froehlich

explanation blue bibcodes open ADS page with paths to full text

Author name code: froehlich
ADS astronomy entries on 2022-09-14
author:"Froehlich, Claus" -title:"nucleosynthesis" -title:"supernova" -title:"nuclei" -title:"isotope" -title:"element"

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Title: VizieR Online Data Catalog: PUSH CCSN to explosions in
spherical symmetry. III. (Curtis+, 2019)
Authors: Curtis, S.; Ebinger, K.; Frohlich, C.; Hempel, M.; Perego,
A.; Liebendorfer, M.; Thielemann, F. -K.
2020yCat..18700002C Altcode:
In a previously presented proof-of-principle study, we established
a parameterized spherically symmetric explosion method (PUSH) that
can reproduce many features of core-collapse supernovae (CCSNe)
for a wide range of pre-explosion models. The method is based
on the neutrino-driven mechanism and follows collapse, bounce,
and explosion. There are two crucial aspects of our model for
nucleosynthesis predictions. First, the mass cut and explosion energy
emerge simultaneously from the simulation (determining, for each stellar
model, the amount of Fe-group ejecta). Second, the interactions between
neutrinos and matter are included consistently (setting the electron
fraction of the innermost ejecta). In the present paper, we use the
successful explosion models from Paper II (Ebinger+, 2019, J/ApJ/870/1)
that include two sets of pre-explosion models at solar metallicity,
with combined masses between 10.8 and 120Mȯ. We perform
systematic nucleosynthesis studies and predict detailed isotopic
yields. The resulting 56Ni ejecta are in overall agreement
with observationally derived values from normal CCSNe. The Fe-group
yields are also in agreement with derived abundances for metal-poor star
HD84937. We also present a comparison of our results with observational
trends in alpha element to iron ratios. (4 data files).

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Title: VizieR Online Data Catalog: PUSH CCSN to explosions in
spherical symmetry. II. (Ebinger+, 2019)
Authors: Ebinger, K.; Curtis, S.; Frohlich, C.; Hempel, M.; Perego,
A.; Liebendorfer, M.; Thielemann, F. -K.
2020yCat..18700001E Altcode:
In a previously presented proof-of-principle study, we established a
parameterized spherically symmetric explosion method (PUSH) that can
reproduce many features of core-collapse supernovae (CCSN). The present
paper goes beyond a specific application that is able to reproduce
observational properties of SN1987A and performs a systematic study of
an extensive set of nonrotating, solar metallicity stellar progenitor
models in the mass range from 10.8 to 120Mȯ. This includes
the transition from neutron stars to black holes as the final result
of the collapse of massive stars, and the relation of the latter
to supernovae, possibly faint supernovae, and failed supernovae. We
discuss the explosion properties of all models and predict remnant
mass distributions within this approach. The present paper provides
the basis for extended nucleosynthesis predictions in a forthcoming
paper to be employed in galactic evolution models. (1 data file).

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Title: Methodology to create a new total solar irradiance record:
Making a composite out of multiple data records
Authors: Dudok de Wit, Thierry; Kopp, Greg; Fröhlich, Claus;
Schöll, Micha
2017GeoRL..44.1196D Altcode: 2017arXiv170202341D
Many observational records critically rely on our ability to merge
different (and not necessarily overlapping) observations into a single
composite. We provide a novel and fully traceable approach for doing
so, which relies on a multiscale maximum likelihood estimator. This
approach overcomes the problem of data gaps in a natural way and uses
data-driven estimates of the uncertainties. We apply it to the total
solar irradiance (TSI) composite, which is currently being revised and
is critical to our understanding of solar radiative forcing. While the
final composite is pending decisions on what corrections to apply to
the original observations, we find that the new composite is in closest
agreement with the PMOD composite and the NRLTSI2 model. In addition, we
evaluate long-term uncertainties in the TSI, which reveal a 1/f scaling.

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Title: Were the May 2012 Emilia-Romagna earthquakes induced? A
coupled flow-geomechanics modeling assessment
Authors: Juanes, R.; Jha, B.; Hager, B. H.; Shaw, J. H.; Plesch, A.;
Astiz, L.; Dieterich, J. H.; Frohlich, C.
2016GeoRL..43.6891J Altcode:
Seismicity induced by fluid injection and withdrawal has emerged
as a central element of the scientific discussion around subsurface
technologies that tap into water and energy resources. Here we present
the application of coupled flow-geomechanics simulation technology
to the post mortem analysis of a sequence of damaging earthquakes
(Mw = 6.0 and 5.8) in May 2012 near the Cavone oil field,
in northern Italy. This sequence raised the question of whether these
earthquakes might have been triggered by activities due to oil and gas
production. Our analysis strongly suggests that the combined effects of
fluid production and injection from the Cavone field were not a driver
for the observed seismicity. More generally, our study illustrates
that computational modeling of coupled flow and geomechanics permits
the integration of geologic, seismotectonic, well log, fluid pressure
and flow rate, and geodetic data and provides a promising approach
for assessing and managing hazards associated with induced seismicity.

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Title: Determination of time-dependent uncertainty of the total
solar irradiance records from 1978 to present
Authors: Fröhlich, Claus
2016JSWSC...6A..18F Altcode:
 Aims: The existing records of total solar irradiance (TSI)
since 1978 differ not only in absolute values, but also show
different trends. For the study of TSI variability these records
need to be combined and three composites have been devised; however,
the results depend on the choice of the records and the way they are
combined. A new composite should be based on all existing records with
an individual qualification. It is proposed to use a time-dependent
uncertainty for weighting of the individual records. Methods:
The determination of the time-dependent deviation of the TSI records
is performed by comparison with the square root of the sunspot number
(SSN). However, this correlation is only valid for timescales of the
order of a year or more because TSI and SSN react quite differently
to solar activity changes on shorter timescales. Hence the results
concern only periods longer than the one-year-low-pass filter used in
the analysis. Results: Besides the main objective to determine an
investigator-independent uncertainty, the comparison of TSI with √SSN
turns out to be a powerful tool for the study of the TSI long-term
changes. The correlation of √SSN with TSI replicates very well the
TSI minima, especially the very low value of the recent minimum. The
results of the uncertainty determination confirm not only the need
for adequate corrections for degradation, but also show that a rather
detailed analysis is needed. The daily average of all TSI values
available on that day, weighted with the correspondingly determined
uncertainty, is used to construct a "new" composite, which, overall,
compares well with the Physikalisch-Meteorologisches Observatorium
Davos (PMOD) composite. Finally, the TSI - √SSN comparison proves to
be an important diagnostic tool not only for estimating uncertainties
of observations, but also for a better understanding of the long-term
variability of TSI.

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Title: Total Solar Irradiance: What Have We Learned from the Last
Three Cycles and the Recent Minimum?
Authors: Fröhlich, Claus
2013SSRv..176..237F Altcode: 2011SSRv..tmp..209F; 2011SSRv..tmp..133F; 2011SSRv..tmp...66F;
2011SSRv..tmp..366F
The record of total solar irradiance (TSI) during the past 35 years
shows similarities of the three solar cycles, but also important
differences. During the recent minimum with an unusually long periods
with no sunspots, TSI was also extremely low, namely 25% of a typical
cycle amplitude lower than in 1996. Together with the values during
the previous minima this points to a long-term change related to the
strength of solar activity. On the other hand, activity indices as
the 10.7 cm radio flux (F10.7), the CaII and MgII indices and also
the Ly- α irradiance, show a much smaller decrease. This means that
proxy models for TSI based on the photometric sunspot index (PSI),
and on e.g. MgII index to represent faculae and network have to
be complemented by a further component for the long-term change. TSI
values at minima are correlated with the simultaneous values of the open
magnetic field of the Sun at 1 AU and thus, these values may be used
as a surrogate for the long-term change component. Such a 4-component
model explains almost 85% of the variance of TSI over the three solar
cycles available. This result supports also the idea that the long-term
change of TSI is not due to manifestations of surface magnetism as the
solar cycle modulation, but due to a change of the global temperature
of Sun modulated by the strength of activity—being lower during low
activity. To explain the difference between the minima in 1996 and
2008 we need a change of only 0.25 K.

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Title: Reaction rate uncertainties and the ν p-process
Authors: Fröhlich, C.; Rauscher, T.
2012AIPC.1484..232F Altcode:
Current hydrodynamical simulations of core collapse supernovae find
proton-rich early ejecta. At the same time, the models fail to eject
neutron-rich matter, thus leaving the origin of the main r-process
elements unsolved. However, the proton-rich neutrino-driven winds
from supernovae have been identified as a possible production site
for light n-capture elements beyond iron (such as Ge, Sr, Y, Zr)
through the νp-process. The detailed nucleosynthesis patterns of
the νp-process depend on the hydrodynamic conditions and the nuclear
reaction rates of key reactions. We investigate the impact of reaction
rate uncertainties on the νp-process nucleosynthesis.

