Determining the verse of magnetic turbulent cascades in the Earth's magnetospheric cusp via transfer entropy analysis: preliminary results

International audienceThe inter-scale coupling in the dynamics of the magnetic field in the Earth's magnetospheric cusp is studied with the technique of transfer entropy. This is a non-linear data analysis technique conceived to determine which is the process that plays the role of the "dynamical driver" between two processes interacting. The time series of the magnetic field components measured along the trajectory of a spacecraft through the cusp are decomposed via continuous wavelets, so a time series of the square modulus of the wavelet coefficients may be associated to each scale ? considered. The coupling between to two nearby scales is studied, with the purpose of singling out turbulent cascade directions from large to small scales and viceversa. Preliminary physical conclusions are proposed

Hábitos alimentares fora do domicílio de estudantes de uma universidade pública de Brasília/ DF

Trabalho de Conclusão de Curso (especialização)—Universidade de Brasília, Faculdade de Ciências da Saúde, Departamento de Nutrição, 2017.Hábitos alimentares de universitários descritos na literatura apresentam-se inadequadamente. Caracterizado por alto consumo de alimentos fora do domicílio. O mercado de alimentação fora do domicílio está em constante crescimento expandindo as áreas consideradas como alimentação saudável, assim como também áreas de alimentação consideradas não saudáveis. Este trabalho tem como objetivo analisar características sobre os hábitos alimentares fora do domicílio de estudantes de uma Universidade Pública de Brasília - DF. Foram coletadas informações sociodemográficas, hábitos de consumo e condições que os levam a realizar a alimentação fora do domicílio e realizada análise descritiva das informações coletadas. A maioria dos pesquisado era do sexo feminino (86,2%), com maioria na faixa etária de18 a 22 anos (74%). Sendo a maioria mediados por renda familiar de 5 a 10 salários mínimos (26%) e contam com gato diário de alimentos fora do domicílio no valor de < R$20,00 (73$ 20.00 (73%). The most consumed meal outside the home was lunch (73.2%), followed by afternoon snack (58.5%). Among the foods most consumed were: milks and derivatives (44.7%) in the daily item and large meals (lunch and dinner) (49.5%) in the category 3 to 5 times a week. The authors reported the most important contributing factor being the coexistence between friends and relatives (86.9%), followed by convenience (83.7%) the reason for choosing to eat outside the home. The results demonstrate the fragility and necessity of new studies with this theme, expanding educational actions to favor healthy eating habits in order to minimize risks favoring health promotion

Scintillations climatology over low latitudes: statistical analysis and WAM modelling

