V. Pierrard
Université catholique de Louvain, Physique, Faculty Member
The electrons are an essential particle species in the solar wind. They often exhibit non-equilibrium features in their velocity distribution function. These include temperature anisotropies, tails (kurtosis), and reflectional asymmetries... more
The electrons are an essential particle species in the solar wind. They often exhibit non-equilibrium features in their velocity distribution function. These include temperature anisotropies, tails (kurtosis), and reflectional asymmetries (skewness), which contribute a significant heat flux to the solar wind. If these non-equilibrium features are sufficiently strong, they drive kinetic micro-instabilities. We develop a semi-graphical framework based on the equations of quasi-linear theory to describe electron-driven instabilities in the solar wind. We apply our framework to resonant instabilities driven by temperature anisotropies. These include the electron whistler anisotropy instability and the propagating electron firehose instability. We then describe resonant instabilities driven by reflectional asymmetries in the electron distribution function. These include the electron/ion-acoustic, kinetic Alfvén heat-flux, Langmuir, electron-beam, electron/ion-cyclotron, electron/electron...
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This webpage provides access to diffusion coefficients and simulated electron distributions used in the article "Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar... more
This webpage provides access to diffusion coefficients and simulated electron distributions used in the article "Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar orbit" by Pierrard V., J.-F. Ripoll, G. Cunningham, E. Botek, O. Santolik, S. Thaller, B. Kurth, M. Cosmides.
of shoulders and plumes in the frame of the interchange
Research Interests: Medicine and Gynecology
This letter presents the results of an advanced parametrization of the solar wind electron temperature anisotropy and the instabilities resulting from the interplay of the (bi-)Maxwellian core and (bi-)Kappa halo populations in the slow... more
This letter presents the results of an advanced parametrization of the solar wind electron temperature anisotropy and the instabilities resulting from the interplay of the (bi-)Maxwellian core and (bi-)Kappa halo populations in the slow solar wind. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. The instabilities are significantly stimulated in the presence of suprathermals, and the instability thresholds shape the limits of the temperature anisotropy for both the core and halo populations re-stating the incontestable role that the selfgenerated instabilities can play in constraining the electron anisotropy. These results confirm a particular implication of the suprathermal electrons which are less dense but hotter than thermal electrons.
Research Interests: Physics, Anisotropy, Instability, Electron, Solar Wind, and 3 moreThermal, Halo, and Electron Temperature
Since the discovery of the magnetosphere-magnetotail system in the1950s-1960s), and the associated beginning of the satellite era, we have gained a well-informed understanding of this space plasma region permeated by the geomagnetic field... more
Since the discovery of the magnetosphere-magnetotail system in the1950s-1960s), and the associated beginning of the satellite era, we have gained a well-informed understanding of this space plasma region permeated by the geomagnetic field and home to a variety of charged particle populations and plasma waves. Over the last six decades, IAGA has played an important role in supporting international magnetospheric research. Here we provide an overview of recent developments in energy transport from the solar wind into the Earth’s environment. Topics include, magnetosphere energy input, the role of the boundary layer. Solar wind interaction with the magnetosphere creates geomagnetic activity and the response of the region leading to sub-storms and steady magnetospheric convection are discussed. The charged particle energy (eV to MeV) inherent/contained in the magnetospheric ring current and Van Allen radiation belts establish many properties of the region, giving rise to boundary region...
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So-called κ-distributions are widely invoked in the analysis of nonequilibrium plasmas from space, although a general macroscopic parametrization as known for Maxwellian plasmas near thermal equilibrium is prevented by the diverging... more
So-called κ-distributions are widely invoked in the analysis of nonequilibrium plasmas from space, although a general macroscopic parametrization as known for Maxwellian plasmas near thermal equilibrium is prevented by the diverging moments of order l ≥ 2κ − 1. To overcome this critical limitation, recently novel regularized κ-distributions (RK) have been introduced, including various anisotropic models with well-defined moments for any value of κ > 0. In this paper, we present an evaluation of the pressure and heat flux of electron populations, as provided by moments of isotropic and anisotropic RKs for conditions typically encountered in the solar wind. We obtained finite values even for low values of κ < 3/2, for which the pressure and heat flux moments of standard κ-distributions are not defined. These results were also contrasted with the macroscopic parameters obtained for Maxwellian populations, which show a significant underestimation especially if an important supra...
