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.

A method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating

Abstract: SUMMARY Spatial variations in the geomagnetic field must be taken into account if secular variation master curves and directional magnetic dates are to be optimized. Two methods for relocating remanence vectors have been proposed and in this paper their relative accuracies are compared using a numerical model based on the present-day field. A method which converts archaeomagnetic directions via a virtual geomagnetic pole is shown to be the more efficient transformation. For an‘archaeomagnetic region’the size of the British Isles, (900 km radius), the maximum error in relocating vectors to a central location is predicted to be of the order of 1.2°.

The secular variation of the earth's magnetic field

Abstract: The magnetic field observable outside a body of conducting fluid in which field is imbedded may be considerably altered by convection currents in the fluid. One possible explanation of the geomagnetic secular variation foci is that localized convection cells in the earth's core disturb the main field present. An analytic solution for such a process is readily obtained by assuming the form and dimensions for such a cell, and shows that the magnitude of the secular variation cannot easily be explained on these lines without the presence of a subsurface toroidal magnetic field of some hundreds of gauss which is ‘convected through’ the surface of the core.

Satellite observations of magnetic fields due to ocean tidal flow.

Abstract: The ocean is an electrically conducting fluid that generates secondary magnetic fields as it flows through Earth's main magnetic field. Extracting ocean flow signals from remote observations has become possible with the current generation of satellites measuring Earth's magnetic field. Here, we consider the magnetic fields generated by the ocean lunar semidiurnal (M2) tide and demonstrate that magnetic fields of oceanic origin can be clearly identified in satellite observations.

Seasonal and solar cycle variations of the zonal mean circulation in the thermosphere

Abstract: The seasonal and solar cycle variations of the zonal mean circulation (longitudinal or, equivalently, diurnal average) and the latitudinal variation of temperature in the earth's thermosphere are calculated by using a numerical model of the zonally symmetric thermosphere. The heat and momentum sources that drive the thermospheric circulation are solar EUV and UV heating, high-latitude heating primarily due to auroral processes, and a momentum source that results from the correlation of diurnal variations of wind and ion drag. The calculations show that the thermospheric circulation is mainly driven by heating due to the absorption of solar electromagnetic energy. However, it is modulated by a high-latitude heat source associated with auroral processes and related to geomagnetic activity. The seasonal variation of the thermosphere is characterized by a persistent solstice type of circulation that undergoes an abrupt transition within a week or two of equinox depending upon geomagnetic activity. The temperature difference from summer pole to winter pole is smaller and the circulation weaker during solar minimum than during solar maximum. To obtain agreement between the calculated and observed latitudinal variation of temperature and circulation, it is necessary to assume a high-latitude energy input during solstice of 2 × 1018 ergs s−1 for average solar maximum conditions and 4.5 × 1017 ergs s−1 for average solar minimum conditions.

Geomagnetic excursions: Knowns and unknowns

Abstract: Geomagnetic excursions are short-lived episodes when Earth’s magnetic field deviates into an intermediate polarity state. Understanding the origin, frequency, amplitude, duration, and field behavior associated with excursions is a forefront research area within solid earth geophysics. Recent advances in excursion research are summarized here, and key further research is suggested to resolve major unanswered questions. Improving the global distribution of excursion records, particularly from the southern hemisphere, obtaining high-resolution sedimentary excursion records with good age control from sites with sedimentation rates >10 cm/kyr, obtaining volcanic excursion records coupled with high-precision geochronology, and estimating excursion duration with high chronological precision will all facilitate hypothesis testing concerning the deep earth dynamics that generate geomagnetic excursions.