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.

Plasma Sheet Behavior During Substorms

Abstract: Auroral or magnetic substorms are periods of enhanced auroral and geomagnetic activity lasting one to a few hours that signify increased dissipation of energy from the magnetosphere to the earth Data acquired during the past decade from satellites in the near-earth sector of the magnetotail have suggested that during a substorm part of the plasma sheet is severed from earth by magnetic reconnection, forming a plasmoid, ie, a body of plasma and closed magnetic loops, that flows out of the tail into the solar wind, thus returning plasma and energy that have earlier been accumulated from the solar wind Very recently this picture has been dramatically confirmed by observations, with the ISEE 3 spacecraft in the magnetotail 220 R/sub E/ from earth, of plasmoids passing that location in clear delayed response to substorms It now appears that plasmoid release is a fundamental process whereby the magnetosphere gives up excess stored energy and plasma, much like comets are seen to do, and that the phenomena of the substorm seen at earth are a by-product of that fundamental process

Surface electric fields and geomagnetically induced currents in the Scottish Power grid during the 30 October 2003 geomagnetic storm

Abstract: A surface electric field model is used to estimate the UK surface E field during the 30 October 2003 severe geomagnetic storm. This model is coupled with a power grid model to determine the flow of geomagnetically induced currents (GIC) through the Scottish part of the UK grid. Model data are compared with GIC measurements at four sites in the power network. During this storm, measured and modeled GIC levels exceeded 40 A, and the surface electric field reached 5 V/km at sites in the United Kingdom (compared with quiet-time levels of less than 0.1 V/km). The electric field and grid models now form part of a GIC monitoring, analysis, and warning software package with Web interface, developed for use by the grid operator. This package also contains a daily geomagnetic activity forecast service, a solar wind shock detector for geomagnetic storm warning, and a near-real-time geomagnetic data stream for storm monitoring.

An approximate flow equation for geomagnetic flux tubes and its application to polar substorms

Abstract: A recent model of polar substorms suggests they are the result of an impulsive recombination of magnetic field lines across the neutral sheet in the tail of the magnetosphere. The flow of flux tubes within the magnetosphere is shown to be dominated by the discharging action of the ionosphere on flux tubes. This fact enables an approximate flow equation for flow within the magnetosphere to be developed by integrating along flux tubes. This equation is applied to the above model of polar substorms and is shown to give reasonable agreement with the following experimental observations: (i) the velocity and flow pattern of auroral patches; (ii) the height and shape of the auroral breakup bulge; and (iii) the bay current system, including the westward electrojet under the assumption that the westward electrojet is current-induced by the southward component of flow of flux tube feet in the high conductivity strips under auroral arcs. These strips are expected to exhibit a Cowling conductivity. The westward traveling surge is probably caused by an increasing width of the recombination slot in the tail of the magnetosphere. The current flow down field lines and through the ionosphere results in a density (and hence pressure) decrease in the neutral sheet at the west edge of the recombination slot, and thus causes a corresponding westward propagation of the west edge of the recombination slot. Application of the flow equations to the viscous bounday layer problem indicates an exponential falloff in velocity from the magnetosphere boundary with a 1/e distance of 5 × 104 m.

Ultrahigh Resolution Marine Magnetic Anomaly Profiles: A Record of Continuous Paleointensity Variations?

Abstract: A distinctive pattern of small-scale marine magnetic anomalies (25-100 nT amplitude, 8-25 km wavelength: tiny wiggles) is superimposed on the more generally recognized seafloor spreading pattern between anomalies 24 and 27 in the Indian Ocean. By normalizing and stacking multiple profiles, it is demonstrated that this pattern of tiny wiggles is a high-resolution recording of paleodipole field behavior between chrons C24 and C27. The pattern of tiny wiggles between anomalies 26 and 27 is compared to an ultrafast spreading (82 mm/yr half rate) profile from the southeast Pacific where a similar signal is observed, confirming the paleodipole field origin of the anomalies. Two basic models are considered in which the tiny wiggles are attributed either to short polarity intervals or to paleointensity fluctuations. We conclude that tiny wiggles are most likely caused by paleointensity fluctuations of the dipole field and are a ubiquitous background signal to most fast spreading magnetic profiles. The implications of this study are that (1) tiny wiggles may provide information on the temporal evolution of the geomagnetic dynamo; (2) the small-scale anomalies observed in the Jurassic quiet zones may be due to paleointensity fluctuations; (3) tiny wiggles are potential time markers in large regions of uniform crustal polarity such as the Cretaceous quiet zones; and (4) much of the variance in anomaly profiles normally attributed to crustal eraplacement processes, particularly at fast and ultrafast spreading rates, is actually due to intensity variations in the paleomagnetic field.

Geomagnetic disturbance effects on power systems

Abstract: In the northern hemisphere, the aurora borealis is visual evidence of simultaneous fluctuations in the earth's magnetic field (geomagnetic field) These geomagnetic disturbances (GMD's), or geomagnetic storms, can affect a number of man-made systems, including electric power systems The GMD's are caused by the electromagnetic interaction of the solar wind plasma of protons and electrons with the geomagnetic field These dynamic impulses in the solar wind are due to solar flares, coronal holes, and disappearing filaments, and reach the earth from one to six days after being emitted by a solar event Instances of geomagnetic storms affecting telegraph systems were noted in England in 1846, and power system disturbances linked to GMD's were first reported in the United States in 1940 This Working Group report is a summary of the state of knowledge and research activity to the present time, and covers the GMD/Geomagnetically-induced currents (GIC) phenomena, transformer effects, the impact on generators, protective relay effects, and communication system effects It also summarizes modeling and predicting GIC, measuring and monitoring GIC, mitigation methods, system operating guidelines during GMD's, and alerting and forecasting procedures and needs for the power industry