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| Vortex circulation on Venus: Dynamical similarities with terrestrial hurricanes |
| Some dynamical and morphological similarities exist between the vortex organization of the atmosphere in the northern and southern hemispheres of Venus and the tropical cyclones/hurricanes on Earth. An S-shape feature detected in the center of the vortices on Venus from Pioneer Venus Orbiter and Venus Express observations has also been seen in tropical cyclones. This feature can be simulated with an idealized nonlinear and non-divergent barotropic model and, like in the vortices on Venus and in tropical cyclones, it is found to be transient. Given the challenges in measuring the deep, atmospheric circulation of Venus, the morphological similarities provide clues toward understanding the processes involved in the maintenance of Venus' atmospheric super rotation. |
| Publication date: 25 Feb 2009 |
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| Reconnection at High Latitudes: Antiparallel Merging |
| New investigations have renewed the debate on the occurrence of magnetic reconnection of Earth's dayside magnetopause. Here, we show for the first time strong evidence for a high-latitude reconnection site, located on initially closed field lines, where the magnetic field orientations inside and outside the magnetopause are close to antiparallel. The evidence centers on repeated sampling of the ion diffusion region and associated null magnetic field by four spacecraft in formation, together with simultaneous monitoring of the local magnetosheath behavior by a fifth spacecraft. |
| Publication date: 20 Feb 2009 |
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| Strong Release of Methane on Mars in Northern Summer 2003 |
| Living systems produce more than 90% of Earth's atmospheric methane; the balance is of geochemical origin. On Mars, methane could be a signature of either origin. Using high-dispersion infrared spectrometers at three ground-based telescopes, we measured methane and water vapor simultaneously on Mars over several longitude intervals in northern early and late summer in 2003 and near the vernal equinox in 2006. When present, methane occurred in extended plumes, and the maxima of latitudinal profiles imply that the methane was released from discrete regions. In northern midsummer, the principal plume contained ~19,000 metric tons of methane, and the estimated source strength (>=0.6 kilogram per second) was comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, California. |
| Publication date: 20 Feb 2009 |
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| Cluster and Double Star multipoint observations of a plasma bubble |
| Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005, during a period of southward, but BY-dominated IMF. In particular the first direct observations of return flows around the edges of a plasma bubble, and the first observations of plasma bubble features within 8 RE of the Earth, consistent with MHD simulations (Birn et al., 2004) are presented. The implications of the presence of a strong BY in the IMF and magnetotail on the propagation of the plasma bubble and development of the associated current systems in the magnetotail and ionosphere are discussed. It is suggested that a strong BY can rotate the field aligned current systems at the edges of the plasma bubble away from its duskward and dawnward flanks. |
| Publication date: 16 Feb 2009 |
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| Magnetosphere response to the 2005 and 2006 extreme solar events as observed by the Cluster and Double Star spacecraft |
| The four identical Cluster spacecraft, launched in 2000, orbit the Earth in a tetrahedral configuration and on a highly eccentric polar orbit (4-19.6 RE). This allows the crossing of critical layers that develop as a result of the interaction between the solar wind and the Earth's magnetosphere. Since 2004 the Chinese Double Star TC-1 and TC-2 spacecraft, whose payload comprise also backup models of instruments developed by European scientists for Cluster, provided two additional points of measurement, on a larger scale: the Cluster and Double Star orbits are such that the spacecraft are almost in the same meridian, allowing conjugate studies. The Cluster and Double Star observations during the 2005 and 2006 extreme solar events are presented, showing uncommon plasma parameters values in the near-Earth solar wind and in the magnetosheath. These include solar wind velocities up to ~900 km/s during an ICME shock arrival, accompanied by a sudden increase in the density by a factor of ~5 and followed by an enrichment in He++ in the secondary front of the ICME. In the magnetosheath ion density values as high as 130 cm-3 were observed, and the plasma flow velocity there reached values even higher than the typical solar wind velocity. These resulted in unusual dayside magnetosphere compression, detection of penetrating high-energy particles in the magnetotail, and ring current development following several successive injections of energetic particles in the inner magnetosphere, which "washed out" the previously formed nose-like ion structures. |
