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  • 1
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    White Light Stray Light Test of the SOHO UVCS (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: During the late stages of the integration phase of the Ultraviolet Coronagraph Spectrometer (UVCS) instrument for the Solar and Heliospheric Observatory (SOHO) at MATRA-Marconi in Toulouse, France, SOHO Project management at Goddard Space Flight Center (GSFC) became concerned that the elaborate stray light rejection system for the instrument had not been tested and might possibly be misaligned such that the instrument could not deliver promised scientific returns. A white light stray light test, which would place an upper bound on the value of UVCS's stray light rejection capability, was commissioned, conceived, and carried out. This upper bound value would be indicative of the weakest coronal features the spectrometer would be capable of discerning. The test was rapidly developed at GSFC in coordination with science team members from Harvard-Smithsonian Center for Astrophysics (CFA) and was carried out at MATRA in late February 1995. The outcome of this test helped to justify similar, much desired tests with visible and far ultraviolet light at CFA in a facility specifically designed to perform such testing.
    Keywords: Optics
    Type: Jul 19, 1998 - Jul 24, 1998; San Diego, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
    Electronic Resource
    Electronic Resource
    In situ absolute calibration of a channel electron multiplier for detection of positive ions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 67-71 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A technique has been developed to determine the absolute single particle counting efficiency of a channel electron multiplier (CEM) for positively charged ions at keV energies. The calibration technique is applicable to positive ion detectors in general. Ion beam currents of C2+ were created by charge transfer of C3+ on H2 in the thin target regime. By adjusting the H2 pressure in the beam scattering chamber from 10−10 to 10−6 Torr, C2+ currents could be created either low enough to be detected by the CEM in the particle counting mode or high enough to be measured as a current using the CEM as a Faraday cup. The CEM counting efficiency was determined by comparing the C2+ count rate to the C2+ current, scaling by the change in H2 pressure, and also scaling by the incident C3+ current for each C2+ measurement. This method, which effectively uses the charge transfer cross section as a "transfer standard,'' allows the CEM counting efficiency to be determined in situ and to be monitored accurately over extended periods of time. The calibration requires that only the relative, not the absolute, pressure change be known. The technique does not require the value of the charge transfer cross section to be known. The accuracy of the calibration technique for the present results was 10% at a confidence level considered to be equivalent to a statistical 90% confidence level. For the present work, the peak counting efficiency of a Galileo 4039 CEM for 32.5 keV C2+ ions was determined to be 96%. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146531
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Inexpensive Electronic Water Level Recorders for Hydrologic Studies (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 16 (1996), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Hydrologic investigations typically involve the collection of water level measurements at discrete points in space and time. The high cost of commercial electronic recorders can be a burden. We have developed an inexpensive (∼$200) electronic water level recorder consisting of a Motorola microcontroller, a clock, memory, pressure transducers, and associated circuitry. The instrument is powered by a 6-V battery. These devices, each capable of monitoring up to eight channels of analog input, are presently providing continuous monitoring of nested piezometers, tide gauges, and rain gauges in hydrologic studies at the Savannah River site and the North Inlet (South Carolina) Long-Term Ecological Research (LTER) site. The instruments can be custom tailored to record water levels at any specified time interval, or whenever the water level changes by a specified amount, and can store up to 32,000 water level observations. These instruments have been used to conduct slug tests and can be configured to monitor observation wells for pumping tests. Simplicity of construction and availability of components offer hydrologists an inexpensive but reliable method of water level recording. Several examples of the use of this instrumentation in diverse hydrologic settings are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.1996.tb00127.x
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  • 4
    Electronic Resource
    Electronic Resource
    First Results from the Soho Ultraviolet Coronagraph Spectrometer (1997)
    Springer
    Solar physics 175 (1997), S. 613-644 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx 610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been observed. Preliminary results for derived H0, O5+, Mg9+, and Fe11+ velocity distributions and initial indications of outflow velocities for O5+ are described. In streamers, the H0 velocity distribution along the line of sight (specified by the value at e-1, along the line of sight) decreases from a maximum value of about 180 km s-1 at 2 R⊙ to about 140 km s-1 at 8 R⊙. The value for O5+ increases with height reaching a value of 150 km s-1 at 4.7 R⊙. In polar coronal holes, the O5+ velocity at e-1 is about equal to that of H0 at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O5+ in both streamers and coronal holes were found to have anisotropic velocity distributions with the smaller values in the radial direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004903206467
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  • 5
    Electronic Resource
    Electronic Resource
    The Ultraviolet Coronagraph Spectrometer for the solar and heliospheric observatory (1995)
    Springer
    Solar physics 162 (1995), S. 313-356 
    Details
    ISSN: 1573-093X
    Keywords: Sun ; Solar Corona ; Solar Wind ; UV Spectroscopy ; UV Coronagraph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is composed of three reflecting telescopes with external and internal occultation and a spectrometer assembly consisting of two toric grating spectrometers and a visible light polarimeter. The purpose of the UVCS instrument is to provide a body of data that can be used to address a broad range of scientific questions regarding the nature of the solar corona and the generation of the solar wind. The primary scientific goals are the following: to locate and characterize the coronal source regions of the solar wind, to identify and understand the dominant physical processes that accelerate the solar wind, to understand how the coronal plasma is heated in solar wind acceleration regions, and to increase the knowledge of coronal phenomena that control the physical properties of the solar wind as determined byin situ measurements. To progress toward these goals, the UVCS will perform ultraviolet spectroscopy and visible polarimetry to be combined with plasma diagnostic analysis techniques to provide detailed empirical descriptions of the extended solar corona from the coronal base to a heliocentric height of 12 solar radii.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00733433
