KOHL, JOHN L.; NOCI, GIANCARLO
1992, In ESA, Proceedings of the First SOHO Workshop: Coronal Streamers, Coronal Loops, and Coronal and Solar Wind Composition p 23-26 (SEE N93-31343 12-92) Category: Solar Physics Origin: STI NASA/STI
The Ultraviolet Coronagraph
Spectrometer (UVCS) will provide spectroscopic observations of the solar
corona out to 10 solar radii from Sun center. This capability is expected
to expand greatly the number of plasma parameters that can be specified
by remote sensing techniques. The UVCS plasma diagnostic techniques are
expected to provide a sufficient number of empirically derived parameters
to significantly constrain theories of solar wind acceleration, coronal
heating, and solar wind composition. The measured line profiles and intensities
are sensitive to random velocity distributions, densities of coronal protons,
electrons, and ions.
1992-03: A Two-Dimensional MHD global
coronal model: steady-state streamers
Wang, A-H, Wu, S. T., Suess, S.
T., Poletto, G. 1992, in Solar Wind VII, E. Marsch and R. Schwenn, Eds.,
Pergamon Press, Oxford, 311
1992-02:
Ly-alpha radiation from coronal
transients
SPADARO, DANIELE; VENTURA, R.;
MARTIN, R.; WU, S. T.; WANG, A. H. The intensity and profile of the
Lyman alpha spectral line expected from the extended coronal plasma evolving
during a coronal transient, when observed in the plane of the sky in the
range of heliocentric distance 1.5 to 4 solar radii, are calculated. The
numerical values of temperature, density and outflow speed inside the coronal
transient are those determined by Wu and Wang under the assumption of a
single fluid, three dimensional, time dependent magnetohydrodynamic model
of the outer solar atmosphere. The dependence of the Lyman alpha line on
the physical parameters of the examined structure is discussed. These results
may help in preparing and interpreting UVCS/SOHO (Ultraviolet Coronagraph/Solar
and Heliospheric Observatory) observations of coronal transients.
1992, in ESA, Proceedings of
the First SOHO Workshop: Coronal Streamers, Coronal Loops, and Coronal
and Solar Wind Composition p 105-108 (SEE N93-31343 12-92)
NOCI, GIANCARLO; POLETTO, GIANNINA; SUESS, STEVEN T.; WANG, A. -H.; WU, S. T.
SOHO (Solar and Heliospheric Observatory)
UVCS (Ultraviolet Coronagraph Spectrometer) will make long term observations
of coronal streamers in UV lines, providing a new tool for the analysis
of structures which have been known for decades but are still far from
being adequately described. Work to evaluate the Lyman alpha brightness
of coronal streamers is reported, adopting the streamer models obtained,
via a time dependent numerical relaxation technique. This will yield understanding
on the role of geometric versus physical factors in determining the streamer
lyman alpha intensity and provide guidelines for UVCS observational operations.
Future prospects along this line of research are summarized.
1992, in ESA, Proceedings of
the First SOHO Workshop: Coronal Streamers, Coronal Loops, and Coronal
and Solar Wind Composition p 93-96 (SEE N93-31343 12-92)
KOHL, J. L.; GARDNER, L. D.; HUBER,
M. C. E.; NICOLOSI, P.; NOCI, G.; NALETTO, G,; ROMOLI, M.; SPADERO, D.;
TONDELLO, G.; and WEISER, H.
(Solar corona and solar wind; Proceedings of Symposium 9 of the 28th COSPAR
Plenary Meeting, The Hague, Netherlands, June 25-July 6, 1990. A91-29501
11-92) Advances in Space Research (ISSN 0273-1177), vol. 11, no. 1, 1991,
p. 359-367. The SOHO Ultraviolet Coronograph
Spectrometer is being developed for spectroscopic determinations of temperatures,
densities and flow velocities in the extended solar corona. Determinations
of plasma parameters for the primary particles (electrons and protons)
and for several minor ions are planned. The techniques and instrumentation
to be used must overcome the relatively low intensity levels and potentially
high stray light levels intrinsic to observations of the extended corona
while also providing high radiometric accuracy and relatively high spectral
and spatial resolution. This paper concentrates on the instrument characteristics
that are required to observe the resonantly scatter H I Lyman-alpha line
at heliocentric heights from 1 to 10 solar radii.
