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Author name code: vonuexkuell
ADS astronomy entries on 2022-09-14
author:"von Uexkull, Marina" OR author:"Uexkull, Marina von"
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Title: Simultaneous Observations of Chromospheric and Transition
Region Oscillations in HI Lyman Transitions and in Optical Lines
Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; Tarbell, T.; von
Uexküll, M.; Wilken, V.
1999ESASP.448..177C Altcode: 1999mfsp.conf..177C; 1999ESPM....9..177C
No abstract at ADS
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Title: Chromospheric Oscillations Observed by SOHO/SUMER and VTT/GCT
on Tenerife
Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; von Uexküll, M.;
Wilken, V.
1999AGAb...15R..11C Altcode: 1999AGM....15..A12C
Previous studies have revealed various oscillations in higher Lyman
lines of hydrogen, as observed with SUMER on SOHO (Curdt & Heinzel
1998). The assumption that these periodic phenomena might be related
to similar effects observed in optical lines like Ca II K led to the
idea of simultaneous observations with the SOHO/SUMER instrument and
the VTT/GCT telescopes on Tenerife. First results are presented here
for the Lyman series and Lyman continuum. Power spectra in network and
internetwork regions have been derived and a preliminary interpretation
based on the wave propagation concept is given. In SUMER spectra
we found a well-pronounced asymmetry of all Lyman lines, which is
related to atmospheric dynamics. The time variation of co-spatial UV
and optical data is presented and basic characteristics are discussed.
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Title: Chromospheric Oscillations
Authors: Schmidt, W.; von Uexküll, M.
1999AGM....15..A14S Altcode:
Sequences of high-resolution filtergrams taken at Ca K2v show regions
in the interior of the Ca network with oscillations at 11 mHz. These
regions do also have strong 3min oscillations. Periodic signals around
2.2 mHz are concentrated in small scale structures located at the cell
boundaries. The observations have been carried at at the Vacuum-Tower
Telescope on Tenerife in May 1999, along with a coordinated SOHO-SUMER
campaign.
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Title: Diagnostics and Dynamics of the Solar Chromosphere
Authors: Kneer, F.; von Uexküll, M.
1999ASSL..239...99K Altcode: 1999msa..proc...99K
Research of the chromosphere of the Sun is exciting, as it has been over
more than a century. The present contribution can only give glimpses
into the wealth of chromospheric structures and dynamics. Likewise, in
view of the limited space, it is not possible to present in due balance
the published work on the solar chromosphere. The reader is referred to
the monographs by Bray and Loughhead (1974, with a historical account
and many references to early work) and by Athay (1976) for the state
of knowledge two decades ago. Among the conferences dealing meanwhile
with the chromosphere we mention the proceedings edited by Bonnet and
Delache (1976) and by Ulmschneider et al. (1991). Withbroe and Noyes
(1977) treated the mass and energy flow in the chromosphere and corona;
a throughout account of the Ca II K<SUB>2v</SUB> cell grains is given
by Rutten and Uitenbroek (1991); the review by Narain and Ulmschneider
(1996) deals with chromospheric and coronal heating mechanisms. Last
but not least, the book “Le Soleil” by Secchi (1877) is historically
precious and full of still viable ideas.
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Title: TESOS, a double Fabry-Perot instrument for solar spectroscopy
Authors: Kentischer, T. J.; Schmidt, W.; Sigwarth, M.; Uexkuell, M. V.
1998A&A...340..569K Altcode:
A double Fabry-Perot spectrometer in a telecentric configuration
(TESOS: Telecentric Etalon SOlar Spectrometer) has been developed and
installed in the Vacuum Tower Telescope at the Observatorio del Teide,
Tenerife. The control system allows to switch from one wavelength band
to another within 2 seconds. The telecentric configuration provides a
constant wavelength passband across the field of view. Servo-stabilized
etalons and a stable thermal environment provide a wavelength stability
of <0.3 picometer per hour. We present initial results obtained
with this instrument.
