scholarly journals Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

2021 ◽  
Vol 42 (3) ◽  
Author(s):  
Paula Possamai Sergipe ◽  
Yára Regina Marangoni ◽  
Roberto Paulo Zanon dos Santos ◽  
Denise Silva de Moura ◽  
Luigi Jovane
Keyword(s):  
Magnetic Field ◽  
Continental Shelf ◽  
Diurnal Variation ◽  
Brazilian Coast ◽  
Observatory Data ◽  
Before And After ◽  
Corrected Data ◽  
Well Correlation ◽  
The Magnetic Field ◽  
Magnetic Observatories

AbstractThe diurnal variation of the magnetic field cannot be predicted or modeled and for that reason, it is monitored during the magnetic surveys, usually by a stationary magnetometer. However, marine surveys have a practical issue with diurnal monitoring, owing to the distance between the survey, stationary magnetometers, and magnetic observatories. This work aims to verify the use of nearby magnetic observatories to estimate the diurnal variation correction in different marine surveys and evaluate its effectiveness. In this study, we selected surveys at the continental shelf near Santos city (Survey 1), continental slope next to the first survey location (Survey 2), continental shelf near Ubatuba city (Survey 3), and Mamanguá ria in the Paraty city (Survey 4), all southeast to the Brazilian coast. The crossing points were implemented to compare the magnetic field values at different times and days at the same measurement point, before and after the correction. Afterwards, we measure the Pearson’s Correlation of the raw data and the diurnal corrected data in all crossing points of each survey which showed an improvement after correction by the value approximating to 1, which indicates a very well correlation. The Ubatuba and Mamanguá surveys allowed comparing the observatory correction results with the base magnetometer results that were rather similar. Our analyses indicate a satisfactory diurnal correction using the observatory data and the crossing points approach, which can be used for every marine magnetometric survey worldwide placed near the coast (< 280 km) that do not have a stationary magnetometer available.

The recent secular variation and the motions at the core surface

1982 ◽  
Vol 306 (1492) ◽  
pp. 271-280 ◽  
Keyword(s):  
Magnetic Field ◽  
Time Derivative ◽  
Step Function ◽  
Second Derivative ◽  
Firm Conclusion ◽  
The Core ◽  
Drift Term ◽  
The Magnetic Field ◽  
Westward Drift ◽  
Magnetic Observatories

The Earth’s magnetic field has been undergoing a remarkably systematic variation during the last 30 years. This variation can be described by a constant time derivative and a step-function second derivative. These parameters are smoothly distributed over the Earth’s surface. The step occurred in 1969 and caused the second derivative to change signs for all of the components at most of the magnetic observatories. Similar but less well documented behavior had been observed around 1900; it seemed to correlate with a jump in the acceleration of the Earth’s rotation. We have investigated the motions at the top of the Earth’s core that are responsible for the recent magnetic variations by inversion procedures. The motions responsible for the time derivative of the magnetic field can be reasonably well assessed and are dominated by a westward drift term of approximately 0.2°/year, although important poloidal motions are also inferred. The data for the jump in the second derivative are much noisier and the motion accelerations are not as well resolved. The poloidal acceleration terms are still fairly well resolved, but the toroidal motions, especially the zonal motions, are very poorly resolved. No firm conclusion about an acceleration of the westward drift can be given on the basis of this analysis. The inversions give evidence that the motions for the lower modes are a strongly decreasing function of their order.

Effect of electric and magnetic fields on operation of insulin pumps under 400 kV power lines

2020 ◽  
Vol 55 (1) ◽  
pp. 51-54
Author(s):  
L. Korpinen ◽  
R. Pääkkönen ◽  
M. Penttilä
Keyword(s):  
Magnetic Field ◽  
Remote Control ◽  
Insulin Pump ◽  
Test Site ◽  
Control Device ◽  
Power Lines ◽  
Insulin Pumps ◽  
Electric And Magnetic Fields ◽  
Before And After ◽  
The Magnetic Field

The aim was to study the operation of insulin pumps under a 400 kV transmission line (two test places) and possible disturbances that the lines could have caused. Three different insulin pumps were attached one at a time to the subject’s clothes. The diabetes nurse started the pumps before the tests to ensure the correct settings were being utilized. After walking under the power lines when meters were running, she tested if the meters had operated properly. At the first test site (A), the electric field was 5.0–5.1 kV/m and the magnetic field 8.6–10.9 μT, and in the second test place (B), the fields were 7.7–8.5 kV/m and 5.7–9.2 μT. The pumps worked perfectly: no disruption was detected in the flow, display or menu movement, and the events were registered correctly. Only the remote control, which worked well before and after the test, could not reliably receive additional doses. However, the functions of the insulin pump are not dependent on the functionality of the remote control device, so the study suggests that insulin pump users can move safely under the power lines.

