Showing papers by "Arthur D. Richmond published in 1971"

Tidal Winds at Ionospheric Heights

Abstract: Tidal winds excited by thermal or gravitational forces propagate into ionospheric altitudes and generate currents by dynamo action. The vertical and horizontal structure of these winds is altered by various dissipative forces which gain importance at these altitudes. In this paper, the dissipative effects of the Lorentz force, molecular viscosity, and molecular heat conductivity are considered in terms of a perturbation treatment. Both the rotation and the sphericity of the earth are explicitly taken into account. For propagating tidal modes, the dissipative effects are found to reduce and reverse the amplitude growth with height predicted by dissipationless tidal theory. Quantitative differences are obtained between the behavior of tides on a rotating earth and of internal gravity waves of comparable frequencies and vertical wavelengths on a non-rotating earth.

Geomagnetic Crochets and Associated Ionospheric Current Systems

Abstract: It is shown that time-structure analysis of geomagnetic crochets can be useful in the ground-based detection of XUV radiation from solar flares. The crochets often manifest a composite structure that consists of a ‘fast’ component presumably produced by EUV radiation (100–1000A) and a ‘slow’ component produced by soft X rays (1–100A). This composite structure is taken into account in the proposed method of analysis for crochet current systems. Some preliminary results are given from the simulation studies of Sq and crochet current systems. These studies are intended to probe into the nature of the atmospheric winds that drive the ionospheric dynamo and that generate both the Sq and crochet currents.