Author name code: simon-george
ADS astronomy entries on 2022-09-14
author:("Simon, George W." OR ="Simon, G.W.") NOT =author:"Simon, G."
------------------------------------------------------------------------
Title: JuliaPlots/Makie.jl: v0.15.2
Authors: Simon; Jkrumbiegel; Singhvi, Anshul; Freyer, Frederic;
Wang, Anthony; Vertechi, Pietro; Holy, Tim; Widmann, David; Krabbe
Borregaard, Michael; Datseris, George; M, Mustafa; Greimel, Fabian;
Butterworth, Ian; Foster, Chris; Dehaybe, Henri; Schauer, Moritz;
Kilpatrick, Logan; Byrne, Simon; Kragol; Weidner, Jan; Hatherly,
Michael; Sharma, Arsh; Micluța-Câmpeanu, Sebastian; T-Bltg;
Herikstad, Roger; Goretkin, Gustavo; TagBot, Julia; Štih, Vilim;
Smldis
Bibcode: 2021zndo...3735092S
Altcode:
Makie v0.15.2 Diff since v0.15.1 Closed issues: Feature request:
rectangular span (axvspan/axhspan) (#1263) Merged pull requests:
remove function special conversion (#1213) (@piever) Adjust default
Camera3D controls (#1220) (@ffreyer) Add Gantt Chart example in
docs (#1243) (@hdavid16) Fix precompilation errors with Julia 1.3
(#1244) (@devmotion) Fix zoom! method, cleanup (#1247) (@ffreyer)
Document contour(::Matrix) in docstring and with example (#1250)
(@kimlaberinto) fix footer spacing (#1251) (@jkrumbiegel) Switch to
GeometryBasics 0.4.1 (#1252) (@devmotion) up MathTeXEngine (#1253)
(@SimonDanisch) new full-width banner (#1255) (@jkrumbiegel) Fix link
to docs in convert_arguments error (#1256) (@felixcremer) add code
copying buttons and code expansion button (#1258) (@jkrumbiegel) add
hspan! / vspan! (#1264) (@jkrumbiegel) fix #1261 (#1265) (@ffreyer)
move axis plotting functions into plotting functions section (#1266)
(@jkrumbiegel)
Title: JuliaPlots/Plots.jl: v1.13.2
Authors: Breloff, Tom; Schwabeneder, Daniel; Krabbe Borregaard,
Michael; Christ, Simon; Heinen, Josef; Yuval; Palugniok, Andrew;
Simon; Vertechi, Pietro; Zhanibek; Chamberlin, Thatcher; ma-laforge;
Rackauckas, Christopher; Schulz, Oliver; Pfitzner, Sebastian; Arakaki,
Takafumi; Yahyaabadi, Amin; Devine, Jack; Pech, Sebastian; Kofod
Mogensen, Patrick; Watson, Samuel S.
Bibcode: 2021zndo...4725318B
Altcode:
Plots v1.13.2 Diff since v1.13.1 Closed issues: [BUG] savefig adds
white lines (#3457)
Title: mschauer/Bridge.jl: v0.11.6
Authors: Schauer, Moritz; Frank; getzdan; Bezanson, Jeff; Corstanje,
Marc; Piibeleht, Morten; Simon; Kelman, Tony
Bibcode: 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])
Title: javaparser/javaparser: Release javaparser-parent-3.16.1
Authors: Van Bruggen, Danny; Tomassetti, Federico; Howell, Roger;
Langkabel, Malte; Smith, Nicholas; Bosch, Artur; Skoruppa, Malte;
Maximilien, Cruz; ThLeu; Panayiotis; Kirsch, Sebastian "@Skirsch79";
Simon; Beleites, Johann; Tibackx, Wim; L, Jean Pierre; Rouél, André;
Edefazio; Schipper, Daan; Mathiponds; Know, Why You Want To; Beckett,
Ryan; Ptitjes; Kotari4u; Wyrich, Marvin; Morais, Ricardo; Coene,
Maarten; Bresai; Implex1v; Haumacher, Bernhard
Bibcode: 2020zndo...3842713V
Altcode:
Java 1-14 Parser and Abstract Syntax Tree for Java, including preview
features to Java 13 –
Title: Global climate modeling of Saturn's atmosphere. Part
III: Global statistical picture of zonostrophic turbulence in
high-resolution 3D-turbulent simulations
Authors: Simon; Cabanes; Aymeric; Spiga; Roland; Young, M. B.
Bibcode: 2020arXiv200102473S
Altcode:
We conduct an in-depth analysis of statistical flow properties
calculated from the reference high-resolution Saturn simulation obtained
by global climate modelling in Part II. In the steady state of this
reference simulation, strongly energetic, zonally dominated, large-scale
structures emerge, which scale with the Rhines scale. Spectral analysis
reveals a strong anisotropy in the kinetic energy spectra, consistent
with the zonostrophic turbulent flow regime. By computing spectral
energy and enstrophy fluxes we confirm the existence of a double cascade
scenario related to 2D-turbulent theory. To diagnose the relevant 3D
dynamical mechanisms in Saturn's turbulent atmosphere, we run a set
of four simulations using an idealized version of our Global Climate
Model devoid of radiative transfer, with a well-defined Taylor-Green
forcing and over several rotation rates (4, 1, 0.5, and 0.25 times
Saturn's rotation rate). This allows us to identify dynamics in three
distinctive inertial ranges: (1) a ``residual-dominated'' range, in
which non-axisymmetric structures dominate with a -5/3 spectral slope;
(2) a ``zonostrophic inertial'' range, dominated by axisymmetric
jets and characterized by the pile-up of strong zonal modes with a
steeper, nearly -3, spectral slope; and (3) a ``large-scale'' range,
beyond Rhines' typical length scale, in which the reference Saturn
simulation and our idealized simulations differ. In the latter range,
the dynamics is dominated by long-lived zonal modes 2 and 3 when a
Saturn-like seasonal forcing is considered (reference simulation),
and a steep energetic decrease with the idealized Taylor-Green
forcing. Finally, instantaneous spectral fluxes show the coexistence
of upscale and downscale enstrophy/energy transfers at large scales,
specific to the regime of zonostrophic turbulence in a 3D atmosphere.
Title: Mschauer/Bridge.Jl: Release V0.6.0
Authors: Schauer, Moritz; getzdan; Kelman, Tony; Simon
Bibcode: 2017zndo....891231S
Altcode:
This release contains a much improved implementation of guided
proposals, which adopt a new interface. The corresponding improvements
for partial guided bridges are postponed for the next release, so they
still use the old interface. New scripts hypo.jl and elliptic.jl in the
example directory to verify the correctness of the implementation. Fix:
The llikelihood function is missing a factor -1/2 from the former
likeliXcirc in SDE.jl, discovered by the method. Add a README.md file
describing the examples Better test coverage
Title: Dynamics and Properties of Supergranulation from TRACE
Observations
Authors: Simon, G. W.; Shine, R. A.
Bibcode: 2004AAS...204.3718S
Altcode: 2004BAAS...36..712S
Using a unique set of white-light images taken by the Transition Region
and Corona Explorer (TRACE) satellite over a 7 day period in April 2000,
we investigate the properties and evolution of supergranulation. A
384x384 arcsec area of the solar photosphere was observed as it
rotated from Stonyhurst longitude 45E to 45W. Granulation is well
defined in these images which were taken at a 60s cadence for most
of the 7 days. Hence we are able to use local correlation tracking
(LCT) with sufficient spatial and temporal resolution to track both
mesogranules and supergranules. Improved techniques for LCT are
discussed and compared. Divergence and other parameters derived
from flow maps are used to identify and accurately trace supergranular
boundaries and tessellate the image areas into distinct supergranules
as well as smaller areas with less coherent flow patterns. We have
used these to derive sizes, lifetimes, and other properties of
supergranules. Motivated by recent work of Rast, Lisle, and Toomre
(2004), and Lisle, Rast, and Toomre (2004), we also present results
comparing the rotational rate of the supergranular and mesogranular
patterns and N/S alignments of these features. This work
was supported by NASA contract NAS5-38099, the Air Force Research
Laboratory, and the National Solar Observatory.
Title: Evolution of small-scale structures in and around a large
solar pore
Authors: Dorotovič, I.; Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 2002ESASP.506..435D
Altcode: 2002ESPM...10..435D; 2002svco.conf..435D
The analysis of an 11-hour series of high resolution white light
observations of a large pore in the sunspot group NOAA 7519, observed
on 5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma, Canary
Islands, is described. We used a total of 1782 frames, with average
time interval of 22 s. Special attention was paid to the evolution of a
filamentary region attached to the pore, to horizontal motions around
the pore, and to small-scale morphological changes. The filamentary
region was observed to change its structure back and forth between
penumbra-like filaments and elongated granules. A clockwise rotation of
this region around the center of the pore was detected during the whole
observing period. This rotation had angular velocities decreasing with
time from 7.6°h-1 to 2.7%deg;h-1. Motions inside
the filamentary region and around the pore, inclduding penetrations
of photospheric granules into the pore, were studied in detail using
local correlation and feature tracking algorithms. It was found that
the observed filamentary region, although having some typical penumbral
features, was different from a normal penumbra.
Title: Evolution and motions of small-scale photospheric structures
near a large solar pore
Authors: Dorotovič, I.; Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 2002A&A...387..665D
Altcode:
The analysis of an 11-hour series of high resolution white light
observations of a large pore in the sunspot group NOAA 7519, observed
on 5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma, Canary
Islands, is described. We used a total of 1782 frames, with average
time interval of 22 s. Special attention was paid to the evolution of a
filamentary region attached to the pore, to horizontal motions around
the pore, and to small-scale morphological changes. The filamentary
region was observed to change its structure back and forth between
penumbra-like filaments and elongated granules. A clockwise rotation
of this region around the center of the pore was detected during the
whole observing period. This rotation had angular velocities decreasing
with time from 7.6deg h-1 to 2.7deg
h-1. Motions inside the filamentary region and around the
pore, including penetrations of photospheric granules into the pore,
were studied in detail using local correlation and feature tracking
algorithms. It was found that the observed filamentary region,
although having some typical penumbral features, was different from
a normal penumbra.
Title: Evolution of Filamentary Structures in and around a Large
Solar Pore
Authors: Simon, G. W.; Dorotovič, I.; Sobotka, M.; Brandt, P. N.
