DERIVATION OF MAGNETIC AND GRAVITATIONAL QUANTITIES BY SURFACE INTEGRATION

Geophysics ◽  
1949 ◽  
Vol 14 (2) ◽  
pp. 133-150 ◽  
Author(s):  
D. C. Skeels ◽  
R. J. Watson
Keyword(s):  
Magnetic Field ◽  
Horizontal Plane ◽  
Plane Surface ◽  
Vertical Component ◽  
Magnetic Anomalies ◽  
Magnetic Intensity ◽  
Artificial Data ◽  
The Earth ◽  
Surface Integration ◽  
Derivatives Of

In an earlier paper by one of the authors, it was pointed out that if the vertical component of a gravitational or magnetic field is known over a horizontal plane surface of sufficient extent, all other components and derivatives of the field can theoretically be calculated by surface integration of the vertical component. In this paper, examples are given to show that within certain limits such calculations are not only theoretically possible but practically so. Examples are given of the calculations of curvatures from observed gradients and of horizontal magnetic intensity from observed vertical intensity, and the calculated values are compared with those obtained by observation. Examples are also given, based on artificial data, of the calculation of plumb‐line deflections from gravity and of the calculation of magnetic anomalies at a given elevation above the earth from data obtained at the surface. The purpose of these calculations is to demonstrate the nonindependence of the various derivatives of gravitational and magnetic potential.

QUANTITATIVE INTERPRETATION OF VERTICAL MAGNETIC ANOMALIES OVER VEINS

Geophysics ◽  
1950 ◽  
Vol 15 (4) ◽  
pp. 667-686 ◽  
Author(s):  
Kenneth L. Cook
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomaly ◽  
Magnetic Induction ◽  
Vertical Component ◽  
Magnetic Anomalies ◽  
Quantitative Interpretation ◽  
Magnetic Intensity ◽  
Magnetic Inclination ◽  
Magnetic North ◽  
The Magnetic Field

By using ordinary magnetic induction methods of analysis, Haalck, Heiland, and others have developed formulas which express the magnetic anomaly over a vertical or inclined vein of tabular shape as a function of the susceptibility, dimensions, shape, and disposition of the vein, and of the strength and direction of the earth’s magnetic field. On the basis of these fundamental formulas, other formulas for the vertical component of the magnetic field are derived in the present paper for such veins in intermediate northern magnetic latitudes. Special emphasis is given to the orientation of the veins relative to the magnetic north direction. Several families of vertical magnetic intensity curves for veins with different strikes and dips are given. All theoretical curves for veins striking magnetic north are plotted in terms of a parametric unit so that, once plotted, they can be used repeatedly in different districts, provided a proper multiplying factor is chosen for the observed curve. The importance of the transverse horizontal magnetization effect under certain conditions of orientation is demonstrated. It is shown mathematically that small vertical magnetic anomalies are to be expected for thin veins striking east and dipping south at an angle equal to, or approximately equal to, the complement of the angle of magnetic inclination.

AN ELECTROMAGNETIC INTERPRETATION PROBLEM IN GEOPHYSICS

Geophysics ◽  
1951 ◽  
Vol 16 (3) ◽  
pp. 431-449 ◽  
Author(s):  
L. B. Slichter
Keyword(s):  
Magnetic Field ◽  
Electrical Properties ◽  
Magnetic Field Intensity ◽  
Vertical Component ◽  
Single Frequency ◽  
Magnetic Intensity ◽  
Conductivity Function ◽  
The Magnetic Field ◽  
Surface Observations ◽  
Interpretation Problem

An interpretation problem in electromagnetic prospecting is discussed. A flat earth in which the three electrical properties of material vary only with depth is subjected to an alternating inducing field produced by a dipole above the surface with axis perpendicular to the surface. Observations of the horizontal or of the vertical component of the magnetic intensity at the ground’s surface are supposed to be available at all distances. From these observations solutions for the three unknown functions are developed. When the magnetic permeability is variable, the solutions for the permeability and dielectric functions require observations at two different frequencies. The conductivity function may be found from observations at a single frequency. It is shown that the horizontal and vertical components of the magnetic field intensity are mutually dependent in the region above the ground’s surface; and formulae independent of the ground’s characteristics are deduced for expressing [Formula: see text] in terms of [Formula: see text], and vice‐versa. Here [Formula: see text] denotes a plane coincident with or above and parallel to, the earth’s surface.

