scholarly journals Shift of the mean magnetic field values: Effect of scatter due to secular variation and errors

2001 ◽  
Vol 53 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Tadahiro Hatakeyama ◽  
Masaru Kono
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
The Mean

scholarly journals Study of the Correction Method of Secular Variation in the Main Geomagnetic Field by the Field Seismogeomagnetic Survey

2021 ◽  
Author(s):  
shupeng su ◽  
ZhaoJing Wang ◽  
Deqiang Liu ◽  
Fenglong Mao
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Least Squares Method ◽  
Weighted Least Squares ◽  
Correction Method ◽  
Original Method ◽  
New Method ◽  
Field Variation ◽  
The Mean

Abstract The correction of the secular variation (SV) of the main geomagnetic field is a key link of field seismogeomagnetic data processing, and the current method relies on the observatory data for the relevant technical processing. To optimize the data products and obtain more accurate and reliable seismomagnetic information, this study adopted a new technical idea, which uses the repeated survey data from field stations to obtain the SV of the main geomagnetic field over the survey area by the weighted least-squares method, and compared the results with those of the current methods. The results were as follows: 1. The SV results of the main geomagnetic field produced by the new method are closer to those of the International Geomagnetic Reference Field (IGRF)_SV model. The mean square error (MSE) of the difference of the three elements F, D, and I between the new method and the IGRF_SV model is 10.7%, 47.0%, and 14.5% of that of the original method, respectively. 2. By applying the new SV correction method, more stable and reasonable variations in Earth’s crustal magnetic field can be obtained. The average amplitude of the Earth’s crustal magnetic field variation in the three elements F, D, and I is 28.5%, 55.4%, and 34.4 of the original results, the MSE is 59.1%, 56.5%, and 40.3% of the original results, and the mean gradient is 93.6%, 91.9%, and 97.0%, respectively. 3. In the processed results of the new method, the seismomagnetic information is clearly optimized, and the location of the epicenter is more consistent with the 0 value line of the Earth’s crustal magnetic field. The processed results of the new method are significantly better than those of the original method and have a higher application value.

Germination and initial growth of triticale seeds under stationary magnetic fields

2014 ◽  
Vol 2 (2) ◽  
pp. 72-79 ◽  
Author(s):  
Mercedes Florez ◽  
Elvira Martinez ◽  
Victoria Carbonell
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Seed Vigor ◽  
Initial Growth ◽  
Practical Application ◽  
Biochemical Processes ◽  
Mean Germination Time ◽  
Nutrition Value ◽  
The Mean ◽  
Growth Of Seedlings

The main objective of this study is to determine the effects of 125 mT and 250mT magnetic treatment on the germination and initial growth of triticale seeds. This objective has a practical application in agriculture science: early growth of triticale. An increase in the percentage and rate of germination of seeds and a stimulation of growth of seedlings as positive response to magnetic field treatment in rice, wheat, maize and barley seeds have been found in previous studies. Germination tests were carried out under laboratory conditions by exposing triticale seeds to magnetic field for different times. The effect was studied by exposure of seeds prior sowing. The mean germination time were reduced for all the magnetic treatments applied. Most significant differences were obtained for time of exposure of 1 and 24 hours and maximum reductions was 12%. Furthermore, seedlings from magnetically treated seeds grew taller than control. The longest mean total length was obtained from seedlings exposed to 125 and 250 mT for 24 hours. External magnetic fields are assumed to enhance seed vigor by influencing the biochemical processes by stimulating activity of proteins and enzymes. Numerous studies suggested that magnetic field increases ions uptake and consequently improves nutrition value.

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.