Attempts of reconstructing the spatial and temporal distribution of the ionospheric irregularities have been conducted developing a scintillation “climatology” technique, which was very promising in characterizing the plasma conditions triggering L-band scintillations at high latitudes ([1.],[2.]) and further analysis on bipolar high sampling rate (50 Hz) GPS data are currently in progress for deeper investigations. The core of the scintillation climatology technique is represented by the maps of percentage of occurrence of the scintillation indices above a given threshold. The maps at high latitude are expressed in terms of geomagnetic coordinates (Magnetic Latitude vs. Magnetic Local Time) and their fragmentation depends on the available statistics. Typically the selected thresholds are 0.25º for the phase scintillation index σΦ and 0.25 for the amplitude one S4, which represent a good compromise between the need of a meaningful sample in each map bin and the necessity to distinguish moderate/strong scintillations. The scintillation climatology technique has been very useful in identifying the main areas of the ionosphere (from mid to cusp/cap latitudes) in which plasma irregularities could lead to scintillation phenomena on GPS signals and their dependence on different geomagnetic conditions of the ionosphere and on different level of the solar activity. As the promising results achieved, we propose to apply the same approach to draw a first raw representation of the scintillations climatology over the Latin America sector. In the development of the study, it will be considered that, at low latitudes, scintillations effects are most severe around the magnetic equator and around the crests of the equatorial anomaly in the early evening hours. Moreover, the morphology of the ionosphere is different from that at other latitudes, because the magnetic field B is nearly parallel to the Earth’s surface, leading to different configurations, dimensions and dynamics of the ionosphere irregularities causing scintillation. Scintillation climatology in geographic coordinates will be performed on scintillation data collected at the site of Presidente Prudente (Brazil, 22.12ºS, 51.41ºW) via a SCINTMON receiver [3.]. The SCINTMON receiver is developed by the space plasma physics group from Cornell University and designed to monitor the amplitude scintillations at the L1 frequency (1.575 MHz). The SCINTMON is capable of logging the signal intensity at 50 samples per second for up to 11 visible satellites simultaneously, then the data collected are post-processed via software, and for each 60 s interval of data the S4 scintillation index is computed for all satellites tracked during the observation nights (0900–2100 UT). In relation with the aforementioned climatology, here we also discuss the extension to low latitudes of the empirical Wernik-Alfonsi-Materassi (WAM) [4.] model. This is a simple phase screen model of propagation of a plane wave through the irregular ionosphere. It ingests the electron density in situ satellite data to reproduce empirically the irregular medium. WAM was originally developed to model high latitude irregularities, and now it is going to be extend to lower latitudes. The concept of such extension is here described. The low latitude scintillation climatology will be used for understanding the key points to be carefully explored to concretely envisage a reliable modelling. The main innovative idea of the WAM model [4.] is that the statistics of the medium, giving rise to the irregular pattern formation called “scintillation” when crossed by an electromagnetic wave, should be constructed from in situ data instead of being assumed a priori. This is because the ionization fluctuations, due to a form of “dirty plasma” turbulence, are expected to show non-trivial statistics, often non Gaussian ones, due to the strong gradients possibly occurring in the ionosphere. WAM was constructed as a phase screen model, good for climatological use, with the statistics of the phase fluctuations δφ directly calculated from the in situ data of the ionization fluctuations δN collected by the DE2 mission in the years 1981-1983. The S4 scintillation index is predicted, along an assigned satellite-ground radio link, via the analytical formulæ for the weak scattering due to Rino [5.]. The location and thickness of the phase screen, and the value of the ionization maximum, all enter in Rino’s formulæ, and these are given in WAM by matching the background ionization as measured by the DE2 satellite with the ionospheric profile provided by some ionospheric background model. In its original form, WAM uses the IRI95 as a profiler [6.]. In its first release, described in [4.], the model predicts the S4 climatology within high invariant latitudes (larger than 50°), and may calculate the most likely S4 along a given radio link of identified geometry, time and geomagnetic conditions (represented through the Kp index). The choice of high latitudes was due to some elements: being DE2 a polar orbiting satellite, its passes form a denser network around poles; real scintillation measurements to compare with are more abundant in the polar regions; the IRI95 profiler is an excellent tool for mid-high latitudes (with some suitable corrections for the topside at high latitudes). In order to extend the WAM model to low latitudes as well, some changes to it must be done. First of all, low latitude in situ observations from DE2 are included, plus other similar data of a low latitude orbiting satellite (in the future, possibly ROCSAT data [7.]). The background ionosphere must be represented via some model which turns out to be more reliable than IRI95 to represent the so Equatorial Anomaly, which is the main feature of the low latitude ionosphere. The successive developments of IRI95 represent improvements of the low latitude background, among the other things, but the choice here was to use the further development referred to as NeQuick model [8.], in its ITU-R version [9.]. Once the WAM model has been expanded to ±40° of latitude thanks to further in situ data and the NeQuick background model, it will be possible to predict a climatology of S4 that will be tested against the real data of the scintillation climatology: this comparison will allow for operation of finer tuning in the low latitude extended WAM model

TRANSMIT: Training Research and Applications Network to Support the Mitigation of Ionospheric Threats

TRANSMIT is an initiative funded by the European Commission through a Marie Curie Initial Training Network (ITN). Main aim of such networks is to improve the career perspectives of researchers who are in the first five years of their research career in both public and private sectors. In particular TRANSMIT will provide a coordinated program of academic and industrial training, focused on atmospheric phenomena that can significantly impair a wide range of systems and applications that are at the core of several activities embedded in our daily life. TRANSMIT deals with the harmful effects of the ionosphere on these systems, which will become increasingly significant as we approach the next solar maximum, predicted for 2013. Main aim of the project is to develop real time integrated state of the art tools to mitigate ionospheric threats to Global Navigation Satellite Systems (GNSS) and several related applications, such as civil aviation, marine navigation and land transportation. The project will provide Europe with the next generation of researchers in this field, equipping them with skills developed through a comprehensive and coordinated training program. Theirs research projects will develop real time integrated state of the art tools to mitigate these ionospheric threats to GNSS and several applications that rely on these systems. The main threat to the reliable and safe operation of GNSS is the variable propagation conditions encountered by GNSS signals as they pass through the ionosphere. At a COST 296 MIERS (Mitigation of Ionospheric Effects on Radio Systems) workshop held at the University of Nottingham in 2008, the establishment of a sophisticated Ionospheric Perturbation Detection and Monitoring (IPDM) network (http://ipdm.nottingham.ac.uk/) was proposed by European experts and supported by the European Space Agency (ESA) as the way forward to deliver the state of the art to protect the range of essential systems vulnerable to these ionospheric threats. Through a set of carefully designed research work packages TRANSMIT will be the enabler of the IPDM network. The goal of TRANSMIT is therefore to provide a concerted training programme including taught courses, research training projects, secondments at the leading European institutions, and a set of network wide events, with summer schools, workshops and a conference, which will arm the researchers of tomorrow with the necessary skills and knowledge to set up and run the proposed service. TRANSMIT will count on an exceptional set of partners, encompassing both academia and end users, including the aerospace and satellite communications sectors, as well as GNSS system designers and service providers, major user operators and receiver manufacturers. TRANSMIT's objectives are: A. Develop new techniques to detect and monitor ionospheric threats, with the introduction of new prediction and forecasting models, mitigation tools and improved system design; B. Advance the physical modeling of the underlying processes associated with the ionospheric plasma environment and the knowledge of its influences on human activity; C. Establish a prototype of a real time system to monitor the ionosphere, capable of providing useful assistance to users, which exploits all available resources and adds value for European services and products; D. Incorporate solutions to this system that respond to all end user needs and that are applicable in all geographical regions of European interest (polar, high and mid-latitudes, equatorial region). TRANSMIT will pave the way to establish in Europe a system capable of mitigating ionospheric threats on GNSS signals in real tim

