[en] The day to day variability of the total electron content (TEC) measured over Tucuman using ATS 3 and GOES 3 geosynchronous satellite signals has been studied for the high solar activity period from April 1982 to March 1983. Two variability parameters have been used in the analysis: the standard deviation from the mean values and the variability index = (standard deviation/mean value) x 100. The diurnal and seasonal variations of both variability parameters have also been studied. The results obtained show that the standard deviation is minimum at hours of minimum TEC at predawn hours and maximum at noon or postnoon hours when the TEC is greater. A seasonal dependence of the parameter with minimum values during the winter months has been found. (author)