Author name code: harvey-jack
ADS astronomy entries on 2022-09-14
=author:"Harvey, John W." OR =author:"Harvey, Jack" OR =author:"Harvey, J. W."
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Title: A Compact Full-disk Solar Magnetograph based on miniaturization
of GONG instrument
Authors: Gosain, Sanjay; Harvey, Jack; Martinez-Pillet, Valentin;
Woods, Tom; Hill, Frank
Bibcode: 2022arXiv220707728G
Altcode:
Designing compact instruments is the key for the scientific exploration
by smaller spacecrafts such as cubesats or by deep space missions. Such
missions require compact instrument designs to have minimal instrument
mass. Here we present a proof of concept for miniaturization of the
Global Oscillation Network Group GONG instrument. GONG instrument
routinely obtains solar full disk Doppler and magnetic field maps of
the solar photosphere using Ni 676 nm absorption line. A key concept
for miniaturization of GONG optical design is to replace the bulky
Lyot filter with a narrow-band interference filter and reduce the
length of feed telescope. We present validation of the concept via
numerical modeling as well as by proof of concept observations.
Title: Magnetograph Saturation and the Open Flux Problem
Authors: Wang, Y. -M.; Ulrich, R. K.; Harvey, J. W.
Bibcode: 2022ApJ...926..113W
Altcode: 2021arXiv211209969W
Extrapolations of line-of-sight photospheric field measurements
predict radial interplanetary magnetic field (IMF) strengths that
are factors of ~2-4 too low. To address this open flux problem, we
reanalyze the magnetograph measurements from different observatories,
with particular focus on those made in the saturation-prone Fe I 525.0
nm line by the Mount Wilson Observatory (MWO) and the Wilcox Solar
Observatory (WSO). The total dipole strengths, which determine the
total open flux, generally show large variations among observatories,
even when their total photospheric fluxes are in agreement. However,
the MWO and WSO dipole strengths, as well as their total fluxes,
agree remarkably well with each other, suggesting that the two data
sets require the same scaling factor. As shown earlier by Ulrich et
al., the saturation correction δ -1 derived by comparing
MWO measurements in the 525.0 nm line with those in the nonsaturating
Fe I 523.3 nm line depends sensitively on where along the irregularly
shaped 523.3 nm line wings the exit slits are placed. If the slits are
positioned so that the 523.3 and 525.0 nm signals originate from the
same height, δ -1 ~ 4.5 at the disk center, falling to ~2
near the limb. When this correction is applied to either the MWO or
WSO maps, the derived open fluxes are consistent with the observed
IMF magnitude. Other investigators obtained scaling factors only
one-half as large because they sampled the 523.3 nm line farther out
in the wings, where the shift between the right- and left-circularly
polarized components is substantially smaller.
Title: The Solaris Solar Polar Mission: Exploring one of the last
Unexplored Regions of the Solar System
Authors: Hassler, D.; Newmark, J. S.; Gibson, S. E.; Duncan, N. A.;
Gosain, S.; Harvey, J. W.; Wuelser, J. P.; Woods, T. N.
Bibcode: 2020AGUFMSH0110003H
Altcode:
The solar poles are one of the last unexplored regions of the solar
system. Although Ulysses flew over the poles in the 1990s, it did
not have remote sensing instruments onboard to probe the Sun's polar
magnetic field or surface/sub-surface flows. I will discuss Solaris,
a proposed Solar Polar MIDEX mission to fly over the solar poles at 75
degrees inclination to address key outstanding, breakthrough problems
in solar physics, & fill holes in our scientific understanding
that will not be addressed by current or planned future missions. Such
a small, focused, "paradigm-breaking" mission is achievable now with
existing launchers and technology, & is enabled by miniaturized
instrument technology such as the Compact Doppler Magnetograph (CDM),
developed for Solaris to provide magnetic field & Doppler velocity
measurements in a small (15kg) package. Solaris will also provide
enabling observations for space weather research & stimulate future
research through new unanticipated discoveries.
Title: Deconstructing Sunlight - A Community Enterprise
Authors: Harvey, J. W.
Bibcode: 2020SoPh..295...70H
Altcode:
Good fortune allowed me to have a career in solar research. With the
aid of many generous and gifted colleagues, I have tried to learn more
about the Sun's magnetic and velocity fields through observation and
instrumentation development. These interests captured me early and
remain strong. In this memoir I describe my path through 60 years of
solar research that was sometimes random but did not deviate much from
my core interests. The chromospheric magnetic field and helioseismology
have been especially intriguing and frequently rewarding topics.
Title: Ca II 854.2 nm spectropolarimetry compared with ALMA and with
scattering polarization theory
Authors: Harvey, J. W.; Solis Team
Bibcode: 2020IAUS..354...42H
Altcode:
Ca II 854.2 nm spectropolarimetric observations of the Sun are
compared with nearly simultaneous ALMA observations. These two types of
chromospheric observations show rough agreement but also several notable
differences. High-sensitivity (≃ 0.01%) observations reveal ubiquitous
linear polarization structures across the solar disk in the core of
the 854.2 nm line that are consistent with previous theoretical studies.
Title: Distant Face-On Spiral
Authors: Keller, Warren; Mazlin, Steve; Harvey, Jack
Bibcode: 2018S&T...135c..75K
Altcode:
No abstract at ADS
Title: Measurements of Photospheric and Chromospheric Magnetic Fields
Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay;
Centeno, Rebecca
Bibcode: 2018smf..book...37L
Altcode:
No abstract at ADS
Title: Harmonizing Mangnetograph Data with end-to-end Instrument
Simulations
Authors: Plowman, J.; Petrie, G. J. D.; Pillet, V. M.; Criscuoli,
S.; Harvey, J. W.; Marble, A.; Uitenbroek, H.
Bibcode: 2017AGUFMSH13A2460P
Altcode:
There are a number of instruments, such as NSO's GONG and SOLIS/VSM,
which measure the magnetic field of the Sun's photosphere. However,
their measurements are not fully consistent, and the factors responsible
for the differences have yet to be isolated. I report on a new effort
to resolve them - we simulate the observing processes from end to
end, beginning with 3D MHD simulations. This allows us to compare the
synthetic observations produced with the MHD simulations' 'ground truth'
and identify the effects of the observational factors at play. The
result will be the best ever calibration of a magnetograph, giving
magnetic field models based on these data a much firmer foundation.
Title: Measurements of Photospheric and Chromospheric Magnetic Fields
Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay;
Centeno, Rebecca
Bibcode: 2017SSRv..210...37L
Altcode: 2015arXiv151006865L; 2015SSRv..tmp..115L
The Sun is replete with magnetic fields, with sunspots, pores
and plage regions being their most prominent representatives on
the solar surface. But even far away from these active regions,
magnetic fields are ubiquitous. To a large extent, their importance
for the thermodynamics in the solar photosphere is determined by the
total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic
structures are shuffled around by the motion of granules, the high-flux
areas like sunspots or pores effectively suppress convection, leading
to a temperature decrease of up to 3000 K. The importance of magnetic
fields to the conditions in higher atmospheric layers, the chromosphere
and corona, is indisputable. Magnetic fields in both active and
quiet regions are the main coupling agent between the outer layers
of the solar atmosphere, and are therefore not only involved in the
structuring of these layers, but also for the transport of energy from
the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and
especially in the chromosphere, is crucial to deepen our understanding
not only for solar phenomena such as chromospheric and coronal
heating, flares or coronal mass ejections, but also for fundamental
physical topics like dynamo theory or atomic physics. In this review,
we present an overview of significant advances during the last decades
in measurement techniques, analysis methods, and the availability of
observatories, together with some selected results. We discuss the
problems of determining magnetic fields at smallest spatial scales,
connected with increasing demands on polarimetric sensitivity and
temporal resolution, and highlight some promising future developments
for their solution.
Title: Update on a Solar Magnetic Catalog Spanning Four Solar Cycles
Authors: Vargas-Acosta, Juan Pablo; Munoz-Jaramillo, Andres; Vargas
Dominguez, Santiago; Werginz, Zachary; DeLuca, Michael D.; Longcope,
Dana; Harvey, J. W.; Windmueller, John; Zhang, Jie; Martens, Petrus C.
Bibcode: 2017SPD....4811202V
Altcode:
Bipolar magnetic regions (BMRs) are the cornerstone of solar
cycle propagation, the building blocks that give structure to the
solar atmosphere, and the origin of the majority of space weather
events. However, in spite of their importance, there is no homogeneous
BMR catalog spanning the era of systematic solar magnetic field
measurements. Here we present the results of an ongoing project to
address this deficiency applying the Bipolar Active Region Detection
(BARD) code to magnetograms from the 512 Channel of the Kitt Peak
Vaccum Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically
identifies BMRs and tracks them as they are rotated by differential
rotation. The output of the automatic detection is supervised by a human
observer to correct possible mistakes made by the automatic algorithm
(like incorrect pairings and tracking mislabels). Extra passes are made
to integrate fragmented regions as well as to balance the flux between
BMR polarities. At the moment, our BMR database includes nearly 10,000
unique objects (detected and tracked) belonging to four separate solar
cycles (21-24).
Title: Mi Gauss es su Gauss: Lessons from Cross-Calibrating 40 years
of Full Disk Magnetograms
Authors: Werginz, Zachary; Munoz-Jaramillo, Andres; Martens, Petrus
C.; Harvey, J. W.
Bibcode: 2017SPD....4811102W
Altcode:
Full-disk line-of-sight magnetograms from the Kitt Peak Vacuum Telescope
(KPVT) are a highly valuable, but underutilized, source of data for
understanding long-term solar variability. Here we present the results
of a project for obtaining a cross-callibrated series of magnetograms
spanning 40 years including KPVT (512 and SPMG), SOHO/MDI and SDO/HMI
magnetographs. The biggest challenge we face is empirically identifying
a calibration factor and estimate of uncertainty between instruments
with little temporal overlap.Here we propose a method that fragments
magnetograms into spherical quadrangles bounded by latitudes and
longitudes and calculates various information such as total area, mean
flux density, and distance from disk center. Our main assumption is that
the Sun does not change significantly over daily time periods.First
a magnetogram to be calibrated is differentially rotated to match
a reference magnetogram in time. Then the smaller magnetogram is
interpolated into the larger one to account for sub-pixel heliographic
coordinates. We then produce equally spaced bands of latitude and
longitude determined from a fragmentation parameter. These are used
to map out regions on each magnetogram that are expected to relay
the same information. Our efforts to cross-calibrate lead to results
that vary with fragmentation parameters, the difference in time of
selected magnetograms, and distance from disk center.Given that this
cross-callibrated series will be made publically available, we are
looking for constructive criticism, suggestions, and feedback. Please
join us in making these data as good as they can be.
Title: Lewis M. Rutherfurd and the First Photograph of Solar
Granulation
Authors: Harvey, J. W.; Briggs, John W.; Prosser, Sian
Bibcode: 2017SPD....4811201H
Altcode:
A major astronomical controversy of the mid-19th century
was discordant descriptions of the small scale structure of the solar
surface. Visual observers contradicted each other by describing the
surface as consisting of “corrugations”, “willow leaves”,
“rice grains”, “cumuli”, “thatch”, “granules”,
etc. Early photographs of the solar surface were not good enough
to settle the controversy. The French astronomer Jules Janssen is
credited with the first 1876 photographs that clearly showed what we
now call solar granulation (1876, CRAS 82, 1363). Upon seeing these
images, New Yorker Lewis M. Rutherfurd (1878, MNRAS 38, 410) praised
the high quality of Janssen’s images but asserted that he had also
photographed granulation as early as 1871 using collodion wet plates. He
sent copies of his best photograph to the Royal Astronomical Society to
support his assertion. Curious about his claim, Briggs and Harvey set
up Rutherfurd’s 13-inch achromatic refractor on Kitt Peak and found
that it easily showed well-resolved solar granulation, so his claim
might well have been justified. But without his plates we could not
confirm the claim. For 140 years the copies of Rutherfurd’s best solar
photograph remained in the archives of the Royal Astronomical Society
and were recently discovered by Prosser (RAS Photographs A3/001B and
A3/002). By coincidence a few days later, Briggs found the original
August 11, 1871 plate. Despite poor condition these photographs show
solar granulation. There are at least two other possible early claimants
(Reade; Vogel) but their plates are almost certainly lost. Rutherfurd
was a master of astronomical instrumentation and photography. He
was reticent about his work, letting results speak for themselves,
so it is satisfying to find that he was justified in making his claim
of priority.
Title: The best of both worlds: Using automatic detection and limited
human supervision to create a homogenous magnetic catalog spanning
four solar cycles
Authors: Muñoz-Jaramillo, Andres; Werginz, Zachary; Vargas-Acosta,
Juan Pablo; DeLuca, Michael; Windmueller, J. C.; Zhang, Jie; Longcope,
Dana; Lamb, Derek; DeForest, Craig; Vargas-Domínguez, Santiago;
Harvey, Jack; Martens, Piet
Bibcode: 2016bida.conf.3194M
Altcode: 2022arXiv220311908M
Bipolar magnetic regions (BMRs) are the cornerstone of solar
variability. They are tracers of the large-scale magnetic processes
that give rise to the solar cycle, shapers of the solar corona,
building blocks of the large-scale solar magnetic field, and significant
contributors to the free-energetic budget that gives rise to flares and
coronal mass ejections. Surprisingly, no homogeneous catalog of BMRs
exists today, in spite of the existence of systematic measurements of
the magnetic field since the early 1970's. The purpose of this work is
to address this deficiency by creating a homogenous catalog of BMRs
from the 1970's until the present. For this purpose, in this paper
we discuss the strengths and weaknesses of the automatic and manual
detection of BMRs and how both methods can be combined to form the basis
of our Bipolar Active Region Detection (BARD) code and its supporting
human supervision module. At present, the BARD catalog contains more
than 10,000 unique BMRs tracked and characterized during every day
of their observation. Here we also discuss our future plans for the
creation of an extended multi-scale magnetic catalog combining the
SWAMIS and BARD catalogs.
Title: Full-Disk Chromospheric Vector Magnetograms with Ca II 854.2
nm line: Some Promising Applications
Authors: Gosain, Sanjay; Harvey, J. W.; Harker, Brian; Pillet, V. M.;
Pevtsov, Alexei A.; Marble, Andrew R.; Bertello, Luca; + SOLIS-Team
Bibcode: 2016SPD....47.0103G
Altcode:
Over the last decade, the focus of solar magnetometry has shifted
outward from the photosphere to the chromospheric layers. The reasons
for this are many. With regards to instrumentation faster detectors
with more sensitivity have become available, as have fast electro-optic
modulators. Also, there are several potential benefits of observing
vector fields in the chromospheric layer as the magnetic field is
more force-free in this layer as compared to the photosphere. Coronal
force-free field extrapolations are more reliable using chromospheric
fields as the lower boundary condition and free magnetic energy is
readily computed using the magnetic virial theorem. Recently, a full
Stokes polarimeter for the chromospheric Ca II 854.2 nm spectral line
was developed and installed in the Vector Spectromagnetograph (VSM)
instrument on the Synoptic Optical Long-term Investigations of the
Sun (SOLIS) telescope. We present details of this new polarimeter,
full disk spectropolarimetric observations and vector magnetograms
of the chromosphere, and examples of some promising applications
(e.g., maps of normal component of electric current density in the
chromosphere, free magnetic energy estimated using virial theorem,
and non-potentiality parameter magnetic shear angle).This work
utilizes SOLIS data obtained by the NSO Integrated Synoptic Program
(NISP), managed by the National Solar Observatory, which is operated
by the Association of Universities for Research in Astronomy (AURA),
Inc. under a cooperative agreement with the National Science Foundation
Title: Current Status of the SOLIS Program: Improved and New Data
Products
Authors: Bertello, Luca; Britanik, John; Callahan, Lorraine; Gosain,
Sanjay; Harker, Brian; Harvey, J. W.; Hughes, A.; Marble, A.; Pevtsov,
Alexei A.; Wentzel, Thomas
Bibcode: 2016SPD....47.1002B
Altcode:
Over the past year the Synoptic Optical Long-term Investigations of the
Sun (SOLIS) team has made significant improvements to the data products
provided to the solar and heliospheric community. In particular,
a considerable effort has been dedicated to reprocess the archive of
vector and longitudinal photospheric magnetograms, from 2003 to present,
using the latest production code. This endeavor is now near completion
and will assure that all derived magnetic products, such as synoptic
maps and flux time series, are consistently calibrated. In addition,
new products have been recently developed. For example, time series of
daily averages of the Sun's polar magnetic field derived from full-disk
photospheric FeI 630.15 nm longitudinal magnetograms are now available
from the SOLIS website at solis.nso.edu/0/vsm/vsm_plrfield.html.New
intensity calibration of high resolution Ca II K & H spectra from
the Integrated Sunlight Spectrometer (ISS) led to significant reduction
in daily variations of parameters derived from these spectra. The
SOLIS team will soon also release Carrington synoptic maps for the
three components of the photospheric magnetic field derived from vector
measurements taken in the Fe I 630.15 nm spectral line. The addition,
in late 2015, of a new Ca II 854.2 nm full-Stokes polarimeter into
the SOLIS core program of magnetic observations will make available to
the community daily chromospheric measurements of the complete Stokes
polarization vector.We present here a summary of these improvements,
with particular emphasis on the new products that can be accessed
from the SOLIS data page at solis.nso.edu/0/solis_data.html. For
a description of the diagnostic capability of the new Ca II 854.2
nm spectro-polarimeter and preliminary results we refer to other
presentations by SOLIS team members at this meeting.This work utilizes
SOLIS data obtained by the NSO Integrated Synoptic Program (NISP),
managed by the National Solar Observatory, which is operated by
the Association of Universities for Research in Astronomy (AURA),
Inc. under a cooperative agreement with the National Science Foundation.
Title: Ca II 854.2 nm Spectromagnetograms: A Powerful Chromospheric
Diagnostic
Authors: Harvey, J. W.; Bertello, Luca; Branston, D.; Britanik, J.;
Bulau, S.; Cole, L.; Gosain, Sanjay; Harker, Brian; Jones, Harrison P.;
Marble, A.; Martinez Pillet, V.; Pevtsov, A.; Schramm, K.; Streander,
Kim; Villegas, H.
Bibcode: 2016SPD....4710106H
Altcode:
The transition from physical dominance by plasma flows in the
photosphere to magnetic pressure in the solar chromosphere motivates
as many diagnostic observations as possible across this important
region. Among the few ground-accessible spectral lines formed within
the chromosphere, the Ca II 854.2 nm line has the desirable properties
of presence everywhere on the solar disk, Zeeman sensitivity, and
narrow line width. Mapped observations of circular polarization within
this line (spectromagnetograms) have been made at NSO infrequently
since 1974, with regular daily full-disk observations starting in
August 1996. Full-disk spectral observations of the complete Stokes
polarization vector are now being made regularly since November
2015. It is not easy to estimate chromospheric magnetic field
properties from the 854.2 nm line profile polarization. To provide
rough quick-look vector field maps we found that the weak-field
approximation provides a fair first estimate of the line-of-sight
component but appears to be too simple to interpret the transverse
magnetic field from frequently asymmetric, linearly-polarized line
profiles. More realistic estimates of the chromospheric vector field,
short of extremely lengthy, full 3D, non-local radiative transfer
inversions, are being investigated. We briefly introduce recent
instrumental modifications and observational characteristics, sample
observations, and results concerning the expansion of the chromospheric
field with increasing height, the presence of large areas of weak,
nearly horizontal fields, and field estimates in plages, sunspots,
flares, filaments, and filament channels. The Stokes spectra will be
freely available to the community.This work utilizes SOLIS data obtained
by the NSO Integrated Synoptic Program (NISP), managed by the National
Solar Observatory, which is operated by the Association of Universities
for Research in Astronomy (AURA), Inc. under a cooperative agreement
with the National Science Foundation.
Title: HMI Vector and Uncertainty Carrington Synoptic Maps
Authors: Bertello, Luca; Hughes, A.; Gosain, Sanjay; Harker, Brian;
Harvey, J. W.; Marble, Andrew R.; Pevtsov, Alexei A.
Bibcode: 2016SPD....47.1001B
Altcode:
Based on our experience with data from the Vector Spectromagnetograph
(VSM) instrument, which is part of the Synoptic Optical Long-term
Investigations of the Sun (SOLIS)facility, we have produced HMI vector
and uncertainty synoptic maps for all Carrington rotations from May
2010 through December 2015. HMI observations provide 12-minute cadence
magnetograms, both for longitudinal and full-Stokes measurements. For
this investigation we have used only two magnetograms per day, 12
hours apart, which are sufficient to produce accurate maps in the
longitude-sine(latitude) projection with 1x1 square-degree resolution
at the equator. From both the HMI longitudinal and vector magnetograms
we have computed radial-flux and spatial-variance synoptic maps. For
the longitudinal data, we have included pole-filled radial-flux maps,
and for the vector data, we have included synoptic maps of the poloidal
and toroidal magnetic flux.We describe here the procedure to generate
those maps and discuss some of their main features. A comparison with
similar products from the SOLIS/VSM is also addressed. The HMI data
used are courtesy of NASA/SDO and HMI science teams.
Title: Contextualizing Solar Cycle 24: Report on the Development of
a Homogenous Database of Bipolar Active Regions Spanning Four Cycles
Authors: Munoz-Jaramillo, A.; Werginz, Z. A.; DeLuca, M. D.;
Vargas-Acosta, J. P.; Longcope, D. W.; Harvey, J. W.; Martens, P.;
Zhang, J.; Vargas-Dominguez, S.; DeForest, C. E.; Lamb, D. A.
Bibcode: 2015AGUFMSH33D..06M
Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).In
this presentation we discuss an ongoing project to address this
deficiency by applying our Bipolar Active Region Detection (BARD)
code on full disk magnetograms measured by the 512 (1975-1993) and
SPMG (1992-2003) instruments at the Kitt Peak Vacuum Telescope (KPVT),
SOHO/MDI (1996-2011) and SDO/HMI (2010-present). First we will discuss
the results of our revitalization of 512 and SPMG KPVT data, then we
will discuss how our BARD code operates, and finally report the results
of our cross-callibration.The corrected and improved KPVT magnetograms
will be made available through the National Solar Observatory (NSO)
and Virtual Solar Observatory (VSO), including updated synoptic maps
produced by running the corrected KPVT magnetograms though the SOLIS
pipeline. The homogeneous active region database will be made public
by the end of 2017 once it has reached a satisfactory level of quality
and maturity. The Figure shows all bipolar active regions present in
our database (as of Aug 2015) colored according to the sign of their
leading polarity. Marker size is indicative of the total active region
flux. Anti-Hale regions are shown using solid markers.
Title: Design of a Full Stokes Polarimeter for Chromospheric
Measurements with SOLIS/VSM
Authors: Gosain, S.; Harvey, J. W.
Bibcode: 2015IAUS..305..186G
Altcode:
The synoptic observations of the magnetic field of the Sun have
continued at the National Solar Observatory (NSO) since 1970s. The
daily full-disk maps of the longitudinal magnetic field are regularly
combined to form Carrington maps of the photospheric magnetic flux per
solar rotation. These maps continue to be used by the international
research community for a variety of studies related to solar magnetism
as well as for space weather studies. The current NSO synoptic facility
is the Synoptic Optical Long-term Investigation of the Sun (SOLIS),
which regularly provides photospheric vector and chromospheric
longitudinal full-disk magnetograms, among other data products. In
the near future, an upgrade of SOLIS to produce chromospheric vector
magnetograms is planned. We present the design of a new polarization
modulator package for full Stokes polarimetry of the chromospheric Ca
II 854.2 nm spectral line.
Title: Two Centuries of Solar Polarimetry
Authors: Harvey, J. W.
Bibcode: 2015IAUS..305....2H
Altcode:
In 1811, François Arago observed the disk of the Sun with his "lunette
polariscopique". From the absence of detectable polarization compared
with his laboratory observations of glowing solids, liquids, and
flames he concluded that the Sun's visible surface is an incandescent
gas. From this beginning, thanks to orders of magnitude technology
improvements, a remarkable amount of what we know about the physics
of the Sun has continued to flow from solar polarimetry. This short
review compares some selected polarimetric discoveries with subsequent
recent observations to illustrate the tremendous progress of solar
polarimetry during the last two centuries.
Title: Understanding the Chromospheric Magnetic Field
Authors: Jin, C. L.; Harvey, J. W.; Pietarila, A.
Bibcode: 2014ASPC..489...77J
Altcode:
The chromospheric magnetic field is an important and essential component
for understanding solar atmospheric fields. Due to the problems
of polarization radiation transfer in the chromosphere and the low
detective sensitivity of chromospheric spectrum lines, observations
of chromospheric magnetic fields are very difficult, so studies
of chromospheric fields are infrequent. However, the understanding
of chromospheric fields is evolving. In this report, we summarize
our current empirical knowledge and basic physical understanding of
chromospheric fields. We concentrate on the comparison of magnetic
fields in the photosphere and chromosphere, and then display their
difference.
Title: Chromospheric Magnetic Fields in the X1.2 Flare of January
7, 2014
Authors: Harvey, J. W.
Bibcode: 2014AAS...22412321H
Altcode:
Measurements of magnetic fields in chromospheric flares are scarce and
many basic magnetic properties of flares are uncertain. A four-ribbon
X1.2 flare occurred near disk center on January 7, 2014. It was
observed at the time of peak soft X-ray emission with the NSO SOLIS
vector spectromagnetograph using the 854.2 nm line of Ca II. A full
vector modulator for this wavelength is under construction, but for
this observation only intensity (I) and circularly polarized (V)
spectral line profiles were obtained. Given the large variations
of physical properties along sight lines through the chromosphere,
especially in a flare, it is difficult to measure the magnetic
field. We apply three simple techniques to estimate chromospheric and
photospheric average flux densities. One method uses the wavelength
difference between selected portions of the I±V line profiles. A
second method integrates |V/I| over portions of the line profile. A
third method uses the simple weak-field approximation, V ∝ dI/dλ,
but with modifications to the observed I profile to better match the
V profile. As is well known in flares, there are asymmetry and line
width variations in the emission and absorption line profiles indicating
complicated mass motions along lines of sight. A tentative conclusion
is that in most areas of the flare the average magnetic flux density
along the line of sight is very similar to the underlying photosphere
but usually weaker. Obtaining more robust measurements and conclusions
requires exploration by forward modeling of the observations with
realistic model atmospheres. Useful inversions may someday be possible
if the atmosphere model parameters to be fit can be restricted enough
to match the information content of the observed spectra.
Title: White-Light Observations of Major Flares Compared to Total
Solar Irradiance and Short-Wavelength Observations
Authors: Petrie, Gordon; Kopp, Greg; Harvey, J. W.
Bibcode: 2014AAS...22412327P
Altcode:
The NSO’s GONG network produces “white light” (WL) continuum
intensity images from one-minute integrations averaged across a 0. Å
wide band pass centered at 676 Å at one minute cadence using six
sites worldwide. Clear WL signatures of solar flares are present in
GONG intensity data for only the largest flares because of low spatial
resolution (2.5 arcsec pixel size). For six major flares (GOES class
X6.5 - X28) observed by GONG, we compare integrated GONG full-disk
WL intensity curves with SORCE/TIM total solar irradiance (TSI)
measurements. Distinctive p-mode signatures are evident in both GONG
and SORCE time series, though the correlation between GONG and SORCE
data varies from flare to flare. In some cases a clear TSI peak and an
interruption of the GONG p-mode pattern accompany the flare. The flare
signature is generally weaker in the GONG data, suggesting that most of
the TIM flare signal arises from wavelengths shorter than the GONG band
pass. The flare kernels nevertheless are clear and last many minutes
in the spatially resolved GONG image time series. We also compare
the GONG active region intensity observations with shorter-wavelength
data. In one case observed by TRACE, the GONG and TRACE WL curves are
very similar and the TRACE 160 Å curve shows a significant precursor
and a long tail. In most cases the GONG WL and RHESSI 25-100 keV counts
appear well correlated in time. This work utilizes GONG data obtained
by the NSO Integrated Synoptic Program (NISP), managed by the National
Solar Observatory, which is operated by AURA, Inc. under a cooperative
agreement with the National Science Foundation.
Title: Image Quality of SOLIS/VSM in Helium vs. Nitrogen
Authors: Harvey, J. W.
Bibcode: 2014arXiv1405.7967H
Altcode:
The National Solar Observatory (NSO) Synoptic Optical Long-term
Investigations of the Sun (SOLIS) Vector SpectroMagnetograph (VSM)
is sealed and was designed to be filled with helium at slightly above
ambient pressure. After 11 years of operation filled with helium,
an acute shortage of helium prompted a test using nitrogen as the
fill gas. Four months of nitrogen-filled observations in 2014 are
compared the same months in 2013 with helium fill. On average, the
image sharpness is slightly degraded when using nitrogen.
Title: NGC 2070, the Tarantula Nebula
Authors: Mazlin, Steve; Harvey, Jack
Bibcode: 2014S&T...127d..77M
Altcode:
No abstract at ADS
Title: The Sun in Time
Authors: Harvey, J. W.
Bibcode: 2014crh..book...47H
Altcode:
No abstract at ADS
Title: Three Decades of Helioseismology at Kitt Peak and South Pole
Authors: Harvey, J. W.
Bibcode: 2013ASPC..478...51H
Altcode:
This is a personal, very selective, brief review of the history of
some work in helioseismology based on observations at Kitt Peak and
at South Pole from 1964 through 1994.
Title: Zeemanfit: Use and Development of the solis_vms_zeemanfit code
Authors: Hughes, Anna L. H.; Harvey, Jack; Marble, Andrew R.; Pevtsov,
Alexei A.
Bibcode: 2013arXiv1312.2026H
Altcode:
The purpose of the SOLIS Zeemanfit Code is to provide a
straight-forward, easily checked measure of the total magnetic-field
strength in the high-strength umbral regions of the solar disk. In the
highest-strength regions, the Zeeman splitting of the 6302-angstrom
Fe line becomes wide enough for the triplet nature of the line to be
visible by eye in non-polarized light. Therefore, a three-line fit
to the spectra should, in principle, provide a fairly robust measure
of the total magnetic-field strength. The code uses the Level-1.5
spec-cube data of the SOLIS VSM 6302-vector observations (specifically
the Stokes-I and Stokes-V components) to fit the line profiles at each
appropriate pixel and calculate the magnetic-field-strength from the
line-center separation of the two fit 6302.5 sigma-components. The
6301.5-angstrom Fe line is also present and fit in the VSM 6302-vector
data, but it is an anomalous-Zeeman line with a weaker response to
magnetic fields. Therefore, no magnetic- field measure is derived from
this portion of the spectral fit.
Title: Improvements to the SOLIS Program: New Data Products and
Recent Science Results
Authors: Bertello, Luca; Callahan, L.; Gusain, S.; Harker, B.; Harvey,
J. W.; Hughes, A.; Marble, A. R.; Pevtsov, A. A.; SOLIS
Bibcode: 2013SPD....44..135B
Altcode:
Over the past two years the Synoptic Optical Long-term Investigations
of the Sun (SOLIS) Team made significant improvements to the data
products provided to the solar and heliospheric community. Longitudinal
photospheric magnetograms were consistently calibrated to form a
uniform magnetic flux series from 2003-present. Improvements in image
geometric corrections enabled providing the high spectral resolution
spectra for each pixel in full disk images taken in Fe 630.2 nm and
Ca II 854.2 nm. New treatment of high resolution spectra from the
Integrated Sunlight Spectrometer (ISS), led to significant reduction
in daily variations of parameters derived from these spectra. Several
new data products were developed, including simultaneous photospheric
and chromospheric longitudinal magnetograms derived from the core and
wings of Ca II 854.2 nm line, and derivation of field strength via
fitting non-polarized I-profiles of Fe I 630.2 nm. We present here a
summary of recent changes to this database, with particular emphasis on
chromospheric longitudinal magnetic field and intensity measurements,
photospheric vector magnetic field products, and high-spectral
resolution integrated sunlight data. Some significant results derived
from the analysis of these data sets will also be presented, while
more detailed descriptions about specific topics will be referred to
other SOLIS-related studies presented at this meeting.
Title: New Synoptic Measurements of Umbral Magnetic Fields
Authors: Harvey, J. W.; Hughes, A.; Marble, A.; Livingston, W. C.;
Pevtsov, A.; SOLIS Team
Bibcode: 2013SPD....44..112H
Altcode:
Apparent cyclic and secular changes of sunspot umbral intensities and
magnetic field strengths have been reported for many decades. Monthly
measurements since 1998 show changes that have been interpreted
as a decline in sunspot vigor that, if continued, may lead to very
few visible sunspots in forthcoming cycles (Livingston, Penn, and
Svalgaard 2012, ApJ 757, L8). This dramatic notion is controversial
(e.g. Nagovitsyn, Pevtsov, and Livingston 2012, ApJ 758, L20),
and additional observational evidence is needed based on a minimum
of interpretational steps and selection effects. The SOLIS vector
spectromagnetograph has recorded photospheric spectra around 630.2
nm over the full solar disk daily since late 2003 with spatial and
spectral pixel dimensions of about one arc second and 2.3 pm. We fit
the unpolarized intensity spectra in sunspots with a simple Zeeman
triplet model using a single field strength, which works well if
the field strength exceeds about 2 kG and the individual spectra
are not affected by strong Doppler and/or Zeeman variations. The
derived total field strengths may be compared with independent
spectrograph-based measurements from NSO, Hinode/SP, and Mt. Wilson
and with filter-based measurements from SoHO/MDI and SDO/HMI. NSO
plans to implement this reduction for all suitable archived SOLIS
spectra and to continue daily umbral field strength measurements
as cycle 24 proceeds. Preliminary comparisons show good agreements
in some cases and systematic differences in others.Abstract (2,250
Maximum Characters): Apparent cyclic and secular changes of sunspot
umbral intensities and magnetic field strengths have been reported for
many decades. Monthly measurements since 1998 show changes that have
been interpreted as a decline in sunspot vigor that, if continued, may
lead to very few visible sunspots in forthcoming cycles (Livingston,
Penn, and Svalgaard 2012, ApJ 757, L8). This dramatic notion is
controversial (e.g. Nagovitsyn, Pevtsov, and Livingston 2012, ApJ
758, L20), and additional observational evidence is needed based on
a minimum of interpretational steps and selection effects. The SOLIS
vector spectromagnetograph has recorded photospheric spectra around
630.2 nm over the full solar disk daily since late 2003 with spatial
and spectral pixel dimensions of about one arc second and 2.3 pm. We
fit the unpolarized intensity spectra in sunspots with a simple Zeeman
triplet model using a single field strength, which works well if the
field strength exceeds about 2 kG and the individual spectra are not
affected by strong Doppler and/or Zeeman variations. The derived total
field strengths may be compared with independent spectrograph-based
measurements from NSO, Hinode/SP, and Mt. Wilson and with filter-based
measurements from SoHO/MDI and SDO/HMI. NSO plans to implement this
reduction for all suitable archived SOLIS spectra and to continue daily
umbral field strength measurements as cycle 24 proceeds. Preliminary
comparisons show good agreements in some cases and systematic
differences in others.
