Author name code: zirker
ADS astronomy entries on 2022-09-14
author:"Zirker, Jack Bernard"
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Title: That was then, this is now; on to the future!
Authors: Zirker, Jack
Bibcode: 2021JAHH...24.1073Z
Altcode:
In this short paper I reflect on the progress of solar physics over
the past 50 years, and identify five major issues that still plague us.
Title: The Fiftieth Anniversary Celebration of the Solar Physics
Division of the American Astronomical Society
Authors: Pasachoff, Jay M.; Dupree, Andrea K.; Foukal, Peter; Weart,
Spencer; Zirker, Jack
Bibcode: 2021JAHH...24.1057P
Altcode:
The fiftieth anniversary celebration of the Solar Physics Division
of the American Astronomical Society was held virtually in August
2020 with joint sponsorship from the Historical Astronomy Division,
following the COVID-19-forced transformation of the original plan to
hold the meeting in Spokane, Washington. The presenters had given
papers at the first meeting in Huntsville, Alabama, in 1970, and
addressed related fields from the vantage point of fifty years.
Title: Chapter 12.2 - High-Resolution Ground-Based Observations of
the Sun
Authors: Engvold, Oddbjørn; Zirker, Jack B.
Bibcode: 2019sgsp.book..419E
Altcode:
To investigate the small-scale interactions between magnetic and
velocity fields that underlie many solar phenomena, solar physicists
need higher spatial and temporal resolution. As a result, they
are gradually introducing telescopes with meter-class mirrors and
instruments with more sensitivity. Adaptive optics systems have been
developed to minimize, in real time, the image distortions caused
by the Earth's atmosphere. Post facto image correcting techniques
facilitate further reduction of the distortions. Combinations of
instruments now observe simultaneously and record the many aspects
of a dynamic solar feature. The infrared spectrum, out to 2 μm and
beyond to submillimeters, is used to a greater extent. The first of a
new generation of 4-m telescopes is being built and 8-m telescopes are
being designed. The future beckons for ground-based solar research. In
this chapter, we survey these developments.
Title: Chapter 1 - Discoveries and Concepts: The Sun's Role in
Astrophysics
Authors: Zirker, Jack B.; Engvold, Oddbjørn
Bibcode: 2019sgsp.book....1Z
Altcode:
The Sun has had an important role in the development of stellar
astrophysics. The discoveries of solar magnetism, solar wind, and global
acoustic vibrations, to name only a few, have launched completely new
topics for research in stellar physics. In addition, concepts such
as magnetic reconnection and neutrino mass first arose in attempts
to explain puzzling solar phenomena. This volume is intended to
remind astronomers, physicists, and students of the Sun's key role,
which is based in part on its proximity and its commonality with other
stars. After a short survey of the subject, successive chapters will
describe the status and future progress in several topics in solar
physics that are relevant to stellar physics. We begin with the simplest
characteristic of the Sun, its luminosity.
Title: The Parallel Worlds of Christoph Scheiner and Galileo Galilei
Authors: Engvold, Oddbjørn; Zirker, Jack B.
Bibcode: 2016JHA....47..332E
Altcode:
No abstract at ADS
Title: Our Sun: The Nearest Star
Authors: Zirker, Jack Bernard
Bibcode: 2012aaa1.book..290Z
Altcode:
This chapter describes the structure of the Sun and the physical
processes that occur within it. The text is without mathematics and
is written for a general audience. Extensive references are given
to allow the reader to pursue certain issues in more depth. In the
first ten sections, the different layers are described, starting from
the core and advancing to the outer atmosphere, the solar wind and
the heliosphere. In the next five sections, some special topics are
considered, such as the internal rotation of the Sun; the physical
origin of the solar cycle; solar activity; and the heating of the
outer atmosphere and acceleration of the solar wind. In the last part,
the Sun's influence on the Earth is discussed briefly.
Title: The Magnetic Universe: The Elusive Traces of an Invisible Force
Authors: Zirker, J. B.; Neukirch, Thomas
Bibcode: 2010PhT....63f..51Z
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No abstract at ADS
Title: An acre of glass : a history and forecast of the telescope
Authors: Zirker, Jack B.
Bibcode: 2005aghf.book.....Z
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No abstract at ADS
Title: Journey from the Center of the Sun
Authors: Zirker, Jack B.; Acton, Loren W.
Bibcode: 2003PhT....56b..62Z
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No abstract at ADS
Title: Journey from the center of the sun
Authors: Zirker, Jack B.
Bibcode: 2002jcs..book.....Z
Altcode:
No abstract at ADS
Title: Journal from the Center of the Sun
Authors: Zirker, Jack B.
Bibcode: 2001jcs..book.....Z
Altcode:
No abstract at ADS
Title: Solar Prominence Chirality
Authors: Zirker, J.
Bibcode: 2000eaa..bookE2279Z
Altcode:
A prominence is a relatively cool sheet of dense plasma embedded in
the hot tenuous corona. They are easily seen as bright clouds at the
`limb' or edge of the solar disk. When viewed on the solar disk,
prominences are long narrow features, i.e. `FILAMENTS'. Prominences
are permeated by weak magnetic fields that are thought to support the
plasma against the pull of gravity, and to guide its flows....
Title: Frank Quimby Orrall (15 October 1925 - 4 February 2000).
Authors: Jefferies, J. T.; Zirker, J. B.
Bibcode: 2000SoPh..194..185J
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No abstract at ADS
Title: Obituary John Wainwright Evans, Jr.
Authors: Dunn, Richard B.; Smartt, Raymond N.; Zirker, Jack B.
Bibcode: 2000PhT....53c..94D
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No abstract at ADS
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: Counter-streaming gas flows in solar prominences as evidence
for vertical magnetic fields
Authors: Zirker, J. B.; Engvold, O.; Martin, S. F.
Bibcode: 1998Natur.396..440Z
Altcode:
Solar prominences are sheets of relatively cool and dense gas embedded
in the surrounding hotter corona. An erupting prominence can inject a
mass of up to 1015g into the solar wind as part of a coronal
mass ejection. These eruptions must depend critically on the topology of
the prominence's magnetic field. In all present models,, the prominence
hangs on horizontal or helical field lines, while an overlying magnetic
arcade temporarily restrains the prominence from erupting. Such models
are inconsistent, however, with the slow upward vertical gas flows that
are seen in prominences. Here we report counter-streaming flows along
closely spaced vertical regions of a prominence, between its top and the
lower solar atmosphere. As the flows must be aligned with the magnetic
field, this observation implies that a field connects the prominence
directly to the photosphere, contrary to all existing models. These
magnetic `tethers' might help prevent a prominence from erupting.
Title: The Sacramento Peak Observatory
Authors: Zirker, J. B.
Bibcode: 1998SoPh..182....1Z
Altcode:
No abstract at ADS
Title: Are All Prominences Either Sinistral or Dextral?
Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V.
Bibcode: 1998ASPC..150..439Z
Altcode: 1998IAUCo.167..439Z; 1998npsp.conf..439Z
No abstract at ADS
Title: Velocity Fields of a Filament Region Observed with Ground-Based
Telescopes and from SOHO
Authors: Mein, P.; Schmieder, B.; Malherbe, J. -M.; Wiik, J. E.;
Engvold, O.; Brekke, P.; Zirker, J. B.; Poland, A. I.; Delaboudiniere,
J. -P.; Staiger, J.
Bibcode: 1998ASPC..150..135M
Altcode: 1998npsp.conf..135M; 1998IAUCo.167..135M
No abstract at ADS
Title: Plasma Streaming as Indicator of Field Topology in a Quiescent
Filament
Authors: Zirker, J. B.; Engvold, O.; Martin, S. F.
Bibcode: 1997AAS...19112004Z
Altcode: 1997BAAS...29.1402Z
Although it is generally accepted that quiescent filaments have strong
horizontal axial magnetic field (Leroy,1984) the field configuration in
the legs (``barbs'' or ``feet'') is controversial. Previous observations
indicate both rising and falling Doppler motions in such appendages,
at speeds less than ``free-fall'' (Dunn,1960; Yi et al,1991; Zirker
et al, 1994). Such observations could be consistent with the presence
of horizontal magnetic fields that are slowly drifting up and down
carrying plasma with them. However the H alpha fine-structure strongly
suggests the presence of vertical or highly inclined magnetic field
lines. Without vector field observations it is difficult to choose
between these alternatives. In an attempt to clarify the issue,
H alpha observations of a quiescent filament were made during its
passage across the disk, from 12 to 20 April, 1993 at the Big Bear
Observatory. Remarkable high-speed flows (of order 20 km/s ) were
seen along the axial "spine" of the filament. Substantially slower
motions were detected in the barbs. The paradox of non-free-fall
motions in the predominantly vertically directed threads of barbs,
will be discussed briefly. Bommier,V., Landi Degli'Innocenti,E.,
Leroy, J-L., and Sahal-Brechot, S.: 1994, Solar Phys. 154,231 Dunn,
R.B.,1960, Ph D Thesis, Harvard University Engvold,O.: 1976,Solar
Phys.49,283. Leroy,J-L. Bommier,V. nd Sahal Brechot,S.:1984, Astronomy
and Astrophysics, 131,33. Yi,Z.,Engvold,O. and Keil,S.L.: 1991, Solar
Phys. 132,63. Zirker,J.B.,Engvold,O.and Yi,Z. 1994, Solar Phys. 150,81.
