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Author name code: frank
ADS astronomy entries on 2022-09-14
author:"Frank, Zoe"
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Title: Changes in granulation scales over the solar cycle seen with
SDO/HMI and Hinode/SOT
Authors: Ballot, J.; Roudier, T.; Malherbe, J. M.; Frank, Z.
2021A&A...652A.103B Altcode: 2021arXiv210603556B
Context. The Sun is the only star where the superficial turbulent
convection can be observed at very high spatial resolution. The
Solar Dynamics Observatory (SDO) has continuously observed the full
Sun from space with multi-wavelength filters since July 2010. In
particular, the Helioseismic and Magnetic Imager (HMI) instrument
takes high-cadence frames (45 s) of continuum intensity in which
solar granulation is visible. <BR /> Aims: We aimed to follow the
evolution of the solar granules over an activity cycle and look for
changes in their spatial properties. <BR /> Methods: We investigated
the density of granules and their mean area derived directly from
the segmentation of deconvolved images from SDO/HMI. To perform the
segmentation, we define granules as convex elements of images. <BR
/> Results: We measured an approximately 2% variation in the density
and the mean area of granules over the cycle, the density of granules
being greater at solar maximum with a smaller granule mean area. The
maximum density appears to be delayed by about one year compared
to classical activity indicators, such as the sunspot number. We
complemented this study with high-spatial-resolution observations
obtained with Hinode/SOTBFI (Solar Optical Telescope Broadband Filter
Imager), which are consistent with our results. <BR /> Conclusions:
The observed variations in solar granulation at the disc centre reveal
a direct insight into the change in the physical properties that occur
in the upper convective zone during a solar cycle. These variations
can be due to interactions between convection and magnetic fields,
either at the global scale or, locally, at the granulation scale.
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Title: mschauer/BridgeLandmarks.jl: v0.4.0
Authors: Frank; Schauer, Moritz
2021zndo...5101751F Altcode:
BridgeLandmarks v0.4.0 Diff since v0.3.1 Closed issues: Registration
(#19) Merged pull requests: CompatHelper: bump compat for "Plots" to
"1.0" (#24) (@github-actions[bot]) CompatHelper: bump compat for
"GaussianDistributions" to "0.4" (#25) (@github-actions[bot])
CompatHelper: bump compat for "DataFrames" to "0.21" (#28)
(@github-actions[bot]) CompatHelper: add new compat entry for
"StatsFuns" at version "0.9" (#38) (@github-actions[bot]) CompatHelper:
bump compat for "JLD2" to "0.3" (#41) (@github-actions[bot])
CompatHelper: bump compat for "DataFrames" to "0.22" (#42)
(@github-actions[bot]) MassInstallAction: Install the Documenter
workflow on this repository (#44) (@mschauer) MassInstallAction: Install
the CI workflow on this repository (#45) (@mschauer) CompatHelper:
bump compat for "DataFrames" to "1.0" (#49) (@github-actions[bot])
CompatHelper: bump compat for "Distributions" to "0.25" (#50)
(@github-actions[bot]) CompatHelper: bump compat for "StaticArrays"
to "1.2" (#51) (@github-actions[bot]) finalchanges (#52) (@fmeulen)
new version nr (#53) (@fmeulen) change version bounds (#54) (@fmeulen)
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Title: mschauer/Bridge.jl: v0.11.6
Authors: Schauer, Moritz; Frank; getzdan; Bezanson, Jeff; Corstanje,
Marc; Piibeleht, Morten; Simon; Kelman, Tony
2021zndo....891230S Altcode: 2019zndo....891230S
Bridge v0.11.6 Diff since v0.11.5 Closed issues: Release 0.11.* (#65)
Merged pull requests: CompatHelper: bump compat for "StaticArrays"
to "1.0" (#84) (@github-actions[bot]) CompatHelper: bump compat for
"SpecialFunctions" to "1.2" (#86) (@github-actions[bot]) CompatHelper:
bump compat for "Polynomials" to "2.0" (#87) (@github-actions[bot])
CompatHelper: bump compat for "StaticArrays" to "1.1" (#88)
(@github-actions[bot])
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Title: Photospheric downflows observed with SDO/HMI, HINODE, and an
MHD simulation
Authors: Roudier, T.; Švanda, M.; Malherbe, J. M.; Ballot, J.; Korda,
D.; Frank, Z.
2021A&A...647A.178R Altcode: 2021arXiv210303077R
Downflows on the solar surface are suspected to play a major role in
the dynamics of the convection zone, at least in its outer part. We
investigate the existence of the long-lasting downflows whose effects
influence the interior of the Sun but also the outer layers. We study
the sets of Dopplergrams and magnetograms observed with Solar Dynamics
Observatory and Hinode spacecrafts and an magnetohydrodynamic (MHD)
simulation. All of the aligned sequences, which were corrected from
the satellite motions and tracked with the differential rotation,
were used to detect the long-lasting downflows in the quiet-Sun at
the disc centre. To learn about the structure of the flows below the
solar surface, the time-distance local helioseismology was used. The
inspection of the 3D data cube (x, y, t) of the 24 h Doppler sequence
allowed us to detect 13 persistent downflows. Their lifetimes lie in
the range between 3.5 and 20 h with a sizes between 2″ and 3″ and
speeds between −0.25 and −0.72 km s<SUP>−1</SUP>. These persistent
downflows are always filled with the magnetic field with an amplitude of
up to 600 Gauss. The helioseismic inversion allows us to describe the
persistent downflows and compare them to the other (non-persistent)
downflows in the field of view. The persistent downflows seem to
penetrate much deeper and, in the case of a well-formed vortex, the
vorticity keeps its integrity to the depth of about 5 Mm. In the MHD
simulation, only sub-arcsecond downflows are detected with no evidence
of a vortex comparable in size to observations at the surface of the
Sun. The long temporal sequences from the space-borne allows us to show
the existence of long-persistent downflows together with the magnetic
field. They penetrate inside the Sun but are also connected with the
anchoring of coronal loops in the photosphere, indicating a link between
downflows and the coronal activity. A links suggests that EUV cyclones
over the quiet Sun could be an effective way to heat the corona.
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Title: python-visualization/folium v0.12.1
Authors: Filipe; Journois, Martin; Frank; Story, Rob; Gardiner,
James; Rump, Halfdan; Bird, Andrew; Lima, Antonio; Cano, Joshua; Dbf;
Leonel, Juliana; Baker, Jason; Sampson, Tim; Reades, Jon; Welsh, Ben;
Kong, Qingkai; Komarov, Oleg; Crosby, Alex; Harris, George; Dumas,
Raphael; KRIEF, David; Kato, Daisuke; Penguindustin; Wilson, Nat;
Paiva Nogueira, Tales; Kenmatsu4; Furtado, Leonardo; Patil, Anand;
Duke, Justin; Signell, Rich
2021zndo...4447642F Altcode:
Minor bugfix on the version number in the source distribution
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Title: Search Tool for Retrieving Level 2 Data from Hinode's
Spectro-Polarimeter (SP)
Authors: Kam, C.; Arbolante, Q.; Frank, Z.; DeRosa, M. L.
2020AGUFMED0260056K Altcode:
A joint project between JAXA and NASA, the Hinode Solar Optical
Telescope (SOT) has observed our Sun since its launch in October
2006. Mission data has been used extensively to study solar flares,
polar magnetic fields, prominence structures, and changes over the
solar cycle. Archived databases of the SOT filtergraph (FG) images
and spectropolarimeter (SP) maps are maintained in the US, Japan,
and Norway. Many tools for accessing SOT data were developed early
in the mission timeline and are based on Harris Geospatial Solutions
Inc. Interactive Data Language (IDL). We demonstrate a new open source
Python-based search and cross referencing tool for the Hinode SOT
SP. This tool maps their associated Level 2 inversion data products
from the Heliophysics Events Knowlegebase (HEK) and enables greater
accessibility to this ongoing international mission.
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Title: Evolution of exploding granules from coordinated observations
by THEMIS, IRIS, SDO/HMI, and HINODE, and a simulation
Authors: Roudier, T.; Malherbe, J. M.; Gelly, B.; Douet, R.; Frank,
Z.; Dalmasse, K.
2020A&A...641A..50R Altcode: 2020arXiv200712438R
Exploding granules constitute the strongest horizontal flows on the
quiet Sun and contribute to the structure of the surface horizontal
velocity fields which build the large-scale organization of the discrete
magnetic field. In this work we explore exploding granule expansion
through the observations of the ground-based THEMIS telescope, IRIS,
SDO, and the Hinode space-borne instruments, and finally with the
magnetohydrodynamics simulation. We evaluate the detection and the
expansion of exploding granules at several wavelengths and at various
spatial and temporal resolutions. To analyze the different temporal
sequences, two methods of image segmentation are applied to select
the granules. The first allows us to follow individually the exploding
granules observed simultaneously by THEMIS, IRIS, and SDO. The second
uses long time independent sequences from THEMIS, IRIS, SDO, Hinode,
and a simulation. In the first method (called manual) the segmentation
isolates the cell of the granules (bright granules and intergranular
parts), while in the second method (called statistical) only the
bright part of the granules are isolated. The results obtained with
simultaneous or distinct temporal observations using the two methods
of segmentation are in good agreement. The granule area evolves
linearly with an expansion velocity that decreases with the radius. A
rapid decrease in the velocity expansion in the first two minutes is
observed. The detection and measurement of the dynamics of the explosive
granules can be performed from ground- and space-based instruments. Our
work reveals the usefulness of SDO data, with low spatial resolution, to
study the dynamics of the exploding granules all over the solar surface.
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Title: mschauer/BridgeLandmarks.jl: v0.3.0
Authors: Schauer, Moritz; Frank
2020zndo...3634591S Altcode:
A changelog is being generated, please check back in a few minutes.
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Title: Link between trees of fragmenting granules and deep downflows
in MHD simulation
Authors: Roudier, T.; Malherbe, J. M.; Stein, R. F.; Frank, Z.
2019A&A...622A.112R Altcode: 2019arXiv190103255R
Context. Trees of fragmenting granules (TFG) and associated flows
are suspected to play a major role in the formation of the network in
the quiet Sun. We investigate the counterparts, in terms of dynamics,
of surface structures detectable by high resolution observations in
deeper layers up to 15 Mm, which are only available from numerical
simulations. <BR /> Aims: The first aim is to demonstrate that TFG
can be evidenced either from surface intensitites, vertical (Vz),
or Doppler (Vdop) velocities. The second is to show that horizontal
flows, which are derived from intensities or Vz/Vdop flows, are in good
agreement, and that this is the case for observations and numerical
simulations. The third objective is to apply this new Vz-based method
to a 3D simulation to probe relationships between horizontal surface
flows, TFG, and deep vertical motions. <BR /> Methods: The TFG were
detected after oscillation filtering of intensities or Vz/Vdop flows,
using a segmentation and labelling technique. Surface horizontal
flows were derived from local correlation tracking (LCT) and from
intensities or Vz/Vdop flows. These methods were applied to Hinode
observations, 2D surface results of a first simulation, and 3D Vz
data of a second simulation. <BR /> Results: We find that TFG and
horizontal surface flows (provided by the LCT) can be detected either
from intensities or Vz/Vdop component, for high resolution observations
and numerical simulations. We apply this method to a 3D run providing
the Vz component in depth. This reveals a close relationship between
surface TFG (5 Mm mesoscale) and vertical downflows 5 Mm below the
surface. We suggest that the dynamics of TFG form larger scales
(the 15-20 Mm supergranulation) associated with 15 Mm downflowing
cells below the surface. <BR /> Conclusions: The TFG and associated
surface flows seem to be essential to understanding the formation
and evolution of the network at the meso and supergranular scale. <P
/>Movies associated to Figs. 3, 11, 12, and 14 are availabe at <A
href="https://www.aanda.org/10.1051/0004-6361/201834283/olm">https://www.aanda.org</A>
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Title: roced-scheduler/ROCED 1.1.0
Authors: GuentherErli; mschnepf; Frank; Hauth, Thomas; GeorgFleig
2018zndo...1888310G Altcode:
ROCED cloud scheduler
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Title: Dynamics of Trees of Fragmenting Granules in the Quiet Sun:
Hinode/SOT Observations Compared to Numerical Simulation
Authors: Malherbe, J. -M.; Roudier, T.; Stein, R.; Frank, Z.
2018SoPh..293....4M Altcode: 2018arXiv180401870M
We compare horizontal velocities, vertical magnetic fields, and the
evolution of trees of fragmenting granules (TFG, also named families of
granules) derived in the quiet Sun at disk center from observations
at solar minimum and maximum of the Solar Optical Telescope (SOT
on board Hinode) and results of a recent 3D numerical simulation
of the magneto-convection. We used 24-hour sequences of a 2D field
of view (FOV) with high spatial and temporal resolution recorded by
the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager
(NFI). TFG were evidenced by segmentation and labeling of continuum
intensities. Horizontal velocities were obtained from local correlation
tracking (LCT) of proper motions of granules. Stokes V provided a
proxy of the line-of-sight magnetic field (BLOS). The MHD simulation
(performed independently) produced granulation intensities, velocity,
and magnetic field vectors. We discovered that TFG also form in the
simulation and show that it is able to reproduce the main properties
of solar TFG: lifetime and size, associated horizontal motions, corks,
and diffusive index are close to observations. The largest (but not
numerous) families are related in both cases to the strongest flows
and could play a major role in supergranule and magnetic network
formation. We found that observations do not reveal any significant
variation in TFG between solar minimum and maximum.
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Title: Comparing Dynamics in Eruptive and Non-Eruptive Flares
Authors: Nitta, Nariaki; Tarbell, Theodore D.; Slater, Gregory L.;
Frank, Zoe Anne
2016SPD....47.0620N Altcode:
Close comparison of EUV and coronagraph data suggests that there may
not be clear distinction between eruptive and non-eruptive flares as
far as the coronal and chromospheric signatures are concerned. Here we
define eruptive and non-eruptive flares in terms of the presence and
absence of the associated coronal mass ejection (CME). We have studied
several flares in both categories using Hinode/SOT and IRIS data. The
pointing of the Hinode/SOT data has been updated by correlating
them with AIA 1700 A images. We show our initial results about how
the flare development compares in eruptive and non-eruptive flares,
including the reconnection rate as derived from the magnetic field
swept over by flare ribbons (in SOT Ca images), and the line-of-sight
velocities at different locations and temperatures (in IRIS spectral
data). We also discuss large-scale disturbances and related CMEs in
SDO/AIA and SOHO/LASCO data as context information.
