Blanketing Sporadic-E Layer Occurrences Over Santa Maria, a Transition Station From Low to Middle Latitude in the South American Magnetic Anomaly (SAMA)

Digisonde data obtained from July 2019 to June 2020 are used to study the overall occurrences of the blanketing types (Es-f,Es- Es-l, Es-h, Es-c) of the sporadic layers (Es-b) over Santa Maria, a transition station from low to middle latitude in the South American Magnetic Anomaly (SAMA). The results show that the average occurrence of the Es-b layers is 54%, being maximum in summer (66%), followed by spring (63%), autumn (55%), and winter (40%). Except during the winter, the Es-f is the predominant type, while the Es-c generally presents the lower occurrence. In general, the top (ftEs) and the blanketing (fbEs) frequencies range from 3 to 4 MHz between 100 and 110 km, with more pronounced values during daytime compared to nighttime. A comparison between the Es-b occurrences between Santa Maria and stations outside the SAMA shows a great reduction in Santa Maria. It is caused by the low intensity of the geomagnetic field, which affects the layer formation process controlled by the ion dynamics. The performance of the E-Region Ionospheric Model (MIRE), which use the tidal wind components provided by the Global Scale Wave Model as input, is analyzed in simulating the fbEs parameter and compared with measurements. The discrepancies between the modeled and measured fbEs are reduced when the meridional/zonal wind components are adjusted by some factor. This comparison contributes to our understanding of the role of the tidal winds over Santa Maria, a transition station from low to middle latitude in Brazil.