Author name code: knoelker
ADS astronomy entries on 2022-09-14
author:"Knoelker, Michael"
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Title: The Visible Spectro-Polarimeter of the Daniel K. Inouye
Solar Telescope
Authors: de Wijn, A. G.; Casini, R.; Carlile, A.; Lecinski, A. R.;
Sewell, S.; Zmarzly, P.; Eigenbrot, A. D.; Beck, C.; Wöger, F.;
Knölker, M.
Bibcode: 2022SoPh..297...22D
Altcode: 2022arXiv220300117D
The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter
(ViSP) is a traditional slit-scanning spectrograph with the ability
to observe solar regions up to a 120 ×78 arcsec2 area. The
design implements dual-beam polarimetry, a polychromatic polarization
modulator, a high-dispersion echelle grating, and three spectral
channels that can be automatically positioned. A defining feature of
the instrument is its capability to tune anywhere within the 380 - 900
nm range of the solar spectrum, allowing for a virtually infinite number
of combinations of three wavelengths to be observed simultaneously. This
enables the ViSP user to pursue well-established spectro-polarimetric
studies of the magnetic structure and plasma dynamics of the solar
atmosphere, as well as completely novel investigations of the solar
spectrum. Within the suite of first-generation instruments at the DKIST,
ViSP is the only wavelength-versatile spectro-polarimeter available to
the scientific community. It was specifically designed as a discovery
instrument to explore new spectroscopic and polarimetric diagnostics
and test improved models of polarized line formation through high
spatial-, spectral-, and temporal-resolution observations of the Sun's
polarized spectrum. In this instrument article, we describe the science
requirements and design drivers of ViSP and present preliminary science
data collected during the commissioning of the instrument.
Title: The National Science Foundation's Daniel K. Inouye Solar
Telescope — Status Update
Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn,
A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.;
Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.;
Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.;
Mathioudakis, M.; Dkist Team
Bibcode: 2021AAS...23810601R
Altcode:
The National Science Foundation's 4m Daniel K. Inouye Solar Telescope
(DKIST) on Haleakala, Maui is now the largest solar telescope in the
world. DKIST's superb resolution and polarimetric sensitivity will
enable astronomers to unravel many of the mysteries the Sun presents,
including the origin of solar magnetism, the mechanisms of coronal
heating and drivers of flares and coronal mass ejections. Five
instruments, four of which provide highly sensitive measurements
of solar magnetic fields, including the illusive magnetic field of
the faint solar corona. The DKIST instruments will produce large and
complex data sets, which will be distributed through the NSO/DKIST Data
Center. DKIST has achieved first engineering solar light in December
of 2019. Due to COVID the start of the operations commissioning phase
is delayed and is now expected for fall of 2021. We present a status
update for the construction effort and progress with the operations
commissioning phase.
Title: Power spectrum of turbulent convection in the solar photosphere
Authors: Yelles Chaouche, L.; Cameron, R. H.; Solanki, S. K.;
Riethmüller, T. L.; Anusha, L. S.; Witzke, V.; Shapiro, A. I.;
Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; van Noort,
M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2020A&A...644A..44Y
Altcode: 2020arXiv201009037Y
The solar photosphere provides us with a laboratory for understanding
turbulence in a layer where the fundamental processes of transport
vary rapidly and a strongly superadiabatic region lies very closely
to a subadiabatic layer. Our tools for probing the turbulence are
high-resolution spectropolarimetric observations such as have recently
been obtained with the two balloon-borne SUNRISE missions, and numerical
simulations. Our aim is to study photospheric turbulence with the
help of Fourier power spectra that we compute from observations
and simulations. We also attempt to explain some properties of the
photospheric overshooting flow with the help of its governing equations
and simulations. We find that quiet-Sun observations and smeared
simulations are consistent with each other and exhibit a power-law
behavior in the subgranular range of their Doppler velocity power
spectra with a power-law index of ≈ - 2. The unsmeared simulations
exhibit a power law that extends over the full range between the
integral and Taylor scales with a power-law index of ≈ - 2.25. The
smearing, reminiscent of observational conditions, considerably reduces
the extent of the power-law-like portion of the power spectra. This
suggests that the limited spatial resolution in some observations
might eventually result in larger uncertainties in the estimation of
the power-law indices. The simulated vertical velocity power spectra
as a function of height show a rapid change in the power-law index
(at the subgranular range) from roughly the optical depth unity layer,
that is, the solar surface, to 300 km above it. We propose that the
cause of the steepening of the power-law index is the transition from
a super- to a subadiabatic region, in which the dominant source of
motions is overshooting convection. A scale-dependent transport of
the vertical momentum occurs. At smaller scales, the vertical momentum
is more efficiently transported sideways than at larger scales. This
results in less vertical velocity power transported upward at small
scales than at larger scales and produces a progressively steeper
vertical velocity power law below 180 km. Above this height, the
gravity work progressively gains importance at all relevant scales,
making the atmosphere progressively more hydrostatic and resulting
in a gradually less steep power law. Radiative heating and cooling of
the plasma is shown to play a dominant role in the plasma energetics
in this region, which is important in terms of nonadiabatic damping
of the convective motions.
Title: The Daniel K. Inouye Solar Telescope - Observatory Overview
Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode,
Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.;
McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich;
von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn,
Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.;
Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang;
Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian;
Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard,
Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross,
Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit;
Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon,
Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret
D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer,
Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.;
Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer,
Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes,
Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag;
Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik;
Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis;
Wampler, Stephen B.; Williams, Timothy R.; White, Charles
Bibcode: 2020SoPh..295..172R
Altcode:
We present an overview of the National Science Foundation's Daniel
K. Inouye Solar Telescope (DKIST), its instruments, and support
facilities. The 4 m aperture DKIST provides the highest-resolution
observations of the Sun ever achieved. The large aperture of
DKIST combined with state-of-the-art instrumentation provide the
sensitivity to measure the vector magnetic field in the chromosphere
and in the faint corona, i.e. for the first time with DKIST we will
be able to measure and study the most important free-energy source
in the outer solar atmosphere - the coronal magnetic field. Over its
operational lifetime DKIST will advance our knowledge of fundamental
astronomical processes, including highly dynamic solar eruptions
that are at the source of space-weather events that impact our
technological society. Design and construction of DKIST took over two
decades. DKIST implements a fast (f/2), off-axis Gregorian optical
design. The maximum available field-of-view is 5 arcmin. A complex
thermal-control system was implemented in order to remove at prime
focus the majority of the 13 kW collected by the primary mirror and
to keep optical surfaces and structures at ambient temperature, thus
avoiding self-induced local seeing. A high-order adaptive-optics
system with 1600 actuators corrects atmospheric seeing enabling
diffraction limited imaging and spectroscopy. Five instruments, four
of which are polarimeters, provide powerful diagnostic capability
over a broad wavelength range covering the visible, near-infrared,
and mid-infrared spectrum. New polarization-calibration strategies
were developed to achieve the stringent polarization accuracy
requirement of 5×10−4. Instruments can be combined and
operated simultaneously in order to obtain a maximum of observational
information. Observing time on DKIST is allocated through an open,
merit-based proposal process. DKIST will be operated primarily in
"service mode" and is expected to on average produce 3 PB of raw
data per year. A newly developed data center located at the NSO
Headquarters in Boulder will initially serve fully calibrated data to
the international users community. Higher-level data products, such as
physical parameters obtained from inversions of spectro-polarimetric
data will be added as resources allow.
Title: Status of the Daniel K. Inouye Solar Telescope: unraveling
the mysteries the Sun.
Authors: Rimmele, Thomas R.; Martinez Pillet, Valentin; Goode, Philip
R.; Knoelker, Michael; Kuhn, Jeffrey Richard; Rosner, Robert; Casini,
Roberto; Lin, Haosheng; von der Luehe, Oskar; Woeger, Friedrich;
Tritschler, Alexandra; Fehlmann, Andre; Jaeggli, Sarah A.; Schmidt,
Wolfgang; De Wijn, Alfred; Rast, Mark; Harrington, David M.; Sueoka,
Stacey R.; Beck, Christian; Schad, Thomas A.; Warner, Mark; McMullin,
Joseph P.; Berukoff, Steven J.; Mathioudakis, Mihalis; DKIST Team
Bibcode: 2018AAS...23231601R
Altcode:
The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under
construction on Haleakala, Maui will be the world’s largest solar
telescope. Designed to meet the needs of critical high resolution and
high sensitivity spectral and polarimetric observations of the sun,
this facility will perform key observations of our nearest star that
matters most to humankind. DKIST’s superb resolution and sensitivity
will enable astronomers to address many of the fundamental problems
in solar and stellar astrophysics, including the origin of stellar
magnetism, the mechanisms of coronal heating and drivers of the
solar wind, flares, coronal mass ejections and variability in solar
and stellar output. DKIST will also address basic research aspects of
Space Weather and help improve predictive capabilities. In combination
with synoptic observations and theoretical modeling DKIST will unravel
the many remaining mysteries of the Sun.The construction of DKIST is
progressing on schedule with 80% of the facility complete. Operations
are scheduled to begin early 2020. DKIST will replace the NSO
facilities on Kitt Peak and Sac Peak with a national facility with
worldwide unique capabilities. The design allows DKIST to operate as
a coronagraph. Taking advantage of its large aperture and infrared
polarimeters DKIST will be capable to routinely measure the currently
illusive coronal magnetic fields. The state-of-the-art adaptive optics
system provides diffraction limited imaging and the ability to resolve
features approximately 20 km on the Sun. Achieving this resolution
is critical for the ability to observe magnetic structures at their
intrinsic, fundamental scales. Five instruments will be available at
the start of operations, four of which will provide highly sensitive
measurements of solar magnetic fields throughout the solar atmosphere
- from the photosphere to the corona. The data from these instruments
will be distributed to the world wide community via the NSO/DKIST data
center located in Boulder. We present examples of science objectives
and provide an overview of the facility and project status, including
the ongoing efforts of the community to develop the critical science
plan for the first 2-3 years of operations.
Title: The Maximum Entropy Limit of Small-scale Magnetic Field
Fluctuations in the Quiet Sun
Authors: Gorobets, A. Y.; Berdyugina, S. V.; Riethmüller, T. L.;
Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Gizon, L.; Hirzberger, J.; van Noort, M.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..233....5G
Altcode: 2017arXiv171008361G
The observed magnetic field on the solar surface is characterized by a
very complex spatial and temporal behavior. Although feature-tracking
algorithms have allowed us to deepen our understanding of this behavior,
subjectivity plays an important role in the identification and tracking
of such features. In this paper, we continue studies of the temporal
stochasticity of the magnetic field on the solar surface without relying
either on the concept of magnetic features or on subjective assumptions
about their identification and interaction. We propose a data analysis
method to quantify fluctuations of the line-of-sight magnetic field by
means of reducing the temporal field’s evolution to the regular Markov
process. We build a representative model of fluctuations converging to
the unique stationary (equilibrium) distribution in the long time limit
with maximum entropy. We obtained different rates of convergence to the
equilibrium at fixed noise cutoff for two sets of data. This indicates
a strong influence of the data spatial resolution and mixing-polarity
fluctuations on the relaxation process. The analysis is applied to
observations of magnetic fields of the relatively quiet areas around an
active region carried out during the second flight of the Sunrise/IMaX
and quiet Sun areas at the disk center from the Helioseismic and
Magnetic Imager on board the Solar Dynamics Observatory satellite.
Title: The Design and Performance of the Gondola Pointing System
for the Sunrise II Balloon-Borne Stratospheric Solar Observatory
Authors: Lecinski, A.; Card, G.; Knölker, M.; Hardy, B.
Bibcode: 2017JAI.....640007L
Altcode:
With its 1m aperture, the Sunrise Balloon-Borne Stratospheric
Solar Observatory was the largest space-based solar telescope. It
was designed to study the magneto-convective processes of the sun at
resolutions higher than 100km and the payload took data during a flight
from June 12 to June 17, 2013. To achieve its science requirements,
the telescope had to point to an accuracy of 26‧‧ for extended
periods of time. Pointing of the instrument was effected by the Sunrise
Pointing System (PS). The PS used measurements provided by a Lockheed
Intermediate Sun Sensor (LISS) and passed the data through a cascade of
up to four digital filters to calculate the best voltages to drive the
azimuthal and elevation motors. All filter settings could be modified
in flight to adapt to changing conditions. Using this design, the PS
met its requirements, pointing the instrument with an accuracy better
than 26‧‧ for 60% of the flight and for continuous time periods
of up to 99min. In this paper, we detail the design and performance
of the PS during the 2013 flight.
Title: Erratum: Morphological Properties of
Slender CaII H Fibrils Observed by sunrise II (ApJS 229, 1, 6)
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..230...11G
Altcode:
No abstract at ADS
Title: Slender Ca II H Fibrils Mapping Magnetic Fields in the Low
Solar Chromosphere
Authors: Jafarzadeh, S.; Rutten, R. J.; Solanki, S. K.; Wiegelmann, T.;
Riethmüller, T. L.; van Noort, M.; Szydlarski, M.; Blanco Rodríguez,
J.; Barthol, P.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.;
Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Schmidt, W.
Bibcode: 2017ApJS..229...11J
Altcode: 2016arXiv161003104J
A dense forest of slender bright fibrils near a small solar active
region is seen in high-quality narrowband Ca II H images from the SuFI
instrument onboard the Sunrise balloon-borne solar observatory. The
orientation of these slender Ca II H fibrils (SCF) overlaps with the
magnetic field configuration in the low solar chromosphere derived
by magnetostatic extrapolation of the photospheric field observed
with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are
qualitatively aligned with small-scale loops computed from a novel
inversion approach based on best-fit numerical MHD simulation. Such
loops are organized in canopy-like arches over quiet areas that differ
in height depending on the field strength near their roots.
Title: Magneto-static Modeling from Sunrise/IMaX: Application to an
Active Region Observed with Sunrise II
Authors: Wiegelmann, T.; Neukirch, T.; Nickeler, D. H.; Solanki, S. K.;
Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller,
T. L.; van Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...18W
Altcode: 2017arXiv170101458N; 2017arXiv170101458W
Magneto-static models may overcome some of the issues facing force-free
magnetic field extrapolations. So far they have seen limited use
and have faced problems when applied to quiet-Sun data. Here we
present a first application to an active region. We use solar vector
magnetic field measurements gathered by the IMaX polarimeter during
the flight of the Sunrise balloon-borne solar observatory in 2013
June as boundary conditions for a magneto-static model of the higher
solar atmosphere above an active region. The IMaX data are embedded
in active region vector magnetograms observed with SDO/HMI. This work
continues our magneto-static extrapolation approach, which was applied
earlier to a quiet-Sun region observed with Sunrise I. In an active
region the signal-to-noise-ratio in the measured Stokes parameters
is considerably higher than in the quiet-Sun and consequently the
IMaX measurements of the horizontal photospheric magnetic field allow
us to specify the free parameters of the model in a special class of
linear magneto-static equilibria. The high spatial resolution of IMaX
(110-130 km, pixel size 40 km) enables us to model the non-force-free
layer between the photosphere and the mid-chromosphere vertically
by about 50 grid points. In our approach we can incorporate some
aspects of the mixed beta layer of photosphere and chromosphere, e.g.,
taking a finite Lorentz force into account, which was not possible with
lower-resolution photospheric measurements in the past. The linear model
does not, however, permit us to model intrinsic nonlinear structures
like strongly localized electric currents.
Title: The Second Flight of the Sunrise Balloon-borne Solar
Observatory: Overview of Instrument Updates, the Flight, the Data,
and First Results
Authors: Solanki, S. K.; Riethmüller, T. L.; Barthol, P.; Danilovic,
S.; Deutsch, W.; Doerr, H. -P.; Feller, A.; Gandorfer, A.; Germerott,
D.; Gizon, L.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.;
Lagg, A.; Meller, R.; Tomasch, G.; van Noort, M.; Blanco Rodríguez,
J.; Gasent Blesa, J. L.; Balaguer Jiménez, M.; Del Toro Iniesta,
J. C.; López Jiménez, A. C.; Orozco Suarez, D.; Berkefeld, T.;
Halbgewachs, C.; Schmidt, W.; Álvarez-Herrero, A.; Sabau-Graziati,
L.; Pérez Grande, I.; Martínez Pillet, V.; Card, G.; Centeno, R.;
Knölker, M.; Lecinski, A.
Bibcode: 2017ApJS..229....2S
Altcode: 2017arXiv170101555S
The Sunrise balloon-borne solar observatory, consisting of a 1 m
aperture telescope that provides a stabilized image to a UV filter
imager and an imaging vector polarimeter, carried out its second science
flight in 2013 June. It provided observations of parts of active regions
at high spatial resolution, including the first high-resolution images
in the Mg II k line. The obtained data are of very high quality, with
the best UV images reaching the diffraction limit of the telescope
at 3000 Å after Multi-Frame Blind Deconvolution reconstruction
accounting for phase-diversity information. Here a brief update is
given of the instruments and the data reduction techniques, which
includes an inversion of the polarimetric data. Mainly those aspects
that evolved compared with the first flight are described. A tabular
overview of the observations is given. In addition, an example time
series of a part of the emerging active region NOAA AR 11768 observed
relatively close to disk center is described and discussed in some
detail. The observations cover the pores in the trailing polarity of
the active region, as well as the polarity inversion line where flux
emergence was ongoing and a small flare-like brightening occurred in
the course of the time series. The pores are found to contain magnetic
field strengths ranging up to 2500 G, and while large pores are clearly
darker and cooler than the quiet Sun in all layers of the photosphere,
the temperature and brightness of small pores approach or even exceed
those of the quiet Sun in the upper photosphere.
