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- Coustenis, A., et al.
(författare)
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TandEM : Titan and Enceladus mission
- 2009
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 893-946
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Tidskriftsartikel (refereegranskat)abstract
- TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (MontgolfiSre) and possibly several landing probes to be delivered through the atmosphere.
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| 2. |
- Hasegawa, H., et al.
(författare)
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Kelvin-Helmholtz waves at the Earth's magnetopause : Multiscale development and associated reconnection
- 2009
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114:12, s. A12207-
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Tidskriftsartikel (refereegranskat)abstract
- We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at similar to 1500 magnetic local time (MLT) by the Geotail spacecraft and at similar to 1900 MLT by the Cluster spacecraft, which detected rolled-up MHD-scale vortices generated by the Kelvin-Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD-scale and ion-scale structures of the vortices, and the formation mechanism of the low-latitude boundary layer (LLBL). The observed KH wavelength (>4 x 10(4) km) is considerably longer than predicted by the linear theory from the thickness (similar to 1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high-latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length similar to 100 km and of magnetic shear similar to 60 degrees existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvenic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field-aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk-flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster.
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| 4. |
- Shell, Y. H., et al.
(författare)
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A generic symbiotic simulation framework
- 2006
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Ingår i: Proceedings - Workshop on Principles of Advanced and Distributed Simulation, PADS. - 0769525873 - 9780769525877
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Konferensbidrag (refereegranskat)abstract
- A symbiotic or online simulation is defined as one that interacts with the physical system in a mutually beneficial way. The simulation is driven by real time data collected from a physical system under control and needs to meet the real-time requirements of the physical system. In turn, the results from the "what-if experiments performed by the simulator can be used to control the dynamic behaviour of the physical system. Such a simulation tool is for real-time planning and is to foresee and advise on real time problems. It aims to improve performance, to adapt to sudden and unexpected events and to improve aspects of safety and security of the physical system. There are some research efforts, for example, the Dynamic Data-Driven Application Systems (DDDAS) which are currently advocated by the National Science Foundation (NSF) of the United States. However, work in this area is far from complete and many of the research issues are not fully addressed. We see the need for a general framework for symbiotic simulation. In this project, simulators based on the same general framework will be developed using symbiotic simulation techniques and will be used to provide adaptive decision support to manage the resources in several application environments. The objectives of this project are: To develop a generic, agent-based, symbiotic simulation system architecture. To develop mechanisms to support dynamic coupling between the symbiotic simulation system and the physical system. To conduct pilot case studies of the simulation framework. To explore and evaluate the service oriented architecture approach for parallel simulation in the multi-agent symbiotic simulation framework.
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| 8. |
- Nakamura, R., et al.
(författare)
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Cluster observations of an ion-scale current sheet in the magnetotail under the presence of a guide field
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A7, s. A07S16-
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Tidskriftsartikel (refereegranskat)abstract
- We report on Cluster observations of a thin current sheet interval under the presence of a strong vertical bar B-Y vertical bar during a fast earthward flow interval between 1655 UT and 1703 UT on 17 August 2003. The strong vertical bar B-Y vertical bar in the tail could be associated with a strong IMF vertical bar B-Y vertical bar, but the large fluctuations in B-Y, not seen in the IMF, suggest that a varying reconnection rate causes a varying transport of B-Y-dominated magnetic flux and/or a change in B-Y due to the Hall-current system. During the encounter of the high-speed flow, an intense current layer was observed around 1655: 53 UT with a peak current density of 182 nA/m(2), the largest current density observed by the Cluster four-spacecraft magnetic field measurement in the magnetotail. The half width of this current layer was estimated to be similar to 290 km, which was comparable to the ion-inertia length. Its unique signature is that the strong current is mainly field-aligned current flowing close to the center of the plasma sheet. The event was associated with parallel heating of electrons with asymmetries, which suggests that electrons moving along the field lines can contribute to a strong dawn-to-dusk current when the magnetotail current sheet becomes sufficiently thin and active in a strong guide field case.
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