Bibcode: 2002AAS...200.3803S
Altcode: 2002BAAS...34..698S
We have studied evolution of a filamentary region attached to a pore,
horizontal motions around the pore, and small-scale morphological
changes, using an 11-hour series of 1782 high resolution white-light
images of a large pore in the sunspot group NOAA 7519, acquired on
5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma, Canary
Islands. We find that the structure of the region between the large pore
and an adjacent micropore was not always filamentary, but varied back
and forth in time between a filamentary structure and a granular one. A
clockwise rotation, at times exceeding 7 deg/h, of this filamentary
region around the center of the pore, was observed during the whole
run. Motions of fine structure around and within the pore were studied
in detail using local correlation and feature tracking. We conclude
that the filamentary region, while it had some typical penumbral
characteristics, was different from a normal penumbra. This research has
been funded by the USAF Research Lab, and by Emeritus Research Services.
Title: Flow Map Studies of Supergranule and Mesogranule Evolution
from TRACE
Authors: Shine, R. A.; Frank, Z. A.; Tarbell, T. D.; Simon, G. W.
Bibcode: 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: Sustaining the Sun's Magnetic Network with Emerging Bipoles
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 2001ApJ...561..427S
Altcode:
The Michelson Doppler Imager experiment on SOHO has revealed a
``magnetic carpet'' dominated by the emergence of bipolar magnetic flux
in ephemeral active regions, which subsequently split into small flux
elements that drift into the magnetic network. The effects of granular
and supergranular convection on these flux elements are represented
here by kinematic modeling: Elementary flux tubes are transported
passively by the supergranular flow, while experiencing small random
displacements produced by granulation. They end up in the magnetic
network that surrounds the supergranules, where they eventually meet
oppositely directed fields and are annihilated. The model calculations
show that the total unsigned magnetic flux will decay within a few
days unless it is continually replenished. A statistically steady
state with a total unsigned flux of 2-3×1023 Mx over the
whole solar surface can be maintained if bipolar flux emerges at a rate
of 7×1022 Mx day-1, as indicated by published
measurements of the rate at which ephemeral active regions appear.
Title: How the Sun Maintains its Magnetic Network
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 2001AAS...198.8601S
Altcode: 2001BAAS...33..913S
The MDI experiment on SOHO has revealed a `magnetic carpet' dominated
by the emergence of bipolar magnetic flux in ephemeral active regions,
which subsequently split into small flux elements that drift into the
magnetic network. The effects of granular and supergranular convection
on these flux elements are represented here by kinematic modeling:
Elementary flux tubes are transported passively by the supergranular
flow, while experiencing small random displacements produced by
granulation. They end up in the magnetic network that surrounds the
supergranules, where they eventually meet oppositely directed fields and
are annihilated. The model calculations show that the total unsigned
magnetic flux will decay within a few days unless it is continually
replenished. A statistically steady state with a total unsigned
flux of 2-3 x 1023 Mx over the whole solar surface can be
maintained if bipolar flux emerges at a rate of 7 x 1022
Mx d-1, as indicated by published measurements of the rate
at which ephemeral active regions appear.
Title: Supergranule and Mesogranule Evolution
Authors: Shine, R. A.; Simon, G. W.; Hurlburt, N. E.
Bibcode: 2000SoPh..193..313S
Altcode:
The MDI instrument on the SOHO satellite obtained a nearly continuous
45.5-hr run in high-resolution mode on 17-18 January 1997, collecting
continuum, Dopplergram, and magnetogram images once per minute. This
is one of the longest data sets yet obtained in this mode and shows
significant evolution of the supergranulation pattern. After allowing
for solar rotation within the fixed field of view, an area spanning
17° in latitude and 11° in longitude was extracted that covers
the same area of the solar surface for the entire run. From the
de-rotated continuum images, we computed flow maps of photospheric
motions using local correlation techniques (LCT). Horizontal divergence
maps constructed from the flow maps show local maxima of the size of
mesogranules (5-10''). We interpret these as mesogranules although
the LCT flow map resolution (4.8'' FWHM) may not completely resolve
smaller mesogranules. Movies made from the divergence maps clearly show
the outward convection (advection) of these mesogranules within each
supergranule, and narrow boundaries of negative divergence outlining the
supergranules. Several new supergranules are observed forming. These
appear as areas of strong divergence that pop up between pre-existing
supergranules and grow, pushing their neighbors apart. Others seem
to perish between growing neighbors. We also computed the vertical
component of vorticity from the flow maps. Movies of this vorticity
do not show any obvious patterns.
Title: John W. Evans died 31 October 1999.
Authors: Dunn, R. B.; Simon, G. W.; Smartt, R. N.; Zirker, J. B.
Bibcode: 2000SoPh..191..227D
Altcode:
No abstract at ADS
Title: Obituary: John Wainwright Evans, 1909-1999
Authors: Dunn, Richard B.; Simon, George W.; Smartt, Raymond N.;
Zirker, Jack B.
Bibcode: 2000BAAS...32.1663D
Altcode:
No abstract at ADS
Title: Fine structure in sunspots. III. Penumbral grains
Authors: Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 1999A&A...348..621S
Altcode:
The properties of penumbral grains (PGs) in a medium-size sunspot are
studied from a 4.5 hour observation series acquired on 5 June 1993 at
the Swedish Vacuum Solar Telescope, La Palma. The application of an
image segmentation procedure and a feature tracking algorithm on a movie
of 360 frames yields proper motions, intensities, and lifetimes for a
set of 469 PGs. Almost 3/4 of the PGs move toward the umbra and more
than 1/4 toward the photosphere. There appears to be a dividing line
(DL) in the penumbra, approximately 0.7 of the distance from the umbra
to the photosphere, such that most PGs outside this line move toward
the photosphere, and those inside move toward the umbra. For inward
moving PGs we find a typical proper motion speed of 0.4 km s(-1) and
a median lifetime of 29 minutes, for outward moving ones 0.5 km s(-1)
and 22 minutes. The average speed of inward moving PGs increases with
distance from the umbra with a maximum near the DL. Outward moving
PGs have maximum speed near the outer penumbral boundary. The measured
instantaneous velocities of individual PGs show only partial agreement
with theoretical model predictions. We find much shorter lifetimes than
earlier authors, and no pronounced dependence of lifetime on position
in the penumbra. We discuss possible reasons for the disagreement with
previous results.
Title: Fine Structure in Sunspots, III: Penumbral Grains
Authors: Simon, G. W.; Sobotka, M.; Brandt, P. B.
Bibcode: 1999AAS...194.5908S
Altcode: 1999BAAS...31..919S
The properties of penumbral grains (PGs) in a medium-size sunspot are
studied from a 4.5 h observation series acquired on 1993 June 5 at the
Swedish Vacuum Solar Telescope, La Palma. The application of an image
segmentation procedure and a feature tracking algorithm on a movie of
360 frames yields proper motions, intensities, and lifetimes for a set
of 469 PGs. Almost 3/4 of the PGs move toward the umbra and more than
1/4 toward the photosphere. There appears to be a dividing line (DL)
in the penumbra, approximately 0.7 of the distance from the umbra to
the photosphere, such that most PGs outside this line move toward the
photosphere, and those inside move toward the umbra. For the inward
moving PGs we find a typical proper motion speed of 0.4 km/s and a
median lifetime of 29 minutes, for the outward moving ones 0.5 km/s
and 22 minutes. The average speed of inward moving PGs increases with
distance from the umbra and has a maximum near the DL. Outward moving
PGs have maximum speed near the outer penumbral boundary. Instantaneous
velocities of individual PGs were measured to compare them with
theoretical model predictions. We find much shorter lifetimes than
earlier authors, and no pronounced dependence of lifetime on position
in the penumbra. We discuss possible reasons for the disagreement in
results, and make some comments on the differences between human and
computer selection and tracking of features.
Title: Supergranule and Mesogranule Evolution
Authors: Shine, Richard; Simon, George; Hurlburt, Neal
Bibcode: 1999soho....9E..15S
Altcode:
The MDI instrument on the SoHO satellite obtained a nearly continuous
46-hour run in high resolution mode on January 17 to 18, 1997,
collecting continuum, dopplergram, and magnetogram images once per
minute. This is one of the longest data sets yet obtained in this mode
and shows significant evolution of the supergranulation pattern. After
allowing for solar rotation within the fixed field of view, an area
spanning 13 degrees in latitude and 10 degrees in longitude was
extracted that covers the same area of the solar surface for the 46
hours. Using the derotated continuum images, we computed flow maps
of photospheric motions using local correlation techniques (LCT). The
accuracy of these LCT's has been verified by comparison with La Palma
ground based data using other data sets (Shine, et al, 1997, B.A.A.S.,
29, 02.62). Horizontal divergence maps constructed from the flow maps
show local maxima of about the size of mesogranules. We interpret
these as mesogranules although the LCT flow map resolution (4.8 arc
seconds FWHM) may not completely resolve all mesogranules. Movies
made from the divergence maps clearly show the outward convection of
these "mesogranules" within each supergranule and narrow boundaries
of negative divergence outlining the supergranules. Several new
supergranules are observed forming as areas of strong divergence
that pop up between pre-existing supergranules and grow, pushing their
neighbors apart. Others seem to perish between growing neighbors. Movies
of the derived vertical curl do not show any obvious patterns. Videos
of these movies and the continuum, dopplergram, and magnetogram images
will be shown. This work was supported by NASA Grant NAG5-3077 at
Stanford and Lockheed Martin.
Title: Lifetimes and motions of penumbral grains.
Authors: Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 1999joso.proc...89S
Altcode:
The properties of penumbral grains (PGs) are studied from a 4.5 hour
sunspot series observed on June 5, 1993 at the Swedish Vacuum Solar
Telescope, La Palma. The application of an image segmentation procedure
yields a set of 605 penumbral grains which are investigated by a feature
tracking algorithm. The authors find a dividing line between inward and
outward moving PGs and give results on their lifetime and proper motion.
Title: 62 Days Around the Sun: A Search for Supergranular Evolution
and Giant Cells
Authors: Strous, Louis H.; Simon, George W.
Bibcode: 1998ASPC..140..161S
Altcode: 1998ssp..conf..161S
No abstract at ADS
Title: Fine structure in sunspots. I. Sizes and lifetimes of
umbral dots
Authors: Sobotka, Michal; Brandt, Peter N.; Simon, George W.