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Title: Relation between trees of fragmenting granules and
supergranulation evolution
Authors: Roudier, Th.; Malherbe, J. M.; Rieutord, M.; Frank, Z.
2016A&A...590A.121R Altcode: 2016arXiv160404118R
Context. The determination of the underlying mechanisms of the
magnetic elements diffusion over the solar surface is still a
challenge. Understanding the formation and evolution of the solar
network (NE) is a challenge, because it provides a magnetic flux over
the solar surface comparable to the flux of active regions at solar
maximum. <BR /> Aims: We investigate the structure and evolution of
interior cells of solar supergranulation. From Hinode observations,
we explore the motions on solar surface at high spatial and temporal
resolution. We derive the main organization of the flows inside
supergranules and their effect on the magnetic elements. <BR />
Methods: To probe the superganule interior cell, we used the trees of
fragmenting granules (TFG) evolution and their relations to horizontal
flows. <BR /> Results: Evolution of TFG and their mutual interactions
result in cumulative effects able to build horizontal coherent flows
with longer lifetime than granulation (1 to 2 h) over a scale up to
12”. These flows clearly act on the diffusion of the intranetwork
(IN) magnetic elements and also on the location and shape of the
network. <BR /> Conclusions: From our analysis during 24 h, TFG appear
as one of the major elements of the supergranules which diffuse
and advect the magnetic field on the Sun's surface. The strongest
supergranules contribute the most to magnetic flux diffusion in the
solar photosphere. <P />Movies are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201628111/olm">http://www.aanda.org</A>
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Title: Families of Granules, Flows, and Acoustic Events in the Solar
Atmosphere from Hinode Observations
Authors: Malherbe, J. -M.; Roudier, T.; Frank, Z.; Rieutord, M.
2015SoPh..290..321M Altcode: 2014SoPh..tmp..189M
We investigate the relationship between trees of fragmenting granules
(TFG), horizontal and vertical flows, and acoustic events (AE) in the
photospheric network. AE are spatially concentrated and short-duration
locations of acoustic energy flux. We performed observations at disk
center of a 2D field of view (FOV) with high spatial and temporal
resolutions provided by the Solar Optical Telescope onboard Hinode. Line
profiles of Fe I 557.6 nm were recorded by the Narrow-band Filter
Imager on an 80″×36″ FOV during five hours with a cadence of
22 seconds and 0.08″ pixel size. Vertical velocities were derived
at two atmospheric levels allowing the determination of the energy
flux at the acoustic frequency of 3.3 mHz. Families of granules and
horizontal velocities were obtained from local correlation tracking
(LCT) after segmentation and labeling of either continuum intensities
or granular Doppler shifts. AE exhibit durations in the range 0.25
to 1 hour compatible with the lifetime of families (80 % do not last
more than two hours). High-energy AE have the shortest lifetimes. We
found that most AE occur in intergranular lanes located in or close
to the boundaries between different families (called inter families)
in regions with predominantly downward vertical motions and horizontal
converging flows. In contrast, diverging flows are observed inside
families, with a few AE in the intergranules. At the beginning of the
sequence, when families are not yet detected, the distribution of AE
is not uniform and is already organized at spatial lengths related to
the mesogranular scale, with maximum contribution in the range 5″
to 10″, fully compatible with the scale of the maximum contribution
of families in the TFG space. Although all sizes and durations seem
to exist for families, their number decreases with increasing size
and lifetime.
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Title: Comparison of solar horizontal velocity fields from SDO/HMI
and Hinode data
Authors: Roudier, Th.; Rieutord, M.; Prat, V.; Malherbe, J. M.; Renon,
N.; Frank, Z.; Švanda, M.; Berger, T.; Burston, R.; Gizon, L.
2013A&A...552A.113R Altcode: 2013arXiv1303.4271R
Context. The measurement of the Sun's surface motions with a high
spatial and temporal resolution is still a challenge. <BR /> Aims:
We wish to validate horizontal velocity measurements all over the
visible disk of the Sun from Solar Dynamics Observatory/ Helioseismic
and Magnetic Imager (SDO/HMI) data. <BR /> Methods: Horizontal velocity
fields are measured by following the proper motions of solar granules
using a newly developed version of the coherent structure tracking
(CST) code. The comparison of the surface flows measured at high
spatial resolution (Hinode, 0.1 arcsec) and low resolution (SDO/HMI,
0.5 arcsec) allows us to determine corrections to be applied to
the horizontal velocity measured from HMI white light data. <BR />
Results: We derive horizontal velocity maps with spatial and temporal
resolutions of respectively 2.5 Mm and 30 min. From the two components
of the horizontal velocity v<SUB>x</SUB> and v<SUB>y</SUB> measured
in the sky plane and the simultaneous line of sight component from
SDO/HMI dopplergrams v<SUB>D</SUB>, we derive the spherical velocity
components (v<SUB>r</SUB>, v<SUB>θ</SUB>, v<SUB>ϕ</SUB>). The
azimuthal component v<SUB>ϕ</SUB> gives the solar differential rotation
with a high precision (± 0.037 km s<SUP>-1</SUP>) from a temporal
sequence of only three hours. <BR /> Conclusions: By following the
proper motions of the solar granules, we can revisit the dynamics of
the solar surface at high spatial and temporal resolutions from hours
to months and years with the SDO data.
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Title: Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.; Tarbell, T.
2012ASPC..454..143R Altcode:
We study dynamics of quiescent prominences using several data sets
taken with the SOT on Hinode. We find a number of processes occurring
at different stages of the prominence evolution that are common for
all the chosen cases, and having universal character, can be related
to a fundamental plasma instabilities. We combine the observational
evidence and theory to identify these instabilities. Here we discuss
only two examples: (1) Coronal cavity formation under a prominence
body and its evolution associated with screw pinch instability, and
(2) Development of a regular series of plumes and spikes typical to
the Rayleigh-Taylor instability modified by solenoidal magnetic field.
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Title: The Power Spectrum of the Solar Surface Flows from Hinode
Data and First Observations with MOF/CALAS Pic-du-Midi
Authors: Roudier, T.; Rieutord, M.; Rincon, F.; Malherbe, J. -M.;
Brito, D.; Berger, T.; Frank, Z.; Parés, L.; Bourrec, E.; Beigbeder,
F.
2012ASPC..454...47R Altcode:
Many features of solar surface turbulence, like the supergranulation,
are still poorly understood.We use long time series of images taken by
the Solar Optical Telescope on board the Hinode satellite to determine
the velocity fields. The dynamics in the subgranulation range can
be investigated with unprecedented precision thanks to the absence
of seeing effects and the use of the MTF of SOT for correcting the
spectra. The first MOF/CALAS/Pic-du-Midi results are also shown.
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Title: Some Dynamic Analysis of the Photosphere from Hinode/SOT and
SDO/HMI Observations
Authors: Roudier, T.; Malherbe, J.; Rieutord, M.; Berger, T.; Frank,
Z.; Prat, V.; Renon, N.; Gizon, L.; Svanda, M.
2012ASPC..456...65R Altcode:
We first present the important role played by the families of granule
(or Tree of Fragmenting granules) in the formation of the photospheric
network. Then, we describe the occurence and characteristics of
acoustic events (AE), defined as spatially concentrated energy flux,
in the quiet Sun. Finally, we present how horizontal velocities obtained
from SDO/HMI data are calibrated by using Hinode/SOT observations.
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Title: Quasi full-disk maps of solar horizontal velocities using
SDO/HMI data
Authors: Roudier, Th.; Rieutord, M.; Malherbe, J. M.; Renon, N.;
Berger, T.; Frank, Z.; Prat, V.; Gizon, L.; Švanda, M.
2012A&A...540A..88R Altcode: 2012arXiv1203.0514R
<BR /> Aims: For the first time, the motion of granules (solar plasma
on the surface on scales larger than 2.5 Mm) has been followed over
the entire visible surface of the Sun, using SDO/HMI white-light
data. <BR /> Methods: Horizontal velocity fields are derived from image
correlation tracking using a new version of the coherent structure
tracking algorithm. The spatial and temporal resolutions of the
horizontal velocity map are 2.5 Mm and 30 min, respectively. <BR
/> Results: From this reconstruction, using the multi-resolution
analysis, one can obtain to the velocity field at different scales
with its derivatives such as the horizontal divergence or the vertical
component of the vorticity. The intrinsic error on the velocity is
~0.25 km s<SUP>-1</SUP> for a time sequence of 30 min and a mesh size
of 2.5 Mm. This is acceptable compared to the granule velocities, which
range between 0.3 km s<SUP>-1</SUP> and 1.8 km s<SUP>-1</SUP>. A high
correlation between velocities computed from Hinode and SDO/HMI has
been found (85%). From the data we derive the power spectrum of the
supergranulation horizontal velocity field, the solar differential
rotation, and the meridional velocity.
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Title: Flares Producing Well-organized Post-flare Arcades (Slinkies)
Have Early Precursors
Authors: Ryutova, M. P.; Frank, Z.; Hagenaar, H.; Berger, T.
2011ApJ...733..125R Altcode:
Exploding loop systems producing X-ray flares often, but not always,
bifurcate into a long-living, well-organized system of multi-threaded
loop arcades resembling solenoidal slinkies. The physical conditions
that cause or prevent this process are not known. To address this
problem, we examined most of the major (X-class) flares that occurred
during the last decade and found that the flares that bifurcate into
long-living slinky arcades have different signatures than those that
do not "produce" such structures. The most striking difference is that,
in all cases of slinky formation, GOES high energy proton flux becomes
significantly enhanced 10-24 hr before the flare occurs. No such effect
was found prior to the "non-slinky" flares. This fact may be associated
with the difference between energy production by a given active region
and the amount of energy required to bring the entire system into
the form of well-organized, self-similar loop arcades. As an example
illustrating the process of post-flare slinky formation, we present
observations taken with the Hinode satellite, in several wavelengths,
showing a time sequence of pre-flare and flare activity, followed by
the formation of dynamically stable, well-organized structures. One
of the important features revealed is that post-flare coronal slinky
formation is preceded by scale invariant structure formation in the
underlying chromosphere/transition region. We suggest that the observed
regularities can be understood within the framework of self-organized
critical dynamics characterized by scale invariant structure formation
with critical parameters largely determined by energy saturation
level. The observed regularities per se may serve as a long-term
precursor of strong flares and may help to study predictability of
system behavior.
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Title: Observation of Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Tarbell, T.; Title, A.
2010SoPh..267...75R Altcode: 2010SoPh..tmp..170R
We study dynamics of quiescent prominences using several data sets taken
with the Solar Optical Telescope (SOT) on Hinode. We find a number of
processes occurring at different stages of prominence evolution that
are common for all of our chosen cases and, having universal character,
can be related to fundamental plasma instabilities. We combine the
observational evidence and theory to identify these instabilities. Here
we discuss three examples: i) prominence cavity formation and its
evolution, associated with a screw-pinch instability; ii) development
of a regular series of plumes and spikes typical to the Rayleigh -
Taylor (RT) instability; and iii) the appearance of growing ripples at
the prominence/corona interface, often followed by a sudden collimated
mass upflow, attributed to the Kelvin - Helmholtz (KH) instability. The
conditions for transition from a linear (rippling mode) to nonlinear
stage of the KH instability, known to have an explosive character,
are specified. Given excellent Hinode data, all three aspects of
prominence dynamics allow quantitative analysis.
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Title: Sharing new data from Solar Dynamics Observatory
Authors: Friedman, Benji; Zita, E. J.; Frank, Zoe
2010APS..NWS.D1004F Altcode:
New data from the Solar Dynamics Observatory (SDO) provides
opportunities to share exciting information about the Sun with people
outside the field of science. This presents the challenge of how best
to communicate important findings to an audience that may not know the
astrophysical vernacular to understand what's going on. This summer,
I worked on various methods, including Facebook and Lockheed Martin's
Picture of the Day website, to inform the public about the Sun, that
mysterious star on which we rely. I will describe methods for finding
interesting new solar events, making pictures and movies of solar
dynamics, and uploading and annotating them for the public.
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Title: Emergence of Helical Flux and the Formation of an Active
Region Filament Channel
Authors: Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.;
Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.
2010ApJ...718..474L Altcode:
We present comprehensive observations of the formation and evolution
of a filament channel within NOAA Active Region (AR) 10978 from
Hinode/Solar Optical Telescope and TRACE. We employ sequences
of Hinode spectro-polarimeter maps of the AR, accompanying Hinode
Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode
Broadband Filter Instrument filtergrams in the Ca II H line and G-band,
Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 Å image
sequences. The development of the channel resembles qualitatively
that presented by Okamoto et al. in that many indicators point to
the emergence of a pre-existing sub-surface magnetic flux rope. The
consolidation of the filament channel into a coherent structure takes
place rapidly during the course of a few hours, and the filament form
then gradually shrinks in width over the following two days. Particular
to this filament channel is the observation of a segment along its
length of horizontal, weak (500 G) flux that, unlike the rest of the
filament channel, is not immediately flanked by strong vertical plage
fields of opposite polarity on each side of the filament. Because this
isolated horizontal field is observed in photospheric lines, we infer
that it is unlikely that the channel formed as a result of reconnection
in the corona, but the low values of inferred magnetic fill fraction
along the entire length of the filament channel suggest that the bulk
of the field resides somewhat above the low photosphere. Correlation
tracking of granulation in the G band presents no evidence for either
systematic flows toward the channel or systematic shear flows along
it. The absence of these flows, along with other indications of these
data from multiple sources, reinforces (but does not conclusively
demonstrate) the picture of an emerging flux rope as the origin of
this AR filament channel.
