UVCS/SOHO PAPERS - 1994

1994-13:    Manifestation of Magnetic Reconnection in Coronal Streamer Current Sheets

Verneta, A. I., Antonucci, E., Marocchi, D.

Space Science Reviews, 70, 299

1994-12:    Delay-line detectors for the UVCS and SUMER instruments on the SOHO Satellite

Siegmund, O. H., Stock, J. M., Marsh, D. R., Gummin, Mark A.; Raffanti, Richard; Hull, J., Gaines, G. A., Welsh, B. Y., Donakowski, B., Jelinsky, P. N., Sasseen, T., Tom, J. L., Higgins, B., Magoncelli, T., Hamilton, J. W., Battel, S. J., Poland, A. I., Jhabvala, M. D., Sizemore, K., Shannon, J.

1994, in the International Society for Optical Engineering 2280, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy V

Microchannel plate based detectors with cross delay line image readout have been rapidly implemented for the SUMER and UVCS instruments aboard the Solar Orbiting Heliospheric Observatory (SOHO) mission to be launched in July 1995. In October 1993 a fast track program to build and characterize detectors and detector control electronics was initiated. We present the detector system design for the SOHO UVCS and SUMER detector programs, and results from the detector test program. Two deliverable detectors have been built at this point, a demonstration model for UVCS, and the flight Ly (alpha) detector for UVCS, both of which are to be delivered in the next few weeks. Test results have also been obtained with one other demonstration detector system. The detector format is 26mm x 9mm, with 1024 x 360 digitized pixels,using a low resistance Z stack of microchannel plates (MCP's) and a multilayer cross delay line anode (XDL). This configuration provides gains of approximately equals 2 X 10(superscript 7) with good pulse height distributions (<50% FWHM) under uniform flood illumination, and background levels typical for this configuration (approximately equals 0.6 event cm(superscript -2) sec(superscript -1)). Local counting rates up to approximately equals 400 event/pixel/sec have been achieved with no degradation of the MCP gain. The detector and event encoding electronics achieves approximately equals 25 micrometers FWHM with good linearity (+/- approximately equals 1 pixel) and is stable to high global counting rates (>4 X 10(superscript 5) events sec(superscript -1)). Flat field images are dominated by MCP fixed pattern noise and are stable, but the MCP multifiber modulation usually expected is uncharacteristically absent. The detector and electronics have also successfully passed both thermal vacuum and vibration tests.

The Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and Heliospheric (SOHO) mission has been developed for spectroscopic and polarimetric determinations of temperatures, densities and flow velocities in the extended solar corona. The instrument consists of two ultraviolet (UV) spectrometers and a visible light (VL) polarimeter. The grating of the UV channel optimized for the H I Lyman (alpha) (Ly-(alpha) ) line ((lambda) 1236 angstrom) and that for the O VI doublet ((lambda) (lambda) 1032/1037 angstrom) have been characterized.

1994-10:   VUV optical performances of the SOHO/Ultraviolet Coronagraph Spectrometer

NALETTO, GIAMPIERO; NICOLOSI, PIERGIORGIO; PERNECHELE, CLAUDIO; POLETTO, L.; TONDELLO, GIUSEPPE

1994, Proc. SPIE Vol. 2011, p. 577-587, Multilayer and Grazing Incidence X-Ray/EUV Optics II, Richard B. Hoover; Arthur B. Walker; Eds.

The optical performances of the spectrometer for the SOHO/UVCS instrument have been tested. A laboratory evaluation unit of the spectrometer assembly consisting of the structure equipped with breadboard models of the entrance slit assembly, a grating drive mechanism mounting a toroidal grating and a MAMA detector has been integrated and aligned. Both tests with visible and UV radiation have been performed. Aberration and stray light measurements have shown satisfactory performances of the instrument almost in compliance with the scientific requirements.

1994-09:   Unsolved problems of solar wind expansion: Can we learn anything from SOHO?

Esser, R.

1994, Space Sci. Rev., 70, 331

Some of the main problems of solar wind expansion are addressed. Emphasis is placed on solar wind acceleration and the mass flux problems. It is demonstrated how these two properties of the flow depend on other plasma parameters such as temperature, density and helium abundance. The importance of placing constraints on a given solar wind flow in the inner corona and at larger distances from the sun simultaneously, is also shown. Whether and how these constraints can be derived from observations carried out by SOHO instruments is then discussed.

