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Alfonsine Tables zij-e Alfonso Fr.: Tables alfonsines A set of tables created in Toledo, under Alfonso X, el sabio, king of Castile and Léon (1252 to 1284) to correct the anomalies in the → Toledan Tables. The starting point of the Alfonsine Tables is January 1, 1252, the year of king's coronation (1 June). The original Spanish version of the tables is lost, but a set of canons (introductory instructions) for planetary tables are extant. They are written by Isaac ben Sid and Judah ben Moses ha-Cohen, two of the most active collaborators of Alfonso X. The Alfonsine Tables were the most widely used astronomical tables in the Middle Ages and had an enormous impact on the development of European astronomy from the 13th to 16th century. They were replaced by Erasmus Reinhold's → Prutenic Tables, based on Copernican models, that were first published in 1551.The Latin version of the Alfonsine Tables first appeared in Paris around 1320, where a revision was undertaken by John of Lignères and John of Murs, accompanied by a number of canons for their use written by John of Saxony. There is a controversy as to the exact relationship of these tables with the work commissioned by the Spanish king. After the Spanish monarch Alfonso X (1221-1284); → table. |
Alfvén Mach number adad-e Mach-e Alfvéni Fr.: nombre de Mach alfvénique The ratio of the flow velocity to the → Alfvén speed in a medium. → Alfvén wave; → number. |
Alfvén 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. |
Alfvén 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. |
Alfvén 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. |
Alfvénic Alfvenik Fr.: alfvénicité Involving → Alfvén waves. |
Alfvénic 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. → Alfvénic; → fluctuation. |
Alfvénicity Alfveniki Fr.: alfvénicité |
Alfven Mach number adad-e Mach-e Alfvéni Fr.: nombre de Mach alfvénique The ratio of the flow velocity to the → Alfvén speed in a medium. → Alfvén wave; → number. |
Alfven point noqte-ye Alfvén Fr.: point d'Alfvén In magnetized disk models, the point where the → poloidal velocity equals the → Alfven speed. Within this point, the magnetic energy density dominates, and the gas is forced to flow along the field lines. Well beyond this point, the kinetic energy acquired by the flowing gas prevails and the field is forced to follow the flow. → Alfven wave; → point. |
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. |
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