Magnetic effects of a finite, arbitrarily oriented line of dipoles

Geophysics ◽  
1991 ◽  
Vol 56 (9) ◽  
pp. 1474-1476
Author(s):  
Birendra K. Jain
Keyword(s):  
Magnetic Field ◽  
Closed Form ◽  
Magnetic Data ◽  
Important Class ◽  
Earth’S Magnetic Field ◽  
Magnetic Effects ◽  
Oriented Line ◽  
Earth's Magnetic Field ◽  
Finite Line ◽  
Limited Depth

Lines of dipoles are an important class of 3-D theoretical bodies and are often used to model the effects due to narrow, elongated magnetic bodies of limited depth extents in the interpretation of magnetic data. The application includes geologic bodies such as mineralized veins and pipes, as well as nongeologic bodies such as well casings. Though closed‐form expressions for the magnetic effects of such a finite line of dipoles are available in the published literature, the cases treated are quite restricted, i.e., the expressions are given for the line either parallel or perpendicular to the plane of observation (e.g., Nettleton, 1942, Hall, 1959, Singh and Sabina, 1978) or for the line inductively magnetized and dipping in the direction of the earth’s magnetic field (e.g., Henderson and Zeitz, 1967).

The Earth's magnetic field variations at the Algerian magnetic observatory of Tamanrasset from 1932 to 2020.

2021 ◽  
Author(s):  
Lemgharbi Abdenaceur ◽  
Hamoudi Mohamed ◽  
Abtout Abdeslam ◽  
Abdelhamid Bendekken ◽  
Ener Aganou ◽  
...  
Keyword(s):  
Magnetic Field ◽  
International Association ◽  
Sampling Rate ◽  
Magnetic Data ◽  
Magnetic Observatory ◽  
Earth’S Magnetic Field ◽  
Data Set ◽  
Secular Variations ◽  
The World ◽  
Earth's Magnetic Field

<p>In order to understand the spatial and temporal behavior of the Earth's magnetic field, scientists, following C.F. Gauss initiative in 1838 have established observatories around the world. More than 200 observatories aiming to continuously record, the time variations of the magnetic field vector and to maintain the best standard of the accuracy and resolution of the measurements.</p><p>This study focused on the acquisition and analysis of the magnetic data provided by the Algerian magnetic observatory of Tamanrasset (labelled TAM by the International Association of Geomagnetism and Aeronomy). This observatory is located in southern Algeria at 5.53°E longitude, 22.79°N Latitude. Its altitude is 1373 meters above msl. TAM is continuously running since 1932, using old brand variometers, like Mascart and La Cour with photographic recording at the very beginning. Nowadays modern electronic equipment are used in the framework of INTERMAGNET project. Very large geomagnetic database collected over a century is available. We will describe the history and the various improvement of the methods and instrumentation.</p><p>Preliminary analysis of time series of the observatory data allowed to distinguish two kinds of data: the first type, with low resolution, collected between 1932 and 1992. This data set comes from the annual, monthly, daily and hourly means. The second one with high resolution is represented by minutes and seconds sampling rate since 1993 when TAM was integrated to the world observatory network, INTERMAGNET. Part of the second dataset contains many gaps. We try to fill these gaps thanks to mathematical methods. Absolute measurements and repeat station data allow better accuracy in the secular variations and an improved regional model.</p><p>Keywords: TAM observatory, temporal variation, terrestrial magnetic field, secular variations, INTERMAGNET.</p>

An analysis of rock magnetic data

1960 ◽  
Vol 256 (1286) ◽  
pp. 291-322 ◽  
Keyword(s):  
Magnetic Field ◽  
Continental Drift ◽  
Magnetic Data ◽  
Rotational Axis ◽  
Earth’S Magnetic Field ◽  
Geological Time ◽  
The Past ◽  
Geological Processes ◽  
Minimum Number ◽  
Earth's Magnetic Field

The data obtained from numerous palaeomagnetic measurements made during the past decade have shown that while the geologically younger rock formations are magnetized in directions close to that of the present earth’s magnetic field, the remanent magnetic polarizations of older rocks depart markedly from this pattern. These observations are widely held by many workers to suggest that the main continental land masses have undergone movements relative to one another during the past. The present paper gives an account of a new analysis of the available data, making a minimum number of theoretical assumptions about the ways in which the rocks became magnetized and about the origin of the geomagnetic field. The results of this analysis strongly support the supposition that the observed wide divergence between the directions of the remanent magnetic vectors of older rocks and that of the present earth’s field is systematic, and not a result of purely random processes occurring throughout geological time. The most reasonable explanations of the phenomenon appear to be that ( a ) the directions of magnetization of the earlier rocks have been changed by some widespread physical or geological processes since the time of their formation, ( b ) the earth’s magnetic field has had strong multipolar components in past geological ages, ( c ) a relative drift of the continents across the earth’s mantle has occurred. Of these hypotheses, ( c ) appears to be the most plausible. On the tentative assumption that the rock magnetic results can be explained by continental drift, it is possible to estimate the ancient latitude and the orientation relative to the earth’s rotational axis, of each continent, although by palaeomagnetic measurements alone changes in relative longitude cannot be revealed.

