scholarly journals Analysis of geomagnetic measurements prior the Maule (2010), Iquique (2014) and Illapel (2015) earthquakes, in the Pacific Ocean sector of the Southern Hemisphere

2019 ◽  
Author(s):  
Enrique G. Cordaro ◽  
Patricio Venegas-Aravena ◽  
David Laroze
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Seismic Event ◽  
Vertical Component ◽  
Time Lapse ◽  
Radial Component ◽  
Cumulative Number ◽  
Research Groups ◽  
Low Frequencies ◽  
Ocean Sector

Abstract. It has been possible to detect variations in the vertical component of the geomagnetic field (Bz) through its first and second derivate in a range of frequencies (microHz); these seem to be roughly related with some major seismic subduction events. We studied the period 2010–2015, analysing the daily values of magnetic records over periods close to the last three significant events that occurred through the Chilean margin, i. e., along a boundary between convergent plates that is characterized by the occurrence of seismic events of magnitude greater than Mw8. These are the events of Iquique 2014, Illapel 2015 and Maule 2010, all at different latitudes, on different dates and characterized by different types of margin (erosive or accretionary). Certain similarities were found in the associated magnetic field variations: 1) Variation in the radial or z component of the geomagnetic field and its first and second temporal derivative, modelled as a small jump, and small oscillations in the second derivative, generating a frequency band between 1c / 48.9 hours and 1c / 79.13 Hrs. 2) A variable time lapse of between 30 and 120 days; and 3) The seismic event. Furthermore, when analysing spectrograms for the second temporal derivate of the radial component, different behaviour is found related to its spectral density. This takes the form of an increase in ultra-low frequencies (0.01–0.4 mHz) between the start of the magnetic jump and the seismic event. These frequencies are lower than those found during the last years by research groups that related magnetic field and earthquakes, furthermore the concept of time lapse close to 30 days is in agreement with those research groups. The previous analyses may not be so robust, this is why additionally a new method is used with stations closer to the events and time periods of two years. We analysed the daily cumulative number of anomalous behaviour in z component of magnetic field on ground based magnetometers. The results show an increase in the number of magnetic anomalies prior to the occurrence of the three earthquakes. The behavior of the anomalies is similar to those presented by other authors for other earthquakes with similar methods in ionosphere. All this magnetic features might recover seismic information of the events and could be related with Lithosphere-Atmosphere-Ionosphere Coupling.

scholarly journals Geomagnetic field influences upward movement of young Chinook salmon emerging from nests

2018 ◽  
Vol 14 (2) ◽  
pp. 20170752 ◽  
Author(s):  
Nathan F. Putman ◽  
Michelle M. Scanlan ◽  
Amanda M. Pollock ◽  
Joseph P. O'Neil ◽  
Ryan B. Couture ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Chinook Salmon ◽  
Geomagnetic Field ◽  
Oncorhynchus Tshawytscha ◽  
Dimensional Space ◽  
Spatial Scales ◽  
Vertical Component ◽  
Life Cycles ◽  
Upward Movement ◽  
The Magnetic Field

Organisms use a variety of environmental cues to orient their movements in three-dimensional space. Here, we show that the upward movement of young Chinook salmon ( Oncorhynchus tshawytscha ) emerging from gravel nests is influenced by the geomagnetic field. Fish in the ambient geomagnetic field travelled farther upwards through substrate than did fish tested in a field with the vertical component inverted. This suggests that the magnetic field is one of several factors that influences emergence from the gravel, possibly by serving as an orientation cue that helps fish determine which way is up. Moreover, our work indicates that the Oncorhynchus species are sensitive to the magnetic field throughout their life cycles, and that it guides their movements across a range of spatial scales and habitats.

scholarly journals Saturation of the magnetosphere during superstorms: new results from the magnetogram inversion technique

2017 ◽  
Vol 3 (3) ◽  
pp. 28-36 ◽  
Author(s):  
Владимир Мишин ◽  
Vladimir Mishin ◽  
Юрий Караваев ◽  
Yuriy Karavaev
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Total Pressure ◽  
Dynamic Pressure ◽  
Vertical Component ◽  
Magnetic Clouds ◽  
Polar Cap ◽  
Thermal Pressure ◽  
Dayside Magnetopause ◽  
Using Data

Using data on three superstorms, we study new features of the saturation of the polar cap area when the solar wind (SW) increases. The polar cap saturation is shown to occur when the SW dynamic pressure and southward vertical (IMF) component rise. The saturation is realized not only during the passage of interplanetary magnetic clouds, but also at significant enhancement of SW density when the SW thermal pressure is comparable with the pressure of the interplanetary magnetic field. We assume that under such conditions the saturation is caused not only by a decrease in the efficiency of reconnection at the dayside magnetopause, but mainly by finite magnetosphere compressibility — stopping the magnetopause compression due to a rapid earthward growth of the geomagnetic field, i.e. the inner magnetospheric structure of the geomagnetic field. We have found signs of saturation depending on the northward IMF component. We assume that the IMF-dependent saturation exists for both signs of its vertical component due to an increase in the total pressure in the magnetosheath. Moreover, when penetrating into the magnetosphere, the southward IMF component reduces the geomagnetic field and thereby causes additional compression of the magnetopause and, accordingly, an increase in the saturation level of the polar cap area.

