scholarly journals Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrew J. Biggin ◽  
Richard K. Bono ◽  
Domenico G. Meduri ◽  
Courtney J. Sprain ◽  
Christopher J. Davies ◽  
...  
Keyword(s):  
Power Law ◽  
Geomagnetic Field ◽  
Recent Observation ◽  
Observational Constraint ◽  
Angular Dispersion ◽  
Geological Time ◽  
Future Studies ◽  
Axial Dipole ◽  
Quantitative Estimates

AbstractA defining characteristic of the recent geomagnetic field is its dominant axial dipole which provides its navigational utility and dictates the shape of the magnetosphere. Going back through time, much less is known about the degree of axial dipole dominance. Here we use a substantial and diverse set of 3D numerical dynamo simulations and recent observation-based field models to derive a power law relationship between the angular dispersion of virtual geomagnetic poles at the equator and the median axial dipole dominance measured at Earth’s surface. Applying this relation to published estimates of equatorial angular dispersion implies that geomagnetic axial dipole dominance averaged over 107–109 years has remained moderately high and stable through large parts of geological time. This provides an observational constraint to future studies of the geodynamo and palaeomagnetosphere. It also provides some reassurance as to the reliability of palaeogeographical reconstructions provided by palaeomagnetism.

scholarly journals Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time

2020 ◽  
Author(s):  
Andrew Biggin ◽  
Richard Bono ◽  
Domenico Meduri ◽  
Courtney Sprain ◽  
Christopher Davies ◽  
...  
Keyword(s):  
Geological Time ◽  
Axial Dipole ◽  
Quantitative Estimates

scholarly journals Reversals in the large-scale αΩ-dynamo with memory

2015 ◽  
Vol 22 (4) ◽  
pp. 361-369 ◽  
Author(s):  
L. K. Feschenko ◽  
G. M. Vodinchar
Keyword(s):  
Magnetic Field ◽  
Power Law ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Magnetic Polarity ◽  
Power Law Model ◽  
The Real ◽  
Geomagnetic Polarity ◽  
With Memory ◽  
The Magnetic Field

Abstract. Inversion of the magnetic field in a model of large-scale αΩ-dynamo with α-effect with stochastic memory is under investigation. The model allows us to reproduce the main features of the geomagnetic field reversals. It was established that the polarity intervals in the model are distributed according to the power law. Model magnetic polarity timescale is fractal. Its dimension is consistent with the dimension of the real geomagnetic polarity timescale.

scholarly journals Review: The Effects of Supersonic Aviation on Ozone and Climate

Aerospace ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 41
Author(s):  
Sigrun Matthes ◽  
David S. Lee ◽  
Ruben Rodriguez De De Leon ◽  
Ling Lim ◽  
Bethan Owen ◽  
...  
Keyword(s):  
Emission Scenario ◽  
Scientific Literature ◽  
Global Climate ◽  
Comprehensive Overview ◽  
Climate Effect ◽  
Regulatory Issues ◽  
Future Studies ◽  
Climate Effects ◽  
Supersonic Transport ◽  
Quantitative Estimates

When working towards regulation of supersonic aviation, a comprehensive understanding of the global climate effect of supersonic aviation is required in order to develop future regulatory issues. Such research requires a comprehensive overview of existing scientific literature having explored the climate effect of aviation. This review article provides an overview on earlier studies assessing the climate effects of supersonic aviation, comprising non-CO2 effects. An overview on the historical evaluation of research focussing on supersonic aviation and its environmental impacts is provided, followed by an overview on concepts explored and construction of emission inventories. Quantitative estimates provided for individual effects are presented and compared. Subsequently, regulatory issues related to supersonic transport are summarised. Finally, requirements for future studies, e.g., in emission scenario construction or numerical modelling of climate effects, are summarised and main conclusions discussed.

scholarly journals Was the Devonian geomagnetic field dipolar or multipolar? Palaeointensity studies of Devonian igneous rocks from the Minusa Basin (Siberia) and the Kola Peninsula dykes, Russia