Bibcode: 1997A&A...328..682S
Altcode:
The analysis of a 4 1/2 hour series of high resolution white light
observations of the umbra in a medium-size sunspot (NOAA 7519, observed
on 5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma) is
described. An automatic identification and tracking algorithm was
applied to umbral dots (UDs) observed in a destretched movie of 360
frames. In total, 662 UDs were tracked and their filling factor, sizes,
and lifetimes were measured. It was found that large (diameter >
0farcs 4) and long-lived (lifetime > 10 minutes) UDs appear mostly
in regions with enhanced umbral diffuse background intensity. UDs
do not have a ``typical'' size. Their number rapidly increases with
decreasing diameter down to the resolution limit. Similarly, UDs do
not have a ``typical'' lifetime, and their number rapidly increases
with decreasing lifetime. UDs with lifetimes below 10 minutes represent
about 2/3 of the population; the median lifetime is 5.9 minutes.
Title: Fine structure in sunspots. II. Intensity variations and
proper motions of umbral dots
Authors: Sobotka, Michal; Brandt, Peter N.; Simon, George W.
Bibcode: 1997A&A...328..689S
Altcode:
Temporal intensity variations of umbral dots (UDs) and dark nuclei
(DNs), and proper motions of UDs, were analyzed in a 4 1/2 hour
time series of high resolution white light images of the umbra in a
medium-size sunspot (NOAA 7519). The observations were made on 5 June
1993 at the Swedish Vacuum Solar Telescope, La Palma. An identification
and tracking algorithm was applied to UDs observed in a destretched
movie of 360 frames. In total, 662 UDs were tracked, and their
intensities, positions, and proper motions were measured. Power
spectra of temporal intensity variations of UDs and DNs were
computed, and several typical periods were found. The histogram of
time-averaged intensities of UDs has two maxima; the UDs belonging to
the brighter part of the population are located mostly at or near the
umbral-penumbral boundary. The number of UDs decreases with increasing
magnitude of the proper motion velocity. Speeds of UDs are grouped
at 100 and 400 m/s. The observed spatial distribution of UDs with
different proper motion velocities is found to be in contradiction to
the generally accepted idea of moving ``peripheral'' and stationary
``central'' UDs. Both ``fast'' and ``slow'' UDs are present in all
parts of the umbra. Thus velocity does not appear to be a good criterion
for separating UDs into ``peripheral'' and ``central'' ones.
Title: Supergranular Evolution, Solar Rotation, and a Search for
Giant Cells, using Full-disk SOHO/SOI/MDI Dopplergrams
Authors: Simon, George W.; Strous, Louis H.
Bibcode: 1997AAS...19112002S
Altcode: 1997BAAS...29.1402S
SOHO/SOI/MDI obtained full-disk dopplergrams of the Sun once per minute
for 62 days from 1996 May 23 to 1996 July 23. From hourly averages
of these dopplergrams we have studied the evolution of supergranules,
measured solar rotation up to high latitudes, and searched for giant
cells.
Title: Kinematic Modeling of Vortices in the Solar Photosphere
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1997ApJ...489..960S
Altcode:
The application of local correlation tracking to the proper motions of
granules yields the horizontal velocity field at the solar surface. The
divergence of the velocity reveals a pattern of sources and sinks. The
vorticity is concentrated at sinks to form local swirls (with either
sense of motion). A simple kinematic model of such a vortex, in
which the radial inflow is balanced by an eddy viscosity, predicts
that the vorticity should have a Gaussian profile. This prediction is
confirmed by comparison with three sets of high-resolution observations,
obtained from Spacelab 2 and from the Swedish Vacuum Solar Telescope
on La Palma. Finally, we develop a more precise version of the model
and provide an estimate of the eddy viscosity due to small-scale
granulation.
Title: Photospheric Differential Rotation from Full-Disk SOI/MDI
Dopplergrams
Authors: Bogart, R. S.; Bai, T.; Scherrer, P. H.; Strous, L. H.;
Simon, G. W.; Tarbell, T. D.
Bibcode: 1997SPD....28.0258B
Altcode: 1997BAAS...29..903B
We report on measurements of the solar surface differential rotation
made from SOI/MDI full-disk Dopplergrams obtained once per minute during
the 2-month Dynamics Program from 23 May through 26 July 1996. We infer
the rotation profile both from the direct photospheric Doppler signal
and also by tracking Doppler features (supergranules) across the solar
disk. We study the rotation curve as a function of latitude, feature
size, and tracking method, and look for global scale flows. 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: Preliminary SoHO/MDI Observations of Supergranular Evolution
Authors: Simon, G. W.; Strous, L. H.; Matt, S.; Title, A. M.;
Schrijver, C. J.
Bibcode: 1997SPD....28.0264S
Altcode: 1997BAAS...29R.904S
We present preliminary results of a study into the evolution of
supergranules, using data from SoHO/MDI. We discuss the supergranular
size spectrum, lifetimes, and topological evolution. We compare
structures of supergranular size visible in high-resolution SoHO/MDI
dopplergrams and in divergence maps derived from tracking of features
in dopplergrams. 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: Horizontal Velocity Structure of Supergranules near Disk
Center from High-Resolution SoHO/MDI Observations
Authors: Strous, L. H.; Simon, G. W.; Shine, R. A.; Hurlburt, N.
Bibcode: 1997SPD....28.0265S
Altcode: 1997BAAS...29S.904S
We determine the average surface flows in supergranules from
high-resolution SoHO/MDI observations near disk center, using local
correlation and feature tracking methods. We present results as a
function of distance to the supergranule center and of supergranule
size, and as a function of normalized distance to the supergranule
center. 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: A search for interaction between magnetic fields and
supergranular flows in the network based on MDI observations
Authors: Schrijver, C. J.; Shine, R. A.; Title, A. M.; Hagenaar,
H. J.; Hurlburt, N. E.; Tarbell, T. D.; Simon, G. W.
Bibcode: 1997SPD....28.0243S
Altcode: 1997BAAS...29..901S
We study the supergranular flow field and its temporal evolution in
the quiet Sun as observed with the Michelson Doppler Imager on board
SOHO. We use the intensity images to derive the flow fields using
local correlation tracking. The data sets span one to two days with a
one--minute cadence. We separate areas with a relatively high filling
factor for magnetic concentrations from areas with a low magnetic
filling factor in order to study to what extent the flows influence
the magnetic network in the quiet Sun and vice versa. This work is
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: Fine structure in sunspots: sizes, lifetimes, motions, and
temporal variations.
Authors: Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 1997joso.proc...84S
Altcode:
No abstract at ADS
Title: GONG Observations of Solar Surface Flows
Authors: Hathaway, D. H.; Gilman, P. A.; Harvey, J. W.; Hill, F.;
Howard, R. F.; Jones, H. P.; Kasher, J. C.; Leibacher, J. W.; Pintar,
J. A.; Simon, G. W.
Bibcode: 1996Sci...272.1306H
Altcode:
Doppler velocity observations obtained by the Global Oscillation Network
Group (GONG) instruments directly measure the nearly steady flows in
the solar photosphere. The sun's differential rotation is accurately
determined from single observations. The rotation profile with respect
to latitude agrees well with previous measures, but it also shows a
slight north-south asymmetry. Rotation profiles averaged over 27-day
rotations of the sun reveal the torsional oscillation signal-weak,
jetlike features, with amplitudes of 5 meters per second, that are
associated with the sunspot latitude activity belts. A meridional
circulation with a poleward flow of about 20 meters per second is
also evident. Several characteristics of the surface flows suggest
the presence of large convection cells.
Title: GONG Observations of Solar Surface Flows
Authors: Hathaway, D. H.; Gilman, P. A.; Jones, H. P.; Kasher, J.;
Simon, G. W.; GONG Nearly Steady Flows Team; GONG Magnetic Fields Team
Bibcode: 1996AAS...188.5304H
Altcode: 1996BAAS...28..903H
Doppler velocity observations obtained by the GONG instruments directly
measure the nearly steady flows in the solar photosphere. The Sun's
differential rotation profile is accurately determined from single
observations. This profile is well represented by a fourth order
polynomial which includes a rapidly rotating equator and a slight
north-south asymmetry. Rotation profiles averaged over 27 day rotations
of the Sun are sufficient to reveal the torsional oscillation signal -
weak, 5 m/s, jet-like features associated with the sunspot latitude
activity belts. A meridional circulation with poleward flow of about 20
m/s is also found from single observations and its spatial structure
is well determined. Several of the observed characteristics of the
surface flows suggest the presence of large convection cells. The
convection spectrum is measured and found to have peak power for cells
with wavelengths of about 50,000 km but the spectrum extends to much
larger wavelengths. Day-to-day variations in the observed structure of
the differential rotation and meridional circulation profiles indicate
the presence of large-scale, nonaxisymmetric velocity signals which may
be of solar origin. Studies correlating the convective flow patterns on
consecutive days also indicate the presence of large cellular patterns
that rotate at the Sun's rotation rate.
Title: Observing large-scale solar surface flows with GONG:
Investigation of a key element in solar activity buildup
Authors: Beck, John G.; Simon, George W.; Hathaway, David H.
Bibcode: 1996msfc.rept.....B
Altcode:
The Global Oscillation Network Group (GONG) solar telescope network has
begun regular operations, and will provide continuous Doppler images
of large-scale nearly-steady motions at the solar surface, primarily
those due to supergranulation. Not only the Sun's well-known magnetic
network, but also flux diffusion, dispersal, and concentration at the
surface appear to be controlled by supergranulation. Through such
magnetoconvective interactions, magnetic stresses develop, leading
to solar activity. We show a Doppler movie made from a 45.5 hr time
series obtained 1995 May 9-10 using data from three of the six GONG
sites (Learmonth, Tenerife, Tucson), to demonstrate the capability of
this system.
Title: Book-Review : Solar Active Region Evolution: Comparing Models
with Observations
Authors: Balasubramaniam, K. S.; Simon, G. W.; Andrews, A. D.
Bibcode: 1996IrAJ...23..119B
Altcode:
No abstract at ADS
Title: Observing Large-Scale Solar Surface Flows with GONG:
Investigation of a Key Element in Solar Activity Buildup
Authors: Beck, John C.; Hathaway, David H.; Simon, George W.
Bibcode: 1996ASPC...95..196B
Altcode: 1996sdit.conf..196B
No abstract at ADS
Title: Temporal evolution of fine-structures in sunspots.
Authors: Sobotka, M.; Brandt, P. N.; Simon, G. W.