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Title: Total Solar Irradiance Observations
Authors: Fröhlich, Claus
2012SGeo...33..453F Altcode: 2011SGeo..tmp..123F
The record of total solar irradiance (TSI) during the past 35 years has
overlapping observations from space which can be merged to a composite,
and three are available, namely the PMOD, the ACRIM and the IRMB
composites. There are important differences between them, which are
discussed in detail in order to find the best representation of solar
variability during the last three cycles, for the following discussions
of solar irradiance variability. Moreover, the absolute value of TSI
from TIM on SORCE is 1,361 Wm-2, substantially lower than
the value 1,365 Wm-2, which was observed by the classical
radiometers. New results from specific experiments are now available,
which are discussed in order to define the value to be used in, e.g.,
climate models. The most important issue regarding the recent TSI
records is the low value observed during the minimum in 2009, which
is 25% of a typical cycle amplitude lower than the value in 1996. The
validity of this low value has been confirmed by comparing all existing
TSI observations during cycle 23. On the other hand, activity indices,
such as the sunspot number, the 10.7-cm radio flux (F10.7), the CaII
and MgII indices and also the Ly-α irradiance or the frequency changes
in low-order p modes, show a much smaller decreases relative to their
respective typical cycle amplitude. It is most likely that an increasing
contrast of the facular and network elements with decreasing magnetic
field is responsible for this discrepancy. The value of TSI at minima
is correlated with the open magnetic field of the Sun, B R,
at minima. Using B R at minima, interpolated linearly in
between as a fourth component of a proxy model based on the photometric
sunspot index and on the MgII index improves the explanation of the
variance of TSI over the full period of the last three solar cycles
to 84.7%. Results from other models are also discussed.

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Title: Astrophysical analysis of the measurement of (α,γ) and
(α,n) cross sections of 169Tm
Authors: Rauscher, T.; Kiss, G. G.; Szücs, T.; Fülöp, Zs.;
Fröhlich, C.; Gyürky, Gy.; Halász, Z.; Kertész, Zs.; Somorjai, E.
2012PhRvC..86a5804R Altcode: 2012arXiv1206.6113R
Reaction cross sections of 169Tm(α,γ)173Lu and
169Tm(α,n)172Lu have been measured in the energy
range 12.6≤Eα≤17.5 MeV and 11.5≤Eα≤17.5
MeV, respectively, using the recently introduced method of combining
activation with x-ray counting. Improved shielding made it possible
to measure the (α,γ) to lower energy than previously possible. The
combination of (α,γ) and (α,n) data made it possible to study the
energy dependence of the α width. While absolute value and energy
dependence are perfectly reproduced by theory at the energies above 14
MeV, the observed change in energy dependence at energies below 14 MeV
requires a modification of the predicted α width. Using an effective,
energy-dependent, local optical α+nucleus potential it is possible
to reproduce the data but the astrophysical rate is still not well
constrained at γ-process temperatures. The additional uncertainty
stemming from a possible modification of the compound formation
cross section is discussed. Including the remaining uncertainties,
the recommended range of astrophysical reaction rate values at 2 GK
is higher than the previously used values by factors of 2-37.

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Title: Observing and Modelling Earth's Energy Flows
Authors: Bengtsson, Lennart; Koumoutsaris, Symeon; Bonnet, Roger;
Allan, Richard P.; Fröhlich, Claus; Heintzenberg, Jost; Ingmann,
Paul; Kandel, Robert; Loeb, Norman G.; Soden, Brian; Trenberth, Kevin
2012omee.book.....B Altcode:
No abstract at ADS

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Title: Total Solar Irradiance Observations
Authors: Fröhlich, Claus
2012omee.book..121F Altcode:
No abstract at ADS

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Title: A four-component proxy model for total solar irradiance
calibrated during solar cycles 21-23
Authors: Fröhlich, C.
2011CoSka..41..113F Altcode:
The last solar activity minimum during 2008/09 was unusually long and
with extended periods without sunspots. During this period the total
solar irradiance (TSI) was much lower than during the previous minima
and no solar activity proxies show similarly low values. Proxy models
for TSI use a measure for the darkening of sunspots, the so-called
photometric sunspot index (PSI) and for the brightening of faculae
and network a chromospheric index. Because none of these can explain
the low TSI, a further component is needed, which describes the trend
between minima due to a still controversially discussed mechanism. A
new algorithm for the calculation of PSI is described which uses
individual factors for the different observing stations and a better
representation of the size-dependent contrast of spots. The proxy
model based on the new PSI, the long- and short-term Mg II index and a
trend based on the minima values of the open field explains almost 85
% of the variance of TSI over the last three solar cycles. Moreover,
it confirms the factor of ≈ 4 between the observed trend of TSI and
those of the chromospheric and other solar activity indices.

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Title: Determining reaction cross sections via characteristic
X-ray detection: α-induced reactions on 169Tm for the
astrophysical γ-process
Authors: Kiss, G. G.; Rauscher, T.; Szücs, T.; Kertész, Zs.; Fülöp,
Zs.; Gyürky, Gy.; Fröhlich, C.; Farkas, J.; Elekes, Z.; Somorjai, E.
2011PhLB..695..419K Altcode: 2010arXiv1012.0660K
The cross sections of the Tm169(α,γ)Lu173 and Tm169(α,n)Lu172
reactions have been measured first time using a new method, by
detecting the characteristic X-ray radiation following the electron
capture-decay of 172,173Lu. Despite the relatively long
half-life of the reaction products (T=500 and 6.7 days,
respectively) it was possible to measure the cross section of the
Tm169(α,γ)Lu173 reaction close to the Gamow window (T=3.5
GK), between E=13.16 and 17.08 MeV. The Tm169(α,n)Lu172
reaction cross section was measured from E=11.21 MeV up to
E=17.08 MeV. The experimental results have been compared
to theoretical predictions.

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Title: Spectral Solar Irradiance over Solar Cycle 23 from
Sunphotometers of VIRGO on SOHO (Invited)
Authors: Frohlich, C.
2010AGUFMGC33C..08F Altcode:
Within the VIRGO experiment on SOHO two 3-channel sunphotometers
(SPM) measure solar spectral irradiance at 402, 500 and 862 nm with a
bandwidth (FWHM) of 5 nm. The time series cover the period from April
1996 until present, more than 14 years and a full solar cycle from the
minimum in 1996 to the one in late 2008. SPMA measures the irradiance
continuously with a 1-minute sampling and after being exposed to the
sun during more than 14 years the sensitivities of the red, green
and blue channels are at 74.1, 24.3 and 7.1 percent of their first
light values, respectively. SPMB, is exposed rarely and is used to
monitor degradation; the result of a detailed analysis of these data
can then be used to correct SPMA for long-term changes and degradation
effects. These are determined by a degradation model and the result
shows that the changes due to exposure to the sun depend not only on the
exposure time and the cumulated dose of radiation received, but also on
the temperature of the instrument (Boltzmann factor). This indicates
that simple degradation corrections by e.g. fitting multi-degree
polynomials may not be adequate. The result of this detailed analysis
are reliable time series of solar spectral irradiance at the three
wavelengths. The results confirm the positive correlation of all
three channels with solar activity and TSI, which is in contrast to
the results from SIM on SORCE - at least for the green channel. A
possible long-term trend of the spectral irradiance is also discussed
in comparison with the behaviour of total solar irradiance (TSI).

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Title: Total Solar Irradiance during the Holocene using cosmogenic
10Be measured in polar ice cores
Authors: Steinhilber, F.; Beer, J.; Fröhlich, C.
2010ems..confE.791S Altcode:
The Sun is the main source of energy for the Earth, and its activity
has changed between states of high and low activity during the
Holocene. From paleo records it is known that climate changes coincide
with these changes in solar activity, raising the question about
the solar radiative forcing in past, present, and future climate. To
answer this question, one has to quantify how much the solar forcing
has changed. One important measure of the solar radiative forcing is
total solar irradiance (TSI). It has been measured with instruments
onboard spacecrafts since 1978. Besides the distinct 11-year solar
cycle variation, these measurements show also a decreasing trend in the
11-year cycle minima. This indicates that like other solar activity
records TSI also varies on time scales longer than 11 years. Prior
to 1978 TSI has to be reconstructed. Of special interest is thereby
to know TSI not only for periods of high solar activity as we had in
the past 50 years, but also for periods when the Sun was very quiet,
such as during the Maunder Minimum (1645-1715). Here we present the
first record of TSI covering almost the entire Holocene. Our record is
based on a relationship between TSI and the open solar magnetic field
both observed with spacebased instruments. The open solar magnetic
field is obtained for the past from cosmogenic radionuclides, such as
e.g. 10Be, which is measured in polar ice cores. Using 10Be enabled
us to reconstruct TSI much further back than the existing record
of sunspots, which is widely used as a proxy for TSI. The resulting
increase in the 11-year cycle averaged TSI from the Maunder Minimum
to the present is (0.9±0.4) Wm^-2, corresponding to a global average
radiative forcing of about (0.16±0.07) Wm^-2. This change compares
well with very recent sunspot-based reconstructions of TSI, but is
smaller by a factor of three than those TSI reconstructions commonly
used in climate studies. Our reconstruction together with climate
models allows for exploring the role of solar forcing in climate change.

