Author name code: pap
ADS astronomy entries on 2022-09-14
author:"Pap, Judit M."
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Title: Active region properties and irradiance variations
Authors: Baranyi, Tünde; Pap, Judit M.
Bibcode: 2012AdSpR..50..676B
Altcode:
Total Solar Irradiance (TSI) has been measured for more than three
decades. These observations demonstrate that total irradiance changes
on time scales ranging from minutes to years and decades. Considerable
efforts have been made to understand the physical origin of irradiance
variations and to model the observed changes using measures of sunspots
and faculae. In this paper, we study the short-term variations in TSI
during the declining portion and minimum of solar cycle 22 and the
rising portion of cycle 23 (1993-1998). This time interval of low solar
activity allows us to study the effect of individual sunspot groups on
TSI in detail. In this paper, we indicate that the effect of sunspot
groups on total irradiance may depend on their type in the Zürich
classification system and/or their evolution, and on their magnetic
configuration. Some uncertainties in the data and other effects are
also discussed.
Title: Statistical Feature Recognition for Multidimensional Solar
Imagery
Authors: Turmon, Michael; Jones, Harrison P.; Malanushenko, Olena V.;
Pap, Judit M.
Bibcode: 2010SoPh..262..277T
Altcode: 2010SoPh..tmp...52T
A maximum a posteriori (MAP) technique is developed to identify solar
features in cotemporal and cospatial images of line-of-sight magnetic
flux, continuum intensity, and equivalent width observed with the
NASA/National Solar Observatory (NSO) Spectromagnetograph (SPM). The
technique facilitates human understanding of patterns in large data
sets and enables systematic studies of feature characteristics for
comparison with models and observations of long-term solar activity
and variability. The method uses Bayes' rule to compute the posterior
probability of any feature segmentation of a trio of observed
images from per-pixel, class-conditional probabilities derived from
independently-segmented training images. Simulated annealing is used
to find the most likely segmentation. New algorithms for computing
class-conditional probabilities from three-dimensional Gaussian
mixture models and interpolated histogram densities are described and
compared. A new extension to the spatial smoothing in the Bayesian
prior model is introduced, which can incorporate a spatial dependence
such as center-to-limb variation. How the spatial scale of training
segmentations affects the results is discussed, and a new method for
statistical separation of quiet Sun and quiet network is presented.
Title: Analysis of Ca II 8542 Å scanning spectroscopy for statistical
feature recognition.
Authors: Malanushenko, O.; Jones, H.; Turmon, M.; Pap, J.
Bibcode: 2010MmSAI..81..801M
Altcode:
Previously, we used Bayesian methods to recognize active regions (AR),
enhanced magnetic network (EN), and sunspots (SS) in National Solar
Observatory/Kitt Peak Vacuum Telescope synoptic observations. In this
paper we study imaging spectroscopy of the chromospheric Ca II 8542
Å and photospheric Fe I 8688 Å lines to improve separation of ARs
and EN. We find that correlation plots between Ca line-center and ±
0.45 Å line-wing intensities show two identifiable but overlapping
distributions. The first includes ARs (bright and faint) and the second
includes ENs, network, and moat (``quiet Sun''). Active and Quiet
distributions overlap in areas of EN and faint AR, so that feature
identification using thresholds is unreliable. The statistical
methodology of our previous work, however, is particularly well
suited for distinguishing features with such partially overlapping
distributions. Additionally, we find features in the Ca line which
are not visible in the Fe observations, including a dark moat around
an AR and narrow dark points associated with network and strong
line-of-sight flows.
Title: Solar Irradiance Variations Related to Intensity and Magnetic
Flux of Solar Features
Authors: Pap, Judit M.; Jones, H.; Parker, D.; Chapman, G.; Floyd, L.
Bibcode: 2010cosp...38.1783P
Altcode: 2010cosp.meet.1783P
Solar total and spectral irradiance have been measured since late
1978. These measurements have demonstrated that solar irradiance changes
from minutes to the 11-year solar cycle. Con-sidering the astrophysical
and climate importance of irradiance variations, considerable efforts
have been put forward to develop irradiance models to explain the origin
of irradiance varia-tions and have information for those time intervals
when measurements don't exist. However, most of the current models are
simple empirical models, using the Photometric Sunspot Index to describe
the darkening effect of sunspots and either the CaK index or the Mg II
h k core-to wing ratio to describe the facular excess flux. While these
models can explain reasonably well the short-term variations, long-term
variations over years to the cycle are not well-accounted. Since the
SOHO era we have combined the MDI intensity images and magnetograms
to ac-count for the effect and the role of active region evolution
to irradiance variations. Similar studies have been done routinely
at the San Fernando Observatory, California State University. More
recently we have used the SPM data from NSO Kitt Peak to deduct various
activity components, and new efforts at UCLA are in progress to develop
a sophisticated method to identify various features. Using observations
by SDO/HMI we will have further insight into active region evolution,
especially during the rising portion of cycle 24, following the long
and deep minimum of cycle 23. In this paper we compare data derived
from various images and compare them to irradiance variations. One of
the main goals is to identify weak magnetic fields and estimate their
contribution to irradiance changes. We will study cycle 23 in detail,
and will discuss how the used methods and techniques can be applied
to HMI on SDO.
Title: Evolution of active regions and irradiance variations
Authors: Baranyi, Tünde; Pap, Judit M.
Bibcode: 2010cosp...38.1768B
Altcode: 2010cosp.meet.1768B
Total solar irradiance have been measured now for more than three
decades. These observations demonstrate the total irradiance changes
on time scales from minutes to years and decades. Considerable efforts
have been put forward to understand the physical origin of irradiance
variations and model the observed changes using measures of sunspots
and faculae. Using the Photometric Sunspot Index developed from the
area and contrast of sunspots and full disk indices for describing the
effect of faculae models have been developed with linear regression
analysis. However these models are limited because of the non-linearity
between irradiance variations and activity indices and that variations
in total irradiance cannot be accounted for by a simple combination of
area and position of sunspots. In this paper we present new findings
which show that the effect of sunspots on total irradiance strongly
depends on their type in the Zurich classification system as well as
on their evolution.
Title: Introduction to Solar Effects on Climate Change
Authors: Pap, Judit M.
Bibcode: 2010cosp...38.1687P
Altcode: 2010cosp.meet.1687P
Introduction to Solar Effects on Climate Change
Title: Comparison of Independent Feature Recognition Method for
Time Series Analysis of Irradiance Variations Based on Statistical
Feature Recognition
Authors: Pap, Judit M.; Bertello, L.; Chapman, G.; Floyd, L. E.;
Jones, H.; Malanushenko, E.; Preminger, D.; Turmon, M.
Bibcode: 2009SPD....41.0934P
Altcode:
Solar total and UV irradiances have been observed over three decades,
and recently spectral irradiance data are available from the Solar
Irradiance Monitor (SIM) on the SORCE Mission. Results of these
measurements show that irradiance varies on various time scales from
minutes to decades. To better understand the origin of irradiance
changes, we need to use spatially resolved data rather than full
disk indices. For this purpose various automated image processing
and analyses techniques have been developed. Using these image
processing techniques, we separated quiet-sun, network, faculae and
sunspots. On one hand, we compare the area data of these features
derived from various images to validate results and discuss future
efforts needed to coordinate efforts between various groups working
on image analysis. Another goal is to compare the variations of the
identified features with total solar and UV irradiances to establish
to what degree the identified images explain short and long-term
irradiance variations.
Title: Training Sets for Statistical Feature Recognition in
Multidimensional Solar Imagery
Authors: Jones, Harrison P.; Turmon, M. J.; Malanushenko, O. V.; Pap,
J. M.
Bibcode: 2009SPD....40.1518J
Altcode:
We have previously reported the multi-dimensional extension of a
statistical maximum likelihood algorithm for segmenting images into
different feature classes developed by Turmon, Pap, and Mukhtar
(2002, ApJ 568, p. 396). The method works best for features which
have overlapping but nonetheless distinct distributions of observed
variables. Developing these empirical class-conditional distributions
from independently classified training sets depends sensitively on
the match of spatial scales between the training segmentations and
the desired feature classes. We discuss recent progress in extracting
well-posed class distributions even when the training segmentations
are mixtures of the classes which we wish to identify. For example,
in addition to large-scale labelings, Harvey and White (1999, ApJ
515, p. 812) provide finely grained information which we use to help
isolate areas of pure quiet Sun. Quiet Sun distributions of observed
quantities can then be separated from distributions derived from
areas labeled as network which also include quiet Sun. Similarly,
these distributions can then be isolated from those mixed with active
regions and/or sunspots. This research is funded by a NASA Supporting
Research and Technology grant.
Title: The application of Gaussian Mixture and Histogram-based
Bayesian methods to NSO/Kitt Peak VT data.
Authors: Malanushenko, O.; Jones, H. P.; Turmon, M.; Pap, J.
Bibcode: 2008AGUFMSH13A1519M
Altcode:
We applied Gaussian Mixture and Histogram-based Bayesian methods to
recognize several solar features using Kitt Peak Vacuum Telescope
(VT) observations from 1992-2003. We used 5D observations in the
868.8 nm line including LoS magnetic field, continuum intensity,
radial velocity, line depth, and EqW. We applied the analysis for
recognition of active regions, magnetic network, and sunspots, for
the purpose of automatic recognition of solar activity, and linking
solar activity to irradiance changes. The success of such a feature
recognition process strongly depends on separation and sensitivity
of observable and derivative parameters for different features. For
some features it works very well for two kind of data, but in some
other cases the probability of correct recognition of a feature is low
without the adding complementary data. We discuss the advantages and
limitations of these statistical methods, review the importance and
possibility of using the complementary data, and compare our results
with other methods which derive feature areas. This methodological
review will help to create the strategy for new SDO/HMI analysis.
Title: Spectral Irradiance Variations and Magnetic Field Changes
During Solar Cycle 23.
Authors: Pap, J. M.; Bertello, L.; Chapman, G.; Floyd, L. E.; Harder,
J.; Jones, H.; Malanuskenko, O.; Preminger, D.; Turmon, M.
Bibcode: 2008AGUFMSH13A1504P
Altcode:
Both total irradiance and the Mg core-to-wing ratio was high at the
maximum of weak solar cycle 23. However, photometric observations
from the San Fernando Observatory show that both the number and size
of active regions (spots and faculae) were low at the maximum of
solar cycle 23 which points to the importance of the role of weak
magnetic fields in irradiance variations. The purpose of this paper
is to use new SOLIS spectromagnetograph observations in conjunction
with a newly developed image analysis technique to compare irradiance
time series as function of wavelengths with various surface magnetic
features. One major goal is to compare features derived from the
SOLIS images using the new technique with well-established features
from SFO. Another important goal is to determine the contribution
of active regions/weak fields to irradiance variations at various
wavelengths, using the SOHO/VIRGO and SORCE/SIM data. A third goal
is to determine the extent of irradiance variations not explained by
magnetic structures. To do this, we use a new analysis technique to
evaluate SOLIS spectromagnetograph observations.
Title: Modeling Tsi Variations Using Automated Pattern Recognition
Software On Mount Wilson Data
Authors: Parker, D. G.; Ulrich, R. K.; Bertello, L.; Boyden, J. E.;
Pap, J. M.
Bibcode: 2008AGUFMSH23A1631P
Altcode:
This poster presents the results of using the AutoClass software,
a Bayesian finite mixture model based pattern recognition program
developed by Cheeseman and Stutz (1996), on Mount Wilson Solar
Observatory (MWO) intensity and magnetogram images to identify
spatially resolved areas on the solar surface associated with TSI
emissions. Using indices based on the resolved patterns identified
by AutoClass from MWO images, and a linear regression fit of those
indices to satellite observations of TSI, we were able to model the
satellite observations from the MWO data with a correlation of better
than 0.96 for the period 1996 to 2007. The association of the spatial
surface regional patterns identified by AutoClass with the indices
developed from them also allows construction of spatially resolved
images of the Sun as it would be "seen" by TSI measuring instruments
like Virgo if they were able to capture resolved images. This approach
holds out the possibility of creating an on-going, accurate, independent
estimate of TSI variations from ground based observations which could
be used to compare, and identify the sources of disagreement among,
TSI observations from the various satellite instruments and to fill
in gaps in the satellite record. Further, the spatial resolution of
these "images" should assist in identifying with greater accuracy the
particular solar surface regions associated with TSI variations. Also,
since the particular set of MWO data on which this analysis is based is
available on a daily basis back to at least 1985, and on an intermittent
basis before then, it may be possible to construct an independent
estimate of TSI emission at several solar minima to ascertain if there
has been any significant increase or decrease, a topic of significance
to determining what part, if any, solar TSI variations play in global
warming. Cheeseman, P. & Stutz, J.,1996, in Advances in Knowledge
Discovery and Data Mining, U.M. Fayyad, G. Piatetsky-Shapiro, P. Smyth,
and R. Uthurusamny (Eds.). (AAAI Press), p.61
Title: Feature Classification of NSO/Kitt Peak Magnetograms
Authors: Malanushenko, O.; Jones, H. P.; Pap, J. M.; Turmon, M.
Bibcode: 2008AGUSMSP31B..04M
Altcode:
We present new segmentations of daily NASA/NSO Spectromagnetograph
(SPM) multidimensional magnetograms obtained at the NSO/Kitt Peak
Vacuum Telescope from 1992-2003. Full-disk images are divided into
areas of quiet Sun, network, active regions, and sunspots using a
three-dimensional adaptation of a statistical image classification
method developed by Turmon, Pap, and Mukhtar (ApJ 568:396-407,
2002). Probability distributions for each feature class are derived
from a training set of images independently segmented using thresholds
in magnetic flux and continuum intensity. We summarize our analysis
procedures and compare segmentations derived from class-conditional
probabilities computed with Gaussian mixture models and histogram
interpolation. We also compare our segmentations with features
identified by other methods and with solar irradiance variation.
Title: A Comparison of Feature Classification Methods for Modeling
Solar Irradiance Variation
Authors: Jones, H. P.; Chapman, G. A.; Harvey, K. L.; Pap, J. M.;
Preminger, D. G.; Turmon, M. J.; Walton, S. R.
Bibcode: 2008SoPh..248..323J
Altcode:
Physical understanding of total and spectral solar irradiance variation
depends upon establishing a connection between the temporal variability
of spatially resolved solar structures and spacecraft observations of
irradiance. One difficulty in comparing models derived from different
data sets is that the many ways for identifying solar features such as
faculae, sunspots, quiet Sun, and various types of "network" are not
necessarily consistent. To learn more about classification differences
and how they affect irradiance models, feature "masks" are compared as
derived from five current methods: multidimensional histogram analysis
of NASA/National Solar Observatory/Kitt Peak spectromagnetograph data,
statistical pattern recognition applied to SOHO/Michelson Doppler
Imager photograms and magnetograms, threshold masks allowing for
influence of spatial surroundings applied to NSO magnetograms, and
"one-trigger" and "three-trigger" algorithms applied to California
State University at Northridge Cartesian Full Disk Telescope intensity
observations. In general all of the methods point to the same areas of
the Sun for labeling sunspots and active-region faculae, and available
time series of area measurements from the methods correlate well with
each other and with solar irradiance. However, some methods include
larger label sets, and there are important differences in detail,
with measurements of sunspot area differing by as much as a factor
of two. The methods differ substantially regarding inclusion of fine
spatial scale in the feature definitions. The implications of these
differences for modeling solar irradiance variation are discussed.
Title: Application of Statistical Image Segmentation to Recognition
of Solar Magnetic Network
Authors: Jones, H. P.; Malanushenko, O. V.; Pap, J. M.; Turmon, M. J.
Bibcode: 2007AGUFMSH13A1096J
Altcode:
We have developed a statistical method for feature identification in NSO
multidimensional imagery which requires a training set of independently
determined image segmentations. The large spatial scale of our initial
training set determined by the algorithm of Harvey and White (1999, ApJ
515, p. 812) mixes the details of magnetic network which are contained
in the observations with quiet Sun and other features. We have found
it difficult to reproduce this large scale in models of conditional
and prior probabilities and are in fact interested in marking smaller
scale structures for comparison with variation of total and spectral
solar irradiance. We describe in this paper the performance of our
technique with finer scale training sets determined by observations
from other instruments and independently for the NSO data.
Title: EUV and UV Irradiance Variations and Evolution of Magnetic
Fields
Authors: Pap, J. M.; Floyd, L. E.; McMullin, D.