Title: The Sinistral-Dextral Regularity: An Independent Test
Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V.
Bibcode: 1997SoPh..176..279Z
Altcode:
Leroy, Bommier, and Sahal-Bréchot (1984) determined the vector magnetic
field in a large sample of quiescent prominences. The direction of
the axial component is in general subject to a 180 deg uncertainty. We
have selected those prominences in the sample whose field direction is
unambiguous. For 95 such prominences, only 3 do not obey the hemispheric
preferences of sinistral or dextral filaments, discovered by Martin,
Tracadas, and Billamoria (1994). No explanation for the exceptional
cases was found.
Title: Global Magnetic Patterns of Chirality
Authors: Zirker, J. B.; Martin, S. F.; Harvey, K.; Gaizauskas, V.
Bibcode: 1997SoPh..175...27Z
Altcode:
During the past five years at least six manifestations of a global
organization of solar magnetic fields have been recognized. The magnetic
chirality (handedness) of the following features shows a hemispheric
preference: filament channels, quiescent filaments, sunspot whorls,
superpenumbral fibrils, coronal arcades, and interplanetary clouds
associated with CMEs. Although the patterns are clear in the data,
their interpretation and their possible connection to the dynamo is
open to question. This paper reviews the observations of the patterns,
corrects some misinterpretations, and offers a scenario for the origin
of the most marked pattern, the chirality of filaments. We suggest
the pattern arises from the reconnection of coronal loops, under
the influence of supergranulation and differential rotation. Unlike
alternative scenarios, ours relies only on observable surface motions
and fields.
Title: Formation of a Solar Filament Channel
Authors: Gaizauskas, V.; Zirker, J. B.; Sweetland, C.; Kovacs, A.
Bibcode: 1997ApJ...479..448G
Altcode:
We present observations of the early stages of formation of a filament
channel when a compact activity complex emerged in a previously quiet,
near-equatorial area. In a few hours, and while flux was rising rapidly
in one bipolar component in the complex, H alpha fine structure
overlying a polarity inversion zone organized into a conspicuous
pattern of parallel fibrils enclosing the trailing end of the new
activity complex. Yet it took another 4 days for a stable filament
to form inside that pattern. It did so at a place where migrating
positive polarity flux from the new activity complex contacted the
negative polarity flux in a plage of an adjacent decaying bipolar
active region. In contrast, no filament formed along an existing
channel inside the adjacent decaying region; the opposite-polarity
fluxes on the borders of the existing channel showed no signs of
convergence. We attribute the fibril-aligning forces in the new channel
to the horizontal component of an extended nonpotential magnetic field
caused by currents in the multipolar activity complex. The channel is,
in this view, an elementary part of the magnetic topology of an activity
complex. We propose that the later formation of the filament in the
new channel requires an additional and separate process. A plausible
candidate for this second step is the development of a current sheet
at the site of converging magnetic flux.
Title: High resolution coronal imaging. 11 July, 1991 total eclipse
with University of Hawaii 2.24 meter telescope on Mauna Kea.
Authors: Labonte, B.; Livingston, W.; Zirker, J.
Bibcode: 1997ASIC..494...35L
Altcode: 1997topr.conf...35L
The authors observed the corona with the potential for unprecedented
spatial resolution afforded by a large stellar instrument at a prime
site. An ambitious experiment involving the recording of 5 narrow-band
1024×1024 CCD images failed because of a last minute software
change. Eclipses are unforgiving in this regard. However, a simple
video camera was also fed by a beam-splitter pickoff with excellent
results. This video tape, shown at the workshop, indicates how the
field of interest was selected, concentrating on a large prominence
at the NW limb. The role of seeing is evident; the smallest features
detected were 0.6 arcsec in size.
Title: Book-Review - Total Eclipses of the Sun
Authors: Zirker, J. B.; McGee, H.
Bibcode: 1995JBAA..105..187Z
Altcode:
No abstract at ADS
Title: Books-Received - Total Eclipses of the Sun - ED.2
Authors: Zirker, J. B.
Bibcode: 1995Sci...268.1641Z
Altcode:
No abstract at ADS
Title: Total eclipses of the sun
Authors: Zirker, Jack B.
Bibcode: 1995tesp.conf.....Z
Altcode:
No abstract at ADS
Title: Solar Variability Enterprise - A Community-wide Program
Authors: Zirker, J. B.
Bibcode: 1995SPD....26..101Z
Altcode: 1995BAAS...27..949Z
No abstract at ADS
Title: Mechanisms of Coronal Heating
Authors: Zirker, J. B.
Bibcode: 1995itsa.conf...13Z
Altcode:
No abstract at ADS
Title: Total eclipses of the sun
Authors: Zirker, Jack B.
Bibcode: 1995tets.book.....Z
Altcode: 1995QB541.Z57......
No abstract at ADS
Title: Flows at Filament Footpoints
Authors: Zirker, J. B.
Bibcode: 1994AAS...185.4411Z
Altcode: 1994BAAS...26.1378Z
Solar filaments form in filament channels, which are narrow regions
of aligned H alpha fibrils along a magnetic neutral line.The growth
of a filament into a pre-existing channel, and the filling of the
filament with cool plasma,is the subject of this paper. A quiescent
filament was observed July 4-10,1994 at the Vacuum Tower Telescope
at Sunspot,N.M. Grids of H alpha spectra and simultaneous H alpha
images were recorded and analyzed. On the day of best seeing (July
9) the Doppler velocities at footpoints at the growing end were
all positive( red-shifted) while those at the opposite stable end
were all negative(blue-shifted).Siphon flow at speeds of a few km/s
are indicated.But on July 6 a long fibril at the growing end of the
filament had a pattern of Doppler velocities consistent with draining
motions.Evidently the growth of filament fine-structure is sporadic.
Title: Searching for Nanoflares
Authors: Zirker, Jack B.; Cleveland, F. M.
Bibcode: 1994SoPh..153..245Z
Altcode:
The evolution of hydrodynamic shocks generated by nanoflares in coronal
loops is investigated in order to suggest requirements for future
observations. The shocks produced by nanoflares of 1024
ergs decay within a few seconds, which sets stringent requirements for
Doppler or transverse velocity measurements. With feasible improvements,
the Normal Incidence X-ray Telescope could observe the time-averaged
emission from a nanoflare, however. We also consider collisions between
shocks and show that these could also be observed.
Title: A Radical in Tweeds: Robert H. Dicke
Authors: Zirker, Jack
Bibcode: 1994Mercu..23d..23Z
Altcode: 1994Mercu..23...23Z
Bucking the trend of scientists who accepted Einstein's General Theory
of Relativity on faith, Robert Dicke has always demanded experimental
proof. What experiments did he devise to test the theory? And, after
conducting those experiments, how did the Theory hold up?
Title: Flows in Quiescent Prominences
Authors: Zirker, Jack B.; Engvold, Oddbjorn; Yi, Zhang
Bibcode: 1994SoPh..150...81Z
Altcode:
Earlier studies of quiescent prominences claim that there is a
systematic downward directed motion of the small-scale structure. Disk
observations, on the other hand, have detected mass motions both
upwards and downwards. The earlier high-resolution observations of
limb prominences have been re-examined using local cross-correlation
techniques for measurements of motion perpendicular to the line of
sight. The new measurements reveal flow speeds and directions that
are in good agreement with current Doppler measurements on the disk.
Title: Very High Resolution Analysis of the Dynamics of a Coronal
Plasmoid
Authors: Bouchard, O.; Koutchmy, S.; November, L.; Vial, J. -C.;
Zirker, J. B.
Bibcode: 1994scs..conf..593B
Altcode: 1994IAUCo.144..593B
The authors present the results of the analysis of a movie taken over a
small field of view in the intermediate corona at a spatial resolution
of 0.5", a temporal resolution of 1 s and a spectral passband of 7
nm. These CCD observations were made at the prime focus of the 3.6 m
aperture CFHT telescope during the 1991 total solar eclipse.
Title: Analysis of Chromospheric Proxies of Coronal Bright Points
Authors: Bocchialini, K.; Vial, J. -C.; Koutchmy, S.; Zirker, J. B.
