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A new probabilistic model aiming to cover all aspects of the solar energetic particle (SEP) environment required for mission specifications is presented; the solar accumulated and peak proton and heavy ion radiation environment model. This model includes an updated reference data set upon which the analysis is based, a thorough evaluation of fitting procedures for SEP fluxes, a probabilistic helium model not based on proton fluxes, an extension to heavier ions based on new analysis of the Advanced Composition Explorer/solar isotope spectrometer data set, and a careful extrapolation of all output spectra to cover energies from 0.1 MeV/nuc to 1 GeV/nuc. Also included in this paper are derivations of spectra for rare solar particle events, which would occur at a given mean frequency and a new description for implementing the model to make it accessible to the public through systems, such as SPace ENVironment Information System or OMERE.

The Solar Accumulated and Peak Proton and Heavy Ion Radiation Environment (SAPPHIRE) model provides environment specification outputs for all aspects of the Solar Energetic Particle (SEP) environment. The model is based upon a thoroughly cleaned and carefully processed data set. Herein the evolution of the solar proton model is discussed with comparisons to other models and data. This paper discusses the construction of the underlying data set, the modelling methodology, optimisation of fitted flux distributions and extrapolation of model outputs to cover a range of proton energies from 0.1 MeV to 1 GeV. The model provides outputs in terms of mission cumulative fluence, maximum event fluence and peak flux for both solar maximum and solar minimum periods. A new method for describing maximum event fluence and peak flux outputs in terms of 1-in-x-year SPEs is also described. SAPPHIRE proton model outputs are compared with previous models including CREME96, ESP-PSYCHIC and the JPL model. Low energy outputs are compared to SEP data from ACE/EPAM whilst high energy outputs are compared to a new model based on GLEs detected by Neutron Monitors (NMs)., 37 pages, 17 figures

The physical processes affecting the dynamics of the Earth’s particle radiation environment are reviewed along with scientific and engineering models developed for its description. The emphasis is on models that are either operational engineering models or models presently under development for this purpose. Three components of the radiation environment, i.e., galactic cosmic rays (GCRs), solar energetic particles (SEPs) and trapped radiation, are considered separately. In the case of SEP models, we make a distinction between statistical flux/fluence models and those aimed at forecasting events. Models of the effects of particle radiation on the atmosphere are also reviewed. Further, we summarize the main features of the models and discuss the main outstanding issues concerning the models and their possible use in operational space weather forecasting. We emphasize the need for continuing the development of physics-based models of the Earth’s particle radiation environment, and their validation with observational data, until the models are ready to be used for nowcasting and/or forecasting the dynamics of the environment.

We present here a set of tools for space applications based on the Geant4 simulation toolkit, developed for radiation shielding analysis as part of the European Space Agency (ESA) activities in the Geant4 collaboration. The Sector Shielding Analysis Tool (SSAT) and the Materials and Geometry Association (MGA) utility will first be described. An overview of the main features of the MUlti-LAyered Shielding SImulation Software tool (MULASSIS) will follow. The tool is specifically addressed to shielding optimization and effects analysis. A Java interface allows the use of MULASSIS by the space community over the World Wide Web, integrated in the widely used SPENVIS package. The analysis of the particle transport output provides automatically radiation fluence, ionising and NIEL dose and effects analysis. ESA is currently funding the porting of this tools to a low-cost parallel processor facility using the GRID technology under the ESA SpaceGRID initiative. Other Geant4 present and future projects will be presented related to the study of space environment effects on spacecrafts.

The Giotto Spacecraft executed an Earth-Gravity-Assist manoeuvre on 2–3 July 1990 and two onboard scientific instruments, namely the energetic particle analyser (EPONA) and the magnetometer (MAG), were set into operation during the associated (33h) encounter. Contemporaneous data show that the magnetosphere was relatively undisturbed during this Earth Swingby so that the signatures recorded by EPONA effectively provide a “snapshot” of the quiet magnetosphere in energetic particles along a unique, hyperbolic, high-inclination orbit. Protons in the range ∼30– 200 keV recorded in the region upstream of the bow shock are interpreted to have been accelerated, via the diffuse shock acceleration mechanism, at the (inbound) quasi-parallel bow shock. The temporal profiles of those proton and electron fluxes recorded near closest approach, where Giotto traversed part of the outer radiation belt, are compared with profiles generated using NASA's AP-8 MIN and AE-8 MIN programs to model particle fluxes along this segment of the trajectory. Characteristic features of the measured energetic proton and (MeV) electron fluxes are, thereby, shown to match the modelled signatures of trapped radiation in the (outer) Belt. The EPONA data provide no evidence of a midnight cusp source of energetic particles. Outbound, where magnetic records show that “flapping” of the magnetopause boundary was a feature, variations in the particle record reflect spacecraft traversals back and forth from the magnetosphere to the magnetosheath. It is inferred that proton fluxes in the range >200 keV identified between both the inbound and the outbound magnetopause and the bow shock comprise a sheath of (Fermi) accelerated protons enveloping the magnetosphere. The transit time damping mechanism is suggested to have contributed to producing the rather high fluxes (relative to the inbound pass) of energetic particles recorded downstream of the bow shock.

High-energy charged particles in the van Allen radiation belts and in solar energetic particle events can damage satellites on orbit leading to malfunctions and loss of satellite service. Here we describe some recent results from the SPACECAST project on modelling and forecasting the radiation belts, and modelling solar energetic particle events. We describe the SPACECAST forecasting system that uses physical models that include wave-particle interactions to forecast the electron radiation belts up to 3 h ahead. We show that the forecasts were able to reproduce the >2 MeV electron flux at GOES 13 during the moderate storm of 7-8 October 2012, and the period following a fast solar wind stream on 25-26 October 2012 to within a factor of 5 or so. At lower energies of 10 - a few 100 keV we show that the electron flux at geostationary orbit depends sensitively on the high-energy tail of the source distribution near 10 R E on the nightside of the Earth, and that the source is best represented by a kappa distribution. We present a new model of whistler mode chorus determined from multiple satellite measurements which shows that the effects of wave-particle interactions beyond geostationary orbit are likely to be very significant. We also present radial diffusion coefficients calculated from satellite data at geostationary orbit which vary with K p by over four orders of magnitude. We describe a new automated method to determine the position at the shock that is magnetically connected to the Earth for modelling solar energetic particle events and which takes into account entropy, and predict the form of the mean free path in the foreshock, and particle injection efficiency at the shock from analytical theory which can be tested in simulations. © R.B. Horne et al., Published by EDP Sciences 2013. ispartof: Journal of Space Weather and Space Climate vol:3 status: published

SEPServer is a three-year collaborative project funded by the seventh framework programme (FP7-SPACE) of the European Union. The objective of the project is to provide access to state-of-the-art observations and analysis tools for the scientific community on solar energetic particle (SEP) events and related electromagnetic (EM) emissions. The project will eventually lead to better understanding of the particle acceleration and transport processes at the Sun and in the inner heliosphere. These processes lead to SEP events that form one of the key elements of space weather. In this paper we present the first results from the systematic analysis work performed on the following datasets: SOHO/ERNE, SOHO/EPHIN, ACE/EPAM, Wind/WAVES and GOES X-rays. A catalogue of SEP events at 1 AU, with complete coverage over solar cycle 23, based on high-energy (~68-MeV) protons from SOHO/ERNE and electron recordings of the events by SOHO/EPHIN and ACE/EPAM are presented. A total of 115 energetic particle events have been identified and analysed using velocity dispersion analysis (VDA) for protons and time-shifting analysis (TSA) for electrons and protons in order to infer the SEP release times at the Sun. EM observations during the times of the SEP event onset have been gathered and compared to the release time estimates of particles. Data from those events that occurred during the European day-time, i.e., those that also have observations from ground-based observatories included in SEPServer, are listed and a preliminary analysis of their associations is presented. We find that VDA results for protons can be a useful tool for the analysis of proton release times, but if the derived proton path length is out of a range of 1 AU

References 1 Moore, F. G., Hymer, T. C, and Mclnville, R. M., "Improved Aeroprediction Code: Part I—Summary of New Methods and Comparison with Experiment," Naval Surface Warfare Center Dahlgren Division, NSWCDD/TR93/91, Dahlgren, VA, May 1993. Moore, F. G., Mclnville, R. M., and Hymer, T. C., "Improved Aeroprediction Code: Part II—Computer Program User's Guide and Listing," Naval Surface Warfare Center Dahlgren Division, NSWCDD/TR-93/241, Dahlgren, VA, Aug. 1993. Moore, F. G., Hymer, T. C., and Mclnville, R. M., "A Planar Nonlinear Missile Aeroprediction Code for all Mach Numbers," AIAA Paper 94-0026, Jan. 1994. Fidler, J. E., and Bateman, M. C., "Aerodynamic Methods for High Incidence Missile Design," Journal of Spacecraft and Rockets, Vol. 12, No. 3, 1975, pp. 162-168. Moore, F. G., and Mclnville, R. M., "A New Method for Calculating WingAlone Aerodynamics to Angle of Attack 180 deg," Naval Surface Warfare Center Dahlgren Division, NSWCDD/TR-94/3, Dahlgren, VA, March 1994. Stallings, R. L., Jr., and Lamb, M., "Wing-Alone Aerodynamic Characteristics for High Angles of Attack at Supersonic Speeds," NASA Technical Paper 1889, July 1981. Baker, W. B., Jr., "Static Aerodynamic Characteristics of a Series of Generalized Slender Bodies with and without Fins at Mach Numbers from 0.6 to 3.0 and Angles of Attack from 0 to 180 deg," Arnold Engineering Development Center, TR-75-124, Vols. I and II, Tullahoma, TN, May 1976. Nielsen, J. N., Hemsch, M. J., and Smith, C. A., "A Preliminary Method for Calculating the Aerodynamic Characteristics of Cruciform Missiles to High Angles of Attack Including Effects of Roll Angle and Control Deflections," Office of Naval Research, Report ONR-CR215-216,4F, Arlington, VA, Nov. 1977.

[1] We investigate the pitch angle distributions of 0.15-1.58 MeV electrons observed during the 9-15 October 1990 storm measured by the Combined Release and Radiation Effects Satellite (CRRES) spacecraft. This storm period is characterized by an enhancement in the electron flux at L approximate to 4 by more than an order of magnitude over the prestorm level. The overall change in flux at L approximate to 6.6 is small in comparison. Previous work shows that radial diffusion underestimates the flux enhancement by up to a factor of 5 for L less than or equal to 4.5 [Brautigam and Albert, 2000], indicating the need for an additional acceleration process. The pitch angle distributions presented here are examined for evidence of the acceleration mechanism. The distributions at L approximate to 2 are rounded and are dominated by Coulomb collisions. They show little variation during the storm. The distributions at L approximate to 3 are pancake-shaped before the storm, characteristic of pitch angle scattering by plasmaspheric hiss. During the main phase, they become broad and flat, and they evolve back into pancake distributions during the recovery phase. At L approximate to 4-6, the pitch angle distributions are characterized as butterfly distributions at storm onset, and they become broad flat top distributions during the recovery phase. The flat top distributions persist throughout the similar to3-day recovery phase and are observed in the region of highest flux enhancement. The flat top distributions are energy dependent and are broader at lower energies (30degrees-150degrees) than at higher energies (50degrees-130degrees). The higher energies exhibit a much faster fall off toward the loss cone than at lower energies. Inward radial diffusion should result in anisotropic distributions peaked near 90degrees and does not explain the observed energy dependence. Furthermore, the direction of diffusion is outward at higher energies. Model calculations of the pitch angles resonant with whistler mode waves show that flat top distributions are consistent with pitch angle and energy scattering in regions where f(pe)/f(ce)similar to1. Although radial diffusion may be very important for particle energization, the observed pitch angle distributions provide strong evidence that wave particle interactions play an important role in the energization process.

[1] We present plasma wave and particle data from the CRRES satellite during three case studies to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by resonant interactions with whistler mode chorus. We first consider a strong geomagnetic storm that contains prolonged substorm activity during its 3-day recovery phase. The recovery phase is characterized by electron injections at subrelativistic energies, enhanced whistler mode chorus amplitudes, and a gradual increase in the flux of relativistic electrons (E > 1 MeV) over the entire outer zone, with fluxes exceeding the prestorm level by an order of magnitude in the region 3.5 < L < 4.5. We next consider a strong geomagnetic storm that contains very little substorm activity during its 3-day recovery phase. Here the recovery phase is characterized by a lack of sustained electron injections at subrelativistic energies, a low level of chorus amplitudes, and a net reduction in the flux of relativistic electrons in the outer zone. Finally, we examine a period of prolonged substorm activity in the absence of a significant storm signature, as measured by Dst. This period is characterized by electron injections at subrelativistic energies, enhanced chorus amplitudes, and a gradual increase in the flux of relativistic electrons in the region 4 < L < 6.5. These results suggest that the gradual acceleration of electrons to relativistic energies seen on a timescale of days during geomagnetic storms can be effective only when there are periods of prolonged substorm activity following the main phase of the geomagnetic storm. Furthermore, gradual electron acceleration to relativistic energies can be obtained during periods of prolonged substorm activity in the absence of a significant storm signature as indicated by Dst. The case studies show that the acceleration mechanism is confined to the region outside of the plasmapause and occurs in the presence of enhanced chorus waves. These results suggest that a local acceleration mechanism involving the energization of a seed population of electrons with energies of the order of a few hundred keV to relativistic energies by wave-particle interactions involving whistler mode chorus contributes to the reformation of the relativistic outer zone population following prolonged substorm activity.

The widely used coordinate system (B,L) has proved very suitable for most of the region covered by the Van Allen belts, but is not very well suited for the low‐altitude regions where the Earth’s atmosphere interacts with the trapped particle population. Several alternative coordinate systems have been proposed that aim to take into account the steep flux gradients in the region of the upper atmosphere. An overview of these coordinates is presented. The effectiveness of each system is assessed by mapping the proton flux distribution of NASA’s AP‐8 model. Special attention is given to Hassitt’s weighted average of the atmospheric density over the drift shells of trapped particles, which appears very efficient in mapping fluxes for low L values.

[1] Relativistic (> 1 MeV) 'killer electrons' are frequently generated in the Earth's inner magnetosphere during the recovery phase of a typical magnetic storm. We test the hypothesis that the energization of electrons takes place by means of stochastic gyroresonant interaction between lower-energy (several 100 keV) seed electrons and whistler-mode chorus waves. We develop a model kinetic equation for the electron energy distribution, and utilize both electron and whistler-mode wave data at L=4 for a typical geomagnetic storm (on October 9, 1990) from instruments carried on the Combined Release and Radiation Effects Satellite (CRRES). Our model solutions are found to match well with the CRRES profiles of the electron flux. We conclude that the mechanism of stochastic acceleration by whistler-mode turbulence is a viable candidate for generating killer electrons, not only for the storm considered, but for similar storms with a several-day recovery phase containing prolonged substorm activity.

Radiation shielding analysis is a crucial process in the spacecraft and space instrument development cycle. A number of dedicated tools have been developed in the last decades for the study of the effects of radiation on materials and instruments in space. We present here a set of detailed analyses based on Monte Carlo radiation transport simulations, and new tools for space applications, both based on the Geant4 simulation toolkit, developed as part of the European Space Agency (ESA) activities in the Geant4 collaboration. Finally we present some activities initiated by ESA for the creation of a Geant4 space users' community.