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Title: Oscillations of the Sun's chromosphere. VIII. Horizontal
motions of CA II K bright points
Authors: Wellstein, S.; Kneer, F.; von Uexkuell, M.
1998A&A...335..323W Altcode:
We present a re-analysis of a time series of solar disc centre Ca ii
K<SUB>2v</SUB> filtergrams taken with the Vacuum Tower Telescope at the
Observatorio del Teide/Tenerife. We concentrate on the measurements of
proper motions of K grains in the internetwork regions and of bright
points in the chromospheric network. For the K grains we find horizontal
velocities of 2-15 km s(-1) , values much lower than those deduced by
Steffens et al. (1996) from a smaller sample, analyzed differently. In
accord with our earlier conclusion from k-omega diagrams (Kneer &
von Uexkuell 1993) and with numerical simulations by Carlsson &
Stein (1997) high-frequency (pseudo-) p-modes can viably explain the
K grains. Yet, the rareness of the K grains may indicate a connection
to magnetic fields. The proper motions of the network bright points
are non-periodic, very impulsive, with velocities of 7-10 km s(-1)
. Estimating the energy flux if these motions are magnetic kink waves
(cf. Choudhuri et al. 1993, Muller et al. 1994), we find it sufficient
to heat the solar corona, but too small to cover the radiative losses
of the chromospheric network.
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Title: Arch Filament Systems Associated with X-Ray Loops
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Mein, N.; Van
Drielgesztelyi, L.; Von Uexküll, M.
1998SoPh..180..265M Altcode:
Using multi-wavelength observations obtained with the Tenerife
telescopes (VTT and GCT) and with the Yohkoh satellite, we observed
new emerging flux with an associated arch filament system (AFS) in
the chromosphere and bright X-ray loops in the corona. We observed the
change of connectivity of the X-ray loop footpoints which may be at the
origin of the occurrence of a subflare. Densities, gas and magnetic
pressures of cold AFS and hot loops were derived and discussed. The
extrapolation of the photospheric magnetic field observed with the GCT
in a linear force-free field assumption (constant α) shows that this
region, in spite of having roughly a global potential configuration,
consists of two systems of arch filaments. We found these two systems
best fitted with two sheared magnetic topologies of opposite α values
of ± 0.1 Mm<SUP>-1</SUP>
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Title: Flare Multi-Line 2D-SPECTROSCOPY
Authors: Mein, P.; Mein, N.; Malherbe, J. -M.; Heinzel, P.; Kneer,
F.; von Uexkull, M.; Staiger, J.
1997SoPh..172..161M Altcode: 1997ESPM....8..161M
A small flare was observed at the Teide Observatory on October 5,
1994. Simultaneous data were obtained at the German Vacuum Tower
Telescope (VTT) with the MSDP spectrograph providing high-resolution
imaging spectroscopy in two chromospheric lines, and the Gregory Coudé
Telescope (GCT) providing information about the magnetic field. Basic
flare characteristics are:
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Title: First Observations SUMER - VTT, SI IV - CA II K
Authors: Balthasar, H.; von Uexkull, M.; Innes, D.; Gigas, D.;
Wilhelm, K.
1997ASPC..118..315B Altcode: 1997fasp.conf..315B
We tried to do a comparison of Ca II K (393.3 nm) filtergrams obtained
at the Vacuum Tower Telescope on Tenerife with spectra in the line Si
IV 139.4 nm obtained simultaneously with the SUMER telescope on the
SOHO-spacecraft. Some bright features can be well identified in both
observations. We compare temporal changes of the brightness for these
common features.
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Title: Oscillations of the Sun's chromosphere. VII. K grains
revisited.
Authors: von Uexkuell, M.; Kneer, F.