Bibcode: 1996joso.proc..145S
Altcode:
No abstract at ADS
Title: Warning: Local Correlation Tracking may BE Dangerous to your
(scientific) Health
Authors: Simon, G. W.; Brandt, P. N.; November, L. J.; Shine, R. A.;
Strous, L. H.
Bibcode: 1995ESASP.376b.223S
Altcode: 1995soho....2..223S; 1995help.confP.223S
No abstract at ADS
Title: Kinematic Models of Supergranular Diffusion on the Sun
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1995ApJ...442..886S
Altcode:
We develop kinematic models of diffusion generated by supergranulation
at the solar surface. These models use current observations for the
size, horizontal velocity, and lifetime of supergranules. Because there
is no observational description of the appearance and disappearance of
supergranules, we investigate models using several plausible evolution
processes, including the effect of different lifetime distribution
functions for the cells. The results are quite insensitive to the
methods chosen to replace old supergranules, the distribution of cell
lifetimes, and even the cell lifetime itself, for mean lifetimes between
15 to 30 hr. Calculated diffusion coefficients range between 500 and 700
sq km/s, in agreement with the best fit diffusion coefficients used by
Sheeley and his collaborators to model the large-scale distribution
of magnetic fields over the solar surface. However, our models do
not explain the field distribution in plage, and they predict that
virtually all the strong field in quiet Sun exists in relatively
isolated clumps. We suggest possible mechanisms for the creation of
plage and the bright network seen in quiet Sun.
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.
Bibcode: 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.
Bibcode: 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: Kinematic modelling of magnetoconvection
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.; Ginet, G. P.
Bibcode: 1994smf..conf..276S
Altcode:
No abstract at ADS
Title: Kinematic Modeling of Magnetic Field Diffusion at the Solar
Surface
Authors: Title, Alan M.; Simon, George W.; Weiss, Nigel O.
Bibcode: 1994ASPC...68...87T
Altcode: 1994sare.conf...87T
No abstract at ADS
Title: Solar active region evolution: comparing models with
observations
Authors: Balasubramaniam, K. S.; Simon, George W.
Bibcode: 1994ASPC...68.....B
Altcode: 1994sare.conf.....B
No abstract at ADS
Title: Velocity Fields in the Solar Atmosphere I. Preliminary Report
Authors: Leighton, R. B.; Noyes, R. W.; Simon, G. W.
Bibcode: 1994snft.book..382L
Altcode:
No abstract at ADS
Title: Large-scale photospheric motions: first results from an
extraordinary eleven-hour granulation observation
Authors: Simon, G. W.; Brandt, P. N.; November, L. J.; Scharmer,
G. B.; Shine, R. A.
Bibcode: 1994ASIC..433..261S
Altcode:
No abstract at ADS
Title: Diffusion of "Corks" Over the Solar Surface
Authors: Title, A. M.; Simon, G. W.; Weiss, N. O.
Bibcode: 1993BAAS...25Q1183T
Altcode:
No abstract at ADS
Title: Diffusion of ``Corks'' Over the Solar Surface
Authors: Title, A. M.; Simon, G. W.; Weiss, N. O.
Bibcode: 1993AAS...182.4804T
Altcode: 1993BAAS...25Q.880T
Test particles in flow fields generated by correlation tracking of
movies of the solar surface and kinematic models of the solar surface
quickly collect in stagnation points of the flow fields and remain
there. Test particles do not form a quasi-stable network pattern. The
diffusion coefficients generated from a net of kinematic models with a
range of cell sizes and lifetimes are not proportional to the cell size
squared divided by the cell lifetime as commonally assumed. Reasonable
estimates of cell sizes and lifetimes yield diffusiion coefficients that
are lower than the 600 km(2) /s used by Sheeley and his collaborators in
their surface diffusion models. We conclude that: 1) The appearance of
plages and enhanced network can not be explained by adjustment of the
cell sizes or surface velocities; and 2) diffusion is not sufficient
to explain the appearance of plages and enhanced network.
Title: The Mechanisms of Solar Variability (MSV) program
Authors: Leibacher, John W.; Noyes, Robert W.; Simon, George W.;
Neidig, Donald F.
Bibcode: 1993STIN...9328585L
Altcode:
The Mechanisms of Solar Variability (MSV) Program aims toward
understanding physical causes of variations in the radiative, magnetic,
and particle emissions from the Sun. Solar particle and field variations
influence the interplanetary medium and the magnetosphere; UV and X-ray
variations affect the Earth's upper atmosphere; and total irradiance
variations are a possibly significant perturber of tropospheric
climate. Solar magnetic variability provides a close-up arena for
studying important but otherwise unobservable astrophysical phenomena
as well. The MSV program will advance our understanding of the causes
of solar variability through high angular resolution observations
of the interaction of solar surface magnetic fields and convective
motions, as well as related x-ray, ultraviolet, and visible brightness
variations. Through these high resolution studies, MSV will complement
national programs aimed at monitoring integrated solar outputs, thus
contributing to the better understanding and ultimate predictability
of global solar variability.
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.
Bibcode: 1993inas.book..100T
Altcode:
No abstract at ADS
Title: Kinematic Modeling of Active Region Decay
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1992AAS...180.1101S
Altcode: 1992BAAS...24..746S
No abstract at ADS
Title: Book Review: Opening the frontiers in solar research /
Pergamon, 1991
Authors: Machado, M. E.; Mattig, W.; Simon, G. W.; Harrison, R. A.
Bibcode: 1992Obs...112...70F
Altcode:
No abstract at ADS
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.
Bibcode: 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 spectroheliograph1,2,
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 observations3-5 to be nestling inside
the bright network. More recently6,7 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: On the Evidence for Mesogranules in Solar Power Spectra
Authors: Ginet, Gregory P.; Simon, George W.
Bibcode: 1992ApJ...386..359G
Altcode:
The hypothesis of Chou et al. (1991) that there is no evidence of
apparent energy excess at the scale of mesogranulation is disproved, and
it is shown that the shape of the observational spectrum confirms the
presence of both supergranules and mesogranules in the solar convective
flow. Existing kinematic models of convection at the solar surface
are extended and power spectra diagnostics are introduced. Models with
supergranule cells alone are found to be unable to produce spectra that
match the observations. If mesogranules are included, then there is
excellent agreement between the model and observational spectra when
the model parameters are chosen to be consistent with proper motion
and Doppler measurements.
Title: Convective structures in the sun
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1991MNRAS.252P...1S
Altcode:
Observed patterns of motion at the solar surface reflect the structure
of subphotospheric convection, which controls the distribution of
angular momentum and magnetic fields. Mesogranules are interpreted
as secondary features associated with supergranular circulation,
and that coupling between mesogranules and granulation triggers the
spasmodic formation of exploding granules. Supergranules are expected
to generate isolated sinking plumes. It is argued that these plumes
can penetrate to the base of the convective zone, and that there is
no organized structure on larger scales.
Title: Modeling Mesogranules and Exploders on the Solar Surface
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1991ApJ...375..775S
Altcode:
Radial outflows in exploders and mesogranules can be modeled by
superposing Gaussian source functions. This model is used to explore
the relationship between mesogranules and exploders. Although it
is demonstarted that there is a mathematical equivalence between
mesogranules and exploders distributed normally about the mesogranule
centers, the results indicate that the observed mesogranular velocity
pattern is not consistent with a flow pattern generated by exploders
dropped randomly on the solar surface. Detailed comparisons with
observations suggest that the averaged mesogranular velocity is produced
by a combination of a persistent outflow from a source together with
exploders distributed randomly about its center. Similar analysis
also shows supergranules are not the result of random occurrences
of mesogranules.
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.
Bibcode: 1991BAAS...23.1034S
Altcode:
No abstract at ADS
Title: Modelling Power Spectra of the Solar Convection
Authors: Ginet, G. P.; Simon, G. W.
Bibcode: 1991BAAS...23.1034G
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.
Bibcode: 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. 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: Simulating exploding granules and mesogranular flows
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1991AdSpR..11e.259S
Altcode: 1991AdSpR..11..259S
Cellular convective motion at the solar surface can be simulated by a
suitable distribution of axisymmetric sources /1/. With this model we
represent randomly distributed exploding granules or mesogranules. The
effect of a given velocity field on the magnetic field is modelled
by inserting test particles (``corks'') and following their resultant
motions. An important question raised by the observations is whether
mesogranular flows are generated entirely by exploding granules
which recur in approximately the same location or whether there is a
persistent underlying circulation. Our model calculations suggest
that a combination of systematic cellular motion on a mesogranular scale
and recurrent exploding granules located near the mesogranular centers
is compatible with observed magnetic structures. We also generate
randomly-distributed exploders not tethered to mesogranular sites, and
the resulting cork patterns do not resemble those observed on the solar
surface. Finally we introduce a large-scale persistent supergranular
flow which transports the mesogranules and exploders towards the
supergranular network and obtain patterns not unlike those seen on
the Sun. Operated by the National Optical Astronomy Observatories
for the Association of Universities for Research in Astronomy, Inc.,
under contract with the National Science Foundation. Partial Support
for the National Solar Observatory is provided by the USAF under a
Memorandum of Understanding with the NSF.
Title: Opening frontiers in solar research. Proceedings. Topical
Meeting of the COSPAR Interdisciplinary Scientific Commission E
(Meetings E6 and E9) of the COSPAR 28. Plenary Meeting: Opening
frontiers in solar research, The Hague (Netherlands), 25 Jun -
6 Jul 1990.
Authors: Falciani, R.; Machado, M. E.; Mattig, W.; Simon, G. W.
Bibcode: 1991AdSpR..11e....F
Altcode: 1991AdSpR..11R....F
Contents: 1. Scientific coordination of solar physics missions in the
1990s (Meeting E6). 2. High-resolution solar physics from space and
the ground (Meeting E9).
Title: Foreword
Authors: Falciani, Roberto; Machado, Marcos E.; Mattig, Wolfgang;
Simon, George W.
Bibcode: 1991AdSpR..11e...1F
Altcode: 1991AdSpR..11R...1F
No abstract at ADS
Title: Convection and Magnetic Fields in the Sun's Atmosphere
Authors: Simon, G. W.
Bibcode: 1990BAAS...22R1234S
Altcode:
No abstract at ADS
Title: Kinematic Modeling of the Relations Among Exploders,
Mesogranules, and Supergranules
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1990BAAS...22R1225S
Altcode:
No abstract at ADS
Title: Observations of solar magnetoconvection from a lunar base
Authors: Simon, George W.
