SUMER Data Analysis
SUMER Analysis at MEDOC
Several scientists are involved in SUMER data analysis at MEDOC and
they are working on very different topics that are summarized below:
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JOP40 : Transition Region Thickness
SUMER contributes to JOP40 with observations aiming at the determination
of Doppler and non-thermal velocities corresponding to the magnetic network
and for a series of spectral lines from the chromosphere up to the corona
for two disk coronal holes observed in May 1999 during MEDOC campaign #2.
For more on JOP40
click here .
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Determination of the Flux of matter in a Polar Coronal Hole via coordinated
observations between SOHO/SUMER and Earth observatories during the 1998
total eclipse:
Polar coronal holes represent the most convincing sites of the origin
of the high-speed solar wind. A precise knowledge of the flux of matter
at the coronal base is extremely important in placing constraints on wind
models. White-light eclipse-observations still remain an excellent way
to determine the electronic density in the solar corona. Here we will combine
high-accuracy Doppler shifts measured in OVI (1037 A) line with SUMER along
with white-light measured electronic densities -during the 26 Feb 1998
eclipse- in the vicinity of the south coronal hole.
Moreover the determination of the energy flux carried by hydromagnetic
waves traversing coronal holes will demonstrate or no their importance
as heating agents in coronal holes.
For more info concerning this observational program go to here
by S. Patsourakos and J.-C. Vial
- Diagnostic of prominence plasma through Lyman lines.
SUMER has the unique capability of observing at very high spectral ??? the whole Lymanseries and the continium. This opens the possibility
to scan different layces of the prominence and throught Non LTE radiative transfer techniques, to modelize the structure.
First profiles of the Lymanseries in prominences and filaments have been obtained with SUMER.
J.-C. Vial in collaboration with Meudon group (B. Schmieder) and Ondrejov (P. Heinzel)
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Search for proton beams signature in Lyman alpha wings: It has been shown
that particle beams - especially proton beams - can affect the wings of
the Lyman alpha line (Balanca, 1997, PhD Thesis). One of the signatures
of this event is a small increase of emission in the wings of Lyman alpha
line. Distance to t he center of the line is a function of the energy of
the beam. The effect is more important when proton's energy is close to
H excitation energy. We then study the effect of bright points on Lyman
alpha wings in order to find this signature, and also investigate the boundary
of coronal holes, where particle beams may occur.
Collaborations : C. Balanca, N. Feautrier, M. Bruston - DAMAp -
Observatoire
de Paris, Section de Meudon - F-92190 Meudon Principal - France
by J. Aboudarham
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Calibrations using stars - PSF determination using computation and stars
Scattered light distribution
Sun as a star: reference spectrum
Network evolution and fine structure
Coronal abundance determination
by P. Lemaire
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Line profiles in/out coronal holes: by D. Hassler and P. Lemaire
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Statistical analysis of Bright Structures detected in the Quiet Sun: The
quiet solar corona has proved to be everything but quiet, and the difference
with active regions would be the reduced dimensions of the areas of activity.
An average quiet Sun region appears to contain bright points or more generally
knots of enhanced emission with respect to the background average corona.
Such an enhanced emission could be the result of (the superposition
of) many non-observable elementary events. From the MHD turbulence models
and in a statistical point of view, it appears that the distribution of
the energy release, due to the disruption of current sheets, follows power
laws.
A large number of small bright structures were observed with EIT, SUMER,
CDS (on board SOHO) and with TRACE, in the frame of the JOP38.
Their possible relationship with the coronal heating problem is discussed
in terms of signatures of MHD turbulence.
by V. Aletti, K. Bocchialini and J.-C. Vial
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Plasma Diagnostics and Oscillations in Prominences: Physical parameters
such as density and line of sight velocity of a prominence observed on
June 12, 1997 in the frame of the JOP9
are derived.
Oscillations in the 3-5 minutes range are evidenced using the wavelet transform technics in
a prominence observed on June 6, 1997 in the frame of JOP9.
by K. Bocchialini, J.-C. Vial and colleagues from IAFE (Buenos Aires)
and BAS (Sofia)
.
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Solar Lyman-alpha line profile measurements: Using the SUMER spectrometer
on SOHO, measurements of the light scattered telescope permitted to obtain
a full solar disc Ly-alpha line profile. In this way, the 1996 September
data provided the first measurement of the solar disc Ly-alpha line profile
free of any geocoronal H absorption (Lemaire et al.,1998). Similar measurements
were systematically performed, every month, in order to measure potential
variations of the profile line center as a function of solar activity.
