TEC behavior over the Mexican region

With the advent of the Navigation Satellites the Total Electron Content (TEC) has become one of the main parameters of the ionosphere. This is the result of a continuous TEC monitoring and rather dense network of GPS receivers. For Mexican region having no ionosondes the use of TEC for ionospheric conditions studies and monitoring has a special value. To study the behaviour of TEC and for its applied aspects two types of source-files are used worldwide: IONEX (global maps) and RINEX (local data) depending on the task solved. Magnetometer and satellite data from CHAMP and DMSP were involved in the analysis. First, benefits and limitations of TEC derived from both types of files are discussed in regard to the estimation of the ionosphere state in the Mexican region. Second, using both methods the specific features of diurnal, seasonal and annual patterns in TEC behaviour over Mexico were revealed, among which are the shift of the diurnal maximum to 14 LT, dependence on solar activity, high probability of night-time enhancements, presence of annual and winter anomalies. Third, it was revealed that the positive short-lived TEC enhancements are characteristic for Mexican region. They may occur even under quiet conditions. The answer is given what part of the ionosphere is responsible for TEC change during these positive disturbances. The results for Mexico were compared to the neighboring regions and South-East zone.