Severe and extreme surface charging on geosynchronous spacecraft is examined through the analysis of 16 years of data from particles detectors on‐board the Los Alamos National Laboratory spacecraft. Analysis shows that high spacecraft frame potentials are correlated with 10 to 50 keV electron fluxes, especially when these fluxes exceed 1 × 108 cm−2 s−1 sr−1. Four criteria have been used to select severe environments: 1) large flux of electrons with energies above 10 keV, 2) large fluxes of electrons with energies below 50 keV and above 200 keV, 3) large flux of electrons with energies below 50 keV and low flux with energies above 200 keV, and 4) long periods of time with a spacecraft potential below ‐ 5 kV. They occur preferentially during either geomagnetic storms or intense isolated substorms, during the declining phase of the solar cycle, during equinox seasons and close to midnight local time. The set of anomalies reported in Choi et al. (2011) is concomitant with a new database constructed from these events. The worst‐case environments exceed the spacecraft design guidelines by up to a factor of 10 for energies below 10 keV. They are fitted with triple Maxwellian distributions in order to facilitate their use by spacecraft designers as alternative conditions for the assessment of worst‐case surface charging.

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Abstract. 3-D PIC (Particle In Cell) simulations of spacecraft-plasma interactions in the solar wind context of the Solar Probe Plus mission are presented. The SPIS software is used to simulate a simplified probe in the near-Sun environment (at a distance of 0.044 AU or 9.5 R S from the Sun surface). We begin this study with a cross comparison of SPIS with another PIC code, aiming at providing the static potential structure surrounding a spacecraft in a high photoelectron environment. This paper presents then a sensitivity study using generic SPIS capabilities, investigating the role of some physical phenomena and numerical models. It confirms that in the near-sun environment, the Solar Probe Plus spacecraft would rather be negatively charged, despite the high yield of photoemission. This negative potential is explained through the dense sheath of photoelectrons and secondary electrons both emitted with low energies (2-3 eV). Due to this low energy of emission, these particles are not ejected at an infinite distance of the spacecraft and would rather surround it. As involved densities of photoelectrons can reach 10 6 cm −3 (compared to ambient ions and electrons densities of about 7 × 10 3 cm −3 ), those populations affect the surrounding plasma potential generating potential barriers for low energy electrons, leading to high recollection. This charging could interfere with the low energy (up to a few tens of eV) plasma sensors and particle detectors, by biasing the particle distribution functions measured by the instruments. Moreover, if the spacecraft charges to large negative potentials, the problem will be more severe as low energy electrons will not be seen at all. The importance of the modelling requirements in terms of precise prediction of spacecraft potential is also discussed.

A practical, inexpensive and scalable synthesis method, based on the Fe 2+ exchange of two commercial zeolites (i.e. Na-A and Na-X) followed by reductive thermal treatment at 1023 K, allowed obtaining nanocomposites where Fe nanoparticles are dispersed within an agglutinitic glassy matrix stemming from the amorphization of the zeolite precursor. The materials were characterized by means of atomic absorption spectrometry; X-ray powder diffraction followed by Rietveld analysis; transmission electron microscopy; N 2 adsorption/desorption isotherms at 77 K; measurements of grain size distribution; magnetic properties measurements; broadband dielectric spectroscopy and DC conductivity measurements.

The purpose of this paper is to propose a simple model for plasma generation and effect on fluids at atmospheric pressure. Experiments are conducted using a wire-to-wire corona discharge actuator in a subsonic boundary layer flow. Velocity gains of several metres per second are observed. A quasi-2D numerical model of the discharge is proposed and explains the creation of two corona discharges around the electrodes. A one-way approach of the plasma aerodynamics coupling gives access to the ionic wind. It is confirmed that the actuator accelerates the flow from the anode to the cathode. Order of magnitudes of the ionic wind and flow velocity profiles are close to experiments. A first attempt to perform a 2D simulation of the wire-to-wire discharge is presented as the starting point of future works.

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Five spacecraft-plasma models are used to simulate the interaction of a simplified geometry Solar Probe Plus (SPP) satellite with the space environment under representative solar wind conditions near perihelion. By considering similarities and differences between results obtained with different numerical approaches under well defined conditions, the consistency and validity of our models can be assessed. The impact on model predictions of physical effects of importance in the SPP mission is also considered by comparing results obtained with and without these effects. Simulation results are presented and compared with increasing levels of complexity in the physics of interaction between solar environment and the SPP spacecraft. The comparisons focus particularly on spacecraft floating potentials, contributions to the currents collected and emitted by the spacecraft, and on the potential and density spatial profiles near the satellite. The physical effects considered include spacecraft charging, photoelectron and secondary electron emission, and the presence of a background magnetic field. Model predictions obtained with our different computational approaches are found to be in agreement within 2% when the same physical processes are taken into account and treated similarly. The comparisons thus indicate that, with the correct description of important physical effects, our simulation models should have the required skill to predict details of satellite-plasma interaction physics under relevant conditions, with a good level of confidence. Our models concur in predicting a negative floating potential V f l $ À10 V for SPP at perihelion. They also predict a "saturated emission regime" whereby most emitted photo-and secondary electron will be reflected by a potential barrier near the surface, back to the spacecraft where they will be recollected. V C 2014 AIP Publishing LLC. [http://dx.