Belgian Institute for Space Aeronomy

Brussels, Belgium

Belgian Institute for Space Aeronomy

Brussels, Belgium

The Belgian Institute for Space Aeronomy is a Belgian federal scientific research institute. Created in 1964, its main tasks are research and public service in space aeronomy, which is the physics and chemistry of the atmosphere of the Earth and other planets, and of outer space. The scientists rely on ground-based, balloon-, air- or space-borne instruments and computer models. Wikipedia.


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Maggiolo R.,Belgian Institute for Space Aeronomy | Kistler L.M.,University of New Hampshire
Journal of Geophysical Research: Space Physics | Year: 2014

We study the spatial distribution of plasma sheet O+ and H + ions using data from the COmposition and DIstribution Function (CODIF) instrument on board the Cluster spacecraft from 2001 to 2005. The densities are mapped along magnetic field lines to produce bidimensional density maps at the magnetospheric equatorial plane for various geomagnetic and solar activity levels (represented by the Kp and F10.7 indexes). We analyze the correlation of the O+ and H+ density with Kp and F10.7 in the midtail region at geocentric distances between 15 and 20 RE and in the near-Earth regions at radial distances between 7 and 8 RE. Near Earth the H+ density slightly increases with Kp and F10.7 while in the midtail region it is not correlated with Kp and F10.7. On the contrary, the amount of O+ ions significantly increases with Kp and F10.7 independently of the region. In the near-Earth region, the effects of solar EUV and geomagnetic activity on the O+ density are comparable. In the midtail region, the O+ density increases at a lower rate with solar EUV flux but strongly increases with geomagnetic activity although the effect is modulated by the solar EUV flux level. We also evidence a strong increase of the proportion of O+ ions with decreasing geocentric distance below ~10 R E. These results confirm the direct entry of O+ ions into the near-Earth plasma sheet and suggest that both energetic outflows from the auroral zone and cold outflow from the high-latitude ionosphere may contribute to feed the near-Earth plasma sheet with ionospheric ions. Key Points O + and H+ densitiy maps at the magnetospheric equatorial plane are produced O+ and H+ density variation with geomagnetic and solar activity are analyzed The direct entry of O+ ions at low geocentric distances is confirmed ©2014. American Geophysical Union. All Rights Reserved.


Mann I.,Belgian Institute for Space Aeronomy | Mann I.,Osaka University
Annual Review of Astronomy and Astrophysics | Year: 2010

A fraction of the dust in the interstellarmedium (ISM) enters the heliosphere and is measured in situ from spacecraft. This review surveys the in situ measurements and discusses a hence derived model of dust in the local interstellar cloud (LIC). The LIC dustmodel bears similarities to pristine cometary dust and is characteristic of the warm ISM clouds that fill a part of the ISM in the vicinity of the Sun. Recent and future dust in situ measurements provide a basis for closely studying physical processes in the ISM surrounding the Solar System. The LIC dust is the only dust component measurable in the Solar System that was not previously incorporated in larger Solar System objects. Issues for future LIC dust studies are measuring dust fluxes at the outer heliosphere, measuring the mass distribution with meteor observations and observations from spacecraft, and measuring the LIC dust composition in situ in space. © 2010 by Annual Reviews.


Stavrakou T.,Belgian Institute for Space Aeronomy | Peeters J.,Catholic University of Leuven | Muller J.-F.,Belgian Institute for Space Aeronomy
Atmospheric Chemistry and Physics | Year: 2010