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Title: The Signature of Flares in VIRGO Total Solar Irradiance
Measurements
Authors: Quesnel, A.; Dennis, B. R.; Fleck, B.; Fröhlich, C.; Hudson,
H. S.; Tolbert, A. K.
2010ASPC..428..133Q Altcode: 2010arXiv1003.4194Q
We use Total Solar Irradiance (TSI) measurements from the VIRGO
(Variability of solar Irradiance and Gravity Oscillations) instrument
on board SOHO to obtain preliminary estimates of the mean total
radiative energy emitted by X-class solar flares. The basic tool is
that of summed-epoch analysis, which has also enabled us to detect and
partially characterize systematic errors present in the basic data. We
describe these errors, which significantly degrade the photometry at
high frequencies. We find the ratio of GOES 1-8 Å luminosity to total
bolometric luminosity to be of order 0.01.

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Title: The quest for the solar g modes
Authors: Appourchaux, T.; Belkacem, K.; Broomhall, A. -M.; Chaplin,
W. J.; Gough, D. O.; Houdek, G.; Provost, J.; Baudin, F.; Boumier,
P.; Elsworth, Y.; García, R. A.; Andersen, B. N.; Finsterle, W.;
Fröhlich, C.; Gabriel, A.; Grec, G.; Jiménez, A.; Kosovichev, A.;
Sekii, T.; Toutain, T.; Turck-Chièze, S.
2010A&ARv..18..197A Altcode: 2010A&ARv.tmp....1A; 2009arXiv0910.0848A
Solar gravity modes (or g modes)—oscillations of the solar interior
on which buoyancy acts as the restoring force—have the potential
to provide unprecedented inference on the structure and dynamics of
the solar core, inference that is not possible with the well-observed
acoustic modes (or p modes). The relative high amplitude of the g-mode
eigenfunctions in the core and the evanesence of the modes in the
convection zone make the modes particularly sensitive to the physical
and dynamical conditions in the core. Owing to the existence of the
convection zone, the g modes have very low amplitudes at photospheric
levels, which makes the modes extremely hard to detect. In this article,
we review the current state of play regarding attempts to detect g
modes. We review the theory of g modes, including theoretical estimation
of the g-mode frequencies, amplitudes and damping rates. Then we go
on to discuss the techniques that have been used to try to detect g
modes. We review results in the literature, and finish by looking to
the future, and the potential advances that can be made—from both
data and data-analysis perspectives—to give unambiguous detections
of individual g modes. The review ends by concluding that, at the time
of writing, there is indeed a consensus amongst the authors that there
is currently no undisputed detection of solar g modes.

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Title: An Investigation Of The Metallicity Dependence Of The Sn Type
Ii Mn Production
Authors: Kim, Yeunjin; Sobeck, J.; Frohlich, C.; Truran, J.
2010AAS...21542509K Altcode: 2010BAAS...42..337K
Element abundance trends over the history of our Galaxy serve as
important guides in establishing relative contributions from supernovae
of Types Ia and II. In particular, spectroscopic studies have revealed a
deficiency of manganese (Mn) relative to the abundances of neighboring
iron-peak nuclei in metal-poor stars. However, more recent analyses
of the observational data have found a constant Mn/Fe abundance ratio
over a wide range of metallicity and hence, contradict these previous
findings. In this project, we will study the nucleosynthetic yields
of Type II supernovae as a function of metallicity by parameterizing
the initial properties of the shock. We will compare our results with
the two distinct manganese abundance trends identified above. Once
we study the metallicity dependency of Type II yields as reflected in
observations at lower metallicities, we will explore the constraints
this imposes on Type Ia supernova contributions to Mn in different
stellar and galactic populations. We acknowledge the financial
support by the National Science Foundation for the Frontier Center
Joint Institute for Nuclear Astrophysics (JINA). C.F. acknowledges an
Enrico Fermi Fellowship.

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Title: Photons - from source to detector
Authors: Wilhelm, Klaus; Frohlich, Claus
2010ISSIR...9...23W Altcode:
The central theme of the book "Observing Photons in Space" is the
detection and characterization of photons with instruments aboard
spacecraft. This chapter presents a global overview of the fundamental
processes that accompany photons all the way from their origin in the
source region to their detection in our instruments. The radiation of
the Sun is taken as example in some cases and is treated in more detail.

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Title: The r-, p-, and νp-Process
Authors: Thielemann, F. -K.; Dillmann, I.; Farouqi, K.; Fischer, T.;
Fröhlich, C.; Kelic-Heil, A.; Korneev, I.; Kratz, K. -L.; Langanke,
K.; Liebendörfer, M.; Panov, I. V.; Martinez-Pinedo, G.; Rauscher, T.
2010JPhCS.202a2006T Altcode:
The processes discussed in this review are three of the four
nucleosynthesis processes involved in producing heavy nuclei beyond
Fe (not counting the rp-process in X-ray bursts). Opposite to the
fourth process (the s-process), which operates in stellar evolution
during He- and C-burning, they are all related to explosive burning
phases, (presumably) linked to core collapse supernova events
of massive stars. The (classical) p-process is identified with
explosive Ne/O-burning in outer zones of the progenitor star. It is
intitiated by the passage of the supernova shock wave and acts via
photodisintegration reactions like a spallation process which produces
neighboring (proton-rich) isotopes from pre-existing heavy nuclei. The
reproduction of some of the so-called lighter p-isotopes with A &lt;
100 faces problems in this environment. The only recently discovered
νp-process is related to the innermost ejecta, the neutrino wind
expelled from the hot proto-neutron star after core collapse in the
supernova explosion. This neutrino wind is proton-rich in its early
phase and reactions with neutrinos permit to overcome decay/reaction
bottlenecks for the flow beyond the Fe-group, thus permitting the
production of those p-isotopes, which face problems in the classical
p-process scenario. The understanding of the r-process, being identified
for a long time with rapid neutron captures - and passing through nuclei
far from stability - is still experiencing major problems. These are
on the one hand related to nuclear uncertainties far from stability
(masses and half-lives), affecting the process speed and abundance
peaks, on the other hand the site is still not definitely located,
yet. Later neutron-rich, high entropy phases of the neutrino wind
could permit its operation, other options include the ejection of
very neutron-rich neutron star matter. Two different environments
are required for a weak and a main/strong r-process, witnessed by
observations of low metallicity stars.

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Title: Solar radiometry
Authors: Frohlich, Claus
2010ISSIR...9..525F Altcode:
The classical radiometry for total solar irradiance (TSI) measurements
is described using examples of the four types of radiometers currently
used in space. The design, characterization and operation of these
radiometers are described. Besides the instrumental characteristics
determining the measurement uncertainties, an important issue is
possible long-term changes of the radiometers exposed to solar
irradiance -- especially in the EUV -- and the space environment. A
model for the degradation has been developed which can explain the
behaviour of most radiometers in space. The TSI record since 1978 from
different platforms and radiometers can be combined in a composite
time series which demonstrates that although the assumed uncertainty
of the present state-of-the-art radiometers is insufficient, their
short- and long-term precision is good enough to produce a reliable
time series of TSI over almost 30 years.

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Title: Total Solar Irradiance during the past 9300 Years inferred
from the Cosmogenic Radionuclide Beryllium-10
Authors: Steinhilber, F.; Beer, J.; Frohlich, C.
2009AGUFMGC24A..03S Altcode:
The Sun is the main source of energy for the Earth. There is growing
evidence that climate changes in the past coincide with changes in
solar activity. This raises the question about the Sun’s role in
past, present, and future global change. To answer this question,
the total solar irradiance (TSI) has to be known not only for the
present period of high solar activity, but also for periods when the
Sun was very quiet, such as the Maunder Minimum (1645-1715). Direct
instrumental data of TSI goes only back to 1978. We present the first
reconstruction of TSI covering the past 9300 years. It is based on a
recently derived relationship between observed TSI and the open solar
magnetic field. The open solar magnetic field can be obtained from
the cosmogenic radionuclide Beryllium-10 measured in ice cores. Thus,
Beryllium-10 allows reconstructing TSI much further back than the
existing record of sunspots, which is often used as a proxy. The
resulting increase in the average TSI from the Maunder Minimum to the
present amounts to (0.9±0.4)Wm-2 corresponding to a global radiative
forcing of (0.16±0.07)Wm-2. This change is smaller than previous
TSI reconstructions commonly used in climate studies. In combination
with climate models, our reconstruction offers the possibility to
quantitatively test the claimed links between solar forcing and
climate change.