1995A&A...294..252V Altcode:
We analyse time sequences of high spatial resolution filtergrams
obtained simultaneously in Mg b_2_ and Ca K_2v_ from quiet Sun disc
centre with the Vacuum Tower Telescope at Observatorio del Teide,
Tenerife. Special attention is paid to the temporal evolution of
the bright points, or K grains, in the interior of the chromospheric
network. These represent the intensity maxima of brightness oscillations
in K_2v_ with large amplitude. The oscillations last 1 to 5 periods
of 150-240s duration and are strongly non-sinusoidal. They do not
appear to be excited by pulses from below and then to decay. They
rather exhibit the beat phenomenon of a horizontally extended wave
field. The high amplitude oscillations occur only rarely, during 5-10%
of the time, if we pose the limit that high amplitude means that the
maximum intensity is a factor 1.5 larger than the average intensity. The
power spectrum does not show any signature of a chromospheric "3 min"
mode nor of a mode at the acoustic cutoff frequency (period 3.5min),
nor do we find a power ridge at constant frequency. Instead, as in
our earlier finding, the chromospheric oscillations are ordered in
modes in continuation of the 5min modes. Modeling will thus need to
adopt that the waves propagate in a three-dimensional medium with,
at least partially, reflecting boundaries. The bright points of the
chromospheric network behave very differently, more chaotic, like
noise. They show most power at low frequencies which we interpret as
the consequence of the stochastic intensity fluctuations.
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Title: Wellen in der Sonnenchromosphäre.
Authors: Kneer, F.; von Uexküll, M.
1994S&W....33..871K Altcode:
No abstract at ADS
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Title: Oscillations of the Sun's chromosphere. VI. K grains,
resonances, and gravity waves.
Authors: Kneer, F.; von Uexkuell, M.
1993A&A...274..584K Altcode:
We present observations of simultaneous filtergram time sequences in
Mg b<SUB>2</SUB>, Ca K and Hα obtained from quiet Sun disc centre with
the Vacuum Tower Telescope at Observatorio del Teide, Tenerife. Fourier
analyses are performed to obtain power, coherence and phase spectra in
the k-ω plane. There, the dominant features are the wellknown ridges
of the 5 min resonant modes. Yet in the chromosphere the ridges extend
to high wavenumbers (wavelengths ≍ 1.3 Mm) and to high frequencies
(periods ≍ 105 s). Neither the famous chromospheric "3 min"
oscillations nor an oscillation at the acoustic cutoff frequency
(period 210 s) appear exceptionally pronounced. The signature of
gravity waves is indicated from phase relations. <P />We distinguish
between the behaviour in the interior of the chromospheric network and
on the boundary. The network boundary behaves less oscillatory than
the interior. In snapshots of chromospheric intensities the K grains
(Beckers 1964), or, synonymously the bright cell points, appear in
the cell interior. They represent the phases of high temperature of
a wave field with partly resonant and coherent properties. (We take
intensity fluctuations as proxies for temperature fluctuations.) The
waves are only partly upward propagating p-modes with a multitude of
eigenvalues in frequency and wavenumber, like the subphotospheric
p-modes. We suggest that an excitation mechanism acts within the
chromosphere itself to drive the waves. This could explain the phase
relations between intensity and velocity oscillations.
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Title: On the structure of spectral line gap regions
Authors: Kneer, F.; von Uexkuell, M.
1991A&A...247..556K Altcode:
The analysis of a photographic spectrogram of the plage region near
the disk center of the sun is undertaken to study small-scale magnetic
features with special attention given to the structure of fluxtubes,
and a related model is developed. Line-gap regions are identified in
the Fe-I line which are characterized by redshifts and fluctuation
velocity as well as an asymmetric profile indicative of a direct
relationship between increasing downflow and increasing depth. The
observations are compared to calculated line profiles in which a
magnetic tube under certain conditions is present. The pressure and
density are calculated for the tube under the assumption of hydrostatic
equilibrium, and the observed intensity profiles can be reproduced
when the correct parameters are used. The calculations demonstrate
that a strong kilogauss magnetic field can be introduced to explain
the line gap in the Fe-II 6149-A line.
