fleck

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Author name code: fleck
ADS astronomy entries on 2022-09-14
author:"Fleck, Bernhard"

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Title: Acoustic-gravity wave propagation characteristics in 3D
radiation hydrodynamic simulations of the solar atmosphere
Authors: Fleck, Bernhard; Khomenko, Elena; Carlsson, Mats; Rempel,
Matthias; Steiner, Oskar; Riva, Fabio; Vigeesh, Gangadharan
2022cosp...44.2503F Altcode:
There has been tremendous progress in the degree of realism of
three-dimensional radiation magneto-hydrodynamic simulations of the
solar atmosphere in the past decades. Four of the most frequently
used numerical codes are Bifrost, CO5BOLD, MANCHA3D, and MURaM. Here
we test and compare the wave propagation characteristics in model
runs from these four codes by measuring the dispersion relation
of acoustic-gravity waves at various heights. We find considerable
differences between the various models.

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Title: Power distribution of oscillations in the atmosphere of a
plage region. Joint observations with ALMA, IRIS, and SDO
Authors: Narang, Nancy; Chandrashekhar, Kalugodu; Jafarzadeh, Shahin;
Fleck, Bernhard; Szydlarski, Mikołaj; Wedemeyer, Sven
2022A&A...661A..95N Altcode: 2022arXiv220211547N
Context. Joint observations of the Atacama Large
Millimeter/Submillimeter Array (ALMA) with other solar observatories
can provide a wealth of opportunities for understanding the coupling
between different layers of the solar atmosphere. Aims: We
present a statistical analysis of the power distribution of oscillations
in a plage region in active region NOAA AR12651, which was observed
jointly with ALMA, the Interface Region Imaging Spectrograph (IRIS),
and the Solar Dynamics Observatory (SDO). Methods: We employ
coordinated ALMA Band 6 (1.25 mm) brightness temperature maps,
IRIS slit-jaw images in the 2796 Å passband, and observations in
six passbands (1600 Å, 304 Å, 131 Å, 171 Å, 193 Å, and 211 Å)
from the Atmospheric Imaging Assembly (AIA) on board SDO. We perform
Lomb-Scargle transforms to study the distribution of oscillation power
by means of dominant period maps and power maps. We study the spatial
association of oscillations through the atmosphere, with a focus on
the correlation of the power distribution of ALMA oscillations with
others. Results: We do not observe any significant association
of ALMA oscillations with IRIS and AIA oscillations. While the global
behavior of the dominant ALMA oscillations shows a similarity with
that of the transition region and coronal passbands of AIA, the ALMA
dominant period maps and power maps do not show any correlation with
those from the other passbands. The spatial distribution of dominant
periods and power in different period intervals of ALMA oscillations
is uncorrelated with those of any other passbands. Conclusions:
We speculate that the non-association of ALMA oscillations with those
of IRIS and AIA is due to significant variations in the height of
formation of the millimeter continuum observed by ALMA. Additionally,
the fact that ALMA directly maps the brightness temperature, in contrast
to the intensity observations by IRIS and AIA, can result in the very
different intrinsic nature of the ALMA oscillations compared to the
IRIS and AIA oscillations.

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Title: Large scale coherent magnetohydrodynamic oscillations in
a sunspot
Authors: Stangalini, M.; Verth, G.; Fedun, V.; Aldhafeeri, A. A.;
Jess, D. B.; Jafarzadeh, S.; Keys, P. H.; Fleck, B.; Terradas, J.;
Murabito, M.; Ermolli, I.; Soler, R.; Giorgi, F.; MacBride, C. D.
2022NatCo..13..479S Altcode:
Although theoretically predicted, the simultaneous excitation of
several resonant modes in sunspots has not been observed. Like any
harmonic oscillator, a solar magnetic flux tube can support a variety
of resonances, which constitute the natural response of the system
to external forcing. Apart from a few single low order eigenmodes
in small scale magnetic structures, several simultaneous resonant
modes were not found in extremely large sunspots. Here we report
the detection of the largest-scale coherent oscillations observed
in a sunspot, with a spectrum significantly different from the Sun's
global acoustic oscillations, incorporating a superposition of many
resonant wave modes. Magnetohydrodynamic numerical modeling agrees
with the observations. Our findings not only demonstrate the possible
excitation of coherent oscillations over spatial scales as large as
30-40 Mm in extreme magnetic flux regions in the solar atmosphere,
but also paves the way for their diagnostic applications in other
astrophysical contexts.

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Title: A novel approach to identify resonant MHD wave modes in solar
pores and sunspot umbrae: B − ω analysis
Authors: Stangalini, M.; Jess, D. B.; Verth, G.; Fedun, V.; Fleck, B.;
Jafarzadeh, S.; Keys, P. H.; Murabito, M.; Calchetti, D.; Aldhafeeri,
A. A.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Terradas, J.;
Soler, R.
2021A&A...649A.169S Altcode: 2021arXiv210311639S
The umbral regions of sunspots and pores in the solar photosphere are
generally dominated by 3 mHz oscillations, which are due to p-modes
penetrating the magnetic region. In these locations, wave power is
also significantly reduced with respect to the quiet Sun. However,
here we study a pore where not only is the power of the oscillations
in the umbra comparable to, or even larger than, that of the quiet
Sun, but the main dominant frequency is not 3 mHz as expected, but
instead 5 mHz. By combining Doppler velocities and spectropolarimetry
and analysing the relationship between magnetic field strength and
frequency, the resultant B − ω diagram reveals distinct ridges that
are remarkably clear signatures of resonant magneto-hydrodynamic (MHD)
oscillations confined within the pore umbra. We demonstrate that these
modes, in addition to velocity oscillations, are also accompanied
by magnetic oscillations, as predicted from MHD theory. The novel
technique of B − ω analysis proposed in this article opens up
an exciting new avenue for identifying MHD wave modes in the umbral
regions of both pores and sunspots.

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Title: An overall view of temperature oscillations in the solar
chromosphere with ALMA
Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.;
Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu,
X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen,
B.; Reardon, K.; White, S. M.
2021RSPTA.37900174J Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J
By direct measurements of the gas temperature, the Atacama Large
Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic
tool to study the solar chromosphere. Here, we present an overview
of the brightness-temperature fluctuations from several high-quality
and high-temporal-resolution (i.e. 1 and 2 s cadence) time series
of images obtained during the first 2 years of solar observations
with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz)
and 1.25 mm (239 GHz), respectively. The various datasets represent
solar regions with different levels of magnetic flux. We perform
fast Fourier and Lomb-Scargle transforms to measure both the spatial
structuring of dominant frequencies and the average global frequency
distributions of the oscillations (i.e. averaged over the entire field
of view). We find that the observed frequencies significantly vary from
one dataset to another, which is discussed in terms of the solar regions
captured by the observations (i.e. linked to their underlying magnetic
topology). While the presence of enhanced power within the frequency
range 3-5 mHz is found for the most magnetically quiescent datasets,
lower frequencies dominate when there is significant influence from
strong underlying magnetic field concentrations (present inside and/or
in the immediate vicinity of the observed field of view). We discuss
here a number of reasons which could possibly contribute to the power
suppression at around 5.5 mHz in the ALMA observations. However,
it remains unclear how other chromospheric diagnostics (with an
exception of Hα line-core intensity) are unaffected by similar
effects, i.e. they show very pronounced 3-min oscillations dominating
the dynamics of the chromosphere, whereas only a very small fraction
of all the pixels in the 10 ALMA datasets analysed here show peak power
near 5.5 mHz. This article is part of the Theo Murphy meeting issue
`High-resolution wave dynamics in the lower solar atmosphere'.

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Title: High-frequency oscillations in small chromospheric bright
features observed with Atacama Large Millimetre/Submillimetre Array
Authors: Guevara Gómez, J. C.; Jafarzadeh, S.; Wedemeyer, S.;
Szydlarski, M.; Stangalini, M.; Fleck, B.; Keys, P. H.
2021RSPTA.37900184G Altcode: 2020arXiv200804179G
We report detection of oscillations in brightness temperature,
size and horizontal velocity of three small bright features in the
chromosphere of a plage/enhanced-network region. The observations,
which were taken with high temporal resolution (i.e. 2 s cadence)
with the Atacama large millimetre/ submillimetre array (ALMA) in Band
3 (centred at 3 mm; 100 GHz), exhibit three small-scale features with
oscillatory behaviour with different, but overlapping, distributions of
period on the order of, on average, 90 ± 22 s, 110 ± 12 s and 66 ±
23 s, respectively. We find anti-correlations between perturbations in
brightness, temperature and size of the three features, which suggest
the presence of fast sausage-mode waves in these small structures. In
addition, the detection of transverse oscillations (although with
a larger uncertainty) may also suggest the presence of Alfvénic
oscillations which are likely representative of kink waves. This work
demonstrates the diagnostic potential of high-cadence observations with
ALMA for detecting high-frequency magnetohydrodynamic waves in the
solar chromosphere. Such waves can potentially channel a vast amount
of energy into the outer atmosphere of the Sun. This article is
part of the Theo Murphy meeting issue `High-resolution wave dynamics
in the lower solar atmosphere'.

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Title: A new method for detecting solar atmospheric gravity waves
Authors: Calchetti, Daniele; Jefferies, Stuart M.; Fleck, Bernhard;
Berrilli, Francesco; Shcherbik, Dmitriy V.
2021RSPTA.37900178C Altcode: 2020arXiv200800210C
Internal gravity waves have been observed in the Earth's atmosphere
and oceans, on Mars and Jupiter, and in the Sun's atmosphere. Despite
ample evidence for the existence of propagating gravity waves in the
Sun's atmosphere, we still do not have a full understanding of their
characteristics and overall role for the dynamics and energetics of
the solar atmosphere. Here, we present a new approach to study the
propagation of gravity waves in the solar atmosphere. It is based on
calculating the three-dimensional cross-correlation function between
the vertical velocities measured at different heights. We apply this
new method to a time series of co-spatial and co-temporal Doppler
images obtained by SOHO/MDI and Hinode/SOT as well as to simulations
of upward propagating gravity wave-packets. We show some preliminary
results and outline future developments. This article is part of
the Theo Murphy meeting issue `High-resolution wave dynamics in the
lower solar atmosphere'.

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Title: Acoustic-gravity wave propagation characteristics in
three-dimensional radiation hydrodynamic simulations of the solar
atmosphere
Authors: Fleck, B.; Carlsson, M.; Khomenko, E.; Rempel, M.; Steiner,
O.; Vigeesh, G.
2021RSPTA.37900170F Altcode: 2020arXiv200705847F
There has been tremendous progress in the degree of realism of
three-dimensional radiation magneto-hydrodynamic simulations of the
solar atmosphere in the past decades. Four of the most frequently
used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here
we test and compare the wave propagation characteristics in model
runs from these four codes by measuring the dispersion relation of
acoustic-gravity waves at various heights. We find considerable
differences between the various models. The height dependence of
wave power, in particular of high-frequency waves, varies by up to
two orders of magnitude between the models, and the phase difference
spectra of several models show unexpected features, including ±180°
phase jumps. This article is part of the Theo Murphy meeting issue
`High-resolution wave dynamics in the lower solar atmosphere'.

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Title: On the influence of magnetic topology on the propagation of
internal gravity waves in the solar atmosphere
Authors: Vigeesh, G.; Roth, M.; Steiner, O.; Fleck, B.
2021RSPTA.37900177V Altcode: 2020arXiv201006926V
The solar surface is a continuous source of internal gravity waves
(IGWs). IGWs are believed to supply the bulk of the wave energy for
the lower solar atmosphere, but their existence and role for the energy
balance of the upper layers is still unclear, largely due to the lack
of knowledge about the influence of the Sun's magnetic fields on
their propagation. In this work, we look at naturally excited IGWs
in realistic models of the solar atmosphere and study the effect
of different magnetic field topographies on their propagation. We
carry out radiation-magnetohydrodynamic simulations of a magnetic
field free and two magnetic models-one with an initial, homogeneous,
vertical field of 100 G magnetic flux density and one with an initial
horizontal field of 100 G flux density. The propagation properties
of IGWs are studied by examining the phase-difference and coherence
spectra in the kh - ω diagnostic diagram. We find that IGWs
in the upper solar atmosphere show upward propagation in the model with
predominantly horizontal field similar to the model without magnetic
field. In contrast to that the model with predominantly vertical fields
show downward propagation. This crucial difference in the propagation
direction is also revealed in the difference in energy transported by
waves for heights below 0.8 Mm. Higher up, the propagation properties
show a peculiar behaviour, which require further study. Our analysis
suggests that IGWs may play a significant role in the heating of
the chromospheric layers of the internetwork region where horizontal
fields are thought to be prevalent. This article is part of the
Theo Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.

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Title: Reply to: Signatures of sunspot oscillations and the case
for chromospheric resonances
Authors: Jess, David B.; Snow, Ben; Fleck, Bernhard; Stangalini,
Marco; Jafarzadeh, Shahin
2021NatAs...5....5J Altcode: 2020NatAs.tmp..149J
No abstract at ADS

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Title: 3D Visualisation of Solar Data with JHelioviewer
Authors: Mueller, D.; Nicula, B.; Verstringe, F.; Bourgoignie, B.;
Csillaghy, A.; Laube, S.; Berghmans, D.; Ireland, J.; Fleck, B.
2020AGUFMSH0360001M Altcode:
The Solar Orbiter and Parker Solar Probe missions focus on exploring
the linkage between the Sun and the heliosphere. These new missions
are collecting unique data that will allow us to study the coupling
between macroscopic physical processes to those on kinetic scales, the
generation of solar energetic particles and their propagation into the
heliosphere and the origin and acceleration of solar wind plasma. The scientific community now has access to large volumes of complex
remote-sensing and in-situ observations from different vantage points,
complemented by petabytes of simulation data. Answering overarching
science questions like "How do solar transients drive heliospheric
variability and space weather?" will only be possible if the science
community has the necessary tools at hand to visualize these data
and assimilate them into sophisticated models. A key piece
needed to bridge the gap between observables, derived quantities like
magnetic field extrapolations and model output is a tool to routinely
and intuitively visualise large heterogeneous, multidimensional,
time-dependent data sets. The open-source JHelioviewer software,
which is part of the ESA/NASA Helioviewer Project, is addressing this
need. This contribution highlights recent extensions of JHelioviewer's
functionality, in particular those of interest for Solar Orbiter.

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Title: Data reduction pipeline for MOF-based synoptic telescopes
Authors: Forte, Roberta; Berrilli, Francesco; Calchetti, Daniele;
Del Moro, Dario; Fleck, Bernhard; Giebink, Cynthia; Giebink, William;
Giovannelli, Luca; Jefferies, Stuart Mark; Knox, Allister; Magrì,
Maria; Murphy, Neil; Nitta, Garry; Oliviero, Maurizio; Pietropaolo,
Ermanno; Rodgers, Wayne; Scardigli, Stefano; Viavattene, Giorgio
2020JSWSC..10...63F Altcode:
There are strong scientific cases and practical reasons for building
ground-based solar synoptic telescopes. Some issues, like the study of
solar dynamics and the forecasting of solar flares, benefit from the
3D reconstruction of the Sun's atmosphere and magnetic field. Others,
like the monitoring and prediction of space weather, require full disk
observations, at the proper sampling rate, combining H-alpha images
and Doppler velocity and magnetic field. The synoptic telescopes
based on Magneto Optical Filters (MOF) using different lines are
capable of measuring the line-of-sight Doppler velocity and magnetic
field over the full solar disk at different ranges of height in the
Sun's photosphere and low chromosphere. Instruments like the MOTH
(Magneto-Optical filters at Two Heights), using a dual-channel based
on MOFs operating at 589.0 nm (Na D2 line) and 769.9 nm
(K D1 line), the VAMOS instrument (Velocity And Magnetic
Observations of the Sun), operating at 769.9 nm (K D1 line), and the
future TSST (Tor Vergata Synoptic Solar Telescope), using a dual-channel
telescope operating at 656.28 nm (H-alpha line) and at 769.9 nm (K D1
line), allow to face both aspects, the scientific and the operative
related to Space Weather applications. The MOTH, VAMOS and TSST data
enable a wide variety of studies of the Sun, from seismic probing of
the solar interior (sound speed, rotation, details of the tachocline,
sub-surface structure of active regions), to the dynamics and magnetic
evolution of the lower part of the solar atmosphere (heating of the
solar atmosphere, identification of the signatures of solar eruptive
events, atmospheric gravity waves, etc.), to the 3D reconstruction
of the solar atmosphere and flare locations. However, the use of MOF
filters requires special care in calibrating the data for scientific
or operational use. This work presents a systematic pipeline that
derives from the decennial use of MOF's technology. More in detail,
the pipeline is based on data reduction procedures tested and validated
on MOTH data acquired at Mees Solar Observatory of the University of
Hawaii Haleakala Observatories and at South Pole Solar Observatory
(SPSO), at the Amundsen-Scott South Pole Station in Antarctica, during
Antarctica Summer Campaign 2016/17.

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Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.

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Title: A New Method for Detecting Solar Atmospheric Gravity Waves
Authors: Calchetti, D.; Jefferies, S.; Fleck, B.; Berrilli, F.
2020SPD....5120403C Altcode:
For the past fifty years, acoustic waves generated near the solar
surface have provided a powerful tool for the seismic mapping of the
Sun's internal structure and dynamics. This field of research, known
as helioseismology, has provided numerous fundamental breakthroughs in
our understanding of the Sun's interior. Interestingly, the convective
sources that produce the acoustic waves also produce internal gravity
waves that propagate throughout the Sun's atmosphere. In principle,
these waves can unlock the secrets of the Sun's atmosphere in much
the same way as helioseismology revolutionized our view of the Sun's
interior. However, despite ample evidence for their existence, we still
do not fully understand the characteristics and overall role of the
internal gravity waves for the dynamics and energetics of the solar
atmosphere. Here we present a new approach to study the propagation
of gravity waves in the solar atmosphere which finally opens the door
for seismic mapping of the Sun's atmosphere. We show some preliminary
results based on the analysis of both simulations and real observations,
and we outline future developments.

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Title: The Sun at millimeter wavelengths. I. Introduction to ALMA
Band 3 observations
Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin;
Eklund, Henrik; Guevara Gomez, Juan Camilo; Bastian, Tim; Fleck,
Bernhard; de la Cruz Rodriguez, Jaime; Rodger, Andrew; Carlsson, Mats
2020A&A...635A..71W Altcode: 2020arXiv200102185W
Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started
regular observations of the Sun in 2016, first offering receiver Band
3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around
1.25 mm (239 GHz). Aims: Here we present an initial study
of one of the first ALMA Band 3 observations of the Sun. Our aim is
to characterise the diagnostic potential of brightness temperatures
measured with ALMA on the Sun. Methods: The observation covers
a duration of 48 min at a cadence of 2 s targeting a quiet Sun region
at disc-centre. Corresponding time series of brightness temperature
maps are constructed with the first version of the Solar ALMA Pipeline
and compared to simultaneous observations with the Solar Dynamics
Observatory (SDO). Results: The angular resolution of the
observations is set by the synthesised beam, an elliptical Gaussian
that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit
network patches, internetwork regions, and elongated thin features
that are connected to large-scale magnetic loops, as confirmed by a
comparison with SDO maps. The ALMA Band 3 maps correlate best with
the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit
network features and, although very weak in the ALMA maps, imprints
of large-scale loops. A group of compact magnetic loops is very
clearly visible in ALMA Band 3. The brightness temperatures in the
loop tops reach values of about 8000-9000 K and in extreme moments
up to 10 000 K. Conclusions: ALMA Band 3 interferometric
observations from early observing cycles already reveal temperature
differences in the solar chromosphere. The weak imprint of magnetic
loops and the correlation with the 171, 131, and 304 SDO channels
suggests, however, that the radiation mapped in ALMA Band 3 might
have contributions from a wider range of atmospheric heights than
previously assumed, but the exact formation height of Band 3 needs to
be investigated in more detail. The absolute brightness temperature
scale as set by total power measurements remains less certain and
must be improved in the future. Despite these complications and the
limited angular resolution, ALMA Band 3 observations have a large
potential for quantitative studies of the small-scale structure and
dynamics of the solar chromosphere. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/201937122/olm">https://www.aanda.org</A>

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Title: Measuring the Dispersion Relation of Acoustic-Gravity Waves
in the Solar Atmosphere
Authors: Fleck, Bernhard; Jefferies, Stuart M.; Murphy, Neil;
Berrilli, Francesco
2020ASSP...57..141F Altcode:
We use localized measurements of the dispersion relation for
acoustic-gravity waves to generate the first maps of the spatial
structure of the sound speed, acoustic cut-off frequency, and radiative
damping time in the Sun's lower atmosphere. These maps offer a new
diagnostic for the solar atmosphere.

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Title: A chromospheric resonance cavity in a sunspot mapped with
seismology
Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert
J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés;
Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini,
Marco; Grant, Samuel D. T.; Christian, Damian J.
2020NatAs...4..220J Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J
Sunspots are intense collections of magnetic fields that pierce through
the Sun's photosphere, with their signatures extending upwards into the
outermost extremities of the solar corona1. Cutting-edge
observations and simulations are providing insights into the
underlying wave generation2, configuration3,4 and
damping5 mechanisms found in sunspot atmospheres. However,
the in situ amplification of magnetohydrodynamic waves6,
rising from a few hundreds of metres per second in the photosphere to
several kilometres per second in the chromosphere7, has,
until now, proved difficult to explain. Theory predicts that the
enhanced umbral wave power found at chromospheric heights may come
from the existence of an acoustic resonator8-10, which
is created due to the substantial temperature gradients experienced
at photospheric and transition region heights11. Here,
we provide strong observational evidence of a resonance cavity
existing above a highly magnetic sunspot. Through a combination of
spectropolarimetric inversions and comparisons with high-resolution
numerical simulations, we provide a new seismological approach to
mapping the geometry of the inherent temperature stratifications across
the diameter of the underlying sunspot, with the upper boundaries of the
chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our
findings will allow the three-dimensional structure of solar active
regions to be conclusively determined from relatively commonplace
two-dimensional Fourier power spectra. The techniques presented are
also readily suitable for investigating temperature-dependent resonance
effects in other areas of astrophysics, including the examination of
Earth-ionosphere wave cavities12.

---------------------------------------------------------
Title: Observed Local Dispersion Relations for Magnetoacoustic-gravity
Waves in the Sun’s Atmosphere: Mapping the Acoustic Cutoff Frequency
Authors: Jefferies, Stuart M.; Fleck, Bernhard; Murphy, Neil;
Berrilli, Francesco
2019ApJ...884L...8J Altcode: 2019arXiv191003198J
We present the observed local dispersion relations for
magnetoacoustic-gravity waves in the Sun’s atmosphere for different
levels of magnetic field strength. We model these data with a
theoretical local dispersion relation to produce spatial maps of the
acoustic cutoff frequency in the Sun’s photosphere. These maps have
implications for the mechanical heating of the Sun’s upper atmosphere,
by magnetoacoustic-gravity waves, at different phases of the solar
magnetic activity cycle.