---------------------------------------------------------
Title: On the power spectrum of solar surface flows
Authors: Rieutord, M.; Roudier, T.; Rincon, F.; Malherbe, J. -M.;
Meunier, N.; Berger, T.; Frank, Z.
2010A&A...512A...4R Altcode: 2009arXiv0911.3319R
Context. The surface of the Sun provides us with a unique and
very detailed view of turbulent stellar convection. Studying its
dynamics can therefore help us make significant progress in stellar
convection modelling. Many features of solar surface turbulence like
the supergranulation are still poorly understood. <BR /> Aims: The aim
of this work is to give new observational constraints on these flows
by determining the horizontal scale dependence of the velocity and
intensity fields, as represented by their power spectra, and to offer
some theoretical guidelines to interpret these spectra. <BR /> Methods:
We use long time-series of images taken by the Solar Optical Telescope
(SOT) on board the Hinode satellite; we reconstruct both horizontal
(by granule tracking) and vertical (by Doppler effect) velocity
fields in a field-of-view of ~ 75 × 75 Mm<SUP>2</SUP>. The dynamics
in the subgranulation range can be investigated with unprecedented
precision thanks to the absence of seeing effects and the use of the
modulation transfer function of SOT for correcting the spectra. <BR />
Results: At small subgranulation scales down to 0.4 Mm the spectral
density of kinetic energy associated with vertical motions exhibits
a k<SUP>-10/3</SUP>-like power law, while the intensity fluctuation
spectrum follows either a k<SUP>-17/3</SUP> or a k<SUP>-3</SUP>-like
power law at the two continuum levels investigated (525 and 450
nm respectively). We discuss the possible physical origin of these
scalings and interpret the combined presence of k<SUP>-17/3</SUP> and
k<SUP>-10/3</SUP> power laws for the intensity and vertical velocity
as a signature of buoyancy-driven turbulent dynamics in a strongly
thermally diffusive regime. In the mesogranulation range and up to a
scale of 25 Mm, we find that the amplitude of the vertical velocity
field decreases like λ<SUP>-3/2</SUP> with the horizontal scale
λ. This behaviour corresponds to a k<SUP>2</SUP> spectral power
law. Still in the 2.5-10 Mm mesoscale range, we find that intensity
fluctuations in the blue continuum also follow a k<SUP>2</SUP>
power law. In passing we show that granule tracking cannot sample
scales below 2.5 Mm. We finally further confirm the presence of a
significant supergranulation energy peak at 30 Mm in the horizontal
velocity power spectrum and show that the emergence of a pore erases
this spectral peak. We tentatively estimate the scale height of the
vertical velocity field in the supergranulation range and find 1 Mm;
this value suggests that supergranulation flows are shallow.
---------------------------------------------------------
Title: Joint STEREO-Hinode Observations of Coronal Dimming and Waves
Associated with a CME/Flare Event
Authors: Nitta, Nariaki; Aschwanden, Markus; Frank, Zoe; Slater,
Gregory; Tarbell, Theodore; Zarro, Dominic
2010cosp...38.2928N Altcode: 2010cosp.meet.2928N
During the solar minimum between cycles 23 and 24, a number of
minor flares from unimpressive active regions were associated with
large-scale dimming and waves as observed by the EUV Imager (EUVI) on
STEREO. We present a detailed study on one of the CME/flare events that
was observed also by the instruments on Hinode. We analyze SOT Ca II
data to explore the origin of the disturbances and EIS slit spectra to
determine the timings of the upflow and associated turbulence that are
presumably correlated with coronal dimming. The sequence of phenomena
as captured by different instruments on STEREO, Hinode and SOHO helps
us identify the key physical processes that gave rise to the event.
---------------------------------------------------------
Title: Response of the Chromosphere to Penumbral Dynamics: Bow Shocks
and Microjets
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.
2009ASPC..415..373R Altcode:
We have analyzed the data sets obtained with the SOT instrument
on Hinode during the disc passage of AR 10923 (November 10--20,
2006). Along with a limited number of jet-like features (Katsukawa
2007), we found other kinds of bright chromospheric transients
abundantly pervading the entire penumbra and drifting as a whole in
a direction perpendicular to their long axes. Quantitative analysis
based on our recent penumbral model (Ryutova et al. 2008a) shows that
they have all the signatures of bow shocks produced in the overlying
chromosphere by post-reconnection penumbral filaments.
---------------------------------------------------------
Title: Supergranulation, Network Formation, and TFGs Evolution from
Hinode Observations
Authors: Roudier, T.; Rincon, F.; Rieutord, M.; Brito, D.; Beigbeder,
F.; Parès, L.; Malherbe, J. -M.; Meunier, N.; Berger, T.; Frank, Z.
2009ASPC..415..203R Altcode:
In this paper, we analyse a a 48h high-resolution time sequence of the
quiet Sun photosphere obtained with the Solar Optical Telescope onboard
Hinode. Using floating corks advected by velocity fields inferred from
photometry measurements, we show that long-living Trees of Fragmenting
Granules play a crucial role in the advection of small-scale magnetic
fields and in the build-up of the magnetic network.
---------------------------------------------------------
Title: Formation and Dynamics of Multi-thread Arcades of Coronal Loops
Authors: Ryutova, M.; Frank, Z.; Berger, T.
2009ASPC..415..291R Altcode:
Coronal structures having various forms and dynamics, often bifurcate
into a long living, well organized multi-thread loop arcades. To
describe this process we use the model of energetically open system,
consisting of current carrying magnetic loops that interconnect a high
β energy production region with a low β dissipation region through
the resistive stresses. The model includes feedback managed by the
transition region. Such a system may be driven into various dynamic
forms including spontaneous process of self-organization.
---------------------------------------------------------
Title: Is Flux Submergence an Essential Aspect of Flux Emergence?
Authors: Lites, B. W.; Frank, Z.; Shine, R. A.; Title, A. M.;
Ichimoto, K.
2009ASPC..415..172L Altcode:
High resolution Hinode Spectro-Polarimeter observations permit one
to examine the detailed structure of the magnetic field vector in
emerging flux regions. We find the field to have a concave-upward
geometry on the smallest scales observed (0.3 arcsec), indicating the
presence of U-loops at the sites of approaching and canceling opposite
polarities. This structure suggests that reconnection is taking place
at or below the surface, allowing the emerging flux to rid itself of
its considerable mass burden. Supersonic down flows are often observed
adjacent to, but not coincident with, the sites of canceling flux. We
propose that these are the sites that drain the mass contained in the
buoyantly-rising flux elements. The observations then suggest a process
of sub-surface reconnection producing O-loops that then are forced to
descend with the intergranular convective down flows, thus making flux
submergence important to the larger scale flux emergence process.
---------------------------------------------------------
Title: Role of the Resistive and Thermal Instabilities in Dynamics
of Quiescent Prominences
Authors: Frank, Z.; Ryutova, M.; Berger, T. E.; Title, A. M.; Tarbell,
T. D.
2009AGUFMSH41B1653F Altcode:
We present the observations taken with the SOT instrument on Hinode in
G-band and Ca H lines. High cadence data compiled in movies show clear
evidence for several fundamental plasma instabilities. We combine
the observational evidence and theoretical estimates to identify
these instabilities. The following can be given as examples. (1)
An analogue of the Kelvin-Helmholtz instability develops at the
prominence/corona interface that manifests itself in growing ripples
during a linear growth phase and may be followed by a nonlinear stage
taking the form of an explosive instability corresponding to a CME
ejection. This instability also includes the regime of "smoke ring"
formation. (2) The appearence of "bubbles and spikes" typical to
the Rayleigh-Taylor instability are observed. Their evolution and
growth rates are found to be modified by both poloidal and toroidal
components of magnetic field. (3) A resistive interchange instability,
associated with an "unfavorable" magnetic field curvature relative to
the density/temperature gradients, may be responsible for a hot barb
formation, its evolution and collapse.
---------------------------------------------------------
Title: Origin of Filamentary Structures and Flows in Quiescent
Prominences
Authors: Ryutova, M.; Berger, T. E.; Tarbell, T. D.; Frank, Z.; Title,
A. M.
2009AGUFMSH23B1540R Altcode:
The paradox of fine vertical structure has usually referred to an
apparent contradiction met when comparing vertical fine structures
of quiescent prominences observed on the limb with the necessary
horizontal magnetic field along their long axis. In addition to this
fundamental problem, the very formation of fine vertical structures
has been a long standing puzzle. Here we address these problems and
show that considering the global structure of a prominence as a large
scale skewed formation with toroidal and poloidal fields removes the
paradox and allows derivation of dynamic stability criteria. This also
includes the mechanism of the fine structure formation and peculiarities
of downward mass motions. Theoretical estimates of key parameters
are compared with the observations taken with the SOT instrument
on Hinode. We find results of comparison very encouraging. For the
approximate 3D reconstruction of the general shape of prominences,
the STEREO A and B images have been used.
---------------------------------------------------------
Title: Has Hinode Revealed the Missing Turbulent Flux of the
Quiet Sun?
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
2009ASPC..405..173L Altcode:
The Hinode Spectro-Polarimeter has revealed the presence of surprisingly
strong horizontal magnetic fields nearly everywhere in the quiet
solar atmosphere. These horizontal fields, along with measures of the
vertical fields, may be the signature of the “hidden turbulent flux”
of the quiet Sun. The measured horizontal fields average at least to
55 Gauss: nearly 5 times that of the measured longitudinal apparent
flux density. The nature of these fields are reviewed, and discussed
in the light of recent magneto-convection numerical simulations of
the quiet Sun.
---------------------------------------------------------
Title: Mesoscale dynamics on the Sun's surface from HINODE
observations
Authors: Roudier, Th.; Rieutord, M.; Brito, D.; Rincon, F.; Malherbe,
J. M.; Meunier, N.; Berger, T.; Frank, Z.
2009A&A...495..945R Altcode: 2009arXiv0902.2299R
Context: <BR />Aims: The interactions of velocity scales on the Sun's
surface, from granulation to supergranulation are still not understood,
nor are their interaction with magnetic fields. We thus aim at giving
a better description of dynamics in the mesoscale range which lies
between the two scales mentioned above. <BR />Methods: We analyse a
48 h high-resolution time sequence of the quiet Sun photosphere at
the disk center obtained with the Solar Optical Telescope onboard
Hinode. The observations, which have a field of view of 100´´ ×
100´´, typically contain four supergranules. We monitor in detail the
motion and evolution of granules as well as those of the radial magnetic
field. <BR />Results: This analysis allows us to better characterize
Trees of Fragmenting Granules issued from repeated fragmentation of
granules, especially their lifetime statistics. Using floating corks
advected by measured velocity fields, we show their crucial role
in the advection of the magnetic field and in the build up of the
network. Finally, thanks to the long duration of the time series, we
estimate that the turbulent diffusion coefficient induced by horizontal
motion is approximately 430 km<SUP>2</SUP> s<SUP>-1</SUP>. <BR
/>Conclusions: These results demonstrate that the long living families
contribute to the formation of the magnetic network and suggest that
supergranulation could be an emergent length scale building up as small
magnetic elements are advected and concentrated by TFG flows. Our
estimate for the magnetic diffusion associated with this horizontal
motion might provide a useful input for mean-field dynamo models.
---------------------------------------------------------
Title: On the Penumbral Jetlike Features and Chromospheric Bow Shocks
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.
2008ApJ...686.1404R Altcode:
We present observations of sunspot penumbrae obtained during the disk
passage of AR 10923 (2006 November 10-20) with the SOT instrument on
Hinode in 4305 Å G band and Ca II λ3968 H line. Along with recently
discovered jetlike features (Katsukawa et al. 2007), we find other
kinds of bright elongated transients abundantly pervading the entire
penumbra and drifting as a whole in a direction almost perpendicular
to their long axes. Their measured velocities strongly depend
on their orientation with respect to the line of sight and range
from simeq1 to simeq20 km s<SUP>-1</SUP>. We present quantitative
analysis of these features and interpret them relative to our recent
penumbral model (Ryutova et al. 2008) to show that they are produced
by shocks resulting from a slingshot effect associated with the ongoing
reconnection processes in neighboring penumbral filaments. Due to sharp
stratification of the low atmosphere, postreconnection flux tubes moving
upward quickly accelerate. At transonic velocities a bow (detached)
shock is formed in front of the flux tube, as usually occurs in cases
of blunt bodies moving with supersonic velocities. Observed parameters
of transients are in good agreement with calculated parameters of
bow shocks. On some, much more rare occasions compared to "drifting"
bow-shock-type transients, there appear compact bright transients
moving in the radial direction, along their long axis, and having
velocities of 20-50 km s<SUP>-1</SUP>. We relate these features to a
category of true microjets.
---------------------------------------------------------
Title: Magnetic Fields of the Quiet Sun: A New Quantitative
Perspective From Hinode
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
2008ASPC..397...17L Altcode:
This article summarizes results of studies presented in two papers
already published: Lites et al. (2007a); Lites et al. (2007b). Please
see these for further details.
---------------------------------------------------------
Title: Hinode Observations of Magnetic Elements in Internetwork Areas
Authors: de Wijn, A. G.; Lites, B. W.; Berger, T. E.; Frank, Z. A.;
Tarbell, T. D.; Ishikawa, R.
2008ApJ...684.1469D Altcode: 2008arXiv0806.0345D
We use sequences of images and magnetograms from Hinode to
study magnetic elements in internetwork parts of the quiet solar
photosphere. Visual inspection shows the existence of many long-lived
(several hours) structures that interact frequently and may migrate
over distances of ~7 Mm over a period of a few hours. About a fifth
of the elements have an associated bright point in G-band or Ca
II H intensity. We apply a hysteresis-based algorithm to identify
elements. The algorithm is able to track elements for about 10 minutes
on average. Elements intermittently drop below the detection limit,
although the associated flux apparently persists and often reappears
some time later. We infer proper motions of elements from their
successive positions and find that they obey a Gaussian distribution
with an rms of 1.57 +/- 0.08 km s<SUP>-1</SUP>. The apparent flows
indicate a bias of about 0.2 km s<SUP>-1</SUP> toward the network
boundary. Elements of negative polarity show a higher bias than elements
of positive polarity, perhaps as a result of the dominant positive
polarity of the network in the field of view or because of increased
mobility due to their smaller size. A preference for motions in X is
likely explained by higher supergranular flow in that direction. We
search for emerging bipoles by grouping elements of opposite polarity
that appear close together in space and time. We find no evidence
supporting Joy's law at arcsecond scales.