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Title: Oscillations of the sun's chromosphere. V - Importance of
network dynamics for chromospheric heating
Authors: von Uexkuell, M.; Kneer, F.; Malherbe, J. M.; Mein, P.
1989A&A...208..290V Altcode:
A 64-min time sequence of disk center H-alpha spectrograms taken
with the MSDP spectrograph at the Observatoire du Pic du Midi
is analyzed. This type of spectrograph allows spectroscopy of a
two-dimensional field of view. From the H-alpha line profiles at each
pixel, line-shift and minimum intensity fluctuation are determined as
functions of spatial and temporal coordinates. A frequency analysis
with standard Fourier techniques is performed. It is confirmed that
in the interior of the chromospheric network cells the oscillatory
behavior dominates, whereas at the boundaries one generally finds random
motions on scales of 2-10 arcsec. The random behavior of the H-alpha
structures outlines the permanent rearrangement of the magnetic field
lines pushed around by the subphotospheric granular flow.
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Title: Two-dimensional spectroscopy of the Sun in Hα.
Authors: von Uexküll, M.; Kneer, F.; Mein, P.
1988AGAb....1...11V Altcode:
No abstract at ADS
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Title: Oscillations of the sun's chromosphere. IV - Temporal evolution
of H-alpha profile
Authors: Kneer, F.; von Uexkuell, M.
1986A&A...155..178K Altcode:
H-alpha observations of the quiet solar chromosphere at disk center are
presented, including a 9 min time sequence of photographic filtergrams
in line center and + or - 0.5 A and a 54 min sequence of photographic
spectrograms. The very different dynamical behavior of the interior and
boundary of the network cells is emphasized. The dominant processes
in the interior are waves in the 5 min period range and with shorter
periods. The energy flux in these waves is estimated to be too small to
account for the radiative losses from standard chromospheric models. In
the cell boundaries, the material flows down, on time average, near the
centers of rosettes. The short time fluctuations are mainly stochastic
while the oscillations are reduced. This suggests that the energy
balance in the cell boundaries is determined by MHD turbulence.
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Title: Oscillations of the sun's chromosphere. III - Simultaneous
H-alpha observations from two sites
Authors: von Uexkuell, M.; Kneer, F.; Mattig, W.; Nesis, A.;
Schmidt, W.
1985A&A...146..192V Altcode:
The authors analyze time sequences of Hα filtergrams taken
simultaneously from two distant observatories, Capri and Izaña. By
means of a coherence analysis the authors discriminate between
instrumental effects including seeing and truly solar intensity
fluctuations. Waves with periods as short as 60 s are present in the
solar chromosphere; the lower limit is set by the time resolution of
the observations.
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Title: Oscillations of the sun's chromosphere. II - H-alpha line
centre and wing filtergram time sequences
Authors: Kneer, F.; von Uexkuell, M.