Title: A Tale of Two Emergences: Sunrise II Observations of Emergence
Sites in a Solar Active Region
Authors: Centeno, R.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger,
J.; Riethmüller, T. L.; van Noort, M.; Orozco Suárez, D.; Berkefeld,
T.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....3C
Altcode: 2016arXiv161003531C
In 2013 June, the two scientific instruments on board the second Sunrise
mission witnessed, in detail, a small-scale magnetic flux emergence
event as part of the birth of an active region. The Imaging Magnetograph
Experiment (IMaX) recorded two small (∼ 5\prime\prime )
emerging flux patches in the polarized filtergrams of a photospheric Fe
I spectral line. Meanwhile, the Sunrise Filter Imager (SuFI) captured
the highly dynamic chromospheric response to the magnetic fields pushing
their way through the lower solar atmosphere. The serendipitous capture
of this event offers a closer look at the inner workings of active
region emergence sites. In particular, it reveals in meticulous detail
how the rising magnetic fields interact with the granulation as they
push through the Sun’s surface, dragging photospheric plasma in
their upward travel. The plasma that is burdening the rising field
slides along the field lines, creating fast downflowing channels at
the footpoints. The weight of this material anchors this field to the
surface at semi-regular spatial intervals, shaping it in an undulatory
fashion. Finally, magnetic reconnection enables the field to release
itself from its photospheric anchors, allowing it to continue its
voyage up to higher layers. This process releases energy that lights
up the arch-filament systems and heats the surrounding chromosphere.
Title: Photospheric Response to an Ellerman Bomb-like Event—An
Analogy of Sunrise/IMaX Observations and MHD Simulations
Authors: Danilovic, S.; Solanki, S. K.; Barthol, P.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.;
Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez, D.;
Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....5D
Altcode: 2016arXiv160903817D
Ellerman Bombs are signatures of magnetic reconnection, which is an
important physical process in the solar atmosphere. How and where they
occur is a subject of debate. In this paper, we analyze Sunrise/IMaX
data, along with 3D MHD simulations that aim to reproduce the exact
scenario proposed for the formation of these features. Although
the observed event seems to be more dynamic and violent than the
simulated one, simulations clearly confirm the basic scenario for the
production of EBs. The simulations also reveal the full complexity of
the underlying process. The simulated observations show that the Fe I
525.02 nm line gives no information on the height where reconnection
takes place. It can only give clues about the heating in the aftermath
of the reconnection. However, the information on the magnetic field
vector and velocity at this spatial resolution is extremely valuable
because it shows what numerical models miss and how they can be
improved.
Title: Transverse Oscillations in Slender Ca II H Fibrils Observed
with Sunrise/SuFI
Authors: Jafarzadeh, S.; Solanki, S. K.; Gafeira, R.; van Noort, M.;
Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.;
Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....9J
Altcode: 2016arXiv161007449J
We present observations of transverse oscillations in slender Ca II
H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long
time series of high- (spatial and temporal-) resolution seeing-free
observations in a 1.1 Å wide passband covering the line core of Ca
II H 3969 Å from the second flight of the Sunrise balloon-borne solar
observatory. The entire field of view, spanning the polarity inversion
line of an active region close to the solar disk center, is covered with
bright, thin, and very dynamic fine structures. Our analysis reveals
the prevalence of transverse waves in SCFs with median amplitudes and
periods on the order of 2.4 ± 0.8 km s-1 and 83 ± 29 s,
respectively (with standard deviations given as uncertainties). We
find that the transverse waves often propagate along (parts of) the
SCFs with median phase speeds of 9 ± 14 km s-1. While the
propagation is only in one direction along the axis in some of the
SCFs, propagating waves in both directions, as well as standing waves
are also observed. The transverse oscillations are likely Alfvénic
and are thought to be representative of magnetohydrodynamic kink
waves. The wave propagation suggests that the rapid high-frequency
transverse waves, often produced in the lower photosphere, can
penetrate into the chromosphere with an estimated energy flux of ≈15
kW m-2. Characteristics of these waves differ from those
reported for other fibrillar structures, which, however, were observed
mainly in the upper solar chromosphere.
Title: Kinematics of Magnetic Bright Features in the Solar Photosphere
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Barthol, P.;
Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon,
L.; Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Riethmüller, T. L.; Schmidt, W.; van Noort, M.
Bibcode: 2017ApJS..229....8J
Altcode: 2016arXiv161007634J
Convective flows are known as the prime means of transporting magnetic
fields on the solar surface. Thus, small magnetic structures are good
tracers of turbulent flows. We study the migration and dispersal
of magnetic bright features (MBFs) in intergranular areas observed
at high spatial resolution with Sunrise/IMaX. We describe the flux
dispersal of individual MBFs as a diffusion process whose parameters are
computed for various areas in the quiet-Sun and the vicinity of active
regions from seeing-free data. We find that magnetic concentrations
are best described as random walkers close to network areas (diffusion
index, γ =1.0), travelers with constant speeds over a supergranule
(γ =1.9{--}2.0), and decelerating movers in the vicinity of flux
emergence and/or within active regions (γ =1.4{--}1.5). The three
types of regions host MBFs with mean diffusion coefficients of 130
km2 s-1, 80-90 km2 s-1,
and 25-70 km2 s-1, respectively. The MBFs in
these three types of regions are found to display a distinct kinematic
behavior at a confidence level in excess of 95%.
Title: Spectropolarimetric Evidence for a Siphon Flow along an
Emerging Magnetic Flux Tube
Authors: Requerey, Iker S.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Blanco Rodríguez, J.; Solanki, S. K.; Barthol,
P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.;
van Noort, M.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...15R
Altcode: 2016arXiv161106732R
We study the dynamics and topology of an emerging magnetic flux
concentration using high spatial resolution spectropolarimetric data
acquired with the Imaging Magnetograph eXperiment on board the sunrise
balloon-borne solar observatory. We obtain the full vector magnetic
field and the line of sight (LOS) velocity through inversions of
the Fe I line at 525.02 nm with the SPINOR code. The derived vector
magnetic field is used to trace magnetic field lines. Two magnetic flux
concentrations with different polarities and LOS velocities are found
to be connected by a group of arch-shaped magnetic field lines. The
positive polarity footpoint is weaker (1100 G) and displays an upflow,
while the negative polarity footpoint is stronger (2200 G) and shows
a downflow. This configuration is naturally interpreted as a siphon
flow along an arched magnetic flux tube.
Title: Morphological Properties of Slender Ca II H Fibrils Observed
by SUNRISE II
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....6G
Altcode: 2016arXiv161200319G
We use seeing-free high spatial resolution Ca II H data obtained by
the SUNRISE observatory to determine properties of slender fibrils
in the lower solar chromosphere. In this work we use intensity images
taken with the SuFI instrument in the Ca II H line during the second
scientific flight of the SUNRISE observatory to identify and track
elongated bright structures. After identification, we analyze theses
structures to extract their morphological properties. We identify
598 slender Ca II H fibrils (SCFs) with an average width of around
180 km, length between 500 and 4000 km, average lifetime of ≈400
s, and average curvature of 0.002 arcsec-1. The maximum
lifetime of the SCFs within our time series of 57 minutes is ≈2000
s. We discuss similarities and differences of the SCFs with other
small-scale, chromospheric structures such as spicules of type I and
II, or Ca II K fibrils.
Title: A New MHD-assisted Stokes Inversion Technique
Authors: Riethmüller, T. L.; Solanki, S. K.; Barthol, P.; Gandorfer,
A.; Gizon, L.; Hirzberger, J.; van Noort, M.; Blanco Rodríguez, J.;
Del Toro Iniesta, J. C.; Orozco Suárez, D.; Schmidt, W.; Martínez
Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...16R
Altcode: 2016arXiv161105175R
We present a new method of Stokes inversion of spectropolarimetric
data and evaluate it by taking the example of a Sunrise/IMaX
observation. An archive of synthetic Stokes profiles is obtained
by the spectral synthesis of state-of-the-art magnetohydrodynamics
(MHD) simulations and a realistic degradation to the level of the
observed data. The definition of a merit function allows the archive
to be searched for the synthetic Stokes profiles that best match the
observed profiles. In contrast to traditional Stokes inversion codes,
which solve the Unno-Rachkovsky equations for the polarized radiative
transfer numerically and fit the Stokes profiles iteratively, the new
technique provides the full set of atmospheric parameters. This gives
us the ability to start an MHD simulation that takes the inversion
result as an initial condition. After a relaxation process of half an
hour solar time we obtain physically consistent MHD data sets with
a target similar to the observation. The new MHD simulation is used
to repeat the method in a second iteration, which further improves
the match between observation and simulation, resulting in a factor
of 2.2 lower mean {χ }2 value. One advantage of the new
technique is that it provides the physical parameters on a geometrical
height scale. It constitutes a first step toward inversions that give
results consistent with the MHD equations.
Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils
from Sunrise/SuFI
Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.;
van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....7G
Altcode: 2017arXiv170102801G
We report the detection of oscillations in slender Ca II H fibrils
(SCFs) from high-resolution observations acquired with the Sunrise
balloon-borne solar observatory. The SCFs show obvious oscillations in
their intensity, but also their width. The oscillatory behaviors are
investigated at several positions along the axes of the SCFs. A large
majority of fibrils show signs of oscillations in intensity. Their
periods and phase speeds are analyzed using a wavelet analysis. The
width and intensity perturbations have overlapping distributions
of the wave period. The obtained distributions have median values
of the period of 32 ± 17 s and 36 ± 25 s, respectively. We
find that the fluctuations of both parameters propagate in
the SCFs with speeds of {11}-11+49 km
s-1 and {15}-15+34 km s-1,
respectively. Furthermore, the width and intensity oscillations have a
strong tendency to be either in anti-phase or, to a smaller extent, in
phase. This suggests that the oscillations of both parameters are caused
by the same wave mode and that the waves are likely propagating. Taking
all the evidence together, the most likely wave mode to explain all
measurements and criteria is the fast sausage mode.
Title: Solar Coronal Loops Associated with Small-scale Mixed Polarity
Surface Magnetic Fields
Authors: Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.;
Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van
Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco
Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....4C
Altcode: 2016arXiv161007484C
How and where are coronal loops rooted in the solar lower
atmosphere? The details of the magnetic environment and its evolution
at the footpoints of coronal loops are crucial to understanding the
processes of mass and energy supply to the solar corona. To address
the above question, we use high-resolution line-of-sight magnetic
field data from the Imaging Magnetograph eXperiment instrument on the
Sunrise balloon-borne observatory and coronal observations from the
Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
of an emerging active region. We find that the coronal loops are
often rooted at the locations with minor small-scale but persistent
opposite-polarity magnetic elements very close to the larger dominant
polarity. These opposite-polarity small-scale elements continually
interact with the dominant polarity underlying the coronal loop through
flux cancellation. At these locations we detect small inverse Y-shaped
jets in chromospheric Ca II H images obtained from the Sunrise Filter
Imager during the flux cancellation. Our results indicate that magnetic
flux cancellation and reconnection at the base of coronal loops due
to mixed polarity fields might be a crucial feature for the supply of
mass and energy into the corona.
Title: Moving Magnetic Features around a Pore
Authors: Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg,
A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; vanNoort,
M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...13K
Altcode: 2016arXiv160905664K
Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013
June, are used for a statistical analysis to determine the physical
properties of moving magnetic features (MMFs) observed near a pore. MMFs
of the same and opposite polarity, with respect to the pore, are found
to stream from its border at an average speed of 1.3 km s-1
and 1.2 km s-1, respectively, with mainly same-polarity MMFs
found further away from the pore. MMFs of both polarities are found to
harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs
are blueshifted, whereas same-polarity MMFs do not show any preference
for up- or downflows. Most of the MMFs are found to be of sub-arcsecond
size and carry a mean flux of ∼1.2 × 1017 Mx.
Title: Construction Status and Early Science with the Daniel K. Inouye
Solar Telescope
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Warner, Mark;
Martinez Pillet, Valentin; Craig, Simon; Woeger, Friedrich; Tritschler,
Alexandra; Berukoff, Steven J.; Casini, Roberto; Goode, Philip R.;
Knoelker, Michael; Kuhn, Jeffrey Richard; Lin, Haosheng; Mathioudakis,
Mihalis; Reardon, Kevin P.; Rosner, Robert; Schmidt, Wolfgang
Bibcode: 2016SPD....4720101M
Altcode:
The 4-m Daniel K. Inouye Solar Telescope (DKIST) is in its seventh
year of overall development and its fourth year of site construction
on the summit of Haleakala, Maui. The Site Facilities (Utility
Building and Support & Operations Building) are in place with
ongoing construction of the Telescope Mount Assembly within. Off-site
the fabrication of the component systems is completing with early
integration testing and verification starting.Once complete this
facility will provide the highest sensitivity and resolution for study
of solar magnetism and the drivers of key processes impacting Earth
(solar wind, flares, coronal mass ejections, and variability in solar
output). The DKIST will be equipped initially with a battery of first
light instruments which cover a spectral range from the UV (380 nm)
to the near IR (5000 nm), and capable of providing both imaging and
spectro-polarimetric measurements throughout the solar atmosphere
(photosphere, chromosphere, and corona); these instruments are being
developed by the National Solar Observatory (Visible Broadband Imager),
High Altitude Observatory (Visible Spectro-Polarimeter), Kiepenheuer
Institute (Visible Tunable Filter) and the University of Hawaii
(Cryogenic Near-Infrared Spectro-Polarimeter and the Diffraction-Limited
Near-Infrared Spectro-Polarimeter). Further, a United Kingdom consortium
led by Queen's University Belfast is driving the development of high
speed cameras essential for capturing the highly dynamic processes
measured by these instruments. Finally, a state-of-the-art adaptive
optics system will support diffraction limited imaging capable of
resolving features approximately 20 km in scale on the Sun.We present
the overall status of the construction phase along with the current
challenges as well as a review of the planned science testing and the
transition into early science operations.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Yuan-Kuen; Moses, John; Laming, John; Strachan, Leonard;
Tun Beltran, Samuel; Tomczyk, Steven; Gibson, Sarah; Auchere, Frederic;
Casini, Roberto; Fineschi, Silvano; Knoelker, Michael; Korendyke,
Clarence; McIntosh, Scott; Romoli, Marco; Rybak, Jan; Socker, Dennis;
Vourlidas, Angelos; Wu, Qian
Bibcode: 2016FrASS...3....1K
Altcode:
Comprehensive measurements of magnetic fields in the solar corona have
a long history as an important scientific goal. Besides being crucial
to understanding coronal structures and the Sun’s generation of space
weather, direct measurements of their strength and direction are also
crucial steps in understanding observed wave motions. In this regard,
the remote sensing instrumentation used to make coronal magnetic field
measurements is well suited to measuring the Doppler signature of waves
in the solar structures. In this paper, we describe the design and
scientific values of the Waves and Magnetism in the Solar Atmosphere
(WAMIS) investigation. WAMIS, taking advantage of greatly improved
infrared filters and detectors, forward models, advanced diagnostic
tools and inversion codes, is a long-duration high-altitude balloon
payload designed to obtain a breakthrough in the measurement of
coronal magnetic fields and in advancing the understanding of the
interaction of these fields with space plasmas. It consists of a 20 cm
aperture coronagraph with a visible-IR spectro-polarimeter focal plane
assembly. The balloon altitude would provide minimum sky background and
atmospheric scattering at the wavelengths in which these observations
are made. It would also enable continuous measurements of the strength
and direction of coronal magnetic fields without interruptions from
the day-night cycle and weather. These measurements will be made
over a large field-of-view allowing one to distinguish the magnetic
signatures of different coronal structures, and at the spatial and
temporal resolutions required to address outstanding problems in
coronal physics. Additionally, WAMIS could obtain near simultaneous
observations of the electron scattered K-corona for context and to
obtain the electron density. These comprehensive observations are not
provided by any current single ground-based or space observatory. The
fundamental advancements achieved by the near-space observations of
WAMIS on coronal field would point the way for future ground based
and orbital instrumentation.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Strachan, L.; Ko, Y. -K.; Moses, J. D.; Laming, J. M.;
Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S.; Knoelker, M.;
Korendyke, C.; Mcintosh, S.; Romoli, M.; Rybak, J.; Socker, D.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
Bibcode: 2015IAUS..305..121S
Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exist only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure, solar
activity, and the role of MHD waves in heating and accelerating the
solar wind. Fortunately, the remote sensing instrumentation used to make
magnetic field measurements is also well suited to measure the Doppler
signature of waves in the solar structures. We present here a mission
concept for the Waves And Magnetism In the Solar Atmosphere (WAMIS)
experiment which is proposed for a NASA long-duration balloon flight.