| Publication date: 16 Feb 2009 |
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| Galaxies Across Cosmic Time with JWST |
| The James Webb Space Telescope (JWST; Gardner et al. 2006) will be a large, cold, infrared-
optimized space telescope designed to enable fundamental breakthroughs in our understanding of
the formation and evolution of galaxies, stars, and planetary systems (see Astro 2010 white papers
by Gardner et al., Stiavelli et al., Meixner et al., G. Rieke et al., & Sonneborn et al.). In the current
white paper, we describe the great potential of JWST in the theme of Galaxy Assembly. |
| Publication date: 13 Feb 2009 |
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| Direct evidence of solar wind deceleration in the foreshock of the Earth |
| Although the solar wind deceleration in the terrestrial foreshock was noticed three decades ago, previous studies show some conflicting results. This paper presents direct evidence of solar wind deceleration in the foreshock of the Earth by using the data of two Cluster satellites. On 2 February 2003, the two satellites (C1 and C3) of Cluster missions are inside and outside the foreshock, respectively, approximately along the solar wind flow line, which can effectively exclude the uncertainty caused by the spatial and temporal changes of solar wind itself. Comparison of the plasma data recorded by two satellites shows that the solar wind velocity decreases in the foreshock and the largest deceleration reaches 22 km/s. The velocity distribution of ions in the phase space indicates that the solar wind ions undergo pitch angle scattering in the foreshock. The solar wind deceleration is associated with diffuse ions and ULF wave activities. The diffuse ion density reached 0.25 cm-3, about 7% of the solar wind density. The interaction of ULF waves with solar wind also deflects the solar wind away from the bow shock in both the ecliptic and the meridian planes. Meanwhile, the solar wind deceleration is accompanied by thermalization during which the solar wind temperature can reach 240 eV. |
| Publication date: 12 Feb 2009 |
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| ESA contribution to the Titan Saturn System Mission |
This report describes the updated baseline of the internal assessment study that was performed with the assistance of the ESTEC Concurrent Design Facility (CDF) in June and July 2008. The main goals of the CDF study
were:-
to assess the feasibility of the proposed mission
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to prepare for the future competitive industrial assessment studies by identifying critical issues that need addressing at higher priority
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to provide the building blocks and feed-back for further interaction with the science team for formulation of feasible mission goals.
To this end, the CDF study established bottom-up designs for three elements: a montgolfière, a long-lived lander (powered by an ASRG), and a minimum sized small lander of limited lifetime (powered by battery).
This report describes the design of the chosen baseline after the first technical iteration and incuding an updated mission profile providing enhanced mass capability of the delivery of the in situ elements, after the addition of a solar electric propulsion stage of the NASA orbiter.
This report is the result of an independent ESA internal assessment study. |
| Publication date: 12 Feb 2009 |
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| Jupiter Ganymede Orbiter: ESA contribution to the Europe Jupiter System Mission |
| This document gives a concise overview of the ESA assessment study based on the "Laplace" proposal for the Cosmic Vision 2015-2025 call. It describes the work performed during the assessment study, which includes the Concurrent Design Facility (CDF) study and subsequent scientific and engineering work. The aim of this study was to quickly assess the technical feasibility, cost and schedule in the framework of a Cosmic Vision 2015-2025 L-class mission and to prepare the follow-on industrial studies. The transition from the submitted "Laplace" proposal to the ESA/NASA/JAXA joint mission called "Europa/Jupiter System Mission" (EJSM) is documented and the baseline of the ESA contribution to this mission, the Jupiter Ganymede Orbiter (JGO), is described in detail.
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| Publication date: 12 Feb 2009 |
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| Spatium 23: Meteorites |
| The present issue of Spatium is devoted to meteorites, more specifically however to the good-natured class of small extraterrestrial bodies that continue reaching the Earth without doing major harm. Science has learned to appreciate them as
cosmic messengers that faithfully recount the billion year history of our solar system. This role of meteorites was the topic of an exciting
lecture by Dr. Beda Hofmann (Natural History Museum of Bern and Institute for Geology, University of Bern) for the Pro ISSI audience on
28 October 2008. |
| Publication date: 01 Feb 2009 |
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