Bibcode: 2007AGUFMSH53A1051P
Altcode:
Continuous solar EUV measurements started by the SEM experiment on
SOHO in late 1995 providing high cadence data in a broad-band channel
(0.1 -- 50 nm) and in the vicinity of the ionospherically important
30.4 nm line. In addition to the SEM experiment, the "EUV Grating
Spectrometer (EGS)" instrument on the "Thermosphere, Ionosphere,
Mesosphere, Energetics and Dynamics (TIMED)" mission has been providing
measurements since December 2001 in the 0 -- 200 nm spectral range,
including the soft X-ray (XUV) from 0 to 30 nm, the extreme ultraviolet
(EUV) from 0 to 120 nm, and the far ultraviolet (FUV) from 120 to 200
nm. In this paper we show results on the observed EUV and UV irradiance
variations related to the changing solar magnetic fields, using the
physical parameters (area, intensity, and magnetic field strength)
of various solar magnetic structures derived from the analysis of the
"Michelson Doppler Imager (MDI)" on SOHO. We show the association
between XUV and EUV variations and magnetic structures on various time
scales:over the solar cycle, on rotational time scales, and on time
scales of minutes to hours.
Title: Statistical Feature Recognition for Multidimensional NSO
Imagery
Authors: Malanushenko, Elena; Jones, H. P.; Pap, J. M.; Turmon, M. J.
Bibcode: 2007AAS...210.2406M
Altcode: 2007BAAS...39..129M
Turmon, Pap, and Mukhtar (2002: Astrophysical Journal 568, 396)
present a statistical method for identifying sunspots, faculae, and
quiet Sun region classes in co-registered SOHO/MDI magnetograms and
intensity images. This paper describes progress toward an extension
of this method for finding a more complete region classification
using multidimensional images (magnetic flux, line-of-sight velocity,
intensity, equivalent width, and central line depth) obtained from
1992-2003 with the NASA/NSO Spectromagnetograph (SPM) and since 2003
with the NSO/SOLIS Vector Spectromagnetograph (VSM). We discuss the
selection of the feature set, training images, and the temporal and
spatial consistency of the NSO data. We determine class-conditional
probability densities using both Gaussian mixture models and direct
histogram interpolation, and compare feature labelings driven by
both methods.
Title: Bayesian Feature Recognition for Multidimensional NSO Imagery
Authors: Jones, H. P.; Pap, J. M.; Turmon, M. J.
Bibcode: 2006AGUFMSH23B0372J
Altcode:
Turmon, Pap, and Mukhtar (2002: Astrophysical Journal 568, 396) present
a statistical method for identifying sunspots, faculae, and quiet Sun
in SOHO/MDI magnetograms and intensity images. This paper describes
progress toward an extension of this method for identifying more
complete feature sets using the multidimensional images (magnetic flux,
line-of-sight velocity, intensity, equivalent width, and central line
depth) obtained from 1992-2003 with the NASA/NSO Spectromagnetograph
(SPM) and since 2003 with the NSO/SOLIS Vector Spectromagnetograph
(VSM). We discuss the selection of the feature set and training images,
and the temporal and spatial consistency of the NSO data. We determine
the class-conditional (Bayesian prior) probability densities using
both Gaussian mixture models and direct histogram interpolation,
and show projections of the multidimensional probability densities
derived from SPM observations. Finally, we compare various feature
identification methods driven by these two types of prior.
Title: Evolution of Sunspots and Their Effect on Solar Irradiance
Variations
Authors: Mezo, G.; Baranyi, T.; Pap, J. M.
Bibcode: 2006AGUFMSH43A1508M
Altcode:
The goal of this paper is to examine the evolution of sunspots and
their relation to solar irradiance variations based on the sunspot data
archive of the Heliophysical Observatory of the Hungarian Academy of
Sciences. Long-term full-disk white-light observations have been made
at the Debrecen Heliophysical Observatory and its Gyula observing
station. Using observations from other observatories when they are
not availabe in this archive is being used to complete a sunspot
catalogue as a continuation of the Greenwich Catalogue and to provide
a homogeneuous data base of the area and position of sunspots covering
a century long time interval. As part of the measurement process, the
photoheliograms are digitized and resolved into a 8K×8K matrix, which
allows to measure and catalogue the area and position of sunspots (both
umbra and penumbra) with high accuracy. These sunspot data are published
in the Debrecen Photoheliographic Data catalogue (DPD). Since 1996,
the SOHO/MDI intensity images have also been processed and analyzed in
the same way as the DPD images and these MDI sunspot area and position
data are published in the SOHO/MDI -- Debrecen Data (SDD) catalogue. In
addition to the MDI intensity images, the MDI magnetograms are used to
gather information about the average magnetic field strength values and
polarities of the investigated sunspot umbra and penumbra.Considering
the availability of the high time cadence MDI observations, we are
able to study the evolution of sunspots in detail. In this paper we
concentrate on the time frame of 1996 to 1997, when individual sunspot
groups can be well-separated and their effect on solar irradiance can
be studied in detail.
Title: Long-Term Solar Irradiance Variations Over Solar Cycles 21
to 23
Authors: Pap, J. M.
Bibcode: 2006AGUFMSH11A0376P
Altcode:
In this paper we present the work accomplished during the three
years long LWS TR&T grant (NAG5-13513). As part of the work we
addressed the following questions: (1) How does various total irradiance
composites relate to each other? (2) How well various solar indices can
be used as surrogates for solar irradiance variations? As part of the
research under question (1) we have constructed a new composite using
both the Nimbus-7 and ERBS/ERBE total irradiance measurements. While
the PMOD composite has shown a symmetrical long-term total irradiance
variations with the same maximum and minimum level over the last
three consecutive solar cycles, the ACRIM composite has shown a slow
0.05% secular trend from the minimum of cycle~21 to the minimum of
cycle~22. Our reconstruction indicates a much smaller trend (about
half of the one shown by the ACRIM composite). Our results also show
that the linear relation between solar variability, as represented
by total irradiance variations, and solar activity, as represented
by magnetic indices, breaks down during the maximum and minimum of
solar cycles 23. While most of the magnetic indices showed that cycle
23 was a weak cycle, both total and UV irradiances reached as high
maxima as during the previous strong cycles. Furthermore, we have
found that during the declining portion of cycle 23, total irradiance
already reached minimum activity levels, while surrogates used in the
empirical models were still in their declining phase. Considering the
lack of good surrogates and physical understanding of the underlying
mechanisms of irradiance variations, we will address briefly the
perspectives of future space-based irradiance experiments.
Title: Evaluation of Solar Indices Used in Semi-Empirical Proxy
Models of Solar Irradiance
Authors: Pap, J.; Floyd, L.
Bibcode: 2006cosp...36.3298P
Altcode: 2006cosp.meet.3298P
The most important environmental problems facing humanity today is to
understand and predict global change both natural and man-induced as
well as the rapid changes in our space environment The critical issue
is to understand the relative impacts of natural and anthropogenic
influences on changes in the Earth s atmosphere However the time
period of interest far exceeds the lifespan of any single experiment
Accordingly composite irradiance time series must be compiled from
data of several irradiance experiments Further on time scales longer
than the three-decade long irradiance measurements or in the absence of
direct space irradiance observations surrogates for irradiance have to
be used to mimic model the irradiance changes The question is however
how well these indices used for irradiance modeling are reliable for
predicting irradiance changes on various time scales In this paper
we compare total solar and UV EUV irradiances with various solar
indices such as the Ca K index He line equivalent width at 1083 nm
full disk magnetic flux facular and sunspot areas the GOES X-ray data
10 7 cm radio flux and the international sunspot number Our goal is to
establish to what degree these indices can represent solar irradiance
variability over the entire solar spectrum and at various wavelengths
Title: The extreme Halloween 2003 solar flares (and Bastille Day, 2000
Flare), ICMEs, and resultant extreme ionospheric effects: A review
Authors: Tsurutani, B. T.; Mannucci, A. J.; Iijima, B.; Guarnieri,
F. L.; Gonzalez, W. D.; Judge, D. L.; Gangopadhyay, P.; Pap, J.
Bibcode: 2006AdSpR..37.1583T
Altcode:
Extreme solar flares can cause extreme ionospheric effects. The Oct
28, 2003 flare caused a ∼25 TECU (a total electron content unit is
10 16 electron/m 2 column density), or a ∼30%,
increase in the local noon equatorial ionospheric column density. This
enhancement occurred within ∼5 min. This TEC increase was ∼5 times
the TEC increases detected for the Oct 29, 2003, Nov 4, 2003, and the
July 14, 2000 (Bastille Day) flares. In the 260-340 Å EUV wavelength
range, the Oct 28 flare peak count rate was more than twice as large as
for the other three flares. Another strong ionospheric effect is the
delayed influence (due to solar wind propagation) of interplanetary
coronal mass ejection (ICME) electric fields on the ionosphere. For
the Oct 28 and 29 flares, the associated ICMEs propagated from the
sun to the Earth at particularly high speeds. The prompt penetration
of the interplanetary electric field caused the dayside equatorial
ionospheric to be strongly convected upward. This led to enhanced TEC
to values >300% nominal values in ∼2 h. Proposed mechanisms for
this TEC enhancement will be discussed.
Title: Evaluation of Solar Indices Used in Semi-Empirical Proxy Models
Authors: Pap, J. M.; Floyd, L. E.
Bibcode: 2005AGUFMSH33C..01P
Altcode:
Space observations of total solar and UV irradiances have been conducted
for about three decades. These are important for both understanding the
physical mechanisms and causal relationships in the sun and also for
their terrestrial climatic impacts. However, to establish their true
role in climate change, irradiance time series covering a century,
or longer time scales, are needed. Accordingly, considerable efforts
have been put forward to constract semi-empirical proxy models for
climate studies which necessarily depend on long-term solar indices
to identify solar changes. In this paper, we compare various solar
indices used for irradiance reconstructions and we will devote special
attention how well they match the observed irradiance data over the
last three solar cycles.
Title: A Critical Review of Measurements and Models of Composite
Total Solar Irradiance
Authors: Pap, J. M.; McIntosh, P.
Bibcode: 2005AGUSMSH23B..01P
Altcode:
After nearly three decades of total solar irradiance monitoring there
is still uncertainty about long-term trends, even whether there is
a significant solar cycle dependence. The curret proxy data used in
irradiance modeling are summarized and their limitations considered. The
recent data obtained during solar cycle 23 provides an enlarged database
and additional short-term irradiance variations associated with active
region developments. New data about large-scale solar features reveal
solar cycle variations and dramatic changes during episodes of extreme
activity. These observations suggest potential mechanisms for irradiance
variation independent of, or in addition to, sunspots and faculae.
Title: Solar Variability and Earth's climate
Authors: Ermolli, Iliaria; Pap, Judit; Fox, Peter
Bibcode: 2005MmSAI..76..705E
Altcode:
No abstract at ADS
Title: Long-Term Total Irradiance Composites
Authors: Pap, J. M.
Bibcode: 2004AGUFMSH51E..07P
Altcode:
Accurate long-term total and spectrally resolved solar irradiance
measurements are required for full understanding of the response of
Earth's atmosphere and climate to irradiance changes. Space-based
irradiance observations over the last two and a half solar cycles
span a time interval too short to reveal secular changes and/or to
establish conclusively whether there are significant changes in the
amplitude or the character of irradiance variations on longer time
scales. Since the time period of interest far exceeds the lifespan
of any single experiment, composite irradiance time series must be
compiled from data of several irradiance experiments. Because the
absolute accuracy of the current measurements is limited (about ±0.2%
in case of total irradiance), overlapping and redundant measurements
are needed to ensure that the resulting composite data sets represent
the ``true'' solar behavior. However, the largest obstacle in creating
the current long-term total irradiance composite is the two-year gap
between the SMM/ACRIM~I and UARS/ACRIM~II measurements. Adjustment of
the ACRIM~I and ACRIM~II data now must be made through the Nimbus-7/ERB
and/or the ERBE measurements. While using the published Nimbus-7/ERB
data set, Willson and Mordvinov (2003) concluded that the minimum of
cycle 22 was higher than the minimum of cycle 21, Fröhlich (2004)
claims that no trend can be seen in total irradiance within the
current measurement accuracy. In this paper we compare various total
irradiance time series, to better understand the differences between
the two total irradiance composites. We will apply a new approach
to adjust the ACRIM~I and ACRIM~II time series to further study the
possible secular trend in total irradiance. Fröhlich, C. 2004, In the
Solar Variability and Its Effect on Earth's Climate, Eds. J. Pap and
P. Fox, AGU Monograph, No. 141, p. 97. Willson, R.C. and Mordvinov,
A.V.: 2003, Geophys. Res. Lett. Vol. 30, 3-1.
Title: Solar Variability and Climate Change
Authors: Pap, J. M.
Bibcode: 2004AGUFM.U11A..01P
Altcode:
One of the most exciting and important challenges in science today is
to understand climate variability and to make reliable predictions. The
Earth's climate is a complex system driven by external and internal
forces. Climate can vary over a large range of time scales as a
consequence of natural variability or anthropogenic influence, or
both. Observations of steadily increasing concentrations of greenhouse
gases --primarily man-made-- in the Earth's atmosphere have led to
an expectation of global warming during the coming decades. However,
the greenhouse effect competes with other climate forcing mechanisms,
such as solar variability, cosmic ray flux changes, desertification,
deforestation, and changes in natural and man-made atmospheric
aerosols. Indeed, the climate is always changing, and has forever
been so, including periods before the industrial era began. Since
the dominant driving force of the climate system is the Sun, the
accurate knowledge of the solar radiation received by Earth at various
wavelengths and from energetic particles with varying intensities,
as well as a better knowledge of the solar-terrestrial interactions
and their temporal and spatial variability are crucial to quantify
the solar influence on climate and to distinguish between natural and
anthropogenic influences. In this paper we give an overview on the
recent results of solar irradiance measurements over the last three
decades and the possible effects of solar variability on climate.
Title: The Extreme Solar Flares of October 28th and November 4th,
2003 and Resultant Extreme Ionospheric Effects
Authors: Tsurutani, B. T.; Judge, D. L.; Jones, A. R.; Guarnieri,
F. L.; Zambon, G. A.; Gangopadhyay, P.; Harmon, M.; Nuttall, J.;
Shemansky, D. E.; Mannucci, A.; Iijima, B.; Hajj, G.; Woods, T. N.;
Floyd, L.; Meier, R. R.; Huba, J.; Solomon, S. C.; Mende, S.; Immel,
T. J.; Kozyra, J. U.; Pap, J.
Bibcode: 2004AGUSMSH43B..03T
Altcode:
Some of the most intense solar flares in recorded history occurred at
the end of 2003. The November 4th event is the largest on record (X28)
and the October 28th flare was the fourth most intense (X17). These will
be compared/contrasted to the July 14, 2000 Bastille Day (X6) event. We
use SOHO EUV (SEM), GOES and TIMED x-ray data to characterize the flare
spectral energy versus time. High time resolution, ~1s ground base
GPS data are used to examine the abrupt increase in path-integrated
ionospheric total electron content (TEC). It will be shown that the
dayside ionosphere responds dramatically to the x-ray, FUV and EUV
input by an abrupt ~20-25 percent increase in ionospheric electron
densities. Polar and IMAGE UV spectra are used to quantify the dayglow
enhancements. The TEC increases are nonlinearly related to the peak
flare intensities. The reasons for this are not understood at this
time. Ionospheric models using the flare input data will be used to
compared against tomographic analyses of the GPS information.
Title: Science Requirements and Required Future Measurements
Authors: Sprigg, William; Pap, Judit M.
Bibcode: 2004GMS...141..357S
Altcode:
The role of solar variability in climate variability and change has
been debated for a long time. Now, new results from various space
experiments for a long time. Now, new results from various space
experiments monitoring the radiative and particle emissions from the
Sun together with detailed studies of their terrestial impacts have
opened an exciting new era in both solar and atmospheric physics. Being
so close, the Sun is the only star where we have a chance to identify
and study in detail the processes responsible for changes in irradiance
on time scales from minutes to decades—the longest time scale over
which high precision data are available. High-resolution spatial and
temporal observations conducted in various space and ground-based
experiments demonstrate that the surface of the Sun and its outer
atmosphere are highly variable on almost all spatial scales, and that
many of the observed changes are linked to interior processes taking
place in the Sun's convective zone or below. The broad collection
of the material in this Monograph clearly shows that the variable
solar energy output affects the Earth's atmosphere and climate in
many fundamental ways. However, a quantitative understanding of all
the involved processes and their relationship to the climate system
and its response remains elusive. Based on the current database and
knowledge, it remains to be seen what role solar forcing will play in
future climate.
