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L-shell
The L-shell, L-value, or McIlwain L-parameter (after Carl E. McIlwain) is a parameter describing a particular set of planetary magnetic field lines. Colloquially, L-value often describes the set of magnetic field lines which cross the Earth's magnetic equator at a number of Earth's radius, Earth-radii equal to the L-value. For example, L = 2 describes the set of the Earth's magnetic field lines which cross the Earth's magnetic equator two earth radii from the center of the Earth. L-shell parameters can also describe the magnetic fields of other planets. In such cases, the parameter is renormalized for that planet's radius and magnetic field model.Galileo - Glossary of Selected Terms'' NASA Jet Propulsion Laboratory, (2003). Although L-value is formally defined in terms of the Earth's true instantaneous magnetic field (or a high-order model like International Geomagnetic Reference Field, IGRF), it is often used to give a general picture of magnetic phenomena near the Earth, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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 magnetic dipole, 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 Earth radius, radius of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Van Allen Radiation Belt
The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes others may be temporarily created. The belts are named after James Van Allen, who published an article describing the belts in 1958. Earth's two main belts extend from an altitude of about above the surface, in which region radiation levels vary. The belts are in the inner region of Earth's magnetic field. They trap energetic electrons and protons. Other nuclei, such as alpha particles, are less prevalent. Most of the particles that form the belts are thought to come from the solar wind while others arrive as cosmic rays. By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction. The belts endanger satellites, which must have their sensitive components protected with adequat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Aurora (astronomy)
An aurora ( aurorae or auroras), also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of radiant lights that appear as curtains, rays, spirals or dynamic flickers covering the entire sky. Auroras are the result of disturbances in the Earth's magnetosphere caused by enhanced speeds of solar wind from coronal holes and coronal mass ejections. These disturbances alter the trajectories of charged particles in the magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere ( thermosphere/exosphere). The resulting ionization and excitation of atmospheric constituents emit light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of accelera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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). Further, Magnetic Local Time (MLT) is the geomagnetic dipole equivalent to geographic longitude. See also * Earth's magnetic field * Geomagnetic equator * Ionosphere * L-shell * Magnetosphere * World Magnetic Model (WMM) References External links Tips on Viewing the Aurora( SWPC) Magnetic Field Calculator(NCEI The National Centers for Environmental Information (NCEI) is a U.S. government agency that manages one of the world's largest archives of atmospheric, coastal, geophysical, and oceanic data. The current director is Deke Arndt. NCEI is operate ...) Ionospheric Electrodynamics Using Magnetic Apex Coordinates( Journal of Geomagnetism and Geoelectricity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Magnetic Mirror Point
In astrophysics, a magnetic mirror point is a point where the motion of a electric charge, charged particle trapped in a magnetic field (such as the (approximately) dipole field of the Earth's magnetic field, Earth) reverses its direction. More precisely, it is the point where the projection of the particle's velocity vector (mathematics), vector in the direction of the field vector is equal to zero. Whenever charged particles from the sun hit Earth's magnetosphere, it is observed that the magnetic field of Earth reverses direction. Since the forces that generate our magnetic field are constantly changing, the field itself is also in continual flux, its strength waxing and waning over time. This causes the location of Earth's magnetic north and south poles to gradually shift, and to even completely flip locations every 300,000 years or so. See also * Magnetic mirror * L-shell * Dipole model of the Earth's magnetic field * List of artificial radiation belts References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
L Shell Global Dipole
L, or l, is the twelfth letter of 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 that it represents a shepherd's staff. Typographic variants In most sans-serif typefaces, the lowercase letter ''ell'' , written as the glyph , may be difficult to distinguish from the uppercase letter "eye" (written as the glyph ); in some serif typefaces, the glyph may be confused with the glyph , the digit ''one''. To avoid such confusion, some newer computer fonts (such as Trebuchet MS) have a finial, a curve to the right at the bottom of the lowercase letter ''ell''. Other style variants are provided in script typefaces and display typefaces. All these variants of the letter are encoded in Unicode as or , allowing presentation to be chosen accor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Pitch Angle (particle Motion)
The pitch angle of a charged particle is the angle between the particle's velocity vector and the local magnetic field. This is a common measurement and topic when studying the magnetosphere, magnetic mirrors, biconic cusps and polywells. Usage It is customary to discuss the direction a particle is heading by its pitch angle. A pitch angle of 0 degrees is a particle whose parallel motion is perfectly along the local magnetic field. In the northern hemisphere this particle would be heading down toward the Earth (and the opposite in the southern hemisphere). A pitch angle of 90 degrees is a particle that is locally mirroring. Special case The equatorial pitch angle of a particle is the pitch angle of the particle at the Earth's geomagnetic equator. This angle defines the loss cone of a particle. The loss cone is the set of angles where the particle will strike the atmosphere and no longer be trapped in the magnetosphere while particles with pitch angles outside the loss co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Imke De Pater
Imke de Pater is a Dutch astronomer working at the University of California, Berkeley. She is known for her research on the large planets and led the team using the Keck Telescope to image the 1994 impact of the comet Comet Shoemaker–Levy 9 with Jupiter. Education and career De Pater was introduced to astronomy in high school when a family friend gave her an astronomy textbook and introduced her to someone in Utrecht so she could learn about the field. She earned her Ph.D. from Leiden University (1980) while working on radio emissions from Jupiter. de Pater is a professor of astronomy, earth and planetary science from the University of California, Berkeley, and served as the chair of the Astronomy Department. In 2015 de Pater was named a fellow of the American Geophysical Union who cited her for: Research De Pater's research centers on observations of the large planets and their rings and satellites (Jupiter, Neptune, Titan, and Uranus) using adaptive optics and radio obs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
