On the critical frequency and height of the E layer peak at noon

Noon ionograms obtained at three Argentine stations (Tucuman, San Juan and Buenos Aires) are used to compare the critical frequency of the E region with the corresponding values predicted by the International Reference Ionosphere. The database includes summer, winter and equinox periods for years of different level of solar activity. For San Juan electron density profiles derived from midday ionograms recorded for different conditions, are used to check the validity of the E peak height assumed by the two versions of the model: 1990 and 1995. In general, the comparisons show: (i) that the constant value of the E peak height of 110 km assumed by the 1995 version seems more reasonable than the value of 105 km used in the 1990 version, (ii) that the situation for the E peak height requires more work and it would be useful an extension of this study using a more complete database. (C) 1999 COSPAR. Published by Elsevier Science Ltd.