Title: Status of UARS solar UV irradiance data
Authors: DeLand, M. T.; Floyd, L. E.; Rottman, G. J.; Pap, J. M.
Bibcode: 2004AdSpR..34..243D
Altcode:
Accurate measurement of solar ultraviolet (UV) irradiance variations
is important for understanding both solar processes and energetic
input to the Earth's atmosphere. Satellite instruments are capable
of providing such data, but must correct for significant spectral
and temporal response changes during the observing lifetime of the
instrument. The Upper Atmospheric Research Satellite (UARS) carries
two instruments dedicated to monitoring long-term solar UV irradiance:
the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) and the Solar
Stellar Intercomparison Experiment (SOLSTICE). Both instruments include
comprehensive on-board calibration systems designed to characterize
and remove response changes from the irradiance data. This paper
presents the status of the SUSIM and SOLSTICE data sets. We find that
both instruments produce meaningful direct estimates of solar cycle
UV irradiance variations in the wavelength range 120-250 nm. Between
250 and 300 nm, the reduced magnitude of solar variability becomes
comparable to the long-term calibration uncertainty. Longward of 300
nm, solar cycle irradiance variations cannot be detected. The SUSIM
and SOLSTICE irradiance data sets represent the first fully calibrated
solar UV irradiance data sets to cover a complete solar cycle.
Title: Study of differences between sunspot area data determined
from ground-based and space-borne observations
Authors: Győri, L.; Baranyi, T.; Turmon, M.; Pap, J. M.
Bibcode: 2004AdSpR..34..269G
Altcode:
The determination of the area of sunspots is important from several
points of view, e.g, in study of the evolution of sunspots and their
effect on solar irradiance. Automated sunspot area measurements are now
replacing time-consuming and subjective hand-made measurements. Also,
terrestrial solar observations have been supplemented by observations
from space. The resolution of the ground observations is limited by the
seeing, while space-borne observations are limited by the size of the
CCD array. The use of different data sources, as well as of different
region identification algorithms, causes discrepancies in reported
sunspot areas. An important task is to determine to what extent these
differences can be attributed to different analysis methods and to
what extent to different data. It is also important to establish the
required spatial resolution of space-based images.
Title: Welcome - Introduction
Authors: Pap, J. M.
Bibcode: 2004cosp...35.4663P
Altcode: 2004cosp.meet.4663P
The purpose of this welcome talk is to shortly inform attendees about
the logistic of the meeting, the major accomplishements which have
been achieved on the field since the 2002 COSPAR meeting and to call
attention to an international research program " Climate And Weather of
the Sun-Earth System" (CAWSES) implemented in 2004 by SCOSTEP. A brief
description of CAWSES, especially its Theme 4 "Space Climatology",
Working Group 1 "Solar Variability" and its relation to the former
SCOSTEP/International Solar Cycle Study (ISCS) will be given. Detailed
description of CAWSES will be given by J. Haigh in her concluding talk.
Title: Solar Variability and its Effects on Climate. Geophysical
Monograph 141
Authors: Pap, Judit M.; Fox, Peter; Frohlich, Claus; Hudson, Hugh S.;
Kuhn, Jeffrey; McCormack, John; North, Gerald; Sprigg, William; Wu,
S. T.
Bibcode: 2004GMS...141.....P
Altcode:
This monograph presents a state-of-the-art description of the most
recent results on solar variability and its possible influence on the
Earth's climate and atmosphere. Our primary goal in doing so is to
review solar energy flux variations (both electromagnetic and particle)
and understand their relations to solar magnetic field changes and
global effects, their impact on different atmospheric layers, and—as
a collaboration of scientists working on solar-terrestrial physics—to
note unresolved questions on an important interdisciplinary area. One of the highest-level questions facing science today is whether
the Earth's atmosphere and climate system changes in a way that we
can understand and predict. The Earth's climate is the result of
a complex and incompletely understood system of external inputs and
interacting parts. Climate change can occur on various time scales as a
consequence of natural variability—including solar variability—or
anthropogenic causes, or both. The Sun's variability in the form
of sunspots and related magnetic activity has been the subject of
careful study ever since the earliest telescopic observations. High
precision photometric observations of solar-type stars clearly show that
year-to-year brightness variations connected with magnetic activity
are a widespread phenomenon among such stars. As our nearest star,
the Sun is the only star where we can observe and identify a variety of
structures and processes which lead to variations in the solar energy
output, in both radiative and particle fluxes. Studying event tiny
changes in solar energy flux variations may teach us about internal
processes taking place in the Sun's convective zone and below.
Title: Solar variability and climate changes
Authors: Labitzke, K.; Pap, J.; Kuhn, J. R.; Shea, M. A.
Bibcode: 2004AdSpR..34..227L
Altcode:
No abstract at ADS
Title: Study of Solar Magnetic Feature Properties and Irradiance
Variations
Authors: Pap, J.; Ermolli, I.; Giorgi, F.; Turmon, M.
Bibcode: 2004cosp...35.4442P
Altcode: 2004cosp.meet.4442P
Since the beginning of THE 1980s it is well established that the
emergence of magnetic features on the solar atmosphere is strictly
associated with irradiance variations. Attempts to model the measured
variations, by the use of photometric proxies as well as through
semi-empirical atmospheric models, include the precise evaluation of
some magnetic feature properties, specifically coverage and contrast,
that depend on the feature identification. With the aim of improving the
irradiance modeling, we compared the results obtained by applying two
different feature identification techniques on the two sets of full-disk
images obtained from the SOHO/MDI and the Rome/PSPT. Reconstruction
of solar irradiance variations obtained from the two sets of images
will be shown as well.
Title: Preface
Authors: Pap, Judit M.; Fox, Peter; Fröhlich, Claus; Hudson, Hugh S.;
Kuhn, Jeffrey; McCormack, John; North, Gerald; Sprigg, William; Wu,
S. T.
Bibcode: 2004GMS...141D...7P
Altcode:
This monograph presents a state-of-the-art description of the most
recent results on solar variability and its possible influence on the
Earth's climate and atmosphere. Our primary goal in doing so is to
review solar energy flux variations (both electromagnetic and particle)
and understand their relations to solar magnetic field changes and
global effects, their impact on different atmospheric layers, and—as
a collaboration of scientists working on solar-terrestrial physics—to
note unresolved questions on an important interdisciplinary area. One of the highest-level questions facing science today is whether
the Earth's atmosphere and climate system changes in a way that we
can understand and predict. The Earth's climate is the result of
a complex and incompletely understood system of external inputs and
interacting parts. Climate change can occur on various time scales as a
consequence of natural variability—including solar variability—or
anthropogenic causes, or both. The Sun's variability in the form
of sunspots and related magnetic activity has been the subject of
careful study ever since the earliest telescopic observations. High
precision photometric observations of solar-type stars clearly show that
year-to-year brightness variations connected with magnetic activity
are a widespread phenomenon among such stars. As our nearest star,
the Sun is the only star where we can observe and identify a variety of
structures and processes which lead to variations in the solar energy
output, in both radiative and particle fluxes. Studying even tiny
changes in solar energy flux variations may teach us about internal
processes taking place in the Sun's convective zone and below.
Title: A Prediction Model Of Solar Euv Irradiance On The Basis Of
Solar Magnetic Flux Evolution
Authors: Wu, S. T.; Wang, A. H.; Fry, C. D.; Tobiska, W. K.; Pap, J.
Bibcode: 2004cosp...35..778W
Altcode: 2004cosp.meet..778W
Harvey (1991, 1994) determined the correlation between total solar
surface magnetic flux and solar irradiance (i.e. F10.7,
1-8 Å and Lyman α). This implies that if one could predict the solar
magnetic flux as it changes over time, then Harvey's correlation could
be used to also predict solar EUV irradiance. Wu et al. (1993) have
developed a magnetohydrodynamic (MHD) photospheric dynamo model which
computes the evolution of the photosphere magnetic flux over time in
a specified region. In this paper, we will use this physics-based MHD
photospheric dynamo model to compute total magnetic flux (TMF) over
specific regions, which will be summed over the solar disk and input
directly into an empirical relationship based on Harvey's correlation to
compute the total EUV irradiance (TEI). To carry out the TMF calculation
using this three-dimensional, time-dependent MHD photospheric dynamo
model, the measured photospheric magnetic fields will be used as inputs
to lower boundary conditions. The differential rotation and meridional
flow serve as the driving force to the photospheric evolution. The
numerical results are: (i) the evolution of magnetic field map over
a time which will be compared with observation; (ii) TMF obtained by
integrating over the region and (iii) to input the computed TMF to the
empirical relationship to obtain solar EUV irradiance as a function
of time. This work promises to lead to improvements in predictions of
solar irradiance hours to days in advance.
Title: Long-Term Total Irradiance Composites and Models
Authors: Helizon, R.; Pap, J. M.
Bibcode: 2003AGUFMSH32A1100H
Altcode:
Accurate long-term total and spectrally resolved solar irradiance
measurements are required for full understanding of the response of
Earth's atmosphere and climate to irradiance changes. Space-based
irradiance observations over the last two and a half solar cycles
span a time interval too short to reveal secular changes and/or to
establish conclusively whether there are significant changes in the
amplitude or the character of irradiance variations on longer time
scales. Since the time period of interest far exceeds the lifespan
of any single experiment, continuous measurement programs must be
formulated to compile composite irradiance time series from data of
several experiments. Because the absolute accuracy of the current
measurements is limited (+/-0.2%) in case of total irradiance,
overlapping and redundant measurements are needed to ensure that
the resulting composite data sets represent the ``true'' solar
behavior. However, the largest obstacle in creating the current
long-term total irradiance composite is the two-year gap between the
SMM/ACRIM~I and UARS/ACRIM~II measurements. Adjustment of the ACRIM~I
and ACRIM~II data now must be made through the Nimbus-7/ERB and/or the
ERBE measurements. While using the published Nimbus-7/ERB data set,
Willson (1997) concluded that the minimum of cycle 22 was higher than
the minimum of cycle 21, while Fröhlich and Lean (1998) claim that no
trend can be seen in total irradiance within the current measurement
accuracy. In this paper we compare various total irradiance time
series and composites. Specifically, we will compare the Nimbus-7,
ERBS, ACRIM~II and EURECA total irradiance data for the 1991-1993
time frame and the ACRIM~II, and VIRGO data for the time frame of
1996-2000 to clarify whether the minimma of cycles 21 and 22 are the
same or they are indeed diffferent. Fröhlich, C. and Lean, J.: 1998,
In Proceedings of the IAU Symposium 185, (ed. F.L. Deubner), Kluwer
Academic Publishers, p. 89. Willson, R.C.: 1997, Science 277, 1963.
Title: Magnetic Field and Long-Term Solar Irradiance Variations Over
Solar Cycles 21 to 23
Authors: Pap, J. M.; Turmon, M.; Shelton, K. E.; Floyd, L. E.;
Helizon, R.
Bibcode: 2003AGUFMSH32A1099P
Altcode:
Total solar and UV irradiance has been measured from various space
platforms over the last two and half solar cycles. Results based on
these multi-decade measurements have demonstrated that both total and
UV irradiances change on time scales of days to decades, confirming
that our Sun is indeed a variable star. High spatial and temporal
resolution photometric and magnetic field observations conducted by the
SOHO/MDI experiment and also from the ground have demonstrated that
the surface of the Sun and its outer atmosphere are highly variable
on almost all spatial scales. To understand the physical causes
of irradiance variations, it is necessary to study the spatial and
temporal characteristics and evolution of the solar magnetic fields and
to establish to what extent solar magnetic features may contribute to
irradiance variations. In this paper we analyze the total solar and UV
irradiance composites compiled from various space measurements starting
in late 1978. To establish the effect of surface magnetic activity
on irradiance variations as a function of the solar cycle, we show
the association of the absolute value of the full disk magnetic field
strength data measured and compiled at the National Solar Observatory
at Kitt Peak for the time interval of 1978 to date. Using various
pattern recognition techniques, we compare the observed irradiance
variations with solar features (sunspots and faculae), derived from
the MDI and Kitt Peak magnetograms from 1996 and 1992, respectively.
Title: 11 years of solar UV irradiance measurements from UARS
Authors: Floyd, Linton; Rottman, Gary; Deland, Matthew; Pap, Judit
Bibcode: 2003ESASP.535..195F
Altcode: 2003iscs.symp..195F
Since its launch in 1991, the Upper Atmosphere Research Satellite (UARS)
has as its goal the study of Earth's stratosphere and mesosphere. Solar
UV radiation deposits significant energy in these layers through
the creation and destruction of ozone. Two UARS experiments, the
Solar-Stellar Intercomparison Experiment (SOLSTICE) and the Solar
Ultraviolet Spectral Irradiance Monitor (SUSIM), have measured the
solar spectral UV irradiance (119-400 nm) for more than 11 years, the
length of a solar activity cycle. These measurements, began during the
latter stages of the solar cycle 22 activity maximum continued both
through the following minimum and solar cycle 23 maximum. Trends in
instrumental responsivity cause some small long-term differences in
the UV irradiance measurements between the two experiments. However,
the least affected of these, the Mg II core-to-wing ratio index, a solar
activity proxy resistant to instrumental changes, shows that peak levels
of the two cycles to be about the same. Other accomplishments include
the construction of 22+ year Ly-α and Mg II index composite time
series, observations of flare enhanced transition regions radiation,
and two new solar reference spectra.
Title: Total Solar and Spectral Irradiance Variations from Near-UV
to Infrared
Authors: Pap, J. M.
Bibcode: 2003LNP...599..129P
Altcode: 2003sssi.conf..129P
Total solar and UV irradiances have been measured from various space
platforms for more than two decades. These measurements established
conclusively that solar irradiance changes on a wide range of time
scales: from minutes to the 11 years solar cycle. The first results
on the spectral distribution of total irradiance variations have
been provided by the SunPhotometers on the SOHO/VIRGO experiment
at 402, 500, and 862 nm, showing that spectral irradiance at these
particular wavelengths changes in a fashion similar to total irradiance
with amplitudes being higher at the shorter wavelengths. Although
considerable information exist on irradiance variations, their physical
origin is not yet fully understood. Current empirical models assume
that most of the irradiance variations can be explained by the effect
of surface magnetic activity features, and it is assumed that there
is a linear relation between solar indices and irradiance changes. In
contrast, current results show that both UV and total irradiances were
higher at the maximum of solar cycle 23 than magnetic indices, such
as the sunspot number and the full disk magnetic field strength. In
addition, there is a growing evidence that global effects, like
temperature changes, may also contribute to irradiance variations. In
this paper we give an overview of the current results on total and
spectral irradiance variations, their relation to magnetic activity
using measurements from the National Solar Observatory an Kitt Peak
and SOHO-MDI. Climate implications of irradiance variations are also
discussed.
Title: Solar variability and its effects on climate
Authors: Pap, Judit M.; Fox, Peter A.
Bibcode: 2003GMS...141.....P
Altcode:
No abstract at ADS
Title: Comparison of Recent Total Irradiance Measurements
Authors: Helizon, R.; Pap, J.
Bibcode: 2002AGUFMSH52A0497H
Altcode:
Total solar irradiance has been measured since 1978 from various
satellites. Since the absolute accuracy of the current irradiance
measurements is about 0.2%, one needs to compile composite irradiance
time series to study long-term changes and to establish whether there
are any secular variations over the last two and half decades. In this
paper we compare the UARS/ACRIM II and SOHO/VIRGO total irradiance data
as well as the SOHO/VIRGO and ACRIM III total irradiance. Our main goal
is to validate the newly processed ACRIM II total irradiance. Comparison
of the SOHO/VIRGO and ACRIM III data will also help to establish
whether the high total irradiance values for the maximum of solar
cycle 23 represent real solar, rather than, instrumental events.
Title: Long-Term Solar Irradiance Variations From Solar Cycle 21 to 23
Authors: Pap, J. M.; Arge, C.; Jones, H.; Floyd, L.
