scholarly journals Features of the next reversal of the geomagnetic field

2021 ◽  
pp. 131-140
Author(s):  
В.В. Кузнецов
Keyword(s):  
Geomagnetic Field ◽  
Dipole Field ◽  
Total Field

В статье обсуждаются возможность проявления очередной инверсии геомагнитного поля (ГМП) и его некоторые особенности. Дипольное поле (ДП) приблизится к нулевой отметке, которую достигнет примерно в 3500 году. С 1500 года, на фоне понижения ДП происходит рост октупольного и квадрупольного компонент ГМП и их суммы (О+К). ДП, согласно нашей модели геомагнетизма, после прохождения нулевой отметки начнет расти с обратным знаком и противодействовать (О+К) полю, понижая его уровень до нуля. В этот момент (≈ 6000 год) поле (N) будет иметь минимальную величину. Затем начнется рост ДП обратного значения (R). Инверсия закончится при достижении этим полем устойчивой величины. The possibility of a new reversal of the geomagnetic field (GMF) and some of its features are discussed. In 3500 the dipole field (DF) will become near zero. Since 1500, along with the decrease of DF, there has been an increase of the octupole and quadrupole components of the GMF as well as their sum (O+Q). According to our model of geomagnetism, after passing the zero the reversing DF will start its rise counteracting the (O+Q) field and lowering its value to zero. In about 6000 the total field DF+O+Q (N) will be minimum. After DF reaches a stable value the reversal will complete.

Using airborne vector magnetic data to calculate the projection of magnetic anomaly vector onto normal geomagnetic field

Geophysics ◽  
2021 ◽  
pp. 1-47
Author(s):  
Rukuan Xie ◽  
Shengqing Xiong ◽  
Shuling Duan ◽  
Jinlong Wang ◽  
Ping Wang ◽  
...  
Keyword(s):  
Magnetic Anomaly ◽  
Geomagnetic Field ◽  
Approximation Error ◽  
Magnetic Data ◽  
Total Field ◽  
Projection Formula ◽  
Total Magnetization ◽  
Vector Formula ◽  
Relationship Of ◽  
Anomaly Formula

The total-field magnetic anomaly [Formula: see text] is an approximation of the projection [Formula: see text] of the magnetic anomaly vector [Formula: see text] onto the normal geomagnetic field [Formula: see text]. However, for highly magnetic sources, the approximation error of [Formula: see text] cannot be ignored. To reduce the error, we have developed a method for calculating [Formula: see text] by using airborne vector magnetic data based on the vector relationship of geomagnetic field [Formula: see text]. The calculation uses the magnitude of the vectors [Formula: see text], [Formula: see text], and [Formula: see text] through a simple approach. To ensure that each magnitude has the same level, we normalize the magnitude of [Formula: see text] using the total-field magnetic data measured by the scalar magnetic sensor. The method is applied to the measured airborne vector magnetic data at the Qixin area of the East Tianshan Mountains in China. The results indicate that the calculated [Formula: see text] has high precision and can distinguish the approximation error less than 3.5 nT. We also analyze the characteristics of the approximation error that are caused by the effects of different total magnetization inclinations. These error characteristics are used to predict the total magnetization inclination of a 2D magnetic source based on the measured airborne vector magnetic data.

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

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.

scholarly journals Possible consequences of a dwindling geomagnetic field

1971 ◽  
Vol 2 (3) ◽  
pp. 46
Author(s):  
I.K. Crain
Keyword(s):  
Geomagnetic Field ◽  
Dipole Field

Recently, Facer (1971) has discussed the problem of the dwindling of the geomagnetic field, and estimated that in 810 years (AD 2781) the dipole and non-dipole fields will be roughly equal and that in 1931 years (AD 3902) the dipole field will be essentially zero. Various authors (Crain and Crain, 1970; Cox, 1968; Parker, 1969) have suggested that these conditions are highly favourable for the production of geomagnetic reversals.

