Geomagnetic Polarity Reversals, Observations

2007 ◽  
pp. 324-328
Author(s):  
Bradford M. Clement
Keyword(s):  
Polarity Reversals ◽  
Geomagnetic Polarity

Cretaceous-Tertiary profile, rhythmic deposition, and geomagnetic polarity reversals of marine sediments near Bjala, Bulgaria

2002 ◽  
Author(s):  
Anton Preisinger ◽  
Selma Aslanian ◽  
Franz Brandstaetter ◽  
Friedrich Grass ◽  
Herbert Stradner ◽  
...  
Keyword(s):  
Marine Sediments ◽  
Polarity Reversals ◽  
Geomagnetic Polarity

scholarly journals Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals

2000 ◽  
Vol 18 (1) ◽  
pp. 11-27 ◽  
Author(s):  
D. M. Willis ◽  
A. C. Holder ◽  
C. J. Davis
Keyword(s):  
Magnetic Field ◽  
Spherical Cavity ◽  
Exact Equation ◽  
Outer Magnetosphere ◽  
Special Cases ◽  
Magnetospheric Configuration And Dynamics ◽  
Polarity Reversals ◽  
Field Lines ◽  
Geomagnetic Polarity ◽  
The Magnetic Field

Abstract. Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals are investigated by considering the idealized problem of a magnetic multipole of order m and degree n located at the centre of a spherical cavity surrounded by a boundless perfect diamagnetic medium. In this illustrative idealization, the fixed spherical (magnetopause) boundary layer behaves as a perfectly conducting surface that shields the external diamagnetic medium from the compressed multipole magnetic field, which is therefore confined within the spherical cavity. For a general magnetic multipole of degree n, the non-radial components of magnetic induction just inside the magnetopause are increased by the factor {1 + [(n + 1)/n]} relative to their corresponding values in the absence of the perfectly conducting spherical magnetopause. An exact equation is derived for the magnetic field lines of an individual zonal (m = 0), or axisymmetric, magnetic multipole of arbitrary degree n located at the centre of the magnetospheric cavity. For such a zonal magnetic multipole, there are always two neutral points and n-1 neutral rings on the spherical magnetopause surface. The two neutral points are located at the poles of the spherical magnetopause. If n is even, one of the neutral rings is coincident with the equator; otherwise, the neutral rings are located symmetrically with respect to the equator. The actual existence of idealized higher-degree (n>1) axisymmetric magnetospheres would necessarily imply multiple (n + 1) magnetospheric cusps and multiple (n) ring currents. Exact equations are also derived for the magnetic field lines of an individual non-axisymmetric magnetic multipole, confined by a perfectly conducting spherical magnetopause, in two special cases; namely, a symmetric sectorial multipole (m = n) and an antisymmetric sectorial multipole (m = n-1). For both these non-axisymmetric magnetic multipoles, there exists on the spherical magnetopause surface a set of neutral points linked by a network of magnetic field lines. Novel magnetospheric processes are likely to arise from the existence of magnetic neutral lines that extend from the magnetopause to the surface of the Earth. Finally, magnetic field lines that are confined to, or perpendicular to, either special meridional planes or the equatorial plane, when the multipole is in free space, continue to be confined to, or perpendicular to, these same planes when the perfectly conducting magnetopause is present.Key words. Geomagnetism and paleomagnetism (reversals-process, time scale, magnetostratigraphy) · Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetospheric configuration and dynamics)

scholarly journals Polar caps during geomagnetic polarity reversals

2018 ◽  
Vol 216 (2) ◽  
pp. 1334-1343 ◽  
Author(s):  
Bruno Zossi ◽  
Mariano Fagre ◽  
Hagay Amit ◽  
Ana G Elias
Keyword(s):  
Polar Caps ◽  
Polarity Reversals ◽  
Geomagnetic Polarity

scholarly journals A simplified correlation between vertebrate evolution and Paleozoic geomagnetism

2019 ◽  
Author(s):  
John P Staub
Keyword(s):  
Atmospheric Oxygen ◽  
Low Frequency ◽  
Strong Relationship ◽  
Evolutionary Patterns ◽  
Geologic Time Scale ◽  
Polarity Reversals ◽  
Low Levels ◽  
Geomagnetic Polarity ◽  
Taxonomic Groups ◽  
Biologic Factors

Background. Despite a fifty-year failure of paleontologists to find a viable connection between geomagnetic polarity reversals and evolutionary patterns, recent paleobiology databases show that the early appearance, radiation, and diversification of Paleozoic vertebrates tends to occur during periods having frequent collapses of the Earth’s geomagnetic field. The transition time during the collapse of the Earth’s protective magnetic shield can last thousands of years, and the effects on biota are unknown. Solar and cosmic radiation, volcanism, climate alteration, low-frequency electromagnetic fields, depletion of ozone, the stripping of atmospheric oxygen, and increasing production of Carbon14 in the stratosphere have been proposed as possible causes, but previous studies have found no effects. Methods. Using published databases, we compiled a spreadsheet showing the first appearance of 2104 genera with each genus assigned to one of 8 major taxonomic groups. From Gradstein’s Geologic Time Scale 2012, we delineated 17 Paleozoic zones with either high or low levels of polarity reversals. Results. From our compilation, 727 Paleozoic vertebrates represent the initial radiation and diversification of individual Paleozoic vertebrate clades. After compensating for sample-size and external geologic and sampling biases, the resulting Pearson’s correlation coefficient between the 727 genera and geomagnetic polarity zones equals 0.8, a result that suggests a strong relationship exists between Paleozoic vertebrates and geomagnetism. Discussion. The question: is this apparent connection between geomagnetism and the evolution of Paleozoic vertebrate due to environmental or biologic factors. If biologic, why are vertebrates the only biota effected? And after an indeterminate period of time, how do vertebrates become immune to the ongoing effects of polarity reversals?