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of the convection electric field models on predicted plasmapause positions during magnetic storms
Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We... more
Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We present an analysis of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESA's Project for On-board Autonomy 2 (PROBA2) satellite as background signal. Combining Energetic Particle Telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. Results. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L=4-6 McIlwain zone, which makes it possible to identify their source. Conclusions. Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in thi...
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The dynamics of the plasmapause position and of the electron outer belt boundaries is studied with satellite observations and then compared with physics-based dynamical simulations. The plasmapause position is determined using the... more
The dynamics of the plasmapause position and of the electron outer belt boundaries is studied with satellite observations and then compared with physics-based dynamical simulations. The plasmapause position is determined using the instrument WHISPER (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation) onboard the CLUSTER satellites. The relationship between plasmapause positions, solar wind parameters and geomagnetic indices is analyzed at highest correlation time-lag. The results show a short time delay in the post-midnight sector, but a time delay increasing with the MLT sector, in good agreement with the simulations of plasmapause formation based on the quasi-interchange mechanism. These plasmapause positions are also compared with the boundaries of the outer electron belt, as determined by CIS and RAPID instruments on CLUSTER. These different plasma populations of the inner magnetosphere are found to be closely related, especially during storm events when the plasmapause and the inner edge of the outer belts move simultaneously closer to the Earth. The dynamics of the radiation belts is also analyzed with the observations of the Energetic Particle Telescope (EPT) instrument, a new compact and modular ionizing particle spectrometer that was launched in May 2013 on board the PROBA-V satellite to a LEO polar orbit at an altitude of 820 km (Pierrard et al., Space Sci. Rev., 184, 2014, pp 87–106). This instrument performs direct electron, proton and heavy ion discrimination with a high resolution, allowing us to obtain maps of particle fluxes in the South Atlantic Anomaly and in the high latitude horns. Electron dropout events are observed during the main phase of geomagnetic storms, generally followed by a flux increase after the minimum value of Dst.
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The IMAGE spacecraft launched in March 2000 provides the first global comprehensive images of the Earth's plasmasphere. The EUV (Extreme Ultra Violet) instrument on board this spacecraft gives intensity maps of the 30,4 nm emissions... more
The IMAGE spacecraft launched in March 2000 provides the first global comprehensive images of the Earth's plasmasphere. The EUV (Extreme Ultra Violet) instrument on board this spacecraft gives intensity maps of the 30,4 nm emissions of Helium ions integrated along the line of sight. It reveals the global behavior of the plasmasphere and its dynamics as influenced by the solar wind and interplanetary magnetic field variations. These observations are compared with the simulations developed at IASB-BIRA for the deformations of the plasmasphere during geomagnetic substonns and other variations in the level of geomagnetic activity.
