Total Electron Content (TEC) allows to evaluate the state of the ionosphere. Radio waves like GNSS signals traversing the ionosphere suffer delays and refraction. Ionospheric plasma irregularities may be generated in the equatorial regions after sunset and extend to low latitudes forming large plasma depleted regions named ionospheric bubbles. Signature of these bubbles can be observed at TEC maps. Inside plasma bubbles smaller scale size irregularities are generated causing scintillation in GNSS signals. This work compared TEC maps from some sources, with different temporal and spatial resolutions/coverage. Significant differences were found. For each source, there are differences in the treatment and preprocessing of raw data in order to get the absolute TEC values, which are interpolated to get grid values of the map. Even for the same source there are significant differences in the density of monitoring stations according to the region. A case of study concerning scintillation is also analyzed using the corresponding TEC and scintillation maps. TEC maps employed here encompass the years from 2022 to 2024, in the growing phase of the current solar cycle 25. The months of March, June, September and December were selected to take into account the TEC seasonal variation.

Total Electron Content (TEC) maps allow the evaluation of the state of the ionosphere. There are many providers/sources of worldwide or regional TEC maps for the continuous monitoring of the ionosphere, which employ different GNSS monitoring networks for data acquisition, TEC calculation or interpolation methods for generating the maps, or different spatial and temporal resolutions and coverage. How reliable are TEC maps over Brazil? We employed TEC maps from four different providers for 2022–2024, in the growing phase of the current solar cycle 25. Seasonality is also taken into account. A systematic comparison of TEC maps over Brazil was performed using correlation and similarity analysis between maps of different sources. Significant differences were found. Even for the same source there are differences in the density of monitoring stations according to the region. An example of bubble signature in TEC maps is also analyzed. Ground truth validation of TEC is performed by comparing TEC point values extracted from the maps with values derived from a set of GNSS stations over Brazil. As a result, no TEC maps of these sources were deemed reliable, due to low spatial and/or temporal resolution, low monitoring station density, or inadequate interpolation scheme.