Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during ... more Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during periods of substorm activity. Nonlinear dynamics of charged particles and scattering processes in such double-humped current sheets are investigated with special emphasis on high-energy particles that have a parameter kappa (defined as the square root of ratio of the minimum field line curvature radius to maximum ion Larmor radius) smaller than one. We demonstrate that the diffusion of the adiabatic invariant Iz results from successive jumps of small amplitude. This differs from the usual case with a bell-shaped current density profile. Such a scattering in splitted sheets leads to stronger diffusion of the adiabatic invariant Iz as well as changes in the structure of Poincaré maps. The regions of quasi-trapped plasma in these maps are found to be larger than in the usual case. The jumps of adiabatic invariant as a function of gyrophase and particle energy also exhibit a complex resonanc...
Mercury is a poorly known planet, since the only space-based information comes from the three fly... more Mercury is a poorly known planet, since the only space-based information comes from the three fly-bys performed in 1974 by the Mariner 10 spacecraft. Ground-based observations also provided some interesting results, but they are particularly difficult to obtain due to the planet's proximity to the Sun. Nevertheless, the fact that the planet's orbit is so close to the Sun makes Mercury a particularly interesting subject for extreme environmental conditions. Among a number of crucial scientific topics to be addressed, Mercury's exosphere, its interaction with the solar wind and its origin from the surface of the planet, can provide important clues about planetary evolution. In fact, the Hermean exosphere is continuously eroded and refilled by these interactions, so that it would be more proper to consider the Hermean environment as a single, unified system -surfaceexosphere-magnetosphere. These three parts are indeed strongly linked to each other. In recent years, the two missions scheduled to explore the iron planet, the NASA MESSENGER mission (launched in March 2004) and the ESA cornerstone mission (jointly with JAXA) BepiColombo (to be launched in 2012), have stimulated new interest in the many unresolved mysteries related to it. New ground-based observations, made possible by new technologies, have been obtained, and new simulation studies have been performed. In this paper some old as well as the very latest observations and studies related to the surface-exosphere-magnetosphere system are reviewed, outlining the investigations achievable by the planned space-based observations. This review intends to support the studies, in preparation of future data, and the definition of specific instrumentation.
Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy stora... more Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy storage. Customarily their dynamics and possible disruptions are associated with different macro- or microscale instabilities. We are considering here another evolutionary type mechanism of thin current sheet disruption related to the scattering of current carrying particles at transient Speiser orbits due to unavoidable non- adiabatic effects. The corresponding current of particles scattered to quasi-trapped orbits is opposite to one of carriers at the center of the current sheet. The process of scattering may be interpreted as the degradation of current sheet by particles reducing the total current at the center of the sheet without significant changing of the TCS thickness. As a result the effective parameter of adiabaticity (which is proportional to the minimum curvature radius of the magnetic field line) is growing, and the process of ion scattering speeds up. This results in development...
Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during ... more Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during periods of substorm activity. Nonlinear dynamics of charged particles and scattering processes in such double-humped current sheets are investigated with special emphasis on high-energy particles that have a parameter kappa (defined as the square root of ratio of the minimum field line curvature radius to maximum ion Larmor radius) smaller than one. We demonstrate that the diffusion of the adiabatic invariant Iz results from successive jumps of small amplitude. This differs from the usual case with a bell-shaped current density profile. Such a scattering in splitted sheets leads to stronger diffusion of the adiabatic invariant Iz as well as changes in the structure of Poincaré maps. The regions of quasi-trapped plasma in these maps are found to be larger than in the usual case. The jumps of adiabatic invariant as a function of gyrophase and particle energy also exhibit a complex resonanc...
Mercury is a poorly known planet, since the only space-based information comes from the three fly... more Mercury is a poorly known planet, since the only space-based information comes from the three fly-bys performed in 1974 by the Mariner 10 spacecraft. Ground-based observations also provided some interesting results, but they are particularly difficult to obtain due to the planet's proximity to the Sun. Nevertheless, the fact that the planet's orbit is so close to the Sun makes Mercury a particularly interesting subject for extreme environmental conditions. Among a number of crucial scientific topics to be addressed, Mercury's exosphere, its interaction with the solar wind and its origin from the surface of the planet, can provide important clues about planetary evolution. In fact, the Hermean exosphere is continuously eroded and refilled by these interactions, so that it would be more proper to consider the Hermean environment as a single, unified system -surfaceexosphere-magnetosphere. These three parts are indeed strongly linked to each other. In recent years, the two missions scheduled to explore the iron planet, the NASA MESSENGER mission (launched in March 2004) and the ESA cornerstone mission (jointly with JAXA) BepiColombo (to be launched in 2012), have stimulated new interest in the many unresolved mysteries related to it. New ground-based observations, made possible by new technologies, have been obtained, and new simulation studies have been performed. In this paper some old as well as the very latest observations and studies related to the surface-exosphere-magnetosphere system are reviewed, outlining the investigations achievable by the planned space-based observations. This review intends to support the studies, in preparation of future data, and the definition of specific instrumentation.
Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy stora... more Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy storage. Customarily their dynamics and possible disruptions are associated with different macro- or microscale instabilities. We are considering here another evolutionary type mechanism of thin current sheet disruption related to the scattering of current carrying particles at transient Speiser orbits due to unavoidable non- adiabatic effects. The corresponding current of particles scattered to quasi-trapped orbits is opposite to one of carriers at the center of the current sheet. The process of scattering may be interpreted as the degradation of current sheet by particles reducing the total current at the center of the sheet without significant changing of the TCS thickness. As a result the effective parameter of adiabaticity (which is proportional to the minimum curvature radius of the magnetic field line) is growing, and the process of ion scattering speeds up. This results in development...
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Papers by D. Delcourt