---------------------------------------------------------
Title: Detection of Three-minute Oscillations in Full-disk Lyman-alpha
Emission during a Solar Flare
Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher,
Lyndsay; Dennis, Brian R.
2018csc..confE..36M Altcode:
In a recent study of spatially-integrated Lyman-alpha line emission
(Lya, 1216A) from GOES/EUVS, we detected the presence of acoustic
3-minute oscillations during an X-class solar flare. Similar
periodicities were also found - in phase - in Lyman continuum data from
SDO/EVE, and the 1600A and 1700A channels on SDO/AIA. The implication
is that the chromosphere responds dynamically at its acoustic cutoff
frequency to an impulsive injection of energy. Since the 3-minute
period was not detected at hard X-ray energies in RHESSI data we can
state that this 3-minute oscillation does not depend on the rate of
energisation of non-thermal electrons. This finding suggests that
chromospheric mechanical energy should be included in the flare
energy budget, and that fluctuations in Lya emission may influence
the composition and dynamics of planetary atmospheres during periods
of high activity. Knowledge of the behaviour of this emission during
flares could be important when interpreting future science results
from the EUI instrument on Solar Orbiter which will obtain high cadence
images in Lya.

---------------------------------------------------------
Title: The MOTH II Doppler-Magnetographs and Data Calibration Pipeline
Authors: Forte, Roberta; Jefferies, Stuart M.; Berrilli, Francesco;
Del Moro, Dario; Fleck, Bernhard; Giovannelli, Luca; Murphy, Neil;
Pietropaolo, Ermanno; Rodgers, Wayne
2018IAUS..335..335F Altcode:
The calibration pipeline of the level zero images obtained from
the Magneto-Optical filters at Two Heights (MOTH II) instrument is
presented. MOTH II consists of two 20 cm aperture instruments, each
using a Magneto-Optical Filter (MOF): one at 5896 Å (Na D2-line), the
other one at 7700 Å (K I-line). MOTH II instruments thus provide full
disk line-of-sight Doppler velocity and magnetic field measurements at
two heights in the solar atmosphere. The developed MOTH II pipeline
employs a set of standard calibration corrections, a correction for
signal leakage, due to the non-ideal behavior of the polarizers, and
the geometrical registration between the eight images acquired by four
CMOS cameras, relative to two components of the signal in two circular
polarization states, in each of the two channels. MOTH II data are used
to investigate atmospheric dynamics (e.g., internal gravity waves and
magneto-acoustic portals) and Space Weather phenomena. Particularly,
flare forecasting algorithms, based on the detection of magnetic active
regions (ARs) and associated flare probability estimation, are currently
under development. The possible matching of MOTH II data with SDO/HMI
and SDO/AIA images into a flux rope model, developed in collaboration
between Harvard-Smithsonian CfA and MIT Laboratory for Nuclear Science,
is being tested.

---------------------------------------------------------
Title: Detection of 3-Minute Oscillations in Full-Disk Lyman-alpha
Emission During A Solar Flare
Authors: Milligan, R. O.; Ireland, J.; Fleck, B.; Hudson, H. S.;
Fletcher, L.; Dennis, B. R.
2017AGUFMSH41A2739M Altcode:
We report the detection of chromospheric 3-minute oscillations in
disk-integrated EUV irradiance observations during a solar flare. A
wavelet analysis of detrended Lyman-alpha (from GOES/EUVS) and
Lyman continuum (from SDO/EVE) emission from the 2011 February 15
X-class flare revealed a 3-minute period present during the flare's
main phase. The formation temperature of this emission locates this
radiation to the flare's chromospheric footpoints, and similar behaviour
is found in the SDO/AIA 1600A and 1700A channels, which are dominated
by chromospheric continuum. The implication is that the chromosphere
responds dynamically at its acoustic cutoff frequency to an impulsive
injection of energy. Since the 3-minute period was not found at hard
X-ray energies (50-100 keV) in RHESSI data we can state that this
3-minute oscillation does not depend on the rate of energization of, or
energy deposition by, non-thermal electrons. However, a second period of
120 s found in both hard X-ray and chromospheric emission is consistent
with episodic electron energization on 2-minute timescales. Our
finding on the 3-minute oscillation suggests that chromospheric
mechanical energy should be included in the flare energy budget, and
the fluctuations in the Lyman-alpha line may influence the composition
and dynamics of planetary atmospheres during periods of high activity.

---------------------------------------------------------
Title: Franz-Ludwig Deubner (1934 - 2017)
Authors: Fleck, Bernhard; von der Lühe, Oskar
2017SoPh..292..178F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 3D Visualization of Solar Data: Preparing for Solar Orbiter
and Parker Solar Probe
Authors: Mueller, D.; Nicula, B.; Felix, S.; Verstringe, F.;
Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; Ireland,
J.; Fleck, B.
2017AGUFMSH23D2686M Altcode:
Solar Orbiter and Parker Solar Probe will focus on exploring the
linkage between the Sun and the heliosphere. These new missions will
collect unique data that will allow us to study, e.g., the coupling
between macroscopic physical processes to those on kinetic scales,
the generation of solar energetic particles and their propagation
into the heliosphere and the origin and acceleration of solar wind
plasma. Combined with the several petabytes of data from NASA's Solar
Dynamics Observatory, the scientific community will soon have access
to multidimensional remote-sensing and complex in-situ observations
from different vantage points, complemented by petabytes of simulation
data. Answering overarching science questions like "How do solar
transients drive heliospheric variability and space weather?" will
only be possible if the community has the necessary tools at hand. In
this contribution, we will present recent progress in visualizing the
Sun and its magnetic field in 3D using the open-source JHelioviewer
framework, which is part of the ESA/NASA Helioviewer Project.

---------------------------------------------------------
Title: Detection of Three-minute Oscillations in Full-disk Lyα
Emission during a Solar Flare
Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher,
Lyndsay; Dennis, Brian R.
2017ApJ...848L...8M Altcode: 2017arXiv170909037M
In this Letter we report the detection of chromospheric 3-minute
oscillations in disk-integrated EUV irradiance observations during a
solar flare. A wavelet analysis of detrended Lyα (from GOES/EUVS) and
Lyman continuum (from Solar Dynamics Observatory (SDO)/EVE) emission
from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed
a ∼3 minute period present during the flare’s main phase. The
formation temperature of this emission locates this radiation at the
flare’s chromospheric footpoints, and similar behavior is found
in the SDO/Atmospheric Imaging Assembly 1600 and 1700 Å channels,
which are dominated by chromospheric continuum. The implication is
that the chromosphere responds dynamically at its acoustic cutoff
frequency to an impulsive injection of energy. Since the 3-minute
period was not found at hard X-ray (HXR) energies (50-100 keV) in
Reuven Ramaty High Energy Solar Spectroscopic Imager data we can
state that this 3-minute oscillation does not depend on the rate of
energization of non-thermal electrons. However, a second period of 120
s found in both HXR and chromospheric lightcurves is consistent with
episodic electron energization on 2-minute timescales. Our finding on
the 3-minute oscillation suggests that chromospheric mechanical energy
should be included in the flare energy budget, and the fluctuations in
the Lyα line may influence the composition and dynamics of planetary
atmospheres during periods of high activity.

---------------------------------------------------------
Title: JHelioviewer. Time-dependent 3D visualisation of solar and
heliospheric data
Authors: Müller, D.; Nicula, B.; Felix, S.; Verstringe, F.;
Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.;
García-Ortiz, J. P.; Ireland, J.; Zahniy, S.; Fleck, B.
2017A&A...606A..10M Altcode: 2017arXiv170507628M
Context. Solar observatories are providing the world-wide community
with a wealth of data, covering wide time ranges (e.g. Solar and
Heliospheric Observatory, SOHO), multiple viewpoints (Solar TErrestrial
RElations Observatory, STEREO), and returning large amounts of data
(Solar Dynamics Observatory, SDO). In particular, the large volume of
SDO data presents challenges; the data are available only from a few
repositories, and full-disk, full-cadence data for reasonable durations
of scientific interest are difficult to download, due to their size
and the download rates available to most users. From a scientist's
perspective this poses three problems: accessing, browsing, and finding
interesting data as efficiently as possible. Aims: To address
these challenges, we have developed JHelioviewer, a visualisation
tool for solar data based on the JPEG 2000 compression standard
and part of the open source ESA/NASA Helioviewer Project. Since the
first release of JHelioviewer in 2009, the scientific functionality
of the software has been extended significantly, and the objective
of this paper is to highlight these improvements. Methods:
The JPEG 2000 standard offers useful new features that facilitate the
dissemination and analysis of high-resolution image data and offers
a solution to the challenge of efficiently browsing petabyte-scale
image archives. The JHelioviewer software is open source, platform
independent, and extendable via a plug-in architecture. 
Results: With JHelioviewer, users can visualise the Sun for any time
period between September 1991 and today; they can perform basic image
processing in real time, track features on the Sun, and interactively
overlay magnetic field extrapolations. The software integrates solar
event data and a timeline display. Once an interesting event has
been identified, science quality data can be accessed for in-depth
analysis. As a first step towards supporting science planning of the
upcoming Solar Orbiter mission, JHelioviewer offers a virtual camera
model that enables users to set the vantage point to the location of
a spacecraft or celestial body at any given time.

---------------------------------------------------------
Title: 20 Years of SOHO
Authors: Fleck, Bernhard; Müller, Daniel
2016ENews..47c..27F Altcode:
The Solar and Heliospheric Observatory (SOHO), a joint mission of ESA
and NASA, has provided unparalleled insight into the Sun over the past
20 years - from its interior, through the hot and dynamic atmosphere,
out to the solar wind and its interaction with the interstellar
medium. SOHO also plays a vital role in forecasting potentially
dangerous space weather situations by continuously monitoring solar
storms, and unexpectedly also became the most prolific discoverer of
comets in the history of astronomy.

---------------------------------------------------------
Title: Solar Science with the Atacama Large Millimeter/Submillimeter
Array—A New View of Our Sun
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Hudson, H.;
Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E. P.; De Pontieu,
B.; Yagoubov, P.; Tiwari, S. K.; Soler, R.; Black, J. H.; Antolin,
P.; Scullion, E.; Gunár, S.; Labrosse, N.; Ludwig, H. -G.; Benz,
A. O.; White, S. M.; Hauschildt, P.; Doyle, J. G.; Nakariakov, V. M.;
Ayres, T.; Heinzel, P.; Karlicky, M.; Van Doorsselaere, T.; Gary,
D.; Alissandrakis, C. E.; Nindos, A.; Solanki, S. K.; Rouppe van
der Voort, L.; Shimojo, M.; Kato, Y.; Zaqarashvili, T.; Perez, E.;
Selhorst, C. L.; Barta, M.
2016SSRv..200....1W Altcode: 2015SSRv..tmp..118W; 2015arXiv150406887W
The Atacama Large Millimeter/submillimeter Array (ALMA) is a new
powerful tool for observing the Sun at high spatial, temporal, and
spectral resolution. These capabilities can address a broad range
of fundamental scientific questions in solar physics. The radiation
observed by ALMA originates mostly from the chromosphere—a complex
and dynamic region between the photosphere and corona, which plays a
crucial role in the transport of energy and matter and, ultimately,
the heating of the outer layers of the solar atmosphere. Based on
first solar test observations, strategies for regular solar campaigns
are currently being developed. State-of-the-art numerical simulations
of the solar atmosphere and modeling of instrumental effects can help
constrain and optimize future observing modes for ALMA. Here we present
a short technical description of ALMA and an overview of past efforts
and future possibilities for solar observations at submillimeter and
millimeter wavelengths. In addition, selected numerical simulations
and observations at other wavelengths demonstrate ALMA's scientific
potential for studying the Sun for a large range of science cases.

---------------------------------------------------------
Title: ALMA Observations of the Sun in Cycle 4 and Beyond
Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.;
Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.;
Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson,
M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.;
Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov,
V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões,
P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig,
A.; White, S.; Yagoubov, P.; Zaqarashvili, T.
2016arXiv160100587W Altcode:
This document was created by the Solar Simulations for the Atacama
Large Millimeter Observatory Network (SSALMON) in preparation of
the first regular observations of the Sun with the Atacama Large
Millimeter/submillimeter Array (ALMA), which are anticipated to start
in ALMA Cycle 4 in October 2016. The science cases presented here
demonstrate that a large number of scientifically highly interesting
observations could be made already with the still limited solar
observing modes foreseen for Cycle 4 and that ALMA has the potential
to make important contributions to answering long-standing scientific
questions in solar physics. With the proposal deadline for ALMA Cycle
4 in April 2016 and the Commissioning and Science Verification campaign
in December 2015 in sight, several of the SSALMON Expert Teams composed
strategic documents in which they outlined potential solar observations
that could be feasible given the anticipated technical capabilities
in Cycle 4. These documents have been combined and supplemented
with an analysis, resulting in recommendations for solar observing
with ALMA in Cycle 4. In addition, the detailed science cases also
demonstrate the scientific priorities of the solar physics community
and which capabilities are wanted for the next observing cycles. The
work on this White Paper effort was coordinated in close cooperation
with the two international solar ALMA development studies led by
T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be
further updated until the beginning of Cycle 4 in October 2016. In
particular, we plan to adjust the technical capabilities of the solar
observing modes once finally decided and to further demonstrate the
feasibility and scientific potential of the included science cases by
means of numerical simulations of the solar atmosphere and corresponding
simulated ALMA observations.

---------------------------------------------------------
Title: SSALMON - The Solar Simulations for the Atacama Large
Millimeter Observatory Network
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson,
H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu,
B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.;
Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.;
Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier,
A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M.
2015AdSpR..56.2679W Altcode: 2015arXiv150205601W
The Solar Simulations for the Atacama Large Millimeter Observatory
Network (SSALMON) was initiated in 2014 in connection with two ALMA
development studies. The Atacama Large Millimeter/submillimeter Array
(ALMA) is a powerful new tool, which can also observe the Sun at
high spatial, temporal, and spectral resolution. The international
SSALMONetwork aims at co-ordinating the further development of solar
observing modes for ALMA and at promoting scientific opportunities
for solar physics with particular focus on numerical simulations,
which can provide important constraints for the observing modes and
can aid the interpretation of future observations. The radiation
detected by ALMA originates mostly in the solar chromosphere - a
complex and dynamic layer between the photosphere and corona, which
plays an important role in the transport of energy and matter and the
heating of the outer layers of the solar atmosphere. Potential targets
include active regions, prominences, quiet Sun regions, flares. Here,
we give a brief overview over the network and potential science cases
for future solar observations with ALMA.

---------------------------------------------------------
Title: Future Mission Concepts for Helioseismology
Authors: Sekii, Takashi; Appourchaux, Thierry; Fleck, Bernhard;
Turck-Chièze, Sylvaine
2015SSRv..196..285S Altcode: 2015SSRv..tmp...15S
Future space-mission concepts currently discussed in the helioseismology
community are reviewed. One popular idea is to observe the Sun from high
latitudes, to explore the polar regions as well as to probe the deep
interior using stereoscopic techniques, by combining observations from
high latitudes with observations from within the ecliptic plane. Another
idea is to stay within the ecliptic plane but still aim for stereoscopic
helioseismology for deep layers. A new instrument and a novel mission
concept for studying the solar core regions are also discussed.

---------------------------------------------------------
Title: The 9 May 2016 transit of Mercury - a great outreach
opportunity in Europe
Authors: Rothery, D. A.; Benkhoff, J.; Zender, J.; Gill, R.; Fleck,
B.; Doressoundiram, A.
2015EPSC...10..108R Altcode:
People across most of the globe will have a chance to witness Mercury's
next solar transit, 11:12-18:42 UT, Monday 9 May 2016. Occurring a
year after the end of the MESSENGER mission and a few months before
the launch of BepiColombo, this transit (the first since 2006) will be
an ideal occasion to draw the public's attention to the science goals
of those missions, to showcase what we have recently learned about
Mercury, and to draw attention to the conundrums that make Mercury
such a fascinating object to study.

---------------------------------------------------------
Title: A steady-state supersonic downflow in the transition region
above a sunspot umbra
Authors: Straus, Thomas; Fleck, Bernhard; Andretta, Vincenzo
2015A&A...582A.116S Altcode: 2015arXiv150704279S
We investigate a small-scale (~1.5 Mm along the slit), supersonic
downflow of about 90 km s-1 in the transition region
above the lightbridged sunspot umbra in AR 11836. The observations
were obtained with the Interface Region Spectrograph (IRIS) on
2013 September 2 from 16:40 to 17:59 UT. The downflow shows up as
redshifted "satellite" lines of the Si iv and O iv transition region
lines and is remarkably steady over the observing period of nearly
80 min. The downflow is not visible in the chromospheric lines,
which only show an intensity enhancement at the location of the
downflow. The density inferred from the line ratio of the redshifted
satellites of the O iv lines (Ne = 1010.6 ± 0.25
cm-3) is only a factor 2 smaller than the one inferred
from the main components (Ne = 1010.95 ± 0.20
cm-3). Consequently, this implies a substantial mass flux
(~5 × 10-7 g cm-2 s-1), which would
evacuate the overlying corona on timescales close to 10 s. We interpret
these findings as evidence of a stationary termination shock of a
supersonic siphon flow in a cool loop that is rooted in the central
umbra of the spot. The movie is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525805/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Solar and Galactic Cosmic Rays Observed by SOHO
Authors: Fleck, Bernhard; Curdt, Werner; Olive, Jean-Philippe; van
Overbeek, Ton
2015TESS....131009F Altcode:
Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs)
have left an imprint on SOHO technical systems. While the solar array
efficiency degraded irreversibly down to 75% of its original level
over 1 ½ solar cycles, Single Event Upsets (SEUs) in the solid state
recorder (SSR) have been reversed by the memory protection mechanism. We
compare the daily CRF observed by the Oulu station with the daily SOHO
SEU rate and with the degradation curve of the solar arrays. The Oulu
CRF and the SOHO SSR SEU rate are both modulated by the solar cycle
and are highly correlated, except for sharp spikes in the SEU rate,
caused by isolated SEP events, which also show up as discontinuities
in the otherwise slowly decreasing solar ray efficiency. This allows
to discriminate between effects with solar and non-solar origin and to
compare the relative strength of both. We find that the total number
of SSR SEUs with solar origin over the 17 ½ years from January 1996
through June 2013 is of the same order as those generated by cosmic ray
hits. 49% of the total solar array degradation during that time can be
attributed to proton events, i.e. the effect of a series of short-lived,
violent events (SEPs) is comparable to the cycle-integrated damage by
cosmic rays.

---------------------------------------------------------
Title: Observations of a Steady-State Supersonic Downflow in the
Transition Region above a Sunspot Umbra
Authors: Fleck, Bernhard; Straus, Thomas; Andretta, Vincenzo
2015TESS....120311F Altcode:
Sunspots have been an area of intense research ever since Hale's
discovery of strong magnetic fields in these structures. Here we report
on the detection of a particular sunspot phenomenon: a small-scale (~
1.5 Mm), supersonic downflow of about 90 km/s in the transition region
above a light-bridged sunspot umbra. The observations were obtained with
the Interface Imaging Region Spectrograph (IRIS) on 2 September 2013
from 16:39 to 17:58 UT in the sunspot of AR 11836 near disk center. Slit
length and width were 68” and 0.166”, respectively. The cadence of
the time series was 3 s, with exposure times of 2 s. The observations
comprise nine spectral windows: C II 1336, Fe XII 1349, Cl I 1352,
O I 1356, Si IV 1394, Si IV 1403, NUV at 2786 and 2831, and Mg II h
and k 2796. The spectral window containing the Si IV 1403 line also
includes the O IV 1400, 1401, and 1405 lines, the last one blended
with a S IV line. The downflow shows up as red-shifted, well-separated
“satellite” lines of the Si IV and O IV transition region lines and
is remarkably steady over the observing period of nearly 80 min. The
satellite lines do not participate in the 3-min shock wave Doppler
maneuvres of the main component. The downflow is not visible in the
chromospheric lines, which only show an intensity enhancement at the
location of the downflow. The density inferred from the line ratio of
the redshifted satellites of the O IV lines (Ne=1010.5
±0.3 cm-3) is only a factor 2.5 smaller than the
one inferred from the main components (Ne=1010.9 ±0.2
cm-3). Consequently, this implies a substantial mass
flux (~ 4×10-7 g cm-2 s-1), which
would evacuate the overlying corona on time scales of the order of 10
s. We interpret these findings as evidence of a stationary termination
shock of a supersonic siphon flow in a cool loop rooted in the central
umbra of the spot. Such stationary shocks have been predicted for
siphon flows in hot coronal loops by Noci (1981).

---------------------------------------------------------
Title: Solar and Heliospheric Observatory (SOHO) (1995)
Authors: Fleck, B.; St. Cyr, O. C.
2015hchp.book..159F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar and Galactic Cosmic Rays Observed by SOHO
Authors: Curdt, W.; Fleck, B.
2015CEAB...39..109C Altcode: 2015arXiv150507952C
Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs)
have left an imprint on SOHO technical systems. While the solar array
efficiency degraded irreversibly down to ≈77% of its original
level over roughly 1 1/2 solar cycles, Single Event Upsets (SEUs)
in the solid state recorder (SSR) have been reversed by the memory
protection mechanism. We compare the daily CRF observed by the Oulu
station with the daily SOHO SEU rate and with the degradation curve
of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both
modulated by the solar cycle and are highly correlated, except for
sharp spikes in the SEU rate, caused by isolated SEP events, which also
show up as discontinuities in the otherwise slowly decreasing solar
ray efficiency. This allows to discriminate between effects with solar
and non-solar origin and to compare the relative strength of both. We
find that during solar cycle 23 (1996 Apr 1 -- 2008 Aug 31) only 6%
of the total number of SSR SEUs were caused by SEPs; the remaining 94%
were due to galactic cosmic rays. During the maximum period of cycle
23 (2000 Jan 1 -- 2003 Dec 31), the SEP contribution increased to 22%,
and during 2001, the year with the highest SEP rate, to 30%. About 40%
of the total solar array degradation during the 17 years from Jan 1996
through Feb 2013 can be attributed to proton events, i.e. the effect
of a series of short-lived, violent SEP events is comparable to the
cycle-integrated damage by cosmic rays.

---------------------------------------------------------
Title: Wave Propagation in the Internetwork Chromosphere: Comparing
IRIS Observations of Mg II h and k with Simulations
Authors: Fleck, B.; De Pontieu, B.; Leenaarts, J.; Pereira, T. M. D.;
Straus, T.
2014AGUFMSH51C4174F Altcode:
The objective of this study is to explore the dynamics of the
upper internetwork chromosphere using high-resolution spectroscopic
"sit-and-stare" time series obtained with the Interface Region Imaging
Spectrogragh (IRIS) in the Mg II h and k lines. The Mg II h and k lines
reveal a particularly complex spatio-temporal behavior, which strongly
depends on the magnetic field topology. We focus on six parameters in
both the h and k line: the Doppler shift and intensity of the central
reversal (h3 and k3) and the blue and red emission peaks (h2v, h2r,
k2v, k2r). In an effort to better understand what physical parameters
can be extracted from these lines and to put our interpretation of
the observations on more solid grounds, we extend our analysis to
synthetic spectra obtained from numerical simulations and compare the
results to the observations.

