9 research outputs found
Goniopolarimetry with Coupled Electric and Magnetic Measurements
International audienc
Goniopolarimetry with Coupled Electric and Magnetic Measurements
International audienc
The seismic OPTIMISM experiment
International audienceThe study of the deep interior of Mars suffers from the very limited amount of data available, particularly seismological data. The objective of the OPTIMISM seismic experiment, lost with the failure of the Mars 96 mission, was to perform a seismic reconnaissance of Mars, to constrain the level of martian seismic noise and its level of seismicity. The seismometer was expected to operate during one year, with a sensitivity one hundred times higher than the Viking seismometer.Observation of relatively frequent low magnitude marsquakes, as well as a few large magnitude quakes might then be probably achieved. The OPTIMISM experiment might then, as a seismic âpath-finderâ, open a new field in Mars exploration and a new era in our present knowledge of the interior of Mars. A seismic experiment on Mars, especially performed by a network of stations, remains as the necessary experiment for the determination of the internal structure of the planet
Alfvén: magnetosphere-ionosphere connection explorers
The aurorae are dynamic, luminous displays that grace the night skies of Earthâs high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earthâs atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The âideal magnetohydrodynamicsâ description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The AlfvĂ©n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets
The seismic OPTIMISM experiment
International audienceThe study of the deep interior of Mars suffers from the very limited amount of data available, particularly seismological data. The objective of the OPTIMISM seismic experiment, lost with the failure of the Mars 96 mission, was to perform a seismic reconnaissance of Mars, to constrain the level of martian seismic noise and its level of seismicity. The seismometer was expected to operate during one year, with a sensitivity one hundred times higher than the Viking seismometer.Observation of relatively frequent low magnitude marsquakes, as well as a few large magnitude quakes might then be probably achieved. The OPTIMISM experiment might then, as a seismic âpath-finderâ, open a new field in Mars exploration and a new era in our present knowledge of the interior of Mars. A seismic experiment on Mars, especially performed by a network of stations, remains as the necessary experiment for the determination of the internal structure of the planet
The NetLander very broad band seismometer
International audienceThe interior of Mars is today poorly known, in contrast to the Earth interior and, to a lesser extent, to the Moon interior, for which seismic data have been used for the determination of the interior structure. This is one of the strongest facts motivating the deployment on Mars of a network of very broad band seismometers, in the framework of the 2007 CNES-NASA joint mission. These seismometers will be carried by the Netlanders, a set of 4 landers developed by a European consortium, and are expected to land in mid-2008. Despite a low mass, the seismometers will have a sensitivity comparable to the present Very Broad Band Earth sensors, i.e. better than the past Apollo Lunar seismometers. They will record the full range of seismic and gravity signals, from the expected quakes induced by the thermoelastic cooling of the lithosphere, to the possible permanent excitation of the normal modes and tidal gravity perturbations. All these seismic signals will be able to constrain the structure of Mars' mantle and its discontinuities, as well as the state and size of the Martian core, shortly after for the centennial of the discovery of the Earth core by Oldham (Quart. J. Geol. Soc. 62(1906) 456â475)