1985A&A...144..443K Altcode:
In order to investigate the dynamics of the solar chromosphere we
perform a Fourier analysis of time sequences (total duration 128 min)
of Hα photographic filtergrams taken simultaneously at disc centre
in line centre and ±0.5 Å from the line centre. The results are: (i)
At low frequencies (periods >450 s) the brightness fluctuations are
caused by the temporal evolution of Hα structures at the boundaries
of the chromospheric network. We observe that much of the coarse
chromospheric structure survives the 128 min time span. We derive
lifetimes of 2-8 min for the small-scale structure and 5-20 min for the
larger structures. (ii) The modal structure of the 5 min oscillation
is clearly visible in the power spectra of the three filtergram. The
fundamental (f) mode can be followed to high horizontal wavenumbers
k<SUB>h</SUB> ≍3.7 Mm<SUP>-1</SUP> and follows the expected
relationship ω<SUP>2</SUP><SUB>f</SUB> = gk<SUB>h</SUB>, where g is
the surface gravity. (iii) A chromospheric resonant mode cannot be
found in the k - ω plane. (iv) The higher resonant p modes reach into
the acoustic wave domain (periods T ≍ 150 s) and thus require the
transition zone as the upper reflecting layer. (v) We find no evidence
for internal gravity waves. (vi) From a coherence and phase analysis we
conclude that the brightness fluctuations of the chromospheric structure
seen in -0.5 Å lead those in +0.5 Å by 2 min at k<SUB>h</SUB> =2 Mm
<SUP>-1</SUP> and by 4 min at k<SUB>h</SUB> =0.5 Mm<SUP>-1</SUP>. (vii)
From the same coherence and phase analysis we can identify acoustic
waves in the solar atmosphere with periods as short as 80 s. They
possess as much power as the 5 min oscillations and are seen better
outside the chromospheric network than within the network. (viii) The
phase difference between intensity in Hα line centre and velocity,
constructed from the two Hα wing filtergrams, decreases from about 90°
at low frequencies and high wavenumbers to 0° at high frequencies and
low wavenumbers. Tentatively we interpret this as a change from mainly
standing waves for the low order p modes to mainly upward propagating
waves in the acoustic wave domain. Acoustic waves are thus candidates
for the heating process of the inter-network regions.
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Title: Waves in the chromosphere observed in Hα.
Authors: Kneer, F.; von Uexküll, M.
1985cdm..proc..282K Altcode:
The authors analyze Hα filtergram time sequences and emphasize the
further development and use of filter spectroscopy for studies on the
dynamics of the solar atmosphere.
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Title: Chromospheric umbral oscillations.
Authors: Mattig, W.; von Uexküll, M.; Kneer, F.
1984ESASP.220...59M Altcode: 1984ESPM....4...59M
No abstract at ADS
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Title: The chromosphere above sunspot umbrae. IV. Frequency analysis
of umbral oscillations.
Authors: von Uexküll, M.; Kneer, F.; Mattig, W.
1983A&A...123..263V Altcode:
The authors analyse time sequences of photographic spectrograms in Ca II
H, K, 8498 Å, and 8542 Å, in Sodium D<SUB>1</SUB> and D<SUB>2</SUB>,
in Ni I 5893 Å and Hα, obtained from two sunspots. The frequency
analysis of line intensities and shifts for the umbral chromospheric
oscillations in the period range 110 s-200 s is discussed.
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Title: The chromosphere above sunspot umbrae. IV - Frequency analysis
of umbral oscillations
Authors: Uexkuell, M. V.; Kneer, F.; Mattig, W.
1983A&A...123..263U Altcode:
An analysis is made of time sequences of photographic spectrograms in Ca
II H, K, 8498 A, and 8542 A, in sodium D1 and D2, and in Ni I 5893 A and
H-alpha obtained from two sunspots with the Vacuum Tower Telescope at
Sacramento Peak Observatory. The two sunspot chromospheres are found to
behave similarly with regard to their phase relationships but somewhat
differently with regard to the oscillation resonant frequencies. In one
and the same umbra, oscillation modes having different frequencies may
be excited. The vertical velocity of propagation of the phase in umbral
chromospheres, which is 10-25 km/s, decreases with increasing frequency
and is much lower than the Alfven speed. The umbral chromospheric
oscillations are thus slow mode waves. The downward motion enhances
the intensity by some 65 deg (H-alpha) to 85 deg (D1), indicating
dissipation of mechanical energy. It is also found that the mechanical
energy flux of the umbral chromospheric oscillations is not sufficient
to account for the chromospheric radiative losses.
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Title: Brightness oscillations of the sun's chromosphere in K
and H-alpha
Authors: Kneer, F.; von Uexkuell, M.
