Paulo P Batista

ABSTRACT. Simultaneous measurements of meteor winds obtained in S˜ao Jo˜ao do Cariri-PB and Cachoeira Paulista-SP, Brazil, during June-July 2008 were used to investigate the occurrence of nonlinear coupling between atmospheric wave modes. The wind spectrum showed the quasi simultaneous presence of spectral energy peaks in the periods near 16, 24 and 48 hours, consistent with the occurrence of interaction between 48-h and 24-h waves, and the generation of 16-h waves. From the bispectral analysis, it was possible to confirm the occurrence of a 16-hour secondary wave generated by non-linear coupling between the 2-day and diurnal tide primary waves.Keywords: atmospheric tide, bispectral analysis, meteor radar. RESUMO. Medidas simultâneas de ventos meteóricos obtidos em São João do Cariri-PB e Cachoeira Paulista-SP, Brasil, durante os meses de junho e julho de 2008, foram usadas para investigar a ocorrência de acoplamento não linear entre modos de ondas atmosféricas. Os espectros dos vent...

ABSTRACT. The terrestrial atmosphere is a dynamical system in which periodic oscillations are present and play a significant role in the dynamics of the upper mesosphere and low thermosphere (MLT). It is already well known that atmospheric tides play an important role in the dynamics of the MLT region, and the purpose of this study is to extend our knowledge of diurnal and semidiurnal oscillations in the equatorial MLT, taking advantage of the measurements of meteor winds over São João do Cariri, Brazil (7◦S, 36◦W), obtained from August 2004 to August 2005. In a preliminary analysis, we have observed that both zonal and meridional wind components exhibited variability with respect to both time and height. The prevailing zonal wind shows a structure characterized by a semiannual oscillation (SAO) and are westward most of the time. The prevailing meridional wind is weaker than the zonal and exhibit an annual cycle. Diurnal and semidiurnal meridional wind oscillations also exhibit ti...

Abstract As the prevailing tidal winds in the E region are generated by heating mechanisms, the dynamics of Es layers impacted by solar tides is a relevant theme in the space weather studies. This paper aims to identify the tidal wind component involved in the mechanism of formation and descending of the high type of sporadic layer (Esh). The Esh layers observed at altitudes between around 120 and 150 km in the Brazilian low latitude stations of Jatai and Sao Jose dos Campos during the months of April, June, September and December of 2016 are used in this analysis. The height variability and altitude descent of the Esh layers are analyzed from the h′Es parameter obtained by ionosonde data. In this study, the observational data are compared with the simulations generated by an extended version of the Ionospheric E-Region Model (MIRE). At higher altitudes in the E region, the results show that the prevailing tidal pattern and wind direction controlling the Esh layer formation and descent are different depending on month: (a) in April and June the zonal wind component and the associated semidiurnal tidal oscillations prevail, with some differences in terms of time of occurrence and descending speeds, and (b) in September and December the diurnal tidal periodicities become dominant, and both the meridional and zonal wind components seem to control the descending of the Esh layers. Since the role of the tidal periodicities and wind directions changed depending on the month, the results suggest a possible seasonal tidal wind pattern, which is not well understood from the present study but requires further investigation. Other relevant aspects of the observations and the modeling are highlighted and discussed.

Meteor wind measurements obtained from São João do Cariri-PB (7.4° S, 36.5° W), Brazil, during 2005, have been used to examine the ultra-fast Kelvin wave characteristics in the mesopause and lower thermosphere region. The hourly winds were subjected to wavelet analysis and the results revealed the presence of 3-4 day oscillation in four episodes along the year. The observed parameters

. We present a study of migrating and non-migrating tidal winds observed simultaneously by three meteor radars situated in the southern equatorial region. The radars are located at Cariri (7.4° S, 36.5° W), Brazil, Kototabang (0.2° S, 100.3° E), Indonesia and Darwin (12.3° S, 130.8° E), Australia. Harmonic analysis was used to obtain amplitudes and phases for diurnal and semidiurnal solar migrating and non-migrating tides between 80 and 100 km altitude during the period 2005 to 2008. They include the important tidal components of diurnal westward-propagating zonal wavenumber 1 (DW1), diurnal eastward-propagating zonal wavenumber 3 (DE3), semidiurnal westward-propagating zonal wavenumber 2 (SW2), and semidiurnal eastward-propagating zonal wavenumber 2 (SE2). In addition, we also present a climatology of these wind tides and analyze the reliability of the fitting through the reference to Whole Atmosphere Community Climate Model (WACCM) winds. The analysis suggests that the migrating tides could be well fitted by the three different radars, but the non-migrating tides might be overestimated. The results based on observations were also compared with the Climatological Tidal Model of the Thermosphere (CTMT). In general, climatic features between observations and model migrating tides were satisfactory in both wind components. However, the features of the DW1, DE3 and SW2 amplitudes in both wind components were slightly different from the results of the CTMT models. This result is probably because tides could be enhanced by the 2006 northern hemisphere stratospheric sudden warming (NH-SSW) event.

