The task of reconstructing the motion of an object by magnetic measurements

We examine the problem of determining the spatial position of a triaxial magnetometer onboard an artificial satellite by measuring the fields in orbit. Such a task is interesting from the point of view that to solve it, data on the satellite and the character of its motion in orbit are not used. We obtain explicit expressions for the Euler angles via the field components measured in orbit and taken from a field model, which is considered given.     

Regional features of the geomagnetic field secular variations

The secular variations in the geomagnetic field have been studied based on the satellite vector magnetic survey. A high data accuracy made it possible to estimate the spatial and temporal characteristics of different variation types on the interval 1980–2007. The growth and decomposition of midlatitude foci have been qualitatively estimated, and the structure and velocity of a drifting equatorial anomaly have been determined.     

Construction of the spatial-temporal model of the main geomagnetic field using satellite data

The spatial-temporal model of the geomagnetic field has been constructed using the data of the high-accuracy survey of the CHAMP German satellite, obtained during its operation from May 2001 to September 2007. The daily average spherical harmonic models calculated at an interval of four days are used as initial data in order to expand these models by the method of natural orthogonal components (NOCs). It has been indicated that the obtained NOC series rapidly converges. The secular variations, secular acceleration, and Dst variation are distinguished as individual NOC components, which makes it possible to construct the spatial-temporal field model. In addition, the models-predictions have been constructed for the year 2008 based on the candidate models of the main field and the secular variation for the year 2005, which were used to obtain the IGRF2005 international model. A comparison of the models-predictions with the model constructed for the year 2008 using our method indicated that the accuracy of our model is not lower than that of the models, obtained by other scientific groups using the traditional method.     

Spatial features of the manifestation of the geomagnetic field westward drift

The specific features of the spatial structure and time dynamics of the main geomagnetic field during the 20th century, proceeding from the present-day concepts of geomagnetic jerks have been studied. The variations, caused by global dissipation of the geomagnetic field dipole part, have been separated from the regional variations, described by nondipole spatial harmonics of the spherical harmonic expansion series. It has been indicated that the geomagnetic field westward drift manifests itself in a limited region of the Earth’s surface, forming the known Brazil anomaly. However, the drift component in the variations in the geomagnetic field morphological structures is globally found out during the considered almost 100-year period along the narrow belt around the geomagnetic axis. However, this drift is northwestward in the Northern Hemisphere, and the structures drift southeastward in the Southern Hemisphere. The detected variations of the drift nature are reflected in the variations in the integral geomagnetic characteristic, when changes in the position of the Earth’s magnetic center are considered. The direct correlation between the global geomagnetic variations of the drift nature and the trend variations in the orientation of the vector of the Earth daily rotation velocity has been detected.     

Taking magnetic deviation into account when it is measured at a moving object

The works devoted to taking magnetic deviation into account on vehicles are reviewed. Different methods for taking deviation into account are presented. These methods can be conditionally divided into three groups: the usage of parameters of magnetic deviation measured at sites, compensation for vehicle deviation using different methods, and removal of magnetic sensors to a certain distance from a vehicle. A substantial disadvantage of all methods consists in that it is impossible to determine deviation in an on-line mode. The on-line technique for determining deviation of magnetized bodies developed by us is briefly described.     

Features of the latitudinal distribution of the annual variation of the geomagnetic field level and circumpolar current system in 1964

The results of investigations of the latitudinal distribution of annual variation of the geomagnetic field level in the seasons of 1964 (International Quiet Sun Year) using the data from 95 world magnetic observatories located at various longitudes in the latitude range 83° N–90° S are reported. The latitudinal features of the X, Y, and Z components of the geomagnetic field have been analyzed. It has been shown that the amplitudes (summer-winter differences) of the annual variation are maximal in the polar regions, decrease continuously to zero towards the equator, and are identical for both the Northern and Southern hemispheres with a half-year delay (local summer). The amplitudes of the equinox-winter difference in the equinox periods are smaller than those in summer, but are manifested simultaneously in the Northern and Southern hemispheres. An equivalent circumpolar current system has been constructed, which is responsible for the annual variation of the geomagnetic field level. Its parameters have been determined.     

