Lunar Magnetic Field Observation and Initial Global Mapping of Lunar Magnetic Anomalies by MAP-LMAG Onboard SELENE (Kaguya)

A contoured map of vertical magnetic field residuals (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 to 5000 km. A magnetic feature of several thousand kilometres wavelength dominates the map, and is probably due in major part to sources in the earth's core. Superimposed on this are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the short wavelength anomalies provide a broad view of major structures and indicate several regimes of distinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of intense anomalies observed near the western edge of the craton.

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Euler’s differential equation and the identification of the magnetic point‐pole and point‐dipole sources

Geophysics ◽

10.1190/1.1441780 ◽

1984 ◽

Vol 49 (9) ◽

pp. 1549-1553 ◽

Cited By ~ 7

Author(s):

J. O. Barongo

Keyword(s):

Magnetic Field ◽

Differential Equation ◽

Magnetic Anomalies ◽

Field Vector ◽

Magnetic Data ◽

Dipole Source ◽

Point Dipole ◽

Main Subject ◽

Depth Extent ◽

Dipole Sources

The concept of point‐pole and point‐dipole in interpretation of magnetic data is often employed in the analysis of magnetic anomalies (or their derivatives) caused by geologic bodies whose geometric shapes approach those of (1) narrow prisms of infinite depth extent aligned, more or less, in the direction of the inducing earth’s magnetic field, and (2) spheres, respectively. The two geologic bodies are assumed to be magnetically polarized in the direction of the Earth’s total magnetic field vector (Figure 1). One problem that perhaps is not realized when interpretations are carried out on such anomalies, especially in regions of high magnetic latitudes (45–90 degrees), is that of being unable to differentiate an anomaly due to a point‐pole from that due to a point‐dipole source. The two anomalies look more or less alike at those latitudes (Figure 2). Hood (1971) presented a graphical procedure of determining depth to the top/center of the point pole/dipole in which he assumed prior knowledge of the anomaly type. While it is essential and mandatory to make an assumption such as this, it is very important to go a step further and carry out a test on the anomaly to check whether the assumption made is correct. The procedure to do this is the main subject of this note. I start off by first using some method that does not involve Euler’s differential equation to determine depth to the top/center of the suspected causative body. Then I employ the determined depth to identify the causative body from the graphical diagram of Hood (1971, Figure 26).

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Measurements of vector magnetic anomalies on board the icebreaker Shirase and the magnetization of the ship

Annals of Geophysics ◽

10.4401/ag-3711 ◽

1999 ◽

Vol 42 (2) ◽

Author(s):

Y. Nogi ◽

K. Kaminuma

Keyword(s):

Magnetic Field ◽

Geomagnetic Field ◽

Magnetic Anomalies ◽

The Other ◽

South Indian Ocean ◽

Permanent Magnetic Field ◽

South Indian ◽

Antarctic Research ◽

Permanent Magnetization ◽

Made In

Vector measurements of the geomagnetic field have been made in the South Indian Ocean since 1988 when a Shipboard Three Component Magnetometer (STCM) was installed on board the icebreaker Shirase by the 30th Japanese Antarctic Research Expedition (JARE-30). Twelve constants related to the ship's induced and permanent magnetic field were determined by the data obtained from the JARE-30 to the JARE-35. The constants related to the ship's magnetic susceptibility distribution are almost stable throughout the cruise and mostly depend on the ship's shape. On the other hand, the constants related to the ship's permanent magnetization are variable. However, absolute values of total intensity geomagnetic field calculated from vector geomagnetic field is possible to use, if the constraints from total intensity geomagnetic field measured by the proton magnetometer and/or satellite derived magnetic anomalies are applied.