---------------------------------------------------------
Title: Interpreting the Helioseismic and Magnetic Imager (HMI)
Multi-Height Velocity Measurements
Authors: Nagashima, Kaori; Löptien, Björn; Gizon, Laurent; Birch,
Aaron C.; Cameron, Robert; Couvidat, Sebastien; Danilovic, Sanja;
Fleck, Bernhard; Stein, Robert
2014SoPh..289.3457N Altcode: 2014arXiv1404.3569N; 2014SoPh..tmp...84N
The Solar Dynamics Observatory/Helioseismic and Magnetic Imager
(SDO/HMI) filtergrams, taken at six wavelengths around the Fe I 6173.3
Å line, contain information about the line-of-sight velocity over
a range of heights in the solar atmosphere. Multi-height velocity
inferences from these observations can be exploited to study wave
motions and energy transport in the atmosphere. Using realistic
convection-simulation datasets provided by the STAGGER and MURaM
codes, we generate synthetic filtergrams and explore several methods
for estimating Dopplergrams. We investigate at which height each
synthetic Dopplergram correlates most strongly with the vertical
velocity in the model atmospheres. On the basis of the investigation,
we propose two Dopplergrams other than the standard HMI-algorithm
Dopplergram produced from HMI filtergrams: a line-center Dopplergram
and an average-wing Dopplergram. These two Dopplergrams correlate most
strongly with vertical velocities at the heights of 30 - 40 km above
(line center) and 30 - 40 km below (average wing) the effective height
of the HMI-algorithm Dopplergram. Therefore, we can obtain velocity
information from two layers separated by about a half of a scale height
in the atmosphere, at best. The phase shifts between these multi-height
Dopplergrams from observational data as well as those from the simulated
data are also consistent with the height-difference estimates in the
frequency range above the photospheric acoustic-cutoff frequency.

---------------------------------------------------------
Title: Helioseismic and Magnetic Imager Multi-height Dopplergrams
Authors: Nagashima, Kaori; Gizon, Laurent; Birch, Aaron; Löptien,
Björn; Couvidat, Sebastien; Fleck, Bernhard
2014arXiv1401.3182N Altcode:
We study Doppler velocity measurements at multiple heights in the solar
atmosphere using a set of six filtergrams obtained by the Helioseismic
magnetic Imager on board the Solar Dynamics Observatory. There are clear
and significant phase differences between core and wing Dopplergrams in
the frequency range above the photospheric acoustic cutoff frequency,
which indicates that these are really "multi-height" datasets.

---------------------------------------------------------
Title: Helioseismic and Magnetic Imager Multi-height Dopplergrams
Authors: Nagashima, K.; Gizon, L.; Birch, A.; Löptien, B.; Couvidat,
S.; Fleck, B.
2013ASPC..479..429N Altcode:
We study Doppler velocity measurements at multiple heights in the solar
atmosphere using a set of six filtergrams, obtained by the Helioseismic
Magnetic Imager on board the Solar Dynamics Observatory. There are clear
and significant phase differences between core and wing Dopplergrams in
the frequency range above the photospheric acoustic cutoff frequency,
which indicates that these are really “multi-height” datasets.

---------------------------------------------------------
Title: JHelioviewer: Visualization software for solar physics data
Authors: Mueller, Daniel; Dimitoglou, George; Caplins, Benjamin; Garcia
Ortiz, Juan Pablo; Wamsler, Benjamin; Hughitt, Keith; Alexanderian,
Alen; Ireland, Jack; Amadigwe, Desmond; Fleck, Bernhard
2013ascl.soft08016M Altcode: 2013ascl.soft08016Y
JHelioview is open source visualization software for solar physics
data. The JHelioviewer client application enables users to browse
petabyte-scale image archives; the JHelioviewer server integrates a
JPIP server, metadata catalog, and an event server. JHelioview uses
the JPEG 2000 image compression standard, which provides efficient
access to petabyte-scale image archives; JHelioviewer also allows
users to locate and manipulate specific data sets.

---------------------------------------------------------
Title: The Intensity-Velocity Phase Spectra of Evanescent Oscillations
and Acoustic Sources
Authors: Severino, G.; Straus, T.; Oliviero, M.; Steffen, M.; Fleck, B.
2013SoPh..284..297S Altcode: 2012SoPh..tmp..295S
There are three major issues in modeling solar evanescent oscillations:
the variation of the intensity [I]-velocity [V] phase difference of
p-modes close to the base of photosphere; the existence of a plateau
of negative I-V phase differences below and between the ridges of the
low-frequency p-modes; the explanation of the I-V cross-spectra of
the evanescent oscillations. We present new interpretations for the
first two issues, based on modeling intensity fluctuations taking steep
temperature gradients, opacity, and non-adiabatic cooling into account.

---------------------------------------------------------
Title: Extracting multi-height velocity information from SDO/HMI
Dopplergrams
Authors: Nagashima, Kaori; Gizon, Laurent; Birch, Aaron; Loeptien,
Bjoern; Couvidat, Sebastien; Fleck, Bernhard; Stein, Robert
2013enss.confE..76N Altcode:
Multi-height velocity information in the solar atmosphere is useful for
many studies of the structure and dynamics of the solar atmosphere. We
discuss the possibility of measuring the vertical velocity at multiple
layers in the solar atmosphere using the six filtergrams of the Fe
I 6173A absorption line obtained by SDO/HMI. In the standard HMI
pipeline processing, these filtergrams are combined to estimate a
single Doppler velocity. Here we construct three Dopplergrams by
computing pair-wise differences between intensities in the blue
and red wings of the line. We use realistic numerical simulations
of convection to evaluate the range of heights that contribute to
each of our multi-height velocity estimates. The cross-spectra of
the Dopplergrams contain interesting information about vertical wave
propagation in the solar atmosphere.

---------------------------------------------------------
Title: On the Effects of the SDO Orbital Motion on the HMI Vector
Magnetic Field Measurements
Authors: Fleck, B.; Centeno, R.; Cheung, M.; Couvidat, S.; Hayashi,
K.; Rezaei, R.; Steiner, O.; Straus, T.
2013enss.confE.145F Altcode:
In a previous study we have investigated the magnetic field diagnostics
potential of SDO/HMI. We have used the output of high-resolution
3D, time-dependent, radiative magneto-hydrodynamics simulations to
calculate Stokes profiles for the Fe I 6173 Å line. From these we
constructed Stokes filtergrams using a representative set of HMI filter
response functions. The magnetic field vector (x,y) and line-of-sight
Doppler velocities V(x,y) were determined from these filtergrams using
a simplified version of the HMI magnetic field processing pipeline,
and the reconstructed magnetic field (x,y) and line-of-sight velocity
V(x,y) were compared to the actual magnetic field (x,y,z) and vertical
velocity V0(x,y,z) in the simulations. The present investigation expands
this analysis to include the effects of the significant orbital motions
of SDO, which, given the limited wavelength range of the HMI filter
profiles, affects the outer wing measurements and therefore might impact
the magnetic field measurements. We find that the effects of the orbital
movement of SDO are noticeable, in particular for the strongest fields
(B &gt; 3 kG) and the maximum wavelength shift of 5.5 km/s (3.5 km/s
orbital movement + 2 km/s solar rotation). Saturation effects for strong
fields (B &gt; 3 kG) are already visible for wavelength shifts of 3.2
km/s (orbital movement, disk center). The measurements of inclination
and vertical velocity are more robust. Compared to other factors of
uncertainty in the inversion of HMI Stokes measurements the orbital
movement is not a major concern or source of error.

---------------------------------------------------------
Title: Preface
Authors: Fleck, Bernhard; Heber, Bernd; Vourlidas, Angelos; van
Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Leibacher, John
2012SoPh..281....1F Altcode: 2012SoPh..tmp..223F
No abstract at ADS

---------------------------------------------------------
Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI
Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno,
R.; Cheung, M.; Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.;
Viticchie, B.
2012decs.confE.104F Altcode:
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO) is designed to study oscillations and the magnetic
field in the solar photosphere. It observes the full solar disk
in the Fe I absorption line at 6173 Å. We use the output of three
high-resolution 3D, time-dependent, radiative magneto-hydrodynamics
simulations (two based on the MURaM code, one on the CO5BOLD code)
to calculate Stokes profiles Fi(λ,x,y; i=I, V, Q, U) for the Fe I
6173 Å line for snapshots of a sunspot, a plage area and an enhanced
network region. Stokes filtergrams are constructed for the 6 nominal
HMI wavelengths by multiplying the Stokes profiles with a representative
set of HMI filter response functions. The magnetic field vector B(x,y)
and line-of-sight Doppler velocities V(x,y) are determined from these
filtergrams using a simplified version of the HMI magnetic field
processing pipeline. Finally, the reconstructed magnetic field B(x,y)
and line-of-sight velocity V(x,y) are compared to the actual magnetic
field B0(x,y,z) and vertical velocity V0(x,y,z) in the simulations.

---------------------------------------------------------
Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI
Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno, R.;
Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.; Viticchie, B.
2011sdmi.confE..74F Altcode:
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO) is designed to study oscillations and the magnetic
field in the solar photosphere. It observes the full solar disk in the
Fe I 6173 absorption line. We use the output of two high-resolution 3D,
time-dependent, radiative magneto-hydrodynamics simulations (one based
on the MURAM code, the other one on the COBOLD code) to calculate
Stokes profiles for the Fe I 6173 line for a snapshot of a plage
region and a snapshot of an enhanced network region. After spatially
degrading the Stokes profiles to HMI resolution, they are multiplied
by a representative set of HMI filter response functions and Stokes
filtergrams are constructed for the 6 nominal HMI wavelengths. The
magnetic field vector and line-of-sight Doppler velocities are
determined from these filtergrams using a simplified version of the HMI
magnetic field processing pipeline. Finally, the reconstructed magnetic
field is compared to the actual magnetic field in the simulation.

---------------------------------------------------------
Title: On the Formation Height of the SDO/HMI Fe 6173 Å Doppler
Signal
Authors: Fleck, B.; Couvidat, S.; Straus, T.
2011SoPh..271...27F Altcode: 2011SoPh..tmp..242F; 2011arXiv1104.5166F; 2011SoPh..tmp..117F;
2011SoPh..tmp..173F
The Helioseismic and Magnetic Imager (HMI) onboard the Solar
Dynamics Observatory (SDO) is designed to study oscillations and the
magnetic field in the solar photosphere. It observes the full solar
disk in the Fe I absorption line at 6173 Å. We use the output of a
high-resolution, 3D, time-dependent, radiation-hydrodynamic simulation
based on the CO5BOLD code to calculate profiles F(λ,x,y,t)
for the Fe I 6173 Å line. The emerging profiles F(λ,x,y,t) are
multiplied by a representative set of HMI filter-transmission profiles
Ri(λ, 1≤i≤6) and filtergrams Ii(x,y,t;
1≤i≤6) are constructed for six wavelengths. Doppler velocities
VHMI(x,y,t) are determined from these filtergrams using
a simplified version of the HMI pipeline. The Doppler velocities are
correlated with the original velocities in the simulated atmosphere. The
cross-correlation peaks near 100 km, suggesting that the HMI Doppler
velocity signal is formed rather low in the solar atmosphere. The same
analysis is performed for the SOHO/MDI Ni I line at 6768 Å. The MDI
Doppler signal is formed slightly higher at around 125 km. Taking
into account the limited spatial resolution of the instruments,
the apparent formation height of both the HMI and MDI Doppler signal
increases by 40 to 50 km. We also study how uncertainties in the HMI
filter-transmission profiles affect the calculated velocities.

---------------------------------------------------------
Title: The Helioviewer Project: Solar Data Visualization and
Exploration
Authors: Hughitt, V. Keith; Ireland, J.; Müller, D.; García Ortiz,
J.; Dimitoglou, G.; Fleck, B.
2011SPD....42.1517H Altcode: 2011BAAS..43S.1517H
SDO has only been operating a little over a year, but in that short
time it has already transmitted hundreds of terabytes of data, making
it impossible for data providers to maintain a complete archive of
data online. By storing an extremely efficiently compressed subset of
the data, however, the Helioviewer project has been able to maintain a
continuous record of high-quality SDO images starting from soon after
the commissioning phase. The Helioviewer project was not designed
to deal with SDO alone, however, and continues to add support for
new types of data, the most recent of which are STEREO EUVI and
COR1/COR2 images. In addition to adding support for new types of data,
improvements have been made to both the server-side and client-side
products that are part of the project. A new open-source JPEG2000 (JPIP)
streaming server has been developed offering a vastly more flexible and
reliable backend for the Java/OpenGL application JHelioviewer. Meanwhile
the web front-end, Helioviewer.org, has also made great strides both
in improving reliability, and also in adding new features such as the
ability to create and share movies on YouTube. Helioviewer users are
creating nearly two thousand movies a day from the over six million
images that are available to them, and that number continues to grow
each day. We provide an overview of recent progress with the various
Helioviewer Project components and discuss plans for future development.

---------------------------------------------------------
Title: Helioviewer: Simplifying Your Access to SDO Data
Authors: Hughitt, V. K.; Ireland, J.; Mueller, D.; Beck, J.; Lyon,
D.; Dau, A.; Dietert, H.; Nuhn, M.; Dimitoglou, G.; Fleck, B.
2010AGUFMSH23C1868H Altcode:
Over the past several years, the Helioviewer Project has evolved
from a simple web application to display images of the sun into a
suite of tools to visualize and interact with heterogeneous types of
solar data. In addition to a modular and scalable back-end server, the
Helioviewer Project now offers multiple browse clients; the original
web application has been upgraded to support high-definition movie
generation and feature and event overlays. For complex image processing
and massive data volumes, there is a stand-alone desktop application,
JHelioviewer. For a quick check of the latest images and events,
there is an iPhone application, hqTouch. The project has expanded from
the original SOHO images to include image data from SDO and event and
feature data from the HEK. We are working on adding additional image
data from other missions as well as spectral and time-series data. We
will discuss the procedure through which interested parties may process
their data for use with Helioviewer, including how to use JP2Gen to
convert FITS files into Helioviewer-compliant JPEG 2000 images, how
to setup a local instance of the Helioviewer server, and how to query
Helioviewer in your own applications using a simple web API.

---------------------------------------------------------
Title: Estimating the Energy Flux of Acoustic-Gravity Waves in the
Solar Atmosphere from SDO/HMI Data
Authors: Fleck, B.; Straus, T.; Jefferies, S.; Scherrer, P.
2010AGUFMSH11A1602F Altcode:
Straus et al. (2008, 2009) demonstrated the existence of internal
gravity waves in the solar atmosphere and showed that they are a
key mediator of mechanical energy in the middle/upper photosphere,
transporting even more energy than high-frequency acoustic waves. Here
we repeat this analysis with data from SDO/HMI, which offers several
distinct advantages, which are particularly relevant for the study
of internal gravity waves (which have long periods and small spatial
scales): excellent image stability over long time intervals, high
spatial resolution, large field-of-view, and good temporal cadence.

---------------------------------------------------------
Title: JHelioviewer: Open-Source Software for Discovery and Image
Access in the Petabyte Age (Invited)
Authors: Mueller, D.; Dimitoglou, G.; Langenberg, M.; Pagel, S.; Dau,
A.; Nuhn, M.; Garcia Ortiz, J. P.; Dietert, H.; Schmidt, L.; Hughitt,
V. K.; Ireland, J.; Fleck, B.
2010AGUFMSH22A..05M Altcode:
The unprecedented torrent of data returned by the Solar Dynamics
Observatory is both a blessing and a barrier: a blessing for making
available data with significantly higher spatial and temporal
resolution, but a barrier for scientists to access, browse and
analyze them. With such staggering data volume, the data is bound
to be accessible only from a few repositories and users will have to
deal with data sets effectively immobile and practically difficult to
download. From a scientist's perspective this poses three challenges:
accessing, browsing and finding interesting data while avoiding
the proverbial search for a needle in a haystack. To address
these challenges, we have developed JHelioviewer, an open-source
visualization software that lets users browse large data volumes
both as still images and movies. We did so by deploying an efficient
image encoding, storage, and dissemination solution using the JPEG
2000 standard. This solution enables users to access remote images at
different resolution levels as a single data stream. Users can view,
manipulate, pan, zoom, and overlay JPEG 2000 compressed data quickly,
without severe network bandwidth penalties. Besides viewing data, the
browser provides third-party metadata and event catalog integration
to quickly locate data of interest, as well as an interface to the
Virtual Solar Observatory to download science-quality data. As part of
the Helioviewer Project, JHelioviewer offers intuitive ways to browse
large amounts of heterogeneous data remotely and provides an extensible
and customizable open-source platform for the scientific community.

---------------------------------------------------------
Title: Adiabatic high degree modes of a rotating star. I. General
features and real pressure modes
Authors: Schmitz, F.; Fleck, B.
2010A&A...515A.103S Altcode:
 Aims: The influence of the rotation of the Sun on non-radial
p-modes with high wave numbers l is studied. To investigate and
understand the basic properties of these modes, it is sufficient to
consider only the outer layers of the Sun, which can be approximated by
a plane layer with constant gravity. Methods: We use a model
with a smooth transition between a polytropic convection zone and
an isothermal atmosphere. The rotation is simulated by a constant
horizontal wind. For this model, using the column mass instead of
the geometrical height, the adiabatic wave equation of the pressure
perturbation can be reduced to Whittaker's differential equation. From
boundary conditions we obtain the dispersion relation. The geometrical
height is a simple elementary function of the column mass. 
Results: The dispersion relation F(ω, k) = 0 is a higher order
algebraic equation in both frequency and horizontal wave number, which
must be solved numerically. We analyze the behavior of the dispersion
curves of modes with an adiabatic exponent γ = 5/3 for layers
with polytropic indices n = 3 and n = 3/2. The f-mode is considered
separately. For the understanding of the results we also consider modes
of a homogeneous gas. We compare the k - ω diagram of our idealized
model with the k - ω diagram of a real solar model. Dedicated to
Franz-Ludwig Deubner, who celebrated his 75th birthday on June 2, 2009.

---------------------------------------------------------
Title: The Signature of Flares in VIRGO Total Solar Irradiance
Measurements
Authors: Quesnel, A.; Dennis, B. R.; Fleck, B.; Fröhlich, C.; Hudson,
H. S.; Tolbert, A. K.
2010ASPC..428..133Q Altcode: 2010arXiv1003.4194Q
We use Total Solar Irradiance (TSI) measurements from the VIRGO
(Variability of solar Irradiance and Gravity Oscillations) instrument
on board SOHO to obtain preliminary estimates of the mean total
radiative energy emitted by X-class solar flares. The basic tool is
that of summed-epoch analysis, which has also enabled us to detect and
partially characterize systematic errors present in the basic data. We
describe these errors, which significantly degrade the photometry at
high frequencies. We find the ratio of GOES 1-8 Å luminosity to total
bolometric luminosity to be of order 0.01.

---------------------------------------------------------
Title: JHelioviewer: Taming The Torrent Of SDO Data
Authors: Mueller, Daniel; Langenberg, M.; Pagel, S.; Schmidt, L.;
Garcia Ortiz, J. P.; Dimitoglou, G.; Hughitt, V. K.; Ireland, J.;
Fleck, B.
2010AAS...21640224M Altcode: 2010BAAS...41..877M
Space missions generate an ever-growing amount of data, as impressively
highlighted by the Solar Dynamics Observatory's (SDO) expected return
of 1.4 TByte/day. In order to fully exploit their data, scientists
need to be able to browse and visualize many different data products
spanning a large range of physical length and time scales. So far, the
tools available to the scientific community either require downloading
all potentially relevant data sets beforehand in their entirety or
provide only movies with a fixed resolution and cadence. For SDO,
the former approach is prohibitive due to the shear data volume, while
the latter does not do justice to the high resolution and cadence of
the images. To address this challenge, we have developed JHelioviewer,
a JPEG 2000-based visualization and discovery software for solar image
data. Using the very efficient lossy compression mode of JPEG 2000,
a full-size SDO image can be compressed to 1 MByte at good visual
quality for browsing purposes. JHelioviewer will make the vast amount
of SDO images available to the worldwide community in this format,
which is already being used for all SOHO images. JHelioviewer is
a cross-platform application that offers movie streaming, real-time
frame-by-frame image processing, feature/event overlays and will enable
users to access SDO science data via a VSO interface. JHelioviewer uses
the JPEG 2000 Interactive Protocol (JPIP) and OpenGL. The random code
stream access of JPIP minimizes data transfer by streaming image data in
a region-of-interest and quality-progressive way, while OpenGL enables
rapid hardware-accelerated image processing and rendering. Currently
focused on solar physics data, JHelioviewer can easily be adapted
for use in other areas of space and earth sciences. This poster will
illustrate the new and expanded functionality of JHelioviewer and
highlight the advantages of JPEG 2000 as a new compression standard
for solar image data.

---------------------------------------------------------
Title: The Helioviewer Project: Browsing, Visualizing and Accessing
Petabytes of Solar Data
Authors: Mueller, Daniel; Hughitt, V. K.; Langenberg, M.; Ireland, J.;
Pagel, S.; Schmidt, L.; Garcia Ortiz, J. P.; Dimitoglou, G.; Fleck, B.
2010AAS...21640223M Altcode: 2010BAAS...41..876M
After its successful launch, NASA's Solar Dynamics Observatory
(SDO) will soon return more than 1 Terabyte worth of images per
day. This unprecedented torrent of data will pose an entirely new
set of challenges with respect to data access, data browsing and
searching for interesting data while avoiding the proverbial search
for "a needle in a haystack". In order to fully exploit SDO's wealth
of data and connect it to data from other solar missions like SOHO,
scientists need to be able to interactively browse and visualize many
different data products spanning a large range of physical length and
time scales. So far, all tools available to the scientific community
either require downloading all potentially relevant data sets beforehand
in their entirety or provide only movies with a fixed resolution and
cadence. The Helioviewer project offers a solution to these challenges
by providing a suite of tools that are based on the new JPEG 2000
compression standard and enable scientists and the general public alike
to intuitively browse visualize and access petabytes of image data
remotely: - JHelioviewer, a cross-platform application that offers
movie streaming and real-time processing using the JPEG 2000 Interactive
Protocol (JPIP) and OpenGL, as well as feature/event overlays. -
helioviewer.org, a web-based image and feature/event browser. -
Server-side services to stream movies of arbitrary spatial and temporal
resolution in a region-of-interest and quality-progressive form, a
JPEG 2000 image database and a feature/event server. All the services
can be accessed through well-documented interfaces (APIs). - Code
to convert images into JPEG 2000 format. This presentation will
give an overview of the Helioviewer Project, illustrate new features
and highlight the advantages of JPEG 2000 as a data format for solar
physics that has the potential to revolutionize the way high-resolution
image data are disseminated and analyzed.

