Interpretation of Helioseismic Travel Times - Sensitivity to Sound Speed, Pressure, Density, and Flows

Time-distance helioseismology uses cross-covariances of wave motions on the solar surface to determine the travel times of wave packets moving from one surface location to another. We review the methodology to interpret travel-time measurements in terms of small, localized perturbations to a horizontally homogeneous reference solar model. Using the first Born approximation, we derive and compute 3D travel-time sensitivity (Fr\'echet) kernels for perturbations in sound-speed, density, pressure, and vector flows. While kernels for sound speed and flows had been computed previously, here we extend the calculation to kernels for density and pressure, hence providing a complete description of the effects of solar dynamics and structure on travel times. We treat three thermodynamic quantities as independent and do not assume hydrostatic equilibrium. We present a convenient approach to computing damped Green's functions using a normal-mode summation. The Green's function must be computed on a wavenumber grid that has sufficient resolution to resolve the longest lived modes. The typical kernel calculations used in this paper are computer intensive and require on the order of 600 CPU hours per kernel. Kernels are validated by computing the travel-time perturbation that results from horizontally-invariant perturbations using two independent approaches. At fixed sound-speed, the density and pressure kernels are approximately related through a negative multiplicative factor, therefore implying that perturbations in density and pressure are difficult to disentangle. Mean travel-times are not only sensitive to sound-speed, density and pressure perturbations, but also to flows, especially vertical flows. Accurate sensitivity kernels are needed to interpret complex flow patterns such as convection

Modes of Authority and Social Character Research

The relationship between prevailing patterns of authority and social character formation teas once a major topic for theory' and research, but has fallen into relatioe neglect of late. This paper elucidates Fromm's three modes of authority, their psychoanalytic and sociological antecedents, their intrinsic strengths and limitations. and their possible application to contemporary sociological issues

German Science Center for the Solar Dynamics Observatory

A data and computation center for helioseismology has been set up at the Max Planck Institute for Solar System Research in Germany to prepare for the SDO mission. Here we present the system infrastructure and the scientific aims of this project, which is funded through grants from the German Aerospace Center and the European Research Council

Application of a salinity-gradient solar pond in a salt affected area of Victoria

This research looks into salt affected areas and energy issues, and how the problems associated with development and intensive agriculture, which include rising water tables and salinity, may be reduced in the future

Realizing the Potential of Mobile Phone Technology for Language Learning

This paper focuses on the exploitation of mobile phone technology for thelearning of foreign languages. It begins by considering the obstaclesfacing the effective use of mobile phone technology for language learning.In doing so, the paper describes four challenges that have to be overcomefor mobile phone technology to become an effective pedagogical tool.Specifically: Intrusiveness, Cost, Practical technological constraints andPedagogical methodologies. Having defined the issues that need to beaddressed, the paper then proceeds to describe how these challenges havebeen met in the design of MobLang, an EU funded Lifelong Learningproject