Magnetic field reversals/Laboratory

The graph shows a comparison of the observed magnetic profile for the seafloor across the East Pacific Rise against a profile calculated from the Earth's known magnetic reversals, assuming a constant rate of spreading. Credit: W. Jacquelyne Kious and Robert I. Tilling, USGS.{{free media}}

This laboratory is an activity for you to describe a magnetic field reversal.

Some suggested reversal entities to consider are electromagnetic radiation, neutrinos, mass, time, Euclidean space, Non-Euclidean space, a dynamo, and spacetime.

More importantly, there are your magnetic field reversal entities.

You may choose to define your entities or use those already available.

Usually, research follows someone else's ideas of how to do something. But, in this laboratory you can create these too.

Okay, this is an astronomy magnetic field reversal laboratory, but you may create what a magnetic field reversal is.

Yes, this laboratory is structured.

I will provide one example of techniques to cause a magnetic field reversal. The rest is up to you.

Questions, if any, are best placed on the discussion page.

Notations

You are free to create your own notation, or use those already presented.

Control groups

For creating a magnetic field reversal technique, what would make an acceptable control group? Think about a control group to compare your magnetic field reversal technique or your process of creating a magnetic field reversal to.

Samplings

Geomagnetic polarity during the last 5 million years (Pliocene and Quaternary, late Cenozoic Era). Dark areas denote periods where the polarity matches today's normal polarity; light areas denote periods where that polarity is reversed. Credit: United States Geological Survey.{{free media}}

Geomagnetic polarity since the middle Jurassic. Dark areas denote periods where the polarity matches today's polarity, while light areas denote periods where that polarity is reversed. The Cretaceous Normal superchron is visible as the broad, uninterrupted black band near the middle of the image. Credit: Anomie.{{free media}}

Searching SAO/NASA Astrophysics Data System (ADS) with "Earth's magnetic reversals" yields 43 abstracts. Here is a sampling of likely causes:

1. 1985: Any "field reversal [may be] linked to biological extinction^7–12 [...] the reversal record of the past 165 Myr [shows that a] stationary periodicity of 30 Myr emerges (superimposed on the non-stationarities already established by others⁵), which predicts pulses of increased reversal activity centred at 10, 40, 70,… Myr BP." See hypotheses 2 and 3. So what's causing the 30 Myr period?
2. 1986: A "recently observed 15 Myr periodicity is probably a harmonic of the 29.5-30.5 Myr period. The calculations do not confirm an inherent magnetic reversal property of the earth. The reversals may arise from tectonic events or from impacts from extraterrestrial objects." Here, can be external events or tectonic events for the origin of reversals.
3. 1994: "The precession peaks found in the δ¹⁸O record from core MD900963 are in excellent agreement with climatic oscillations predicted by the astronomical theory of climate." In other words, orbital changes have produced or induced magnetic field reversals.
4. 1994: "The Earth's geomagnetic field reverses its polarity at irregular time intervals. [It] is not clear whether a reversal is a deterministic (low dimensional) or a random (high-dimensional) process; the duration-frequency distribution of the polarity time intervals resembles those generated by random processes, but many models suggest that a geomagnetic field reversal can be the outcome of a deterministic dynamics, that of the convection in the Earth's outer core. [The] limited size of the magnetic reversal data (282 points) and the poor convergence of the correlation integrals make a quantitative assessment of low-dimensional chaos impossible."
5. 2000: "Earth's magnetic field is generated by fluid motion in the liquid iron core. Details of how this occurs are now emerging from numerical simulations that achieve a self-sustaining magnetic field. Early results predict a dominant dipole field outside the core, and some models even reproduce magnetic reversals." Here, the geodynamo is the source of the reversals.
6. 2003: The "redistribution of magnetic polarities in the inner heliosphere during [a 10.5-month period of maximum solar activity] can be simply described by a gradual 180 degree rotation of the dipole axis from near-alignment with one solar rotational pole to the other."
7. 2013: "Regeneration of the Earth's magnetic field by convection in the liquid core produces a broad spectrum of time variation. [...] the amplitude of convective fluctuations in the core [is predictable], and establish a physical connection to the rates of magnetic reversals and excursions."

Verification

File:Polarity reversal global event.jpg

The polarity reversal some 41,000 years ago was a global event. Credit: Norbert Nowaczyk and Helge Arz, Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences.{{free media}}

In the sampling section above the most recent geomagnetic polarity reversal occurred 780,000 b2k.

"Paleomagnetic samples were obtained from cores taken during the drilling of a research well along Coyote Creek in San Jose, California, in order to use the geomagnetic field behavior recorded in those samples to provide age constraints for the sediment encountered. The well reached a depth of 308 meters and material apparently was deposited largely (entirely?) during the Brunhes Normal Polarity Chron, which lasted from 780 ka to the present time."

"Three episodes of anomalous magnetic inclinations were recorded in parts of the sedimentary sequence; the uppermost two we correlate to the Mono Lake (~30 ka) geomagnetic excursion and 6 cm lower, tentatively to the Laschamp (~45 ka) excursion."

