19 research outputs found
The consequences of a nearby supernova on the early Solar System
If the Sun was born in a relatively compact open cluster, it is quite likely
that a massive (10MSun) star was nearby when it exploded in a supernova. The
repercussions of a supernova can be rather profound, and the current Solar
System may still bear the memory of this traumatic event. The truncation of the
Kuiper belt and the tilt of the ecliptic plane with respect to the Sun's
rotation axis could be such signatures. We simulated the effect of a nearby
supernova on the young Solar System using the Astronomical Multipurpose
Software Environment. Our calculations are realized in two subsequent steps in
which we study the effect of the supernova irradiation on the circumstellar
disk and the effect of the impact of the nuclear blast-wave which arrives a few
decades later. We find that the blastwave of our adopted supernova exploding at
a distance of --\,pc and at an angle of -- with
respect to the angular-momentum axis of the circumsolar disk would induce a
misalignment between the Sun's equator and its disk to ,
consistent with the current value. The blast of a supernova truncates the disk
at a radius between and \,au, which is consistent with the current
edge of the Kuiper belt. For the most favored parameters, the irradiation by
the supernova as well as the blast wave heat the majority of the disk to \,K, which is sufficiently hot to melt chondrules in the circumstellar
disk. The majority of planetary system may have been affected by a nearby
supernova, some of its repercussions, such as truncation and tilting of the
disk, may still be visible in their current planetary system's topology. The
amount of material from the supernova blast wave that is accreted by the
circumstellar disk is too small by several orders of magnitude to explain the
current abundance of the short live radionuclide Al.Comment: Accepted for publication in A&
Non-intrusive hierarchical coupling strategies for multi-scale simulations in gravitational dynamics
Hierarchical code coupling strategies make it possible to combine the results
of individual numerical solvers into a self-consistent symplectic solution. We
explore the possibility of allowing such a coupling strategy to be
non-intrusive. In that case, the underlying numerical implementation is not
affected by the coupling itself, but its functionality is carried over in the
interface. This method is efficient for solving the equations of motion for a
self-gravitating system over a wide range of scales. We adopt a dedicated
integrator for solving each particular part of the problem and combine the
results to a self-consistent solution. In particular, we explore the
possibilities of combining the evolution of one or more microscopic systems
that are embedded in a macroscopic system. The here presented generalizations
of Bridge include higher-order coupling strategies (from the classic 2nd order
up to 10th-order), but we also demonstrate how multiple bridges can be nested
and how additional processes can be introduced at the bridge time-step to
enrich the physics, for example by incorporating dissipative processes. Such
augmentation allows for including additional processes in a classic Newtonian
N-body integrator without alterations to the underlying code. These additional
processes include for example the Yarkovsky effect, dynamical friction or
relativistic dynamics. Some of these processes operate on all particles whereas
others apply only to a subset.
The presented method is non-intrusive in the sense that the underlying
methods remain operational without changes to the code (apart from adding the
get- and set-functions to enable the bridge operator). As a result, the
fundamental integrators continue to operate with their internal time step and
preserve their local optimizations and parallelism.
... abridged ...Comment: Accepted for publication in Communications in Nonlinear Science and
Numerical Simulation (CNSNS) The associated software is part of the AMUSE
framework and can be downloaded from http:www.amusecode.or
Fast in-database cross-matching of high-cadence, high-density source lists with an up-to-date sky model
Coming high-cadence wide-field optical telescopes will image hundreds of thousands of sources per minute. Besides inspecting the near real-time data streams for transient and variability events, the accumulated data archive is a wealthy laboratory for making complementary scientific discoveries. The goal of this work is to optimise column-oriented database techniques to enable the construction of a full-source and light-curve database for large-scale surveys, that is accessible by the astronomical community. We adopted LOFAR's Transients Pipeline as the baseline and modified it to enable the processing of optical images that have much higher source densities. The pipeline adds new source lists to the archive database, while cross-matching them with the known cataloguedsources in order to build a full light-curve archive. We investigated several techniques of indexing and partitioning the largest tables, allowing for faster positional source look-ups in the cross matching algorithms. We monitored all query run times in long-term pipeline runs where we processed a subset of IPHAS data that have image source density peaks over 170,000 per field of view (500,000 deg−2). Our analysis demonstrates that horizontal table partitions of declination widths of one-degree control the query run times. Usage of an index strategy where the partitions are densely sorted according to source declination yields ano
The Oceanographic Multipurpose Software Environment (OMUSE v1.0)
In this paper we present the Oceanographic Multipurpose Software Environment (OMUSE). OMUSE aims to provide a homogeneous environment for existing or newly developed numerical ocean simulation codes, simplifying their use and deployment. In this way, numerical experiments that combine ocean models representing different physics or spanning different ranges of physical scales can be easily designed. Rapid development of simulation models is made possible through the creation of simple high-level scripts. The low-level core of the abstraction in OMUSE is designed to deploy these simulations efficiently on heterogeneous high-performance computing resources. Cross-verification of simulation models with different codes and numerical methods is facilitated by the unified interface that OMUSE provides. Reproducibility in numerical experiments is fostered by allowing complex numerical experiments to be expressed in portable scripts that conform to a common OMUSE interface. Here, we present the design of OMUSE as well as the modules and model components currently included, which range from a simple conceptual quasi-geostrophic solver to the global circulation model POP (Parallel Ocean Program). The uniform access to the codes' simulation state and the extensive automation of data transfer and conversion operations aids the implementation of model couplings. We discuss the types of couplings that can be implemented using OMUSE. We also present example applications that demonstrate the straightforward model initialization and the concurrent use of data analysis tools on a running model. We give examples of multiscale and multiphysics simulations by embedding a regional ocean model into a global ocean model and by coupling a surface wave propagation model with a coastal circulation model
Creating a reusable cross-disciplinary multi-scale and multi-physics framework: From AMUSE to OMUSE and beyond
Here, we describe our efforts to create a multi-scale and multi-physics framework that can be retargeted across different disciplines. Currently we have implemented our approach in the astrophysical domain, for which we developed AMUSE (github.com/amusecode/amuse ), and generalized this to the oceanographic and climate sciences, which led to the development of OMUSE (bitbucket.org/omuse ). The objective of this paper is to document the design choices that led to the successful implementation of these frameworks as well as the future challenges in applying this approach to other domains