As a matter of fact, this poorly known parameter is of interest in many
fields such as solar physics, interplanetary medium, or planetary and cometary
H envelopes.
The line profile variation will also be studied during the different
seasons, in order to attempt detecting partial and time variable absorption
of the solar profile by interplanetary H. Such measurements should provide
a better estimate of the corresponding hydrogen local density (very poorly
known at present).
by C. Emerich
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Modelisation of quiescent solar prominences: After introducing the most
recent atomical data for Helium in the numerical code established by P.
Gouttebroze, some helium transitions (such as 584 and 304 angstroms) important
to understand the physical parameters of those chromospheric structures
are computed. The code will be used as a diagnostic tool since the results
will be compared with SUMER and CDS helium profiles.
by N. Labrosse, P. Gouttebroze and J.-C. Vial
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Measurement of the electron temperature gradient in solar coronal holes:
It has long been established that the high speed solar wind streams observed
at 1 A.U. originate from the coronal hole regions of the sun. Theoretical
modelling of the acceleration mechanism depends critically on the value
of the maximum of temperature ex isting close to the sun. Measurements
of the temperature in coronal holes prior to SOHO are unreliable, due to
the very low luminosity, leading to extreme observational difficulties,
in particular due to light scattering in the instrument telescopes. Usi
ng the two SOHO spectrometers CDS and SUMER, electron temperatures have
now been measured as a function of height above the limb in a polar coronal
hole. Temperatures of around 0.8 MK are found close to the limb, rising
to a maximum of less than 1 MK at 1 .15 solar radius, then falling to around
0.4 MK at 1.3 solar radius. With these low temperatures, the classical
Parker mechanism cannot alone explain the high wind velocities, which must
therefore be due to the direct transfer of momentum from MHD wave s to
the ambient plasma.
by C. David and A. Gabriel
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Oscillation modes in the high chromosphere and the transition region:
Variations
of intensity and wavelength in several UV lines have been observedwith
SUMER (in January and February 97), and analysed in order to obtain mean
oscillatory spectra and di agnostic diagrams and to study phase differences
between lines of different ions. Mean spectra obtained from lines of neutral
or singly ionized atoms (with temperature of formation less than 30000
K) exhibit an increase of power between 2.5 and 7 mHz, whi ch may be considered
as the signature of p-modes. On the contrary, lines of highly ionized elements
(with temperature of formation more than 50000 K) yield power spectra which
are regularly decreasing with frequency. Brightness variations of the continuum
at different wavelengths between 1000 and 1400 A present oscillations in
the same frequency range. Thus, p-modes seen to be efficiently stopped
by the transition region. No clear evidence is found for the existence
of a chromospheric oscillation mode. Phase comparisons between lines formed
at different altitudes (in particular Si I and Si II) indicate that these
lines oscillate in phase, within the precision of the measurements. The
wavelet technics will be applied on these observations as well as on data
from JOP58.
by P. Gouttebroze and K. Bocchialini
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Active region diagnostic: Following the SOHO/YOHKOH workshop held at MEDOC
in October 97, data obtained in the active region observed in July, August
and September 96 have been processed and are analysed.
by K. Bocchialini
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Polarization of the O VI 103.2 nm line of the solar corona : The aims of
this study are to get information about the magnetic and velocity fields
in the solar corona that are necessary to the MHD modelling for understanding
the coronal heating and the acceleration of the solar wind. It is known
that atom and ion li nes are not only shifted but also their intensities
are dimmed by the Doppler effect due to the coronal matter velocity field.
Moreover some lines of the corona (as Li-like ion lines : O VI, N V, C
IV, ...) are sensitive to the Hanle effect due to the magnetic field. So
the determination of their polarization parameters (degree anddirection
of the polarization) and the study of their profiles permit an indirect
measure of the velocity a nd magnetic fields in the solar corona.
