The second Z-propagation window

Abstract

ELLIS1,2investigated the condition in the ionosphere under which an upgoing ordinary radio wave is converted, through a coupling process, into an upgoing extraordinary wave in the Z mode. (Propagation in the Z mode requires the presence of both an ionised gas and a magnetic field; hence such waves cannot be received in free space.) This occurs for a wave incident on the ionosphere from below with its wave normal close to a critical direction in the magnetic meridian plane. This direction is such that when the wave reaches the level where X = 1, which is normally a complete reflector for the ordinary wave, its wave-normal direction has become close to the magnetic field line direction. The symbols X and Y are as usually defined in magnetoionic theory (see Ratcliffe3). The level X = 1 becomes semi-transparent for a cone of angles centred on the critical direction. This cone is called the ‘Ellis window’. The Z-mode waves are reflected at a higher level where X = 1+Y. Here I wish to draw attention to a window which is relevant to the escape of Z-mode radiation produced naturally in the topside ionosphere

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References

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    Ellis, G. R. A., J. atmos. terr. Phys., 8, 243 (1956).

  2. 2

    Ellis, G. R. A., Nature, 193, 862 (1962).

  3. 3

    Ratcliffe, J. A., Magnetoionic Theory (Cambridge, 1959).

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    Mosier, R. M., Kaiser, M. L., and Brown, L. W., J. geophys. Res., 78, 1673 (1973).

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    Gurnett, D. A., J. geophys. Res., 79, 4227 (1974).

  6. 6

    Jorgensen, T. S., J. geophys. Res., 73, 1055 (1968).

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