58 research outputs found

    Modeling the Subsurface Structure of Sunspots

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    While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

    The Origin, Early Evolution and Predictability of Solar Eruptions

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    Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

    Track D Social Science, Human Rights and Political Science

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

    Cohort Profile: Pregnancy And Childhood Epigenetics (PACE) Consortium.

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    Development Psychopathology in context: famil

    Modeling Microstructure and Irradiation Effects

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    Overview of the JET results in support to ITER

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    Propagation and augmentative releases of predators and parasitoids for control of arthropod pests.

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    A decrescente disponibilidade e os efeitos adversos de pesticidas sobre os organismos nao alvos, mormente sobre o homem e especies ameacadas de extincao, resultam no reduzido emprego de pesticidas convencionais como medidas destinadas a suprimir populacoes de pragas. Assim, tecnicas alternativas de controle de pragas, inclusive controle biologico, estao recebendo atencao cada vez maior. As populacoes naturais de insetos ou plantas favoraveis ao homem sao, muitas vezes, pequenas demais para manter em niveis aceitaveis as populacoes de pragas. O seu aumento e uma das tecnicas de controle biologico particularmente util num meio ambiente perturbado. Ha duas maneiras basicas de aumento: periodicas liberacoes de predadores, ou sua manipulacao no sentido de aumentar o seu numero e seus efeitos beneficos. Esta discussao focalizara a factibilidade tecnica e economica de aumentar os inimigos naturais selecionados. Serao discutidos, tambem, os impedimentos ao aumento, inclusive a producao em massa de inimigos naturais a precos bastante medicos.Made available in DSpace on 2011-04-09T12:15:22Z (GMT). No. of bitstreams: 1 pab20abresp92.pdf: 685358 bytes, checksum: 9a0e6ce370f6b32489701bcf7bd7e309 (MD5) Previous issue date: 2001-08-27199
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