Bibcode: 2002AGUFMSH21B..03P
Altcode:
In this paper we show the recent results on total solar and UV
irradiance variations and their relation to solar magnetic activity
over solar cycles 21 to 23. Comparison of the multi-decade long
irradiance and magnetic field measurements indicates that the shape and
magnitude of irradiance variations are different from that of magnetic
indices. Specifically, while magnetic indices show that solar cycle
23 is weaker than the two previous cycles, the long-term variation of
total solar irradiance over solar cycles 21 to 23 is rather symmetrical,
showing that its maximum and minimum levels were about the same within
their measuring uncertainties. In this paper we address the questions:
(1) is there a strict linear relationship between solar variability and
irradiance variations; (2) what is the role of polar magnetic fields in
irradiance changes; (3) is there a significant non-magnetic component
in the observed irradiance variations? The results presented in this
paper underscore the need to further develop new analysis techniques
to determine whether there is a secular variation in solar irradiance
over years to decades - a necessary step to study and predict the
climate impact of solar variability.
Title: Comparison of image-processing methods to extract solar
features
Authors: Györi, L.; Baranyi, T.; Turmon, M.; Pap, J. M.
Bibcode: 2002ESASP.508..203G
Altcode: 2002soho...11..203G
Large numbers of high precision solar images are now available from
both terrestrial and space observatories, which has made it necessary to
develop automated iamge processing techniques. In this paper we compare
analysis of two sets of full-disk solar images: ground-based white light
photographic films from Gyula and allied observatories, and magnetograms
and quasi-continuum images from the Michelson Doppler Imager (MDI) on
SOHO. We use two different automated image analysis techniques. The
Sunspot Automatic Measurement (SAM) program has been developed at
the Heliophysical Observatory at Debrecen for compiling the Debrecen
Photoheliographic Data which are used to measure and catalogue the area
and position of sunspots (umbra and penumbra). This project is part of
the continuation of the Greenwich Catalogue. Startool is a general image
analysis tool developed at the Jet Propulsion Laboratory, and applied
to the MDI imagery as part of the SOHO Guest Investigator Program. As
used with MDI, Startool identifies sunspots, faculae/network, and quiet
sun using statistical pattern recognition techniques. Here we compare
the area of sunspots as derived by Startool from the MDI images and
by the SAM program as derived from the Debrecen and MDI images for
the pilot interval of the second half of the year 1996.
Title: Solar Irradiance Variations over Solar Cycles 21 to 23
Authors: Pap, J. M.; Kuhn, J.; Jones, H.; Turmon, M.; Arge, N.;
Schmutz, W.; Floyd, L.
Bibcode: 2002AAS...200.2803P
Altcode: 2002BAAS...34..679P
In this paper we describe the science requirements and a new measurement
strategy to better understand solar variability and its potential effect
on climate. We study the relation between the variations in solar total
and UV irradiances and solar magnetic fields as observed within the last
three decades. The results of our analysis raise important questions:
(1) is there a significant non-magnetic component in the observed
irradiance variations?; (2) may polar magnetic fields play a role
in irradiance changes?; (3) is there a strict linear relationship
between solar variability and irradiance variations as the current
irradiance models used in climate studies assume? The results presented
in this paper underscore the need to further develop new measurement
and analysis techniques to study and predict the climate impact of
solar variability.
Title: Statistical Pattern Recognition for Labeling Solar Active
Regions: Application to SOHO/MDI Imagery
Authors: Turmon, M.; Pap, J. M.; Mukhtar, S.
Bibcode: 2002ApJ...568..396T
Altcode:
This paper presents a new application of statistical methods
for identifying the various surface structures on the Sun that
may contribute to observed changes in total and spectral solar
irradiance. These structures are divided for our purposes into three
types: quiet Sun, faculae, and sunspots (umbra and penumbra). Each
region type is characterized by the observed data present at pixels
of that type. Statistical models characterizing these observables
are found from expert identification of a sample set of regions or
unsupervised clustering. Information about the spatial continuity
of regions is incorporated into the model via a prior distribution
on the label image; the contribution of the prior can be interpreted
as a regularizing term. Once the parameters defining the models are
fixed, the inference procedure becomes to maximize the probability
of an image labeling given the observed data. This allows objective
and automated classification of a large set of images. We describe the
application of these procedures to computing labelings from synchronized
full-disk high-resolution magnetic-field and light-intensity maps from
the Michelson Doppler Imager experiment on the Solar and Heliospheric
Observatory.
Title: Total solar and spectral irradiance variations from solar
cycles 21 to 23
Authors: Pap, J. M.; Turmon, M.; Floyd, L.; Fröhlich, C.; Wehrli, Ch.
Bibcode: 2002AdSpR..29.1923P
Altcode:
Total solar and UV irradiances have been measured from various space
platforms for more than two decades. More recently, observations of the
"Variability of solar IRradiance and Gravity Oscillations" (VIRGO)
experiment on SOHO provided information about spectral irradiance
variations in the near-UV at 402 nm, visible at 500 nm, and near-IR at
862 nm. Analyses based on these space-borne irradiance measurements have
convinced the skeptics that solar irradiance at various wavelengths
and in the entire spectrum is changing with the waxing and waning
solar activity. The main goal of this paper is to review the short- and
long-term variations in total solar and spectral irradiances and their
relation to the evolution of magnetic fields from solar cycles 21 to 23.
Title: A discussion of recent evidence for solar irradiance
variability and climate
Authors: Pap, Judit; Fröhlich, Claus; Kuhn, Jeff; Sofia, Sabatino;
Ulrich, Roger
Bibcode: 2002AdSpR..29.1417P
Altcode:
One of the over-arching questions, among others, to be addressed by
studying Sun-Earth connections is: "Is the climate changing in a way
we can understand and predict?" The Earth's climate is the result of
a complex and incompletely understood system of external inputs and
interacting parts. Climate change can occur over a range of time scales,
may be driven by natural variability, including solar variability,
and/or anthropogenic causes and may be identified through the study of
a variety of measurable parameters. Global climate change in response
to human influences is one of the pressing threats facing science
today. However, many of the external factors that govern our climate,
including solar variability, cannot be adequately determined from
existing operational observations. Since the Sun is the fundamental
source of energy that sustains life on Earth, establishing its radiation
environment, controls its temperature and atmospheric composition,
the accurate knowledge of the solar radiation received by the Earth
and understanding of its variability are critical for environmental
science and climate studies. In this paper we point out the necessity
of a new strategy, i.e., to study global solar properties, such as
solar irradiance, solar shape, shape oscillations, and radius, to
better understand the origin of solar-induced climate changes.
Title: Study of differences between sunspot area data determined
from ground- based and space-borne observations
Authors: Gyori, L.; Baranyi, T.; Turmon, M.; Pap, J.
Bibcode: 2002cosp...34E1849G
Altcode: 2002cosp.meetE1849G
The determination of the area of sunspots is of high importance
from several points of view, i.e. evolution of sunspots , their
effect on solar irradiance. Nowadays, the new automated sunspot
area measurements start to replace the time consuming, hand-made
measurements. In addition, the ground-based solar observations are
supplemented by observations from space. However, the resolution
of the ground based observations is limited by the seeing, while in
the case of the space-born observations by the size of the used CCD
array. There are differences between the sunspot areas derived by
different methods from different observations and even in the case of
the same observations too. An important task is to determine to what
extent these differences can be attributed to the different analysis
methods and to what extent to the different observations. It is also
important to establish the required spatial resolution of space-based
images. In this paper we address these questions.
Title: ISCS Working Group1 Activities
Authors: Pap, J.; Frohlich, C.
Bibcode: 2002cosp...34E.493P
Altcode: 2002cosp.meetE.493P
International Solar Cycle Study,Working Group 1, "Solar Energy Flux
Variations: From the Interior to the Outer Atmosphere" is concerned
about measuring and analyzing solar irradiance variations and their
underlying physical mechanisms. In this paper we report the latest
results on WG 1 activities, i.e., the variations of solar total
irradiance and spectral irradiance from EUV to infrared. The most
interesting result is that while solar cycle 23 was relatively weak
compared to the previous two cycles as far as sunspots are concerned,
both total and UV irradiances reached about the same maximum level
than during cycle 22. The implications of this observation will
be discussed. A summary of future irradiance measurements, plans,
perspectives and organization efforts will also be presented.
Title: A comparison of feature classification methods for modeling
solar irradiancevariation
Authors: Jones, H.; Harvey, K.; Pap, J.; Preminger, D.; Turmon, M.;
Walton, S.
Bibcode: 2002cosp...34E.641J
Altcode: 2002cosp.meetE.641J
A physical understanding of both total (bolometric) and spectral solar
irradiance variations depends upon establishing a connection between
the temporal variability of spatially resolved solar structures and
spacecraft observations of irradiance. One difficulty in comparing
models derived from different data sets is that the many ways for
identifying solar features such as faculae, sunspots, quiet sun, and
various flavors of "network" are not necessarily consistent. To learn
more about classification differences and how they affect irradiance
models, we compare feature "masks" on selected days together with
the temporal variation of feature areas derived from four current
methods: multidimensional histogram analysis of NASA/NSO Kitt Peak
spectromagnetograph data (Jones et al., 2000, ApJ 529, 1070);
statistical pattern recognition applied to SOHO/MDI photograms
and magnetograms (Turmon et al., 2002, ApJ 568, 396); threshhold
masks allowing for influence of spatial surroundings applied to
NSO magnetograms (Harvey and White, 1999, ApJ 515, 541); and the
"three-trigger" algorithm applied to CSUN CFDT images (Preminger et al.,
2001, Sol. Phys. 202, 53.). Developing a more uniform classification
system of features contributing to irradiance variations will help
to improve irradiance models used for climate studies. A practical
benefit of understanding the relationships between various methods is
the possibility of constructing a more continuous and extensive time
series from several incomplete sources.
Title: EUV irradiance measurements from SOHO during Cycle 23
Authors: Brekke, P.; Thompson, W.; Pap, J.; McMullin, D.
Bibcode: 2002cosp...34E..97B
Altcode: 2002cosp.meetE..97B
EUV irradiance variability of the double peak feature of cycle 23 is
presented. EUV irradiance measurements are being made from SOHO on a
regular basis by the Solar Extreme-Ultra-Violet Monitor (SEM) and the
Coronal Diagnostic Spectrometer (CDS). SEM continuously measures the
full solar disk absolute photon flux at the prominent and scientifically
important He II 304 A line, as well as the absolute integral flux
between 1 and 500 A. CDS produces full disk spectra in two bands in
the range 307-380 A and 515-632 A. The "Sun as a Star" spectrum has
been made roughly once a month starting 25 March 1997 to present. As
well as irradiance values, the most recent observations also provide
moderate resolution solar images to help quantify the important sources
of irradiance variability. The EUV irradiance variability is compared
to measurements of total irradiance from VIRGO and other solar cycle
indices such as sunspot number, magnetic field measurements, and the
10.7 radio flux.
Title: Solar UV irradiance variations from the UARS SUSIM and
SOLSTICE instruments
Authors: Deland, M.; Pap, J.; Floyd, L.; Rottman, G.
Bibcode: 2002cosp...34E1089D
Altcode: 2002cosp.meetE1089D
Accurate knowledge of long-term changes in solar ultraviolet (UV)
irradiance is crucial for assessing the impact of solar variability
on climate change. The UARS SUSIM and SOLSTICE instruments provide the
first long-term solar UV irradiance data sets with complete in-flight
calibration of instrument behavior. The current data sets from both
instruments cover the full range of solar activity levels, from the
end of the maximum of solar cycle 22 through solar minimum and the rise
of solar cycle 23. In this paper, selected 5 nm bands are averaged to
characterize broader spectral regions in the middle and near UV. We
use the Singular Spectrum Analysis (SSA) technique to separate the
irradiance time series into multiple components, representing short
-term and long-term variations. Similar analysis is performed on both
versions of the Mg II core -t o-wing ratio index, a common proxy for
solar UV activity, derived from the corresponding irradiance data from
each instrument. We find that the first two reconstructed components
of each time series typically capture the long-term behavior (both
solar-cycle-related changes and instrumental degradation effects),
while intermediate-term and short-term variations are represented by
progressively higher components. Comparisons of the relative importance
of different components between the irradiance data and proxy data
will be shown.
Title: Long-term solar irradiance variations: results and perspectives
Authors: Pap, J.; Fleck, B.; Frohlich, C.; Jones, H.; Kuhn, J.;
Schmutz, W.
Bibcode: 2002cosp...34E.553P
Altcode: 2002cosp.meetE.553P
In this paper we show the recent result on irradiance variations and
their relation to solar magnetic activity over solar cycles 21 to
23. Comparison of the multi-decade long irradiance and magnetic field
measurements indicates that the shape and magnitude of irradiance
variations are different from that of magnetic indices. Specifically,
while magnetic indices show that solar cycle 23 is weaker than the two
previous cycles, the long-term variation of total solar irradiance
over solar cycles 21 to 23 is rather symmetrical, showing that its
maximum and minimum levels were about the same within their measuring
uncertainties. These results raise questions like: (1) is there a
strict linear relationship between solar variability and irradiance
variations as the current irradiance models used in climate studies
assume?; (2) what is the role of polar magnetic fields in irradiance
changes?; (3) is there a significant non-magnetic component in the
observed irradiance variations? The results presented in this paper
underscore the need to further develop new measurement and analysis
techniques to study and predict the climate impact of solar variability.
Title: Preface
Authors: Fröhlich, Claus; Pap, Judit M.
Bibcode: 2002AdSpR..29.1879F
Altcode:
No abstract at ADS
Title: Solar irradiance variations over solar cycles 21 to 23
Authors: Pap, J.; Arge, N.; Floyd, L.; Helizon, R.; Jones, H.
Bibcode: 2002cosp...34E1521P
Altcode: 2002cosp.meetE1521P
The Sun's radiative output has been monitored at various UV wavelengths
and integrated over the entire solar spectrum - hence total irradiance -
for almost three consecutive solar cycles. These multi-decade long
measurements of total solar and spectral irradiance established
conclusively that the Sun's radiative output varies on time scales
from minutes to the 11-year solar cycle. To study long-term irradiance
variations and their possible effects on climate, solar irradiance
has been modeled empirically using the Photometric Sunspot Index and
proxy indicators for facular brightening. These empirical models assume
that solar irradiance varies in phase with the 11-year solar cycle,
being higher during high solar activity cycles and lower during weaker
cycles. However, direct photometric measurements of sunspots and faculae
have shown that both the number and size of active regions were smaller
during cycle 23 than during cycle 22. In addition, both the sunspot
number and the full disk magnetic flux show that cycle 23 was weaker
than the previous two solar cycles, while solar irradiance reached about
the same maximum level during cycle 23 as during the last cycles. In
this paper we compare the long-term variations of the composite total
and UV irradiances with solar magnetic indices, such as the Photometric
Sunspot Index, the equivalenth width of the He-line at 1083 nm, full
disk magnetic flux, polar magnetic fields and facular proxies. The
controversy between measured irradiance variations and their magnetic
surrogates over solar cycles 21 to 23 is discussed in the paper.
Title: The SOHO CELIAS/SEM EUV database from SC23 minimum to the
present
Authors: Judge, D. L.; Ogawa, H. S.; McMullin, D. R.; Gangopadhyay,
P.; Pap, J. M.
Bibcode: 2002AdSpR..29.1963J
Altcode:
The SOHO Solar EUV Monitor has been in operation since December
1995 onboard the SOHO spacecraft. This instrument is a highly stable
transmission grating solar extreme ultraviolet spectrometer. It has
made nearly continuous full disk solar irradiance measurements both
within an 8 nm bandpass centered at 30.4 nm and throughout the 0.1 to
50 nm solar flux region since launch. The 30.4 nm flux, the 0.1 to 50
nm flux and the extracted soft X-ray (0.1 to 5 nm) flux are presented
and compared with the behavior of solar proxies.
