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  • 1
    Electronic Resource
    Electronic Resource
    Doppler Shifts in the Quiet-Sun Transition Region and Corona Observed with Sumer on Soho (1997)
    Springer
    Solar physics 175 (1997), S. 349-374 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New observations of systematic red shifts of transition region and coronal lines obtained with SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (the Solar and Heliospheric Observatory) are presented. With the extensive wavelength coverage of SUMER it is possible to extend the measurements of the red shifts to much higher temperatures compared to previous instruments. We find lines formed in the upper transition region (e.g. Ov, Sv, and Svi) to be red-shifted similar to lower temperature lines (T ≤ 1.8 x 10-5 K). Even hotter lines such as Ovi, Neviii and Mgx show systematic red shifts on the order of 5 km s-1 in the quiet Sun. This is a new and significant result since previous measurements of the red shifts were less well constrained. The behavior of the red shifts above T = 10-5 K has been somewhat controversial. In some earlier investigations the magnitude of the red shift has been found to increase with temperature, reaching a maximum at T = 10-5 K and then to decrease toward higher temperatures. Thus, our results will put new constraints on theoretical models. The measured shifts are compared to recent observations of red-shifted emission in stellar spectra obtained with the Hubble Space Telescope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004985226553
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ultraviolet spectroscopy of the extended solar corona during the Spartan 201 mission (1994)
    Springer
    Space science reviews 70 (1994), S. 253-261 
    Details
    ISSN: 1572-9672
    Keywords: Solar corona ; Solar wind ; UV spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The instruments on the Spartan 201 spacecraft are an Ultraviolet Coronal Spectrometer and a White Light Coronagraph. Spartan 201 was deployed by the Space Shuttle on 11 April 1993 and observed the extended solar corona for about 40 hours. The Ultraviolet Coronal Spectrometer measured the intensity and spectral line profile of HI Lyα and the intensities of OVI 103.2 and 103.7 nm. Observations were made at heliocentric heights between 1.39 and 3.5 R⊙. Four coronal targets were observed, a helmet streamer at heliographic position angle 135°, the north and south polar coronal holes, and an active region above the west limb. Measurements of the HI Lyα geocorona and the solar irradiance were also made. The instrument performed as expected. Straylight suppression, spectral focus, radiometric sensitivity and background levels all appear to be satisfactory. The uv observations are aimed at determining proton temperatures and outflow velocities of hydrogen, protons and oxygen ions. Preliminary results from the north polar coronal hole observations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777876
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Broadening of Fe X (6374 Å) profiles above the limb in a coronal hole (1994)
    Springer
    Space science reviews 70 (1994), S. 373-377 
    Details
    ISSN: 1572-9672
    Keywords: Solar corona ; Coronal holes ; Solar wind ; UV spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Profiles of the visible Fe X (6374 Å) coronal emission line as a function of height above the limb were obtained out to 1.16 solar radii in a coronal hole using the NSO/Sacramento Peak Observatory Coronagraph, Universal Spectrograph and a CCD camera. These are the first coronal line profiles obtained as a function of height in a coronal hole from the ground. Analysis of the line widths suggests a large component of nonthermal broadening which increases with height ranging from 40 to 60 km/s, depending upon the assumed temperature or thermal component of the profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777895
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  • 4
    Electronic Resource
    Electronic Resource
    SUMER - Solar Ultraviolet Measurements of Emitted Radiation (1995)
    Springer
    Solar physics 162 (1995), S. 189-231 
    Details
    ISSN: 1573-093X
    Keywords: Solar EUV Emission Lines ; Coronal Heating ; Solar Wind Acceleration ; EUV Spectrometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 × 106 K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00733430
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  • 5
    Electronic Resource
    Electronic Resource
    FIRST RESULTS OF THE SUMER TELESCOPE AND SPECTROMETER ON SOHO – II. Imagery and Data Management (1997)
    Springer
    Solar physics 170 (1997), S. 105-122 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract SUMER – Solar Ultraviolet Measurements of Emitted Radiation – is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We report on some aspects of the observation programmes that have already led us to a new view of many aspects of the Sun, including quiet Sun, chromospheric and transition region network, coronal hole, polar plume, prominence and active region studies. After an introduction, where we compare the SUMER imaging capabilities to previous experiments in our wavelength range, we describe the results of tests performed in order to characterize and optimize the telescope under operational conditions. We find the spatial resolution to be 1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along the slit. Resolution and sensitivity are adequate to provide details on the structure, physical properties, and evolution of several solar features which we then present. Finally some information is given on the data availability and the data management system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004994702333
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Observations of Polar Plumes with the Sumer Instrument on Soho (1997)
    Springer
    Solar physics 175 (1997), S. 375-391 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present new observations of O vi 1032 Å line profiles in polar plumes, and inter-plume regions, on the disk and above the limb in the north coronal hole obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on the SOHO (Solar and Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min spectroheliogram was scanned above the north polar coronal hole with the entrance slit extending from 1.03 to 1.33 solar radii with 1.5 arc sec spatial resolution and ≈ 0.044 Å per pixel spectral resolution in the wavelength range 1020–1040 Å. Detailed plume structure in O vi 1032 Å can be seen extending beyond 1.3 solar radii, with intensities in the plume regions 10–50% brighter, but line widths 10–15% narrower, than the inter-plume regions. Possible explanations for this observed anti-correlation between line width and intensity in the plume and inter-plume regions are discussed. We conclude that the source of the high-speed solar wind may not be polar plumes, but the inter-plume lanes associated with open magnetic field regions of the chromospheric network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004959324214
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  • 7
    Electronic Resource
    Electronic Resource
    FIRST RESULTS OF THE SUMER TELESCOPE AND SPECTROMETER ON SOHO – I. Spectra and Spectroradiometry (1997)
    Springer
    Solar physics 170 (1997), S. 75-104 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract SUMER – the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) – observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 × 106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004923511980
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  • 8
    Electronic Resource
    Electronic Resource
    Statistical Analysis of EUV and UV Lines Inside and Outside of Solar Coronal Holes (1999)
    Springer
    Space science reviews 87 (1999), S. 161-164 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two studies performed with SUMER (the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on SOHO) in September 1996 are presented. Spatial scans, a long exposure time and a broad spectral window provide reliable line profiles for various regions of the Sun (off-limb corona, coronal hole, quiet Sun, bright and dark regions on disk) and for different formation temperatures (Si II, 14 000 K; C IV, 100 000 K; Ne VIII, 630 000 K). Line intensity, position and width distributions are presented together with the line positions relative to the wavelength seen above the limb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005103224223
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  • 9
    Electronic Resource
    Electronic Resource
    Preliminary results from Spartan 201: Coronal streamer observations (1994)
    Springer
    Space science reviews 70 (1994), S. 263-266 
    Details
    ISSN: 1572-9672
    Keywords: Coronal Streamers ; Solar Wind ; UV Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ultraviolet Coronal Spectrometer on Spartan 201 obtained measurements of HI Ly α line profiles and O VI λ103.2/103.7 nm integrated intensities in a helmet streamer. Similar measurements were made on the solar disk to characterize the incident radiation which is the source for the resonantly scattered component of the lines. A description of the H I Ly α observations in the streamer will be presented. A more complete physical description of the observed coronal regions will become available after the analysis of additional data from coordinated observations made by visible coronagraphs and x-ray telescopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777877
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