---------------------------------------------------------
Title: Evershed Flows as an Integral Part of Penumbral Formation
and its Fine Structure
Authors: Ryutova, M.; Berger, T.; Lites, B.; Title, A.; Frank, Z.
2008AGUSMSP41B..07R Altcode:
Observations of Evershed flows with the Solar Optical Telescope (SOT)
on Hinode (Ichimito, Shine, Lites, et al. 2008, PASJ, 59, S593) showed
that penumbral flows have small scale structures and much more complex
properties than those of a simple outflow of material with unique
direction and appearence. We address this problem and show that the
flow properties are directly connected to the observed properties of
penumbral filaments and are an integral part of penumbral development
during sunspot formation. In our recent model (Ryutova, Berger, &
Title, 2008, ApJ, 676, April), based on the observations that sunspot
has a filamentary structure and consists of a dense conglomerate of
non-collinear interlaced flux tubes, the penumbra is formed due to
an on-going reconnection processes that leads to branching out of the
peripheral flux tubes from the "trunk". As flux tubes have different
parameters, branching occurs at different heights and with different
inclinations, thus forming an "uncombed" penumbra. Each elemental act
of reconnection generates an inevitable twist in the post-reconnection
filaments that acquire a screw pinch configuration. This explains
the remarkable dynamic stability of penumbral filaments and their
observed properties, such as presence of dark cores, wrapping and
spinning of filaments around each other, bright footpoints, etc. Here
we show that propagation of twist along current carrying helical flux
tubes is accompanied by plasma flows that may have diverse properties
depending on the location of interacting flux tubes, their inclination
and pitch. We apply the model to observations taken with the SOT
instrument, which includes spectro-polarimetric data, and perform
quantitative analysis.
---------------------------------------------------------
Title: The Horizontal Magnetic Flux of the Quiet-Sun Internetwork
as Observed with the Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
2008ApJ...672.1237L Altcode:
Observations of very quiet Sun using the Solar Optical
Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft
reveal that the quiet internetwork regions are pervaded by horizontal
magnetic flux. The spatial average horizontal apparent flux density
derived from wavelength-integrated measures of Zeeman-induced linear
polarization is B<SUP>T</SUP><SUB>app</SUB> = 55 Mx cm <SUP>-2</SUP>, as
compared to the corresponding average vertical apparent flux density of
| B<SUP>L</SUP><SUB>app</SUB>| = 11 Mx cm <SUP>-2</SUP>. Distributions
of apparent flux density are presented. Magnetic fields are organized on
mesogranular scales, with both horizontal and vertical fields showing
"voids" of reduced flux density of a few granules spatial extent. The
vertical fields are concentrated in the intergranular lanes, whereas the
stronger horizontal fields are somewhat separated spatially from the
vertical fields and occur most commonly at the edges of the bright
granules. High-S/N observations from disk center to the limb help
to constrain possible causes of the apparent imbalance between |
B<SUP>L</SUP><SUB>app</SUB>| and B<SUP>T</SUP><SUB>app</SUB>, with
unresolved structures of linear dimension on the surface smaller by at
least a factor of 2 relative to the SOT/SP angular resolution being one
likely cause of this discrepancy. Other scenarios for explaining this
imbalance are discussed. The horizontal fields are likely the source of
the "seething" fields of the quiet Sun discovered by Harvey et al. The
horizontal fields may also contribute to the "hidden" turbulent flux
suggested by studies involving Hanle effect depolarization of scattered
radiation.
---------------------------------------------------------
Title: Hinode Observations of Flux Emergence in Quiet and Active
Regions
Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger,
T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.;
Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
2008ASPC..383...71L Altcode:
We review briefly the observational understanding of emergence of
flux in both the quiet Sun and active regions in the light of first
results from the joint Japan/US/UK Hinode mission. That spacecraft
is now providing us with our first continuous, high resolution
measurements of the photospheric vector magnetic field, along with
high resolution observations of the thermal and dynamic properties
of the chromosphere and corona. This review is intended to present a
few very early results and to highlight the potential for discovery
offered by this extraordinary new mission. The discovery of ubiquitous
horizontal magnetic flux in the quiet internetwork regions is presented.
---------------------------------------------------------
Title: On the Chromospheric Micro-jets Associated with the Penumbral
Filaments
Authors: Ryutova, M.; Berger, T.; Tarbell, T.; Frank, Z.; Title, A.
2007AGUFMSH22A0843R Altcode:
We present observations of sunspot penumbrae obtained during the disk
passage of AR 10923 (November 10--20, 2006) with the Solar Optical
Telescope (SOT) on the Hinode satellite. Co-aligned multi-hour movies
taken simultaneously in several wavelengths show fine-scale dynamics
at the sub-arcsecond level. The dynamics include helical flows along
penumbral filaments, branching of filaments, and penumbral "micro-jets"
recently described by Katsukawa et al. (AAS 210, 94.13). We present
quantitative analyzes of the penumbral jets and interpret them relative
to our recent model of penumbral filaments (Ryutova, Berger and Title,
2007, in "Collective phenomena in macroscopic systems", Ed. G. Bertin,
et al., World Scientific) to show that the jets are the result of
magnetic reconnection of the helical field lines in neighboring
non-collinear filaments.
---------------------------------------------------------
Title: Transient Phenomena in Multi-thread Arcades of Coronal Loops
Authors: Frank, Z.; Ryutova, M.
2007AGUFMSH22A0842F Altcode:
The post-flare coronal loops having well defined filamentary
structure, often appear as an arcades of thin magnetic threads
resembling winding in a curved solenoid or a funnel. Compared
to flare timescales, post-flare arcades are long living, well
organized structures. Elemental filaments in arcades are, however,
in highly dynamic state, showing oscillations, and harboring frequent
microflares. These microflares often appear simultaneously in different
places. Besides, many individual filaments produce homologous,
repetitive microflares. Microflares are often accompanied by short
living jets. We present the observations of these events using the
data taken with SOT and XRT instruments on Hinode combined with the
TRACE 195 ~Å coronal line. The object of the observation is AR 10930
which exhibited several flare events in December, 2006. After a major
flare on 13 December, a typical "solenoidal" system of coronal threads
was formed that lasted over 6 hours. The observed spatial and temporal
regularities in appearence of the EUV transients can be well understood
on basis of a spatio-temporal echoes resulted from nonlinear response of
a system ("coupled oscillators") to impulsive disturbences associated
with the changes in the photospheric magnetic fields. Observations in
the SOT chromospheric lines show appearence of precursors of coronal
jets and microflares.
---------------------------------------------------------
Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux
and the “Hidden Turbulent Magnetic Flux”
Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger,
Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title,
Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu,
Yoshinori; Shimizu, Toshifumi
2007PASJ...59S.571L Altcode:
We present observations of magnetic fields of the very quiet Sun
near disk center using the Spectro-Polarimeter of the Solar Optical
Telescope aboard the Hinode satellite. These observations reveal for
the first time the ubiquitous presence of horizontal magnetic fields in
the internetwork regions. The horizontal fields are spatially distinct
from the vertical fields, demonstrating that they are not arising mainly
from buffeting of vertical flux tubes by the granular convection. The
horizontal component has an average “apparent flux density” of
55Mxcm<SUP>-2</SUP> (assuming the horizontal field structures are
spatially resolved), in contrast to the average apparent vertical flux
density of 11Mxcm<SUP>-2</SUP>. The vertical fields reside mainly in
the intergranular lanes, whereas the horizontal fields occur mainly
over the bright granules, with a preference to be near the outside
edge of the bright granules. The large apparent imbalance of vertical
and horizontal flux densities is discussed, and several scenarios are
presented to explain this imbalance.
---------------------------------------------------------
Title: Penumbral Dynamics and its Manifestation in the Overlying
Chromosphere
Authors: Ryutova, Margarita; Berger, Thomas; Tarbell, Theodor; Frank,
Zoe; Title, Alan
2007APS..DPPYP8056R Altcode:
Mature sunspots are usually surrounded by penumbra - a dense
conglomerate of a random interlaced flux tubes with varying
inclinations. High resolution observations show a fine sub-structure
of penumbral filaments and new regularities in their dynamics. These
regularities fit well our recent model of penumbra based on cascading
reconnection events occurring in the system of non-collinear flux
tubes. Each act of reconnection generates twist in the reconnected
filaments and facilitates the onset of a screw pinch instability,
consistent with the observations showing that individual filaments
are cylindrical helices with a pitch/radius ratio providing their
stability. In addition, the post-reconnection products produce a
sling-shot effect that generates oblique shocks and leads to appearence
of a lateral jets. Here we report high resolution (120-180 km) high
cadence (15-30 sec) observations taken with the Solar Optical Telescope
(SOT) on the Hinode satellite. Co-aligned multi-hour movies taken
simultaneously in several wavelengths show detailed behavior of penumbra
filaments and their effect on the overlying chromosphere. We confirm
the ubiquitous nature of penumbral micro-jets recently discovered by
SOT instrument (Katsukawa et al. 2007, AAS 210, 94.13), and present
quantitative analysis of chromospheric jets based on our recent model
of penumbra.
---------------------------------------------------------
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields with Hinode/SOT
Authors: Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Nagata,
Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.;
Frank, Zoe A.; Lites, Bruce; Elmore, David
2007PASJ...59S.607K Altcode: 2007arXiv0709.1853K
Vector magnetic fields of moving magnetic features (MMFs) were well
observed with the Solar Optical Telescope (SOT) aboard the Hinode
satellite. We focused on the evolution of three MMFs with the SOT in
this study. We found that an MMF having relatively vertical fields
with the same polarity as the sunspot was detached from the penumbra
around the granules appearing in the outer penumbra. This suggests
that granular motions in the outer penumbra are responsible for
disintegration of the sunspot. Two MMFs with polarity opposite to
the sunspot are located around the outer edge of horizontal fields
extending from the penumbra. This is evidence that the MMFs with
polarity opposite to the sunspot are the prolongation of penumbral
horizontal fields. Redshifts larger than the sonic velocity in the
photosphere are detected for some of the MMFs with polarity opposite
to the sunspot.
---------------------------------------------------------
Title: Emergence of Small-Scale Magnetic Loops in the Quiet-Sun
Internetwork
Authors: Centeno, R.; Socas-Navarro, H.; Lites, B.; Kubo, M.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Shimizu, T.; Nagata, S.
2007ApJ...666L.137C Altcode: 2007arXiv0708.0844C
We study the emergence of magnetic flux at very small spatial
scales (less than 2") in the quiet-Sun internetwork. To this aim,
a time series of spectropolarimetric maps was taken at disk center
using the instrument SP/SOT on board Hinode. The LTE inversion of
the full Stokes vector measured in the Fe I 6301 and 6302 Å lines
allows us to retrieve the magnetic flux and topology in the region
of study. In the example presented here, the magnetic flux emerges
within a granular structure. The horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field disappear, while the vertical dipoles
drift-carried by the plasma motions-toward the surrounding intergranular
lanes. These events take place within typical granulation timescales.
---------------------------------------------------------
Title: Emerging And Rotating Magnetic Flux Structures Associated
With Solar Eruptions In AR10930 As Observed By Hinode/SOT, TRACE,
And SOHO/MDI
Authors: Nightingale, Richard W.; Schrijver, C. J.; Frank, Z. A.
2007AAS...210.9423N Altcode: 2007BAAS...39..221N
During the period of December 6-14, 2006 AR10930 produced 4 X-flares
in what was otherwise a quiet solar minimum. The multiple flaring
appears to be associated with small emerging and rotating magnetic flux
structures around a larger stable sunspot. The eruptions were observed
by several solar instruments, including the Solar Optical Telescope
(SOT) on the recently launched Hinode Spacecraft, as well as TRACE
and SOHO/MDI. The high resolution of SOT highlights the rotation of
the small emerging flux regions, which can carry magnetic energy and
helicity up into the solar atmosphere from the interior of the sun
to help facilatate the eruptions. Images at several wavelengths from
the suite of observational instrumentation mentioned above will be
utilized to illustrate these events. <P />This work was supported by
NASA in part under the TRACE contract NAS5-38099 and in part under
the Hinode/SOT contract NNM07AA01C.
---------------------------------------------------------
Title: Magnetic Flux Emergence In The Quiet Sun Photosphere
Authors: Centeno, Rebecca; Lites, B.; Socas-Navarro, H.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Kubo, M.; Shimizu, T.
2007AAS...210.9406C Altcode: 2007BAAS...39..218C
We study the emergence of magnetic flux at very small spacial scales
(less than 1 arcsec) in the quiet Sun internetwork. To this aim, several
time series of spectropolarimetric maps were taken at disk center using
the instrument SP/SOT on board Hinode. The LTE inversion of the full
Stokes vector measured in the Fe I 6301 and 6302 lines will allow us
to retrieve the magnetic flux and topology in the region of study. We
find that the magnetic flux emerges typically within the granular
structures. In many cases, the horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field dissapear while the the vertical
dipoles drift -carried by the plasma motions- towards the surrounding
intergranular lanes. Sometimes they stay trapped there for a while
but they eventually either disappear by disgregation/cancelation
or agregate to other magnetic field concentrations giving rise to
larger flux elements. The time scale of these events is of the order
of 10-20 minutes.
---------------------------------------------------------
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields
Authors: Kubo, Masahito; Ichimoto, K.; Shimizu, T.; Tsuneta, S.;
Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Lites, B. W.; Frank, Z.;
Tarbell, T. D.; Shine, R. A.; Title, A. M.