Title: International Solar Cycle Studies (ISCS), "Solar Energy
Flux Study: from the interior to the outer layer" — Working Group
1 report
Authors: Pap, Judit; Fröhlich, Claus
Bibcode: 2002AdSpR..29.1571P
Altcode:
The purpose of this report is to describe the research activities and
plans of Working Group 1: "Solar Energy Flux Study: From the Interior
to the Outer Layer" of the International Solar Cycle Study (ISCS),
which is an international research organization operating under the
auspices of the Scientific Committee on Solar-Terrestrial Physics
(SCOSTEP). As part of the report, we also summarize the status of
the measurements and results on the solar energy flux variations. The
main objective of ISCS's Working Group 1 is to coordinate and support
comprehensive international research of the variations in the solar
energy flux during the rising portion and maximum of solar cycle 23. The
research activities of ISCS's Working Group 1 will concentrate on the
following tasks: (1) to measure and study the variations in the solar
radiative and mass output and solar activity indices during the solar
activity cycle, (2) to understand why the solar radiative and mass
output and the solar activity indices vary during the solar cycle,
and (3) to study the role of solar variability in solar-terrestrial
changes and its contribution to global change. ISCS WG1 "Solar Energy
Flux Study: From the Interior to the Outer Layer" has been divided
into three panels: •| Panel 1: Variations in Total and Spectral
Irradiance from Infrared to Far UV. Panel leaders: Martin Anklin of
the Physikalisch-Meteorologishes Observatorium Davos, Switzerland
(total irradiance), Gerard Thuillier of the Service d'Aeronomie-CNRS,
Verrieres, France (visible and infrared), and Linton Floyd of the Naval
Research Laboratory, Washington, DC, USA (ultraviolet). •| Panel
2: Variations in EUV, X-ray and Particle Fluxes. Panel leaders: Gerhard
Schmidtke of Fraunhofer IPM, Freiburg, Germany and W. Kent Tobiska of
FDC/Jet Propulsion Laboratory, Pasadena, CA, USA (EUV/XUV), and David
Winningham of the Southwest Research Institute, San Antonio, TX, USA
(particles). •| Panel 3: Solar Indices, Cosmogenic Isotopes,
Solar-Stellar Relations. Panel leaders: Gary Chapman of the San Fernando
Observatory, CSUN, Northridge, CA, USA (solar indices), Juerg Beer
of Institute for Environmental Science and Technology, Dübendorf,
Switzerland (cosmogenic isotopes), and Sallie Baliunas of the Harvard
Smithsonian Center for Astrophysics, Cambridge, MA, USA (solar-stellar
relations). The first two panels concentrate on solar energy flux
measurements, whereas the third panel concentrates on solar indices
and alternative ways to model and predict irradiance variations at
various wavelengths and their terrestrial/climate effects. Working
Group 1 of ISCS has supported and adopted the "Thermospheric-Ionospheric
Geospheric Research (TIGER)" program as part of ISCS/WG1/Panel 2. The
main objectives of TIGER are to measure, model, and interpret solar
EUV/UV and particle fluxes and to study and model their effect on the
Earth's thermosphere and ionosphere (see details by Schmidtke et al.,
2001, this volume). This approach links ISCS/WG1 activities directly
with studies of our space environment.
Title: Variations in Total Solar and Spectral Irradiance During
Solar Cycle 23
Authors: Turmon, M.; Pap, J.; Floyd, L.; Judge, D.; McMullin, D.
Bibcode: 2001AGUFMSH11C0734T
Altcode:
Observations of total solar and spectral irradiance in near-UV (402
nm), visible (500 nm) and near-IR (862 nm) have been conducted by the
SOHO VIRGO experiment since January 1996, providing information about
irradiance changes during the minimum, rise, and maximum of solar
cycle 23. Solar EUV and UV irradiance measurements are available
for the same time interval by the SOHO/CELIAS/SEM and UARS/SUSIM
experiments. Analysis of the SOHO/MDI images makes it also possible to
compare irradiance variations with the evolution of magnetic structures,
such as sunspots, facuale and the network. In this paper we study
the spectral distribution of irradiance changes and their relation to
magnetic activity. Results on longer-term variations between 1978 and
2001 are also presented.
Title: Effect of Magnetic Fields on Solar Irradiance Variations
Authors: Pap, J. M.; Arge, N.; Chapman, G.; Floyd, L. E.; Turmon, M.
Bibcode: 2001AGUFMSH11C0731P
Altcode:
In this paper we show the relation between solar total and UV irradiance
and magnetic field variations. Comparison of the multi-decade long
irradiance and magnetic field measurements indicates that the shape and
magnitude of irradiance variations are different from that of magnetic
indices. Specifically, while magnetic indices show that solar cycle
23 is weaker than the two previous cycles, the long-term variation of
total solar irradiance within the last three solar cycles is rather
symmetrical, showing that its maximum and minimum levels were about
the same within their measuring uncertainties. Study of UV irradiance
variations also shows that UV irradiance is higher at the maximum of
cycle 23 than magnetic indices, such as sunspot number, the full disk
magnetic flux, and faculae indices. The long-term irradiance data
bases are compared with the Kitt Peak full disk magnetic field and
the Wilcox polar magnetic field measurements as well as photometric
measurements of sunspots and faculae.
Title: Solar Irradiance Variations Measured from Spacecraft
Authors: Pap, J. M.
Bibcode: 2001AAS...199.3602P
Altcode: 2001BAAS...33.1360P
As the solar energy flux is deposited in various parts of the Earth's
atmosphere, oceans, and land, it controls the heating, ionization,
radiative, chemical, and dynamical processes characterizing the
terrestrial atmosphere and climate system. Therefore, the accurate
knowledge of the solar energy received by Earth and understanding its
variability are critical issues for an understanding of the climate
response to the increasing greenhouse gas concentrations. Solar
irradiance (both bolometric and at UV wavelengths) has been measured
continuously from various space platforms since late 1978. These
irradiance measurements established conclusively that solar irradiance
varies on time scales from minutes to decades. The most important
discovery of the space-based irradiance measurements is that total
irradiance varies with about 0.1% over the solar cycle, being higher
during maximum activity conditions. Since even small variations in
total irradiance over long time scales may lead to climate changes,
it is extremely important (1) to maintain a long-term high precision
irradiance data base for climate studies and (2) to understand
the underlying physical mechanisms. In this paper we summarize the
results gained from the multi-decade long space-based irradiance
measurements. This research was supported by a grant NAG5-10876 from
the SOHO Office of NASA's Office of Space Science and by NASA grants
NAG5-9207 and NAG5-11326 from NASA's Office of Earth Science. SOHO is
a mission of international cooperation between ESA and NASA.
Title: Multi-Decade Long Total Solar Irradiance Measurements
Authors: Helizon, R.; Pap, J. M.
Bibcode: 2001AGUFM.A51E0086H
Altcode:
Total solar irradiance has been measured from space for more than
two decades by various instruments. These irradiance observations
demonstrate that total irradiance changes on time scales from minutes to
decades. While studying short-term irradiance variations are important
for solar physics, establishing the amplitude of irradiance variations
within a particular solar cycle and from one cycle to another is
important also for climate studies. The composite total irradiance,
compiled from various time series, indicates that the amplitude of
total irradiance is about the same during the minima and maxima of
solar cycles 21, 22, and 23 within the measuring uncertainties. Since
the ACRIM time series provides the longest data set in the composite
total irradiance, the ACRIM data are compared to the measurements of
the Nimbus-7/ERB, ERBS and SOHO/VIRGO total irradiance using various
processings of the UARS/ACRIM II measurements.
Title: Variations of solar spectral irradiance from near UV to the
infrared-measurements and results
Authors: Fligge, M.; Solanki, S. K.; Pap, J. M.; Fröhlich, C.;
Wehrli, C.
Bibcode: 2001JASTP..63.1479F
Altcode: 2001JATP...63.1479F
Solar spectral irradiance variations are known to exhibit a strong
wavelength dependence with the amount of variability increasing towards
shorter wavelengths. The bulk of solar radiation is emitted at visible
and infrared wavelengths. Thus, the spectral radiation length of 300nm
accounts for 99% of the total solar radiative output. Deposited in the
Earth's troposphere and biosphere, this part of the solar irradiance
spectrum determines direct solar radiative forcing and is therefore
of particular interest for climate studies. First, measurements of
solar irradiance and irradiance variability from near UV to the IR are
reviewed with particular emphasis on the results obtained from the
Variability of Irradiance and Gravity Oscillations (VIRGO) on SOHO
and Solar Spectrum Measurement (SOLSPEC) instruments. In the second
part a model is presented which describes solar spectral irradiance
variations in terms of the changing distribution of solar surface
magnetic features.
Title: On the relation between total irradiance and radius variations
Authors: Pap, J.; Rozelot, J. P.; Godier, S.; Varadi, F.
Bibcode: 2001A&A...372.1005P
Altcode:
We use Singular Spectrum Analysis (SSA) to analyze total solar
irradiance variations and CERGA radius measurements. Total solar
irradiance has been monitored from space for more than two decades,
whilst ground-based radius measurements are available as a coherent time
series from 1975. We compare these indicators to try to understand the
origin of energy production inside the Sun. One of the main objectives
was to assess the reality of the observed variations of the Sun's radius
by distinguishing the signal from the noise. Two approaches were used:
one using SSA on ground-based data averaged over 90 days, in order to
smooth the signal (especially over periods when no data were obtained,
mainly in winter time); the second repeats the analysis on individual
measurements corrected by reporting data to the zenith. As expected,
the level of noise is higher in the first case and the reconstructed
noise level, which is large, indicates the difficulty in ascertaining
the solar origin in the apparent variability of the solar radius. It
is shown from the reconstructed components that the main variation
in amplitude (over 930 days) is pronounced during the first part of
the measurements and seems to disappear after 1988. There is also
a variation with a periodicity of 1380 days, of lower amplitude than
that of the shorter component. In both cases, these variations disappear
during the rising portion of cycle 23. The first reconstructed component
shows that total irradiance varies in parallel with the solar cycle,
being higher during maximum activity conditions. The reconstructed
radius trend indicates that the solar radius was higher during the
minimum of solar cycle 21, but its decrease with the rising activity
of cycle 23 is less obvious. The observed value of the solar radius
increased by about 0.11 arcsec from the maximum of cycle 21 to the
minimum between cycles 21 and 22. Most importantly, we report a
long-term radius variation which increased from the maximum of cycle
21 to minimum by about 0.015%, while a smaller decrease (around 0.01%)
is seen from the minimum of cycle 21 to the maximum of cycle 22. This
study indicates need for measurements of the degree of the radius
changes taken from space, together with total irradiance measurements
to establish the phase relation between these two quantities.
Title: Using Precise Solar Limb Shape Measurements to Study the
Solar Cycle
Authors: Kuhn, J. R.; Floyd, L.; Fröhlich, C.; Pap, J. M.
Bibcode: 2000SSRv...94..169K
Altcode:
Despite 20 years of total solar irradiance measurements from space, the
lack of high precision spatially resolved observations limits definitive
answers to even simple questions like ``Are the solar irradiance changes
caused solely by magnetic fields perturbing the radiative flux at the
photosphere?" More subtle questions like how the aspheric structure
of the sun changes with the magnetic cycle are only now beginning to
be addressed with new tools like p-mode helioseismology. Solar 5-min
oscillation studies have yielded precise information on the mean radial
interior solar structure and some knowledge about the rotational
and thermal solar asphericity. Unfortunately this progress has not
been enough to generate a self-consistent theory for why the solar
irradiance and luminosity vary with the magnetic cycle. We need sharper
tools to describe and understand the sun's global aspheric response
to its internal dynamo, and we need to be able to measure the solar
cycle manifestation of the magnetic cycle on entropy transport from
the interior to the photosphere in much the same way that we study the
fundamentally more complex problem of magnetic flux transport from the
solar interior. A space experiment called the Solar Physics Explorer for
Radius, Irradiance and Shape (SPHERIS) and in particular its Astrometric
and Photometric Telescope (APT) component will accomplish these goals.
Title: Using Precise Solar Limb Shape Measurements to Study the
Solar Cycle
Authors: Kuhn, J. R.; Floyd, L.; Fröhlich, C.; Pap, J. M.
Bibcode: 2000svc..book..169K
Altcode:
No abstract at ADS
Title: Searching for Signal in Noise by Random-Lag Singular Spectrum
Analysis
Authors: Varadi, F.; Pap, J. M.; Ulrich, R. K.; Bertello, L.; Henney,
C. J.
Bibcode: 1999ApJ...526.1052V
Altcode:
Singular spectrum analysis, a technique to detect oscillations in
short and noisy time series, was first developed for geophysical
applications. This work offers a generalization for long and noisy
time series in astrophysical applications. The motivating problem is
the detection of low-amplitude solar oscillations.
Title: The Role of Weak Magnetic Fields in the Solar Cycle as Measured
at the 150-foot Tower on Mt. Wilson
Authors: Ulrich, R. K.; Parker, D. G.; Pap, J. M.
Bibcode: 1999AAS...194.9203U
Altcode: 1999BAAS...31..986U
Weak magnetic fields on the solar surface are measured using the Babcock
magnetograph system at the 150-foot solar tower on Mt. Wilson. The
coverage of the solar surface by weak fields can be quantified in terms
of a distribution function which gives the fraction of the solar surface
covered by fields in small field strength bands. Observations of these
fields over the past solar cycle shows that the gaussian core width
of the distribution function decays after the strong magnetic fields
have passed their maximum. The delay is approximately 18 months. The
new cycle has first appeared as a strengthening of the distribution
function wings. This strengthening then migrates to the core and finally
increases the core width. This behavior together with the amplitude
of core variation suggests that the weak fields arise from the strong
fields with a lag time of 10 to 20 years. A forced oscillator model with
the strong fields as the driver and a decay time of 15 years yields the
conclusion that the weak fields could have systematically increased
in strength during the 20th century. Attribution of one third of the
solar cycle luminosity variation to this component suggests that the
weak fields may have played a role in the global temperature rise since
1910. This research is supported by NASA, ONR and NSF through a series
of grants which began at UCLA in 1986. The 150-foot tower telescope
was built on Mt. Wilson under the direction of G.E. Hale. The digital
form of magnetograph was developed by R.F. Howard.
Title: Total solar irradiance variations
Authors: Pap, J. M.; Fröhlich, C.
Bibcode: 1999JASTP..61...15P
Altcode: 1999JATP...61...15P
Total solar irradiance has been monitored from space for nearly
two decades. These space-borne observations have established
conclusively that total solar irradiance changes over a wide range
of periodicities-from minutes to the 11-year solar cycle. Since the
total energy flux of the Sun is the principal driver for all Earths
atmospheric phenomena, the accurate knowledge of the solar radiation
received by the Earth and its variations is an extremely important
issue. In this paper we review the long-term variations of total solar
irradiance during solar cycles 21 and 22. We conclude that, within the
current accuracy and precision of the measurements, the minimum level
of total solar irradiance is about the same for both solar cycles 21
and 22.
Title: Variations in total solar and spectral irradiance as measured
by the VIRGO experiment on SOHO
Authors: Pap, Judit; Anklin, Martin; Fröhlich, Claus; Wehrli,
Christoph; Varadi, Ferenc; Floyd, Linton
Bibcode: 1999AdSpR..24..215P
Altcode:
The Variability IRradiance Gravity Oscillation (VIRGO) experiment on
SOHO has been observing total solar and spectral irradiances at 402
nm (blue channel), 500 nm (green channel), and 862 nm (red channel)
since January 1996. The VIRGO observations have shown that solar
active regions influence both total and spectral irradiances in a
similar fashion, although the amplitude of the variations seems to
be the largest for the near-UV and visible wavelengths. Comparison
of the VIRGO total solar irradiance and the UARS/SUSIM Mg II h &
k core-to-wing ratio shows that total irradiance started to rise in
prior to UV irradiance, as represented by the Mg core-to-wing ratio. In
this paper we review the most recent results on the VIRGO irradiance
variations related to solar activity. We dedicate this paper to the
memory of Dr. Guenther Brueckner, the late Principal Investigator of
the UARS/SUSIM experiment, who will always remain in the heart and
memory of the authors of this paper.
Title: APT: an astrometric and photometric telescope
Authors: Kuhn, Jeff R.; Bush, Rock I.; Coulter, Roy; Froehlich, Claus;
Gwo, Dz-Hung; Jones, A.; Pap, Judit M.; Scherrer, Philip H.; Sofia,
Sabatino; Ulrich, Roger
Bibcode: 1998SPIE.3442..203K
Altcode:
Helioseismic and precise solar photometric measurements reveal that the
Sun varies globally as a start during the source of an 11 year solar
cycle. To understand the physical mechanisms of the magnetic cycle in
the solar interior we must learn how to measure the tiny changes in
the Sun's global properties, like its radius, internal temperature
distribution and surface luminosity. The SoHO/MDI experimental has
proven that exceedingly small solar shape fluctuations are measurable
from outside our atmosphere. We describe here an instrument which
will not only measure limb shape oscillations with unprecedented
accuracy, but it will also detect solar radius changes with heretofore
unachieved accuracy and precision. Variations in these parameters are
caused by physical changes, both in the photosphere and the deep solar
interior. Solar radius and shape observations will teach us how the
Sun's convective envelope responds to emergent energy fluctuations. The
determination of this outer boundary condition is essential to
understand the solar total irradiance and luminosity variations.
Title: Modeling Solar UV Variations Using Mount Wilson Observatory
Indices
Authors: Parker, D. G.; Ulrich, R. K.; Pap, J. M.
