8/11/20063 rd SPENVIS USERS WORKSHOP The Solar Energetic Particle Environment : How to Transition from Science to International Standard Models Stephen B Gabriel Professor of Aeronautics and Astronautics University of Southampton England

8/11/20063 rd SPENVIS USERS WORKSHOP Outline Background Problems Process-based Standard Current State of Knowledge Some possible ways forward Conclusions

8/11/20063 rd SPENVIS USERS WORKSHOP Intermittency: Bursty or Spiky Behaviour

8/11/20063 rd SPENVIS USERS WORKSHOP “Bastille Day Event” (July 14 th 2000) Sampling: 5 minutes

8/11/20063 rd SPENVIS USERS WORKSHOP What does standard mean Oxford Concise English Dictionary: ‘Something used as a measure, norm or model in comparative evaluations’ In context of International Standards Organisation(ISO)( or ECSS), a standard can be described as: ‘A reference framework, or a common technological language, between suppliers and their customers which facilitates trade and the transfer of technology’ 1 ‘Compliance with an International Standard means compliance with a set of requirements that will facilitate the exchange of data or products among diverse communities’ 1 1 ‘Status of ISO Draft International Standard for Determining Solar Irradiances (DIS 21348), W. Kent Tobiska and Anatoliy A. Nusinov

8/11/20063 rd SPENVIS USERS WORKSHOP Difficulties with arriving at a standard for SEPE environment Several different models available within engineering community ( eg JPL 91, Xapsos, Nymmik models) Nymmik model was proposed as the ISO standard but no concensus could be reached by international experts as to its scientific correctness Poor understanding of the basic physics involved in solar energetic particle events

8/11/20063 rd SPENVIS USERS WORKSHOP Concept of a Process based standard Standardises the process for determining the space environment in question –No specific product is selected as a standard – enables suppliers and users of products to exchange information with a common understandable language

8/11/20063 rd SPENVIS USERS WORKSHOP Example of a process based standard : Solar Irradiances Different product types: Type 1- measurement set Type 2 - reference spectrum Type 3 - empirical model Type 4 - theoretical or first-principles model Type 5 - surrogate or proxy Compliance Criteria : –Reporting, documenting, publishing, and archiving

8/11/20063 rd SPENVIS USERS WORKSHOP Example of a process based standard : Solar Irradiances(cont) Reporting : Use SI units, supply conversion factors to other appropriate conventional units, state whether corrected to 1 AU, spectral sampling and resolution given if applicable Documenting : –Method of determining solar irradiances should include as appropriate : –Data collection, retrieval, processing, calibration, validation, verification, accuracy and precision methodology and/or algorithms as well as archiving information Publishing: in an internationally-accessible journal which uses scientific or discipline-area peer review

8/11/20063 rd SPENVIS USERS WORKSHOP Brief review of what we know about SEPEs Observations(data): –Spacecraft : Helios 1 and 2, Ulysses, SOHO, ACE, GOES and IMP( Russian data eg Meteor) –Ground based: neutron monitors ( proxy) –Historical: ice-cap, radionuclides in meteorites and lunar samples Theory : –No comprehensive theory exists –Current view: Particle acceleration is caused by coronal mass ejection (CME) driven shocks in the corona and interplanetary medium

8/11/20063 rd SPENVIS USERS WORKSHOP Modelling approaches Statistical Physical Data Driven Computational Combination

8/11/20063 rd SPENVIS USERS WORKSHOP Combined modelling: Radial heliocentric scaling Almost no data at radial distances other than 1 AU Use shock+particle model ( SOLPENCO + MHD shock model) to generate virtual or simulated events ( physics + computational) Generate statistical model ( as at 1AU) by running code for a variety of input conditions at a range of heliocentric distances and gives semi- empirical radial scaling model: –Validate using 1 AU statistical model and spacecraft data( even though very sparse) at 1AU –Compare with physical based models where possible

8/11/20063 rd SPENVIS USERS WORKSHOP Possible Methodology for the development of SEPE Standards Space instruments Ground based observations Historical data Raw Data Statistical models Processed Data Sets Standard? Standard Data Driven models Physical modelling Computational modelling Standard/ s?

8/11/20063 rd SPENVIS USERS WORKSHOP Standard Solar Energetic Particle Environment Products Standardised Data Sets using standard processing techniques Standardised process to develop statistical models from standardised data sets? Others(?): –Standard radial scaling for flux and fluence –Standard for solar cycle variations –Standard abundance ratios ( for heavy ions) –Standard technique for scaling to higher(lower) energies

8/11/20063 rd SPENVIS USERS WORKSHOP Conclusions Agreement on a ‘standard’ model for the solar energetic particle environment is problematic due to –Poor understanding of the physics –Lack of data Use of a process based standard may help but ultimately more solar observations, spacecraft data and physical insight will be needed In the meantime combining statistical models with physical/computational modelling seems to be the best approach but standard validation/verification methodologies will need to be developed