Long- and short-period oscillations in the lunar semidiurnal tidal amplitudes in the ionosphere derived from the total electron content were investigated over Brazil from 2011 to 2014. The results showed  annual, semiannual and triannual oscillations as the dominant components. Additionally, the most pronounced short-period oscillations were observed between 7 and 11 d, which suggest a possible coupling of the lunar tide and planetary waves.

Effects of space weather events in technological systems were studied in the tropical region of Brazil by investigating the Bolivia–Brazil pipeline during space weather events with different intensities. The results presented significant corrosion levels during the 17 March 2015 geomagnetic storm and showed that the effects of space weather must be accounted for, even in low latitudes, since the lifetime of the pipelines can be reduced.

The paper focuses on the analyses of the global occurrence of equatorial plasma bubble events using S4 data that were calculated from GPS radio occultation measurements of the FormoSat-3/COSMIC mission. The advantage in using radio occultation data is that we get information not only on the occurrence and intensity of the equatorial bubble events, but also on the altitude distribution. We analyzed a 10.5-year time series of COSMIC data and demonstrated a strong dependence on the solar cycle.

The monthly averages of the F2 critical frequency (foF2), its peak height (hmF2), and the E-region critical frequency (foE) acquired by the DPS4-D installed in Santa Maria, Brazil, is compared to the International Reference Ionosphere (IRI-2016) model predictions. It is important to test the performance of the IRI over Santa Maria because it is located in the SAMA, which is a region particularly important for high-frequency (HF) ground-to-satellite navigation signals.

In this paper, an extensive study has been done in order to investigate periodic oscillations in the start times of equatorial plasma bubbles observed over Brazil. Using OI6300 airglow images and ionograms, it was possible to detect semimonthly oscillations in the start times of equatorial plasma bubbles (EPBs) and equatorial Spread-F. This semimonthly oscillation is likely related to the lunar tide, which represents an important mechanism acting in the day-to-day variability of EPBs.

In this work, we studied the HILDCAA disturbance time effects in the TEC by analyzing local time and seasonal dependences, and the influences of the solar wind velocity on a sample of 10 intervals occurring in 2015 and 2016. The main results show great variability in the hourly distribution of the dTEC between one interval and another, seasonal behavior different from that presented by geomagnetic storms, and interestingly no relation between the dTEC disturbances and the magnitude of the HSS.

For the first time, the climatology of intermediate descending layers (~150 km) over Brazilian equatorial and low-latitude regions during the extreme solar minimum period of 2009 was investigated. The results are interesting and innovative. For this analysis we used data of height and top frequency of intermediate layers collected from a digisonde located at São Luis and Cachoreira Paulista.

We analyze tidal phases and related wind shear in the mesosphere and lower thermosphere as observed by a meteor radar. The wind shear phases are compared with those of sporadic E occurrence rates, which were derived from GPS radio occultation observations. We find good correspondence between radar derived wind shear and sporadic E phases for the semidiurnal, terdiurnal, and quarterdiurnal tidal components, but not for the diurnal tide.

The Brazilian Space Weather Study and Monitoring Program (Embrace) has been developing different indexes that describe ionospheric effects in the Brazilian sector. The main purpose of this work was to produce a new ionospheric scale based on the analysis of the ionospheric plasma drift velocity. We analyzed 7 years of data in order to construct a standardized scale. The results of this new index allow us to evaluate the impacts of ionospheric phenomena in the space weather environment.

This study concerns postmidnight ionospheric irregularities observed during low solar activity conditions. We analyze data from digisondes and optical imaging systems located in an equatorial region over Brazil. The results show that they occur under unfavorable and unexpected conditions. This work can be useful for space weather forecasting during low solar activity.

Sporadic E (Es) layers in the Earth's ionosphere are produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth's magnetic field. We present analyses of the 6 h tidal signatures in ES occurrence rates derived from GPS radio observations. Times of maxima in ES agree well with those of negative wind shear obtained from radar observation. The global distribution of ES amplitudes agrees with wind shear amplitudes from numerical modeling.

Equatorial ionospheric irregularities have a significant detrimental impact on a variety of space application systems in navigation and communication areas that utilize satellites, especially the Global Navigation Satellite Systems (GNSS) network. The development of these irregularities in the nighttime ionosphere is controlled primarily by ionospheric electric fields and instabilities. The effect of magnetic disturbance on these electric fields and on the irregularities is investigated here.

Global coverage measurements made by satellites have provided observational studies which have shown the presence of four peaks in global longitudinal structures from global local time observations of equatorial ionization anomalies. The structures seen in the ionosphere are related to the diurnal non-migrating wave that comes from the troposphere and can be noticed in periods of low and high solar activity in the low-latitude ionosphere regions, mainly at altitudes from ~ 250 km up to ~ 800 km.

We have analyzed the low-latitude ionospheric responses to solar flares. In particular we show for the first time that 5 to 8 min of time delay is present in the peak effect in the EEJ, with respect that of S_q current outside the magnetic equator, in response to the flare radiation enhancement. We propose that the flare induced enhancement in neutral wind occurring with a time delay could be responsible for a delayed zonal electric field disturbance driving the EEJ.

This paper analyzes the influence of the recent deep and prolonged solar minimum on the daytime zonal and vertical plasma drift velocities during quiet time over Jicamarca, Peru. Our results show that an anomalously low zonal wind was mainly responsible for the observed anomalous behavior in the zonal drift followed by a decrease in the E-region conductivity and the dynamo electric field during 2008.