---------------------------------------------------------
Title: Solar Mashups: Interacting With, Extending, And Embedding
Helioviewer.org And Jhelioviewer
Authors: Hughitt, V. Keith; Ireland, J.; Müller, D.; Langenberg,
M.; Pagel, S.; Schmidt, L.; Harper, J.; Dimitoglou, G.; Fleck, B.
2010AAS...21640225H Altcode: 2010BAAS...41..877H
Helioviewer.org is a JPEG 2000-driven web application for searching
and displaying heterogeneous solar data sets, including both image
and catalog information. Helioviewer.org has been written from the
ground up with extensibility in mind. The result of this effort is a
rich Application Programming Interface (API) from which third-party
applications can interact with Helioviewer.org. In addition to being
able to launch Helioviewer.org with a specified state (by giving
it a time and a set of instruments, wavelengths, etc), it is also
possible to generate composite images and movies, and to search for
catalog data from the Heliophysics Event Knowledgebase (HEK). We are
developing our software so that you will be able to embed instances
of Helioviewer.org in your own web pages, in much the same way that
it is now possible to embed Google Maps (tm) into any webpage. This
will make it very easy to overlay your data with that provided by
the Helioviewer Project. JHelioviewer, Helioviewer.org's Java-based
counterpart, shares many of the same features as Helioviewer.org, but
also offers some new ones when it comes to extensibility, including a
custom plugin architecture that supports custom image filters, overlay
layers, GUI components, and more. Both of the projects are free to
use and completely open-source, and anyone is welcome to contribute
to their development.

---------------------------------------------------------
Title: High frequency waves in the solar atmosphere?.
Authors: Fleck, B.; Straus, T.; Carlsson, M.; Jefferies, S. M.;
Severino, G.; Tarbell, T. D.
2010MmSAI..81..777F Altcode: 2010arXiv1002.3285F
The present study addresses the following questions: How representative
of the actual velocities in the solar atmosphere are the Doppler
shifts of spectral lines? How reliable is the velocity signal derived
from narrowband filtergrams? How well defined is the height of the
measured Doppler signal? Why do phase difference spectra always pull
to 0o phase lag at high frequencies? Can we actually observe
high frequency waves (P&lt; 70 s)? What is the atmospheric MTF of high
frequency waves? How reliably can we determine the energy flux of high
frequency waves? We address these questions by comparing observations
obtained with Hinode/NFI with results from two 3D numerical simulations
(Oslo Stagger and CO5BOLD). Our results suggest that the
observed high frequency Doppler velocity signal is caused by rapid
height variations of the velocity response function in an atmosphere
with strong velocity gradients and cannot be interpreted as evidence of
propagating high frequency acoustic waves. Estimates of the energy flux
of high frequency waves should be treated with caution, in particular
those that apply atmospheric MTF corrections.

---------------------------------------------------------
Title: On the detection of fast moving upflows in the quiet solar
photosphere.
Authors: Straus, Th.; Fleck, B.; Jefferies, S. M.; Carlsson, M.;
Tarbell, T. D.
2010MmSAI..81..751S Altcode: 2010arXiv1002.3305S
In our studies of the dynamics and energetics of the solar atmosphere,
we have detected, in high-quality observations from Hinode SOT/NFI,
ubiquitous small-scale upflows which move horizontally with supersonic
velocities in the quiet Sun. We present the properties of these fast
moving upflows (FMUs) and discuss different interpretations.

---------------------------------------------------------
Title: JHelioviewer: Exploring Petabytes of Solar Images
Authors: Mueller, Daniel; Fleck, Bernhard; Dimitoglou, George; Garcia
Ortiz, Juan Pablo; Schmidt, Ludwig; Hughitt, Keith; Ireland, Jack
2010cosp...38.2880M Altcode: 2010cosp.meet.2880M
Space missions generate an ever-growing amount of data, as impressively
highlighted by the Solar Dynamics Observatory's (SDO) expected return
of 1.4 TByte/day. In order to fully ex-ploit their data, scientists
need to be able to browse and visualize many different data products
spanning a large range of physical length and time scales. So far, the
tools available to the scientific community either require downloading
all potentially relevant data sets beforehand in their entirety or
provide only movies with a fixed resolution and cadence. For SDO,
the former approach is prohibitive due to the shear data volume,
while the latter does not do justice to the high resolution and
cadence of the images. To address this challenge, we have developed
JHelioviewer, a JPEG 2000-based visualization and discovery software
for solar image data. JHelioviewer makes the vast amount of SDO images
available to the worldwide community, lets users browse more than
14 years worth of images from the Solar and Heliospheric Observatory
(SOHO) and facilitates browsing and analysis of complex time-dependent
data sets from mul-tiple sources in general. The user interface for
JHelioviewer is a multi-platform Java client that communicates with a
remote server via the JPEG 2000 interactive protocol JPIP. The random
code stream access of JPIP minimizes data transfer and can encapsulate
metadata as well as multiple image channels in one data stream. This
presentation will illustrate the features of JHelioviewer and highlight
the advantages of JPEG 2000 as a new data compression standard.

---------------------------------------------------------
Title: On the Role of Acoustic-Gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; McIntosh, S. W.;
Severino, G.; Steffen, M.; Tarbell, T. D.
2009ASPC..415...95S Altcode: 2010arXiv1003.3773S
In a recent paper (Straus et al. 2008) we determined the energy
flux of internal gravity waves in the lower solar atmosphere using
a combination of 3D numerical simulations and observations obtained
with the IBIS instrument operated at the Dunn Solar Telescope and
the Michelson Doppler Imager (MDI) on SOHO. In this paper we extend
these studies using coordinated observations from SOT/NFI and SOT/SP
on Hinode and MDI. The new measurements confirm that gravity waves
are the dominant phenomenon in the quiet middle/upper photosphere and
that they transport more mechanical energy than the high-frequency
(&gt; 5 mHz) acoustic waves, even though we find an acoustic flux 3-5
times larger than the upper limit estimate of Fossum &amp; Carlsson
(2006). It therefore appears justified to reconsider the significance of
(non-M)HD waves for the energy balance of the solar chromosphere.

---------------------------------------------------------
Title: Helioviewer.org: Browsing Very Large Image Archives Online
Using JPEG 2000
Authors: Hughitt, V. K.; Ireland, J.; Mueller, D.; Dimitoglou, G.;
Garcia Ortiz, J.; Schmidt, L.; Wamsler, B.; Beck, J.; Alexanderian,
A.; Fleck, B.
2009AGUFMSH51B1279H Altcode:
As the amount of solar data available to scientists continues to
increase at faster and faster rates, it is important that there exist
simple tools for navigating this data quickly with a minimal amount
of effort. By combining heterogeneous solar physics datatypes such
as full-disk images and coronagraphs, along with feature and event
information, Helioviewer offers a simple and intuitive way to browse
multiple datasets simultaneously. Images are stored in a repository
using the JPEG 2000 format and tiled dynamically upon a client's
request. By tiling images and serving only the portions of the image
requested, it is possible for the client to work with very large
images without having to fetch all of the data at once. In addition
to a focus on intercommunication with other virtual observatories
and browsers (VSO, HEK, etc), Helioviewer will offer a number of
externally-available application programming interfaces (APIs) to
enable easy third party use, adoption and extension. Recent efforts
have resulted in increased performance, dynamic movie generation,
and improved support for mobile web browsers. Future functionality
will include: support for additional data-sources including RHESSI,
SDO, STEREO, and TRACE, a navigable timeline of recorded solar events,
social annotation, and basic client-side image processing.

---------------------------------------------------------
Title: JHelioviewer: Visualizing Large Sets of Solar Images Using
JPEG 2000
Authors: Muller, D.; Fleck, B.; Dimitoglou, G.; Caplins, B. W.;
Amadigwe, D. E.; García Ortiz, J. P.; Wamsler, B.; Alexanderian,
A.; Hughitt, V. K.; Ireland, J.
2009CSE....11...38M Altcode: 2009arXiv0906.1582M
All disciplines that work with image data-from astrophysics to medical
research and historic preservation-increasingly require efficient ways
to browse and inspect large sets of high-resolution images. Based on
the JPEG 2000 image-compression standard, the JHelioviewer solar image
visualization tool lets users browse petabyte-scale image archives as
well as locate and manipulate specific data sets.

---------------------------------------------------------
Title: A Novel Approach to Discovery and Access to Solar Data in
the Petabyte Age
Authors: Mueller, Daniel; Dimitoglou, G.; Hughitt, V. K.; Ireland,
J.; Wamsler, B.; Fleck, B.
2009SPD....40.1706M Altcode:
Space missions generate an ever-growing amount of data, as impressively
highlighted by SDO's expected data rate of 1.4 TByte/day. In order
to fully exploit their data, scientists need to be able to browse
and visualize many different data products spanning a large range
of physical length and time scales. So far, the tools available to
the scientific community either require downloading all potentially
relevant data sets beforehand in their entirety or provide only
movies with a fixed resolution and cadence. To facilitate browsing and
analysis of complex time-dependent data sets from multiple sources,
we are developing JHelioviewer, a JPEG 2000-based visualization and
discovery infrastructure for solar image data. Together with its
web-based counterpart helioviewer.org, JHelioviewer offers intuitive
ways to browse large amounts of heterogeneous data remotely and allows
users to search related event data bases. The user interface for
JHelioviewer is a multi-platform Java client that can both communicate
with a remote server via the JPEG 2000 interactive protocol JPIP
and open local data. The random code stream access of JPIP minimizes
data transfer and can encapsulate meta data as well as multiple image
channels in one data stream. This presentation will illustrate some
of the features of JHelioviewer and the advantages of JPEG 2000 as a
new data compression standard.

---------------------------------------------------------
Title: Helioviewer.org: An Open-source Tool for Visualizing Solar Data
Authors: Hughitt, V. Keith; Ireland, J.; Schmiedel, P.; Dimitoglou,
G.; Mueller, D.; Fleck, B.
2009SPD....40.1502H Altcode:
As the amount of solar data available to scientists continues to
increase at faster and faster rates, it is important that there exist
simple tools for navigating this data quickly with a minimal amount
of effort. By combining heterogeneous solar physics datatypes such
as full-disk images and coronagraphs, along with feature and event
information, Helioviewer offers a simple and intuitive way to browse
multiple datasets simultaneously. Images are stored in a repository
using the JPEG 2000 format and tiled dynamically upon a client's
request. By tiling images and serving only the portions of the image
requested, it is possible for the client to work with very large
images without having to fetch all of the data at once. Currently,
Helioviewer enables users to browse the entire SOHO data archive,
updated hourly, as well as data feature/event catalog data from
eight different catalogs including active region, flare, coronal
mass ejection, type II radio burst data. In addition to a focus on
intercommunication with other virtual observatories and browsers (VSO,
HEK, etc), Helioviewer will offer a number of externally-available
application programming interfaces (APIs) to enable easy third party
use, adoption and extension. Future functionality will include:
support for additional data-sources including TRACE, SDO and STEREO,
dynamic movie generation, a navigable timeline of recorded solar events,
social annotation, and basic client-side image processing.

---------------------------------------------------------
Title: The Helioviewer Project: Discovery For Everyone Everywhere
Authors: Ireland, Jack; Hughitt, K.; Müller, D.; Dimitoglou, G.;
Schmiedel, P.; Fleck, B.
2009SPD....40.1501I Altcode:
The Helioviewer Project: discovery for everyone everywhere There is
an ever increasing amount of solar and heliospheric data gathered
from multiple sources such as space-based facilities and ground based
observatories. There are also multiple feature and event catalogs
arising from human and computer based detection methods. The Helioviewer
Project is developing a suite of technologies to allow users around the
world to visualize, browse and access these heterogeneous datasets in an
intuitive and highly customizable fashion. Helioviewer technologies
are based on the JPEG2000 file format, an extremely flexible format that
allows for the efficient transfer of data (and meta-data, such as FITS
keywords) between client and server. Rather then having to download an
entire image and then examine the small portion- for example, an active
region - that you are interested in, the JPEG2000 file format lets you
preferentially download only those portions you are interested in. This
dramatically reduces the amount of data transferred, making possible
responsive and flexible scientific discovery applications that can
browse populous archives of large images, such as those from the Solar
Dynamics Observatory. In addition, the Helioviewer Project is
designed to be flexible and extensible to data sources as they become
available. Helioviewer.org (www.helioviewer.org) works seamlessly with
the Virtual Solar Observatory (VSO) whilst an application programming
interface (API) is being developed for interaction with the Solar
Dynamics Observatory Heliophysics Event Knowledgebase. After a
short introduction to the underlying technology, a live demonstration
of the web application www.helioviewer.org will be given. We will also
comment on other client applications (Jhelioviewer, a Java-based browse
tool), and the application of Helioviewer technology to existing and
future solar and heliospheric data and feature/event repositories. This
project is funded by NASA VxO and LWS awards and an ESA science award.

---------------------------------------------------------
Title: Helioviewer: A Web 2.0 Tool for Visualizing Heterogeneous
Heliophysics Data
Authors: Hughitt, V. K.; Ireland, J.; Lynch, M. J.; Schmeidel, P.;
Dimitoglou, G.; Müeller, D.; Fleck, B.
2008AGUFMSM11B1617H Altcode:
Solar physics datasets are becoming larger, richer, more numerous and
more distributed. Feature/event catalogs (describing objects of interest
in the original data) are becoming important tools in navigating these
data. In the wake of this increasing influx of data and catalogs there
has been a growing need for highly sophisticated tools for accessing and
visualizing this wealth of information. Helioviewer is a novel tool for
integrating and visualizing disparate sources of solar and Heliophysics
data. Taking advantage of the newly available power of modern web
application frameworks, Helioviewer merges image and feature catalog
data, and provides for Heliophysics data a familiar interface not unlike
Google Maps or MapQuest. In addition to streamlining the process of
combining heterogeneous Heliophysics datatypes such as full-disk images
and coronagraphs, the inclusion of visual representations of automated
and human-annotated features provides the user with an integrated
and intuitive view of how different factors may be interacting on the
Sun. Currently, Helioviewer offers images from The Extreme ultraviolet
Imaging Telescope (EIT), The Large Angle and Spectrometric COronagraph
experiment (LASCO) and the Michelson Doppler Imager (MDI) instruments
onboard The Solar and Heliospheric Observatory (SOHO), as well as
The Transition Region and Coronal Explorer (TRACE). Helioviewer also
incorporates feature/event information from the LASCO CME List, NOAA
Active Regions, CACTus CME and Type II Radio Bursts feature/event
catalogs. The project is undergoing continuous development with many
more data sources and additional functionality planned for the near
future.

---------------------------------------------------------
Title: Preface: SOHO 20 - Transient events on the Sun and in the
heliosphere
Authors: Robbrecht, E.; Hochedez, J. -F.; Fleck, B.; Gurman, J.;
Forsyth, R.
2008AnGeo..26.2953R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Severino, G.;
Straus, T.; Tarbell, T. D.
2008ESPM...12.2.39F Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum &amp; Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient
to heat the solar chromosphere. The same conclusion was reached by
Carlsson et al. (2007) from an analysis of Hinode SOT/BFI Ca II H and
blue continuum observations. Other authors (e.g. Cuntz et al. 2007;
Wedemeyer-Boehm et al. 2007, Kalkofen 2007), however, questioned
these results for a number of reasons. Because of its limited spatial
resolution and limited sensitivity there are inherent difficulties
when comparing TRACE observations with numerical simulations. Further,
intensity oscillations are difficult to interpret, as they result from
a phase-sensitive mix of temperature and pressure fluctuations, and
non-local radiation transfer effects may complicate the picture even
more. Here we revisit the role of high frequency acoustic waves in the
dynamics and energetics of the Sun's atmosphere using high cadence,
high resolution Doppler velocity measurements obtained with SOT/SP
and SOT/NFI on Hinode.

---------------------------------------------------------
Title: On the Role of Acoustic-gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; Cauzzi, G.; McIntosh,
S. W.; Reardon, K.; Severino, G.; Steffen, M.; Suter, M.; Tarbell,
T. D.
2008ESPM...12.2.11S Altcode:
We revisit the dynamics and energetics of the solar atmosphere, using a
combination of high-quality observations and 3D numerical simulations
of the overshoot region of compressible convection into the stable
photosphere. We discuss the contribution of acoustic-gravity waves
to the energy balance of the photosphere and low chromosphere. We
demonstrate the presence of propagating internal gravity waves at
low frequencies (&lt; 5mHz). Surprisingly, these waves are found
to be the dominant phenomenon in the quiet middle/upper photosphere
and to transport a significant amount of mechanical energy into the
atmosphere outweighing the contribution of high-frequency (&gt; 5mHz)
acoustic waves by more than an order of magnitude. We compare the
properties of high-frequency waves in the simulations with results
of recent high cadence, high resolution Doppler velocity measurements
obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in
conflict with the simple picture of upward propagating sound waves. We
discuss the implications of our findings on the energy flux estimate
at high-frequencies.

---------------------------------------------------------
Title: The Energy Flux of Internal Gravity Waves in the Lower Solar
Atmosphere
Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.;
Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe;
Steffen, Matthias
2008ApJ...681L.125S Altcode:
Stably stratified fluids, such as stellar and planetary atmospheres,
can support and propagate gravity waves. On Earth these waves,
which can transport energy and momentum over large distances and can
trigger convection, contribute to the formation of our weather and
global climate. Gravity waves also play a pivotal role in planetary
sciences and modern stellar physics. They have also been proposed
as an agent for the heating of stellar atmospheres and coronae, the
exact mechanism behind which is one of the outstanding puzzles in solar
and stellar physics. Using a combination of high-quality observations
and 3D numerical simulations we have the first unambiguous detection
of propagating gravity waves in the Sun's (and hence a stellar)
atmosphere. Moreover, we are able to determine the height dependence of
their energy flux and find that at the base of the Sun's chromosphere it
is around 5 kW m-2. This amount of energy is comparable to
the radiative losses of the entire chromosphere and points to internal
gravity waves as a key mediator of energy into the solar atmosphere.

---------------------------------------------------------
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Straus, T.;
Tarbell, T. D.
2008AGUSMSP41B..04F Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum &amp; Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient to heat
the solar chromosphere. The same conclusion was reached by Carlsson et
al. (2007) from an analysis of Hinode SOT/BFI Ca II H and blue continuum
observations. Other authors (e.g. Cuntz et al. 2007; Wedemeyer-Boehm
et al. 2007, Kalkofen 2007), however, questioned these results for
a number of reasons. Because of its limited spatial resolution and
limited sensitivity there are inherent difficulties when comparing TRACE
observations with numerical simulations. Further, intensity oscillations
are difficult to interpret, as they result from a phase-sensitive mix of
density, temperature, and pressure fluctuations, and radiation transfer
effects may complicate the picture even more. Here we revisit the role
of high frequency acoustic waves in the Sun's atmosphere using high
cadence, high resolution Doppler velocity measurements obtained with
SOT/SP and SOT/NFI on Hinode.

---------------------------------------------------------
Title: Solar Orbiter: A Mission Update
Authors: Marsden, R. G.; Fleck, B.
2007ASPC..368..645M Altcode:
The Solar Orbiter Mission will study the Sun in greater detail than
ever before due the close proximity of the spacecraft as it orbits
the Sun. At its closest point, Solar Orbiter will be about 0.22 AU
from the Sun, closer than any other satellite to date. In addition
to providing high-resolution images of the solar surface, perihelion
passes at these distances occur in near co-rotation with the Sun,
allowing the instruments to track features on the surface for several
days. The mission profile also includes a high-latitude phase that
will allow observations from up to 35° above the solar equator. The
combination of near-Sun, quasi-heliosynchronous and high-latitude
observations by remote-sensing and in-situ instruments makes Solar
Orbiter a unique platform for the study of the links between the Sun
and the inner heliosphere.

---------------------------------------------------------
Title: Disentangling The Magnetic Field Structure Of Sunspots -
Stereoscopic Polarimetry With Solar Orbiter
Authors: Müller, D. A. N.,; Schlichenmaier, R.; Fleck, B.; Fritz, G.
2007ESASP.641E..32M Altcode:
Sunspots exhibit complex, highly structured magnetic fields and
flows. Disentangling the atmospheric structure of sunspots is a
great challenge, and can only be achieved by the combination of
spectropolarimetry at high spatial resoultion and detailed modeling
efforts. We use a generalized 3D the embeds magnetic flux tuber in
a stratified atmosphere and calculates the emerging polarization
of spectrail lines for arbitrary viewing angles. The resulting
polarization maps are a very efficient tool to distinguish between
different atmospheric scenarios and determine the 3D structure of the
magnetic field and the flow field. In this contribution, we present
synthetic maps of the net circular polarication (NCP) as a function of
the heliocentric angle for different spectral lines of interest. Among
these are the Fe I 617.3 nm line which would be observed by the VIM
instrument abard Solar Orbiter and the Fe I 630.2 nm line which will
be observed by Hinode (formerly known as Solar-B).

---------------------------------------------------------
Title: Future solar space missions
Authors: Fleck, B.
2007msfa.conf...17F Altcode:
The coming years promise to be the golden era of solar and heliospheric
physics, with STEREO, Hinode (Solar-B) and SDO enhancing the current
fleet of solar space missions and affording new opportunities for
improved understanding of the Sun-heliosphere system. Looking beyond
that, however, there is a significant gap until Solar Orbiter will be
launched in 2015 (nearly 20 years after the launch of SOHO). This paper
provides an overview of the next generation of solar space missions.

---------------------------------------------------------
Title: Magnetoacoustic Portals and the Basal Heating of the Solar
Chromosphere
Authors: Jefferies, Stuart M.; McIntosh, Scott W.; Armstrong, James
D.; Bogdan, Thomas J.; Cacciani, Alessandro; Fleck, Bernhard
2006ApJ...648L.151J Altcode:
We show that inclined magnetic field lines at the boundaries of
large-scale convective cells (supergranules) provide “portals”
through which low-frequency (&lt;5 mHz) magnetoacoustic waves can
propagate into the solar chromosphere. The energy flux carried by
these waves at a height of 400 km above the solar surface is found
to be a factor of 4 greater than that carried by the high-frequency
(&gt;5 mHz) acoustic waves, which are believed to provide the dominant
source of wave heating of the chromosphere. This result opens up
the possibility that low-frequency magnetoacoustic waves provide a
significant source of energy for balancing the radiative losses of
the ambient solar chromosphere.

---------------------------------------------------------
Title: Low-frequency magneto-acoustic waves in the solar chromosphere
Authors: Jefferies, S. M.; McIntosh, S. W.; Armstrong, J. D.; Cacciani,
A.; Bogdan, T. J.; Fleck, B.
2006IAUJD...3E..62J Altcode:
We demonstrate that low-frequency (&lt; 5 mHz) propagating
magneto-acoustic waves provide a larger source of energy for balancing
the radiative losses of the solar chromosphere than their high-frequency
(&gt; 5 mHz) counterparts. The low-frequency waves, which are normally
evanescent in the solar atmosphere, are able to propagate through
"acoustic portals" that exist in areas of strong, significantly
inclined (&gt; 30° with respect to the vertical), magnetic field. Such
conditions are found both in active regions and at the boundaries of
supergranules. The latter implies that acoustic portals are omnipresent
over the solar surface and throughout the magnetic activity cycle,
an essential prerequisite for any baseline heating mechanism.