SURVEI GEOFISIKA DENGAN METODE MAGNETIK UNTUK MENGETAHUI INTRUSI BATUAN BEKU

2008 ◽  
Vol 5 (2) ◽  
Author(s):  
Khristian Enggar Pamuji
Keyword(s):  
Magnetic Field ◽  
Data Processing ◽  
Diurnal Variation ◽  
Igneous Rock ◽  
Magnetic Data ◽  
Survey Area ◽  
Central Java ◽  
Single Sensor ◽  
The Subject ◽  
The Magnetic Field

<em><span>The magnetic research had been carried out in Karangsambung, Kebumen, Central Java, for eight days. The subject of this research is mapping of the anomaly of magnetic field in the survey area Budjil mountain, that will be proceed in order to interpret the contact of the rock with surroundings area.  This measurement used two units of Proton precision Magnetometer (PPM) Model G-856, PPM with single sensor was used to measure diurnal variation and PPM double sensor (Gradiometer) that was used to measure the magnetic field meanwhile, GPS Garmin was used for the positioning.  Magnetic data processing includes IGRF correction and diurnal variation correction. After this correction has done, contouring was made using Surfer based on the total magnetic field anomaly in order to understand the occurrence of igneous rock</span></em>

scholarly journals A study of transient variations in the Earth's electromagnetic field at equatorial electrojet latitudes in western Africa (Mali and the Ivory Coast)

1998 ◽  
Vol 16 (6) ◽  
pp. 677-697 ◽  
Author(s):  
J. Vassal ◽  
M. Menvielle ◽  
Y. Cohen ◽  
M. Dukhan ◽  
V. Doumouya ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diurnal Variation ◽  
Apparent Resistivity ◽  
Equatorial Electrojet ◽  
The Other ◽  
Source Effect ◽  
The Earth ◽  
Magnetic Signature ◽  
Transient Variations ◽  
The Magnetic Field

Abstract. In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the SRE source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the SR*E source) was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at dip equator latitudes with the electromagnetic diurnal variation is consequently impossible to perform. In the case of irregular variations, the source effect related to the equatorial electrojet is also discussed. A Gaussian model of equatorial electrojet was considered, and apparent resistivities were computed for two models of stratified Earth corresponding to the average resistive structure of the two tectonic provinces crossed by the profile: a sedimentary basin and a cratonic shield. The apparent resistivity curves were found to depend significantly on both the model used and the distance to the center of the electrojet. These numerical results confirm the existence of a daytime source effect related to the equatorial electrojet. Furthermore, we show that the results account for the observed differences between daytime and night-time apparent resistivity curves. In particular, it was shown that electromagnetic probing of the Earth using the classical Cagniard-Tikhonov magnetotelluric method is impossible with daytime recordings made at dip latitude stations.Key words. Electromagnetics (Transient and time do- main) Geomagnetism and paleomagnetism (geomagne- tic induction) Ionosphere (equatorial ionosphere)

Screen Elements Made of Perforated Steel Tape and their Application for Shielding Electromagnetic Fields

2016 ◽  
Vol 674 ◽  
pp. 41-47 ◽  
Author(s):  
Viktor Mironov ◽  
Tarmo Koppel ◽  
Mihails Lisicins ◽  
Irina Boiko
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Fields ◽  
Three Dimensional ◽  
Waste Products ◽  
Field Source ◽  
Low Weight ◽  
Before And After ◽  
Copper Composite ◽  
The Magnetic Field ◽  
Shielding Material

