Growth of electric space-charge and radio waves in moving ion streams

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Abstract
The following conclusions are reached: (i) In a medium comprising two identical interpenetrating ion streams, four electric space-charge phenomena may occur. The 'fast' and 'slow' travelling waves do not concern us; the two effects of interest are non-travelling in a system in which the medium as a whole is at rest. (ii) The first is most probably a set of evanescent waves. These have erroneously been interpreted aa spatially growing waves and as the basis of the electron-wave and similar amplifiers. (iii) The second effect is not an oscillation at all but an instability in the medium. A single space-charge cloud, however low its density, will, if its linear dimension is large enough, continuously increase in density with time. The mechanism disclosed is quite simple and does not require. aa previously suggested, a series of ion clouds (that is, a spatial wave). (iv) The effect may occur widely in nature, for example in the solar atmosphere (leading to patchiness and increased radio emission) in interstellar space and in the ionosphere (sporadio -E). It also provides a physical picture of the action of the electron-wave tube. (v) An earlier criticism of Bailey's theory of radio waves growing in a medium which drifts along a magnetic field is consistent with special relativity theory. The consistency depends on a suitable definition of 'growth', being increase in amplitude away from the source of the wave. The originat definition-increase in amplitude in the direction of travel–indicates growth of virtually all waves to suitably moving observers. (vi) The earlier criticism is also confirmed in discussing a previous Laplace transform analysis of the same situation plus a reflecting boundary. A new type of wave (the transverse space-charge wave') described in this analysis is shown to be spurious and a correeponding theory of solar radio noise untenable.