Title: Daniel K. Inouye Solar Telescope: Overview and Status
Authors: Rimmele, Thomas; McMullin, Joseph; Warner, Mark; Craig,
Simon; Woeger, Friedrich; Tritschler, Alexandra; Cassini, Roberto;
Kuhn, Jeff; Lin, Haosheng; Schmidt, Wolfgang; Berukoff, Steve; Reardon,
Kevin; Goode, Phil; Knoelker, Michael; Rosner, Robert; Mathioudakis,
Mihalis; DKIST TEAM
Bibcode: 2015IAUGA..2255176R
Altcode:
The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under
construction on Haleakala, Maui will be the world’s largest solar
telescope. Designed to meet the needs of critical high resolution and
high sensitivity spectral and polarimetric observations of the sun,
this facility will perform key observations of our nearest star that
matters most to humankind. DKIST’s superb resolution and sensitivity
will enable astronomers to unravel many of the mysteries the Sun
presents, including the origin of solar magnetism, the mechanisms of
coronal heating and drivers of the solar wind, flares, coronal mass
ejections and variability in solar output. The all-reflecting, off-axis
design allows the facility to observe over a broad wavelength range and
enables DKIST to operate as a coronagraph. In addition, the photon flux
provided by its large aperture will be capable of routine and precise
measurements of the currently elusive coronal magnetic fields. The
state-of-the-art adaptive optics system provides diffraction limited
imaging and the ability to resolve features approximately 20 km on
the Sun. Five first light instruments, representing a broad community
effort, will be available at the start of operations: Visible Broadband
Imager (National Solar Observatory), Visible Spectro-Polarimeter (High
Altitude Observatory), Visible Tunable Filter (Kiepenheuer Institute,
Germany), Diffraction Limited NIR Spectro-Polarimeter (University
of Hawaii) and the Cryogenic NIR Spectro-Polarimeter (University of
Hawaii). High speed cameras for capturing highly dynamic processes
in the solar atmosphere are being developed by a UK consortium. Site
construction on Haleakala began in December 2012 and is progressing
on schedule. Operations are scheduled to begin in 2019. We provide an
overview of the facility, discuss the construction status, and present
progress with DKIST operations planning.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Y. K.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson,
S. E.; Knoelker, M.; Korendyke, C.; Laming, J. M.; Mcintosh, S. W.;
Moses, J. D.; Romoli, M.; Rybak, J.; Socker, D. G.; Strachan, L.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
Bibcode: 2014AGUFMSH53B4221K
Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exists only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure,
solar activity and the role of MHD waves in heating and accelerating
the solar wind. Fortunately, the remote sensing instrumentation used
to make magnetic field measurements is also well suited for measuring
the Doppler signature of waves in the solar structures. With this
in mind, we are proposing the WAMIS (Waves and Magnetism in the
Solar Atmosphere) investigation. WAMIS will take advantage of greatly
improved infrared (IR) detectors, forward models, advanced diagnostic
tools and inversion codes to obtain a breakthrough in the measurement
of coronal magnetic fields and in the understanding of the interaction
of these fields with space plasmas. This will be achieved with a high
altitude balloon borne payload consisting of a coronagraph with an IR
spectro-polarimeter focal plane assembly. The balloon platform provides
minimum atmospheric absorption and scattering at the IR wavelengths in
which these observations are made. Additionally, a NASA long duration
balloon flight mission from the Antarctic can achieve continuous
observations over most of a solar rotation, covering all of the key
time scales for the evolution of coronal magnetic fields. With these
improvements in key technologies along with experience gained from
current ground-based instrumentation, WAMIS will provide a low-cost
mission with a high technology readiness leve.
Title: Comparison between Mg II k and Ca II H Images Recorded by
SUNRISE/SuFI
Authors: Danilovic, S.; Hirzberger, J.; Riethmüller, T. L.; Solanki,
S. K.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Gizon, L.; Knölker,
M.; Schmidt, W.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.
Bibcode: 2014ApJ...784...20D
Altcode:
We present a comparison of high-resolution images of the solar surface
taken in the Mg II k and Ca II H channels of the Filter Imager on the
balloon-borne solar observatory SUNRISE. The Mg and Ca lines are sampled
with 0.48 nm and 0.11 nm wide filters, respectively. The two channels
show remarkable qualitative and quantitative similarities in the quiet
Sun, in an active region plage and during a small flare. However, the Mg
filtergrams display 1.4-1.7 times higher intensity contrast and appear
more smeared and smoothed in the quiet Sun. In addition, the fibrils
in a plage are wider. Although the exposure time is 100 times longer
for Mg images, the evidence suggests that these differences cannot be
explained only with instrumental effects or the evolution of the solar
scene. The differences at least partially arise because of different
line-formation heights, the stronger response of Mg k emission peaks
to the higher temperatures, and the larger height range sampled by
the broad Mg filter used here. This is evidently manifested during
the flare when a surge in Mg evolves differently than in Ca.
Title: First High-resolution Images of the Sun in the 2796 Å Mg II
k Line
Authors: Riethmüller, T. L.; Solanki, S. K.; Hirzberger, J.;
Danilovic, S.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Gizon, L.;
Knölker, M.; Schmidt, W.; Del Toro Iniesta, J. C.
Bibcode: 2013ApJ...776L..13R
Altcode: 2013arXiv1309.5213R
We present the first high-resolution solar images in the Mg II k 2796
Å line. The images, taken through a 4.8 Å broad interference filter,
were obtained during the second science flight of Sunrise in 2013 June
by the Sunrise Filter Imager (SuFI) instrument. The Mg II k images
display structures that look qualitatively very similar to images taken
in the core of Ca II H. The Mg II images exhibit reversed granulation
(or shock waves) in the internetwork regions of the quiet Sun, at
intensity contrasts that are similar to those found in Ca II H. Very
prominent in Mg II are bright points, both in the quiet Sun and in plage
regions, particularly near the disk center. These are much brighter than
at other wavelengths sampled at similar resolution. Furthermore, Mg II k
images also show fibril structures associated with plage regions. Again,
the fibrils are similar to those seen in Ca II H images, but tend to
be more pronounced, particularly in weak plage.
Title: The Advanced Technology Solar Telescope: Science Drivers and
Construction Status
Authors: Rimmele, Thomas; Berger, Thomas; McMullin, Joseph; Keil,
Stephen; Goode, Phil; Knoelker, Michael; Kuhn, Jeff; Rosner, Robert;
Casini, Roberto; Lin, Haosheng; Woeger, Friedrich; von der Luehe,
Oskar; Tritschler, Alexandra; Atst Team
Bibcode: 2013EGUGA..15.6305R
Altcode:
The 4-meter Advance Technology Solar Telescope (ATST) currently
under construction on the 3000 meter peak of Haleakala on Maui,
Hawaii will be the world's most powerful solar telescope and the
leading ground-based resource for studying solar magnetism. The
solar atmosphere is permeated by a 'magnetic carpet' that constantly
reweaves itself to control solar irradiance and its effects on Earth's
climate, the solar wind, and space weather phenomena such as flares and
coronal mass ejections. Precise measurement of solar magnetic fields
requires a large-aperture solar telescope capable of resolving a few
tens of kilometers on the solar surface. With its 4 meter aperture,
the ATST will for the first time resolve magnetic structure at the
intrinsic scales of plasma convection and turbulence. The ATST's
ability to perform accurate and precise spectroscopic and polarimetric
measurements of magnetic fields in all layers of the solar atmosphere,
including accurate mapping of the elusive coronal magnetic fields,
will be transformative in advancing our understanding of the magnetic
solar atmosphere. The ATST will utilize the Sun as an important astro-
and plasma-physics "laboratory" demonstrating key aspects of omnipresent
cosmic magnetic fields. The ATST construction effort is led by the US
National Solar Observatory. State-of-the-art instrumentation will be
constructed by US and international partner institutions. The technical
challenges the ATST is facing are numerous and include the design of the
off-axis main telescope, the development of a high order adaptive optics
system that delivers a corrected beam to the instrument laboratory,
effective handling of the solar heat load on optical and structural
elements, and minimizing scattered light to enable observations
of the faint corona. The ATST project has transitioned from design
and development to its construction phase. The project has awarded
design and fabrication contracts for major telescope subsystems. Site
construction has commenced following the successful conclusion of
the site permitting process. Science goals and construction status of
telescope and instrument systems will be discussed.
Title: Evolution of the Fine Structure of Magnetic Fields in the
Quiet Sun: Observations from Sunrise/IMaX and Extrapolations
Authors: Wiegelmann, T.; Solanki, S. K.; Borrero, J. M.; Peter,
H.; Barthol, P.; Gandorfer, A.; Martínez Pillet, V.; Schmidt, W.;
Knölker, M.
Bibcode: 2013SoPh..283..253W
Altcode:
Observations with the balloon-borne Sunrise/Imaging Magnetograph
eXperiment (IMaX) provide high spatial resolution (roughly 100 km at
disk center) measurements of the magnetic field in the photosphere of
the quiet Sun. To investigate the magnetic structure of the chromosphere
and corona, we extrapolate these photospheric measurements into
the upper solar atmosphere and analyze a 22-minute long time series
with a cadence of 33 seconds. Using the extrapolated magnetic-field
lines as tracer, we investigate temporal evolution of the magnetic
connectivity in the quiet Sun's atmosphere. The majority of magnetic
loops are asymmetric in the sense that the photospheric field strength
at the loop foot points is very different. We find that the magnetic
connectivity of the loops changes rapidly with a typical connection
recycling time of about 3±1 minutes in the upper solar atmosphere and
12±4 minutes in the photosphere. This is considerably shorter than
previously found. Nonetheless, our estimate of the energy released by
the associated magnetic-reconnection processes is not likely to be the
sole source for heating the chromosphere and corona in the quiet Sun.
Title: Construction of the Advanced Technology Solar Telescope -
A Progress Report.
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Goode, P. R.;
Knoelker, M.; Kuhn, J. R.; Rosner, R.; ATST Team
Bibcode: 2012IAUSS...6E.206R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading ground-based resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. The ATST
will provide high resolution and high sensitivity observations of the
dynamic solar magnetic fields throughout the solar atmosphere, including
the corona at infrared wavelengths. With its 4 m aperture, ATST will
resolve magnetic features at their intrinsic scales. A high order
adaptive optics system delivers a corrected beam to the initial set of
five state-of-the-art, facility class instrumentation located in the
coude laboratory facility. Photopheric and chromospheric magnetometry
is part of the key mission of four of these instruments. Coronal
magnetometry and spectroscopy will be performed by two of these
instruments at infrared wavelengths. The ATST project has transitioned
from design and development to its construction phase. Site construction
is expected to begin in the first half of 2012. The project has awarded
design and fabrication contracts for major telescope subsystems. A
robust instrument program has been established and all instruments
have passed preliminary design reviews or critical design reviews. A
brief summary of the science goals and observational requirements of
the ATST will be given, followed by a summary of the project status of
the telescope and discussion of the approach to integrating instruments
into the facility.
Title: Construction of the Advanced Technology Solar Telescope
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Knölker, M.; Kuhn,
J. R.; Goode, P. R.; Rosner, R.; Casini, R.; Lin, H.; Tritschler,
A.; Wöger, F.; ATST Team
Bibcode: 2012ASPC..463..377R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading ground-based resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. The
project has entered its construction phase. Major subsystems have
been contracted. As its highest priority science driver ATST shall
provide high resolution and high sensitivity observations of the
dynamic solar magnetic fields throughout the solar atmosphere,
including the corona at infrared wavelengths. With its 4m aperture,
ATST will resolve features at 0.″03 at visible wavelengths and
obtain 0.″1 resolution at the magnetically highly sensitive near
infrared wavelengths. A high order adaptive optics system delivers a
corrected beam to the initial set of state-of-the-art, facility class
instrumentation located in the Coudé laboratory facility. The initial
set of first generation instruments consists of five facility class
instruments, including imagers and spectro-polarimeters. The high
polarimetric sensitivity and accuracy required for measurements of
the illusive solar magnetic fields place strong constraints on the
polarization analysis and calibration. Development and construction
of a four-meter solar telescope presents many technical challenges,
including thermal control of the enclosure, telescope structure and
optics and wavefront control. A brief overview of the science goals
and observational requirements of the ATST will be given, followed by a
summary of the design status of the telescope and its instrumentation,
including design status of major subsystems, such as the telescope
mount assembly, enclosure, mirror assemblies, and wavefront correction
Title: 2nd ATST-EAST Workshop in Solar Physics: Magnetic Fields from
the Photosphere to the Corona
Authors: Rimmele, T. R.; Tritschler, A.; Wöger, F.; Collados Vera,
M.; Socas-Navarro, H.; Schlichenmaier, R.; Carlsson, M.; Berger, T.;
Cadavid, A.; Gilbert, P. R.; Goode, P. R.; Knölker, M.
Bibcode: 2012ASPC..463.....R
Altcode:
No abstract at ADS
Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
W.; Steiner, O.; Title, A. M.
Bibcode: 2012ASPC..455..143S
Altcode:
The SUNRISE balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that reveal the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the SUNRISE data, which include a number of discoveries.
Title: Advanced Technology Solar Telescope Construction: Progress
Report
Authors: Rimmele, Thomas R.; McMullin, J.; Keil, S.; Goode, P.;
Knoelker, M.; Kuhn, J.; Rosner, R.; ATST Team
Bibcode: 2012AAS...22012202R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) on Haleakala will be
the most powerful solar telescope and the world’s leading ground-based
resource for studying solar magnetism that controls the solar wind,
flares, coronal mass ejections and variability in the Sun’s
output. The ATST will provide high resolution and high sensitivity
observations of the dynamic solar magnetic fields throughout the solar
atmosphere, including the corona at infrared wavelengths. With its 4
m aperture, ATST will resolve magnetic features at their intrinsic
scales. A high order adaptive optics system delivers a corrected
beam to the initial set of five state-of-the-art, facility class
instrumentation located in the coude laboratory facility. Photopheric
and chromospheric magnetometry is part of the key mission of four
of these instruments. Coronal magnetometry and spectroscopy will be
performed by two of these instruments at infrared wavelengths. The
ATST project has transitioned from design and development to its
construction phase. Site construction is expected to begin in April
2012. The project has awarded design and fabrication contracts for major
telescope subsystems. A robust instrument program has been established
and all instruments have passed preliminary design reviews or critical
design reviews. A brief overview of the science goals and observational
requirements of the ATST will be given, followed by a summary of the
project status of the telescope and discussion of the approach to
integrating instruments into the facility. The National Science
Foundation (NSF) through the National Solar Observatory (NSO) funds
the ATST Project. The NSO is operated under a cooperative agreement
between the Association of Universities for Research in Astronomy,
Inc. (AURA) and NSF.
Title: Detection of Vortex Tubes in Solar Granulation from
Observations SUNRISE
Authors: Steiner, O.; Franz, M.; González, N. B.; Nutto, C.; Rezaei,
R.; Pillet, V. M.; Bonet, J. A.; Iniesta, J. C. d. T.; Domingo, V.;
Solanki, S. K.; Knölker, M.; Schmidt, W.; Barthol, P.; Gandorfer, A.
Bibcode: 2012ASPC..455...35S
Altcode:
We investigated a time series of continuum intensity maps and
Dopplergrams of granulation in a very quiet solar region at the disk
center, recorded with the Imaging Magnetograph eXperiment (IMaX)
on board the balloon-borne solar observatory SUNRISE. We find that
granules frequently show substructure in the form of lanes composed of
a leading bright rim and a trailing dark edge, which move together
from the boundary of a granule into the granule itself. We find
strikingly similar events in synthesized intensity maps from an ab
initio numerical simulation of solar surface convection. We conclude
that these granular lanes are the visible signature of (horizontally
oriented) vortex tubes. The characteristic optical appearance of vortex
tubes at the solar surface is explained. This paper is a summary and
update of the results previously presented in Steiner et al. (2010).
Title: Sunrise - Prospects for the Second Science Flight
Authors: Knoelker, Michael
Bibcode: 2012AAS...22020618K
Altcode:
The Sunrise balloon-borne solar observatory had a first successful
science flight in June of 2009. Sunrise included of a 1m aperture
Gregory telescope, a filter imager observing at 214, 300, 312, 388
and 397 nm and an imaging vector polarimeter observing in the Fe I
5250.2 line. An image stabilization system allowed for high-quality
data at a resolution of around 100 km in the quiet Sun. Observations
of unprecedented quality of magneto-convective processes were
achieved. Extensive analysis of flight engineering data and the science
data led to an impressive number of significant publications. For
the proposed second science flight improvements in the pointing and
stabilization system will be employed. The addition of a magnetometer
for the red-to-near-infrared wavelength range would allow for extending
the high-resolution observations into the chromosphere. The
anticipated flight in June of 2013 will allow for study of large
structures such as sunspots.
Title: Diffusivity of Isolated Internetwork Ca II H Bright Points
Observed by SuFI/SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.;
Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A.
Bibcode: 2012decs.confE..99J
Altcode:
We analyze trajectories of the proper motion of intrinsically magnetic,
isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to
obtain their diffusivity behaviors. We use high spatial and temporal
resolution image sequences of quiet-Sun, disc-centre observations
obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager
(SuFI) on board the SUNRISE balloon-borne solar observatory. In
order to avoid misidentification, the BPs are semi-manually selected
and then automatically tracked. The trajectory of each BP is then
calculated and its diffusion index is described by a power law
exponent, using which we classify the BPs' trajectories into sub-,
normal and super- diffusive. In addition, the corresponding diffusion
coefficients (D) based on the observed displacements are consequently
computed. We find a strong super-diffusivity at a height sampled by the
SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to
the temperature minimum). We find that 74% of the identified tiny BPs
are super-diffusive, 18% move randomly (i.e. their motion corresponds
to normal diffusion) and only 8% belong to the sub-diffusion regime. In
addition, we find that 53% of the super-diffusion regime (i.e. 39% of
all BPs) have the diffusivity index of 2 which are termed as "Ballistic
BPs". Finally, we explore the distribution of diffusion index with the
help of a simple simulation. The results suggest that the BPs are random
walkers superposed by a systematic (background) velocity in which the
magnitude of each component (and hence their ratio) depends on the time
and spatial scales. We further discuss a simple sketch to explain the
diffusivity of observed BPs while they migrate within a supergranule
(i.e. internetwork areas) or close to the network regions.