Bibcode: 1990AIPC..207..111S
Altcode: 1990am...proc..111S
Extremely-high-resolution observations are required in order to make
significant progress in solving some of the major problems in solar
magnetoconvection. Temporal resolution demands a data stream that is
uninterrupted for a minimum of thirty days, collected at very high
rates of at least 100 megabits per second. Spatial resolution must
be better than 35 km (0.05 arcsec). Finally, spectral resolution of
at least 105 is needed. Since the magnetic structures of interest are
very much three-dimensional, extending from below the solar surface up
into the corona, observations from the IR, visible, EUV, XUV, and X-ray
portions of the spectrum are essential. The above requirements
preclude the use of Earth-based observatories, which are handicapped
by turbulence (seeing) in the Earth's atmosphere, absorption of EUV
and X-ray radiation, and the 24 hour day-night cycle. Thus the relevant
facilities must operate from space. Whether they should be free-flyers
or lunar-based depends partly on specific experiment requirements,
and also on factors of cost, logistics, and timing. The results
of an informal poll of some two dozen solar physicists regarding the
advantages of solar observations from the Moon are discussed.
Title: Simulation of Large-Scale Flows at the Solar Surface
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1989ApJ...345.1060S
Altcode:
A simple analytic axisymmetric function is used to represent the radial
outflow associated with an isolated convection plume at the solar
surface. The vertical velocity can be deduced from the continuity
equation. A regular cellular pattern of convection can be created
by superposing a number of such sources. The function is applied
to the large-scale horizontal motions observed by the Solar Optical
Universal Polarimeter (SOUP) instrument on Spacelab 2. The flow pattern
visible in three different regions covered by the SOUP observations
is simulated. In each case a superposition of the plume functions
mimics the observed mesogranular and supergranular motions well. The
model flows are used to compute the motion of passive test particles
(corks) which accumulate in a network that outlines mesogranular
cells. Detailed comparisons suggest that magnetic flux tubes are
affected more by outflow from sources at the centers of mesogranules
than by flow into sinks within the network.
Title: Simulating plumes and sinks observed at the solar surface
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1989hsrs.conf..529S
Altcode:
No abstract at ADS
Title: Modeling the Flow in Solar Vortices
Authors: Simon, G. W.; Weiss, N. O.; Scharmer, G. B.
Bibcode: 1989BAAS...21Q.829S
Altcode:
No abstract at ADS
Title: Details of Large Scale Solar Motions Revealed by Granulation
Test Particles
Authors: Simon, G. W.; November, L. J.; Ferguson, S. H.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1989ASIC..263..371S
Altcode: 1989ssg..conf..371S
No abstract at ADS
Title: Magnetoconvection on the solar surface.
Authors: Simon, G. W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.
Bibcode: 1989GMS....54...53S
Altcode: 1989sspp.conf...53S
The authors describe and illustrate the first high-resolution
observations of horizontal flows on the solar surface and their relation
to magnetic field structure seen in the Sun's photosphere.
Title: Solar Observations on Magneto Convection
Authors: Simon, G. W.
Bibcode: 1989gmca.conf....8S
Altcode:
No abstract at ADS
Title: A Simple Model of Mesogranular and Supergranular Flows
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1989ASIC..263..595S
Altcode: 1989ssg..conf..595S
No abstract at ADS
Title: Precise Proper-Motion Measurement of Solar Granulation
Authors: November, Laurence J.; Simon, George W.
Bibcode: 1988ApJ...333..427N
Altcode:
A powerful cross-correlation method for the precise measurement of the
proper motion of tracers seen on successive images of a time series
of solar granulation is proposed. The time average of the spatially
localized cross correlation is shown to provide a measure of the
displacement that is not biased by atmospheric seeing. The technique is
applied to the analysis of an 80-minute run of white-light observations
made with the Sacramento Peak Vacuum Tower Telescope. From the vector
displacements, solar mesogranulations and supergranulation flows having
spatial scales from 10 to 40 arcsec are found, and it is noted that
the measured flow amplitudes are much larger that the rms 100 m/s
noise which is attributed principally to solar granulation evolution.
Title: Simulation of Large-Scale Flows at the Solar Surface
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1988BAAS...20.1008S
Altcode:
No abstract at ADS
Title: On the Relation between Photospheric Flow Fields and the
Magnetic Field Distribution on the Solar Surface
Authors: Simon, George W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.; SOUP Team
Bibcode: 1988ApJ...327..964S
Altcode:
Using the technique of local correlation tracking on a 28 minute time
sequence of white-light images of solar granulation, the horizontal
flow field on the solar surface is measured. The time series was
obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2
(Space Shuttle flight 51-F) and is free from atmospheric blurring and
distortion. The SOUP flow fields have been compared with carefully
aligned magnetograms taken over a nine hour period at the Big Bear
Solar Observatory before, during, and after the SOUP images. The flow
field and the magnetic field agree in considerable detail: vectors which
define the flow of the white-light intensity pattern (granulation) point
toward magnetic field regions, magnetic fields surround flow cells, and
magnetic features move along the flow arrows. The projected locations
of free particles ('corks') in the measured flow field congregate at
the same locations where the magnetic field is observed.
Title: Variability of solar mesogranulation
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Ferguson, S. H.;
Shine, R. A.; Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1988AdSpR...8g.169S
Altcode: 1988AdSpR...8..169S
From white-light photographs of solar granulation obtained with the
SOUP instrument on Space Shuttle Flight STS-19 we have measured the
motions of granules using local correlation tracking techniques. The
granules are organized into larger-scale structures (mesogranular and
supergranular) which exhibit outflow from upwellings, convergence into
sinks, as well as significant vorticity. Magnetic fields follow these
same flow patterns. We describe these velocity structures, and suggest
that their effect on magnetic field structures may be important to
the solar flare buildup process.
Title: The relation between convection flows and magnetic structure
at the solar surface
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Title, A. M.;
Tarbell, T. D.; Topka, K. P.; Shine, R. A.; Ferguson, S. H.; Weiss,
N. O.; Zirin, H.
Bibcode: 1988AdSpR...8k.133S
Altcode: 1988AdSpR...8..133S
We describe recent results from the comparison of data from the Solar
Optical Universal Polarimeter instrument on Spacelab 2 and magnetograms
from Big Bear Solar Observatory. We show that the Sun's surface velocity
field governs the structure of the observed magnetic field over the
entire solar surface outside sunspots and pores. We attempt to describe
the observed flows by a simple axisymmetric plume model. Finally,
we suggest that these observations may have important implications
for the prediction of solar flares, mass ejections, and coronal heating.
Title: Large-scale horizontal flows from SOUP observations of solar
granulation.
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.;
Ferguson, S. H.
Bibcode: 1987NASCP2483..121N
Altcode: 1987tphr.conf..121N
Using high-resolution time-sequence photographs of solar granulation
from the SOUP experiment on Spacelab 2 the authors observed large-scale
horizontal flows in the solar surface. The measurement method is
based upon a local spatial cross correlation analysis. The horizontal
motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of
granulation from a sunspot penumbra into the surrounding photosphere is
a striking new discovery. Both the supergranulation pattern and cellular
structures having the scale of mesogranulation are seen. The vertical
flows that are inferred by continuity of mass from these observed
horizontal flows have larger upflow amplitudes in cell centers than
downflow amplitudes at cell boundaries.
Title: What Determines the Temperature of a Sunspot?
Authors: Spruit, H. C.; Simon, G. W.
Bibcode: 1987BAAS...19..943S
Altcode:
No abstract at ADS
Title: New Ideas About Granulation Based on Data from the Solar
Optical Universal Polarimeter Instrument on Spacelab 2 and Magnetic
Data from Big Bear Solar Observatory
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Shine, R. A.;
Simon, G. W.; Zirin, H.; SOUP Team
Bibcode: 1987LNP...292..173T
Altcode: 1987ssp..conf..173T
The SOUP flow fields have been compared with carefully aligned
magnetograms taken at the BBSO before, during, and after the SOUP
images. The magnetic field is observed to exist in locations where
either the flow is convergent or on the boundaries of the outflow from
a flow cell center. Streamlines calculated from the flow field agree
very well with the observed motions of the magnetic field in the BBSO
magnetogram movies.
Title: Simulation of Surface Flows in Supergranulation
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1986BAAS...18R.990S
Altcode:
No abstract at ADS
Title: Measurements of Transverse Flows in the Solar Photosphere
from Spacelab 2 SOUP Images
Authors: Tarbell, T. D.; Title, A. M.; Ferguson, S. H.; November,
L. J.; Simon, G. W.
Bibcode: 1986BAAS...18R.992T
Altcode:
No abstract at ADS
Title: Initial Solar Observations at Sacramento Peak Using the
Lockheed Active Optics System
Authors: Smithson, R. C.; Sharbaugh, R. J.; Ramsey, H. E.; Acton,
D. S.; Pari, M.; Keil, S. L.; Radick, R. R.; Simon, G. W.; von der
Luehe, O.; Zirker, J. B.
Bibcode: 1986BAAS...18..933S
Altcode:
No abstract at ADS
Title: Precise Proper Motion Measurement of Solar Granulation
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.
Bibcode: 1986BAAS...18..665N
Altcode:
No abstract at ADS
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.
Bibcode: 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.
Title: Flux changes in small magnetic regions. II - Further
observations and analysis
Authors: Simon, G. W.; Wilson, P. R.
Bibcode: 1985ApJ...295..241S
Altcode:
Further examples of flux changes are described in which the flux
associated with small magnetic knots of dimension 2-3 arcsec is
observed to increase or decrease by 50-100 percent during periods
of order 20-40 minutes. Within the same regions both positive and
negative flux knots have been studied. In one case the positive and
negative flux fluctuations appeared to be almost out of phase, but in
another they were roughly in phase. From measurements of the velocity
field within each region, an estimate of the vertical velocity shear has
been calculated, and correlations of order 0.5 between the fluctuations
in this shear and in both the positive and negative flux counts have
been obtained in several, but not all cases. The possibility that
these apparent flux changes are due to instrumental or seeing effects,
changes in the line equivalent width, or vertical velocity gradients
is discussed, but it is concluded that none of these effects provides
a tenable alternative explanation of the observed changes. It is
therefore suggested that these changes may provide examples of the
generation of nonpotential magnetic fields (i.e., electric currents)
within the photospheric layers, as has been proposed by several authors
from time to time.