scholarly journals A magnetometer for the measurement of the Earth's vertical magnetic intensity in C. G. S. measure

1928 ◽  
Vol 117 (777) ◽  
pp. 434-458 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vertical Component ◽  
Field Measurements ◽  
Horizontal Component ◽  
Magnetic Intensity ◽  
Earth’S Magnetic Field ◽  
Simple Operation ◽  
Horizontal Field ◽  
Earth's Magnetic Field

The measurement of the vertical component of the earth’s magnetic field is a less simple operation than that of the horizontal component. The horizontal field measurements are on a satisfactory basis, whether made by the swinging magnet method, or by the more recently developed electric magnetometers, in which known magnetic fields may be provided by means of known currents flowing through coils of known dimensions.

scholarly journals Whistler waves produced by monochromatic currents in the low nighttime ionosphere

2020 ◽  
Author(s):  
Vera G. Mizonova ◽  
Peter A. Bespalov
Keyword(s):  
Magnetic Field ◽  
Horizontal Plane ◽  
Ground Surface ◽  
Arbitrary Distribution ◽  
Wave Polarization ◽  
Whistler Waves ◽  
Horizontal Magnetic Field ◽  
Full Wave ◽  
The Earth ◽  
Source Current

Abstract. We use a full-wave approach to find the field of monochromatic whistler waves which are excited and propagating in the low nighttime ionosphere. The source current is located in the horizontal plane and can have arbitrary distribution over horizontal coordinates. The ground-based horizontal magnetic field and electric field at 125 km are calculated. The character of wave polarization on the ground surface is investigated. The percentages of source energy supplied to the Earth-ionosphere waveguide and carried upward ionosphere are estimated. Received results are important for the analysis of ELF/VLF emission phenomena observed both on the satellites and on the ground.

Implications of magnetic secular variation for interpretation of crustal field anomalies

2020 ◽  
Author(s):  
Rick Saltus ◽  
Aaron Canciani ◽  
Brian Meyer ◽  
Arnaud Chulliat
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomalies ◽  
Source Inversion ◽  
Magnetic Minerals ◽  
The Earth ◽  
Crustal Field ◽  
Data Compilation ◽  
Initial Work ◽  
Navigation Accuracy ◽  
Changes Over Time

<p>We usually think of crustal magnetic anomalies as static (barring some major seismic or thermal disruption).  But a significant portion of the crustal magnetic field is caused by the interaction of magnetic minerals with the Earth’s magnetic field.  This induced magnetic effect is dependent on the direction and magnitude of the ambient field.  So, of course, as the Earth’s magnetic field changes over time, the form and magnitude of induced magnetic anomalies will vary as well.  These changes will often be negligible for interpretation when compared with measurement and other interpretational uncertainties.  However, with the reduction of various sources of measurement noise and increased fidelity of interpretation, these temporal anomaly changes may need to be considered.</p><p>In addition to considerations relating to interpretation uncertainty, these temporal anomaly changes, if they are measured in multiple magnetic epochs, can theoretically provide valuable information for use in source inversion.  For example, since crustal magnetic anomalies arise from a combination of induced (dependent the ambient field) and remanent (not dependent on ambient field) magnetic sources, measurements of secular magnetic variation can assist in separating these two sources during inversion.</p><p>We will report modeling of the expected form and magnitude of predicted induced anomaly variations, the possible implications of these variations for data compilation and interpretation, and on the availability of relevant data for measuring them.  Recent research into the use of high-resolution magnetic anomaly maps for airborne magnetic navigation has also brought the issue of changing magnetic fields into focus.  Initial work indicates that changes in induced anomalies could affect navigation accuracy in certain situations.</p>

scholarly journals 33. The present state of the corpuscular theory of magnetic storms

1958 ◽  
Vol 6 ◽  
pp. 295-311
Author(s):  
V. C. A. Ferraro
Keyword(s):  
Magnetic Field ◽  
Magnetic Storm ◽  
Ring Current ◽  
Plane Surface ◽  
Magnetic Storms ◽  
Main Phase ◽  
Polar Regions ◽  
Stream Surface ◽  
The Earth ◽  
The Magnetic Field