New technique to diagnose the geomagnetic field based on the single circular current loop model

2020 ◽  
Author(s):  
Zhaojin Rong ◽  
Yong Wei ◽  
Wenyao Xu ◽  
Dali Kong ◽  
Jun Cui ◽  
...  
Keyword(s):  
Electric Current ◽  
Geomagnetic Field ◽  
Dipole Field ◽  
New Technique ◽  
Current Loop ◽  
Loop Model ◽  
Effective Technique ◽  
Circular Current ◽  
Planetary Magnetism ◽  
Geomagnetic Dipole

<p>A quick and effective technique is developed to diagnose the geomagnetic dipole field based on an unstrained single circular current loop model. In comparsion with previous studies, this technique is able to separate and solve the loop parameters successively. With this technique, one can search the optimum full loop parameters quickly, including the location of loop center, the loop orientation, the loop radius, and the electric current carried by the loop, which can roughly indicate the locations, sizes, orientations of the interior current sources. The technique tests and applications demonstrate that this technique is effective and applicable. This technique could be applied widely in the fields of geomagnetism, planetary magnetism and palaeomagnetism. The further applications and constrains are discussed and cautioned.</p>

scholarly journals Theoretically possible spatial accuracy of geomagnetic maps used by migrating animals

2017 ◽  
Vol 14 (128) ◽  
pp. 20161002 ◽  
Author(s):  
Andrei V. Komolkin ◽  
Pavel Kupriyanov ◽  
Andrei Chudin ◽  
Julia Bojarinova ◽  
Kirill Kavokin ◽  
...  
Keyword(s):  
Field Intensity ◽  
Geomagnetic Field ◽  
Site Fidelity ◽  
Large Scale ◽  
Migratory Birds ◽  
Time Of Day ◽  
Northern Europe ◽  
Spatial Accuracy ◽  
Total Field ◽  
Migrating Birds

Many migrating animals, belonging to different taxa, annually move across the globe and cover hundreds and thousands of kilometres. Many of them are able to show site fidelity, i.e. to return to relatively small migratory targets, from distant areas located beyond the possible range of direct sensory perception. One widely debated possibility of how they do it is the use of a magnetic map, based on the dependence of parameters of the geomagnetic field (total field intensity and inclination) on geographical coordinates. We analysed temporal fluctuations of the geomagnetic field intensity as recorded by three geomagnetic observatories located in Europe within the route of many avian migrants, to study the highest theoretically possible spatial resolution of the putative map. If migratory birds measure total field intensity perfectly and take the time of day into account, in northern Europe 81% of them may return to a strip of land of 43 km in width along one of coordinates, whereas in more southern areas such a strip may be narrower than 10 km. However, if measurements are performed with an error of 0.1%, the strip width is increased by approximately 40 km, so that in spring migrating birds are able to return to within 90 km of their intended goal. In this case, migrating birds would probably need another navigation system, e.g. an olfactory map, intermediate between the large-scale geomagnetic map and the local landscape cues, to locate their goal to within several kilometres.

TWO‐DIMENSIONAL HARMONIC ANALYSIS AS A TOOL FOR MAGNETIC INTERPRETATION

Geophysics ◽  
1965 ◽  
Vol 30 (5) ◽  
pp. 829-857 ◽  
Author(s):  
B. K. Bhattacharyya
Keyword(s):  
Geomagnetic Field ◽  
Polarization Vector ◽  
Double Fourier Series ◽  
Fourier Series Expansion ◽  
Magnetic Data ◽  
Block Type ◽  
Total Field ◽  
Magnetic Pole ◽  
Magnetic Interpretation ◽  
Derivatives Of

The total magnetic field values over an area can be represented exactly by a double Fourier series expansion. In this analysis, such an expansion is used to evaluate very accurately the fields continued downward and upward from the plane of observation and the vertical derivatives of the total field. This harmonic expansion of the anomalous total field makes it possible to calculate, with exceptional accuracy, the field reduced to the magnetic pole and its second derivative. The results of the calculations are free from the effect of the inclination of the earth’s main geomagnetic field and that of the polarization vector, at all magnetic latitudes and for all possible directions of polarization. In order to determine the influence of remanence on the above field, a number of anomalies caused by rectangular block‐type bodies with known polarization are reduced to the magnetic pole, correcting only for the obliquity of the earth’s normal field. It is concluded from a study of these anomalies that the interpretation of magnetic data based on the assumption of rock magnetization due solely to induction in the earth’s field may yield erroneous results, particularly when remanence is important.

