257 research outputs found
Solar wind observations with the ion composition instrument aboard the ISEE-3 ICE spacecraft
The principal observations obtained by the Ion Composition Instrument (ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind from September 1978 to the end of 1982, before being directed to the far magnetotail of the Earth are discussed. Almost continuous observations were made of the abundances of 3He++, 4He++, O6+, O7+, Ne, Si and Fe in various charge states, and of their bulk speeds and temperatures. The results show that there is a strong tendency in the collisionless solar wind for the ionic temperatures to be proportional to the masses. For heavier ions these temperatures exceed typical coronal electron temperatures. 4He++, especially in high speed streams, moves faster than H+, and travels at the same speed as heavier ions. The mechanism leading to this heating and rapid streaming is still not entirely clear
Composition of Light Solar Wind Noble Gases in the Bulk Metallic Glass flown on the Genesis Mission
We discuss data of light noble gases from the solar wind implanted into a metallic glass target flown on the Genesis mission. Helium and neon isotopic compositions of the bulk solar wind trapped in this target during 887 days of exposure to the solar wind do not deviate significantly from the values in foils of the Apollo Solar Wind Composition experiments, which have been exposed for hours to days. In general, the depth profile of the Ne isotopic composition is similar to those often found in lunar soils, and essentially very well reproduced by ion-implantation modelling, adopting the measured velocity distribution of solar particles during the Genesis exposure and assuming a uniform isotopic composition of solar wind neon. The results confirm that contributions from high-energy particles to the solar wind fluence are negligible, which is consistent with in-situ observations. This makes the enigmatic "SEP-Ne” component, apparently present in lunar grains at relatively large depth, obsolete. 20Ne/ 22Ne ratios in gas trapped very near the metallic glass surface are up to 10% higher than predicted by ion implantation simulations. We attribute this superficially trapped gas to very low-speed, current-sheet-related solar wind, which has been fractionated in the corona due to inefficient Coulomb dra
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Noble gases from the interstellar medium trapped on the MIR space station and analyzed by in vacuo etching
Introduction: The composition of the present interstellar medium (ISM) provides an important benchmark in cosmochemistry. It serves as a reference for galactic chemical evolution (GCE) models, solar mixing predictions and provides information for understanding Big Bang nucleosynthesis. The present-day ISM 3He abundance allows, combined with the protosolar 3He, deduced from the Jovian atmosphere or meteorites [1,2], tracing the GCE over the past 4.56 Ga. 3He/4He = (2.5 0.6) x 10-4 has been determined for the local ISM [3]. However, the uncertainty is too large to better constrain GCE models and - in combination with the present-day solar wind value - the protosolar D/H [4]
Applications of graphics to support a testbed for autonomous space vehicle operations
Researchers describe their experience using graphics tools and utilities while building an application, AUTOPS, that uses a graphical Machintosh (TM)-like interface for the input and display of data, and animation graphics to enhance the presentation of results of autonomous space vehicle operations simulations. AUTOPS is a test bed for evaluating decisions for intelligent control systems for autonomous vehicles. Decisions made by an intelligent control system, e.g., a revised mission plan, might be displayed to the user in textual format or he can witness the effects of those decisions via out of window graphics animations. Although a textual description conveys essentials, a graphics animation conveys the replanning results in a more convincing way. Similarily, iconic and menu-driven screen interfaces provide the user with more meaningful options and displays. Presented here are experiences with the SunView and TAE Plus graphics tools used for interface design, and the Johnson Space Center Interactive Graphics Laboratory animation graphics tools used for generating out out of the window graphics
Isotopic Composition of Solar Wind Calcium: First in Situ Measurement by CELIAS/MTOF on Board SOHO
We present first results on the Ca isotopic abundances derived from the high
resolution Mass Time-of-Flight (MTOF) spectrometer of the charge, element, and
isotope analysis system (CELIAS) experiment on board the Solar and Heliospheric
Observatory (SOHO). We obtain isotopic ratios 40Ca/42Ca = (128+-47) and
40Ca/44Ca = (50+-8), consistent with terrestrial values. This is the first in
situ determination of the solar wind calcium isotopic composition and is
important for studies of stellar modeling and solar system formation since the
present-day solar Ca isotopic abundances are unchanged from their original
isotopic composition in the solar nebula.Comment: 14 pages, 3 figure
On the linear fractional self-attracting diffusion
In this paper, we introduce the linear fractional self-attracting diffusion
driven by a fractional Brownian motion with Hurst index 1/2<H<1, which is
analogous to the linear self-attracting diffusion. For 1-dimensional process we
study its convergence and the corresponding weighted local time. For
2-dimensional process, as a related problem, we show that the renormalized