1994-08:   Ultraviolet coronagraph spectrometer (UVCS) for the solar and heliospheric (SOHO) mission

FINESCHI, SILVANO; NALETTO, GIAMPIERO; NICOLOSI, PIERGIORGIO; NOCI, G.; PERNECHELE, CLAUDIO; ROMOLI, MARCO; SPADARO, D.; TONDELLO, GIUSEPPE

1994, Proc. SPIE Vol. 2209, p. 348-359, Space Optics 1994: Earth Observation and Astronomy, M. G. Cerutti-Maori; Philippe Roussel; Eds.

The optical performances of the Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and Heliospheric Observatory (SOHO) mission have been tested. A laboratory evaluation unit (LEU) of the spectrometer assembly (SPA) consisting of the structure equipped with breadboard models of the entrance slit assembly (ESA), a grating drive mechanism (GDM) mounting a toroidal grating for the Ly(alpha) channel and a multi-anode microchannel array (MAMA) detector has been integrated and aligned. Both tests with visible and UV radiation have been performed. Aberration and stray light measurements have shown satisfactory performances of the instrument almost in compliance with the scientific requirements. A LEU and a flight unit of the White Light Channel (WLC) have been integrated and aligned in a proper light-tight housing and in the flight spectrometer assembly respectively. Measurements of the polarimeter modulation curve and the relative error have shown performances within the specificated requirements.

1994-07:   The Ultraviolet Coronagraph Spectrometer

G. Noci, J.L. Kohl, M.C.E. Huber, E. Antonucci, S. Fineschi, L.D. Gardner, G. Naletto, P. Nicolosi, J.C. Raymond, M. Romoli, D. Spadaro, L. Strachan, G. Tondello, A. Van Ballegooijen

1994, Invited paper at the CESRA Symposium, Lecture Notes in Physics, Eds. A. Benz and A. Kruger, 261-270

1994-06:   Magnetohydrodynamic Simulation of a streamer beside a realistic coronal hole

Suess, S. T., Wu, S.-T., Wang, A.-H., Poletto, G.

Space Science Reviews, 70, 295.

1994-05:   Understanding solar streamers: the role of SOHO

Poletto, G.

1994 in "Mass Supply and Flow in the Solar Corona", B. Fleck, G. Noci, G. Poletto, Eds., Kluwer Acad. Publ., 241.

1994-04:   UVCS/SOHO Capability for determining coronal conditions before, during, and after CME's,

L. Strachan, J.C.Raymond, J.L.Kohl, G.Noci, E.Antonucci, G.Tondello, M.C.E.Huber, S.Fineschi, L.D.Gardner, P.Nicolosi, M.Romoli

1994, in the Third SOHO Workshop, Solar Dynamic Phenomena and Solar Wind Consequences, ESA SP-373, p.421

The following three are from the 2nd SOHO Workshop in Elba
 

1994-03:   Simulated observations of the electron coronal density irregularity {n^}2/{n}^2

ROMOLI, M.; FINESCHI,

S. Journal: Space Science Reviews, v. 70, p. 359. Publication Date: 10/1994

1994-02:   Electron coronal density irregularity $\overline{n^2} / (\overline{n})^2$ from measurements of K-coronal and Lyman lines brightnesses

FINESCHI, S.; ROMOLI,

M. Journal: Space Science Reviews, v. 70, p. 353. Publication Date: 10/1994

1994-01:   Working group 3: coronal streamers

KOPP, R. A. Journal

Space Science Reviews, v. 70, p. 309. Publication Date: 10/1994

The working group on coronal streamers convened on the first day of the 2nd SOHO Workshop, which took place in Marciana Marina, Isola d'Elba, 27 September--1 October 1993. Recent progress in streamer observational techniques and theoretical modeling was reported. The contribution of streamers to the mass and energy supply for the solar wind was discussed. Moreover, the importance of thin electric current sheets for determining both the gross dynamical properties of streamers and the fine-scale filamentary structure within streamers, was strongly emphasized. Potential advances to our understanding of these areas of coronal physics that could be made by the contingent of instruments aboard SOHO were shown.