Wavelet analysis was employed to identify the major frequencies of low-frequency waves present in the Martian magnetosheath. The Morlet wavelet transform was selected and applied to the electron density data, obtained from the Analyzer of Space Plasmas and Energetic Atoms experiment (ASPERA-3), onboard the Mars Express (MEX) spacecraft. We have selected magnetosheath crossings and analyzed electron density data. From a preliminary study of 502 magnetosheath crossings (observed during the year of 2005), we have found 1409 periods between 0.005 and 0.06Hz. The major frequencies observed were in the range 0.005-0.02 Hz with 58.5% of the 1409 frequencies identified.
ABSTRACT. This work used micrometeorological measurements of temperature and wind in order to characterize the turbulence due to wind in a terra firme forest in central Amazonia as part of the ATTO-CLAIRE / IOP-1 (2012) (Amazon Tall Tower Observatory – Cooperative LBA Airborne Regional Experiment / Intensive Observation Period – 2012 / LBA – Large Scale Biosphere-Atmosphere Experiment in the Amazon). This research was conducted at the Uatumã ATTO Sustainable Development Reserve in the State of Amazonas, Brazil, from February to September, 2012, and used data from February 26 to September 07, 2012, dates that partially encompass the wet and dry seasons, respectively. The ATTO site has 5 towers: one that is 320m, and four that are 80 m in height, and this research was conducted on an 80 m triangular tower. A total of ten 3D and 2D ultrasonic anemometers were installed on the tower, and the importance of these instruments used for flux measurements is also evident when taking into account the fact that the dissemination and diffusion of seeds and chemical composts in the forest happens through the action of turbulent fluxes. In order to understand the wind profile, the inflection point of the wind velocity, and coherent structures (ECs) and local turbulence, box-plot diagrams, quadrant analyses, wavelet potential spectrum, and energy potential analyses were conducted. The turbulence characterized at the ATTO had a roll or ramp structure during the study period, which represents favorable conditions for the maintenance of the forest during the wet and dry seasons in the Central Amazon. Keywords: inflection point, ramp, wavelet, turbulence. RESUMO. Este trabalho faz uso de medidas micrometeorológicas de temperatura e vento, com finalidade de caracterizar a turbulência aerotransportada em uma floresta de terra firme na Amazônia Central, realizadas no experimento ATTO-CLAIRE / IOP-1 (2012) (Amazon Tall Tower Observatory – Cooperative LBA Airborne Regional Experiment / Intensive Observation Period – 2012 / LBA – Large Scale Biosphere-Atmosphere Experiment in Amazônia), no sítio do ATTO, na Reserva de Desenvolvimento Sustentável do Uatumã – AM (Brasil) nos meses de fevereiro a setembro de 2012, com dados analisados a partir do dia 26 de fevereiro de 2012 até o dia 7 de setembro de 2012, entre as estações úmida e seca na Amazônia Central, no complexo de torres altas composta de 5 (cinco) torres; uma de 320 m e 4 (quatro) de 80 m. Este trabalho foi realizado na torre triangular (80 m). Foram instalados 10 (dez) anemômetros ultrassônicos de 3D e 2D. Equipamentos necessários em método de fluxos, visto que, a disseminação e difusão de sementes e compostos químicos da floresta, faz-se também por fluxos turbulentos. Para compreensão do perfil de vento, ponto de inflexão do perfil da velocidade do vento, estruturas coerentes e a turbulência local, para tal desenvolveu-se a partir dos dados processados, diagrama de caixa (box-plot ), análise de quadrantes, espectro de potência em ondeletas, espectro de energia. A turbulência caracterizada no ATTO, foi de estruturas do tipo “rolo” ou rampa, para o período estudado, condições favoráveis para manutenção da floresta em período úmido-seco na Amazônia Central.Palavras-chave: ponto de inflexão, rampa, ondeleta, turbulência.
We present a statistical model for the distribution of increments of wind velocity and temperature of turbulence data measured in the atmospheric surface layer above the Amazonian forest, on a micrometeorological tower in Rebio-Jaru Reserve (10°04' S; 61°56' W) during LBA (Large Scale Biosphere Atmosphere Experiment in Amazonia) wet season campaign. The data were measured using 3D Campbell sonic anemometer and a Campbell fast response thermometer located at a height of 66 m (the forest canopy has a mean height of 35 m; but some of the higher tree branches may reach the height of 45 m), at a sampling rate of 60 Hz. The goal of this investigation is to detect noextensivity properties of the turbulent field in such a peculiar environment. To do this we calculate the probability density function (PDF) for wind velocity increments Vr(x) = V(x) - V(x+r) (and temperature increments) at different length scales r. The preliminary results show some evidence that the nonextensive thermostatistics modelling proposed by Tsallis (1988) provides a new and simple framework for explaining the statistical behavior of fully developed mechanical turbulence. We also investigate the relationship between intermittency and nonextensivity using a single parameter q, from Tsallis thermostatistics. The results of the wind velocity turbulent signals measured at the level of 66m show a very good agreement with the Tsallis model but the temperature signals show some discrepancy with respect to the proposed model. Physical discussions are proposed to explain our results.
<p><strong>Abstract</strong></p><p>Geomagnetic field variations in 2018 due to solar and lunar tides in the Brazilian sector were studied using data provided by magnetometers installed at S&#227;o Jos&#233; dos Campos (23.21<sup>o</sup>S, 0345.97<sup>o</sup>W; Dip latitude 20.9<sup>o</sup>S), Eus&#233;bio, Cear&#225; (3.89&#176; S, 38.46&#176; W) and S&#227;o Lu&#237;s, Maranh&#227;o (2.53&#176; S, 44.30&#176; W). Variations associated with these tides were identified using the horizontal component of the geomagnetic field, H(nT). Least square fit method was employed in determining the monthly amplitudes and phases of the diurnal, semidiurnal and ter-diurnal solar tides. The monthly amplitudes and phases of the lunar tide were then calculated using the residual measurements (obtained after subtracting the solar tidal components from each day), converting the solar local time to lunar time and subjecting the residuals to harmonic analysis. The maximum solar tide amplitude recorded was 23.96nT(diurnal) in March, at Eus&#233;bio whereas the minimum amplitude was 0.45nT(terdiurnal) recorded in December at S&#227;o Jos&#233; dos Campos. The lunar tide recorded a maximum amplitude of 4.33nT(semidiurnal) in February, at S&#227;o Lu&#237;s and a minimum amplitude of 0.13nT(diurnal) in August, at Eus&#233;bio.</p><p>&#160;</p><p>&#160;</p><p><strong>Keywords</strong>: Solar tides, Lunar tides, Geomagnetic field, Magnetometer.</p><p>&#160;</p>
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