Saturday, April 21, 2012

The Laschamp Geomagnetic Excursion 41,000 B.P.

Since I couldn't seem to load my comments at the end without destroying other articles by printing over them I will put my end comments at the beginning to see if that works better:

Not being a trained Geophysicist I had trouble deciphering what they were saying  in the abstract below. for example:

Magnetic declination

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Example of magnetic declination showing a compass needle with a "positive" (or "easterly") variation from geographic north.
Magnetic declination is the angle between magnetic north (the direction the north end of a compass needle points) and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation. Isogonic lines are where the declination has the same value, and the lines where the declination is zero are called agonic lines.
Somewhat more formally, Bowditch defines variation as “the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. The angle between magnetic and grid meridians is called grid magnetic angle, grid variation, or grivation. Called magnetic variation when a distinction is needed to prevent possible ambiguity. Also called magnetic declination.” [1] and second

Orbital inclination

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  (Redirected from Inclination)
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Fig. 1: One view of inclination i (green) and other orbital parameters
Inclination in general is the angle between a reference plane and another plane or axis of direction.



[edit] Orbits

The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit. It is the angular distance of the orbital plane from the plane of reference (usually the primary's equator or the ecliptic), normally stated in degrees.[1]
In the Solar System, the inclination of the orbit of a planet is defined as the angle between the plane of the orbit of the planet and the ecliptic — which is the plane containing Earth's orbital path.[2] It could be measured with respect to another plane, such as the Sun's equator or even Jupiter's orbital plane, but the ecliptic is more practical for Earth-bound observers. Most planetary orbits in the Solar System have relatively small inclinations, both in relation to each other and to the Sun's equator. There are notable exceptions in the dwarf planets Pluto and Eris, which have inclinations to the ecliptic of 17 degrees and 44 degrees respectively, and the large asteroid Pallas, which is inclined at 34 degrees.

Name Inclination
to ecliptic
to Sun's equator
to invariable plane[3]
Terrestrials Mercury 7.01° 3.38° 6.34°
Venus 3.39° 3.86° 2.19°
Earth 7.155° 1.57°
Mars 1.85° 5.65° 1.67°
Gas giants Jupiter 1.31° 6.09° 0.32°
Saturn 2.49° 5.51° 0.93°
Uranus 0.77° 6.48° 1.02°
Neptune 1.77° 6.43° 0.72°
end quote from Wikipedia under the headings Magnetic declination and Inclination. After I was able to better define declination and Inclination in a Geophysical reference some of the following began to make some sense to me:
begin quote from:
Cited By (20)
Deep-sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present)
Steve P. Lund
Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
Martha Schwartz
Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
Lloyd Keigwin
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
Thomas Johnson
Large Lakes Observatory, University of Minnesota at Duluth, Duluth, Minnesota, USA
We have recovered two new high-resolution paleomagnetic records of the Laschamp Excursion (∼41,000 calendar years B.P.) from deep-sea sediments of the western North Atlantic Ocean. The records document that the Laschamp Excursion was characterized locally by (1) declination changes of ±120°, (2) inclination changes of more than 140°, (3) ∼1200-year oscillations in both inclination and declination, (4) near 90° out-of-phase relationships between inclinations and declinations that produced two clockwise loops in directions and virtual geomagnetic poles (VGPs) followed by a counterclockwise loop, (5) excursional VGPs during both intervals of clockwise looping, (6) magnetic field intensities less than 10% of normal that persisted for almost 2000 years, (7) marked similarity in excursional directions over ∼5000 km spatial scale length, and (8) secular variation rates comparable to historic field behavior but persisting in sign for hundreds of years. All of these features, with the exception of anomalously large directional amplitude, are consistent with normal magnetic field secular variation. Comparison of our Laschamp Excursion paleomagnetic records with other late Quaternary excursion records suggests that there is a group of excursions, which we term class I, which have strikingly similar patterns of field behavior and likely share a common cause as part of the overall core dynamo process. Three general models of secular variation are described that can qualitatively produce class I excursions. On the basis of these observations we conclude that class I excursions, epitomized by the Laschamp Excursion, are more closely related to normal secular variation and are not necessarily a prelude to magnetic field reversal.
Figure 1 of 15
Received 16 December 2003; accepted 26 October 2004; published 2 April 2005.
Citation: Lund, S. P., M. Schwartz, L. Keigwin, and T. Johnson (2005), Deep-sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present), J. Geophys. Res., 110, B04101, doi:10.1029/2003JB002943.

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