Topic
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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TL;DR: The validity of Cagniard's analysis of the behavior of telluric earth currents is questioned in view of the fact that the harmonic components of the electric field and the magnetic field tangential to the ground are only proportional to one another if the fields are sufficiently slowly varying over the surface of the ground as mentioned in this paper.
Abstract: The validity of Cagniard’s analysis of the behaviour of telluric earth currents is questioned in view of the fact that the harmonic components of the electric field and the magnetic field tangential to the ground are only proportional to one another if the fields are sufficiently slowly varying over the surface of the ground. His result is extended to include the effects of a layered ground with both conductivity and susceptibility variations. Finally the corresponding transient problem is solved for a two‐layer horizontally stratified earth.
147 citations
TL;DR: Aspherical harmonic model of the magnetic field of Uranus was obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems as mentioned in this paper.
Abstract: Aspherical harmonic model of the planetary magnetic field of Uranus is obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems. The Goddard Space Flight Center 'Q3' model is characterized by a large dipole tilt (58.6 deg) relative to the rotation axis, a dipole moment of 0.228 G R(Uranus radii cubed) and an unusually large quadrupole moment. Characteristics of this complex model magnetic field are illustrated using contour maps of the field on the planet's surface and discussed in the context of possible dynamo generation in the relatively poorly conducting 'ice' mantle.
144 citations
TL;DR: In this article, the particle scattering and current sheet stability features in the geomagnetic tail during the phase of substorm growth were investigated using Tsyganenko's (1989) magnetic field model.
Abstract: The particle scattering and current sheet stability features in the geomagnetic tail during the phase of substorm growth were investigated using Tsyganenko's (1989) magnetic field model. In a study of four substorm events which were observed both in the high-altitude nightside tail and in the auroral ionosphere, the model magnetic field was adjusted to each case so as to represent the global field development during the growth phase of the substorms. The model results suggest that the auroral brightenings are connected with processes taking place in the near-earth region inside about 15 earth radii. The results also suggest that there is a connection between the chaotization of the electrons and the auroral brightenings at substorm onset.
143 citations
TL;DR: The signatures of magnetospheric substorms near 6.6 earth radii were statistically examined using data obtained on board ATS 6 by magnetic field and energetic particle measurements as discussed by the authors, and it was confirmed that the configuration change toward a tail-like field in the dusk-to-midnight sector typically began about one hour before the onset of the expansion phase of a substorm.
Abstract: The signatures of magnetospheric substorms near 6.6 earth radii are statistically examined using data obtained on board ATS 6 by magnetic field and energetic particle measurements. It is confirmed that the configuration change toward a tail-like field in the dusk-to-midnight sector typically begins about one hour before the onset of the expansion phase of a substorm. Configuration changes before the onsets of moderate substorms are characterized by a directional change of magnetic field at magnetic latitude of approximately 10 deg, rather than by a change in the field magnitude. It is found during storm periods that the magnetic field orientation occasionally becomes almost parallel to the magnetic equator before expansion phase onsets. Here, the field magnitude usually increases above background levels. These facts are seen as strongly suggesting that a tail-like configuration is caused by an intensification and earthward motion of the cross-tail current system, often close to 6.6 earth radii, rather than by development of diamagnetic ring current.
143 citations
TL;DR: In this article, the authors show that the fluid flow at the surface of the core is consistent with the presence of two large waves that have been proposed to explain the temporal variation of the magnetic field at the core-mantle boundary.
Abstract: An estimate of the magnitude and geometry of the magnetic field within the Earth's core would be valuable for understanding the dynamics of the liquid outer core and for constraining numerical models of the geodynamo. The magnetic field down to the core–mantle boundary can be estimated from surface observations by assuming that the mantle is an insulator1, but such estimates cannot be further extrapolated into the conducting core itself. The magnetic field within the core has therefore remained largely unconstrained. Here we construct a simple picture of part of the magnetic field within the core by first showing that the fluid flow at the surface of the core is consistent with the presence of two large waves—‘torsional oscillations’ of the type that have been proposed to explain the temporal variation of the magnetic field at the core–mantle boundary. We then use the structure of these waves to calculate a one-dimensional map of the part of the magnetic field that points away from the rotation axis. These results may help distinguish between the different dynamic states proposed for outer-core flow2,3,4,5 and provide a test for recent numerical models of the geodynamo6,7,8,9.
143 citations