Bibcode: 1994ASPC...68..389B
Altcode: 1994sare.conf..389B
No abstract at ADS
Title: Analysis of the Chromospheric Proxies of Coronal Bright Points
- Preliminary Results
Authors: Bocchialini, K.; Koutchmy, S.; Vial, J. -C.; Zirker, J. B.
Bibcode: 1994emsp.conf..173B
Altcode:
No abstract at ADS
Title: Photospheric Vortices and Coronal Heating
Authors: Zirker, J. B.
Bibcode: 1994scs..conf..478Z
Altcode: 1994IAUCo.144..478Z
No abstract at ADS
Title: Coronal Heating
Authors: Zirker, J. B.
Bibcode: 1993SoPh..148...43Z
Altcode:
The prospects for observational tests of coronal heating theories
are examined. Three heating mechanisms (Alfvén waves, D.C. electric
currents, and MHD turbulence) are reviewed from this point of view. Some
suggestions are offered for future tests but none, so far, would give
unambiguous critical results.
Title: Photospheric Vortices and Coronal Heating
Authors: Zirker, Jack B.
Bibcode: 1993SoPh..147...47Z
Altcode:
We have used the results of a realistic simulation of convection
to estimate the power input to coronal loops from the twisting
of photospheric magnetic field in intergranular vortices. In this
simulation, the vorticity is large (a mean of 0.03 s−1)
nearly everywhere in the intergranular lanes, not merely at the corners
of three granules. We found the autocorrelation time of vorticity images
to be 45 s, but individual vortices last as long as 144 s. Our estimate
suggests that field line twisting could supply a substantial fraction,
if not all, of the required power to the quiet corona.
Title: Avalanche Models of Active Region Heating and Flaring
Authors: Zirker, Jack B.; Cleveland, F. M.
Bibcode: 1993SoPh..145..119Z
Altcode:
In a previous paper, we suggested that the twisting of coronal magnetic
fiels by photospheric motions produces the steady heating of an active
region, while braiding of these fields stores energy which is eventually
released in an avalanche process, as sporadic large flares. We explore
these ideas with numerical simulations. Our results indicate that the
combined effect of twisting and braiding can account for the observed
power input and the flare frequency spectrum of typical active regions.
Title: Nanoflare Mechanisms - Twisting and Braiding
Authors: Zirker, J. B.; Cleveland, F. M.
Bibcode: 1993SoPh..144..341Z
Altcode:
In this paper we will show that the twisting mechanism of Sturrock and
Uchida is as viable a heating source for the active corona as Parker's
braiding. This conclusion contradicts that of Berger (1990). Moreover,
we shall show that if we adopt Berger's criterion for reconnection,
braiding produces far more flare energy than is observed. A modified
criterion, consistent with twisting, produces insufficient heating but,
coupled to an avalanche process, could account for active region flares.
Title: The anatomy of the Sun
Authors: Zirker, J. B.
Bibcode: 1992Natur.357..552Z
Altcode:
No abstract at ADS
Title: Structural changes in the solar corona during the July
1991 eclipse
Authors: Zirker, J. B.; Koutchmy, S.; Nitschelm, C.; Stellmacher, G.;
Zimmermann, J. P.; Martinez, P.; Kim, I.; Dzyubenko, N.; Kurochka,
L.; Makarov, V.
Bibcode: 1992A&A...258L...1Z
Altcode:
Preliminary results of the analysis of radially filtered pictures
obtained at several hours interval during the July 11, 1991 total
solar eclipse are given. Instrumental parameters and method are
outlined. Structural changes are discussed.
Title: The solar corona of July 11, 1991. Observations in Brazil
(MICE).
Authors: Dzyubenko, N. I.; Kurochka, L. N.; Rubo, G. A.; Kim,
I. S.; Artamonov, B. P.; Boczko, R.; Matsuura, O. T.; Koutchmy, S.;
Zimmermann, J. P.; Zirker, J. B.
Bibcode: 1992ATsir1552...21D
Altcode:
No abstract at ADS
Title: Nanoflare mechanisms: twisting and braiding.
Authors: Zirker, J. B.; Cleveland, F. M.
Bibcode: 1992mrpa.work..159Z
Altcode:
The authors show that the twisting mechanism of Sturrock and Uchida
is as viable a heating source for the active corona as Parker's
braiding. This conclusion contradicts that of Berger (1990).
Title: Eclipse Plans for NSO/SP
Authors: Zirker, J. B.; Koutchmy, S.; Coulter, R. L.; November, L. J.;
Smartt, R. N.
Bibcode: 1991BAAS...23.1063Z
Altcode:
No abstract at ADS
Title: High spatial resolution V-Stokes polarimetry to measure the
Zeeman effect in flux tubes and prominence filament threads.
Authors: Koutchmy, S.; Zirker, J. B.; Darvann, T.; Koutchmy, O.;
Stauffer, F.; Mann, R.; Coulter, R.; Hegwer, S.
Bibcode: 1991sopo.work..263K
Altcode:
No abstract at ADS
Title: Coronal activity.
Authors: Koutchmy, Serge; Zirker, Jack B.; Steinolfson, Richard S.;
Zhugzhda, Iosif D.
Bibcode: 1991sia..book.1044K
Altcode:
This chapter considers the rather extended, very inhomogeneous and
dynamical part of the solar atmosphere called the corona. Coronal
structures are first described from the point of view of quasi-static
structure in order to consider their thermodynamical gross properties,
including heating and magnetic fields. The solar-cycle-related
variations of coronal structures are reviewed as well. Solar prominences
are a well-observed ingredient of the corona; they form its cool
component. Their properties, including magnetic field, thermal and
velocity field structures are reviewed before considering the problem of
their formation. Coronal mass ejections are the most dramatic phenomena
occurring in a short time in the corona and are almost inevitably
phenomena occurring in a short time in the corona and are almost
inevitably related to a prominence ejection. Their observations are
described with reference to several related solar phenomena in order
to understand the driving mechanism. Models of coronal mass ejections
are described based on numerical simulations including consideration
of waves. Finally, the very important and still open question of the
waves in the solar corona is briefly discussed from a theoretical
point of view, emphasizing the possible role of hydromagnetic waves.
Title: Prominence Fine Structure - Part Two - Diagnostics
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1991SoPh..131..107Z
Altcode:
A random-clustering model of prominence fine-structure has been applied
to observations of prominence Hα spectra. The model yields an estimate
of the number of unresolved elements that form an individual resolved
feature, and sets limits on their velocity and Hα profile dispersions.
Title: Prominence Fine Structure
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1990SoPh..127..109Z
Altcode:
The vertical fine structure in a quiescent prominence was modelled as an
assembly of very narrow, optically thin threads. Random clusterings of
the threads can account for the observed contrast and Hα line profiles
of the fine structures. In this picture, each structure consists of
a cluster of 7-20 elementary threads.
Title: Video Magnetograms with Sub-Arcsecond Resolution
Authors: Koutchmy, S.; Stauffer, F.; Zirker, J.; Keil, S.; Mann, R.;
Coulter, R.; Hegwer, S.
Bibcode: 1990BAAS...22..880K
Altcode:
No abstract at ADS
Title: Estimation of the line of sight amplitude of the magnetic
field on threads of an active region prominence
Authors: Koutchmy, S.; Zirker, J. B.
Bibcode: 1990LNP...363..242K
Altcode: 1990IAUCo.117..242K; 1990doqp.coll..242K
No abstract at ADS
Title: On the Spatial Distribution of Prominence Threads
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1990LNP...363..237Z
Altcode: 1990doqp.coll..237Z; 1990IAUCo.117..237Z
No abstract at ADS
Title: A movie of small-scale Doppler velocities in a quiescent
prominence
Authors: Koutchmy, Serge; Zirker, Jack; Gilliam, Lou B.; Coulter,
Roy; Hegwer, Stephen; Mann, Richard; Stauffer, Fritz
Bibcode: 1990LNP...363..240K
Altcode: 1990doqp.coll..240K; 1990IAUCo.117..240K
A movie made of selected H off-band images of a typical Quiescent
Prominences has been produced with the optical printer of NSO-S.P. High
speed pictures were obtained with the UBF of the VTT on June 21, 1987
during 30 min of very good seeing, at a 20 sec cycling rate. Blue and
red wings images are made at plus and minus .040 nm from line center,
with a .022 nm passband. Original Pictures were enlarged to give an
effective field of view of 100 × 80 arcsec2. Negative to positive
superposition allows the mapping of strongly Doppler-shifted features
(± 20 km sec-1) on a grey scale. The prominence threads are mostly
discrete, allowing accurate measurement of proper motions. Typical
transverse velocities of proper motions of small knots moving
vertically downward are about 10 km sec-1 The movie also demonstrates
the turbulent behaviour of the prominence plasma. Large-scale motions
at lower transverse velocities are also clearly present.
Title: High Resolution Analysis of Quiescent Prominences at National
Solar Observatory / Sacramento Peak Observatory
Authors: Darvann, Tron A.; Koutchmy, Serge; Stauffer, Fritz; Zirker,
Jack B.
