In the present work, the lunar semidiurnal tide (M₂) was investigated in the equatorial plasma bubble (EPB) zonal drifts over Brazil from 2000 to 2007. On average, the M₂ contributes 5.6 % to the variability of the EPB zonal drifts. A strong seasonal and solar cycle dependency was also observed, the amplitudes of the M₂ being stronger during the summer and high solar activity periods.

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.

Some strong gravity wave activity occurred and was observed on 8 April 2005. This work reports the spectral characteristics of these waves using OH airglow images captured by the all-sky imager installed at São João do Cariri (7.4° S, 36.5° W). A preferential propagation direction was observed due to the positioning of the source and also due to the wind filtering effect. Furthermore, the source of these waves was identified by performing reverse-ray tracing analysis.

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.

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.

We describe a technique used to locate and classify critical points in 2-D flow fields at the solar photosphere obtained from the evolution of the line-of-sight magnetic field in a region close to the magnetic polarity inversion line of a fully emerged active region. We apply this technique to locate a particular kind of critical point associated to vortex flows, which are considered important, since they can twist and interweave the foot points of flux tubes and generate magnetic reconnection.

Present work reports seasonal characteristics of small- and medium-scale gravity waves in the mesosphere and lower thermosphere region. All-sky images of the hydroxyl airglow emission layer over São João do Cariri (7.4° S, 36.5° W) were observed from September 2000 to December 2010, during a total of 1496 nights and obtained 2343 SSGW and 537 MSGW events. The horizontal propagation directions of SSGWs and MSGWs showed clear seasonal variations based on the influence of the wind filtering process.

On 3 October 2005, a mesospheric front was observed over São João do Cariri (7.4° S, 36.5° W) propagating to the northeast in the OH airglow images. One and a half hours later, it disappeared completely and ripples were observed in the eastern part of the images. After studying the background atmosphere, the main conclusion of this work was that the instability in the airglow layer did not allow the propagation of the front to the other side of the local zenith.

This article presents characteristics of periodic waves observed in the thermosphere from airglow images collected in the Northeast of Brazil. Using simultaneous measurements of the background wind in the airglow emission altitudes, it was possible to estimate the intrinsic parameters and the role of the wind in the propagation of the waves into the thermosphere. An anisotropy in the propagation direction of the waves was observed and it could be explained by the wind filtering process.

This work presents four events of mesosphere fronts observed on King George Island, Antarctic Peninsula, in the year 2011. The atmospheric background environment was analyzed to investigate the propagation conditions for all cases. To investigate the sources for such cases, satellite images were used. In two cases, we found that strong tropospheric instabilities were potential sources, and in the other two cases, it was not possible to associate them with tropospheric sources.

Periodic waves have been observed over São João do Cariri during almost one solar cycle. Similarities between the characteristics of these events with observations at other places around the world were noted, primarily the spectral parameters. Most observed waves have appeared during magnetically quiet nights, and the occurrence of those waves followed the solar activity. Due to their characteristics, most of them must have had different generation mechanisms from the Perkins instability.

This paper reports two consecutive mesospheric bores observed in the airglow emissions (OH and OI5577). Both bores propagated to the east and showed similar spectral characteristics. However, the first one exhibited a dark leading front with several trailing waves behind and progressed into a brighter airglow region. However, the second bore, observed in the OH layer, was comprised of several bright waves propagating into a darker airglow region.