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

scholarly journals Modelling of the Magnetic Configuration of CP Stars from Polarimetric Observations

1998 ◽  
Vol 11 (2) ◽  
pp. 679-681
Author(s):  
M. Landolfi
Keyword(s):  
Magnetic Field ◽  
Stokes Parameter ◽  
Quadratic Field ◽  
Mean Field ◽  
Longitudinal Component ◽  
Stokes Parameters ◽  
Longitudinal Field ◽  
The Mean ◽  
The Magnetic Field ◽  
Polarized Radiation

The observational quantities commonly used to study the magnetic field of CP stars – the mean field modulus and the mean longitudinal field, as well as the ‘mean asymmetry of the longitudinal field’ and the ‘mean quadratic field’ recently introduced by Mathys (1995a,b) – are based either on the Stokes parameter / or on the Stokes parameter V. However, a complete description of polarized radiation requires the knowledge of the full Stokes vector: in other words, we should expect that useful information is also contained in linear polarization (the Stokes parameters Q and U); or rather we should expect the information contained in (Q, U) and in V to be complementary, since linear and circular polarization are basically related to the transverse and the longitudinal component of the magnetic field, respectively.

scholarly journals Simulating Solar Global Magnetism in 3-D

2012 ◽  
Vol 10 (H16) ◽  
pp. 101-103
Author(s):  
A. S. Brun ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Recent Progress ◽  
Convection Zone ◽  
Thermal Structure ◽  
Solar Convection ◽  
Self Consistent ◽  
The Mean ◽  
The Magnetic Field

AbstractWe briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.

scholarly journals The Combined Effect of Rotation and Magnetic Field on Finite-Amplitude Thermal Convection

1973 ◽  
Vol 26 (5) ◽  
pp. 617 ◽  
Author(s):  
R Van der Borght ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Field Approximation ◽  
Finite Amplitude ◽  
Combined Effect ◽  
Mean Field Approximation ◽  
Free Boundaries ◽  
Wide Range ◽  
The Mean ◽  
Basic Equations

The combined effect of an imposed rotation and magnetic field on convective transfer in a horizontal Boussinesq layer of fluid heated from below is studied in the mean field approximation. The basic equations are derived by a variational technique and their solutions are then found over a wide range of conditions, in the case of free boundaries, by numerical and analytic techniques, in particular by asymptotic and perturbation methods. The results obtained by the different techniques are shown to be in excellent agreement. As for the linear theory, the calculations predict that the simultaneous presence' of a magnetic field and rotation may produce conflicting tendencies.

scholarly journals The mean magnetic field of the Sun: Observations at Stanford

Solar Physics ◽  
1977 ◽  
Vol 54 (2) ◽  
pp. 353-361 ◽  
Author(s):  
Philip H. Scherrer ◽  
John M. Wilcox ◽  
Leif Svalgaard ◽  
Thomas L. Duvall ◽  
Phil H. Dittmer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
The Sun ◽  
The Mean

Elaboration, Structure and Mössbauer Spectroscopy of Nanostructured Fe100−xSix Powders Elaborated by Mechanical Alloying

SPIN ◽  
2017 ◽  
Vol 07 (02) ◽  
pp. 1750002 ◽  
Author(s):  
M. Hemmous ◽  
A. Guittoum
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Mechanical Alloying ◽  
Hyperfine Magnetic Field ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
The Mean ◽  
Xrd Studies

We have studied the effect of the silicon concentration on the structural and hyperfine properties of nanostructured Fe[Formula: see text]Six powders ([Formula: see text], 20, 25 and 30[Formula: see text]at.%) prepared by mechanical alloying. The X-ray diffraction (XRD) studies indicated that after 72[Formula: see text]h of milling, the solid solution bcc-[Formula: see text]-Fe(Si) is formed. The grain sizes, [Formula: see text]D[Formula: see text] (nm), decreases with increasing Si concentration and reaches a minimum value of 11[Formula: see text]nm. We have found that the lattice parameter decreases with increasing Si concentration. The changes in values are attributed to the substitutional dissolution of Si in Fe matrix. From the adjustment of Mössbauer spectra, we have shown that the mean hyperfine magnetic field, [Formula: see text]H[Formula: see text] (T), decreases with increasing Si concentration. The substitutional dependence of [Formula: see text]H[Formula: see text] (T) can be attributed to the effect of p electrons Si influencing electrons d of Fe.

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