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2D potential theory using complex algebra: New equations and visualization for the interpretation of potential field data

Geophysics ◽

10.1190/geo2016-0611.1 ◽

2018 ◽

Vol 83 (2) ◽

pp. J1-J13 ◽

Cited By ~ 1

Author(s):

Pauline Le Maire ◽

Marc Munschy

Keyword(s):

Magnetic Field ◽

Complex Plane ◽

Potential Field ◽

Single Point ◽

Magnetic Anomalies ◽

Analytic Signal ◽

Power Functions ◽

Field Equations ◽

Complex Algebra ◽

Location Depth

The shape of an anomaly (magnetic or gravity) along a profile provides information on the geometry, horizontal location, depth, and magnetization of the source. For a 2D source, the horizontal location, depth, and geometry of a source are determined through the analysis of the curve of the analytic signal. However, the amplitude of the analytic signal is independent of the dips of the structure, the apparent inclination of magnetization, and the regional magnetic field. To better characterize the parameters of the source, we have developed a new approach for studying 2D potential field equations using complex algebra. Complex equations for different geometries of the sources are obtained for gravity and magnetic anomalies in the spatial and spectral domains. In the spatial domain, these new equations are compact and correspond to logarithmic or power functions with a negative integer exponent. We found that modifying the shape of the source changes the exponent of the power function, which is equivalent to differentiation or integration. We developed anomaly profiles using plots in the complex plane, which is called mapping. The obtained complex curves are loops passing through the origin of the plane. The shape of these loops depends only on the geometry and not on the horizontal location of the source. For source geometries defined by a single point, the loop shape is also independent of the source depth. The orientation of the curves in the complex plane is related to the order of differentiation or integration, the geometry and dips of the structures, and the apparent inclination of magnetization and of the regional magnetic field. The application of these equations and mapping on total field magnetic anomalies across a magmatic dike in Norway shows coherent results, allowing us to determine the geometry and the apparent inclination of magnetization.

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ROOM TEMPERATURE MAGNETIC ANOMALIES IN BENZENE TREATED Bi–Pb–Sr–Ca–Cu–O POWDER

Modern Physics Letters B ◽

10.1142/s021798499100174x ◽

1991 ◽

Vol 05 (21) ◽

pp. 1447-1456 ◽

Cited By ~ 7

Author(s):

A. R. HARUTUNYAN ◽

L. S. GRIGORYAN ◽

A. S. KUZANYAN ◽

A. A. KUZNETSOV ◽

A. A. TERENTIEV ◽

...

Keyword(s):

Magnetic Field ◽

Chemical Composition ◽

Room Temperature ◽

Microprobe Analysis ◽

Magnetic Anomalies ◽

X Ray Diffraction ◽

X Ray ◽

Two Samples ◽

Field Dependent ◽

History Of

Two samples of benzene-treated Bi–Pb–Sr–Ca–Cu–O powder exhibited at 300 K magnetic field dependent diamagnetism and magnetization irreversibility. The treatment with benzene resulted also in the appearance of microwave absorption at low magnetic fields, while is sensitive to magnetic history of the sample. From X-ray diffraction data one can see that upon benzene treatment the reflections of 85 K and 110 K phases do not change practically, but a series of new reflections appeared, indicating a lattice modulation with 4.9 nm periodicity. A microprobe analysis revealed substantial inhomogeneity of chemical composition across the samples. The room temperature anomalies were weakened in one sample and vanished in the second upon thermal cycling.

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Was the moon magnetized by impact plasmas?

Science Advances ◽

10.1126/sciadv.abb1475 ◽

2020 ◽

Vol 6 (40) ◽

pp. eabb1475

Author(s):

Rona Oran ◽

Benjamin P. Weiss ◽

Yuri Shprits ◽

Katarina Miljković ◽

Gábor Tóth

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Magnetic Anomalies ◽

The Moon ◽

Crustal Field ◽

Impact Simulations ◽

Magnetizing Field

The crusts of the Moon, Mercury, and many meteorite parent bodies are magnetized. Although the magnetizing field is commonly attributed to that of an ancient core dynamo, a longstanding hypothesized alternative is amplification of the interplanetary magnetic field and induced crustal field by plasmas generated by meteoroid impacts. Here, we use magnetohydrodynamic and impact simulations and analytic relationships to demonstrate that although impact plasmas can transiently enhance the field inside the Moon, the resulting fields are at least three orders of magnitude too weak to explain lunar crustal magnetic anomalies. This leaves a core dynamo as the only plausible source of most magnetization on the Moon.

