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  • ASTROPHYSICS  (17)
  • Solar Physics  (8)
  • COMPUTER OPERATIONS AND HARDWARE  (1)
  • 1
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    The sun at minimum activity: Results from the CELIAS experiment on SOHO (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The charge element and isotope analysis system (CELIAS) experiment, designed to continuously measure the composition of the solar wind and solar suprathermal particles, is presented. Information on proton velocity, kinetic temperature, density and out-of-ecliptic flow angle is obtained. A preliminary statistical analysis of proton parameters and freeze-in temperatures, obtained during the first 18 months of the operation of the Solar and Heliospheric Observatory (SOHO), is presented. The first determinations of neon isotopic abundances with CELIAS yielded an excellent agreement with the Apollo-foil experiment. The magnesium isotopic composition in the solar wind agrees with the data acquired from earth.
    Keywords: Solar Physics
    Type: ; 37-43
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    NASA TECHNICAL REPORTS
  • 2
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    Elemental composition before, during and after the January 6, 1997, CME event measured by CELIAS/SOHO (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Using solar wind particle data from the charge, element and isotope analysis system (CELIAS) experiment on the SOHO mission, densities of the elements O, Ne, Mg, Si, S, Ca, and Fe are derived, and their abundance is analyzed before, during and after the 6 Janaury 1997 coronal mass ejection event (CME). In the interstream and coronal hole regions before and after this event, typical solar wind abundances for the elements investigated were found. However, during the passage of the coronal mass ejection and during the passage of the erupted filament, the elemental composition differed markedly from typical solar wind. For the passage of the CME and for the passage of the erupted filament, a mass-dependent enhancement of the elements was found, with a monotonic increase towards heavier elements. Si/O and Fe/O ratios of the order of one during these time periods were observed.
    Keywords: Solar Physics
    Type: Proceedings of the 31st ESALB Symposium on Correlated Phenomena at the Sun, in the Heliosphere and in Geospace; 395-400; ESA-SP-415
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    NASA TECHNICAL REPORTS
  • 3
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    Interstellar-gas experiment (A0038) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objectives of this experiment are to collect and isotopically analyze interstellar gas atoms around the orbit of the Earth for the purpose of obtaining new data relevant to understanding nucleosynthesis, and to study the dynamics of the interstellar wind inside the heliosphere and the isotopic composition of the interstellar medium outside the heliosphere. The experiment hardware will act as a set of simple cameras with high-purity copper-beryllium collecting foils serving as the film. The experiment housing will mount and thermally control the foils, establish the viewing angles and viewing direction, provide baffling to reject ambient neutral particles, provide a voltage grid to reject ionospheric charged particles, sequence collecting foils, control exposure times, and protect the foils from contamination during the deployment and retrieval of the LDEF. After being returned to Earth, the entrapped atoms can be analyzed by mass spectroscopy to determine the relative abundance of the different isotopes of helium and neon. An attempt will also be made to detect argon.
    Keywords: ASTROPHYSICS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 98-100
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  • 4
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    Large-scale variations of solar wind elemental composition and charge states with heliospheric latitude (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Solar Wind Ion Composition Spectrometer (SWICS) onboard Ulysses allows determination of the elemental composition of the solar wind and the charge states of all major solar wind ion species. Ulysses left the ecliptic plane in early 1992, crossed the Sun's south polar region in late 1994 and made a fast approach back towards the ecliptic in the first half of 1995. Data from this period were investigated for long-term variations in the solar wind composition. At midlatitudes Ulysses encountered periodically the fast solar wind stream emerging from the south coronal hole. As a consequence, dramatic variations in the charge-states arise, between high charge-states dominating in the current sheet solar wind and low charge states in the coronal hole stream. However, the initial analysis indicates that from midlatitudes onwards, with Ulysses permanently immersed in the coronal hole stream, the charge state and elemental abundance ratios of the major solar wind ion species stayed essentially constant. This implies that the temperature profile in the coronal hole at solar wind source altitudes exhibit no variation with solar latitude. It confirms that the south coronal hole is essentially unstructured down to scale lengths of several degrees in solar latitude.
    Keywords: Solar Physics
    Type: International Solar Wind 8 Conference; 74; NASA-CR-199940
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  • 5
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    SWICS/Ulysses and MASS/wind observations of solar wind sulfur charge states (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: As Ulysses journeys from the southern to the northern solar pole, the newly launched Wind spacecraft is monitoring the solar wind near 1 AU, slightly upstream of the Earth. Different solar wind structures pass over both spacecraft as coronal holes and other features rotate in and out of view. Ulysses and Wind are presently on opposing sides of the sun allowing us to monitor these streams for extended periods of time. Composition measurements made by instruments on both spacecraft provide information concerning the evolution and properties of these structures. We have combined data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and the high mass resolution spectrometer (MASS) on Wind to determine the charge state distribution of sulfur in the solar wind. Both instruments employ electrostatic deflection with time-of-flight measurement. The high mass resolution of the MASS instrument (M/Delta-M approximately 100) allows sulfur to be isolated easily while the stepping energy/charge selection provides charge state information. SWICS measurements allow the unique identification of heavy ions by their mass and mass/charge with resolutions of M/Delta-M approximately 3 and M/q/Delta(M/q) approximately 20. The two instruments complement each other nicely in that MASS has the greater mass resolution while SWICS has the better mass/charge resolution and better statistics.