Title: Buoyant magnetic flux tubes. II - Three-dimensional behaviour
in granules and supergranules
Authors: Schmidt, H. U.; Simon, G. W.; Weiss, N. O.
Bibcode: 1985A&A...148..191S
Altcode:
A simple model is used to study the interaction of isolated magnetic
flux tubes with convection in the sun. Convective motion in granules and
supergranules is represented by prescribed flows in three-dimensional
cells with square cross-sections and thin flux tubes move under the
action of magnetic buoyancy, Lorentz curvature forces and aerodynamic
drag. Inflow at the base of a cell competes with outflow at its upper
surface; small flux tubes tend to be swept to the cell boundaries while
larger, more buoyant tubes are dragged to the axis of the cell. These
results are compared with recent observations of small-scale granular
and intergranular magnetic fields.
Title: 3-D Behavior of Buoyant Magnetic Flux Tubes in Granules and
Supergranules
Authors: Simon, G. W.; Schmidt, H. U.; Weiss, N. O.
Bibcode: 1985BAAS...17Q.642S
Altcode:
No abstract at ADS
Title: Evolution of solar magnetic flux.
Authors: Boris, J. P.; DeVore, C. R.; Golub, L.; Howard, R. F.; Low,
B. C.; Sheeley, N. R., Jr.; Simon, G. W.; Tsinganos, K. C.
Bibcode: 1984NASRP1120....3B
Altcode:
Contents: Introduction. Appearance of magnetic flux: models for flux
emergence, unexplained observations. Dynamics of surface magnetic
flux: magnetic flux transport, magnetic flux structure. Disappearance
of magnetic flux: theoretical considerations, observations of flux
disappearance. Summary.
Title: Flux changes in small magnetic regions
Authors: Wilson, P. R.; Simon, G. W.
Bibcode: 1983ApJ...273..805W
Altcode:
High spatial and temporal resolution observations of continuum,
velocity, and magnetic fields in active regions of the sun have
been obtained which reveal rapid changes in the total magnetic flux
associated with surface magnetic features. Attention is given to two
cases. In the first, during February 1980, the total positive flux
associated with a magnetic feature increased by about 50 percent in
about 90 min without observable negative flux change. The topology
of the feature developed from a single intense core to one exhibiting
several discrete cores, all of like polarity. The second case, during
July 1981, involved large fluctuations in the flux associated with a
small negative feature over 20-min time intervals. Calculations of the
correlation between velocity gradients and magnetic field gradients
show values in the 0.4-0.7 range at times of good seeing, reaching a
peak when the flux is greatest.
Title: Simple models for magnetic flux tubes.
Authors: Simon, G. W.; Weiss, N. O.; Nye, A. H.
Bibcode: 1983SoPh...87...65S
Altcode:
Known potential field solutions can be used to model the structure of
magnetic fields in the solar photosphere. Several two-dimensional and
axisymmetric solutions are compared. In the most satisfactory model
the vertical component of the field is prescribed on a horizontal
plane so as to be uniform within a finite disc and zero outside it. The
resulting flux distribution provides a good description of small scale
intergranular magnetic fields and of the observed field structure in
a pore, but is inadequate for sunspots.
Title: Simple models for magnetic flux tubes.
Authors: Simon, G. W.; Weiss, N. O.; Nye, A. H.
Bibcode: 1983BAAS...15R.874S
Altcode:
No abstract at ADS
Title: Relation of Ephemeral Magnetic Regions to the Low Amplitude
Branch of Persistent Vertical Velocities
Authors: Gebbie, K. B.; Toomre, J.; Haber, D. A.; Hill, F.; Simon,
G. W.; November, L. J.; Gurman, J. B.; Shine, R. A.
Bibcode: 1982BAAS...14R.939G
Altcode: 1982BAAS...14..939G
No abstract at ADS
Title: Vertical flows of supergranular and mesogranular scale observed
on the sun with OSO 8
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.
Bibcode: 1982ApJ...258..846N
Altcode:
A program of observations was carried out in order to study the
penetration of supergranular flows over a broad range of heights in
the solar atmosphere. Steady Doppler velocities are determined from
observations of a Si II spectral line using the Ultraviolet Spectrometer
on the Orbiting Solar Observatory 8 (OSO 8) satellite and Fe I and
Mg I lines with the diode-array instrument on the vacuum telescope at
Sacramento Peak Observatory (SPO). The heights of formation of these
spectral lines span about 1400 km or nearly 11 density scale heights
from the photosphere to the middle chromosphere. Steady vertical flows
on spatial scales typical of supergranulation and mesogranulation have
been detected in the middle chromosphere with OSO 8. The patterns of
intensity and steady velocity of granular scale are reproducible in
successive data sets. The patterns appear to evolve slowly over the
9 hr period spanned by six orbits.
Title: Steady flows in the solar transition region observed with SMM
Authors: Gebbie, K. B.; Hill, F.; November, L. J.; Gurman, J. B.;
Shine, R. A.; Woodgate, B. E.; Athay, R. G.; Tandberg-Hanssen, E. A.;
Toomre, J.; Simon, G. W.
Bibcode: 1981ApJ...251L.115G
Altcode:
Steady flows in the quiet solar transition region have been observed
with the Ultraviolet Spectrometer and Polarimeter experiment on the
Solar Maximum Mission (SMM) satellite. The persistent vertical motions
seen at disk center have spatial rms amplitudes of 1.4 km/s in the C
II line, 3.9 km/s in Si IV, and 4.2 km/s in C IV. The amplitudes of
the more horizontal flows seen toward the limb tend to be somewhat
higher. Plots of steady vertical velocity versus intensity seen at
disk center in Si IV and C IV show two distinct branches.
Title: The detection of mesogranulation on the sun.
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.
Bibcode: 1981ApJ...245L.123N
Altcode:
Time averages of velocity measurements at disk center on the quiet sun
reveal the presence of a fairly stationary pattern of cellular flow
with a spatial scale of 5-10 Mm. Such mesogranulation has a spatial rms
vertical velocity amplitude of about 60 m/s superposed on the larger
scale supergranular flows. The lifetimes of mesogranules appear to be
at least 2 hr.
Title: Flux Changes in Small Magnetic Regions
Authors: Wilson, P. R.; Simon, G. W.
Bibcode: 1981BAAS...13..882W
Altcode:
No abstract at ADS
Title: Post-Facto Dark Current and Gain Determinations for Solar
Data Obtained with a Diode Array
Authors: Simon, G. W.; November, L. J.
Bibcode: 1981BAAS...13Q.878S
Altcode:
No abstract at ADS
Title: Height Dependence of Steady Flows Determined from Coordinated
SMM and SPO Observations
Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon,
G. W.; Gurman, J. B.; Shine, R. A.; Woodgate, B. E.
Bibcode: 1981BAAS...13..914G
Altcode:
No abstract at ADS
Title: Steady Flows in the Solar Transition Region Observed with
the UVSP Experiment on SMM
Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon,
G. W.; Athay, R. G.; Bruner, E. C.; Rehse, R.; Gurman, J. B.; Shine,
R. A.; Woodgate, B. E.; Tandberg-Hanssen, E. A.
Bibcode: 1980BAAS...12..907G
Altcode:
No abstract at ADS
Title: The Lifetime of Solar Mesogranulation
Authors: November, L. J.; Gebbie, K. B.; Hill, F.; Toomre, J.; Simon,
G. W.
Bibcode: 1980BAAS...12..895N
Altcode:
No abstract at ADS
Title: Mesogranulation -- An Intermediate Scale of Motion on the Sun
Authors: Toomre, J.; November, L. J.; Gebbie, K. B.; Simon, G. W.
Bibcode: 1979BAAS...11..641T
Altcode:
No abstract at ADS
Title: Buoyant magnetic flux tubes in supergranules.
Authors: Meyer, F.; Schmidt, H. U.; Simon, G. W.; Weiss, N. O.
Bibcode: 1979A&A....76...35M
Altcode:
The motion of filamentary flux tubes is described by a simplified
model. Relative to the prescribed supergranular flow, the tubes drift at
a rate determined by magnetic buoyancy, Lorentz forces and aerodynamic
drag. The effect of buoyancy is most pronounced near the surface:
small flux tubes are swept towards the network at the edge of a cell
but those with larger fluxes float vertically at the center. New flux
emerges at the center of the cell. These results are related to the
emergence of active regions and ephemeral active regions, and to the
slow decay of sunspots.
Title: The height variation of supergranular velocity fields
determined from simultaneous OSO 8 satellite and ground-based
observations.
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.
Bibcode: 1979ApJ...227..600N
Altcode:
Results are reported for simultaneous satellite and ground-based
observations of supergranular velocities in the sun, which were made
using a UV spectrometer aboard OSO 8 and a diode-array instrument
operating at the exit slit of an echelle spectrograph attached to a
vacuum tower telescope. Observations of the steady Doppler velocities
seen toward the limb in the middle chromosphere and the photosphere
are compared; the observed spectral lines of Si II at 1817 A and Fe
I at 5576 A are found to differ in height of formation by about 1400
km. The results show that supergranular motions are able to penetrate
at least 11 density scale heights into the middle chromosphere, that
the patterns of motion correlate well with the cellular structure seen
in the photosphere, and that the motion increases from about 800 m/s in
the photosphere to at least 3000 m/s in the middle chromosphere. These
observations imply that supergranular velocities should be evident
in the transition region and that strong horizontal shear layers in
supergranulation should produce turbulence and internal gravity waves.
Title: The Variation with Height of Supergranular Velocity Fields
Authors: Gebbie, K. B.; November, L. J.; Toomre, J.; Simon, G. W.
Bibcode: 1978BAAS...10Q.672G
Altcode:
No abstract at ADS
Title: Observations of nonradial p-mode oscillations on the sun.
Authors: Rhodes, E. J., Jr.; Ulrich, R. K.; Simon, G. W.
Bibcode: 1977ApJ...218..901R
Altcode:
Observations of the solar velocity field with a diode array attached
to the echelle spectrograph of a vacuum tower telescope are described
which resolve the solar five-minute oscillatory motion into distinct
bands of power. Previous observations are discussed which show that
the solar five-minute oscillations can be resolved into frequencies
having the character of nonradial p-mode eigenfrequencies of the solar
envelope. The present observations confirm the observed frequencies
and sharpen the previous resolution of the five-minute oscillations
into ridges on the (wavenumber, frequency) plane. A comparison with
earlier calculations indicates that the theoretical frequencies are in
good but not perfect agreement with those observed. It is concluded
that the identification of the five-minute oscillations as nonradial
p-mode oscillations in the solar envelope is established beyond doubt.