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Title: Total solar irradiance during the Holocene
Authors: Steinhilber, F.; Beer, J.; Fröhlich, C.
2009GeoRL..3619704S Altcode:
For the first time a record of total solar irradiance covering 9300
years is presented, which covers almost the entire Holocene. This
reconstruction is based on a recently observationally derived
relationship between total solar irradiance and the open solar
magnetic field. Here we show that the open solar magnetic field can
be obtained from the cosmogenic radionuclide 10Be measured
in ice cores. Thus, 10Be allows to reconstruct total solar
irradiance much further back than the existing record of the sunspot
number which is usually used to reconstruct total solar irradiance. The
resulting increase in solar-cycle averaged TSI from the Maunder Minimum
to the present amounts to (0.9 ± 0.4) Wm-2. In combination
with climate models, our reconstruction offers the possibility to test
the claimed links between climate and TSI forcing.

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Title: Solar Surface Magnetism and Irradiance on Time Scales from
Days to the 11-Year Cycle
Authors: Domingo, V.; Ermolli, I.; Fox, P.; Fröhlich, C.; Haberreiter,
M.; Krivova, N.; Kopp, G.; Schmutz, W.; Solanki, S. K.; Spruit, H. C.;
Unruh, Y.; Vögler, A.
2009SSRv..145..337D Altcode:
The uninterrupted measurement of the total solar irradiance during the
last three solar cycles and an increasing amount of solar spectral
irradiance measurements as well as solar imaging observations
(magnetograms and photometric data) have stimulated the development
of models attributing irradiance variations to solar surface
magnetism. Here we review the current status of solar irradiance
measurements and modelling efforts based on solar photospheric
magnetic fields. Thereby we restrict ourselves to the study of solar
variations from days to the solar cycle. Phenomenological models
of the solar atmosphere in combination with imaging observations of
solar electromagnetic radiation and measurements of the photospheric
magnetic field have reached high enough quality to show that a large
fraction (at least, about 80%) of the solar irradiance variability
can be explained by the radiative effects of the magnetic activity
present in the photosphere. Also, significant progress has been made
with magnetohydrodynamic simulations of convection that allow us to
relate the radiance of the photospheric magnetic structures to the
observations.

---------------------------------------------------------
Title: Evidence of a long-term trend in total solar irradiance
Authors: Fröhlich, C.
2009A&A...501L..27F Altcode:
Aims: During the solar minimum of 2008, the value of total solar
irradiance at 1 AU (TSI) was more than 0.2 Wm-2 lower
than during the last minimum in 1996, indicating for the first time a
directly observed long-term change. On the other hand, chromospheric
indices and hence solar UV irradiance do not exhibit a similar
change. Methods: Comparison of TSI with other activity parameters
indicates that only the open solar magnetic field, BR,
observed from satellites at 1 AU show a similar long-term behaviour. The
values at the minima correlate well and the linear fit provides a
direct physical relationship between TSI and BR during the
minimum times. Results: This correlation allows an unambiguous
reconstruction of TSI back in time, provided the open solar magnetic
field can be determined from e.g. geomagnetic indices or cosmogenic
radionucleides. Since the solar UV irradiance has no long-term trend,
the mechanism for the secular change of TSI must differ from the effect
of surface magnetism, as manifested by sunspots, faculae, and network
which indeed explain well the intra-cycle variability of both total and
spectral irradiance. Conclusions: The long-term trend of TSI is
most probably caused by a global temperature change of the Sun that
does not influence the UV irradiance in the same way as the surface
magnetic fields. Appendix is only available in electronic form
at http://www.aanda.org

---------------------------------------------------------
Title: Recent Anomalous TSI Decrease Not Due To Low Polar Facula and
Network Areas: Time to Broaden Our View of Solar Luminosity Variation?
Authors: Foukal, Peter V.; Bernasconi, P.; Frohlich, C.
2009SPD....40.1113F Altcode:
Total solar irradiance (TSI) values measured during the present activity
minimum by the VIRGO, ACRIM, and TIM radiometers are significantly (
0.018% +/- 0.006 % rms) lower than reported during the last minimum
in 1996 (1). This decrease represents 1/4 the amplitude of 11 -
yr TSI variation. Differences in spots, faculae and active network
cannot account for this anomalous decrease. A sufficient difference
in the TSI contribution from quiet network also seems unlikely, since
the solar microwave flux index, F10.7, has dipped only 4 % below
its 1996 minimum. This is an order of magnitude less than required
to explain the TSI decrease by a decline in network area. The
remaining explanation in terms of photospheric magnetic structures,
might lie in a decrease in the area of polar faculae, whose cycle
amplitude is presently at a minimum for this century. We evaluate
their TSI contribution using area and contrast measurements with
the Solar Bolometric Imager (SBI), together with polar facula counts
(2). We find that their TSI contribution between the present and 1996
activity minima, is below 0.002%. This is again, an order of magnitude
below the observed TSI decrease. We conclude that the anomalous TSI
decrease is unlikely to be caused by photospheric magnetic changes. This
suggests that solar luminosity may be able to change significantly
over decadal time scales through an as- yet- unidentified, relatively
shallow mechanism that avoids the 10*5 year thermal relaxation time of
the solar convection zone. This work was supported at Heliophysics,
Inc by NSF grant ATM 0718305, and at APL by NASA grant NNG 05WC07G References: 1. Frohlich, C. 2008, AGU Fall Meeting, Abstract #
SH21C-05. 2. Sheeley, N. 2008, Ap.J. , 680, 1553.

---------------------------------------------------------
Title: Total solar irradiance variability: What have we learned
about its variability from the record of the last three solar cycles?
Authors: Fröhlich, C.
2009cwse.conf..217F Altcode:
Since November 1978 a set of total solar irradiance (TSI)
measurements from space is available, yielding a time series of
almost 30~years. Presently, there are three TSI composites available,
called PMOD, ACRIM and IRMB, which are all constructed from the same
original data, but use different procedures to correct for sensitivity
changes. The PMOD composite is the only one which also corrects the
early HF data for degradation. The origin of the differences between
the three composite are discussed by comparison with the record of
ERBE. For the discussion of the similarities and differences of the
three cycles the PMOD composite is used. The most interesting feature
is the low value of TSI at the present minimum which cannot be seen
in proxies such as F10.7, CaK and MgII indices. Thus,
we see for the first time an effect on TSI which is not due to the
direct effect of the superficial magnetic structures of solar activity

---------------------------------------------------------
Title: Erratum: "Iron-60 Evidence for Early Injection and
Efficient Mixing of Stellar Debris in the Protosolar Nebula" <A
href="bib_query\?2008ApJ...686..560D">(2008, APJ, 686, 560)</A>
Authors: Dauphas, N.; Cook, D. L.; Sacarabany, A.; Fröhlich, C.;
Davis, A. M.; Wadhwa, M.; Pourmand, A.; Rauscher, T.; Gallino, R.
2009ApJ...691.1943D Altcode:
Due to an error in processing the data, some values of
epsilon60 Ni corrected for instrumental mass
fractionation using 61Ni/58Ni ratios are
incorrect. The corrected Table 2 is appended below. Nevertheless,
the shifts that result from this correction are all within error bars
and do not affect the conclusions of the paper. The figures are also
unaffected.

---------------------------------------------------------
Title: Cause of Deep Moonquakes
Authors: Nakamura, Y.; Frohlich, C.
2008AGUFM.P31B1407N Altcode:
It is well known that the occurrence of deep moonquakes is highly
correlated with the solid tides raised by Earth and the Sun. However,
it has long been debated whether the tides are simply acting as a
triggering mechanism for a release of accumulated tectonic stresses
in the Moon's interior or the tides themselves are responsible for
their generation, releasing tidally dissipated energy in the form of
moonquakes. One way to test which of these two hypotheses is correct
is to see when deep moonquakes occur relative to the long- term tidal
amplitude variations caused by the changing position of the Sun relative
to the eccentric orbit of the Moon around Earth. If the tides are simply
acting as a trigger mechanism, deep moonquakes are more likely to occur
when the tidal stress amplitudes are increasing, while if the tides
are the main cause of deep moonquakes, they are more likely to occur
shortly after the peaks in tidal stress amplitudes. We thus examined
the frequency of deep moonquake occurrence as reported in the recently
updated lunar event catalog relative to the difference between the
anomalistic and synodic phases. Tidal stress amplitude reaches maxima
when this phase difference is 0°, i.e., a new moon coincides with a
perigee crossing, and when it is 180°, i.e., a full moon coincides with
a perigee crossing. The result shows a general trend of maximum activity
shortly following each of the tidal amplitude maxima, supporting the
tidal generation hypothesis. However, an additional peak activity is
found shortly before the tidal amplitude maximum at phase difference
of 180°, also supporting the tidal triggering hypothesis in certain
restricted cases. This secondary peak is limited only to some, but not
all, deep moonquake nests. These trends are independent of whether the
deep moonquake epicenters are located in either of the E-W hemispheres
and in which of the tidal stress regimes as determined by the distance
to the sub-earth point. Thus it appears that deep moonquakes generally
represent release of tidally dissipated energy with additional triggered
release of accumulated tectonic stress at a limited number of specific
locations. However, this conclusion is provisional because the Apollo
data did not cover the entire 18-year tidal cycle of the Moon.

