Constraining the wind launching region in Herbig Ae stars: AMBER/VLTI spectroscopy of HD 104237

Astronomy and Astrophysics, 464, pp. 55-58, http://dx.doi.org./10.1051/0004-6361:20065719International audienc

A hybrid beta Cephei-SPB star in a binary system: gamma Pegasi

Astronomy and Astrophysics, v. 448, p. 697-701, 2006. http://dx.doi.org/10.1051/0004-6361:20053815International audienc

Waves and turbulence in the cusp, at the magnetopause and its vicinity as seen by the Cluster STAFF experiment : characterisation and role on particle dynamics.

Key regions of the interface between the Solar Wind and the Earth's magnetosphere, as the cusp and the magnetopause are known to be populated by plasma waves and turbulence. The role of the strong ULF waves at the magnetopause, recognised as being "turbulent like" and very intense is questioned on its possibility to transfer particle mass, energy and momentum from the Solar Wind into the magnetosphere, for instance via the so-called Flux Transfer Events. The Cluster spacecraft, thanks to the tetrahedron position of the 4 spacecraft, specially with small separations, allow to use special tools, as the k-filtering method to identify "linear" modes in turbulent-like structures, the curl B method to calculate currents e.g. in FTEs (to which turbulent like ULF waves are associated). These new results can now be compared with theoretical predictions. A special emphasis will be put on the cusp region, seat of a different kind of waves. In particular the same k-filtering tool will be applied to determine the modes of the turbulent like waves, and whose role in diffusing injected ions will be evidenced

Universality of Lower Hybrid Waves at Earth's Magnetopause

Waves around the lower hybrid frequency are frequently observed at Earth's magnetopause and readily reach very large amplitudes. Determining the properties of lower hybrid waves is crucial because they are thought to contribute to electron and ion heating, cross-field particle diffusion, anomalous resistivity, and energy transfer between electrons and ions. All these processes could play an important role in magnetic reconnection at the magnetopause and the evolution of the boundary layer. In this paper, the properties of lower hybrid waves at Earth's magnetopause are investigated using the Magnetospheric Multiscale mission. For the first time, the properties of the waves are investigated using fields and direct particle measurements. The highest-resolution electron moments resolve the velocity and density fluctuations of lower hybrid waves, confirming that electrons remain approximately frozen in at lower hybrid wave frequencies. Using fields and particle moments, the dispersion relation is constructed and the wave-normal angle is estimated to be close to 90° to the background magnetic field. The waves are shown to have a finite parallel wave vector, suggesting that they can interact with parallel propagating electrons. The observed wave properties are shown to agree with theoretical predictions, the previously used single-spacecraft method, and four-spacecraft timing analyses. These results show that single-spacecraft methods can accurately determine lower hybrid wave properties