2007AAS...210.9410K Altcode: 2007BAAS...39..218K
We investigate the formation process of Moving Magnetic Features
(MMFs) observed with Hinode/SOT. Moving magnetic features are small
magnetic elements moving outward in the moat region surrounding
mature sunspots. We derive vector magnetic fields of MMFs around
simple sunspots near the disk center. Most of MMFs with polarity
opposite to the sunspot have large redshift around the penumbral outer
boundary. We find that some of them have Doppler velocities of about
10 km/s and such large Doppler motion is observed only in the Stokes
V profile. The Stokes Q and U profiles in the same pixel do not have
any significant Doppler motions. Horizontal magnetic fields of the
penumbra frequently extend to the moat region and the MMFs having
horizontal fields with polarity same as the sunspot are formed. The
MMFs with polarity opposite to the sunspot appear around the outer
edge of the extending penumbral fields. We also find penumbral spines,
which have more vertical magnetic fields than the surroundings, branch
off at their outer edge and MMFs having relatively vertical fields
with polarity same as the sunspot are detached from the outer edge
of the branch. The branch of penumbral spine is formed when granular
cells in the moat region go into the penumbra.
---------------------------------------------------------
Title: Ubiquitous Horizontal Magnetic Fields in the Quiet Solar
Photosphere as Revealed by HINODE Meaurements
Authors: Lites, Bruce W.; Socas Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Kubo, M.; Shimizu, T.; Nagata, S.;
Hinode Team
2007AAS...210.6303L Altcode: 2007BAAS...39..171L
Measurements with the HINODE Spectro-Polarimeter (SP) of the quiet
Sun allow characterization of the weak, mixed-polarity magnetic
flux at the highest angular resolution to date (0.3"), and with good
polarimetric sensitivity(0.025% relative to the continuum). The image
stabilization of the HINODE spacecraft allows long integrations with
degradation of the image quality only by the evolution of the solar
granulation. From the Stokes V profile measurements we find an average
solar "Apparent Flux Density" of 14 Mx cm-2, with significant Stokes V
signals at every position on the disk at all times. However, there are
patches of meso-granular size (5-15") where the flux is very weak. At
this high sensitivity, transverse fields produce measurable Stokes
Q,U linear polarization signals over a majority of the area, with
apparent transverse flux densities in the internetwork significantly
larger than the corresponding longitudinal flux densities. When viewed
at the center of the solar disk, the Stokes V signals (longitudinal
fields) show a preference for occurrence in the intergranular lanes,
and the Q,U signals occur preferably over the granule interiors,
but neither association is exclusive. <P />Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful to the
Hinode team for all their efforts in the design, build and operation
of the mission.
---------------------------------------------------------
Title: Moving Magnetic Features Observed in Photosphere, Chromosphere,
and Transition Region
Authors: Hagenaar, H. J.; Frank, Z. A.
2006ESASP.617E..64H Altcode: 2006soho...17E..64H
No abstract at ADS
---------------------------------------------------------
Title: TRACE and SOHO/MDI Observations of Five X-Flares from AR10720,
the "Fireworks Active Region", on January 15-20, 2005
Authors: Nightingale, R. W.; Frank, Z. A.; Metcalf, T. R.; Kang, C. A.
2005AGUSMSP21A..10N Altcode:
Both TRACE and SOHO/MDI observed the five X-flares that were produced
by AR10720 during January 15-20, 2005. This active region appears
to be "special" because it is occurring so late in the solar cycle,
about two-thirds of the way toward solar minimum. Also its structure
is initially one large penumbral region with several umbral spots that
are being stretched out east to west with rotating sunspots emerging
in leading and trailing positions during the transit across the solar
disk, similar to fireworks with pin-wheels attached. With a neutral line
running almost east-west in between two of the stretched umbral regions
and with opposite magnetic polarities on both sides of the neutral line
adjacent to each other, the beta-delta region starts the "fireworks"
with the first X-flare on January 15, continuing every one to one and
one-half days over the next five days. Images and movies will be shown
of these eruptive events in white light and 1600A from TRACE, and as
magnetograms from MDI. Two of the three rotating sunspots also change
their direction of rotation during this period. These X-flares add to
those observed by TRACE since its launch in April 1998, all of which
have been associated with rotating sunspots in the associated active
regions. These X-flares consist of over half of the X-flares observed by
GOES since April 1998 and many are associated with geo-effective CMEs
in the form of solar energetic particle events. Rotating sunspots may
be a good predictor of solar eruptions. This work has been supported
by NASA, in part under the TRACE project at LMSAL (contract NAS5-38099)
and in part under the MDI/SOHO project (NAG5-13261).
---------------------------------------------------------
Title: Solar Filaments and Photospheric Network
Authors: Lin, Yong; Wiik, Jun Elin; Engvold, Oddbjørn; Van Der Voort,
Luc Rouppe; Frank, Zoe A.
2005SoPh..227..283L Altcode:
The locations of barbs of quiescent solar filaments are compared with
the photospheric/chromospheric network, which thereby serves as a
proxy of regions with enhanced concentrations of magnetic flux. The
study covers quiet regions, where also the photospheric network as
represented by flow converging regions, i.e., supergranular cell
boundaries, contain largely weak magnetic fields. It is shown that
close to 65% of the observed end points of barbs falls within the
network boundaries. The remaining fraction points into the inner areas
of the network cells. This confirms earlier findings (Lin et al.,
Solar Physics, 2004) that quiescent filaments are basically connected
with weaker magnetic fields in the photosphere below.
---------------------------------------------------------
Title: Bright Points and Coronal Jets as Models for Eruptive Phenomena
in the Solar Atmosphere
Authors: Frank, Z. A.; Slater, G. L.
2002AAS...201.8304F Altcode: 2002BAAS...34.1242F
Bright points in X-rays and EUV are an ever-present phenomena in
the solar atmosphere and are often the origin of coronal jets. When
bright points are examined at high resolution ( 1 arcesec or less)
they show structures remarkably similar in morphology to larger scale
coronal structures. Furthermore, their dynamics and evolution also
show similarities to larger structures. We examine bright points
and coronal jets in X-rays and EUV using Yohkoh SXT, TRACE, and EIT
imagery in order to determine the extent to which they can be viewed
as miniature counterparts of active regions. This work is supported by
NASA contract numbers NAS8-40801, NAS5-38099, NAS5-32966, and Stanford
University contract PR9162.
---------------------------------------------------------
Title: TRACE, SOHO/EIT, and SOHO/MDI Observations of AR0030, Including
Rotating Sunspots and the July 15, 2002 X3.0 Flare in Ultraviolet
and Extreme Ultraviolet
Authors: Nightingale, R. W.; Shine, R. A.; Alexander, D.; Freeland,
S. L.; Frank, Z. A.; Brown, D. S.
2002AGUFMSH52A0467N Altcode:
On July 15, 2002 TRACE and several SOHO instruments observed an X3.0
flare in AR0030 near 2000 UT. During this period TRACE was primarily
observing in its 1600Å ultraviolet (UV) channel (most sensitive
to temperatures around 100,000 K in the flare). The 195Å extreme
ultraviolet (EUV) channel of SOHO/EIT (which is most sensitive to about
1.6 MK) will be utilized in this poster, in addition to the magnetic
field measurements of SOHO/MDI during this event period. TRACE followed
the active region for over 10 days, starting about 4 days before the
flare. Broadband white light TRACE images of the photosphere indicate
that one or more of the sunspots were rotating, a possible precursor to
the flare. Images and movies of AR0030 in the various wavelengths will
be shown. The flare region was so intense in the TRACE UV that it is
very difficult to show both the quiescent and flaring regions, so the UV
movie will focus on the flaring plasma with its 2 eruptions. In the EIT
EUV, more coronal structure away from the flare can be seen. Analysis
of the rotational rates of the sunspots will be given along with their
possible coupling to the flare. This work was supported by NASA under
contract NAS5-38099.
---------------------------------------------------------
Title: Photospheric Magnetic Activities Responsible for Soft
X-Ray Pointlike Microflares. I. Identifications of Associated
Photospheric/Chromospheric Activities
Authors: Shimizu, T.; Shine, R. A.; Title, A. M.; Tarbell, T. D.;
Frank, Z.
2002ApJ...574.1074S Altcode:
By combining Yohkoh soft X-ray images with high-resolution magnetograms
simultaneously obtained at La Palma, we studied photospheric magnetic
signatures responsible for soft X-ray microflares (active-region
transient brightenings). In order to have a reliable correspondence
between the photosphere and the corona, we studied 16 pointlike
transient brightenings with X-ray source size less than 10" occurring
during periods when the seeing was excellent at La Palma, although a
lot of transient brightenings were in forms of multiple- or single-loop
structures. In half of the studied events, small-scale emergences
of magnetic flux loops are found in the vicinity of the transient
brightenings. Six events of that half show that a small-scale flux
emergence accompanies the X-ray brightening 5-30 minutes prior to
its onset. In the other half of the studied events, no apparent
evolutionary change of magnetic flux elements is found associated
with the transient brightenings. Many of these events are found in
rather strong magnetic fields, such as sunspots and pores, implying
that small-scale changes of magnetic flux are obscured or suppressed
by strong magnetic fields. The horizontal plasma flows derived from
local cross-correlation tracking of granules in continuum images are
suppressed at the feet of some X-ray transient brightenings.
---------------------------------------------------------
Title: Flow Map Studies of Supergranule and Mesogranule Evolution
from TRACE
Authors: Shine, R. A.; Frank, Z. A.; Tarbell, T. D.; Simon, G. W.
2001AGUFMSH11A0702S Altcode:
From 00:44 UT 22-April-2000 to 00:09 UT 29-April-2000 we obtained a
nearly continuous set of white light images using the Transition Region
and Corona Explorer (TRACE) satellite. A 384x384 arc second field of
view was used that tracked solar rotation from Stonyhurst longitudes
45E to 45W along the solar equator. The total time is nearly 7 days
with images taken every minute over most of the interval. The largest
temporal gap was 45m and there were only 9 gaps longer than 10m. The
area was mostly free of active regions. These images are broad band
white light with 0.5 arc second pixels. Granulation is well defined and
we used local correlation techniques (LCT) to compute flow maps of the
horizontal velocities with a resolution of about 5 arc seconds. The flow
map resolution and quality suffer somewhat near the longitude extrema
but the maps are usable throughout the 7 days to define supergranules
and mesogranules. We compute horizontal divergence to study the motions
of mesogranules and the evolution and lifetime of supergranules. When
enough telemetry capacity was available, we also obtained co-spatial
images in the TRACE Fe IX/X 171Å channel and the 1600Å channel. We
use these to study the response of the corona and chromosphere to the
photospheric motions. During times with particularly high telemetry
throughput, we took white light images every 30 seconds. This allows
us to empirically determine the noise in our flow maps using two
interleaved and disjoint sets of white light data, each with one minute
intervals. This work was supported by NASA contract NAS5-38099.
---------------------------------------------------------
Title: More Rotating Sunspot Observations by TRACE With Twisting
EUV Coronal Fans
Authors: Nightingale, R. W.; Shine, R. A.; Brown, D. S.; Wolfson,
C. J.; Frank, Z. A.; Title, A. M.
2001AGUSM..SH41B11N Altcode:
In an on-going search several sunspots, rotating about their umbral
centers, have been identified in TRACE photospheric white light (WL)
images. In many cases the rotation can also be seen in the corresponding
UV (1600 Å) and/or EUV (171, 195 Å) images. Preliminary analysis of
one such rotating sunspot and the coronal response to the rotation,
observed in AR9114 on August 8-10, 2000, was presented at the fall
AGU meeting (Nightingale et al., Abstract SH11A-10, EOS, AGU 2000 Fall
Meeting, Vol. 81, p. F977, Nov. 2000). Further detailed analysis and
modeling of this event, where loops appear to cross over one another,
is in progress. Meanwhile, we are finding other examples within the
TRACE data set. Twisting EUV coronal fans have been observed above
rotating sunspots on August 16, 1999 for AR8667, where a sigmoid was
visible in Yohkoh SXT data, and on May 20, 2000. Several rotating
sunspots were also seen in the active region of the July 14, 2000
Bastille Day event. More recent rotations observed only in WL and UV
occurred on December 11 and 22, 2000. Movies of some of these rotations
will be shown, as well as magnetic field data from MDI on SOHO where
available. Analysis of the rotational rates of the sunspots will be
given. These observations display the coupling of the magnetic field
from the photosphere into the corona. This work was supported by NASA
under contract NAS5-38099.
---------------------------------------------------------
Title: Instrumental Effects and their Removal from TRACE Images
Authors: Tarbell, T. D.; Nightingale, R. N.; Metcalf, T. R.; Frank,
Z. A.; TRACE Team
2000SPD....31.0291T Altcode: 2000BAAS...32..827T
TRACE raw images often show fine structures at such high contrast
that compensation for instrumental effects is not necessary to study
their morphology and evolution. Nevertheless, TRACE team members have
gradually been developing the techniques and calibrations necessary
to understand and (sometimes) remove the principal instrumental
degradations. These degradations include CCD pedestal variation
with temperature and time, flat-field response, CCD sensitivity loss
varying with position and wavelength, electrical interference during
CCD readout, permanent dim pixels, intermittent hot pixels, overall
system point spread function, diffraction of EUV radiation by the front
entrance filters, scattered light at off-limb pointings, tracks of
electrons and protons from the radiation belts, and artifacts from JPEG
compression of solar strucures and the above defects. Characterization
and removal of some of these will be presented in the poster, such
as the following. A deconvolution routine can partially compensate
for the EUV diffraction, which is described in the adjacent poster by
Frank et al. White light flat fields are derived using the Kuhn-Lin
algorithm. CCD sensitivity degradation (presumably lumogen damage) is
measured both from crude UV and EUV flat fields and from mission-long
analysis of synoptic disk center images; combining these results with
the WL flats yields flat fields at all wavelengths. Some information on
scattered light and point spread functions are obtained from the August,
1999, eclipse observations and the Mercury transit. SSW routines for
dealing with some of these degradations will be identified. This work
is supported by the TRACE project at LMSAL (contract NAS5-38099).
---------------------------------------------------------
Title: Diffraction Pattern Analysis of Bright TRACE Flares
Authors: Frank, Z. A.; Lin, A. C.; Nightingale, R. W.; Tarbell, T. D.