Amplitude growth rates of monochromatic gravity waves were estimated and compared from multiple instrument measurements carried out in Brazil. Wave dynamic parameters were obtained from sodium density profiles from lidar observations carried out in Sao Jose dos Campos (23°S, 46°W), while all-sky images of multiple airglow layers provided amplitudes and parameters of waves over Cachoeira Paulista (23°S, 45°W). Growth rates of gravity wave amplitudes from lidar and airglow imager data were consistent with dissipative wave behavior. Only a small amount of the observed wave events presented freely propagating behavior. Part of the observed waves presented saturated amplitude. The general saturated/damped behavior is consistent with diffusive filtering processes imposing limits to amplitude growth rates of the observed gravity waves.

Atmospheric tides in the mesopause region based on 24 hour measurements of sodium density with a laser radar are discussed. The average variation of the layer during 24 hours displays strong oscillations with 12 and 24 hour periods. Oscillations are separated into diurnal and semidiurnal components and the results are interpreted by a theory of atmospheric wave propagation for minor constituent layers. It is shown that the vertical wind is important because of its effects on sodium density measured at a fixed height. The wind over a limited height range is determined. The 24 hour component shows characteristics of an evanescent mode in disagreement with tidal theory. The 24 hour component shows vertical phase propagation with a wavelength of minus 50 km, which agrees with recent theories, but the relative amplitude of this component is greater than expected.

Quando um feixe laser interage com a atmosfera podem ocorrer diversos tipos de espalhamento, dependendo do comprimento de onda do laser e da natureza das partículas atmosféricas: espalhamento Rayleigh pelos constituintes majoritários (N2, O2), espalhamento Mie por aerossóis estratosféricos, espalhamento ressonante e espalhamento Raman por átomos ou moléculas. Cada um destes tipos de espalhamento pode ser utilizado para medir diferentes parâmetros atmosféricos na região de 15-105 km de altura. O radar de laser é um equipamento para sensoriamento remoto ativo da atmosfera que se utiliza destes espalhamentos. Baseado no mesmo princípio dos radares convencionais, sua técnica (LIDAR - Light Detection and Ranging)consiste basicamente na transmissão e recepção da luz quase monocromática radiada por um laser pulsado. Uma pequena fração desta luz é retroespalhada por átomos, moléculas e partículas presentes na atmosfera e é detectada por meio de um tubo fotomultiplicador (PMT). A análise tem...

In this work, results of the study of the solar atmospheric tide at mesospheric heights as observed by measuring sodium density variations are presented. The observations were obtained by means of INPE's laser radar, at São José dos Campos (23° 12' S, 45° 51' W). In Chapter I, a brief historical summary of the study of atmospheric tides is presented as well as the early theories regarding them. Some observational techniques used for the measurements are also described. Chapter II deals with the classical theory of atmospheric tides. In Chapter III, data obtained will be presented. Data reduction and analysis will also be discussed. Theoretical calculations of diurnal and semidiurnal tides at our latitude, and comparison with observations, are given at Chapter IV. It is shown that the oscillating structures observed in the sodium layer are consistents with tidal atmospheric density variations. Vertical wavelenghts greater than 20 km are normally found in the observational...

[1] Atmospheric lunar semidiurnal tides are studied using 10 years of temperature data collected by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere Using Broadband Emission Radiometry satellite. The amplitudes and phases in the temperature field are calculated by performing least mean square fit in a data set of about 60 day interval (combining ascending and descending data together). The mean tidal structures are studied for the height range from 20 to 120 km, between ±50° latitude and centered on each month from February 2002 to January 2012. A clear signature of the 12.42 h (lunar semidiurnal tide) is observed in the data. Characteristic of propagating waves is observed in the vertical amplitude and phase profiles in almost all heights. The best conditions of propagation for the lunar semidiurnal tide are reached in the lower thermosphere region. Asymmetry between the hemispheres and seasonal variability is observed in the amplitudes of t...