The evidence in favour of a corpuscular theory of magnetic storms is briefly reviewed and reasons given for believing that the stream must be neutral but ionized and carry no appreciable current. It is shown that under suitable conditions the stream is able to pass freely through a solar magnetic field; the stream may also be able to carry away with it a part of this field. However, because of geometrical broadening of the stream during its passage from the sun to the earth, the magnetic field imprisoned in the gas may be wellnigh unobservable near the earth.The nature, composition and dimensions of the stream near the earth are discussed and it is concluded that on arrival the stream will present very nearly a plane surface to the earth if undistorted by the magnetic field.Because of its large dimensions, the stream will behave as if it were perfectly conducting. During its advance in the earth's magnetic field the currents induced in the stream will therefore be practically confined to the surface. The action of the magnetic field on this current is to retard the surface of the stream which being highly distortible will become hollowed out. Since the stream surface is impervious to the interpenetration of the magnetic tubes of force, these will be compressed in the hollow space. The intensity of the magnetic field is thereby increased and this increase is identified with the beginning of the first phase of a magnetic storm. This increase will be sudden, as observed, owing to the rapid approach of the stream to the earth.The distortion of the stream surface is discussed and it is pointed out that two horns will develop on the surface, one north and the other south of the geomagnetic equator. Matter pouring through these two horns will find its way to the polar regions.The main phase of a magnetic storm seems most simply explained as due to a westward ring-current flowing round the earth in its equatorial plane. Under suitable conditions such a ring-current would be stable if once set up. The mode of formation of the ring is, however, largely conjectural. The possibility that the main phase may be of atmospheric origin is also briefly considered. It is shown that matter passing through the two horns to the polar regions could supply the energy necessary for the setting up of the field during the main phase. The magnetic evidence in favour of such a hypothesis, however, seems wanting.

Broad-scale magnetic anomalies over central and eastern Canada: a discussion

1981 ◽  
Vol 18 (3) ◽  
pp. 657-661 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford
Keyword(s):  
Magnetic Field ◽  
Sea Level ◽  
Vertical Component ◽  
Magnetic Anomalies ◽  
Superior Province ◽  
The South ◽  
Earth’S Magnetic Field ◽  
Eastern Canada ◽  
Earth's Magnetic Field ◽  
Broad Scale

Profiles of anomalies in the vertical component of the Earth's magnetic field over central and eastern Canada, observed at an average altitude of 4 km above sea level, show broad regions with distinctive anomaly character. These subdivisions indicate major differences in the evolutions of regions within individual structural provinces. Particularly notable is a region of intense anomalies in the northern part of the Superior Province in Quebec, contrasting with much weaker anomaly relief to the south and east.

scholarly journals Pemodelan 2D Batuan Bawah Permukaan Daerah Mamuju Sulawesi Barat Dengan Menggunakan Metode Magnetik

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Muhammad Irsyad ◽  
Sutrisno Sutrisno ◽  
Dwi Haryanto
Keyword(s):  
Magnetic Anomaly ◽  
Magnetic Anomalies ◽  
Magnetic Method ◽  
Government Agencies ◽  
Quantitative Interpretation ◽  
Magnetic Intensity ◽  
Contour Map ◽  
A Value ◽  
Qualitative Interpretation ◽  
The Earth