2000SPD....31.0290F Altcode: 2000BAAS...32..827F
A study of the diffraction patterns seen in TRACE images of bright
flares was undertaken to better understand the properties of the
telescope. The pattern caused by light from a bright solar flare passing
through the wire mesh in front of the telescope has been examined, and
a method has been developed to use this pattern to determine the zeroth
order intensity of bright flares. This intensity cannot usually be
measured directly due to saturation of the Analog to Digital Converter
(ADC) electronics in the CCD camera package. The validity of this
method has been tested on dimmer flares, whose intensity do not saturate
the ADC. The diffraction pattern allows us to measure intensities far
brighter than the camera package permits. For the bright flare on May
16, 1999 at 13:49:21 UT the range has been effectively increased by at
least 41 times. The light defracted away from any point was observed
to be 18%, a significant amount which affects the contrast of TRACE
images. An accurate determination of the ratio of the square slit
size to slit spacing of the wire mesh has been obtained. This is an
important parameter for a deconvolution routine that can remove the
diffraction patterns from the image (see adjacent SPD poster paper
by Tarbell et al.). Wavelength dispersion, the phenomenon that as the
higher order diffracted peaks lie further from the center they spread
out until double peaks are observed, has also been examined as part of
this study. This effect is observable because there are two principal
wavelengths, Fe IX at 171.06 Angstroms and Fe X at 174.52 Angstroms
in the TRACE 171 Angstroms passband used in present analysis. This
study is a part of the TRACE Team educational outreach program and is
supported by contract NAS5-38099 at LMSAL.
---------------------------------------------------------
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26: Addendum
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
1998ApJ...495..502M Altcode:
Video segments are presented that were processed from a quantitative
study of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare. The high spatial resolution of the Swedish
Vacuum Solar Telescope (SVST) at La Palma provided a unique set of
data for such an event.
---------------------------------------------------------
Title: Photospheric flows as measured by SOI/MDI
Authors: Hurlburt, N.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Simon, G.
1997ASSL..225..285H Altcode: 1997scor.proc..285H
On 2 February and 7 March 1996, MDI on the SOHO spacecraft ran several
hours to provide high resolution continuum images to map the horizontal
flows near the equator and pole by correlation tracking. Here we present
preliminary results on the performance of the tracking technique
in measuring the differential rotation profile. These preliminary
results are compared with each other and with corresponding results
of previous studies.
---------------------------------------------------------
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
1997ApJ...482..535M Altcode:
The main objective of this paper is to present a quantitative study
of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare and the processed videos produced from the
observations. The high spatial resolution of the Swedish Vacuum Solar
Telescope (SVST) at La Palma has provided a unique set of data for such
an event. A Gaussian fitting method is proposed to derive intensities
and Doppler shifts from observations taken at three wavelengths (Hα
center and Hα +/- 0.07 nm). Moving condensations or “blobs” of cold
material provide transverse velocities, which, together with the radial
component, enable us to derive their velocity vector magnitude. Plasma
velocities are around free-fall velocities near the top of the loops
but are significantly smaller close to their footpoints, suggesting
a deceleration mechanism. The loops are anchored in the chromosphere,
which shows tremendous activity in the active region and in the nearby
“quiet Sun.” Spicules and ejection of plasmoids are also observed
at the limb.
---------------------------------------------------------
Title: Comparison of supergranular flows from doppler and local
correlation tracking velocities
Authors: Frank, Z.; Hurlburt, N.; Shine, R.; Tarbell, T.; Simon, G.;
Strous, L.; Matt, S.
1997SPD....28.0259F Altcode: 1997BAAS...29..903F
Measurements of the flows in the solar photosphere rely upon two
techniques: doppler measurements of the line-of-sight velocity
or tracking of features or patterns moving perpendicular to the
line-of-sight. These methods have differing characteristics. Doppler
measurements can easily measure surface flows near the limb
which are not seriously contaminated by p-modes or other solar
sources. However, they require excellent instrument calibration over
the full field of view. Even then vertical flows within supergranules
are barely detectable. Correlation and feature tracking have proven
useful for estimating transverse velocity using granules and other
tracers. Nevertheless, they can be degraded by the intensity variations
of p-modes and possibly other oscillatory motions, as well as by effects
of limb darkening and foreshortening. The two methods would both be
strengthened through detailed comparisons. Data collected by MDI/SOHO is
ideal for this purpose. The data is co-spatial and co-temporal, and is
all obtained through the same instrument. We compare Doppler velocities
with those obtained through correlation tracking using high-resolution
MDI/SOHO images. We focus on motions at positions exceeding 30 degrees
from disk center. After taking projection effects into account, we
combine the two measurements to form a three-dimensional picture of
the flows in the average supergranule. This work was supported by NASA
Grant NAG5-3077 at Stanford and Lockheed Martin, and by AFOSR and the
Fellows Program of AF Phillips Lab at NSO/SP.
---------------------------------------------------------
Title: Initial Results from SOI/MDI High Resolution Magnetograms
Authors: Title, A.; Tarbell, T.; Frank, Z.; Schrijver, C.; Shine,
R.; Wolfson, J.; Zayer, I.; Scherrer, P.; Bush, R.; Deforest, C.;
Hoeksema, T.
1996AAS...188.6915T Altcode: 1996BAAS...28..938T
The Michelson Doppler Imager (MDI) on SoHO takes magnetogram
s with resolutions of 1.2 (high resolution) and 4 (full disk)
arcseconds. Movies of 16 hour duration have been constructed in full
disk and high resolution mode. High resolution movies of the south
polar region also have been obtained. In sums of nine high resolution
magnetograms it is possible to detect fields as low as 5 gauss and
total fluxes as low as 5 10(1) 6 Mx. In mid latitude regions new flux
is observed to emerge everywhere. At all latitudes below 60 degrees
flux is mixed on the scale of supergranulation. In the polar region
above 60 degrees only fields of a single polarity are observed above
the detection limit.
---------------------------------------------------------
Title: Preliminary SOI/MDI Observations of Surface Flows by
Correlation Tracking in the Quiet Solar Photosphere and an Emerging
Active Region
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Saba, J.; Schrijver,
C.; Shine, R.; Title, A.; Simon, G.; Strous, L.
1996AAS...188.6914T Altcode: 1996BAAS...28..937T
The extended observation of the solar surface with frequent sampling
provided by MDI on SoHO offers the chance to observe the evolution of
supergranules and to measure surface flows associated with active
regions and perhaps larger scale zonal and meridonal flows. We
have used local correlation tracking of the granulation pattern for
measuring surface flows from MDI high resolution continuum images. The
datasets consist of 1024 x 1024 pixel images collected with a cadence
of one minute and extending many hours each. The images are typically
centered upon the central meridian of the sun and offset to the north
of sun center, spanning roughly 40 degrees of solar longitude and from
approximately -10 to +30 degrees of solar latitude. The latitude
dependence of the differential rotation is evident. We present
preliminary results of our search for signatures of mesogranules,
supergranules and giant cells. On 23 Feb. 1996, we obtained a 12-hour
continuous sequence including quiet sun near disk center and NOAA
region 7946 at about N08 E30. The active region grew rapidly over this
interval, forming several sunpots. We show preliminary comparisons of
the measured flow fields with coaligned SOI/MDI magnetograms taken
at 15-minute intervals. The SOI/MDI program is supported by NASA
grant NAG5-3077.
---------------------------------------------------------
Title: SOI/MDI Measurements of Horizontal Flows in the South Polar
Region of the Sun by Correlation Tracking and Doppler Shifts
Authors: Simon, G.; Frank, Z.; Hurlburt, N.; Schrijver, C.; Shine,
R.; Tarbell, T.; Title, A.; Deforest, C.
1996AAS...188.6913S Altcode: 1996BAAS...28R.937S
On 7 March 1996, the SOHO spacecraft was offset from its usual
disk center pointing for an 11-hour observation of the South
Polar region. MDI took a continuous time series of high resolution
longitudinal magnetograms during this period, in support of the
SOHO-wide Joint Observing Program on polar plumes. It also ran several
hours each of two other programs: one to map the horizontal flows near
the pole by correlation tracking and Doppler shifts, and another to
study wave propagation (e.g., by time-distance helioseismology) at
these high latitudes. In this poster we present preliminary results
from the first program. Both techniques yield measurements of the
differential rotation profile near the pole and of horizontal flows of
supergranulation. These results are compared with each other and with
corresponding measurements in low latitudes. The location of magnetic
features in the horizontal flows is also shown. The SOI/MDI program
is supported by NASA grant NAG5-3077.
---------------------------------------------------------
Title: Photospheric Surface Flows and Small Magnetic Structures in
Sunspot Moats
Authors: Shine, R. A.; Title, A.; Frank, Zoe; Scharmer, G.
1996AAS...188.3501S Altcode: 1996BAAS...28Q.871S
We have computed horizontal flow maps of the photosphere around
and within three different sunspots using high spatial resolution
continuum movies obtained at the Swedish Vacuum Solar Telescope on
La Palma on June 5, 1993, August 29, 1993, and July 14, 1994. Two
of the data sets also included magnetograms and dopplergrams. A new
feature found in the flow maps is azimuthal structure in the moat
flows surrounding sunspots. Instead of a simple radial flow, there
are zones of azimuthal divergence and convergence resulting in radial
“spokes” of convergence. These are not uniformly distinct around the
entire circumference but are seen in part of the surrounding area for
all 3 sunspots. The angular spacing is about 10 to 20 degrees and the
pattern persists for several hours. For one of the sunspots, we have
concurrent movies made with a 3 Angstrom wide K line filter. A time
average of these images shows bright spokes in the K line congruent with
the convergence spokes. Much of the magnetic flux that is continually
emerging and moving outward in the moat is in the vicinity of the
“spokes.” In addition, these data show several good examples of
so called “streakers.” These are small bright structures seen in
continuum movies that appear to be emitted from the outer edge of the
penumbral and travel a few thousand km at about 2 to 3 km/s before
fading. We find that these are associated with a magnetic field of
opposite polarity to the sunspot and that they travel toward another
larger and slower moving magnetic feature with the same polarity as
the sunspot. When the streaker catches up, it disappears, sometimes
coincident with a brightening of the merged feature which continues
outward at the previous velocity, about 0.5 km/s. This work was
supported by NSF grant ATM-9213879, NASA contracts NAS8-39746 and
NAS8-39747, Lockheed Independent Research Funds, and the Swedish Royal
Academy of Sciences.
---------------------------------------------------------
Title: Heating of Active Region Corona by Transient Brightenings
(Microflares)
Authors: Shimizu, T.; Tsuneta, T.; Title, A.; Tarbell, T.; Shine,
R.; Frank, Z.
1996mpsa.conf...37S Altcode: 1996IAUCo.153...37S
No abstract at ADS
---------------------------------------------------------
Title: The Possible Ascent of a Closed Magnetic System through
the Photosphere
Authors: Lites, B. W.; Low, B. C.; Martinez Pillet, V.; Seagraves,
P.; Skumanich, A.; Frank, Z. A.; Shine, R. A.; Tsuneta, S.
1995ApJ...446..877L Altcode:
We present a comprehensive interpretation of the evolution of a small
magnetic region observed during its entire disk passage. The vector
magnetic field measurements from the Advanced Stokes Polarimeter,
along with Hα and magnetogram measurements from the Lockheed SOUP
instrument operating at the Swedish Solar Observatory on La Palma,
and soft X-ray images from the Yohkoh satellite support the hypothesis
that we have observed the passage of a nearly closed magnetic system
through the photosphere into the corona. The observations suggest that
as the magnetic flux begins to emerge into the photosphere it shows a
rather simple geometry, but it subsequently develops a small δ-sunspot
configuration with a highly sheared vector field along the polarity
inversion line running through it. At that stage, the vector field is
consistent with a concave upward magnetic topology, indicative of strong
electric currents above the photosphere. An Hα prominence is found
above this inversion line when the δ-sunspot is fully formed. These
observed features and the sequence of events are interpreted in terms
of a nearly closed magnetic system that rises through the photosphere
into the corona as a result of magnetic buoyancy. The magnetic system
persists in the corona well after the dark δ-sunspot has disappeared
in the photosphere We suggest that this coronal structure is in
quasi-static equilibrium with its buoyancy partially countered by
the weight of the plasma trapped at the bottom of closed magnetic
loops. The plausibility of such a scenario is demonstrated by a
three-dimensional magnetostatic model of the emergence of a closed,
spheroidal magnetic system in the corona, in which the Lorentz force
arising from cross-field currents is balanced by the gravitational
and pressure forces. This theoretical model carries many features in
common with the observed morphology of our active region.
---------------------------------------------------------
Title: Flux Emergence in a Sunspot Moat and Young Active Region
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Simon, G. W.; Brandt, P. N.
1995SPD....26.1007T Altcode: 1995BAAS...27..978T
No abstract at ADS
---------------------------------------------------------
Title: Flux Emergence in the Sunspot Moat
Authors: Title, A. M.; Shine, R. A.; Frank, Z. A.; Simon, G. W.;
Brandt, P. N.
1994AAS...185.8602T Altcode: 1994BAAS...26.1464T
On 13-15 June 1994 we obtained simultaneous movies of a sunspot in
NOAA active region 7731 through a 3 Angstroms band K line filter, the
LPARL tunable filter, and an 8 Angstroms G band filter. The data sets
allow us to make aligned magnetic, continuum, Doppler, K line, and
G band movies. The sunspot had a well developed moat. Flux emergence
occured throughout the moat. The initial signature of the emergence
was a transient dark elongated structure in the K line images that was
aligned radially with respect to the spot. Bright point pairs appeared
at the ends of these features in the K line and G band shortly after
their emergence. Magnetic field is observed cospatial with the K line
bright point pairs. The magnetic polarity of the end of the pair closest
to the spot is the same as the spot. The pairs of bright points move
across the moat in a radial direction away from the spot. When the
pairs reach the moat boundary the leading bright point merges with a
moat feature and the two disappear. The leading bright point's field
and the moat field cancel, since the moat boundary and the spot have
the same polarity. We believe that these features are different from
the long observed moving magnetic features associated with sunspots.