---------------------------------------------------------
Title: 10 years of SOHO
Authors: Fleck, Bernhard; Müller, Daniel; Haugan, Stein; Sánchez
Duarte, Luis; Siili, Tero; Gurman, Joseph B.
2006ESABu.126...24F Altcode:
Since its launch on 2 December 1995, SOHO has revolutionised
our understanding of the Sun. It has provided the first images of
structures and flows below the Sun's surface and of activity on the
far side. SOHO has revealed the Sun's extremely dynamic atmosphere,
provided evidence for the transfer of magnetic energy from the surface
the outer solar atmosphere, the corona, through a "magnetic carpet",
and identified the source regions of the fast solar wind. It has
revolutionised our understanding of solar-terrestrial relations and
dramatically improved our space weather-forecasting by its continuous
stream of images covering the atmosphere, extended corona and far
side. The findings are documented in an impressive number of scientific
publications: over 2500 papers in refereed journals since launch,
representing the work of over 2300 individual scientists. At the
same time, SOHO's easily accessible, spectacular data and fundamental
scientific results have captured the imagination of the space science
community and the general public alike. As a byproduct of the efforts
to provide real-time data to the public, amateurs now dominate SOHO's
discovery of over 1100 Sungrazing comets.

---------------------------------------------------------
Title: 10 Years of SOHO: Some lessons and where to go next
Authors: Fleck, B.
2006cosp...36.3397F Altcode: 2006cosp.meet.3397F
SOHO has brought us a wealth of new information about the Sun the
heliosphere and space weather and has provided an exemplary model for
international cooperation The scientific achievements of the SOHO
mission are the results of a concerted multi-disciplinary effort
by a large international community of solar scientists involving
sound investment in space hardware coupled with a vigorous and
well-coordinated scientific operation and interpretation effort
From the beginning SOHO was conceived as an integrated package
of complementary instruments and great emphasis has been placed
on coordinated observations both internally among different
SOHO instruments as well as externally with other spacecraft and
ground-based observatories The next five years promise to be the golden
era of solar and heliospheric physics with STEREO Solar-B and SDO
SOHO s lineal descendant enhancing the current fleet of solar space
missions and affording new opportunities for improved understanding
of the Sun-heliosphere system Looking beyond that however there is a
significant gap until Solar Orbiter will be launched in 2015 nearly 20
years after the launch of SOHO I will review some of the key findings
from SOHO discuss how future missions will achieve new understanding
built on the foundation laid by SOHO and what in my view are the key
challenges for future missions

---------------------------------------------------------
Title: Evolution of the Magnetic Energy Budget in AR 10486 from
Potential and Nonlinear Force-Free Models
Authors: Régnier, S.; Fleck, B.; Abramenko, V.; Zhang, H. -Q.
2005ESASP.596E..61R Altcode: 2005ccmf.confE..61R
No abstract at ADS

---------------------------------------------------------
Title: Connecting Sun and Heliosphere (Solar Wind 11 / SOHO 16)
Authors: Fleck, B.; Zurbuchen, T. H.; Lacoste, H.
2005ESASP.592.....F Altcode: 2005soho...16E....F
No abstract at ADS

---------------------------------------------------------
Title: Foreword
Authors: Zurbuchen, T. H.; Fleck, B.
2005ESASP.592....3Z Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The TRACE Inter-Network Oscillations (INO) Program II:
Observations of Limb and Coronal Hole Regions
Authors: McIntosh, S. W.; Crotser, D.; Leamon, R. J.; Fleck, B.;
Tarbell, T. D.
2005AGUSMSH13C..06M Altcode:
We will present results of the TRACE Inter-Network Oscillations (INO)
observing program from 2003 to the present. The INO program uses
near-simultaneous observations in the 1600Å and 1700Å UV continuum
pass bands as an acoustic probe of chromospheric structure. In
this poster we will discuss the INO observations of limb, polar and
coronal hole regions and show the key results found, thus far. These
observations offer us a remote means to study the structure and behavior
of the chromopsheric plasma topography at a potential driving base
for the heliospheric plasma system.

---------------------------------------------------------
Title: Travel Time and Phase Analysis of Waves in the Lower Solar
Chromosphere
Authors: Fleck, B.; Armstrong, J.; Cacciani, A.; de Pontieu, B.;
Finsterle, W.; Jefferies, S. M.; McIntosh, S. W.; Tarbell, T. D.
2005AGUSMSH13C..04F Altcode:
In an effort to better understand how the chromospheric plasma and
magnetic fields are guiding, converting and dissipating acoustic waves,
we analyze high-cadence time series taken in Na I D2 589.0 nm and K I
769.9 nm that were obtained with the Magneto Optical Filters at Two
Heights (MOTH) experiment at the South Pole in January 2003. These
data are complemented by a very high spatial resolution time series
taken in Na D with the Swedish Vacuum Solar Telescope in June 1992. The
travel time maps, power maps, and phase diagrams show some unexpected
behaviour, in particular in and around active regions.

---------------------------------------------------------
Title: Energetics of AR 0486 from line-of-sight and vector
magnetograms
Authors: Regnier, S.; Fleck, B.
2005AGUSMSH51C..09R Altcode:
Over two weeks in October/November 2003, the Sun featured unusually
strong activity, with three large sunspot groups (including the
largest one of this solar cycle), twelve X-class flares (including the
strongest ever recorded), numerous halo coronal mass ejections (two
with near-recorded speeds) and two significant proton storms. Eight of
the twelve X-class flares originated from active region AR 10486. To
understand the reasons of this peculiar activity, we investigate the
evolution of the coronal magnetic field configuration as well as the
energetics of AR 10486 before and after the X17.2 flare on October
28. To determine the coronal magnetic fields, we use potential and
nonlinear force-free reconstruction techniques using line-of-sight
(SOHO/MDI) and vector (MSO/IVM, Huairou, BBSO) magnetograms on the
photosphere as boundary conditions. We identify the source region
of the flare as related to the existence of null point or separator
field line evidenced in a reversed-Y magnetic configuration. From the
3D configurations we derive the magnetic energy budget which can be
released during the impulsive phase of the flare. The estimated free
magnetic energy is enough to trigger an X-class flare. The continuous
evolution of the magnetic energy derived from the potential field
extrapolations indicates that the flare does not modify the distribution
of magnetic field on the photosphere. We also study the distribution
of energy before and after the flare using different vector magnetic
field measurements.

---------------------------------------------------------
Title: Space Weather Effects on SOHO and its Leading Role as a Space
Weather Wãtchdog
Authors: Brekke, P.; Fleck, B.; Haugan, S. V.; van Overbeek, T.;
Schweitzer, H.; Simonin, B.
2005mcsp.conf...83B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Eight years of SOHO: some highlights
Authors: Fleck, B.
2005ASSL..320..139F Altcode: 2005smp..conf..139F
No abstract at ADS

---------------------------------------------------------
Title: Solar Orbiter—mission profile, main goals and present status
Authors: Marsch, Eckart; Marsden, Richard; Harrison, Richard;
Wimmer-Schweingruber, Robert; Fleck, Bernhard
2005AdSpR..36.1360M Altcode:
The main goals and present status of the Solar Orbiter mission are
briefly described. solar orbiter will determine in situ the properties
of fields and particles in the unexplored near-Sun heliosphere in
three dimensions, investigate remotely the fine-scale structures and
events in the magnetically coupled layers of the Sun’s atmosphere,
identify through near corotation the links between activity on the
solar surface and the resulting evolution of the inner heliosphere, and
observe from relatively high latitudes the polar regions and equatorial
corona. Some results from recent activities, such as industrial studies,
payload working group meetings, science definition team meetings and
ESA internal studies are briefly reviewed. Solar Orbiter is currently
planned for launch in October 2013.

---------------------------------------------------------
Title: SOHO 15 Workshop - Coronal Heating
Authors: Walsh, R. W.; Ireland, J.; Danesy, D.; Fleck, B.
2004ESASP.575.....W Altcode: 2004soho...15.....W
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Field Evolution of AR 0486 Before and after the X17
Flare on October 28, 2003
Authors: Régnier, S.; Fleck, B.
2004ESASP.575..519R Altcode: 2004soho...15..519R
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Oscillations in an Equatorial Coronal Hole
Authors: McIntosh, Scott W.; Fleck, Bernhard; Tarbell, Theodore D.
2004ApJ...609L..95M Altcode:
We report phase-difference and travel-time analyses of propagating
chromospheric oscillations in and around an equatorial coronal hole
as observed by TRACE. Our results suggest a significant change in
atmospheric conditions at the base of the chromosphere inside the
coronal hole relative to its boundary and quiet-Sun regions.

---------------------------------------------------------
Title: Probing Chromospheric Structure with the TRACE Inter-Network
Oscillation Program
Authors: Fleck, B.; McIntosh, S. W.
2004AAS...204.3717F Altcode: 2004BAAS...36..711F
We discuss the structure and dynamics of the solar chromosphere through
the application of several diagnostics to the Transition Region and
Coronal Explorer (TRACE) Inter-Network Oscillation (INO) ”synoptic”
observing sequence. Using several newly developed diagnostics we
investigate the generation and interplay of the observed chromospheric
oscillations and the ubiquitous magnetic field that permeates the
TRACE field of view.

---------------------------------------------------------
Title: The Magnetic Field Evolution of AR 10486 and AR 10488 Before
and After the X17 Flare on Oct. 28, 2003
Authors: Regnier, S.; Fleck, B.
2004AAS...204.0205R Altcode: 2004BAAS...36..668R
We investigate the causes and the consequences of the X17 flare
which occured in active region (AR) 10486 on Oct. 28, 2003. Using MDI
high-cadence longitudinal magnetograms, we first follow the evolution
of the photospheric magnetic field of both AR 10486 (site of the flare)
and AR 10488 (new emerged active region). We then identify the main
photospheric motions in AR 10486 which are precursors of the eruptive
phenomena (e.g., emergence of flux, cancellation of flux). We also
focus our study on the fast emergence of AR 10488 and the change of
connectivity between the two active regions after the flare. We
also study the evolution of the coronal magnetic fields assuming a
potential field equilibrium state. This is a case study to know if
we can forecast a solar eruption using a time series of potential
field extrapolations. For both active regions, an IVM vector
magnetogram is available almost 16 hours before the flare and is
used as a snapshot. Those two magnetograms allow us to determine
the nonlinear force-free magnetic configurations as well as the
free energy budgets. These computations allow us to estimate how far
those active regions are from the potential field configurations. S. Regnier's research is funded by the European Community's Human
Potential Programme through the European Solar Magnetism Network
(contract HPRN-CT-2002-00313).

---------------------------------------------------------
Title: Summary of the Solar Orbiter payload working group activities
Authors: Fleck, Bernhard; Harrison, Richard A.; Marsden, Richard G.;
Wimmer-Schweingruber, Robert
2004SPIE.5171..123F Altcode:
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission, the Solar Orbiter will study the Sun and unexplored
regions of the inner heliosphere from a unique orbit that brings the
probe to within 45 solar radii (0.21 AU) of our star, and to solar
latitudes as high as 38°. The scientific payload to be carried by
the Orbiter will include a sophisticated remote-sensing package, as
well as state-of-the-art in-situ instruments. Given the technical and
financial constraints associated with this mission, it is essential
that key technologies requiring significant development be identified
as early as possible. ESA has therefore set up a Payload Working Group
(PWG), made up of members of the scientific community with expertise
in instrumentation of the kind envisaged for the Solar Orbiter. The
tasks of the PWGs included: 1) a realistic assessment of the strawman
payload, including definition of mass, size, power requirements; 2)
identification of key problem areas arising as a result of the extreme
thermal and radiation environments; 3) identification of necessary
technological developments; and 4) provision of detailed input to a
Solar Orbiter Payload Definition Document (PDD). This contribution
summarizes the activities and findings by the Solar Orbiter Payload
Working Group.

---------------------------------------------------------
Title: Development of imaging arrays for solar UV observations based
on wide band gap materials
Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis;
Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul;
Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock,
Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex,
Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos;
Omnes, Franck; John, Joachim; Van Hoof, Chris
2004SPIE.5171..231S Altcode:
Solar ultraviolet imaging instruments in space pose most demanding
requirements on their detectors in terms of dynamic range, low noise,
high speed, and high resolution. Yet UV detectors used on missions
presently in space have major drawbacks limiting their performance
and stability. In view of future solar space missions we have started
the development of new imaging array devices based on wide band gap
materials (WBGM), for which the expected benefits of the new sensors -
primarily visible blindness and radiation hardness - will be highly
valuable. Within this initiative, called "Blind to Optical Light
Detectors (BOLD)", we have investigated devices made of AlGa-nitrides
and diamond. We present results of the responsivity measurements
extending from the visible down to extreme UV wavelengths. We discuss
the possible benefits of these new devices and point out ways to build
new imaging arrays for future space missions.

---------------------------------------------------------
Title: Mapping the Chromospheric Plasma Topography Through
Chromospheric Oscillations
Authors: McIntosh, S. W.; Fleck, B.
2004ESASP.547..149M Altcode: 2004soho...13..149M
Recent research has shown that understanding the physical nature of
chromospheric oscillations hinges critically upon the understanding of
the plasma structure in which they are formed and observed. To this
end we discuss the mapping of the chromospheric plasma topography
through the analysis of simultaneous SOHO/MDI and TRACE time-series
observations through a combination of Fourier and Wavelet based analysis
techniques. We are able to construct a picture of the chromospheric
plasma and its interaction with the wave modes present. Such a picture
will focus studies on topographic regions that will form a simulation
test-bed for theories of modeconversion, dissipation and wave heating
in the solar chromosphere.

---------------------------------------------------------
Title: Eight Years of SOHO
Authors: Fleck, Bernhard
2004IAUS..223..589F Altcode: 2005IAUS..223..589F
Since its launch on 2 December 1995, the joint ESA/NASA SOHO mission
has provided a wealth of information about the Sun, from its interior,
through the hot and dynamic atmosphere, to the solar wind and its
interaction with the interstellar medium. At the same time, SOHO's
easily accessible images and movies have captured the imagination
of the science community and the general public alike. This article
summarizes some of the key findings from 8 years of SOHO.

---------------------------------------------------------
Title: Spatial Correlations of Phase Relationships in TRACE
Ultraviolet Bandpasses
Authors: McIntosh, S. W.; Fleck, B.
2004IAUS..219..696M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Saving SOHO
Authors: Fleck, B.
2004ESASP.547..543F Altcode: 2004soho...13..543F
No abstract at ADS

---------------------------------------------------------
Title: Sunspot Umbral Oscillations: Results from SOHO JOP097
Authors: O'Shea, E.; Muglach, K.; Fleck, B.
2003csss...12..601O Altcode:
We present results of an ongoing analysis of time series data, which
were obtained in the context of the Joint Observing Program (JOP) 97 of
the year 2000. This JOP included the Coronal Diagnostic Spectrometer
(CDS) and the Michelson Doppler Imager (MDI) instrument, both part of
SOHO, the TRACE satellite and various ground based observatories. We
show evidence for apparently upwardly propagating in a sunspot umbra
which we suggest are due to magnetoacoustic waves. These waves manifest
themselves as oscillations in lines ranging in temperature from the
upper photosphere/chromosphere to the corona. To our knowledge this
is the first time umbral oscillations have been conclusively seen in
coronal lines. This research is part of the European Solar Magnetometry
Network (ESMN) supported by the EU through the TMR programme.

---------------------------------------------------------
Title: Investigating the role of plasma topography on chromospheric
oscillations observed by TRACE
Authors: McIntosh, S. W.; Fleck, B.; Judge, P. G.
2003A&A...405..769M Altcode:
We present the results of an investigation into the interaction of
the topographic structure of the solar chromospheric plasma with the
wave modes manifesting themselves in the UV continua formed there. We
show that there is a distinct correlation between the inferred
plasma topography, the phase-differences between and suppression of
oscillations in different levels of the solar atmosphere. We interpret
these factors as evidence of interaction between the oscillations and
the extended magnetic “canopy”. This work is based on the analysis of
joint observations made by the Solar and Heliospheric Observatory (SOHO)
spacecraft and the Transition Region and Coronal Explorer (TRACE).

---------------------------------------------------------
Title: Chromospheric Oscillations observed by SUMER and TRACE:
Their Interplay with the Solar Plasma Topography
Authors: McIntosh, S. W.; Fleck, B.
2003SPD....34.0701M Altcode: 2003BAAS...35R.819M
We present the results of an investigation into the interaction of
wave modes with the solar chromospheric plasma's topography through
the analysis of joint SOHO/SUMER and TRACE observations. We show
that there is a distinct correlation between the inferred solar plasma
topography (specifically the height of the transition from a high to low
plasma-beta regime) and the phase differences between, and suppression
of, atmospheric/chromospheric oscillations in different levels of the
solar atmosphere. Indeed, we demonstrate that the spectroscopic signal
observed changes dramatically in the passage from the high to low beta
regimes. We propose that the dependences presented can be used as an
interpretative tool for simulations seeking to model chromospheric
oscillations and as a diagnostics of the plasma conditions in the
important region in the mid-chromosphere where the plasma-beta is of
order unity, through the signatures of the wave-modes present.

---------------------------------------------------------
Title: Solar Orbiter: a mission overview and status update
Authors: Fleck, Bernhard; Marsden, Richard G.
2003SPIE.4853..150F Altcode:
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission and re-confirmed in May 2002 as an element in the new
ESA science programme "Cosmic Vision", the Solar Orbiter will study
the Sun and unexplored regions of the inner heliosphere from a unique
orbit that brings the probe to within 45 solar radii of our star,
and to solar latitudes as high as 38 degrees. The scientific payload
to be carried by the Solar Orbiter will include both remote-sensing
instruments and an in situ package. Launch is currently scheduled for
2012. Given the technical challenges associated with this mission, it
is essential that key technologies requiring significant development
be identified as early as possible. ESA has therefore set up Payload
Working Groups whose task it is to address potential problem areas
arising as a result of the extreme thermal and radiation environment
and to identify necessary technological developments.

---------------------------------------------------------
Title: New UV detectors for solar observations
Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.;
Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.;
Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.;
Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider,
Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.;
Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock,
Anthony J.; Van Hoof, Chris A.
2003SPIE.4853..419H Altcode:
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide bandgap
materials (in particular diamond and Al-Ga-nitrides). The investigation
is proposed in view of the Solar Orbiter (S.O.) UV instruments, for
which the expected benefits of the new sensors -primarily visible
blindness and radiation hardness- will be highly valuable. Despite
various advances in the technology of imaging detectors over the last
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations inherent to their actual material
and technology. Yet, the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will be decisive for
the forthcoming solar space missions. The advent of imagers based on
wide-bandgap materials will permit new observations and, by simplifying
their design, cheaper instruments. As for the Solar Orbiter, the
aspiration for wide-bandgap material (WBGM) based UV detectors is still
more sensible because the spacecraft will approach the Sun where the
heat and the radiation fluxes are high. We describe the motivations,
and present the program to achieve revolutionary flight cameras within
the Solar Orbiter schedule as well as relevant UV measurements.

---------------------------------------------------------
Title: Towards an explanation of features in the diagnostic diagram
of a model atmosphere. I. Linear wave equations with convenient
invariants
Authors: Schmitz, F.; Fleck, B.
2003A&A...399..723S Altcode:
New standard forms of the time-independent linear adiabatic wave
equation of plane atmospheres are presented. The main objective is
to obtain equations with invariants as simple as possible so that
oscillation theorems can be applied effectively. By transformations
of both the independent and the dependent variables, equations with
simple invariants are formulated. We present a standard form of the wave
equation the invariant of which depends only on the first derivative
of the equilibrium density, as opposed to the common standard form
the invariant of which depends also on second derivatives. Further,
we discuss a procedure which replaces the wave equation by a system
of two simple second order differential equations. In this case we
try to draw conclusions on the general behavior of solutions by use
of oscillation theorems. In addition, a re-formulation of the wave
equation is presented, which eliminates terms with first derivatives
of atmospheric quantities. The independent variable of the resulting
equation depends not only on the geometrical height but also on the
ratio omega /k. In this case, it is necessary to use a diagnostic
diagram the axes of which are given by omega /k and omega instead of
the common k-omega diagram. Therefore we discuss the meaning of the
parameter omega /k for the representation of dispersion curves. Finally,
for the VAL-atmosphere (Vernazza et al. \cite{vernazza}), regions of
certainly nonoscillatory waves are considered.

---------------------------------------------------------
Title: Solar observing facilities
Authors: Fleck, B.; Keller, C. U.
2003dysu.book..403F Altcode:
An overview is given of current and planned ground-based solar
telescopes and instruments, balloon-borne and suborbital solar
telescopes, and solar and heliospheric space missions. These observing
facilities operate in all areas of solar physics, from the solar
interior to interplanetary space and from regimes of high energy to
observations requiring high resolution. The next generation of solar
telescopes and instruments promise us the ability to investigate solar
processes on their fundamental scales, whether sub-arc second or global
in nature.

---------------------------------------------------------
Title: The Solar Orbiter mission
Authors: Marsden, R. G.; Fleck, B.
2003AdSpR..32.2699M Altcode:
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission, the Solar Orbiter will studythe Sun and unexplored
regions of the inner heliosphere from a unique orbit that brings
the probe to within 45 solar radii (0.21 AU) of our star, and to
solar latitudes as high as 38°. This orbit will allow the Solar
Orbiter to make fundamental contributions to our understanding of the
acceleration and propagation of energetic particles in the extended
solar atmosphere. During quasi-heliosynchronous phases of the orbit,
Solar Orbiter will track a given region of the solar surface for several
days, making possible unprecedented studies of the sources of impulsive
and CME-related particle events. The scientific payload to be carried
by the probe will include a sophisticated remote-sensing package, as
well as state-of-the-art in-situ instruments. The multi-wavelength,
multi-disciplinary approach of Solar Orbiter, combined with its novel
location, represents a powerful tool for studies of energetic particle
phenomena.

---------------------------------------------------------
Title: Prospects in ESA for young researchers in solar physics
Authors: Wenzel, K. -P.; Fleck, B.
2002ESASP.506.1001W Altcode: 2002svco.conf.1001W; 2002ESPM...10.1001W
SOHO, the solar physics flagship mission, being operational over a
solar cycle, and the upcoming Solar Orbiter form strong elements in the
ESA space science programme. The paper gives a brief overview of ESA
and its space science programme, summarises the scope and staffing of
ESA's Research and Scientific Support Department (RSSD), and describes
career and training opportunities for young researchers within ESA.

---------------------------------------------------------
Title: Solar Orbiter: a mission overview and status update
Authors: Fleck, B.; Marsden, R.
2002ESASP.506..919F Altcode: 2002ESPM...10..919F; 2002svco.conf..919F
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission and re-confirmed in May 2002 as an element in the new
ESA science programme "Cosmic Vision", the Solar Orbiter will study
the Sun and unexplored regions of the inner heliosphere from a unique
orbit that brings the probe to within 45 solar radii of our star,
and to solar latitudes as high as 38 degrees. The scientific payload
to be carried by the Solar Orbiter will include both remote-sensing
instruments and an in situ package. Launch is currently scheduled for
2012. Given the technical challenges associated with this mission, it
is essential that key technologies requiring significant developement
be identified as early as possible. ESA has therefore set up Payload
Working Groups whose task it is to address potential problem areas
arising as a result of the extreme thermal and radiation environment
and to identify necessary technological developments.