Title: The Sun in Time
Authors: Harvey, J. W.
Bibcode: 2013SSRv..176...47H
Altcode: 2010SSRv..tmp..187H
The Sun varies in time over at least twenty orders of magnitude. In
this highly selective look at a vast subject, the focus is on solar
variations related to the magnetic field structure of the heliosphere
since these changes affect the propagation of cosmic rays in the
heliosphere. The root of the changes is the magnetic field pattern near
the solar surface. Some key aspects of the behavior of this pattern
are reviewed. Recent solar activity has been unlike any experienced in
living memory and several of the observed oddities are noted. Included
here is a first attempt to directly compare three decades of magnetic
field measurements in coronal holes with the heliospheric magnetic field
at 1 AU. Results support the idea that nearly all the open magnetic
flux from the Sun originates in coronal holes (including those close
to active regions).
Title: Synoptic Mapping of Chromospheric Magnetic Flux
Authors: Jin, C. L.; Harvey, J. W.; Pietarila, A.
Bibcode: 2013ApJ...765...79J
Altcode:
We used daily full-disk Ca II 854.2 nm magnetograms from the Synoptic
Optical Long Term Investigations of the Sun (SOLIS) facility to
study the chromospheric magnetic field from 2006 April through 2009
November. We determined and corrected previously unidentified zero
offsets in the SOLIS magnetograms. By tracking the disk passages of
stable unipolar regions, the measured net flux densities were found to
systematically decrease from the disk center to the limb by a factor
of about two. This decrease was modeled using a thin flux tube model
with a difference in signal formation height between the center and
limb sides. Comparison of photospheric and chromospheric observations
shows that their differences are largely due to horizontal spreading of
magnetic flux with increasing height. The north polar magnetic field
decreased nearly linearly with time during our study period while
the south polar field was nearly constant. We used the annual change
in the viewing angle of the polar regions to estimate the radial and
meridional components of the polar fields and found that the south
polar fields were tilted away from the pole. Synoptic maps of the
chromospheric radial flux density distribution were used as boundary
conditions for extrapolation of the field from the chromosphere into the
corona. A comparison of modeled and observed coronal hole boundaries
and coronal streamer positions showed better agreement when using the
chromospheric rather than the photospheric synoptic maps.
Title: Ca II 854.2 nm Bisectors and Circumfacular Regions
Authors: Pietarila, A.; Harvey, J. W.
Bibcode: 2013ApJ...764..153P
Altcode:
Active regions appear bright in Ca II 854.2 nm line core intensity
while the surrounding areas, referred to as circumfacular regions, are
darker than the active region or the quiet Sun. We use Synoptic Optical
Long-term Investigations of the Sun Vector Spectromagnetograph Ca II
854.2 nm data (photospheric and chromospheric full disk magnetograms
as well as high spectral resolution Stokes I and V profiles) to study
the connection between magnetic canopies, circumfacular regions, and Ca
II 854.2 nm bisector amplitudes (spans). The line bisector amplitude
is reduced in circumfacular regions, where the 3 minute period power
in chromospheric Hα intensity oscillations is also reduced relative
to the surrounding quiet Sun. The latter is consistent with magnetic
canopies in circumfacular regions suppressing upward propagating
steepening acoustic waves. Our results provide further strong evidence
for shock waves as the cause of the inverse C-shaped bisector and
explain the observed solar cycle variation of the shape and amplitude
of Sun-as-a-star Ca II 854.2 nm bisectors.
Title: Comparison of Ground-Based and Space-Based Longitudinal
Magnetograms
Authors: Pietarila, A.; Bertello, L.; Harvey, J. W.; Pevtsov, A. A.
Bibcode: 2013SoPh..282...91P
Altcode: 2012arXiv1209.6390P; 2012SoPh..tmp..274P
We compare photospheric line-of-sight magnetograms from the
Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector
Spectro-Magnetograph (VSM) instrument with observations from the
150-foot Solar Tower at Mt. Wilson Observatory (MWO), the Helioseismic
and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO),
and the Michelson Doppler Imager (MDI) on the Solar and Heliospheric
Observatory (SOHO). We find very good agreement between VSM and
the other data sources for both disk-averaged flux densities and
pixel-by-pixel measurements. We show that the VSM mean flux density
time series is of consistently high signal-to-noise ratio with no
significant zero offsets. We discuss in detail some of the factors -
spatial resolution, flux dependence, and position on the solar disk -
affecting the determination of scaling between VSM and SOHO/MDI or
SDO/HMI magnetograms. The VSM flux densities agree well with spatially
smoothed data from MDI and HMI, although the scaling factors show a
clear dependence on flux density. The factor to convert VSM to HMI
increases with increasing flux density (from ≈1 to ≈1.5). The
nonlinearity is smaller for the VSM vs. SOHO/MDI scaling factor (from
≈1 to ≈1.2).
Title: Chromospheric Magnetic Field Measurements in a Flare and an
Active Region Filament
Authors: Harvey, J. W.
Bibcode: 2012SoPh..280...69H
Altcode: 2012SoPh..tmp..175H
Intensity (I) and circular polarization (V) spectra using the 854.2
nm line of Ca II with 3.65 pm spectral and 1 arcsecond spatial
sampling were obtained with the SOLIS vector spectromagnetograph on
8 November 2011. An active region filament showing Doppler shifts
as large as 50 km s−1 and an unrelated C1.8 flare were
observed. Line-of-sight flux density estimates of the magnetic field
(BLOS) were mapped as a function of wavelength in both of
these features using the weak-field Zeeman-splitting approximation that
V∝dI/dλ. The filament had a large amount of structure in intensity
and velocity but remarkably little BLOS structure, which
varied smoothly from 35 to 55 G (gauss). Two flare emission kernels
showed average BLOS values of 415 and − 215 G, about
84 % of the underlying photospheric fields. Counter to this modest
strength decrease with increasing height, in nearly all parts of the
brighter flare kernel there appears to be a substantial gradient
of BLOS over the heights corresponding to the core of
the 854.2 nm line. This variation, if verified, may be related
to compression of the chromosphere associated with flare-induced
evaporation. Alternatively, it might be a spurious result if the
profile of the line core is narrowed in the magnetic part of the flare
kernel. The results presented here are generally similar to previous,
rather sparse observations. Observations of the type reported here
are made daily and could be used to greatly increase knowledge about
the chromospheric magnetic field in active solar features.
Title: Circumfacular regions and magnetic canopies as seen in Ca II
8542 Å
Authors: Pietarila, Anna; Harvey, Jack
Bibcode: 2012decs.confE...8P
Altcode:
Active regions appear bright in Ca II 8542 Å line core intensity
while the surrounding areas are darker than the active region or the
quiet Sun. These areas are referred to as circumfacular regions. We
use SOLIS VSM Ca II 8542 Å data (photospheric and chromospheric
full disk magnetograms as well as high spectral resolution Stokes I
and V profiles) to study the relationship between photospheric and
chromospheric LOS magnetic fields and detailed properties (e.g., line
bisectors, Stokes V asymmetries) of the spectral profiles. There is
a connection between magnetic canopies, circumfacular regions and Ca
II 8542 Å bisector spans which may explain the observed solar cycle
variation of the Sun-as-a-star Ca II 8542 Å bisectors.
Title: Stokes Profile Compression Applied to VSM Data
Authors: Toussaint, W. A.; Henney, C. J.; Harvey, J. W.
Bibcode: 2012SoPh..276..415T
Altcode:
The practical details of applying the Expansion in Hermite Functions
(EHF) method to compression of full-disk full-Stokes solar spectroscopic
data from the SOLIS/VSM instrument are discussed in this paper. The
algorithm developed and discussed here preserves the 630.15 and
630.25 nm Fe I lines, along with the local continuum and telluric
lines. This compression greatly reduces the amount of space required
to store these data sets while maintaining the quality of the data,
allowing these observations to be archived and made publicly available
with limited bandwidth. Applying EHF to the full-Stokes profiles and
saving the coefficient files with Rice compression reduces the disk
space required to store these observations by a factor of 20, while
maintaining the quality of the data and with a total compression time
only 35% slower than the standard gzip (GNU zip) compression.
Title: The Longitudinal Solar Magnetic Field Measured by SOLIS
Authors: Bertello, L.; Pevtsov, A. A.; Harvey, J. W.; Pietarila, A.
Bibcode: 2011AGUFMSH13B1934B
Altcode:
The SOLIS (Synoptic Optical Long-term Investigations of the Sun) Vector
SpectroMagnetograph (VSM) instrument operating at the National Solar
Observatory at Kitt Peak (Arizona) measures the full-disk longitudinal
solar magnetic field in the neutral iron spectral lines at 630.15-630.25
nm (photosphere) and ionized calcium spectral line at 854.2 nm (lower
chromosphere). Over the past two years a considerable effort has
been made to improve the quality of the computed magnetograms. Major
modifications to the original data reduction pipeline include a
new determination of the instrumental magnetic bias and an improved
calibration of the computed solar magnetic flux density. As a result of
these changes SOLIS-VSM is now able to provide, among other products,
more reliable values of the full-disk mean magnetic flux measured in
the photosphere and low chromosphere. In addition, these improvements
open the possibility to extend the current SOLIS-VSM catalog with new
products of interest to the solar and heliospheric communities. We
describe some of these changes and their impact on the quality of the
derived SOLIS-VSM data.
Title: Improving Data Drivers for Coronal and Solar Wind Models
Authors: Arge, C. N.; Henney, C. J.; Koller, J.; Toussaint, W. A.;
Harvey, J. W.; Young, S.
Bibcode: 2011ASPC..444...99A
Altcode:
Global estimates of the solar photospheric magnetic field distribution
are critical for space weather forecasting. These global maps are the
essential data input for accurate modeling of the corona and solar
wind, which is vital for gaining the basic understanding necessary
to improve space weather forecasting models. We are now testing
the global photospheric field maps generated by the Air Force Data
Assimilative Photospheric flux Transport (ADAPT) model as input to the
Wang-Sheeley-Arge (WSA) coronal and solar wind model. ADAPT incorporates
data assimilation within a modified version of the Worden & Harvey
photospheric magnetic flux transport model to provide an instantaneous
snapshot of the global photospheric field distribution compared to that
of traditional synoptic maps. In this paper we provide an overview of
the WSA and ADAPT models, plus discuss preliminary results obtained
from WSA when using a traditional versus an ADAPT photospheric field
synoptic map as its input.
Title: Improvements in the Determination of ISS Ca II K Parameters
Authors: Bertello, L.; Pevtsov, A. A.; Harvey, J. W.; Toussaint, R. M.
Bibcode: 2011SoPh..272..229B
Altcode: 2011arXiv1106.4265B
Measurements of the ionized Ca II K line are one of the major resources
for long-term studies of solar and stellar activity. They also play a
critical role in many studies related to solar irradiance variability,
particularly as a ground-based proxy to model the solar ultraviolet flux
variation that may influence the Earth's climate. Full disk images of
the Sun in Ca II K have been available from various observatories for
more than 100 years and latter synoptic Sun-as-a-star observations
in Ca II K began in the early 1970s. One of these instruments, the
Integrated Sunlight Spectrometer (ISS) has been in operation at Kitt
Peak (Arizona) since late 2006. The ISS takes daily observations
of solar spectra in nine spectra bands, including the Ca II K and H
lines. We describe recent improvements in data reduction of Ca II K
observations, and present time variations of nine parameters derived
from the profile of this spectral line.
Title: Comparing ADAPT-WSA Model Predictions With EUV And Solar
Wind Observations
Authors: Arge, Charles; Henney, C. J.; Shurkin, K.; Toussaint, W.;
Koller, J.; Harvey, J. W.
Bibcode: 2011SPD....42.2403A
Altcode: 2011BAAS..43S.2403A
Global estimates of the solar photospheric magnetic field distribution
are critical for space weather forecasting. These global maps are the
essential data input for accurate modeling of the corona and solar wind,
which is vital for gaining the basic understanding necessary to improve
forecasting models needed for Air Force operations. We are now testing
the global photospheric field maps generated by the A</u>ir
Force D</u>ata A</u>ssimilative P</u>hotospheric flux
T</u>ransport (ADAPT) model as input to the WSA coronal and solar
wind model. ADAPT incorporates the Los Alamos National Laboratory data
assimilation methodology with a modified version of the Worden and
Harvey photospheric magnetic flux transport model. The ADAPT maps
provide a more instantaneous snapshot of the global photospheric
field distribution compared to traditional synoptic maps. In this
presentation, we make a detailed comparison of WSA coronal and solar
wind model output with STEREO EUVI disk observations and in situ
plasma observations from the STEREO and ACE spacecraft. The current
orbital configuration of the two STEREO spacecraft is such that they
provide a nearly instantaneous global snapshot of the Sun's coronal
hole distribution. In addition, the STEREO observations along with
those from the ACE spacecraft provide three widely spaced ecliptic
locations at 1 AU to sample the solar wind plasma. In combination,
these differing observations from multiple spacecraft provide a unique
and highly sensitive test of the ability of the WSA model to capture
the global coronal hole and solar wind structure. This is done using
both ADAPT and standard updated photospheric field maps as input to
the model.
Title: Ca Ii K and H Measurements from the SOLIS ISS Instrument
Authors: Bertello, Luca; Pevtsov, A. A.; Pietarila, A.; Harvey, J. W.;
Toussaint, R. M.; SOLIS Team
Bibcode: 2011SPD....42.1744B
Altcode: 2011BAAS..43S.1744B
Precise measurements of the disk integrated solar Ca II K and H
lines play a critical role in many investigations of solar activity
and studies related to solar irradiance variability. The Integrated
Sunlight Spectrometer(ISS) operating at the National Solar Observatory
at Kitt Peak (Arizona) since December 2006 is designed to obtain
high spectral resolution (R = 300,000) observations of the Sun as
a star in a broad range of wavelengths (350 nm -1100 nm). The ISS
is one of three instruments, with the Vector Spectro-Magnetograph
(VSM) and the Full Disk Patrol (FDP), comprising the Synoptic Optical
Long-term Investigations of the Sun (SOLIS) - a synoptic facility for
solar observations operating at NSO/Kitt Peak. The ISS takes daily
observations of solar spectra in nine spectral bands, including the Ca
II K and H lines. We describe recent improvements in data reduction of
Ca II K and H observations, and present time variations of parameters
derived from the profiles of these spectral lines. Some properties of
these time series are also discussed.
Title: Abrupt Longitudinal Magnetic Field Changes During A Flare
Observed By Hmi And Gong
Authors: Petrie, Gordon; Sudol, J. J.; Harvey, J. W.
Bibcode: 2011SPD....42.2226P
Altcode: 2011BAAS..43S.2226P
We characterize the photospheric longitudinal magnetic field changes
that occurred during the 6 November 2010 M5.4 flare observed by both
the Helioseismic and Magnetic Imager (HMI) and the Global Oscillation
Network Group (GONG). We compare maps of the field changes as well
as pixel-by-pixel mosaic plots of the field against time across the
active region. The HMI data show larger-amplitude field changes and
more complex spatial structure and temporal variation than the GONG
data. Besides obvious differences in spatial resolution and seeing
conditions, these discrepancies might be due to differences in the
structure of the photosphere at the different formation heights of
the absorption lines used in measuring the magnetic field strength.
Title: Full-disk Solar H-alpha Images From GONG
Authors: Harvey, J. W.; Bolding, J.; Clark, R.; Hauth, D.; Hill, F.;
Kroll, R.; Luis, G.; Mills, N.; Purdy, T.; Henney, C.; Holland, D.;
Winter, J.
Bibcode: 2011SPD....42.1745H
Altcode: 2011BAAS..43S.1745H
Since mid-2010 the Global Oscillation Network Group (GONG) has collected
H-alpha images at six sites around the world. These images provide
a near real-time solar activity patrol for use in space weather
applications and also an archive for research purposes. Images are
collected once per minute, dark, smear, and flat corrected, compressed
and then sent via the Internet to a 'cloud' server where reduction
is completed. Various reduced images are usually available within a
minute after exposure. The H-alpha system is an add-on to the normal
GONG helioseismology instrument and does not interfere with regular
observations. A polarizing beamsplitter sends otherwise unused 656 nm
light through two lenses to a Daystar 0.04 nm mica etalon filter. The
filter is matched to an image of the GONG light feed entrance pupil
and sees an image of the Sun at infinity. Two lenses behind the filter
form the solar image on a DVC-4000 2k x 2k interline transfer CCD
camera. Exposure times are automatically adjusted to maintain the
quiet disk center at 20% of full dynamic range to avoid saturation
by bright flares. Image resolution is limited by diffraction,
seeing and some high-order wavefront errors in the filters. A unique
dual-heater system was developed by Daystar to homogenize the passband
characteristics of the mica etalons. The data are in regular use for
space weather forecasting by the U.S. Air Force Weather Agency, which
funded construction and installation of the instruments. Operational and
reduction improvements are underway and archived data are already being
used for research projects. The Web site URL is http://halpha.nso.edu.
Title: WSA Derived Coronal Hole Comparison with STEREO EUVI
Observations
Authors: Arge, C. N.; Henney, C.; Shurkin, K.; Koller, J.; Toussaint,
W. A.; Harvey, J. W.; Young, S. L.
Bibcode: 2010AGUFMSM51A1749A
Altcode:
Global estimates of the solar photospheric magnetic field distribution
are critical for space weather forecasting. These global maps are the
essential data input for accurate modeling of the corona and solar
wind, which is vital for gaining the basic understanding necessary to
improve forecasting models needed for Air Force operations. We are
now testing the global photospheric field maps generated by the Air
Force Data Assimilative Photospheric flux Transport (ADAPT) model as
input to the WSA coronal and solar wind model. ADAPT incorporates the
Los Alamos National Laboratory data assimilation methodology with
a modified version of the Worden and Harvey photospheric magnetic
flux transport model. The ADAPT maps provide a more instantaneous
snapshot of the global photospheric field distribution compared to
traditional synoptic maps. In this poster, we compare WSA model output
with EUVI observations from the two STEREO spacecraft. The current
orbital configuration of the two STEREO spacecraft are such that, in
combination, they provide a nearly instantaneous global snapshot of
the Sun’s coronal hole distribution. Global EUVI observations from
STEREO A & B provide an unique and ideal opportunity to directly
compare WSA coronal hole predictions using both ADAPT and standard
updated photospheric field maps as input to the model.
Title: Ensemble Solar Global Magnetic Field Modeling
Authors: Henney, C. J.; Arge, C. N.; Koller, J.; Toussaint, W. A.;
Young, S. L.; Harvey, J. W.
Bibcode: 2010AGUFMSH31B1797H
Altcode:
The ability to forecast geoeffective space weather events
is critically dependent on the estimation of the global solar
photospheric magnetic field distribution as input to coronal and
heliospheric models. Currently, the solar magnetic field can only be
recorded for approximately half of the solar surface at any given
time. Since the rotation period of the Sun as observed from Earth
is approximately 27 days, any global map of the solar magnetic field
includes data more than 13 days old. In this poster, we describe our
efforts and progress toward developing the Air Force Data Assimilative
Photospheric flux Transport (ADAPT) model. ADAPT incorporates data
assimilation with a modified version of the Worden and Harvey (WH)
photospheric magnetic flux transport model. The flux transport model
evolves the solar magnetic flux by incorporating rotational, meridional,
and super-granular diffusive transport processes when measurements are
not available. The modified WH model version now utilizes an ensemble
of model realizations using different model parameters constrained
by the estimated errors of each parameter. In addition, the modified
version allows for the hemispheres to be decoupled with regards to
differential rotation and meridional flow. When new observations are
available, the modeled flux is updated using an Ensemble Least Squares
(EnLS) estimation method. The EnLS data assimilation utilizes model
and observational uncertainties, where the model error is estimated
from the ensemble variance. Besides providing an estimate of the model
uncertainty, the different flux transport model realizations provide
model parameter feedback. For model parameter feedback, we compare polar
fluxes obtained by different ensemble realizations, using different
meridional flow profiles at high latitude, with data recorded during
periods when the poles are well observed. In addition, the challenges
and benefits of ensemble modeling with regards to selecting metric
parameters for model feedback and validation on different timescales
are discussed.
Title: Nebula in Carina
Authors: Mazlin, Steve; Harvey, Jack; Gilbert, Rick; Verschatse, Daniel
Bibcode: 2010S&T...120b..79M
Altcode:
No abstract at ADS
Title: Ensemble Solar Global Magnetic Field Modeling
Authors: Henney, Carl John; Arge, C. Nick; Koller, Josef; Toussaint,
W. Alex; Young, Shawn; Harvey, John W.
Bibcode: 2010shin.confE..50H
Altcode:
The ability to forecast geoeffective space weather events is critically
dependent on the estimation of the global solar photospheric
magnetic field distribution as input to coronal and heliospheric
models. Currently, the solar magnetic field can only be recorded for
approximately half of the solar surface at any given time. Since the
rotation period of the Sun as observed from Earth is approximately
27 days, any global map of the solar magnetic field includes data
more than 13 days old. In this poster, we describe our efforts and
progress toward developing the Air Force Data Assimilative Photospheric
flux Transport (ADAPT) model. ADAPT incorporates data assimilation
with a modified version of the Worden and Harvey (WH) photospheric
magnetic flux transport model. The flux transport model evolves the
observed solar magnetic flux by incorporating rotational, meridional,
and supergranular diffusive transport processes when measurements are
not available. The modified WH model version now utilizes an ensemble
of model realizations using different model parameters constrained
by the estimated errors of each parameter. In addition, the modified
version allows for the hemispheres to be decoupled with regards to
differential rotation and meridional flow. When new observations are
available, the modeled flux is updated using an Ensemble Least Squares
(EnLS) estimation method. The EnLS data assimilation utilizes model
and observational uncertainties, where the model error is estimated
from the ensemble variance. Besides providing an estimate of the model
uncertainty, the different flux transport model realizations provide
model parameter feedback. For model parameter feedback, we compare polar
fluxes obtained by different ensemble realizations, using different
meridional flow profiles at high latitude, with data recorded during
periods when the poles are well observed. In addition, the challenges
and benefits of ensemble modeling with regards to selecting metric
parameters for model feedback and validation on different timescales
are discussed.
Title: WSA Derived Coronal Hole Comparison with STEREO EUVI
Observations
Authors: Arge, C. Nick; Henney, Carl J.; Shurkin, Kathleen; Koller,
Josef; Toussaint, W. Alex; Young, Shawn; MacKenzie, David; Harvey,
John W.
Bibcode: 2010shin.confE..52A
Altcode:
Global estimates of the solar photospheric magnetic field distribution
are critical for space weather forecasting. These global maps are the
essential data input for accurate modeling of the corona and solar
wind, which is vital for gaining the basic understanding necessary to
improve forecasting models needed for Air Force operations. We are now
testing the global photospheric field maps generated by the Air Force
Data Assimilative Photospheric flux Transport (ADAPT) model as input
to the WSA coronal and solar wind model. ADAPT incorporates the Los
Alamos National Laboratory data assimilation methodology with a modified
version of the Worden and Harvey photospheric magnetic flux transport
model. The ADAPT maps provide a more instantaneous snapshot of the
global photospheric field distribution compared to traditional synoptic
(i.e., Carrington) maps. In this poster, we compare WSA model output
with EUVI observations from the two STEREO spacecraft. The current
orbital configuration of the two STEREO spacecraft are such that,
in combination, they provide a nearly instantaneous global snapshot
of the Sun's coronal hole distribution. Global EUVI observations from
STEREO A & B provide an unique and ideal opportunity to directly
compare WSA coronal hole predictions using both ADAPT and standard
Carrington maps as input to the model.
Title: Global Solar Magnetic Field Maps using ADAPT
Authors: Henney, Carl John; Arge, C. N.; Koller, J.; Toussaint, W. A.;
Young, S.; MacKenzie, D.; Harvey, J. W.
Bibcode: 2010AAS...21640115H
Altcode:
Estimates of the global solar photospheric magnetic field distribution
are critical for space weather forecasting. These global magnetic charts
are the essential data input for accurate modeling of the corona and
solar wind, which is vital for gaining the basic understanding necessary
to improve forecasting models needed for Air Force operations. In this
poster, we describe our efforts and progress toward developing the Air
Force Data Assimilative Photospheric flux Transport (ADAPT) model. ADAPT
incorporates the Los Alamos National Laboratory data assimilation
methodology with a modified version of the Worden and Harvey
photospheric magnetic flux transport model. The flux transport model
evolves the observed solar magnetic flux by incorporating rotational,
meridional, and super-granular diffusive transport processes when
measurements are not available. When new observations are available,
the modeled flux is updated using an Ensemble Least Squares (EnLS)
estimation method. The data assimilation with EnLS rigorously takes
into account model and observational uncertainties. In traditional
photospheric magnetic field synoptic maps the field measurements
residing at the poles are usually the least reliable because of
their close proximity to the limb. This is due to the highly variable
horizontal magnetic signal that becomes increasingly prevalent in the
field measurements near the solar limb. In ADAPT, the polar fields
are filled naturally via the model transport processes. This poster
will compare polar fluxes obtained using the ADAPT model with those
using more traditional polar correction/fill methods as well as for
periods when the poles are well observed.
Title: Air Force Data Assimilative Photospheric Flux Transport
(ADAPT) Model
Authors: Arge, C. Nick; Henney, Carl J.; Koller, Josef; Compeau,
C. Rich; Young, Shawn; MacKenzie, David; Fay, Alex; Harvey, John W.
Bibcode: 2010AIPC.1216..343A
Altcode:
As the primary input to coronal and solar wind models, global
estimates of the solar photospheric magnetic field distribution
are critical to space weather forecasting. These global magnetic
maps are essential for accurate modeling of the corona and solar
wind, which is vital for gaining the basic understanding necessary
to improve forecasting models needed for Air Force operations. In
this paper, we describe our efforts and progress toward developing
the Air Force Data Assimilative Photospheric flux Transport (ADAPT)
model. ADAPT incorporates the various data assimilation techniques,
including an ensemble Kalman filter, with a photospheric magnetic
flux transport model. The flux transport model evolves the magnetic
flux on the Sun using relatively well understood transport processes
when observations are not available and then updates the modeled flux
with new observations using data assimilation. The data assimilation
rigorously takes into account model and observational uncertainties,
as well as accounting for regional correlations. The flux transport
model and the data assimilation codes have been fully coupled and are
now being extensively verified. After verification the model output
will then be compared directly with observations (e.g., photospehric
field strength and polarity, coronal hole boundaries, polar field
strength, and ultimately solar wind). Anticipated outcomes of the ADAPT
model include improvement in: 1) the estimation of solar corona and
polar fields, 2) understanding the nature and behavior of solar super
granular diffusion and meridional flows over the solar cycle, and 3)
modeling and forecasting the solar wind near Earth.
Title: New Global Solar Magnetic Field Maps Using the ADAPT Data
Assimilation and Flux Transport Model
Authors: Arge, C. N.; Henney, C.; Koller, J.; Young, S. L.; Compeau,
C. R.; MacKenzie, D.; Harvey, J. W.
Bibcode: 2009AGUFMSM54A..06A
Altcode:
As the primary input to all coronal and solar wind models, global
estimates of the solar photospheric magnetic field distribution are
critical to space weather forecasting. These global magnetic maps are
essential for accurate modeling of the corona and solar wind, which
is vital for gaining the basic understanding necessary to improve
forecasting models needed for Air Force operations. In this poster,
we describe our efforts and progress toward developing the Air Force
Data Assimilative Photospheric flux Transport (ADAPT) model. ADAPT
incorporates the Los Alamos National Laboratory ensemble Kalman filter
data assimilation technique with a modified version of the Worden and
Harvey photospheric magnetic flux transport model. The flux transport
model evolves the observed solar magnetic flux using relatively well
understood transport processes when measurements are not available and
then updates the modeled flux with new observations using the ensemble
Kalman filter. The data assimilation with the ensemble Kalman filter
rigorously takes into account model and observational uncertainties,
as well as accounting for regional correlations. In traditional
photospheric field synoptic maps the magnetic field measurements
residing at the poles are usually the least reliable because of
their close proximity to the limb. This is due to the highly variable
horizontal magnetic signal that becomes increasingly prevalent in the
field measurements near the solar limb. In ADAPT, the polar fields
are filled naturally via the model transport processes. In this paper,
we report on comparisons between polar fluxes obtained using the ADAPT
model with those using more traditional polar correction/fill methods
as well as for periods when the poles are well observed.
Title: Messier 104
Authors: Mazlin, Steve; Harvey, Jack; Gilbert, Rick; Verschatse, Daniel
Bibcode: 2009S&T...118Q..76M
Altcode:
No abstract at ADS
Title: On the Latitude Distribution of the Polar Magnetic Flux as
Observed by SOLIS-VSM
Authors: Raouafi, N. -E.; Harvey, J. W.; Henney, C. J.
Bibcode: 2009ASPC..405..201R
Altcode:
Magnetograms from the Vector SpectroMagnetograph (VSM) of the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) project are
utilized to study the latitude distribution of magnetic flux elements
as a function of latitude in the polar solar caps. We find that the
density distribution of the magnetic flux normalized by the surface
of the polar cap and averaged over months decreases close to the
solar poles. This trend is more pronounced when considering only flux
elements with relatively large size. The flux density of the latter
is relatively flat from the edge of the polar cap up to latitudes of
70°-75° and decreases significantly to the solar pole. This result
is important in studying meridional flows that bring the magnetic
flux from lower to higher solar latitudes resulting in the solar
cycle reversal. The results are also of importance in studying polar
structures contributing to the fast solar wind, such as polar plumes.
Title: Chromospheric Magnetic Fields
Authors: Harvey, J. W.
Bibcode: 2009ASPC..405..157H
Altcode:
Observed for nearly 100 years, the solar chromospheric magnetic
field is, to first order, a weaker and more diffuse extension of the
underlying photospheric magnetic field. With closer scrutiny, the
chromospheric magnetic field exhibits many wonderful and mysterious
differences. This brief review focuses on some aspects of our present
understanding of the nature of the chromospheric field emphasizing
differences with the photospheric field. Some areas are highlighted
which have unexpected discrepancies that need further study.
Title: SOLIS Vector Spectromagnetograph: Status and Science
Authors: Henney, C. J.; Keller, C. U.; Harvey, J. W.; Georgoulis,
M. K.; Hadder, N. L.; Norton, A. A.; Raouafi, N. -E.; Toussaint, R. M.
Bibcode: 2009ASPC..405...47H
Altcode: 2008arXiv0801.0013H
The Vector Spectromagnetograph (VSM) instrument has recorded
photospheric and chromospheric magnetograms daily since August
2003. Full-disk photospheric vector magnetograms are observed
at least weekly and, since November 2006, area-scans of active
regions daily. Quick-look vector magnetic images, plus X3D and FITS
formated files, are now publicly available daily. In the near future,
Milne-Eddington inversion parameter data will also be available and
a typical observing day will include three full-disk photospheric
vector magnetograms. Besides full-disk observations, the VSM is
capable of high temporal cadence area-scans of both the photosphere
and chromosphere. Carrington rotation and daily synoptic maps are
also available from the photospheric magnetograms and coronal hole
estimate images.
Title: Solar Mean Magnetic Field Observed by GONG
Authors: Harvey, J. W.; Petrie, G.; Clark, R.; GONG Team
Bibcode: 2009SPD....40.0916H
Altcode:
The average line-of-sight (LOS) magnetic field of the Sun has been
observed for decades, either by measuring the circular polarization
across a selected spectrum line using integrated sunlight or by
averaging such measurements in spatially resolved images. The
GONG instruments produce full-disk LOS magnetic images every
minute, which can be averaged to yield the mean magnetic field
nearly continuously. Such measurements are well correlated with
the heliospheric magnetic field observed near Earth about 4 days
later. They are also a measure of solar activity on long and short time
scales. Averaging a GONG magnetogram, with nominal noise of 3 G per
pixel, results in a noise level of about 4 mG. This is low enough that
flare-related field changes have been seen in the mean field signal
with time resolution of 1 minute. Longer time scales readily show
variations associated with rotation of magnetic patterns across the
solar disk. Annual changes due to the varying visibility of the polar
magnetic fields may also be seen. Systematic effects associated with
modulator non-uniformity require correction and limit the absolute
accuracy of the GONG measurements. Comparison of the measurements
with those from other instruments shows high correlation but suggest
that GONG measurements of field strength are low by a factor of about
two. The source of this discrepancy is not clear. Fourier analysis of
2007 and 2008 time series of the GONG mean field measurements shows
strong signals at 27.75 and 26.84/2 day (synodic) periods with the later
period showing more power. The heliospheric magnetic field near Earth
shows the same periods but with reversed power dominance. The
Global Oscillation Network Group (GONG) project is managed by NSO,
which is operated by AURA, Inc. under a cooperative agreement with
the National Science Foundation.
Title: A New Solar H-alpha Distributed Observing System
Authors: Hill, Frank; Harvey, J. W.; Luis, G.; Purdy, T.; Bolding,
J.; Eliason, P.; Kroll, R.; Lewis, F.; Berman, L.; Parsons, A.
Bibcode: 2009SPD....40.1806H
Altcode:
Space weather forecasts and nowcasts require rapid-cadence, continual,
and robust solar observations. A useful strategy to accomplish this
is to deploy a network of ground-based observing systems distributed
in geographic longitude. The US Air Force Weather Agency (AFWA) has
been operating the Solar Optical Observing Network (SOON) for many
years, and is now replacing SOON with ISOON, an improved SOON. As
a back-up during the development and installation of ISOON, AFWA is
supporting the addition of an H-alpha observing system into the existing
sites of the Global Oscillation Network Group (GONG) program. GONG
comprises six sites in California, Hawaii, Australia, India, Spain,
and Chile, and currently provides one per minute continual magnetic
field, Doppler, and intensity measurements in the Ni 6768 line. The
additional H-alpha capability will comprise a 0.4-A bandpass filter,
a 2kX2k CCD, beamsplitter, transfer optics, and a dedicated data
acquisition system. The observing cadence will be one per minute
at a given site, with the acquisition time shifted between adjacent
sites to potentially provide an image every 20 sec. The data will be
transmitted back to Tucson, processed, and then transferred to AFWA
within one minute of acquisition.
Title: Causes of Solar Activity
Authors: Giampapa, Mark S.; Gibson, Sarah; Harvey, J. W.; Hill, Frank;
Norton, Aimee A.; Pevtsov, A.