2017 ◽  
Vol 209 (2) ◽  
pp. 1265-1286 ◽  
Author(s):  
V V Shcherbakova ◽  
A J Biggin ◽  
R V Veselovskiy ◽  
A V Shatsillo ◽  
L M A Hawkins ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Geomagnetic Field ◽  
Mantle Convection ◽  
Geological Time ◽  
Southern Siberia ◽  
Planetary Evolution ◽  
Low Intensity ◽  
Order Of Magnitude ◽  
Earth’S Climate ◽  
The Impact

Abstract Defining variations in the behaviour of the geomagnetic field through geological time is critical to understanding the dynamics of Earth's core and its response to mantle convection and planetary evolution. Furthermore, the question of whether the axial dipole dominance of the recent palaeomagnetic field persists through the whole of Earth's history is fundamental to determining the reliability of palaeogeographic reconstructions and the efficacy of the magnetosphere in shielding Earth from solar wind radiation. Previous palaeomagnetic directional studies have suggested that the palaeofield had a complex configuration in the Devonian period (419–359 Ma). Here we present new high-quality palaeointensity determinations from rocks aged between 408 and 375 Ma from the Minusa Basin (southern Siberia), and the Kola Peninsula that enable the first reliable investigation of the strength of the field during this enigmatic period. Palaeointensity experiments were performed using the thermal Thellier, microwave Thellier and Wilson methods on 165 specimens from 25 sites. Six out of eight successful sites from the Minusa Basin and all four successful sites from the Kola Peninsula produced extremely low palaeointensities (<10 μT). These findings challenge the uniformitarian view of the palaeomagnetic field: field intensities of nearly an order of magnitude lower than Neogene values (except during relatively rare geomagnetic excursions and reversals) together with the widespread appearance of strange directions found in the Devonian suggest that the Earth's field during this time may have had a dominantly multipolar geometry. A persistent, low intensity multipolar magnetic field and associated diminished magnetosphere would increase the impact of solar particles on the Earth's magnetosphere, ionosphere and atmosphere with potential major implications for Earth's climate and biosphere.

Inflation with non-minimally derivative coupling

2015 ◽  
Vol 30 (28n29) ◽  
pp. 1545004 ◽  
Author(s):  
Nan Yang ◽  
Qing Gao ◽  
Yungui Gong
Keyword(s):  
Gravitational Waves ◽  
Power Law ◽  
Second Order ◽  
Order Correction ◽  
Observational Constraint ◽  
Derivative Coupling ◽  
Primordial Gravitational Waves ◽  
Inflationary Models

We derive the second order correction to the scalar and tensor spectral tilts for the inflationary models with non-minimally derivative coupling. In the high friction limit, the quartic power law potential is consistent with the observational constraint at 95% CL because the amplitude of the primordial gravitational waves is smaller, and the inflaton excursion is sub-Planckian.

scholarly journals A full sequence of the Matuyama–Brunhes geomagnetic reversal in the Chiba composite section, Central Japan

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Yuki Haneda ◽  
Makoto Okada ◽  
Yusuke Suganuma ◽  
Takahiro Kitamura
Keyword(s):  
Field Intensity ◽  
Geomagnetic Field ◽  
Central Japan ◽  
Virtual Geomagnetic Pole ◽  
Geomagnetic Reversal ◽  
Full Sequence ◽  
Intensity Index ◽  
Axial Dipole ◽  
Composite Section ◽  
Stratigraphic Position

Abstract Geological records of the Matuyama–Brunhes (M–B) geomagnetic reversal facilitate the development of an age model for sedimentary and volcanic sequences and help decipher the dynamics of the Earth’s magnetic field. However, the structure of the geomagnetic field during the M–B geomagnetic reversal remains controversial due to its complex field behavior. In this study, we conducted paleo- and rock-magnetic analyses of samples from the Chiba composite section (CbCS), a continuous and expanded marine succession in Central Japan, to reconstruct the full sequence of the M–B geomagnetic reversal. We define an average stratigraphic position of the M–B boundary and estimate its age based on three sections in the CbCS and a neighboring drill core, TB-2. The average stratigraphic position of the M–B boundary in the CbCS is established at 1.1 ± 0.3 m above a widespread volcanic ash bed (the Byk-E tephra). Assuming a chronological error associated with orbital tuning of 5 kyr and stratigraphic uncertainty of 0.4 kyr, the M–B boundary in CbCS is at 772.9 ± 5.4 ka (1σ). The virtual geomagnetic pole, which is calculated from the paleomagnetic directions, shows several short fluctuations between 783 and 763 ka, with concomitant decreases in geomagnetic field intensity index. After termination of the field instabilities, the field intensity recovered and became higher than before the M–B boundary, with a stable normal polarity direction. The paleomagnetic records in the CbCS exhibit a field asymmetry between the axial dipole decay and field recovery, providing a full sequence of the M–B reversal, suggesting that the non-axial dipole field dominated several times during periods ca. 20 kyr long across the M–B boundary, due to depletion in the main axial dipole component. Our results provide probably the most detailed sedimentary record of the M–B geomagnetic reversal and offer valuable information to further understand the mechanism and dynamics of geomagnetic reversals. Graphical abstract

