The power spectra of the daily peak electron content measured at Hawaii are estimated via covariance estimations, bivariate autoregressive estimations and fast Fourier transforms for a year of data close to minimum solar activity (1965) and a year of data close to maximum solar activity (1969). The strong peaks about 6 days and 15 days in the 1965 and 1969 power spectra, respectively, suggest an influence of the interplanetary magnetic sector structure on the electron content at low latitude (21·3°N, geographic). The daily solar flux ( Sa ) at 2800 MHz of 1965 and 1969 are analysed similarly. The decrease in energy content with period range of 3–7 days in the 1969 Sa power spectrum supports the above point of view.