Bibcode: 2009astro2010S..92G
Altcode:
No abstract at ADS
Title: Asteroseismology: The Next Frontier in Stellar Astrophysics
Authors: Giampapa, Mark S.; Aerts, Conny; Bedding, Tim; Bonanno,
Alfio; Brown, Timothy M.; Christensen-Dalsgaard, Jorgen; Dominik,
Martin; Ge, Jian; Gilliland, Ronald L.; Harvey, J. W.; Hill, Frank;
Kawaler, Steven D.; Kjeldsen, Hans; Kurtz, D. W.; Marcy, Geoffrey W.;
Matthews, Jaymie M.; Monteiro, Mario Joao P. F. G.; Schou, Jesper
Bibcode: 2009astro2010S..91G
Altcode:
No abstract at ADS
Title: An intelligent modulator system
Authors: Luis, George; Harvey, Jack; Purdy, Tim; Soukup, Mike; Eliason,
Patricia A.
Bibcode: 2008SPIE.7014E..60L
Altcode: 2008SPIE.7014E.199L
In 2001, the GONG+ instruments began acquiring solar magnetic field
images (magnetograms) every minute. These observations offer a useful
resource for the solar physics community. However, the quality of
the magnetograms was reduced by a significant zero point error in the
observations that varied across the solar image and with time. This
precluded using the magnetograms for meaningful extrapolations of weak
photospheric fields into the corona. The error was caused by the slow,
asymmetric, locally varying switching of the LCD modulator (LCM) from
one retardation state to the other. This generated a false magnetic
field pattern as a result of different responses to weak instrumental
linear polarization ahead of the LCM. The original modulator driver
used a very simple design to excite the LCM. Liquid crystals like
those in the LCM take different times to switch from one polarization
state to the other than to return to the first polarization state. To
eliminate the difference in switching times, a driver capable of
varying its output during the change in LCM state was needed. A
microcontroller-based design was chosen. The final driver design
resulted in a factor of 100 improvement in the zero point error.
Title: A global SOLIS vector spectromagnetograph (VSM) network
Authors: Streander, K. V.; Giampapa, M. S.; Harvey, J. W.; Henney,
C. J.; Norton, A. A.
Bibcode: 2008SPIE.7014E..7PS
Altcode: 2008SPIE.7014E.251S
Understanding the Sun's magnetic field related activity is far
from complete as reflected in the limited ability to make accurate
predictions of solar variability. To advance our understanding of solar
magnetism, the National Solar Observatory (NSO) constructed the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) suite of instruments
to conduct high precision optical measurements of processes on the Sun
whose study requires sustained observations over long time periods. The
Vector Spectromagnetograph (VSM), the principal SOLIS instrument,
has been in operation since 2003 and obtains photospheric vector data,
as well as photospheric and chromospheric longitudinal magnetic field
measurements. Instrument performance is being enhanced by employing
new, high-speed cameras that virtually freeze seeing, thus improving
sensitivity to measure the solar magnetic field configuration. A major
operational goal is to provide real-time and near-real-time data for
forecasting space weather and increase scientific yield from shorter
duration solar space missions and ground-based research projects. The
National Solar Observatory proposes to build two near-duplicates of
the VSM instrument and place them at international sites to form a
three-site global VSM network. Current electronic industry practice
of short lifetime cycles leads to improved performance and reduced
acquisition costs but also to redesign costs and engineering impacts
that must be minimized. The current VSM instrument status and experience
gained from working on the original instrument is presented herein and
used to demonstrate that one can dramatically reduce the estimated
cost and fabrication time required to duplicate and commission two
additional instruments.
Title: A Determination of the Value and Variability of the Sun's
Open Magnetic Flux using a Global MHD Model
Authors: Riley, P.; Mikic, Z.; Linker, J.; Harvey, J. W.; Hoeksema,
T.; Liu, Y.; Bertello, L.
Bibcode: 2008AGUSMSH44A..03R
Altcode:
The underlying value and variation of the Sun's open, unsigned magnetic
flux is of fundamental scientific importance, yet its properties remain
poorly known. For example, do long term (on the time-scale of ~ 100
years) changes in the strength of the solar magnetic field exist and
do they persist through the heliosphere? If present, they may have
a direct impact on space climate, including implications for the
transport of cosmic rays (CRs), and as such, may affect technology,
space, and even terrestrial climate. Global MHD models are capable of
reproducing the structure of the large-scale solar and interplanetary
magnetic field (at least in the absence of transient phenomena such as
Coronal Mass Ejections), and should, in principle, be able to address
this topic. However, they rely - and depend crucially - on boundary
conditions derived from observations of the photospheric magnetic
field. In spite of ~ 40 years of measurements, accurate estimates of the
radial component of the photospheric magnetic field remain difficult
to make. In this study, we attempt to find a "ground truth" estimate
of the photospheric magnetic field by carefully comparing both disk
magnetograms and diachronic (previously known as synoptic) maps from
6 different observatories (KPVT, SOLIS, GONG, MDI, WSO, and MWO). We
find that although there is a general consensus between several of
them, there are also some significant discrepancies. Using data from
these observatories, we compute global heliospheric solutions for a
selection of epochs during the last 3 solar cycles and compare the
results with in situ observations. We apply these results to several
topics related to the Sun's open flux.
Title: The global solar magnetic field according to GONG during WHI
Authors: Petrie, G. J.; Bolding, J.; Clark, R.; Donaldson-Hanna, K.;
Harvey, J. W.; Hill, F.; Toner, C.; Thomas, W. M.
Bibcode: 2008AGUSMSH53A..03P
Altcode:
Line-of-sight photospheric magnetograms are produced every minute at
GONG's six sites. Based on these low- noise images, near-real-time
synoptic full-surface magnetograms are produced hourly around
the clock. In the usual way, potential-field models for the global
coronal field are then extrapolated from the photospheric maps hourly,
giving a description of large-scale magnetic structure including field
changes caused by quasi-static evolution and by flares and coronal
mass ejections. This study focuses on the large-scale features of the
corona during WHI that have consequences for the heliosphere and space
weather: coronal holes, the streamer belt, magnetic flux open to the
ecliptic plane and large-scale changes in the field topology. GONG is
the official provider of magnetograms for NASA's STEREO mission.
Title: Ca II H & K Spectra From The National Solar Observatory
Authors: Livingston, W. C.; Giampapa, M. S.; Harvey, J. W.; Keil,
S. L.; Toussaint, R. M.
Bibcode: 2008AGUSMSP53B..04L
Altcode:
When the Sun is observed as a star (i.e., spatially integrated full
disk) the cores of the chronospheric H and K resonance lines of
singly ionized calcium show the greatest cycle variability (up to
40% peak-to-peak) accessible from the ground. Synoptic archives are
available at monthly intervals from 1974 (Kitt Peak) and for K only
at almost a daily cadence from 1984 (Sacramento Peak). We discuss
these time series and compare them with, for example, sunspot numbers
and magnetic fields. Less frequent are center disk observations in
which the activity cycle is found to be absent, implying the quiet
basal atmosphere is constant and not, say, heated by cycle magnetic
activity. New, near daily, spatially integrated full disk solar data
from the SOLIS Integrated Sunlight Spectrometer (ISS)agree well with
the older work. We now propose to produce calibrated (Houtgast 1970;
Solar Phys 15, 273, high points: 387.5, 395.3, and 402.0 nm), low
dispersion full disk spectra that may be directly compared with that
from solar-type stars.
Title: Space Weather with GONG+ Data
Authors: Hill, F.; Komm, R.; Gonzalez-Hernandez, I.; Petrie, G.;
Harvey, J. W.
Bibcode: 2008AGUSMSP54A..08H
Altcode:
The Global Oscillation Network Group (GONG) is now routinely
producing several data products that are useful for space weather
predictions. These products are one-minute cadence full-disk
magnetograms obtained continually; ten-miniute averages of these
magnetograms; one-hour cadence synoptic magnetic field maps and
potential field source-surface extrapolations; and twelve-hour far-side
maps that show the presence of large active regions. Most of these these
products are made available over the Internet in near-real time. In
addition, we are developing flare predictors based on subsurface
vorticity obtained from helioseismic ring diagrams in conjunction
with surface magnetic field observations. We find that, when both the
subsurface vorticity and the surface magnetic field are above certain
thresholds for a specific active region, then that active region has
a very high probability of producing vigorous flare activity. We will
present the quantitative results for this predictor and also report
on progress developing a predictor based on the temporal evolution of
the vorticity.
Title: New Observations of the Magnetic Vector Field across the
Solar Disk
Authors: Keller, C. U.; Harvey, J. W.; Henney, C. J.
Bibcode: 2008ASPC..384..166K
Altcode: 2008csss...14..166K
Full disk solar magnetograms have been available for more than three
decades. However, those maps only show the line-of-sight magnetic
flux. The physical quantity we really want to know is the magnetic
field vector along with the filling factor, i.e. the fractional area
of the resolution element that is occupied by the magnetic field. Since
August 2003, the SOLIS Vector-SpectroMagnetograph has been recording the
photospheric magnetic field vector across the full solar disk with high
sensitivity and resolution. Some of the data are now becoming available
for beta testing, and the first science results are emerging. Here we
provide a brief introduction to the instrument and its data products and
then present some of the data from the first three years of operation.
Title: Temporal Variations of High-Cadence GONG+ Magnetic Field Images
Authors: Hill, F.; Bolding, J.; Clark, R.; Donaldson-Hanna, K.;
Harvey, J. W.; Petrie, G. J. D.; Toner, C. G.; Wentzel, T. M.
Bibcode: 2008ASPC..383..227H
Altcode:
The Global Oscillation Network Group (GONG) program now produces
full-disk line-of-sight magnetic field images at the rate of one per
minute. These high-cadence data enable unprecedented studies of the
rapid variations of the solar magnetic field over the entire disk. We
present samples of the data, and power spectra of the magnetic field in
three different types of areas (sunspot, network, and quiet Sun). The
power spectra can be used to measure velocities of moving magnetic
features.
Title: GONG Synoptic Magnetogram Program: Near-real-time Coronal
Magnetic Field Model
Authors: Petrie, G. J. D.; Bolding, J.; Clark, R.; Donaldson-Hanna,
K.; Harvey, J. W.; Hill, F.; Toner, C.; Wentzel, T. M.
Bibcode: 2008ASPC..383..181P
Altcode:
Line-of-sight photospheric magnetograms are produced every minute
at GONG's six sites. All modulators and driving circuitry have
recently been replaced, improving the sensitivity, accuracy and zero
point by orders of magnitude. Information on the solar atmospheric
field can most reliably be derived from such photospheric data,
from which model coronal fields are then extrapolated. Two types of
near-real-time synoptic magnetogram are produced by GONG every hour:
one representing the steady-state field and the other designed to
capture hour-by-hour field changes on the earthward side of the
Sun. Potential-field source-surface (PFSS) models are produced from
the standard steady-state magnetogram every hour yielding insight into
large-scale coronal field changes caused by quasi-static evolution and
by flares and coronal mass ejections. GONG is the official provider
of magnetograms for NASA's STEREO mission.}
Title: Magnetic Evolution of X-Ray Bright Points
Authors: Deluca, Edward; van Ballegooijen, Adriaan; Harvey, Jack
Bibcode: 2008cosp...37..690D
Altcode: 2008cosp.meet..690D
The evolution of magnetic structures that form X-Ray Bright Points will
be studied using local high resolution potential field extrapolations
of GONG magnetograph observations. The relationship between the X-ray
structures seen in Hinode/XRT and the magnetic structures will be
discussed.
Title: On the Polar Field Distribution as Observed by SOLIS
Authors: Raouafi, N. -E.; Harvey, J. W.; Henney, C. J.
Bibcode: 2008ASPC..383...49R
Altcode: 2008arXiv0801.0764R
We use Vector Spectromagnetograph (VSM) chromospheric full-disk
magnetograms, from the Synoptic Optical Long-term Investigations of
the Sun (SOLIS) project, to study the distribution of magnetic field
flux concentrations within the polar caps. We find that magnetic flux
elements preferentially appear toward lower latitudes within the polar
caps away from the poles. This has implications for numerous solar
phenomena such as the formation and evolution of fine polar coronal
structures (i.e., polar plumes). Our results also have implications
for the processes carrying the magnetic flux from low to high latitudes
(e.g., meridional circulation).
Title: On the Latitude Distribution of the Polar Magnetic Flux as
Observed by SOLIS-VSM
Authors: Raouafi, N. -E.; Harvey, J. W.; Henney, C. J.
Bibcode: 2008arXiv0801.0260R
Altcode:
Magnetograms from the Vector SpectroMagnetograph (VSM) of the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) project are utilized
to study the latitude distribution of magnetic flux elements as a
function of latitude in the polar solar caps. We find that the density
distribution of the magnetic flux normalized by the surface of the polar
cap and averaged over months decreases close to the solar poles. This
trend is more pronounced when considering only flux elements with
relatively large size. The flux density of the latter is relatively flat
from the edge of the polar cap up to latitudes of 70$^\circ$--75$^\circ$
and decreases significantly to the solar pole. The density of smaller
flux features is more uniformly distributed although the decrease is
still present but less pronounced. This result is important in studying
meridional flows that bring the magnetic flux from lower to higher
solar latitudes resulting in the solar cycle reversal. The results
are also of importance in studying polar structures contributing to
the fast solar wind, such as polar plumes.
Title: GONG Synoptic Magnetograms and Coronal Magnetic Field Modeling
Authors: Petrie, G. J.; Bolding, J.; Clark, R.; Donaldson-Hanna, K.;
Harvey, J. W.; Hill, F.; Toner, C.; Wentzel, T. M.
Bibcode: 2007AGUFMSH53A1068P
Altcode:
Line-of-sight photospheric magnetograms are produced every minute at
GONG's six sites. All modulators and driving circuitry have recently
been replaced, improving the sensitivity, accuracy and zero point
by orders of magnitude. Information on the solar atmospheric field
can most reliably be derived from such photospheric data, from
which model coronal fields are then extrapolated. Near-real-time
synoptic magnetogram are produced by GONG every hour. Potential-field
source-surface (PFSS) models are then produced every hour yielding
insight into large-scale coronal field changes caused by quasi-static
evolution and by flares and coronal mass ejections. We also provide
a synoptic map and model summarizing each integral Carrington
rotation. Features highlighted in the plots and movies include coronal
holes, the streamer belt, magnetic flux open to the ecliptic plane
and large-scale changes in the field topology. GONG is the official
provider of magnetograms for NASA's STEREO mission.
Title: The Magnetic Structure of X-Ray Bright Points
Authors: Deluca, E. E.; van Ballegooijen, A. A.; Harvey, J. W.;
Henney, C. J.
Bibcode: 2007AGUFMSH53A1058D
Altcode:
The magnetic structure of X-Ray Bright Points (XBPs) observed by Hinode,
SOLIS and GONG are well represented by potential field extrapolation
models. SOLIS observations are used to compare the magnetic field
model with X-ray observations. GONG observation allow us to follow
the evolution of the magnetic structures that form the XBPs. Detailed
examination of the nulls in the corona around the bright points will
presented and discussed.
Title: Latitude Distribution of Polar Magnetic Flux in the
Chromosphere Near Solar Minimum
Authors: Raouafi, N. -E.; Harvey, J. W.; Henney, C. J.
Bibcode: 2007ApJ...669..636R
Altcode:
The distribution of magnetic flux elements as a function of latitude
in the polar solar caps at a time close to solar cycle minimum is
explored. High-sensitivity line-of-sight magnetograms acquired by the
Synoptic Optical Long-term Investigations of the Sun (SOLIS) vector
spectromagnetograph (VSM) in the chromospheric line Ca II 854.2 nm are
utilized. The area density distribution of the magnetic flux averaged
over months is found to decrease close to the solar poles. This trend
is more pronounced when considering only flux elements with relatively
large size (larger than ~5''×5''). The flux
density of the latter is relatively flat from the edge of the polar
cap up to latitudes of 75°-80° and decreases by more than 50%
up to the solar pole. The density of smaller flux features is more
uniformly distributed. Although the density decrease is still present,
it is less pronounced. Hence, we believe there are two populations of
flux elements in the polar caps. The small flux elements are probably
produced uniformly across the polar area, in contrast to the large
flux elements that are the product of magnetic fields of decaying
active regions. The latter are concentrated by solar convection and
carried up to high latitudes by differential rotation and meridional
circulation. This result is important in studying meridional flows
that transport the magnetic flux from lower to higher solar latitudes
resulting, in particular, to the solar-cycle-related polar reversal. It
is also of importance in studying polar structures contributing to
the fast solar wind, such as polar plumes.
Title: Thackeray's Globules in IC 2944
Authors: Gilbert, Rick; Harvey, Jack; Verschatse, Daniel
Bibcode: 2007S&T...114Q..91G
Altcode:
No abstract at ADS
Title: GONG Synoptic Magnetograms and Coronal Magnetic Field Modeling
Authors: Petrie, Gordon; Bolding, J.; Clark, R.; Donaldson-Hanna,
K.; Hill, F.; Harvey, J. W.; Toner, C.; Wentzel, T. M.
Bibcode: 2007AAS...210.9107P
Altcode: 2007BAAS...39..205P
Line-of-sight photospheric magnetograms are produced every minute
at GONG’s six sites. All modulators and driving circuitry have
recently been replaced, improving the sensitivity, accuracy and zero
point by orders of magnitude. Information on the solar atmospheric
field can most reliably be derived from such photospheric data,
from which model coronal fields are then extrapolated. Two types of
near-real-time synoptic magnetogram are produced by GONG every hour:
one representing the steady-state field and the other designed to
capture hour-by-hour field changes on the earthward side of the
Sun. Potential-field source-surface (PFSS) models are produced from
each type of magnetogram every hour yielding insight into large-scale
coronal field changes caused by quasi-static evolution and by flares and
coronal mass ejections. GONG is the official provider of magnetograms
for NASA’s STEREO mission
Title: Seething Horizontal Magnetic Fields in the Quiet Solar
Photosphere
Authors: Harvey, J. W.; Branston, D.; Henney, C. J.; Keller, C. U.;
SOLIS Team; GONG Team
Bibcode: 2007AAS...21010001H
Altcode: 2007BAAS...39S.227H
The photospheric magnetic field outside of active regions and the
network has a ubiquitous and dynamic line-of-sight component that
strengthens away from disk center as expected for a nearly horizontal
orientation. This component shows a striking time variation with an
average temporal rms of 1.7 G at 3 arcsec resolution. In our moderate
resolution observations the nearly horizontal component has a frequency
variation power law exponent of -1.4 below 1.5 mHz and is spatially
patchy on scales up to 15 arcsec. The field may be a manifestation
of changing magnetic connections between eruptions and evolution of
small magnetic flux elements in response to convective motions. It shows
no detectable latitude or longitude variations. Preliminary observations
show no evidence of this field in the 854.2 nm chromosphere.
Title: Seething Horizontal Magnetic Fields in the Quiet Solar
Photosphere
Authors: Harvey, J. W.; Branston, D.; Henney, C. J.; Keller, C. U.;
SOLIS and GONG Teams
Bibcode: 2007ApJ...659L.177H
Altcode: 2007astro.ph..2415H
The photospheric magnetic field outside of active regions and the
network has a ubiquitous and dynamic line-of-sight component that
strengthens from disk center to limb as expected for a nearly horizontal
orientation. This component shows a striking time variation with an
average temporal rms near the limb of 1.7 G at ~3" resolution. In our
moderate-resolution observations the nearly horizontal component has
a frequency variation power-law exponent of -1.4 below 1.5 mHz and is
spatially patchy on scales up to ~15". The field may be a manifestation
of changing magnetic connections between eruptions and evolution of
small magnetic flux elements in response to convective motions. It
shows no detectable latitude or longitude variations.
Title: Properties of Solar Polar Coronal Plumes Constrained by
Ultraviolet Coronagraph Spectrometer Data
Authors: Raouafi, N. -E.; Harvey, J. W.; Solanki, S. K.
Bibcode: 2007ApJ...658..643R
Altcode: 2007astro.ph..3745R
We investigate the plasma dynamics (outflow speed and turbulence)
inside polar plumes. We compare line profiles (mainly of O VI) observed
by the Ultraviolet Coronagraph Spectrometer (UVCS) instrument on
SOHO at the minimum of solar cycle 22-23 with model calculations. We
consider Maxwellian velocity distributions with different widths in
plume and interplume regions. Electron densities are assumed to be
enhanced in plumes and to approach interplume values with increasing
height. Different combinations of the outflow and turbulence velocity
in the plume regions are considered. We compute line profiles and total
intensities of the H I Lyα and the O VI doublets. The observed profile
shapes and intensities are reproduced best by a small solar wind speed
at low altitudes in plumes that increases with height to reach ambient
interplume values above roughly 3-4 Rsolar, combined with
a similar variation of the width of the velocity distribution of the
scattering atoms/ions. We also find that plumes very close to the
pole give narrow profiles at heights above 2.5 Rsolar,
which are not observed. This suggests a tendency for plumes to be
located away from the pole. We find that the inclusion of plumes in
the model computations provides an improved correspondence with the
observations and confirms previous results showing that published UVCS
observations in polar coronal holes can be roughly reproduced without
the need for large temperature anisotropy. The latitude distributions
of plumes and magnetic flux distributions are studied by analyzing
data from different instruments on SOHO and with SOLIS.
Title: SOLIS-VSM Solar Vector Magnetograms
Authors: Henney, C. J.; Keller, C. U.; Harvey, J. W.
Bibcode: 2006ASPC..358...92H
Altcode: 2006astro.ph.12584H
The Vector SpectroMagnetograph (VSM) instrument has recorded full-disk
photospheric vector magnetograms weekly since August 2003 as part
of the Synoptic Optical Long-term Investigations of the Sun (SOLIS)
project. After the full deployment of the VSM data processing system,
a typical observing day will include three Fe I 630.2 nm full-disk
photospheric vector magnetograms, one full-disk photospheric and
three Ca II 854.2 nm chromospheric longitudinal magnetograms, along
with three He I 1083 nm spectroheliograms. The photospheric vector
magnetograms will be available over the Internet in two stages: first,
as a quick-look product within minutes of data acquisition, and then
as a Milne-Eddington inversion product within a day of each observation.
Title: Chromospheric Magnetism
Authors: Harvey, J. W.
Bibcode: 2006ASPC..358..419H
Altcode:
Magnetic fields have been measured using chromospheric spectrum lines
since Hale's discovery of magnetic fields in sunspots. This is a brief
selective review of the history of research on chromospheric magnetism,
including some of the key results and future prospects. The topic is
challenging both from the observational and analysis perspectives, but
major advances on both fronts have recently invigorated this research
area. Selected recent results are highlighted with some emphasis on
results from NSO. One notable result is that the chromosphere has large
areas with predominantly horizontal magnetic field and these areas
have structural, dynamical and radiative properties that are different
from the quiet Sun, sunspots, plages and filaments and deserve more
study. The near term prospects are bright for improved understanding
of chromospheric magnetism.
Title: Sunspots with the Strongest Magnetic Fields
Authors: Livingston, W.; Harvey, J. W.; Malanushenko, O. V.;
Webster, L.
Bibcode: 2006SoPh..239...41L
Altcode: 2006SoPh..tmp...85L
The strongest observed solar magnetic fields are found in sunspot
umbrae and associated light bridges. We investigate systematic
measurements of approximately 32 000 sunspot groups observed from 1917
through 2004 using data from Mt. Wilson, Potsdam, Rome and Crimea
observatories. Isolated observations from other observatories are
also included. Corrections to Mt. Wilson measurements are required
and applied. We found 55 groups (0.2%) with at least one sunspot
with one magnetic field measurement of at least 4000 G including five
measurements of at least 5000 G and one spot with a record field of
6100 G. Although typical strong-field spots are large and show complex
structure in white light, others are simple in form. Sometimes the
strongest fields are in light bridges that separate opposite polarity
umbras. The distribution of strongest measured fields above 3 kG appears
to be continuous, following a steep power law with exponent about
−9.5. The observed upper limit of 5 - 6 kG is consistent with the
idea that an umbral field has a more or less coherent structure down
to some depth and then fragments. We find that odd-numbered sunspot
cycles usually contain about 30% more total sunspot groups but 60%
fewer >3 kG spots than preceding even-numbered cycles.
Title: Large-Scale Chromospheric Magnetic Fields
Authors: Harvey, J. W.
Bibcode: 2006IAUJD...3E...3H
Altcode:
A decade of regular full-disk observations of the longitudinal Zeeman
splitting of the chromospheric 854.2 nm CaII spectrum line reveals
many interesting magnetic phenomena in the chromosphere. The most
prominent is a large-scale, mainly horizontal diffuse field surrounding
active regions. This extended canopy field is not present in the
photosphere and is closely related to chromospheric fibrils and the
circumfacule phenomenon. The properties of the field are described in
this report. The atmosphere where this field is present has different
dynamics, structure and radiative properties than other parts of the
solar atmosphere and deserves more study. A method of measuring the
longitudinal Zeeman splitting that accounts for the highly variable
chromospheric line profile is also described.
Title: Properties of Plasma Dynamics In The Polar Coronal Plumes
Authors: Raouafi, N. -E.; Harvey, J. W.; Solanki, S. K.
Bibcode: 2006ESASP.617E..16R
Altcode: 2006soho...17E..16R
No abstract at ADS
Title: Solar Wind Forecasting with Coronal Holes
Authors: Robbins, S.; Henney, C. J.; Harvey, J. W.
Bibcode: 2006SoPh..233..265R
Altcode: 2007astro.ph..1275R
An empirical model for forecasting solar wind speed related geomagnetic
events is presented here. The model is based on the estimated location
and size of solar coronal holes. This method differs from models that
are based on photospheric magnetograms (e.g., Wang-Sheeley model)
to estimate the open field line configuration. Rather than requiring
the use of a full magnetic synoptic map, the method presented here can
be used to forecast solar wind velocities and magnetic polarity from
a single coronal hole image, along with a single magnetic full-disk
image. The coronal hole parameters used in this study are estimated with
Kitt Peak Vacuum Telescope He I 1083 nm spectrograms and photospheric
magnetograms. Solar wind and coronal hole data for the period between
May 1992 and September 2003 are investigated. The new model is found
to be accurate to within 10% of observed solar wind measurements for
its best 1-month period, and it has a linear correlation coefficient
of ∼0.38 for the full 11 years studied. Using a single estimated
coronal hole map, the model can forecast the Earth directed solar wind
velocity up to 8.5 days in advance. In addition, this method can be
used with any source of coronal hole area and location data.
Title: Plasma dynamics in the polar coronal plumes
Authors: Raouafi, N. -E.; Harvey, J. W.; Solanki, S. K.
Bibcode: 2006IAUS..233..193R
Altcode:
We use the spectral shapes of the EUV line profiles to study the plasma
dynamics, acceleration and heating, in polar plumes (PP). We find
that the observed profiles are reproduced fairly well when considering
low plume wind speeds and velocity turbulence (α_S) at low altitudes
followed by a rapid acceleration and heating of the plasma to reach
the properties of inter-plumes (IP) by ≈3-4~R_⊙. We also find that
plumes very close to the pole give narrow profiles at all heights
that are not observed above ≈2.5~R_⊙. This suggests a tendency
for plume footpoints to lie more than 10° away from the pole. High
resolution magnetograms of SOLIS and EUV images support this hypothesis.
Title: Editorial Appreciation
Authors: Engvold, Oddbjørn; Harvey, Jack; Leibacher, John; Sakurai,
Takashi; Švestka, Zdeněk; van Driel-Gesztelyi, Lidia; Solar Physics
editors
Bibcode: 2006SoPh..233....1E
Altcode:
No abstract at ADS
Title: Automated Coronal Hole Detection using He 1083 nm
Spectroheliograms and Photospheric Magnetograms
Authors: Henney, C. J.; Harvey, J. W.
Bibcode: 2005ASPC..346..261H
Altcode: 2007astro.ph..1122H
A method for automated coronal hole detection using He I 1083-nm
spectroheliograms and photospheric magnetograms is presented here. The
unique line formation of the helium line allows for the detection of
regions associated with solar coronal holes with minimal line-of-sight
obscuration across the observed solar disk. The automated detection
algorithm utilizes morphological image analysis, thresholding and
smoothing to estimate the location, boundaries, polarity and flux of
candidate coronal hole regions. The algorithm utilizes thresholds based
on mean values determined from over 10 years of the Kitt Peak Vacuum
Telescope daily hand-drawn coronal hole images. A comparison between
the automatically created and hand-drawn images for a 11-year period
beginning in 1992 is outlined. In addition, the creation of synoptic
maps using the daily automated coronal hole images is also discussed.
Title: Longitudinal Magnetic Field Changes Accompanying Solar Flares
Authors: Sudol, J. J.; Harvey, J. W.
Bibcode: 2005ApJ...635..647S
Altcode:
We have used Global Oscillation Network Group (GONG) magnetograms to
characterize the changes in the photospheric longitudinal magnetic field
during 15 X-class solar flares. An abrupt, significant, and persistent
change in the magnetic field occurred in at least one location within
the flaring active region during each event. We have identified a
total of 42 sites where such field changes occurred. At 75% of these
sites, the magnetic field change occurred in less than 10 minutes. The
absolute values of the field changes ranged between 30 and almost 300 G,
the median being 90 G. Decreases in the measured field component were
twice as frequent as increases. The field changes ranged between 1.4 and
20 times the rms noise of the observations. In all but one equivocal
case, the field changes occurred after the start of the flare. In
all cases, the field changes were permanent. At least two-thirds of
the field changes occurred in the penumbrae of sunspots. During three
events for which simultaneous Transition Region and Coronal Explorer
(TRACE) images are available, we have found excellent spatial and
temporal correlation between the change in the magnetic field and an
increase in brightness of the footpoints of flare ribbons, but not vice
versa. Among many possible explanations for the observations, we favor
one in which the magnetic field changes result from the penumbral field
relaxing upward by reconnecting magnetic fields above the surface. One
of the basic assumptions of flare theories is that the photospheric
magnetic field does not change significantly during flares. These
results suggest that this assumption needs to be re-examined.
Title: Editorial
Authors: Engvold, Oddbjorn; Harvey, Jack; Švestka, Zdenek
Bibcode: 2005SoPh..229....1E
Altcode:
No abstract at ADS
Title: Reduction of SOLIS/Vector Spectromagnetograph He I 1083
nm Observations
Authors: Jones, H. P.; Malanushenko, O. V.; Harvey, J. W.; Henney,
C. J.; Keller, C. U.
Bibcode: 2005AGUSMSP51A..02J
Altcode:
The SOLIS/Vector Spectromagnetograph (VSM) now continues the
three-decade record of full-disk He I 1083 nm spectroheliograms from
NSO/Kitt Peak (see poster by Henney et al.). Although the sensitivity
of the VSM interim cameras at 1083 nm is far greater than that of
previous NSO/KP instruments, the observations are compromised by
strong interference fringes produced within the detectors. We discuss
in some detail the extent to which this difficulty is overcome
in the simple algorithm used to produce the synoptic observations
and explore methods for removing remaining fringe effects for true
imaging spectroscopy. These techniques include Fourier and Wavelet
filtering, the flat-fielding algorithm used for earlier NASA/NSO
Spectromagnetograph (SPM) observations, and physical modeling of the
detector fringe pattern.
Title: Are You Being Served? - Solar Data Management at the National
Solar Observatory
Authors: Hill, F.; Suarez-Sola, I.; Harvey, J. W.; Henney, C. J.;
Keller, C.; Wampler, S.
Bibcode: 2005AGUSMSH43B..04H
Altcode:
Solar physics is a data driven field, where no progress can be made
without multi-wavelength and multi-cadence information about the
sun's behavior. The National Solar Observatory (NSO) has provided
data to the research community for over 30 years and thus has
considerable experience in the areas of data processing, archiving,
and distribution. This presentation will describe the development of
NSO's data services, outline what lessons have been learned along the
way, and attempt to forecast the future of data management at NSO.
Title: Solar Wind Forecasting with the SOLIS-VSM
Authors: Robbins, S. J.; Henney, C. J.; Harvey, J. W.
Bibcode: 2005AGUSMSP51B..01R
Altcode:
A web based solar wind forecasting resource applying a simple
empirical model with SOLIS-VSM (Vector Spectromagnetograph) data is
presented here. The solar wind empirical model uses the locations of
coronal holes on the observed solar disk to forecast an estimated
solar wind velocity at Earth. The model coefficients are estimated
minimizing the difference between 10+ years of coronal hole images
and the corresponding measured solar wind velocities. The coronal
hole training data set was derived from Kitt Peak Vacuum Telescope
(KPVT) He I 1083 nm images and photospheric magnetograms. The model
can forecast up to 8.5 days in advance. The VSM estimated coronal hole
images are derived from daily full-disk photospheric magnetograms
and He I 1083 nm spectroheliograms using an automated coronal hole
detection algorithm. Daily solar wind forecasts are planned to be
automated using SOLIS-VSM data and made available publicly during the
year 2005. The coronal hole data used here was compiled by K. Harvey
and F. Recely using National Solar Observatory (NSO) KPVT observations
under a grant from the National Science Foundation (NSF). Solar
wind data utilized for this project is provided on the Internet at
http://nssdc.gsfc.nasa.gov/omniweb/. This work is carried out through
the NSO Research Experiences for Undergraduate (REU) site program,
which is co-funded by the Department of Defense in partnership with the
National Science Foundation REU Program. This research was supported
in part by the Office of Naval Research Grant N00014-91-J-1040. The NSO
is operated by AURA, Inc. under a cooperative agreement with the NSF.
Title: Calcium Circumfacules: New Findings About a Neglected
Phenomenon
Authors: Harvey, J. W.
Bibcode: 2005AGUSMSP41B..05H
Altcode:
In 1903, Hale and Ellerman noted faint, elliptical dark regions
surrounding CaII K232 plages. Deslandres in 1910 showed these
features to be more prominent in CaII K3 spectroheliograms and named
them circumfacules. In 1930, d'Azambuja found them to be strikingly
prominent in CaII 8542 Å spectroheliograms. Bumba and Howard in
1965 suggested that the calcium circumfacules are composed of broad
dark features corresponding to dark Hα fibrils. They noted that the
visibility is greatest at the time of maximum K plage brightness. The
small handful of available descriptions of this phenomenon leave one
with the impression that the calcium circumfacules are manifestations of
dark fibrils fanning out from the edges of plages to form the outermost
chromospheric boundaries of active regions. Many questions remain: Why
are they most prominent in 8542 Å? Are they really fuzzy dark fibrils
or something different? Are they associated with the diffuse, mainly
horizontal chromospheric magnetic field surrounding some plages? What is
their effect on sun-as-a-star spectral irradiance measurements? Daily
full disk observations of the 8542 Å line have been made at NSO
since 1996. Using these data, and new SOLIS vector spectromagnetograph
8542 Å observations of Stokes I and V line profiles, these and other
questions are addressed. The National Solar Observatory is operated by
the Association of Universities for Research in Astronomy, Inc. (AURA),
under cooperative agreement with the National Science Foundation.
Title: SOLIS-VSM Synoptic Products
Authors: Henney, C. J.; Harvey, J. W.; Keller, C. U.