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Improving the crosscorrelation method to estimate the total magnetization direction vector of isolated sources: A space-domain approach for unstable inclination values

Geophysics ◽

10.1190/geo2019-0008.1 ◽

2020 ◽

Vol 85 (4) ◽

pp. J59-J70 ◽

Cited By ~ 1

Author(s):

Nelson Ribeiro-Filho ◽

Rodrigo Bijani ◽

Cosme Ponte-Neto

Keyword(s):

Magnetic Field ◽

Real Data ◽

Magnetic Anomalies ◽

Direction Vector ◽

Total Field ◽

Magnetization Direction ◽

Ambient Magnetic Field ◽

Total Magnetization ◽

Synthetic Test ◽

Equivalent Sources

Knowledge of the total magnetization direction of geologic sources is valuable for interpretation of magnetic anomalies. Although the magnetization direction of causative sources is assumed to be induced by the ambient magnetic field, the presence of remanence should not be neglected. An existing method of correlating total and vertical gradients of the reduced-to-the-pole (RTP) anomaly estimates the total magnetization direction well. However, due to the numerical instability of RTP transformation in the Fourier domain, an assumption should be considered for dealing with inclination values at approximately 0°. We have adopted an extension to the standard crosscorrelation method for estimating the total magnetization direction vector, computing the RTP anomaly by means of the classic equivalent layer technique for low inclination values. Additionally, an ideal number of equivalent sources within the layer is considered for reducing the computational demands. To investigate the relevant aspects of the adopted method, two simple synthetic scenarios are presented. First, a magnetic anomaly produced by a homogeneous and isolated vertical dike is considered. This test illustrates the good performance of the adopted approach, finding the true magnetization direction, even for low inclination values. In the second synthetic test, a long-wavelength component is added to the previous magnetic total-field anomaly. In this case, the method adopted here fails to estimate a reliable magnetization direction vector, showing weak performance for strong interfering magnetic anomalies. On the real data example, the application tests an isolated total-field anomaly of the Carajás Mineral Province, in northern Brazil, where the inclination of the ambient magnetic field is close to zero. The obtained results indicate weak remanence in the estimated total magnetization direction vector, which would never be reached in the standard formulation of the crosscorrelation technique.

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A Simple Method of the Electric/Magnetic Field Observation by a Conventional Transmission Electron Microscope

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.4029 ◽

2005 ◽

Vol 475-479 ◽

pp. 4029-4034 ◽

Cited By ~ 4

Author(s):

Katsuhiro Sasaki ◽

Hiroyasu Saka

Keyword(s):

Magnetic Field ◽

Electron Microscope ◽

Field Distribution ◽

Transmission Electron Microscope ◽

Electrostatic Field ◽

Field Observation ◽

Simple Method ◽

Transmission Electron ◽

Novel Method ◽

Conventional Transmission Electron Microscope

A novel method to observe the electrostatic field distribution with a conventional transmission electron microscope has been developed. The method allows measurements of a potential difference less than 1V/µm. This method can be performed in any kind of conventional transmission electron microscope and applied to the observation of the electric/magnetic field at the level of a specimen.

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Experimental Study on the Localization of Moving Object by Total Geomagnetic Field

Journal of Sensors ◽

10.1155/2017/7948930 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7

Author(s):

Chong Kang ◽

Liming Fan ◽

Quan Zheng ◽

Xiyuan Kang ◽

Jian Zhou ◽

...

Keyword(s):

Magnetic Field ◽

Geomagnetic Field ◽

High Sensitivity ◽

Magnetic Anomalies ◽

Target Localization ◽

Total Field ◽

Detection Range ◽

Vector Sensors ◽

Field Localization ◽

Low Sensitivity

In the method of target localization based on magnetic anomalies, the scheme of vector field localization and experimental research are significant. Because more information of magnetic field can be measured by vector sensors, the position of the target can be directly calculated by the equations. However, the vector magnetic anomaly generated by the target is difficult to measure. And the detection range is small due to the low sensitivity of vector sensors. A method for target localization based on the total geomagnetic field is proposed. Its advantages are that the measurement of total magnetic field is not affected by the orientation of the total field sensors and the detection range is large due to their high sensitivity. In this paper, we focus on the localization using the array with the total field magnetometers. And we design an array structure with the total field magnetometers. Then, we obtain the higher order nonlinear equations for the target localization based on this array. The numerical method is used to solve the equations. Meanwhile, we present a method for eliminating the effect of geomagnetic field variations and uneven spatial distribution. In suburban roads, localization experiments were carried out. And the results showed that the relative error of target localization is less than 5% by using the proposed method.

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