In the present work the methods for producing flat and three-dimensional shielding screens from the perforated steel tape are proposed. The possible application variants of mentioned screens are offered and analyzed. Main attention is given for producing one-layer and multi-layer screens with cellular structure due to its relatively low weight and technological elasticity – complex three-dimensional structures could be done successfully.Examples of produced shielding screens from the perforated steel tape for protection from electromagnetic fields in different frequency range are offered and tested. The efficiency of a shielding material was determined by measuring the magnetic field before and after applying the shielding material. Distribution of the magnetic field behind the shielding screen was determined by software vector mapping. Shielding efficiency was measured for 1) a three-layer perforated steel screen; 2) an one-layer perforated steel screen - shielding screen was placed in between the magnetic field source and the measurement point forming a two dimensional screen; 3) copper composite sprayed screen. During experimental investigation it was established, that a three-layer perforated steel screen application allowed the 27% reduction in the magnetic field, while one-layer perforated steel screen gave only 12% reduction. Copper composite sprayed screen reduced magnetic field by 15%.Recommendations for producing the multi-layer perforated steel screen accordingly to shielding efficiency are elaborated and laid down. The discussed material carries also ecological significance, since the material is produced by waste products (after stumping etc.). Therefore the production of such materials comes with reduced cost both in light of capital expenditures and ecological footprint.

scholarly journals Maximum-variance gradiometer technique for removal of spacecraft-generated disturbances from magnetic field data

2020 ◽  
Vol 9 (2) ◽  
pp. 451-469
Author(s):  
Ovidiu Dragoş Constantinescu ◽  
Hans-Ulrich Auster ◽  
Magda Delva ◽  
Olaf Hillenmaier ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Measurements ◽  
Magnetic Field Data ◽  
Maximum Variance ◽  
Service Oriented ◽  
Corrected Data ◽  
Sensor Configuration ◽  
Time Required ◽  
The Magnetic Field

Abstract. In situ measurement of the magnetic field using spaceborne instruments requires a magnetically clean platform and/or a very long boom for accommodating magnetometer sensors at a large distance from the spacecraft body. This significantly drives up the costs and the time required to build a spacecraft. Here we present an alternative sensor configuration and a technique allowing for removal of the spacecraft-generated AC disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness programme and allowing for shorter boom length. The final expression of the corrected data takes the form of a linear combination of the measurements from all sensors, allowing for simple onboard software implementation. The proposed technique is applied to the Service Oriented Spacecraft Magnetometer (SOSMAG) on board the Korean geostationary satellite GeoKompsat-2A (GK2A). In contrast to other missions where multi-sensor measurements were used to clean the data on the ground, the SOSMAG instrument performs the cleaning on board and transmits the corrected data in real time, as needed by space weather applications. The successful elimination of the AC disturbances originating from several sources validates the proposed cleaning technique.

Alignment of HAp Crystal Using a Sample Rotation in a Static Magnetic Field

2007 ◽  
Vol 539-543 ◽  
pp. 716-719 ◽  
Author(s):  
Kazuhiko Iwai ◽  
Jun Akiyama ◽  
Tomohiko Tanase ◽  
Shigeo Asai
Keyword(s):  
Magnetic Field ◽  
High Magnetic Field ◽  
Crystal Orientation ◽  
Slip Casting ◽  
Casting Process ◽  
Biological Properties ◽  
X Ray Diffraction ◽  
Sample Rotation ◽  
Before And After ◽  
The Magnetic Field

Formation of crystallographically orientaed hydroxyapatite (HAp) is one of the promising ways to utilize their anisotropic nature of chemical and biological properties. On the other hand, the development of super conducting magnet technology enables to introduce a high magnetic field which can control crystal orientation of non-magnetic materials with magnetic anisotropy. In this study, a high magnetic field and sample rotation are simultaneously imposed on the hydroxyapatite during a slip casting process in order to align its c-plane within a horizontal plane. From X-ray diffraction, it has been found that the HAp crystals in the sample treated with the magnetic field and the sample rotation were oriented to a particular direction in the slip casting process and it was enhanced by the subsequent sintering process, while the c-axis crystal orientation of the sample treated without the magnetic field and with the sample rotation was not observed before and after the sintering.