Title: The Frontier between Small-scale Bipoles and Ephemeral Regions
in the Solar Photosphere: Emergence and Decay of an Intermediate-scale
Bipole Observed with SUNRISE/IMaX
Authors: Guglielmino, S. L.; Martínez Pillet, V.; Bonet, J. A.;
del Toro Iniesta, J. Carlos; Bellot Rubio, L. R.; Solanki, S. K.;
Schmidt, W.; Gandorfer, A.; Barthol, P.; Knölker, M.
Bibcode: 2012ApJ...745..160G
Altcode: 2011arXiv1110.1405G
We report on the photospheric evolution of an intermediate-scale (≈4
Mm footpoint separation) magnetic bipole, from emergence to decay,
observed in the quiet Sun at high spatial (0farcs3) and temporal (33 s)
resolution. The observations were acquired by the Imaging Magnetograph
Experiment imaging magnetograph during the first science flight of the
SUNRISE balloon-borne solar observatory. The bipole flux content is 6 ×
1017 Mx, representing a structure bridging the gap between
granular scale bipoles and the smaller ephemeral regions. Footpoints
separate at a speed of 3.5 km s-1 and reach a maximum
distance of 4.5 Mm before the field dissolves. The evolution of the
bipole is revealed to be very dynamic: we found a proper motion of
the bipole axis and detected a change of the azimuth angle of 90° in
300 s, which may indicate the presence of some writhe in the emerging
structure. The overall morphology and behavior are in agreement with
previous analyses of bipolar structures emerging at the granular scale,
but we also found several similarities with emerging flux structures
at larger scales. The flux growth rate is 2.6 × 1015 Mx
s-1, while the mean decay rate is one order of magnitude
smaller. We describe in some detail the decay phase of the bipole
footpoints that includes break up into smaller structures, and
interaction with preexisting fields leading to cancellation, but it
appears to be dominated by an as-yet unidentified diffusive process
that removes most of the flux with an exponential flux decay curve. The
diffusion constant (8 × 102 km2 s-1)
associated with this decay is similar to the values used to describe
the large-scale diffusion in flux transport models.
Title: Magnetic field emergence in mesogranular-sized exploding
granules observed with sunrise/IMaX data
Authors: Palacios, J.; Blanco Rodríguez, J.; Vargas Domínguez, S.;
Domingo, V.; Martínez Pillet, V.; Bonet, J. A.; Bellot Rubio, L. R.;
Del Toro Iniesta, J. C.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Berkefeld, T.; Schmidt, W.; Knölker, M.
Bibcode: 2012A&A...537A..21P
Altcode: 2011arXiv1110.4555P
We report on magnetic field emergences covering significant
areas of exploding granules. The balloon-borne mission Sunrise
provided high spatial and temporal resolution images of the solar
photosphere. Continuum images, longitudinal and transverse magnetic
field maps and Dopplergrams obtained by IMaX onboard Sunrise are
analyzed by local correlation traking (LCT), divergence calculation
and time slices, Stokes inversions and numerical simulations are also
employed. We characterize two mesogranular-scale exploding granules
where ~1018 Mx of magnetic flux emerges. The emergence
of weak unipolar longitudinal fields (~100 G) start with a single
visible magnetic polarity, occupying their respective granules' top
and following the granular splitting. After a while, mixed polarities
start appearing, concentrated in downflow lanes. The events last around
20 min. LCT analyses confirm mesogranular scale expansion, displaying
a similar pattern for all the physical properties, and divergence
centers match between all of them. We found a similar behaviour
with the emergence events in a numerical MHD simulation. Granule
expansion velocities are around 1 kms-1 while magnetic
patches expand at 0.65 kms-1. One of the analyzed events
evidences the emergence of a loop-like structure. Advection of
the emerging magnetic flux features is dominated by convective
motion resulting from the exploding granule due to the magnetic
field frozen in the granular plasma. Intensification of the
magnetic field occurs in the intergranular lanes, probably
because of being directed by the downflowing plasma. Movies
associated to Figs. 2-4 are available in electronic form at http://www.aanda.org
Title: The Sun at high resolution: first results from the Sunrise
mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller,
A.; Gandorfer, A.; Hirzberger, J.; Lagg, A.; Riethmüller, T. L.;
Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; Pillet, V. Martínez;
Khomenko, E.; del Toro Iniesta, J. C.; Domingo, V.; Palacios, J.;
Knölker, M.; González, N. Bello; Borrero, J. M.; Berkefeld, T.;
Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M.
Bibcode: 2011IAUS..273..226S
Altcode:
The Sunrise balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system and further infrastructure. The first
science flight of Sunrise yielded high-quality data that reveal the
structure, dynamics and evolution of solar convection, oscillations
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the Sunrise data, which include a number of discoveries.
Title: Mesogranulation and the Solar Surface Magnetic Field
Distribution
Authors: Yelles Chaouche, L.; Moreno-Insertis, F.; Martínez Pillet,
V.; Wiegelmann, T.; Bonet, J. A.; Knölker, M.; Bellot Rubio, L. R.;
del Toro Iniesta, J. C.; Barthol, P.; Gandorfer, A.; Schmidt, W.;
Solanki, S. K.
Bibcode: 2011ApJ...727L..30Y
Altcode: 2010arXiv1012.4481Y
The relation of the solar surface magnetic field with mesogranular
cells is studied using high spatial (≈100 km) and temporal (≈30
s) resolution data obtained with the IMaX instrument on board
SUNRISE. First, mesogranular cells are identified using Lagrange
tracers (corks) based on horizontal velocity fields obtained through
local correlation tracking. After ≈20 minutes of integration, the
tracers delineate a sharp mesogranular network with lanes of width
below about 280 km. The preferential location of magnetic elements in
mesogranular cells is tested quantitatively. Roughly 85% of pixels with
magnetic field higher than 100 G are located in the near neighborhood
of mesogranular lanes. Magnetic flux is therefore concentrated in
mesogranular lanes rather than intergranular ones. Second, magnetic
field extrapolations are performed to obtain field lines anchored in
the observed flux elements. This analysis, therefore, is independent
of the horizontal flows determined in the first part. A probability
density function (PDF) is calculated for the distribution of distances
between the footpoints of individual magnetic field lines. The PDF has
an exponential shape at scales between 1 and 10 Mm, with a constant
characteristic decay distance, indicating the absence of preferred
convection scales in the mesogranular range. Our results support
the view that mesogranulation is not an intrinsic convective scale
(in the sense that it is not a primary energy-injection scale of solar
convection), but also give quantitative confirmation that, nevertheless,
the magnetic elements are preferentially found along mesogranular lanes.
Title: The Imaging Magnetograph eXperiment (IMaX) for the Sunrise
Balloon-Borne Solar Observatory
Authors: Martínez Pillet, V.; del Toro Iniesta, J. C.;
Álvarez-Herrero, A.; Domingo, V.; Bonet, J. A.; González Fernández,
L.; López Jiménez, A.; Pastor, C.; Gasent Blesa, J. L.; Mellado, P.;
Piqueras, J.; Aparicio, B.; Balaguer, M.; Ballesteros, E.; Belenguer,
T.; Bellot Rubio, L. R.; Berkefeld, T.; Collados, M.; Deutsch, W.;
Feller, A.; Girela, F.; Grauf, B.; Heredero, R. L.; Herranz, M.;
Jerónimo, J. M.; Laguna, H.; Meller, R.; Menéndez, M.; Morales, R.;
Orozco Suárez, D.; Ramos, G.; Reina, M.; Ramos, J. L.; Rodríguez,
P.; Sánchez, A.; Uribe-Patarroyo, N.; Barthol, P.; Gandorfer, A.;
Knoelker, M.; Schmidt, W.; Solanki, S. K.; Vargas Domínguez, S.
Bibcode: 2011SoPh..268...57M
Altcode: 2010SoPh..tmp..181M; 2010arXiv1009.1095M
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter
built by four institutions in Spain that flew on board the Sunrise
balloon-borne solar observatory in June 2009 for almost six days over
the Arctic Circle. As a polarimeter, IMaX uses fast polarization
modulation (based on the use of two liquid crystal retarders),
real-time image accumulation, and dual-beam polarimetry to reach
polarization sensitivities of 0.1%. As a spectrograph, the instrument
uses a LiNbO3 etalon in double pass and a narrow band
pre-filter to achieve a spectral resolution of 85 mÅ. IMaX uses the
high-Zeeman-sensitive line of Fe I at 5250.2 Å and observes all four
Stokes parameters at various points inside the spectral line. This
allows vector magnetograms, Dopplergrams, and intensity frames to be
produced that, after reconstruction, reach spatial resolutions in the
0.15 - 0.18 arcsec range over a 50×50 arcsec field of view. Time
cadences vary between 10 and 33 s, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in
various ways depending on the applied observing mode, from just two
points inside the line to 11 of them. All observing modes include
one extra wavelength point in the nearby continuum. Gauss equivalent
sensitivities are 4 G for longitudinal fields and 80 G for transverse
fields per wavelength sample. The line-of-sight velocities are estimated
with statistical errors of the order of 5 - 40 m s−1. The
design, calibration, and integration phases of the instrument,
together with the implemented data reduction scheme, are described in
some detail.
Title: The Wave-Front Correction System for the Sunrise Balloon-Borne
Solar Observatory
Authors: Berkefeld, T.; Schmidt, W.; Soltau, D.; Bell, A.;
Doerr, H. P.; Feger, B.; Friedlein, R.; Gerber, K.; Heidecke, F.;
Kentischer, T.; v. d. Lühe, O.; Sigwarth, M.; Wälde, E.; Barthol,
P.; Deutsch, W.; Gandorfer, A.; Germerott, D.; Grauf, B.; Meller, R.;
Álvarez-Herrero, A.; Knölker, M.; Martínez Pillet, V.; Solanki,
S. K.; Title, A. M.
Bibcode: 2011SoPh..268..103B
Altcode: 2010SoPh..tmp..236B; 2010arXiv1009.3196B
This paper describes the wave-front correction system developed for
the Sunrise balloon telescope, and it provides information about its
in-flight performance. For the correction of low-order aberrations,
a Correlating Wave-Front Sensor (CWS) was used. It consisted of a
six-element Shack - Hartmann wave-front sensor (WFS), a fast tip-tilt
mirror for the compensation of image motion, and an active telescope
secondary mirror for focus correction. The CWS delivered a stabilized
image with a precision of 0.04 arcsec (rms), whenever the coarse
pointing was better than ± 45 arcsec peak-to-peak. The automatic
focus adjustment maintained a focus stability of 0.01 waves in the
focal plane of the CWS. During the 5.5 day flight, good image quality
and stability were achieved during 33 hours, containing 45 sequences,
which lasted between 10 and 45 min.
Title: The Sunrise Mission
Authors: Barthol, P.; Gandorfer, A.; Solanki, S. K.; Schüssler,
M.; Chares, B.; Curdt, W.; Deutsch, W.; Feller, A.; Germerott, D.;
Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.; Meller, R.;
Müller, R.; Riethmüller, T. L.; Tomasch, G.; Knölker, M.; Lites,
B. W.; Card, G.; Elmore, D.; Fox, J.; Lecinski, A.; Nelson, P.;
Summers, R.; Watt, A.; Martínez Pillet, V.; Bonet, J. A.; Schmidt,
W.; Berkefeld, T.; Title, A. M.; Domingo, V.; Gasent Blesa, J. L.;
del Toro Iniesta, J. C.; López Jiménez, A.; Álvarez-Herrero, A.;
Sabau-Graziati, L.; Widani, C.; Haberler, P.; Härtel, K.; Kampf,
D.; Levin, T.; Pérez Grande, I.; Sanz-Andrés, A.; Schmidt, E.
Bibcode: 2011SoPh..268....1B
Altcode: 2010arXiv1009.2689B; 2010SoPh..tmp..224B
The first science flight of the balloon-borne Sunrise telescope took
place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset
Island in northern Canada. We describe the scientific aims and
mission concept of the project and give an overview and a description
of the various hardware components: the 1-m main telescope with its
postfocus science instruments (the UV filter imager SuFI and the imaging
vector magnetograph IMaX) and support instruments (image stabilizing
and light distribution system ISLiD and correlating wavefront sensor
CWS), the optomechanical support structure and the instrument mounting
concept, the gondola structure and the power, pointing, and telemetry
systems, and the general electronics architecture. We also explain
the optimization of the structural and thermal design of the complete
payload. The preparations for the science flight are described,
including AIV and ground calibration of the instruments. The course
of events during the science flight is outlined, up to the recovery
activities. Finally, the in-flight performance of the instrumentation
is discussed.
Title: The Filter Imager SuFI and the Image Stabilization and Light
Distribution System ISLiD of the Sunrise Balloon-Borne Observatory:
Instrument Description
Authors: Gandorfer, A.; Grauf, B.; Barthol, P.; Riethmüller, T. L.;
Solanki, S. K.; Chares, B.; Deutsch, W.; Ebert, S.; Feller, A.;
Germerott, D.; Heerlein, K.; Heinrichs, J.; Hirche, D.; Hirzberger,
J.; Kolleck, M.; Meller, R.; Müller, R.; Schäfer, R.; Tomasch,
G.; Knölker, M.; Martínez Pillet, V.; Bonet, J. A.; Schmidt, W.;
Berkefeld, T.; Feger, B.; Heidecke, F.; Soltau, D.; Tischenberg, A.;
Fischer, A.; Title, A.; Anwand, H.; Schmidt, E.
Bibcode: 2011SoPh..268...35G
Altcode: 2010SoPh..tmp..176G; 2010arXiv1009.1037G
We describe the design of the Sunrise Filter Imager (SuFI) and the
Image Stabilization and Light Distribution (ISLiD) unit onboard the
Sunrise balloon borne solar observatory. This contribution provides the
necessary information which is relevant to understand the instruments'
working principles, the relevant technical data, and the necessary
information about calibration issues directly related to the science
data.
Title: SUNRISE: Instrument, Mission, Data, and First Results
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Riethmüller, T. L.; Schüssler, M.;
Bonet, J. A.; Martínez Pillet, V.; del Toro Iniesta, J. C.; Domingo,
V.; Palacios, J.; Knölker, M.; Bello González, N.; Berkefeld, T.;
Franz, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.127S
Altcode: 2010arXiv1008.3460S
The SUNRISE balloon-borne solar observatory consists of a 1 m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that revealed the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. After a brief description of instruments and data, the first
qualitative results are presented. In contrast to earlier observations,
we clearly see granulation at 214 nm. Images in Ca II H display narrow,
short-lived dark intergranular lanes between the bright edges of
granules. The very small-scale, mixed-polarity internetwork fields
are found to be highly dynamic. A significant increase in detectable
magnetic flux is found after phase-diversity-related reconstruction
of polarization maps, indicating that the polarities are mixed right
down to the spatial resolution limit and probably beyond.
Title: Supersonic Magnetic Upflows in Granular Cells Observed with
SUNRISE/IMAX
Authors: Borrero, J. M.; Martínez-Pillet, V.; Schlichenmaier, R.;
Solanki, S. K.; Bonet, J. A.; del Toro Iniesta, J. C.; Schmidt, W.;
Barthol, P.; Gandorfer, A.; Domingo, V.; Knölker, M.
Bibcode: 2010ApJ...723L.144B
Altcode: 2010arXiv1009.1227B
Using the IMaX instrument on board the SUNRISE stratospheric balloon
telescope, we have detected extremely shifted polarization signals
around the Fe I 5250.217 Å spectral line within granules in the solar
photosphere. We interpret the velocities associated with these events
as corresponding to supersonic and magnetic upflows. In addition, they
are also related to the appearance of opposite polarities and highly
inclined magnetic fields. This suggests that they are produced by the
reconnection of emerging magnetic loops through granular upflows. The
events occupy an average area of 0.046 arcsec2 and last for
about 80 s, with larger events having longer lifetimes. These supersonic
events occur at a rate of 1.3 × 10-5 occurrences per second
per arcsec2.
Title: Detection of Vortex Tubes in Solar Granulation from
Observations with SUNRISE
Authors: Steiner, O.; Franz, M.; Bello González, N.; Nutto, Ch.;
Rezaei, R.; Martínez Pillet, V.; Bonet Navarro, J. A.; del Toro
Iniesta, J. C.; Domingo, V.; Solanki, S. K.; Knölker, M.; Schmidt,
W.; Barthol, P.; Gandorfer, A.
Bibcode: 2010ApJ...723L.180S
Altcode: 2010arXiv1009.4723S
We have investigated a time series of continuum intensity maps and
corresponding Dopplergrams of granulation in a very quiet solar region
at the disk center, recorded with the Imaging Magnetograph eXperiment
(IMaX) on board the balloon-borne solar observatory SUNRISE. We
find that granules frequently show substructure in the form of lanes
composed of a leading bright rim and a trailing dark edge, which move
together from the boundary of a granule into the granule itself. We
find strikingly similar events in synthesized intensity maps from an
ab initio numerical simulation of solar surface convection. From cross
sections through the computational domain of the simulation, we conclude
that these granular lanes are the visible signature of (horizontally
oriented) vortex tubes. The characteristic optical appearance of vortex
tubes at the solar surface is explained. We propose that the observed
vortex tubes may represent only the large-scale end of a hierarchy of
vortex tubes existing near the solar surface.
Title: Where the Granular Flows Bend
Authors: Khomenko, E.; Martínez Pillet, V.; Solanki, S. K.; del Toro
Iniesta, J. C.; Gandorfer, A.; Bonet, J. A.; Domingo, V.; Schmidt,
W.; Barthol, P.; Knölker, M.
