Radial evolution of sunward strahl electrons in the inner heliosphere

The heliospheric magnetic field (HMF) exhibits local inversions, in which the field apparently “bends back” upon itself. Candidate mechanisms to produce these inversions include various configurations of upstream interchange reconnection; either in the heliosphere, or in the corona where the solar wind is formed. Explaining the source of these inversions, and how they evolve in time and space, is thus an important step towards explaining the origins of the solar wind. Inverted heliospheric magnetic field lines can be identified by the anomalous sunward (i.e. inward) streaming of the typically anti-sunward propagating, field aligned (or anti-aligned), beam of electrons known as the “strahl”. We test if the pitch angle distribution (PAD) properties of sunward-propagating strahl are different from those of outward strahl.We perform a statistical study of strahl observed by the Helios spacecraft, over heliocentric distances spanning ≈ 0.3 – 1 AU. We find that sunward strahl PADs are broader and less intense than their outward directed counterparts; particularly at distances 0.3 – 0.75 AU. This is consistent with sunward strahl being subject to additional, path-length dependent, scattering in comparison to outward strahl.We conclude that the longer and more variable path from the Sun to the spacecraft, along inverted magnetic field, leads to this additional scattering. The results also suggest that the relative importance of scattering along this additional path length drops off with heliocentric distance. These results can be explained by a relatively simple, constant-rate, scattering process

Space plasma physics science opportunities for the lunar orbital platform - Gateway

The Lunar Orbital Platform - Gateway (LOP - Gateway, or simply Gateway) is a crewed platform that will be assembled and operated in the vicinity of the Moon by NASA and international partner organizations, including ESA, starting from the mid-2020s. It will offer new opportunities for fundamental and applied scientific research. The Moon is a unique location to study the deep space plasma environment. Moreover, the lunar surface and the surface-bounded exosphere are interacting with this environment, constituting a complex multi-scale interacting system. This paper examines the opportunities provided by externally mounted payloads on the Gateway in the field of space plasma physics, heliophysics and space weather, and also examines the impact of the space environment on an inhabited platform in the vicinity of the Moon. It then presents the conceptual design of a model payload, required to perform these space plasma measurements and observations. It results that the Gateway is very well-suited for space plasma physics research. It allows a series of scientific objectives with a multi-disciplinary dimension to be addressed

A New Technique for the Calculation and 3D Visualisation of Magnetic Complexities on Solar Satellite Images

YesIn this paper, we introduce two novel models for processing real-life satellite images to quantify and then visualise their magnetic structures in 3D. We believe this multidisciplinary work is a real convergence between image processing, 3D visualization and solar physics. The first model aims to calculate the value of the magnetic complexity in active regions and the solar disk. A series of experiments are carried out using this model and a relationship has been indentified between the calculated magnetic complexity values and solar flare events. The second model aims to visualise the calculated magnetic complexities in 3D colour maps in order to identify the locations of eruptive regions on the Sun. Both models demonstrate promising results and they can be potentially used in the fields of solar imaging, space weather and solar flare prediction and forecasting

DSLP Operations on Board Proba 2 - Raw Data Processing and Archiving: FINAL REPORT

A complete DSLP data archive has been developed including full automated data processing chain from raw data up to higher level products. The archive, based on PDS and CDF standards, is available online including full documentation on the DSLP instrument and its operations on board Proba 2 satellite

Étude du caractère non-thermique des fonctions de distributions électroniques du vent solaire