Detecting the propped fracture by injection of magnetic proppant during fracturing

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. JM1-JM14 ◽  
Author(s):  
Junrong Liu ◽  
Shijie Cao ◽  
Xingru Wu ◽  
Jun Yao
Keyword(s):  
Magnetic Field ◽  
Hydraulic Fracturing ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Field Measurement ◽  
Geothermal Resources ◽  
Deep Wells ◽  
Well Pattern ◽  
Before And After ◽  
Susceptibility Contrast ◽  
The Magnetic Field

Hydraulic fracturing is key to enhancing the productivity of shale and tight hydrocarbon reservoirs, as well as geothermal resources from hot dry rock. Assessing the range and efficiency of hydraulic fracturing is very important for onsite fracturing operations and decision making on subsequent fracturing plans and well-pattern deployment. The idea of injecting fluid mixed with magnetic material into a formation to detect subterranean structure has been considered for a long time. The detectability of the characteristics of propped fractures using magnetic field measurement is discussed and evaluated with an analytical model. The magnetic proppants synthesized with superparamagnetic nanoparticles should be “silent” during injection and could be activated by an external current. By measuring the magnetic field before and after the fracture was created and the magnetic proppants were magnetized, the magnetic anomalies can be obtained. The result indicates that the magnetic field caused by a fracture filled with magnetic proppants is very weak, so that magnetometers with higher precision and resolution should be used to capture such subtle signal. The higher susceptibility contrast of the magnetic nanoparticles is, the stronger external magnetic induction field could be detected. It is suggested that the superparamagnetic nanomaterial with effective magnetic susceptibility contrast of greater than 0.4–0.5 should be used for fracture monitoring in deep wells. To infer the fracture characteristics with the magnetic anomaly, the ground and adjacent wells’ monitoring practices are recommended.

scholarly journals Rapid Disappearance of Penumbra-Like Features near a Flaring Polarity Inversion Line: The Hinode Observations

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
B. Ravindra ◽  
Sanjay Gosain
Keyword(s):  
Magnetic Field ◽  
Vertical Component ◽  
Vector Magnetic Field ◽  
Polarity Inversion ◽  
X Ray ◽  
Horizontal Flows ◽  
Before And After ◽  
Polarity Inversion Line ◽  
The Magnetic Field ◽  
Class Flare

We present the observations of penumbra-like features (PLFs) near a polarity inversion line (PIL) of flaring region. The PIL is located at the moat boundary of active region (NOAA 10960). The PLFs appear similar to sunspot penumbrae in morphology but occupy small area, about6×107 km2, and are not associated with sunspot or pore. We observed a rapid disappearance of the PLFs after a C1.7 class flare, which occurred close to the PIL. The local correlation tracking (LCT) of these features shows presence of horizontal flows directed away from the end-points of the PLFs, similar to the radial outward flow found around regular sunspots, which is also known as the moat flow. Hard X-ray emission, coincident with the location of the PLFs, is found in RHESSI observations, suggesting a spatial correlation between the occurrence of the flare and decay of the PLFs. Vector magnetic field derived from the observations obtained by Hinode spectropolarimeter SOT/SP instrument, before and after the flare, shows a significant change in the horizontal as well as the vertical component of the field, after the flare. The weakening of both the components of the magnetic field in the flare interval suggests that rapid cancellation and/or submergence of the magnetic field in PLFs occurred during the flare interval.

scholarly journals APPLICATION OF STEM-CP BASED MAGNETIC FIELD AND ELECTROMAGNETIC INDUCTION MODULE TO IMPROVE STUDENTS CREATIVE THINKING SKILLS AT VOCATIONAL HIGH SCHOOL

2020 ◽  
Vol 8 (11) ◽  
pp. 346-350
Author(s):  
Sutarto a ◽  
◽  
Marinda Resti Sari ◽  
Sudarti b ◽  
◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Induction ◽  
Creative Thinking ◽  
Thinking Skills ◽  
Vocational High School ◽  
Design Data ◽  
Engineering Mathematics ◽  
Before And After ◽  
The Magnetic Field ◽  
Better Than

Materials in physics learning at school are considered difficult to understand, especially in the concept of magnetic field and electromagnetic induction. Contextual issues are required to overcome this problem.STEM-Cp (science, technology, engineering, mathematics-contextual problem) is seen to help students understand the concept of magnetic field and electromagnetic induction through contextual issues. The purpose of this study was to determine the effect of using STEM-Cp based moduleon students creative thinking skill on magnetic field and electromagnetic induction material.The research design used in this study is one-group pretest-posttest design . Data obtained from the results of creative thinking tests conducted in the experimental class before and after learning. The results showed that the students creative thinking skills taught using magnetic field modules and electromagnetic induction based on STEM-Cp before and after learning improved. The effect of the application of the magnetic field module and electromagnetic induction based on STEM-Cp has an average increase of 80,3in the good category. This shows that the creative thinking skills of students learning with magnetic field modules and electromagetic induction are better than before being applied in learning.

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