Transformation from total-field magnetic anomaly to the projection of the anomalous vector onto the normal geomagnetic field based on an optimization method

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. J43-J55 ◽  
Author(s):  
Huixiang Zhen ◽  
Yuanyuan Li ◽  
Yushan Yang
Keyword(s):  
Data Processing ◽  
Magnetic Anomaly ◽  
Geomagnetic Field ◽  
Southern China ◽  
Quadratic Function ◽  
Maximum Error ◽  
Magnetic Data ◽  
Optimization Strategy ◽  
Total Field ◽  
The Difference

The total-field magnetic anomaly [Formula: see text] is approximated as the component [Formula: see text] of the anomalous vector [Formula: see text] along the direction of the normal geomagnetic field. It is widely used in magnetic data processing and interpretation practices as a routine if [Formula: see text] is relatively small. But in highly magnetic environments, the distinction between [Formula: see text] and [Formula: see text] is often too large to be ignored. We carefully investigate the difference between [Formula: see text] and [Formula: see text] and find that it will increase rapidly in the trend of the quadratic function as [Formula: see text] strengthens. We also test the effects of approximation on the component transformation and reduction to the pole on a synthetic single-sphere model. As expected, the error caused by inaccurate information will propagate into subsequent data processing procedures and adversely affect the results. Therefore, we have developed an optimization strategy based on the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm to transform the total-field anomaly into [Formula: see text]. First, we have constructed an objective function after transforming [Formula: see text] into [Formula: see text] through the component transformation in the frequency domain. Then, using [Formula: see text] as the initial value of [Formula: see text], [Formula: see text] is calculated iteratively by the L-BFGS algorithm. To test the validity of the optimization algorithm, [Formula: see text] is transformed for noise-free and noise-corrupted models and models with a background field. The synthetics indicate that the transformed [Formula: see text] is almost the same as the model [Formula: see text], whose maximum error is approximately one-hundredth (30 nT) of the difference (8000 nT) between the modeled [Formula: see text] and [Formula: see text]. The synthetics and field data example from the Yangshan Iron Mine, Fujian Province, southern China, also indicate that the data transformation and forward-modeling results can benefit from the direct use of transformed [Formula: see text] instead of [Formula: see text].

Geophysical Studies of North African Cenozoic Volcanic Areas: III. Garian, Libya

1975 ◽  
Vol 12 (8) ◽  
pp. 1264-1271 ◽  
Author(s):  
J. M. Ade-Hall ◽  
Susann Gerstein ◽  
Robert E. Gerstein ◽  
Peter H. Reynolds ◽  
P. Dagley ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Field Direction ◽  
Dipole Field ◽  
Plate Motion ◽  
Paleomagnetic Data ◽  
North African ◽  
Axial Dipole ◽  
Repeated Sampling ◽  
Absolute Age ◽  
E 32

Paleomagnetic and K/Ar whole rock absolute age data are described for material from the Garian area of Libya, centered at 13°E, 32°N. Within-unit cleaned paleomagnetic directions from the essentially unaltered lavas are very well defined and can almost certainly be taken as reliable measurements of the geomagnetic field direction during the initial cooling of each flow. However, the distributions of mean direction, from which the effect of repeated sampling of the field at one time has been removed, does not suggest that a reversing axial dipole field has been recorded in a representative manner. Both N and R groups of directions are azimuthally elongated, and the average poles for the N and R groups differ by 21°, or four times the 95% level uncertainty for each average pole. A number of possible physical explanations for the paleomagnetic results are discussed. The conventional overall average pole at 88°N, 123°E, δp: 3°, δm: 7 °does not differ significantly from the geographic pole, a result which agrees closely with that of Schult and Soffel (1973). However, the value of these overall average poles in estimating absolute plate motion must await an understanding of the sources of the asymmetries in the paleomagnetic data.

When the dipole geomagnetic field dwindles away

1971 ◽  
Vol 2 (2) ◽  
pp. 29 ◽  
Author(s):  
R.A. Facer
Keyword(s):  
Geomagnetic Field ◽  
Dipole Field ◽  
Magnetic Studies ◽  
The Past ◽  
The Future ◽  
Intensity Study

It is now widely accepted that the geomagnetic field changes sign from time to time, generally irregularly, this "reversal" being accompanied by a decrease in intensity. Study of these changes in the past geomagnetic field has been limited to consideration of the dipole field. Unfortunately, the non-dipole geomagnetic field is more significant than has been considered previously - not only in palaeo-magnetism (Facer, 1970), but perhaps in the future in exploration magnetic studies also.

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