Bibcode: 1998SoPh..177..229P
Altcode:
Understanding the magnitude and temporal structure of variations in
solar ultraviolet and extreme ultraviolet irradiance is critical
to understanding solar forcing of the Earth's upper and middle
atmosphere and hence to assessing the relative impact of natural and
anthropogenic influences on Earth's atmospheric environment. Satellite
based measurements of such variations are limited to recent times, are
short in duration and subject to gaps making necessary ground-based
surrogates with longer and more continuous coverage. Using indices
derived from synoptic solar magnetograms taken at the Mount Wilson
150-foot solar tower, we have constructed models of several UV and
near EUV lines and fluxes which correlate strongly (r > 0.90)
with satellite data. These lines and fluxes include the Mgii h and k
core-to-wing ratio, the Lα line and the 200-205 nm flux.
Title: Automatically Finding Solar Active Regions using SOHO/MDI
Photograms and Magnetograms
Authors: Turmon, M.; Pap, J. M.; Mukhtar, S.
Bibcode: 1998ESASP.418..979T
Altcode: 1998soho....6..979T
No abstract at ADS
Title: Importance of Monitoring Solar Global Properties: Luminosity,
Radius and Oscillations
Authors: Pap, J. M.; Kuhn, J. R.; Fröhlich, C.; Ulrich, R.; Jones,
A.; Rozelot, J. P.
Bibcode: 1998ESASP.417..267P
Altcode: 1998cesh.conf..267P
No abstract at ADS
Title: Solar Electromagnetic Radiation Study for Solar Cycle
22. Proceedings. SOLERS22 Workshop, Sakramento Peak, Sunspot, NM
(USA), 17 - 21 Jun 1996.
Authors: Pap, J. M.; Fröhlich, C.; Ulrich, R. K.
Bibcode: 1998SoPh..177.....P
Altcode: 1998SoPh..177....1P
The following topics were dealt with: the prototype RISE-PSPT
instrument, solar total irradiance, solar disk spectral intensity,
proxy solar activity studies, solar variability, solar UV activity,
EUV irradiance, solar-terrestrial relationships, solar magnetic field,
spectroheliogram studies, network and plage regions, solar cycle, solar
diameter measurements, solar wind, prominences and coronal activity,
coronal holes and polar field reversals, magnetograms, reconnection,
nanoflares, radio burst chains, and gyrosynchrotron radiation.
Title: Modeling Solar UV Variations Using Mount Wilson Observatory
Indices
Authors: Parker, D. G.; Ulrich, R. K.; Pap, J. M.
Bibcode: 1998sers.conf..229P
Altcode:
No abstract at ADS
Title: SOHO/VIRGO Total Solar and Spectral Irradiance Variations
Authors: Pap, J. M.; Frohlich, C.; Anklin, M.; Wehrili, Ch.; Varadi,
F.; Floyd, L.
Bibcode: 1998ESASP.418..951P
Altcode: 1998soho....6..951P
No abstract at ADS
Title: Solar Electromagnetic Radiation Study for Solar Cycle 22
Authors: Pap, J. M.; Frohlich, C.; Ulrich, R. K.
Bibcode: 1998sers.conf.....P
Altcode:
No abstract at ADS
Title: Automated Recognition and Characterization of Solar Active
Regions Based on the SOHO/MDI Images
Authors: Pap, J. M.; Turmon, M.; Mukhtar, S.; Bogart, R.; Ulrich,
R.; Fröhlich, C.; Wehrli, Ch.
Bibcode: 1997ESASP.415..477P
Altcode: 1997cpsh.conf..477P
No abstract at ADS
Title: Long-Term Variations in Total Solar and UV Irradiances
Authors: Pap, J. M.; Floyd, L.; Lee, R. B.; Parker, D.; Puga, L.;
Ulrich, R.; Varadi, F.; Viereck, R.
Bibcode: 1997ESASP.415..251P
Altcode: 1997cpsh.conf..251P
No abstract at ADS
Title: On the Effect of Active Regions on the Solar Irradiance
Authors: Domingo, V.; Sanchez, L.; Appourchaux, T.; Fröhlich, C.;
Wehrli, C.; Crommelynck, D.; Pap, J.
Bibcode: 1997ESASP.415..469D
Altcode: 1997cpsh.conf..469D
No abstract at ADS
Title: Estimating Long-Term Solar Irradiance Variability: A New
Approach
Authors: Vigouroux, Anne; Pap, Judit M.; Delache, Philippe
Bibcode: 1997SoPh..176....1V
Altcode:
The detection of solar irradiance variations (both bolometric and at
various wavelengths) by satellite-based experiments during the last
one-and-a-half decades stimulated modeling efforts to help identify
their causes and to provide estimates of irradiance data for those time
intervals when no satellite observations exist. In this paper we present
estimates of the long-term irradiance changes developed with Fourier
and wavelet transforms. The month-to-month irradiance variations,
after removing the solar cycle related long-term changes, are studied
with the cross-correlation technique. Results of the analysis reveal
a significant phase shift at 3 months between the full-disk magnetic
field strength and total solar and UV irradiance, with irradiance
leading the magnetic field variability. In addition to this time
delay between the changes in solar irradiance and the magnetic field,
a 10-month phase shift has been found between the UV flux at 280 nm and
total solar irradiance corrected for sunspot darkening. The existence
of these phase shifts suggests the possibility of a coupling between the
physical processes taking place below, in, and above the photosphere.
Title: Study of the Effect of Active Regions on the Solar Irradiance
During Solar Minimum
Authors: Domingo, V.; Sanchez, L.; Appourchaux, T.; Froehlich, C.;
Wehrli, C.; Hoeksema, T.; Pap, J.
Bibcode: 1997SPD....28.0206D
Altcode: 1997BAAS...29..893D
We have determined both the size of the area that contributes to the
solar irradiance increase around an active region and the angular
distribution of the radiance excess in it, using data obtained during
about one year around solar minimum (April 1996 - April 1997). During
the solar minimum and the early raising phase of the new maximum it
is possible to study the effect of isolated active regions while there
are few of them. The result of this study will be important to separate
the contribution of the active regions to the solar irradiance change
during the solar cycle from any underlying long term effect, if there
is one. The solar radiance measured by the Low-resolution Oscillations
Imager (LOI) of the VIRGO instrument and by the MDI instrument aboard
SOHO is used to determine the dimension of the radiating area. The
increase in irradance is determined by the Sun Photometers (SPM)
and Radiometers on the VIRGO instrument.
Title: Comparison of UV Irradiance Variations during Solar Cycles
21 and 22
Authors: Varadi, F.; Pap, J. M.; Parker, D.; Ulrich, R.; Floyd, L.;
Prinz, D.; Puga, L.; Viereck, R.
Bibcode: 1997SPD....28.0106V
Altcode: 1997BAAS...29..880V
The main goal of this paper is to study the UV irradiance variations in
the Mg II h & k core-to-wing ratio derived from the SUSIM irradiance
observations on board the Upper Atmosphere Research Satellite and
the SBUV instruments on the Nimbus-7 and NOAA satellites. The SUSIM
instrument has been monitoring solar UV irradiance since October 12,
1991. The combined Nimbus-7/SBUV1 and NOAA9/SBUV2 data cover the time
interval of November 1978 to present and provide information about the
UV irradiance variations for almost two solar cycles. The observed UV
irradiance changes are compared to the Magnetic Plage Strength Index
(MPSI) and Mt. Wilson Sunspot Index (MWSI) derived from the ground-based
observations at the Mt. Wilson Observatory at 525 nm. Previous results
show that the linear relationship between UV irradiance and proxy data
representing the changing emission of plages and the magnetic network
breaks down at the minimum of solar cycle 21. In this paper we examine
the variations observed in UV irradiance during the various phases of
solar cycles 21 and 22, with emphasis on studying the UV irradiance
variability during the two solar minima.
Title: Developing New Mount Wilson Magnetic Indices to Model Solar
UV Variations
Authors: Parker, D. G.; Pap, J. M.; Ulrich, R. K.; Floyd, L. E.;
Prinz, D. K.
Bibcode: 1997SPD....28.0254P
Altcode: 1997BAAS...29..902P
Understanding the magnitude and temporal structure of variations in
solar ultraviolet irradiance is a key component of understanding the
Sun as a variable star and is critical to understanding solar forcing
of the Earth's upper and middle atmosphere. We have used indices
derived from the daily, spatially resolved, magnetograms taken at the
Mount Wilson Observatory to develop models of UV observations. These
magnetograms, which have been taken in the magnetically sensitive FeI
525.0 nm line on a daily basis since 1968, offer the possibility of
long term modeling of solar UV variations, including periods for which
satellite observations are unavailable or unreliable. One index used
in this modeling is the "Magnetic Plage Strength Index" (MPSI), which
is defined as the sum of the absolute magnetic fields of all pixels
with magnetic strength between 10 and 100 gauss and is associated with
the strong fields of plage/facular regions. We have found the MPSI to
describe reasonably well both short and long term variations in the UV
irradiance observations from the Solar Mesosphere Explorer, Nimbus-7,
NOAA9, and Upper Atmosphere Research Satellites with correlation
coefficients of from 0.93 to over 0.98. However, there remains a
substantial fraction of solar UV variations which appears not to be
associated with these strong fields. In this paper we describe our
efforts to improve on the MPSI model of these satellite observations
by (1) using different field strength limits for a plage index, (2)
creating new and improving on old magnetic indices by including in the
model surface magnetic features with field strengths lower and higher
than associated with the MPSI, and (3) correcting the Mount Wilson
indices for certain changes in the observation protocol. Since the bulk
of the magnetogram pixels have field strengths between 0.5 and 2.0 gauss
as measured at 525.0 nm, and since pixels with field strengths between
2.0 and 10 gauss may be associated with active network, we think,
and our results so far confirm, that indices based on fields lower
than 10.0 gauss will significantly improve modeling of UV variations.
Title: Spectral Distribution of Total Irradiance Variability
Authors: Pap, J.; Floyd, L.; Prinz, D.; Parker, D.; Ulrich, R.;
Varadi, F.; SOHO/Virgo Team
Bibcode: 1997SPD....28.1402P
Altcode: 1997BAAS...29..918P
Since January 1996, the SOHO/VIRGO experiment has been observing the
total (spectrally integrated) solar irradiance with the DIARAD and
PMO6-V instruments, as well as the solar spectral irradiance in three
channels - in the near-UV at 402 nm, in the visible at 500 nm, and in
the infrared at 862 nm - with the SPM instrument. The VIRGO total and
spectral irradiance measurements have revealed variations related to
the appearance of active regions on time scales of days to weeks. Both
the DIARAD and PMO6-V total irradiance data show that the total solar
irradiance started to increase in late October, 1996, similar to the
behavior of the Mg II index (core-to-wing ratio) derived from the UV
irradiance observations of the SUSIM instrument on the Upper Atmosphere
Research Satellite (UARS). The main goal of this paper is to compare
the VIRGO total and spectral irradiance as well as the UARS/SUSIM UV
irradiance with the magnetic plage and sunspot indices derived from
the observations of the 525 nm line at the Mt. Wilson Observatory.
Title: Long-term solar-irradiance variability
Authors: Pap, J. M.
Bibcode: 1997IAUS..181..235P
Altcode:
No abstract at ADS
Title: First results from VIRGO on SoHO
Authors: Frohlich, C.; Andersen, B. N.; Appourchaux, T.; Berthomieu,
G.; Crommelynck, D. A.; Domingo, V.; Fichot, A.; Finsterle, W.;
Gómez, M. F.; Gough, D.; Jiménez, A.; Leifsen, T.; Lombaerts, M.;
Pap, J. M.; Provost, J.; Roca Cortés, T.; Romero, J.; Roth, H. -J.;
Sekii, T.; Telljohann, U.; Toutain, T.; Wehrli, C.
Bibcode: 1997IAUS..181...67F
Altcode:
No abstract at ADS
Title: Segmenting Chromospheric Images with Markov Random Fields
Authors: Turmon, Michael J.; Pap, Judit M.
Bibcode: 1997scma.conf..409T
Altcode:
No abstract at ADS
Title: Total Solar irradiance variability: A review
Authors: Pap, J. M.
Bibcode: 1997ppvs.conf....1P
Altcode:
Introduction Variations observed in total solar irradiance Modeling
total solar irradiance variations Modeling variations on active-regions
time scale Results of multivariate spectral analysis Results of
singular spectrum analysis Modeling variations over the solar cycle
Uncertainties of irradiance measurements Limitation of the irradiance
models Conclusions
Title: First Results from VIRGO, the Experiment for Helioseismology
and Solar Irradiance Monitoring on SOHO
Authors: Fröhlich, Claus; Andersen, Bo N.; Appourchaux, Thierry;
Berthomieu, Gabrielle; Crommelynck, Dominique A.; Domingo, Vicente;
Fichot, Alain; Finsterle, Wolfgang; Gómez, Maria F.; Gough, Douglas;
Jiménez, Antonio; Leifsen, Torben; Lombaerts, Marc; Pap, Judit M.;
Provost, Janine; Roca Cortés, Teodoro; Romero, José; Roth, Hansjörg;
Sekii, Takashi; Telljohann, Udo; Toutain, Thierry; Wehrli, Christoph
Bibcode: 1997SoPh..170....1F
Altcode:
First results from the VIRGO experiment (Variability of solar IRradiance
and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and
Heliospheric Observatory) are reported. The observations started
mid-January 1996 for the radiometers and sunphotometers and near the
end of March for the luminosity oscillation imager. The performance of
all the instruments is very good, and the time series of the first 4-6
months are evaluated in terms of solar irradiance variability, solar
background noise characteristics and p-mode oscillations. The solar
irradiance is modulated by the passage of active regions across the
disk, but not all of the modulation is straightforwardly explained in
terms of sunspot flux blocking and facular enhancement. Helioseismic
inversions of the observed p-mode frequencies are more-or-less in
agreement with the latest standard solar models. The comparison of
VIRGO results with earlier ones shows evidence that magnetic activity
plays a significant role in the dynamics of the oscillations beyond
its modulation of the resonant frequencies. Moreover, by comparing
the amplitudes of different components ofp -mode multiplets, each of
which are influenced differently by spatial inhomogeneity, we have
found that activity enhances excitation.
Title: Contribution of Chromospheric Features to UV Irradiance
Variability from Spatially-Resolved CA II K Spectroheliograms,
Authors: Kariyappa, R.; Pap, J. M.
Bibcode: 1996SoPh..167..115K
Altcode:
We have digitized the Ca II K spectroheliograms, observed at the
National Solar Observatory at Sacramento Peak, for the period 1980
(maximum of solar cycle 21), 1985 (minimum of solar cycle 21),
1987 (beginning of the ascending phase of solar cycle 22), 1988
and 1989 (ascending phase and maximum of solar cycle 22), and 1992
(declining phase of solar cycle 22). A new method for analyzing the
K spectroheliograms has been developed and applied to the K images
for the time interval of 1992. Using histograms of intensity, we
have segregated and measured the cumulative intensity and area of
various chromospheric features like the plages, magnetic network and
intranetwork elements. Also, the full width at half maximum (FWHM)
derived from the histograms has been introduced as a new index for
describing the chromospheric activity in the K-line. The full-disk
intensity (spatial K index) has been derived from spatially-resolved
K images and compared to the spectral K index derived from the line
profiles for the full disk. Both the spatial K index and FWHM have
been compared to the UV irradiance measured in the Mg II h and k lines
by the NOAA9 satellite and found that they are highly correlated with
the Mg II h and k c/w ratio.
Title: Book Review: The Sun as a variable star ; solar and stellar
irradiance variations (IAU colloquium 143) / Cambridge U Press, 1994
Authors: Pap, J. M.; Fröhlich, C.; Hudson, H. D.; Solanki, S. K.
