| Abstrakt: |
Signals recorded by two stations in the Brazilian region: [Fortaleza (3.74°S, 38.57°W) and Inconfidentes (22.31°S, 46.32°W)], receiving L1 transmissions from different geostationary satellites, were used to evaluate the amplitude scintillation index S4 and several characteristics of scintillation events (continuous record with S4 > 0.2) during nighttime hours (18:00 LT–02:00 LT) in the years 2014–2016. The effects from solar activity, season, and local time on the number of scintillation events per night, maximum scintillation, scintillation event duration, and spacing between consecutive events will be discussed. The results indicate that: (a) scintillation occurs from September to March in both links; (b) the most likely numbers of observed scintillation events per night were two or three, particularly during the first 2 years; (c) on average, the first scintillation event usually had larger maximum S4 values when compared to those of the later ones along the night; (d) the first scintillation event had a longer mean duration than the succeeding ones in a given night; (e) the durations of scintillation events, regardless of their numbers per night and the location, decreased with local time; (f) the opposite dependence of spacings between consecutive events on local time was observed; (g) the cumulative distribution functions of the scintillation onset time indicated a strong dependence on the dip latitude of the station; and (h) early occurrences of onset times are directly related to the increased probability of the occurrence of multiple scintillation events. Plain Language Summary: This study used radio signals from geostationary satellites collected from two ground‐based stations in distinct dip latitudes over Brazil to evaluate aspects of amplitude scintillation. The investigation focused on the number of occurrences and in their specific characteristics such as intensity, duration, and spacing between consecutive scintillation events. The early nighttime hours, when scintillation is more likely to affect the signals were considered during the months of September to March over the years of 2014–2016, covering varied seasonal and solar flux conditions. The findings indicate that scintillation events earlier in the night have larger S4 values and longer duration, being more severe for transionospheric signals. The results also show that earlier onset of scintillation events is likely to indicate multiple events over the night. These new findings contribute to the understanding of scintillation phenomenon and provide valuable insights for improving satellite‐based systems in equatorial and low‐latitude regions. Key Points: The first scintillation event has larger maximum S4 values and longer mean duration when compared to the subsequent eventsThe durations of the scintillation events decrease with local time. The spacing between consecutive events shows the opposite trend; andEarlier occurrences of onset times are related to the increased probability of the occurrence of multiple scintillation events [ABSTRACT FROM AUTHOR] |
