Transporte térmico no local en la corona solar

El flujo de calor electrónico toma valores cercanos al millón de K a 1.03 r⊙. La función de distribución electrónica medida observacionalmente muestra en esta región una cola supratérmica. Se trata entonces de derivar analíticamente una expresión que reproduzca esta población de alta energía mediante un formalismo cinético autoconsistente. Si se resuelve la ecuación de Fokker-Planck para un plasma de H y se considera un campo magnético externo, se obtiene una expresión analítica para el flujo de calor que resulta ser no local. Además se observa que la corrección a la anisotropía de la función de distribución debida al campo magnético es de sólo el 5%. Este análisis describe adecuadamente el flujo para distancias del orden de 4 r⊙ . Para energías mucho mayores que la térmica, la fuerza de fricción dinámica no es suficiente para retener a las partículas supratérmicas, que son continuamente aceleradas y escapan (runaway). Es necesario entonces utilizar otra función de distribución. La teoría arroja valores coherentes con los datos observacionales para el flujo de calor y para la dependencia angular de la función de distribución, mostrando esta última un pico característico cuando θ = 0.Asociación Argentina de Astronomí

Vientos MHD en estrellas tempranas

As a part of a modeling plan for early type stars winds which considers its dynamic structure, thermal flux and the system's stability, we present in this paper the basic concepts of the origin of the problem as well as some preliminary results of the MHD winds.Asociación Argentina de Astronomí

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Excitation of gravity modes in the parameter space of the tidal wind system (II): Magnetic effects

The Navier-Stokes, continuity and energy balance equations including magnetic effects for an inviscid compressible fluid in the ionospheric F-region were perturbed around the tidal phenomenological solution. We imposed adiabaticity and incompressibility to the perturbation. Our results satisfy the internal gravity wave (IGW) dispersion relation. The stable and unstable regions of these modes were derived as a function of two control parameters, the colatitude θ and the slow time evolution for tidal modes τ. These regions were obtained for different values of the magnetic field intensity, showing good agreement with observational data for the South Atlantic anomaly. Our model predictions for other magnetic field intensities corresponding to other latitude dependences need to be contrasted with new observational data. In addition we show for some hours and latitudes that, resonant interaction occurs between low frequency tidal waves and two high frequency gravity waves. In these regions, where tidal modes are linearly unstable, the gravity group velocity is modulated by a function of the tidal phase velocity.Fil:Blanco, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Canullo, M.V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

TRY plant trait database, enhanced coverage and open access

Plant traits-the morphological, ahawnatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives