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With new satellite constellations being launched into low Earth orbit, the growing use of medium Earth orbit for radio-navigation and timing signals, slot region orbits for telecommunications and the introduction of electric propulsion to reach geostationary orbit, there is a growing need to develop services to protect satellites from space weather. Here we highlight two recent events in relation to satellite operations. We summarise ten user needs that arose out of meetings with satellite operators, designers, underwriters and space agency staff. We present the satellite risk prediction and radiation forecast (SaRIF) system which is designed to meet most of these needs. The system uses real-time data as input to the BAS radiation belt model (BAS-RBM) to solve the Fokker Planck equation and provides a forecast of the electron flux throughout the outer radiation belt with 1-hour resolution up to 24 hours ahead. The electron flux is used to calculate charging currents, and is combined with GOES near real time proton fluxes to calculate dose rate and total ionizing dose behind set levels of shielding for satellites in Medium Earth orbit, Geostationary orbit and slot region orbits. The results are compared against design standards and presented as risk indicators to forecast the risk of damage. The system works automatically and is updated every hour. We also present data and a best reconstruction of the radiation environment which are held in a searchable archive for satellite anomaly resolution. The SaRIF system is available via the European Space Agency space weather web portal.

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.

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

[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.

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.