The effect of neutrals on the global heliosphere and interplanetary shock propagation time to the heliopause

A two-dimensional time-dependent two-fluid hydrodynamic model has been used to study numerically the effect of interstellar neutrals on the size and structure of the heliosphere. The interstellar neutrals, coupled to the plasma by charge-exchange collisions, lead to a dramatic decrease in the size of the heliosphere -- 30% for the parameters studied. We find that a build up of neutral hydrogen in front of the leading edge of the heliospbere, seen in earlier models, occurs only when the flow in the interstellar medium is supersonic. When the flow is subsonic, no such hydrogen ``wall`` is seen in the simulations, suggesting that the distribution of scattered solar H Ly a light may be quite different for this case. We have also calculated the propagation of an interplanetary shock to the heliopause as a possible trigger for the 1992 Voyager 2--3 kHz radio emission event. We find that the interstellar plasma density, observed emission cut-off frequency, and heliopause location can all b made consistent once the effect of the reduction in the size of the heliosphere by the interaction with the neutrals is included

Solar cycle influence on the interaction of the solar wind with Local Interstellar Cloud

We present results of a new time-dependent kinetic model of the H atom penetration through the solar wind - interstellar medium interaction region. A kinetic 6D (time, two dimensions in space, and three dimensions in velocity-space) equation for interstellar H atoms was solved self-consistently with time-dependent Euler equations for the solar wind and interstellar charged components. We study the response of the interaction region to 11-year solar cycle variations of the solar wind dynamic pressure. It is shown that the termination shock location varies within ±7 AU, the heliopause variation is ~4 AU, and the bow shock variation is negligible. At large heliocentric distances, the solar cycle induces 10-12% fluctuations in the number density of both primary and secondary interstellar H atoms and atoms created in the inner heliosheath. We underline the kinetic behavior of the fluctuations of the H atom populations. Closer to the Sun the fluctuations increase up to 30-35% at 5 AU due to solar cycle variation of the charge exchange rate. Solar cycle variations of interstellar H atoms in the heliospheric interface and within the heliosphere may have major importance for the interpretation of H atom observations inside the heliosphere

Generic programming in POOMA and PETE

POOMA is a C++ framework for developing portable scientific applications for serial and parallel computers using high-level physical abstractions. PETE is the expression template library used by POOMA. This paper discusses generic programming techniques that are used to achieve flexibility and high performance in POOMA and PETE. POOMA uses an engine class that factors the data representation out of its array classes. PETE`s expression templates are used to build up and operate efficiently on expressions. PETE itself uses generic techniques to adapt to a variety of client-class interfaces, and to provide a powerful and flexible compile-time expression-tree traversal mechanism

A Parallel Three-dimensional Electromagnetic Particle-in-Cell Code for Non-Orthogonal Meshes

We describe a new parallel three dimensional electromagnetic particle-in-cell code that uses body fitted curvilinear coordinates for modeling plasma and beam devices. Cells in the structure grid are deformable hexahedra in physical space and are mapped to unit cubes in logical space for particle interpolations. The algorithms conserve particle charge and current, and update the electromagnetic fields in a divergence preserving manner. The code is modular and portable, and we present numerical results of convergence rates and benchmarks on serial, vector and parallel computers for the components separately and together. 1 Introduction An electromagnetic particle-in-cell (EMPIC) code seeks to simulate a plasma or charged particle beam through a direct simulation of the evolution of the electromagnetic fields and the charged particle positions and velocities. The overall accuracy of the code depends on (1) how well it models the geometry of the problem, (2) the algorithms it uses to upda..

Compressed fields in the POOMA framework: Design, implementation, and performance

The POOMA framework is a C++ class library for doing large scale parallel computations. POOMA`s Field class implements a multidimensional data parallel array annotated with mesh coordinate information. The Field class breaks up the whole domain into sub-blocks and transparently compresses constant blocks down to a single value to improve the memory and computational efficiency. This allows the user to simply and efficiently simulate phenomena that are taking place in a small fraction of the domain. We examine the cache and computational benefits associated with this capability. The algorithm implementation is based on the fact that if we have a large constant region in the field we only need to store one value for that region. In this paper we will describe the design of compressed fields, their implementation in the POOMA framework, and the performance of this technique on an Silicon Graphics Inc. Origin 2000

Optimising Shared Reduction Variables in MPI Programs

CFL (Communication Fusion Library) is an experimental C++ library which supports shared reduction variables in MPI programs

SMARTS: Exploiting Temporal Locality and Parallelism through Vertical Execution

In the solution of large-scale numerical prob- lems, parallel computing is becoming simultaneously more important and more difficult. The complex organization of today's multiprocessors with several memory hierarchies has forced the scientific programmer to make a choice between simple but unscalable code and scalable but extremely com- plex code that does not port to other architectures. This paper describes how the SMARTS runtime system and the POOMA C++ class library for high-performance scientific computing work together to exploit data parallelism in scientific applications while hiding the details of manag- ing parallelism and data locality from the user. We present innovative algorithms, based on the macro -dataflow model, for detecting data parallelism and efficiently executing data- parallel statements on shared-memory multiprocessors. We also desclibe how these algorithms can be implemented on clusters of SMPS