self-intersection local time exists in L^2 if .Comment: 14 Pages. To appear in Journal of Theoretical Probabilit
Determination of Interstellar O Parameters Using the First Two Years of Data from the Interstellar Boundary Explorer
The direct measurements of interstellar matter by the Interstellar Boundary Explorer ( IBEX ) mission have opened a new and important chapter in our study of the interactions that control the boundaries of our heliosphere. Here we derive for the quantitative information about interstellar O flow parameters from IBEX low-energy neutral atom data for the first time. Specifically, we derive a relatively narrow four-dimensional parameter tube along which interstellar O flow parameters must lie. Along the parameter tube, we find a large uncertainty in interstellar O flow longitude, 76°.0 ± 3°.4 from χ 2 analysis and 76°.5 ± 6°.2 from a maximum likelihood fi t, which is statistically consistent with the fl ow longitude derived for interstellar He, 75°.6 ± 1°.4. The best-fit O and He temperatures are almost identical at a reference flow longitude of 76°, which provides a strong indication that the local interstellar plasma near the Sun is relatively unaffected by turbulent heating. However, key differences include an oxygen parameter tube for the interstellar speed (relation between speed and longitude) that has higher speeds than those in the corresponding parameter tube for He, and an upstream flow latitude for oxygen that is southward of the upstream flow latitude for helium. Both of these differences are likely the result of enhanced filtration of interstellar oxygen due to its charge-exchange ionization rate, which is higher than that for helium. Furthermore, we derive an interstellar O density near the termination shock of - + - 5 .8 X 10^-5 cm that, within uncertainties, is consistent with previous estimates. Thus, we use IBEX data to probe the interstellar properties of oxygen
Coral Disease and Health Workshop: Coral Histopathology II
The health and continued existence of coral reef ecosystems are threatened by an increasing array of environmental and anthropogenic impacts. Coral disease is one of the prominent causes of increased mortality among reefs globally, particularly in the Caribbean. Although over 40 different coral diseases and syndromes have been reported
worldwide, only a few etiological agents have been confirmed; most pathogens remain unknown and the dynamics of disease transmission, pathogenicity and mortality are not
understood. Causal relationships have been documented for only a few of the coral diseases, while new syndromes continue to emerge. Extensive field observations by coral
biologists have provided substantial documentation of a plethora of new pathologies, but our understanding, however, has been limited to descriptions of gross lesions with names reflecting these observations (e.g., black band, white band, dark spot). To determine etiology, we must equip coral diseases scientists with basic biomedical knowledge and specialized training in areas such as histology, cell biology and pathology. Only through
combining descriptive science with mechanistic science and employing the synthesis epizootiology provides will we be able to gain insight into causation and become equipped to handle the pending crisis.
One of the critical challenges faced by coral disease researchers is to establish a framework to systematically study coral pathologies drawing from the field of diagnostic
medicine and pathology and using generally accepted nomenclature. This process began in April 2004, with a workshop titled Coral Disease and Health Workshop: Developing Diagnostic Criteria co-convened by the Coral Disease and Health Consortium (CDHC), a working group organized under the auspices of the U.S. Coral Reef Task Force, and the International Registry for Coral Pathology (IRCP). The workshop was hosted by the U.S. Geological Survey, National Wildlife Health Center (NWHC) in Madison, Wisconsin and was focused on gross morphology and disease signs observed in the field. A resounding recommendation from the histopathologists participating in the workshop was the urgent need to develop diagnostic criteria that are suitable to move from gross observations to morphological diagnoses based on evaluation of microscopic anatomy. (PDF contains 92 pages
Argon, krypton, and xenon abundances in the solar wind measured in silicon from the genesis mission
Up to now solar wind (SW) abundances of Kr and Xe
have been exclusively determined using SW irradiated regolith [1]. Hence,
one of Genesis’s major objectives is to obtain the heavy noble gas
composition of the present-day SW using artificial targets exposed to the SW
for 2.5 years. SW abundances will allow to study fractionation processes
upon SW formation, e.g., due to the first ionization potential (FIP-effect) [2].
This is of importance to deduce solar abundances of noble gases and other
elements from SW data. Solar, i.e., photospheric, abundances of noble gases
are indirectly determined due to the lack of suitable lines in the spectrum.
Recently, solar abundance estimates for Ne and Ar were strongly reduced
whereas Kr and Xe changed only slightly [3]. This led to a dramatic decrease
of the solar Ar/Kr ratio by a factor of ~3 from the earlier value [4] of 2140. If
true, this change would invalidate theories of heavy noble gas fractionation in
the SW identified with regolith data [1, 5]. The Kr and Xe composition in
present-day SW will enable us to reassess solar abundances and fractionation
theories. Thus, we concentrate here on abundances of Ar, Kr and Xe in the
bulk SW
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