---------------------------------------------------------
Title: Prospects of future solar space missions
Authors: Fleck, B.
2002ESASP.505..311F Altcode: 2002IAUCo.188..311F; 2002solm.conf..311F
Recent results from solar space missions like Yohkoh, SOHO, TRACE,
ACE, and Ulysses have produced stunning results that are invigorating
solar research and challenging existing models of the Sun. Future
space missions and new ground-based instruments promise to continue
this "solar renaissance" in all areas of solar physics. This paper
provides an overview of the next generation of solar space missions. The
scientific objectives, mission profiles and payload capabilities of
Solar-B, STEREO, Picard, SST, SDO, ASCE, Solar Probe, Solar Orbiter,
Sentinels, and RAM are summarized.

---------------------------------------------------------
Title: Automated detection of CMEs in LASCO data
Authors: Berghmans, D.; Foing, B. H.; Fleck, B.
2002ESASP.508..437B Altcode: 2002soho...11..437B
We have developed software that autonomously detects CMEs in image
sequences from LASCO. the crux of the software is the detection of CMEs
as bright ridges in (height, time) maps using the Hough transform. The
output is a list of events, similar to the classic catalogs, with
principle angle, angular width and velocity estimation for each
CME. In contrast to catalogs assembled by human operators, these CME
detections by software can be faster, which is especially important in
the context of space weather, and possibly also more objective, as the
detection criterion is written explicitly in a program. In this paper
we describe the software and validate its performance by comparing its
output with the visually assembled CME catalogs. We discuss its present
success rate (about 75%) and prospects for improvement. Finally, we
show that the software can also reveal CMEs that have not been listed
in the catalogs. Such unreported cases might be of influence on CME
statistics and prove that also the present catalogs do not have a 100%
success rate.

---------------------------------------------------------
Title: Trawling around in the Noise
Authors: Fleck, B.; McIntosh, S. W.
2002AAS...200.3905F Altcode: 2002BAAS...34..701F
We investigate the possible presence of low amplitude, high-frequency
oscillations in short time exposure SUMER timeseries. Using a variety
of profile fitting methods and a combination of real and synthetic
data we examine the detection thresholds and limits. As a result we
can assess the likelyhood that certain long-duration, high cadence,
SUMER datasets contain meaningful information about the propagation
of high frequency waves in the Solar Chromosphere and Transition Region.

---------------------------------------------------------
Title: Oscillations above sunspots: Evidence for propagating waves?
Authors: O'Shea, E.; Muglach, K.; Fleck, B.
2002A&A...387..642O Altcode:
We present results of an analysis of time series data observed in
sunspot umbral regions. The data were obtained in the context of
the SOHO Joint Observing Program (JOP) 97 in September 2000. This
JOP included the Coronal Diagnostic Spectrometer (CDS) and the
Michelson Doppler Imaging (MDI) instrument, both part of SOHO, the
TRACE satellite and various ground based observatories. The data
was analysed by using both Fourier and wavelet time series analysis
techniques. We find that oscillations are present in the umbra at all
temperatures investigated, from the temperature minimum as measured by
TRACE 1700 Å up to the upper corona as measured by CDS Fe Xvi 335 Å
(log T=6.4 K). Oscillations are found to be present with frequencies in
the range of 5.4 mHz (185 s) to 8.9 mHz (112 s). Using the techniques
of cross-spectral analysis time delays were found between low and high
temperature emission suggesting the possibility of both upward and
downward wave propagation. It is found that there is typically a good
correlation between the oscillations measured at the different emission
temperatures, once the time delays are taken into account. We find
umbral oscillations both inside and outside of sunspot plume locations
which indicates that umbral oscillations can be present irrespective
of the presence of these sunspot plumes. We find that a number of
oscillation frequencies can exist co-spatially and simultaneously
i.e. for one pixel location three different frequencies at 5.40,
7.65 and 8.85 mHz were measured. We investigate the variation of the
relative amplitudes of oscillation with temperature and find that
there is a tendency for the amplitudes to reach a maximum at the
temperature of O Iii (and less typically O V and Mg Ix) and then to
decrease to reach a minimum at the temperature of Mg X (log T=6.0 K),
before increasing again at the temperature of Fe Xvi. We discuss a
number of possible theoretical scenarios that might explain these
results. From a measurement of propagation speeds we suggest that
the oscillations we observe are due to slow magnetoacoustic waves
propagating up along the magnetic field lines.

---------------------------------------------------------
Title: Space weather aspects of the ESA Solar Orbiter mission
Authors: Marsden, R.; Fleck, B.
2002ESASP.477..359M Altcode: 2002scsw.conf..359M
No abstract at ADS

---------------------------------------------------------
Title: Space Weather Aspects of the ESA Solar Orbiter Mission
Authors: Marsden, R. G.; Fleck, B.
2002stma.conf..443M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Sun During The Ulysses Fast Latitude Scan and Northern
Polar Pass As Seen By Soho
Authors: Fleck, B.; Brekke, P.; Haugan, S. V. H.
2002EGSGA..27.3839F Altcode:
In 2001, during the Ulysses fast latitude scan (January - September)
and second north- ern polar pass (September - December), the Sun showed
a remarkable resurgence of solar activity after its rapid drop-off
following the activity maximum in the summer of 2000. In early April
active region 9393, the largest active region of the current cycle,
produced a series of events, among them the biggest X-ray flare on
record. In the fall there were three severe proton storms, one of them
the third largest on record since measurements began in 1976. It is
interesting to note that five out of the eight proton storms with flux
densities greater than 10,000 cm-2 s-1 sr-1 (&gt;10 MeV) since 1976
occurred in cycle 23, and three of these five in 2001. The overall
change in solar ac- tivity in 2001 will be reviewed and some of the
most dramatic events from that year discussed.

---------------------------------------------------------
Title: Long-term solar irradiance variations: results and perspectives
Authors: Pap, J.; Fleck, B.; Frohlich, C.; Jones, H.; Kuhn, J.;
Schmutz, W.
2002cosp...34E.553P Altcode: 2002cosp.meetE.553P
In this paper we show the recent result on irradiance variations and
their relation to solar magnetic activity over solar cycles 21 to
23. Comparison of the multi-decade long irradiance and magnetic field
measurements indicates that the shape and magnitude of irradiance
variations are different from that of magnetic indices. Specifically,
while magnetic indices show that solar cycle 23 is weaker than the two
previous cycles, the long-term variation of total solar irradiance
over solar cycles 21 to 23 is rather symmetrical, showing that its
maximum and minimum levels were about the same within their measuring
uncertainties. These results raise questions like: (1) is there a
strict linear relationship between solar variability and irradiance
variations as the current irradiance models used in climate studies
assume?; (2) what is the role of polar magnetic fields in irradiance
changes?; (3) is there a significant non-magnetic component in the
observed irradiance variations? The results presented in this paper
underscore the need to further develop new measurement and analysis
techniques to study and predict the climate impact of solar variability.

---------------------------------------------------------
Title: JOSO report 200-2001 - The Netherlands. Solar Physics in
The Netherlands
Authors: Rutten, R.; Keppens, R.; Fleck, B.
2002joso.book...81R Altcode:
Solar physics research in the Netherlands is carried out at Nijmegen,
Utrecht, Nieuwegein, and Noordwijk.

---------------------------------------------------------
Title: Space Weather Effects on SOHO
Authors: Brekke, P.; Fleck, B.; Haugan, S.; Schweitzer, H.; Chaloupy,
M.
2002cosp...34E2156B Altcode: 2002cosp.meetE2156B
Since its launch on 2 December 1995, the Solar and Heliospheric
Observatory (SOHO) has provided an unparalleled breadth and depth of
information about the Sun, from its interior, through the hot and
dynamic atmosphere, and out to the solar wind. SOHO is in a halo
orbit around L1 Lagrangian point where it views the Sun 24 hours a
day. Thus, it is situated outside the Earth's protective magnetosphere
which shields other satellites from high energy particles from the
Sun. We present a summary of the observed effects on the instruments
and electronics on SOHO throughout the mission. In particular we will
focus on a number of large particle events during the recent years
while the Sun was approaching maximum activity, and how they affected
both the scientific data as well as hardware components.

---------------------------------------------------------
Title: The Solar Orbiter mission
Authors: Marsden, R.; Fleck, B.
2002cosp...34E.222M Altcode: 2002cosp.meetE.222M
Approved in October 2000 by ESA's Science Programme Committee as a
flexi mission, the Solar Orbiter will study the Sun and unexplored
regions of the inner heliosphere from a unique orbit that brings
the probe to within 45 solar radii (0.21 AU) of our star, and to
solar latitudes as high as 38° This orbit will allow the Solar
Orbiter to make fundamental contributions to our understanding of the
acceleration and propagation of energetic particles in the extended
solar atmosphere. During the quasi-heliosynchronous phases of the orbit,
Solar Orbiter will track a given region of the solar surface for several
days, making possible unprecedented studies of the sources of impulsive
and CME-related particle events. The scientific payload to be carried
by the probe will include a sophisticated remote-sensing package, as
well as state-of-the-art in-situ instruments. The multi-wavelength,
multi-disciplinary approach of Solar Orbiter, combined with its novel
location, represents a powerful tool for studies of energetic particle
phenomena.

---------------------------------------------------------
Title: Solar orbiter, a high-resolution mission to the sun and
inner heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Langevin, Y.; Marsden, R.; Pace, O.; Schwenn,
R.; Vial, J. -C.
2002AdSpR..29.2027M Altcode:
The scientific rationale of the Solar Orbiter is to provide, at high
spatial (35 km pixel size) and temporal resolution, observations of the
solar atmosphere and unexplored inner heliosphere. Novel observations
will be made in the almost heliosynchronous segments of the orbits at
heliocentric distances near 45 R⊙ and out of the ecliptic plane at
the highest heliographic latitudes of 30° - 38°. The Solar Orbiter
will achieve its wide-ranging aims with a suite of sophisticated
instruments through an innovative design of the orbit. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. Over extended periods
the Solar Orbiter will deliver the first images of the polar regions
and the side of the Sun invisible from the Earth.

---------------------------------------------------------
Title: Solar Orbiter: a high-resolution mission to the sun and
inner heliosphere
Authors: Fleck, Bernhard; Marsch, E.; Antonucci, Ester; Bochsler,
Peter A.; Bougeret, J. L.; Harrison, R.; Marsden, R. P.; Coradini,
M.; Pace, Oscar; Schwenn, Rainer; Vial, Jean-Claude
2001SPIE.4498....1F Altcode:
The key mission objective of the Solar Orbiter is to study the Sun
from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar
rotation in order to examine the solar surface and the space above from
a co-rotating vantage point at high spatial resolution. Solar Orbiter
will also provide images of the Sun's polar regions from heliographic
latitudes as high as 38 degrees. The strawman payload encompasses
two instrument packages: Solar remote-sensing instruments: EUV
full-sun and high resolution imager, high-resolution EUV spectrometer,
high-resolution and full-sun visible light telescope and magnetograph,
EUV and visible-light coronagraphs, radiometers. Heliospheric
instruments: solar wind analyzer, radio and plasma wave analyzer,
magnetometer, energetic particle detectors, interplanetary dust
detector, neutral particle detector, solar neutron detector. To
reach its novel orbit, Solar Orbiter will make use of low-thrust
solar electric propulsion (SEP) interleaved by Earth and Venus gravity
assists. Solar Orbiter was selected by ESA's Science Programme Committee
(SPC) in October 2000 as a Flexi-mission, to be implemented after the
BepiColombo cornerstone mission to Mercury before 2013. This paper
summarizes the science to be addressed with the Solar Orbiter, followed
by brief descriptions of the strawman payload, the mission profile,
and the spacecraft and ground segment designs.

---------------------------------------------------------
Title: Measuring Solar Abundances
Authors: von Steiger, R.; Vial, J. -C.; Bochsler, P.; Chaussidon, M.;
Cohen, C. M. S.; Fleck, B.; Heber, V. S.; Holweger, H.; Issautier, K.;
Lazarus, A. J.; Ogilvie, K. W.; Paquette, J. A.; Reisenfeld, D. B.;
Teriaca, L.; Wilhelm, K.; Yusainee, S.; Laming, J. M.; Wiens, R. C.
2001AIPC..598...13V Altcode: 2001sgc..conf...13V
This is the rapporteur paper of Working Group 2 on Measuring Solar
Abundances. The working group presented and discussed the different
observations and methods for obtaining the elemental and isotopic
composition of the Sun, and critically reviewed their results and
the accuracies thereof. Furthermore, a few important yet unanswered
questions were identified, and the potential of future missions to
provide answers was assessed. .

---------------------------------------------------------
Title: Visible Imager / Magnetograph: summary of splinter session
Authors: von der Lühe, O.; Fleck, B.
2001ESASP.493..149V Altcode: 2001sefs.work..149V
Both splinter sessions for the Visible Imager and Magnetograph (VIM)
were well attended by approximately 30 participants. The goals of the
session was to review the scientific objectives for VIM, to discuss
specific technological issues, and to refine the approach to science
operation during all orbital phases. The session was closed by the
formation of a definition team which will look in detail into these
matters in order to prepare a VIM Phase A proposal.

---------------------------------------------------------
Title: Solar Orbiter, a high-resolution mission to the Sun and
inner heliosphere
Authors: Marsch, E.; Harrison, R.; Pace, O.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Fleck, B.; Langevin, Y.; Marsden, R.; Schwenn,
R.; Vial, J. -C.
2001ESASP.493D..11M Altcode: 2001sefs.workD..11M
Solar Orbiter will provide, at very high spatial (35 km pixel size)
and temporal resolution, novel observations of the solar atmosphere
and unexplored inner heliosphere. It will achieve its wide-ranging
scientific aims with a suite of sophisticated instruments through an
innovative orbit design. Unprecedented observations will be made in
the heliosynchronous segments of the orbits at heliocentric distances
near 45 Rsolar and out of the ecliptic plane at the highest
heliographic latitudes of 30° - 38°. The first near-Sun interplanetary
measurements together with concurrent remote-sensing observations of
the Sun and its corona will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in the source regions on the Sun. Solar Orbiter will deliver
the first images of the polar regions and the far side of the Sun
invisible from the Earth.

---------------------------------------------------------
Title: Solar encounter
Authors: Battrick, Bruce; Sawaya-Lacoste, H.; Marsch, E.; Martinez
Pillet, V.; Fleck, B.; Marsden, R.
2001ESASP.493.....B Altcode: 2001sefs.work.....B
The prime objectives of the workshop were to: inform the community
about the science opportunities of the Solar Orbiter mission; to
provide a forum for sharpening and focussing the science goals; allow
the hardware groups and instrument proposers to critically review the
payload; establish international contacts and collaborations.

---------------------------------------------------------
Title: Highlights from SOHO and Future Space Missions
Authors: Fleck, Bernhard
2001ASSL..259....1F Altcode: 2001dysu.conf....1F
The Solar and Heliospheric Observatory (SOHO) has provided an
unparalleled breadth and depth of information about the Sun, from its
interior, through the hot and dynamic atmosphere, out to the solar
wind. Analysis of the helioseismology data from SOHO has shed new light
on a number of structural and dynamic phenomena in the solar interior,
such as the absence of differential rotation in the radiative zone,
subsurface zonal and meridional flows, sub-convection-zone mixing, a
possible circumpolar jet, and very slow polar rotation. Evidence for
an upward transfer of magnetic energy from the Sun's surface toward
the corona has been established. The ultraviolet instruments have
revealed an extremely dynamic solar atmosphere where plasma flows
play an important role. Electrons in coronal holes were found to be
relatively “cool", whereas heavy ions are extremely hot and have
highly anisotropic velocity distributions. The source regions for
the high speed solar wind has been identified and the acceleration
profiles of both the slow and fast solar wind have been measured. This
paper tries to summarize some of the most recent findings from the
SOHO mission. Present plans for future solar space missions are also
briefly discussed.

---------------------------------------------------------
Title: Active Region Oscillations: Results from SOHO JOP 097
Authors: O'Shea, E.; Fleck, B.; Muglach, K.; Sütterlin, P.
2001AGUSM..SH41A02O Altcode:
We present here an analysis of data obtained in a sunspot region,
using the Coronal Diagnostic Spectrometer (CDS) on SOHO. These data
were obtained in the context of the Joint Observing Program (JOP)
97 which, together with CDS, included the Michelson Doppler Imaging
(MDI) instrument on SOHO, the TRACE satellite and various ground
based observatories, e.g. the DOT on La Palma. Using the lines of
Fe XVI 335, Mg IX 368, He I 584, O III 599, Mg X 624 and O V 624 of
CDS time series data were obtained in the pore and plage regions of
sunspots associated with active regions AR 9166, 9166 and 9169 between
September 19-29 2000. In addition to the time series datasets we also
obtained 240 arcsec x 240 arcsec raster images of the sunspot regions
examined. Using different time series analysis techniques we analyse
the different periods of oscillation found in time series datasets and
present the results here. This research is part of the European Solar
Magnetometry Network supported by the EC through the TMR programme.

---------------------------------------------------------
Title: Correlated Wavelet Transforms of SOHO Chromospheric and
Transition Region Timeseries Observations
Authors: McIntosh, S. W.; Fleck, B.
2001AGUSM..SH41A03M Altcode:
We consider the wavelet transform study of correlated SOHO (SUMER,
CDS and EIT) time-series observations with a view to understanding
inter-network plasma structure along the line-of-sight. By implementing
wavelet transforms in a novel way we able to study the behavior of
upward propagating wave-packets as a function of their height in the
atmosphere. Using this information we will infer properties of the
inter-network thermodynamic plasma structure of the chromosphere and
transition region.

---------------------------------------------------------
Title: Helioseismology - What is Next?
Authors: Scherrer, P. H.; Fleck, B.; Ulrich, R. K.
2001AGUSM..SP22A09S Altcode:
The helioseismology instruments on SOHO have produced a rich set of
new insights into the solar interior. Combined with GONG and other
ground-based networks these instruments have, for the most part, met the
goals set for them. These instruments have demonstrated the usefulness
of helioseismic techniques for imaging solar interior structure and
motions but do not have all the capabilities necessary to fully exploit
the method. Future mission plans call for pushing helioseismic imaging
to regions nearer the surface, to higher latitudes, and deeper into the
interior. The capabilities of the planned or possible instruments on the
Solar Dynamics Observatory, Solar Orbiter, and Farside/Safari missions
will enable these presently inaccessible domains to be exploited.

---------------------------------------------------------
Title: Space Weather Aspects of the Solar Orbiter Mission
Authors: Fleck, B.; Marsden, R.
2001AGUSM..SH22C06F Altcode:
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission, the Solar Orbiter will study the Sun and unexplored
regions of the inner heliosphere from a unique orbit that brings the
probe to within 45 solar radii of our star, and to solar latitudes
as high as 38 deg. This orbit will allow the Solar Orbiter to make
fundamental contributions to our understanding of the transient
phenomena driving space weather, including coronal mass ejections
(CMEs) and flare-related effects. Being closer to the sources of such
transients in the solar atmosphere, the Solar Orbiter will be ideally
located to measure the input into the heliosphere and to determine the
boundary conditions near the Sun. The scientific payload to be carried
by the probe will include a sophisticated remote-sensing package, as
well as state-of-the-art in situ instruments. The multi-wavelength,
multi-disciplinary approach of the Solar Orbiter, combined with its
novel location, represents a powerful tool for studies of the influence
of space weather-related events on interplanetary space.

---------------------------------------------------------
Title: Active region oscillations
Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G.; Fleck, B.; Murtagh, F.
2001A&A...368.1095O Altcode:
We report here on an investigation of high frequency oscillations in
active regions, carried out using high cadence observations of O V
629 Å, Mg Ix 368 Å and Fe Xvi 335 Å, with the Coronal Diagnostic
Spectrometer (cds) on soho. Using the techniques of wavelet analysis
on various temporal series datasets, we find that certain oscillation
frequencies are favoured for each line. We find furthermore that
a ~ 5 min oscillation signature is commonly present in all lines,
suggesting a coupling of the photospheric driver with the transition
region and coronal loop modes. We report on the tendency for higher
frequency oscillations to be present at lower intensity values,
suggesting that higher frequency oscillations occur in interloop
regions or at loop boundaries, possibly as a result of some resonant
absorption process. In addition, we find that the coronal lines of
Fe Xvi and Mg Ix show more significant oscillations in the velocity
than in the intensity, which suggests that in the velocity we measure
additional non-compressive wave modes not visible in the intensity. As
this effect is not seen in the transition region line of O V it would
seem that these additional non-compressive modes are produced in and
limited to the corona. We suggest that there are two main mechanisms
responsible for the observed oscillations; either resonant Alfvén
and/or fast kink waves or propagating slow magnetoacoustic waves,
both present in coronal loops.

---------------------------------------------------------
Title: Solar Orbiter
Authors: Fleck, B.; Marsden, R.; Pace, O.
2001ESABu.105...56F Altcode:
The scientific goals of the Solar Orbiter are to: - determine in-situ
the properties and dynamics of plasma, fields and particles in the
near-Sun heliosphere - investigate the fine-scale structure and dynamics
of the Sun's magnetised atmosphere, using close-up, high-resolution
remote sensing - identify the links between activity on the Sun's
surface and the resulting evolution of the corona and inner heliosphere,
using solar corotation passes - observe and fully characterise the
Sun's polar regions and equatorial corona from high latitudes.

---------------------------------------------------------
Title: On the nature of network oscillations
Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M.;
Fleck, B.
2001ESASP.464..175B Altcode: 2001soho...10..175B
We examine time-series of spectral data obtained from the Solar
Ultraviolet Measurements of Emitted Radiation instrument (SUMER), on
board SOHO in the period 10-31 July 1996. Observations were obtained
in lines, ranging in temperature from 12,000 K to 106K,
covering the low chromosphere to the corona. In this short contribution
we report on the time series analysis on one of these dataset, using
wavelet methods, of small individual network regions in the quiet
Sun. The wavelet analysis allows us to derive the duration as well
as the periods of the oscillations. The statistical significance of
the oscillations was estimated by using a randomisation method. The
oscillations are considered to be due to waves, which are produced
in short bursts with coherence times of about 10-20 minutes. The
low chromospheric and transition region lines show intensity and
velocity power in the 2.4 mHz range. The observed 2-4 mHz network
oscillations can be interpreted in terms of kink and sausage waves
propagating upwards along thin magnetic flux tubes. The kink waves can
be generated by random foot-point motions, e.g. by exploding granules,
at the photospheric level. As they propagate within flux tubes, their
amplitude grows exponentially with height and becomes non-linear. The
waves can thereby undergo a mode transformation and become sausage
type waves, which are more easily detected on the disk.

