Abstract
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.
Highlights
In October of 2014 the Mexican Space WeatherService (SCiESMEX) was established with aims to study, analyze and forecast Space Weather (SW) impacts over the Mexican region
There are no ionosondes in Mexico, so for the ionosphere state estimation SCiESMEX relies on Total Electron Content (TEC) derived from Global Positioning System (GPS) data
After analyzing mapping functions for a number of observation points using the stations of International GNSS Service (IGS) network and simulations based on IRI-2012 the authors [Mylnikova and Yasyukevich 2016, Yasyukevich et al 2015a, Yasyukevich et al 2015b] showed that the changes of slant TEC (sTEC) occurred with different velocities in various regions of the Earth due to different angles of the satellite passage at different latitudes
Summary
Service (SCiESMEX) was established with aims to study, analyze and forecast Space Weather (SW) impacts over the Mexican region (geographic latitudes 14o–32oN, geomagnetic latitudes 23o-38oN). In the present work we try to partly fill this gap and to describe diurnal, monthly, seasonal and annual trends in the ionosphere. Another task is to reveal advantages and limitations of using TEC derived from data of local GNSS receiver stations versus those obtained from global ionospheric maps. The third task is to reveal specific features of TEC behavior during positive disturbances for the periods of high and low solar activity.
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