Bibcode: 2010ApJ...723L.159K
Altcode: 2010arXiv1008.0517K
Based on IMaX/SUNRISE data, we report on a previously undetected
phenomenon in solar granulation. We show that in a very narrow region
separating granules and intergranular lanes, the spectral line width
of the Fe I 5250.2 Å line becomes extremely small. We offer an
explanation of this observation with the help of magneto-convection
simulations. These regions with extremely small line widths correspond
to the places where the granular flows bend from upflow in granules
to downflow in intergranular lanes. We show that the resolution and
image stability achieved by IMaX/SUNRISE are important requisites to
detect this interesting phenomenon.
Title: Bright Points in the Quiet Sun as Observed in the Visible
and Near-UV by the Balloon-borne Observatory SUNRISE
Authors: Riethmüller, T. L.; Solanki, S. K.; Martínez Pillet, V.;
Hirzberger, J.; Feller, A.; Bonet, J. A.; Bello González, N.; Franz,
M.; Schüssler, M.; Barthol, P.; Berkefeld, T.; del Toro Iniesta,
J. C.; Domingo, V.; Gandorfer, A.; Knölker, M.; Schmidt, W.
Bibcode: 2010ApJ...723L.169R
Altcode: 2010arXiv1009.1693R
Bright points (BPs) are manifestations of small magnetic elements
in the solar photosphere. Their brightness contrast not only gives
insight into the thermal state of the photosphere (and chromosphere) in
magnetic elements, but also plays an important role in modulating the
solar total and spectral irradiance. Here, we report on simultaneous
high-resolution imaging and spectropolarimetric observations of
BPs using SUNRISE balloon-borne observatory data of the quiet Sun
at the disk center. BP contrasts have been measured between 214 nm
and 525 nm, including the first measurements at wavelengths below
388 nm. The histograms of the BP peak brightness show a clear trend
toward broader contrast distributions and higher mean contrasts at
shorter wavelengths. At 214 nm, we observe a peak brightness of up to
five times the mean quiet-Sun value, the highest BP contrast so far
observed. All BPs are associated with a magnetic signal, although in
a number of cases it is surprisingly weak. Most of the BPs show only
weak downflows, the mean value being 240 m s-1, but some
display strong down- or upflows reaching a few km s-1.
Title: Transverse Component of the Magnetic Field in the Solar
Photosphere Observed by SUNRISE
Authors: Danilovic, S.; Beeck, B.; Pietarila, A.; Schüssler, M.;
Solanki, S. K.; Martínez Pillet, V.; Bonet, J. A.; del Toro Iniesta,
J. C.; Domingo, V.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.149D
Altcode: 2010arXiv1008.1535D
We present the first observations of the transverse component of
a photospheric magnetic field acquired by the imaging magnetograph
SUNRISE/IMaX. Using an automated detection method, we obtain statistical
properties of 4536 features with significant linear polarization
signal. We obtain a rate of occurrence of 7 × 10-4
s-1 arcsec-2, which is 1-2 orders of magnitude
larger than the values reported by previous studies. We show that
these features have no characteristic size or lifetime. They appear
preferentially at granule boundaries with most of them being caught
in downflow lanes at some point. Only a small percentage are entirely
and constantly embedded in upflows (16%) or downflows (8%).
Title: Detection of Large Acoustic Energy Flux in the Solar Atmosphere
Authors: Bello González, N.; Franz, M.; Martínez Pillet, V.; Bonet,
J. A.; Solanki, S. K.; del Toro Iniesta, J. C.; Schmidt, W.; Gandorfer,
A.; Domingo, V.; Barthol, P.; Berkefeld, T.; Knölker, M.
Bibcode: 2010ApJ...723L.134B
Altcode: 2010arXiv1009.4795B
We study the energy flux carried by acoustic waves excited by convective
motions at sub-photospheric levels. The analysis of high-resolution
spectropolarimetric data taken with IMaX/SUNRISE provides a total
energy flux of ~6400-7700 W m-2 at a height of ~250 km
in the 5.2-10 mHz range, i.e., at least twice the largest energy
flux found in previous works. Our estimate lies within a factor of
two of the energy flux needed to balance radiative losses from the
chromosphere according to the estimates of Anderson & Athay and
revives interest in acoustic waves for transporting energy to the
chromosphere. The acoustic flux is mainly found in the intergranular
lanes but also in small rapidly evolving granules and at the bright
borders, forming dark dots and lanes of splitting granules.
Title: Discovery of a 1.6 Year Magnetic Activity Cycle in the
Exoplanet Host Star ι Horologii
Authors: Metcalfe, T. S.; Basu, S.; Henry, T. J.; Soderblom, D. R.;
Judge, P. G.; Knölker, M.; Mathur, S.; Rempel, M.
Bibcode: 2010ApJ...723L.213M
Altcode: 2010arXiv1009.5399M
The Mount Wilson Ca HK survey revealed magnetic activity variations in
a large sample of solar-type stars with timescales ranging from 2.5
to 25 years. This broad range of cycle periods is thought to reflect
differences in the rotational properties and the depths of the surface
convection zones for stars with various masses and ages. In 2007, we
initiated a long-term monitoring campaign of Ca II H and K emission
for a sample of 57 southern solar-type stars to measure their magnetic
activity cycles and their rotational properties when possible. We report
the discovery of a 1.6 year magnetic activity cycle in the exoplanet
host star ι Horologii and obtain an estimate of the rotation period
that is consistent with Hyades membership. This is the shortest activity
cycle so far measured for a solar-type star and may be related to the
short-timescale magnetic variations recently identified in the Sun
and HD 49933 from helioseismic and asteroseismic measurements. Future
asteroseismic observations of ι Hor can be compared to those obtained
near the magnetic minimum in 2006 to search for cycle-induced shifts in
the oscillation frequencies. If such short activity cycles are common
in F stars, then NASA's Kepler mission should observe their effects
in many of its long-term asteroseismic targets.
Title: Magnetic Loops in the Quiet Sun
Authors: Wiegelmann, T.; Solanki, S. K.; Borrero, J. M.; Martínez
Pillet, V.; del Toro Iniesta, J. C.; Domingo, V.; Bonet, J. A.;
Barthol, P.; Gandorfer, A.; Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.185W
Altcode: 2010arXiv1009.4715W
We investigate the fine structure of magnetic fields in the atmosphere
of the quiet Sun. We use photospheric magnetic field measurements from
SUNRISE/IMaX with unprecedented spatial resolution to extrapolate
the photospheric magnetic field into higher layers of the solar
atmosphere with the help of potential and force-free extrapolation
techniques. We find that most magnetic loops that reach into the
chromosphere or higher have one footpoint in relatively strong magnetic
field regions in the photosphere. Ninety-one percent of the magnetic
energy in the mid-chromosphere (at a height of 1 Mm) is in field
lines, whose stronger footpoint has a strength of more than 300 G,
i.e., above the equipartition field strength with convection. The
loops reaching into the chromosphere and corona are also found to be
asymmetric in the sense that the weaker footpoint has a strength B <
300 G and is located in the internetwork (IN). Such loops are expected
to be strongly dynamic and have short lifetimes, as dictated by the
properties of the IN fields.
Title: SUNRISE/IMaX Observations of Convectively Driven Vortex Flows
in the Sun
Authors: Bonet, J. A.; Márquez, I.; Sánchez Almeida, J.; Palacios,
J.; Martínez Pillet, V.; Solanki, S. K.; del Toro Iniesta, J. C.;
Domingo, V.; Berkefeld, T.; Schmidt, W.; Gandorfer, A.; Barthol, P.;
Knölker, M.
Bibcode: 2010ApJ...723L.139B
Altcode: 2010arXiv1009.1992B
We characterize the observational properties of the convectively driven
vortex flows recently discovered on the quiet Sun, using magnetograms,
Dopplergrams, and images obtained with the 1 m balloon-borne SUNRISE
telescope. By visual inspection of time series, we find some 3.1
× 10-3 vortices Mm-2 minute-1,
which is a factor of ~1.7 larger than previous estimates. The mean
duration of the individual events turns out to be 7.9 minutes, with
a standard deviation of 3.2 minutes. In addition, we find several
events appearing at the same locations along the duration of the time
series (31.6 minutes). Such recurrent vortices show up in the proper
motion flow field map averaged over the time series. The typical
vertical vorticities are lsim6 × 10-3 s-1,
which corresponds to a period of rotation of some 35 minutes. The
vortices show a preferred counterclockwise sense of rotation, which
we conjecture may have to do with the preferred vorticity impinged by
the solar differential rotation.
Title: Surface Waves in Solar Granulation Observed with SUNRISE
Authors: Roth, M.; Franz, M.; Bello González, N.; Martínez Pillet,
V.; Bonet, J. A.; Gandorfer, A.; Barthol, P.; Solanki, S. K.;
Berkefeld, T.; Schmidt, W.; del Toro Iniesta, J. C.; Domingo, V.;
Knölker, M.
Bibcode: 2010ApJ...723L.175R
Altcode: 2010arXiv1009.4790R
Solar oscillations are expected to be excited by turbulent flows in
the intergranular lanes near the solar surface. Time series recorded
by the IMaX instrument on board the SUNRISE observatory reveal solar
oscillations at high spatial resolution, which allow the study of
the properties of oscillations with short wavelengths. We analyze
two time series with synchronous recordings of Doppler velocity and
continuum intensity images with durations of 32 minutes and 23 minutes,
respectively, recorded close to the disk center of the Sun to study
the propagation and excitation of solar acoustic oscillations. In
the Doppler velocity data, both the standing acoustic waves and the
short-lived, high-degree running waves are visible. The standing
waves are visible as temporary enhancements of the amplitudes of the
large-scale velocity field due to the stochastic superposition of
the acoustic waves. We focus on the high-degree small-scale waves by
suitable filtering in the Fourier domain. Investigating the propagation
and excitation of f- and p 1-modes with wavenumbers k>1.4
Mm-1, we also find that exploding granules contribute to
the excitation of solar p-modes in addition to the contribution of
intergranular lanes.
Title: Fully Resolved Quiet-Sun Magnetic flux Tube Observed with
the SUNRISE/IMAX Instrument
Authors: Lagg, A.; Solanki, S. K.; Riethmüller, T. L.; Martínez
Pillet, V.; Schüssler, M.; Hirzberger, J.; Feller, A.; Borrero,
J. M.; Schmidt, W.; del Toro Iniesta, J. C.; Bonet, J. A.; Barthol, P.;
Berkefeld, T.; Domingo, V.; Gandorfer, A.; Knölker, M.; Title, A. M.
Bibcode: 2010ApJ...723L.164L
Altcode: 2010arXiv1009.0996L
Until today, the small size of magnetic elements in quiet-Sun areas has
required the application of indirect methods, such as the line-ratio
technique or multi-component inversions, to infer their physical
properties. A consistent match to the observed Stokes profiles could
only be obtained by introducing a magnetic filling factor that specifies
the fraction of the observed pixel filled with magnetic field. Here,
we investigate the properties of a small magnetic patch in the quiet
Sun observed with the IMaX magnetograph on board the balloon-borne
telescope SUNRISE with unprecedented spatial resolution and low
instrumental stray light. We apply an inversion technique based on
the numerical solution of the radiative transfer equation to retrieve
the temperature stratification and the field strength in the magnetic
patch. The observations can be well reproduced with a one-component,
fully magnetized atmosphere with a field strength exceeding 1 kG and
a significantly enhanced temperature in the mid to upper photosphere
with respect to its surroundings, consistent with semi-empirical flux
tube models for plage regions. We therefore conclude that, within the
framework of a simple atmospheric model, the IMaX measurements resolve
the observed quiet-Sun flux tube.
Title: Quiet-sun Intensity Contrasts in the Near-ultraviolet as
Measured from SUNRISE
Authors: Hirzberger, J.; Feller, A.; Riethmüller, T. L.; Schüssler,
M.; Borrero, J. M.; Afram, N.; Unruh, Y. C.; Berdyugina, S. V.;
Gandorfer, A.; Solanki, S. K.; Barthol, P.; Bonet, J. A.; Martínez
Pillet, V.; Berkefeld, T.; Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.154H
Altcode:
We present high-resolution images of the Sun in the near-ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1 m SUNRISE balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range are
among the highest values ever obtained for quiet-Sun solar surface
structures—up to 32.8% at a wavelength of 214 nm. We compare the
rms contrasts obtained from the observational data with theoretical
intensity contrasts obtained from numerical magnetohydrodynamic
simulations. For 388 nm and 312 nm the observations agree well with
the numerical simulations whereas at shorter wavelengths discrepancies
between observed and simulated contrasts remain.
Title: A Chromospheric Conundrum?
Authors: Judge, Philip; Knölker, Michael; Schmidt, Wolfgang;
Steiner, Oskar
Bibcode: 2010ApJ...720..776J
Altcode: 2010arXiv1007.1203J
We examine spectra of the Ca II H line, obtained under good seeing
conditions with the VTT Echelle Spectrograph in 2007 June, and
higher resolution data of the Ca II λ8542 line from Fabry-Pérot
instruments. The VTT targets were areas near disk center which included
quiet Sun and some dispersed plage. The infrared data included quiet
Sun and plage associated with small pores. Bright chromospheric network
emission patches expand little with wavelength from line wing to line
center, i.e., with increasing line opacity and height. We argue that
this simple observation has implications for the force and energy
balance of the chromosphere, since bright chromospheric network
emission is traditionally associated with enhanced local mechanical
heating which increases temperatures and pressures. Simple physical
considerations then suggest that the network chromosphere may not be
able to reach horizontal force balance with its surroundings, yet the
network is a long-lived structure. We speculate on possible reasons for
the observed behavior. By drawing attention to a potential conundrum,
we hope to contribute to a better understanding of a long-standing
unsolved problem: the heating of the chromospheric network.
Title: Quiet-Sun intensity contrasts in the near ultraviolet
Authors: Hirzberger, Johann; Feller, Alex; Riethmüller, Tino L.;
Schüssler, Manfred; Borrero, Juan M.; Afram, Nadine; Unruh, Yvonne C.;
Berdyugina, Svetlana V.; Gandorfer, Achim; Solanki, Sami K.; Barthol,
Peter; Bonet, Jose A.; Martínez Pillet, Valentin; Berkefeld, Thomas;
Knölker, Michael; Schmidt, Wolfgang; Title, Alan M.
Bibcode: 2010arXiv1009.1050H
Altcode:
We present high-resolution images of the Sun in the near ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1-m Sunrise balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range
are among the highest values ever obtained for quiet-Sun solar
surface structures - up to 32.8% at a wavelength of 214 nm. We
compare with theoretical intensity contrasts obtained from numerical
magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations
agree well with the numerical simulations whereas at shorter wavelengths
discrepancies between observed and simulated contrasts remain.
Title: The Visible Spectro-Polarimeter (ViSP) for the Advanced
Technology Solar Telescope
Authors: Nelson, Peter G.; Casini, Roberto; de Wijn, Alfred G.;
Knoelker, Michael
Bibcode: 2010SPIE.7735E..8CN
Altcode: 2010SPIE.7735E.271N
The Visible Spectro-Polarimeter (ViSP) is one of the first light
instruments for the Advanced Technology Solar Telescope (ATST). It is
an echelle spectrograph designed to measure three different regions
of the solar spectrum in three separate focal planes simultaneously
between 380 and 1600nm. It will use the polarimetric capabilities
of the ATST to measure the full Stokes parameters across the line
profiles. By measuring the polarization in magnetically sensitive
spectral lines the magnetic field vector as a function of height
in the solar atmosphere, along with the associated variation of
the thermodynamic properties can be obtained. The ViSP will have a
spatial resolution of 0.04 arc seconds over a 2 minute field of view
(at 600nm). The minimum resolving power for all the focal planes is
180,000. The spectrograph supports up to 5 diffraction gratings and
is fully automated to allow for rapid reconfiguration.
Title: Flight control software for the wave-front sensor of SUNRISE
1m balloon telescope
Authors: Bell, Alexander; Barthol, Peter; Berkefeld, Thomas; Feger,
Bernhard; Gandorfer, Achim M.; Heidecke, Frank; Knoelker, Michael;
Martinez Pillet, Valentin; Schmidt, Wolfgang; Sigwarth, Michael;
Solanki, Sami K.; Soltau, Dirk; Title, Alan M.
Bibcode: 2010SPIE.7740E..03B
Altcode: 2010SPIE.7740E...2B
This paper describes the flight control software of the wave-front
correction system that flew on the 2009 science flight of the Sunrise
balloon telescope. The software discussed here allowed fully automated
operations of the wave-front sensor, communications with the adaptive
optics sub-system, the pointing system, the instrument control unit
and the main telescope controller. The software was developed using
modern object oriented analysis and design techniques, and consists
of roughly 13.000 lines of C++ code not counting code written for the
on-board communication layer. The software operated error free during
the 5.5 day flight.
Title: SUNRISE Impressions from a successful science flight
Authors: Schmidt, W.; Solanki, S. K.; Barthol, P.; Berkefeld, T.;
Gandorfer, A.; Knölker, M.; Martínez Pillet, V.; Schüssler, M.;
Title, A.
