Articulos(IAFE)
http://hdl.handle.net/11336/338
Articulos de INST.DE ASTRONOMIA Y FISICA DEL ESPACIO(I)Fri, 19 Jul 2019 20:46:36 GMT2019-07-19T20:46:36ZAssessment of remotely-sensed sea-surface temperature and chlorophyll-a concentration in San Matías Gulf (Patagonia, Argentina)
http://hdl.handle.net/11336/79540
Assessment of remotely-sensed sea-surface temperature and chlorophyll-a concentration in San Matías Gulf (Patagonia, Argentina)
Williams, Gabriela Noemí; Dogliotti, Ana Inés; Zaidman, Paula Cecilia; Solis, Miriam Edith; Narvarte, Maite Andrea; González, Raul Alberto Candido; Esteves, Jose Luis; Gagliardini, Domingo Antonio
Field measurements of surface temperature and chlorophyll-a concentration were used to evaluate for the first time the performance of the standard sea surface temperature and chlorophyll-a algorithms of the Moderate Resolution Imaging Spectroradiometer (MODIS) in San Matías Gulf, northern of the Argentine Patagonian Continental Shelf (between 40°47'S and 42°13'S). The fit of the temperature data to a Standard Major Axis (SMA) type II regression model indicated that a high proportion of the total variance (r 2 ≥0.80) was explained by the model. For chlorophyll-a, the low correlation (r 2 =0.15) and high dispersion indicated a poor performance and a general overestimation of Chl-a by the OC3Mv5 algorithm as indicated by the Relative Percent Difference (RPD=113%). However, for stations located in the northern area of the gulf the result showed a higher correlation (r 2 =0.76) and less dispersion (RPD=31%). The feasible reasons and explanations for the performance of NLSST and OC3Mv5 algorithms are discussed. The results of the temporal variability analysis of SST and Chl-a in different areas of the gulf agreed with previous studies.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11336/795402013-01-01T00:00:00ZModeling the behavior of an underwater acoustic relative positioning system based on Complementary Set of Sequences
http://hdl.handle.net/11336/78382
Modeling the behavior of an underwater acoustic relative positioning system based on Complementary Set of Sequences
Aparicio, Joaquín; Jimenez, Ana; Álvarez, Fernando J.; Ureña, Jesús; de Marziani, Carlos Manuel; Diego, Cristina
The great variability usually found in underwater media makes modeling a challenging task, but helpful for better understanding or predicting the performance of future deployed systems. In this work, an underwater acoustic propagation model is presented. This model obtains the multipath structure by means of the ray tracing technique. Using this model, the behavior of a relative positioning system is presented. One of the main advantages of relative positioning systems is that only the distances between all the buoys are needed to obtain their positions. In order to obtain the distances, the propagation times of acoustic signals coded by Complementary Set of Sequences (CSS) are used. In this case, the arrival instants are obtained by means of correlation processes. The distances are then used to obtain the position of the buoys by means of the Multidimensional Scaling Technique (MDS). As an early example of an application using this relative positioning system, a tracking of the position of the buoys at different times is performed. With this tracking, the surface current of a particular region could be studied. The performance of the system is evaluated in terms of the distance from the real position to the estimated one.
Thu, 01 Dec 2011 00:00:00 GMThttp://hdl.handle.net/11336/783822011-12-01T00:00:00ZAlternative derivation of exact law for compressible and isothermal magnetohydrodynamics turbulence
http://hdl.handle.net/11336/78178
Alternative derivation of exact law for compressible and isothermal magnetohydrodynamics turbulence
Andrés, Nahuel; Sahraoui, F.
The exact law for fully developed homogeneous compressible magnetohydrodynamics (CMHD) turbulence is derived. For an isothermal plasma, without the assumption of isotropy, the exact law is expressed as a function of the plasma velocity field, the compressible Alfvén velocity, and the scalar density, instead of the Elsasser variables used in previous works. The theoretical results show four different types of terms that are involved in the nonlinear cascade of the total energy in the inertial range. Each category is examined in detail, in particular, those that can be written either as source or flux terms. Finally, the role of the background magnetic field B0 is highlighted and a comparison with the incompressible MHD (IMHD) model is discussed. This point is particularly important when testing this exact law on numerical simulations and in situ observations in space plasmas.
Wed, 01 Nov 2017 00:00:00 GMThttp://hdl.handle.net/11336/781782017-11-01T00:00:00ZExact scaling laws for helical three-dimensional two-fluid turbulent plasmas
http://hdl.handle.net/11336/78177
Exact scaling laws for helical three-dimensional two-fluid turbulent plasmas
Andrés, Nahuel; Galtier, Sebastien; Sahraoui, Fouad
We derive exact scaling laws for a three-dimensional incompressible helical two-fluid plasma, without the assumption of isotropy. For each ideal invariant of the two-fluid model, i.e., the total energy, the electron helicity, and the proton helicity, we derive simple scaling laws in terms of two-point increment correlation functions expressed in terms of the velocity field of each species and the magnetic field. These variables are appropriate for comparison with direct numerical simulation data and with in situ measurements in the near-Earth space over a broad range of spatial scales. Finally, using the exact scaling laws and dimensional analysis we predict the magnetic energy and electron helicity spectra for different ranges of scales.
Thu, 01 Dec 2016 00:00:00 GMThttp://hdl.handle.net/11336/781772016-12-01T00:00:00Z