1983A&A...119..124K Altcode:
The authors have performed a power analysis of time sequences of
photographic K and Hα filtergrams from disc center of the sun. The
results are: In the k-ω-diagram from the Ca II K filtergrams, the modal
structure of the 5-min-oscillation is clearly seen. The 5-min modes
are difficult to detect in the k-ω-diagrams from the Hα sequences. In
both lines, K and Hα, the authors observe ridges in the k-ω-diagrams
running parallel to the k<SUB>h</SUB>-axis. Their periods correspond to
the chromospheric 3-min-oscillation. But power appears also, in discrete
ridges, at shorter periods P = 60 s...150 s, where the lower limit is
given by the Nyquist frequency of the observations. After subtraction
of the time averaged intensity at each position in the filtergrams,
the rms fluctuations are 3.5% in K and 4.0% in Hα.
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Title: New features of the oscillation spectrum of the sun
Authors: Kneer, F.; von Uexkuell, M.; Newkirk, G., Jr.
1982A&A...113..129K Altcode:
The results of a Fourier analysis of observations of brightness
fluctuations in a sequence of CN 3883 Angstrom filtergrams are
presented. From the 75 min time interval and field of view of 170 x
220 sq arcsec, a 40 sec sampling interval was examined, maintaining
a spatial resolution as high as 1600 km. The data is filtered for a
high wavenumber power spectrum, and an average power coefficient is
calculated by examining power spectra for each of the sub-arrays. It
is concluded that the 5 min velocity oscillation modal structure is
easily detected in brightness fluctuations in the CN band, the surface
gravity mode is the strongest single feature aside from the zero
frequency ridge caused by convection, and the trapped chromospheric
mode may be represented by a constant frequency ridge. Improved broad
band filtergrams may be used to analyze little explored regions of
the oscillation spectrum and to interpret intensity fluctuations as
temperature fluctuations.
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Title: Zur Struktur der Chromosphäre über Sonnenflecken
Authors: Kneer, F.; Mattig, W.; von Uexküll, M.
1982MitAG..55...65K Altcode:
No abstract at ADS
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Title: Chromosphärische Helligkeits-oszillationen
Authors: Kneer, F.; Newkirk, G.; von Uexküll, M.
1982MitAG..55...70K Altcode:
No abstract at ADS
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Title: The Chromosphere above Sunspot Umbrae - Part Three - Spatial
and Temporal Variations of Chromospheric Lines
Authors: Kneer, F.; Mattig, W.; Uexkull, M. V.
1981phss.conf..318K Altcode:
No abstract at ADS
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Title: Observations of Chromospheric Lines from OSO-8
Authors: Grossmann-Doerth, U.; Kneer, F.; Uexkuell, M.; Artzner,
G. E.; Vial, J. C.
1980SoPh...66....3G Altcode:
The line profiles of Lα, Ca II K and Mg IIk were measured with the
spectrometer of the `Laboratoire de Physique Stellaire et Planétaire'
on board of OSO-8. The results of these measurements are presented.
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Title: Spectral investigation of the chromosphere. VI: Observations
of Halpha close to the limb.
Authors: Grossmann-Doerth, U.; von Uexkuell, M.
1977SoPh...55..321G Altcode:
Several hundred Hα spectrograms from areas close to the solar
limb were taken with the 35 cm Coudé refractor at Anacapri. The
41 spectra with the greatest spatial resolution were selected and
analysed. At the supergranular boundaries a considerable fraction of
the line profiles were found to correspond to Beckers' Cloud Model
(BCM). Moreover, the BCM parameters of the dark mottles at the limb
appear to be approximately equal to those from the center of the
disk. On the other hand, we also obtained evidence in disagreement
with the general applicability of the BCM to all features of the
chromospheric fine structure.
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Title: Spectral Investigation of the Chromosphere. V: Observation
and Analysis of Hβ
Authors: Grossmann-Doerth, U.; Uexkuell, M. V.
