Equatorial Ionosphere Characterization for Sub-Saharan Africa SBAS

Performance Based Navigation (PBN) is a concept developed by ICAO (International Civil Aviation Organization) that specifies the operational performance required in an airspace, route or approach procedure. A Satellite Based Augmentation System (SBAS) enhances the performances of the existing satellite navigation system. It is used to deploy Global Navigation Satellite System (GNSS) approach for PBN procedures. The required performance level for vertical guidance is directly linked to approach category criteria. The real performance provided by an SBAS for a single-frequency user depends on the physical characteristics of the ionospheric layer. As Sub-Saharan Africa corresponds to geomagnetic equator region, the question of ionosphere dynamics characterization in equatorial zone is central to gauge what SBAS performance level can be achievable. In the equatorial zone the dynamics of the ionosphere is subject to complex physical phenomena, involving rapid recombination of ion-electron pairs. Moreover these phenomena are transient with high local spatial and temporal gradients. These zones promote the occurrence of scintillation phenomena, bubbles (strong local fall of TEC (Total Electron Content)), and small scale gradients, which must be evaluated for the ionosphere modeling and integrity data generation. Based on a large volume of GNSS measurements covering more than four years of data collected, Thales Alenia Space associated with IRAP (Astrophysics and Planetology Research Institute, Toulouse, France), present a panorama of observed physical events through the ionosphere in Sub-Saharan Africa zone. The main purpose of this study is to establish a clear view on the physical mechanisms that drive the equatorial ionosphere dynamics and the effects on GNSS measurements. This study is supported by information coming from TEC values, TEC gradients amplitudes, and the nature of scintillation events as intensity, impact area and occurrence in time. Conclusion of these activities is to highlight that ionosphere conditions above sub-Saharan area are consistent with the performances level of SBAS approach with vertical guidance. Indeed scientific analyses show that a precise service level is possible on this zone with a very good level of availability above the main airports

Solar cycle variations in the ionosphere of Mars

Solar cycle variations in solar radiation create notable changes in the Martian ionosphere, which have been analysed with Mars Express plasma datasets in this paper. In general, lower densities and temperatures of the ionosphere are found during the low solar activity phase, while higher densities and temperatures are found during the high solar activity phase. In this paper, we assess the degree of influence of the long term solar flux variations in the ionosphere of Mars

Ionosphere of Mars during the consecutive solar minima 23/24 and 24/25 as seen by MARSIS-Mars Express

The Mars' ionospheric behavior during two consecutive solar minima (23/24 and 24/25) is investigated with the same dataset. In particular, we use the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board Mars Express to investigate the total electron content behavior of the whole atmosphere in relation to the solar irradiance (EUV and X-ray fluxes), the solar zenith angle and the heliocentric distance. The topside variability of the electron density profiles is also investigated through variations in the peak density and neutral scale height. Moreover, the equations of the NeMars empirical model of the Martian ionosphere for low solar activity are tested for both minima. We have found that the topside ionosphere of Mars behaved similarly at both solar minima. However, when considering the bottomside, a pronounced reduction in ionization in particular cases is suggested. In addition, larger TEC values are found during the solar minimum 24/25 in the nightside sector that may indicate possible larger plasma transport than during the minimum 23/24. Finally, this study confirms that the ionospheric empirical NeMars model equations derived by Sanchez-Cano et al. (2016) for the low solar activity period during the solar minimum 23/24 are also valid and accurate for the solar minimum 24/25. The long duration of Mars Express is a critical factor for determining the long-term Martian ionospheric variability, which in turn, is essential for understanding the global evolution of the planet's atmosphere

Spatial, Seasonal, and Solar Cycle Variations of the Martian Total Electron Content (TEC): Is the TEC a Good Tracer for Atmospheric Cycles?

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.We analyze 10 years of Mars Express total electron content (TEC) data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument. We describe the spatial, seasonal, and solar cycle behavior of the Martian TEC. Due to orbit evolution, data come mainly from the evening, dusk terminator and postdusk nightside. The annual TEC profile shows a peak at Ls = 25–75° which is not related to the solar irradiance variation but instead coincides with an increase in the thermospheric density, possibly linked with variations in the surface pressure produced by atmospheric cycles such as the CO or water cycles. With the help of numerical modeling, we explore the contribution of the ion species to the TEC and the coupling between the thermosphere and ionosphere. These are the first observations which show that the TEC is a useful parameter, routinely measured by Mars Express, of the dynamics of the lower-upper atmospheric coupling and can be used as tracer for the behavior of the thermosphere.©2018. The Authors.B. S. -C. and M. L. acknowledge support through STFC grant ST/N000749/1. ESA-ESTEC Faculty and Europlanet funding are also gratefully acknowledged. MEX MARSIS RDR and EDR data can be downloaded from the ESA-PSA archive, TIMED-SEE data at the University of Colorado's website (http://lasp.colorado.edu/lisird/index.html), REMS data at the NASA Planetary Data System (http://atmos.nmsu.edu/PDS/data/mslrem_1001/DATA/), the MCD model at the Mars Climate Database web interface (http://www-mars.lmd.jussieu.fr/mars/access.html), and the IPIM model at the IRAP CDPP web interface (http://transplanet.irap.omp.eu/)

A Preliminary Study of Magnetosphere-Ionosphere-Thermosphere Coupling at Jupiter: Juno Multi-Instrument Measurements and Modeling Tools

