1. Axford, W.I., Hines, C.O.: 1961, Can. J. Phys.
39, 1453.
2. Baker, W.G., Martyn, D.F.: 1953, Phil. Trans. Roy. Soc. A.
246, 281.
3. Banks, P.M., Schunk, R.W., Raitt, W.J.: 1974, Geophys. Res. Letters
1, 239.
4. Bauer, P., Cole, K.D., Lejeune, G.: 1975, ‘Field-Aligned Electric Currents and Their Measurement by the Incoherent Backscatter Technique’, Planetary Space Sci. (in press).
5. Beynon, W.J.G., Winstanley, E.H.: 1969, Nature
222, 1262.