Research Interests: Geology and Plasmasphere
本研究は,教育実習Bにおける教育実習生の顕著な課題を析出し,課題克服の働きかけを考察することで教育実習Bで使用する観察実習生による記述シートを改善・修正するものである。研究最終年次である三年次の本年度では,観察実習生の主体化する国語の授業観を指摘し,このテキスト観からする国語の授業の問題点を議論の俎上にのぼせ分析し,有効な働きかけの足場を示すものである。また,その足場からする観察実習Bへの参加が授業力獲得に繋がることを,観察記録や講話記録を分析することで明らかにする。以上の考... more
本研究は,教育実習Bにおける教育実習生の顕著な課題を析出し,課題克服の働きかけを考察することで教育実習Bで使用する観察実習生による記述シートを改善・修正するものである。研究最終年次である三年次の本年度では,観察実習生の主体化する国語の授業観を指摘し,このテキスト観からする国語の授業の問題点を議論の俎上にのぼせ分析し,有効な働きかけの足場を示すものである。また,その足場からする観察実習Bへの参加が授業力獲得に繋がることを,観察記録や講話記録を分析することで明らかにする。以上の考察を通して,広く実習生の“学び"を呼びかける。
Research Interests: Geodesy and Gravimeter
Research Interests: Ionosphere and AGU
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A suprathermal halo population of electrons is ubiquitous in space plasmas, as evidence of their departure from thermal equilibrium even in the absence of anisotropies. The origin, properties, and implications of this population, however,... more
A suprathermal halo population of electrons is ubiquitous in space plasmas, as evidence of their departure from thermal equilibrium even in the absence of anisotropies. The origin, properties, and implications of this population, however, are poorly known. We provide a comprehensive description of solar wind halo electrons in the ecliptic, contrasting their evolutions with heliospheric distance in the slow and fast wind streams. At relatively low distances less than 1 AU, the halo parameters show an anticorrelation with the solar wind speed, but this contrast decreases with increasing distance and may switch to a positive correlation beyond 1 AU. A less monotonic evolution is characteristic of the high-speed winds, in which halo electrons and their properties (e.g., number densities, temperature, plasma beta) exhibit a progressive enhancement already distinguishable at about 0.5 AU. At this point, magnetic focusing of electron strahls becomes weaker and may be counterbalanced by the...
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Space plasmas are essentially collisionless systems out of thermal equilibrium, where enhanced populations of suprathermal particles are observed. The typical distributions are generally better described by kappa distributions than by... more
Space plasmas are essentially collisionless systems out of thermal equilibrium, where enhanced populations of suprathermal particles are observed. The typical distributions are generally better described by kappa distributions than by Maxwellians, especially for electrons, which has serious consequences since their small electron mass makes them major agents for plasma energy transport. This chapter presents suprathermal electrons and their critical role in the heating and acceleration of plasmas in several important space and astrophysical contexts. They affect the generation of the ambipolar electric field and contribute to the collisionless electron heat flux. In the solar corona, such electrons make a dominant contribution to the electron heat flux and play an important role in the coronal heating energy budget. They also support large ambipolar electric fields along open magnetic flux tubes in solar/stellar coronae and in planetary ionospheres and thus contribute significantly to solar and stellar wind acceleration, outflow from planetary ionospheres, and possibly even exoplanetary atmospheric loss. For the Earth’s environment, it has been demonstrated that suprathermal electrons play a controlling role in the plasmasphere thermal structure, have a major effect on ionospheric outflows, and control the electron temperature and consequently the topside ionospheric scale height through the generation of heat flux.
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Abstract. Simulations of plasmapause formation described in Pierrard and Lemaire (2004) predict the shape and equatorial distance of the plasmapause as a function of the geomagnetic activity index Kp. The equatorial positions predicted by... more
Abstract. Simulations of plasmapause formation described in Pierrard and Lemaire (2004) predict the shape and equatorial distance of the plasmapause as a function of the geomagnetic activity index Kp. The equatorial positions predicted by this model are compared with the observations of EUV/IMAGE during the geomagnetic storm of 24 May
Space plasmas are essentially collisionless systems out of thermal equilibrium, where enhanced populations of suprathermal particles are observed. The typical distributions are generally better described by kappa distributions than by... more
Space plasmas are essentially collisionless systems out of thermal equilibrium, where enhanced populations of suprathermal particles are observed. The typical distributions are generally better described by kappa distributions than by Maxwellians, especially for electrons [Pierrard and Lazar, 2010]. This has large consequences since the small electron mass makes them major agents for plasma energy transport. More than 120 000 velocity distributions measured by Helios, Cluster and Ulysses in the ecliptic have been analyzed within an extended range of heliocentric distances from 0.3 to over 4 AU [Pierrard et al., 2016]. The velocity distribution of electrons reveal a dual structure with a thermal (Maxwellian) core and a suprathermal (Kappa) halo. A detailed observational analysis of these two components provides estimations of their temperatures and temperature anisotropies. For low values of the power-index kappa, these two components manifest a clear tendency to deviate from isotrop...