Bibcode: 2010AN....331..601S
Altcode:
SUNRISE is a balloon-borne telescope with an aperture of one meter. It
is equipped with a filter imager for the UV wavelength range between
214 nm and 400 nm (SUFI), and with a spectro-polarimeter that measures
the magnetic field of the photosphere using the Fe I line at 525.02
nm that has a Landé factor of 3. SUNRISE performed its first science
flight from 8 to 14 June 2009. It was launched at the Swedish ESRANGE
Space Center and cruised at an altitude of about 36 km and geographic
latitudes between 70 and 74 degrees to Somerset Island in northern
Canada. There, all data, the telescope and the gondola were successfully
recovered. During its flight, Sunrise achieved high pointing stability
during 33 hours, and recorded about 1.8 TB of science data. Already at
this early stage of data processing it is clear that SUNRISE recorded
UV images of the solar photosphere, and spectropolarimetric measurements
of the quiet Sun's magnetic field of unprecedented quality.
Title: High resolution imaging and polarimetry with SUNRISE, a
balloon-borne stratospheric solar observatory
Authors: Barthol, Peter; Chares, Bernd; Deutsch, Werner; Feller, Alex;
Gandorfer, Achim; Grauf, Bianca; Hirzberger, Johann; Meller, Reinhard;
Riethmueller, Tino; Schuessler, Manfred; Solanki, Sami K.; Knoelker,
Michael; Martinez Pillet, Valentin; Schmidt, Wolfgang; Title, Alan
Bibcode: 2010cosp...38.4063B
Altcode: 2010cosp.meet.4063B
SUNRISE is an international collaboration for the development
and operation of a meter-class balloon-borne stratospheric solar
observatory. Prime science goal is the study of structure and dynamics
of the magnetic field in the solar atmosphere and the interaction of
the magnetic field with convective plasma flows. These processes are
studied by high resolution imaging in the UV and polarimetry at visible
wavelengths. The instrument has been successfully launched on June 8,
2009 from ESRANGE, Kiruna, Northern Sweden. During the more than 5
days flight about 1.5 TByte of scientific data were collected. The
paper gives an overview of the instrument and mission, examples of
the scientific output will also be presented. SUNRISE is a joint
project of the Max-Planck-Institut fuer Sonnensystemforschung (MPS),
Katlenburg-Lindau, with the Kiepenheuer-Institut fuer Sonnenphysik
(KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the
Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and
the Spanish IMaX consortium.
Title: The Ultraviolet Filter Imager (SuFI) onboard the Sunrise
balloon-borne solar observatory: Instrument description and first
results
Authors: Gandorfer, Achim; Barthol, Peter; Feller, Alex; Grauf,
Bianca; Hirzberger, Johann; Riethmueller, Tino; Solanki, Sami K.;
Berkefeld, Thomas; Knoelker, Michael; Martinez Pillet, Valentin;
Schmidt, Wolfgang; Title, Alan
Bibcode: 2010cosp...38.4064G
Altcode: 2010cosp.meet.4064G
We describe the design of the near UV filter imager SuFi onboard
Sunrise, which was successfully flown in the stratosphere in June
2009. During its five days flight SuFI captured the highest contrast
images of solar granulation ever. SuFI is a diffraction limited filter
imager with an effective focal length of 121m, working in 5 distinct
wavelength bands between 210nm and 397nm. It is based on a two mirror
modified Schwarzschild microscope, which is integral part of the central
Image stabilization and light Distribution unit (ISLiD) of Sunrise,
which acts as the reimaging optics between the 1m telescope and the
science instruments. The key technical features of the instrument are
presented under the view of the specific demands of balloon-borne
optical systems. First results obtained with the instrument are
presented to demonstrate the capabilities of the instrument.
Title: UV intensity distributions of the quiet Sun observed with
Sunrise
Authors: Hirzberger, Johann; Feller, A.; Riethmueller, T.; Borrero,
J. M.; Schüssler, M.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knoelker, M.; Martínez Pillet, V.; Schmidt, W.; Solanki, S.; Title, A.
Bibcode: 2010cosp...38.1735H
Altcode: 2010cosp.meet.1735H
High resolution solar images in the near UV have been obtained with
the Solar UV Filtergraph (SUFI) onboard the Sunrise balloon borne
observatory, amongst others in wavelength regions not accessible
from the ground. We present intensity distributions of the quiet
Sun at different heliocentric angles, from disk center to the solar
limb. These results, obtained in spectral windows at 214 nm, 313 nm
(OH band), 388 nm (CN band) and 396.7 nm (CaIIH), represent an important
validation of numerical models of the solar photosphere and are, thus,
fundamental ingredients for our understanding of the thermal processes
in the solar surface region.
Title: Activity Cycles of Southern Asteroseismic Targets
Authors: Metcalfe, Travis S.; Judge, P. G.; Basu, S.; Henry, T. J.;
Soderblom, D. R.; Knoelker, M.; Rempel, M.
Bibcode: 2010AAS...21542416M
Altcode: 2010BAAS...42..333M
The Mount Wilson Ca HK survey revealed magnetic activity variations in
a large sample of solar-type stars with timescales ranging from 2.5
to 25 years. This broad range of cycle periods is thought to reflect
differences in the rotational properties and the depths of the surface
convection zones for stars with various masses and ages. Asteroseismic
data will soon provide direct measurements of these quantities for
individual stars, but many of the most promising targets are in the
southern sky (e.g., alpha Cen A & B, beta Hyi, mu Ara, tau Cet,
nu Ind), while long-term magnetic activity cycle surveys are largely
confined to the north. In 2007 we began using the SMARTS 1.5-m telescope
to conduct a long-term monitoring campaign of Ca II H & K emission
for a sample of 57 southern solar-type stars to measure their magnetic
activity cycles and their rotational properties when possible. This
sample includes the most likely southern asteroseismic targets to be
observed by the Stellar Oscillations Network Group (SONG), currently
scheduled to begin operations in 2012. We present selected results from
the first two years of the survey, and from the longer time baseline
sampled by a single-epoch survey conducted in 1992.
Title: Radiative MHD simulations of sunspot structure
Authors: Rempel, M.; Schuessler, M.; Cameron, R.; Knoelker, M.
Bibcode: 2009AGUFMSH53B..07R
Altcode:
For a long time radiative MHD simulations of entire sunspots from
first principles were out of reach due to insufficient computing
resources. Over the past 4 years simulations have evolved from
6x6x2 Mm size domains focusing on the details of umbral dots to
simulations covering a pair of opposite polarity sunspots in a
100x50x6 Mm domain. Numerical simulations point toward a common magneto
convective origin of umbral dots and filaments in the inner and outer
penumbra. Most recent simulations also capture the processes involved
in the formation of an extended outer penumbra with strong horizontal
outflows averaging around 5 km/s in the photosphere. In this talk I
will briefly review the progress made in this field over the past 4
years and discuss in detail the magneto convective origin of penumbral
fine structure as well as the Evershed flow.
Title: Radiative MHD simulations of sunspot structure
Authors: Rempel, M.; Schüssler, M.; Cameron, R.; Knölker, M.
Bibcode: 2009iac..talk..192R
Altcode: 2009iac..talk..106R
No abstract at ADS
Title: Activity Cycles of Southern Asteroseismic Targets
Authors: Metcalfe, T. S.; Judge, P. G.; Basu, S.; Henry, T. J.;
Soderblom, D. R.; Knoelker, M.; Rempel, M.
Bibcode: 2009arXiv0909.5464M
Altcode:
The Mount Wilson Ca HK survey revealed magnetic activity variations in
a large sample of solar-type stars with timescales ranging from 2.5
to 25 years. This broad range of cycle periods is thought to reflect
differences in the rotational properties and the depths of the surface
convection zones for stars with various masses and ages. Asteroseismic
data will soon provide direct measurements of these quantities for
individual stars, but many of the most promising targets are in the
southern sky (e.g., alpha Cen A & B, beta Hyi, mu Ara, tau Cet,
nu Ind), while long-term magnetic activity cycle surveys are largely
confined to the north. In 2007 we began using the SMARTS 1.5-m telescope
to conduct a long-term monitoring campaign of Ca II H & K emission
for a sample of 57 southern solar-type stars to measure their magnetic
activity cycles and their rotational properties when possible. This
sample includes the most likely southern asteroseismic targets to be
observed by the Stellar Oscillations Network Group (SONG), currently
scheduled to begin operations in 2012. We present selected results from
the first two years of the survey, and from the longer time baseline
sampled by a single-epoch survey conducted in 1992.
Title: Penumbral Structure and Outflows in Simulated Sunspots
Authors: Rempel, M.; Schüssler, M.; Cameron, R. H.; Knölker, M.
Bibcode: 2009Sci...325..171R
Altcode: 2009arXiv0907.2259R
Sunspots are concentrations of magnetic field on the visible solar
surface that strongly affect the convective energy transport in their
interior and surroundings. The filamentary outer regions (penumbrae)
of sunspots show systematic radial outward flows along channels of
nearly horizontal magnetic field. These flows were discovered 100
years ago and are present in all fully developed sunspots. By using
a comprehensive numerical simulation of a sunspot pair, we show
that penumbral structures with such outflows form when the average
magnetic field inclination to the vertical exceeds about 45 degrees. The
systematic outflows are a component of the convective flows that provide
the upward energy transport and result from anisotropy introduced by
the presence of the inclined magnetic field.
Title: Radiative MHD Simulations of Sunspot Structure
Authors: Rempel, Matthias D.; Schuessler, M.; Cameron, R.; Knoelker, M.
Bibcode: 2009SPD....40.0604R
Altcode:
We summarize the recent progress made in magneto convection simulations
of sunspot structure. Over the past 4 years simulations have evolved
from local 6x6x2 Mm size domains focusing on the details of umbral
dots to simulations covering a pair of opposite polarity spots in
a 100x50x6 Mm domain. The simulations point out the common magneto
convective origin of umbral dots and filaments in the inner penumbra
and most recently also reveal the processes involved in the formation
of an extended outer penumbra with strong horizontal outflows averaging
around 5 km/s in the photosphere.
Title: Radiative Magnetohydrodynamic Simulation of Sunspot Structure
Authors: Rempel, M.; Schüssler, M.; Knölker, M.
Bibcode: 2009ApJ...691..640R
Altcode: 2008arXiv0808.3294R
Results of a three-dimensional MHD simulation of a sunspot with
a photospheric size of about 20 Mm are presented. The simulation
has been carried out with the MURaM code, which includes a realistic
equation of state with partial ionization and radiative transfer along
many ray directions. The largely relaxed state of the sunspot shows
a division in a central dark umbral region with bright dots and a
penumbra showing bright filaments of about 2-3 Mm length with central
dark lanes. By a process similar to the formation of umbral dots,
the penumbral filaments result from magnetoconvection in the form of
upflow plumes, which become elongated by the presence of an inclined
magnetic field; the upflow is deflected in the outward direction while
the magnetic field is weakened and becomes almost horizontal in the
upper part of the plume near the level of optical depth unity. A dark
lane forms owing to the piling up of matter near the cusp-shaped top
of the rising plume that leads to an upward bulging of the surfaces of
constant optical depth. The simulated penumbral structure corresponds
well to the observationally inferred interlocking-comb structure of
the magnetic field with Evershed outflows along dark-laned filaments
with nearly horizontal magnetic field and overturning perpendicular
("twisting") motion, which are embedded in a background of stronger
and less inclined field. Photospheric spectral lines are formed at the
very top and somewhat above the upflow plumes, so that they do not
fully sense the strong flow as well as the large field inclination
and significant field strength reduction in the upper part of the
plume structures.
Title: SUNRISE: High resolution UV/VIS observations of the sun from
the stratosphere
Authors: Sunrise Team; Barthol, P.; Gandorfer, A. M.; Solanki,
S. K.; Knölker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.;
SUNRISE Team
Bibcode: 2008AdSpR..42...70S
Altcode:
SUNRISE is an international project for the development, construction
and operation of a balloon-borne solar telescope with an aperture
of 1 m, working in the UV/VIS spectral domain. The main scientific
goal of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
near diffraction-limited images of the photosphere and chromosphere
with an unprecedented resolution down to 35 km on the solar surface
at wavelengths around 220 nm. Active in-flight alignment and image
stabilization techniques are used. The focal-plane instrumentation
consists of a polarization sensitive spectrograph, a Fabry Perot
filter magnetograph and a phase-diverse filter imager working in
the near UV. The first stratospheric long-duration balloon flight
of SUNRISE is planned in summer 2009 from the Swedish ESRANGE
station. SUNRISE is a joint project of the German Max-Planck-Institut
für Sonnensystemforschung (MPS), Katlenburg-Lindau, with the
Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, Germany, the
High-Altitude Observatory (HAO), Boulder, USA, the Lockheed-Martin
Solar and Astrophysics Laboratory (LMSAL), Palo Alto, USA, and the
Spanish IMaX consortium. This paper will give an overview about the
mission and a description of its scientific and technological aspects.
Title: ChroTel: a robotic telescope to observe the chromosphere of
the Sun
Authors: Kentischer, T. J.; Bethge, Ch.; Elmore, D. F.; Friedlein,
R.; Halbgewachs, C.; Knölker, M.; Peter, H.; Schmidt, W.; Sigwarth,
M.; Streander, K.
Bibcode: 2008SPIE.7014E..13K
Altcode: 2008SPIE.7014E..36K
The Chromospheric Telescope (ChroTel) is a 10 cm robotic telescope
to observe the full solar disk with a 2k × 2k CCD at high temporal
cadence. It is located at the Observatorio del Teide, Tenerife, Spain,
next to the 70 cm German Vacuum Tower Telescope (VTT). ChroTel contains
a turret system that relays a stabilized image of the solar disk into
a laboratory within the VTT building. The control design allows a fully
robotic operation. Observations are carried out in three chromospheric
wavelengths (CaK: 393 nm, Ha: 652 nm, HeI 1083 nm).
Title: Observations of the atmospheres of extrasolar planets
Authors: Brown, T. M.; Alonso, R.; Knölker, M.; Rauer, H.; Schmidt, W.
Bibcode: 2008depn.conf...50B
Altcode:
No abstract at ADS
Title: SUNRISE: High resolution UV/VIS observations of the Sun from
the stratosphere
Authors: Gandorfer, A. M.; Solanki, S. K.; Barthol, P.; Martínez
Pillet, V.; Schmidt, W.; Title, A. M.; Knölker, M.
Bibcode: 2007msfa.conf...69G
Altcode:
SUNRISE is an international project for the development, construction,
and operation of a balloon-borne solar telescope with an aperture
of 1 m, working in the UV/VIS spectral domain. The main scientific
goal of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
near diffraction-limited images of the photosphere and chromosphere
with an unpredecented resolution down to 35 km on the solar surface at
wavelengths around 220 nm. The focal-plane instrumentation consists of a
polarization sensitive spectrograph, a Fabry-Perot filter magnetograph,
and a phase-diverse filter imager working in the near UV. The first
stratospheric long-duration balloon flight of SUNRISE is planned in
summer 2009 from the Swedish ESRANGE station. SUNRISE is a joint project
of the German Max-Planck-Institut für Sonnensystemforschung (MPS),
Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik
(KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder,
USA, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo
Alto, USA, and the Spanish IMaX consortium. In this paper we will
present a brief description of the scientific and technological aspects
of SUNRISE.
Title: Calibrating the solar dynamo: magnetic activity cycles of
southern Sun-like stars
Authors: Metcalfe, T. S.; Henry, T. J.; Knölker, M.; Soderblom, D. R.
Bibcode: 2006ESASP.624E.111M
Altcode: 2006astro.ph..9051M; 2006soho...18E.111M
The solar magnetic activity cycle is responsible for periodic episodes
of severe space weather, which can perturb satellite orbits, interfere
with communications systems, and bring down power grids. Much progress
has recently been made in forecasting the strength and timing of this
11-year cycle, using a predictive flux-transport dynamo model (Dikpati
2005, Dikpati et al. 2006). We can strengthen the foundation of this
model by extending it to match observations of similar magnetic
activity cycles in other Sun-like stars, which exhibit variations
in their Ca II H and K emission on time scales from 2.5 to 25 years
(Baliunas et al. 1995). This broad range of cycle periods is thought
to reflect differences in the rotational properties and the depth
of the surface convection zone for stars with various masses and
ages. Asteroseismology is now yielding direct measurements of these
quantities for individual stars, but the most promising asteroseismic
targets are in the southern sky (alpha Cen A, alpha Cen B, beta Hyi),
while the existing activity cycle survey is confined to the north. We
are initiating a long-term survey of Ca II H and K emission for a sample
of 92 southern Sun-like stars to measure their magnetic activity cycles
and rotational properties, which will ultimately provide independent
tests of solar dynamo models.
Title: Magneto-Convection
Authors: Schüssler, M.; Knölker, M.
Bibcode: 2001ASPC..248..115S
Altcode: 2001mfah.conf..115S
No abstract at ADS
Title: Free-fall Downflow Observed in HE I 1083.0 Nanometers and Hβ
Authors: Schmidt, W.; Muglach, K.; Knölker, M.
Bibcode: 2000ApJ...544..567S
Altcode:
In a short time sequence of simultaneously observed slit spectra
of He I 1083.0 nm and Hβ we find the signature of material flowing
toward the solar surface with up to 42 km s-1, in addition
to material which is almost at rest. The constant acceleration of the
moving material is about 200 m s-2. These multiple velocities
occur in a small region of about 5'' in a plage region. We
observe a highly dynamical phenomenon which lasts a few minutes. The
duration and constant acceleration suggest free fall of matter
unobstructed by magnetic structures or along vertical field lines.
Title: Report on the Astronomy and Astrophysics Decadal Survey
Authors: Knoelker, M.; Title, A.
