1. Balsiger, H., Eberhardt, P., Geiss, J., Ghielmetti, A., Walker, H.-P., Young, D. T., Loidl, H., and Rosenbauer, H.: 1976, Space Sci. Instrum. 2, 499.
2. Balsiger, H., Eberhardt, P., Geiss, J., and Young, D. T.: 1978 J. Geophys. Res. (to be submitted).
3. Bailey, G. J., Moffet, R. J., and Murphy, J. A.: 1977, Planet. Space Sci. 25, 967.
4. Banks, P. N. and Kockarts, G.: 1973, Aeronomy, Academic Press, New York.
5. Breig, E. L., Torr, M. R., Torr, D. G., Hanson, W. B., Hoffman, J. H., Walker, J. C. G., and Nier, A. O.: 1977, J. Geophys. Res. 82, 1008.