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Research Interests: Physics and Solar Physics
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ABSTRACT Astrophysical and space plasmas are commonly found to be out of thermal equilibrium; i.e., the velocity distribution functions of their particles are not well described by Maxwellian distributions. They generally have more... more
ABSTRACT Astrophysical and space plasmas are commonly found to be out of thermal equilibrium; i.e., the velocity distribution functions of their particles are not well described by Maxwellian distributions. They generally have more suprathermal particles in the tail of the distribution. The kappa distribution provides a generalization to successfully describe such plasmas with tails decreasing as a power law of the velocity. In the present work, we improve the solar wind model developed on the basis of such kappa distributions by incorporating azimuthally varying 1 AU boundary conditions to produce a spatially structured view of the solar wind expansion. By starting from the top of the chromosphere to the heliosphere and by applying relevant boundary conditions in the ecliptic plane, a global model of the corona and the solar wind is developed for each particle species. The model includes the natural heating of the solar corona automatically appearing when an enhanced population of suprathermal particles is present at low altitude in the solar (or stellar) atmosphere. This applies not only for electrons and protons but also for the minor ions which then have a temperature increase proportional to their mass. Moreover, the presence of suprathermal electrons contributes to the acceleration of the solar wind to high bulk velocities when Coulomb collisions are neglected. The results of the model are illustrated in the solar corona and in solar wind for the different particle species and can now be directly compared in two dimensions with spacecraft observations in the ecliptic plane.
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In space plasmas and gas, the kinetic approach requires to find the solution of the Fokker-Planck and Boltzmann equations to determine the velocity distribution function (VDF) of the particles. A spectral method of expansion of the... more
In space plasmas and gas, the kinetic approach requires to find the solution of the Fokker-Planck and Boltzmann equations to determine the velocity distribution function (VDF) of the particles. A spectral method of expansion of the solution in orthogonal polynomials has been developed to solve these equations. This discrete ordinate method is especially adapted to find solutions of integral and differential equations. The choice of the polynomials is crucial to obtain a good precision. The calculations of the moments give the macroscopic quantities like the number density, bulk velocity, temperatures and heat flux. Kinetic models based on this method of solution have been developed for planetary exospheres and stellar plasmas, especially the terrestial polar wind and the solar wind.
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Kinetic models of the inner magnetosphere have been developed at BISA. The 3D dynamic model of the plasmasphere is based on the velocity distribution functions of the particles obtained from the kinetic approach. The position of the... more
Kinetic models of the inner magnetosphere have been developed at BISA. The 3D dynamic model of the plasmasphere is based on the velocity distribution functions of the particles obtained from the kinetic approach. The position of the plasmapause, the limit of the plasmasphere, is determined by the interchange instability mechanism and depends on the level of geomagnetic activity. The dynamics of the plasmasphere is mainly determined by the convection electric field combined with the corotation electric field. The highly dynamic region of the plasmasphere is disturbed during geomagnetic storms and substorms, with formation of a sharp plasmapause closer to the Earth and generation of a plume in the afternoon MLT sector. The plasmasphere model has been coupled with the IRI ionospheric model to determine the composition, the number density and the temperature in the plasmasphere. Correspondence exists between the plasmapause position and the F region ionospheric trough. Coincident observ...
In this presentation, the capabilities developed to study inner and outer magnetosphere coupling will be explained. Dynamic models have been developed for the plasmasphere coupled to the ionosphere, the polar wind and the radiation belts.... more
In this presentation, the capabilities developed to study inner and outer magnetosphere coupling will be explained. Dynamic models have been developed for the plasmasphere coupled to the ionosphere, the polar wind and the radiation belts. These models are provided on the space weather portal www.spaceweather.eu. A 3D dynamic model of the plasmasphere has been developed using the kinetic approach and coupled to the International Reference Ionosphere model. The coupled model determines at any chosen time the number density and the temperatures of the electrons and ions for altitudes from 60 km to the position of the plasmapause and even at higher radial distances in the plasmaspheric trough. The plasmapause position is dependent on the geomagnetic activity and solar wind variability. The polar wind is modeled using a similar kinetic approach, but along open magnetic field lines at high latitudes so that particles escape from the terrestrial atmosphere. The model determines the profile...