Effect of wave-particle interaction on the outflow of ions at high latitudes

The objective of the research is to use the low-frequency wave spectrum measured by the Plasma Wave Instrument on the DE-1 spacecraft to include the wave-particle interaction (WPI) in the different polar wind models that are available at Utah State University. A Monte Carlo technique was used to simulate the ion diffusion in the velocity space due to scattering by the waves. This enabled us to study the effect of WPI on the magnitude as well as the composition of the outflow of the ionospheric ions. In particular, in the first year the 1-D semi-kinetic code developed by Barakat and Schunk (1983) was modified in order to include the effect of the WPI

On the Transport Equations for Anisotropic Plasmas

First, I attempt to present a unified approach to the study of transport phenomena in multicoponent anisotropic space plasmas. In the limit of small temperature anisotropies this system of generalized transport equations reduces to Grad\u27s 13-moment system of transport equations. In the collisionless limit, the generalized transport equations account for collisionless heat flow, cillisionless viscosity, and large temperature anisotropies. Also, I show that with the appropriate assumptions, the system of generalized transport equations reduces to all of the other major systems of transport equations for anisotropic plasmas that have been derived to date. Next, for application to aeronomy and space physics problems involving strongly magnetized plasma flows, I derive momentum and energy exchange collision terms for interpenetrating bi-Maxwellian gases. Collision terms are derived for Coulomb, Maxwell molecule, and constant collision cross section interaction potentials. The collision terms are valid for arbitrary flow velocity differences and temperature differences between the interacting gases as well as for arbitrary temperature anisotropies. The collision terms have to be evaluated numerically and the appropriate coefficients are presented in tables However, the collision terms are also fitted with simplified expressions, the accuracy of which depends on both the interaction potential and the temperature anisotropy. In addition, I derive the closed set of transport equations that are associated with the momentum and energy collision terms. Finally, I study the extent to which Maxwellian and bi-Maxwellian series expansions can describe plasma flows characterized by non-Maxwellian velocity distributions, with emphasis given to modeling the anisotropic character of the distribution function. The problem considered is the steady state flow of a weakly-ionized plasma subjected to homogeneous electric and magnetic fields, and different collision models are used. In the case of relaxation collision model, a closed form expression is found for the ion velocity distribution function, while for more regorous models (polarization and hard sphere) I have to use the Monte Carlo simulation. These provided a basis for determining the adequacy of a given series expansion. I find that, in general, the bi-Maxwellian-based expansions for the velocity distribution function is better suited to describing anisotropic plasmas than the Maxwellian-based expansions. (166 pages

Radio Astronomical Polarimetry and the Lorentz Group

In radio astronomy the polarimetric properties of radiation are often modified during propagation and reception. Effects such as Faraday rotation, receiver cross-talk, and differential amplification act to change the state of polarized radiation. A general description of such transformations is useful for the investigation of these effects and for the interpretation and calibration of polarimetric observations. Such a description is provided by the Lorentz group, which is intimately related to the transformation properties of polarized radiation. In this paper the transformations that commonly arise in radio astronomy are analyzed in the context of this group. This analysis is then used to construct a model for the propagation and reception of radio waves. The implications of this model for radio astronomical polarimetry are discussed.Comment: 10 pages, accepted for publication in Astrophysical Journa

Visual rhythm perception improves through auditory but not visual training

SummaryMemory research has shown that test performance is optimal when testing and practice occur in identical contexts [1]. However, recent research in object recognition and perceptual learning has shown that multisensory practice leads to improved test performance, even when the test is unisensory [2,3]. It is also known that different sensory modalities can have differing proficiencies in a given domain. For instance, research shows that, compared to the auditory modality, the visual modality is significantly less proficient at discriminating the rhythms of temporal sequences [4,5]. Although rhythm perception is typically thought of as residing in the auditory domain, instances of visual rhythm perception abound in daily life, for example, when one watches a dancer or a drummer, or when a doctor examines a patient’s breathing or heart rate on a monitor (such as when diagnosing arrhythmia). However, no previous study has examined whether visual rhythm discrimination is a trainable perceptual skill. In light of this, we examined the extent to which visual rhythm perception can be improved through two sessions of visual, auditory, or audiovisual training. We found that visual rhythm discrimination was significantly improved in the auditory and audiovisual training groups, but not in the visual training group. Our results show that, in certain tasks, within-modality training may not be the best approach and that, instead, training in a different sensory modality can be a necessary approach to achieve learning

Modelling SDG scenarios for Educational Attainment and Development. CESDEG: Education for all Global Monitoring Report (EFA-GMR)