Bibcode: 2005AGUSMSP51A..04H
Altcode:
Since August 2003, the Vector Spectromagnetograph (VSM) instrument has
recorded full-disk photospheric and chromospheric magnetograms along
with He I 1083 nm spectroheliograms daily as part of the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) project. In
addition, the VSM measured full-disk photospheric vector magnetograms
weekly. After the full deployment of the VSM data processing system,
a typical observing day will include three full-disk photospheric
vector magnetograms. Products from observations for the past year
and half are expected to become available during the year 2005, these
include Dopplergrams, equivalent width and line depth images. Besides
individual full-disk images, several derived products are also or
soon will be available via the SOLIS web site. These products include
integrated full-disk magnetogram and helium spectroheliogram time
series. Additionally, Carrington rotation and daily synoptic maps
are now available from the photospheric magnetograms. Daily coronal
hole estimate images using VSM data, along with the creation of solar
wind source maps will also be available. The VSM synoptic products
are available on the NSO-SOLIS web site cooperatively by NSF/NSO
and NASA/GSFC. The National Solar Observatory is operated by AURA,
Inc. under a cooperative agreement with the National Science Foundation.
Title: Helicity and the SOLIS Vector-Spectromagnetograph
Authors: Keller, Christoph U.; Harvey, John W.; Henney, Carl. J.;
Jones, Harrison P.
Bibcode: 2005HiA....13..126K
Altcode:
SOLIS (Synoptic Optical Long-term Investigations of the Sun)
is a suite of three innovative instruments that greatly improve
ground-based synoptic solar observations. The main instrument the
Vector Spectro-Magnetograph (VSM) is a compact high-throughput
vector-polarimeter that measures the magnetic field strength and
direction over the full solar disk within 15 minutes. Helicity can
be directly calculated from the full-disk vector field data provided
by the Stokes inversion of the observed polarized line profiles. We
present an anlysis of the difficulties and problems that one faces
when interpreting the the helicity derived from VSM data.
Title: Solar Wind Forecasting with Coronal Holes
Authors: Robbins, S. J.; Henney, C. J.; Harvey, J. W.
Bibcode: 2004AAS...205.1009R
Altcode: 2004BAAS...36.1350R
An empirical model for forecasting solar wind speed related
geomagnetic events is presented. The model is based on the location
and size of solar coronal holes determined with Kitt Peak Vacuum
Telescope \ion{He}{1} 1083.0 nm spectroheliograms and photospheric
magnetograms. This method differs from the Wang-Sheeley model that
is based on photospheric magnetograms to estimate the open field line
configuration. Solar wind and coronal hole data for the period between
May 1992 and September 2003 are investigated. The new model is
found to be accurate to within 4.5-5.7% (the range depends upon the
number of days ahead forecast) of observed solar wind measurements
for the best one-month periods within the time frame studied; the
overall 11-year correlation is as high as 0.382. Using coronal hole
maps, the model can predict the solar wind velocity up to 8.5 days
in advance with an average fractional deviation as low as 9.4-10.0%
for a given one-month period. This is further in advance forecasting
and up to a factor of 2 improvement over the Wang-Sheeley model. Its
main features are a strong southern hemisphere bias, sunspot cycle
dependence, and that a complete forecast of up to 9 days can be made
from a single solar image, as opposed to a full synoptic map required
by the Wang-Sheeley model. This work is carried out through the
National Solar Observatory Research Experiences for Undergraduate
(REU) site program, which is co-funded by the Department of Defense
in partnership with the National Science Foundation REU Program. This
research was supported in part by the Office of Naval Research Grant
N00014-91-J-1040. The National Solar Observatory is operated by AURA,
Inc. under a cooperative agreement with the National Science Foundation.
Title: Changes in the Longitudinal Magnetic Field during Solar Flares
Authors: Sudol, J. J.; Harvey, J. W.
Bibcode: 2004ESASP.559..643S
Altcode: 2004soho...14..643S
No abstract at ADS
Title: Two White Light Flares in AR10486 observed by the GONG
instruments
Authors: Howe, R.; Gonzalez-Hernandez, I.; Harvey, J. W.; Hill, F.
Bibcode: 2004AAS...204.0212H
Altcode: 2004BAAS...36R.669H
The GONG (Global Oscillation Network Group) program operates a worldwide
network of six instruments, primarily intended to give continuous
Doppler velocity images of the full solar disk for helioseismology. The
instruments also produce images in magnetic field strength, total
intensity and line depth for a 1Å band centered on the Ni I (6768 Å)
line, all at 60 second cadence with a spatial resolution of around 2
arcsecond. The X10 flare of 2003 October 29 and the X8.3 flare of 2003
November 2 both produced clear signatures in the GONG images, with
local 20 to 30 per cent enhancements in the total intensity and a 50
per cent drop in the line strength, indicating the presence of white
light emission. There are also both transient and persistent changes
in the magnetic field. This work was supported by NASA and NSF.
Title: SOLIS-VSM Longitudinal Magnetogram Calibration
Authors: Henney, C. J.; Harvey, J. W.; Keller, C. U.; Jones, H. P.
Bibcode: 2004AAS...204.3702H
Altcode: 2004BAAS...36..709H
The VSM (Vector SpectroMagnetograph) instrument started recording
daily full-disk magnetograms during August, 2003 at a temporary
site in Tucson, Arizona. Along with the other instruments that
constitute the SOLIS (Synoptic Optical Long-term Investigations of
the Sun) project, the VSM will be relocated to Kitt Peak in April,
2004. The VSM instrument provides a unique record of solar full-disk
vector magnetograms along with the high sensitivity photospheric and
chromospheric longitudinal magnetograms. In addition, the VSM takes
daily full-disk He I 1083 nm equivalent width observations. These
parameter-grams are constructed from individual scans in declination
of the projected solar image on the entrance slit with a relatively
large field angle of over a half of a degree in the spectrograph. The
calibration of the VSM longitudinal magnetic observations is reviewed,
along with a comparison between the VSM mean field, sun-as-a-star,
measurements with those by the Wilcox Solar Observatory. In addition,
the making of synoptic maps derived from the VSM magnetograms is
discussed, including the filling of data gaps in polar regions and
the use of accompanying weight maps. VSM magnetograms and synoptic
maps are available via the Internet at: http://solis.nso.edu/. This
research was supported in part by the Office of Naval Research Grant
N00014-91-J-1040. The National Solar Observatory is operated by AURA,
Inc. under a cooperative agreement with the National Science Foundation.
Title: Remarkable Low Temperature Emission of the 4 November 2003
Limb Flare
Authors: Leibacher, J. W.; Harvey, J. W.; Kopp, G.; Hudson, H.;
GONG Team
Bibcode: 2004AAS...204.0213L
Altcode: 2004BAAS...36..669L
Strong (> 1.5 times normal intensity) continuum and photospheric line
emission of the 4 November 2003 X28 flare was recorded simultaneously
by three widely separated GONG instruments. Emission was seen from
on the disk to > 20" above the limb for nearly one hour, likely
making this event the longest duration white light flare observed
to date. GONG observations are one-minute duration integrations of
intensity averaged across a Lyot filter bandpass of about 90 pm FWHM
centered on the Ni I line at 676.8 nm with 2.5" instrument pixel
size. Spatial resolution is limited by diffraction and seeing to
greater than 5". Additional measurements include the Doppler shift and
strength of the spectrum line. These latter measurements indicate that
continuum and line emission contributed about equally to the observed
intensity signal. Light curves and images of the flare show a notable
two-kernel disk event starting at about 19:33 UTC followed by a much
stronger event that peaked at about 19:44. Rare, white-light prominences
were visible above the limb after 19:34. Comparison of total solar
irradiance measurements from the TIM instrument on board the SORCE
spacecraft with full-disk integrated GONG intensities shows the global
five-minute oscillation and the white light flare. The latter is much
weaker in the GONG data, suggesting that most of the TIM flare signal
arises from other, most likely shorter, wavelengths. This work
utilizes data obtained by the Global Oscillation Network Group (GONG)
Program, managed by the National Solar Observatory, which is operated
by AURA, Inc. under a cooperative agreement with the National Science
Foundation. SORCE is supported by NASA NAS5-97045
Title: Local Changes in Longitudinal Magnetic Field during Solar
Flare Events
Authors: Sudol, J. J.; Harvey, J. W.; Howe, R.
Bibcode: 2004AAS...204.3902S
Altcode: 2004BAAS...36..714S
We present preliminary results from an investigation of local changes
in the longitudinal magnetic field during solar flare events using
GONG+ magnetograms. The one-minute cadence, 5" resolution, and near
continuous coverage of the GONG+ magnetograms make them well suited for
this kind of investigation. We have reviewed all of the available GONG+
magnetograms for two or more hours on either side of the X-class solar
flare events that occurred between April 2001 and December 2003. In most
cases, we have observed a discrete shift in the apparent, longitudinal
magnetic field during the flare event that persists for more than two
hours after the event. The shifts in the magnetic field are consistent
with one another to within their uncertainties and average 120 ±
20 gauss. Such consistency, though, could be a selection effect. In
some cases, we have observed weaker shifts in the apparent magnetic
field that occur at later times at increasing distance from the flare
center. The rate of propagation of these shifts in the magnetic field
from the flare center is 30 km s-1. We discuss the observed
phenomena and possible explanations for them.
Title: Measurement Scale of the SOLIS Vector Spectromagnetograph
Authors: Jones, H. P.; Harvey, J. W.; Henney, C. J.; Keller, C. U.;
Malanushenko, O. M.
Bibcode: 2004AAS...204.3703J
Altcode: 2004BAAS...36Q.709J
Longitudinal magnetograms obtained with the SOLIS Vector
Spectromagnetograph (VSM) during a cross-calibration period are
compared with similar data from the NASA/NSO Spectromagnetograph (SPM)
at the NSO/Kitt Peak Vacuum Telescope as well as with SOHO/MDI and GONG
magnetograms. The VSM began observations at the University of Arizona
agricultural test site and collaborative observations were obtained
with both the VSM and SPM from 2003 Aug 05 through 2003 Sep 21 when
the SPM was officially retired. The VSM replaces the SPM and continues
the 30-year NSO/Kitt Peak synoptic magnetogram record. Magnetograms
are compared by equating histograms and, for selected examples, by
pixel-by-pixel comparison of coregistered images. The VSM was not
corrected for polarization crosstalk and was operated without fast
guiding. Solar activity was at best moderate during this period. Over
the range of observed fields, the VSM magnetograms show greatly
improved sensitivity but are otherwise virtually identical with "raw"
SPM magnetograms. GONG magnetograms are also closely comparable with
the SPM while MDI flux values tend to be stronger by a factor of 1.2 -
1.4. Dependence of the results on seeing will be discussed. Partial
funding for this work was provided through Solar and Heliospheric
Research Supporting Research and Technology grants from NASA's Office
of Space Sciences.
Title: Improved Convergence for CCD Gain Calibration Using
Simultaneous-Overrelaxation Techniques
Authors: Toussaint, R. M.; Harvey, J. W.; Toussaint, Doug
Bibcode: 2003AJ....126.1112T
Altcode:
Simple modifications to the analysis used in the Kuhn, Lin,
& Loranz flat-field CCD calibration method yield significant
improvements in both speed and accuracy. In this method, multiple
exposures are taken of a time-independent signal at different spatial
positions. The flat field is then expressed in the form of a Jacobi
relaxation solution to Poisson's equation. By applying the technique
of simultaneous overrelaxation, we have improved the convergence rate
to require approximately the square root of the number of iterations
(sqrt(r)) needed by the Jacobi method. For large arrays, where r is
correspondingly large, this improvement is significant. Furthermore,
we have improved the accuracy by extending the method to account for
fractional pixel shifts.
Title: Calibration and Data Analysis for the SOLIS-VSM
Authors: Henney, C. J.; Harvey, J. W.; Keller, C. U.; Jones, H. P.;
SOLIS Team
Bibcode: 2003SPD....34.0303H
Altcode: 2003BAAS...35..808H
The Vector Spectromagnetograph (VSM) instrument of the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) project will
provide a unique 25-year record of synoptic solar observations with
daily full-disk photospheric vector and high sensitivity longitudinal
magnetograms. In addition, the VSM will produce daily full-disk
chromospheric longitudinal magnetograms along with various He I 1083
nm parameter images. The VSM is being prepared for installation at a
temporary site in Tucson for a comparison period with observations from
the Kitt Peak Vacuum Telescope (KPVT). After the cross-calibration
period, the VSM will replace the KPVT spectromagnetograph at Kitt
Peak. We outline the various VSM data products, with emphasis on the
calibration and data reduction efforts. The data transmission
and storage resources are such that the reduction of VSM data will be
performed at the observing site on Kitt Peak. Reduced data products
will be transmitted via a DS3 link from Kitt Peak to the National Solar
Observatory's digital archive in Tucson. During a typical observing day,
three full-disk photospheric vector magnetograms will be available over
the Internet in two stages: first, as a ``quick-look'' product within
10 minutes of data acquisition, and then as a full Milne-Eddington
(ME) inversion product within 12 hours of each observation. The
quick-look parameters will include estimates of the magnetic field
strength, azimuth and inclination based on Auer, Heasley, House (1977,
Solar Physics 55, p. 47). The high-precision vector products will be
determined with the High Altitude Observatory ME inversion technique
implemented by Skumanich and Lites (1987, ApJ, 322, p.473). The
flexible design of the VSM data handling system can incorporate
future improvements under consideration (e.g., principal component
analysis). This research was supported in part by the Office of
Naval Research Grant N00014-91-J-1040.
Title: SOLIS: an innovative suite of synoptic instruments
Authors: Keller, Christoph U.; Harvey, John W.; Giampapa, Mark S.
Bibcode: 2003SPIE.4853..194K
Altcode:
SOLIS (Synoptic Optical Long-term Investigations of the Sun) is
a suite of three innovative instruments under construction that
will greatly improve ground-based synoptic solar observations. The
Vector Spectromagnetograph (VSM) is a compact, high-throughput
vector-polarimeter with an active secondary mirror, an actively
controlled grating spectrograph, and two high-speed cameras with
silicon-on-CMOS-multiplexer hybrid focal plane arrays. It will measure
the magnetic field strength and direction over the full solar disk
within 15 minutes. The Full-Disk Patrol (FDP) takes full-disk solar
intensity and Doppler images in various spectral lines and in the
continuum at a high cadence through liquid-crystal tuned birefringent
filters. The Integrated Sunlight Spectrometer (ISS) uses a fiber-fed
spectrograph to measure minute changes of the Sun-as-a-star in
many spectral lines. A high degree of automation and remote control
provides fast user access to data and flexible interaction with the
data-collection process. SOLIS is currently in the final assembly
phase and will become operational early in 2003.
Title: The SOLIS Vector-Spectromagnetograph
Authors: Keller, C. U.; Harvey, J. W.; Solis Team
Bibcode: 2003ASPC..307...13K
Altcode:
No abstract at ADS
Title: Helicity and the SOLIS Vector-Spectromagnetograph
Authors: Keller, Christoph U.; Harvey, John W.; Henney, Carl J.;
Jones, Harrison P.
Bibcode: 2003IAUJD...3E..18K
Altcode:
SOLIS (Synoptic Optical Long-term Investigations of the Sun)
is a suite of three innovative instruments that greatly improve
ground-based synoptic solar observations. The main instrument the
Vector Spectro-Magnetograph (VSM) is a compact high-throughput
vector-polarimeter that measures the magnetic field strength and
direction over the full solar disk within 15 minutes. Helicity can
be directly calculated from the full-disk vector field data provided
by the Stokes inversion of the observed polarized line profiles. We
present an anlysis of the difficulties and problems that one faces
when interpreting the the helicity derived from VSM data.
Title: A Method for Measuring the Image Distortion in the GONG Solar
Telescopes II
Authors: Sudol, J. J.; Harvey, J. W.; Toner, C. G.
Bibcode: 2002AAS...201.5502S
Altcode: 2002BAAS...34.1202S
Knowledge of the distortion in an image is important in a number of
applications. This is especially true in helioseismology where errors
in either time or position degrade inferences about internal solar
structure and dynamics. Previously (BAAS 34(2), 732, 2002), we proposed
a method for measuring the distortion in the images obtained with
the Global Oscillation Network Group solar telescopes. After running
a number of simulations, we have made some critical modifications to
our method. Our attempts to solve simultaneously for the image center
and the distortion have proven to be unstable. We now solve first for
the image center and then for the distortion. Methods that involve
a large number of free parameters are imprecise because the solution
space tends to be shallow and littered with local minima. The large
number of calibration images and image points required to improve on
this situation is impractical. In an effort to reduce the number of
free parameters in our method, our error metric is now based on the
differences in the distances between pairs of image points across all
of the calibration images obtained. In addition to these modifications,
we now register the calibration images before and after correcting
the images for distortion. The scatter in the image point positions
in the first case sets an upper limit on the distortion and in the
second case sets an upper limit on the extent to which corrections
for the distortion can be made. In simulations, we have been able to
correct for distortion to 0.1 pixel, an order of magnitude above our
desired correction of 0.01 pixel, which is comparable to the error in
determining the positions of the image points.
Title: Two solar cycles of nonincreasing magnetic flux
Authors: Arge, C. N.; Hildner, E.; Pizzo, V. J.; Harvey, J. W.
Bibcode: 2002JGRA..107.1319A
Altcode:
Since measurements began in the late nineteenth century, there has
been a secular increase (with superposed ripples due to solar cycles)
of the aa geomagnetic index [, 1972]. Starting from this observation,
[1999a, 1999b] conclude that the total open solar magnetic flux has
increased by 41% from 1964 to 1995 and by 130% over all but the last
5 years of the twentieth century. However, solar data for more than
two solar cycles - Carrington maps from Mount Wilson, and Wilcox
Solar Observatories and newly reanalyzed data from the National
Solar Observatory - show no secular trend in overall photospheric
flux. More importantly, the magnetic flux open to interplanetary space
(as calculated from photospheric measurements and assuming potential
fields to a height of 2.5 R⊙) fails to show evidence of
a secular increase over the last two solar cycles. Like Lockwood et
al., we do not explicitly take account of transient events. Thus both
data and calculations imply that the Sun's average coronal magnetic
flux has not increased over the last two solar cycles. Analysis of
simulations with the potential field source surface model shows that
the interplanetary magnetic flux is not simply related to the erupted
photospheric solar magnetic flux. Both results are in agreement with
the findings of [2000]. The topology, rather than the strength, of
the emergent solar magnetic field may be a major determinant of the
interplanetary magnetic field experienced at Earth.
Title: Data analysis for the SOLIS Vector Spectromagnetograph
Authors: Jones, Harrison P.; Harvey, John W.; Henney, Carl J.; Hill,
Frank; Keller, Christoph U.
Bibcode: 2002ESASP.505...15J
Altcode: 2002solm.conf...15J; 2002IAUCo.188...15J
The National Solar Observatory's SOLIS Vector Spectromagnetograph, which
will produce three or more full-disk maps of the Sun's photospheric
vector magnetic field every day for at least one solar magnetic cycle,
is in the final stages of assembly. Initial observations, including
cross-calibration with the current NASA/NSO spectromagnetograph (SPM),
will soon be carried out at a test site in Tucson. This paper discusses
data analysis techniques for reducing the raw data, calculation of
line-of-sight magnetograms, and both quick-look and high-precision
inference of vector fields from Stokes spectral profiles. Existing
SPM algorithms, suitably modified to accommodate the cameras, scanning
pattern, and polarization calibration optics for the VSM, will be used
to "clean" the raw data and to process line-of-sight magnetograms. A
recent version of the High Altitude Observatory Milne-Eddington (HAO-ME)
inversion code will be used for high-precision vector fields.
Title: Phase Coherence Analysis of Solar Magnetic Activity
Authors: Henney, Carl J.; Harvey, John W.
Bibcode: 2002SoPh..207..199H
Altcode: 2006astro.ph.12606H
Over 24 years of synoptic data from the NSO Kitt Peak Vacuum Telescope
is used to investigate the coherency and source of the 27-day (synodic)
periodicity that is observed over multiple solar cycles in various
solar-related time series. A strong 27.03-day period signal, recently
reported by Neugebauer et al. (2000), is clearly detected in power
spectra of time series from integrated full-disk measurements of the
magnetic flux in the 868.8 nm Fe i line and the line equivalent width
in the 1083.0 nm He i line. Using spectral analysis of synoptic maps
of photospheric magnetic fields, in addition to constructing maps
of the surface distribution of activity, we find that the origin of
the 27.03-day signal is long-lived complexes of active regions in the
northern hemisphere at a latitude of approximately 18 deg. In addition,
using a new time series analysis technique which utilizes the phase
variance of a signal, the coherency of the 27.03-day period signal is
found to be significant for the past two decades. However, using the
past 120 years of the sunspot number time series, the 27.03-day period
signal is found to be a short-lived, no longer than two 11-year solar
cycles, quasi-stationary signal.
Title: Signatures of CMEs in HeI 1083 nm Images and Estimation of
ICME Bz Direction
Authors: Harvey, J. W.; Harvey, K. L.; Henney, C. J.
Bibcode: 2002AAS...200.3706H
Altcode: 2002BAAS...34..695H
Coronal Mass Ejections (CMEs) are expulsions from the corona of material
at coronal and chromospheric temperatures. Since the strength of the
HeI absorption line multiplet at 1083 nm partly depends on the amount of
mass in the chromosphere and overlying corona, CME signatures appear in
1083 nm observations. We examined daily time-difference images for such
signatures in comparison with direct CME observations. We found that by
using good spatial resolution, the time-difference images readily show
disappearing filaments and sudden expansions of coronal holes which are
known to be frequently associated with CMEs. The images also show the
enhanced footpoints of arcades of post-flare loops as increases of line
strength, and plage intensity changes. The 1083 nm changes are often
spread widely over a large fraction of the solar disk, consistent with
direct coronal disk observations of CMEs. These difference images will
be available on NSO's web site, along with other data, as part of a
transition to new a new suite of synoptic instruments called SOLIS. As
an example of the utility of comparing different data, we examined
contemporaneous photospheric and chromospheric magnetograms to see if
the magnetic field Bz direction (north-south GSE coordinate) of the
interplanetary CME (ICME) could be predicted. A southward directed Bz is
associated with severe geomagnetic storms. Several predictive schemes
are promising but their reliability needs improvement. A significant
observational difficulty is that the detectable mass loss occurs where
the magnetic field is relatively weak. This work was supported in part
by ONR grant N00014-91-J-1040 and NSF grant ATM-9819842.
Title: GONG+ Synoptic Magnetic Field Maps
Authors: Donaldson Hanna, K. L.; Harvey, J. W.
Bibcode: 2002AAS...200.0403D
Altcode: 2002BAAS...34..643D
Having completed the upgrade of its observing equipment, the Global
Oscillation Network Group (GONG) now acquires longitudinal component
magnetograms every minute using a 1024 X 1024 square-pixel detector
compared to the previous (Classic GONG) program of recording a
(1-minute integrated) magnetogram once per hour using a 256 X
242 rectangular-pixel detector. To demonstrate the registration
accuracy and the quality of these magnetograms, synoptic maps were
created using magnetograms from GONG+, Kitt Peak Vacuum Telescope
(KPVT), UCLA Astronomy Group - Mt. Wilson, and Solar Heliospheric
Observatory/Michelson-Doppler Imager (SOHO/MDI) for a common Carrington
rotation cycle. Comparisons between independent maps constructed from
the GONG+ sites (Big Bear, Cerro Tololo, and Learmonth) are also shown
to display the excellent geometric agreement between the sites. The
Global Oscillation Network Group project is supported by the National
Science Foundation and operates in collaboration with the Big Bear Solar
Observatory, High Altitude Observatory, Learmonth Solar Observatory,
Udaipur Solar Observatory, Instituto de Astrofisico de Canarias,
and Cerro Tololo Interamerican Observatory.
Title: A Method for Measuring the Image Distortion in the GONG
Solar Telescopes
Authors: Sudol, J. J.; Harvey, J. W.; Toner, C. G.
Bibcode: 2002AAS...200.5501S
Altcode: 2002BAAS...34R.732S
The accuracy of the results of local helioseismology studies is limited
in part by image distortion. The Global Oscillation Network Group (GONG)
operates six identical solar telescopes worldwide which continuously
obtain full disk intensity images, velocity images, and magnetograms at
one minute intervals at a resolution of 2.5 arcseconds per pixel. The
theoretical distortion in the images obtained with these telescopes
is 0.004 pixel at the solar limb. The true distortion, though,
is unknown and might be higher than the theoretical distortion
depending on the quality of the alignment of the optics and the
extent to which the optical components deviate from their design
specifications. Observations of sources other than the Sun are not
possible with the GONG solar telescopes, so traditional methods for
measuring distortion cannot be used. We propose a method for measuring
the distortion in the images obtained with the GONG solar telescopes
to 0.01 pixel, and we present the results of several simulations of
this method. We intend to construct an optical system to project
sunlight onto a pinhole plate that lies at the focus of a lens in
front of the entrance window of the solar telescope. An optical wedge
between the lens and the entrance window will allow us to translate
the image of the pinhole plate to sample the distortion across the
image plane. Given a sequence of images of the pinhole plate, we will
solve simultaneously for the relative positions of the pinholes on
the plate and the distortion.
Title: New NSO Solar Surface Activity Maps
Authors: Henney, C. J.; Harvey, J. W.
Bibcode: 2001AGUSM..SP51B03H
Altcode:
Using NSO-Kitt Peak Vacuum Telescope (KPVT) synoptic data, we present
several new solar surface activity maps. The motivation is to test
conventional wisdom about conditions that are likely to produce
solar activity such as flares, coronal mass ejections and high
speed solar wind streams. The ultimate goal is to improve real-time,
observation-based models for the purpose of predicting solar activity. A
large number of maps will eventually be produced based on the wide range
of ideas and models of the conditions thought to lead to solar activity
events. When data from the new SOLIS instruments becomes available,
the range of possible models that can be tested will be greatly
expanded. At present, the daily maps include ones that show magnetic
field complexity, emerging flux and high speed solar wind sources. As a
proxy for local magnetic potential energy, each element of the magnetic
complexity map is the distance-weighted rms of the opposing ambient
magnetic field. The flux emergence map is the difference between the
two most recent absolute magnetic flux images. The solar wind source
map is produced from coronal hole area data. The new maps are available
on the NSO-Kitt Peak World Wide Web page. This research was supported
in part by the Office of Navel Research Grant N00014-91-J-1040. The
NSO-Kitt Peak data used here are produced cooperatively by NSF/AURA,
NASA/GSFC, and NOAA/SEC.
Title: Three Solar Cycles of Non-Increasing Magnetic Field
Authors: Hildner, E.; Arge, N.; Pizzo, V. J.; Harvey, J. W.
Bibcode: 2001AGUSM..SH51A08H
Altcode:
Since measurements started in the late 19th century, there has been
a secular increase (with superposed ripples due to solar cycles) of
the aa geomagnetic index. Starting from this observation, Lockwood,
Stamper, and Wild (hereafter, LSW) conclude (Nature, 399, 1999; see
also Lockwood et al., Astronomy and Geophysics, 40, 1999) that the
total source's magnetic flux in the Sun's atmosphere has risen by 41%
since 1964\" and by 130% in the 20th century. However, solar data over
nearly three solar cycles - near-daily magnetograms from Mt Wilson, and
Wilcox Solar Observatories and newly reanalyzed data from the National
Solar Observatory - show no secular trend in overall photospheric
flux. More importantly, the magnetic field open to interplanetary space
(as calculated from photospheric measurements and assuming potential
fields to a height of 2.5 Rsun) fails to show a secular increase over
the last three solar cycles. Like LSW, we do not explicitly take account
of transient events. Thus, both data and calculations imply that the
Sun's average coronal magnetic flux has not increased over the last
three solar cycles. Analysis of simulations with the potential field
source surface model shows that the interplanetary magnetic flux is not
simply related to the overall, photospheric, solar magnetic flux. Both
results are in agreement with the findings of Wang, Lean, and Sheeley
(GRL, 27, 2000). The topology, not just the strength, of the emergent
solar magnetic field is a major determinant of the interplanetary
magnetic field experienced at Earth. In principle, secular change in
non-potentiality of the coronal field could lead to secular increase
in interplanetary magnetic flux, but this seems unlikely.
Title: Analysis of the 27.03 day Period found in Synoptic Data from
NSO-Kitt Peak
Authors: Henney, C. J.; Harvey, J. W.
Bibcode: 2001AGUSM..SP51B04H
Altcode:
Over 25 years of synoptic data from the NSO-Kitt Peak Vacuum Telescope
(KPVT) is used to investigate recent reports of a 27.03 day period
observed in solar wind and solar surface magnetic field data. We present
analysis of this signal using time series of integrated KPVT full-disk
measurements of the magnetic flux in 868.8 nm and the line equivalent
width in 1083.0 nm. In particular, we analyze the coherency of the 27.03
day signal, along with a search for potential solar surface sources
of the signal. As a measure the coherency, a phase coherency spectrum
was created using the signal phase measured for different segments of
the time series. For comparison, we also analyze the international
sunspot number (ISN) for the same period as the KPVT time series,
along with the full period of the ISN time series. Similar to earlier
results, we find that the signal is coherent for the last few decades
but not over longer time periods. By constructing maps of the surface
distribution of activity synchronized to different rotation periods,
we find that the origin of the signal is long-lived complexes of active
regions. This research was supported in part by the Office of Navel
Research Grant N00014-91-J-1040. The NSO-Kitt Peak data used here are
produced cooperatively by NSF/AURA, NASA/GSFC, and NOAA/SEC.
Title: Search for Photospheric Magnetic Field Changes with Flares
and CMEs
Authors: Harvey, J. W.
Bibcode: 2001AGUSM..SH22A01H
Altcode:
A common belief is that solar events such as flares and coronal mass
ejections (CME) are produced by magnetic field changes. Yet there
is scant direct observational support of this idea. Modifications
of the instruments used by the Global Oscillation Network Group
permit full disk measurements of the line-of-sight component of the
photospheric magnetic field to be made every minute. The observations
have a resolution of 5 arc sec and a noise level of about 5 G per 2.5
arc second pixel. Several day-long sequences were studied to see if
changes of the magnetic field at the times of flares and CMEs could
be detected. The magnetograms were viewed as movies after various
preprocessing steps. They were also used to make time series of the
field strength averaged over the entire disk, over zones of selected
latitudes and as coefficients of spherical harmonic transforms of
the data. To date no signature of a magnetic field change that can be
directly associated with flares or CMEs has been detected. Evidently
such associated changes are either below our noise level of a fraction
of a Gauss (depending on analysis method), take place predominantly
outside the photosphere, or are mainly of a component of the vector
magnetic field that is not well represented along the line of
sight. This work utilizes data obtained by the Global Oscillation
Network Group, managed by the NSO. The NSO is sponsored by the the
National Science Foundation through a cooperative agreement with the
Association of Universities for Research in Astronomy, Inc. This work
was supported in part by ONR award N00014-91-J-1040.
Title: Helioseismic Diagnostics of Solar Convection and Activity
Authors: Svestka, Zdenek; Harvey, John W.
Bibcode: 2000hdsc.conf.....S
Altcode:
This book focuses on the recent advances in our understanding of
solar convection and activity, and on new methods and results of
helioseismic diagnostics of the internal structures and dynamics
of solar convection and active regions. The methods of local
helioseismology (time-distance tomography, ring-diagram analysis,
acoustic imaging, and holography) intensively developed in the past
few years have provided promising results on the deep structure
of large-scale convection and flows, emerging active regions, and
sunspots. The book includes reviews and contributed papers presented at
the SOHO-9 Workshop held on July 12-15, 1999, at Stanford University,
California, U.S.A. It provides a comprehensive overview of the
current status of the field and presents new ideas and approaches
to helioseismic diagnostics and theoretical modeling of the physical
processes inside the Sun. The book is recommended for graduate students
and specialists in solar physics, astrophysics, and geophysics. Link:
http://www.wkap.nl/book.htm/0-7923-6520-8
Title: Helioseismic diagnostics of solar convection and activity. Part
1, 2. Proceedings. SOHO-9 Workshop, Stanford, CA (USA), 12 - 15
Jul 1999.
Authors: Švestka, Z.; Harvey, J. W.; Kosovichev, A. G.; Duvall,
T. L., Jr.
Bibcode: 2000SoPh..192....1S
Altcode:
The following topics were dealt with: theories of solar convection,
rotation and activity, helioseismic tomography, acoustic imaging and
holography, ring-diagram analysis, magnetic fields and oscillations,
solar cycle variations of the internal structure and rotation, solar
convective structures and oscillations.
Title: Filament Channel Magnetic Field Changes and Prominence
Eruptions
Authors: Donaghy, T. Q.; Harvey, J. W.
Bibcode: 1999AAS...19510705D
Altcode: 1999BAAS...31.1531D
Daily full-disk measurements of the chromospheric magnetic field have
been made using the 854.2 nm Ca II line and the NSO/Kitt Peak Vacuum
Telescope since June 1996. These observations have revealed previously
unobserved features of the solar magnetic field, chief of which are
fields associated with filament channels. These fields are apparent
in the chromosphere, but do not appear in the photosphere. They are
diffuse, unipolar fields that exhibit a reversal of sign as solar
rotation carries them across the disk, indicating a predominant
horizontal component to the field. We explore the changes in these
fields before and after a prominence eruption and we study six strong
events, showing the chromospheric and photospheric magnetic fields both
before and after an eruptive event. In the cases where we could detect
the filament channel fields, we were also able to detect noticeable
change in the fields with the advent of the prominence eruption. Many
more events need to be studied before a consistent pattern of field
changes can be considered as certain. Such a extensive study should
also help elucidate the mechanisms of filament eruption. The NSO is one
of the National Optical Astronomy Observatories which are sponsored by
the National Science Foundation. The NSO data used here are produced
cooperatively by NSF/NOAO, NASA/GSFC, and NOAA/SEC.
Title: Estimation Of Seeing Quality Using Low-Resolution Solar
Image Data
Authors: Bell, Eric F.; Hill, Frank; Harvey, John W.
Bibcode: 1999SoPh..185...15B
Altcode:
Modulation transfer functions (MTFs), generated as a by-product of the
analysis of low-resolution solar images taken for the Global Oscillation
Network Group, were used to estimate the quality of seeing at its six
sites. These MTFs, after approximate correction for the effects of the
instrumental point spread function, were fitted with physically-motived
functional forms representing the effects of seeing and scattering. It
was found that the estimates of seeing quality were relatively robust
to the effects of scattering, but were severely biased by effects
caused by changes in instrumental focus. Relative trends in seeing
quality are preserved on time scales shorter than a few months and
it is found that local topography dominates the observed trends in
daytime seeing quality.
Title: Acoustic interferometry of the solar atmosphere: p-modes with
frequencies near the `acoustic cut-off'
Authors: Vorontsov, S. V.; Jefferies, S. M.; Duval, T. L., Jr.;
Harvey, J. W.