LIMITING VALUES OF GRAVITATIONAL AND MAGNETIC ANOMALIES DUE TO A SUBTERRANEAN STRUCTURE BOUNDED BY A SINGLE DIFFERENTIAL SURFACE

Geophysics ◽  
1941 ◽  
Vol 6 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. W. Fisher
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Magnetic Anomalies ◽  
Effective Thickness ◽  
Earth’S Magnetic Field ◽  
Magnetic Effects ◽  
Earth's Magnetic Field ◽  
Survey Results ◽  
Limiting Values

Calculations are made of gravitational and magnetic anomalies supposed due to local variations in the form of a single differential surface separating an overlying rock from an underlying one, the effective thickness of the latter being infinite. Both layers are homogeneous in density or magnetic susceptibility and only those magnetic effects are considered which are due to induction in the earth’s magnetic field. The maximum possible values of these anomalies and of their first and second horizontal derivatives are calculated under these simplified conditions, and it is pointed out that the numerical readings of these quantities, provided by survey results, may lead to useful estimates of the extreme depth and proportions of the structure responsible.

scholarly journals Observing Earth’s magnetic environment with the GRACE-FO mission

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
C. Stolle ◽  
I. Michaelis ◽  
C. Xiong ◽  
M. Rother ◽  
Th. Usbeck ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Local Time ◽  
Noise Level ◽  
High Amplitude ◽  
Magnetic Data ◽  
Storm Event ◽  
Earth’S Magnetic Field ◽  
Magnetic Field Model ◽  
Earth's Magnetic Field ◽  
The Mean

AbstractThe Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission carries magnetometers that are dedicated to enhance the satellite’s navigation. After appropriate calibration and characterisation of artificial magnetic disturbances, these observations are valuable assets to characterise the natural variability of Earth’s magnetic field. We describe the data pre-processing, the calibration, and characterisation strategy against a high-precision magnetic field model applied to the GRACE-FO magnetic data. During times of geomagnetic quiet conditions, the mean residual to the magnetic model is around 1 nT with standard deviations below 10 nT. The mean difference to data of ESA’s Swarm mission, which is dedicated to monitor the Earth’s magnetic field, is mainly within ± 10 nT during conjunctions. The performance of GRACE-FO magnetic data is further discussed on selected scientific examples. During a magnetic storm event in August 2018, GRACE-FO reveals the local time dependence of the magnetospheric ring current signature, which is in good agreement with results from a network of ground magnetic observations. Also, derived field-aligned currents (FACs) are applied to monitor auroral FACs that compare well in amplitude and statistical behaviour for local time, hemisphere, and solar wind conditions to approved earlier findings from other missions including Swarm. On a case event, it is demonstrated that the dual-satellite constellation of GRACE-FO is most suitable to derive the persistence of auroral FACs with scale lengths of 180 km or longer. Due to a relatively larger noise level compared to dedicated magnetic missions, GRACE-FO is especially suitable for high-amplitude event studies. However, GRACE-FO is also sensitive to ionospheric signatures even below the noise level within statistical approaches. The combination with data of dedicated magnetic field missions and other missions carrying non-dedicated magnetometers greatly enhances related scientific perspectives.

The Atlas of the Earth's Magnetic Field

2012 ◽  
Author(s):  
A. Soloviev ◽  
A. Khokhlov ◽  
E. Jalkovsky ◽  
A. Berezko ◽  
A. Lebedev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field

Atlas of Earth's magnetic field

2011 ◽  
Vol 12 (2) ◽  
pp. 1-9
Author(s):  
A. E. Berezko ◽  
A. V. Khokhlov ◽  
A. A. Soloviev ◽  
A. D. Gvishiani ◽  
E. A. Zhalkovsky ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field

scholarly journals Night-time Sferic Propagation at Frequencies Below 10 KHz

1967 ◽  
Vol 20 (1) ◽  
pp. 101 ◽  
Author(s):  
KJW Lynn ◽  
J Crouchley
Keyword(s):  
Magnetic Field ◽  
Geographic Distribution ◽  
Angle Of Incidence ◽  
European Studies ◽  
Earth’S Magnetic Field ◽  
Night Time ◽  
The West ◽  
Earth's Magnetic Field ◽  
Effective Angle

Results of a study at Brisbane of individual night-time sferics of known origin are described. A propagation attenuation minimum was observed in the 3-6 kHz range. The geographic distribution of sferic types was also examined. Apparent propagation asynunetries were observed, since sferics were detected at greater ranges to the west than to the east at 10 kHz, whilst the number of tweek-sferics arising from the east was about four times that arising from the west. Comparison with European studies suggest that these asymmetries are general. These results are then " interpreted in terms of an ionospheric reflection cgefficient which is a function of the effective angle of incidence of the wave on the ionosphere and of orientation with respect to the Earth's magnetic field within the ionosphere.

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