Stimulated by recent important developments regarding the oxidation chemistry of isoprene, this study evaluates and quantifies the impacts of different mechanism updates on the boundary layer concentrations of OH and HO2 radicals using the IMAGESv2 global chemistry transport model. The model results for HOx, isoprene, NO, and ozone are evaluated against air-based observations from the GABRIEL campaign, conducted over the Guyanas in October 2005, and from the INTEX-A campaign over the Eastern US in summer 2004. The version 2 of the Mainz Isoprene Mechanism (MIM2, Taraborrelli et al., 2009) used as reference mechanism in our simulations, has been modified to test (i) the artificial OH recycling proposed by Lelieveld et al. (2008), (ii) the epoxide formation mechanism proposed by Paulot et al. (2009b), and finally (iii) the HOx regeneration of the Leuven Isoprene Mechanism (LIM0) proposed by Peeters and Müller (2010). The simulations show that the LIM0 scheme holds by far the largest potential impact on HOx concentrations over densely vegetated areas in the Tropics as well as at mid-latitudes. Strong increases, by up to a factor of 4 in the modelled OH concentrations, and by a factor of 2.5-3 in the HO2 abundances are estimated through the LIM0 mechanism compared to the traditional isoprene degradation schemes. Comparatively much smaller OH increases (<25%) are associated with the implementation of the mechanism of Paulot et al. (2009b); moreover, the global production of epoxides is strongly suppressed (by a factor of 4) when the LIM0 scheme is combined with this mechanism. Hydroperoxy- aldehydes (HPALDs) are found to be major first-generation products in the oxidation of isoprene by OH, with a combined globally averaged yield of 50-60%. The use of the LIM0 chemistry in the global model allows for reconciling the model with the observed concentrations at a satisfactory level, compared to the other tested mechanisms, as the observed averaged mixing ratios of both OH and HO2 in the boundary layer can be reproduced to within 30%. In spite of the remaining uncertainties in the theoretically-predicted rates of critical radical reactions leading to the formation of HPALDs, and even more in the subsequent degradation of these new compounds, the current findings make a strong case for the newly proposed chemical scheme. Experimental confirmation and quantification is urgently needed for the formation of HPALDs and for their fast OH-generating photolysis. © 2010 Author(s).


Peeters J.,Catholic University of Leuven | Muller J.-F.,Belgian Institute for Space Aeronomy
Physical Chemistry Chemical Physics | Year: 2010

A consistent body of experimental evidence from work of other groups is presented in support of the novel, theoretically based, isoprene oxidation mechanism we recently proposed to rationalize the unexpectedly high OH concentrations observed over areas with high isoprene emissions. Some explicit or implicit criticisms on the new mechanism are addressed. A particular photochemical mechanism is newly proposed for the OH-regenerating photolysis of the crucial hydroperoxy-methyl-butenals (HPALDs), formed by isomerisation of the initial isoprene hydroxy-peroxy radicals, that rationalizes a quantum yield close to 1. A similar photolysis mechanism of the resulting photolabile peroxy-acid-aldehydes (PACALDs) is shown to generate ample additional OH. Global modeling demonstrates the major importance of the new chemistry for the oxidizing capacity of the atmosphere over continents. The globally averaged yield of the HPALDs in the oxidation of isoprene by OH is estimated to be of the order of 0.6. The isomerisation reactions of isoprene peroxy radicals are found to result in modelled [OH] increases in the planetary boundary layer by up to a factor of 3, in agreement with the reported observations as in the Amazon basin. © the Owner Societies 2010.


Compernolle S.,Belgian Institute for Space Aeronomy | Muller J.-F.,Belgian Institute for Space Aeronomy
Atmospheric Chemistry and Physics | Year: 2014

Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. While deriving HLC and depending on the case, also infinite dilution activity coefficients (IDACs), solid state vapour pressures or activity coefficient ratios are obtained as intermediate results. An error analysis on the intermediate quantities and the obtained HLC is included. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014), an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol. © Author(s) 2014.


Compernolle S.,Belgian Institute for Space Aeronomy | Muller J.-F.,Belgian Institute for Space Aeronomy
Atmospheric Chemistry and Physics | Year: 2014

In spite of the importance of diacids and functionalised diacids for organic aerosol formation through aqueous-phase processes in droplets and aerosol water, there seems to be no reliable set of experimental values for their Henry's law constants (HLCs). We show that their estimation through the use of infinite dilution activity coefficients is also prone to error. Here we present HLC values for diacids and hydroxy polyacids determined from solubilities, water activities and vapour pressures of solids or solutions, by employing thermodynamic relationships. The vapour pressures are found to be the largest source of error, but the analysis of the obtained HLC points to inconsistencies among specific vapour pressure data sets. Although there is considerable uncertainty, the HLC defined as aqueous concentration per unit gaseous partial pressure of linear α-and ω-diacids appear to be higher than estimated by the often cited review work of Saxena and Hildemann (1996). © 2014 Author(s).


