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A workflow-oriented approach to Propagation Models in Heliophysics

Pierantoni G., Carley E., Byrne J., Perez-Suarez D., Gallagher P. T.

Computer Science

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2014

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Vol. 15 (3)

271--291

EN

The Sun is responsible for the eruption of billions of tons of plasma and the generation of near light-speed particles that propagate throughout the solar system and beyond. If directed towards Earth, these events can be damaging to our tecnological infrastructure. Hence there is an effort to understand the cause of the eruptive events and how they propagate from Sun to Earth. However, the physics governing their propagation is not well understood, so there is a need to develop a theoretical description of their propagation, known as a Propagation Model, in order to predict when they may impact Earth. It is often difficult to define a single propagation model that correctly describes the physics of solar eruptive events, and even more difficult to implement models capable of catering for all these complexities and to validate them using real observational data. In this paper, we envisage that workflows offer both a theoretical and practical framework for a novel approach to propagation models. We define a mathematical framework that aims at encompassing the different modalities with which workflows can be used, and provide a set of generic building blocks written in the TAVERNA workflow language that users can use to build their own propagation models. Finally we test both the theoretical model and the composite building blocks of the workflow with a real Science Use Case that was discussed during the 4th CDAW (Coordinated Data Analysis Workshop) event held by the HELIO project. We show that generic workflow building blocks can be used to construct a propagation model that succesfully describes the transit of solar eruptive events toward Earth and predict a correct Earth-impact time.

2

Extending the sheba propagatio model to reduce parameter-related uncertainties

Pierantoni G., Coghlan B., Kenny E., Gallagher P., Perez-Suarez D.

Computer Science

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2013

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Vol. 14 (2)

253--272

EN

Heliophysics is the branch of physics that investigates the interactions and correlation of different events across the Solar System. The mathematical models that describe and predict how physical events move across the solar system (ie. Propagation Models ) are of great relevance. These models depend on parameters that users must set, hence the ability to correctly set the values is key to reliable simulations. Traditionally, parameter values can be inferred from data either at the source (the Sun) or arrival point (the target) or can be extrapolated from common knowledge of the event under investigation. Another way of setting parameters for Propagation Models is proposed here: instead of guessing a priori parameters from scientific data or common knowledge, the model is executed as a parameter-sweep job and selects a posteriori the parameters that yield results most compatible with the event data. In either case ( a priori and a posteriori ), the correct use of Propagation Models requires information to either select the parameters, validate the results, or both. In order to do so, it is necessary to access sources of information. For this task, the HELIO project proves very effective as it offers the most comprehensive integrated information system in this domain and provides access and coordination to services to mine and analyze data. HELIO also provides a Propagation Model called SHEBA, the extension of which is currently being developed within the SCI-BUS project (a coordinated effort for the development of a framework capable of offering to science gateways seamless access to major computing and data infrastructures).

3

The use of standards in HELIO

Pierantoni G., Coghlan B., Kenny E.

Computer Science

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2012

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Vol. 13 (2)

93-102

EN

HELIO [8] is a project funded under the FP7 program for the discovery and analysis of data for heliophysics. During its development, standards and common frameworks were adopted in three main areas of the project: query services, processing services, and the security infrastructure. After a first, proprietary implementation of the security service, it was suggested moving it to a standard security framework to simplify the enforcement of security on the different sites. As the HELIO front end is built with Spring and the TAVERNA server (HELIO workflow engine) has a security framework compatible with Spring, it has been decided to move the CIS in Spring security [2]. HELIO has two different processing services: one is a generic processing service called HELIO Processing Services (HPS), the other is called Context Service (CTX) and it runs specific IDL procedures. The CTX implements the UWS [4] interface from the IVOA [5], a standard interface for job submission used in the helio and astrophysics community. In its final release, the HPS will expose an UWS compliant interface. Finally, some of the HELIO services perform queries, to simplify the implementation and usage of this services a single query interface (the HELIO Query Interface) has been designed for all these services. The use of these solutions for security, execution, and query allows for easier implementation of the original HELIO architecture and for a simpler deployment of the services.