Bibcode: 1998MNRAS.298..464V
Altcode:
High-frequency p-mode intensity data, obtained from the South Pole in
1987, 1988, 1990 and 1994, show a sharp variation in the phase-shift
function and in the frequency spacings near 5.5 mHz. Using a simple
theoretical model, we demonstrate that this behaviour is caused by an
acoustic resonance in the atmosphere between the excitation source and
the upper reflection level. We discuss the diagnostic properties of this
resonance, which is sensitive to the acoustic reflectivity of the solar
atmosphere and to the location and parity of the excitation source. When
applied to the solar data, our model indicates that the average acoustic
reflectivity increases with increasing solar activity. The model also
shows that the acoustic source has composite parity and is located
within one pressure scaleheight of the base of the photosphere.
Title: Synoptic Solar Physics -- 18th NSO/Sacramento Peak Summer
Workshop
Authors: Balasubramaniam, K. S.; Harvey, Jack; Rabin, D.
Bibcode: 1998ASPC..140.....B
Altcode: 1998ssp..conf.....H
No abstract at ADS
Title: The Procyon campaign: Observations from Kitt Peak
Authors: Pilachowski, C. A.; Barden, S.; Hill, F.; Harvey, J. W.;
Keller, C. U.; Giampapa, M. S.
Bibcode: 1998IAUS..185..319P
Altcode:
Time series spectra of the F5IV star Procyon (alpha CMi) were obtained
at the Kitt Peak National Observatory during a 35-night observing run
in January-February 1997. The observations were obtained as part of an
international collaboration to detect and study acoustic oscillations
in solar-type stars. Spectra covered the wavelength range from 4000
to 5300 AA , with a resolving power of approximately 3500 (1.3 AA
resolution). The sampling rate was one observation per minute, and
the typical S/N ratio per observation is in excess of 1000. At the
time of writing, we have obtained over 10,000 spectra. The spectra
will be analyzed to identify any periodic signals due to acoustic
oscillations in Procyon. In addition to measuring the equivalent widths
of the three Balmer lines (Kjeldsen et al. 1995) covered by our spectra
(Hβ, Hγ, and Hdelta) we will also examine the spectra for variations
in the average metal line strength. Preliminary power spectra will
be presented.
Title: Asteroseismology from equivalent widths: a test of the sun
Authors: Keller, C. U.; Harvey, J. W.; Barden, S. C.; Giampapa, M. S.;
Hill, F.; Pilachowski, C. A.
Bibcode: 1998IAUS..185..375K
Altcode:
Kjeldsen et al. (1995) reported a probable detection of solar-like,
low-amplitude, p-mode oscillations of eta Bootes using equivalent
width measurements from low-resolution spectra of the hydrogen Balmer
lines. We tested the usefulness of this technique using observations of
the Sun in integrated light. Despite the very high signal-to-noise ratio
of the data stretching over six continuous days, no solar oscillation
signal was found so far in the equivalent width of Hβ. Spatially
resolved observations of the Hβ equivalent width at solar disk center
reveal that the oscillation signal is suppressed in the wings of Hβ
as compared to the continuum. Extrapolation of the oscillation signal
seen in the spatially resolved data suggests an amplitude of about
1ppm for integrated light measurements, which is about a factor of
5 lower than expected from simple theoretical arguments. We explore
other methods to deduce an oscillation signal from all spectral lines
simultaneously. cont has: Deng, L. et al.; auths fixed below
Title: Sounding the Sun's Chromosphere
Authors: Jefferies, S. M.; Osaki, Y.; Shibahashi, H.; Harvey, J. W.;
D'Silva, S.; Duvall, T. L., Jr.
Bibcode: 1997ApJ...485L..49J
Altcode:
Time-distance analysis of solar acoustic waves with frequencies above
the nominal atmospheric acoustic cutoff frequency (~5.3 mHz) shows
partial reflection of the waves at both the Sun's photosphere and a
layer located higher in the atmosphere. This result supports recent
reports of chromospheric modes.
Title: Association of Extreme-Ultraviolet Imaging Telescope (EIT)
Polar Plumes with Mixed-Polarity Magnetic Network
Authors: Wang, Y. -M.; Sheeley, N. R.; Dere, K. P.; Duffin, R. T.;
Howard, R. A.; Michels, D. J.; Moses, J. D.; Harvey, J. W.; Branston,
D. D.; Delaboudinière, J. -P.; Artzner, G. E.; Hochedez, J. F.;
Defise, J. M.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert,
W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Clette, F.
Bibcode: 1997ApJ...484L..75W
Altcode:
SOHO EIT spectroheliograms showing the polar coronal holes during the
present sunspot minimum are compared with National Solar Observatory
(Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The
chromospheric λ8542 magnetograms, obtained on a routine, near-daily
basis since 1996 June, reveal the Sun's strong polar fields with
remarkable clarity. We find that the Fe IX λ171 polar plumes occur
where minority-polarity flux is in contact with flux of the dominant
polarity inside each polar hole. Moreover, the locations of ``plume
haze'' coincide approximately with the patterns of brightened He
II λ304 network within the coronal hole. The observations appear
to be consistent with mechanisms of plume formation involving
magnetic reconnection between unipolar flux concentrations and nearby
bipoles. The fact that minority-polarity fields constitute only a small
fraction of the total magnetic flux within the polar holes suggests
that plumes are not the main source of the high-speed polar wind.
Title: The seismic structure of the Sun from GONG
Authors: Anderson, E.; Antia, H. M.; Basu, S.; Chaboyer, B.; Chitre,
S. M.; Christensen-Dalsgaard, J.; Eff-Darwich, A.; Elliott, J. R.;
Giles, P. M.; Gough, D. O.; Guzik, J. A.; Harvey, J. W.; Hill,
F.; Leibacher, J. W.; Kosovichev, A. G.; Monteiro, M. J. P. F. G.;
Richard, O.; Sekii, T.; Shibahashi, H.; Takata, M.; Thompson, M. J.;
Toomre, J.; Vauclair, S.; Vorontsov, S. V.
Bibcode: 1997IAUS..181..151A
Altcode:
No abstract at ADS
Title: Concept for a miniature solar magnetograph
Authors: Keller, Christoph U.; Harvey, John W.
Bibcode: 1996SPIE.2804...14K
Altcode:
We present a novel concept for a solar magnetograph that uses a
photo-refractive crystal to reflect and focus the light from the wings
of many spectral lines onto a camera. The crystal acts simultaneously as
multiple, narrow-band filters and as an off-axis telescope. Polarization
measurements are performed close to the final focus. Since this approach
uses the light from many spectral lines simultaneously, the required
telescope aperture is substantially reduced and exposure times can be
so short that accurate tracking is not necessary. Such a concept is
particularly attractive for NASA's Minimum Solar Mission where very
compact, light-weight instruments are required.
Title: Helioseismic Tomography
Authors: D'Silva, Sydney; Duvall, Thomas L., Jr.; Jefferies, Stuart
M.; Harvey, John W.
Bibcode: 1996ApJ...471.1030D
Altcode:
"Helioseismic tomography" is a method using observations to construct
slices of the Sun's internal structure. It is based on a reduction of
observations to time-distance surfaces and hypersurfaces. We present
a procedure for measuring time-distance surfaces and hypersurfaces,
and thereby a method of studying localized inhomogeneities in the
interior of the Sun, such as abnormalities in the sound speed (e.g., a
thermal shadow, Parker 1987a), or local subsurface flows, or magnetic
fields. We also present a simulation of measuring time-distance
surfaces and illustrate how to measure the size of an inhomogeneity,
its location in depth, and the deviation of its sound speed compared
to its local surroundings.
Title: Dynamics of the Chromospheric Network: Mobility, Dispersal,
and Diffusion Coefficients
Authors: Schrijver, Carolus J.; Shine, Richard A.; Hagenaar, Hermance
J.; Hurlburt, Neal E.; Title, Alan M.; Strous, Louis H.; Jefferies,
Stuart M.; Jones, Andrew R.; Harvey, John W.; Duvall, Thomas L., Jr.
Bibcode: 1996ApJ...468..921S
Altcode:
Understanding the physics behind the dispersal of photo spheric magnetic
flux is crucial to studies of magnetoconvection, dynamos, and stellar
atmospheric activity. The rate of flux dispersal is often quantified by
a diffusion coefficient, D. Published values of D differ by more than a
factor of 2, which is more than the uncertainties allow. We propose that
the discrepancies between the published values for D are the result of
a correlation between the mobility and flux content of concentrations of
magnetic flux. This conclusion is based on measurements of displacement
velocities of Ca II K mottles using an uninterrupted 2 day sequence
of filtergrams obtained at the South Pole near cycle minimum. We
transform the Ca II K intensity to an equivalent magnetic flux density
through a power-law relationship defined by a comparison with a nearly
simultaneously observed magnetogram. One result is that, wherever the
network is clearly defined in the filtergrams, the displacement vectors
of the mottles are preferentially aligned with the network, suggesting
that network-aligned motions are more important to field dispersal than
deformation of the network pattern by cell evolution. The rms value
of the inferred velocities, R = <|v|2>½,
decreases with increasing flux, Φ, contained in the mottles, from R
≍ 240 m s-1 down to 140 s-1. The value of R(Φ)
appears to be independent of the flux surrounding the concentration,
to the extreme that it does not matter whether the concentration is
in a plage or in the network. The determination of a proper effective
diffusion coefficient requires that the function R(Φ) be weighted
by the number density n(Φ) of mottles that contain a total flux. We
find that n(Φ) decreases exponentially with Φ and propose a model
of continual random splitting and merging of concentrations of flux to
explain this dependence. Traditional methods used to measure D tend to
be biased toward the larger, more sluggish flux concentrations. Such
methods neglect or underestimate the significant effects of the
relatively large number of the more mobile, smaller concentrations. We
argue that the effective diffusion coefficient for the dispersal of
photo spheric magnetic flux is ∼600 km2 s-1.
Title: Asteroseismology via equivalent widths - tests on Procyon,
Eta Bootis, and Alpha Trianguli.
Authors: Harvey, J. W.; Pilachowski, C.; Barden, S.; Giampapa, M.;
Keller, C. U.; Hill, F.
Bibcode: 1996BAAS...28..917H
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: The Current State of Solar Modeling
Authors: Christensen-Dalsgaard, J.; Dappen, W.; Ajukov, S. V.;
Anderson, E. R.; Antia, H. M.; Basu, S.; Baturin, V. A.; Berthomieu,
G.; Chaboyer, B.; Chitre, S. M.; Cox, A. N.; Demarque, P.; Donatowicz,
J.; Dziembowski, W. A.; Gabriel, M.; Gough, D. O.; Guenther, D. B.;
Guzik, J. A.; Harvey, J. W.; Hill, F.; Houdek, G.; Iglesias, C. A.;
Kosovichev, A. G.; Leibacher, J. W.; Morel, P.; Proffitt, C. R.;
Provost, J.; Reiter, J.; Rhodes, E. J., Jr.; Rogers, F. J.; Roxburgh,
I. W.; Thompson, M. J.; Ulrich, R. K.
Bibcode: 1996Sci...272.1286C
Altcode:
Data from the Global Oscillation Network Group (GONG) project and
other helioseismic experiments provide a test for models of stellar
interiors and for the thermodynamic and radiative properties, on which
the models depend, of matter under the extreme conditions found in the
sun. Current models are in agreement with the helioseismic inferences,
which suggests, for example, that the disagreement between the predicted
and observed fluxes of neutrinos from the sun is not caused by errors in
the models. However, the GONG data reveal subtle errors in the models,
such as an excess in sound speed just beneath the convection zone. These
discrepancies indicate effects that have so far not been correctly
accounted for; for example, it is plausible that the sound-speed
differences reflect weak mixing in stellar interiors, of potential
importance to the overall evolution of stars and ultimately to estimates
of the age of the galaxy based on stellar evolution calculations.
Title: The Seismic Structure of the Sun
Authors: Gough, D. O.; Kosovichev, A. G.; Toomre, J.; Anderson,
E.; Antia, H. M.; Basu, S.; Chaboyer, B.; Chitre, S. M.;
Christensen-Dalsgaard, J.; Dziembowski, W. A.; Eff-Darwich, A.;
Elliott, J. R.; Giles, P. M.; Goode, P. R.; Guzik, J. A.; Harvey,
J. W.; Hill, F.; Leibacher, J. W.; Monteiro, M. J. P. F. G.; Richard,
O.; Sekii, T.; Shibahashi, H.; Takata, M.; Thompson, M. J.; Vauclair,
S.; Vorontsov, S. V.
Bibcode: 1996Sci...272.1296G
Altcode:
Global Oscillation Network Group data reveal that the internal
structure of the sun can be well represented by a calibrated standard
model. However, immediately beneath the convection zone and at the
edge of the energy-generating core, the sound-speed variation is
somewhat smoother in the sun than it is in the model. This could be a
consequence of chemical inhomogeneity that is too severe in the model,
perhaps owing to inaccurate modeling of gravitational settling or to
neglected macroscopic motion that may be present in the sun. Accurate
knowledge of the sun's structure enables inferences to be made about
the physics that controls the sun; for example, through the opacity,
the equation of state, or wave motion. Those inferences can then be
used elsewhere in astrophysics.
Title: The Global Oscillation Network Group (GONG) Project
Authors: Harvey, J. W.; Hill, F.; Hubbard, R. P.; Kennedy, J. R.;
Leibacher, J. W.; Pintar, J. A.; Gilman, P. A.; Noyes, R. W.; Title,
A. M.; Toomre, J.; Ulrich, R. K.; Bhatnagar, A.; Kennewell, J. A.;
Marquette, W.; Patron, J.; Saa, O.; Yasukawa, E.
Bibcode: 1996Sci...272.1284H
Altcode:
Helioseismology requires nearly continuous observations of the
oscillations of the solar surface for long periods of time in
order to obtain precise measurements of the sun's normal modes of
oscillation. The GONG project acquires velocity images from a network
of six identical instruments distributed around the world. The GONG
network began full operation in October 1995. It has achieved a duty
cycle of 89 percent and reduced the magnitude of spectral artifacts by
a factor of 280 in power, compared with single-site observations. The
instrumental noise is less than the observed solar background.
Title: Differential Rotation and Dynamics of the Solar Interior
Authors: Thompson, M. J.; Toomre, J.; Anderson, E. R.; Antia, H. M.;
Berthomieu, G.; Burtonclay, D.; Chitre, S. M.; Christensen-Dalsgaard,
J.; Corbard, T.; De Rosa, M.; Genovese, C. R.; Gough, D. O.; Haber,
D. A.; Harvey, J. W.; Hill, F.; Howe, R.; Korzennik, S. G.; Kosovichev,
A. G.; Leibacher, J. W.; Pijpers, F. P.; Provost, J.; Rhodes, E. J.,
Jr.; Schou, J.; Sekii, T.; Stark, P. B.; Wilson, P. R.
Bibcode: 1996Sci...272.1300T
Altcode:
Splitting of the sun's global oscillation frequencies by large-scale
flows can be used to investigate how rotation varies with radius
and latitude within the solar interior. The nearly uninterrupted
observations by the Global Oscillation Network Group (GONG) yield
oscillation power spectra with high duty cycles and high signal-to-noise
ratios. Frequency splittings derived from GONG observations confirm
that the variation of rotation rate with latitude seen at the surface
carries through much of the convection zone, at the base of which is
an adjustment layer leading to latitudinally independent rotation at
greater depths. A distinctive shear layer just below the surface is
discernible at low to mid-latitudes.
Title: The Global Oscillation Network Group Project
Authors: Leibacher, J. W.; Harvey, J. W.; Hill, F.; Hubbard, R.;
Kennedy, J. R.; Pintar, J. A.; Bhatnagar, A.; Kennewell, J. A.;
Marquette, W.; Patron, J.; Saa, O.; Yasukawa, E.; GONG Project Team
Bibcode: 1996AAS...188.5301L
Altcode: 1996BAAS...28..903L
The NSF-sponsored Global Oscillation Network Group (GONG) project
has developed and is operating a network of six velocity imaging
instruments around the world, and a data analysis system that can keep
up with the massive data flow, in support of a vigorous community that
shares in all aspects of this program to explore the structure and
dynamics of the solar interior. Data from the first three stations
were obtained starting in March 1995, and the full six-station
network became operational in early October 1995. The system noise
is below the solar background of incoherent surface motions, and the
overall data processing pipeline is maintaining cadence with the data
flood. The scientific objectives, design and performance of the network,
instrumentation, and data processing, and plans for the future will be
presented. The National Optical Astronomy Observatories are operated
by the Association of Universities for Research in Astronomy, Inc.,
under cooperative agreement with the National Science Foundation.
Title: The Solar Acoustic Spectrum and Eigenmode Parameters
Authors: Hill, F.; Stark, P. B.; Stebbins, R. T.; Anderson, E. R.;
Antia, H. M.; Brown, T. M.; Duvall, T. L., Jr.; Haber, D. A.;
Harvey, J. W.; Hathaway, D. H.; Howe, R.; Hubbard, R. P.; Jones,
H. P.; Kennedy, J. R.; Korzennik, S. G.; Kosovichev, A. G.; Leibacher,
J. W.; Libbrecht, K. G.; Pintar, J. A.; Rhodes, E. J., Jr.; Schou, J.;
Thompson, M. J.; Tomczyk, S.; Toner, C. G.; Toussaint, R.; Williams,
W. E.
Bibcode: 1996Sci...272.1292H
Altcode:
The Global Oscillation Network Group (GONG) project estimates
the frequencies, amplitudes, and linewidths of more than 250,000
acoustic resonances of the sun from data sets lasting 36 days. The
frequency resolution of a single data set is 0.321 microhertz. For
frequencies averaged over the azimuthal order m, the median formal
error is 0.044 microhertz, and the associated median fractional error
is 1.6 x 10-5. For a 3-year data set, the fractional error
is expected to be 3 x 10-6. The GONG m-averaged frequency
measurements differ from other helioseismic data sets by 0.03 to 0.08
microhertz. The differences arise from a combination of systematic
errors, random errors, and possible changes in solar structure.
Title: Downflows under sunspots detected by helioseismic tomography
Authors: Duvall, T. L.; D'Silva, S.; Jefferies, S. M.; Harvey, J. W.;
Schou, J.
Bibcode: 1996Natur.379..235D
Altcode:
SUNSPOTS are areas of cooler gas and stronger magnetic fields in the
Sun's photosphere (its 'surface'), but just how they form and are
maintained has long been a puzzle. It has been proposed1
that small vertical magnetic flux tubes, generated deep within the Sun,
develop downflows around them when they emerge at the surface. The
downflows bring together a large number of flux tubes in a cluster
to form a sunspot, which behaves as a single flux bundle as long as
the downflows bind the flux tubes together. Until now, however,
it has not been possible to test this model with subsurface
observations. Here we use the recently developed technique of
travel-time helioseismology2 to detect the presence of
strong downflows beneath both sunspots and the bright features known
as plages. The flows have a velocity of ~2 kms-1, and they
persist to a depth of about 2,000 km. The data suggest, however, that
the vertical magnetic field can be a coherent flux bundle only to a
depth of ~600 km; below this depth it is possible that the downflows
hold together a loose collection of flux tubes to maintain the sunspots
that we see.
Title: Characteristic Size and Diffusion of Quiet Sun Magnetic
Patterns
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1995SoPh..158..213K
Altcode:
We have previously studied large-scale motions using high-resolution
magnetograms taken from 1978 to 1990 with the NSO Vacuum Telescope on
Kitt Peak. Latitudinal and longitudinal motions were determined by
a two-dimensional crosscorrelation analysis of pairs of consecutive
daily observations using small magnetic features as tracers. Here we
examine the shape and amplitude of the crosscorrelation functions. We
find a characteristic length scale as indicated by the FWHM of the
crosscorrelation functions of 16.6 ± 0.2 Mm. The length scale
is constant within ±45° latitude and decreases by about 5% at
52.5° latitude; i.e., the characteristic size is almost latitude
independent. The characteristic scale is within 3% of the average value
during most times of the solar cycle, but it increases during cycle
maximum at latitudes where active regions are present. For the time
period 1978-1981 (solar cycle maximum), the length scale increases
up to 1.7 Mm or 10% at 30° latitude. In addition, we derive the
average amplitude of the crosscorrelation functions, which reflects
the diffusion of magnetic elements and their evolutionary changes
(including formation and decay). We find an average value of 0.091 ±
0.003 for the crosscorrelation amplitude at a time lag of one day, which
we interpret as being caused by the combined effect of the lifetime
of magnetic features and a diffusion process. Assuming a lifetime
of one day, we find a value of 120 km2 s−1
for the diffusion constant, while a lifetime of two days leads to 230
km2 s−1.
Title: Measurement of High-Degree Solar Oscillation Frequencies
Authors: Bachmann, K. T.; Duvall, T. L., Jr.; Harvey, J. W.; Hill, F.
Bibcode: 1995ApJ...443..837B
Altcode:
We present m-averaged solar p- and f-mode oscillation frequencies over
the frequency range nu greater than 1.8 and less than 5.0 mHz and the
spherical harmonic degree range l greater than or equal to 100 and
less than or equal to 1200 from full-disk, 1000 x 1024 pixel, Ca II
intensity images collected 1993 June 22-25 with a temporal cadence
of 60 s. We itemize the sources and magnitudes of statistical and
systematic uncertainties and of small frequency corrections, and we
show that our frequencies represent an improvement in accuracy and
coverage over previous measurements. Our frequencies agree at the 2
micro Hz level with Mount Wilson frequencies determined for l less
than or equal to 600 from full-disk images, and we find systematic
offsets of 10-20 micro Hz with respect to frequencies measured from
Big Bear and La Palma observations. We give evidence that these latter
offsets are indicative of spatial scaling uncertainties associated with
the analysis of partial-disk images. In comparison with theory, our
p-mode frequencies agree within 10 micro Hz of frequencies predicted
by the Los Alamos model but are as much as 100 micro Hz smaller than
frequencies predicted by the Denmark and Yale models at degrees near
1000. We also find systematic differences between our n = 0 frequencies
and the frequencies closely agreed upon by all three models.
Title: Solar Polar Magnetic Field in 1994 and 1995
Authors: Harvey, J. W.
Bibcode: 1995SPD....26..302H
Altcode: 1995BAAS...27..952H
No abstract at ADS
Title: Mapping Wave Speed in the Outer Convection Zone
Authors: Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.
Bibcode: 1995SPD....26..105D
Altcode: 1995BAAS...27..950D
No abstract at ADS
Title: Weak Magnetic Fields in the Network
Authors: Keller, C. U.; Harvey, J. W.
Bibcode: 1995SPD....26..206K
Altcode: 1995BAAS...27..952K
No abstract at ADS
Title: Frequencies of High Degree Solar Oscillations
Authors: Bachmann, K. T.; Duvall, T. L., Jr.; Harvey, J. W.; Hill, F.
Bibcode: 1995ASPC...76..156B
Altcode: 1995gong.conf..156B
No abstract at ADS
Title: The NSO/NASA He I 1083.0 nm Video Filtergraph/Magnetograph
Authors: Jones, H. P.; Harvey, J. W.
Bibcode: 1995itsa.conf...97J
Altcode:
No abstract at ADS
Title: Measurements of High-Degree Solar Oscillation Parameters
Authors: Bachmann, K. T.; Duvall, T. L., Jr.; Harvey, J. W.; Hill, F.
Bibcode: 1994AAS...185.4405B
Altcode: 1994BAAS...26R1377B
We present results obtained from full-disk, 1000times 1024 pixel, Ca II
intensity images of the Sun collected with the High-L Helioseismometer
(HLH). Our measurement of p- and f-mode oscillation frequencies over
the frequency range 1.8<=nu <=5.0 mHz and the spherical harmonic
degree range 100<=l<=1200 from 22-25 June 1993 data represents an
improvement over previous measurements. We are able to differentiate
among the predictions of several solar models, thus constraining
physical models of the solar convection zone. We also include recent
splitting and frequency results from data collected during the entire
month of June 1994. The purpose of the HLH research program is to
measure high-degree solar oscillation parameters for the remainder
of this decade in support of the Solar Oscillations Investigation -
Michelson Doppler Imager collaboration, which is part of the Solar
and Heliospheric Observatory, a joint ESA-NASA satellite mission.
Title: Joint observations of the chromosphere, transition region,
and corona from SOHO and NSO/Kitt Peak
Authors: Jones, H. P.; Harvey, John W.; Andretta, Vincenzo
Bibcode: 1994ESASP.373..345J
Altcode: 1994soho....3..345J
No abstract at ADS
Title: Use of Acoustic Wave Travel-Time Measurements to Probe the
Near-Surface Layers of the Sun
Authors: Jefferies, S. M.; Osaki, Y.; Shibahashi, H.; Duvall, T. L.,
Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1994ApJ...434..795J
Altcode:
The variation of solar p-mode travel times with cyclic frequency
nu is shown to provide information on both the radial variation of
the acoustic potential and the depth of the effective source of the
oscillations. Observed travel-time data for waves with frequency
lower than the acoustic cutoff frequency for the solar atmosphere
(approximately equals 5.5 mHz) are inverted to yield the local acoustic
cutoff frequency nuc as a function of depth in the outer
convection zone and lower atmosphere of the Sun. The data for waves
with nu greater than 5.5 mHz are used to show that the source of the
p-mode oscillations lies approximately 100 km beneath the base of the
photosphere. This depth is deeper than that determined using a standard
mixing-length calculation.
Title: Solar Fine-Scale Structures in the Corona, Transition Region,
and Lower Atmosphere
Authors: Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.;
Martin, S. F.; Zirin, H.
Bibcode: 1994ApJ...430..913M
Altcode:
The American Science and Engineering Soft X-ray Imaging Payload and the
Naval Research Laboratory High Resolution Telescope and Spectrograph
(HRTS) were launched from White Sands on 1987 December 11 in coordinated
sounding rocket flights. The goal was to investigate the correspondence
of fine-scale structures from different temperature regimes in the
solar atmosphere, and particularly the relationship between X-ray bright
points (XBPs) and transition region explosive events. We present results
of the analysis of co-aligned X-ray images, maps of sites of transition
region explosive events observed in C IV 105, HRTS 1600
A spectroheliograms of the Tmin region, and ground-based
magnetogram and He I 10830 A images. We examined the relationship
of He I 10830 A dark features and evolving magnetic features which
correspond to XBPs. We note a frequent double ribbon pattern of the
He I dark feature counterparts to XBPs. We discuss an analysis of the
relationship of XBPs to evolving magnetic features by Webb et al.,
which shows that converging magnetic features of opposite polarity are
the most significant magnetic field counterparts to XBPs. The magnetic
bipolar features associated with XBPs appear as prominent network
elements in chromospheric and transition region images. The features
in C IV observations corresponding to XBP sites are in general bright,
larger scale (approximately 10 arcsec) regions of complex velocity
fields of order 40 km/s, which is typical of brighter C IV network
elements. These C IV features do not reach the approximately 100 km/s
velocities seen in the C IV explosive events. Also, there are many
similar C IV bright network features without a corresponding XBP in the
X-ray image. The transition region explosive events do not correspond
directly to XBPs. The explosive events appear to be concentrated in
the quiet Sun at the edges of strong network, or within weaker field
strength network regions. We find a greater number of C IV events than
expected from the results of a previous Spacelab 2 HRTS disk survey. We
attribute this at least partly to better spatial resolution with the
newer HRTS data. The full-disk X-ray image shows a pattern of dark
lanes in quiet Sun areas. The number density of C IV events is twice
as large inside as outside a dark lane (4.6 x 10-3 vs. 2.3
x 10-3 explosive events per arcsec 2). The dark
lane corresponds to an old decaying magnetic neutral line. We suggest
that this provides an increased opportunity for small-scale convergence
and reconnection of opposite polarity magnetic field features, in
analogy with the results of Webb et al. for XBPs but at a reduced
scale of reconnection.
Title: The Covariance of Latitudinal and Longitudinal Motions of
Small Magnetic Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1994SoPh..151...15K
Altcode:
We study the covariance of longitudinal and latitudinal motions of small
magnetic features after subtracting long-term averages of differential
rotation and meridional flow. The covariance is generally interpreted
as Reynolds stress and linked to the equatorward transport of angular
momentum. Using high-resolution magnetograms taken daily with the NSO
Vacuum Telescope on Kitt Peak, we determine large-scale motions by
a two-dimensional crosscorrelation analysis of pairs of consecutive
daily observations from which active regions are excluded, i.e., we
analyze the motions of small magnetic features. In the present work,
we focus on 107 day pairs obtained during the year 1988 and on 472
day pairs taken in selected intervals from 1978 to 1990. We find
that all covariance values are very small (below 250 m2
s−2), which is about one to two orders of magnitude smaller
than the values from sunspot measurements derived by other authors. At
active region latitudes, the masking process increases the noise,
which increases the chance that the covariances at these latitudes
are not significantly different from zero. We find that the results
depend strongly on the temporal averaging involved. Daily unaveraged
crosscorrelations lead to no apparent correlation between the residual
velocities, while in the monthly averages of the 1988 data, we find a
covariance of −37 ± 15 m2 s−2 at 45° with
a linear correlation of −0.59, which is significantly different from
zero and has the right sign for an equatorial transport of angular
momentum. When we average over longer time periods, the covariance
values decrease again. The annual averages of the 1978-1990 data
show both no significant covariances and the smallest errors. These
small covariances imply that the motions of small magnetic features
do not reflect the transport of angular momentum via the mechanism of
Reynolds stress.
Title: Limits on Coronal Reflection Using High-Frequency Solar
Oscillations
Authors: Kumar, P.; Fardal, M. A.; Jefferies, S. M.; Duvall, T. L.,
Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1994ApJ...422L..29K
Altcode:
Acoustic waves in the Sun with frequencies above about 5.3 mHz can
propagate in the chromosphere. We examine imaged solar intensity data
for evidence of reflection of these waves in the upper chromosphere,
where the temperature increases by a large factor over a short
distance. Our method is to compare the observed and theoretically
derived frequency spacings between peaks in the power spectrum. We find
that our theoretical frequencies provide the best fit to the data when
the reflection in the upper atmosphere is eliminated. In particular, the
model of Kumar (1993b), which includes the source depth, and radiative
damping, in the calculation of power spectra but ignores chromospheric
reflection, gives peak frequencies that are in good agreement with
the observations. For acoustic waves of frequency greater than 6 mHz
we put an upper limit to the reflectivity of chromosphere and corona,
using our method, of about 10%. At a given spherical harmonic degree,
the frequency spacing between peaks in the data generally decreases
with increasing frequency, because the lower turning point of the
waves is moving inward. However, between 5 and 5.5 mHz the frequency
spacing increases slightly. This feature is probably associated
with the acoustic cutoff frequency in the solar atmosphere, i.e., it
indicates a transition from trapped waves to propagating waves. We
are able to reproduce the observed behavior by a crude modeling of
the solar atmosphere. Further study of these peaks should provide an
independent way of exploring the mean structure of the solar atmosphere,
particularly around the temperature minimum region.
Title: Internal Rotation of the Sun
Authors: Duvall, T. L., Jr.; Dziembowski, W.; Goode, P. R.; Gough,
D. O.; Harvey, J. W.; Leibacher, J. W.
Bibcode: 1994snft.book..414D
Altcode:
No abstract at ADS
Title: Variability of the Solar He 110830 Angstrom Triplet
Authors: Harvey, J. W.; Livingston, W. C.
Bibcode: 1994IAUS..154...59H
Altcode:
No abstract at ADS
Title: Solar non-rotational motions
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1994smf..conf...68K
Altcode:
No abstract at ADS
Title: Ulysses observations of a recurrent high speed solar wind
stream and the heliomagnetic streamer belt
Authors: Bame, S. J.; Goldstein, B. E.; Gosling, J. T.; Harvey, J. W.;
McComas, D. J.; Neugebauer, M.; Phillips, J. L.
Bibcode: 1993GeoRL..20.2323B
Altcode:
Near-ecliptic solar wind observations by Ulysses on its way to the polar
regions of the Sun, compared with those from IMP 8 at 1 AU, showed that
high-speed streams decay and broaden with heliocentric distance from
IMP 8 to Ulysses, as expected. In July 1992 while travelling south
at ∼13°S and 5.3 AU, Ulysses encountered a recurrent high-speed
stream, that may also have been observed at IMP 8. The stream has been
observed a total of 14 times, once in each solar rotation through
June 1993 at ∼34°S. The source of the high-speed stream is an
equatorward extension of the south polar coronal hole. From July
1992 through June 1993, averages of solar wind peak speed increased
while density decreased with heliographic latitude. Both the stream
and a low-speed, high-density flow, presumably associated with the
heliomagnetic (coronal) streamer belt encircling the heliomagnetic
equator, crossed Ulysses with the solar rotation period until April
1993 when the spacecraft was at ∼29°S heliographic latitude. After
this time, as the spacecraft climbed to higher latitudes, the central
portion of the streamer belt with lowest speed and highest density
disappeared. Therefore, at its maximum inclination, the belt was tilted
at ∼29° to the heliographic equator at this point in the solar cycle.
Title: Meridional Flow of Small Photospheric Magnetic Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1993SoPh..147..207K
Altcode:
We study the meridional flow of small magnetic features, using
high-resolution magnetograms taken from 1978 to 1990 with the NSO
Vacuum Telescope on Kitt Peak. Latitudinal motions are determined by a
two-dimensional crosscorrelation analysis of 514 pairs of consecutive
daily observations from which active regions are excluded. We find a
meridional flow of the order of 10 m s−1, which is poleward
in each hemisphere, increases in amplitude from 0 at the equator,
reaches a maximum at mid-latitude, and slowly decreases poleward. The
average observed meridional flow is fit adequately by an expansion
of the formM (θ) = 12.9(±0.6) sin(2θ) + 1.4(±0.6) sin(4θ), in m
s−1 whereθ is the latitude and which reaches a maximum of
13.2 m s−1 at 39°. We also find a solar-cycle dependence
of the meridional flow. The flow remains poleward during the cycle, but
the amplitude changes from smaller-than-average during cycle maximum to
larger-than-average during cycle minimum for latitudes between about
15° and 45°. The difference in amplitude between the flows at cycle
minimum and maximum depends on latitude and is about 25% of the grand
average value. The change of the flow amplitude from cycle maximum to
minimum occurs rapidly, in about one year, for the 15-45° latitude
range. At the highest latitude range analyzed, centered at 52.5°,
the flow is more poleward-than-average during minimumand maximum,
and less at other times. These data show no equatorward migration of
the meridional flow pattern during the solar cycle and no significant
hemispheric asymmetry. Our results agree with the meridional flow and
its temporal variation derived from Doppler data. They also agree on
average with the meridional flow derived from the poleward migration
of the weak large-scale magnetic field patterns but differ in the
solar-cycle dependence. Our results, however, disagree with the
meridional flow derived from sunspots or plages.