Structure functions and intermittency in ionospheric plasma turbulence

Low frequency electrostatic turbulence in the ionospheric E-region is studied by means of numerical and experimental methods. We use the structure functions of the electrostatic potential as a diagnostics of the fluctuations. We demonstrate the inherently intermittent nature of the low level turbulence in the collisional ionospheric plasma by using results for the space-time varying electrostatic potential from two dimensional numerical simulations. An instrumented rocket can not directly detect the one-point potential variation, and most measurements rely on records of potential differences between two probes. With reference to the space observations we demonstrate that the results obtained by potential difference measurements can differ significantly from the one-point results. It was found, in particular, that the intermittency signatures become much weaker, when the proper rocket-probe configuration is implemented. We analyze also signals from an actual ionospheric rocket experiment, and find a reasonably good agreement with the appropriate simulation results, demonstrating again that rocket data, obtained as those analyzed here, are unlikely to give an adequate representation of intermittent features of the low frequency ionospheric plasma turbulence for the given conditions

Multifractal structure of turbulence in the magnetospheric cusp

Magnetospheric cusps are regions which are characterized by highly turbulent plasma. We have used Polar magnetic field data to study the structure of turbulence in the cusp region. The wavelet transform modulus maxima method (WTMM) has been applied to estimate the scaling exponent of the partition function and singularity spectra. Their features are similar to those found in the nonlinear multifractal systems. We have found that the scaling exponent does not allow one to conclude which intermittency model fits the experiment better. However, the singularity spectra reveal that different models can be ascribed to turbulence observed under various IMF conditions. For northward IMF conditions the turbulence is consistent with the multifractal &lt;i&gt;p&lt;/i&gt;-model of fully developed fluid turbulence. For southward IMF experimental data agree with the model of non-fully developed Kolmogorov-like fluid turbulence

Low-frequency electrostatic waves in the ionospheric E-region: a comparison of rocket observations and numerical simulations

International audienceLow frequency electrostatic waves in the lower parts of the ionosphere are studied by a comparison of observations by instrumented rockets and of results from numerical simulations. Particular attention is given to the spectral properties of the waves. On the basis of a good agreement between the observations and the simulations, it can be argued that the most important nonlinear dynamics can be accounted for in a 2-D numerical model, referring to a plane perpendicular to a locally homogeneous magnetic field. It does not seem necessary to take into account turbulent fluctuations or motions in the neutral gas component. The numerical simulations explain the observed strongly intermittent nature of the fluctuations: secondary instabilities develop on the large scale gradients of the largest amplitude waves, and the small scale dynamics is strongly influenced by these secondary instabilities. We compare potential variations obtained at a single position in the numerical simulations with two point potential-difference signals, where the latter is the adequate representation for the data obtained by instrumented rockets. We can demonstrate a significant reduction in the amount of information concerning the plasma turbulence when the latter signal is used for analysis. In particular we show that the bicoherence estimate is strongly affected. The conclusions have implications for studies of low frequency ionospheric fluctuations in the E and F regions by instrumented rockets, and also for other methods relying on difference measurements, using two probes with large separation. The analysis also resolves a long standing controversy concerning the supersonic phase velocities of these cross-field instabilities being observed in laboratory experiments

L-band scintillations and calibrated total electron content gradients over Brazil during the last solar maximum

This work presents a contribution to the understanding of the ionospheric triggering of L-band scintillation in the region over São Paulo state in Brazil, under high solar activity. In particular, a climatological analysis of Global Navigation Satellite Systems (GNSS) data acquired in 2012 is presented to highlight the relationship between intensity and variability of the total electron content (TEC) gradients and the occurrence of ionospheric scintillation. The analysis is based on the GNSS data acquired by a dense distribution of receivers and exploits the integration of a dedicated TEC calibration technique into the Ground Based Scintillation Climatology (GBSC), previously developed at the Istituto Nazionale di Geofisica e Vulcanologia. Such integration enables representing the local ionospheric features through climatological maps of calibrated TEC and TEC gradients and of amplitude scintillation occurrence. The disentanglement of the contribution to the TEC variations due to zonal and meridional gradients conveys insight into the relation between the scintillation occurrence and the morphology of the TEC variability. The importance of the information provided by the TEC gradients variability and the role of the meridional TEC gradients in driving scintillation are critically described