Time filter

Source Type

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.

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. Source

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. Source

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. Source

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. Source

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. Source

Discover hidden collaborations