The solar wind is a sparse and relatively hot plasma. In such a medium the effect of Coulomb collisions is quite limited and one can expect that the velocity distribution functions (VDF) of the particles present strong deviations from thermodynamic equilibrium and this is what we actually observe. Indeed, the FDVs of solar wind electrons permanently present three different components: a thermal core and a suprathermal halo, which are always isotropic, and a "strahl" aligned along the magnetic field in the antisolar direction. We performed a statistical study of a large number of electronic FDVs observed in the ecliptic between 0. 3 to 4 AU. For this study, a new model was proposed which describes, for the first time in an analytical way, the three populations of VDFs observed. The main characteristics of these distributions, i.e. density, temperature and heat flux are examined as a function of the heliocentric distance. In addition, we studied the constraints imposed by Coulomb collisions and wave-particle interactions on, on the one hand, the temperature anisotropy of FDV core electrons and, on the other hand, the heat flux. We show that Coulomb collisions and wave instabilities are effective control mechanisms of the global properties of electronic FDVs.Le vent solaire est un plasma peu dense et relativement chaud. Dans un tel milieu l'effet des collisions Coulombiennes est assez limité et l’on peut s’attendre à ce que les fonctions de distribution des vitesses (FDV) des particules présentent des déviations fortes par rapport à l’équilibre thermodynamique et c’est effectivement ce que l’on observe. En effet, les FDV des électrons du vent solaire présentent de manière permanente trois composantes différentes: un coeur thermique et un halo suprathermique, qui sont toujours isotropes, et un "strahl" aligné le long du champ magnétique dans la direction antisolaire. Nous avons effectué une étude statistique d'un grand nombre FDV électroniques observées dans l'écliptique entre 0. 3 à 4 UA. Pour cette étude, un nouveau modèle a été proposé qui décrit, pour la première fois de manière analytique, les trois populations des FDV observées. Les caractéristiques principales de ces distributions, c'est-à-dire la densité, la température et le flux de chaleur sont examinées en fonction de la distance héliocentrique. Par ailleurs, nous avons étudié les contraintes imposées par les collisions Coulombiennes et les interactions onde-particule sur, d’une part, l'anisotropie de température des électrons du cœur des FDV et, d’autre part, le flux de chaleur. Nous montrons que les collisions Coulombiennes et les instabilités d’ondes et constituent des mécanismes de contrôle efficaces des propriétés globales des FDV électroniques

Étude du caractère non-thermique des fonctions de distributions électroniques du vent solaire

The solar wind is a sparse and relatively hot plasma. In such a medium the effect of Coulomb collisions is quite limited and one can expect that the velocity distribution functions (VDF) of the particles present strong deviations from thermodynamic equilibrium and this is what we actually observe. Indeed, the FDVs of solar wind electrons permanently present three different components: a thermal core and a suprathermal halo, which are always isotropic, and a "strahl" aligned along the magnetic field in the antisolar direction. We performed a statistical study of a large number of electronic FDVs observed in the ecliptic between 0. 3 to 4 AU. For this study, a new model was proposed which describes, for the first time in an analytical way, the three populations of VDFs observed. The main characteristics of these distributions, i.e. density, temperature and heat flux are examined as a function of the heliocentric distance. In addition, we studied the constraints imposed by Coulomb collisions and wave-particle interactions on, on the one hand, the temperature anisotropy of FDV core electrons and, on the other hand, the heat flux. We show that Coulomb collisions and wave instabilities are effective control mechanisms of the global properties of electronic FDVs.Le vent solaire est un plasma peu dense et relativement chaud. Dans un tel milieu l'effet des collisions Coulombiennes est assez limité et l’on peut s’attendre à ce que les fonctions de distribution des vitesses (FDV) des particules présentent des déviations fortes par rapport à l’équilibre thermodynamique et c’est effectivement ce que l’on observe. En effet, les FDV des électrons du vent solaire présentent de manière permanente trois composantes différentes: un coeur thermique et un halo suprathermique, qui sont toujours isotropes, et un "strahl" aligné le long du champ magnétique dans la direction antisolaire. Nous avons effectué une étude statistique d'un grand nombre FDV électroniques observées dans l'écliptique entre 0. 3 à 4 UA. Pour cette étude, un nouveau modèle a été proposé qui décrit, pour la première fois de manière analytique, les trois populations des FDV observées. Les caractéristiques principales de ces distributions, c'est-à-dire la densité, la température et le flux de chaleur sont examinées en fonction de la distance héliocentrique. Par ailleurs, nous avons étudié les contraintes imposées par les collisions Coulombiennes et les interactions onde-particule sur, d’une part, l'anisotropie de température des électrons du cœur des FDV et, d’autre part, le flux de chaleur. Nous montrons que les collisions Coulombiennes et les instabilités d’ondes et constituent des mécanismes de contrôle efficaces des propriétés globales des FDV électroniques

Étude du caractère non-thermique des fonctions de distributions électroniques du vent solaire