Bibcode: 1996SSRv...76..354P
Altcode:
No abstract at ADS
Title: Studying Solar Irradiance Variability With Wavelet Technique
Authors: Vigouroux, Anne; Pap, Judit
Bibcode: 1996ASPC...95..586V
Altcode: 1996sdit.conf..586V
No abstract at ADS
Title: Application of Singular Spectrum Analysis to Solar Irradiance
Variability
Authors: Pap, Judit M.; Varadi, Ferenc
Bibcode: 1996ASPC...95..576P
Altcode: 1996sdit.conf..576P
No abstract at ADS
Title: VIRGO: Experiment for Helioseismology and Solar Irradiance
Monitoring
Authors: Fröhlich, Claus; Romero, José; Roth, Hansjörg; Wehrli,
Christoph; Andersen, Bo N.; Appourchaux, Thierry; Domingo, Vicente;
Telljohann, Udo; Berthomieu, Gabrielle; Delache, Philippe; Provost,
Janine; Toutain, Thierry; Crommelynck, Dominique A.; Chevalier,
André; Fichot, Alain; Däppen, Werner; Gough, Douglas; Hoeksema,
Todd; Jiménez, Antonio; Gómez, Maria F.; Herreros, José M.; Cortés,
Teodoro Roca; Jones, Andrew R.; Pap, Judit M.; Willson, Richard C.
Bibcode: 1995SoPh..162..101F
Altcode:
The scientific objective of the VIRGO experiment (Variability of solar
IRradiance and Gravity Oscillations) is to determine the characteristics
of pressure and internal gravity oscillations by observing irradiance
and radiance variations, to measure the solar total and spectral
irradiance and to quantify their variability over periods of days to
the duration of the mission. With these data helioseismological methods
can be used to probe the solar interior. Certain characteristics of
convection and its interaction with magnetic fields, related to, for
example, activity, will be studied from the results of the irradiance
monitoring and from the comparison of amplitudes and phases of the
oscillations as manifest in brightness from VIRGO, in velocity from
GOLF, and in both velocity and continuum intensity from SOI/MDI. The
VIRGO experiment contains two different active-cavity radiometers for
monitoring the solar `constant', two three-channel sunphotometers (SPM)
for the measurement of the spectral irradiance at 402, 500 and 862 nm,
and a low-resolution imager (LOI) with 12 pixels, for the measurement
of the radiance distribution over the solar disk at 500 um. In this
paper the scientific objectives of VIRGO are presented, the instruments
and the data acquisition and control system are described in detail,
and their measured performance is given.
Title: Intensity Oscillations in Nal d1 and d2 Lines
Authors: Kariyappa, R.; Pap, J. M.
Bibcode: 1995ESASP.376b.521K
Altcode: 1995soho....2..521K; 1995help.confP.521K
No abstract at ADS
Title: Preliminary Results of the Analysis of CAII K Spectroheliograms
Authors: Kariyappa, R.; Pap, J. M.; Balasubramaniam, K. S.; Kuhn, J. R.
Bibcode: 1995ESASP.376b.429K
Altcode: 1995help.confP.429K; 1995soho....2..429K
No abstract at ADS
Title: Books-Received - the Sun as a Variable Star - Solar and
Stellar Irradiance Variations
Authors: Pap, J. M.
Bibcode: 1995Sci...267.1845P
Altcode:
No abstract at ADS
Title: Solar UV flux measurements from the SBUV2 monitor on the
NOAA9 satellite. Part 1: MG II H and K line core-to-wing ratios
for 1986-1988
Authors: Donnelly, R. F.; Puga, L. C.; Barrett, J.; Bouwer, S. D.;
Pap, J.; Stevens, D. E.; Tobiska, W. K.
Bibcode: 1994STIN...9528007D
Altcode:
Analyses of the discrete-wavelength mode of observations of the
solar full-disk MG 2 h and k line spectral irradiance measured by
the Solar Backscatter UV Monitor (SBUV2) on the NOAA9 satellite
are presented. Relative photometry techniques were used to derive
a core-to-wing. This ratio has been modified, relative to that used
by Heath and Schlesinger's (1986) classical MG 2 ratio derived for
solar UV measurements made by their SBUV experiment aboard the
Nimbus-7 satellite, to avoid inter-range instrumentation drifts
encountered in the NOAA9 SBUV2 monitor. Prior research of the solar
MG 2 h and k lines is reviewed. The raw measurements and observational
parameters, such as the angle of the Sun as seen at the SBUV2 monitor
are discussed. Temporal interpolations among the sets of discrete-mode
measurements are used to account for most of the Sun-angle dependence
and to reduce the sensitivity of the results to any errors in the
Sun angles. Wavelength 'jitter' and long-term drift are studied,
and intensity linearity and inter-range drift are analyzed. The NOAA9
results are compared with same-day Nimbus-7 data, the Kitt Peak Ca K1
angstrom index, the Canadian 10.7 cm solar radio flux, and observations
of the solar H Lyman alpha line.
Title: Preface
Authors: Pap, Judit M.; Fröhlich, Claus; Hudson, Hugh S.; Tobiska,
W. Kent
Bibcode: 1994SoPh..152D...9P
Altcode:
No abstract at ADS
Title: Improvement of the Photometric Sunspot Index and Changes of
the Disk-Integrated Sunspot Contrast with Time
Authors: Froehlich, Claus; Pap, Judit M.; Hudson, Hugh S.
Bibcode: 1994SoPh..152..111F
Altcode: 1994IAUCo.143..111F; 1994svs..coll..111F
The photometric sunspot index (PSI) was developed to study the
effects of sunspots on solar irradiance. It is calculated from the
sunspot data published in theSolar-Geophysical Data catalogue. It
has been shown that the formerPSI models overestimate the effect of
dark sunspots on solar irradiance; furthermore results of direct
sunspot photometry indicate that the contrast of spots depends on
their area. An improvedPSI calculation is presented; it takes into
account the area dependence of the contrast and calculates 'true'
daily means for each observation using the differential rotation of
the spots. Moreover, the observations are screened for outliers which
improves the homogeneity of the data set substantially, at least for
the period after December 1981 when NOAA started to report data from
a few instead of one to two stations. A detailed description of the
method is provided. The correlation between the newly calculatedPSI
and total solar irradiance is studied for different phases of the solar
cycles 21 and 22 using bi-variate spectral analysis. The results can be
used as a `calibration' ofPSI in terms of gain, the factor by whichPSI
has to be multiplied to yield the observed irradiance change. This
factor changes with time from about 0.6 in 1980 to 1.1 in 1990. This
unexpected result cannot be interpreted by a change of the contrast
relative to the quiet Sun (as it is normally defined and determined by
direct photometry) but rather as a change of the contrast between the
spots and their surrounding as seen in total irradiance (integrated
over the solar disk). This may partly be explained by a change in the
ratio between the areas of the spots and the surrounding faculae.
Title: Long-term variations in total solar irradiance
Authors: Pap, Judit M.; Willson, Richard C.; Froelich, Claus; Donnelly,
Richard F.; Puga, Larry
Bibcode: 1994SoPh..152...13P
Altcode: 1994svs..coll...13P; 1994IAUCo.143...13P
For more than a decade total solar irradiance has been monitored
simultaneously from space by different satellites. The detection of
total solar irradiance variations by satellite-based experiments
during the past decade and a half has stimulated modeling efforts
to help identify their causes and to provide estimates of irradiance
data, using `proxy' indicators of solar activity, for time intervals
when no satellite observations exist. In this paper total solar
irradiance observed by the Nimbus-7/ERB, SMM/ACRIM I, and UARS/ACRIM
II radiometers is modeled with the Photometric Sunspot Index and the
Mg II core-to-wing ratio. Since the formation of the Mg II line is very
similar to that of the Ca II K line, the Mg core-to-wing ratio, derived
from the irradiance observations of the Nimbus-7 and NOAA9 satellites,
is used as a proxy for the bright magnetic elements. It is shown that
the observed changes in total solar irradiance are underestimated
by the proxy models at the time of maximum and during the beginning
of the declining portion of solar cycle 22 similar to behavior just
before the maximum of solar cycle 21. This disagreement between total
irradiance observations and their model estimates is indicative of the
fact that the underlying physical mechanism of the changes observed
in the solar radiative output is not well-understood. Furthermore,
the uncertainties in the proxy data used for irradiance modeling and
the resulting limitation of the models should be taken into account,
especially when the irradiance models are used for climatic studies.
Title: The sun as a variable star: Solar and stellar irradiance
variations
Authors: Pap, Judit M.; Froehlich, Claus; Hudson, Hugh S.; Tobiska,
W. Kent
Bibcode: 1994SoPh..152.....P
Altcode: 1994svs..coll.....P; 1994IAUCo.143.....P
Variations in solar and stellar irradiances have long been of
interest. An International Astronomical Union (IAU) colloquium reviewed
such relevant subjects as observations, theoretical interpretations,
and empirical and physical models, with a special emphasis on climatic
impact of solar irradiance variability. Specific topics discussed
included: (1) General Reviews on Observations of Solar and Stellar
Irradiance Variability; (2) Observational Programs for Solar and
Stellar Irradiance Variability; (3) Variability of Solar and Stellar
Irradiance Related to the Network, Active Regions (Sunspots and Plages),
and Large-Scale Magnetic Structures; (4) Empirical Models of Solar Total
and Spectral Irradiance Variability; (5) Solar and Stellar Oscillations,
Irradiance Variations and their Interpretations; and (6) The Response
of the Earth's Atmosphere to Solar Irradiance Variations and Sun-Climate
Connections. For individual titles, see A95-78168 through A95-78218.
Title: Panel discussions on Total solar irradiance variations and
the Maunder minimum
Authors: Pap, J. M.; White, O. R.
Bibcode: 1994seit.conf..235P
Altcode:
No abstract at ADS
Title: Poster Proceedings from IAU Colloquium 143: The Sun as a
Variable Star: Solar and Stellar Irradiance Variations
Authors: Pap, J. M.; Frohlich, C.; Hudson, H. S.; Solanki, S. K.
Bibcode: 1994svsp.coll.....P
Altcode: 1994IAUCo.143P....P
No abstract at ADS
Title: Variability of Solar UV Irradiance and Solar Activity Indices
During Solar Minimum
Authors: Guhathakurta, M.; Pap, J.
Bibcode: 1994step.conf..129G
Altcode:
No abstract at ADS
Title: The Sun as a Variable Star: Solar and Stellar Irradiance
Variations
Authors: Pap, Judit M.
Bibcode: 1994STIN...9671752P
Altcode:
The main objective of this Colloquium was to review the most recent
results on the observations, theoretical interpretations, empirical
and physical models of the variations observed in solar and stellar
irradiances, as well as on Sun-climate connections. The Colloquium
was divided into six sessions as defined by the key topics. Included
for each session were the 36 invited talks and 110 contributed poster
papers. A special session of the Solar Electromagnetic Radiation
Study for Solar Cycle 22 (SOLERS22) was held on 25 Jun. 1993, where
the five working groups discussed their progress and future plans on
measuring the absolute value of solar total and spectral irradiances and
studying their temporal variations. Papers on both theoretical models
and solar irradiance observations have shown that the solar energy
output changes on different time scales: the short-term (from minutes
to months) variations are related to surface modulations mainly caused
by the evolution of active regions, the solar cycle related long-term
variations are directly linked with the evolution of magnetic fields
over the activity cycle, while the secular variations over centuries
are associated with long-term modulations.
Title: Workshop on the Sun as a variable star
Authors: Pap, J. M.
Bibcode: 1993EOSTr..74..526P
Altcode:
The main objectives of International Astronomical Union Colloquium
143, “The Sun as a Variable Star: Solar and Stellar Irradiance
Variations,” were to review recent observations, theoretical
interpretations, and empirical and physical models of the
variations observed in solar and stellar irradiances and Sun-climate
connections. Held in Boulder, Colo., June 20-25, 1993, the colloquium
was sponsored by IAU Commission 10, cosponsored by IAU Commissions
12, 27, 29, and 44, and hosted by the Jet Propulsion Laboratory and
the National Oceanographic and Atmospheric Administration's Space
Environment Laboratory. The cosponsoring International Council of
Scientific Unions organizations were the Committee on Space Research,
the International Association of Meteorology and Atmospheric Physics,
and the International Association of Geomagnetism and Aeronomy.
Title: Variations in solar Lyman alpha irradiance on short time scales
Authors: Pap, J. M.
Bibcode: 1992A&A...264..249P
Altcode:
Variations in solar UV irradiance at Lyman alpha are studied on short
time scales (from days to months) after removing the long-term changes
over the solar cycle. The SME/Lyman alpha irradiance is estimated from
various solar indices using linear regression analysis. In order to
study the nonlinear effects, Lyman alpha irradiance is modeled with a
5th-degree polynomial as well. It is shown that the full-disk equivalent
width of the He line at 1083 nm, which is used as a proxy for the plages
and active network, can best reproduce the changes observed in Lyman
alpha. Approximately 72 percent of the solar-activity-related changes
in Lyman alpha irradiance arise from plages and the network. The
network contribution is estimated by the correlation analysis to be
about 19 percent. It is shown that significant variability remains
in Lyman alpha irradiance, with periods around 300, 27, and 13.5d,
which is not explained by the solar activity indices. It is shown that
the nonlinear effects cannot account for a significant part of the
unexplained variation in Lyman alpha irradiance. Therefore, additional
events (e.g., large-scale motions and/or a systematic difference in
the area and intensity of the plages and network observed in the lines
of Ca-K, He 1083, and Lyman alpha) may explain the discrepancies found
between the observed and estimated irradiance values.
Title: Estimating Solar Chromospheric UV Fluxes from Sunspot and
Solar Radio Data
Authors: Donnelly, R. F.; Hudson, H.; Pap, J.; Willson, R.
Bibcode: 1992sers.conf..275D
Altcode:
No abstract at ADS
Title: Working Group 1 Research Activities Report on the SOLERS22
1991 Workshop
Authors: Pap, J. M.; Wehrli, C.
Bibcode: 1992sers.conf...90P
Altcode:
No abstract at ADS
Title: Correlation Between Total Solar Irradiance and 115 cm (260 MHz)
Radio Flux
Authors: Pap, J. M.; Tlamicha, A.
Bibcode: 1992sers.conf...76P
Altcode:
No abstract at ADS
Title: Multi-Variate Spectral Analysis of Short-Term Irradiance
Variations
Authors: Pap, J. M.; Frohlich, C.
Bibcode: 1992sers.conf...62P
Altcode:
No abstract at ADS
Title: Variability of Solar UV Irradiance and Solar Activity Indices
During Solar Minimum
Authors: Guhathakurta, M.; Pap, J.
Bibcode: 1992AAS...180.5206G
Altcode: 1992BAAS...24..816G
No abstract at ADS
Title: Two-Parameter Model of Total Solar Irradiance Variation over
the Solar Cycle
Authors: Pap, Judit M.; Willson, Richard C.; Donnelly, Richard F.
Bibcode: 1992ASPC...27..491P
Altcode: 1992socy.work..491P
No abstract at ADS
Title: Variability of Solar UV Irradiance and Its Relation to the
Variability in Coronal Green Line Index and Equivalent Width of He
Line at 1083nm
Authors: Pap, J.; Gohathakurta, M.
Bibcode: 1992ASPC...27..483P
Altcode: 1992socy.work..483P
No abstract at ADS
Title: Variability of solar ultraviolet irradiance.
Authors: Pap, J. M.; Donnelly, R. F.; Hudson, H. S.; Rottman, G. J.;
Willson, R. C.
Bibcode: 1991JATP...53..999P
Altcode:
A model of solar Lyman alpha irradiance developed by multiple linear
regression analysis, including the daily values and 81-day running
means of the full disk equivalent width of the Helium line at 1083
nm, predicts reasonably well both the short- and long-term variations
observed in Lyman alpha. In contrast, Lyman alpha models calculated
from the 10.7 cm radio flux overestimate the observed variations in the
rising portion and maximum period of solar cycle, and underestimates
them during solar minimum. The authors show models of Lyman alpha based
on the He line equivalent width and 10.7 cm radio flux for those time
intervals when no satellite observations exist, namely back to 1974
and after April 1989, when the measurements of the Solar Mesosphere
Satellite were terminated.
Title: Variability of solar Lyman alpha and total solar irradiance
Authors: Pap, J. M.; London, J.; Rottman, G. J.
Bibcode: 1991A&A...245..648P
Altcode:
Variation of ultraviolet and total solar irradiance is investigated
during the declining portion of solar cycle 21, through solar cycle
minimum and into the rising portion of solar cycle 22. Both the Lyman
alpha and total irradiance decrease during the declining phase of
solar cycle 21 and increase with the growing new activity of solar
cycle 22. The same changes are evident in a variety of solar activity
indices, such as 10.7 cm radio flux, Ca-K plage index and projected
sunspot areas. However, while the total irradiance, 10.7 cm radio flux,
Ca-K plage index and projected sunspot areas each reach minimum levels
in early 1985 with a flat background during the following two years,
the Lyman alpha flux slowly decays to a brief minimum in mid-1986,
around the time of magnetic solar minimum.
