Ricardo Buriti

Response of the airglow OH emission, temperature and mesopause wind to the atmospheric wave propagation over Shigaraki, Japan

Simultaneous observations of the night airglow OH (6, 2) band emission intensity and rotational temperature, by a sky scanning airglow spectrophotometer, and meteor winds, by a middle and upper atmosphere radar (MU radar), were carried out at Shigaraki (34.9°N, 136.1°E), Japan, from October 29 to November 11, 1994, as the first phase of a campaign, and from July 25 to July 31, 1995 as the second phase. Horizontal structures in the OH emission intensity and rotational temperature were monitored optically, together with the background wind and its wave induced fluctuations, measured by MU radar. Since the MU radar makes a direct measurement of the vertical wavelength, and the OH spectrophotometer makes a direct measurement of the horizontal wavelength, the two techniques are mutually complementary to determine intrinsic wave parameters. Gravity waves with intrinsic periods of 2 to 9 hours, horizontal wavelengths of 500 to 3000 km and vertical wavelengths of 12 to 75 km were identified. Between the two different observation techniques, there is a reasonable agreement in the inferred wave characteristics.

Dynamical influence on the equatorial airglow observed from the South American sector

The upper atmospheric airglow emissions, OI 557.7 nm, NaD 589.3 nm, OH (9,4) and O2 atmospheric (0,1) bands and their rotational temperatures have been measured using ground-based multichannel airglow photometers, one located near the equator at Fortaleza (3.9 S, 38.4 W) and the other at lowmiddle latitude Cachoeira Paulista (22.7 S, 45.0 W). Monthly averaged nocturnal variations calculated from the data from 1987 to 1993 were used to study the influence of atmospheric dynamical processes on these emissions. Harmonic analysis revealed that the Cachoeira Paulista data are mainly represented by a 12 hour period oscillation. Phase differences between the different emissions reveal that the vertical phase velocity is about 4 km/h and the vertical wavelength about 50 km. Fortaleza data on the other hand showed longer period, 24 hours, slow vertical propagation velocity, 1.1 km/h, and short vertical wavelength, about 30 km. These facts lead us to conclude that the Cachoeira Paulista data are mainly controlled by the semidiurnal tidal oscillation and the Fortaleza data are controlled by the diurnal tide.

Simultaneous measurements of airglow oh emissionand meteor wind by a scanning photometer and the muradar

Abstract Simultaneous observations of the night airglow OH (6,2) band emission intensity androtational temperature, by a sky scanning airglow spectrophotometer, and meteor winds, by amiddle and upper atmosphere radar (MU radar), were carried out at Shigaraki (34.9°N, 136.1°E), Japan, from 29 October to 11 November 1994, during the CRISTA/MAHRSIcampaign. Horizontal structures in the OH emission intensity and rotational temperature weremonitored optically, together with the background wind and its wave induced fluctuations,measured by MU radar. A total of 5 nights among the 7 nights of useful data showed wavelikeoscillations in both the emission intensity and temperature. Good agreement was found betweenindividual wave parameters—intrinsic period, phase velocity, horizontal and verticalwavelength—obtained from the radar and optical techniques. On some occasions a short period(∼3 h) gravity wave was observed to propagate, superposed on a long period (∼9 h) wave.

3-4 day Kelvin waves observed in the MLT region at 7.4º S, Brazil

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 were used to check if the 3-4 days oscillations satisfy the dispersion relation for Kelvin waves. The results showed that only the oscillations that occurred in February-March and May-June (first and second events), are compatible with equatorial ultra-fast Kelvin wave propagation, with zonal wave number s=1. During these two events, the zonal wind amplitudes reached maximum values of 25 m/s and 20 m/s respectively. The vertical phase structure showed descending phase, compatible with ascending wave energy, and vertical wavelengths of about 40 km were found for both events.

The spread F Experiment (SpreadFEx): Program overview and first results

We performed an extensive experimental campaign (the spread F Experiment, or SpreadFEx) from September to November 2005 to attempt to define the role of neutral atmosphere dynamics, specifically wave motions propagating upward from the lower atmosphere, in seeding equatorial spread F and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12 and the GUVI instrument aboard the TIMED satellite. Initial results of our analyses of SpreadFEx and related data indicate 1) extensive gravity wave (GW) activity apparently linked to deep convection predominantly to the west of our measurement sites, 2) the presence of small-scale GWactivity confined to lower altitudes, 3) larger-scaleGWactivity apparently penetrating to much higher altitudes suggested by electron density and TEC fluctuations in the E and F regions, 4) substantial GW amplitudes implied by digisonde electron densities, and 5) apparent direct links of these perturbations in the lower F region to spread F and plasma bubbles extending to much higher altitudes. Related efforts with correlative data are defining 6) the occurrence and locations of deep convection, 7) the spatial and temporal evolutions of plasma bubbles, the 8) 2D (height-resolved) structures of plasma bubbles, and 9) the expected propagation of GWs and tides from the lower atmosphere into the thermosphere and ionosphere.