The solar wind is a sparse and relatively hot plasma. In such a medium the effect of Coulomb collisions is quite limited and one can expect that the velocity distribution functions (VDF) of the particles present strong deviations from thermodynamic equilibrium and this is what we actually observe. Indeed, the FDVs of solar wind electrons permanently present three different components: a thermal core and a suprathermal halo, which are always isotropic, and a "strahl" aligned along the magnetic field in the antisolar direction. We performed a statistical study of a large number of electronic FDVs observed in the ecliptic between 0. 3 to 4 AU. For this study, a new model was proposed which describes, for the first time in an analytical way, the three populations of VDFs observed. The main characteristics of these distributions, i.e. density, temperature and heat flux are examined as a function of the heliocentric distance. In addition, we studied the constraints imposed by Coulomb collisions and wave-particle interactions on, on the one hand, the temperature anisotropy of FDV core electrons and, on the other hand, the heat flux. We show that Coulomb collisions and wave instabilities are effective control mechanisms of the global properties of electronic FDVs.Le vent solaire est un plasma peu dense et relativement chaud. Dans un tel milieu l'effet des collisions Coulombiennes est assez limité et l’on peut s’attendre à ce que les fonctions de distribution des vitesses (FDV) des particules présentent des déviations fortes par rapport à l’équilibre thermodynamique et c’est effectivement ce que l’on observe. En effet, les FDV des électrons du vent solaire présentent de manière permanente trois composantes différentes: un coeur thermique et un halo suprathermique, qui sont toujours isotropes, et un "strahl" aligné le long du champ magnétique dans la direction antisolaire. Nous avons effectué une étude statistique d'un grand nombre FDV électroniques observées dans l'écliptique entre 0. 3 à 4 UA. Pour cette étude, un nouveau modèle a été proposé qui décrit, pour la première fois de manière analytique, les trois populations des FDV observées. Les caractéristiques principales de ces distributions, c'est-à-dire la densité, la température et le flux de chaleur sont examinées en fonction de la distance héliocentrique. Par ailleurs, nous avons étudié les contraintes imposées par les collisions Coulombiennes et les interactions onde-particule sur, d’une part, l'anisotropie de température des électrons du cœur des FDV et, d’autre part, le flux de chaleur. Nous montrons que les collisions Coulombiennes et les instabilités d’ondes et constituent des mécanismes de contrôle efficaces des propriétés globales des FDV électroniques

Whistler Waves and Electron Properties in the Inner Heliosphere: Helios Observations

International audienceWe present the analysis of narrowband whistler wave signatures observed in the inner heliosphere (0.3–1 au). These signatures are bumps in the spectral density in the 10–200 Hz frequency range of the AC magnetic field as measured by the search coil magnetometer on board the Helios 1 spacecraft. We show that the majority of whistler signatures are observed in the slow solar wind (600 km s−1), whistler activity is significantly lower; whistler signatures start to appear for R > 0.6 au and their number increases from ~0.03% at 0.65 au to ~1% at 0.9 au. We have studied the variation of the electron core and halo anisotropy (T e⊥/T e∥), as well as the electron normalized heat flux as a function of R and of the solar wind speed. We find that, in the slow wind electron core and halo anisotropy is higher than in fast one, and also that these anisotropies increase radially in both types of winds, which is in line with the occurrence of whistler signatures. We hypothesize the existence of a feedback mechanism to explain the observed radial variations of the occurrence of whistlers in relation with the halo anisotropy

Science goals of the COMPASS instrument consortium on M-MATISSE

International audienceMars-Magnetosphere ATmosphere Ionosphere and Space-weather SciencE (M-MATISSE) is a candidate for the ESA M7 mission opportunity, currently being studied by ESA in Phase A. It consists of two spacecraft with largely identical scientific payloads that will be placed into orbit around Mars in 2037. On inclined elliptical orbits they will encounter all relevant regions of the Mars-induced magnetosphere and upper atmosphere for further refining our understanding of the exchange of material, energy and momentum between the solar wind and space environment, and the Martian system. The Combined Magnetic and Plasma Sensor Suite, COMPASS, consists of dual Fluxgate Magnetometers (MAG), dual Langmuir Probes (LP), a Mutual Impedance eXperiment (MIX) (composed of an electronic card Mutual Impedance Board (MIB) that supplies driving electric signals to the Mutual Impedance Probe (MIP)) and a 3D Velocity of Ion (3DVI) instrument (composed of Ion Drift Meter (IDM) and a Retarding Potential Analyzer (RPA) in a combined instrument package), with redundant integrated Wave Analyzer Processing Unit (WAPU) for handling digital data processing and redundant Low Voltage Power Supply (LVPS). Design heritage for COMPASS is derived from the Dust and Fields Package to be flown on Comet Interceptor and from the Radio And Plasma Wave Investigation on the Jupiter Icy Moons Explorer. By sharing physical and electrical resources where possible, COMPASS provides an integrated suite of sensors and data handling systems that will provide highly configurable measurements of plasma properties (density, temperature, velocity and basic composition), as well as the vector magnetic field, a single component of the electric field, and the spacecraft potential. In this presentation, we will review the initial design, expected performance and scientific goals of the COMPASS consortium within the M-MATISSE mission