Title: The Covariance of Latitudinal and Longitudinal Motions of
Small Magnetic Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1993BAAS...25.1220K
Altcode:
No abstract at ADS
Title: Transition Region Explosive Events in an X-Ray Dark Lane
Region of the Quiet Sun
Authors: Cook, J. W.; Moses, D.; Brueckner, G. E.; Dere, K. P.;
Bartoe, J. -D. F.; Webb, D.; Davis, J. M.; Harvey, J. W.; Recely,
F.; Martin, S. F.; Zirin, H.
Bibcode: 1993BAAS...25.1181C
Altcode:
No abstract at ADS
Title: Time-Distance Helioseismology
Authors: Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.;
Pomerantz, M. A.
Bibcode: 1993BAAS...25.1220D
Altcode:
No abstract at ADS
Title: Asymmetries of Solar Oscillation Line Profiles
Authors: Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.; Osaki,
Y.; Pomerantz, M. A.
Bibcode: 1993ApJ...410..829D
Altcode:
Asymmetries of the power spectral line profiles of solar global
p-modes are detected in full-disk intensity observations of the Ca
II K Fraunhofer line. The asymmetry is a strong function of temporal
frequency being strongest at the lowest frequencies observed and
vanishing near the peak of the power distribution. The variation with
spherical harmonic degree is small. The asymmetry is interpreted in
terms of a model in which the solar oscillation cavity is compared
to a Fabry-Perot interferometer with the source slightly outside
the cavity. A phase difference between an outward direct wave and
a corresponding inward wave that passes through the cavity gives
rise to the asymmetry. The asymmetry is different in velocity and
intensity observations. Neglecting the asymmetry when modeling the
power spectrum can lead to systematic errors in the measurement of
mode frequencies of as much as 10 exp -4 of the mode frequency. The
present observations and interpretation locate the source of the
oscillations to be approximately 60 km beneath the photosphere, the
shallowest position suggested to date.
Title: Rotation Rates of Small Magnetic Features from Two-Dimensional
and One-Dimensional Cross-Correlation Analyses
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1993SoPh..145....1K
Altcode:
We present results of an analysis of 628 high-resolution magnetograms
taken daily with the NSO Vacuum Telescope on Kitt Peak from 1975 to
1991. Motions in longitude on the solar surface are determined by a
two-dimensional cross-correlation analysis of consecutive day pairs. We
find that the measured rotation rate of small magnetic features, i.e.,
excluding active regions, is in excellent agreement with the results
of the previous one-dimensional analysis of the same data (Komm,
Howard, and Harvey, 1993). The polynomial fits show magnetic torsional
oscillations, i.e., a more rigid rotation during cycle maximum and
a more differential rotation during cycle minimum, but with smaller
amplitudes than the one-dimensional analysis. The full width at half
maximum of the cross-correlations is almost constant over latitude
which shows that the active regions are effectively excluded. The
agreement between the one- and two-dimensional cross-correlation
analyses shows that the two different techniques are consistent and that
the large-scale motions can be divided into rotational and meridional
components that are not affected by each other.
Title: Time-distance helioseismology
Authors: Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.;
Pomerantz, M. A.
Bibcode: 1993Natur.362..430D
Altcode:
THE application of seismology to the study of the solar interior1,
2(helioseismology) has advanced almost solely by the prediction
and measurement of the Sun's frequencies of free oscillation, or
normal modes. Direct measurement of the travel times and distances
of individual acoustic waves-the predominant approach in terrestrial
seismology3-would appear to be more difficult in view of the
number and stochastic nature of solar seismic sources. Here, however,
we show that it is possible to extract time-distance information from
temporal cross-correlations of the intensity fluctuations on the solar
surface. This approach opens the way for seismic studies of local
solar phenomena, such as subsurface in homogeneities near sunspots,
and should help to refine global models of the internal velocity
stratification in the Sun.
Title: The Correspondence Between X-Ray Bright Points and Evolving
Magnetic Features in the Quiet Sun
Authors: Webb, D. F.; Martin, S. F.; Moses, D.; Harvey, J. W.
Bibcode: 1993SoPh..144...15W
Altcode:
Coronal bright points, first identified as X-ray Bright Points (XBPs),
are compact, short-lived and associated with small-scale, opposite
polarity magnetic flux features. Previous studies have yielded
contradictory results suggesting that XBPs are either primarily a
signature of emerging flux in the quiet Sun, or of the disappearance
of pre-existing flux. With the goal of improving our understanding of
the evolution of the quiet Sun magnetic field, we present results of
a study of more recent data on XBPs and small-scale evolving magnetic
structures. The coordinated data set consists of X-ray images obtained
during rocket flights on 15 August and 11 December, 1987, full-disk
magnetograms obtained at the National Solar Observatory - Kitt Peak,
and time-lapse magnetograms of multiple fields obtained at Big Bear
Solar Observatory. We find that XBPs were more frequently associated
with pre-existing magnetic features of opposite polarity which appeared
to be cancelling than with emerging or new flux regions. Most young,
emerging regions were not associated with XBPs. However, some XBPs
were associated with older ephemeral regions, some of which were
cancelling with existing network or intranetwork poles. Nearly all of
the XBPs corresponded to opposite polarity magnetic features which
wereconverging towards each other; some of these had not yet begun
cancelling. We suggest that most XBPs form when converging flow brings
oppositely directed field lines together, leading to reconnection and
heating of the newly-formed loops in the low corona.
Title: Torsional Oscillations and Internal Rotation
Authors: Komm, R. W.; Harvey, J. W.; Howard, R. F.
Bibcode: 1993ASPC...42..269K
Altcode: 1993gong.conf..269K
No abstract at ADS
Title: Torsional Oscillation Patterns in Photospheric Magnetic
Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1993SoPh..143...19K
Altcode:
We analyzed 689 high-resolution magnetograms taken daily with the NSO
Vacuum Telescope on Kitt Peak from 1975 to 1991. Motions in longitude on
the solar surface are determined by a one-dimensional crosscorrelation
analysis of consecutive day pairs. The main sidereal rotation rate
of small magnetic features is best fit byω = 2.913(±0.004) −
0.405(±0.027) sin2φ − 0.422(±0.030) sin4φ,
in µrad s−1, whereφ is the latitude. Small features and
the large-scale field pattern show the same general cycle dependence;
both show a torsional oscillation pattern. Alternating bands of
faster and slower rotation travel from higher latitudes toward the
equator during the solar cycle in such a way that the faster bands
reach the equator at cycle minimum. For the magnetic field pattern,
the slower bands coincide with larger widths of the crosscorrelations
(corresponding to larger features) and also with zones of enhanced
magnetic flux. Active regions thus rotate slower than small magnetic
features. This magnetic torsional oscillation resembles the pattern
derived from Doppler measurements, but its velocities are larger by a
factor of more than 1.5, it lies closer to the equator, and it leads
the Doppler pattern by about two years. These differences could be
due to different depths at which the different torsional oscillation
indicators are rooted.
Title: Chromospheric Oscillations and the Background Spectrum
Authors: Harvey, J. W.; Duvall, T. L., Jr.; Jefferies, S. M.;
Pomerantz, M. A.
Bibcode: 1993ASPC...42..111H
Altcode: 1993gong.conf..111H
No abstract at ADS
Title: Solar Meridional Flow Detected in Small Magnetic Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.
Bibcode: 1992AAS...181.8102K
Altcode: 1992BAAS...24.1252K
We present results of an analysis of 514 high-resolution magnetograms
taken daily with the NSO Vacuum Telescope on Kitt Peak from 1978 to
1990. Motions in latitude on the solar surface are determined by a
two-dimensional crosscorrelation analysis of consecutive day pairs
after excluding large active regions. We find a meridional flow of the
order of 10 ms(-1) , which is poleward in each hemisphere, increases
in amplitude from 0 at the equator, reaches a maximum at mid-latitude,
and slowly decreases poleward. The average meridional flow is fit by an
expansion of derivatives of even Legendre polynomials $M(theta ) = 8.88
(+/- 0.45) {{partial P_2}/{partial theta }} - 0.66 (+/-0.26) {{partial
P_4}/{partial theta }} in ms^{-1}\ where \theta is the latitude, which
reaches a maximum of 13.2 ms^{-1}\ at 39 deg. We also find a solar
cycle dependence of the meridional flow. The flow remains poleward
during the cycle, but the amplitude (at latitudes poleward of 20 deg)
changes from smaller-than-average during maximum to larger-than-average
during minimum. The meridional flow fit of the maximum activity years
1980--1982 peaks at 10.9 ms^{-1}, while the fit of the minimum years
1984--1986 reaches a maximum velocity of 14.5 ms^{-1}$; the difference
is about 27% of the average value.
Title: The NASA/NSO Spectromagnetograph
Authors: Jones, Harrison P.; Duvall, Thomas L., Jr.; Harvey, John W.;
Mahaffey, Charles T.; Schwitters, Jan D.; Simmons, Jorge E.
Bibcode: 1992SoPh..139..211J
Altcode:
The NASA/NSO Spectromagnetograph is a new focal plane instrument
for the National Solar Observatory/Kitt Peak Vacuum Telescope which
features real-time digital analysis of long-slit spectra formed on a
two-dimensional CCD detector. The instrument is placed at an exit port
of a Littrow spectrograph and uses an existing modulator of circular
polarization. The new instrument replaces the 512-channel Diode Array
Magnetograph first used in 1973. Commercial video processing boards are
used to digitize the spectral images at video rates and to separate,
accumulate, and buffer the spectra in the two polarization states. An
attached processor removes fixed-pattern bias and gain from the spectra
in cadence with spatial scanning of the image across the entrance
slit. The data control computer performs position and width analysis
of the line profiles as they are acquired and records line-of-sight
magnetic field, Doppler shift, and other computed parameters. The
observer controls the instrument through windowed processes on a
data control console using a keyboard and mouse. Early observations
made with the spectromagnetograph are presented and plans for future
development are discussed.
Title: Scattering of p-Modes by a Sunspot
Authors: Braun, D. C.; Duvall, T. L., Jr.; Labonte, B. J.; Jefferies,
S. M.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1992ApJ...391L.113B
Altcode:
The acoustic scattering properties of a large sunspot are determined
from a Fourier-Hankel decomposition of p-mode amplitudes as measured
from a 68-hr subset of a larger set of observations made at the
South Pole in 1988. It is shown that significant improvement in the
measurement of p-mode scattering amplitudes results from the increased
temporal frequency resolution provided by these data. Scattering
phase shifts are unambiguously determined for the first time, and the
dependence of the p-mode phase shift and absorption with wavenumber
and frequency is presented.
Title: Crosscorrelation Analysis of Small Photospheric Magnetic
Features
Authors: Komm, Rudolf W.; Howard, Robert F.; Harvey, John W.
Bibcode: 1992AAS...180.5110K
Altcode: 1992BAAS...24..815K
We present results of an analysis of high-resolution magnetograms
taken daily with the NSO Vacuum Telescope on Kitt Peak from 1975 to
1991. Motions in longitude on the solar surface are determined by a
one-dimensional crosscorrelation analysis of consecutive day pairs. The
mean sidereal rotation rate of small magnetic features is best fit by
$omega = 2.913 (+/- 0.004) -0.405 (+/- 0.027) sin(2phi ) -0.422 (+/-
0.030) sin(4phi ) in \mu rad s^{-1} where \phi$ is the latitude. The
small features show a torsional oscillation pattern; alternating bands
of faster and slower rotation travel from higher latitudes toward the
equator during the solar cycle in such a way that the faster bands
reach the equator at cycle minimum. The magnetic torsional oscillation
resembles the pattern derived from Doppler measurements, but is
different in three respects. Its velocities are larger by a factor of
more than 1.5, it lies closer to the equator, and leads the Doppler
pattern by about two years. Motions in longitude and also in latitude
are determined by a two-dimensional crosscorrelation analysis. The mean
sidereal rotation rate of the two-dimensional analysis is in excellent
agreement with the one-dimensional rate which assures the robustness of
the two-dimensional analysis. In latitude, we find meridional motions
of the order of 10 m/s which are poleward in each hemisphere.
Title: Scattering of p-Modes by a Sunspot
Authors: Braun, D. C.; Duvall, T. L., Jr.; Labonte, B. J.; Jefferies,
S. M.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1992AAS...180.0604B
Altcode: 1992BAAS...24..737B
For the first time the scattering phase shifts of solar p-modes
from a sunspot have been unambiguously determined. This is made
possible by the recent availability of long duration, high duty
cycle observations. The results presented here are determined from a
Fourier-Hankel decomposition of p-mode amplitudes as measured from a
68 hr subset of a larger set of observations made at the South Pole in
1988. In addition to the detection of the phase shifts, the quality of
the data allows the dependence of the p-mode scattering and absorption
with azimuthal order, spatial wavenumber and temporal frequency to
be independently determined. Thus, unlike previous observations, our
measurements of absorption and phase shifts do not represent averages
over a range of p-modes. With this information we have for the first
time a complete description of the acoustic scattering amplitudes
from a large sunspot. Interpretation of these observations requires a
suitable theory of the interaction of p-modes and sunspots. However,
with the complete scattering amplitudes now available one may apply
inverse scattering algorithms, based on a few simplifying assumptions,
to deduce a 3-dimensional map of the scattering strength of the active
region. This offers the hope that general information about subsurface
morphology of active regions might be gained even without a detailed
understanding of the physical scattering processes involved. DCB is
supported by Air Force URI grant AFOSR-90-0116. The South Pole program
is supported in part by National Science Foundation grants DPP87-15791
and 89-17626, and by the Solar Physics Branch of the Space Physics
Division of NASA.
Title: Rotation Rate Determined from Small Photospheric Magnetic
Features
Authors: Komm, R. W.; Howard, R. F.; Harvey, J. W.; Forgach, S.
Bibcode: 1992ASPC...27..325K
Altcode: 1992socy.work..325K
No abstract at ADS
Title: Helioseismology from South Pole: Surprises from Near the
Solar Surface
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.; Harvey,
J. W.
Bibcode: 1992AnJUS..27..322J
Altcode:
No abstract at ADS
Title: Characteristics of Intermediate-Degree Solar p-Mode Line Widths
Authors: Jefferies, S. M.; Duvall, T. L., Jr.; Harvey, J. W.; Osaki,
Y.; Pomerantz, M. A.
Bibcode: 1991ApJ...377..330J
Altcode:
Measurements of the p-mode linewidths over the frequency range v =
1.87-4.93 mHz and degree range 1 = 1-150 are presented. The linewidth
is observed to vary with mode frequency and degree. The variation with
frequency is consistent with the observations of Libbrecht although
the measurements are systematically narrower. The frequency variation
has been explained in terms of radiative and convective damping
of the modes. The observed variation with degree resolves previous
contradictory results and is shown to exceed the 1/S variation that is
expected in theoretical grounds. Here S is the travel time of a mode
from its lower turning point in the solar interior, to its reflection
at the solar surface. The deviations from a 1/S variation suggest that
there are two possible damping mechanisms, in addition to radiative
and convective damping, that affect the modes.
Title: Measurements of High-Frequency Solar Oscillation Modes
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Jefferies, S. M.;
Pomerantz, M. A.
Bibcode: 1991ApJ...373..308D
Altcode:
The spatial-temporal spectrum of solar oscillations exhibits modelike
structure at frequencies above the nominal photospheric acoustic cutoff
of about 5.3 mHz. The linewidth and frequency of these features are
measured as functions of degree from high-quality spectra obtained from
observations made at the geographic South Pole. From 5.3 to 6.5 mHz the
linewidths are relatively constant with a value of about 70 microHz,
approximately one-half the frequency difference between modes of the
same degree but successive values of radial order number. This width
is larger than can be accounted for by simple considerations of the
leakage of trapped acoustic waves. The frequencies of the high-frequency
modes adhere to a simple dispersion law if one uses a substantially
larger effective phase shift that applies at lower frequencies. The
frequency variation of this phase shift changes markedly above the
acoustic cutoff frequency.
Title: The Solar Equatorial Internal Rotation Rate Estimated from
Combined South Pole and NSO/Sac Peak Helioseismic Data Sets
Authors: Hill, F.; Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.,
Jr.; Harvey, J. W.
Bibcode: 1991BAAS...23.1050H
Altcode:
No abstract at ADS
Title: Wavelength Variation of p-Mode Intensity Fluctuations
Authors: Ronan, R. S.; Harvey, J. W.; Duvall, T. L., Jr.
Bibcode: 1991ApJ...369..549R
Altcode:
The oscillatory signal in the solar p-mode band has been measured
as a function of optical wavelength using a grating spectrometer and
Fourier transform spectrometer. The relative intensity fluctuations
are found to increase with height in the solar photosphere, while the
absolute level of intensity fluctuations in the p-mode band is reduced
by about 50 percent in the cores and wings of Ca II H and K, H-delta,
and H-gamma compared to the neighboring spectral regions. Thus, these
spectral regions of diminished absolute p-mode signal could be exploited
as signal references by spectrophotometers while attempting to observe
nonradial p-mode oscillations in stars from the ground. High spectral
and temporal resolution observations of several unblended lines in the
red portion of the visible spectrum show an asymmetry in the relative
and absolute p-mode intensity oscillations across the line profiles. The
peak in intensity oscillations lies in the blue wing of the lines.
Title: Characteristics of Intermediate-Degree Solar p-mode Line Widths
Authors: Duvall, T. L., Jr.; Jefferies, S. M.; Harvey, J. W.; Osaki,
Y.; Pomerantz, M. A.
Bibcode: 1991BAAS...23.1032D
Altcode:
No abstract at ADS
Title: Helioseismology from South Pole: 1990 High Resolution Campaign
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.; Harvey,
J. W.
Bibcode: 1991AnJUS..26..285J
Altcode:
No abstract at ADS
Title: Measurement of crystal retarders
Authors: Chidester, Steven D.; Harvey, John W.; Hubbard, Robert P.
Bibcode: 1991ApOpt..30...12C
Altcode:
Accurate measurements of calcite, quartz, and ammonium dihydrogen
phosphate (ADP) retarder plates were required as part of a project to
measure the characteristics of the solar interior. Important criteria
were absolute retardation of multiple-order quartz wave plates,
uniformity of retardation of relatively thick calcite and ADP plates,
and alignment of the crystal optical axis with the polished surfaces
of the calcite and ADP plates. Here, procedures for measuring the
retardation, the uniformity of retardation, and optical axis alignment
of birefringent crystals are discussed, and some measurement results
are presented.
Title: Solar Surface Velocity Fields Determined from Small Magnetic
Features
Authors: Howard, R. F.; Harvey, J. W.; Forgach, S.
Bibcode: 1990SoPh..130..295H
Altcode:
We describe a method for the analysis of magnetic data taken daily
at the Vacuum Telescope at Kitt Peak. In this technique, accurate
position differences of very small magnetic features on the solar
surface outside active regions are determined from one day to the next
by a cross-correlation analysis. In order to minimize systematic errors,
a number of corrections are applied to the data for effects originating
in the instrument and in the Earth's atmosphere. The resulting maps
of solar latitude vs central meridian distance are cross-correlated
from one day to the next to determine daily motions in longitude and
latitude. Some examples of rotation and meridional motion results are
presented. For the months of May 1988 and October-November 1987, we find
rotation coefficients A = 2.894 ± 0.011, B = - 0.428 ± 0.070, and C =
-0.370 ± 0.077 in μrad s−1 from the expansion ω = A +
B sin2φ + C sin4φ, where φ is the latitude. The
differential rotation curve for this interval is essentially flat within
20 deg of the equator in these intervals. For the same intervals we
find a poleward meridional motion a = 16.0 ± 2.8 m sec -1
from the relation v = a sinφ, where v is the line-of-sight velocity.
Title: The solar probe mission
Authors: Feldman, W. C.; Anderson, J.; Bohlin, J. D.; Burlaga, L. F.;
Farquhar, R.; Gloeckler, G.; Goldstein, B. E.; Harvey, J. W.; Holzer,
T. E.; Jones, W. V.; Kellogg, P. J.; Krimigis, S. M.; Kundu, M. R.;
Lazarus, A. J.; Mellott, M. M.; Parker, E. N.; Rosner, R.; Rottman,
G. J.; Slavin, J. A.; Suess, S. T.; Tsurutani, B. T.; Woo, R. T.;
Zwickl, R. D.
Bibcode: 1990AIPC..203..101F
Altcode: 1990pacr.rept..101F
The Solar Probe will deliver a 133.5 kg science payload into a 4 Rs
perihelion solar polar orbit (with the first perihelion passage in 2004)
to explore in situ one of the last frontiers in the solar system-the
solar corona. This mission is both affordable and technologically
feasible. Using a payload of 12 (predominantly particles and
fields) scientific experiments, it will be possible to answer many
long-standing, fundamental problems concerning the structure and
dynamics of the outer solar atmosphere, including the acceleration,
storage, and transport of energetic particles near the Sun and in the
inner (<65 Rs) heliosphere.
Title: Observed Characteristics of High-Frequency Solar Global
Oscillations
Authors: Harvey, J. W.; Duvall, T. L., Jr.; Jefferies, S. M.;
Pomerantz, M. A.
Bibcode: 1990BAAS...22..896H
Altcode:
No abstract at ADS
Title: Trends in Helioseismology Observation and Data Reduction
Authors: Harvey, J. W.
Bibcode: 1990LNP...367..115H
Altcode: 1990LNP...367..113H; 1990psss.conf..115H
Rapid growth of observational helioseismology continues
unabated. Several major trends are obvious in instrumentation for the
observation of p-mode oscillations. These include great improvements
in angular resolution and fidelity, temporal coverage, signal quality
and the planning of long-term and cooperative measurements. While
progress in the observation of g modes is slow, p-mode seismic imaging
is advancing rapidly. Major trends are also affecting the reduction
of p-mode observations. Among these are the development of techniques
for handling huge amounts of data and reduction methods which either
suppress or allow for imperfect data. These imperfections include
leakages in temporal and spatial domains as well as random noise
and various systematic biases. Analysis of oscillation spectra is
moving to fitting of individual spectral features rather than the use
of dangerous cross-correlation methods. Special reduction methods
are being developed for seismic imaging and localized oscillation
observations. Recent observational results have mainly dealt with the
form of internal solar rotation, changes in the frequencies of p modes
perhaps related to the solar activity cycle and seismic imaging. In
the next decade a flood of high quality data, reduced and analyzed
with improved techniques and with cooperation of solar modelers and
theoreticians, will lead to a high fidelity picture of the structure
and dynamics of the solar interior.
Title: What are the Observed High-Frequency Solar Acoustic Modes?
Authors: Kumar, P.; Duvall, T. L., Jr.; Harvey, J. W.; Jefferies,
S. M.; Pomerantz, M. A.; Thompson, M. J.
Bibcode: 1990LNP...367...87K
Altcode: 1990psss.conf...87K
Jefferies et al. (1988) observe discrete peaks up to 7mHz in the power
spectra of their intermediate degree solar intensity oscillation data
obtained at South Pole. This is perhaps surprising since waves with
frequency greater than the acoustic cut-off frequency at the temperature
minimum ( 5.5mHz), unlike their lower frequency counterparts, are not
trapped in the solar interior. We propose that the observed peaks are
associated with what are principally progressive waves emanating from
a broad-band acoustic source. The geometrical effect of projecting
observations of these progressive waves onto spherical harmonics
then gives rise to peaks in the power spectra. The frequencies and
amplitudes of the peaks will depend on the spatial characteristics of
the source. Partial reflections in the solar atmosphere modify the power
spectra, but in this picture they are not the primary reason for the
appearance of the peaks. We estimate the frequency and power which would
be expected from this model and compare it with the observations. We
argue that these high frequency mock-modes are not overstable, and
that they are excited by acoustic emission from turbulent convection.
Title: Helioseismology from South Pole: Solar Cycle Connection
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.; Harvey,
J. W.
Bibcode: 1990AnJUS..25..271J
Altcode:
No abstract at ADS
Title: Helioseismology from the South Pole: Results from the 1987
Campaign
Authors: Jefferies, S. M.; Duvall, T. L., Jr.; Harvey, J. W.;
Pomerantz, M. A.
Bibcode: 1990LNP...367..135J
Altcode: 1990psss.conf..135J
This paper presents some results on the frequencies and line widths
of features in solar p-mode spectra obtained from 460 hours of
observations made at South Pole in 1987. To investigate the possibility
of temporal variations in these quantities, a comparison is made with
measurements obtained from data taken in 1981. The differences between
the frequencies measured from the 1981 and 1987 data sets appear to be
independent of both frequency (2.4 v 4.8 mHz) and degree (3 98). The
mean difference (v 1981 - v 1987) averaged. over v and is found to be
224 ± 19 nl1z. The line width measurements display the same variation
with v as that previously reported (Libbrecht 1988a), an increase
with ℓ (Duvall et ad. 1988) and with solar activity. Measurement of
the rotational splittings of sectoral modes (m = ±ℓ) in the range
(3 ≤ ℓ ≤ 15), shows no indication of a dependence on the depth
of the lower turning points of these modes.
Title: The Effect of Newly Erupting Flux on the Polar Coronal Holes
Authors: Sheeley, N. R.; Wang, Y. -M.; Harvey, J. W.
Bibcode: 1989SoPh..119..323S
Altcode:
He I 10830 Å images show that early in sunspot cycles 21 and 22,
large bipolar magnetic regions strongly affected the boundaries of the
nearby polar coronal holes. East of each eruption, the hole boundary
immediately contracted poleward, leaving a band of enhanced helium
network. West of the eruption, the boundary remained diffuse and
gradually expanded equatorward into the leading, like-polarity part of
the bipolar magnetic region. Comparisons between these observations
and simulations based on a current-free coronal model suggest that:
The Sun's polar magnetic fields are confined to relatively small caps of
high average field strength, apparently by a poleward meridional flow.
Title: Rotational Splitting of the Low-Degree Solar P-Modes
Authors: Jefferies, S. M.; Duvall, T. L., Jr.; Harvey, J. W.;
Pomerantz, M. A.
Bibcode: 1989BAAS...21..831J
Altcode:
No abstract at ADS
Title: Selecting a Camera for the GONG Doppler Analyzer
Authors: Hubbard, R. P.; Ball, W. F.; Chidester, C. D.; Dowdney,
K. C.; Harvey, J. W.
Bibcode: 1989BAAS...21..849H
Altcode:
No abstract at ADS
Title: Helioseismology from the South Pole: 1987 Results and 1988
Campaign
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.; Harvey,
J. W.
Bibcode: 1989AnJUS..24..244J
Altcode:
No abstract at ADS
Title: Helioseismology from the South Pole: comparison of 1987 and
1981 results.
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L., Jr.;
Harvey, J. W.; Jaksha, D. B.
Bibcode: 1988ESASP.286..279J
Altcode: 1988ssls.rept..279J
Full disk images with ≡10 arc sec pixels and filtered to a ≡7 Å
passband centered on the Ca II K line were obtained from the geographic
South Pole in 1981 and 1987. In 1981, about 50 hours of essentially
uninterrupted data were obtained. In 1987, three such runs were
obtained over a period of 325 hours for a duty cycle of about 47%. The
1987 observations are characterized by a much lower level of solar
activity than 1981, a much improved CCD camera, considerably better
image stability and a varying amount of instrumental scatter. The 1987
data have a substantially better signal-to-noise ratio than the 1981
data so that oscillations with degrees from 0 to 150 and frequencies
from 2 to 7 mHz are well observed. The observations were reduced to
spectra in l, m and ν. This paper presents a comparison of p-mode
frequencies measured in 1981 and 1987 and coefficients of Legendre
polynomial expansions of frequency shifts caused by solar rotation. The
authors also study the time behavior of systematic frequency shifts
which depend upon m but which do not arise from rotation.
Title: Solar internal rotation from helioseismology.
Authors: Harvey, J. W.
Bibcode: 1988ESASP.286...55H
Altcode: 1988ssls.rept...55H
Observations of solar oscillations allow one to determine the
properties of internal solar rotation. This branch of helioseismology,
like most others, is enjoying rapid growth. Many diverse methods are
used to determine the internal solar rotation. Measurements of p-mode
frequencies made by several groups are in essential agreement that
rotation within the convection zone differs in depth and latitude only
slightly from the observed rotation of the surface. Deeper layers seem
to rotate with less latitudinal differential rotation. The rotation of
the energy-generating core is not well determined by p-mode oscillations
and it may be rotating somewhat faster or at about the same rate as
the surface. Observations of g-modes support the notion of a rapidly
rotating core. Great improvements in knowledge of solar internal
rotation are certain as higher resolution is obtained in images,
frequency, and spherical harmonic degree and order. Signal-to-noise
ratio will also improve greatly with the availability of continuous
data from networks and from spacecraft.
Title: The Correspondence Between Small-Scale Coronal Structures
and the Evolving Solar Magnetic Field
Authors: Webb, D. F.; Moses, J. D.; Davis, J. M.; Harvey, J. W.;
Martin, S. F.; Zirin, H.
Bibcode: 1988BAAS...20..722W
Altcode:
No abstract at ADS
Title: The Global Oscillation Network Group (GONG)
Authors: Harvey, J. W.; Hill, F.; Kennedy, J. R.; Leibacher, J. W.;
Livingston, W. C.
Bibcode: 1988AdSpR...8k.117H
Altcode: 1988AdSpR...8..117H
As a community facility, the National Solar Observatory is establishing
a six-site ground-based solar observing network around the world. This
Global Oscillation Network Group (GONG) aims at essentially continuous
imaged observations of global solar oscillations for a minimum of three
years. Resulting data will be used to study the solar interior using
helioseismology. The heart of the observing instrument is a thermally
compensated, wide-field Fourier Techometer operated automatically by a
computer control system. Data from the six GONG stations is expected to
total over one gigabyte per day. Pipeline processing of these data will
proceed contemporaneously, reducing the raw data to several standard
product data sets at sustained throughput rates in excess of 6 megaflops
and peak rates that may exceed 50 megaflops. In support of widespread
scientific participation, software analysis tools based on the Image
Reduction and Analysis Facility (IRAF) and data distribution will be
provided. Science teams have been formed and are actively supporting
the project. The field instrument will reach the prototype stage in
early 1989 and full operation of the network is expected in 1992. Operated by the Association of Universities for Research in Astronomy,
Inc., under contract to the National Science Foundation.
Title: Techniques for Observing Stellar Oscillations
Authors: Harvey, J. W.
Bibcode: 1988IAUS..123..497H
Altcode:
Two major techniques are reviewed: Doppler spectroscopy and
photometry. Fundamental limitations are described using the sun as a
representative stellar target. The current state of the art is limited
by lack of light in the case of Doppler methods and by atmospheric
noise in the case of photometry.
Title: Frequencies of Solar p-Mode Oscillations
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Libbrecht, K. G.; Popp,
B. D.; Pomerantz, M. A.
Bibcode: 1988ApJ...324.1158D
Altcode:
Acoustic oscillations of the Sun were observed by measuring Doppler
shifts at Big Bear Solar Observatory in 1985 and by measuring intensity
fluctuations at the geographic South Pole in 1981. These data are
reduced to spectra in frequency and spherical harmonic degree, l,
by averaging over azimuthal order after removing frequency shifts
caused by rotation. Distinct spectral features are identified and
fitted with models to produce estimates of multiplet frequencies and
errors. The authors present a table of measured frequencies for 4 ≤
l ≤ 99, with measurement uncertainties of the order of one part in
104. Tables of published frequency measurements for l ≤
5 are also included.
Title: Intermediate Degree Solar Oscillations
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1988IAUS..123...37D
Altcode:
Spectra of solar intensity oscillations in the degree range l =
20 - 98 were obtained with a 92% duty cycle over a 50 hour period
from the geographic South Pole. After correction for solar rotation,
the spectra have been averaged over azimuthal order m and fit with
Lorentzian functions to provide values of background noise, amplitude,
frequency and line width for 636 oscillation modes.
Title: Helioseismology from the South Pole: 1987 Campaign
Authors: Jefferies, S. M.; Pomerantz, M. A.; Duvall, T. L.; Harvey,
J. W.; Jaksha, D.
Bibcode: 1988AnJUS..23..191J
Altcode:
No abstract at ADS
Title: GONG: To See Inside Our Sun
Authors: Harvey, John W.; Kennedy, James R.; Leibacher, John W.
Bibcode: 1987S&T....74..470H
Altcode:
A world-wide program called GONG (Global Oscillation Network Group)
will permit scientists to study the depths of the sun's interior by
means of its naturally occurring oscillations. Oscillation measurements
have revealed that the rotation rate slows very slightly with deeper
penetration into the sun. Preliminary data suggest that GONG should
be able to monitor the sun 96 percent of the time; the observations
should be free from contamination by the 24-hr periodicity.
Title: The Solar P-Mode Signal as a Function of Optical Wavelength;
3800 through 4400 A. and 6500 through 6900 A.
Authors: Ronan, R. S.; Harvey, J. W.; Duvall, T. L.; Noyes, R. W.
Bibcode: 1987BAAS...19..936R
Altcode:
No abstract at ADS
Title: Temperature variation of ADP birefringence
Authors: Harvey, J. W.
Bibcode: 1987ApOpt..26.2057H
Altcode:
As a prelude to producing a very stable, i.e., temperature-compensated,
0.1-nm passband filter made of calcite and ammonium dihydrogen phosphate
(ADP) centered at 676.8 nm, measurements of the temperature variation of
ADP birefringence (delta B/delta T) were undertaken at two wavelengths,
632.8 and 670.7 nm; the temperature variation of calcite birefringence
were calculated from published data. The measurements were performed
at 23.8 C on a high-quality piece of ADP cut to a cylindrical shape, of
72.809-mm length and 31.95-mm diameter, in such a way that the optical
axis was parallel to a diameter within a few minutes of arc. Final
results for delta B/delta T are 48.50 and 48.13 x 10 to the -6th at
632.8 and 670.7 nm, respectively.
Title: Detector Requirements for the GONG Doppler Imaging Instrument
Authors: Hubbard, R. P.; Harvey, J. W.
Bibcode: 1987BAAS...19..928H
Altcode:
No abstract at ADS
Title: Sunspots as Sinks of P-Mode Wave Energy
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Braun, D. C.; Labonte,
B. J.; Pomerantz, M. A.
Bibcode: 1987BAAS...19R.934D
Altcode:
No abstract at ADS
Title: Diagnostics of solar magnetic fluxtubes with the infrared
line Fe I lambda 15648.54 A
Authors: Stenflo, J. O.; Solanki, S. K.; Harvey, J. W.
Bibcode: 1987A&A...173..167S
Altcode:
Fourier Transform Spectrometer recordings of May 1984 have been used to
explore the center-to-limb variation of the Stokes I, V, and Q profiles
of the solar infrared Fe I line at 15,648.54 A. The aim is to examine
the new possibilities offerred for the diagnostics of the spatially
unresolved magnetic flux tubes on the sun when lines with complete
Zeeman splitting are used. Comparison is made with the line-ratio
method, which must be used at visible wavelengths, where the splitting
is incomplete. The Stokes V asymmetries observed in the infrared line
are small or even of opposite sign as compared with the corresponding
asymmetries observed at visible wavelengths. This suggests that the
time-averaged height gradient of the Doppler velocities inside the
fluxtubes becomes small and may change its sign when moving down to
the bottom of the fluxtube photosphere.