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  • 6
    Electronic Resource
    Electronic Resource
    Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer (1997)
    Springer
    Solar physics 175 (1997), S. 645-665 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940–1350 Å range as well as the 470–630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a few lines, but electron collisional excitation produces most of the lines observed. Resonance, intercombination and forbidden lines are seen, and their relative line intensities are diagnostics for the ionization state and elemental abundances of the coronal gas. The elemental composition of the solar corona and solar wind vary, with the abundance of each element related to the ionization potential of its neutral atom (First Ionization Potential–FIP). It is often difficult to obtain absolute abundances, rather than abundances relative to O or Si. In this paper, we study the ionization state of the gas in two coronal streamers, and we determine the absolute abundances of oxygen and other elements in the streamers. The ionization state is close to that of a log T = 6.2 plasma. The abundances vary among, and even within, streamers. The helium abundance is lower than photospheric, and the FIP effect is present. In the core of a quiescent equatorial streamer, oxygen and other high-FIP elements are depleted by an order of magnitude compared with photospheric abundances, while they are depleted by only a factor of 3 along the edges of the streamer. The abundances along the edges of the streamer (‘legs’) resemble elemental abundances measured in the slow solar wind, supporting the identification of streamers as the source of that wind component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004948423169
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  • 7
    Electronic Resource
    Electronic Resource
    UVCS/SOHO Ion Kinetics in Coronal Streamers (1999)
    Springer
    Space science reviews 87 (1999), S. 189-192 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We made streamer observations with the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) during the early part of 1998, which was a time of moderate solar activity. We present an empirical study of coronal ion kinetics using the line profiles from these observations. Our first and most striking result is that the mid-latitude (ML) streamers have much narrower O VI 1032 Å line profiles than the solar minimum equatorial (SME) streamers. Our second result is that the line profiles from a small collection of ions in ML streamers do not seem to be consistent with the ions having a single temperature and turbulent velocity. We discuss several interpretations, including line of sight (LOS) effects. This work is supported by the National Aeronautics and Space Administration under grant NAG-3192 to the Smithsonian Astrophysical Observatory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005184014654
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  • 8
    Electronic Resource
    Electronic Resource
    UVCS/SOHO Observations of Spectral Line Profiles in Polar Coronal Holes (1999)
    Springer
    Space science reviews 87 (1999), S. 233-236 
    Details
    ISSN: 1572-9672
    Keywords: corona ; solar wind ; UV radiation ; spectroscopy ; line profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ultraviolet emission line profiles have been measured on 15-29 September 1997 for H I 1216 Å, O VI 1032, 1037 Å and Mg X 625 Å in a polar coronal hole, at heliographic heights ϱ (in solar radii) between 1.34 and 2.0. Observations of H I 1216 Å and the O VI doublet from January 1997 for ϱ = 1.5 to 3.0 are provided for comparison. Mg X 625 Å is observed to have a narrow component at ϱ = 1.34 which accounts for only a small fraction of the observed spectral radiance, and a broad component that exists at all observed heights. The widths of O VI broad components are only slightly larger than those for H I at ϱ = 1.34, but are significantly larger at ϱ = 1.5 and much larger for ϱ 〉 1.75. In contrast, the Mg X values are less than those of H I up to 1.75 and then increase rapidly up to at least ϱ = 2.0, but never reach the values of O VI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005156703267
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  • 9
    Electronic Resource
    Electronic Resource
    Inorganic Sediment Budget for the North Inlet Salt Marsh, South Carolina, U.S.A. (1996)
    Springer
    Mangroves and salt marshes 1 (1996), S. 23-35 
    Details
    ISSN: 1572-977X
    Keywords: sediment flux ; sediment accumulation ; tidal discharge model ; 210Pb dating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most salt marshes along the east coast of North America appear to accumulate sediment at a rate sufficient to keep pace with the rise in eustatic sea level and local subsidence. Thus, these marshes must be importing sediment from the coastal ocean and/or the adjacent estuaries. The sediment accumulating in the North Inlet salt marsh, South Carolina, is 80% inorganic, and, based on 210Pb dating, is accreting at a rate of 0.098 g cm−2 yr−1, equal to a 2.7 mm yr−1 vertical sedimentation rate. Tide gauge records show a relative sea level rise of 2.2 to 3.4 mm yr−1, indicating this marsh is maintaining its elevation relative to mean sea level rise. The North Inlet salt marsh has two avenues of sediment exchange: (1) through the tidal inlet to the ocean and (2) through Winyah Bay, the adjoining estuary. Long-term inorganic suspended sediment flux through the inlet is calculated to be a net import of 1.35 kg s−1, based on application of a tidal hypsometric flow model to seven years of daily suspended sediment concentrations. However, the import required to balance relative sea level rise is only 0.80 kg s−1, implying an excess net import of 0.55 kg s−1. The difference between import and accumulation is explained by the progradation of the marsh toward Winyah Bay, a conclusion which is supported by the geomorphology and stratigraphy of the marsh-estuary border. Thus, the North Inlet marsh imports sediment on the average through the tidal inlet, at a rate which allows for both vertical accumulation at a rate approximately equal to the relative sea level rise and also lateral expansion of the marsh.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1025990027312
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  • 10
    Electronic Resource
    Electronic Resource
    Geochemical Reaction Modeling (2000)
    Springer
    Mathematical geology 32 (2000), S. 143-145 
    Details
    ISSN: 1573-8868
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007515120405
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