Nov 1998)
Supernova events that were sufficiently close to have left some terrestrial isotope signature, but far enough not to have triggered a mass extinction, are expected to have been more frequent.
In this connection, various authors have noted the enhancement of 10Be in ice cores and marine sediments ∼ 35 kyr bp ( bp = before the present). In particular, Ellis, Fields, & Schramm (1996)discussed the possibility that this might have arisen from the supernova event that gave birth to the Geminga pulsar, and proposed looking at deep-ocean sediments, suggesting that the long-lived isotopes 129I, 146Sm, and 244Pu, as well as the shorter-lived 10Be, 26Al, 36Cl, 53Mn, 60Fe, and 59Ni, might provide geological evidence of a nearby supernova event at any time during the past 108 yr or more.
Potential implications of a nearby supernova explosion for earth�s biosphere have been considered by a number of authors (Ruderman 1974; Ellis & Schramm 1995; Ellis, Fields, & Schramm 1996), and recent work has suggested that the most important effects might be induced by cosmic rays.
In particular, their possible role in destroying the earth�s ozone layer and opening the biosphere up to irradiation by solar ultraviolet radiation has been emphasized (Ellis & Schramm 1995; Ellis, Fields, & Schramm 1996).
We observe in passing that a weak correlation has been observed between magnetic field reversals and mass extinctions (Raup 1985). We note that an enhanced cosmic-ray flux is one consequence of such a reversal.
It is natural to ask at this point whether any significant extinction events are known to have occurred within the past 10 Myr or so during which the apparent excess of 60Fe may have been deposited. Indeed, there is evidence for a couple of minor extinctions: one during the middle Miocene, about 13 Myr ago, and one of lesser significance during the Pliocene, about 3 Myr ago (Sepkoski 1986).
We find that a distance of about 30 pc is consistent with the magnitude of the 60Fe signal, and that it should have occurred about 4 Myr ago. If the supernova origin of the observed 60Fe is confirmed.
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The genetic signature of (astronomically induced) life extinctions Authors: Robersy Sanchez, Rolando Cardenas (Submitted on 24 Sep 2005)
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Life Extinction Due To Neutron Star Mergers Authors: Arnon Dar, Ari Laor, Nir J. Shaviv (Submitted on 30 Jul 1996 (v1), last revised 24 Nov 1996 (this version, v2))
The lethality of the CRB depends as well on the vulnerability of the various living species and vegetation to the primary ionizing radiation, to the drastic changes in the environment (e.g., radioactive pollution and destruction of the ozone layer) and to the massive damage and radioactive poisoning of the food chain.
Biological mutations induced by ionizing radiation could have caused a fast appearance of new species after mass extinctions.
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