Bibcode: 2000SPD....31.0702K
Altcode: 2000BAAS...32Q.839K
The Decadal Survey of Astronomy and Astrophysics is a review that
recommends priorities for all projects in astrophysics in the coming
decade. The priorities are established by a secret vote of the members
of the Astronomy and Astrophysics Survey Committee (AASC). Voting is on
projects recommended by a set of discipline panels. One of us (Knoelker)
chaired the Solar Panel and the other (Title) was a member of the AASC
and vice chair of the Solar Panel. Christopher McKee of the University
of California and Joseph Taylor of Princeton University jointly chaired
the current review. Projects were prioritized in categories of large,
moderate, and small for both ground and space. The output of the study
is a report - Astronomy and Astrophysics in the New Millennium. The
report is in two volumes the main report and an appendix that contains
reports of the AASC panels. We will discuss the process and the
priorities of the survey with special emphasis of the impacts on and
implications for Solar Physics.
Title: Dynamics of solar magnetic elements
Authors: Sigwarth, M.; Balasubramaniam, K. S.; Knölker, M.;
Schmidt, W.
Bibcode: 1999A&A...349..941S
Altcode:
We present observational results that demonstrate a strong increase in
the dynamic behavior of magnetic elements at the solar photosphere,
when observed at high spatial and temporal resolution. The HAO/NSO
Advanced Stokes Polarimeter was used to obtain an extensive set of
high resolution Stokes-V spectra from network, intranetwork and active
region magnetic fields at a low noise level. We performed a statistical
analysis of Doppler shifts and asymmetries of the V spectra of FeI
630.15 and 630.25 nm to obtain information on the dynamics of magnetic
elements of different sizes. The spatial resolution of 0.8-1 arcsec in
combination with high polarimetric precision allowed us to investigate
Stokes-V spectra of magnetic elements down to a size of ~ 150 km. The
Doppler velocity within magnetic elements as well as the amplitude and
area asymmetries of the Stokes-V profiles show a strong dependence on
the size of the magnetic elements as well as on the granular velocity
in their vicinity. Applying an absolute velocity calibration we find
that the smallest magnetic features have velocities of up to 5 km s(-1)
in both up- and downflows whereas for larger elements or clusters of
several flux tubes the velocities become smaller and more uniform. The
V-profile asymmetries are larger (both positive and negative) for
small fill fraction than for higher fill fraction within the resolution
element. Averaged over all individual profiles, there remains a positive
amplitude and area asymmetry and a downflow exceeding 0.5 km s(-1)
. The properties of spatially and temporally integrated V profiles are
consistent with results from FTS-observations. Our observations are
in qualitative agreement with results from numerical MHD simulations.
Title: Strategic Plans for the Future of Solar Physics: a community
discussion of the NASA Sun-Earth Connection Program Roadmap and the
NAS Decadal Survey of Astronomy and Astrophysics (Solar Astronomy
section)
Authors: Schrijver, K.; Knoelker, M.
Bibcode: 1999AAS...194.6101S
Altcode: 1999BAAS...31..920S
The NASA Sun-Earth Connections Program is currently revising its
Roadmap, the long-range plan for science goals, technology development,
and missions between 2000 and 2040. From the interior dynamics of
the Sun, to the interactions of plasma, fields, and radiation in the
photosphere and solar atmosphere, to the heating and structure of the
corona, to the acceleration, structure, and evolution of the solar wind,
to the interactions of the heliosphere with the interstellar medium,
to the processes of solar, stellar, and solar system evolution -
progress in each of these domains will help us understand how the Sun
impacts our home in space. The Roadmap Committee is seeking to refine
and extend the SEC's vision and identify the milestone missions for
the future. During this session, an outline of the current draft
Roadmap will be presented, and further community involvement will
be solicited to ensure the strongest possible concensus on the
revised Roadmap. The National Academy of Sciences' Space Science
Board has appointed a committee to perform a Decadal Survey of
Astronomy and Astrophysics, which is surveying the field of space-
and ground-based astronomy and astrophysics, recommending priorities
for the most important new initiatives of the decade 2000-2010. The
prioritization delivered by the earlier Decadal Surveys has played
an important role in guiding the funding agencies in setting their
priorities for astronomy and astrophysics. Therefore it will be of
crucial importance for solar physics to contribute a strong case
for its own set of future projects to be incorpoprated into the
survey. The solar physics of the next decade will be characterized by
its increasing societal relevance in the context of the National Space
Weather Program and related issues, as well as its classical importance
as a ``base" for many astrophysical questions. The presentation and
subsequent discussion at the Chicago meeting is intended to solicit
further community input, to achieve optimal representation for solar
physics in the Decadal Survey. The Roadmap Committee and the Decadal
Survey's solar panel encourage the whole solar physics community to
contact them prior to the meeting. The list of the committee/panel
members and their e-mail addresses, as well as related information,
can be accessed via their websites at http://www.lmsal.com/sec/ and
http://www.nas.edu/bpa/projects/astrosurvey/solar/ , respectively.
Title: High Resolution Observations of the Dynamics of Magnetic
Elements
Authors: Sigwarth, M.; Balasubramaniam, K.; Knölker, M.
Bibcode: 1999ASPC..183...36S
Altcode: 1999hrsp.conf...36S
No abstract at ADS
Title: Thermal Structure of a Sunspot: An Application of Phase
Diversity
Authors: Tritschler, A.; Schmidt, W.; Knölker, M.
Bibcode: 1999ASPC..183..108T
Altcode: 1999hrsp.conf..108T
No abstract at ADS
Title: Dynamical Interaction of Solar Magnetic Elements and Granular
Convection: Results of a Numerical Simulation
Authors: Steiner, O.; Grossmann-Doerth, U.; Knölker, M.; Schüssler,
M.
Bibcode: 1998ApJ...495..468S
Altcode:
Nonstationary convection in the solar photosphere and its
interaction with photospheric magnetic structures (flux sheets in
intergranular lanes) have been simulated using a numerical code
for two-dimensional MHD with radiative energy transfer. Dynamical
phenomena are identified in the simulations, which may contribute to
chromospheric and coronal heating. Among these are the bending and
horizontal displacement of a flux sheet by convective flows and the
excitation and propagation of shock waves both within and outside the
magnetic structure. Observational signatures of these phenomena are
derived from calculated Stokes profiles of Zeeman-sensitive spectral
lines. We suggest that the extended red wings of the observed Stokes
V profiles are due to downward coacceleration of magnetized material
in a turbulent boundary layer between the flux sheet and the strong
external downflow. Upward-propagating shocks in magnetic structures
should be detectable if a time resolution of about 10 s is achieved,
together with a spatial resolution that allows one to isolate individual
magnetic structures. Determination of the complicated internal dynamics
of magnetic elements requires observations with a spatial resolution
better than 100 km in the solar photosphere.
Title: Multiple velocities observed in HeI 1083 nm
Authors: Muglach, K.; Schmidt, W.; Knölker, M.
Bibcode: 1997SoPh..172..103M
Altcode: 1997SoPh..172..103S; 1997ESPM....8..103M
We present a time sequence of slit spectra of Hei 1083.03 nm (and Hβ)
taken with the German Vacuum Tower Telescope at Tenerife. We find the
signature of an onset of a downflow accelerating up to 42 km/s . The
Hei 1083.03 nm line splits into two well separated components during
the event, one of which shows the usual absorption profile of material
which is almost at rest. We calculate the velocity, line depth and
area of both line profiles. Possible explanations for these observed
multiple velocities are discussed.
Title: Phase Diversity Applied to Sunspot Observations
Authors: Tritschler, A.; Schmidt, W.; Knolker, M.
Bibcode: 1997ASPC..118..170T
Altcode: 1997fasp.conf..170T
We present preliminary results of a multi-colour phase diversity
experiment carried out with the Multichannel Filter System of the
Vacuum Tower Telescope at the Observatorio del Teide on Tenerife. We
apply phase-diversity imaging to a time sequence of sunspot filtergrams
taken in three continuum bands and correct the seeing influence for
each image. A newly developed phase diversity device allowing for
the projection of both the focused and the defocused image onto a
single CCD chip was used in one of the wavelength channels. With the
information about the wavefront obtained by the image reconstruction
algorithm the restoration of the other two bands can be performed as
well. The processed and restored data set will then be used to derive
the temperature and proper motion of the umbral dots. Data analysis
is still under way, and final results will be given in a forthcoming
article.
Title: Numerical simulations of magnetic flux sheets.
Authors: Steiner, O.; Knölker, M.; Schüssler, M.
Bibcode: 1997smf..conf...31S
Altcode:
Non-stationary convection in the solar photosphere and its interaction
with photospheric magnetic structures (flux sheets in intergranular
lanes) has been simulated using a numerical code for two-dimensional
MHD with radiative transfer. Dynamical phenomena, which may contribute
to chromospheric and coronal heating, like bending and horizontal
displacement of a flux sheet by convective flows as well as the
excitation and propagation of shock waves within and outside the
magnetic structure are found. Observational signature of transversal
displacement and shocks are derived. It is shown that upward propagating
shocks in magnetic structures should be detectable. The evolution of
an initially homogeneous vertical magnetic field is followed, starting
from an evolved state of a two-dimensional numerical simulation of
solar granulation.
Title: Polarized Radiation Diagnostics of Magnetohydrodynamic Models
of the Solar Atmosphere
Authors: Steiner, O.; Grossmann-Doerth, U.; Schüssler, M.; Knölker,
M.
Bibcode: 1996SoPh..164..223S
Altcode:
Solar magnetic elements and their dynamical interaction with
the convective surface layers of the Sun are numerically
simulated. Radiation transfer in the photosphere is taken into
account. A simulation run over 18.5 minutes real time shows that the
granular flow is capable of moving and bending a magnetic flux sheet
(the magnetic element). At times it becomes inclined by up to 30°
with respect to the vertical around the level τ5000 =
1 and it moves horizontally with a maximal velocity of 4 km/s. Shock
waves form outside and within the magnetic flux sheet. The latter
cause a distinctive signature in a time series of synthetic Stokes
V-profiles. Such shock events occur with a mean frequency of about
2.5 minutes. A time resolution of at least 10 seconds in Stokes V
recordings is needed to reveal an individual shock event by observation.
Title: Convective intensification of photospheric magnetic fields.
Authors: Schüssler, M.; Grossmann-Doerth, U.; Steiner, O.; Knölker,
M.
Bibcode: 1996AGAb...12...89S
Altcode:
No abstract at ADS
Title: Waves in Radiating Fluids
Authors: Bogdan, T. J.; Knoelker, M.; MacGregor, K. B.; Kim, E. -J.
Bibcode: 1996ApJ...456..879B
Altcode:
We derive from first principles the equations which govern the behavior
of small-amplitude fluctuations in a homogeneous and isotropic
radiating fluid. Products of the fluctuating quantities are shown
to obey a wave-energy conservation law from which it follows that
all perturbations must ultimately decay in time. Under fairly general
circumstances the governing equations may be solved through the use of
integral transforms which affords an accounting of the various wave
modes supported by the radiating fluid. In addition to the familiar
radiatively modified acoustic mode, the radiation-diffusion mode, the
radiative-relaxation mode, and the isotropization and exchange modes
which constitute the discrete spectrum of the differential equation,
we find a continuous spectrum of wave modes associated with the
"collisionless" nature of the photons on timescales short compared
to the photon lifetime. This continuous spectrum is eliminated
if an Eddington approximation is used to close the hierarchy of
equations that relate the fluctuating angular moments of the radiation
field. Quantitative results are obtained for the simple case in which
the opacity may be regarded as being independent of the frequency of
the photon and the source function may be approximated by the (local)
Planck function.
Title: Observation at 892 nm of impact "L" with the solar Vacuum
Tower Telescope at Tenerife.
Authors: Schleicher, H.; Balthasar, H.; Jockers, K.; Knölker, M.;
Schmidt, W.
Bibcode: 1995ESOC...52..171S
Altcode: 1995eslj.work..171S; 1995esl9.conf..171S
During the period of SL-9 impacting Jupiter, the authors observed
Jupiter with the solar VTT. The impact of fragment "L" was monitored
with a time series of filtergrams in the CH4-band at 892 nm.
Title: Simulation of the Interaction of Convective Flow with Magnetic
Elements in the Solar Atmosphere.
Authors: Steiner, O.; Grossmann-Doerth, U.; Knoelker, M.; Schuessler,
M.
Bibcode: 1995RvMA....8...81S
Altcode:
No abstract at ADS
Title: Impact L observed at a wavelength of 892 nm with the solar
vacuum telescope on Tenerife
Authors: Schleicher, H.; Balthasar, H.; Knölker, M.; Schmidt, W.;
Jockers, K.
Bibcode: 1995HiA....10..632S
Altcode:
No abstract at ADS
Title: Limb observations of the HeI 1083.0 NM line.
Authors: Schmidt, W.; Knoelker, M.; Westendorp Plaza, C.
Bibcode: 1994A&A...287..229S
Altcode:
The He 1083.0 nm line has been observed at the solar limb and the
strength of the line has been measured as a function of height above
it. The maximum of the emission is found to be at 2400 km.
Title: The deep layers of solar magnetic elements
Authors: Grossmann-Doerth, U.; Knoelker, M.; Schuessler, M.; Solanki,
S. K.
Bibcode: 1994A&A...285..648G
Altcode:
We compare self-consistent theoretical models of solar magnetic
flux sheets with spectropolarimetric observations of a solar plage
and a network region. Our observational diagnostics mainly provide
information on temperature and magnetic field of the deep photospheric
layers. They are used to constrain the two free parameters of the
models, viz. width and initial evacuation of the flux sheets. We find
that the width of flux sheets in the network is approximately 200 km,
while it is 300-350 km in an active plage. The flux sheets turn out
to be less evacuated than previously thought, so they have continuum
intensities close to unity. Since these are average values, however,
our results do not exclude the presence of either smaller and brighter
or larger and darker magnetic structures.
Title: Dynamic interaction of convection with magnetic flux sheets:
first results of a new MHD code
Authors: Steiner, O.; Knölker, M.; Schüssler, M.
Bibcode: 1994ASIC..433..441S
Altcode:
No abstract at ADS
Title: Observations at 891 nm of the impact "L" of SL-9 on Jupiter.
Authors: Balthasar, H.; Jockers, K.; Knölker, M.; Schleicher, H.;
Schmidt, W.
Bibcode: 1994AGAb...10..122B
Altcode:
No abstract at ADS
Title: The Impact of Fragment ``L'' of Comet SL-9 on Jupiter
Authors: Schleicher, H.; Balthasar, H.; Knolker, M.; Schmidt, W.;
Jockers, K.
Bibcode: 1994EM&P...66...13S
Altcode:
Filtergrams of high spatial and temporal resolution were obtained in
the methane band centred at 892 nm during the impact of fragment L of
comet Shoemaker-Levy 9 on Jupiter. The light curve shows two maxima of
an emission ball observed above the limb shortly after the impact. The
second maximum was the brightest and had a short life time of about 90
seconds. During it's life, the apparent height of the emission ball
declined towards the surface of Jupiter; the amount of displacement
is larger than the expected effect caused by Jupiter's rotation. About
half an hour after the impact, a domelike feature became visible when
the location of the impact rotated into the illuminated hemisphere
of Jupiter.
Title: Solar Magnetic Elements: Models Compared with Observations
Authors: Grossmann-Doerth, U.; Knolker, M.; Schussler, M.; Solanki,
S. K.
Bibcode: 1994ASPC...68...96G
Altcode: 1994sare.conf...96G
No abstract at ADS
Title: MHD simulations with adaptive mesh refinement
Authors: Steiner, O.; Grossmann-Doerth, U.; Knölker, M.; Schüssler,
M.
Bibcode: 1994smf..conf..282S
Altcode:
No abstract at ADS
Title: Simulation of magneto-convection with radiative transfer
Authors: Steiner, O.; Grossmann-Doerth, U.; Knölker, M.; Schüssler,
M.
Bibcode: 1994smf..conf..286S
Altcode:
No abstract at ADS
Title: Damping of solar p-mode oscillations. 1. Radial modes with
eddy viscosity
Authors: Stix, M.; Rudiger, G.; Knolker, M.; Grabowski, U.
Bibcode: 1993A&A...272..340S
Altcode:
A Fourier transform method is used to derive shear and volume
eddy viscosities arising from small-scale turbulent motions
in the solar convection zone. For homogeneous and isotropic
turbulence the volume viscosity exceeds the shear viscosity by a
factor 6. For oscillations with a large-scale spatial structure the
viscosities depend on the frequency of oscillation in the form exp(-
|ωoscτcorr|), where τcorr is the
correlation time of the turbulence. This dependence restricts the
damping effect upon the solar p modes to a layer of at most several
thousand kilometers just below the Sun's surface. The damping
rates of radial solar p modes were calculated with the help of an
energy integral. The result is that turbulent damping may account for
up to 20% of the total damping derived from the observed width of the
lines in the oscillation spectrum. If convective overshoot into the
solar atmosphere is included, the effect increases to 25 - 30%.
Title: Evidence for Transonic Flows in the Solar Granulation
Authors: Nesis, A.; Bogdan, T. J.; Cattaneo, F.; Hanslmeier, A.;
Knoelker, M.; Malagoli, A.
Bibcode: 1992ApJ...399L..99N
Altcode:
High-resolution observations of the solar granulation are interpreted
in the light of recent numerical simulations of compressible
convection. The observations show a negative correlation between
the width of suitably chosen, nonmagnetic lines and the continuum
intensity. This result is consistent with a model of granular convection
where regions of supersonic horizontal flow form intermittently in
the vicinity of the downflow lanes. We conjecture that the observed
line broadening in the regions of low intensity is caused by enhanced
turbulent fluctuations generated by the passage of shock fronts bounding
the regions of supersonic motion.
