Frequent Polarity Reversals in the Cretaceous Normal Superchron

2021 ◽  
Author(s):  
Dawen Zhang ◽  
Maodu Yan ◽  
Chunhui Song ◽  
Weilin Zhang ◽  
Xiaomin Fang ◽  
...  
Keyword(s):  
Polarity Reversals

scholarly journals The role of buoyancy in polarity reversals of the geodynamo

2014 ◽  
Vol 199 (3) ◽  
pp. 1698-1708 ◽  
Author(s):  
Binod Sreenivasan ◽  
Swarandeep Sahoo ◽  
Gaurav Dhama
Keyword(s):  
Polarity Reversals

Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Stark Formation

1976 ◽  
Vol 13 (4) ◽  
pp. 563-578 ◽  
Author(s):  
D. K. Bingham ◽  
M. E. Evans
Keyword(s):  
Northwest Territories ◽  
North American ◽  
Geomagnetic Field ◽  
Pole Position ◽  
The West ◽  
Stratigraphic Sequence ◽  
Polar Wander ◽  
Early Proterozoic ◽  
The North ◽  
Polarity Reversals

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.

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 Multidecadally resolved polarity oscillations during a geomagnetic excursion

2018 ◽  
Vol 115 (36) ◽  
pp. 8913-8918 ◽  
Author(s):  
Yu-Min Chou ◽  
Xiuyang Jiang ◽  
Qingsong Liu ◽  
Hsun-Ming Hu ◽  
Chung-Che Wu ◽  
...  
Keyword(s):  
20Th Century ◽  
Geomagnetic Field ◽  
Early 20Th Century ◽  
Human Society ◽  
Before Present ◽  
Earth History ◽  
Geomagnetic Excursion ◽  
Deep Interior ◽  
Polarity Reversals ◽  
Chinese Stalagmite

Polarity reversals of the geomagnetic field have occurred through billions of years of Earth history and were first revealed in the early 20th century. Almost a century later, details of transitional field behavior during geomagnetic reversals and excursions remain poorly known. Here, we present a multidecadally resolved geomagnetic excursion record from a radioisotopically dated Chinese stalagmite at 107–91 thousand years before present with age precision of several decades. The duration of geomagnetic directional oscillations ranged from several centuries at 106–103 thousand years before present to millennia at 98–92 thousand years before present, with one abrupt reversal transition occurring in one to two centuries when the field was weakest. These features indicate prolonged geodynamo instability. Repeated asymmetrical interhemispheric polarity drifts associated with weak dipole fields likely originated in Earth’s deep interior. If such rapid polarity changes occurred in future, they could severely affect satellites and human society.

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