1991-03:
UV observational techniques
for the extended solar corona
1991-02:
Coronal observations with SOHO
HUBER, MARTIN C. E.; VON DER LUEHE,
OSKAR
(Solar corona and
solar wind; Proceedings of Symposium 9 of the 28th COSPAR Plenary Meeting,
The Hague, Netherlands, June 25-July 6, 1990. A91-29501 11-92) Advances
in Space Research (ISSN 0273-1177), vol. 11, no. 1, 1991, p. 339-348.
The Solar and Heliospheric
Observatory (SOHO) is described along with its main purpose - the measurement
of the physical properties of coronal structures and the processes occurring
in them. The observatory will be launched in 1995 and injected into a halo
orbit around the first Lagrange point L1 on the earth-sun line. Attention
is focused on experiments performing in the soft X-ray and ultraviolet
domains, as well as coronagraphs allowing corona observations on and beyond
the solar disk. Experiments related to the energy and composition of the
solar wind and more energetic solar particles are outlined. A complementary
four-spacecraft Cluster mission targeting plasma structures and processes
in the magnetosphere in three dimensions is also described.
1991-01:
Model Dependence of Velocities
Derived from Coronal Resonance Lines
Ruth Esser Intensity measurements of coronal
resonance lines can be used to determine the outflow velocities of the
scattering particles, provided the distribution of the densities, temperatures
and velocities along the line of sight is known. A parameter study is designed
and carried out to investigate the effect of surrounding denser regions
with different temperatures and velocities, on the velocity deduced from
intensity measurements of the H I Lyman alpha line in low density coronal
holes. Adv. Space Res., 11, 317, 1991.
Ruth Esser
J. Geophys. Res., 95, 10 261, 1990.
Alfven waves propagating outward
from the coronal base set the solar wind into oscillatory motion. The effect
of this wave motion on the broadening and shape of the spectral lines of
the resonantly scattered Ly-alpha radiation emitted by a low-density coronal
hole is investigated at heights above 1.5 R_s from Sun center. Usually
it has been assumed that the broadening due to waves can be characterized
by a kinetic temperature proportional to the wave velocity amplitude squared,
delta v{^2}. It is shown that the accuracy of this approximation depends
on the wave velocity amplitude and the assumed wave spectrum.
Ruth Esser and George L. Withbroe
J. Geophys. Res., 94, 6886, 1989.
The effect of the integration along the line of sight on the spectral line profiles of the resonantly scattered Lyman alpha radiation emitted by low-density coronal holes at heights above 1.5 R_s from Sun center is investigated. It is shown how the spectral lines from this region are influenced by the Lyman alpha emission from surrounding regions with higher densities. The coronal hole and the surrounding areas are described by a two-fluid solar wind model. It is shown that the line-of-sight effects can be important for the interpretation of the Lyman alpha spectral line measurements in the outer corona and inner solar wind.
KOHL, J. L.; HARTMANN, L. W.; VANBALLEGOOIJEN,
A. A.; WITHBROE, G. L.; RAYMOND, J. C.; WEISER, H.; NOCI, G.; ANTONUCCI,
E.; GEISS, J.; GLOECKLER, G.
ESA, SP-1104, 49-54 (SEE N90-13302 04-92)
The UltraViolet Coronagraph Spectrometer (UVCS) of SOHO (solar and heliospheric observatory) provides ultraviolet spectroscopic observations of the solar corona out to ten solar radii from sun-center. This capability is expected to greatly expand the number of plasma parameters that can be specified by remote sensing techniques. Plasma diagnostic techniques are expected to provide a sufficient number of empirically derived parameters to significantly constrain theories of solar wind acceleration, coronal heating, and solar wind composition. The spectral line profiles and intensities are sensitive to random velocity distributions and to the effective temperatures of protons, minor ions, and electrons. Ion densities, chemical abundances, and outflow velocities of coronal protons and ions into the solar wind are also taken into consideration.