---------------------------------------------------------
Title: Total solar irradiance during the last three cycles:
Uncertainities of the long-term behaviour
Authors: Frohlich, C.
2008AGUFMGC32A..06F Altcode:
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of 30 years. Presently,
there are three TSI composites available, called PMOD, ACRIM and
IRMB, which are all constructed from the same original data, but use
different procedures to correct for long-term sensitivity changes. The
PMOD composite is the only one which also corrects the early HF data for
degradation and thus allows to compare all three cycles. This composite
can now be used to assess the uncertainty of the long-term behaviour
of TSI by comparison with independent measurements from ERBE and for
the cycle 23 which is based on VIRGO data also with ACRIM-II on UARS,
ACRIM-III on ACRIM-Sat and TIM on SORCE. Also different reconstructions
from magnetograms and proxy data can be used, although the long-term
behaviour of the reconstructions may not be comparable to the one of
TSI. The result of this assessment is important not only for climate
studies, but also for reconstructions of TSI back to e.g. the Maunder
Minimum time.

---------------------------------------------------------
Title: Total solar irradiance during the last three cycles: What
does the low present solar minimum tell us about long-term trends?
Authors: Frohlich, C.
2008AGUFMSH21C..05F Altcode:
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of 30 years. Presently,
there are three TSI composites available, called PMOD, ACRIM and IRMB,
which are all constructed from the same original data, but use different
procedures to correct for long-term sensitivity changes. The PMOD
composite is the only one which also corrects the early HF data for
degradation. The results are not only important for solar radiometry
from space, but they also provide a more reliable TSI during cycle
21. The comparison with a 3-component proxy model during this cycle
allows also to expand it back to the minimum around 1975. Moreover,
the PMOD composite uses VIRGO TSI data which cover the full cycle
23 with the same radiometers. This allows a direct comparison of the
present minimum with the one in 1996 which can then be used to determine
trends over a solar cycle. Comparison with the minima of the other two
cycles allows some conclusions about the origin of long-term trends in
TSI. The long- term variation of TSI must be due to another mechanism
than the well established cycle variation, which is very similar to the
variation of the spectral irradiance. This mechanism is most probably
a global temperature change which is somewhat related to the amplitude
of the cycle, that is to the total magnetic field.

---------------------------------------------------------
Title: Mass measurements in the vicinity of the rp-process and
the νp-process paths with the Penning trap facilities JYFLTRAP
and SHIPTRAP
Authors: Weber, C.; Elomaa, V. -V.; Ferrer, R.; Fröhlich, C.;
Ackermann, D.; Äystö, J.; Audi, G.; Batist, L.; Blaum, K.; Block,
M.; Chaudhuri, A.; Dworschak, M.; Eliseev, S.; Eronen, T.; Hager,
U.; Hakala, J.; Herfurth, F.; Heßberger, F. P.; Hofmann, S.;
Jokinen, A.; Kankainen, A.; Kluge, H. -J.; Langanke, K.; Martín,
A.; Martínez-Pinedo, G.; Mazzocco, M.; Moore, I. D.; Neumayr,
J. B.; Novikov, Yu. N.; Penttilä, H.; Plaß, W. R.; Popov, A. V.;
Rahaman, S.; Rauscher, T.; Rauth, C.; Rissanen, J.; Rodríguez, D.;
Saastamoinen, A.; Scheidenberger, C.; Schweikhard, L.; Seliverstov,
D. M.; Sonoda, T.; Thielemann, F. -K.; Thirolf, P. G.; Vorobjev, G. K.
2008PhRvC..78e4310W Altcode: 2008arXiv0808.4065W
The masses of very neutron-deficient nuclides close to the
astrophysical rp- and νp-process paths have been determined with the
Penning trap facilities JYFLTRAP at JYFL/Jyväskylä and SHIPTRAP at
GSI/Darmstadt. Isotopes from yttrium (Z=39) to palladium (Z=46) have
been produced in heavy-ion fusion-evaporation reactions. In total,
21 nuclides were studied, and almost half of the mass values were
experimentally determined for the first time: Tc88, Ru90-92, Rh92-94,
and Pd94,95. For the Pd95m, (21/2+) high-spin
state, a first direct mass determination was performed. Relative mass
uncertainties of typically δm/m=5×10-8 were obtained. The
impact of the new mass values has been studied in νp-process
nucleosynthesis calculations. The resulting reaction flow and the
final abundances are compared with those obtained with the data of
the Atomic Mass Evaluation 2003.

---------------------------------------------------------
Title: Iron 60 Evidence for Early Injection and Efficient Mixing of
Stellar Debris in the Protosolar Nebula
Authors: Dauphas, N.; Cook, D. L.; Sacarabany, A.; Fröhlich, C.;
Davis, A. M.; Wadhwa, M.; Pourmand, A.; Rauscher, T.; Gallino, R.
2008ApJ...686..560D Altcode: 2008arXiv0805.2607D
Among extinct radioactivities present in meteorites,60Fe
(t1/2 = 1.49 Myr) plays a key role as a high-resolution
chronometer, a heat source in planetesimals, and a fingerprint of the
astrophysical setting of solar system formation. A critical issue with
60Fe is that it could have been heterogeneously distributed
in the protoplanetary disk, calling into question the efficiency
of mixing in the solar nebula or the timing of 60Fe
injection relative to planetesimal formation. If this were the case,
one would expect meteorites that did not incorporate 60Fe
(either because of late injection or incomplete mixing) to show
60Ni deficits (from lack of 60Fe decay)
and collateral effects on other neutron-rich isotopes of Fe and Ni
(coproduced with 60Fe in core-collapse supernovae and AGB
stars). Here, we show that measured iron meteorites and chondrites have
Fe and Ni isotopic compositions identical to Earth. This demonstrates
that 60Fe must have been injected into the protosolar
nebula and mixed to less than 10% heterogeneity before formation of
planetary bodies.

---------------------------------------------------------
Title: 60Fe in the cosmic blender
Authors: Dauphas, N.; Cook, D. L.; Sacarabany, A.; Fröhlich, C.;
Davis, A. M.; Wadhwa, M.; Pourmand, A.; Rauscher, T.; Gallino, R.
2008GeCAS..72Q.200D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: What can observed solar irradiance variability tell us about
possible long-term changes of the Sun?
Authors: Frohlich, C.; Beer, J.; Steinhilber, F.
2008AGUSMSP23A..05F Altcode:
Total solar irradiance (TSI) measurements from different satellites
are available since late 1978 and may be extended by reliable models
back to the minimum between cycles 19 and 20 around 1976. This time
series shows a downward trend of the cycle averaged data since the
eighties. Although this trend is also present in other solar activity
related parameters, such as the sunspot numbers, the 10.7cm radio flux,
or the MgII index, only the open magnetic flux from the sun (from OMNI2
IMF-B data set) shows besides the same trend values during the minima
which are comparable to the ones observed in TSI. Thus, a sensitivity
of TSI during the minima relative to the ones of the open magnetic
field can be determined. This sensitivity allows to determine TSI
during past minima back to the 1880ties when the measurements started
on which the reconstruction of the open field can be based. This allows
also to compare TSI with the 10Be data and possibly 'calibrate' them
back in time.

---------------------------------------------------------
Title: Iron-60 Injection in the Protosolar Nebula: How Early and
How Well Mixed?
Authors: Dauphas, N.; Cook, D. L.; Sacarabany, A.; Frohlich, C.;
Davis, A. M.; Wadhwa, M.; Pourmand, A.; Rauscher, T.; Gallino, R.
2008LPI....39.1170D Altcode:
Iron and nickel isotopic analyses of meteorites indicate that
60Fe must have been injected into the protosolar nebula
and mixed at the 10% level before formation of planetary bodies.

---------------------------------------------------------
Title: How Tides Control Some Individual Deep Moonquake Nests
Authors: Frohlich, C.; Nakamura, Y.
2007AGUFM.P43C..06F Altcode:
Seismic stations emplaced during the Apollo missions operated from 1969
to 1977, and the most numerous signals identified in these data were
deep moonquakes (DMQ). These occurred mostly at depths of 700-1200 km
within a few hundred discrete clusters or nests, and within individual
nests DMQ occurrence times correlated strongly with the gravitational
tide generated by the Earth. However, the relationship with tides
differs markedly at different nests, and we still don't understand
either the mechanical origin of DMQ or why the tides exercise such
strong control on their occurrence. We here investigate what controls
episodes of DMQ occurrence in about a dozen DMQ nests where the
temporal pattern is distinct and highly repeatable. In these nests,
plots of occurrence times vs anomalistic phase exhibit a very regular
drift pattern influenced by both the anomalistic and draconic periods,
and often modulated by a roughly sinusoidal component having a period
of about seven months. We show that extrema of the normal component of
the tidal stress often exhibit a nearly identical pattern. In several
of these nests there is a linear relationship between the normal and
shear components of the tidal stress when DMQ occur. If we use a Mohr
circle analysis to interpret these observations they suggest the static
friction coefficient is extraordinarily low, about 0.1 or less. This is
lower than ordinary geological materials, and may indicate that trapped
fluids or other exotic phases play a role in the faulting process.