Extraction of the anomaly magnetic field of the earth from stratospheric balloon magnetic surveys at altitudes of 20–40 km

The solution to the problem of extraction of the anomaly Earth’s magnetic field (EMF) from stratospheric balloon magnetic surveys with the help of global analytical models of the normal EMF is proposed. In the problem solution, errors for the analytical models of the normal EMF and its secular variation at a set moment of time are assessed; the found error is introduced as a correction to the extracted anomaly EMF. The error of the model is determined in the places where significant magnetic anomalies are absent. In this case, the error of the model corresponds to deviations of the normal EMF components, synthesized by coefficients of analytical models, and to deviations of the EMF secular variations from the measured values at quite a low value of the variable EMF or one being taken into account. These places are determined when carrying out additional measurements in vertical gradients of the EMF with the use of scalar magnetometers at the gauge length of 6 km. It has been shown that the found places can be considered as nonanomaly, if the difference of values of the anomaly EMF at the gauge length of 6 km does not exceed 1.5 nT within the profile’s portion of about 100 km in length. An experiment in nature has revealed that errors for the IGRF-2005 and IGRF-2010 models, corrected for secular variation of the EMF, can reach 200 and 140 nT, respectively, within the limits of the territory where the Kama-Emba magnetic anomaly is located; these errors are determined by the considered causes. Comparison of aerostatic profiles of magnetic anomalies with data on the anomaly EMF, derived from the maps, has shown that the realizations derived from the maps contain overestimated negative values of the anomaly EMF, because they reflect processes in the near-surface layer of the Earth’s crust. This fact causes the situation when attempts to recalculate the anomaly EMF into the upper half-space by the near-surface data still have not been successful. Only realizations derived at the altitudes comparable to the thickness of the Earth’s crust can give an adequate model of the anomaly EMF in the circumterrestrial space and enable us to recalculate magnetic anomalies reliably into any altitude levels.     

Space-time modeling of the main magnetic field by combined methods of spherical harmonic analysis and natural orthogonal components

A simple method for obtaining a space-time model of the main magnetic field from the high-precision satellite survey data is described. At the first stage, the CHAMP satellite data for one-day interval are expanded into the spherical harmonics with constant coefficients. This yields a set of daily mean spherical harmonic models (DMSHM) over the survey interval of a few years. At the second stage, the coefficients of this set are used as source data for expansion into the natural orthogonal components (NOC). It is shown that the terms of the NOC series decrease rapidly, and the accuracy of the space-time model of the main geomagnetic field over the time interval under discussion is not worse than the accuracy of the models obtained by traditional methods.     

The geomagnetic field in the 20th century

The continuous spatial-temporal model of variations in the main geomagnetic field in the 20th century has been elaborated. All available data—from the navigation to the satellite surveys at the beginning and end of the century, respectively—have been used to construct the model. Since the accuracy of measurements was different during the century and the data are nonuniformly distributed over the Earth’s surface, the methods for regulating solutions based on global parameters of the magnetic field and its secular variation, invariant on the simulation interval, have been used to correct the model. The secular variation model has been represented as the sum of the models obtained by means of expansion in terms of natural orthogonal components. The conclusions that the character of field variations is complex have been made and the spatial and temporal characteristics of the secular variations of different origin have been estimated based on the simulation results.     

东亚地区地磁场的理论分析与矩谐模型

根据东亚地磁场三分量绝对测量资料,使用矩谐分析方法研究了东亚地区（北纬２０-７０,东径４０-１６０）的地磁异常场,计算出地磁异常的矩谐模型．据此模型编绘了Ｘ．ＹＺ三分量磁异常图．结果表明,在东亚的中心地区地磁异常的分布比较均匀,表现出区域特征．而在边界地区,特别是西南角和东南角一带,由于缺乏实测数据,边界效应很大．