An improved analytic/empirical model of F-layer plasma density is developed by modifying the Chiu (1975) model so as to: (1) better approximate middle latitude F-layer peak heights (hmF2's) as derived from ionosonde data, and (2) better model features such as the post-sunset rise in the F-layer peak height, and the equatorial anomaly maxima in plasma density near + or - 15 geomagnetic latitude. The latter is accomplished by applying analytic low-latitude correction as derived from differences between the Chiu model and the SLIM model of Anderson et al. Results of a numerical model are also presented that demonstrate the importance of these low-latitude plasma structures to the neutral dynamics of the thermosphere.

Observations of the O2 (1 Sigma, 0-1) atmospheric band at 8645A (O2A) and the rotational temperature, with the OH(9,4) band and OI 5577A airglow emissions, using multichannel tilting filter type photometers, were carried out at Cachoeira Paulista (22.7 S, 45.0 W) Brazil. The O2A band intensities occasionally vary from 200 to 1000 Rayleighs during a night. Covariations in nocturnal and seasonal variation with the OI 5577A emissions are observed. The rotational temperatures determined from the P branch of the O2 (1 Sigma) vary between 180 and 230 K. The amplitude of the nocturnal temperature variation is frequently larger than that determined from the OH emission, and the phase of the variation can lead that of the OH.

Regular observations of the O2(1 sigma, 0-1) atmospheric band at 864A (O2S(0,1)) and the rotational temperature, together with the OH(94,4) band and OI 5577A airglow emissions, using multichannel tilting filter type photometers, have been carried out at Cachoeira Paulista (22.7 deg S, 45.0 deg W), Brasil, since February 1983. The O2(0,1) band intensities occasionally vary from 200 to 1000 Rayleighs during a night. Covariations in nocturnal and seasonal variation with the OI 5577A emission were observed. The temperatures determined from the P branch of the O2A(0,1) band vary between 180 K and 230 K. The amplitude of the nocturnal temperature variation is sometimes larger than that determined from the OH emission, and the phase of the variation, on some occasions, leads that of the OH.

A tilting filter type multi-channel airglow photometer was constructed. Band intensities and rotational temperatures of the six OH band emissions were measured with this photometer. Vibrational population rates and the excitation rates derived from observed band intensities indicate a preferential excitation to the levels v = 8 and v = 9, probably due to the hydrogen-ozone mechanism. Additional excitation mechanisms are considered to explain an increase of the excitation rate in the level v = 5.

The effect of the sodium ion in sodium layer theory is treated in relation to wind shear theory by calculating semidiurnal and diurnal tides, together with the effect of an ionospheric electic field, while accounting for variable ion velocity. The 86-100-km region at low latitudes is considered. A downward motion of the ion convergence is obtained, but only for one-half of the diurnal center. The net vertical velocity tends to decrease when the electric-field-induced vertical ion velocity component is included. During the dark hours, the electric-field-induced vertical ion velocity tends to inhibit the downward motion of the ion convergence center, which remains fixed at 99 km between 4 and 8 hours. The downward motion of the center during sunlit hours (10 to 16 hours) is also effective in the presence of the electric field, which increases the height of the center by only 1 km.

Regular observations of the O2 (1Sigma, 0 to 1) atmospheric band at 8645A (02A) and the rotational temperature, together with the OH(9,4) band and OI 5577A airglow emissions, using multichannel tilting filter type photometers, have been carried out at Cachoeira Paulista (22.7 deg D, 45. 0 deg. W) Brazil, since February 1983. The O2A band intensities occasionally vary from 200 to 1000 Rayleighs during a night. Covariations in nocturnal and seasonal variation with the OI 5577A emissions were observed. The rotational temperatures determined from the P branch of the O2 (1 sigma) vary between 180 and 230 K. The amplitude of the noctural temperature variation is frequently larger than that determined from the OH emission, and the phase of the variation, on some occasions, leads that of the OH.

Results and conclusions of the paper by Llewellyn et al. (1978) are compared with airglow data. The experimental observations do not support the very high vibrational relaxation rates determined by Llewllyn et al. It appears that chemical quenching by atomic oxygen must be significant, and that the H-O3 process alone for the OH* production cannot account for the observed intensity ratios.