---------------------------------------------------------
Title: High-Resolution Observations of the Evershed Effect in Sunspots
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, Goran
1994ApJ...430..413S Altcode:
High spatial resolution movies of sunspots taken at the Swedish
Solar Observatory on La Palma reveal that the Evershed effect is time
dependent. Outward proper motions are visible in both the continuum
and Dopplergrams. These can be tracked over most of the width of
the penumbra and overlap regions that show inward moving penubral
grains. The radial spacing between the moving structures is about 2000
km, and they exhibit irregular repetitive behavior with a typical
interval of 10 minutes. These are probably the cause of 10 minutes
oscillations sometimes seen in a penumbral power spectra. Higher
velocities are spatially correlated with the relatively darker regions
between bright filaments. Regions with a strong variation in the Doppler
signal show peak-to-peak modulations of 1 km/s on an average velocity
of about 3-4 km/s. The proper motion velocity is approximately constant
from the iner penumbra and generally larger than the Doppler velocity
when both are interpreted as projections of horizontal motion. Regions
where thay are consistent suggest a typical horizontal velocity of
3.5 km/s. Some proper motion velocites as high as 7 km/s are seen,
but these are less certain. The temporal behavoir shows a correlation
between increased Doppler signal and increased continuum intensity,
the opposite of the spatial correlation. When spatially averaged
across filaments and over time, the averaged Evershed effect has a peak
horizontal component near the outer edge of the penumbra of 2.0 km/s
with evidence for a 200-400 m/s upward component. The latter depends
on an uncertain absolute velocity calibration. If real it could be
an actual upward component or a penumbral analogue of the convective
blueshift seen in the quiet Sun.
---------------------------------------------------------
Title: Dynamics of the Evershed effect
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, G.
1994ASIC..433..197S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Vector-Stokes polarimetry in a sunspot
Authors: Hofmann, A.; Shine, R. A.; Frank, Z. A.; Schmidt, W.;
Balthasar, H.
1994smf..conf..204H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High resolution vector polarimetry of sunspot magnetic fields.
Authors: Balthasar, H.; Hofmann, A.; Schmidt, W.; Shine, R. A.; Frank,
Z. A.
1994AGAb...10..112B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
1993BAAS...25.1208T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: La Palma Observations During the CoMStOC'92 Campaign
Authors: Shine, R.; Tarbell, T.; Topka, K.; Frank, Z.; Title, A.;
Scharmer, G.
1993BAAS...25S1223S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: “The Active Sun”: Educational Videotapes on Solar Physics
for College Astronomy
Authors: Hurlburt, N.; Title, A.; Tarbell, T.; Frank, Z.; Topka, K.;
Shine, R.
1993AAS...182.1002H Altcode: 1993BAAS...25..809H
We present a series of short, educational documentaries on solar
physics aimed at college-level general astronomy courses. These
tapes highlight recent advances in high-resolution solar astronomy
and in theoretical and computational modeling of solar physics
with particular focus on dynamical phenomena. The relevant physical
mechanisms, theoretical interpretations and observational techniques
are discussed. These include granulation, the theory of convection,
five-minute oscillations, sunspots, magnetic fields, seeing and
dopplergrams. VHS tapes are available to researchers and educators
through a variety of distributors. This work supported by Lockheed
Independent Research Funds.
---------------------------------------------------------
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
1993AAS...182.4805T Altcode: 1993BAAS...25R.880T
We are using high resolution digital movies of solar active regions
in optical and X-ray wavelengths to study solar flares and other
transients. The optical movies were collected at the Swedish Solar
Observatory on La Palma using the Lockheed tunable filtergraph
system, in May - July, 1992. They include longitudinal and transverse
magnetograms, H-alpha Doppler and intensity images at many wavelengths,
Ca K, Na D, and white light images. Simultaneous X-ray images from
Yohkoh are available much of the time. We are learning several ways to
establish the connectivity of some coronal magnetic field lines. Some
of the clues available are: magnetic footpoint polarities and transverse
field directions; H-alpha fibrils and loops seen in several wavelengths;
proper motion and Doppler shifts of blobs moving along field lines;
footpoint brightening in micro-flares; spreading of flare ribbons
during gradual phases of flares; X-ray morphology and correlations with
H-alpha; and draining of flare loops. Examples of each of these will
be shown on video. This work is supported by NASA Contracts NASW-4612
and NAS8-37334 and by Lockheed Independent Research Funds.
---------------------------------------------------------
Title: On the Magnetic and Velocity Field Geometry of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
Theodore D.; Topka, Kenneth P.; Scharmer, Goran; Schmidt, Wolfgang
1993ApJ...403..780T Altcode:
It is presently shown that a simple sunspot model with azimuthal
variations in inclination, but lacking azimuthal field-strength
variations, is free from azimuthal Lorentz forces. The meridional
currents arising from the inclination variations are parallel to the
field lines, suggesting that a cylindrically symmetric magnetostatic
sunspot model can be perturbed into one with azimuthal variations in
inclination with adjustment of the meridional force balance.
---------------------------------------------------------
Title: The High-Frequency P-Mode Spectrum
Authors: Milford, P. N.; Scherrer, P. H.; Frank, Z.; Kosovichev,
A. G.; Gough, D. O.
1993ASPC...42...97M Altcode: 1993gong.conf...97M
No abstract at ADS
---------------------------------------------------------
Title: High Resolution Magnetic Field Measurements in the Sunspot
Photosphere (Invited)
Authors: Hofmann, A.; Schmidt, W.; Balthasar, H.; Tarbell, T. T.;
Frank, Z. A.
1993ASPC...46...11H Altcode: 1993IAUCo.141...11H; 1993mvfs.conf...11H
No abstract at ADS
---------------------------------------------------------
Title: White-light movies of the solar photosphere from the SOUP
instrument on Spacelab 2 (Advances in Space Research 1986)
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
1993inas.book..100T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Polarimetry and spectroscopy of a simple sunspot. I - On the
magnetic field of a sunspot penumbra
Authors: Schmidt, W.; Hofmann, A.; Balthasar, H.; Tarbell, T. D.;
Frank, Z. A.
1992A&A...264L..27S Altcode:
We investigate the magnetic field structure of a medium sized sunspot
using high resolution magnetograms and spectrograms and derive a
relationship between the brightness of penumbral structures and the
inclination of the magnetic field. The field inclination to the spot
normal is larger in the dark structures than in the bright ones. We
show that the field strength does not vary between dark and bright
structures. At the inner penumbral boundary the field strength is 2000
Gauss and about 1000 Gauss at the outer penumbral edge. The line-of
sight component of the material flow decreases rapidly within one
arcsecond at the photospheric boundary of the spot.
---------------------------------------------------------
Title: High resolution observations: the state of the art and beyond.
Authors: Title, A.; Tarbell, T.; Shine, R.; Topka, K.; Frank, Z.
1992ESASP.344....9T Altcode: 1992spai.rept....9T
Excellent telescopes on excellent sites with fast digital CCD cameras
and special purpose computers allow the collection of broad band images
at just the instants of good seeing. This has resulted in nearly optimal
movies of the solar surface for several hours. When longer exposures
are required for narrowband filtergrams or spectra it is not enough to
capture single images. However, big fast memories allow the collection
of many selected low signal-to-noise ratio images in real time, which
can be summed to achieve the desired signal to noise ratios. Adaptive
optics shows promise of diffraction limited images for limited fields
of view. Nevertheless, groundbased observations will always be limited
in their duration, uniformity, and resolution qualities which are
essential for understanding the development and evolution of small scale
processes. Until there are observations in space we will not be able
to completely understand either the processes in the solar atmosphere
or how processes occurring at different height are interrelated.
---------------------------------------------------------
Title: Evolution and advection of solar mesogranulation
Authors: Muller, Richard; Auffret, Herve; Roudier, Thierry; Vigneau,
Jean; Simon, George W.; Frank, Zoe; Shine, Richard A.; Title, Alan M.
1992Natur.356..322M Altcode:
GRANULAR structure on the Sun's surface, with a typical scale
of 1-2 Mm, has been known since 1800, and one hundred years ago,
with the first observations by spectroheliograph<SUP>1,2</SUP>,
a mesh-like bright network was found with a characteristic scale
of 30 Mm (40”). This pattern was found, thirty years ago, to be
coincident with close-packed convective cells ('supergranulation')
revealed by Doppler observations<SUP>3-5</SUP> to be nestling inside
the bright network. More recently<SUP>6,7</SUP> an intermediate
'mesogranular' structure was found, with a characteristic scale of
3-10 Mm. We have obtained a three-hour sequence of observations at
the Pic du Midi observatory which shows the evolution of mesogranules
from appearance to disappearance with unprecedented clarity. We see
that the supergranules, which are known to carry along (advect) the
granules with their convective motion, also advect the mesogranules to
their boundaries. This process controls the evolution and disappearance
of mesogranules.
---------------------------------------------------------
Title: High Resolution Observations of the Magnetic and Velocity
Field of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
T. D.; Topka, K. P.; Scharmer, Goran; Schmidt, Wolfgang
1992ASIC..375..195T Altcode: 1992sto..work..195T
We have observed the disk passage of relatively simple round sunspots
using a narrowband filter and a large format CCD detector and have
created magnetograms, Dopplergrams, and continuum images nearly
simultaneously. In addition the spectral resolution of the filter
allows the construction of 'spectra' for all points in the field of
view. The mean inclination of the magnetic field increases from 45-50
deg to 70-75 deg across the penumbra and there is a fluctuation of the
inclination angle about the mean of about 4 +/- 18 deg. The variation in
inclination is large enough that substantial amounts of magnetic field
are parallel to the solar surface from the mid to outer penumbra. The
Evershed flow tends to occur in the regions where the magnetic field
is horizontal. This suggests that the Evershed flow is confined to the
regions of horizontal fields. We show that a simple sunspot model with
azimuthal variations in inclination but no azimuthal variations of
field strength is free from azimuthal Lorentz forces. The meridional
component of the currents which arise from the azimuthal variation
in inclination are parallel to the field lines. This suggests that a
cylindrically symmetric magnetostatic sunspot model can be perturbed
into one with azimuthal variations in inclination with some adjustment
in the meridional force balance.
---------------------------------------------------------
Title: On the magnetic field of a sunspot penumbra.
Authors: Balthasar, H.; Schmidt, W.; Hofmann, A.; Tarbell, T. D.;
Frank, Z. A.
1992AGAb....7..153B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fine-Scale Magnetic Field in a Sunspot Penumbra and Adjacent
Photosphere
Authors: Frank, Z. A.; Scharmer, G. B.; Keller, C.; Lundstedt, H.
1991BAAS...23.1052F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of the Birth and Death of Mesogranules
Authors: Simon, G. W.; Title, A. M.; Shine, R. A.; Frank, Z.; Muller,
R.; Auffret, H.
1991BAAS...23.1034S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Power Spectra of Flows and Magnetic Fields in the Solar
Photosphere
Authors: Tarbell, T. D.; Slater, G. L.; Frank, Z. A.; Topka, K. P.;
Scharmer, G.; Schmidt, W.
1991BAAS...23.1048T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Field Geometry of Sunspots Inferred from Inclination Effects
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.
1991BAAS...23R1052T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sunspot Umbral and Penumbral Oscillations in Hα
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Smith, K.
1991BAAS...23.1033S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stokes Polarimetry of a Sunspot from the Swedish Solar
Observatory at La Palma
Authors: Topka, K. P.; Frank, Z. A.; Tarbell, T. D.; Title, A. M.;
Scharmer, G.
1991BAAS...23Q1052T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from high resolution solar images and spectra obtained
at the Pic du Midi Observatory (1986-1990)
Authors: Roudier, Th.; Muller, R.; Vigneau, J.; Auffret, H.; Espagnet,
O.; Simon, G. W.; Title, A. M.; Frank, Z.; Shine, R. A.; Tarbell,
T. D.; Mein, P.; Malherbe, J. M.
1991AdSpR..11e.205R Altcode: 1991AdSpR..11..205R
We present an overview of our recent results about solar granulation and
mesogranulation, obtained with Pic du Midi observations. These results
were obtained during 1986-1990 using image and spectrographic analysis
of high spatial resolution data. The study of the solar granulation,
with 2 Dim. “Multichannel Subtractive Double Pass” (M.S.D.P.) spectra,
shows a clear change of the dynamical regime at 3” (⋍ 2200 km)
of the photospheric velocity field when oscillatory components are
filtered out. <P />A three hour movie obtained on film at Pic du Midi
Observatory and analyzed at the Lockheed Research Laboratory and the
National Solar Observatory (Sacramento Peak) was used to calculate
the horizontal flow pattern. The mean lifetime of the diverging areas
related to mesogranulation is estimated at 3 hours; these diverging
areas are swept by the supergranulation flow towards the supergranule
boundary with a mean speed of 0.4 km/s.
---------------------------------------------------------
Title: Generation of Electric Currents and Waves on Magnetic Flux
Tubes by Horizontal Velocities in the Photosphere (With 1 Figure)
Authors: Tarbell, T. D.; Slater, G. L.; Frank, Z. A.; Shine, R. A.;
Topka, K. P.
1991mcch.conf...39T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Generation of Waves and Electric Currents on Magnetic Flux
Tubes by Horizontal and Vertical Velocities in the Photosphere
Authors: Frank, Z. A.; Shine, R. A.; Slater, G.; Tarbell, T.; Topka, K.
1990BAAS...22..878F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High-Resolution Observations of Emerging Magnetic Fields and
Flux Tubes in Active Region Photosphere
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Shine, R.; Title, A.;
Topka, K.; Scharmer, G.
1990IAUS..138..147T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Structure and Evolution of the Large Scale Granulation
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
1990PDHO....7...44M Altcode: 1990dysu.conf...44M; 1990ESPM....6...44M
A granulation movie of 3 hours has been performed at the Pic du Midi
Observatory on September 20, 1988.
---------------------------------------------------------
Title: Formation of Network Bright Points by Granule Compression
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
1990PDHO....7..150M Altcode: 1990dysu.conf..150M; 1990ESPM....6..150M
No abstract at ADS
---------------------------------------------------------
Title: Intial Results of the Lockheed 1989 La Palma Observing Campaign
Authors: Topka, K.; Frank, Z.; Shine, R.; Smith, K.; Tarbell, T.;
Title, A.; Scharmer, G.