Abstrak. Batuan merupakan benda yang berasal dari magma yang mendingin di dalam bumi. Untuk mengetahui kondisi batuan perlu di lakukan penelitian. Mamuju merupakan daerah yang sedang hangat dalam perbincangan peneliti tentang bagaimana kandungan di bawah permukaan daerah Mamuju, Sulawesi Barat. Daerah ini juga merupakan daerah yang diteliti oleh instansi-instansi pemerintah termasuk PTBGN-BATAN. Penelitian ini bertujuan untuk melakukan pemodelan bawah permukaan bumi. Tujuannya untuk memberikan informasi tentang kondisi baik itu bentuk maupun kedalaman batuan. penelitian ini menggunakan metode magnetik dan metode ini merupakan metode yang tepat untuk membuat model bawah permukaan bumi. Hasil interpretasi kualitatif diperoleh peta kontur intensitas magnetik total dan anomali magnetik. Peta kontur intensitas magnetik total memiliki nilai sebesar 41286,5 – 42280 nT. Sedangkan anomali magnetik memiliki nilai -760,1 – 231,8 nT. Daerah A dan daerah B merupakan daerah yang memiliki anomali tinggi. Hasil interpretasi kuantitatif didapat ada 4 model bawah permukaan yang masing-masing terdapat batuan yang sama yaitu batuan breksi dengan nilai suseptibilitas 0,0006 – 0,00075 satuan cgs dan batuan lava dengan nilai suseptibilitas 0.001 – 0.0015 satuan cgs. daerah yang dilakukan pemodelan fokus pada daerah Hulu Mamuju, hal ini disebabkan karena menurut peta kontur daerah tersebut merupakan daerah yang memiliki anomali magnetik yang tinggi.   Abstract. The rocks are objects derived from the magma cooled in the earth. To determine the condition of the rock is necessary to do research. Mamuju is an area that is warm in conversation investigators about how the content of subsurface area Mamuju, West Sulawesi. This area is also the area investigated by government agencies including PTBGN-BATAN. This study aimed to modeling subsurface. The goal is to provide information about the condition of both the shape and depth of rock. This study uses a magnetic method and this method is an appropriate method to create a model of the earth's subsurface. Qualitative interpretation of results obtained contour map of total magnetic intensity and magnetic anomalies. The total magnetic intensity contour map has a value of 41286.5 to 42280 nT. While the magnetic anomaly has a value of -760.1 - 231.8 nT. Area A and area B is an area that has a high anomaly. Results obtained quantitative interpretation there are 4 models of the subsurface that each contained the same rock is rock breccia with values susceptibility of 0.0006 to 0.00075 cgs units and lava rock with susceptibility value 0.001 - 0.0015 cgs unit. modeling area focuses on upstream area Mamuju, this is because according to the contour map of the area is an area that has a high magnetic anomaly.

7. The Earth’s magnetic field

2018 ◽  
pp. 106-126
Author(s):  
William Lowrie
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Plate Tectonics ◽  
Magnetic Anomalies ◽  
Earth’S Magnetic Field ◽  
The Earth ◽  
Earth's Magnetic Field ◽  
Reversed Polarity ◽  
Harmful Radiation ◽  
The Magnetic Field

The Earth is surrounded by a magnetic field, which originates inside its molten core, and which for centuries has helped travellers to navigate safely across uncharted regions. The magnetic field protects life on the Earth by acting as a shield against harmful radiation from space, especially from the Sun. ‘The Earth’s magnetic field’ explains that the magnetic field at the Earth’s surface is dominantly that of an inclined dipole. The Sun’s deforming effect on the magnetic field outside the Earth is described, as are the magnetic fields of other planets. The magnetism of rocks forms the basis of palaeomagnetism, which explains how plate tectonics displaced the continents and produced oceanic magnetic anomalies whenever the geomagnetic field reversed polarity.

STUDY ON PROPERTIES OF CoNi FILMS WITH Mn DOPING PREPARED BY MAGNETIC FIELDS INDUCED CODEPOSITION TECHNOLOGY

2018 ◽  
Vol 25 (01) ◽  
pp. 1850037 ◽  
Author(s):  
LIANG GANG ◽  
YUNDAN YU ◽  
HONGLIANG GE ◽  
GUOYING WEI ◽  
LI JIANG ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Magnetic Fields ◽  
Copper Substrate ◽  
Vertical Component ◽  
Magnetic Intensity ◽  
Parallel Magnetic Field ◽  
Alloy Films ◽  
Cathode Current ◽  
Progressive Nucleation

Magnetic field parallel to electric field was induced during plating process to prepare CoNiMn alloy films on copper substrate. Electrochemistry mechanism and properties of CoNiMn alloy films were investigated in this paper. Micro magnetohydrodynamic convection phenomenon caused by vertical component of current density and parallel magnetic field due to deformation of current distribution contributed directly to the improvement of cathode current and deposition rate. Cathode current of the CoNiMn plating system increased about 30% with 1[Formula: see text]T magnetic field induced. It was found that CoNiMn films electrodeposited with magnetic fields basically belonged to a kind of progressive nucleation mode. Higher magnetic intensity intended to obtain CoNiMn films with good crystal structures and highly preferred orientations. With the increase of magnetic intensities, surface morphology of CoNiMn alloy films changed from typically nodular to needle-like structures. Compared with coatings electrodeposited without magnetic field, CoNiMn alloy films prepared with magnetic fields possessed better magnetic properties. Coercivity, remanence and saturation magnetization of samples increased sharply when 1[Formula: see text]T magnetic field was induced during plating process.

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