---------------------------------------------------------
Title: Solar Orbiter - A high resolution mission to the Sun and the
inner heliosphere (Oral papers and posters which were given at the
conference, but for which no manuscripts were submitted)
Authors: Marsch, E.; Fleck, B.; Schwenn, R.
2001ohnf.conf..445M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: From solar min to solar max: half a solar cycle of SOHO
observations
Authors: Brekke, P.; Fleck, B.
2001ICRC...27I..21B Altcode:
The Solar and Heliospheric Observatory (SOHO) has provided an
unparalleled breadth and depth of information about the Sun, from its
interior, through the hot and dynamic atmosphere, out to the solar
wind. Analysis of the helioseismology data from SOHO has shed new light
on a number of structural and dynamic phenomena in the solar interior,
such as the absence of differential rotation in the radiative zone,
subsurface zonal and meridional flows, subconvection-zone mixing, a
possible circumpolar jet, and very slow polar rotation. Evidence for
an upward transfer of magnetic energy from the Sun's surface toward the
corona has been established. The ultraviolet instruments have revealed
an extremely dynamic solar atmosphere where plasma flows play an
important role. Electrons in coronal holes were found to be relatively
`cool', whereas heavy ions are extremely hot and have highly anisotropic
velocity distributions. The source regions for the high speed solar
wind has been identified and the acceleration profiles of both the slow
and fast solar wind have been measured. This paper tries to summarize
some of the findings from the SOHO mission from the past five years.

---------------------------------------------------------
Title: Solar Orbiter, a High-Resolution Mission to the Sun and
Inner Heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Marsden, R.; Schwenn, R.; Vial, J. -C.
2001IAUS..203..565M Altcode:
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rodot and
out-of-ecliptic at the highest heliographic latitudes of 38 degrees. The
SO will achieve its many and varied aims with a suite of small and
innovative instruments through a clever choice of orbits. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind and
energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. The SO will, during
the high-latitude orbital passes, provide the first observations of
the Sun's polar regions as seen from outside the ecliptic and also
measure the magnetic field at the poles.

---------------------------------------------------------
Title: Recent insights into the physics of the sun and heliosphere
: highlights from SOHO and other space missions : IAU Symposium
203, proceedings of the 24th General Assembly of the IAU held at
Manchester, United Kingdom, 7-11 August 2000
Authors: Brekke, Pål; Fleck, Bernhard; Gurman, Joseph B.
2001IAUS..203.....B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Quiet Sun Oscillation Packets
Authors: Ireland, J.; McIntosh, S. W.; Fleck, B.
2000SPD....31.0132I Altcode: 2000BAAS...32..807I
This paper combines the novel techniques of wavelet analysis
and genetic algorithms to exploit SOHO-SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) data in a new way. The data consists
of time series in O I 1306.03 Angstroms, Si II 1309.28 Angstroms,
C I 1311.36 Angstroms, C II 1334.53 Angstroms, He I 584 Angstroms,
O I 1152 Angstroms, and C III 1176 Angstroms tracking specific pieces
of quiet Sun westward across the disk. To analyse this data, genetic
algorithms (McIntosh et. al, A.&amp; A. Suppl. Ser., 132, 145, 1998)
are used to fit quiet Sun emission spectra, allowing the unbiassed
determination of spectral properties such as total line intensity
and Doppler velocity. Time series of line intensity and Doppler
velocity are formed which are then analysed using wavelet techniques,
permitting the distinguishing of distinct oscillation wave packets in
the time series. Correlations of wave packets between different lines
and physical quantities are discussed, as are the distributions of
oscillation packets seen.

---------------------------------------------------------
Title: Solar Orbiter --- A High Resolution Mission to the Sun and
Inner Heliosphere
Authors: Fleck, B.; Marsch, E.; Schwenn, R.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Harrison, R. A.; Marsden, R.; Vial, J. -C.
2000SPD....31.0296F Altcode: 2000BAAS...32..828F
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rsun and
out-of-ecliptic at heliographic latitudes of up to 38o. By
going to 45 Rsun the SO will allow remote sensing of the
solar atmosphere with unprecedented spatial resolution, and the almost
heliosynchronous orbit segments will permit us to disentangle spatial
and temporal variations in the solar wind in close linkage with the
plasma and radiation conditions in the source regions of the Sun. The
strawman payload encompasses two instrument packages: Heliospheric
Instruments --- high-res visible light telescope and magnetograph
(&lt;40 km), high-res X-ray/EUV imager (&lt;30 km), high-res EUV
spectrometer (&lt;100 km), EUV and visible-light coronagraphs, solar
neutron and γ -ray detectors, radiometers. Heliospheric Instruments
--- solar wind analyzer, magnetometer, energetic particle detectors, IP
dust detector, plasma wave analyser, radio experiment, neutral particle
detector. Using solar electric propulsion (SEP) in conjunction with
multiple planet swing-by manoeuvres, it will take SO two years to reach
a perihelion of 45 Rsun at an orbital period of 149 days,
with an inclination ranging from 6.7o to 23.4o
w.r.t. the ecliptic. During an extended mission phase of about 2
years the inclination will increase to 31.7o, leading to
a maximum heliographic latitude of 38.3o. The SO was one
of the about 40 responses to the Call for Proposals for the next two
"flexi-missions" (F2 and F3) within ESA's Scientific Programme. At
its meeting on 1 March 2000, ESA's Space Science Advisory Committee
recommended the Solar Orbiter among 5 other proposals for an assessment
study. Launch is expected by the end of the decade.

---------------------------------------------------------
Title: Four years of SOHO discoveries - some highlights.
Authors: Fleck, B.; Brekke, P.; Haugan, S.; Duarte, L. S.; Domingo,
V.; Gurman, J. B.; Poland, A. I.
2000ESABu.102...68F Altcode:
Analysis of the helioseismic data from SOHO has shed new light on
solar and heliosheric physics: the structure and dynamics of the
solar interior, the heating and dynamics of the solar corona, and the
acceleration and composition of the solar wind.

---------------------------------------------------------
Title: Dynamics of Chromiospheric and Transition Region Lines Observed
with SOHO/SUMER and the GCT/Tenerife
Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing,
B. H.; Wilhelm, K.
2000AdSpR..25.1731M Altcode:
High-resolution spectroscopic observations of the quiet Sun have been
carried out in September 1996 at the German Gregory Coudé Telescope
(GCT) in Tenerife and in May 1997 with the SUMER instrument onboard
SOHO. Time sequences of spectra in the visible and near infrared
as well as in the ultraviolet have been taken, covering a range of
heights from the solar photosphere up into the transition region. In
this contribution we present the dynamical behaviour observed at the
various heights in the solar atmosphere

---------------------------------------------------------
Title: Waves in the Quiet Sun's Chromosphere
Authors: Muglach, K.; Fleck, B.
1999ESASP.446..499M Altcode: 1999soho....8..499M
High resolution spectroscopic observations of the quiet sun have been
carried out in May 1997 with the SUMER instrument onboard of SOHO. Nine
hour time sequences at disk center in various UV lines have been taken,
covering a range of height between the solar chromosphere and the
transition region. In this contribution we will present the dynamics we
find in the various heights/temperature regimes in the solar atmosphere.

---------------------------------------------------------
Title: Observational Constraints on Models of the Solar Background
Spectrum
Authors: Straus, Th.; Severino, G.; Deubner, F. -L.; Fleck, B.;
Jefferies, S. M.; Tarbell, T.
1999ApJ...516..939S Altcode:
We discuss the properties of the solar background signal as observed in
high-quality, l-ν power and phase difference spectra of the continuum
(C), velocity (V), and line intensity (I) fluctuations of the Ni
I 6768 Å line. These spectra were generated from high-resolution
images acquired by the Michelson Doppler Imager on board SOHO. We
confirm that the background signal in the velocity power spectra can be
reproduced by a composite model with two quasi-stationary components,
describing large-scale and small-scale convective motions, and a
periodic component. The line and continuum intensity power spectra
require additional quasi-stationary and periodic components. The
extra quasi-stationary component dominates the intensity and
continuum background signals over the spectral region where the I-V
phase difference spectra show essentially constant negative phase
difference: i.e., below and in between the p-mode ridges (called the
plateau-interridge regime by Deubner et al.). Since the I-V phase
between the p-mode ridges is not random, the solar background beneath
the p-modes must be considered as coherent. We thus speculate that
the negative phase regime may be the manifestation of a correlated
background. Such a background has been proposed to explain the opposite
sense of the asymmetries of the p-mode line profiles in velocity and
brightness oscillations.

---------------------------------------------------------
Title: Diary of a drama.
Authors: Vandenbussche, F.; Fleck, B.
1999AsNow..13...56V Altcode: 1999AstNw..13...56V
"Focus: Basking in the Sun". When on 24 Jun 1998 contact was lost with
SOHO a rescue mission was immediately started.

---------------------------------------------------------
Title: On wave equations and cut-off frequencies of plane atmospheres
Authors: Schmitz, F.; Fleck, B.
1998A&A...337..487S Altcode:
This paper deals with the one-dimensional vertical propagation of
linear adiabatic waves in plane atmospheres. In the literature there
are various representations of the standard form of the wave equation
from which different forms of the so called cut-off frequency are
inferred. It is not uncommon that statements concerning the propagation
behavior of waves are made which are based on the height dependence
of a cut-off frequency. In this paper, first we critically discuss
concepts resting on the use of cut-off frequencies. We add a further
wave equation to three wave equations previously presented in the
literature, yielding an additional cut-off frequency. Comparison
among the various cut-off frequencies of the VAL-atmosphere reveals
significant differences, which illustrate the difficulties of
interpreting a height dependent cut-off frequency. We also discuss
the cut-off frequency of the parabolic temperature profile and the
behavior of the polytropic atmosphere. The invariants of the four
wave equations presented contain first and second derivatives of the
adiabatic sound speed. These derivatives cause oscillations and peaks
in the space dependent part of the invariants, which unnecessarily
complicate the discussion. We therefore present a new form of the
wave equation, the invariant of which is extremely simple and does
not contain derivatives of the thermodynamic variables. It is valid
for any LTE equation of state. It allows us to make effective use of
strict oscillation theorems. We calculate the height-dependent part
of the invariant of this equation for the VAL-atmosphere including
ionization and dissociation. For this real atmosphere, there is no
obvious correspondence between the behavior of the invariant and the
temperature structure or the sound speed profile. The invariant of the
wave equation is nearly constant around the temperature minimum. In
the chromosphere, the invariant is almost linear. The case of the wave
equation with a linear invariant is studied analytically.

---------------------------------------------------------
Title: NSO/AFRL/Sac Peak K-line Monitoring Program
Authors: Keil, Stephen L.; Henry, Timothy W.; Fleck, Bernhard
1998ASPC..140..301K Altcode: 1998ssp..conf..301K
No abstract at ADS

---------------------------------------------------------
Title: Phase spectra seen from space
Authors: Straus, Th.; Deubner, F. -L.; Fleck, B.; Marmolino, C.;
Severino, G.; Tarbell, T.
1998IAUS..185..455S Altcode:
We discuss preliminary results of a study of the dynamics of the solar
atmosphere including a first space based investigation of k-omega phase
difference spectra between velocity and intensity perturbations. The
data, including simultaneous line shift, line depth, and continuum
intensity measurements at disk center, have been obtained from a MDI
time series in its high resolution mode. Line depth and continuum
intensity are used to calculate the line intensity which is the more
frequently used parameter in phase difference studies. We compare the
results to ground based observations.

---------------------------------------------------------
Title: K-ϖ Phase Spectra Obtained from Space
Authors: Straus, Th.; Fleck, B.; Severino, G.; Deubner, F. -L.;
Marmolino, C.; Tarbell, T.
1998ESASP.417..293S Altcode: 1998cesh.conf..293S
No abstract at ADS

---------------------------------------------------------
Title: Wave Propagation in the Chromosphere and Transition Region:
Where Have All the Shock Waves Gone?
Authors: Fleck, B.; Steffens, S.; Deubner, F. -L.; Wilhelm, K.;
Harrison, R.; Gurman, J.
1997SPD....28.0120F Altcode: 1997BAAS...29..882F
We present first results from a joint observing program (SOHO JOP 26)
involving SUMER, CDS and EIT on SOHO, coordinated with ground-based
observations at the Vacuum Tower Telescope at Iza{\ n}a, Tenerife. The
objective of this study is to characterize the wave propagation
properties in the solar atmosphere, from the photosphere through the
chromosphere up into the transition region. Particular emphasis is laid
on the 3-min shock waves observed in the Ca II K line. How do they
impact the transition region and what signature do they leave there
and in the lower corona? The ground-based measurements comprise high
resolution time series (both filtergrams and spectrograms) in Ca II K,
Hα and Mgb_2. With SUMER we ran four sequences covering different
temperature regimes: a) O I 1302, O I 1306, Si II 1309, C I 1311,
C II 1334, C II 1335, b) Si I 1256, N V 1242, O V 629 c) He I 584,
C III 1175, O I 1152, d) H I 1025, O VI 1031, O VI 1037. With CDS we
took spectral time series in O VI 554, He I 584, He II 607, Mg IX 368,
and O V 629 as well as wide-slit (90x240”) “movies” in He I 584,
Mg IX 368 and O V 629, while EIT ran sub-field high cadence sequences
in He II 304.

---------------------------------------------------------
Title: First Results from SOHO
Authors: Fleck, B.
1997Ap&SS.258...57F Altcode: 1997ESAC....7...57F
SOHO, the Solar and Heliospheric Observatory, is a project of
international cooperation between ESA and NASA to study the Sun,
from its deep core to the outer corona, and the solar wind. Three
helioseismology instruments are providing unique data for the study
of the structure and dynamics of the solar interior, from the very
deep core to the outermost layers of the convection zone. A set of
five complementary remote sensing instruments, consisting of EUV,
UV and visible light imagers, spectrographs and coronagraphs, give us
our first comprehensive view of the outer solar atmosphere and corona,
leading to a better understanding of the enigmatic coronal heating and
solar wind acceleration processes. Finally, three experiments complement
the remote sensing observations by making in- situ measurements of
the composition and energy of the solar wind and charged energetic
particles, and another instrument maps the neutral hydrogen in the
heliosphere and its dynamic change by the solar wind. This paper
reports some of the first results from the SOHO mission.

---------------------------------------------------------
Title: The Whole Sun Catalogue
Authors: Sanchez Duarte, L.; Fleck, B.; Bentley, R.
1997ASPC..118..382S Altcode: 1997fasp.conf..382S
To maximize the scientific outcome of the wealth of solar observations
available, it would be extremely useful to have a complete, central
catalogue giving some basic information such as `where, when, what'
about all solar observations made. This paper presents a proposal
for such a catalogue based on the infrastructure developed for the
SOHO Archive, but being independent of it. Our goal is to refine this
proposal with the help of the JOSO group and to implement it by 1997.

---------------------------------------------------------
Title: First Results from SOHO on Waves Near the Solar Transition
Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.;
Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten,
R. J.
1997ASPC..118..284S Altcode: 1997fasp.conf..284S
We present first results from simultaneous observations with the
CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995)
for a description of the instruments} onboard SOHO and the VTT at
Tenerife. Our aim is to study the wave propagation, shock formation,
and transmission properties of the upper chromosphere and transition
region. The preliminary results presented here include the variation
of velocity power spectra with height, difference in power between
internetwork and network regions, and variations in mean flows displayed
by different spectral lines.

---------------------------------------------------------
Title: Tracing CA K Grains Through the Chromosphere into the
Transition Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.
1997ESASP.404..685S Altcode: 1997cswn.conf..685S
No abstract at ADS

---------------------------------------------------------
Title: The Solar and Heliospheric Observatory (SOHO) in 1996.
Authors: Domingo, V.; Fleck, B.; Martens, P.; Sanchez, L.
1997joso.proc....4D Altcode:
This report gives a brief overview of SOHO's scientific production in
its first year of operation.

---------------------------------------------------------
Title: Wave Propagation in the Chromosphere and Transition Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Harrison, R.; Gurman, J.
1997ESASP.404..679S Altcode: 1997cswn.conf..679S
No abstract at ADS

---------------------------------------------------------
Title: The first results from SOHO.
Authors: Fleck, B.; Švestka, Z.
1997frfs.book.....F Altcode:
This volume contains papers reporting the first scientific results from
the SOHO mission as well as descriptions of the in-flight performance of
some of the instruments. A CD-ROM with multimedia material is included
as an integral part of this volume. Reprinted from Sol. Phys., Vol. 170,
No. 1 (Jan 1997) (see AAA, Vol. 67) and Vol. 175, No. 2 (Oct 1997)
(see AAA, Vol. 68).

---------------------------------------------------------
Title: First Results from SOHO.
Authors: Fleck, B.
1997RvMA...10..273F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The first results from SOHO.
Authors: Domingo, V.; Fleck, B.; Poland, A.
1996ESABu..87....7D Altcode:
SOHO, launched by an Atlas II-AS from Cape Canaveral on 2 December 1995,
was inserted into its halo orbit around the L1 Lagrangian point. Typical
examples of the unique results being obtained with SOHO's instruments
are presented.

---------------------------------------------------------
Title: High resolution Lyalpha images obtained with the transition
region camera (TRC): a comparison with Hα observations
Authors: Wiik, J. E.; Foing, B. H.; Martens, P.; Fleck, B.;
Schmieder, B.
1996AdSpR..17d.105W Altcode: 1996AdSpR..17..105W
Comparing high spatial resolution (~ 1”) images observed in Lyalpha
with the Transition Region Camera (TRC) and in Hα at Sacramento Peak
and Meudon Observatories, we notice that some structures are well
correlated in the two lines (plages), while others are less correlated
(chromospheric network, filaments). This is an indication of the
inhomogeneous distribution of physical parameters in these structures.

---------------------------------------------------------
Title: Preface
Authors: Fleck, B.; Domingo, V.; Poland, A.
1995SoPh..162D...9F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The SOHO mission.
Authors: Fleck, B.; Domingo, V.; Poland, A. I.
1995SoPh..162.....F Altcode:
SOHO, the Solar and Heliospheric Observatory, is a project of
international cooperation between ESA and NASA to study the Sun, from
its deep core to the outer corona. This special issue is dedicated to
the SOHO payload and to its operation.

---------------------------------------------------------
Title: The SOHO Mission: an Overview
Authors: Domingo, V.; Fleck, B.; Poland, A. I.
1995SoPh..162....1D Altcode:
The Solar and Heliospheric Observatory (SOHO) is a space mission
that forms part of the Solar-Terrestrial Science Program (STSP),
developed in a collaborative effort by the European Space Agency (ESA)
and the National Aeronautics and Space Administration (NASA). The
STSP constitutes the first "cornerstone" of ESA's long-term
programme known as "Space Science — Horizon 2000". The principal
scientific objectives of the SOHO mission are a) to reach a better
understanding of the structure and dynamics of the solar interior
using techniques of helioseismology, and b) to gain better insight
into the physical processes that form and heat the Sun's corona,
maintain it and give rise to its acceleration into the solar wind. To
achieve these goals, SOHO carries a payload consisting of 12 sets of
complementary instruments. SOHO is a three-axis stabilized spacecraft
with a total mass of 1850 kg; 1150 W of power will be provided by
the solar panels. The payload weighs about 640 kg and will consume
450 W in orbit. SOHO will be launched by an ATLAS II-AS and will
be placed in a halo orbit around the Sun-Earth L1 Lagrangian point
where it will be continuously pointing to Sun centre with an accuracy
of 10 arcsec. Pointing stability will be better than 1 arcsec over
15 min intervals. The SOHO payload produces a continuous science
data stream of 40 kbits/s which will be increased by 160 kbits/s
whenever the solar oscillations imaging instrument is operated in its
highrate mode. Telemetry will be received by NASA's Deep Space Network
(DSN). Planning, coordination and operation of the spacecraft and the
scientific payload will be conducted from the Experiment Operations
Facility (EOF) at NASA's Goddard Space Flight Center (GSFC).

---------------------------------------------------------
Title: Is there a chromospheric mode at 6 mHz?
Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B.
1995A&A...302..277S Altcode:
We present time series of Na D_1_ and Ca K_2v_ filtergrams of the
quiet sun obtained simultaneously with the Vacuum Tower Telescope at
Observatorio del Teide, Tenerife. Special interest is taken in the
distribution of power in the Fourier domain. We distinguish power
"on" and "between" the ridges of the p-modes and pseudo p-modes. The
latter are found to extend beyond the acoustic cutoff frequency up to
12mHz in Na D_1_ and 8.5mHz in Ca K_2v_. Most of the power of the broad
chromospheric feature detected in Ca II K by Harvey et al. (???) in the
background of a one-dimensional power spectrum is found preferentially
between the p-mode ridges at about 6mHz, as our two-dimensional analysis
reveals. This behaviour would be consistent with the nature of "avoided
crossing" (Ulrich &amp; Rhodes ???) of a chromospheric mode and the
p-modes. We note that the center frequency of the interridge feature
appears independent of height, whereas the power distribution of the
p-mode ridges extends to higher frequencies as height increases. We
suppose that different mechanisms are responsible for the generation of
these two wave fields. In our investigation the broad band of enhanced
power at 6mHz is even more conspicuous in Na D_1_ than in Ca K_2v_.

---------------------------------------------------------
Title: On the generation of resonance oscillations in plane
atmospheres.
Authors: Schmitz, F.; Fleck, B.
1995A&A...301..483S Altcode:
The paper deals with some selected properties of linear 1-D resonance
oscillations of plane stratified atmospheres. First, we study the
response of a bounded isothermal atmosphere to a velocity pulse
injected at the bottom of the atmosphere. For a family of pulses,
we calculate the Lagrangian density perturbation at the bottom as
this quantity indicates the response of the whole atmosphere. The
analytical expressions give insight into details of the onset and the
decay of the oscillation for finite times. We find that the principle
asymptotic term governs the resonance oscillation only at large
times. Further, we consider the influence of weak radiative damping on
the oscillation. To study conditions for the existence of a resonance
oscillation in non-isothermal atmospheres, we use transformations of
the wave equation. By suitable transformations of the wave equation of
a non-isothermal atmosphere to the wave equation of the homogeneous
gas, we obtain some particular temperature stratifications which
do not show the resonance oscillation. The solution of the wave
equation of polytropic atmospheres with negative half-integral index
is discussed. By transformations of the wave equation to the wave
equation of the isothermal atmosphere, we obtain temperature structures
of atmospheric layers the dynamical behavior of which is equal to the
behavior of the isothermal atmosphere. Further, we determine temperature
stratifications which do not produce a real resonance oscillation,
but significant distortions of sharp pulses.

