World Magnetic Model: Difference between revisions
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The '''World Magnetic Model''' ('''WMM''') is a large spatial-scale representation of the Earth's magnetic field. It consists of a degree and order 12 spherical-harmonic expansion of the magnetic potential of the geomagnetic main field generated in the Earth’s core. Apart from the 168 spherical-harmonic "Gauss" coefficients, the model also has an equal number of spherical-harmonic Secular-Variation (SV) coefficients predicting the temporal evolution of the field over the upcoming five-year epoch. WMM is the standard geomagnetic model of the [[United States Department of Defense]] (DoD), the [[Ministry of Defence (United Kingdom)]], the [[North Atlantic Treaty Organization]] (NATO), and the [[World Hydrographic Office]] (WHO) navigation and attitude/heading reference. It is also used widely in civilian navigation systems. The WMM is produced by the U.S. National Geophysical Data Center (NGDC) in collaboration with the British Geological Survey (BGS). The model, associated software, and documentation are distributed by the [[National Geophysical Data Center]] (NGDC) on behalf of [[National Geospatial-Intelligence Agency]] (NGA). Updated model coefficients are released at 5-year intervals, with the current model (WMM2010) expiring on December 31, 2014. |
The '''World Magnetic Model''' ('''WMM''') is a large spatial-scale representation of the Earth's magnetic field. It consists of a degree and order 12 spherical-harmonic expansion of the magnetic potential of the geomagnetic main field generated in the Earth’s core. Apart from the 168 spherical-harmonic "Gauss" coefficients, the model also has an equal number of spherical-harmonic Secular-Variation (SV) coefficients predicting the temporal evolution of the field over the upcoming five-year epoch. WMM is the standard geomagnetic model of the [[United States Department of Defense]] (DoD), the [[Ministry of Defence (United Kingdom)]], the [[North Atlantic Treaty Organization]] (NATO), and the [[World Hydrographic Office]] (WHO) navigation and attitude/heading reference. It is also used widely in civilian navigation systems. The WMM is produced by the U.S. National Geophysical Data Center (NGDC) in collaboration with the British Geological Survey (BGS). The model, associated software, and documentation are distributed by the [[National Geophysical Data Center]] (NGDC) on behalf of [[National Geospatial-Intelligence Agency]] (NGA). Updated model coefficients are released at 5-year intervals, with the current model (WMM2010) expiring on December 31, 2014. |
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[[Image:eej obs.png|thumb|400px| EEJ magnetic signals measured by an equatorial geomagnetic observatory. The horizontal intensity of magnetic field peaks at ~12 LT. The build up flank in the morning hours is steeper than that of the decay phase. |
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== See also == |
== See also == |
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Revision as of 22:13, 21 December 2009
The World Magnetic Model (WMM) is a large spatial-scale representation of the Earth's magnetic field. It consists of a degree and order 12 spherical-harmonic expansion of the magnetic potential of the geomagnetic main field generated in the Earth’s core. Apart from the 168 spherical-harmonic "Gauss" coefficients, the model also has an equal number of spherical-harmonic Secular-Variation (SV) coefficients predicting the temporal evolution of the field over the upcoming five-year epoch. WMM is the standard geomagnetic model of the United States Department of Defense (DoD), the Ministry of Defence (United Kingdom), the North Atlantic Treaty Organization (NATO), and the World Hydrographic Office (WHO) navigation and attitude/heading reference. It is also used widely in civilian navigation systems. The WMM is produced by the U.S. National Geophysical Data Center (NGDC) in collaboration with the British Geological Survey (BGS). The model, associated software, and documentation are distributed by the National Geophysical Data Center (NGDC) on behalf of National Geospatial-Intelligence Agency (NGA). Updated model coefficients are released at 5-year intervals, with the current model (WMM2010) expiring on December 31, 2014.
See also
- IGRF: International Geomagnetic Reference Field
External links
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