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Earth's magnetic field
About: Earth's magnetic field is a research topic. Over the lifetime, 20360 publications have been published within this topic receiving 446747 citations. The topic is also known as: magnetic field of Earth & geomagnetic field.
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113 citations
TL;DR: In this article, the authors developed the fundamental equations required in the reconstructions, both for isotropic pressure and, in Appendix A, for the case where the pressures parallel and perpendicular to the magnetic field are described by the double-polytropic laws.
Abstract: [1] Grad-Shafranov reconstruction is a data analysis tool for the reconstruction of two-dimensional (2-D) coherent field and flow structures from data collected as the structures move past an observing platform. To date, the method has been applied with good success to reconstruct magnetohydrostatic structures in Earth's magnetopause, in the solar wind, and in the geomagnetic tail, as the structures move past one or more observing spacecraft. However, with suitable modification, the reconstruction method can be extended to other applications, three of which are presented here: 2-D magneto-hydrodynamic structures in which dynamically important field-aligned flow is present, 2-D flow transverse to the magnetic field in the magnetospheric low-latitude boundary layer, and 2-D ordinary gasdynamic/hydrodynamic flow. We develop the fundamental equations required in the reconstructions, both for isotropic pressure and, in Appendix A, for the case where the pressures parallel and perpendicular to the magnetic field are described by the double-polytropic laws. Applications to actual or simulated data are discussed but not included in the present paper.
113 citations
TL;DR: The dayside geomagnetic field disturbances in the auroral oval monitored by satellite in polar orbit at 1100 km were reported in this paper, where the satellite was placed at polar orbit.
Abstract: Dayside geomagnetic field disturbances in auroral oval monitored by satellite in polar orbit at 1100 km
113 citations
TL;DR: In biology, the study of geomagnetic orientation has gained new momentum since the discovery of magnetic field detectors in aquatic organisms and the ability of sharks and rays to orient to the earth's magnetic field has been demonstrated in behavioral experiments as discussed by the authors.
Abstract: In biology, the study of geomagnetic orientation has gained new momentum since the discovery of magnetic field detectors in aquatic organisms. Sharks and rays respond to dc and low frequency voltage gradients of 0.005 μV/cm. By moving through the earth's magnetic field, they induce electric fields well within the sensitivity range of their keen electric sense. As these fields depend on the direction in which the animal is heading, the induced voltage gradients may serve as the biophysical basis of an electromagnetic compass sense. The ability of sharks and rays to orient to the earth's magnetic field has been demonstrated in behavioral experiments. Also, various marine and freshwater mud bacteria are endowed with permanent magnetic dipole moments, directed parallel to the axis of motility. When separated from the sediments, these bacteria return to the mud by migrating downward along the earth's inclined magnetic field lines. Their orientation is largely determined by the principles of statistical mechanics and may be expressed in terms of the directive magnetic force, the randomizing effect of thermal agitation, and the cells' flagellar thrust. Observations on live bacteria yield individual dipole moments circa 15 × kT/G.
113 citations
TL;DR: In this paper, the authors presented DTU's candidate field models for IGRF-12 and the parent field model from which they were derived, CHAOS-5.
Abstract: We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived, CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. The internal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, compared with CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based on low-altitude CHAMP data, which was used in CHAOS-4. We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites: Orsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variation measured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarm magnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data are lower than those to Orsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5 shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013 pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.
112 citations