---------------------------------------------------------
Title: Phase Analysis of the K-Grain Excitation Pattern
Authors: Hofmann, J.; Deubner, F. –L.; Steffens, S.; Fleck, B.
1995ESASP.376b.493H Altcode: 1995help.confP.493H; 1995soho....2..493H
No abstract at ADS

---------------------------------------------------------
Title: On the Phenomenology of K-Grains
Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B.
1995ESASP.376b.487S Altcode: 1995soho....2..487S; 1995help.confP.487S
No abstract at ADS

---------------------------------------------------------
Title: Is There an Atmospheric Mode Near 6 mHz?
Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B.
1995ESASP.376b.481S Altcode: 1995soho....2..481S; 1995help.confP.481S
No abstract at ADS

---------------------------------------------------------
Title: Helioseismology
Authors: Hoeksema, J. T.; Domingo, V.; Fleck, B.; Battrick, Bruce
1995ESASP.376b....H Altcode: 1995help.confP....H
No abstract at ADS

---------------------------------------------------------
Title: SOHO: The Solar and Heliospheric Observatory
Authors: Domingo, V.; Fleck, B.; Poland, A. I.
1995SSRv...72...81D Altcode:
The Solar and Heliospheric Observatory (SOHO), together with the Cluster
mission, constitutes ESA's Solar Terrestrial Science Programme (STSP),
the first “Cornerstone” of the Agency's long-term programme “Space
Science — Horizon 2000”. STSP, which is being developed in a strong
collaborative effort with NASA, will allow comprehensive studies
to be made of the both the Sun's interior and its outer atmosphere,
the acceleration and propagation of the solar wind and its interaction
with the Earth. This paper gives a brief overview of one part of STSP,
the SOHO mission.

---------------------------------------------------------
Title: On the reflection of linear 3-D hydrodynamic waves in a plane
atmosphere by an ionization step.
Authors: Schmitz, F.; Fleck, B.
1995A&A...294..206S Altcode:
We investigate the influence of a variable ionization rate on the
propagation behavior of evanescent and acoustic waves in an isothermal
atmosphere. For isothermal waves in a pure atomic hydrogen atmosphere
the wave equation of the total pressure perturbation can be transformed
into the hypergeometric equation, from which by a linear transformation
formula of the hypergeometric function simple analytical expressions
for the reflection of waves can be obtained. For vertical evanescent
waves we compare the reflection caused by a continuous ionization step
with that of a corresponding temperature step for which in the 1-D
case an analytical approach exists. The reflection is significantly
different for the two cases, although the sound speed is equal in
both atmospheres. We also consider the reflection by a discontinuous
ionization step and compare it with the continuous model in order
to study the usefulness of such an approximation. We also compare
the reflection of waves by a discontinuous ionization step with the
reflection by a discontinuous temperature step. We again find basic
differences between the two reflection mechanisms which are due to
the different behaviour of the first derivatives of the velocity and
the pressure perturbation at the discontinuous step.

---------------------------------------------------------
Title: Is there an atmospheric mode near 6 mHz?
Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B.
1995AGAb...11..138S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: He 10830 Angstrom Confirms Non-Propagation Component of
Chromospheric Oscillations
Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.
1995ASPC...76..342H Altcode: 1995gong.conf..342H
No abstract at ADS

---------------------------------------------------------
Title: What Have We Learned About Chromospheric Oscillations from
HeI 10830Å?
Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J.
1995itsa.conf..437F Altcode:
Time series of He I 10830 spectra taken simultaneously with spectra
of other chromospheric lines (Ca II 8542 Å and Ca II K) are analyzed
to study wave propagation in the solar chromosphere. Rather than
providing conclusive answers to some of the long standing questions
concerning chromospheric oscillations, the new results derived from
the He 10830 line raise new puzzling questions. The spatio-temporal
wave pattern deduced from the Doppler displacements of the He line
differs significantly from those of the two Ca II lines, while the
phase difference between the Doppler displacements of He 10830 and Ca
K_3 stays close to zero in the whole frequency range observed. This
is difficult to reconcile with the low oscillation amplitude observed
in the He 10830 line (RMS≈1100 m/s), which is less than half the
velocity amplitude derived from the core displacement of Ca K_3. Another
surprising result is that the Ca K “bright point” events are only
barely visible in the Doppler displacement of the He 10830 line.

---------------------------------------------------------
Title: The SOHO mission
Authors: Fleck, B.; Domingo, V.; Poland, A.
1995somi.book.....F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SOHO: The Solar and Heliospheric Observatory
Authors: Domingo, V.; Fleck, B.; Poland, A. I.
1995hlh..conf...81D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Books-Received - Mass Supply and Flows in the Solar Corona
Authors: Fleck, B.
1995Sci...267..119F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The SOHO Mission
Authors: Fleck, B.
1995LNP...444..233F Altcode: 1995cmer.conf..233F
SOHO, the Solar and Heliospheric Observatory, is a joint ESA/NASA
mission to study the sun from its interior to, and including, the solar
wind in interplanetary space. It is currently scheduled for launch in
1995. In this paper a mission overview is given, comprising scientific
objectives, payload, spacecraft, operations, and data and ground system.

---------------------------------------------------------
Title: On the phenomenology of K-grains.
Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B.
1995AGAb...11..140S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Helioseismology
Authors: Hoeksema, J. T.; Domingo, V.; Fleck, B.; Battrick, Bruce
1995ESASP.376a....H Altcode: 1995heli.conf.....H
No abstract at ADS

---------------------------------------------------------
Title: The SOHO mission Poland.
Authors: Fleck, B.; Domingo, V.; Poland, Arthur I.
1995sohp.book.....F Altcode: 1995QB521.S5828....
No abstract at ADS

---------------------------------------------------------
Title: Preparing for SOHO: results from the transition region camera
Authors: Wiik, J. E.; Foing, B. H.; Schmieder, B.; Martens, P.;
Fleck, B.
1994ESASP.373..433W Altcode: 1994soho....3..433W
No abstract at ADS

---------------------------------------------------------
Title: The scientific payload of the space-based Solar and
Heliospheric Observatory (SOHO)
Authors: Domingo, V.; Fleck, B.; Poland, A. I.
1994SSRv...70....7D Altcode:
The space-based Solar and Heliospheric Observatory (SOHO) is a joint
venture of ESA and NASA within the frame of the Solar Terrestrial
Science Programme (STSP), the first “Cornerstone” of ESA's long-term
programme “Space Science — Horizon 2000”. The principal scientific
objectives of the SOHO mission are: a) a better understanding of
the structure and dynamics of the solar interior using techniques of
helioseismology, and b) a better insight into the physical processes
that form and heat the Sun's corona, maintain it and give rise to
its acceleration into the solar wind. To achieve these goals, SOHO
carries a payload consisting of 12 sets of complementary instruments
which are briefly described here.

---------------------------------------------------------
Title: SOHO operations and ground system
Authors: Poland, A. I.; Domingo, V.; Fleck, B.
1994SSRv...70...13P Altcode:
SOHO is a joint ESA/NASA mission to study the sun from its interior to,
and including, the solar wind in interplanetary space. It is currently
scheduled for launch in 1995. After launch SOHO with be operated from
the Experiment Operations Facility (EOF) at Goddard Space Flight Center
(GSFC). The EOF will consist of facilities for instrument commanding,
data reception, data reduction and data analysis. In this paper the
operations concepts including instrument ground commanding from the EOF
and communications capabilities between the EOF and ground observatories
and the public networks in general will be described.

---------------------------------------------------------
Title: Foreword
Authors: Fleck, B.; Noci, G.; Poletto, G.
1994SSRv...70D..17F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass Supply and Flows in the Solar Corona - Conference
Authors: Fleck, B.; Noci, G.; Poletto, G.
1994SSRv...70....1F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass supply and flows in the solar corona. Proceedings. 2. SOHO
Workshop, Marciana Marina, Island of Elba (Italy), 27 Sep - 1
Oct 1993.
Authors: Fleck, B.; Noci, G.; Poletto, G.
1994SSRv...70.....F Altcode:
This workshop focused on the following topics: 1. Fine scale
structures. 2. Loops and prominences. 3. Coronal streamers. 4. Coronal
holes and solar wind. Each of these four topics was introduced by an
observational and a theoretical overview highlighting the most recent
advances in their area. A third review illustrated how SOHO might help
in solving open problems.

---------------------------------------------------------
Title: On the propagation of linear 3-D hydrodynamic waves in plane
non-isothermal atmospheres
Authors: Schmitz, F.; Fleck, B.
1994A&AS..106..129S Altcode:
Closed solutions of the time independent wave equation of 3-D linear
adiabatic waves in non-isothermal atmospheres are presented and
discussed. Three temperature stratifications are considered applying
the full wave equation without any approximations: a continuous
temperature step between two asymptotically isothermal layers, an
exponentially decreasing, and an exponentially increasing temperature
stratification. In this first paper we present the fundamental systems,
discuss general properties, and present some tools for more detailed
investigations. For the exponential temperature stratifications, the
wave equation is transformed to the hypergeometric equation. Linear
transformation formulas are used to study details of the solutions. For
the exponentially decreasing temperature stratification the second
solution of the fundamental mode is calculated, and the convective
and Rayleigh-Taylor instabilities are considered. In the case of the
continuous temperature step the wave equation can be reduced to Heun's
differential equation. Various representations of the solutions are
presented and the continuation of the solutions is discussed.

---------------------------------------------------------
Title: On the strength of solar intra-network fields.
Authors: Keller, C. U.; Deubner, F. -L.; Egger, U.; Fleck, B.; Povel,
H. P.
1994A&A...286..626K Altcode:
The combination of the German Vacuum Tower Telescope and the prototype
of ZIMPOL I (Zuerich Imaging Stokes Polarimeter I), a novel, very
sensitive imaging polarimeter, has resulted in the first spectra
of solar intra-network (IN) fields in circular polarization. The
sensitivity in terms of flux density is 0.7 Mx/cm^2^. While magnetic
fields in solar spots, pores, plages, and in the network have
predominantly kG field strengths, the magnetic field strength of
the IN flux is a controversial subject due to the absence of direct
measurements. We first summarize the current ideas on IN fields and
examine previous arguments for their field strength. Our measurements
of the magnetic line ratio formed between the amplitudes of the Stokes
V profiles of Fe I 5247.1 A and Fe I 5250.2 A are consistent with a
field strength well below 1 kG. Since the sensitivity of the magnetic
line ratio becomes low for small field strengths, we can only set an
upper limit on the field strength of IN fields of 500 G at the level
of line formation with a probability of 68% and an upper limit of 1
kG with a probability of 95%. We emphasize that these are the first
observations of a magnetic line ratio of unity near disk center.

---------------------------------------------------------
Title: On the correlation of magnetic field strength and inclination
with continuum brightness of a sunspot penumbra.
Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W.
1994A&A...284..269H Altcode:
A fairly regular sunspot penumbra has been observed near disk center
using a Stokes V polarimeter at the German Vacuum-Tower-Telescope in
Izana, Tenerife. We obtained two-dimensional spectral data by scanning
the limbside sector of the penumbra in steps of 1 arcsecond with the
slit oriented parallel to the solar limb. From Stokes V and Stokes I
spectra of four magnetically sensitive lines (FeI5247.1A, CrI5247.6A,
FeI5250.2A, and FeI5250.7A) recorded with 1024 x 1024 pixel CCD
cameras we have determined several magnetic parameters. The results
of a correlation analysis show a clear relation between continuum
brightness and magnetic field inclination, field lines beeing flatter
in the dark penumbral filaments. We also find a correlation between
field strength and brightness; this correlation is not uniform across
the penumbra, however.

---------------------------------------------------------
Title: Non-linearities of chromospheric oscillations
Authors: Deubner, F. -L.; Hofmann, J.; Kossack, E.; Fleck, B.
1994ASIC..433..155D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of Solar Oscillations in He 110830 Angstrom
Authors: Fleck, B.; Deubner, F. -L.; Maier, D.; Schmidt, W.
1994IAUS..154...65F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Wave propagation in the solar chromosphere: some new results
from CaII K, CaII 8542 and HeI 10830 observations
Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J.; Steffens, S.
1994chdy.conf..103F Altcode:
Time series of spectra taken simultaneously in the three chromospheric
lines Ca II 8542 A, Ca II K, and He I 10830 AA are analyzed to study
the wave propagation behaviour in the solar chromosphere. The V-V
phase difference between the three chromospheric lines stays close to
0 deg in the whole frequency range observed and thus confirms previous
observations of a non-propagating component dominating the acoustic
wave spectrum in the solar chromosphere. In particular, the dominant
3-min oscillations observed in the core displacement of the Ca II
8542 and Ca K line are highly correlated, contrary to the numerical
NLTE radiating shock dynamic simulations of Carlsson and Stein (1993)
which revealed a significant phase delay between the two lines. The
oscillation amplitude observed in the He 10830 line (RMS ~ 1100 m/s)
is only about half the velocity amplitude derived from the core
displacement of Ca K3. We also present a first He 10830 k-omega diagram.

---------------------------------------------------------
Title: SOHO Science Opportunities
Authors: Fleck, B.; Domingo, V.; Poland, A. I.
1994scs..conf..609F Altcode: 1994IAUCo.144..609F
The principal scientific objectives of the SOHO mission are: a)
a better understanding of the structure and dynamics of the solar
interior using techniques of helioseismology, and b) a better insight
into the physical processes that form and heat the Sun's corona,
maintain it and give rise to its acceleration into the solar wind. To
achieve these goals, SOHO carries a payload consisting of 12 sets of
complementary instruments which are briefly described here.

---------------------------------------------------------
Title: SOHO Operations
Authors: Fleck, B.; Domingo, V.; Poland, A. I.
1994scs..conf..614F Altcode: 1994IAUCo.144..614F
SOHO, the Solar and Heliospheric Observatory, is currently scheduled
for launch in 1995. After launch SOHO will be operated from the
Experiment Operations Faciliy (EOF) at Goddard Space Flight Center
(GSFC). The EOF will consist of facilities for instrument commanding,
data reception, data reduction and data analysis. This paper briefly
describes the operations concepts.

---------------------------------------------------------
Title: Mass supply and flows in the solar corona
Authors: Fleck, B.; Noci, G.; Poletto, G.
1994msfs.conf.....F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line profile asymmetries in a sunspot penumbra
Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.
1994smf..conf..182H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Investigations on Laser Induced Dynamic Gratings in Azo-Dye
Doped Polymer Layers and Their Application
Authors: Fleck, B.; Rehn, H.; Friedrich, V.; Wenke, L.; Janietz, D.
1994ESOC...48..413F Altcode: 1994aao..conf..413F
No abstract at ADS

---------------------------------------------------------
Title: Experimental Investigations on Two-Wave Mixing in
Photorefractive Crystals with Spherical Waves
Authors: Kiessling, A.; Fleck, B.; Wenke, L.
1994ESOC...48..419K Altcode: 1994aao..conf..419K
No abstract at ADS

---------------------------------------------------------
Title: SOHO - The Solar and Heliospheric Observatory
Authors: Fleck, B.; Domingo, V.
1994smf..conf..408F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SOHO: science objectives and capabilities
Authors: Fleck, B.; Domingo, V.; Poland, A. I.
1994ASIC..433..517F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Phases and amplitudes of acoustic-gravity waves. 2: The
effects of reflection
Authors: Marmolino, C.; Severino, G.; Deubner, F. -L.; Fleck, B.
1993A&A...278..617M Altcode:
We study wave reflection caused by the temperature stratification
of the solar atmosphere, assumed to be a succession of two layers
of different temperatures and radiative decay times. Considering
waves which propagate energy upward in the atmosphere, we compute
the complex amplitude reflection and transmission coefficients and
investigate the effects that reflection introduces on the phases of
acoustic-gravity waves. In the evanescent region of the kx
- omega diagram, between the Lamb waves and the acoustic cut-off
frequency, the reflection coefficient is small, in particular zero on
the fundamental mode. Therefore, in this region, the reflected wave
has a small amplitude and its superposition to the incident wave does
not affect the latter in a significant way. In particular, the T - V
phase differences of the total wave are very similar to those of the
incident wave. Furthermore, a heruisitic formula is presented which
describes the observed coexistence of two different phase regimes
between velocity and intensity oscillations in the evanescent area
above the fundamental mode.

---------------------------------------------------------
Title: On the numerical calculation of hydrodynamic shock waves in
atmospheres by an FCT method
Authors: Schmitz, F.; Fleck, B.
1993A&A...279..499S Altcode:
The numerical calculation of vertically propagating hydrodynamic shock
waves in a plane atmosphere by the ETBFCT-version of the Flux Corrected
Transport (FCT) method by Boris and Book is discussed. The results
are compared with results obtained by a characteristic method with
shock fitting. We show that the use of the internal energy density
as a dependent variable instead of the total energy density can give
very inaccurate results. Consequent discretization rules for the
gravitational source terms are derived. The improvement of the results
by an additional iteration step is discussed. It appears that the FCT
method is an excellent method for the accurate calculation of shock
waves in an atmosphere.

---------------------------------------------------------
Title: On the interactions of hydrodynamic shock waves in stellar
atmospheres
Authors: Fleck, B.; Schmitz, F.
1993A&A...273..671F Altcode:
We study the effects of non-linear interactions of hydrodynamic shock
waves in the solar atmosphere and their influence on the resonant
oscillations at the cut-off frequency The shock waves originate from
randomly generated wave packets with broad frequency distributions as
opposed to previous studies which start with monochromatic wave trains,
single pulses or, at the most, regular waves trains with stochastically
changing periods. We consider only one-dimensional (vertical) adiabatic
or isothermal hydrodynamics using a numerical code based on a modified
flux corrected transport algorithm. The results are analyzed by applying
Fourier methods, i.e. power and phase difference spectra. The dynamical
behaviour of an atmosphere excited by a broad spectrum.of acoustic waves
differs extremely from that disturbed by monochromatic waves. Due to
shock overtaking processes almost all the high frequency shock waves
merge and form strong long period shock waves. Comparing the results of
three different frequency spectra it is shown that the detailed form
of the excitation spectrum is only of minor importance. The results
show that shock overtaking does not generate the characteristic cut-off
frequency oscillations. We observe these particular oscillations only
when we add a long period evanescent component with ω≤ωac
to the acoustic spectrum at the base of the atmosphere. Consequences
for the shock heating of the solar chromosphere are briefly discussed.

---------------------------------------------------------
Title: Invited Talk: (SOHO Operations and Coordination with
Ground-based Observatories)
Authors: Domingo, V.; Fleck, B.
1993BAAS...25.1195D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Polanmetric Measurements of the Fine Structure of a Sunspot
Penumbra
Authors: Hofmann, J.; Deubner, F. L.; Fleck, B.
1993ASPC...46...44H Altcode: 1993mvfs.conf...44H; 1993IAUCo.141...44H
No abstract at ADS

---------------------------------------------------------
Title: Observations of Waves and Oscillations in the Solar Magnetic
Fine Structure
Authors: Fleck, B.; Deubner, F. -L.; Schmidt, W.
1993ASPC...46..522F Altcode: 1993IAUCo.141..522F; 1993mvfs.conf..522F
No abstract at ADS

---------------------------------------------------------
Title: Dynamics of the solar atmosphere. V - Partial reflection and
forced oscillation, and their signature in phase diagrams
Authors: Deubner, F. -L.; Fleck, B.; Schmitz, F.; Straus, Th.
1992A&A...266..560D Altcode:
An overview of several new dynamic phenomena detected by means of
velocity-brightness (V-I) and V-V phase diagrams is presented. The great
diagnostic value of this kind of data analysis is demonstrated and used
in order to develop a consistent description and interpretation of the
surprisingly broad spectrum of linear hydrodynamic wave motions that
occur in a stellar atmosphere. The significance of partial reflection
and the role of forced oscillations in practically all layers of the
solar atmosphere are demonstrated. With reference to the concept of
continuous partial reflection, a model of the 'background' of coherent
wave motions found at frequencies and wavenumbers in between the
well-known p-mode ridges is presented.

---------------------------------------------------------
Title: On the reflection of linear hydrodynamic waves at continuous
temperature steps in stellar atmospheres
Authors: Schmitz, F.; Fleck, B.
1992A&A...260..447S Altcode:
A simple analytical expression which describes a smooth temperature
step is used to study the behavior of vertically propagating adiabatic
waves in non-isothermal plane atmospheric layers. With this expression
the one-dimensional equation of adiabatic linear atmospheric
waves is reduced to a hypergeometric differential equation. From
the asymptotic evaluations of the solutions we obtain formulas for
reflection coefficients and phases. In the case of acoustic waves the
reflection coefficients can be given in terms of simple functions. It is
shown how the photospheric temperature decrease and the chromospheric
temperature increase of the solar atmosphere can be approximated by
the temperature formula. For these approximations various results
are presented for both evanescent and acoustic waves. The results
of the reflection at continuous steps are compared with those at a
temperature discontinuity. The WKB-approximation of the velocity of a
wave passing a continuous temperature step is given. A limiting form
of the temperature function is used to study the behavior of evanescent
waves in a photosphere.

---------------------------------------------------------
Title: Is mesogranulation a distinct regime of convection?
Authors: Straus, Th.; Deubner, F. -L.; Fleck, B.
1992A&A...256..652S Altcode:
We investigate the dynamics of the mesogranulation phenomenon by
analyzing spatially 2D spectral time series taken at disk center
and cos Theta = 0.8. After a 3D Fourier transformation, we integrate
the power and crosspower spectra in azimuth, and calculate k - omega
power, phase difference, and cross-power spectra. The spatial power
spectra are compared with those obtained from numerical simulations of
stationary cell patterns. In the deepest atmospheric layers the V - I
phase difference spectra reveal a uniform regime of convective motions
at frequencies below the Lamb mode. The power spectra exhibit at all
levels a significant distinction between supergranulation and convective
patterns of smaller scales. On the other hand, the 'mesogranulation'
phenomenon cannot be identified as an independent convective regime
in the deep photosphere, distinct from granulation. Rather, the
mesostructures that appear to emerge in the middle photosphere and
temperature minimum seem to be a product of the overshoot driving only
the largest elements of an extended distribution of granular sizes
while the smaller elements have already died out at a lower level.

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Title: Polarimetric measurements of the fine structure of a sunspot
penumbra.
Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W.
1992AGAb....7..149H Altcode:
No abstract at ADS

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Title: An analysis of non-linear oscillations in the solar
chromosphere.
Authors: Kossack, E.; Deubner, F. -L.; Fleck, B.
1992AGAb....7..148K Altcode:
No abstract at ADS

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Title: The 3-min oscillations of the solar chromosphere - A basic
physical effect?
Authors: Fleck, B.; Schmitz, F.
1991A&A...250..235F Altcode:
The resonant excitation of the acoustic cut-off frequency mode in a
stratified atmosphere, an affect which provides a simple explanation
of the observed 3-min oscillations of the solar chromosphere, is
discussed. It is demonstrated that the cut-off frequency mode is excited
also by long period disturbances, which, in the case of the sun, could
be the wave trains of the photospheric 5-min oscillations. Due to the
spatial attenuation of the evanescent waves, the oscillations at the
cut-off frequency dominate the oscillatory signal above a certain
height (about 6 to 8 scale heights above the moving piston). The
oscillations at the cut-off frequency are very persistent and vanish
for t approaches infinity only in an infinitely extended atmosphere
without any reflecting boundaries. In a finite atmosphere with an upper
boundary at which total or partial reflection occurs, the Omega = 1
oscillations are permanently excited. It is concluded that there is no
need for a chromospheric cavity to explain the observed chromospheric
3-min resonance, as was previously assumed.

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Title: Observations of Waves and Oscillations in Solar Magnetic
Fluxtube Concentrations (With 1 Figure)
Authors: Fleck, B.; Deubner, F. -L.
1991mcch.conf...19F Altcode:
No abstract at ADS