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The International Geomagnetic Reference Field (IGRF) is a standard mathematical description of the large-scale structure of the Earth's main magnetic field and its secular variation. It was created by fitting parameters of a mathematical model of the magnetic field to measured magnetic field data from surveys, observatories and satellites ...
The International Real-time Magnetic Observatory Network (INTERMAGNET) is a world-wide consortium of institutes operating ground-based magnetometers recording the absolute level of the Earth's time-varying magnetic field, [2] [3] [4] to an agreed set of standards. INTERMAGNET has its roots in discussions held at the Workshop on Magnetic ...
A magnetic anomaly detector (MAD) is an instrument used to detect minute variations in the Earth's magnetic field. [1] The term typically refers to magnetometers used by military forces to detect submarines (a mass of ferromagnetic material creates a detectable disturbance in the magnetic field ).
The Bangui magnetic anomaly in central Africa and the Kursk magnetic anomaly in eastern Europe (both in red) In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by ...
The Enhanced Magnetic Model (EMM) is a sister product of the NGDC featuring a much higher amount of data to degree and order 790, giving a wavelength of 51 km as opposed to the 3000 km of WMM. At this resolution, it is not only able to model the Earth's magnetic field at the core-mantle boundary ("main field"), but also take into account ...
Somewhat more formally, Bowditch defines variation as "the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. The angle between magnetic and grid meridians is called grid magnetic angle, grid variation, or grivation." [1]
The World Digital Magnetic Anomaly Map (WDMAM) was first made available by the Commission for the Geological Map of the World in 2007. Compiled with data from governments and institutes, [1] the project was coordinated by the International Association of Geomagnetism and Aeronomy, and was presented by Mike Purucker of NASA and Colin Reeves of the Netherlands. [2]
The amplitude of the daily variation of the horizontal magnetic intensity (ΔH) measured at a geomagnetic observatory near the dip-equator is 3–5 fold higher than the variation of data from other regions of Earth. A typical diurnal equatorial observatory data show a peak of strength ~80 nT at 12:00 LT, with respect to the night-time level.