The large amplitude event observed over the period 22 may to 4 June, 1973

The enhanced diurnal variation of cosmic-ray intensity observed over the period 22 May to 4 June, 1973 was analysed. The main characteristic of this large amplitude wave train is that the enhanced diurnal variation shows a maximum around 1600 h. For this analysis data from high-latitude neutron monitors and from the satellite HEOS-2 were used. This diurnal variation is caused by the superposition of convection and field-aligned diffusion due to an enhanced density gradient of 8% AU^–1. It is shown that the diffusive vector is field-aligned on the days which are separated from magnetic sector boundaries.