scholarly journals Magnetorotational instability in diamagnetic, misaligned protostellar discs

2019 ◽  
Vol 491 (4) ◽  
pp. 5481-5488
Author(s):  
Ebru Devlen ◽  
Ayse Ulubay ◽  
E Rennan Pekünlü
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Growth Rates ◽  
Vertical Component ◽  
Radial Component ◽  
Magnetorotational Instability ◽  
Radial Gradient ◽  
Dipole Magnetic Field ◽  
Protostellar Discs ◽  
The Magnetic Field

ABSTRACT In this study, we addressed the question of how the growth rate of the magnetorotational instability is modified when the radial component of the stellar dipole magnetic field is taken into account in addition to the vertical component. Considering a fiducial radius in the disc where diamagnetic currents are pronounced, we carried out a linear stability analysis to obtain the growth rates of the magnetorotational instability for various parameters such as the ratio of the radial-to-vertical component and the gradient of the magnetic field, the Alfvenic Mach number, and the diamagnetization parameter. Our results show that the interaction between the diamagnetic current and the radial component of the magnetic field increases the growth rate of the magnetorotational instability and generates a force perpendicular to the disc plane that may induce a torque. It is also shown that considering the radial component of the magnetic field and taking into account a radial gradient in the vertical component of the magnetic field causes an increase in the magnitudes of the growth rates of both the axisymmetric (m = 0) and the non-axisymmetric (m = 1) modes.

scholarly journals Imprint of magnetic flux expulsion at the core–mantle boundary on geomagnetic field intensity variations

2020 ◽  
Vol 221 (3) ◽  
pp. 1984-2009 ◽  
Author(s):  
M Troyano ◽  
A Fournier ◽  
Y Gallet ◽  
C C Finlay
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Field Intensity ◽  
Geomagnetic Field ◽  
Western Europe ◽  
Vertical Component ◽  
Core Mantle Boundary ◽  
The Core ◽  
Flux Expulsion ◽  
Upper Boundary

SUMMARY During the last decade, rapid or extreme geomagnetic field intensity variations associated with rates greater than the maximum currently observed have been inferred from archeomagnetic data in the Near-East and in Western Europe. The most extreme events, termed geomagnetic spikes, are defined as intensity peaks occurring over a short time (a few decades), and are characterized by high variation rates, up to several μT yr–1. Magnetic flux expulsion from the Earth’s outer core has been suggested as one possible explanation for these peaks but has not yet been examined in detail. In this study, we develop a 2-D kinematic model for magnetic flux expulsion whose key control parameter is the magnetic Reynolds number Rm, the ratio of magnetic diffusion time to advection time. This model enables the tracking of magnetic field lines which are distorted and folded by a fixed flow pattern. Two processes govern the magnetic evolution of the system. The first is the expulsion of magnetic flux from closed streamlines, whereby flux gradually concentrates near the boundaries of the domain, which leads to an increase of the magnetic energy of the system. If the upper boundary separates the conducting fluid from an insulating medium, a second process then takes place, that of diffusion through this interface, which we can quantify by monitoring the evolution of the vertical component of magnetic induction along this boundary. It is the conjunction of these two processes that defines our model of magnetic flux expulsion through the core–mantle boundary. We analyse several configurations with varying flow patterns and magnetic boundary conditions. We first focus on flux expulsion from a single eddy. Since this specific configuration has been widely studied, we use it to benchmark our implementation against analytic solutions and previously published numerical results. We next turn our attention to a configuration which involves two counter-rotating eddies producing an upwelling at the centre of the domain, and comprises an upper boundary with an insulating medium. We find that the characteristic rise time and maximum instantaneous variation rate of the vertical component of the magnetic field that escapes the domain scale like $\sim R_m^{0.15}$ and $\sim R_m^{0.45}$, respectively. Extrapolation of these scaling laws to the Earth’s régime is compared with various purported archeointensity highs reported in the Near-East and in Western Europe. According to our numerical experiments magnetic flux expulsion is unlikely to produce geomagnetic spikes, while intensity peaks of longer duration (one century and more) and smaller variation rates appear to be compatible with this process.

scholarly journals Predictions of the geomagnetic secular variation based on the ensemble sequential assimilation of geomagnetic field models by dynamo simulations

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Sabrina Sanchez ◽  
Johannes Wicht ◽  
Julien Bärenzung
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Wave Number ◽  
Main Magnetic Field ◽  
Candidate Model ◽  
Uncertainty Estimates ◽  
Geomagnetic Field Models ◽  
Dipole Configuration