---------------------------------------------------------
Title: Geographic Variations in the Tidal Control of Deep Moonquake
Nests and Speculation About Their Mechanical Origin
Authors: Frohlich, C.; Nakamura, Y.
2007LPI....38.1749F Altcode:
We group nests of deep moonquakes into categories depending on how
their occurrence depends on the anomalistic or draconic month. For
well-located nests having 20 or more individual events, we show that
epicenters of some categories are geographically sep

---------------------------------------------------------
Title: Reconstruction of solar irradiance variations in cycles 21-23
based on surface magnetic fields
Authors: Wenzler, T.; Solanki, S. K.; Krivova, N. A.; Fröhlich, C.
2006A&A...460..583W Altcode:
Aims.We present a reconstruction of total solar irradiance (TSI) back
to 1974, i.e. from the minimum of cycle 21 to the declining phase of
cycle 23. We also present a cross-calibration between the magnetograms
obtained by the 512 channel magnetograph and the spectromagnetograph
at Kitt Peak. Methods: .The TSI reconstruction is carried out
using data from the 512-channel Diode Array Magnetograph and the newer
spectromagnetograph on Kitt Peak. The model is based on the assumption
that all irradiance changes on time-scales of a day and longer are
entirely due to the variations of the surface distribution of the
solar magnetic field. The reconstructed irradiance is compared with
the composite of total solar irradiance measurements from PMOD/WRC
(version 41). Results: .A good correspondence is found with the
PMOD TSI composite, with no bias between the three cycles on time-scales
longer than the solar rotation period, although the accuracy of the
TSI reconstruction is somewhat lower when 512 channel magnetograph
data are used. This suggests that the same driver of the irradiance
variations, namely the evolution of the magnetic flux at the solar
surface, is acting in cycles 21-23. Different methods of comparing
the magnetograms obtained by the two Kitt Peak magnetographs give
somewhat different results, with factors by which 512 channel data
must be divided in the range 1.38-1.63 being found. This is due to the
non-linearity of the relationship between the magnetic field measured
by the two instruments.

---------------------------------------------------------
Title: Geographic Variations in Tidal Control of Deep Moonquake Nests
Authors: Frohlich, C.; Nakamura, Y.
2006AGUFM.U41C0831F Altcode:
Understanding variations in the tidal response of deep moonquake
(DMQ) nests may help us understand the origin of deep moonquakes. We
have grouped nests of deep moonquakes into categories depending on
how strongly their occurrence is influenced by the anomalistic or
draconic month and the phase of this dependence. For well-located nests
having 20 or more individual events, epicenters of some categories
are geographically separated from one another on the Moon. The tidal
potential caused by the Earth with mass M at distance R varies over
the Moon's surface and is proportional to (3cos2θ - 1)M/R3, where θ
is the angle between the point of interest and an axis E-M joining the
line of centers. The solid tidal deformation causes the Moon's shape
to be ellipsoidal with the long axis directed along E-M. The potential
is zero when θ is 24° and thus along a small circle of this radius
the tangential strain is zero. When θ is 55° the surface curvature
of the tidal ellipsoid is unchanged and thus the radial strain is
zero. For any fixed location on the Moon the tidal deformation changes
because the E-M axis moves ±8° EW over the Moon's surface during
the anomalistic month as the Earth-Moon distance changes and affects
the angular rate at which the Moon orbits Earth. The E-M axis moves
±7° NS during the draconic month because the orbital plane doesn't
coincide with the Moon's equator. The Sun affects the orientation
of the long axis of the tidal deformation ellipsoid by less than
0.3°. We thus determine the angular distance θ between individual
DMQ and the E-M axis, and search for features in the distribution
of hypocenters near the nodes at 24° and 55°. We separate DMQ into
three categories: wA - occurrence weakly correlated with anomalistic
phase; sAp - occurrence strongly correlated with anomalistic phase;
DMQ occur mostly as Moon approaches perigee; sAa - occurrence strongly
correlated with anomalistic phase; DMQ occur mostly as Moon approaches
apogee. DMQ in the sAp group are rare or absent at θ&lt;~20°; DMQ in
the sAa group are common at θ&lt;~20°; the wA group doesn't appear to
correlate with distance. Similarly, if we use draconic phase behavior as
a classifier we find that DMQ strongly correlated with draconic phase
are rare or absent at θ&lt;~20° whereas DMQ weakly correlated with
draconic phase do not appear to correlate with distance. We speculate
that the different categories of DMQ may represent distinct mechanical
phenomena. For example, the sAa group may represent the growth of faults
as the shape of the Moon changes in response to its slow retreat from
the Earth. The sAp group may come about because tidal shear stresses
drive fluids that repeatedly shift blocks within the lunar mantle.

---------------------------------------------------------
Title: The internal structure of the Sun inferred from g modes and
low-frequency p modes
Authors: Elsworth, Y. P.; Baudin, F.; Chaplin, W; Andersen, B;
Appourchaux, T.; Boumier, P.; Broomhall, A. -M.; Corbard, T.;
Finsterle, W.; Fröhlich, C.; Gabriel, A.; García, R. A.; Gough,
D. O.; Grec, G.; Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii,
T.; Toutain, T.; Turck-Chièze, S.
2006ESASP.624E..22E Altcode: 2006soho...18E..22E
The Phoebus group is an international collaboration of
helioseismologists, its aim being to detect low-frequency solar g
modes. Here, we report on recent work, including the development and
application of new techniques based on the detection of coincidences
in contemporaneous datasets and the asymptotic properties of the g-mode
frequencies. The length of the time series available to the community is
now more than ten years, and this has reduced significantly the upper
detection limits on the g-mode amplitudes. Furthermore, low-degree p
modes can now be detected clearly at frequencies below 1000 μHz.

---------------------------------------------------------
Title: Variations in solar luminosity and their effect on the
Earth's climate
Authors: Foukal, P.; Fröhlich, C.; Spruit, H.; Wigley, T. M. L.
2006Natur.443..161F Altcode:
Variations in the Sun's total energy output (luminosity) are caused
by changing dark (sunspot) and bright structures on the solar
disk during the 11-year sunspot cycle. The variations measured from
spacecraft since 1978 are too small to have contributed appreciably to
accelerated global warming over the past 30 years. In this Review,
we show that detailed analysis of these small output variations
has greatly advanced our understanding of solar luminosity change,
and this new understanding indicates that brightening of the Sun is
unlikely to have had a significant influence on global warming since
the seventeenth century. Additional climate forcing by changes in the
Sun's output of ultraviolet light, and of magnetized plasmas, cannot
be ruled out. The suggested mechanisms are, however, too complex to
evaluate meaningfully at present.

---------------------------------------------------------
Title: Solar Irradiance Variability Since 1978. Revision of the
PMOD Composite during Solar Cycle 21
Authors: Fröhlich, C.
2006SSRv..125...53F Altcode: 2006SSRv..tmp...90F
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of more than 25
years. Presently, there are three TSI composites available, called PMOD,
ACRIM and IRMB, which are all constructed from the same original data,
but use different procedures to correct for sensitivity changes. The
PMOD composite is the only one which also corrects the early HF data
for degradation. The results from the detailed analysis of the VIRGO
radiometry allow a good understanding of the effects influencing
the long-term behaviour of classical radiometers in space. Thus,
a re-analysis of the behaviour of HF/NIMBUS-7 and ACRIM-I/SMM was
indicated. For the former the situation is complicated by the fact that
there are no in-flight means to determine changes due to exposure to
solar radiation by comparison with a less exposed radiometer on the same
spacecraft. The geometry and optical property of the cavity of HF is,
however, very similar to the PMO6-type radiometers, so the behaviour
of the PMO6V radiometers on VIRGO can be used as a model. ACRIM-I had
to be revised mainly due to a henceforth undetected early increase and
a more detailed analysis of its degradation. The results are not only
important for solar radiometry from space, but they also provide a more
reliable TSI during cycle 21. The differences between the revised PMOD
composite and the ACRIM and IRMB are discussed by comparison with a
TSI reconstruction from Kitt-Peak magnetograms. As the PMOD composite
is the only one which has reliable data for cycle 21, the behaviour
of the three solar cycles can now be compared and the similarities
and differences discussed.

