dispersion measure


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dispersion measure

(DM) The number of electrons per unit volume, n e, integrated along the line of sight to a source:
DM = n e dl

where dl is an element of the path. It is the factor that determines, for example, the time delay (i.e. dispersion) between the arrival of radio pulses from a pulsar at two different frequencies. The value of n e in the plane of our Galaxy is typically 0.03 cm–3.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

dispersion measure

[də′spər·zhən ‚mezh·ər]
(astronomy)
A quantity that describes the dispersion of a radio signal, proportional to the product of the density of interstellar electrons and the distance to the source.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
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However, the studies relating unemployment to dispersion measures have largely ignored the effects of demographic changes and other traditional labor-market variables.
Replacing |g.sub.it~ with |Mathematical Expression Omitted~ in (2) gives a dispersion measure |Mathematical Expression Omitted~ that has average aggregate and industry growth rates removed.
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Following a list of concrete examples of such risk and deviation measures used in practice, the relationship between dispersion measures and probability metrics is introduced, albeit rather superficially.
"The striking difference between the evolution of the two dispersion measures argues against the importance of changing distortions that affect both capital and labor at the same time," the authors write.
These studies are concerned with regional labour market variables (Dixon et al., 2001; Dixon, 2006; Dixon and Mahmood, 2006), following Martin's (1997) application of absolute dispersion and relative dispersion measures to regional unemployment data for the United Kingdom.