The scenarios of educational expansion underlying the population projections presented here result from a further refinement of the education model presented in Lutz et al. (2014). In summary, we project the share of the population ever reaching or exceeding a given attainment level. This is done seperately by country, and gender, but with ‘shrinkage’ within a Bayesian framework (with weakly informative priors). The mean expansion trajectories are modelled as random walks with drift (and potential mean reversion) and independent noise at a probit-transformed scale. The trend parameters are estimated based on reconstructed attainment histories, and extrapolated, subject to additional and some exogenously imposed convergence within regions and between females and males. Under the target scenarios, SDG targets are treated as ‘future data’ (in other words, target trajectories are modeled looking back from 2030 under the assumption that the target will have been met), with a potential trend break in 2015. Limitations shared with all existing global projections of educational development include the fact that in the absence of a detailed theoretical basis, they are forced to rely heavily on statistical extrapolations. For example, there is little consensus on whether “higher education is the new secondary education” (as claimed by Andreas Schleicher of OECD), or is fundamentally different from lower levels of schooling (e.g. in terms of institutional framework, its role in the life cycle, economic returns. In addition, global projections can necessarily not account in a satisfactory manner for idiosyncratic policy changes or shocks. In addition, the specific modelling choices outlined above imply a number of trade-offs. Using highest school attainment as the underlying measure solves many problems associated with historic enrolment data by allowing the consistent reconstruction of time series of attainment from relatively recent cross-sectional data, but comes with challenges of its own. While nevertheless preferable overall, the principal disadvantage of attainment measures deserves mention, namely the relatively long time lag with which outcomes can be observed. Late attainment is common in many developing countries, so that attainment cannot safely be assumed to be ‘final’ until several years above the typical graduation age

Supervised physical activity during pregnancy improves fetal cardiac response

Objetivo: Valorar la influencia de un programa de ejercicio físico durante la gestación en la adaptación de la frecuencia cardiaca fetal (FCF). Se espera encontrar una mejor adaptación de la FCF especialmente en cuanto a recuperaciones más rápidas. Método: 45 gestantes participantes en un ensayo clínico aleatorizado sin complicaciones ni contraindicaciones para el ejercicio fueron estudiadas durante el tercer trimestre de embarazo. Se midieron las siguientes variables: FCF en reposo, FCF post-ejercicio y tiempo de recuperación de la FCF a los niveles de reposo. Resultados: La FCF en reposo fue similar en ambos grupos. La FCF post-ejercicio fue significativamente mayor en el grupo control (GC) que en el grupo ejercicio (GE) en ambas pruebas, al 40% GE=138,5±6,4GE vs 141±7,5 GC (p=0,001), al 60% 141,6±10,8 GE vs 150,3±16,8GC. Lo mismo ocurre en los tiempos de recuperación, al 40% 78,2±95,7GE vs 328,4±315,2GC (p=0,001), al 60% 193,3±257,8 GE vs 542,6±482,9GC (p=0,003). Conclusión: El ejercicio físico desarrollado durante el embarazo tiene como consecuencia una mejor adaptación de la FCF post-ejercicio, así como recuperaciones más rápidas.Objective: To assess the influence of a physical activity program during pregnancy on the adaptation of the fetal heart rate (FHR). Greater adaptations and faster recovery are expected to find. Methods: 45 pregnant women included in a randomized control trial, all with uncomplicated pregnancies for exercise were studied in their third trimester of pregnancy. Rest FHR, post-exercise FHR and recovery time were assessed. Results: Rest FHR was similar in both groups. Post-exercise FHR were significantly higher in control group (CG) than in exercise group (EG) in both test, 40% 138,5±6,4EG vs 141±7,5CG (p=0,001), 60% 141,6±10,8EG vs 150,3±16,8CG. The same was found in recovery time, 40% 78,2±95,7EG vs 328,4±315,2CG (p=0,001), al 60% 193,3±257,8EG vs 542,6±482,9CG (p=0,003)

Ion Temperatures in the Low Solar Corona: Polar Coronal Holes at Solar Minimum

In the present work we use a deep-exposure spectrum taken by the SUMER spectrometer in a polar coronal hole in 1996 to measure the ion temperatures of a large number of ions at many different heights above the limb between 0.03 and 0.17 solar radii. We find that the measured ion temperatures are almost always larger than the electron temperatures and exhibit a non-monotonic dependence on the charge-to-mass ratio. We use these measurements to provide empirical constraints to a theoretical model of ion heating and acceleration based on gradually replenished ion-cyclotron waves. We compare the wave power required to heat the ions to the observed levels to a prediction based on a model of anisotropic magnetohydrodynamic turbulence. We find that the empirical heating model and the turbulent cascade model agree with one another, and explain the measured ion temperatures, for charge-to-mass ratios smaller than about 0.25. However, ions with charge-to-mass ratios exceeding 0.25 disagree with the model; the wave power they require to be heated to the measured ion temperatures shows an increase with charge-to-mass ratio (i.e., with increasing frequency) that cannot be explained by a traditional cascade model. We discuss possible additional processes that might be responsible for the inferred surplus of wave power.Comment: 11 pages (emulateapj style), 10 figures, ApJ, in press (v. 691, January 20, 2009