Bibcode: 1990LNP...363..239D
Altcode: 1990doqp.coll..239D; 1990IAUCo.117..239D
We present preliminary results of several experiments carried out at
the National Solar Observatory / Sacramento Peak (NSO/SP) Vacuum Tower
Telescope (VTT) with the aim to resolve velocities and magnetic fields
of the fine scale structures of filaments and prominences.
Title: High Resolution Observations of Motions and Structure of
Prominence Threads
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1990LNP...363..244Z
Altcode: 1990doqp.coll..244Z; 1990IAUCo.117..244Z
H profiles and filtergrams were obtained of quiescent prominences at
the National Solar Observatory, Sunspot, NM, with spatial resolution
better than 1.6 arcseconds. The H profiles of individual threads are
often Gaussian, but may show marked asymmetries, particularly near
the prominence edges. Filtergrams, taken at ± 0.7 Å (± 30 km/sec)
in H (with a 0.18 Å passband) show high speed knots and threads
at the prominence edges, that persist with no perceptible change
for at least 10 minutes. This result implies plasma motions (along
essentially horizontal magnetic fields) over distances as large as
18000 km, i.e. much larger than typical thicknesses (5000 km) of H
filaments. These motions may be associated with thread formation or
decay, but continuous observations of this prominence over 6 hours
show that the large-scale form of the prominence remained unchanged.
Title: An Automated Procedure for Measurement of Prominence Transverse
Velocities
Authors: Darvann, Tron Andre; Koutchmy, Serge; Zirker, Jack B.
Bibcode: 1990LNP...363..267D
Altcode: 1990doqp.coll..267D; 1990IAUCo.117..267D
A computer algorithm for measurment of transverse velocities (proper
motion) in prominences has been developed. We present the method and
examples of computed proper motion maps. The method is a modified
version of the local cross correlation technique previously applied to
granulation images (November 1986, Title et al 1987, November and Simon
1988, November 1988, Darvann 1988, Brandt et al 1988). Prominence images
show much steeper intensity gradients and a wider range of spatial
scales of fine structure than granulation images. Due to this we find
it necessary to replace the prominence images by an image showing the
intensity gradients (derivative of the intensity image). Furthermore,
in our algorithm we compute absolute differences instead of correlation
coefficients in order to reduce the influence of large scale intensity
gradients across a local window (Karud 1988). We have tested the method
on datasets obtained at the Vacuum Tower Telescope of NSO/SP. The
accuracy of the algorithm is seen to be ±0.3 pixels which, in our
data, corresponds to about 1/10 arcsec. Seeing effects are effectively
reduced by averaging N cross correlation functions formed from images
sampled t apart. We find that t = 120s gives the highest accuracy in
the proper motion measurement when applied to our data consisting
of quiescent prominences. The correlation coefficient between two
interlaced, independent proper motion maps is as high as 0.92 when
N=50. The size of the smallest structure for which a proper motion
velocity can be measured is limited by the size of the smallest local
window that can successfully be applied in the measurement. It needs
to be large enough to contain some high contrast structures, typically
4×4 arcsec in our data. Our algorithm is self-adaptive to the data in
the sense that the window size is changed automatically depending on
the presence of local high contrast structures. We conclude that the
method successfully produces prominence proper motion maps in addition
to being able to correlation track prominence images. Furthermore the
algorithm will be useful for destretching of prominence images before
producing Doppler-grams or carrying out oscillation studies at high
spatial resolution.
Title: Quiescent Prominences
Authors: Zirker, J. B.
Bibcode: 1989SoPh..119..341Z
Altcode:
This review surveys recent research on quiescent solar prominences. The
main topics considered are magnetic structure, thermal structure,
and formation. Sub-arc sec fine-structures undoubtedly play a crucial
role in all three topics. Current attempts to model the magnetic and
thermal structure are hampered, in part, by the lack of observations
with sufficient spatial resolution. The process of formation is
quite complicated, but is yielding slowly to detailed numerical
simulations. Unfortunately, observations of prominence `condensation'
from the corona (the favored hypothesis) are lacking. Some suggestions
for future work are offered.
Title: Interferometric Imaging - Part Two
Authors: Zirker, J. B.
Bibcode: 1989SoPh..120..253Z
Altcode:
Non-redundant arrays offer a promising technique for producing
diffraction-limited solar images. Pairs of two-dimensional non-redundant
arrays yield sufficient information to recover the phases of all the
spatial frequencies to which they respond. The algorithms to select
and test such pairs are given and applied to a particular example.
Title: Prospects for solar interferometry.
Authors: von der Lühe, O.; Zirker, J. B.
Bibcode: 1989hsrs.conf..191V
Altcode:
No abstract at ADS
Title: Prospects for solar interferometry
Authors: Lühe, O. V. D.; Zirker, J. B.
Bibcode: 1989hsrs.conf..191L
Altcode:
No abstract at ADS
Title: Phase recovery with dual non-redundant 2-D arrays
Authors: Zirker, J. B.
Bibcode: 1989hsrs.conf..187Z
Altcode:
No abstract at ADS
Title: On the Spatial Distribution of Prominence Threads
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1989HvaOB..13...41Z
Altcode:
No abstract at ADS
Title: An Automated Procedure for Measurement of Prominence Transverse
Velocities
Authors: Darvann, T. A.; Koutchmy, S.; Zirker, J. B.
Bibcode: 1989HvaOB..13..243D
Altcode:
No abstract at ADS
Title: Prominence fine structure.
Authors: Zirker, J. B.; Koutchmy, S.
Bibcode: 1989BAAS...21.1027Z
Altcode:
No abstract at ADS
Title: Spectroscopic Coronal Observations Using A High-Sensitivity
Camera
Authors: Smartt, R. N.; Colley, S. A.; Gilliam, L. B.; Koutchmy, S.;
Zirker, J. B.
Bibcode: 1988BAAS...20..704S
Altcode:
No abstract at ADS
Title: Wind, holes and bright points.
Authors: Zirker, J. B.
Bibcode: 1988sscd.conf...71Z
Altcode:
In this review, the author summarizes recent attempts to explain
the heating of the corona and the acceleration of the solar wind,
particularly in high speed streams that originate in coronal
holes. Acceleration by Alfven wave pressure remains a possibility,
but has not yet been confirmed observationally. Meanwhile, coronal
heating by transient events has emerged as an interesting alternative
to magnetic reconnection.
Title: Correlation Lifetimes of Quiet and Magnetic Granulation from
the SOUP Instrument on Spacelab 2
Authors: Title, A.; Tarbell, T.; Topka, K.; Acton, L.; Duncan, D.;
Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill,
M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Simon, G.; Harvey,
J.; Leibacher, J.; Livingston, W.; November, L.; Zirker, J.
Bibcode: 1988ApL&C..27..141T
Altcode:
The time sequences of diffraction limited granulation images obtained by
the Solar Optical Universal Polarimeter on Spacelab 2 are presented. The
uncorrection autocorrelation limetime in magnetic regions is dominated
by the 5-min oscillation. The removal of this oscillation causes the
autocorrelation lifetime to increase by more than a factor of 2. The
results suggest that a significant fraction of granule lifetimes are
terminated by nearby explosions. Horizontal displacements and transverse
velocities in the intensity field are measured. Lower limits to the
lifetime in the quiet and magnetic sun are set at 440 s and 950 s,
respectively.
Title: Scientific goals for solar interferometry.
Authors: von der Lühe, O.; Zirker, J. B.
Bibcode: 1988ESOC...29...77V
Altcode: 1988hrii.conf...77V
The authors review scientific programs for solar research that can be
carried out using interferometric techniques. They establish boundary
conditions for interferometric experiments. The performance and
achievable resolution of interferometry is studied using an empirical
model spectrum of the intensity fluctuation of solar granualtion as an
example of extended, low-contrast small scale structure. The authors
conclude that, with interferometric techniques, a ten-fold increase
in resolution beyound today's seeing-limited performance is possible.
Title: Interferometric imaging: a numerical simulation.
Authors: Zirker, J. B.
Bibcode: 1987SoPh..111..235Z
Altcode:
Non-redundant arrays offer the possibility of reconstructing optical
solar images to the diffraction limit of resolution, with minimal
data processing. A particular algorithm, due to W. T. Rhodes, for the
analysis of the fringes produced by a set of non-redundant arrays,
has been evaluated numerically. The algorithm can give satisfactory
results with S/N ∼ 100, but can also break down at moments of
unfavorable seeing.
Title: Imaging interferometry with non-redundant arrays.
Authors: Zirker, J. B.