    Keywords: Solar Physics
    Type: International Solar Wind 8 Conference; 73; NASA-CR-199940
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  • 6
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    Giotto IMS measurements of the production rate of hydrogen cyanide in the coma of Comet Halley (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The ion composition measurements in the ionosphere of Comet Halley by the ion mass spectrometer (IMS) experiment on the Giotto spacecraft are used to estimate the relative abundance of HCN. From a comparison of the normalized number density of ions with mass-to-charge (M/q) ratio of 28 AMU/e with steady-state photochemical models, it can be determined that the production rate of HCN directly from the central nucleus is Q(HCN) is less than about 0.0002 Q(H2O) at the time of Giotto encounter. The related photochemical- model calculations also indicate that Q(NH3)/Q(H2O) at the time of Giotto encounter. The related photo-chemical model calculations also indicate that Q(HN3)/Q(H2O) equals about 0.005, in agreement with recent determination from ground-based observations. The estimated value of Q(HCN) is lower than the relative abundance of Q(HCN)/Q(H2O) of about 0.001, as derived from radio observations of the 88.6 GHz emission of the J = 1 - 0 transition of HCN. The difference may be the result of time variations of the coma composition and dynamics, as well as other model-dependent effects.
    Keywords: ASTROPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 8; 319-325
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  • 7
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    Ion composition and dynamics at comet Halley (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The Giotto space probe's ion mass spectrometer has obtained data on the composition and velocity distributions of cometary ions at distances of between 7.5 million and 1300 km from the comet Halley nucleus. Solar wind He(2+) was found throughout the coma, as close as 5000 km, with the He(+) produced by charge exchange being within about 200,000 km. A pile-up of heavy cometary ions was found at about 10,000 km from the nucleus. Inside the contact surface, which was found at about 4600 km, ion temperatures as low as about 340 K and outflow velocities of about 1 km/sec were found.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 321; 330-334
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  • 8
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    Thermal diffusion in partially ionized gases - The case of unequal temperatures (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Previous calculations of thermal diffusion coefficients in partially ionized gases are extended to the case of unequal neutral and ion temperatures and/or temperature gradients. Formulas are derived for the general case of a major gas as well as for minor atoms and ions. Strong enhancements of minor-ion thermal diffusion coefficients over their values in the fully ionized gas are found when the degree of ionization in the main gas is relatively low. However, compared to the case of equal temperatures, the enhancements are less strong when the neutrals are cooler than the ions. The specific case of the H-H(+) mixture, which is important in the study of solar and stellar atmospheres, is discussed as an application.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 178; 1-2,; 286-291
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  • 9
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    Ion composition and upstream solar wind observations at comet Giacobini-Zinner (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The observations by the ion composition instrument (ICI) on the ICE spacecraft made during the encounter with comet P/Giacobini-Zinner (Ogilvie et al., 1986) are discussed in detail. Solar wind He-4(2+) kinetic temperatures, densities, and velocities before, during, and after the encounter are presented. These data combined with He-4(2+) velocity distributions provide evidence for the existence of a thick diffuse shock. Relative abundances of water group ions and CO(+) are derived along with an estimate of the abundance of an ion with M/Q = 24 + or - 1 amu/e. The ICI data are compared with electron data from two other experiments (Bame et al., 1986; Meyer-Vernet et al., 1986) and found to be in reasonable agreement in the region outside the tail. Spectroscopic data for several neutral and ionic species are compared with the ICI results for the water group ions and CO(+). The spectroscopic data are also used to eliminate Mg(+) and CN(+) as candidates for the M/Q = 24 peak. The two most likely candidates are C2(+) and Na(+), but neither photoionization of parent neutrals nor sputtering from dust grains is sufficient to explain the observed abundance relative to H2O(+).
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 39-46
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  • 10
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    Origin of metal ions in the coma of P/Giacobini-Zinner (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: During the crossing of the ICE spacecraft through the coma of the comet Giacobini-Zinner, ions with a mass/charge ratio 24 + or - 1 were unexpectedly found. Na(+) and/or Mg(+) would fit into this mass range. Processes that could lead to high metal ion abundances in cometary comas are discussed and it is concluded that evaporation or sputtering from silicate grains are not likely to be responsible. A remaining possibility is the occurrence of alkali metals in the icy phase as a result of either cometary differentiation or cocondensation of these elements with the icy component prior to the accretion of cometary bodies.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 166; 1-2,; L1-L4
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