Title: On the Origin of Oscillations in the Solar Limb Position.
Authors: Worden, S. P.; Simon, G. W.
Bibcode: 1977BAAS....9..358W
Altcode:
No abstract at ADS
Title: Vertical and Horizontal Components of Supergranulation Velocity
Fields Observed with OSO-8
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.
Bibcode: 1977BAAS....9..337N
Altcode:
No abstract at ADS
Title: On the origin of the 2h40m solar
oscillations.
Authors: Worden, S. P.; Simon, G. W.
Bibcode: 1976ApJ...210L.163W
Altcode:
The existence of a 2-hr 40-min global solar velocity oscillation has
recently been reported. The present letter examines the possibility that
this phenomenon represents the rotation of large-scale solar velocity
cells (supergranulation) through the field of view of the instrument
used to detect the oscillations. On the basis of high-resolution
full-disk velocity data, it is concluded that this mechanism can
produce apparent oscillations with periods near 2 hr 40 min.
Title: Acoustic Spectroscopy of the Solar Envelope.
Authors: Rhodes, S. J., Jr.; Ulrich, R. K.; Simon, G. W.
Bibcode: 1976BAAS....8..533R
Altcode:
No abstract at ADS
Title: Supergranulation Velocity Fields Observed in the Solar
Transition Region with OSO-8
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.;
Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Shine, R. A.;
Orrall, F. Q.; Athay, R. G.; White, O. R.
Bibcode: 1976BAAS....8..311N
Altcode:
No abstract at ADS
Title: A study of supergranulation using a diode array magnetograph.
Authors: Worden, S. P.; Simon, G. W.
Bibcode: 1976SoPh...46...73W
Altcode:
The evolution of the velocity and magnetic fields associated with
supergranulation has been investigated using the Sacramento Peak
Observatory Diode Array Magnetograph. The observations consist of time
sequences of simultaneous velocity, magnetic field, and chromospheric
network measurements. From these data it appears that the supergranular
velocity cells may have lifetimes in excess of the accepted value
of 24 hours. Magnetic field motions associated with supergranulation
were infrequent and seem to be accompanied by changes in the velocity
field. More prevalent were the slow dissipation and diffusion of
stationary flux points. Vertical velocity fields of 200 m s−1 appear
to be confined to downflows in magnetic field regions at supergranular
boundaries. These downflows are only observed using certain absorption
lines. Corresponding upflows in the center of supergranules of less
than 50 m s−1 may be present but cannot be confirmed.
Title: Velocities Observed in Super-Granules
Authors: Worden, S. P.; Simon, G. W.
Bibcode: 1976IAUS...71..121W
Altcode:
No abstract at ADS
Title: Heights of Formation of Non-Magnetic Solar Lines Suitable
for Velocity Studies
Authors: Altrock, R. C.; November, L. J.; Simon, G. W.; Milkey, R. W.;
Worden, S. P.
Bibcode: 1975SoPh...43...33A
Altcode:
Heights of formation of lines that do not exhibit Zeeman splitting
are calculated using an LTE, partial non-LTE, and full non-LTE
approach. Non-magnetic (g=0) lines are valuable for velocity
investigations in quiet-Sun magnetic field regions, and a knowledge
of their formation heights is useful for obtaining three dimensional
velocity profiles in these regions.
Title: The Character of 300-Second Oscillators.
Authors: November, L. J.; Simon, G. W.; Worden, S. P.
Bibcode: 1975BAAS....7..407N
Altcode:
No abstract at ADS
Title: A Phenomenological Study of High Resolution Granulation
Photography
Authors: Labonte, B. J.; Simon, G. W.; Dunn, R. B.
Bibcode: 1975BAAS....7..366L
Altcode:
No abstract at ADS
Title: Observed Heights of EUV Lines Formed in the Transition Zone
and Corona. II: NRL Rocket Observations
Authors: Simon, G. W.; Seagraves, P. H.; Tousey, R.; Purcell, J. D.;
Noyes, R. W.
Bibcode: 1974SoPh...39..121S
Altcode:
Using high resolution (3-5″) rocket spectroheliograms obtained by
NRL, we have analyzed hundreds of small, bright, quiet Sun features
to determine the heights of formation of five transition zone lines:
He I 584, He II 304, O V 630, Ne VII 465, and Mg IX 368. The results
are in excellent agreement with theoretical model calculations.
Title: A Search for the Footpoints of Solar Magnetic Fields
Authors: Simon, G. W.; Zirker, J. B.
Bibcode: 1974SoPh...35..331S
Altcode:
High-resolution measurements of magnetic fields have been made in quiet
and active regions in order to determine whether the photospheric
fine-structures (`crinkles'), recently photographed by Dunn (1972),
coincide with the footpoints of strong, compact fields. Magnetic
fields ranging up to 1400 G have been measured in small structures
that lie at the centers of spicule bushes or within a plage. However,
the diameters of the flux tubes, at the height where FeI 6302.5 forms,
are typically 1″-2″, compared with crinkle dimensions of 0.25″ ×
1″. This discrepancy cannot be explained by a sharp height variation
of the flux tube cross-section. By comparing our results with Dunn's
photographs, we conclude that although crinkles appear to lie at or
near the strongest field intensities, photospheric magnetic flux is
not confined solely within the area of the crinkles, but may extend
over a larger area defined by the `abnormal' granulation (Dunn et al.,
1973; Dunn and Zirker, 1973).
Title: A Phenomenological Study of High-Resolution Granulation
Photographs
Authors: LaBonte, Barry J.; Simon, George W.; Dunn, Richard B.
Bibcode: 1974BAAS....6..285L
Altcode:
No abstract at ADS
Title: Rocket Spectroheliogram Observations of the Heights of
Formation and Sizes of Bright Features in the Transition Zone
Authors: Simon, George W.; Seagraves, Paul H.; Tousey, R.; Noyes,
Robert W.
Bibcode: 1974BAAS....6U.294S
Altcode:
No abstract at ADS
Title: A Search for the Roots of Photospheric Magnetic Fields
Authors: Simon, G. W.; Zirker, J. B.
Bibcode: 1973BAAS....5Q.280S
Altcode:
No abstract at ADS
Title: Cinematography of Solar Granulation
Authors: Dunn, R. B.; Mann, G. R.; Simon, G. W.
Bibcode: 1973BAAS....5S.271D
Altcode:
No abstract at ADS
Title: Solar Rotation as Measured in EUV Chromospheric and Coronal
Lines
Authors: Simon, George W.; Noyes, Robert W.
Bibcode: 1972SoPh...26....8S
Altcode:
Active regions were followed across the disk on OSO 4 spectroheliograms
in the Lyman continuum (LC) and in Mg X λ625. These observations
indicate differential rotation with latitude, but not with height in
the atmosphere. The measured equatorial sidereal rotation velocity
is 14.7° ±0.2° per day in both chromospheric LC and coronal Mg X,
where the quoted error is the standard deviation of a least-squares
fit to the data.
Title: Rotation of Active Regions in the Corona
Authors: Simon, G. W.
Bibcode: 1972BAAS....4V.391S
Altcode:
No abstract at ADS
Title: Correlation between the Intensity Fields of the Chromospheric
and Coronal Networks
Authors: Simon, G. W.; Lynch, D. K.
Bibcode: 1972BAAS....4U.391S
Altcode:
No abstract at ADS
Title: Observed Heights of EUV Lines Formed in the Transition Zone
and Corona
Authors: Simon, George W.; Noyes, Robert W.
Bibcode: 1972SoPh...22..450S
Altcode:
The heights of formation of a number of extreme ultraviolet lines in
active regions have been measured from OSO-IV spectroheliograms. Using
the Lyman continuum at 2000 km above the white light limb as
a reference, we find heights for HeI, HeII, CIII, NIII, OIV, OVI,
NeVIII, MgX, SiXII, FeXV and FeXVI that are in approximate agreement
with models based on analysis of EUV emission intensities. The height of
CII is anomalously high. The accuracy of measurement is typically about
2000 km. The data suggest that the transition zone is less steep than
calculated from EUV emission intensities; however, higher resolution
observations are necessary to resolve the discrepancy.
Title: Solar rotation as measured in EUV chromospheric and coronal
lines.
Authors: Noyes, R. W.; Simon, G. W.
Bibcode: 1971BAAS....3R.263N
Altcode:
No abstract at ADS
Title: Observed heights of EUV lines formed in the transition zone
and corona.
Authors: Simon, G. W.; Noyes, R. W.
Bibcode: 1971BAAS....3R.264S
Altcode:
No abstract at ADS
Title: Observation of the Coronal Network
Authors: Simon, G. W.; Noyes, R. W.
Bibcode: 1971IAUS...43..663S
Altcode:
No abstract at ADS
Title: On the Magnetic Field in Pores
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1970SoPh...13...85S
Altcode:
The magnetic field in an axisymmetric pore is current free and
can be represented by a flux tube with a magnetic potential of the
formAJ0(kr)e-kz. For a given magnetic flux the
field in this pore model is uniquely defined if the magnetic pressure
balances the gas pressure at two levels. For models with fluxes of
0.5-3.0 × 1020 mx the surface radius varies from 1100-2700
km (diameters of 3-8 arc-sec) and the Wilson depression is estimated
at 200 km. As the flux increases, the field becomes nearly horizontal
at the edge of the pore and eventually a penumbra is formed. The
distinction between pores and sunspots is investigated; the critical
flux is about 1020 Mx, corresponding to a radius of 1500 km.
Title: Events around the Sun. (Book Reviews: Mass Motions in
Solar Flares and Related Phenomena. Proceedings of the ninth Nobel
Symposium, Capri, Italy, 1968)
Authors: Simon, George W.
Bibcode: 1970Sci...167B1714S
Altcode: 1970Sci...167B1714O
No abstract at ADS
Title: On the Magnetic Field in Pores
Authors: Weiss, N. O.; Simon, G. W.
Bibcode: 1969BAAS....1S.295W
Altcode:
No abstract at ADS
Title: Resolution of the Hα Double-Limb Controversy
Authors: White, O. R.; Simon, G. W.