Title: Center-to-limb variation of Stokes profiles and the diagnostics
of solar magnetic fluxtubes
Authors: Stenflo, J. O.; Solanki, S. K.; Harvey, J. W.
Bibcode: 1987A&A...171..305S
Altcode:
Simultaneous recordings of the Stokes I, Q, and V spectra have been
performed with a Fourier transform spectrometer in 10 solar regions
distributed over various center-to-limb distances, from disk center
to the extreme limb. The observational material and the recording
technique used are presented. The authors then evaluate the Stokes
profile parameters for a small selected set of spectral lines to explore
the potential of this qualitatively new data set for the diagnostics
of spatially unresolved magnetic fluxtubes.
Title: Latitude and Depth Variation of Solar Rotation
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1987ASSL..137...19D
Altcode: 1987isav.symp...19D
Spectra of solar intensity oscillations in the degree range l = 20 -
98 were obtained with a 92% duty cycle over a 50 hour period from the
geographic south pole. The spectra have been analyzed for frequency
shifts caused by solar internal rotation as functions of latitude
and depth. Some of the intermediate steps in producing the results
are illustrated.
Title: Helioseismology Results from South Pole Observations
Authors: Harvey, J. W.; Duvall, T. L., Jr.; Pomerantz, M. A.
Bibcode: 1986BAAS...18R1011H
Altcode:
No abstract at ADS
Title: Book-Review - Solar-Space Observations and Stellar Prospects
Authors: Harvey, J. W.; Stenflo, J. O.; Hudson, H. S.; Noyes, R. W.;
Kotrc, P.
Bibcode: 1986BAICz..37..252H
Altcode:
No abstract at ADS
Title: Latitude and depth variation of solar rotation
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1986Natur.321..500D
Altcode:
Measurements of the frequencies of various modes of trapped acoustic
waves provide information about rotation and structure within the
Sun. Previous work dealt with observations of wave modes confined
near the solar equator, which provided some information about the
depth variation of rotation without resolving a possible latitude
variation1,2. Recent work extended measurements to modes
covering various latitude ranges from which the variation with latitude
of solar rotation can be studied3-5. Since these measurements
were restricted to modes with spherical harmonic degrees less than 50,
they provide averages of rotation over great depth ranges that do not
resolve the convective envelope. We now present new results for degrees
up to 98 which allow the convective envelope to be isolated. For degrees
between 20 and 98 we find no evidence that internal rotation differs
significantly with depth or latitude from the rotation of surface
magnetic field patterns. Modes covering a wide latitude range have
systematically lower frequencies than those confined near the equator,
indicating the existence of a structural asymmetry within the Sun.
Title: Solar Doppler shifts: sources of continuous spectra.
Authors: Duvall, T. L., Jr.; Harvey, J. W.
Bibcode: 1986ASIC..169..105D
Altcode: 1986ssds.proc..105D
Oscillation observations can be used to study non-oscillatory solar
phenomena that exhibit Doppler shifts. The authors discuss several
effects of these phenomena and their associated temporal and spatial
power spectra: (1) They limit the signal-to-noise ratio and sometimes
detectability of oscillation modes. (2) There is the potential for
better understanding and/or detection of solar phenomena: surface
rotation, supergranulation, granulation, active regions, giant cells,
and mesogranulation. (3) Large-scale convection may spatially modulate
oscillation modes, leading to a continuous background spectrum. (4)
In regions of the spectrum where the resolution to separate modes is
lacked, it is possible to determine upper limits for the integrated
effects of modes.
Title: Rotation of the Solar Interior
Authors: Duvall, T. L.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1986AnJUS..21..280D
Altcode:
No abstract at ADS
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: Optical Interferometry of Solar Fine Structure
Authors: Harvey, J. W.
Bibcode: 1985tphr.conf..183H
Altcode:
No abstract at ADS
Title: Book-Review - Solar Space Observations and Stellar Prospects
Authors: Harvey, J. W.; Hudson, H. S.; Noyes, R. W.
Bibcode: 1985Natur.317...91H
Altcode:
No abstract at ADS
Title: Book-Review - Solar / Space Observations and Stellar Prospects
Authors: Harvey, J. W.; Hudson, H. S.; Noyes, R. W.
Bibcode: 1985Sci...229..787H
Altcode:
No abstract at ADS
Title: Temporal characteristics of the solar UV flux and He i line
at 1083 nm
Authors: Donnelly, R. F.; Repoff, T. P.; Harvey, J. W.; Heath, D. F.
Bibcode: 1985JGR....90.6267D
Altcode:
Temporal variations of the Nimbus 7 measurements of solar UV
flux, important for their stratospheric effects, are compared with
ground-based measurements of the solar infrared He ¢i absorption line
at 1083 nm. The close similarity of their temporal characteristics
shows that the 1083-nm line is a better estimator of the UV flux than
the classical indices of solar activity, the 10.7-cm radio flux and
the sunspot number, for short time scales (days, weeks). The power
spectrum of the Hei line intensity matches that of the Nimbus 7 205-nm
flux at the 27-day period peak but is weaker at the peak near 13 to
14 days period. The 27-day peak is caused by the combination of solar
rotation of active regions with one major concentration in their solar
longitude distribution, and the 13-day case involves two concentrations
with solar longitude roughly 180° apart. The 13-day periodicity is
not simply a second harmonic of the 27-day periodicity, because some
episodes of activity are dominated by the 13-day periodicity with very
weak 27-day periodicity while other episodes are dominated by 27-day
periodicity with weak 13-day periods. These episodes of activity,
which last typically 4 to 8 months, are caused mainly by groups of
strong active regions that dominate the solar-rotational variations
for several months. In addition to the enhanced short-term modulation
during these episodes, the valleys in the solar-rotational modulation
also slowly rise and decay. F10 and R tend to rise more steeply and
peak earlier during these episodes than the UV flux and the Hei line.
Title: Speed of sound in the solar interior
Authors: Christensen-Dalsgaard, J.; Duvall, T. L., Jr.; Gough, D. O.;
Harvey, J. W.; Rhodes, E. J., Jr.
Bibcode: 1985Natur.315..378C
Altcode:
Frequencies of solar 5-min oscillations can be used to determine
directly the sound speed of the solar interior. The determination
described here does not depend on a solar model, but relies only on a
simple asymptotic description of the oscillations in terms of trapped
acoustic waves.
Title: Trends in measurement of solar vector magnetic fields using
the Zeeman effect
Authors: Harvey, J. W.
Bibcode: 1985svmf.nasa..109H
Altcode:
Trends in spectropolarimetry as applied to the problem of Zeeman effect
measurement are discussed. The use of detector arrays to improve
observing efficiency is obtained. Which required new polarization
modulation schemes that match the time required to read detector
arrays. Another significant trend is narrowband filters, to improve
angular and temporal coverage, and to Fourier transform spectrometers,
to improve spectral coverage and precision. Low-polarization designs
and improved methods for compensating instrumental polarization were
developed. A requirement for high angular resolution suggests using
adaptive optical devices to subdue the effects of bad seeing. The
ultimate strategy to beat the seeing is to loft the telescope above
the atmosphere such as is planned with a 30-cm telescope in 1985 and
a 1250-cm telescope in 1990.
Title: Amplitude Ratio of Solar p-Mode Intensity and Doppler
Oscillations
Authors: Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.
Bibcode: 1985BAAS...17..643D
Altcode:
No abstract at ADS
Title: A Movie of the Solar Magnetic Field 1974-1984
Authors: Harvey, J. W.; Ditsler, W.
Bibcode: 1985BAAS...17..634H
Altcode:
No abstract at ADS
Title: Solar/Stellar Seismology Instruments
Authors: Harvey, J. W.
Bibcode: 1985IAUTA..19...51H
Altcode: 1985IAUT...19...51H
No abstract at ADS
Title: Dependence of the Properties of Magnetic Flux Tubes on Area
Factor or amount of Flux
Authors: Stenflo, J. O.; Harvey, J. W.
Bibcode: 1985SoPh...95...99S
Altcode:
Stokes I and V line profiles with high signal-to-noise ratio of the 1
FeI λλ 5247.06 and 5250.22 Å lines have been recorded in a number of
regions with different amount of magnetic flux near disc center, from
`non-magnetic' regions to strong plages. The objective has been to
study how the intrinsic fluxtube properties may depend on the amount
of flux concentration, i.e., on the magnetic area factor. Indirectly,
the area factor should be related to the average fluxtube diameter.
Title: Advances in Solar Seismology at the South Pole
Authors: Pomerantz, M. A.; Fossat, E.; Gelly, B.; Grec, C.; Harvey,
J. W.; Duvall, T. L.
Bibcode: 1985AnJUS..20..221P
Altcode:
No abstract at ADS
Title: An implementation plan for priorities in solar-system space
physics
Authors: Krimigis, Stamatios M.; Athay, R. Grant; Baker, Daniel; Fisk,
Lennard A.; Fredricks, Robert W.; Harvey, John W.; Jokipii, Jack R.;
Kivelson, Margaret; Mendillo, Michael; Nagy, Andrew F.
Bibcode: 1985STIN...9014154K
Altcode:
The scientific objectives and implementation plans and priorities
of the Space Science Board in areas of solar physics, heliospheric
physics, magnetospheric physics, upper atmosphere physics,
solar-terrestrial coupling, and comparative planetary studies are
discussed and recommended programs are summarized. Accomplishments
of Skylab, Solar Maximum Mission, Nimbus-7, and 11 other programs are
highlighted. Detailed mission plans in areas of solar and heliospheric
physics, plasma physics, and upper atmospheric physics are also
described.
Title: Speckle Interferometry Technique Applied to the Study of
Granular Velocities
Authors: Aime, C.; Borgnino, I.; Druesne, P.; Harvey, J. W.; Martin,
F.; Ricort, G.
Bibcode: 1985LNP...233..103A
Altcode: 1985hrsp.proc..103A
The correlation between intensity and velocity in solar granulation
is studied. A speckle experiment which consisted of recording signals
collected by two photomultipliers set 0.25 A apart on the wings of
the Fe 5233 A was conducted at the McMath main telescope of the Kitt
Peak National Observatory on July 1980. The data was processed, and
brightness and velocity spectra and brightness-velocity cross spectrum
matrices are computed. A cross-analysis technique is applied to the
brightness power spectrum. It is observed that the phase of the cross
spectrum reveals where the velocity/brightness correlation is accurately
measured; between 0.5/Mm and 6/Mm the correlation is positive. A linear
coherence function is calculated and the amplitude of the coherence
function reveals a maximum linear correlation coefficient of about 0.6
for a wave number of about 3.5/Mm, and a steep decrease in lower anad
higher wave number.
Title: Observations of intermediate-degree solar oscillations.
Authors: Harvey, J. W.; Duvall, T. L., Jr.
Bibcode: 1984sses.nasa..165H
Altcode: 1984sss..conf..165H
A progress report on observations of intermediate degree oscillations
is presented. The authors list frequencies of zonal p-mode oscillations
with amplitudes in excess of ≡2 cm s-1. These frequencies
show systematic disagreement with recent theoretical calculations. The
frequencies are compared with asymptotic formula estimates. Small
scatter is obtained for low degree modes but large scatter at large
degree. A first look at sectoral harmonic observations shows that
magnetic active regions provide a major signal at low frequencies.
Title: Internal rotation of the Sun
Authors: Duvall, T. L., Jr.; Dziembowski, W. A.; Goode, P. R.; Gough,
D. O.; Harvey, J. W.; Leibacher, J. W.
Bibcode: 1984Natur.310...22D
Altcode:
The frequency difference between prograde and retrograde sectoral
solar oscillations is analysed to determine the rotation rate of
the solar interior, assuming no latitudinal dependence. Much of the
solar interior rotates slightly less rapidly than the surface, while
the innermost part apparently rotates more rapidly. The resulting
solar gravitational quadrupole moment is J2 = (1.7+/-0.4)
× 10-7 and provides a negligible contribution to current
planetary tests of Einstein's theory of general relativity.
Title: Rotational frequency splitting of solar oscillations
Authors: Duvall, T. L., Jr.; Harvey, J. W.
Bibcode: 1984Natur.310...19D
Altcode:
Prograde and retrograde sectoral oscillations of the Sun have
been observed so as to determine frequency differences produced by
rotation. Oscillations in the frequency range 2.1 - 3.7 mHz and with
spherical harmonic degrees from 1 to 100 have been identified. Average
frequency shifts due to rotation in a sidereal reference frame are found
to range from a high of ≡660 nHz at degree 1 to a low of ≡423 nHz
at degree 6, rising to ≡471 nHz at degree 100. These results indicate
that most of the Sun's volume rotates at a rate close to that of the
surface, but also that the energy-generating core may rotate more
rapidly than the surface.
Title: Helium 10830 Å irradiance: 1975 - 1983.
Authors: Harvey, J. W.
Bibcode: 1984NASCP2310..197H
Altcode: 1984siva.work..197H
Digital spectroheliograms made daily at Kitt Peak are processed
to determine values of the equivalent width of the He I 10830 Å
chromospheric spectrum line averaged over the visible solar disk. A
fairly complete time series from late-1974 to mid-1983 is available. A
solar-cycle variation from about 28 mÅ in 1975 to about 80 mÅ in
late 1981 is the major component of the signal. The variation reaches
minimum about a year before the sunspot minimum and reaches maximum
about a year after sunspot maximum. Power spectral analysis of the
time series shows a major peak at a synodic rotation period of 27.42
days and smaller peaks at 1/2, 1/4 and 1/6 of this period.
Title: Rotational Frequency Splitting of Solar Oscillations
Authors: Harvey, J. W.; Duvall, T. L., Jr.
Bibcode: 1984BAAS...16Q.451H
Altcode:
No abstract at ADS
Title: Diagnostics of solar magnetic fluxtubes using a Fourier
transform spectrometer
Authors: Stenflo, J. O.; Solanki, S.; Harvey, J. W.; Brault, J. W.
Bibcode: 1984A&A...131..333S
Altcode:
An overview is presented of the diagnostic contents for fluxtube
modelling of Fourier transform spectrometer recordings of the
longitudinal Zeeman effect near the solar disk center made in
April 1979. The observations and data reductions are summarized
and the application of the weak-field model to the Stokes profiles
is examined. The significance of telluric lines and blends and the
validity of LS coupling are considered. The magnetic fluxes, intrinsic
field strengths, and area factors are discussed and the thermodynamic
properties of fluxtubes are addressed. Mass motions inside the fluxtubes
and the height variation of fluxtube parameters are considered.
Title: Frequencies of Solar P-Modes Oscillations
Authors: Harvey, J. W.; Duvall, T. L., Jr.
Bibcode: 1984LIACo..25..209H
Altcode: 1984trss.conf..209H; 1984tpss.conf..209H
No abstract at ADS
Title: Preface
Authors: Harvey, J. W.; Hudson, H. S.; Noyes, R. W.
Bibcode: 1984AdSpR...4d...1H
Altcode: 1984AdSpR...4....1H
No abstract at ADS
Title: Solar-space observations and stellar prospects. Proceedings
of the Topical Meeting of the COSPAR Interdisciplinary Scientific
Commission E (Meetings E1, E2, and E6) of the COSPAR Twenty-fifth
Plenary Meeting held in Graz, Austria, 25th June - 7th July 1984.
Authors: Harvey, J. W.; Hudson, H. S.; Noyes, R. W.
Bibcode: 1984AdSpR...4h....H
Altcode: 1984AdSpR...4..180H; 1984AdSpR...4.....H
Selected topics pertaining to solar-space observations and stellar
prospects are discussed. Papers are presented on the fine-scale
structure of solar magnetic fields, increasing solar chromosphere
line intensities with solar activity, and ulraviolet spectroscopy
of the chromosphere and transition zone at high spatial and temporal
resolution. Consideration is also given to solar coronal studies using
normal-incidence X-ray optics, immediate and long-term prospects for
helioseismology, and a compact Dopplergraph/Magnetograph suitable for
space-based measurements of solar oscillations and magnetic fields.
Title: Erratum - the Theory of Quadrupolar Sunspots and the Active
Region of 1972AUG
Authors: Yang, H. S.; Chang, H. M.; Harvey, J. W.
Bibcode: 1984SoPh...92..391Y
Altcode:
No abstract at ADS
Title: Coherent scattering in the solar spectrum - Survey of linear
polarization in the range 4200-9950 A
Authors: Stenflo, J. O.; Twerenbold, D.; Harvey, J. W.; Brault, J. W.
Bibcode: 1983A&AS...54..505S
Altcode:
Solar-limb linear polarization observations are reported and
discussed. A linearly polarized 4200-9950-A spectrum was obtained using
the Fourier-transform spectrometer on the KPNO McMath telescope with
an entrance aperture of 10 x 17.5 arcsec centered 10 arcsec inside
the solar limb near one of the heliograhic poles, in seven 48-95-min
exposures on October 2-3, 1978, and April 27-28, 1979, and recorded
using the special modulation scheme described by Brault (1978). The
noise level varies from 0.01 to 0.1 percent, and the continuum
polarization decreases from over 0.1 percent below 4200 A to less than
0.01 percent above 6000 A. The polarization amplitudes of the clearly
significant lines are listed in a table, and the polarization profiles
of the most interesting cases are illustrated and discussed. It is
shown that the conventional model of dipole and isotropic scattering
is contradicted by the observations of fluorescent scattering within
and between multiplets and of quantum-mechanical interferences between
atomic states with different combinations of total angular momenta.
Title: Patterns of the Sun
Authors: Gaizauskas, V.; Harvey, K. L.; Harvey, J. W.; Zwaan, C.
Bibcode: 1983S&T....66..291G
Altcode:
No abstract at ADS
Title: Solar oscillations with 13-day period
Authors: Duvall, T. L., Jr.; Jones, H. P.; Harvey, J. W.
Bibcode: 1983Natur.304..517D
Altcode:
Reference is made to the solar observations made by Claverie et
al. (1982) over a three-month period in the summer of 1981 which
show oscillatory velocity with a period of 13.1 days and amplitude
of 6.6 m/s. These investigators reject the possibility that they see
the Doppler shift from a radial oscillation, because the amplitude
is implausibly large. They also do not believe that their signal was
induced by solar magnetic fields, since typical mean solar fields are
too small. Photo-electric drift-scan measurements of the solar diameter
and full-disk magnetograms taken at Kitt Peak National Observatory are
examined here for evidence of variations corresponding to the velocity
oscillations of the 13.1-day period. An upper limit on radius variations
is reported which is a factor of six below the amplitude needed to
explain the velocity observations as a radial oscillation. Attention
is also given to the possible role of the rotation of large-scale
surface magnetic features.
Title: Comparison of coronal holes observed in soft X-ray and He i
10 830 Å spectroheliograms
Authors: Kahler, S. W.; Davis, J. M.; Harvey, J. W.
Bibcode: 1983SoPh...87...47K
Altcode:
We compare coronal holes observed in solar soft X-ray images obtained
with rocket-borne telescopes during 1974 to 1981 with holes observed on
nearly simultaneous 10830 Å maps. Hole boundaries are frequently poorly
defined, and after 1974 the brightness contrast between the large scale
structure and holes appears substantially diminished in both X-rays
and 10830 Å. We find good agreement between soft X-rays and 10830 Å
for large area holes but poor agreement for mid and low latitude small
area holes, which are generally of low contrast. These results appear
inconsistent with the popular view that the quiet corona is sharply
separated into open magnetic field regions consisting of coronal holes
and closed field regions consisting of the large scale structure.
Title: Theory of quadrupolar sunspots and the active region of
August, 1972
Authors: Yang, Hai-Shou; Chang, Hou-Mei; Harvey, J. W.
Bibcode: 1983SoPh...84..139Y
Altcode:
Energy is stored when the force-free magnetic field in an active region
departs from a potential field, the departure showing up as a shear in
the field. As soon as the field untwists, energy will be released to
produce flares. Based on this idea, we derived an analytical solution
of the equation of force-free field under the assumption of a constant
force-free factor, and found expressions for seven important quantities
for quadrupolar sunspots: the magnetic energy of the twisted field, that
of potential field, the extractable free energy ΔM, the magnetic flux,
the total current, the force-free factor and the field decay factor,
in terms of three observables: the field intensity, the twist angle
and the distance between two spots of the same polarity. The expression
for ΔM can be useful in solar prediction work.
Title: Coherent scattering in the solar spectrum - Survey of linear
polarization in the range 3165-4230 A
Authors: Stenflo, J. O.; Twerenbold, D.; Harvey, J. W.
Bibcode: 1983A&AS...52..161S
Altcode:
The linear polarization 10 sec of arc inside the solar limb has been
recorded over the wavelength range 3165-4230 Å with the vertical
spectrograph of the Kitt Peak McMath telescope. This polarization is
caused by coherent resonant and fluorescent scattering in the solar
atmosphere. The polarization observed in several multiplets of Fe I, as
well as in 1Ca II, 3Mg I, and 22Co I, is affected by quantum-mechanical
interference between the excited states of different total angular
momenta. The CN molecule shows significant polarization, increasing
to a maximum at each band head. Unexpectedly large polarization is
found among others in 21Ni I, 2Ti II, 1Cu I, as well as in a number
of Fe I lines. The continuum polarization increases steeply with
decreasing wavelength, and is generally larger than the intrinsic line
polarization. Contrary to theoretical expectations, the Balmer jump
does not show up in the continuum polarization.
Title: Observations of solar oscillations of low and intermediate
degree
Authors: Duvall, T. L., Jr.; Harvey, J. W.
Bibcode: 1983Natur.302...24D
Altcode:
Measurements are presented of solar velocity oscillations with
spherical harmonic degree 1-139 and angular order ~0. With an amplitude
sensitivity of ~2 cm s -1, trapped acoustic wave modes of
radial orders 2-26 are observed at frequencies between 1.7 and 5.5
mHz. The radial order identifications of low-degree modes previously
inferred from theory are confirmed. Only marginal evidence of
long-period, gravity-mode oscillations is found
Title: Large-scale patterns formed by solar active regions during
the ascending phase of cycle 21
Authors: Gaizauskas, V.; Harvey, K. L.; Harvey, J. W.; Zwaan, C.
Bibcode: 1983ApJ...265.1056G
Altcode:
Synoptic maps of photospheric magnetic fields prepared at the Kitt Peak
National Observatory are used in investigating large-scale patterns
in the spatial and temporal distribution of solar active regions
for 27 solar rotations between 1977 and 1979. The active regions are
found to be distributed in 'complexes of activity' (Bumba and Howard,
1965). With the working definition of a complex of activity based
on continuity and proximity of the constituent active regions, the
phenomenology of complexes is explored. It is found that complexes of
activity form within one month and that they are typically maintained
for 3 to 6 solar rotations by fresh injections of magnetic flux. During
the active lifetime of a complex of activity, the total magnetic flux
in the complex remains steady to within a factor of 2. The magnetic
polarities are closely balanced, and each complex rotates about the
sun at its own special, constant rate. In certain cases, the complexes
form two diverging branches.
Title: Recent Observations of High-Degree Solar P-Mode Oscillations
at the Kitt-Peak National Observatory
Authors: Rhodes, Edward J.; Harvey, John W.; Duvall, Thomas L.
Bibcode: 1983SoPh...82..111R
Altcode: 1983IAUCo..66..111R
A brief summary is given of a program which is currently being carried
out with the McMath telescope of the Kitt Peak National Observatory in
order to study high-degree (l ≳ 150) solar p-mode oscillations. This
program uses a 244 × 248 pixel CID camera and the main spectrograph of
the McMath telescope to obtain velocity-time maps of the oscillations
which can be converted into two-dimensional (kh - ω)
power spectra of the oscillations. Several different regions of the
solar spectrum have been used in order to study the oscillations at
different elevations in the solar atmosphere. The program concentrates
on eastward- and westward-propagating sectoral harmonic waves so
that measurements can be made of the absolute rotational velocities
of the solar photospheric and shallow sub-photospheric layers. Some
preliminary results from this program are now available. First, we
have been unable to confirm the existence of a radial gradient in the
equatorial rotational velocity as was previously suggested. Second,
we have indeed been able to confirm the presence of p-mode waves
in the solar chromosphere as was first suggested by Rhodes et
al. (1977). Third, we have been able to demonstrate differences in
photospheric and chromospheric power spectra.
Title: Dynamics of the Preflare Magnetic Field
Authors: Harvey, J. W.
Bibcode: 1983SSRv...34...55H
Altcode:
Many theories of the solar flare process invoke storage of energy in the
active region magnetic field above the solar photosphere. Observational
evidence relating to such storage is rather unsatisfactory owing to our
inability to observe the three-dimensional structure of the magnetic
field. Indirect evidence comes from changes in structures presumed
to trace the magnetic field, from changes in the line-of-sight and
transverse components of the photospheric magnetic field, from mass
flow patterns observed by proper motions and line-of-sight Doppler
shifts, and from radio observations. These data tend to confirm that
energy sufficient to produce flares can be stored in active region
magnetic fields with a characteristic time scale of hours but critical
observation are not yet available.
Title: Magnetic measurements of coronal holes during 1975 1980
Authors: Harvey, K. L.; Sheeley, N. R., Jr.; Harvey, J. W.
Bibcode: 1982SoPh...79..149H
Altcode:
Photospheric magnetic fluxes and average field strengths have been
measured beneath 33 coronal holes observed on 63 occasions during
1975-1980. The principal result is that low-latitude holes contained
3 times more flux near sunspot maximum than near minimum despite the
fact that their sizes were essentially the same. Average magnetic
field strengths ranged from 3-36 G near sunspot maximum compared to
1-7 G near minimum. Evidently the low-latitude coronal holes received
a proportion of the extra flux that was available at low latitudes
near sunspot maximum.
Title: Observations of coronal structure during sunspot maximum.
Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels,
D. J.; Harvey, K. L.; Harvey, J. W.
Bibcode: 1982SSRv...33..219S
Altcode:
This paper presents some of the results that have been obtained from
the Kitt Peak observations of coronal holes and the NRL observations
of coronal transients during the recent years near sunspot maximum
(1979 1981). On the average, low-latitude coronal holes of comparable
size contained 3 times more flux near sunspot maximum than near the
previous minimum. In the outer corona, transients occurred at the
observed rate of at least 2 per day, and quiet conditions persisted
during less than 15 % of the observed days. We describe a sample of
the more than 800 events that we have observed so far, including the
observation of a comet apparently colliding with the Sun.
Title: Large Scale Motions and the Structure of the Sun
Authors: Pomerantz, M. A.; Harvey, J. W.; Duvall, T. L.
Bibcode: 1982AnJUS..17..232P
Altcode:
No abstract at ADS
Title: Flare build up: 21 May 1980
Authors: Harvey, J. W.
Bibcode: 1982AdSpR...2k..31H
Altcode: 1982AdSpR...2...31H
The decaying solar active region that crossed the central meridian on
May 20, 1980 at latitude S13° produced a major flare (2B/X1) at 2054
on May 21. This region was a target of the international Flare Buildup
Study and was well observed. The buildup was characterized by little
flare activity during two days prior to the major flare but a great
deal of activity in the filament that separated the opposite magnetic
polarities of the active region. Large proper motions of sunspots and
magnetic fields suggest that the magnetic field was stressed prior to
the flare. The immediate trigger of the flare appears to have been an
eruption of new magnetic flux in the center of the active region. The
new flux erupted in a configuration that decreased the net flux of
the active region and contributed to the decay of the region. Kitt Peak National Observatory is operated by the Association of
Universities for Research in Astronomy, Inc., under contract with the
National Science Foundation.
Title: Table of solar diatomic molecular lines. IV - Spectral range:
7600-8100 A
Authors: Boyer, R.; Sotirovski, P.; Harvey, J. W.
Bibcode: 1982A&AS...47..145B
Altcode:
The present publication of results between 7600-8100 Å represents
the fourth part of an analysis of molecular lines in the spectrum of
a sunspot. It is an extension of results already published covering
6100-6600, 6600-7100 and 7100-7600 Å. According to this investigation,
equivalent widths of molecular lines become increasingly difficult to
measure beyond 8030 Å. As no valuable quantitative information is to be
expected from the study of the near infrared part of our spectrograms,
the analysis stops at 8100 Å.
Title: Variation of the solar He I 1830 A line: 1977 - 1980
Authors: Harvey, J. W.
Bibcode: 1981NASCP2191..265H
Altcode: 1981vsc..conf..265H
Daily measurements of the equivalent width of the 10830 A He I line
integrated over the visible disk show: (1) an increase from about
32 to about 74 mA in the monthly mean values from the minimum to the
maximum of the current solar cycle; (2) the monthly mean values are
more smoothly varying than most other indices of solar activity; (3)
rotation modulates the daily values in a highly variable manner with
amplitudes as large as plus or minus 20%; (4) the apparent synodic
rotation period is 29 days rather than the expected 27 days associated
with active regions; (5) despite great differences in the appearance
of the sun in 3933 A Ca I and 10830 A He I, the central intensity of
the former correlates with the equivalent width of the latter with a
value r = 0.97.
Title: Coronal holes, solar wind streams, and geomagnetic disturbances
during 1978 and 1979
Authors: Sheeley, N. R., Jr.; Harvey, J. W.
Bibcode: 1981SoPh...70..237S
Altcode:
We have extended our long-term study of coronal holes, solar wind
streams, and geomagnetic disturbances through the rising phase of
sunspot cycle 21 into the era of sunspot maximum. During 1978 and
1979, coronal holes reflected the influence of differential rotation,
and existed within a slowly-evolving large-scale pattern despite the
relatively high level of sunspot activity. The long-lived 28.5-day
pattern is not produced by a rigidly-rotating quasi-stationary
structure on the Sun, but seems to be produced by a non-stationary
migratory process associated with solar differential rotation. The
association between coronal holes and solar wind speed enhancements at
Earth continues to depend on the latitude of the holes (relative to
the heliographic latitude of Earth), but even the best associations
since 1976 have speeds of only 500-600 km s-1 rather than
the values of 600-700 km s-1 that usually occurred during
the declining phase of sunspot cycle 20.
Title: Power Spectrum of Differential Refraction and Comparison with
Solar Diameter Fluctuation Measurements
Authors: Fosset, E.; Grec, G.; Harvey, J. W.
Bibcode: 1981A&A....94...95F
Altcode:
Two different observations are used to estimate the level of
atmospheric noise present in solar diameter measurements. First, a
direct measurement of the fluctuation of the angular distance between
two stars separated by about one solar diameter. Second, a differential
measurement of fluctuation of air mass along the two lines of sight to
opposite solar limbs, which allows a determination of the power spectrum
of these fluctuations in the frequency range 0.15-3.2 mHz. Our results,
together with other direct stellar measurements, are used to estimate
the r.m.s. atmospheric noise in solar diameter measurements to be 60
milli arc s in this frequency range, with a variance of a factor of 2
on this value. The shape of the atmospheric noise power spectrum in
this frequency range is well fit by a ν-1 function. The broad shape of the power spectrum of apparent solar diameter
fluctuations published by Brown et al. (1978) is interpreted as a sum
of aliased high frequency noise, atmospheric noise consistent with the
present results and the solar five-minute oscillation. Our conclusion is
that the published power spectrum does not clearly prove the presence
of long-period solar pulsation modes because of the noise introduced
by atmospheric fluctuations.
Title: Coronal Holes, Solar Wind Streams, and Geomagnetic Disturbances
During 1978 and 1979
Authors: Sheeley, N. R., Jr.; Harvey, J. W.
Bibcode: 1980BAAS...12R.545S
Altcode:
No abstract at ADS
Title: Observations of magnetic fields on two late-type dwarf stars.
Authors: Robinson, R. D.; Worden, S. P.; Harvey, J. W.
Bibcode: 1980ApJ...236L.155R
Altcode:
The detection of magnetic fields on the G8 V star Xi Boo A and on
the K0 B star 70 Oph A is reported. A method has been developed
and applied which provides estimates of the total field strength
and fraction of the visible stellar surface covered by fields. The
essence of this method is to perform the Fourier deconvolution of a
nonmagnetically sensitive line profile from a magnetically sensitive
one. This method is insensitive to magnetic field geometry and does not
depend on polarization measurements. Results indicate fields of 2550 +
or 390 gauss covering 20-45% Xi Boo A, and that fields of 1880 + or -
350 gauss may cover 10% of 70 Oph A. Comparison observations of solar
active regions show fields of 1800 + or - 550 gauss covering 10% of
the solar active regions, in line with previous work. Tests of solar
quiet regions and sunspots also support the validity of the stellar
measurements.
Title: Photospheric Velocity Fields as Indicators of Flare Activity
Authors: Harvey, K. L.; Harvey, J. W.
Bibcode: 1980STP.....3...41H
Altcode:
No abstract at ADS
Title: The five-minute oscillations: What's left to be done
Authors: Rhodes, E. J., Jr.; Ulrich, R. K.; Harvey, J. W.; Duvall,
T. L., Jr.
Bibcode: 1980STIN...8115929R
Altcode:
Current observational methods for studying these oscillations at
large horizontal wavenumbers are discussed in detail and several
two dimensional power spectra obtained with a CID camera on the main
spectrograph of the McMath telescope at Kitt Peak National Observatory
are described. The best-resolved observations of the p-mode obtained at
chromospheric elevations are also presented. Recent progress in studies
of the p-modes at low wavenumbers with full-disk velocity detection
schemes is summarized. These full-disk observations of radial and
low-degree non-radial modes were shown to place severe constraints
on the theoretical calculation of solar interior structure. Progress
in making fully-consistent solar models which fit both the high- and
low-wave number observations is described. Finally, the observational
and theoretical improvements that are necessary for further progress
in solar seismology are summarized.
Title: A promising technique for achieving high resolution solar
observations
Authors: Harvey, J. W.; Stein, M. K.
Bibcode: 1980fsoo.conf..303H
Altcode:
No abstract at ADS
Title: Adaptive optics for solar observations?
Authors: Harvey, J. W.
Bibcode: 1980fsoo.conf...81H
Altcode:
No abstract at ADS
Title: Summary of the Workshop
Authors: Harvey, J. W.
Bibcode: 1980fsoo.conf..313H
Altcode:
No abstract at ADS
Title: Coronal Holes and Solar Magnetic Fields (Article published in
the special issues: Proceedings of the Symposium on Solar Terrestrial
Physics held in Innsbruck, May- June 1978. (pp. 137-538))
Authors: Harvey, J. W.; Sheeley, N. R., Jr.
