Models and Observations of Sunspot Penumbrae

The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution. To help explaining these new observations I propose some modifications to each of them. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.Comment: 9 pages, 1 color figure. Review talk to appear in the proceedings of the International Workshop of 2008 Solar Total Eclipse: Solar Magnetism, Corona and Space Weather--Chinese Space Solar Telescope Scienc

Ocupação tardia e o desenvolvimento da agropecuária no Estado de Rondônia Uma história da bovinocultura no desenvolvimento regional.

Neste artigo se discute a ocupação tardia e sem planejamento de Rondônia e sua influência na bovinocultura. É uma pesquisa bibliográfica e qualitativa na qual foram levantadas informações sobre penetração do gado bovino no Estado do século XVIII ao XXI cujo objetivo é mostrar a configuração da atividade no desenvolvimento regional. Extraiu-se que somente a partir da década de setenta a criação de gado tornou-se importante para a economia regional, mas faltaram políticas públicas de ordenação e planejamento do território ocupado, tornando-a uma atividade competitiva. Aqui as baixas tecnologias provocaram a substituição da floresta pela criação extensiva, e sabe-se que na exploração bovina feita de forma correta poucos danos se verificam em sua área de atuação

Fully resolved quiet-Sun magnetic flux tube observed with the Sunrise IMaX instrument

Until today, the small size of magnetic elements in quiet Sun areas has required the application of indirect methods, such as the line-ratio technique or multi-component inversions, to infer their physical properties. A consistent match to the observed Stokes profiles could only be obtained by introducing a magnetic filling factor that specifies the fraction of the observed pixel filled with magnetic field. Here, we investigate the properties of a small magnetic patch in the quiet Sun observed with the IMaX magnetograph on board the balloon-borne telescope Sunrise with unprecedented spatial resolution and low instrumental stray light. We apply an inversion technique based on the numerical solution of the radiative transfer equation to retrieve the temperature stratification and the field strength in the magnetic patch. The observations can be well reproduced with a one-component, fully magnetized atmosphere with a field strength exceeding 1 kG and a significantly enhanced temperature in the mid- to upper photosphere with respect to its surroundings, consistent with semi-empirical flux tube models for plage regions. We therefore conclude that, within the framework of a simple atmospheric model, the IMaX measurements resolve the observed quiet-Sun flux tube.Comment: Accepted for publication in The Astrophysical Journal Letters on Aug 11 201

Global Sustainability Index (GSI) construction: an evaluation tool for public policies directed at sustainable milk production in contemporary time.

Desenvolvimento sustentável se refere a atividades agropecuárias e industriais e o entendimento da IGSe assume maior complexidade, que exige ênfases econômica, social, ambiental, institucional, tecnológica, cultural e geográfica a serem consideradas, pois, o que é sustentável para uma região pode não ser para outra. O artigo objetiva mostrar critérios metodológicos para a construção de Índice Global de Sustentabilidade (IGS) e sua importância na avaliação de políticas públicas da produção de leite sustentável em épocas contemporâneas. A metodologia considera as dimensões econômica, social, ambiental, institucional e tecnológicas, por melhor avaliarem a sustentabilidade de atividades economicamente ativas. A pesquisa ocorreu em Rondônia com 400 produtores de leite, onde se obteve o IGS que alcançou sustentabilidade média, IGS=0,42. A dimensão econômica apresentou índice de 0,52, sendo a mais sustentável entre as dimensões analisadas. Seguindo a ordem decrescente, vem a social e ambiental, com sustentabilidade média de 0,44 e 0,41, e, com baixa sustentabilidade, ficou a dimensão tecnológica, que apresentou índice de 0,39, e, a institucional com 0,32 pontos decimais de sustentabilidade. Tal resultado indica a necessidade de esforços políticos e tecnológicos para melhor desempenho do setor

Rare earth magnetism in CeFeAsO: A single crystal study

Single crystals of CeFeAsO, large enough to study the anisotropy of the magnetic properties, were grown by an optimized Sn-flux technique. The high quality of our single crystals is apparent from the highest residual resistivity ratio, RRR = 12, reported among undoped RFeAsO compounds (R=rare earth) as well as sharp anomalies in resistivity, specific heat, C(T), and thermal expansion at the different phase transitions. The magnetic susceptibility chi(T) presents a large easy-plane anisotropy consistent with the lowest crystal electric field doublet having a dominant Gamma_6 character. Curie-Weiss like susceptibilities for magnetic field parallel and perpendicular to the crystallographic c-axis do not reveal an influence of a staggered field on the Ce site induced by magnetic ordering of the Fe. Furthermore, the standard signatures for antiferromagnetic order of Ce at T_N = 3.7 K observed in chi(T) and C(T) are incompatible with a Zeeman splitting Delta = 10 K of the CEF ground state doublet at low temperature due to the Fe-magnetic order as previously proposed. Our results can be reconciled with the earlier observation by assuming a comparatively stronger effect of the Ce-Ce exchange leading to a reduction of this Zeeman splitting below 15 K.Comment: 15 pages, 6 figures, added section on magn. susceptibilit