Surges and Si IV bursts in the solar atmosphere. Understanding IRIS and SST observations through RMHD experiments

Surges often appear as a result of the emergence of magnetized plasma from the solar interior. Traditionally, they are observed in chromospheric lines such as H$\alpha$ 6563 \AA and Ca II 8542 \AA. However, whether there is a response to the surge appearance and evolution in the Si IV lines or, in fact, in many other transition region lines has not been studied. In this paper we analyze a simultaneous episode of an H$\alpha$ surge and a Si IV burst that occurred on 2016 September 03 in active region AR12585. To that end, we use coordinated observations from the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1-m Solar Telescope (SST). For the first time, we report emission of Si IV within the surge, finding profiles that are brighter and broader than the average. Furthermore, the brightest Si IV patches within the domain of the surge are located mainly near its footpoints. To understand the relation between the surges and the emission in transition region lines like Si IV, we have carried out 2.5D radiative MHD (RMHD) experiments of magnetic flux emergence episodes using the Bifrost code and including the non-equilibrium ionization of silicon. Through spectral synthesis we explain several features of the observations. We show that the presence of Si IV emission patches within the surge, their location near the surge footpoints and various observed spectral features are a natural consequence of the emergence of magnetized plasma from the interior to the atmosphere and the ensuing reconnection processes.Comment: 13 pages, 8 figures. The Astrophysical Journal (Accepted

The subjective body of nursing academic: dimensions of sensoperception

Objetivo: identificar a maneira como acadêmicos de enfermagem visualizam o próprio corpo a partir do tato. Metodologia: estudo descritivo, de abordagem qualitativa com destaque para a subjetividade, feito com 33 alunos de graduação em enfermagem da Universidade Federal do Rio Grande do Norte/UFRN. Resultados: as respostas obedecem a um roteiro céfalo-caudal frente a um modelo anatomicamente incorporado para o exame físico. Os acadêmicos manifestaram gostar das partes que se situam na cabeça, tronco e não gostar daquelas referentes aos membros inferiores configurando um esquema corporal idealizado frente um corpo concreto e não aceito, embora tenha que conviver com o mesmo. Conclusão: mediante o estudo foi possível avaliar o quão importante é a relação desses estudantes com seu corpo e sua influência de cunho psicossocial e, ainda num sentido projetivo reflete a relação frente ao corpo dos portadores de transtornos mentais e comportamentais, objeto do seu cuidado

Ambipolar diffusion in the Bifrost code

Ambipolar diffusion is a physical mechanism related to the drift between charged and neutral particles in a partially ionized plasma that is key in many different astrophysical systems. However, understanding its effects is challenging due to basic uncertainties concerning relevant microphysical aspects and the strong constraints it imposes on the numerical modeling. Our aim is to introduce a numerical tool that allows us to address complex problems involving ambipolar diffusion in which, additionally, departures from ionization equilibrium are important or high resolution is needed. The primary application of this tool is for solar atmosphere calculations, but the methods and results presented here may also have a potential impact on other astrophysical systems. We have developed a new module for the stellar atmosphere Bifrost code that improves its computational capabilities of the ambipolar diffusion term in the Generalized Ohm's Law. This module includes, among other things, collision terms adequate to processes in the coolest regions in the solar chromosphere. As a key feature of the module, we have implemented the Super Time-Stepping (STS) technique, that allows an important acceleration of the calculations. We have also introduced hyperdiffusion terms to guarantee the stability of the code. We show that to have an accurate value for the ambipolar diffusion coefficient in the solar atmosphere it is necessary to include as atomic elements in the equation of state not only hydrogen and helium but also the main electron donors like sodium, silicon and potassium. In addition, we establish a range of criteria to set up an automatic selection of the free parameters of the STS method that guarantees the best performance, optimizing the stability and speed for the ambipolar diffusion calculations. We validate the STS implementation by comparison with a self-similar analytical solution.Comment: Accepted in A&A, 10 pages, 7 figure

Digestão de amostras assistida por microondas.

Conceitos teóricos; Relações básicas fundamentais; Migração Iônica; Rotação de dipolo; Tempo de relaxação e freqüência da energia de microondas; Capacidade de penetração das microondas; Água como solvente; Sistema com cavidade (forno de microondas); Recepientes para a digestão; Sistema com microondas focalizadas; Aplicações e tendências em digestão com microondas; Medidas de segurança no uso de microondas

On the effect of the wall slip boundary conditon

This work describes the implementation and assessment of the wall slip boundary condition in a 3D numerical modelling code, based on the finite volume method, that is being developed by the research team. Several phenomenological models relating the velocity and the shear stress at the wall were implemented. The capabilities of the new numerical code are illustrated with three case studies where the wall slip boundary conditions play an important role, namely the flow in a smooth contraction, the stick-slip phenomenon an the flow in a profile extrusion die. The results obtained are qualitatively in accordance with the theoretical expectations and evidence the importance of wall slip