THE RELATION OF JET QUENCHING AND POWER-LAW OBSERVED IN pT-DISTRIBUTIONS IN RELATIVISTIC HEAVY-ION COLLISIONS

2006 ◽  
Vol 15 (04) ◽  
pp. 865-876
Author(s):  
WANG LI ◽  
XIAO DONG WANG
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Recent Observation ◽  
Fractal Dimensions ◽  
Heavy Ion ◽  
High Energy ◽  
Jet Quenching ◽  
Relativistic Heavy Ion Collisions ◽  
Distribution Data ◽  
Ion Collisions

Recent observation of high-pT hadron spectra suppression and mono-jet production in central Au-Au collisions and Cu-Cu collisions at RHIC have confirmed the long predicted phenomenon of jet quenching in high-energy-ion collisions. Detailed analyses of the experimental data show parton energy loss as the mechanism for the discovered jet quenching. Preconception-free analyses of the inclusive invariant transverse-momentum distribution data taken from the measurements of Au-Au collisions at [Formula: see text] and [Formula: see text] have been performed. It is observed that the distribution exhibits for pT≥2 GeV/c remarkably good power-law behavior (pT-scaling) with general regularities. It may explain the data coming from the STAR or PHENIX to some extent. Using the power-law by a simple model, its underlying geometrical structure has to be understood in terms of fractal dimensions. A simple model is proposed which approximately reproduces the above-mentioned data for the phenomenon, and it affords a new way to research the QGP matter and jet quenching. Further heavy-ion collision experiments are suggested.

scholarly journals At the forefront: evidence of the applicability of using environmental DNA to quantify the abundance of fish populations in natural lentic waters with additional sampling considerations

2017 ◽  
Vol 74 (12) ◽  
pp. 2030-2034 ◽  
Author(s):  
Stephen L. Klobucar ◽  
Torrey W. Rodgers ◽  
Phaedra Budy
Keyword(s):  
Aquatic Ecosystems ◽  
Salvelinus Alpinus ◽  
Species Abundance ◽  
Environmental Dna ◽  
Future Studies ◽  
Natural Lakes ◽  
Quantitative Estimates ◽  
Promising Application ◽  
The Relationship ◽  
Lentic Waters

Environmental DNA (eDNA) sampling has proven to be a valuable tool for detecting species in aquatic ecosystems. Within this rapidly evolving field, a promising application is the ability to obtain quantitative estimates of relative species abundance based on eDNA concentration rather than traditionally labor-intensive methods. We investigated the relationship between eDNA concentration and Arctic char (Salvelinus alpinus) abundance in five well-studied natural lakes; additionally, we examined the effects of different temporal (e.g., season) and spatial (e.g., depth) scales on eDNA concentration. Concentrations of eDNA were linearly correlated with char population estimates ([Formula: see text] = 0.78) and exponentially correlated with char densities ([Formula: see text] = 0.96 by area; 0.82 by volume). Across lakes, eDNA concentrations were greater and more homogeneous in the water column during mixis; however, when stratified, eDNA concentrations were greater in the hypolimnion. Overall, our findings demonstrate that eDNA techniques can produce effective estimates of relative fish abundance in natural lakes. These findings can guide future studies to improve and expand eDNA methods while informing research and management using rapid and minimally invasive sampling.

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