Bibcode: 1987NASCP2483..143Z
Altcode: 1987tphr.conf..143Z
The performance of a set of nonredundant arrays, that convert an
existing telescope to an interferometer, was simulated. Each array is a
perforated mask, placed at an image of the objective. Each pair of holes
in a mask transmits a unique spatial frequency that is present in the
target; hence the term nonredundant. Each mask produces a fringe I(f)
in the focal plane that is the product of the Fourier transforms of
the object and the optical transfer function S(f).
Title: Joint Discussion on Topics of Session 12
Authors: Zirker, J. B.
Bibcode: 1987rfsm.conf..348Z
Altcode:
No abstract at ADS
Title: Imaging Interferometry with Non-Redundant Arrays
Authors: Zirker, J. B.
Bibcode: 1987rfsm.conf..342Z
Altcode:
No abstract at ADS
Title: Spectroscopy of the solar corona
Authors: Zirker, J. B.
Bibcode: 1987soap.conf..165Z
Altcode: 1987sap..book..165Z
Recent spectroscopic observations of the solar corona are reviewed
and illustrated with sample images and spectra. The techniques used
in the observations are discussed, and particular attention is given
to coronal structures, temperature diagnostics, electron-density
measurements, the electron temperature and density in flares, the
velocity of coronal material, and magnetic fields. The value of the
observations obtained on Skylab is stressed.
Title: Phase recovery with dual nonredundant arrays
Authors: Zirker, J. B.; Brown, T. M.
Bibcode: 1986JOSAA...3.2077Z
Altcode: 1986OSAJ....3.2077Z
Nonredundant arrays inserted at the pupil plane of a telescope permit
recovery of both amplitude and phase of numerous Fourier components of a
small target. A single array, however, yields insufficient information
with which to solve for all the Fourier components to which that array
responds. A method is proposed here for selecting pairs of arrays that
yield complete information within some passband of spatial frequencies.
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: Prominence hydrogen lines at 10 20 microns
Authors: Zirker, J. B.
Bibcode: 1985SoPh..102...33Z
Altcode:
An analysis of prominence hydrogen lines is presented in the spectral
band 10-20 μ. The results are consistent with earlier work.
Title: Book-Review - Solar / Space Observations and Stellar Prospects
Authors: Harvey, J. W.; Hudson, H. S.; Noyes, R. W.; Zirker, J. B.
Bibcode: 1985Sci...230..660H
Altcode:
No abstract at ADS
Title: Solar Astronomy. (Book Reviews: Solar Maximum Analysis;
Solar-Space Observations and Stellar Prospects)
Authors: Zirker, J. B.
Bibcode: 1985Sci...230..660S
Altcode:
No abstract at ADS
Title: Solar Astronomy. (Book Reviews: Solar Maximum Analysis;
Solar-Space Observations and Stellar Prospects)
Authors: Zirker, J. B.
Bibcode: 1985Sci...230..660Z
Altcode:
No abstract at ADS
Title: Progress in Coronal Physics
Authors: Zirker, J. B.
Bibcode: 1985SoPh..100..281Z
Altcode:
This paper reviews research highlights of the past five
years. Considerable progress has been made in observing and interpreting
coronal mass ejections. The stability of coronal loops is much
better understood and new observations of the onset of wind streams
in coronal holes have been made. Observations from the Solar Maximum
Mission should helpt to clarify the physics of the active corona.
Title: Book-Review - Total Eclipse of the Sun
Authors: Zirker, J. B.
Bibcode: 1985S&T....70..230Z
Altcode:
No abstract at ADS
Title: Testing Einstein's General Relativity during Eclipses of
the Sun
Authors: Zirker, J. B.
Bibcode: 1985Mercu..14...98Z
Altcode:
No abstract at ADS
Title: Solar Meridional Flow During 1982 - 1984
Authors: Zirker, J. B.; Howard, R. F.
Bibcode: 1985BAAS...17..634Z
Altcode:
No abstract at ADS
Title: Relations between chromospheric-coronal heating and mass loss
in stars. Proceedings of the Trieste Workshop 1984, held at Sacramento
Peak Observatory, Sunspot, New Mexico, USA, 18 - 24 August 1984.
Authors: Stalio, R.; Zirker, J. B.
Bibcode: 1985rbcc.conf.....S
Altcode:
No abstract at ADS
Title: A review of the summer workshop on "Chromospheric diagnostics
and modelling", held at Sacramento Peak Observatory, Sunspot, New
Mexico, August 13 - 16, 1984.
Authors: Zirker, J. B.
Bibcode: 1985rbcc.conf....3Z
Altcode:
No abstract at ADS
Title: Total eclipses of the sun
Authors: Zirker, Jack B.
Bibcode: 1984tes..book.....Z
Altcode: 1984QB544.80.Z57...
No abstract at ADS
Title: The Structure and Variability of the Solar Wind
Authors: Zirker, J. B.
Bibcode: 1984evml.conf...25Z
Altcode:
The purpose of this paper is to focus on the question: Does the total
mass loss of the solar wind vary in time; and if so, by what amount?
Title: Book-Review - Total Eclipses of the Sun
Authors: Zirker, J. B.
Bibcode: 1984SciN..126...78Z
Altcode:
No abstract at ADS
Title: A Review of the Summer Workshop on "Chromospheric Diagnostics
and Modelling"
Authors: Zirker, J. B.
Bibcode: 1984rcch.conf....3Z
Altcode:
No abstract at ADS
Title: New observations of the Solar Emission Corona in Fe X and
Fe XIV
Authors: Smartt, R. N.; Zirker, J. B.
Bibcode: 1984stp..conf..269S
Altcode:
No abstract at ADS
Title: An Air Force/NSF initiative to study the origins of solar
activity.
Authors: Worden, S. P.; Dunn, R. B.; Smith, M. A.; Zirker, J. B.
Bibcode: 1982SAOSR.392B.221W
Altcode: 1982csss....2..221W
No abstract at ADS
Title: Interferometric eclipse observations of the Fe XIV inner
corona.
Authors: Smartt, R. N.; Zirker, J. B.; Mauter, H. A.
Bibcode: 1982PINSA..48..102S
Altcode:
No abstract at ADS
Title: Interferometric Eclipse Observations of the Fe XIV Inner Corona
Authors: Smartt, R. N.; Zirker, J. B.; Mauter, H. A.
Bibcode: 1982PIAS...48..102S
Altcode:
No abstract at ADS
Title: Solar Wind
Authors: Zirker, J. B.
Bibcode: 1982obvf.conf..181Z
Altcode:
No abstract at ADS
Title: Solar Physics at Future Solar Eclipses
Authors: Zirker, J. B.
Bibcode: 1982tsef.conf....6Z
Altcode:
No abstract at ADS
Title: Interferometric Eclipse Observations of the Fe XIV Inner Corona
Authors: Smartt, R. N.; Zirker, J. B.; Mauter, H. A.
Bibcode: 1982tsef.conf..102S
Altcode:
No abstract at ADS
Title: The solar corona and the solar wind.
Authors: Zirker, J. B.
Bibcode: 1981NASSP.450..135Z
Altcode: 1981suas.nasa..135Z
A stellar corona is an extended atmospheric region that is maintained at
a significantly higher temperature than that of the stellar photosphere
by nonthermal energy input. The solar corona stands as a prototype for
all stellar coronas and is a prime example of a stellar atmosphere
in which nonthermal processes predominate. Nonthermal processes are
those in which the local flux of energy bears no direct relation to
the internal energy of the gas or the quality of the radiation the gas
emits and absorbs. Observations of the solar corona and the solar wind
were surveyed and are presented.
Title: Sacramento Peak Observatory, Sunspot, New Mexico 88349. Report.
Authors: Zirker, J. B.; Durney, B. R.
Bibcode: 1981BAAS...13..389Z
Altcode:
No abstract at ADS
Title: Eclipse observations of coronal Fe XIV emission.
Authors: Smartt, R. N.; Zirker, J. B.; Mauter, H. A.
Bibcode: 1981otse.conf...36S
Altcode:
No abstract at ADS
Title: Coronal holes and solar mass loss.
Authors: Zirker, J. B.
Bibcode: 1981ASIC...68..301Z
Altcode: 1981spss.conf..301Z
Current understandings of the solar wind, particularly the high-speed
streams originating in coronal holes, are reviewed in view of the
importance of the high-speed streams to mass loss in the sun and other
stars. Salient properties of the average solar wind are summarized,
and calculations are presented which show that, although the total mass
loss is insignificant for solar evolution, the solar wind could have
been a significant factor in spinning down the sun. The properties of
the high-speed solar wind streams, with velocities above 650 km/sec,
are then distinguished, and the observed and derived properties of the
coronal holes confirmed to be the source of the streams are examined. A
model for the three-dimensional solar wind just before solar minimum,
when it is dominated by long-lived, stable streams from a relatively
small number of holes, is then presented which accounts for the
influence of polar holes. Questions remaining regarding the origin
of the solar wind and the structure and evolution of coronal holes
are indicated.
