Effect of porosity on the rate of magnetic polarity reversal of a polycrystalline Li-Ni-Zn ferrite

1971 ◽  
Vol 10 (3) ◽  
pp. 219-221
Author(s):  
K. D. Dugar-Zhabon
Keyword(s):  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Zn Ferrite ◽  
Magnetic Polarity Reversal

Davis Creek silt, an Early Pleistocene or Late Pliocene deposit in the Cypress Hills of Saskatchewan

1989 ◽  
Vol 26 (1) ◽  
pp. 192-198 ◽  
Author(s):  
W. J. Vreeken ◽  
R. W. Klassen ◽  
R. W. Barendregt
Keyword(s):  
Volcanic Ash ◽  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Early Pleistocene ◽  
The South ◽  
Glacial Deposits ◽  
Late Pliocene ◽  
Late Wisconsinan ◽  
Weathering Zone ◽  
Magnetic Polarity Reversal

Davis Creek silt is the informal name for a previously unreported loess and its reworked detritus encountered at several locations to the south of the east and centre blocks of the Cypress Hills. This unit intervenes between a pediment with an estimated age of 10 Ma and Late Wisconsinan glacial deposits. Because the unit has reversed magnetization, it is older than 788 ka, the astronomical age of the Matuyama–Brunhes magnetic polarity reversal. The unit also contains an undated volcanic ash from the Pearlette ash family that could represent the Mesa Falls (1.27 Ma) or the Huckleberry Ridge (2.02 Ma) ash bed. Davis Creek silt overlies an oxidized weathering zone and contains large secondary carbonate nodules near its truncated top that were, in places, reworked into a lag deposit or stone line before accumulation of the glacial overburden. At one location Davis Creek silt is separated from this overburden by a unit of cryoturbated gravelly loam with remnants of a reddish-yellow paleosolic B horizon.

scholarly journals Magnetic cycles of the planet-hosting star τ Bootis - II. A second magnetic polarity reversal

2009 ◽  
Vol 398 (3) ◽  
pp. 1383-1391 ◽  
Author(s):  
R. Fares ◽  
J.-F. Donati ◽  
C. Moutou ◽  
D. Bohlender ◽  
C. Catala ◽  
...  
Keyword(s):  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Magnetic Cycles ◽  
Magnetic Polarity Reversal

scholarly journals Elevated paleomagnetic dispersion at Saint Helena suggests long-lived anomalous behavior in the South Atlantic

2020 ◽  
Vol 117 (31) ◽  
pp. 18258-18263 ◽  
Author(s):  
Yael A. Engbers ◽  
Andrew J. Biggin ◽  
Richard K. Bono
Keyword(s):  
Geomagnetic Field ◽  
Anomalous Behavior ◽  
Magnetic Polarity ◽  
South Atlantic ◽  
Polarity Reversal ◽  
The South ◽  
Geomagnetic Secular Variation ◽  
Core Dynamics ◽  
Geocentric Axial Dipole ◽  
Magnetic Polarity Reversal

Earth’s magnetic field is presently characterized by a large and growing anomaly in the South Atlantic Ocean. The question of whether this region of Earth’s surface is preferentially subject to enhanced geomagnetic variability on geological timescales has major implications for core dynamics, core−mantle interaction, and the possibility of an imminent magnetic polarity reversal. Here we present paleomagnetic data from Saint Helena, a volcanic island ideally suited for testing the hypothesis that geomagnetic field behavior is anomalous in the South Atlantic on timescales of millions of years. Our results, supported by positive baked contact and reversal tests, produce a mean direction approximating that expected from a geocentric axial dipole for the interval 8 to 11 million years ago, but with very large associated directional dispersion. These findings indicate that, on geological timescales, geomagnetic secular variation is persistently enhanced in the vicinity of Saint Helena. This, in turn, supports the South Atlantic as a locus of unusual geomagnetic behavior arising from core−mantle interaction, while also appearing to reduce the likelihood that the present-day regional anomaly is a precursor to a global polarity reversal.

