Abstract
DR. MCDONALD writes that meteoric dust is of spherical shape so that no preferred axis can occur; it must be pointed out, however, that the ferromagnetic materials occurring in meteorites such as pure iron and nickel, magnetite and hæmatite possess magnetic anisotropy which increases with decreasing temperature so that orientation along the axis of maximum magnetization takes place. Serpolay and Toye1 have shown, moreover, that ice shows epitaxial growth on magnetite (Fe3O4); between − 12° and − 22° C, the ice crystals form whiskers. This epitaxial growth is probably facilitated by the formation of hydrogen bonds between the adsorbed water and the oxygen of the magnetite. Since the strength of the hydrogen bond is of the order of 7–10 kcal, the orientation of the magnetite nuclei in the geomagnetic field would enforce a corresponding orientation of the epitaxial growth of ice. It would be of interest to know whether a correlation could be established between the frequency of the appearance of meridionally-aligned cirrus clouds and the periodic meteoric showers. With regard to the dynamics of the problem, it was pointed out in the original communication that this alignment is unstable, that is, the forces of the motion of the air overcome the magnetic forces.
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References
Serpolay, R., and Toye, M. J., C.R. Acad. Sci., Paris, 254, 4187 (1962).
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KELLNER, L. Meridional Alignment of Tropical Cirrus Clouds. Nature 201, 1317 (1964). https://doi.org/10.1038/2011317a0
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DOI: https://doi.org/10.1038/2011317a0
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