Title: Total Eclipses of the Sun
Authors: Zirker, J. B.
Bibcode: 1980Sci...210.1313Z
Altcode:
Total eclipses of the sun offer research opportunities in a variety of
sciences. Some of the advances in solar physics resulting from eclipse
observations are discussed. Experiments at the total eclipse of 16
February 1980 in India are also described. These included a test of
general relativity, studies in coronal physics, investigations of solar
prominences, diameter measurements, a search for interplanetary dust,
a study of the gravity waves in the earth's atmosphere, and experiments
on the biological effects on animals and humans.
Title: Interferometric Eclipse Observations of Coronal Fexiv Emission
Authors: Smartt, R. N.; Zirker, J. B.; Mauter, H. A.
Bibcode: 1980BASI....8...59S
Altcode:
No abstract at ADS
Title: Solar corona spectra observations in active, quiescent and
hole regions.
Authors: Gilliam, L. B.; Smartt, R. N.; Zirker, J. B.
Bibcode: 1980BAAS...12..751G
Altcode:
No abstract at ADS
Title: Summary of the SCADM Meeting
Authors: Zirker, J.
Bibcode: 1980NASCP2098..315Z
Altcode: 1980sscs.nasa..315Z
No abstract at ADS
Title: Study of the solar cycle from space. Proceedings of a symposium
held at Wellesley, Massachusetts, June 14 - 15, 1979.
Authors: Newkirk, G.; Zirker, J. B.
Bibcode: 1980NASCP2098.....N
Altcode:
No abstract at ADS
Title: Solar pulsations.
Authors: Zirker, J. B.
Bibcode: 1980AIAAJ..18..176Z
Altcode:
Oscillations of the surface of the sun, with periods between 5 and
160 min, have been observed by several spectroscopic techniques, and
preliminary interpretations have been offered. The 5-min oscillations
are global, nonradial, acoustic standing waves in the subsurface
zone. Internal differential rotation speeds have been deduced from
the Doppler splitting of these waves. Oscillations with longer periods
have been reported, but need confirmation. The longest periods offer
a tool for investigating the solar interior.
Title: Sacramento-Peak Observatory
Authors: Zirker, J. B.; Cram, L. E.
Bibcode: 1980BAAS...12..351Z
Altcode:
No abstract at ADS
Title: The large-scale structure of the corona.
Authors: Zirker, J. B.
Bibcode: 1980HiA.....5..549Z
Altcode:
No abstract at ADS
Title: Sacramento Peak Observatory, Sunspot, New Mexico 88349. Report.
Authors: Zirker, J. B.
Bibcode: 1979BAAS...11..300Z
Altcode:
No abstract at ADS
Title: A Solar Observatory in the Canary Islands
Authors: Zirker, Jack B.
Bibcode: 1978S&T....55..216Z
Altcode:
No abstract at ADS
Title: Sacramento Peak Observatory, Sunspot, New Mexico. Report.
Authors: Zirker, J. B.
Bibcode: 1978BAAS...10..309Z
Altcode:
No abstract at ADS
Title: Coronal holes and high-speed wind streams.
Authors: Zirker, J. B.
Bibcode: 1977RvGSP..15..257Z
Altcode: 1977RvGeo..15..257Z
Coronal holes, regions of unusually low density and low temperature
in the solar corona, are identified as Bartel's M regions, i.e.,
sources of high-speed wind streams that produce recurrent geomagnetic
variations. Throughout the Skylab period the polar caps of the sun were
coronal holes, and at lower latitudes the most persistent and recurrent
holes were equatorial extensions of the polar caps. The holes rotated
'rigidly' at the equatorial synodic rate. They formed in regions of
unipolar photospheric magnetic field, and their internal magnetic
fields diverged rapidly with increasing distance from the sun. The
geometry of the magnetic field in the inner corona seems to control
both the physical properties of the holes and the global distribution
of high-speed wind streams in the heliosphere. Phenomenological models
for the birth and decay of coronal holes have been proposed.
Title: A model for X-ray emission from loop prominences.
Authors: Phillips, K. J. H.; Zirker, J. B.
Bibcode: 1977SoPh...53...41P
Altcode:
A study is made of X-ray line emission observed during the developing
stages of a set of post-flare loop prominences. The time behaviour of
the line emission can be described by a model consisting of two flux
tubes containing plasma heated impulsively at the flash phase; the
plasma cools by radiation and by conduction to the chromosphere. These
ideas are extended to the possible formation of Hα prominences from
low-lying hot loops.
Title: Coronal holes and high speed wind streams: a monograph from
Skylab solar workshop I.
Authors: Zirker, J. B.
Bibcode: 1977chhs.conf.....Z
Altcode:
No abstract at ADS
Title: Energy Balance in Coronal Holes and Solar Wind Streams
Authors: Zirker, J. B.
Bibcode: 1977ebhs.coll..421Z
Altcode: 1977IAUCo..36..421Z
No abstract at ADS
Title: Coronal holes - an overview.
Authors: Zirker, J. B.
Bibcode: 1977chhs.conf....1Z
Altcode:
No abstract at ADS
Title: Observational research on solar coronal waves
Authors: Zirker, J. B.
Bibcode: 1976huha.rept.....Z
Altcode:
An observational search has been made for intensity fluctuations
associated with the wave motions that are thought to heat the
corona. Brightness changes in the coronal green line (Fe XIV lambda
5303) and the coronal continuum were measured with the University of
Hawaii's polarimeter at Mt. Haleakala. Upper limits of fluctuations
associated with wave heating were 0.2% and 6% in the line and continuum,
respectively. Spectra of quiescent prominences have been analyzed
to determine whether any correlation exists between temperature
and microturbulence, which could be consistent with wave heating
of prominences. Kinetic temperatures range from 8000 to 11000 K,
rms turbulent velocities range from 3 to 8 km/s. No correlation
between temperature and microturbulence was found. Some evidence for
a gradient in kinetic temperature and for gross oscillations of an
entire prominence, was found.
Title: The Sun's Atmosphere. (Book Reviews: The Solar Chromosphere
and Corona. Quiet Sun)
Authors: Zirker, Jack B.
Bibcode: 1976Sci...194.1048Z
Altcode: 1976Sci...194.1048A
No abstract at ADS
Title: Lyman-alpha emission from nonthermal proton beams.
Authors: Orrall, F. Q.; Zirker, J. B.
Bibcode: 1976ApJ...208..618O
Altcode:
Nonthermal fast protons penetrating an atmosphere containing neutral
hydrogen will produce some nonthermal fast neutrals which will radiate
Doppler-shifted photons. The hydrogen line profiles observed from such
an atmosphere will thus have nonthermal, partially polarized wings that
contain information on the flux, energy spectrum, and direction of the
incident proton beam. This paper develops the theory of this effect
and applies it to proton beams from impulsive solar flares impacting
on the sun's atmosphere. Calculations of the L-alpha profile from the
region of impact have been made for the Vernazza-Avrett-Loeser solar
atmosphere assuming proton energy fluxes and power-law spectra similar
to those inferred for the electron beams believed responsible for hard
X-ray bursts. The resulting profiles show that the effect should be
detectable and that it could serve as a diagnostic for flare protons
near their place of origin on the sun.
Title: INVITED PAPER - Recent Progress in the Study of Coronal Holes
Authors: Zirker, J. B.
Bibcode: 1976BAAS....8..376Z
Altcode:
No abstract at ADS
Title: On The Cooling of Loop Prominences
Authors: Phillips, K. J. H.; Zirker, J. B.
Bibcode: 1976BAAS....8..345P
Altcode:
No abstract at ADS
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: Properties of the Solar Filigree Structure
Authors: Dunn, R. B.; Zirker, J. B.; Beckers, J. M.
Bibcode: 1974IAUS...56...45D
Altcode:
No abstract at ADS
Title: The Solar Filigree
Authors: Dunn, Richard B.; Zirker, Jack B.
Bibcode: 1973SoPh...33..281D
Altcode:
As a birefringent filter is tuned from the center of Hα to the
continuum the Hα bright mottles appear to break up into a network of
grains. The name `filigree' is suggested for this bright network. Its
size, shape, contrast and time evolution is described as well as its
relation to the `abnormal' granulation, magnetic field and spicules.
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: A Search for the Photospheric Origin of Spicules
Authors: Dunn, R. B.; Zirker, J. B.
Bibcode: 1972BAAS....4T.381D
Altcode:
No abstract at ADS
Title: The Interpretation of Total Line Intensities from Optically
Thin Gases. III: Application to Coronal Forbidden Line Spectra
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1972SoPh...22..327J
Altcode:
The diagnostic method developed in the two preceding papers of this
series is applied to coronal forbidden line intensity data obtained at
eclipses in 1952, 1961, 1965, 1966, and 1970. The application of the
method is limited by the nature of the data but allows a first inference
of the relationship between electron density and temperature in the
condensations observed at these eclipses, and of the distribution of
the electrons within the temperature range samples by the observations
effectively 106 to 2.4 × 106 K. We determine the
relative abundance of nickel to iron in the corona, finding a value in
agreement with latest photospheric determinations and with a similar
(factor of two) uncertainty. We are also able to set lower limits to
the abundance of iron with respect to hydrogen, again finding values
consistent with recent photospheric determinations.