The dynamics of the Jovian magnetosphere are controlled by the interplay of the planet's fast rotation, its main iogenic plasma source and its interaction with the solar wind. Magnetosphere-Ionosphere-Thermosphere (MIT) coupling processes controlling this interplay are significantly different from their Earth and Saturn counterparts. At the ionospheric level, they can be characterized by a set of key parameters: ionospheric conductances, electric currents and fields, exchanges of particles along field lines, Joule heating and particle energy deposition. From these parameters, one can determine (a) how magnetospheric currents close into the ionosphere, and (b) the net deposition/extraction of energy into/out of the upper atmosphere associated to MIT coupling. We present a new method combining Juno multi-instrument data (MAG, JADE, JEDI, UVS, JIRAM and Waves) and modeling tools to estimate these key parameters along Juno's trajectories. We first apply this method to two southern hemisphere main auroral oval crossings to illustrate how the coupling parameters are derived. We then present a preliminary statistical analysis of the morphology and amplitudes of these key parameters for eight among the first nine southern perijoves. We aim to extend our method to more Juno orbits to progressively build a comprehensive view of Jovian MIT coupling at the level of the main auroral oval

EUropean Heliospheric FORecasting Information Asset 2.0

Aims: This paper presents a H2020 project aimed at developing an advanced space weather forecasting tool, combining the MagnetoHydroDynamic (MHD) solar wind and coronal mass ejection (CME) evolution modelling with solar energetic particle (SEP) transport and acceleration model(s). The EUHFORIA 2.0 project will address the geoeffectiveness of impacts and mitigation to avoid (part of the) damage, including that of extreme events, related to solar eruptions, solar wind streams, and SEPs, with particular emphasis on its application to forecast geomagnetically induced currents (GICs) and radiation on geospace. Methods: We will apply innovative methods and state-of-the-art numerical techniques to extend the recent heliospheric solar wind and CME propagation model EUHFORIA with two integrated key facilities that are crucial for improving its predictive power and reliability, namely (1) data-driven flux-rope CME models, and (2) physics-based, self-consistent SEP models for the acceleration and transport of particles along and across the magnetic field lines. This involves the novel coupling of advanced space weather models. In addition, after validating the upgraded EUHFORIA/SEP model, it will be coupled to existing models for GICs and atmospheric radiation transport models. This will result in a reliable prediction tool for radiation hazards from SEP events, affecting astronauts, passengers and crew in high-flying aircraft, and the impact of space weather events on power grid infrastructure, telecommunication, and navigation satellites. Finally, this innovative tool will be integrated into both the Virtual Space Weather Modeling Centre (VSWMC, ESA) and the space weather forecasting procedures at the ESA SSCC in Ukkel (Belgium), so that it will be available to the space weather community and effectively used for improved predictions and forecasts of the evolution of CME magnetic structures and their impact on Earth. Results: The results of the first six months of the EU H2020 project are presented here. These concern alternative coronal models, the application of adaptive mesh refinement techniques in the heliospheric part of EUHFORIA, alternative flux-rope CME models, evaluation of data-assimilation based on Karman filtering for the solar wind modelling, and a feasibility study of the integration of SEP models.</p

Etude de la transition collisionnelle - non collisionnelle dans les atmosphères planétaires (application à Mars et Titan)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Du soleil à la Terre

Du Soleil à la Terre présente l’aéronomie et la météorologie de l’espace. L’objectif de l’ouvrage est avant tout de faire connaître et comprendre les interactions qui existent entre le Soleil et la Terre, qu’elles relèvent de la physique classique, de la physique atomique et corpusculaire, ou de la chimie. Le lecteur découvre le Soleil qui émet photons et particules, puis la Terre, notre planète, avec son environnement matériel (atmosphère neutre et ionisée) et immatériel (champ géomagnétique). On comprendra les orages magnétiques, les aurores boréales… Certains passages, de lecture plus difficile, sont destinés aux passionnés et aux professionnels. Il sont repérés dans le texte ou font l’objet d’annexes (théories fluide et cinétique, physique des plasmas…). Ce livre, avec plus de 150 illustrations couleur mêlant souvent esthétique et science, n’a pas d’équivalent en langue française

A Generalized Model for the Proton Expansion in Astrophysical Winds. III. The Collisional Transfers and Their Properties

International audienceThis is the third and last of a series of papers that present a new theoretical approach to modeling the expansion of the solar and terrestrial polar winds by solving the Fokker-Planck equation. The Coulomb collisional transfers between the different species that compose these winds are presented after the velocity distribution function and the set of transport equations associated with the generalized model. The method and the assumptions used to calculate these terms are described. They are derived from generic expressions, which must be numerically estimated for specific applications. Their new properties are analyzed in the context of the terrestrial polar wind, and their potential importance in the processes of heating and acceleration of the solar wind is discussed. Because the generalized model is adapted to reproduce the high suprathermal part of the velocity distribution function currently observed in the solar wind, we also emphasize the role of this contribution in the collisional transfers. In the terrestrial polar wind, the region of energy transfer between H+ and O+ ions is thinner than previously predicted. In the solar wind, the region of energy transfer between electrons and protons in the inner corona is larger than previously thought. The role of the thermal and mirror forces and the mechanisms of isotropization of the electrons are underlined