Plasma bubble zonal drift characteristics observed by airglow images over Brazilian tropical region

Using airglow images observed at Sao Joao do Cariri (7.4oS, 36.5oW; dip angle: -11oS) from September 2000 to April 2007, plasma bubblezonal drifts for ninety-seven geomagnetically quiet nights (Dst index higher than -30 nT) were calculated. The plasma bubble eastward averaged drifts presented an increase from 18:00 to 22:00 local time (LT), and followed by a deceleration. The plasma bubbles observed during high solar activity were faster after 22:00 LT. Eastward drifts observed during the summer, after 21:00 LT, were higher than drifts observed during the equinox months. Few nights had plasma bubble eastward drifts higher than 100 m/s and almost all bubbles disappeared after 02:00 LT. Averaged zonal drifts observed between -9.5 and -5.5oS were almost constant, primarily,around 23:00 LT.

First observation of the diurnal and semidiurnal ocillation in the mesospheric winds over São João do Cariri-PB, Brazil

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 Sao Joao do Cariri, Brazil (7oS, 36oW), 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 time and height variability. In general, the diurnal and semidiurnal amplitudes for the meridional wind component were larger than that for the zonal component.From the phase structures, it was found that the vertical wavelength of the diurnal variations exhibited values from 20 to 30 km for the meridional wind component, whereas for the semidiurnal oscillation they were between 50 and 70 km during equinoxes when the meridional amplitudes were stronger.

Mesospheric 2-Day waves observed simultaneously in the equatorial and low latitudes regions of Brazil

Simultaneous observations of the atmospheric neutral winds in the mesosphere and lower thermosphere (MLT) by meteor radar have been carried out at SJodo Cariri (7.4 ◦ S, 36.5 ◦ W) and Cachoeira Paulista (22.7 ◦ S, 45.0 ◦ W). From the wind variability we investigate the atmospheric planetary-scale quasi-two-day waves, which were present at both the sites during the winter of 2004 and summer of 2004/2005. The amplitude of the meridional component was larger than that of the zonal component, reaching a maximum value of � 60 m/s at the equatorial site and � 25 m/s at the low latitude site during the winter. During the January-February period the 2-day wave was very similar at the two sites, with a maximum amplitude of � 50 m/s. The phase propagation with height shows a descending mode and upward energy propagation. The vertical wavelength estimated for Cachoeira Paulista (40-67 km) was longer than for SJodo Cariri (30-35 km), for all of the observed events. Cross-spectral analysis showed a significant coherence between the quasi-two-day oscillations observed at the two sites. From the phase difference between the two sites we concluded that SJodo Cariri leads Cachoeira Paulista. These results denote that amplitude peak at 36.5 ◦ W and subsequently at 45 ◦ W, compatible

Mesosphere–Ionosphere Coupling Processes Observed in the F Layer Bottom-Side Oscillation

During the Spread FEx campaign, under the NASA Living with a star (ILWS) program which was carried out in the South American Magnetic Equatorial region from September to November 2005, we observed formation of the bottom-type spread F and simultaneous occurrence of mesospheric gravity wave events. The events were monitored by the ionosonde, coherent radar and airglow OI 630.0 nm and OH imager. It is found that the bottom-type scattering layer has a wave form generated most probably by local gravity waves. Reverse ray-tracing of the observed gravity waves indicate their possible sources in the troposphere or thermosphere. Forward ray-tracing indicates their penetration into the ionosphere. The present work summarizes the observational evidence and results of the data analysis and discusses the mesosphere–ionosphere coupling processes.

APPLICATION OF REMOTE SENSING IN THE RECONSTRUCTION OF TEMPORAL SERIES OF MESOSPHERIC TEMPERATURE FOR A REGION WITH LOW LATITUDE

R E S U M O Medidas da temperatura atmosférica para altitudes entre 80 e 100 km a partir do coeficiente de difusão ambipolar observado por radar meteórico é uma técnica relativamente nova. Porém, devido à falta de informações menos incertas dos modelos de pressão atmosférica nessa região, esta técnica apresenta problemas. Surgiu, então, a necessidade de se desenvolver uma técnica na qual a temperatura, na altitude onde ocorre a maior contagem de meteoros, é calculada a partir do gradiente de temperatura (Hocking, 1999). Neste trabalho aplicamos tal técnica e a temperatura foi calculada para cada dia de observação entre julho de 2004 e junho de 2009. Os valores foram comparados com dados de temperatura do TIMED/ SABER e com dados de temperatura rotacional do OH(6,2) obtida pelo fotômetro Multi-3, no sítio de observação de São João do Cariri-PB (7,4°S; 36,5°W). A média diária anual da temperatura, obtida pelos equipamentos, apresentou forte variação sazonal com máximos nos meses em torno dos equinócios, porém, com valores médios bem distintos. A média total obtida pelo radar meteórico SKiYMET foi de 226,2 K, acima das médias dos outros instrumentos. As temperaturas mesosféricas foram submetidas à análise espectral e os resultados revelaram a presença de oscilações de 80, 181,7, 274,5, 364 e 718 dias, para os dados do radar meteórico SKiYMET. Para a temperatura rotacional, as oscilações observadas foram 183,1, 403,9 e 647 dias. Nos dados do TIMED/SABER, as oscilações detectadas nas 3 altitudes analisadas foram de ~90, ~182,5 e ~365 dias. Palavras-chave: Temperatura Mesosférica, Sensoriamento Remoto, Baixas Latitudes