scholarly journals Polarity Reversals in the Earth's Magnetic Field

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Fabio Florindo
Keyword(s):  
Magnetic Field ◽  
Solid Earth ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Polarity Reversals ◽  
Geomagnetic Polarity

Studies of geomagnetic polarity reversals have generated some of the biggest and most interesting debates in the paleomagnetic and wider solid Earth geophysics communities over the last 25 years.

scholarly journals A simplified correlation between vertebrate evolution and Paleozoic geomagnetism

2019 ◽  
Author(s):  
John P Staub
Keyword(s):  
Atmospheric Oxygen ◽  
Low Frequency ◽  
Strong Relationship ◽  
Evolutionary Patterns ◽  
Geologic Time Scale ◽  
Polarity Reversals ◽  
Low Levels ◽  
Geomagnetic Polarity ◽  
Taxonomic Groups ◽  
Biologic Factors

Background. Despite a fifty-year failure of paleontologists to find a viable connection between geomagnetic polarity reversals and evolutionary patterns, recent paleobiology databases show that the early appearance, radiation, and diversification of Paleozoic vertebrates tends to occur during periods having frequent collapses of the Earth’s geomagnetic field. The transition time during the collapse of the Earth’s protective magnetic shield can last thousands of years, and the effects on biota are unknown. Solar and cosmic radiation, volcanism, climate alteration, low-frequency electromagnetic fields, depletion of ozone, the stripping of atmospheric oxygen, and increasing production of Carbon14 in the stratosphere have been proposed as possible causes, but previous studies have found no effects. Methods. Using published databases, we compiled a spreadsheet showing the first appearance of 2210 age-dated genera with each genus assigned to one of eleven major taxonomic groups. From Gradstein’s Geologic Time Scale 2012, we delineated 17 Paleozoic zones with either high or low levels of polarity reversals. Results. From our compilation, 737 Paleozoic vertebrates represent the initial radiation and diversification of individual Paleozoic vertebrate clades. After compensating for sample-size and external geologic and sampling biases, the resulting Pearson’s correlation coefficient between the 737 genera and geomagnetic polarity zones equals 0.89. These results suggest a strong relationship exists between Paleozoic vertebrates and geomagnetism. Discussion. The question: is this apparent connection between geomagnetism and the evolution of Paleozoic vertebrate due to environmental or biologic factors. If biologic, why are vertebrates the only biota effected? And after an indeterminate period of time, how do vertebrates become immune to the ongoing effects of polarity reversals?

scholarly journals Paleozoic geomagnetism shapes vertebrate evolution

2018 ◽  
Author(s):  
John P Staub
Keyword(s):  
Atmospheric Oxygen ◽  
Low Frequency ◽  
Strong Relationship ◽  
Age Dating ◽  
P Value ◽  
Evolutionary Patterns ◽  
Natural Group ◽  
Polarity Reversals ◽  
Geomagnetic Polarity ◽  
Taxonomic Groups

Background. Despite a fifty-year failure of paleontologists to find a viable connection between geomagnetic polarity reversals and evolutionary patterns, recent databases show that the early appearance, radiation, and diversification of Paleozoic vertebrates tend to occur during periods having frequent collapses of the Earth’s geomagnetic field. The transition time during the collapse of the Earth’s protective magnetic shield can last thousands of years, and the effects on biota are unknown. Solar and cosmic radiation, volcanism, weather alteration, low-frequency electromagnetic fields, depletion of ozone, and the stripping of atmospheric oxygen have been proposed as possible causes, but previous studies have found no effects. Methods. Using published databases, we compiled a spreadsheet that shows the first appearance of 1809 age-dated genera with each genus assigned to one of 28 taxonomic groups. From Gradstein’s Geologic Time Scale 2012, we delineated 17 Paleozoic zones with either high or low levels of polarity reversals. Results. From our compilation, we counted 508 Paleozoic vertebrates that first appeared within 20 million-years of the origin of their clade or natural group. These genera represent the initial radiation and diversification of individual Paleozoic vertebrate clades. After compensating for sample-size and external geologic biases, the resulting Pearson’s coefficient between these genera and polarity zones equals 0.781. Using 11 commonly accepted clades and assuming a natural competition existed between them, we counted each genus from a clade’s inception until it was bypassed by a subsequent clade. Here, Pearson's equals 0.901 with a p-value of <0.000001. In a blindfold study, we separated the Paleozoic into a dozen equally-sized temporal bins, then 13 bins, up to 31 bins. The mean Pearson coefficient for these bins is 0.810. After calculating coefficients for four distinct taxonomies, two paleomagnetic systems, three systematics for age-dating within geologic stages, and seven independent spreadsheets, the results suggest a strong relationship exists between Paleozoic vertebrates and polarity reversals. In addition, the earliest species of the major divisions of Paleozoic vertebrates (jawless fish, armored fish, jawed fish, cartilage fish, fish with bones, lobe-finned fish, tetrapods, amphibians, reptiles, and synapsids) first appeared in zones with relatively high levels of polarity reversals. Discussion. The question: is this apparent connection between geomagnetism and the evolution of Paleozoic vertebrate due to environmental or biologic factors. If biologic, why are vertebrates the only biota effected? And after an indeterminate period of time, how do vertebrate families become immune to the ongoing effects of polarity reversals?

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