| Section R | R index | 291-299 of 589 terms |
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recirculation—A closed circulation system within a larger oceanic circulation, in which water is returned to its place of departure through a much shorter route than by following the main circulation path.
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recombination coefficient—A measure of the specific rate at which oppositely charged ions join to form neutral particles (a measure of ion recombination). Mathematically, if q is the ionization rate expressed in terms of ion pairs created per unit volume per unit time, n1 the number of positive small ions per unit volume at time t, and n2 the number of negative small ions per unit volume at the same instant, then the time rate of change in, for example, positive small-ion density is  if we ignore effects due to Aitken nuclei and large ions. In this expression a is the recombination coefficient for small ions and is of the order of 10−6 cm3 s−1 at sea level. The recombination coefficient between large and small ions is of the same magnitude; the recombination coefficient for large ions neutralizing large ions is much smaller, of the order of 10−9 cm3 s−1. See combination coefficient.
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recombination energy—The energy released as heat or light when two oppositely charged portions of an atom or molecule rejoin to form a neutral atom or molecule.
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recombination—The process by which a positive and a negative ion join to form a neutral molecule or other neutral particle. In the literature of atmospheric electricity this term is applied both to the simple case of capture of free electrons by positive atomic or molecular ions, and to the more complex case of neutralization of a positive small ion by a negative small ion or a similar (but much rarer) neutralization of large ions. Recombination is, in general, a process accompanied by emission of radiation. The light emitted from the channel of a lightning stroke is recombination radiation. The much less concentrated recombinations steadily occurring in all parts of the atmosphere where ions are forming and disappearing do not yield observable radiation. The intermediate case of glow discharge may be thought of as the most diffuse case of visibly detectable recombination. The rate at which electrons, small ions, and large ions recombine is a function of their respective mobilities and of their concentrations. The former dependence is expressed in terms of the recombination coefficient of the particular ion type. See also airglow, aurora.
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record observation—(Commonly called hourly observation.) A type of aviation weather observation; the most complete of all such observations, usually taken at regularly specified and equal intervals (hourly, usually on the hour). This type of observation has been replaced by the METAR.
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recording albedometer—An instrument that chronicles the ratio of the radiation reflected by a surface to the radiation incident upon it.
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