---------------------------------------------------------
Title: Review of the Long-Term Performance of the PMO6 Radiometers
on VIRGO/SOHO
Authors: Finsterle, W.; Fröhlich, C.; Schlifkowitz, U.
2006ESASP.617E..58F Altcode: 2006soho...17E..58F
No abstract at ADS

---------------------------------------------------------
Title: Recent Progresses on g-Mode Search
Authors: Appourchaux, T.; Andersen, B.; Baudin, F.; Boumier, P.;
Broomhall, A. -M.; Chaplin, W.; Corbard, T.; Elsworth, Y.; Finsterle,
W.; Fröhlich, C.; Gabriel, A.; Garcia, R.; Gough, D. O.; Grec, G.;
Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii, T.; Toutain, T.;
Turck-Chièze, S.
2006ESASP.617E...2A Altcode: 2006soho...17E...2A
No abstract at ADS

---------------------------------------------------------
Title: Total Solar Irradiance Variability: What Have We Learned from
SOHO/VIRGO about Solar Cycle 23?
Authors: Fröhlich, C.
2006ESASP.617E..60F Altcode: 2006soho...17E..60F
No abstract at ADS

---------------------------------------------------------
Title: Possible Extra-Solar-System Cause for Certain Lunar Seismic
Events
Authors: Nakamura, Y.; Frohlich, C.
2006LPI....37.1048N Altcode:
All but a few of a rare class of events detected by the Apollo lunar
seismic network occurred when the Moon faced a fixed direction on the
celestial sphere. This suggests that a source outside the solar system
may be responsible for causing them.

---------------------------------------------------------
Title: ISS-SOLAR: Total (TSI) and spectral (SSI) irradiance
measurements
Authors: Schmidtke, G.; Fröhlich, C.; Thuillier, G.
2006AdSpR..37..255S Altcode:
The primary objective of the ISS-SOLAR mission on Columbus (to be
launched in 2006) is the quasi-continuous measurement of the solar
irradiance variability with highest possible accuracy. For this reason
the total spectral range will be recorded simultaneously from 3000 to
17 nm by three sets of instruments: SOVIM is combining two types of
absolute radiometers and three-channel filter radiometers. SOLSPEC
is composed of three double monochromators using concave gratings,
covering the wavelength range from 3000 to 180 nm. SOL-ACES has four
grazing incidence planar grating spectrometers plus two three-signal
ionization chambers (two signals from a two stage chamber plus a
third signal from a silicon diode at the end of the chamber) with
exchangeable band pass filters to determine the absolute fluxes from
220 to 17 nm repeatedly during the mission. For the TSI the relative
standard uncertainty (RSU) to be achieved is of the order of 0.15%
and for the SSI from 1% in the IR/Vis, 2% in the UV, 5% in the FUV up
to 10% in the XUV spectral regions. The general requirements for the
TSI and SSI measurements and their conceptual realization within this
payload will be discussed with emphasis on instrumental realization
and calibration aspects.

---------------------------------------------------------
Title: Possible extra-solar-system cause for shallow moonquakes
Authors: Frohlich, C.; Nakamura, Y.
2006epsc.conf..301F Altcode:
Reanalysis of lunar seismic data collected during the Apollo program
indicates that 23 of the 28 rare events known as high-frequency
teleseismic (HFT) events or shallow moonquakes occurred during one-half
of the sidereal month when the seismic network on the Moon's near
side faced approximately towards right ascension of 12 hours on the
celestial sphere. Statistical analysis demonstrates that there is about
a 1 per cent probability that this pattern would occur by chance. In
a coordinate system fixed to the celestial sphere, the 26 located HFT
events tend to cluster around a direction approximately between the
constellations Leo and Cancer (L-C); in this coordinate system the
clustering is significant at about the 97% level. With respect to this
celestial coordinate system and direction L-C, 13 of 26 events are
situated near the Moon's limb (between 70° and 110° from the point
on the lunar surface closest to L-C). Although there is a possibility
that the observed clustering of HFT events is purely a statistical
coincidence, if it isn't a random phenomenon it has great scientific
importance and thus we here seriously consider other possibilities. HFT
events are clearly a seismic phenomenon and not an artifact of the
data collection process. Most are observed on all four stations of
the Apollo lunar network, exhibiting onset times of P and S that are
separated by intervals appropriate for seismic wave transmission through
the Moon. These observations cannot be explained by, for example,
a shower of cosmic rays that interferes with seismograph electronics
or data transmission. We also show that HFT events are not caused by
ordinary meteoroid impacts or by tidal stresses. One possibility is
that high-energy objects from a fixed source outside the solar system
trigger or even cause the HFT events. High-energy astrophysicists
have proposed that exotic particles such as nuggets of strange quark
matter (SQM) might cause or trigger HFT events and this has motivated
so-far-unsuccessful searches for terrestrial seismic signals produced
by SQM passage. Recent estimates show that the seismically quiet lunar
surface provides a better environment than Earth to observe the signals
produced by SQM nuggets. The observations of HFT events occurring
preferentially near the Moon's limb as observed from direction L-C
might indicate that these exotic particles release residual seismic
stresses as they pass horizontally through the Moon's lithosphere.

---------------------------------------------------------
Title: A renewed look at deep moonquakes in the Apollo seismic data
Authors: Nakamura, Y.; Frohlich, C.
2006epsc.conf..281N Altcode:
We have recently been reanalyzing the deep moonquake data from the US
Apollo project because recent advancement of computer capability now
allows us to perform much more sophisticated analyses to extract further
information from this 30-year old data set. In this presentation, we
will review our new findings to date and discuss future directions. We
started with identifying the more than 9000 catalogued but unidentified
events with waveform cross-correlation and single-link analysis, which
resulted in more than fivefold increase in positively identified
deep moonquakes to over 7000 and a discovery of nearly 250 new
deep moonquake nests. We then examined the newly discovered deep
moonquake nests to see if any of them were located on the far side,
considering that seismic sources located on the opposite side from
seismic stations would provide information on very deep interior of the
Moon, including a possible lunar core. About 30 nests were identified
as likely candidates, but none of them were within 40 degrees from
the antipode of the Moon, suggesting that either that the antipodal
region of the Moon is aseismic, or the very deep interior of the Moon
severely attenuates or deflects seismic waves. With the newly expanded
list of deep moonquakes, we reexamined the distribution of hypocenters
in the A1 deep moonquake nest using relative hypocenter locations with
cross-spectral analysis. Contrary to our expectations with greatly
increased number of events belonging to this nest, the extent of the
A1 source region remained the same as in our earlier analysis, i.e.,
within about 1-km radius. This strengthens our earlier conclusion that
time-varying slip direction at the source is necessary to explain the
variation in waveforms of events belonging to the nest. Similar analyses
for several other nests appear to show similar results. Although
the data clearly indicate that tidal stress influences many nests,
the physical mechanism responsible is not apparent. Our new analysis
correlating the tidal deformation of the Moon with temporal distribution
of events at different nests appears to suggest some systematic trends,
but it is too early to draw any conclusions. A good understanding of
this relationship will be a great help in understanding of earthquake
occurrence here on Earth, where tidal triggering of earthquakes has
been an elusive subject for a long time.

---------------------------------------------------------
Title: Weak interaction rates
Authors: Martinez-Pinedo, Gabriel; Kelic, A.; Langanke, K.; Schmidt,
K. -H.; Mocelj, D.; Fröhlich, C.; Thielemann, F. -K.; Panov, I.;
Rauscher, T.; Liebendörfer, M.; Zinner, N. T.; Pfeiffer, B.; Buras,
R.; Janka, H. -Th.
2006isna.confE..64M Altcode: 2006PoS....28E..64M
This manuscript reviews recent progress in our understanding of the
nucleosynthesis of medium and heavy elements in supernovae. Recent
hydrodynamical models of core-collapse supernovae show that a
large amount of proton rich matter is ejected under strong neutrino
fluxes. This matter constitutes the site of the ν p-process where
antineutrino absorption reactions catalyze the nucleosynthesis
of nuclei with A &gt; 64. Supernovae are also associated with the
r-process responsible for the synthesis of the heaviest elements
in nature. Fission during the r-process can play a major role in
determining the final abundance patter and in explaining the almost
universal features seen in metal-poor r-process-rich stars.

---------------------------------------------------------
Title: Correlation Between Cosmic-Ray Intensity and Total Solar
Irradiance during the last three Solar Cycles
Authors: Frohlich, C.; Beer, J.; Muscheler, R.
2005AGUFMSH41A1110F Altcode:
For reconstructions of the total solar irradiance (TSI) into the past
it is important to understand the relation between the production of
cosmogenic isotopes and TSI. The production rate is a function of the
cosmic-ray intensity reaching the Earth, which is well represented by
the neutron monitors. As theses data are available since well before
the start of cycle 21 a direct comparison with the PMOD composite of TSI
can be performed. For the correlation different lags of the cosmic-ray
intensity for the odd and even cycles have to be taken into account,
as well as different amplitudes. Both the cosmic-ray intensity and TSI
are modulated by the solar activity related magnetic fields. While the
cosmic ray intensity depends only on the open fields a major question
is still how the open fields are related to the weak fields in the
network on the Sun which seem to be responsible for the solar-cycle
modulation of TSI. The much stronger fields on the solar surface on
the other hand are responsible for the short-term variation related
to sunspots and faculae. The implications of this comparison for the
understanding of the relation between the production of cosmogenic
isotopes and TSI will be discussed.