Franssens G.R.,Belgian Institute for Space Aeronomy
Mathematical Methods in the Applied Sciences | Year: 2011

The set of associated homogeneous distributions (AHDs) on R, H ′(R), consists of the distributional analogues of power-log functions with domain in R. This set contains the majority of the (one-dimensional) distributions one typically encounters in physics applications. The recent work done by the author showed that the set H ′(R) admits a closed convolution structure (H ′(R),*). By combining this structure with the generalized convolution theorem, a distributional multiplication product was defined, resulting in also a closed multiplication structure (H′(R),.). In this paper, the general multiplication product formula for this structure is derived. Multiplication of AHDs on R is associative, except for critical triple products. These critical products are shown to be non-associative in a simple and interesting way. The non-associativity is necessary and sufficient to circumvent Schwartz's impossibility theorem on the multiplication of distributions. © 2011 John Wiley & Sons, Ltd.


Franssens G.R.,Belgian Institute for Space Aeronomy
Mathematical Methods in the Applied Sciences | Year: 2011

The set of Associated Homogeneous Distributions (AHDs) on R, H(R), consists of distributional analogues of power-log functions with domain in R. This set contains the majority of the (one-dimensional) distributions typically encountered in physics applications. In earlier work of the author it was shown that H(R) admits a closed convolution structure, provided that critical convolution products are defined by a functional extension process. In this paper, the general convolution product formula is derived. Convolution of AHDs on R is found to be associative, except for critical triple products. Critical products are shown to be non-associative in a minimal and interesting way. © 2010 John Wiley & Sons, Ltd.


Vranjes J.,Belgian Institute for Space Aeronomy
Physics of Plasmas | Year: 2011

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar and stellar winds. This is a current-less kinetic instability which develops in permeating plasmas, i.e., when one quasi-neutral electron-ion wind plasma in its propagation penetrates through another quasi-neutral plasma which contains dust, electrons, and ions. © 2011 American Institute of Physics.


Vranjes J.,Belgian Institute for Space Aeronomy
Monthly Notices of the Royal Astronomical Society | Year: 2011

The transverse drift wave, which is unstable due to purely kinetic effects, and driven by the density and magnetic field gradients, is discussed in context of its application to the solar corona. The gradients of the two quantities are opposite to each other, as required by the equilibrium pressure balance, and they are in the plane perpendicular to the magnetic field vector. The transverse drift wave has such properties that it propagates strictly perpendicularly to both the magnetic field vector and the mentioned gradients. It is electromagnetic, with the perturbed electric field in the direction of the equilibrium magnetic field, while the perturbed magnetic field vector is in the direction of the equilibrium gradients. Such an orientation of the electric field implies a possibility of acceleration of coronal plasma particles along the background magnetic field, in both directions, outward and inward. In the case of locally open magnetic structures, the outwardly moving particles should contribute to the solar wind. Those moving inwards eventually arrive in the lower solar atmosphere where the mean free path is short and, due to collisions, they should disperse their energy to the surrounding plasma and contribute to heating. It is also shown that accelerated particles can additionally be stochastically heated by the wave. This completely new stochastic heating mechanism is found here for the first time. It takes place provided that the particles are simultaneously accelerated by the wave to large enough velocities in the parallel direction. The model is applicable to any inhomogeneous coronal environment, like magnetic loops, coronal holes and the so-called EIT waves, named after the Extreme-ultraviolet Imaging Telescope (EIT) used for their first detection. © 2011 The Author Monthly Notices of the Royal Astronomical Society © 2011 RAS.

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