Title: The Interpretation of Total Line Intensities from Optically
Thin Gases. II: The Coronal Forbidden Lines
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1972SoPh...22..317J
Altcode:
We discuss the application of a general diagnostic procedure, developed
in the preceding paper of this series, to the inference of the physical
state of coronal condensations from a knowledge of their forbidden
line emission. We consider the limitations set on such an analysis by
inadequacies in existing data and indicate the additional observations
in the infrared and ultraviolet, as well as the visible, which will
be needed for development of the full power of the diagnostic method.
Title: The Interpretation of Total Line Intensities from Optically
Thin Gases. I: A General Method
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1972SoPh...22..307J
Altcode:
We describe a general method for inferring, from the line emission of an
optically thin medium, the physical state of the gas along the column in
the line of sight which is sampled by the observations. Since it is not
possible to infer the distribution of the physical state parameters with
position in the line of sight - any arbitrary rearrangement of material
giving equivalent line emission - we seek instead to specify the
state in another way. A unique specification is found in terms of the
bivariate distribution function μ (n, T), describing the partitioning
of the matter in the gas over the density and temperature. We show
that, given sufficient observational data, it is in principle possible
to determine both μ (n, T), and the chemical composition. With less
complete data the acuity of the analysis is correspondingly reduced.
Title: The Corona
Authors: Zirker, J. B.
Bibcode: 1971spas.conf..112Z
Altcode:
No abstract at ADS
Title: The spectrum of the chromosphere and corona from lambda 3000
to lambda 7000 on March 7, 1970.
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1971BAAS....3Q.262J
Altcode:
No abstract at ADS
Title: Coronal models and coronal chemical abundances.
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1971BAAS....3..261J
Altcode:
No abstract at ADS
Title: Institute for Astronomy, University of Hawaii, Honolulu,
Hawaii. Report 1969-1970.
Authors: Zirker, J. B.
Bibcode: 1971BAAS....3...83Z
Altcode:
No abstract at ADS
Title: Coronal Active Regions and Flare-Associated Events
Authors: Zirker, J. B.
Bibcode: 1971ASSL...27..140Z
Altcode: 1971psc..conf..140Z
No abstract at ADS
Title: The Spectrum of the Inner Corona Observed during the Total
Solar Eclipse of 30 May, 1965
Authors: Jefferies, John T.; Orrall, Frank Q.; Zirker, J. B.
Bibcode: 1971SoPh...16..103J
Altcode:
A series of spectrograms of the inner solar corona were obtained at
the total solar eclipse of 30 May 1965 using a fast spectrograph with
a circular slit that recorded the spectrum from λ3000 to λ9000 at all
position angles around the limb simultaneously. In this paper absolute
intensity is given as a function of position angle for the stronger
lines and the continuum. In the coronal enhancement or condensation
centered at heliocentric position angle 293°, absolute intensity is
given for 34 forbidden emission lines and the continuum.
Title: The Excitation Equilibrium of Coronal Ions
Authors: Zirker, J. B.
Bibcode: 1970SoPh...11...68Z
Altcode:
The relative populations of levels of highly ionized Fe, Ni and Ca
ions have been calculated for physical conditions appropriate to the
solar corona. The results are presented in the form of tables. Line
intensity ratios in the EUV and visible that are sensitive to electron
density are discussed and compared with observations.
Title: Models for Coronal Condensations
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1969BAAS....1Q.246J
Altcode:
No abstract at ADS
Title: 22. Eission Line Spectrum of the Solar Corona
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1969LIACo..15..235J
Altcode: 1969MSRSL..17..235J
No abstract at ADS
Title: Emission line spectrum of the solar corona.
Authors: Jefferies, J. T.; Orrall, F. Q.; Zirker, J. B.
Bibcode: 1969MSRSL..25..235J
Altcode: 1969tisa.conf..235J
No abstract at ADS
Title: The Chromospheric Spectrum at the 1962 Eclipse
Authors: Dunn, R. B.; Evans, J. W.; Jefferies, J. T.; Orrall, F. Q.;
White, O. R.; Zirker, J. B.
Bibcode: 1968ApJS...15..275D
Altcode:
A joint expedition of the High Altitude Observatory, Sacramento Peak
Observatory, and the National Bureau of Standards obtained slitless
spectrograms of the flash spectrum at the February 5,1962, total eclipse
of the Sun. The spectrograms covered the wavelength range of about
3200 to 9100 A with a height resolution of 100 km. The spectrographic
equipment, the observations, the photometric calibration procedures,
and the methods adopted to reduce the large quantity of data are
described. The results are presented in a set of tables that show the
wavelength and identification (where known) of each of the 3500 lines
recorded. A separate set of tables lists the intensity of each line at
each height. The latter tables are ordered according to the element,
ionization stage, and multiplet number associated with the line.
Title: The Solar H and K Lines of Ionized Calcium
Authors: Zirker, J. B.
Bibcode: 1968SoPh....3..164Z
Altcode:
Photographic observations of the mean H and K profiles are given for
several positions across the solar disk (0.1 < μ < 0.6). The
core profiles of H and K are nearly identical at the same position on
the sun.
Title: On the Motions of Chromospheric Fine-Structure in a Weak Plage
Authors: Zirker, J. B.
Bibcode: 1967SoPh....1..204Z
Altcode:
Motions in an old center of activity have been studied at the limb
with the use of timeresolved Hα spectra. The observations were made
at intervals of 5 seconds over a period of 3/4 hour of good seeing at
Sacramento Peak Observatory.
Title: The Calcium H and K Lines in Solar Plages
Authors: Zirker, J. B.
Bibcode: 1965SAOSR.174..397Z
Altcode:
No abstract at ADS
Title: Introductory report
Authors: Zirker, J. B.
Bibcode: 1965IAUS...22..208Z
Altcode:
No abstract at ADS
Title: On the periods of large-amplitude photospheric oscillations
Authors: Zirker, J. B.
Bibcode: 1964AnAp...27..429Z
Altcode:
No abstract at ADS
Title: On the Oscillations of the Solar Atmosphere.
Authors: Schmidt, H. U.; Zirker, J. B.
Bibcode: 1963ApJ...138.1310S
Altcode:
No abstract at ADS
Title: Prominences and the Solar Corona.
Authors: Orrall, Frank Q.; Zirker, Jack B.
Bibcode: 1963IAUS...16...39O
Altcode:
No abstract at ADS
Title: Ionization and Excitation Equilibrium of CA II in the Solar
Atmosphere.
Authors: Athay, R. Grant; Zirker, J. B.
Bibcode: 1962ApJ...136..242A
Altcode:
Ionization and excitation configurations for Ca ii are computed for
conditions appropriate to the solar chromosphere. The populations
of energy levels are found to depart sharply from the LTE values at
corresponding values of T . The dominant ionization process of Ca ii is
shown to be via collisions from the 3D level and to exhibit fundamental
differences from H, He, and Mg I, as well as some similarities. For
electron densities and temperatures such as are expected in most of
the solar chromosphere and corona, the ratio Ca u/Ca iii is shown to
be essentially independent of electron density rather than directly
proportional, as predicted by the Saha equation. Computations of
opacities and occupation numbers indicate that the Ca ii H and K lines
in the Fraunhofer spectrum are formed near the top of the hydrogen
temperature plateau, where T 150OO , and that the Ca ii emission from
spicules arises from regions where T0 15000 rather than the much higher
temperature derived from profiles of hydrogen and helium lines
Title: Spectral Observations of Solar Chromospheric Spicules.
Authors: Zirker, J. B.
Bibcode: 1962ApJ...136..250Z
Altcode:
Chromospheric spicules have been observed with high spectral and
moderate spatial resolution in Ha, HP, D2, H, and K. The observations
confirm previous results published by Athay and Michard. Individual
spicules seem to have much larger line widths than do quiescent
prominences. All strong lines (including H and K) except D2 change
from self-reversed or flat-topped to Gaussian profiles with increasing
height. D2 has a Gaussian profile whose half-width increases with
height.
Title: Ionization and Excitation Equilibrium of Call in the Solar
Atmosphere.
Authors: Athay, R. Grant; Zirker, J. B.
