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Dipole Model Of The Earth's Magnetic Field
The dipole model of the Earth's magnetic field is a first order approximation of the rather complex true Earth's magnetic field. Due to effects of the interplanetary magnetic field (IMF), and the solar wind, the dipole model is particularly inaccurate at high L-shells (e.g., above L=3), but may be a good approximation for lower L-shells. For more precise work, or for any work at higher L-shells, a more accurate model that incorporates solar effects, such as the Tsyganenko magnetic field model, is recommended. Formulation The following equations describe the dipole magnetic field. First, define B_0 as the mean value of the magnetic field at the magnetic equator on the Earth's surface. Typically B_0=3.12\times10^\ \textrm. Then, the radial and latitudinal fields can be described as :B_r = -2B_0\left(\frac\right)^3\cos\theta :B_\theta = -B_0\left(\frac\right)^3\sin\theta :, B, = B_0\left(\frac\right)^3 \sqrt where R_E is the mean radius of the Earth (approximately 6 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L Shell Global Dipole
L, or l, is the twelfth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''el'' (pronounced ), plural ''els''. History Lamedh may have come from a pictogram of an ox goad or cattle prod. Some have suggested a shepherd's staff. Use in writing systems Phonetic and phonemic transcription In phonetic and phonemic transcription, the International Phonetic Alphabet uses to represent the lateral alveolar approximant. English In English orthography, usually represents the phoneme , which can have several sound values, depending on the speaker's accent, and whether it occurs before or after a vowel. The alveolar lateral approximant (the sound represented in IPA by lowercase ) occurs before a vowel, as in ''lip'' or ''blend'', while the velarized alveolar lateral approximant (IPA ) occurs in ''bell'' and ''milk''. This velarization does not occur in many Europe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Latitude
Geomagnetic latitude, or magnetic latitude (MLAT), is a parameter analogous to geographic latitude, except that, instead of being defined relative to the geographic poles, it is defined by the axis of the geomagnetic dipole, which can be accurately extracted from the International Geomagnetic Reference Field (IGRF). See also * Earth's magnetic field * Geomagnetic equator * Ionosphere * L-shell * Magnetosphere * World Magnetic Model (WMM) References External links Space Weather: Maps of Geomagnetic Latitude(Northwest Research Associates) Tips on Viewing the Aurora( SWPC) Magnetic Field Calculator(NCEI The National Centers for Environmental Information (NCEI), an agency of the United States government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United St ...) Ionospheric Electrodynamics Using Magnetic Apex Coordinates( Journal of Geomagnetism and Geoelectricity) Geomagnetism Geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamo Theory
In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets. History of theory When William Gilbert published ''de Magnete'' in 1600, he concluded that the Earth is magnetic and proposed the first hypothesis for the origin of this magnetism: permanent magnetism such as that found in lodestone. In 1919, Joseph Larmor proposed that a dynamo might be generating the field. However, even after he advanced his hypothesis, some prominent scientists advanced alternative explanations. Einstein believed that there might be an asymmetry between the charges of the electron and proton so that the Earth's magnetic field would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Magnetic Model
The World Magnetic Model (WMM) is a large spatial-scale representation of the Earth's magnetic field. It was developed jointly by the US National Geophysical Data Center and the British Geological Survey. The data and updates are issued by the US National Geospatial Intelligence Agency and the UK Defence Geographic Centre. The model consists of a degree and order 12 spherical harmonic expansion of the magnetic scalar 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), the World Hydrographic Office (WHO) navigation and attitude/heading reference, and the F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo. In the space environment close to a planetary body, the magnetic field resembles a magnetic dipole. Farther out, field lines can be significantly distorted by the flow of electrically conducting plasma, as emitted from the Sun (i.e., the solar wind) or a nearby star. Planets having active magnetospheres, like the Earth, are capable of mitigating or blocking the effects of solar radiation or cosmic radiation, that also protects all living organisms from potentially detrimental and dangerous consequences. This is studied under the specialized scientific subjects of plasma physics, space physics and aeronomy. History Study of Earth's magnetosphere began in 1600, when William Gilbert discovered that the magnetic field on the surface ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Geomagnetic Reference Field
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 across the globe. The IGRF has been produced and updated under the direction of the International Association of Geomagnetism and Aeronomy (IAGA) since 1965. The IGRF model covers a significant time span, and so is useful for interpreting historical data. (This is unlike the World Magnetic Model, which is intended for navigation in the next few years.) It is updated at 5-year intervals, reflecting the most accurate measurements available at that time. The current 13th edition of the IGRF model (IGRF-13) was released in December 2019 and is valid from 1900 until 2025. For the interval from 1945 to 2015, it is "definitive" (a "DGRF"), meaning t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipole
In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system is a pair of charges of equal magnitude but opposite sign separated by some typically small distance. (A permanent electric dipole is called an electret.) *A magnetic dipole is the closed circulation of an electric current system. A simple example is a single loop of wire with constant current through it. A bar magnet is an example of a magnet with a permanent magnetic dipole moment. Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity. For the simple electric dipole, the electric dipole moment points from the negative charge towards the positive charge, and has a magnitude equal to the strength of each charge times the separation between the charges. (To be precise: for the definition of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Pole
The geomagnetic poles are antipodal points where the axis of a best-fitting dipole intersects the surface of Earth. This ''theoretical'' dipole is equivalent to a powerful bar magnet at the center of Earth, and comes closer than any other point dipole model to describing the magnetic field observed at Earth's surface. In contrast, the magnetic poles of the actual Earth are not antipodal; that is, the line on which they lie does not pass through Earth's center. Owing to motion of fluid in the Earth's outer core, the actual magnetic poles are constantly moving (secular variation). However, over thousands of years, their direction averages to the Earth's rotation axis. On the order of once every half a million years, the poles reverse (i.e., north switches place with south) although the time frame of this switching can be anywhere from every 10 thousand years to every 50 million years. The poles also swing in an oval of around in diameter daily due to solar wind deflecting the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Introduction To Space Physics
Introduction, The Introduction, Intro, or The Intro may refer to: General use * Introduction (music), an opening section of a piece of music * Introduction (writing), a beginning section to a book, article or essay which states its purpose and goals ** Foreword, a beginning section * Introduction (British House of Commons), a ceremonial seating for members elected in by-elections * Introduction (House of Lords), a ceremonial seating for some new members * Intro (demoscene), in the demoscene, a short computer program produced for promotion or to meet competition requirements * Introduced species or introduction, a species established by humans outside its natural range * Right of initiative (legislative), the ability of an entity to introduce a bill or other proposed legislation before a Legislature. * Product launch, the introduction of a new product to market Music Performers * Intro (R&B group), an American R&B trio * Introduction (rock band), a Swedish rock group Albums ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pole, with 0° at the Equator. Lines of constant latitude, or ''parallels'', run east–west as circles parallel to the equator. Latitude and ''longitude'' are used together as a coordinate pair to specify a location on the surface of the Earth. On its own, the term "latitude" normally refers to the ''geodetic latitude'' as defined below. Briefly, the geodetic latitude of a point is the angle formed between the vector perpendicular (or ''normal'') to the ellipsoidal surface from the point, and the plane of the equator. Background Two levels of abstraction are employed in the definitions of latitude and longitude. In the first step the physical surface is modeled by the geoid, a surface which approximates the mean sea level over the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