Bibcode: 1979SSRv...23..139H
Altcode:
Since 1972, nearly continuous observations of coronal holes and their
associated photospheric magnetic fields have been made using a variety
of satellite and ground-based equipment. The results of comparisons
of these observations are reviewed and it is demonstrated that the
structure and evolution of coronal holes is basically governed by the
large-scale distribution of photospheric magnetic flux. Non-polar
holes form in the decaying remnants of bipolar magnetic regions in
areas with a large-scale flux imbalance. There is strong indirect
evidence that the magnetic field in coronal holes is always open to
interplanetary space but not all open-field regions have associated
coronal holes. The well-observed declining phase of the last solar
cycle was characterized by stable magnetic field and coronal hole
patterns which were associated with recurrent, high-speed wind streams
and interplanetary magnetic field patterns at the Earth. The ascending
phase of the current cycle has been characterized by transient magnetic
field and coronal hole patterns which tend to occur at high solar
latitudes. This shift in magnetic field and coronal hole patterns
has resulted in a less obvious and more complicated association with
high-speed wind streams at the Earth.
Title: Aspects of solar research at Kitt Peak in the 1980's.
Authors: Harvey, J. W.
Bibcode: 1979MmArc.106..228H
Altcode:
No abstract at ADS
Title: Proceedings of the JOSO workshop: Future solar optical
observations - needs and constraints. Firenze, November 7 - 10, 1978.
Authors: Godoli, G.; Noci, G.; Righini, A.; Pacini, F.; Engvold, O.;
Harvey, J. W.
Bibcode: 1979MmArc.106....1G
Altcode:
No abstract at ADS
Title: Adaptive optics for solar observations?
Authors: Harvey, J. W.
Bibcode: 1979MmArc.106...81H
Altcode:
No abstract at ADS
Title: A promising technique for achieving high resolution solar
observations.
Authors: Harvey, J. W.; Stein, M. K.
Bibcode: 1979MmArc.106..303H
Altcode:
No abstract at ADS
Title: Coronal holes, solar wind streams, and geomagnetic activity
during the new sunspot cycle.
Authors: Sheeley, N. R., Jr.; Harvey, J. W.
Bibcode: 1978SoPh...59..159S
Altcode:
The paper presents results obtained for 1976-1977 using daily He I 10830
A spectroheliograms and photospheric magnetograms. It was found that as
the magnetic field patterns changed, the solar atmosphere evolved from
a structure with a few large long-lived low-latitude coronal holes to
one with numerous small short-lived high-latitude holes. High-latitude
holes recurred with a synodic rotation period of 28-29 days instead of
the 27-day period already known to be characteristic of low-latitude
holes. A Bartels display of the occurrence of holes, wind speed,
and geomagnetic activity is considered.
Title: Motions in solar magnetic tubes. II: The oscillations.
Authors: Giovanelli, R. G.; Livingston, W. C.; Harvey, J. W.
Bibcode: 1978SoPh...59...49G
Altcode:
The method of Giovanelli and Brown (1977) has been used with a variety
of spectral lines to study oscillating longitudinal gas velocities
inside solar magnetic elements. Oscillations have been found inside all
elements observed, the amplitudes increasing with height from typically
±0.27 km s−1 in Fe I 5166 Å (a line of low origin)
to ±0.75 km s−1 in Hα. Simultaneous observations in
pairs of lines show that a given disturbance occurs later with height,
so that disturbances propagate outwards. The period is typically 5
min in all lines originating near or below Mg b1, but is
about 3 min in Hα.
Title: Coronal holes, solar wind streams, and geomagnetic activity
during the new sunspot cycle
Authors: Harvey, J. W.; Sheeley, N. R.
Bibcode: 1978SoPh...59..159H
Altcode:
We have extended our previous study of coronal holes, solar wind
streams, and geomagnetic disturbances from the declining phase
(1973-1975) of sunspot cycle 20 through sunspot minimum (1976)
into the rising phase (1977) of cycle 21. Using daily He I 10830
Å spectroheliograms and photospheric magnetograms, we found the
following results: As the magnetic field patterns changed, the solar
atmosphere evolved from a structure having a few, large, long-lived,
low-latitude coronal holes to one having numerous small, short-lived,
high-latitude holes (in addition to the polar holes which persisted
throughout this 5-year interval).
Title: Table of solar diatomic molecular lines. III. Spectral range:
7100 - 7600 Å.
Authors: Boyer, R.; Sotirovski, P.; Harvey, J. W.
Bibcode: 1978A&AS...33..145B
Altcode:
The present publication of results between 7100-7600 A represents
the third part of an analysis of molecular lines in the spectrum
of a sunspot (wavelength range: 6100-8300 A'). It is an extension of
results already published covering 6100-6600 and 6600-7100 A. Key words:
solar photosphere - molecular spectra - sunspots
Title: Motions in solar magnetic tubes. III: Outward wave propagation
in sunspot umbras.
Authors: Giovanelli, R. G.; Harvey, J. W.; Livingston, W. C.
Bibcode: 1978SoPh...58..347G
Altcode:
The line-centre magnetogram technique has been used to study velocities
at spatial scales ≃5″ in several umbras without interference from
light scattered from the surrounding non-magnetic photosphere. In
addition, more traditional velocity observations of one sunspot were
also analysed. The velocities are highly variable within any spot and
from one spot to another. Rms velocities in Hα, b1, 5233
and 5166 Å were typically ±0.6, ±0.20, ±0.10,
and ±0.17 km s−1 during present observations,
but factors of 2 smaller or larger are not uncommon. In 5166 and 5233
Å these velocities are about two-thirds of those in non-magnetic
photospheric regions.
Title: Coronal Holes, Solar Wind Streams and Geomagnetic Activity
During the New Solar Cycle.
Authors: Sheeley, N. R.; Harvey, J. W.
Bibcode: 1978BAAS...10Q.461S
Altcode:
No abstract at ADS
Title: A Promising Technique for Achieving High Resolution Solar
Observations
Authors: Harvey, J. W.; Stein, M. K.
Bibcode: 1978OMOAA.106..303H
Altcode:
No abstract at ADS
Title: Summary of the Workshop
Authors: Harvey, J. W.
Bibcode: 1978fsoo.conf..313H
Altcode:
No abstract at ADS
Title: A promising technique for achieving high resolution solar
observations
Authors: Harvey, J. W.; Stein, M. K.
Bibcode: 1978fsoo.conf..303H
Altcode:
No abstract at ADS
Title: Adaptive optics for solar observations?
Authors: Harvey, J. W.
Bibcode: 1978fsoo.conf...81H
Altcode:
No abstract at ADS
Title: Adaptive Optics for Solar Observations?
Authors: Harvey, J. W.
Bibcode: 1978OMOAA.108...81H
Altcode:
No abstract at ADS
Title: Aspects of Solar Research at Kitt Peak in the 1980's
Authors: Harvey, J. W.
Bibcode: 1978OMOAA.106..228H
Altcode:
No abstract at ADS
Title: Summary of the Workshop
Authors: Harvey, J. W.
Bibcode: 1978OMOAA.106..313H
Altcode:
No abstract at ADS
Title: A comparison of He ii 304 Å and He i 10 830 Å
spectroheliograms
Authors: Harvey, J. W.; Sheeley, N. R., Jr.
Bibcode: 1977SoPh...54..343H
Altcode:
Spectroheliograms were obtained simultaneously in the He II 304 Å
emission line and the He I 10 830 Å absorption line with an angular
resolution of approximately 5″. A negative print of the 304 Å
image is matched with a positive print of the 10 830 Å image so that
corresponding features of the chromospheric network (including active
regions) appear identical in the two images. Differences between these
images include the facts that: Disk filaments and limb darkening are
strongly visible in the 10 830 Å positive image, but they are weakly
visible (as lightenings) in the 304 Å negative image.
Title: Magnetic properties of X-ray bright points.
Authors: Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S.
Bibcode: 1977SoPh...53..111G
Altcode:
Using high resolution KPNO magnetograms and sequences of simultaneous
S-054 soft X-ray solar images we have compared the properties of X-ray
bright points (XBP) and ephemeral active regions (ER). All XBP appear on
the magnetograms as bipolar features, except for very newly emerged or
old and decayed XBP. We find that the separation of the magnetic bipoles
increases with the age of the XBP, with an average emergence growth
rate of 2.2 ± 0.4 km s−1. The total magnetic flux in a
typical XBP living about 8 hr is found to be ≈ 2 x 1019
Mx. A proportionality is found between XBP lifetime and total magnetic
flux, equivalent to ≈ 1020 Mx per day of lifetime.
Title: Open magnetic structures on the sun.
Authors: Levine, R. H.; Altschuler, M. D.; Harvey, J. W.; Jackson,
B. V.
Bibcode: 1977ApJ...215..636L
Altcode:
High-resolution harmonic analysis of the solar magnetic field has
been used succesfully to calculate the geometry of open magnetic field
lines in the solar corona. Comparison of the loci of open-field-line
footpoints with solar X-ray photographs shows that all the coronal
holes during two solar rotations are successfully represented, including
details of their evolution. Some open magnetic configurations derived in
the calculations precede by up to one solar rotation the manifestation
of coincident dark areas on the X-ray photographs. The only other
areas that contribute open field lines to the corona are separations
between active-region loop systems. By varying the radius at which
field lines are forced to be open in the calculation, it is possible to
reproduce more closely the surface configuration of particular coronal
holes. Comparison of the size of X-ray holes with the fraction of the
solar surface covered by open field lines leads to the conclusion
that a significant part of the area of coronal holes must contain
closed magnetic fields. Comparison of open field lines which lie in
the equatorial plane of the sun with solar-wind data indicates that
eventual high-speed solar-wind streams are associated with those parts
of open magnetic structures that diverge the least.
Title: A pictorial comparison of interplanetary magnetic field
polarity, solar wind speed, and geomagnetic disturbance index during
the sunspot cycle.
Authors: Sheeley, N. R., Jr.; Asbridge, J. R.; Bame, S. J.; Harvey,
J. W.
Bibcode: 1977SoPh...52..485S
Altcode:
Observations of interplanetary magnetic field polarity, solar wind
speed, and geomagnetic disturbance index (C9) during the years
1962-1975 are compared in a 27-day pictorial format that emphasizes
their associated variations during the sunspot cycle. This display
accentuates graphically several recently reported features of solar
wind streams including the fact that the streams were faster, wider,
and longer-lived during 1962-1964 and 1973-1975 in the declining
phase of the sunspot cycle than during intervening years (Bame et al.,
1976; Gosling et al., 1976). The display reveals strikingly that these
high-speed streams were associated with the major, recurrent patterns
of geomagnetic activity that are characteristic of the declining
phase of the sunspot cycle. Finally, the display shows that during
1962-1975 the association between long-lived solar wind streams and
recurrent geomagnetic disturbances was modulated by the annual variation
(Burch, 1973) of the response of the geomagnetic field to solar wind
conditions. The phase of this annual variation depends on the polarity
of the interplanetary magnetic field in the sense that negative sectors
of the interplanetary field have their greatest geomagnetic effect in
northern hemisphere spring, and positive sectors have their greatest
effect in the fall. During 1965-1972 when the solar wind streams
were relatively slow (500 km s-1), the annual variation
strongly influenced the visibility of the corresponding geomagnetic
disturbance patterns.
Title: Solar sources of the interplanetary magnetic field and
solar wind
Authors: Levine, R. H.; Altschuler, M. D.; Harvey, J. W.
Bibcode: 1977JGR....82.1061L
Altcode:
Open magnetic field lines, those which extend from the solar photosphere
to interplanetary space, are traced in the current-free (potential
field) approximation using measured photospheric fields as a boundary
condition. It is found that (1) only a relatively small fraction of the
photospheric area connects via open field lines to the interplanetary
magnetic field; (2) those photospheric areas which do contribute open
field lines lie beneath coronal holes and within the boundaries of the
holes as projected onto the photosphere or else between loop systems
of an active region; (3) the interplanetary magnetic field in the plane
of the sun's equator, essentially the field in the ecliptic plane, may
connect to photospheric regions of high latitude; and (4) the fastest
solar wind streams are correlated with those magnetic flux tubes which
expand least in cross-sectional area over the distance between the
photosphere and the coronal height where the solar wind begins.
Title: Observations of K I Line Emission in the Circumstellar Shell
of Alpha Orionis.
Authors: Lynds, C. R.; Harvey, J. W.; Goldberg, L.
Bibcode: 1977BAAS....9Q.345L
Altcode:
No abstract at ADS
Title: A Comparison of He II 304 Å and He I 10830 Å
Spectroheligrams.
Authors: Harvey, J. W.; Sheeley, N. R., Jr.
Bibcode: 1977BAAS....9..325H
Altcode:
No abstract at ADS
Title: Non-Spot Magnetic Fields
Authors: Harvey, J. W.
Bibcode: 1977ASSL...69...13H
Altcode: 1977igss.conf...13H
General Magnetic Field Polar Magnetic Field Large-Scale Magnetic Field
Sector Structure Unipolar Magnetic Region Magnetic Puka Network Field
Magnetic Hills Magnetic Element or Fluxule Magnetic Rope (Flux Rope)
Magnetic Filament Magnetic Microturbulence Crossover Effect Magnetograph
Stokesmeter Lambdameter or Recording Doppler Comparator
Title: Observations of Small-Scale Photospheric Magnetic Fields
Authors: Harvey, J. W.
Bibcode: 1977HiA.....4B.223H
Altcode: 1977HiA.....4..223H
No abstract at ADS
Title: The Kitt Peak CID Systems
Authors: Aikens, R. S.; Harvey, J. W.; Lynds, C. R.
Bibcode: 1977aaid.coll...25A
Altcode: 1977IAUCo..40...25A
No abstract at ADS
Title: Direct observations of the heterogeneity of supergiant disks.
Authors: Harvey, J. W.; Lynds, C. R.; Worden, S. P.
Bibcode: 1977oehs.conf..405H
Altcode:
No abstract at ADS
Title: Reconstructed images of Alpha Orionis using stellar speckle
interferometry.
Authors: Worden, S. P.; Lynds, C. R.; Harvey, J. W.
Bibcode: 1976JOSA...66.1243W
Altcode: 1976OSAJ...66.1243W
A recently developed technique to recover nearly diffraction-limited
images of supergiant stars such as Alpha Orionis (Betelgeuse)
from speckle interferometry data is discussed. This method relies
on the digital identification and coaddition of the brightest
individual speckles within a large number of short-exposure speckle
photographs. The resulting average speckle may be thought of as the
convolution of a point source speckle profile with the actual object
intensity pattern. By making use of this point angular diameters and
limb darkening coefficients are derived in addition to finding evidence
of possible surface structure on the star.
Title: Coronal holes, solar wind streams, and recurrent geomagnetic
disturbances: 1973 1976
Authors: Sheeley, N. R., Jr.; Harvey, J. W.; Feldman, W. C.
Bibcode: 1976SoPh...49..271S
Altcode:
Observations of coronal holes, solar wind streams, and geomagnetic
disturbances during 1973-1976 are compared in a 27-day pictorial format
which shows their long-term evolution. The results leave little doubt
that coronal holes are related to the high-speed streams and their
associated recurrent geomagnetic disturbances. In particular, these
observations strongly support the hypothesis that coronal holes are
the solar origin of the high-speed streams observed in the solar wind
near the ecliptic plane.
Title: Digital image reconstruction applied to Alpha Orionis.
Authors: Lynds, C. R.; Worden, S. P.; Harvey, J. W.
Bibcode: 1976ApJ...207..174L
Altcode:
Short-exposure photographs at high magnification have been obtained
for the M2 Ia-b supergiant alpha Ori with a 4-m telescope. Optical
passbands were chosen which isolate a temperature-sensitive TiO band
and, for comparison, a nearby section of continuum. The photographs
have been digitized and subjected to a deconvolution procedure which
gives reconstructed images of the surface of the star. The images
indicate a small difference in the angular dimensions of the star as
observed through the two different filters, and there is some evidence
supporting the presence of surface structure. The particular procedure
employed in the reconstruction of the images has only a limited range
of validity, but application of the procedure to photographs of the
unresolved star gamma Ori not only served the necessary function of
determining the final point-spread function but also yielded images
showing a diffraction pattern apparently related to the theoretical
Airy pattern of the telescope.
Title: Table of solar diatomic molecular lines. II. Spectral range:
6600 - 7100 Å.
Authors: Boyer, R.; Sotirovski, P.; Harvey, J. W.
Bibcode: 1976A&AS...24..111B
Altcode:
The present publication of results between 6600 and 7100 A represents
the second part of a work of analysis of molecular lines observed
in the spectrum of a sunspot (wavelength range: 61( A). It is an
extension of results already published concerning the area: 61 ()(
6600 A. Key words: solar photosphere - molecular spectra - sunspots
Title: Open Magnetic Structures on the Sun
Authors: Levine, R. H.; Altschuler, M. D.; Harvey, J. W.
Bibcode: 1976BAAS....8..326L
Altcode:
No abstract at ADS
Title: A study of the magnetic and velocity fields in an active
region.
Authors: Harvey, K. L.; Harvey, J. W.
Bibcode: 1976SoPh...47..233H
Altcode:
A time sequence of magnetograms and velocity-grams in the Hα and
Fe I 6569 Å lines has been made at a rate of 12 h−1
of McMath Region 10385 from 26 to 29 October, 1969. The 14 flares
observed during this period have been studied in relation to the
configuration and changes in the magnetic and velocity fields. There
was little correlation between flare position and the evolutionary
changes in the photospheric magnetic and velocity field, except
at large central meridian distances where the velocity observations
suggested shearing taking place at flare locations. At central meridian
distances > 30° we found that flares are located in areas of low
line-of-sight photospheric velocity surrounded by higher velocity
hills. The one exception to this was the only flare which produced a
surge. Blue-shifted velocity changes in the photosphere of 0.3 to 1
km s−1 were observed in localized areas at the times of
8 of 14 flares studied.
Title: Recent Solar Magnetograph Results
Authors: Harvey, J. W.
Bibcode: 1976saop.book...51H
Altcode:
No abstract at ADS
Title: The Kitt Peak 60-cm Vacuum Telescope
Authors: Pierce, A. K.; Livingston, W. C.; Harvey, J. W.; Schrage,
D.; Gillespie, B.; Simmons, J.; Slaughter, C.
Bibcode: 1976ApOpt..15...33P
Altcode:
No abstract at ADS
Title: Reconstructed images of Alpha Orionis using stellar speckle
interferometry.
Authors: Worden, S. P.; Harvey, J. W.; Lynds, C. R.
Bibcode: 1976JOSA...66..181W
Altcode: 1976OSAJ...66..181W
No abstract at ADS
Title: Results of observations with a solar magnetograph.
Authors: Harvey, J. W.
Bibcode: 1976npsa.conf...33H
Altcode:
No abstract at ADS
Title: The Calculation of Force-Free Fields from Discrete Flux
Distributions
Authors: Sheeley, N. R., Jr.; Harvey, J. W.
Bibcode: 1975SoPh...45..275S
Altcode:
This paper presents particularly simple mathematical formulas for the
calculation of force-free fields of constant α from the distribution
of discrete sources on a flat surface. The advantage of these formulas
lies in their physical simplicity and the fact that they can be easily
used in practice to calculate the fields. The disadvantage is that they
are limited to fields of `sufficiently small α'. These formulas may be
useful in the study of chromospheric magnetic fields by the comparison
of high-resolution Hα photographs and photospheric magnetograms.
Title: Flares and Their Relation to the Photospheric Velocity Field.
Authors: Harvey, K. L.; Harvey, J. W.
Bibcode: 1975BAAS....7..438H
Altcode:
No abstract at ADS
Title: Comparison of Skylab X-Ray and Ground-Based Helium Observations
Authors: Harvey, J. W.; Krieger, A. S.; Davis, J. M.; Timothy, A. F.;
Vaiana, G. S.
Bibcode: 1975BAAS....7..358H
Altcode:
No abstract at ADS
Title: Table of solar diatomic molecular lines I. Spectral range:
6100-6600 Å
Authors: Boyer, R.; Sotirovski, P.; Harvey, J. W.
Bibcode: 1975A&AS...19..359B
Altcode:
A table of molecular lines observed in the spectrum of a sunspot
in the wavelength range 61O( 8300 A is in preparation. The present
publication of results between 6100 and 6600 A represents the first
part of this work. An introductory text gives a detailed description of
each column of the table. For each identified line the rotation branch
quantum number and the vibration band are indicated. We measured the
equivalent widths for all lines with profiles as free from blending
as possible, the effect of scattering from the photosphere and the
edges of strong Fraunhofer lines being taken into account. Key words:
solar photosphere - molecular spectra - sunspots
Title: Photoelectric speckle interferometry of the solar granulation.
Authors: Harvey, J. W.; Schwarzschild, M.
Bibcode: 1975ApJ...196..221H
Altcode:
Using the Mc Math solar telescope on a morning of average seeing
it has been found possible, with the help of photoelectric speckle
interferometry, to detect securely the existence of details in the
quiet solar granulation up to a wavenumber of 240 x 10-6 km-1, i.e.,
a wavelength of one-third of an arc second. Subject headings: granules
and supergranules, solar - image processing
Title: Comparison of Skylab X-ray and Ground-Based Helium Observations
Authors: Harvey, J. W.; Krieger, A. S.; Timothy, A. F.; Vaiana, G. S.
Bibcode: 1975OMOAA.104...50H
Altcode:
No abstract at ADS
Title: Ephemeral Active Regions in 1970 and 1973
Authors: Harvey, K. L.; Harvey, J. W.; Martin, S. F.
Bibcode: 1975SoPh...40...87H
Altcode:
A study of ephemeral active regions (ER) identified on good quality
full-disk magnetograms reveals: On the average 373 and 179 ER were
present on the Sun in 1970 and 1973 respectively. The number varies
with the solar cycle.
Title: Digital Image Reconstruction Applied to Betelgeuse.
Authors: Lynds, C. R.; Worden, S. P.; Harvey, J. W.
Bibcode: 1974BAAS....6Q.459L
Altcode:
No abstract at ADS
Title: A study of the magnetic and velocity fields in an active center
Authors: Harvey, K. L.; Harvey, J. W.
Bibcode: 1974lock.reptQ....H
Altcode:
The report compares in detail the magnetic fields and velocity fields
between the chromosphere and photosphere and investigates changes
occurring in association with flares. Three aspects of the analysis are
discussed: (1) flare location and development relative to the magnetic
and velocity field configuration, (2) slow or evolutionary changes
in the magnetic and velocity field in relation to flare occurrence,
(3) rapid changes (i.e., changes having time scales comparable to that
of flares) in the magnetic and velocity field occurring at the times
of flares.
Title: Ephemeral active regions in 1970 and 1973
Authors: Harvey, K. L.; Martin, S. F.; Harvey, J. W.
Bibcode: 1974lock.reptR....H
Altcode:
The work reported here was undertaken to learn more about the spatial
distribution of Ephemeral active regions (ER), lifetime, solar
cycle variation, and association with major active centers. Primary
consideration was given to the question of whether or not ER represent,
in part, a new class of solar activity or are simply small active
regions.
Title: A Comparison of EUV Spectroheliograms and Photospheric
Magnetograms
Authors: Gurman, Joseph B.; Withbroe, George L.; Harvey, John W.
Bibcode: 1974SoPh...34..105G
Altcode:
A comparison of EUV data from the Harvard College Observatory
experiment on OSO-6 with photospheric magnetograms from Kitt Peak
National Observatory indicates a bipartite relationship between values
of the longitudinal field strength B and Mg x intensity I averaged over
square areas 35″ × 35″: in quiet regions ¦B¦ ∼ Ik,
where 0.0 ≲ k ≲ 0.3, and in active regions ¦B¦ ∼ I. From these
relationships we infer that ¦B¦ ∼ ne2k
in quiet regions and ¦B¦ ∼ ne2 in active
regions. In addition, the photospheric field beneath a coronal hole
is found to be virtually identical to that beneath normal quiet regions.
Title: The Topological Association of Hα Structures and Magnetic
Fields
Authors: Nakagawa, Y.; Raadu, M. A.; Harvey, J. W.
Bibcode: 1973SoPh...30..421N
Altcode:
The topological associations between Hα structures and magnetic
fields are examined for an active region observed on two different
dates. The structures seen in the on and off band of Hα filtergrams
are compared with the contour maps of magnetic fields at the level
of magnetogram observations. Similar comparisons are made also with
the configurations of force-free magnetic lines of force at various
heights evaluated with the use of formulations developed previously
by Nakagawa and Raadu (1972).
Title: Solar Speckle Interferometry
Authors: Harvey, J. W.; Breckinridge, J. B.
Bibcode: 1973ApJ...182L.137H
Altcode:
The technique of speckle interferometry has been applied to solar
photographs. Spatial frequencies as high as 4 cycles per arc second
have been detected in sunspots. Subject headings: faculae, solar -
granules, solar - image processing - sunspots
Title: Solar Speckle Interferometry
Authors: Harvey, J. W.; Breckinridge, J. B.
Bibcode: 1973BAAS....5Q.273H
Altcode:
No abstract at ADS
Title: Fraunhofer Lines with Large Zeeman Splitting
Authors: Harvey, J. W.
Bibcode: 1973SoPh...28....9H
Altcode:
A list of solar spectral lines having simple Zeeman triplet splitting
with Landé g-factors equal to or greater than 2.5 is presented.
Title: Polarization of Red System CN Lines in Sunspots
Authors: Harvey, J. W.
Bibcode: 1973SoPh...28...43H
Altcode:
The relative intensities of the Zeeman components of molecular spectral
lines are not necessarily symmetric in a strong magnetic field. This
leads to non-zero net polarization for molecular lines formed in
sunspots. The effect is particularly striking for lines of the (0, 0)
band of the red system of CN.
Title: Observations of Sunspot Umbral Velocity Oscillations
Authors: Bhatnagar, Arvind; Livingston, W. C.; Harvey, J. W.
Bibcode: 1972SoPh...27...80B
Altcode:
Sunspot umbral molecular lines have been used to look for the
oscillatory velocities in the umbra. Power spectrum analysis showed
conspicuous power for periods in the range between 448 and 310 s. The
maximum peak-to-peak amplitude of the umbral oscillatory velocity
component is observed to be in the order of 0.5 km s−1.
Title: C2 in sunspots
Authors: Harvey, J. W.
Bibcode: 1972SoPh...24..354H
Altcode:
No abstract at ADS
Title: Interferometric Observations of Small Solar Continuum Features
Authors: Harvey, J. W.
Bibcode: 1972BAAS....4U.383H
Altcode:
No abstract at ADS
Title: Observations of Sunspot Umbral Velocity Oscillations
Authors: Bhatnagar, A.; Livingston, W. C.; Harvey, J. W.
Bibcode: 1972BAAS....4R.378B
Altcode:
No abstract at ADS
Title: A Comparison between the Helium 10830 Å and the Hydrogen
H&alpha Chromospheres
Authors: Giovanelli, R. G.; Hall, D. N. B.; Harvey, J. W.
Bibcode: 1972SoPh...22...53G
Altcode:
Spectroheliograms of resolution about 2 arc sec obtained simultaneously
in He 10830 Å and Hα show in the network a very close agreement
in position of dark Hα mottles and of bright Hα plage remnants
with 10830 Å absorption, though there is not a one-to-one relation
between the intensities; the typical intensity in 10830 Å, corrected
for overlapping lines, is I≈ 0.91 of the continuum. Some parts of
the network do not appear in 10830 Å. This line is much weaker over
supergranule centres (I≈ 0.98), though near active regions dark Hα
fibrils coincide with faint 10830 Å fibrils (I≈0.93-0.98).
Title: Interferometry applied to Visible Solar Features
Authors: Harvey, J. W.
Bibcode: 1972NPhS..235...90H
Altcode: 1972Natur.235...90H
THE study of the solar atmosphere at visible wavelengths has clearly
shown that it is inhomogeneous, with a small scale structure, and that
interpretation of observational results in terms of simple homogeneous
models can give misleading or even completely spurious results. The best
resolution that has been obtained in visible light solar observations is
of the order of 1/3 arc s, equivalent to 240 km at the solar distance,
and many solar features are unresolved even on this scale. Prospects for
a significant improvement in the resolution obtainable with instruments
on the Earth are poor because of the presence of the Earth's atmosphere.
Title: Real-time masking of solar photographs with photochromic glass.
Authors: Harvey, J. W.
Bibcode: 1972AASPB...5....5H
Altcode:
No abstract at ADS
Title: Recent Solar Magnetograph Results
Authors: Harvey, J. W.
Bibcode: 1972PrAA...30...51H
Altcode:
No abstract at ADS
Title: Observations of Magnetic Field Changes in Active Regions
Authors: Harvey, K. L.; Livingston, W. C.; Harvey, J. W.; Slaughter,
C. D.
Bibcode: 1971IAUS...43..422H
Altcode:
No abstract at ADS
Title: Fraunhofer Lines without Zeeman Splitting
Authors: Sistla, Gopal; Harvey, J. W.
Bibcode: 1970SoPh...12...66S
Altcode:
No abstract at ADS
Title: Short Period Oscillations and Doppler Velocity Gradients
Authors: Harvey, J. W.
Bibcode: 1970SoPh...11...26H
Altcode:
No abstract at ADS
Title: The Improved Solar Magnetograph of the High Altitude
Observatory
Authors: Harvey, J. W.; Lee, R. H.; Tandberg-Hanssen, E.
Bibcode: 1969ApOpt...8.2370H
Altcode:
No abstract at ADS
Title: The Improved Solar Magnetograph of the High Altitude
Observatory
Authors: Lee, R. H.; Harvey, J. W.; Tandberg-Hanssen, E.
Bibcode: 1969ApOpt...8.2370L
Altcode:
No abstract at ADS
Title: The magnetic field in some prominences measured with the He I,
5876 Å line
Authors: Harvey, J. W.; Tandberg-Hanssen, E.
Bibcode: 1968SoPh....3..316H
Altcode:
Observations of the longitudinal magnetic field of several prominences
were made with the D3, Hα, and Hβ lines. There is no
significant difference in the magnetic field measured with the helium
and hydrogen lines. The possibility of a true difference in the fields
on a scale much finer than that of our observations is not excluded.
Title: Observations of Active Prominence and Coronal Magnetic Fields.
Authors: Harvey, John W.
Bibcode: 1968AJS....73R..62H
Altcode:
The magnetograph of the High Altitude Observatory was used to
obtain more than 200 measurements of the longitudinal magnetic
field in limb prominences in and near active regions with the Ha
line. A few additional observations were made with the D2, D3,
and Hfl lines. Seven measurements of the coronal field with the
N5303 line were attempted. Noise in the observations was generally
less than 5 gauss. Field strengths in active prominences ranged from
undetectable to about 150 gauss. The observed fields tend to decrease
with increasing height unlike the field of quiescent prominences
(Rust, Astrophys. J. 150, 313,1967). The field frequently appears to
be oriented predominantly along the axis of both active and quiescent
prominences. Simultaneous radial velocity recordings show periodic
oscillations in about 15% of the active prominences and about 30% of
the quiescent prominences observed; no evidence for a corresponding
magnetic field oscillation was found. A few surges showed strong
longitudinal fields (100 gauss) but most had fields less than 30
gauss. Large surges are usually associated with weak fields and
strong fields with small surges. Field strengths from 10 to 60 gauss
were observed in loop prominences. The spatial characteristics of the
loop fields are similar to those of the fields inferred from potential
theory but the observed strengths are about ten times greater. Coronal
magnetic fields are not easy to observe. Our best measurements of the
longitudinal field strength in the corona about 30,000 km above two
moderately active regions are 1.5 and 2.0 gauss. Nearby prominences
showed fields two to three times stronger.
Title: Photospheric Changes Observable in Integrated Light
Authors: Harvey, J. W.
Bibcode: 1965PASP...77..129H
Altcode:
No abstract at ADS
Title: Coronal Polar Rays and Polar Magnetic Fields.
Authors: Harvey, J. W.
Bibcode: 1965ApJ...141..832H
Altcode:
No abstract at ADS
Title: Photospheric Magnetic Fields and Chromospheric Features.
Authors: Howard, Robert; Harvey, J. W.
Bibcode: 1964ApJ...139.1328H
Altcode:
Fine-scan magnetograms and large-scale Ha filtergrams of an active
region were made simultaneously. From the on-band pictures we could
identify bright and dark fine mottles (<1600 km), coarse dark mottles
( 5000 km), bright and dark fibrils, and filaments. Small dark mottles
have lifetimes of about 10 min, and large dark mottles have lifetimes of
about 15 min. The lifetimes of bright fine mottles are much longer than
those of the dark mottles. There are two clear-cut distinctions between
dark fibrils and filaments. The fibrils show increased contrast when
seen on the blue wing of Ha, while on the same filtergrams the contrast
of the filaments decreases. The fibrils seem to lie perpendicular to
isogauss lines of the longitudinal field measured in the photosphere,
and the filaments in general lie parallel to these isogauss lines and
over the null line of the field. It is evident that the filaments lie at
higher layers than do the fibrils, and are different in nature. A ring
of fibrils is found to occupy the position of the 15-G contour line
(also the outline of the calcium plage). The calcium network pattern
can be seen on the bluewing Ha filtergrams as regions of small plages
surrounded by fibrils. We suggest that these fibrils are associated
with spicules. In Ha movies it is evident that the portion of the
chromosphere outside the 15-G contour lines is undergoing some type
of random seething motion. Most of this (seen on-band) is actually
a change in size and shape of the mottles. An important 1- flare
occurred during the observations. No changes in the isogauss maps
could be detected before and after the flare, but some slight changes
in some chromospheric structures were noted.
Title: Photospheric Granulation in the Near Ultraviolet
Authors: Harvey, J. W.; Ramsey, H. E.
Bibcode: 1963PASP...75..283H
Altcode:
No abstract at ADS
Title: Height of an Ellerman "bomb"
Authors: Harvey, J. W.
Bibcode: 1963Obs....83...37H
Altcode:
No abstract at ADS
Title: Photographic Detection of Solar Magnetic Fields with an Hα
Birefringent Filter.
Authors: Harvey, J. W.
Bibcode: 1963AJ.....68R.537H
Altcode:
Use of a Lyot type filter for detection of chromospheric magnetic
fields was suggested by R. G. Giovanelli (Trans. IAU 10, t97, t958). A
modification of his technique has been developed. A quarter-wave
plate mounted in front of the entrance polarizer of a 0.5 A bandpass
birefringent Ha filter renders it capable of detecting circularly
polarized light. As a result of the presence of a longitudinal magnetic
field, the wings of the Ha line are partially circularly polarized. To
detect the polarized light resulting from magnetic fields the filter
is carefully tuned to the steepest part of the Ha line profile and two
photographs of the sun are taken. The quarter-wave plate is oriented
so that left-hand circularly polarized light is blocked during the
first photograph. Right-hand circularly polarized light is blocked
during the second photograph. Densities of corresponding areas on the
two photographs are identical except in areas where a longitudinal
magnetic field is present. Photographic subtraction reveals the
location and polarity of the magnetic fields. For features of average
intensity and linewidths, the sensitivity of this technique is about
too G. Preliminary observations show strong fields in the chromosphere
above sunspots. With the possible exception of a disk surge, fields
in other chromospheric features have not been positively detected.