Abstract The IGRF offers an important incentive for testing algorithms predicting the Earth’s magnetic field changes, known as secular variation (SV), in a 5-year range. Here, we present a SV candidate model for the 13th IGRF that stems from a sequential ensemble data assimilation approach (EnKF). The ensemble consists of a number of parallel-running 3D-dynamo simulations. The assimilated data are geomagnetic field snapshots covering the years 1840 to 2000 from the COV-OBS.x1 model and for 2001 to 2020 from the Kalmag model. A spectral covariance localization method, considering the couplings between spherical harmonics of the same equatorial symmetry and same azimuthal wave number, allows decreasing the ensemble size to about a 100 while maintaining the stability of the assimilation. The quality of 5-year predictions is tested for the past two decades. These tests show that the assimilation scheme is able to reconstruct the overall SV evolution. They also suggest that a better 5-year forecast is obtained keeping the SV constant compared to the dynamically evolving SV. However, the quality of the dynamical forecast steadily improves over the full assimilation window (180 years). We therefore propose the instantaneous SV estimate for 2020 from our assimilation as a candidate model for the IGRF-13. The ensemble approach provides uncertainty estimates, which closely match the residual differences with respect to the IGRF-13. Longer term predictions for the evolution of the main magnetic field features over a 50-year range are also presented. We observe the further decrease of the axial dipole at a mean rate of 8 nT/year as well as a deepening and broadening of the South Atlantic Anomaly. The magnetic dip poles are seen to approach an eccentric dipole configuration.

THE INVESTIGATION OF THE PG PULSATIONS WITH USING DATA OF ARASE, GOES SATELLITES AND GROUND-BASED STATIONS

2021 ◽  
Vol 44 ◽  
pp. 63-66
Author(s):  
V.B. Belakhovsky ◽  
◽  
V.A. Pilipenko ◽  
K. Shiokawa ◽  
Y. Miyoshi ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Conjugate Point ◽  
Physical Nature ◽  
Recovery Phase ◽  
Radial Component ◽  
Field Lines ◽  
Using Data ◽  
Giant Pulsations ◽  
Favorable Conditions ◽  
Phase Relationships

The physical nature of Pg (pulsation giant) pulsations, which were observed in the magnetosphere by the Japanese satellite Arase, geostationary satellites GOES, and ground stations of the THEMIS and CARISMA networks, was investigated in this work. Pg pulsations belong to the Pc4 frequency range and are characterized by a very monochromatic shape. For the event on 5 June, 2018, according to the data from the Arase satellite, the Pg pulsation wave packet was recorded in the dawn sector during 3 hours. The pulsations are most pronounced in the radial component of the geomagnetic field, their frequency was about 11 mHz. Pg pulsations observed in the magnetosphere were accompanied by pulsations with the same period according to data from a number of ground-based magnetic stations located near the conjugate point. According to the data of ground stations, the pulsations were most strongly expressed in the Y-component of the geomagnetic field. Pg pulsations were accompanied by pulsations in electron and proton fluxes according to the Arase, GOES satellite observations. There are no clear phase relationships between geomagnetic pulsations and pulsations in charge particle fluxes. Pg pulsations were excited under quiet geomagnetic conditions (SYM-H = -10 nT, AE = 100-400 nT) on the recovery phase of the small geomagnetic storm. It is assumed that the expansion of the plasmasphere at low geomagnetic activity leads to an increase in the plasma density in the region of the geostationary orbit, which creates favorable conditions for the excitation of Pg pulsations due to the drift-bounce resonance of protons with the geomagnetic field lines oscillations in the magnetosphere.

Humanity Imperiled by the Geomagnetic Field and Human Corruption

2021 ◽  
Vol 8 (1) ◽  
pp. 456-478
Author(s):  
J. Marvin Herndon
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Charged Particle ◽  
Geomagnetic Field ◽  
Paradigm Shift ◽  
Government Officials ◽  
The Public ◽  
Person Perspective ◽  
First Person Perspective ◽  
The Many

Earth’s magnetic field acts as a shield, protecting life and our electrically-based infrastructure from the rampaging, charged-particle solar wind. In the geologic past, the geomagnetic field has collapsed, with or without polarity reversal, and inevitably it will again. The potential consequences of geomagnetic collapse have not only been greatly underestimated, but governments, scientists, and the public have been deceived as to the underlying science. Instead of trying to refute or advance a paradigm shift that occurred in 1979, global geoscientists, individuals and institutions, chose to function as a cartel and continued to promote their very-flawed concepts that had their origin in the 1930s and 1940s, consequently wasting vast amounts of taxpayer-provided research money, and making no meaningful advances or understanding. Here, from a first person perspective, I describe the logical progression of understanding from that paradigm shift, review the advances made and their concomitant implications, and touch upon a few of the many efforts that were made to deceive government officials, scientists, and the public. It is worrisome that geoscientists almost universally have engaged in suppressing or ignoring sound scientific advances, including those with potentially adverse implications for humanity. All of this suggests that the entire institutional structure of the geophysical sciences, funding, institutions, and bureaucracies should be radically reformed.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

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