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Alfven radius šo'â'-e Alfvén Fr.: rayon d'Alfvén 1) In theories of magnetized → accretion disks,
the distance from a non-rotating star where the → free fall
of a spherical accretion flow is stopped, which occurs where the
→ ram pressure of the infalling matter equals the
→ magnetic pressure of the star. → Alfvén wave; → radius. |
Alfven speed tondâ-ye Alfvén Fr.: vitesse d'Alfvén The speed at which → Alfven waves are propagated along the magnetic field. It is a characteristic velocity at which perturbations of the lines of force travel. Alfvén speed is given by: v_{A} = B/(μ_{0}.ρ)^{1/2}, where B is the → magnetic field strength, μ_{0} is the → magnetic permeability, and ρ is the density of the plasma. Alfvén speed plays a role analogous to the sound speed in non-magnetized fluid dynamics. Same as Alfvén velocity. → Alfvén wave; → speed. |
Alfven surface ruye-ye Alfvén Fr.: surface d'Alfvén In a magnetized wind, the geometric loci of the points where the magnetic pressure equals the flow pressure. See also → Alfven point. → Alfven wave; → surface. |
Alfven velocity tondâ-ye Alfvén Fr.: vitesse d'Alfvén same as → Alfven speed. → Alfven wave; → velocity. |
Alfven wave mowj-e Alfvén Fr.: onde d'Alfvén A → magnetohydrodynamic wave in a → magnetized plasma, arising as a result of restoring forces associated with the magnetic field. It is a → transverse wave which propagates in the direction of the magnetic field. Also called magnetohydrodynamic wave. Named after Hannes Alfvén (1908-1995), Swedish physicist, who developed the theory of → magnetohydrodynamics, and was awarded the Nobel Prize in Physics in 1970; → wave. |
Alfvenic Alfvenik Fr.: alfvénicité Involving → Alfvén waves. |
Alfvenic fluctuation oftâxiz-e Alfvenik Fr.: fluctuation alfvénique Large amplitude fluctuations in the → solar wind with properties resembling those of → Alfvén waves. A fluctuation is said to be Alfvénic if the following relationship between the velocity fluctuations (Δv) and magnetic field fluctuations (ΔB) is satisfied: Δv = ± ΔB/(μ_{0}ρ)^{1/2}. Also called Alfvénicity. → Alfvén wave; → fluctuation. |
Alfvenicity Alfveniki Fr.: alfvénicité |
alga jolbak (#) Fr.: algues A single-celled or multicellular plant living in water or moist conditions, which contain chlorophyll and other pigments but has no true root, stem, or leaf. Algae include seaweeds and pond scum. From alga (singular), from L. alga "seaweed," of uncertain origin. Jolbak "alga." |
algebra jabr (#) Fr.: Algèbre The branch of mathematics which deals with the properties and relations of numbers using symbols (usually letters of the alphabet) to represent numbers or members of a specified set; the generalization and extension of arithmetic. Algebra, from M.L., from Ar. al jabr "reunion of broken bones," the first known use in the title of a book by the Persian mathematician and astronomer Abu Ja'far Mohammad ibn Musa al-Khwarizmi (c780-c850), who worked in Baghdad under the patronage of Caliph Al-Mamun. The full title of the tratise was Hisab al-Jabr w'al-Muqabala "Arithmetic of Completion and Balancing." → algorithm. Jabr, from Ar. al jabr, as above. |
algebraic jabri (#) Fr.: algébrique Relating to, involving, or according to the laws of algebra. |
algebraic equation hamugeš-e jabri Fr.: équation algébrique An equation in the form of P = 0, where P is a → polynomial having a finite number of terms. |
algebraic function karyâ-ye jabri Fr.: fonction algébrique A function expressed in terms of → polynomials and/or roots of polynomials. In other words, any function y = f(x) which satisfies an equation of the form P_{0}(x)y^{n} + P_{1}(x)y^{n - 1} + ... + P_{n}(x) = 0, where P_{0}(x), P_{1}(x), ..., P_{n}(x) are polynomials in x. |
algebraic number adad-e jabri (#) Fr.: nombre algébrique A number, → real or → complex, that is a → root of a → non-zero polynomial equation whose → coefficients are all → rational. For example, the root x of the polynomial x^{2} - 2x + 1 = 0 is an algebraic number, because the polynomial is non-zero and the coefficients are rational numbers. The imaginary number i is algebraic, because it is the solution to x^{2} + 1 = 0. |
Algenib (γ Pegasi) Aljanb (#) Fr.: Algenib A star which lies at the lower left-hand corner of → Pegasus. Its apparent magnitude varies between +2.80 and +2.86 over a period of 3.6 hours; → spectral type B2 IV. Algenib, from Ar. Aljanb al-Faras "the horse's flank," from al "the" + janb "flank" + faras "horse". |
Algieba (γ Leo) Jebhé (#) Fr.: Algieba A binary system in Leo the brighter component of which (magnitude 2.6) is a giant K star and the partner a giant G (magnitude 3.8). The angular separation of just over 4'' means that the two stars are at least 170 AU apart, for a distance of 126 → light-years, and have an orbital period of over 500 years. Algieba, from Ar. Al-Jabhah "the forehead" (of the Lion). |
Algol (β Persei) Alqul, Ra's-ol-Qul (#) Fr.: Algol A variable star in the constellation → Perseus, which was the first eclipsing binary discovered. Its brightness varies between 2.2 and 3.5 magnitudes. Lying at a distance of about 82 → light-years, it consists of at least three components. The brightest component (A) is of spectral type B8 V, and the second one (B) a K type giant. The components A and B turn around each other with a period of about 68.8 hours. Algol, from Ar. Ra's al-ghul "the ghoul's head". |
Algol-type variables vartandegân-e Alqulguné Fr.: variables de type Algol The same as eclipsing binary stars, the prototype of which is Algol. |
algorithm xârazmik (#) Fr.: algorithme 1) A step-by-step problem-solving procedure, especially an established,
recursive computational procedure for solving a problem in a
finite number of steps. From M.L. algorismus, a mangled transliteration of al-Khwarizmi, "native of Khwarazm," the surname of the Persian mathematician and astronomer Abu Ja'far Mohammad ibn Musa al-Khwarizmi (c780-c850). Xârazmik, from Xârazmi (or Xwârazmi, from Xwârazm), the name of the Persian mathematician, + Persian affix → -ik, → -ics. |
alias anyâ Fr.: alias General:An assumed name; otherwise called. From L. alius "(an)other". Compare with Skt. anya "other, different," Av. anya-, O.Pers. aniya- "the one or the other," Arm. ail, Gk. allos "another," Goth. aljis "other". PIE *al- "beyond". Anyâ from Mid.Pers. anya "other, otherwise," from Av. anya "other". This term is used as eyni in the Modern Persian Aftari dialect: eyni sâl "other year," eyni vacé "other child". |
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