Band intensities and the rotational temperatures for the OH(9,4), (8,3), (7,2), (6,2) and (5,1) bands were measured by means of a multichannel tilting filter photometer at Cachoeira Paulista, Brazil. The nocturnal variations of the five bands show good correlation between them, but there are small differences in the amplitudes of the variations between the bands from the upper vibrational levels and those from the lower levels. The cross correlation between the band intensities show that the nocturnal variations of the upper vibrational bands lead those of the lower levels. Vibrational population rates and initial excitation rates for each vibrational level are calculated. An increase of the initial excitation rate in the v = 5 and v = 6 levels was observed. The different features of the intensity variations and the excitation rates of the lower vibrational levels suggest the existence of the mechanism HO2 + 0 yields OH + 02, capable of exciting OH to the v = 5 and v = 6 levels, in addition to the principal mechanism, assumed to be the reaction H + O3 yields OH + O2.

The upper mesosphere airglow emissions OI 5577, NaD and OH were observed at Cachoeira Paulista (22.7 S; 45.0 W) Brazil. Nocturnal variations and their seasonal dependencies in amplitude and phase, and the annual variations of these emissions are presented, analyzing the data obtained from 1977 to 1982 during the ascending phase of the last solar cycle. The nocturnal variations of the OI 5577 emission and the OH rotational temperature showed a significant semidiurnal oscillation, with the phase of maximum moving from the midnight in January to early morning in June. Semiannual variation of the OI 5577 and NaD emissions with the maximum intensities in April/May and October/November were observed. The OH rotational temperature, however, showed an annual variation, maximum in summer and minimum in winter, while no significant seasonal variation was found in the OH emission intensities. Long term intensity variations are also presented with the solar sunspot numbers and the 10.7 cm flux.

The O2 measurements of atmospheric band at 8645A and the rotational temperature together with OI5577A, NaD and OH(9,4) band emissions were recorded. Multichannel tilting filter type photometers were used. The O sub 2 band intensities occasionally vary from 200 Rayleighs to 1000 Rayleighs during a night. Covariations with OI5577A emissions were observed. The rotational temperature determined from the P-branch of the O sub 2 measurement vary between 180 K and 230 K. The amplitude of the nocturnal temperature variations is frequently larger than that derived from the OH emission, and the phase of the variation normally leads that of the OH. It is observed on some nights that the temperature variations of both the emissions are out of phase, which suggests a vertical phase propagation of the atmospheric wavelike perturbations.

A tilting filter type multi-channel airglow photometer was constructed. Band intensities and rotational temperatures of the six OH band emissions were measured with this photometer. Vibrational population rates and the excitation rates derived from observed band intensities indicate a preferential excitation to the levels v = 8 and v = 9, probably due to the hydrogen-ozone mechanism. Additional excitation mechanisms are considered to explain an increase of the excitation rate in the level v = 5.

A numerical application of the wind shear theory is made for the sodium ion aiming at a better understanding of the role of this ion in the sodium layer theory. The vertical ion drift velocity is calculated as induced by the summation of all semidiurnal and diurnal tidal wind modes, as well as the vertical drift component induced by the average ionospheric electric field. An ion layer convergence zone is formed between 2 and 16 hrs. The addition of the electric field inhibits a tendency for downward propagation of the convergence center between 2 and 8 hrs, but the downward motion is little affected between 10 and 16 hrs. Between 18 and 24 hrs the ions are swept out of the region since a divergence center is present between about 98 and 95 kin, also with a downward movement. The addition of the electric field induced vertical drift decreases the net vertical drift and increases the height of convergence by about I km The calculations are made for low latitudes. Pages: 509-514

The upper mesospheric and lower thermospheric nightglow OI5577A, O Atmospheric band at 8645A, NaD and OH(8,3) band emissions by multichannel tilting filter type zenith photometers, and the NaD and OH(8,3) band emissions by a meridional scanning photometer were measured simultaneously. The nocturnal intensity variations and the meridional scanning observations show vertical and horizontal phase propagation, respectively, in the emission layers. The observations are presented and the effects of the upper atmosphere tidal wave and gravity wave propagations are discussed.

A SkiYmet all-sky meteor radar has been operating at Cachoeira Paulista (22° S, 46° W), Brazil, since March 1999. The total numbers of meteor detections ascribable to the Leonids stream were 21 on November 18, 1999, 74 on November 17, 2000, 63 on November 18, 2000, and 115 on November 18, 2001. All the detect ions clearly associated with the Leonids were for heights above 95 km, except for 2001, when 27 detections were for heights between 90 and 95 km. The detected Leonids fluxes represent 6, 13, 11 and 23% respectively of the total daily meteor detections from above 95 km, implying that they make a significant contribution to the total input of meteoric material in the relevant height range.