Abstract Continuous Faraday rotation measurements of VHF signals from the synchronous satellite Early Bird were made from a Northern mid-latitude station during two months in the summer of 1965. The experimental technique and method of calculating the total electron content ( n t ) are described, and the main types of variation of n t during the daytime are classified. Using a continuous 42-day time series of measurements, cross correlation functions of several parameters with magnetic activity indices are calculated. A significant positive correlation at zero time shift is found between noon n t and K p , marginally significant positive correlations between n t at 20 hr and K p , between the time displacement from sunset of the diurnal peak in n t and ∑ 24 K p , And between noon slab thickness and K p , are also found. The apparent linear loss coefficient at midnight shows no significant correlation either with K p or with noon n t on the following day. The integrated electron production rate at dawn shows some long term correlation with both the decimetric solar flux and the sunspot number. The correlation between noon n t and K p can be explained as a natural consequence of shifts in the time of occurrence of the evening peak on moderately disturbed days. This behaviour is not observed in the maximum electron density, as it is probably masked by increases in slab thickness. Horizontal transport of plasma in the upper F-region must be occurring, this could be driven either by the neutral air wind or by electric fields.