"Some 41,000 years ago, a complete and rapid reversal of the geomagnetic field occured. Magnetic studies on sediment cores from the Black Sea show that during this period, during the last ice age, a compass at the Black Sea would have pointed to the south instead of north."

"[A]dditional data from other studies in the North Atlantic, the South Pacific and Hawaii, prove that this polarity reversal was a global event."

"The field geometry of reversed polarity, with field lines pointing into the opposite direction when compared to today's configuration, lasted for only about 440 years, and it was associated with a field strength that was only one quarter of today's field."

"The actual polarity changes lasted only 250 years. In terms of geological time scales, that is very fast."

"During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased radiation exposure."

"This is documented by peaks of radioactive beryllium (¹⁰Be) in ice cores from this time, recovered from the Greenland ice sheet. ¹⁰Be as well as radioactive carbon (¹⁴C) is caused by the collision of high-energy protons from space with atoms of the atmosphere."

"The polarity reversal [...] has already been known for 45 years. It was first discovered after the analysis of the magnetisation of several lava flows near the village Laschamp near Clermont-Ferrand in the Massif Central, which differed significantly from today's direction of the geomagnetic field. Since then, this geomagnetic feature is known as the 'Laschamp event'."

The "new data from the Black Sea give a complete image of geomagnetic field variability at a high temporal resolution."

Report

Testing that the Brunhes–Matuyama reversal is the most recent

by --Marshallsumter (discuss • contribs) 00:23, 5 November 2016 (UTC)

Abstract

The most recent geomagnetic reversal has been documented extensively as recently as 10 June 2003. It should be relatively easy to verify this. A quick check of w:Brunhes–Matuyama reversal appeared to do so. A quick search on Google using "most recent magnetic reversal"+Earth suggested a check of w:Geomagnetic reversal. This included a link to the w:Laschamp event.

Introduction

File:29831501.jpg

These three maps show a succession of artifacts in western and southern Europe. Credit: Catherine Brahic.{{fairuse}}

"Genetics suggests Neanderthal numbers dropped sharply around 50,000 years ago. This coincides with a sudden cold snap, hinting climate struck the first blow."

The "Hasselo stadial [occurred] at approximately 40-38,500 ¹⁴C years B.P. (Van Huissteden, 1990)." The "Hasselo Stadial [is a glacial advance] (44–39 ka ago)". Approximate to the time of the Hasselo Stadial Neanderthals were leaving Europe and moving eastward. If this was in response to a global event then that event must have left its mark.

Experiment

To test this possibility of a global event, it was necessary to search for an event much more recent than the Brunhes–Matuyama reversal.

Results

A quick search on Google using "most recent magnetic reversal"+Earth suggested a quick check of w:Geomagnetic reversal. This included a link to the w:Laschamp event which occurred about 42,000 b2k.

Discussion

There are other glacial advances before and after the Hasselo stadial. The Karmøy stadial begins in the high mountains of Norway about 60 kyr B.P. and expands to the outer coast by 58 kyr B.P. But, there is no apparent corresponding geomagnetic reversal. This could mean there are more geomagnetic reversals to be found or that these are coincident events.

Conclusion

A global event has been found which may explain the sudden cold snap that caused Neanderthals to leave Europe.

Evaluation

To assess your magnetic field reversal method, including your justification, analysis and discussion, I will provide such an assessment of my example for comparison.

Evaluation

There are three stadials near in time to this reversal. These have not been addressed. Are you suggesting that the glaciation caused the reversal, the reversal caused the glaciation, or that a third entity caused both? The Earth's internal dynamo also has not been addressed.

Hypotheses

Main resource: Hypotheses

1. Magnetic field reversals affect the local magnetic fields within crystallizing liquids.
2. Magnetic field reversals may cause the ionosphere to contact the surface of the Earth during the reversal period.
3. Magnetic field reversals may allow increased radiation to irradiate the upper crustal rocks to significant depths during the reversal period.
4. Subject to the origin of magnetic field reversals, they may cause significant increases in volcanic activity during the reversal period.
5. Magnetic field reversals of the Sun occur with the sunspot cycle which may have its origins in enhanced electron current from Jupiter and Venus when perihelion is coincident.

See also

• Analytical astronomy
• Cosmogony
• Cratering
• Electric orbits
• Electron beam heating
• Galaxies
• Intergalactic medium
• Locating the Sun
• Meteorites
• Neutrinos from the Sun
• Spectrum of Vega
• Standard candles
• Vertical precession
• X-ray classification of a star
• X-ray trigonometric parallax

External links

• International Astronomical Union
• NASA/IPAC Extragalactic Database - NED
• NASA's National Space Science Data Center
• Office of Scientific & Technical Information
• The SAO/NASA Astrophysics Data System
• Scirus for scientific information only advanced search
• SDSS Quick Look tool: SkyServer
• SIMBAD Astronomical Database
• SIMBAD Web interface, Harvard alternate
• Spacecraft Query at NASA
• Universal coordinate converter

{{Charge ontology}}

{{History of science resources}}{{Principles of radiation astronomy}}