Scaling Theory of 3D Magnetic Reconnection X-Line Spreading

Magnetic reconnection is fundamental process in plasmas that converts magnetic energy into kinetic and thermal energy via a change in magnetic topology. Magnetic reconnection is known to mediate eruptive solar flares, geomagnetic substorms that create the Northern lights, heating and particle acceleration in controlled fusion devices, and is thought to be an important process in numerous settings in high-energy astrophysics. Classical models of reconnection are two-dimensional (2D), but naturally occurring reconnection is three-dimensional (3D), and a manifestation of the 3D nature is that the x-line where the magnetic field topology changes has a finite extent in the direction normal to the plane of reconnection. The x-line can also elongate or spread over time, and this trait has been observed in the laboratory, Earth\u27s magnetosphere, and is thought to be related to the elongation of chromospheric ribbons during solar flares. This dissertation presents a first‐principles scaling theory of the three-dimensional spreading of quasi-2D magnetic reconnection of finite extent in the out of plane direction. This theory addresses systems with or without an out of plane (guide) magnetic field, with or without Hall physics, in current sheets with thicknesses that are both uniform and non‐uniform in the out of plane direction. The theory reproduces known spreading speeds and directions with and without guide fields, unifying previous knowledge in a single theory, along with new results: (1) Reconnection spreads in a particular direction if an x‐line is induced at the interface between reconnecting and non‐reconnecting regions, which is controlled by the out of plane gradient of the electric field in the outflow direction. (2) The theory explains why anti‐parallel reconnection in resistive‐magnetohydrodynamics does not spread. (3) Numerical simulations of anti-parallel reconnection initiated with a pressure pulse instead of a magnetic perturbation suggest magnetosonic waves do not play a role in the propagation of quasi-2D anti-parallel reconnection, as had previously been speculated. (4) In current sheets of non‐uniform thickness, when anti-parallel reconnection spreads from a thinner to a thicker region of a current sheet, the spreading speed is both sub‐Alfv\\u27enic and slower than the speed of the local current carriers predicted for a uniform current sheet of equivalent local thickness; this is due to the initial reconnecting magnetic field being effectively reduced. We confirm these results using 3D two‐fluid and resistive‐magnetohydrodynamics simulations. The result can be used to predict the time scale of reconnection spreading in Earth\u27s magnetotail, where the near Earth cross‐tail current sheet has a thickness that varies along the dawn‐dusk direction. It is also potentially important for understanding observations of two‐ribbon solar flares and dayside magnetopause reconnection in which reconnection spreads at sub‐Alfv\\u27enic and sub‐current carrier speeds

Las iniciativas para el acceso abierto a la información científica en el contexto de la Web Semántica

Access to information sources on Science and Technology is the corner stone in the generation processes of new scientific knowledge, and key factor in the development of the society of the 21st century. The elimination of economic and copyright barriers that supposes the restriction of the access to information by the main editorial groups of scientific diffusion, constitutes a challenge for the scientific international community. The present work gathers the importance of the open Access initiatives to the scientific and academic information as change agent. It is analyzed the structure and functioning of the information repositories, as well as the creation of the OAI-PMH protocol as provider of the interoperability between the different repositories, in the context of the Semantic Web

Os retos da xestión do coñecemento en enerxía para os municipios de Cuba

[Resumo] Co fin de abordar a problemática enerxética no ámbito do desenvolvemento dos municipios cubanos, a Redenerg (Rede Nacional de Xestión do Coñecemento en Enerxía) desenvolveu unha ferramenta de xestión do coñecemento denominada NOME (nodos municipais de enerxía) que permite organizar o capital intelectual do municipio na temática enerxética, co obxectivo de apoiar os gobernos municipais na xestión dos problemas enerxéticos vinculados ao desenvolvemento local municipal. A experiencia da creación de NOME en catro municipios da rexión central do país (Jatibonico, Placetas, Fomento e Aguada de Pasajeros) permitiu identificar os problemas que dificultan a xestión enerxética local desde a perspectiva da xestión do coñecemento. O traballo expón a árbore dos problemas identificados nos municipios, a estratexia de traballo para abordar esta problemática, os resultados alcanzados e as súas perspectivas no ámbito da xeneralización.[Abstract] In order to tackle the energy problem in the development of the Cuban municipalities, Redenerg (National Network for Energy Knowledge Management) developed a knowledge management tool known as NOME (municipal energy nodes) that allows the intellectual capital in energy matters within the municipality to be organized, in order to support municipal governments in the management of energy problems linked to local municipal development. The experience of setting up NOME in four municipalities in the country’s central region (Jatibonico, Placetas, Fomento and Aguada de Pasajeros) led to the identification of the problems that hinder local energy management from the point of view of knowledge management. The paper presents the problems identified in the municipalities, the work strategy designed to tackle those problems, the results achieved and the prospects in the area of generalization