Timing of the Brunhes-Matuyama magnetic polarity reversal in Chinese loess using 10Be

Geology ◽  
2014 ◽  
Vol 42 (6) ◽  
pp. 467-470 ◽  
Author(s):  
Weijian Zhou ◽  
J. Warren Beck ◽  
Xianghui Kong ◽  
Zhisheng An ◽  
Xiaoke Qiang ◽  
...  
Keyword(s):  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Chinese Loess ◽  
Magnetic Polarity Reversal

scholarly journals Synchronizing volcanic, sedimentary, and ice core records of Earth’s last magnetic polarity reversal

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw4621 ◽  
Author(s):  
Brad S. Singer ◽  
Brian R. Jicha ◽  
Nobutatsu Mochizuki ◽  
Robert S. Coe
Keyword(s):  
Magnetic Field ◽  
Short Duration ◽  
Ice Core ◽  
Magnetic Polarity ◽  
Lava Flows ◽  
Polarity Reversal ◽  
Field Polarity ◽  
Reversal Process ◽  
Complex Process ◽  
Magnetic Polarity Reversal

Reversal of Earth’s magnetic field polarity every 105 to 106 years is among the most far-reaching, yet enigmatic, geophysical phenomena. The short duration of reversals make precise temporal records of past magnetic field behavior paramount to understanding the processes that produce them. We correlate new 40Ar/39Ar dates from transitionally magnetized lava flows to astronomically dated sediment and ice records to map the evolution of Earth’s last reversal. The final 180° polarity reversal at ~773 ka culminates a complex process beginning at ~795 ka with weakening of the field, succeeded by increased field intensity manifested in sediments and ice, and then by an excursion and weakening of intensity at ~784 ka that heralds a >10 ka period wherein sediments record highly variable directions. The 22 ka evolution of this reversal suggested by our findings is mirrored by a numerical geodynamo simulation that may capture much of the naturally observed reversal process.

scholarly journals Causes and Consequences of Geomagnetic Field Collapse

2020 ◽  
pp. 60-76
Author(s):  
J. Marvin Herndon
Keyword(s):  
Geomagnetic Field ◽  
Ohmic Heating ◽  
Electrical Current ◽  
Magnetic Polarity ◽  
Self Control ◽  
Polarity Reversal ◽  
Rift System ◽  
Stable Operation ◽  
East African Rift System ◽  
Charge Particle

Consequences of the next geomagnetic field collapse, concomitant with a magnetic polarity reversal or excursion, have been greatly underestimated as based upon a widely-accepted, but physically-impossible geoscience paradigm. The underlying causes of geomagnetic field collapse are inexplicable in that flawed paradigm wherein geomagnetic field production is assumed to be produced in the Earth’s fluid core. Here I review the causes and consequences of geomagnetic field collapse in terms of a new geoscience paradigm, called Whole-Earth Decompression Dynamics, specifically focusing on nuclear fission georeactor generation of the geomagnetic field and the intimate connection between its energy production and the much greater stored energy of protoplanetary compression. The nuclear georeactor is subject to a staggering range and variety of potential instabilities. Yet, its natural self-control mechanism allows stable operation without geomagnetic reversals for times longer than 20 million years. Geomagnetic reversals and excursions occur when georeactor sub-shell convection is disrupted. Disrupted sub-shell convection can occur due to (1) major trauma to Earth such as an asteroid collision or (2) change in the charge particle flux from the sun or change in the ring current either of which can induce electrical current into the georeactor via the geomagnetic field causing ohmic-heating that can potentially disrupt sub-shell convection. Further, humans could deliberately or unintentionally disrupt sub-shell convection by disrupting the charge-particle environment across portions of the geomagnetic field by nuclear detonations or by heating the ionosphere with focused electromagnetic radiation. The use of electromagnetic pulse weapons is potentially far more devastating to humanity than previously imagined, and should be prohibited. During the next polarity reversal or excursion, increased volcanic activity may be expected in areas fed by georeactor heat, such as the East African Rift System, Hawaii, Iceland, and Yellowstone in the USA. One potentially great risk is triggering the eruption of the Yellowstone super-volcano.

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