Bibcode: 1968SoPh....3..269W
Altcode:
The discussion of the Hα double limb had reached the point where
the question of its existence as a real solar phenomenon could not be
resolved without new observations made with the Lockheed filter and the
Mount Wilson spectroheliograph. A study of the instrumental profiles
had indicated that there was sufficient off-band light to produce
the observed inner limb step in the Mount Wilson instrument, but this
analysis was not completely satisfactory because of limitations inherent
in the measurement of instrument functions with a Hg-198 source. The
instrumental profile work did indicate, however, that the spectral
purity of the instruments in question could be substantially improved
by the use of narrow-band interference filters. An experimental program
was thus launched to determine the effect of such a blocking filter on
the appearance of the Hα limb. The results of these observations with
three Halle filter systems and the Mount Wilson spectroheliograph are
that the inner limb completely disappears at the center of Hα when a
blocking filter is used to reduce unwanted light, which originates at
wavelengths beyond ±0.8 Å. In addition, the contrast and visibility
of the chromospheric fine structure is increased by eliminating the
off-band light. Thus the experiment conclusively demonstrates that
the apparent inner limb is not a solar feature but is due entirely to
instrumental parasitic light.
Title: Supergranules and the Hydrogen Convection Zone
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1968ZA.....69..435S
Altcode:
No abstract at ADS
Title: Supergranules and the Hydrogen Convection Zone.
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1968AJS....73S..77S
Altcode:
The strong magnetic fields observed between supergranules indicate
that there must be subphotospheric convection in cells with a
preferred diameter of about 30 000 km. Orthodox mixing length theory
assumes that the dimensions of cells are limited by the density scale
height. This is adequate fot explaining granules but cannot account
for supergranulation. A model is therefore proposed in which cellular
motions extend over several scale heights. In addition to granules
~nd supergranules, this model predicts a third characteristic scale
of motion, with giant cells around 300 000 km in diameter, These cells
may produce a pattern of magnetic fields like that suggested by Bumba
and Howard for complexes of activity.
Title: Concentration of Magnetic Fields in the Deep Convection Zone
Authors: Simon, G. W.; Weiss, N. O.
Bibcode: 1968IAUS...35..108S
Altcode:
No abstract at ADS
Title: On the Correlation Between Granule and Supergranule Intensity
Fields
Authors: Simon, George W.
Bibcode: 1966ApJ...145..411S
Altcode:
Simultaneous photographs taken in Ha (AX = +0.6 A) and in white light
(X 6400 A) show a correlation in intensity features of +0.25; i.e.,
that dark (bright) features in one correspond to dark (bright) ones in
the other. It is suggested that the correlation could arise both from
the velocity pattern in a supergranule and from temperature variations
across such a cell.
Title: A Practical solution of the atmospheric dispersion problem
Authors: Simon, George W.
Bibcode: 1966AJ.....71..190S
Altcode:
The classical equation for refraction by a spherically symmetric
atmosphere is solved numerically, with particular emphasis on the
wavelength dependence (atmospheric dispersion) of the refraction. The
results are presented as a table of coefficients from which one
can easily and accurately compute, by desk calculator or electronic
computer, the atmospheric dispersion under any atmospheric conditions,
between 3000 and 11 000 A'.
Title: The H-Alpha Double Limb: a Scattered-Light Phenomenon
Authors: Simon, G. W.; White, O. R.
Bibcode: 1966ApJ...143...38S
Altcode:
Two independent methods are used to demonstrate that the inner
limb observed in Ha spectroheliograms by Cragg, Howard, and Zirin
is an instrumental, not a solar, phenomenon. First, we show that
low-scattered-light spectrograms do not display a double limb. Second,
by photometric analysis of the Iount ilson observations, we find that
there is more than sufficient imaged scattered light in the Iount Vilson
spectroheliograph to produce the observed inner limb by the scattering
of light from the continuum into the Ha core. It is also shown that the
concept of an inner limb is inconsistent with both theoretical models
and other observations of the solar chromosphere. A real Ha double limb,
not previously described, is seen at about 1.0 A in the line wing.
Title: Velocity Fields in the Solar Atmosphere. III. Large-Scale
Motions, the Chromospheric Network, and Magnetic Fields.
Authors: Simon, G. W.; Leighton, R. B.
Bibcode: 1964ApJ...140.1120S
Altcode:
Results of a detailed study of large-scale cellular motions in the solar
photosphere are presented. The velocity cells (called "supergranules")
are of various sizes and shapes and have an average diameter of 32000
km and a 20-hour lifetime; the motion within each cell is mainly
horizontal, proceeding from the center toward the outer boundary
with a velocity of 0.3-0.5 km/sec. A strong spatial correspondence is
found between the cell boundaries and several other features: (1) the
chromospheric Ca+ X 3934 network; (2) the network of descending matter
(1.0-2.0 km/sec) observed in Ha and Hp; and (3) the magnetic field
pattern. The characteristics of the velocity cells suggest that they
are non-stationary convection currents originating perhaps at a quite
deep level inside the convective envelope. These observations, together
with the theoretical predictions of Parker (1963a, b) and Osterbrock
(1961), suggest an explanation for the origin of the chromospheric
network seen in Ca+ and in the Balmer lines
Title: Correlations between Large-Scale Photospheric and Chromospheric
Motions, CA I (K) Emission, and Magnetic Fields.
Authors: Simon, George W.; Leighton, Robert B.
Bibcode: 1963AJ.....68S.291S
Altcode:
Nuovo Cimento Suppi. 22, 321,1961; Leighton, R., Noyes, R., and Simon,
G. Astrophys. J. 135, 474, 1962), large-scale, principally horizontal,
motions have been observed in the solar photospliere. These motions
have a cellular appearance, ai~d the flow proceeds from the center
of each "cell" toward the outer boundary, with velocities of 0.3-0.5
km/sec. These cells are arranged in a more-or-less regular pattern
over the solar surface, with an average cell diameter of 3.0-3.5 X 10~
km. Cross-correlation measurements obtained by superposition of velocity
plates and Ca+(X3933) plates show that the K2,3 emission network
occurs directly above the boundaries of the velocity cells. Downward
velocities of 1.0-2.0 km/sec are observed in the wings of Ha (Ax=0.7 A)
and HP (AX=0.4A). These localized motions exist in a network pattern
which coincides with the position of the K2,3 emission and the velocity
cell boundaries. The lifetime of the K2,3 network has been measured by
cross-correlating plates taken at various time intervals and has a mean
life of 17-21 h in excellent agreement with the finding of C. Macris
(Mcm. Soc. Astron. Ital. 33, 85,1962). Using magnetograph measurements
obtained by R. Howard (Astrophys. J. 130, 193, 1959), we find a very
high degree of correlation between the positions of weak magnetic
fields (1.5-5.0 G) and the K2,3 network. The probability that the
observed correlation is a random statistical ~uctuation is 10-~. For
stronger fields (>~ 5 G) the corresponding probability is less than
10-11. These observations suggest that the average solar magnetic field
(0.5-1.0 G) is swept to the cell boundaries by the horizontal currents,
and concentrates there in strengths perhaps two to ten times greater
than the average field. These narrow regions of enhanced field strength
could then account for the presence of the K2,3 emission at the cell
boundaries, and perhaps also for the downflow of chromospheric material
in this region, as well as small "dots" of rising material seen at the
edges of the downward flowing network, which may be spicules seen on
the disk. This work was assisted by the Office of Naval Research.
Title: Correlations Between Large-Scale Solar Photospheric and
Chromospheric Motions, Calcium II (k) Emission, and Magnetic Fields.
Authors: Simon, George Warren
Bibcode: 1963PhDT.........7S
Altcode: 1963PhDT.......106S
No abstract at ADS
Title: Velocity Fields in the Solar Atmosphere. I. Preliminary Report.
Authors: Leighton, Robert B.; Noyes, Robert W.; Simon, George W.
Bibcode: 1962ApJ...135..474L
Altcode:
Velocity fields in the solar atmosphere have been detected and measured
by an adaptation of a technique previously used for measuring magnetic
fields Data obtained during the summers of 1960 and 1961 have been
partially analyzed and yield the following principal results: 1. Large
"cells" of horizontally moving material are distributed roughly
uniformly over the entire solar surface. The motions within each
cell suggest a (horizontal) outward flow from a source inside the
cell. Typical diameters are 1.6 X 10 km; spacings between centers,
3 X 10 km ( 5 X 10 cells over the solar surface); r.m S. velocities
of outflow, 0.5 km sec-1 lifetimes, sec. There is a similarity
in appearance to the Ca+ network. The appearance and properties
of these cells suggest that they are a surface manifestation of a
"supergranulation" pattern of convective currents which come from
relatively great depths inside the sun. 2. A distinct correlation
is observed between local brightness fluctuations and vertical
velocities: bright elements tend to move upward, at the levels at
which the lines Fe X 6102 and Ca X 6103 are formed. In the line Ca
X 6103, the correlation coefficient is 0.5. This correlation appears
to reverse in sign in the height range spanned by the Doppler wings
of the Na D1 line and remains reversed at levels up to that of Ca+ X
8542. At the level of Ca X 6103, an estimate of the mechanical energy
transport yields the rather large value 2 W cm . 3. The characteristic
"cell size" of the vertical velocities appears to increase with
height from 1700 km at the level of Fe X 6102 to 3500 km at that
of Na X 5896. The r.m s. vertical velocity of 0 4 km appears nearly
constant over this height range. 4. The vertical velocities exhibit
a striking repetitive time correlation, with a period T = 296 * 3
sec. This quasi-sinusoidal motion has been followed for three full
periods in the line Ca 6103, and is also clearly present in Fe X 6102,
Na X 5896, and other lines. The energy contained in this oscillatory
motion is about 160 J cm the "losses" can apparently be compensated for
by the energy transport (2). 5. A similar repetitive time correlation,
with nearly the same period, seems to be present in the brightness {
observed on ordinary spectroheliograms taken at the center of the Na D1
line. We believe that we are observing the transformation of potential
energy into wave energy through the brightness-velocity correlation
in the photosphere, the upward propagation of this energy by waves
of rather well-defined frequency, and its dissipation into heat in
the lower chromosphere. 6. Doppler velocities have been observed at
various heights in the upper chromosphere by means of the Ha line. At
great heights one finds a granular structure with a mean size of about
3600 km, but at lower levels one finds predominantly downward motions,
which are concentrated in "tunnels" which presumably follow magnetic
lines of force and are geometrically related to the Ca+ network. The
Doppler field changes its appearance very y at higher levels, typical
lifetimes being about 30 seconds.