Bibcode: 1962AJ.....67S.110A
Altcode:
The ionization and excitation equilibrium of Caii is computed for
conditions appropriate to the outer solar atmosphere. Populations of
energy levels are found to depart sharply from the LTE populations at
corresponding values of Te. The dominant ionization process of Caii is
shown to be via collisions from the 3D level and to exhibit fundamental
differences from H, He, and Mgi. For electron densities and temperatures
such as are expected in most of the chromosphere and corona, the ratio
Caii/Caiii is shown to be inversely proportional to electron density,
rather than directly proportional as predicted by the Saha equation. The
50% ionization stage of Caii is reached for Te =10000~140000, depending
upon the degree of radiative detailed balance attained in the H and
K lines. Computations of opacities and occupation numbers indicate
that the Caii H and K lines in the Fraunhofer spectrum are formed near
the top of the hydrogen temperature plateau where Te~l3 0000 and that
Te 15 0000 in the regions within spicules and prominences where the
Caii emission arises. % ionization stage of Caii is reached for Te
=10000~140000, depending upon the degree of radiative detailed balance
attained in the H and K lines. Computations of opacities and occupation
numbers indicate that the Caii H and K lines in the Fraunhofer spectrum
are formed near the top of the hydrogen temperature plateau where Te~l3
0000 and that Te 15 0000 in the regions within spicules and prominences
where the Caii emission arises. % ionization stage of Caii is reached
for Te =10000~140000, depending upon the degree of radiative detailed
balance attained in the H and K lines. Computations of opacities
and occupation numbers indicate that the Caii H and K lines in the
Fraunhofer spectrum are formed near the top of the hydrogen temperature
plateau where Te~l3 0000 and that Te 15 0000 in the regions within
spicules and prominences where the Caii emission arises.
Title: On the Brightness of Chromospheric Spicules.
Authors: Zirker, J. B.
Bibcode: 1962ApJ...135..515Z
Altcode:
Athay and Michard have interpreted the line widths of chromospheric
spicules in terms of an electron temperature of 50000 or higher. This
paper demonstrates that such high-temperature spicules would be
invisible in both Ha and K. A temperature below 20000 and an electron
density of 1011 are sufficient to produce the observed emission and
contrast in these lines.
Title: The Source Function in a Non-Equilibrium
Atmosphere. VIII. Solution for a Two Level Atom in a Finite
Atmosphere.
Authors: Thomas, R. N.; Zirker, J. B.
Bibcode: 1961ApJ...134..733T
Altcode:
The solution for the variation with optical depth of the source
function for a two-level atom in a finite atmosphere, with and without
temperature gradient, is presented. Even for an optical thickness
of the atmosphere as high as tO , the emergent intensity differs by
an order of magnitude from that for the semi-infinite case. For the
case of non-symmetric temperature gradient, the asymmetry in source
function is very considerably less than for B (T ). The use of a model
consisting of a finite slab isolated in space is a better approximation
for such high-excitation ions as He ii, in a low-excitation atmosphere
such as the sun, than is the model of a semi-infinite atmosphere.
Title: Departure from the Saha Equation for Ionized
Helium. II. Atmospheric Thicknesses too Small to Satisfy Detailed
Balance in the Resonance Lines.
Authors: Thomas, R. N.; Zirker, J. B.
Bibcode: 1961ApJ...134..740T
Altcode:
The results of the preceding paper for the variation of the source
function in a finite atmosphere are applied to the case of He ii. A
two-level atom is shown to be adequate for the treatment of the
ionization equilibrium. Some comment is made on the observed values
of Ly-a, Ly-fi, and 4686.
Title: The Coefficient of Thermal Conductivity in the Sun's
Atmosphere.
Authors: Orrall, F. Q.; Zirker, J. B.
Bibcode: 1961ApJ...134...63O
Altcode:
Expressions for the coefficients of thermal conductivity and
viscosity for a partially ionized mixture of hydrogen and helium are
given as functions of the number densities of the particles and the
temperature. Such expressions are required for energy-balance studies,
since it is well known that, over much of the sun's atmosphere,
ionization is far less advanced than one would predict from the Saha
formula. The effect of a magnetic field on the thermal conductivity
is discussed. It is pointed out that in the presence of a transverse
magnetic eld, even for a nearly ionized gas, the conduction of heat may
be due almost entirely to the neutral particles. A sample calculation
is given for physical conditions in a prominence.
Title: Heat Conduction and the Fine Structure of Solar
Prominences. I. Optically Thin Model Prominences.
Authors: Orrall, F. Q.; Zirker, J. B.
Bibcode: 1961ApJ...134...72O
Altcode:
It is found that large portions of some quiescent prominences may
remain with no detectable change in the form and brightness of their
threadlike fine structure for as long as 1O seconds. Since this is
at least one hundred times longer than the time required for the
prominence to radiate its internal energy, a steady source of energy
input is implied. The possibility is investigated that quasi-static
equilibrium is set up everywhere in a prominence thread between
radiative losses and energy supplied by the coronal heating source
and distributed by heat conduction. Transparency in all radiations
and constant pressure are assumed. When the effect of the magnetic
field on the thermal conductivity is considered, the computed model
prominences are much too narrow. It is suggested, however, that when
the opacity of prominence material is taken into account, the computed
models will be in much better agreement with observations.
Title: Departures from the Saha Equation for Ionized
Helium. I. Condition of Detailed Balance in the Resonance Lines.
Authors: Thomas, Richard N.; Zirker, J. B.
Bibcode: 1961ApJ...133..588T
Altcode:
Conditions for the validity of the assumption of detailed balance in
the Lyman lines of He ii are investigated. An opacity of 106 in Lyman-a
is required, which implies high opacity in the subordinate lines and
resonance continuum. The are computed, including the transfer problem
in the subordinate lines and resonance continuum.
Title: The Excitation of Ionized Helium
Authors: Thomas, R. N.; Zirker, J. B.
Bibcode: 1961LIACo..10..562T
Altcode: 1961MSRSL...4..561T; 1961LIACo..10..561T
No abstract at ADS
Title: The Energy Balance of Opaque Atmospheres.
Authors: Zirker, J. B.
Bibcode: 1960ApJ...131..684Z
Altcode:
Expressions for the net loss of radiative energy as a function of
depth in an opaque atmosphere are developed. The theory takes into
account the transfer of radiation through atmospheres whose hydrogen
and helium excitation departs from thermodynamic equilibrium. The
temperature-dependence of the energy loss from uniform model
chromospheres is calculated.
Title: The Energy Equilibrium of the Solar Chromosphere.
Authors: Zirker, J. B.
Bibcode: 1960AJ.....65R..59Z
Altcode:
Athay and Thomas (1956) investigated theoretically the temperature
structure of the solar chromosphere permitted by the requirements of
energy equilibrium. They were able to apply their results in either of
two extremes: either (a) under conditions of very high local opacity,
when the net emission at the wavelength in question is zero, or (b)
under conditions of very low local opacity when self-absorption can
be neglected. Methods for the treatment of situations intermediate to
these extremes have been developed since 1956. This paper presents
one formulation of these methods and applies them to the solar
chromosphere. Stable temperature intervals emerge below 10 000~K and
around 60 000~K based, respectively, on hydrogen and ionized helium
emission. The interval between 15 000~K and 40 000~K appears to be
unstable.
Title: The High-Temperature Excitation of Ionized Helium.
Authors: Zirker, J. B.
Bibcode: 1959ApJ...129..424Z
Altcode:
Calculations are presented here for the ezcitation and ionization
of He ii in atmospheres which depart from local thermodynamic
equilibrium. Lyman-a of hydrogen may strongly influence the observed
intensity of X 4686 of He ii. The temperature in the helium-emitting
regions of the solar chromosphere may range from 2.5 X 10 to 4 X 10 ,
depending upon the importance of the coupling of H and He ii in Lyman-a.
Title: The Metallic Chromosphere at the Khartoum Eclipse.
Authors: Zirker, J. B.
Bibcode: 1958ApJ...127..680Z
Altcode:
Logarithmic emission gradients and absolute integrated emission as
functions of height are presented for moderately strong metal lines
observed at the Khartoum eclipse by the High Altitude 0bservatory
expedition. The gradients are controlled by the combined action of
self-absorption and the chromospheric density gradient. Self-absorption
is evaluated for a number of metal lines, from which follows an estimate
of the density distribution through the low chromosphere The cores of
many metallic Fraunhofer lines appear to originate in the chromosphere.
Title: Time Available for the Optical Observation of an Earth
Satellite
Authors: Zirker, J. B.; Whipple, F. L.; Davis, R. J.
Bibcode: 1958sues.conf...23Z
Altcode:
No abstract at ADS
Title: The Orbit of a Small Earth Satellite
Authors: Davis, R. J.; Whipple, F. L.; Zirker, J. B.
Bibcode: 1958sues.conf....1D
Altcode:
No abstract at ADS
Title: An Investigation of the Solar Chromosphere.
Authors: Zirker, Jack Bernard
Bibcode: 1957PhDT.........1Z
Altcode:
No abstract at ADS