This study is carried out using the SUMER instrument as an analyser
ofpolarization via its sensitivity to the linear polarization state of
anincident radiation. The observations were taken in March 19, 1996. Exploiting
the satellite rotation, it was possi ble to observe the same region in
the south polar hole, at roughly 270 arcsec of the solar limb, under different
angles. We hope by the study of the intensity variation with the angle
of observation and the profile of the O VI 103.2 nm line to get measure
of the magnetic and velocity fields in the corona (polar hole).
by N. Raouafi and P. Lemaire
Recent publications:
- Regnier S., Bocchialini K., Vial J.-C., Delaboudiniere J.-P., Thomson
W. : Analyse statistique de points brillants de la couronne solaire, observes par SoHO, 1998, C.R. ACAD. SCI. SER. II, 1998, 326, p. 211
- Lamartinie S., Bocchialini K., Vial J.-C., Chiuderi-Drago F., Harrison
R., Alissandrakis C.E., 1998, JOSO report, p.139
- Chiuderi-Drago F., Bocchialini K., Vial J.-C., Lamartinie S., Bastian
T, Alissandrakis C.E., Harrison R., Delaboudiniere J.-P., Lemaire P., 1998,
IAU 167, vol. 150, p. 55
Bocchialini K., Vial J.-C., Einaudi G., 1998, ESA Report SP-404, p.
211
- Patsourakos S., Bocchialini K., Vial J.-C., 1998, ESA Report SP-404,
p. 577
Patsourakos S., Bocchialini K., Vial J.-C. : Solar chromospheric structures observed in UV resonance lines, C.R. ACAD. SCI. SER. II, 1998
, 326, pp. 337
- Schmieder, B., Heinzel, P., Kucera, T., Vial, J.-C. : Filament observations with SoHO/CDS : The behaviour of hydrogen Lyman lines,
SOL. PHYS. , 1998, 181, 309
- David C., Gabriel A., Bely-Dubau F., 1998, ESA Report SP-404, p.313
- David C., Gabriel A., Bely-Dubau F., 1998, ESA Report SP-404, p.319
- Lemaire P., Schuehle U., Curdt W., Wilhelm K., Poland A., Falciani
R., 1998, ESA Report SP-404, p. 517
- Vial, J.-C., SoHO : derniers resultats, 1998, C.R.A.S., to be published
- Kucera, T., Aulanier, G., Schmieder, B., Mein, N., and Vial, J.-C., Filament channel fine structures in UV SI IVrelated to a 3D
magnetic model, 1999, Solar Physics, 186, 259
- Labrosse N., Gouttebroze P., 1999, SOHO8 Workshop, ESA proceedings,
to be published
- Gouttebroze P., Vial J.-C., Bocchialini K., Lemaire P., Leibacher J., Oscillations of the upper chromosphere,
1999, Sol. Phys., 184, 253 .
- Heinzel, P., Schmieder, B., De Boer, C., Vial, J.-C., Wilhelm, K. : Basic characteristics of hydrogen Lyman lines observed in solar
prominences, 1999, Adv. Space Res. submitted
- Heinzel, P., Schmieder, B., Vial, J.-C., Rudawy, P. : Solar prominemces observed by SoHO (SUMER, CDS, EIT) and GBOs, 1999, Adv. Space
Res. submitted
- Hassler, D. M., Dammasch, I. E., Lemaire, P., Brekke, P., Curdt, W., Mason, H. E., Vial, J.-C., Wilhelm, K., Solar wind outflow and
the chromospheric magnetic network., Science, 283, 810-813
- S. Patsourakos, J.C. Vial, J.-R. Gabryl
S. Koutchmy and U. Schuhle ,Solar Wind Nine, 1999, Ed. S. R.
Habbal,
R. Esser, J. V. Hollweg and P. A. Isenberg ,American Institute
of Physics ,471, 285-288
- S. Patsourakos, J.C. Vial, J.-R. Gabryl
S. Koutchmy and U. Schuhle Space Science Reviews, 1999, 87, 291-294
- Lemaire P., Bocchialini K., Aletti V., Hassler D. , Whilhelm K., 1999,
Space Science Review, 87, p. 249, SOHO 7 workshop, in Coronal Holes and
Solar Wind Acceleration, Northeast Harbor, Kohl and Cranmer Eds..
- Blanco S., Bocchialini K., Costa A., Domenech G., Rovira M., Vial J.-C. : Multiresolution wavelet analysis of SUMER/SoHO observations
in a solar prominence, 1999, Sol. Phys., 186, 281
- Van Driel-Gesztelyi L., Thompson B., Demoulin P., Orlando S., Bocchialini
K., et al., 1999, SOHO8 workshop, ESA proceedings, to be published
- Aletti V., Bocchialini K., Vial J.-C., 1999, SOHO8 workshop, ESA
proceedings,
to be published
- Madjarska M., Vial J.-C., Bocchialini K., Dermendjiev V., 1999, SOHO8
workshop, ESA proceedings, to be published
All, K.Bocchialini/ latest update : August 1999