Title: MHD simulations with adaptive mesh refinement.
Authors: Steiner, O.; Grossmann-Doerth, U.; Knölker, M.; Schüssler,
M.
Bibcode: 1992AGAb....7..213S
Altcode:
No abstract at ADS
Title: Scattering of Acoustic Waves from a Magnetic Flux Tube Embedded
in a Radiating Fluid
Authors: Bogdan, T. B.; Knoelker, M.
Bibcode: 1991ApJ...369..219B
Altcode:
The effect of the radiation field in mediating the interaction between
the solar acoustic oscillations and isolated magnetic flux tubes is
studied using a refinement of the basic seismology paradigm introduced
by Wilson (1980) and studied by Abdelatif and Thomas (1987). The
calculation of the mode conversion of acoustic to radiation-diffusion
modes by a uniformly magnetized flux tube is described in detail. An
embedding procedure is introduced that allows the magnetic flux
tube to be completely specified by essentially two parameters, the
radius and magnetic field strength, once the external atmosphere is
described. The use of the projection of the wave vector onto the axis
of the magnetic flux tube to describe the incident acoustic plane wave
is discussed. Radiative effects are found to be almost inconsequential
over most of the parameter space appropriate for the interaction
p-modes with magnetic flux concentrations near the solar surface.
Title: Solar magnetic elements: results of MHD simulations.
Authors: Grossmann-Doerth, U.; Knölker, M.; Schüssler, M.;
Weisshaar, E.
Bibcode: 1991AGAb....6...31G
Altcode:
No abstract at ADS
Title: Some developments in the theory of magnetic flux concentrations
in the solar atmosphere
Authors: Knoelker, M.; Grossmann-Doerth, U.; Schuessler, M.;
Weisshaar, E.
Bibcode: 1991AdSpR..11e.285K
Altcode: 1991AdSpR..11..285K
Most of the magnetic flux in the solar photosphere is concentrated
in small-scale structures of large field strength, called magnetic
elements. We discuss briefly the observationally determined properties
of magnetic elements and the theoretical concepts for the origin of
magnetic flux filamentation and concentration. New results of model
calculations for 2D magnetic flux sheets on the basis of numerical
simulation of the compressible MHD equations including a full (grey)
radiative transfer are presented. Synthetic Stokes profiles of spectral
lines and continuum intensity distributions serve to compare the
theoretical models with observational data. Among the key results are:
(1) The upper layers of the magnetic structure become hotter than
the environment due to radiative illumination effects; (2) a strong
convective flow evolves with horizontal velocity of 2 km/s towards the
flux sheet and a narrow ``downflow jet'' with velocity up to 6 km/s
adjacent to the magnetic structure; (3) both flux sheet and non-magnetic
environment oscillate with a period around 5 minutes. Comparison with
observed properties of solar magnetic elements reveals: (4) Calculated
and semi-empirical temperature profiles as function of height in the
photosphere are in reasonable agreement; (5) the calculated velocity
field around flux concentrations explains the area asymmetry of the
observed Stokes V-profiles including their center-limb variation; (6)
the calculated continuum intensity of a flux sheet model is compatible
with the values inferred from high spatial resolution observations
of bright points at solar disk center; (7) the observed center-limb
variation of facular contrast at low or medium spatial resolution is
reproduced by arranging calculated flux sheets in arrays. We stress the
importance of MHD simulation models for the analysis and interpretation
of data from future facilities for high spatial resolution observations
like OSL and LEST.
Title: Model calculations of magnetic flux concentrations in the
solar photosphere.
Authors: Grossmann-Doerth, U.; Knölker, M.; Schüssler, M.;
Weisshaar, E.
Bibcode: 1990AGAb....5...44G
Altcode:
No abstract at ADS
Title: Observational aspects of magnetic flux sheet models
Authors: Grossmann-Doerth, U.; Knölker, M.; Schüssler, M.;
Weisshaar, E.
Bibcode: 1989hsrs.conf..427G
Altcode:
No abstract at ADS
Title: 2 - D multiwavelength center-to-limb analysis of a
magnetostatic sunspot model
Authors: Pizzo, V. J.; Knölker, M.
Bibcode: 1989hsrs.conf..351P
Altcode:
No abstract at ADS
Title: On the Progagation of Compressive Waves in a Radiating
Magnetized Fluid
Authors: Bogdan, T. J.; Knoelker, M.
Bibcode: 1989ApJ...339..579B
Altcode:
Using the Mihalas and Mihalas (1983) treatment of the radiation field,
the dispersion relation for linear compressive plane waves in a
homogeneous, unstratified, uniformly magnetized, radiating fluid has
been obtained. In the opticallly thick limit, the present relation
is shown to predict two weakly damped anisotropic radiation-modified
magnetoacoustic modes and a strongly damped radiation-diffusion
mode. The theory has been applied to the example of the interaction
of the solar acoustic oscillations with discrete photospheric magnetic
structures such as sunspots, pores, and knots.
Title: Models of Magnetic Flux Sheets
Authors: Grossmann-Doerth, U.; Knölker, M.; Schüssler, M.;
Weisshaar, E.
Bibcode: 1989ASIC..263..481G
Altcode: 1989ssg..conf..481G
No abstract at ADS
Title: Theoretical aspects and modelling of photospheric flux tubes.
Authors: Knölker, M.; Schüssler, M.
Bibcode: 1989ftsa.conf...17K
Altcode:
This paper discusses some aspects of the theoretical description of
concentrated magnetic fields in the solar photosphere. The authors
focus on processes leading to the formation and destruction of magnetic
elements and on the properties of their quasi-equilibrium state. Results
of 2D model calculations of flux slabs are discussed in some detail with
emphasis on the continuum intensity and its center-to-limb variation.
Title: On the radiative damping of p-modes in solar magnetic flux
concentrations.
Authors: Knoelker, M.; Bogdan, T. J.
Bibcode: 1988ESASP.286..265K
Altcode: 1988ssls.rept..265K
In a generalization of a work by Mihalas and Mihalas (1983) describing
the propagation of compressive disturbances in a radiating fluid,
the authors include the dynamical influence of a uniform magnetic
field. The radiating fluid is treated to be gray, in LTE and assumed
to obey the Eddington approximation. The authors apply these results
to the interaction of solar p-modes with sunspots in the context of
a simple model developed by Abdelatif and Thomas (1987). For physical
conditions representative of the solar envelope and for a variety of
embedded magnetic structures, the temperature fluctuations associated
with compressive waves are reduced inside the magnetic regions. Hence,
radiative damping of these disturbances is suppressed to an extent that
depends upon the nature of the mode (fast or slow magnetoacoustic)
and the propagation direction relative to the uniform background
field. This conclusion raises some interesting predictions concerning
the observational signatures of compressive waves in the solar envelope.
Title: Model calculations of magnetic flux tubes. IV - Convective
energy transport and the nature of intermediate size flux
concentrations
Authors: Knoelker, M.; Schuessler, M.
Bibcode: 1988A&A...202..275K
Altcode:
Results of 2D-MHD simulations of solar (sub-) photospheric magnetic flux
concentrations with sizes between 500 km and 1000 km are presented. A
residual level of convective energy transport within the magnetic
structure is assumed to be maintained by oscillatory convection or by
motions driven by the Rayleigh-Taylor instability since pure radiative
transport leads to density inversions. The calculated flux sheet models
demonstrate the decreasing efficiency of heating by lateral influx of
radiation with increasing size of the structure. Flux concentrations
with sizes greater than about 500 km appear darker than the mean
pahotosphere if observed at the center of the solar disk but display a
significant brightness enhancement near the limb. The results are used
to resolve the apparent contradiction between the data obtained with
the Fourier Transform Spectrometer in network and plage regions which
imply small, hot and bright structures and spectra with high spatial
resolution (less than about 1 arcsec) which reveal comparatively
large (1-2 arcsecs), dark magnetic structures in active regions. All
observations can be reconciled if the larger structures are clusters
of small magnetic elements and partly suppress the convective energy
transport.
Title: Model calculations of magnetic flux tubes. III - Properties
of solar magnetic elements
Authors: Knoelker, M.; Schuessler, M.; Weisshaar, E.
Bibcode: 1988A&A...194..257K
Altcode:
The paper presents the results of 2D-MHD simulations of small magnetic
flux concentrations in the solar photosphere. Consideration is given
to the effects of extended boundary layers (i.e., a smooth transition
to the nonmagnetic environment and inhibition of convective energy
transport in the flux concentration surroundings). A comparison is made
with observational data, and it is found that the boundary layer is
likely to be thin compared to the diameter of a magnetic element while
convective transport does not seem to be strongly inhibited outside the
flux concentration. It is found that all models of magnetic elements
are slightly unstable against fluting in the absence of a surrounding
whirl flow.
Title: Models of small magnetic flux concentrations in the solar
photosphere.
Authors: Grossmann-Doerth, U.; Knölker, M.; Schüssler, M.
Bibcode: 1988AGAb....1...11G
Altcode:
No abstract at ADS
Title: Einige Aspekte der Erfordernisse und Möglichkeiten zeitlicher
Auflösung in der optischen Sonnenphysik
Authors: Kneer, F.; Knölker, M.
Bibcode: 1987MitAG..68..167K
Altcode:
No abstract at ADS
Title: On the frequencies of solar oscillations.
Authors: Stix, M.; Knoelker, M.
Bibcode: 1987ppcs.work...67S
Altcode:
Solar oscillations, with frequencies between 2 and 5 mHz, can be
identified as p modes with well-determined degree 1 and overtone number
n, but minor discrepancies, of order 10 μHz, between observed and
calculated frequencies remain. The authors describe the computation
of solar models and their frequencies of oscillation, check the
accuracy of the numerical results, and study the influence of the
atmosphere. Attempts to improve the calculated frequencies for
low degree and intermediate order (n = 10...20) have so far been
unsuccessful.
Title: High Resolution Spectroscopy of Sunspot Penumbrae
Authors: Wiehr, E.; Knölker, M.; Grosser, H.; Stellmacher, G.
Bibcode: 1987rfsm.conf..162W
Altcode:
The spatial variation of velocity- and magnetic field within penumbral
finestructures is investigated from two very highly resolved spectra.
Title: Evidence for quasi-periodic Doppler motions in solar
prominences
Authors: Balthasar, H.; Knoelker, M.; Wiehr, E.; Stellmacher, G.
Bibcode: 1986A&A...163..343B
Altcode:
Observations of Doppler displacements in solar prominences have been
performed using the Hα emission line. Evidence is found for the
existence of quasi-periodic line-of-sight velocities in the range of
2.5 - 4.7 mHz. Former findings of long time variations near one hour
are confirmed. Possible influences by misguiding and by image motion
can be excluded. Scattered light from the solar aureola cannot produce
the observed amplitudes.
Title: The sharp decrease of Evershed effect and magnetic field at
the outer sunspot border
Authors: Wiehr, E.; Knoelker, M.; Grosser, H.; Stellmacher, G.
Bibcode: 1986A&A...155..402W
Altcode:
Spatially high-resolved spectra of a small split line (g = 0.5) in
four sunspots at different heliographic angles show that the combined
effect of line core velocities and line asymmetries (defined as Evershed
effect) is strongly limited to the sunspot area defined by the continuum
intensity step. Occasionally observed 'adjoining velocity maxima'
just outside the sunspot edges are not related to line asymmetries,
thus indicating a different origin than that of the classical Evershed
effect. A similar concentration of the very spot area is found for
the magnetic line broadening of two large split lines. Both results
indicate that magnetic field and velocity field are sharply restricted
to the visible sunspot, the often observed smooth discontinuity of
both quantities are thus considered to be due to seeing.
Title: Small Scale Magnetic Flux Concentrations in the Solar
Photosphere
Authors: Deinzer, W.; Knölker, M.; Voigt, H. H.
Bibcode: 1986ssmf.conf.....D
Altcode: 1986ssmf.book.....D
No abstract at ADS
Title: A Note on the Radiative Equilibrium in 2-D Fluxtube Models
Authors: Knölker, M.
Bibcode: 1986ssmf.conf..165K
Altcode:
No abstract at ADS
Title: Model Calculations of Solar Photospheric Flux Concentrations
Authors: Knoelker, M.; Schussler, M.; Weisshaar, E.
Bibcode: 1985tphr.conf..195K
Altcode:
No abstract at ADS
Title: Model calculations of solar photospheric flux concentrations.
Authors: Knölker, M.; Schüssler, M.; Weisshaar, E.
Bibcode: 1985MPARp.212..195K
Altcode:
No abstract at ADS
Title: The influence of penumbral fine structures on line profiles
Authors: Wiehr, E.; Koch, A.; Knoelker, M.; Kueveler, G.; Stellmacher,
G.
Bibcode: 1984A&A...140..352W
Altcode:
An experimental investigation of the effect of penumbral fine structure
on the line profiles of Ti 5222.7 A and Fe(+) 5264.8 is presented. The
highly resolved penumbral spectrum was observed with the evacuated
Locarno telescope of the Goettingen observatory. It is shown that the
highly excited Fe(+) line has a strong correlation in its line symmetry
to bright spectrum streaks. Line core shift was correlated with dark
spectrum streaks. The Doppler shift of the Be(+) line increased by 1.2
km/s, and that of the Ti line by 0.7 km/s for a continuum brightness
decrease of 20 percent. On the basis of the observational data, it
is concluded that the two-component model of sunspot penumbrae is
unlikely. It is suggested that Evershed asymmetry originates mainly
from a mixture of fine structure.
Title: Solar oscillations as an algebraic eigenvalue problem
Authors: Knoelker, M.; Stix, M.
Bibcode: 1984MmSAI..55..305K
Altcode:
The 'Cowling approximation', where the Eulerian perturbation of the
gravitational potential is neglected, is used to obtain the frequencies
of adiabatic solar oscillations as eigenvalues of a real symmetric
matrix. The computed p-mode spectra of low and high degree are compared
with observational results. It is suggested that the influence of
the Coulomb interactions on the equation of state, which is presently
neglected, will probably improve the degree of agreement obtained.
Title: Solar Oscillations and the Equation of State
Authors: Kaisig, M.; Knolker, M.; Stix, M.
Bibcode: 1984LIACo..25..239K
Altcode: 1984trss.conf..239K; 1984tpss.conf..239K
No abstract at ADS
Title: A Convenient Method to Obtain Stellar Eigenfrequencies
Authors: Knoelker, M.; Stix, M.
Bibcode: 1983SoPh...82..331K
Altcode: 1983IAUCo..66..331K
The differential equations describing stellar oscillations are
transformed into an algebraic eigenvalue problem. Frequencies
of adiabatic oscillations are obtained as the eigenvalues of a
banded real symmetric matrix. We employ the Cowling-approximation,
i.e. neglect the Eulerian perturbation of the gravitational potential,
and, in order to preserve selfadjointness, require that the Eulerian
pressure perturbation vanishes at the outer boundary. For a solar model,
comparison of first results with results obtained from a Henyey method
shows that the matrix method is convenient, accurate, and fast.
Title: Solare Oszillationen als algebraisches Eigenwertproblem
Authors: Knoelker, M.; Stix, M.
Bibcode: 1983MitAG..60..221K
Altcode:
No abstract at ADS
Title: Neuere Ergebnisse der Beobachtung und Interpretation solarer
Oszillationen
Authors: Knoelker, M.
Bibcode: 1983MitAG..60..215K
Altcode:
No abstract at ADS
Title: Magnetfeld, Intensität und Strömung in
Penumbra-Feinstrukturen
Authors: Stellmacher, G.; Wiehr, E.; Knölker, M.
Bibcode: 1982MitAG..55...68S
Altcode:
No abstract at ADS
Title: Eine bequeme Methode zur Berechnung stellarer Eigenfrequenzen -
Anwendungen auf Sonnenmodelle
Authors: Knölker, M.; Stix, M.
Bibcode: 1982MitAG..55..138K
Altcode:
No abstract at ADS
Title: Das OPTRONICS S-3000 Microdensitometer in Freiburg (KIS)
Authors: Großmann-Doerth, U.; Knölker, M.
Bibcode: 1982MitAG..55..168G
Altcode:
No abstract at ADS
Title: Rms-value and power spectrum of the photospheric
intensity-fluctuations
Authors: Schmidt, W.; Knoelker, M.; Schroeter, E. H.
Bibcode: 1981SoPh...73..217S
Altcode:
The power spectrum and the rms-value of the granular intensity
fluctuations were studied using granulation photographs of
excellent quality obtained during the JOSO site testing campaign
1979 at Izaña. The observed power spectrum was corrected using
various effective modulation transfer functions of the system:
telescope+aberrations+atmospheric seeing, assuming different
contributions of the atmospheric seeing. With this procedure a
lower and upper limit for the `true' power spectrum of the granular
intensity fluctuations and thus for the rms-value could be derived:
7.2% <Irms <12% at λ = 550 nm, with a most probable
value of Irms = 10.5%. We checked the validity of the
upper limit by applying to our data a MTF (Deubner and Mattig, 1975),
which certainly must lead to an overcorrection. This procedure lead
to Irms = 13.4%. Thus we can state that the true rms-value
of the granular intensity fluctuations does certainly not exceed 13%
at λ = 550 nm.
Title: Powerspektrum und rms-Wert der photosphärischen
Intensitätsfluktuationen
Authors: Schmidt, W.; Knölker, M.; Schröter, E. H.
Bibcode: 1981MitAG..52Q.127S
Altcode:
No abstract at ADS
Title: Modellrechnungen solarer p-modes
Authors: Knölker, M.
Bibcode: 1979MitAG..45..188K
Altcode:
No abstract at ADS