RADECS Short Course Session I: The Space Radiation Environment

The presented slides and accompanying paper focus on radiation in the space environment. Since space exploration has begun it has become evident that the space environment is a highly aggressive medium. Beyond the natural protection provided by the Earth's atmosphere, various types of radiation can be encountered. Their characteristics (energy and nature), origins and distributions in space are extremely variable. This environment degrades electronic systems and on-board equipment in particular and creates radiobiological hazards during manned space flights. Based on several years of space exploration, a detailed analysis of the problems on satellites shows that the part due to the space environment is not negligible. It appears that the malfunctions are due to problems linked to the space environment, electronic problems, design problems, quality problems, other issues, and unexplained reasons. The space environment is largely responsible for about 20% of the anomalies occurring on satellites and a better knowledge of that environment could only increase the average lifetime of space vehicles. This naturally leads to a detailed study of the space environment and of the effects that it induces on space vehicles and astronauts. Sources of radiation in the space environment are discussed here and include the solar activity cycle, galactic cosmic rays, solar particle events, and Earth radiation belts. Future challenges for space radiation environment models are briefly addressed

The Space Radiation Environment

The effects of the space radiation environment on spacecraft systems and instruments are significant design considerations for space missions. Astronaut exposure is a serious concern for manned missions. In order to meet these challenges and have reliable, cost-effective designs, the radiation environment must be understood and accurately modeled. The nature of the environment varies greatly between low earth orbits, higher earth orbits and interplanetary space. There are both short-term and long-term variations with the phase of the solar cycle. In this paper we concentrate mainly on charged particle radiations. Descriptions of the radiation belts and particles of solar and cosmic origin are reviewed. An overview of the traditional models is presented accompanied by their application areas and limitations. This is followed by discussion of some recent model developments

Impact of the Earth’s magnetic field secular drift on the low altitude proton radiation belt from years 1900 to 2050

International audienceThe effects of the space radiation environment on spacecraft systems and instruments are significant design considerations for space missions. In order to meet these challenges and have reliable, cost-effective designs, the radiation environment must be understood and accurately modeled. The low altitude proton environment varies slowly in time due to the secular drift of the Earth’s main magnetic field and due to the evolution of the solar cycle. The purpose of this paper is to extend the OPAL model [1] capabilities by introducing a prediction of the Earth’s main magnetic field model up to year 2050. Impact on low altitude spacecraft radiation specification for next space missions is then assessed

Three-dimensional test simulations of the outer radiation belt electron dynamics including electron-chorus resonant interactions

We present results from our three-dimensional (3-D) simulations using the Salammbô electron radiation belt physical model. We have run steady state and dynamic storm test case simulations to study the effect of electron-chorus resonant interactions on the radiation belt electron dynamics. When electron-chorus interactions are introduced in the code outside the plasmasphere, results show that a seed population with a kappa distribution and a characteristic energy of 2 keV is accelerated up to a few MeV in the outer radiation belt. MeV electron fluxes increase by an order of magnitude during high magnetic activity conditions especially near L* ∼ 5 and for equatorial mirroring particles. We have also performed a parametric study of various important parameters to investigate how our results could be influenced by the uncertainty that characterizes their values. Results of this study show that if we consider higher values of the radial diffusion coefficients, different initial states, and different boundary conditions, we always observe a peak in the L* profile of the MeV electrons when electron-chorus interactions are included

Simulation of the outer radiation belt electrons near geosynchronous orbit including both radial diffusion and resonant interaction with Whistler-mode chorus waves

We present the first simulation results for electrons in the outer radiation belt near geosynchronous orbit, where radial diffusion and resonant interactions with whistler-mode chorus outside the plasmasphere are taken into account. Bounce averaged pitch-angle and energy diffusion rates are introduced in the Salammbô code for L ≤ 6.5, for electron energies between 10 keV and 3 MeV and fpe/fce values between 1.5 and 10. Results show that an initial seed population with a power law (Kappa) distribution and a characteristic plasmasheet energy of ∼5 keV can be accelerated up to a few MeV, for 4.5 < L < 6.6 and give a steady state profile similar to the one obtained from average satellite measurements. For a Kp = 4 magnetic storm simulation MeV electron fluxes increase by more than a factor of 10 on a timescale of 1 day. We conclude that whistler-mode chorus waves can be a major electron acceleration process at geostationary orbit