1989BAAS...21.1111T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High - resolution observations of emerging magnetic flux
Authors: Tarbell, T. D.; Topka, K.; Ferguson, S.; Frank, Z.; Title,
A. M.
1989hsrs.conf..506T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Proper Motion and Lifetime of Mesogranules
Authors: Frank, Z.; Muller, R.; Roudier, T.; Vigneau, J.; Shine, R.;
Tarbell, T.; Title, A.; Topka, K.; Simon, G.
1989BAAS...21..841F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Short Term Evolution of Fine Scale Magnetic Structures
Authors: Topka, K.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Scharmer, G.; Balke, A.
1989BAAS...21..842T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Field Inclination in Penumbra of a Round Sunspot
Observed at Very High Spatial Resolution
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Scharmer, G.
1989BAAS...21Q.837T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of Running Penumbral Waves
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Scharmer, G.
1989BAAS...21..837S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Generation of Waves on Magnetic Flux Tubes by Horizontal
Velocities in the Photosphere
Authors: Tarbell, T. D.; Ferguson, S. H.; Frank, Z. A.; Shine, R. A.
1989BAAS...21..830T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Active Optics, Anisoplanatism, and the Correction of
Astronomical Images
Authors: Peri, M. L.; Smithson, R. C.; Acton, D. S.; Frank, Z. A.;
Title, A. M.
1989ASIC..263...77P Altcode: 1989ssg..conf...77P
No abstract at ADS
---------------------------------------------------------
Title: Investigation of active regions at high resolution by balloon
flights of the Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.;
Topka, K.; Wolfson, J.
1989dots.work..310T Altcode:
SOUP is a versatile, visible-light solar observatory, built for space
or balloon flight. It is designed to study magnetic and velocity
fields in the solar atmosphere with high spatial resolution and
temporal uniformity, which cannot be achieved from the surface of the
earth. The SOUP investigation is carried out by the Lockheed Palo Alto
Research Laboratory, under contract to NASA's Marshall Space Flight
Center. Co-investigators include staff members at a dozen observatories
and universities in the U.S. and Europe. The primary objectives of the
SOUP experiment are: to measure vector magnetic and velocity fields in
the solar atmosphere with much better spatial resolution than can be
achieved from the ground; to study the physical processes that store
magnetic energy in active regions and the conditions that trigger
its release; and to understand how magnetic flux emerges, evolves,
combines, and disappears on spatial scales of 400 to 100,000 km. SOUP
is designed to study intensity, magnetic, and velocity fields in the
photosphere and low chromosphere with 0.5 arcsec resolution, free of
atmospheric disturbances. The instrument includes: a 30 cm Cassegrain
telescope; an active mirror for image stabilization; broadband film
and TV cameras; a birefringent filter, tunable over 5100 to 6600 A
with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera
behind the filter; and a high-speed digital image processor.
---------------------------------------------------------
Title: Observations of f- and p-mode oscillations of high degree
(500 < l < 2500) in quiet and active Sun.
Authors: Tarbell, T. D.; Peri, M.; Frank, Z.; Shine, R.; Title, A. M.
1988ESASP.286..315T Altcode: 1988ssls.rept..315T
Spectra (l-ν diagrams) from high resolution observations taken at
the Vacuum Tower Telescope (NSO/Sunspot) are presented. The raw data
are CCD images taken through the SOUP narrowband filter in Fe I 5576
Å. Four filtergrams spaced through the spectral line are combined to
form velocity movies. Spectra for 80 minutes of data with 0.5 - 1.5
arcsecond resolution are presented for the entire field-of-view and
for quiet and magnetic (plage) subregions. Ridges f and p<SUB>1</SUB> -
p<SUB>5</SUB> are evident in velocity spectra, extending to l = 2500(f),
l = 1800(p<SUB>1</SUB>), and l = 1200(p<SUB>2</SUB>). Much less power is
seen in the magnetic region than in the quiet sun. Three-dimensional
Fourier filtering shows that oscillation velocity amplitude drops
sharply at the boundary of the active region for each family of modes
considered.
---------------------------------------------------------
Title: High-resolution digital movies of emerging flux and horizontal
flows in active regions on the sun
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.
1988fnsm.work..283T Altcode:
High-resolution observations of active regions in many wavelength bands
obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak)
are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera,
and a sunspot tracker for image stabilization were used. Subarrays of
512 x 512 pixels were processed digitally and recorded on videodisk
in movie format. The movies with 0.5 to 1 arcsecond resolution of
the following simultaneous observations were shown: green continuum,
longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center,
H alpha wings, and H alpha line center. The best set of movies show a
90 x 90 arcsecond field-of-view of an active region at S29, W11. When
viewed at speeds of a few thousand times real-time, the photospheric
movies clearly show the active region fields being distorted by a
remarkable combination of systematic flows and small eruptions of new
flux. Flux emergence is most easily discovered in line center movies:
an elongated dark feature appears first, followed soon after by bright
points at one or both ends. A brief, strong upflow is seen when the
dark feature first appears; downflow in the bright points persists
much longer. The magnetic flux appears to increase gradually over this
extended period. Some of the flux emergence events were studied in
detail, with measurements of horizontal and vertical velocities and
magnetic flux versus time within one footpoint of the loop.
---------------------------------------------------------
Title: Observations of photospheric magnetic fields and shear flows
in flaring active regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
1988fnsm.work...50T Altcode:
Horizontal flows in the photosphere and subsurface convection zone move
the footpoints of coronal magnetic field lines. Magnetic energy to power
flares can be stored in the corona if the flows drive the fields far
from the potential configuration. Videodisk movies were shown with 0.5
to 1 arcsecond resolution of the following simultaneous observations:
green continuum, longitudinal magnetogram, Fe I 5576 A line center
(mid-photosphere), H alpha wings, and H alpha line center. The movies
show a 90 x 90 arcsecond field of view of an active region at S29,
W11. When viewed at speeds of a few thousand times real-time, the
photospheric movies clearly show the active region fields being
distorted by a remarkable combination of systematic flows and small
eruptions of new flux. Magnetic bipoles are emerging over a large area,
and the polarities are systematically flowing apart. The horizontal
flows were mapped in detail from the continuum movies, and these may
be used to predict the future evolution of the region. The horizontal
flows are not discernable in H alpha. The H alpha movies strongly
suggest reconnection processes in the fibrils joining opposite
polarities. When viewed in combination with the magnetic movies,
the cause for this evolution is apparent: opposite polarity fields
collide and partially cancel, and the fibrils reconnect above the
surface. This type of reconnection, driven by subphotospheric flows,
complicates the chromospheric and coronal fields, causing visible
braiding and twisting of the fibrils. Some of the transient emission
events in the fibrils and adjacent plage may also be related.
---------------------------------------------------------
Title: Observations of Granulation in Quiet and Magnetic Sun from
the Swedish Solar Observatory on LaPalma
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell, T.;
Title, A.; Wolfson, J.; Scharmer, G.; Brandt, P.
1988BAAS...20S1010T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Activity and Flare Observations from the Swedish Solar
Observatory on La Palma
Authors: Wolfson, J.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell,
T.; Title, A.; Topka, K.; Scharmer, G.; Brandt, P.; Gurman, J.
1988BAAS...20..978W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of F-and P-Mode Oscillations of High Degree
(500< <3500) in Quiet and Active Sun
Authors: Peri, M.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.
1988BAAS...20..702P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of Photospheric Magnetic Fields and Shear Flows
in Flaring Active Regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
1988BAAS...20..744T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High-Resolution Digital Movies of Emerging Flux and Horizontal
Flows in Active Regions on the Sun
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
1988BAAS...20..680T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Correlation Lifetimes of Quiet and Magnetic Granulation from
the SOUP Instrument on Spacelab 2
Authors: Title, A.; Tarbell, T.; Topka, K.; Acton, L.; Duncan, D.;
Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill,
M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Simon, G.; Harvey,
J.; Leibacher, J.; Livingston, W.; November, L.; Zirker, J.
1988ApL&C..27..141T Altcode:
The time sequences of diffraction limited granulation images obtained by
the Solar Optical Universal Polarimeter on Spacelab 2 are presented. The
uncorrection autocorrelation limetime in magnetic regions is dominated
by the 5-min oscillation. The removal of this oscillation causes the
autocorrelation lifetime to increase by more than a factor of 2. The
results suggest that a significant fraction of granule lifetimes are
terminated by nearby explosions. Horizontal displacements and transverse
velocities in the intensity field are measured. Lower limits to the
lifetime in the quiet and magnetic sun are set at 440 s and 950 s,
respectively.
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Title: High-Resolution CCD Observations of Doppler and Magnetic
Images in the Solar Photosphere
Authors: Tarbell, T. D.; Frank, Z. A.; Morrill, M. E.; Shine, R. A.;
Topka, K. P.; Title, A. M.
1987BAAS...19.1117T Altcode:
No abstract at ADS
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Title: Sunspot observations from the SOUP instrument on Spacelab 2.
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan,
D.; Ferguson, S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.
1987NASCP2483..133S Altcode: 1987tphr.conf..133S
A series of white light images obtained by the SOUP instrument on
Spacelab 2 of active region 4682 on August 5, 1985 were analyzed
in the area containing sunspots. Although the umbra of the spot is
underexposed, the film is well exposed in the penumbral regions. These
data were digitally processed to remove noise and to separate p-mode
oscillations from low velocity material motions. The results of this
preliminary investigation include: (1) proper motion measurements of
a radial outflow in the photospheric granulation pattern just outside
the penumbra; (2) discovery of occasional bright structures (streakers)
that appear to be ejected outward from the penumbra; (3) broad dark
clouds moving outward in the penumbra in addition to the well known
bright penumbral grains moving inward; (4) apparent extensions and
contractions of penumbral filaments over the photosphere; and (5)
observation of a faint bubble or loop-like structure which seems to
expand from two bright penumbral filaments into the photosphere.
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Title: First results on quiet and magnetic granulation from SOUP.
Authors: Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan, D.; Ferguson,
S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.
1987NASCP2483...55T Altcode: 1987tphr.conf...55T
The flight of Solar Optical Universal Polarimeter (SOUP) on Spacelab
2 allowed the collection of time sequences of diffraction limited (0.5
arc sec) granulation images with excellent pointing (0.003 arc sec) and
completely free of the distortion that plagues groundbased images. The
p-mode oscillations are clearly seen in the data. Using Fourier
transforms in the temporal and spatial domain, it was shown that the
p-modes dominate the autocorrelation lifetime in magnetic regions. When
these oscillations are removed the autocorrelation lifetime is found
to be 500 sec in quiet and 950 sec in magnetic regions. In quiet
areas exploding granules are seen to be common. It is speculated that
a significant fraction of granule lifetimes are terminated by nearby
explosions. Using local correlation tracking techniques it was able to
measure horizontal displacements, and thus transverse velocities, in
the magnetic field. In quiet sun it is possible to detect both super
and mesogranulation. Horizontal velocities are as great as 1000 m/s
and the average velocity is 400 m/s. In magnetic regions horizontal
velocities are much less, about 100 m/s.
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Title: White-light movies of the solar photosphere from the soup
instrument on spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
1986AdSpR...6h.253T Altcode: 1986AdSpR...6..253T
We present initial results on solar granulation, pores and sunspots
from the white-light films obtained by the Solar Optical Universal
Polarimeter (SOUP) instrument on Spacelab 2. SOUP contains a
30-cm Cassegrain telescope, an active secondary mirror for image
stabilization, and a white-light optical system with 35-mm film
and video cameras. Outputs from the fine guidance servo provided
engineering data on the performance of the ESA Instrument Pointing
System (IPS). Several hours of movies were taken at various
disk and limb positions in quiet and active regions. The images
are diffraction-limited at 0.5 arc second resolution and are, of
course, free of atmospheric seeing and distortion. Properties of the
granulation in magnetic and non-magnetic regions are compared and are
found to differ significantly in size, rate of intensity variation,
and lifetime. In quiet sun on the order of fifty percent of the area
has at least one “exploding granule” occurring in it during a 25
minute period. Local correlation tracking has detected several types
of transverse flows, including systematic outflow from the penumbral
boundary of a spot, motion of penumbral filaments, and cellular flow
patterns of supergranular and mesogranular size. Feature tracking has
shown that in quiet sun the average granule fragment has a velocity
of about one kilometer per second.
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Title: The helium 10830 angstrom line in early-type stars : an atlas
of Fabry-Perot scans.
Authors: Meisel, D. D.; Saunders, B. A.; Frank, Z. A.; Packard, M. L.
1982ApJ...263..759M Altcode:
Representative profiles of He I 10830 A in 65 early-type (O6-A1)
stars over a wide range of luminosity are presented. The atlas scans
were obtained using the Vaughan Fabry-Perot interferometer on the
C. E. K. Mees 0.6 m and KPNO 0.9 m telescopes and usually cover a range
of plus or minus 15 A at 1 A resolution with sampling distances between
0.5 A and 2 A depending on the photometer integration time required to
reach reasonable Poisson counting statistics. The majority of the scans
show very shallow, broad features which do not agree with plane-parallel
NLTE model atmosphere calculations of the 10830 line by Auer and Mihalas
(1972). Difficulties connected with previous theoretical studies of
this line are briefly discussed, and suggestions for possible future
modifications to the theory are made.
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Title: He I lambda 10830 in some O6 - B3 III, IV, V stars.
Authors: Frank, Z.; Meisel, D. D.; Saunders, B.
1980BAAS...12Q.751F Altcode:
No abstract at ADS
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Title: Very wideband corrugated horns.
Authors: Frank, Z.
1975ElL....11..131F Altcode:
An expression for the input impedance of a short-circuited,
linearly-tapered transmission line is derived. The use of tapered
slots in a corrugated horn is proposed as a means of broadening their
bandwidth to greater than 3:1. Test results are presented for an
experimental horn operating over the full 7.5-18 GHz range of DR14
waveguide.