1975SoPh...42..303G Altcode:
The results of the analysis of 16 Hβ spectra taken with high spatial
resolution are presented. The properties of the line profile in
the boundary regions of supergranular cells (SGB) are described by
the statistical distribution functions and correlation coefficients
of four parameters which determine the shape of a suitable fitting
curve. Although some of the line profile properties of both Hβ and Hα
in the SGB can be interpreted in terms of a model which was recently
proposed by Durrant (1975) the agreement between that theory and our
observations is not entirely satisfactory.
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Title: Properties of the solar Ca ii K-Line at high spatial
resolution
Authors: Grossmann-Doerth, U.; Kneer, F.; Uexküll, M. v.
1974SoPh...37...85G Altcode:
The analysis of three Ca II K-spectra with spatial resolution of
∼1″ is described and its results presented. The comparison of
the observed single peak line profiles with model computation leads
to some conclusions regarding the non-uniform large-scale velocity
fields in the chromosphere.
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Title: Spectroscopic Investigation of the Chromosphere. III: Hα
Line Profile from the Interior Supergranular Cells
Authors: Grossmann-Doerth, Ulrich; Von Uexküll, Marina
1973SoPh...30...71G Altcode:
The line profile of H⇓ as emanating from the interior of supergranular
cells was measured at sin θ = 0, 0.6, 0.8 and 0.9. The measurements
are described and the results presented.
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Title: Spectral Investigation of the Chromosphere. II. The Nature
of the Mottles and a Model of the Overall Structure
Authors: Grossmann-Doerth, Ulrich; Von Uexküll, Marina
1973SoPh...28..319G Altcode:
Highly resolved Hα spectra and filtergrams obtained at the Fraunhofer
Observatory on Capri were analysed by a method whose principles have
been described before. As a result the tentative conclusion of our
previous work has been confirmed: The mottles of the chromospheric fine
structure are clouds superimposed on the low chromosphere. Furthermore,
it is proposed that the latter is identical with the interior of
the supergranular cells whose spatial averages lend themselves to an
interpretation in terms of a spherically symmetric model. On the other
hand, we present evidence that the boundary regions which are formed
by the mottles of the fine structure pattern and which constitute
the upper chromosphere are not adequately described by spatial
averages. Instead, the properties of the individual structural elements
should be taken into account by an appropriate theory, if only in a
statistical fashion. Some of these properties, viz. source function,
optical thickness, Doppler width and velocity, were measured for a
large number of elements. On the basis of indirect evidence we suggest
that the spicules seen on limb photographs of chromospheric lines are
identical with the elements of the supergranule boundary structure.
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Title: Die Struktur der solaren Chromosphäre
Authors: Grossmann-Doerth, U.; von Uexküll, M.
1973MitAG..32..187G Altcode:
No abstract at ADS
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Title: Spectral Investigation of Chromospheric Fine Structure
Authors: Grossmann-Doerth, Ulrich; Von Uexküll, Marina
1971SoPh...20...31G Altcode:
Hα spectra and effectively simultaneous filtergrams were taken at the
Fraunhofer Observatory on Capri with the 35 cm domeless Coudé. The
spatial resolution of the 19 best spectra selected for analysis was
estimated to be 1-2 arc sec. The comparison of several hundred Hα
line profiles emitted by typical chromospheric structure elements
with theoretical prediction yielded strong evidence to suggest that
the chromosphere consists of two parts: A lower, rather uniform
layer at rest superposed by `clouds' (condensations of great spatial
variability) which constitute the well-known structure pattern of
Hα filtergrams. For most image points the line-of-sight velocity,
optical thickness, source function and Doppler broadening of these
clouds could be determined. While the values of the latter three
quantities were found to be similar to what Beckers (1968) has found
for limb spicules the velocity of the bright and of the dark mottles
is considerably smaller than to be expected if these features were
the spicules as seen on the disk. However, our results do not rule
out the possibility that the spicules rise at the centers of rosettes
where they are difficult to detect.
