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Dipole model of the Earth's magnetic field

About: Dipole model of the Earth's magnetic field is a research topic. Over the lifetime, 2756 publications have been published within this topic receiving 83021 citations.


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01 Jan 1977
TL;DR: A quantitative model of the magnetospheric magnetic field and associated procedures for accurately cataloging charged-particle data out to and beyond geosynchronous orbit is developed in this paper.
Abstract: A quantitative model of the magnetospheric magnetic field and associated procedures for accurately cataloging charged-particle data out to and beyond geosynchronous orbit is developed. The magnetic field model incorporates all major magnetospheric current systems and is valid for all tilt angles; i.e., angles of incidence of the solar wind on the dipole axis. The model accurately represents the total magnetospheric magnetic field for conditions of low magnetic activity and to a geocentric distance of 15 earth radii or to the magnetopause. A new (B, I) coordinate system is developed to organize charged-particle data more accurately. The electric field produced by the daily varying tilt angle is computed.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the synoptic appearance of solar magnetic sectors was studied using 454 sector boundaries observed at Earth during 1959-1973, and the typical flux imbalance for a magnetic sector is about 4 × 1021 Mx.
Abstract: The synoptic appearance of solar magnetic sectors is studied using 454 sector boundaries observed at Earth during 1959–1973. The sectors are clearly visible in the photospheric magnetic field. Sector boundaries can be clearly identified as north-south running demarcation lines between regions of persistent magnetic polarity imbalances. These regions extend up to about 35 ° of latitude on both sides of the equator. They generally do not extend into the polar caps. The polar cap boundary can be identified as an east-west demarcation line marking the poleward limit of the sectors. The typical flux imbalance for a magnetic sector is about 4 × 1021 Mx.

65 citations

Journal ArticleDOI
A. F. Kuckes1
TL;DR: In this paper, it is shown that the electrical conductivity within an object can often be related to simple properties of fluctuating magnetic fields observed and generated outside of it, and the specific question to which we are addressing ourselves is the determination of the electric conductivity as a function of depth into a geological body by observing the properties of fluctuations magnetic fields outside that body.
Abstract: Summary It is shown that the ratio of the vertical field to the horizontal field gradient outside a geological body can often be used to measure the electrical conductivity at depth within it. The in-phase part of this ratio, at a given frequency, gives the penetration depth of the magnetic field, the out-of-phase component yields approximately the conductivity at the penetration depth. In this paper it will be shown that the electrical conductivity within an object can often be related to simple properties of fluctuating magnetic fields observed and generated outside of it. The specific question to which we address ourselves is the determination of the electrical conductivity as a function of depth into a geological body by observing the properties of fluctuating magnetic fields outside that body. In the case of the Earth, we are concerned with the fluctuating magnetic fields which are excited by electric currents flowing in the ionosphere, in the case of the Moon by magnetic fields which are convected by the solar wind. We shall mathematically analyse the interaction of an oscillating magnetic field which is slightly non-uniform in the horizontal plane with a laterally uniform body whose electrical conductivity increases with depth. It will be shown that, above and outside the body, the magnetic field has two simply interpretable properties whose importance for interpreting magnetic deep sounding data has not been realized heretofore. The ratio of the ' in phase ' part of the vertical field to the ' gradient ' of the oscillating horizontal field component is equal to an appropriately defined field penetration depth. The ratio of the out-of-phase part of the vertical field and the same horizontal field gradient is approximately equal to the field attenuation length associated with the electrical conductivity of the body evaluated at the field penetration depth. Chapman (1919) pointed out that the fluctuating magnetic fields observed at the surface of the Earth could be resolved into normal modes and that the part of each normal mode which is due to eddy currents flowing inside the body could be separated from that due to currents flowing externally. By noting that the internal currents were coupled to and excited by the external currents, he obtained an approximate value for the Earth's conductivity. Various combinations of the ' complex ' ratio of the internal current and the external current have subsequently been denoted as magnetic response functions. By studying these response functions as a function frequency means have been devised to generate conductivity profiles of the Earth and Moon from experimental data (Rikitake 1966). Most analyses have seriously utilized only the real part of this response function (e.g. Banks 1969), i.e. they have considered only the magnitude of the horizontal

64 citations

Journal ArticleDOI
TL;DR: For example, the velocity of the North magnetic pole reached some 40 km/yr in 2001, the highest recorded so far in the last two centuries as discussed by the authors, which is an order of magnitude faster than its natural decay time, a reflection of the growth of patches of reverse flux at the coremantle boundary.
Abstract: Many Earth system processes generate magnetic fields, either primary magnetic fields or in response to other magnetic fields. The largest of these magnetic fields is due to the dynamo in the Earth's core, and can be approximated by a geocentric axial dipole that has decayed by nearly 10% during the last 150 years. This is an order of magnitude faster than its natural decay time, a reflection of the growth of patches of reverse flux at the core-mantle boundary. The velocity of the North magnetic pole reached some 40 km/yr in 2001. This velocity is the highest recorded so far in the last two centuries. The second largest magnetic field in the solid Earth is caused by induced and remanent magnetization within the crust. Controlled in part by the thermo-mechanical properties of the crust, these fields contain signatures of tectonic processes currently active, and those active in the distant past. Recent work has included an estimate of the surface heat flux under the Antarctic ice cap. In order to understand the recent changes in the Earth's magnetic field, new high-quality measurements are needed to continue those being made by Orsted (launched in 1999), CHAMP and the Orsted-2 experiment onboard SAC-C (both launched in 2000). The present paper is motivated by the advent of space surveys of the geomagnetic field, and illustrates how our way of observing, modeling, and interpreting the Earth's magnetic field has changed in recent years due to the new magnetic satellite measurements.

64 citations

Journal ArticleDOI
TL;DR: In this article, a scale-free search for magnetic holes in the solar wind using Wind magnetometer observations between 1994 and 2004 is described, and magnetic holes are shown to be pressure-balanced structures with similar properties on all scales.
Abstract: [1] We describe a scale-free search for magnetic holes in the solar wind using Wind magnetometer observations between 1994 and 2004. Using magnetic field and ion measurements on the Wind spacecraft, we present the first statistical study of magnetic hole plasma signatures on the kinetic scale and we evaluate magnetic holes as kinetic and fluid phenomena. Magnetic holes are shown to be pressure-balanced structures with similar properties on all scales. Temperature anisotropy measurements are combined with magnetic field measurements to give direct evidence that magnetic holes observed at 1 AU are stable remnants of magnetic pressure depletions generated in a source region closer to the Sun, likely through the mirror-mode instability.

64 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202312
202220
20181
201751
201656
201546