Title: Modelling Solar UV Irradiance
Authors: Pap, J. M.
Bibcode: 1991BAAS...23R1069P
Altcode:
No abstract at ADS
Title: Multi-Variate Spectral Analysis of Solar Irradiance Variations
Authors: Pap, J. M.; Frohlich, C.
Bibcode: 1991BAAS...23Q1069P
Altcode:
No abstract at ADS
Title: Two-parameter model of total solar irradiance variation over
the solar cycle
Authors: Pap, Judit M.; Willson, Richard C.; Donnelly, Richard F.
Bibcode: 1991STIA...9355111P
Altcode:
Total solar irradiance measured by the SMM/ACRIM radiometer is modelled
from the Photometric Sunspot Index and the Mg II core-to-wing ratio
with multiple regression analysis. Considering that the formation of
the Mg II line is very similar to that of the Ca II K line, the Mg
II core-to-wing ratio, measured by the Nimbus-7 and NOAA9 satellites,
is used as a proxy for the bright magnetic elements, including faculae
and the magnetic network. It is shown that the relationship between
the variations in total solar irradiance and the above solar activity
indices depends upon the phase of the solar cycle. Thus, a better fit
between total irradiance and its model estimates can be achieved if
the irradiance models are calculated for the declining portion and
minimum of solar cycle 21, and the rising portion of solar cycle 22,
respectively. There is an indication that during the rising portion
of solar cycle 22, similar to the maximum time of solar cycle 21,
the modelled total irradiance values underestimate the measured
values. This suggests that there is an asymmetry in the long-term
total irradiance variability.
Title: Modelling solar irradiances using ground-based measurements
Authors: Pap, J. M.; Marquette, W. H.; Donnelly, R. F.
Bibcode: 1991AdSpR..11e.271P
Altcode: 1991AdSpR..11..271P
The preliminary results of the photometry of Ca-K plage remnants
show that during the fall of 1986 the remnants gave a significant
contribution to the irradiance variations. The contribution of the
plage remnants to the combined plage and remnant index was on average
about 13 % and it changed with time.
Title: Periodicities of Solar Irradiance and Solar Activity Indices -
Part One
Authors: Pap, Judit; Tobiska, W. Kent; Bouwer, S. David
Bibcode: 1990SoPh..129..165P
Altcode:
Using a standard FFT time series analysis, our results show an 8-11
months periodicity in the solar total and UV irradiances, 10.7 cm radio
flux, Ca-K plage index, and sunspot blocking function. The physical
origin of this period is not known, but the evidence in the results
exclude the possibility that the observed period is a harmonic due
to the FFT transform or detrending. Periods at 150-157 and 51 days
are found in those solar data which are related to strong magnetic
fields. The 51-day period is the dominant period in the projected
areas of developing complex sunspot groups, but it is missing from the
old decaying sunspot areas. This evidence suggests that the 51-day
period is related to the emergence of new magnetic fields. A strong
13.5-day period is found in the total irradiance and projected areas of
developing complex groups. This confirms those results (e.g., Donnelly
et al., 1983, 1984; Bai, 1987, 1989) which show that `active centers'
are located 180 deg apart from each other.
Title: Dynamic power spectral analysis of solar measurements from
photospheric, chromospheric, and coronal sources.
Authors: Bouwer, S. D.; Pap, J.; Donnelly, R. F.
Bibcode: 1990NASCP3086..125B
Altcode: 1990cisv.nasa..125B
An important aspect in the power spectral analysis of solar
variability is the quasistationary and quasiperiodic nature of solar
periodicities. In other words, the frequency, phase, and amplitude
of solar periodicities vary on time scales ranging from active region
lifetimes to solar cycle time scales. In this study the authors employ
a dynamic, or running, power spectral density analysis to determine
many periodicities and their time-varying nature in the projected
area of active sunspot groups (Sact), the SMM/ACRIM total
solar irradiance (S), the Nimbus-7 Mg II center-to-wing ratio (R(Mg
IIc/w)), the Ottawa 10.7 cm flux (F10.7), and the
GOES background X-ray flux (Xb) for the maximum, descending,
and minimum portions of solar cycle 21 (i.e., 1980-1986). This
technique dramatically illustrates several previously unrecognized
periodicities. For example, a relatively stable period at about 51 days
has been found in those indices which are related to emerging magnetic
fields. The majority of solar periodicities, particularly around 27,
150 and 300 days are quasiperiodic because they vary in amplitude and
frequency throughout the solar cycle. Finally, it is shown that there
are clear differences between the power spectral densities of solar
measurements from photospheric, chromospheric, and coronal sources.
Title: Modeling solar Lyman alpha irradiance.
Authors: Pap, J.; Hudson, H. S.; Rottman, G. J.; Willson, R. C.;
Donnelly, R. F.; London, J.
Bibcode: 1990NASCP3086..189P
Altcode: 1990cisv.nasa..189P
Solar Lyman alpha irradiance is estimated from various solar indices
using linear regression analyses. Models developed with multiple linear
regression analysis, including daily values and 81-day running means
of solar indices, predict reasonably well both the short-and long-term
variations observed in Lyman alpha. It is shown that the full disk
equivalent width of the He line at 1083 nm offers the best proxy for
Lyman alpha, and that the total irradiance corrected for sunspot effect
also has a high correlation with Lyman alpha.
Title: Sunspot Photometry and the Total Solar Irradiance Deficit
Measured in 1980 BY ACRIM
Authors: Steinegger, M.; Brandt, P. N.; Pap, J.; Schmidt, W.
Bibcode: 1990Ap&SS.170..127S
Altcode:
Until now a simple Photometric Sunspot Index (PSI) model was used
(e.g. Willsonet al., 1981) to describe the contribution of sunspots
to the solar irradiance deficit measurement by ACRIM. In this work we
replace this model by a photometry of sunspot pictures for the period
of 19 August to 4 September, 1980 taking into account the individual
features, like lightbridges or umbral dots, of each spot. The main
results of this preliminary analysis are: (1) theA u/A
p ratios and alsos the α values vary in a wide range and
are by no means constant as in the PSI model; (2) the general trend of
the irradiance deficit from our analysis agrees well with the ACRIM
measurements; (3) on some days there are differences of more than
50% between the deficits derived from our measurements and from the
PSI model.
Title: Variation of the solar constant and its connection with the
solar activity.
Authors: Pap, J.
Bibcode: 1990PADEU...9..296P
Altcode:
This paper investigates the connection between the variation of the
solar constant and the phenomena of solar activity on the basis of
measurements of the Nimbus-7 and SMM satellites, and of the data of
the catalogues "NOAA's Boulder Solar Geophysical Data" and "Solnechye
Dannye, Byulleten' (Solar Data)".
Title: Observed solar near UV variability: A contribution to
variations of the solar constant
Authors: London, Julius; Pap, Judit; Rottman, Gary J.
Bibcode: 1989maph...29....9L
Altcode:
Continuous Measurements of the Solar UV have been made by an instrument
on the Solar Mesosphere Explorer (SME) since October 1981. The results
for the wavelength interval 200 to 300 nm show an irradiance decrease
to a minimum in early 1987 and a subsequent increase to mid-April
1989. The observed UV changes during part of solar cycles 21 to 22
represent approx. 35 percent (during the decreasing phase) and 25
percent (during the increasing phase) of the observed variations of
the solar constant for the same time period as the SME measurements.
Title: Multi-spectral analysis of total solar irradiance variations
Authors: Froehlich, C.; Pap, J.
Bibcode: 1989A&A...220..272F
Altcode:
A multi-variate spectral analysis is used to investigate the influence
of sunspots by their area and classified according to their age and
bright magnetic elements as shown by the full-disk equivalent width
of the 1987 nm He-line on the total solar irradiance during 1980 and
1984/85. Most of the power in the spectrum of the SMM/ACRIM irradiance
variance is explained by the effect of the complex sunspots groups
showing new activity. The correlation with old sunspots is different
and in general much lower. During the solar minimum, when only a few
active regions are on the sun, the main contribution to the irradiance
variations arises from the active network, which is formed by the
breakup and dispersion of active regions. After eliminating the effect
of sunspots and bright magnetic elements from the irradiance power
spectrum, there are still peaks around 9 and 27 days, the strength of
which seems to vary with solar activity. This indicates that other large
scale effects produce irradiance variations, which may be modulated
by same effect as produces solar activity.
Title: Photometry of Solar Active Regions for the Analysis of
Irradiance Defects Measured in 1980 by ACRIM
Authors: Steinegger, M.; Brandt, P. N.; Pap, J.; Schmidt, W.
Bibcode: 1989AGAb....3....6S
Altcode:
No abstract at ADS
Title: SYSTEMATIC OBSERVATIONS OF THE SUN (In honour of Helen Dodson
Prince): Observations
Authors: McIntosh, P.; Snodgrass, H.; Mouradian, Z.; Harvey, K.;
Altrock, R.; Simon, P.; Legrand, J. -P.; Alissandrakis, G.; Neckel,
H.; Petropoulos, P.; Poulakis, X.; Gokhale, M. H.; Sivaraman, K. R.;
Pap, J.
Bibcode: 1989HiA.....8..672M
Altcode:
No abstract at ADS
Title: Solar irradiance variations and their relation with solar
flares.
Authors: Pap, J.; Vrsnak, B.
Bibcode: 1989sasf.confP.243P
Altcode: 1988sasf.conf..243P; 1989IAUCo.104P.243P
A clear association is demonstrated between the dips in the total solar
irradiance and flare occurrence. It is found that both the irradiance
dips and flares are related to emerging new activity.
Title: Correlation of solar irradiance variability with evolution
of activity
Authors: Pap, J.; Froehlich, C.
Bibcode: 1988AdSpR...8g..31P
Altcode: 1988AdSpR...8...31P
Results of multivariate analysis show that most of the total solar
irradiance variability is explained by the effect of active and to
a less amount by passive sunspots and bright magnetic elements. This
paper also demonstrates the limitation of simple analyses, as linear
regression or even bivariate analysis which can reveal only the most
obvious correlations between the used data sets.
Title: Variation of the Solar Constant Connected with the Coronal
Activity
Authors: Pap, Judit
Bibcode: 1987SoPh..109..373P
Altcode:
A strong correlation was found between the dips in the total solar
irradiance and the peaks in the active sunspot areas as well as in
the 260 MHz coronal radio flux. This connection might indicate that
Alfvén-waves, generated during the interaction of the magnetic fields
of the active sunspot groups with the convection, are able to transport
away part of the missing energy in the solar constant decreases. These
waves can heat the solar corona above the sunspot groups. Another part
of the missing energy could be re-radiated later, for example during
the decay of the active regions.
Title: Variation of the Solar Constant during 1983 and 1984
Authors: Pap, Judit
Bibcode: 1987SoPh..112..181P
Altcode:
Measurements of the Nimbus-7/ERB and SMM/ACRIM radiometers indicated
several dips in the total solar irradiance in 1983 and in the first part
of 1984. The dips in 1983, which should have a real solar origin, were
selected according to the peaks of the projected areas of the active
sunspot groups above the 2σ error limit of their data set. In the
first part of 1984 the sunspot activity was strong and few irradiance
dips with relatively large amplitudes were observed. In the second
part of 1984 the sunspot activity disappeared and at that time the
solar constant only fluctuated around its mean.
Title: Sunspot groups as tracers of radial differential rotation.
Authors: Gesztelyi, L.; Pap, J.
Bibcode: 1987PAICz..66...77G
Altcode: 1987eram....1...77G
Measurements of the proper motions of young bipolar sunspot groups show
that these groups rotate faster than the surrounding photosphere. The
faster proper motion of the young sunspot groups as well as the 24
days periodicity of the young active spot areas might indicate that
the young sunspots are connected to the deeper regions of the Sun
which rotate faster than the photosphere. Thus, the sunspot groups
in the early stage of their life would be an indicator of rotation of
the deeper layers of the Sun.
Title: Variation of the solar constant during the solar cycle.
Authors: Pap, Judit
Bibcode: 1986Ap&SS.127...55P
Altcode:
Measurements of the Nimbus-7 and Solar Maximum Mission satellites
reported temporary large decreases of the solar constant of the order
of a few tenths of a percent on a time-scale from days to weeks. Our
investigations show that these decreases were caused by ‘active’
sunspot groups with fast development and complex structure. This
connection between the solar constant variation and the appearance of
the active groups seems to be more clear in the maximum of the solar
activity. At the time of the solar minimum, mainly in the second part
of 1984, there were not any active sunspot groups practically on the
solar disk, the value of the solar constant only fluctuated around
its mean without large variation. The results of time series analyses
show that the periodicity of the solar constant values, of young and
active spot areas was nearly 23.5 days in 1980, which increases to 28
days towards the minimum of the solar cycle till 1983. During this
time interval the main periodicity of the old, ‘passive’ spot
areas was around 28 days. In 1984, at the time of the solar minimum,
there were not any obvious periodicities practically in the projected
areas of the different types of the sunspot groups.
Title: Variation of the Solar Constant during 1978-79 and 1981
Authors: Pap, J.
Bibcode: 1986BAICz..37..202P
Altcode:
The measurements of the Nimbus-7 and the SMM satellites indicate
decreases of the solar constant in the order of a few hundredths and
tenths of a percent on a time scale from days to weeks. It seems that
the largest decreases of the solar constant occurred when quickly
developing sunspot groups with complex structure were on the solar
disk. It seems that the magnetic fields of the 'active' sunspot groups
could stop the convection, and that the MHD waves originating during
this process could transport one part of the radiation deficit due to
the sunspots.
Title: Variation of the solar constant in connection with the solar
activity
Authors: Pap, J.
Bibcode: 1986CoSka..15..361P
Altcode:
Decreases of the solar constant were caused by the "active" sunspot
groups. At the time of the irradiance dips there were some peaks in the
values of the X-ray and radio flux intensity. It would be possible that
MHD-waves, generated during the interaction of the magnetic fields of
the active groups with the convection, could transport the "missing"
energy in the solar constant decreases.
Title: Connection of the solar constant variations with the age and
activity of sunspots
Authors: Pap, J.
Bibcode: 1986AdSpR...6h..65P
Altcode: 1986AdSpR...6...65P
Sunspot-related decreases of the solar constant appear mainly to depend
upon the activity of the sunspot groups. At the time of the irradiance
dips the increased solar radio flux on 260 MHz suggests that MHD-waves
could play an important role in the transportation of the missing energy
in the solar constant decreases. With disappearing sunspot activity,
in the second part of 1984, there were no large variations in the solar
constant or in the 260 MHz radio flux. This could indicate that the
level of the ``activity layers'' in the convective zone would be nearer
to the photosphere at the time of the solar minimum than of the maximum.
Title: Activity of Sunspots and Solar Constant Variations during 1980
Authors: Pap, J.
Bibcode: 1985SoPh...97...21P
Altcode:
A strong inverse correlation is shown between the irradiance dips
observed by the SMM/ACRIM radiometer and the projected areas of
the `active' sunspots. This strong correlation and the results of a
preliminary time series analysis indicate that the value of the solar
constant decreased when quickly developing sunspot groups with complex
structure occurred on the solar disk. On the other hand, when the
old groups with simple structure were dominant the value of the solar
constant increased slightly or these groups could reduce the effects
of the `active' spots. On the basis of our investigations it seems that
the formation of the sunspots and the new activity of the older ones as
well as the decreases of the solar constant may be the common symptoms
of such a physical process which takes place in deeper regions of the
Sun through the interaction of magnetic fields with the convection.
Title: Modulation of solar constant by active regions during 1980
Authors: Pap, J.
Bibcode: 1984AN....305...13P
Altcode:
The connection between the solar constant and the solar active regions
in the 1980s is considered. Solar geophysical data, solar data catalogs,
and satellite irradiance records are used to investigate how the value
of the solar constant is altered either by sunspot groups developing
quickly over time with a very complex magnetic structure or by 'older'
groups with a simple structure. It is found that large dips in the 1 AU
total solar irradiance occurred when the former type of sunspot could
be seen on the solar disk. When the recurring older groups with simple
structure were dominant, the value of the solar constant increased
slightly, or these older groups compensated for the effects of the
other group.
Title: Die Modulation der Solarkonstanten durch aktive Gebiete im
Jahre 1980
Authors: Pap, J.
Bibcode: 1984AN....305Q..13P
Altcode:
No abstract at ADS
Title: Modulation of Solar Constant by Active Regions during 1980
Authors: Pap, J.
Bibcode: 1984AN....305R..13P
Altcode:
No abstract at ADS