Acimed en el Web Citation Index: de la Biblioteca Virtual de Salud al ISI Web of Knowledge, 15 años después

Editor´s page on the Acimed journal and it´s inclusion in the Web Citation Index, a new service of Thomson Scientific

El “núcleo racional” de la teleología natural: la interacción dialéctica como forma de desarrollo de lo concreto-universal

It is often believed that the only alternative to an idealist conception of natural phenomena excludes both the presence of objective universal forms and their progression towards higher forms as the finality of processes in the natural world. Realism regarding the universal and teleological approaches regarding processes are signs of idealism. Therefore, materialism, it would seem, must conform to a nominalist and mechanical view of nature. However, an intelligent materialist reading of idealism’s classics reveals a more complex scenario. A real fact is expressed in a mystical fashion in idealism’s conceptions of objective universals and teleology. This article attempts to show such a real fact in its authentic (materialist) form. With that goal in mind, the present article discusses the notion of nature’s alienation, the distinction between abstract and concrete universals, and the concept of dialectical interaction. The natural-historical emergence of a higher form of matter’s organization assimilates, as its organs, the conditions that preceded it in time, transforming itself into an active producer of such conditions. That is the secret glimpsed but not correctly understood by idealism that a consistent materialist should not ignore.A menudo se cree que la única alternativa a una concepción idealista de los fenómenos naturales excluye tanto la presencia de formas universales objetivas como su progresión hacia formas superiores como finalidad de los procesos en el mundo natural. El realismo con respecto a lo universal y los enfoques teleológicos en los procesos son signos de idealismo. Por lo tanto, el materialismo, al parecer, debe ajustarse a una visión nominalista y mecanicista de la naturaleza. Sin embargo, una lectura inteligentemente materialista de los clásicos del idealismo revela un escenario más complejo. Un hecho real se expresa de manera mística en las concepciones idealistas de los universales objetivos y la teleología. Este artículo intenta mostrar tal hecho real en su forma auténtica (materialista). Con ese objetivo en mente, el presente artículo discute la noción de alienación de la naturaleza, la distinción entre universales abstractos y concretos, y el concepto de interacción dialéctica. El surgimiento histórico-natural de una forma superior de organización de la materia asimila, como sus órganos, las condiciones que le precedieron en el tiempo, transformándose en productor activo de tales condiciones. Ese es el secreto vislumbrado pero no correctamente comprendido por el idealismo que un materialista consecuente no debe ignorar

Box 4. Review of the European Central Bank's monetary policy strategy

Artículo de revist

EFFICIENT VERSUS NON-EFFICIENT STATED CHOICE DESIGNS. A COMPARISON IN A MODE CHOICE CONTEXT

This paper evaluates gains in efficiency produced by the use of efficient designs to analyze stated choice (SC) data. Based on a standard experiment used in a previous research, we compare the efficiency of this design with that of the efficient design obtained according to the minimization of the D-error, considering different modelling strategies. The experiment was conducted in the context of the choice between the plane and the new high speed train in the route Madrid-Barcelona. As the levels assigned to some attributes in the stated choice exercise were customized to each respondent experience, pivoting the information provided by preliminary revealed preference questions around the reference alternative (the plane, in this case), a different efficient design was created for every respondent in the sample. Results of the analysis demonstrate that substantial gains in the significance level of the parameter estimates could have been attained if the efficient design had been used to analyze SC data.Stated Choice Data, Efficient Designs, Discrete Choice Models