The application of the well-known moment equation approach to neoclassical transport requires the use of Hamada coordinates in three-dimensional toroidal plasmas. The lack of analytical expressions and the difficulty associated with the numerical calculation of these coordinates has strongly limited the use of this approach. In this paper analytical calculations of Hamada coordinates for a large-aspect-ratio tokamak are presented. Knowledge of these coordinates for this relatively simple two-dimensional case will allow, for the first time, a general analytical application of the moment equation approach, and also a check of this approach against well-known results. In particular, it is shown here that the approach correctly reproduces the Pfirsch–Schlüter diffusion rate.
The stability properties of the filament model of Low (1981) are investigated. We use a two-dimensional formalism based on the magnetohydrodynamic energy principle of Bernstein et al. (1958). For the parameter range observed in quiescent prominences this model describes stable horizontal oscillations with periods of about 3-6 min. In other parameter ranges we find instability which is driven exclusively by compressional effects. The Lorentz force has a continuously stabilizing influence. In addition, it seems that gravity is practically unimportant for the stability state of the equilibrium.
Abstract. With the advent of the 2004 transit of Venus, interest in historical observations of past transits has been rekindled. We present evidence suggesting that the Maya of the postclassic period actually observed at least one transit of Venus. The frescoes of Mayapan, which are proposed as a record of 12 th -or 13 th -century transits, are described and discussed in their astronomical context
A finales de los años ochenta y principios de los noventa Carolyn Tate analizó una serie de rituales, descritos en las inscripciones de Yaxchilán, que sucedían al término del mes Yaxkin, el cual corresponde con las fechas cercanas al solsticio de verano en el calendario juliano, y surgió que existió una relación entre estos rituales y el evento solar. Parte de la evidencia textual fue plasmada en los dinteles de la Estructura 33. Además de presentar la evidencia epigráfica e iconográfica, Tate observó que la Estructura 33 fue orientada hacia el punto de salida del sol en el solsticio de verano, de tal modo que la luz del sol saliente iluminaba los cuartos de la estructura incidientdo sobre la estatua de Pájaro Jaguar IV. Las mediociones que hicimos en esta ciudad mostraron la falacia de estas suposiciones y condujeron al rechazo de sus ideas acerca de que el punto de la salida del sol en el solsticio de verano se utilizó en la planificación urbana.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.