---------------------------------------------------------
Title: Comparison of the PMOD, ACRIM and IRMB Composite Total Solar
irradiance time series
Authors: Frohlich, C.
2005AGUFMSH33C..02F Altcode:
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of more than 25
years. From measurements made by different space radiometers (HF
on NIMBUS~7, ACRIM I on SMM, ACRIM II on UARS, VIRGO on SOHO, ACRIM
III on ACRIMSat and TIM on SORCE) a composite record of TSI can be
constructed. Presently, there are three composites available, called
PMOD, ACRIM and IRMB, which all are based on the same original data
before the advent of VIRGO on SOHO. Afterwards, the ACRIM composite is
using ACRIM-II and III and the PMOD and IRMB VIRGO data. The differences
arise from the different ways to correct for sensitivity changes. A
further difference is that the PMOD composite also corrects the early
HF data for degradation and thus can provide reliable data for TSI
around the maximum of solar cycle 21 before the advent of ACRIM-I. The
origin of the differences will be discussed in detail and illustrated
by comparison with ERBE data and a independent TSI reconstruction from
Kitt-Peak magnetograms.

---------------------------------------------------------
Title: Solar Irradiance Variability since 1978
Authors: Fröhlich, C.
2005MmSAI..76..731F Altcode:
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of more than 25
years. From measurements made by different space radiometers (HF
on NIMBUS 7, ACRIM I on SMM, ACRIM II on UARS, VIRGO on SOHO, ACRIM
III on ACRIMSat and TIM on SORCE) a composite record of TSI can be
constructed. Presently, there are three such composites available,
called PMOD, ACRIM and IRMB, which all are based on the same original
data, but use different ways to correct for sensitivity changes. The
PMOD composite is the only one which also corrects the early HF data for
degradation and can provide reliable data for TSI around the maximum of
solar cycle 21. The results from the detailed analysis of the VIRGO
radiometry allow a good understanding of the effects influencing
the long-term behaviour of classical radiometers in space. Thus,
a re-analysis of the long-term behaviour of HF and ACRIM-I was
performed. The results are not only important for solar radiometry
from space, but they also provide a more credible TSI during cycle
21. Thus the revised PMOD composite allows to better quantify the
behaviour of solar cycle 21 relative to the two recent ones which
differ in several aspects.

---------------------------------------------------------
Title: The Sun, from Core to Corona and Solar Wind
Authors: von Steiger, R.; Fröhlich, C.
2005ISSIR...3...99V Altcode: 2005ssb..book...99V; 2005ESASR...3...99V
No abstract at ADS

---------------------------------------------------------
Title: Solar radiative output and its variability: evidence and
mechanisms
Authors: Fröhlich, Claus; Lean, Judith
2004A&ARv..12..273F Altcode: 2004A+ARv..12..273F
Electromagnetic radiation from the Sun is Earth’s primary energy
source. Space-based radiometric measurements in the past two decades
have begun to establish the nature, magnitude and origins of its
variability. An 11-year cycle with peak-to-peak amplitude of order 0.1 %
is now well established in recent total solar irradiance observations,
as are larger variations of order 0.2 % associated with the Sun’s
27-day rotation period. The ultraviolet, visible and infrared spectral
regions all participate in these variations, with larger changes at
shorter wavelengths. Linkages of solar radiative output variations with
solar magnetism are clearly identified. Active regions alter the local
radiance, and their wavelength-dependent contrasts relative to the quiet
Sun control the relative spectrum of irradiance variability. Solar
radiative output also responds to sub-surface convection and to
eruptive events on the Sun. On the shortest time scales, total
irradiance exhibits five minute fluctuations of amplitude ≈ 0.003 %,
and can increase to as much as 0.015 % during the very largest solar
flares. Unknown is whether multi-decadal changes in solar activity
produce longer-term irradiance variations larger than observed thus
far in the contemporary epoch. Empirical associations with solar
activity proxies suggest reduced total solar irradiance during the
anomalously low activity in the seventeenth century Maunder Minimum
relative to the present. Uncertainties in understanding the physical
relationships between direct magnetic modulation of solar radiative
output and heliospheric modulation of cosmogenic proxies preclude
definitive historical irradiance estimates, as yet.

---------------------------------------------------------
Title: Re-analysis of the long-term changes of the NIMBUS-7 radiometer
and behaviour of total solar irradiance during solar cycle 21
Authors: Frohlich, C.
2004AGUFMSH53A0301F Altcode:
Only one radiometer - called Hickey-Frieden (HF) - is within the ERB
package on NIMBUS-7 for the measurement of total solar irradiance
(TSI) and thus changes due to exposure to solar radiation cannot be
directly determined by comparison with a less exposed radiometer
on the same spacecraft. The geometry and optical property of the
cavity of HF is, however, very similar to the PMO6-type radiometers,
it is essentially a copy of it with increased size. For the PMO6V
on VIRGO/SOHO two main effects have been identified, a rapid early
increase and a slow decrease, normally termed degradation, which can
be modelled with a hyperbolic function taking the actual dose into
account (Fröhlich, 2003). The corrections used by Fröhlich and Lean
(1998) for the composite were based on early results from VIRGO and
used simple exponential functions. With the recent results from VIRGO
a re-analysis of the long-term behaviour of HF is necessary. The
results are not only important for solar radiometry from space, but
also to improve the reliability of TSI before the start of ACRIM-I in
early 1980. The latter will allow to better quantify the behaviour
of solar cycle 21 and to compare it with the two recent ones which
differ in several aspects. C. Fröhlich. Long-term behaviour of space
radiometers. Metrologia, 40:60--65, 2003. C. Fröhlich and J. Lean. The
sun's total irradiance: Cycles and trends in the past two decades
and associated climate change uncertainties. Geophys. Res. Lett.,
25:4377--4380, 1998.

---------------------------------------------------------
Title: Total Solar Irradiance Variation During Rapid Sunspot Growth
Authors: Zahid, H. Jabran; Hudson, Hugh S.; Fröhlich, Claus
2004SoPh..222....1Z Altcode:
Large sunspot areas correspond to dips in the total solar irradiance
(TSI), a phenomenon associated with the local suppression of
convective energy transport in the spot region. This results in a
strong correlation between sunspot area and TSI. During the growth
phase of a sunspot other physics may affect this correlation; if the
physical growth of the sunspot resulted in surface flows affecting
the temperature, for example, we might expect to see an anomalous
variation in TSI. In this paper we study NOAA active region 8179,
in which large sunspots suddenly appeared near disk center, at a time
(March 1998) when few competing sunspots or plage regions were present
on the visible hemisphere. We find that the area/TSI correlation does
not significantly differ from the expected pattern of correlation,
a result consistent with a large thermal conductivity in solar
convection zone. In addition we have searched for a smaller-scale
effect by analyzing white-light images from MDI (the Michelson Doppler
Imager) on SOHO. A representative upper-limit energy consistent with
the images is on the order of 3×1031 ergs, assuming the
time scale of the actual spot area growth. This is of the same order
of magnitude as the buoyant energy of the spot emergence even if it
is shallow. We suggest that detailed image analyses of sunspot growth
may therefore show `transient bright rings' at a detectable level.

---------------------------------------------------------
Title: Excess facular emission from an isolated active region during
solar minimum: the example of NOAA AR 7978
Authors: Ortiz, A.; Domingo, V.; Sanahuja, B.; Fröhlich, C.
2004JASTP..66...67O Altcode: 2004JATP...66...67O
The facular contribution to solar irradiance variations on the short
time scale is studied by analyzing a simple case of an isolated active
region that crossed the solar disk during the 1996 minimum of activity,
NOAA AR 7978. Its passage during several Carrington rotations,
specifically from rotation 1911 to 1916, allows us to analyze the
evolution of the angular distribution of the excess radiance of
the facular region using SOHO/VIRGO and MDI data. We associate this
evolution with the evolution of the extent corresponding to the isolated
active region as well as with the aging of the region itself. Finally,
we evaluate the total (i.e. in all directions) emission of this facular
region and its spectral and temporal evolution.

---------------------------------------------------------
Title: Resonance analysis of 147 Sm ( n,α
) cross sections: Comparison to optical model calculations and
indications of nonstatistical effects
Authors: Koehler, P. E.; Gledenov, Yu. M.; Rauscher, T.; Fröhlich, C.
2004PhRvC..69a5803K Altcode: 2003astro.ph.12088K
We have measured the 147 Sm ( n,α ) cross
section from 3 eV to 500 keV and performed an R -matrix analysis in the
resolved region ( En &lt;700 eV ) to extract α widths for
104 resonances. We computed strength functions from these resonance
parameters and compared them to transmission coefficients calculated
using optical model potentials similar to those employed as inputs to
statistical model calculations. The statistical model often is used
to predict cross sections and astrophysical reaction rates. Comparing
resonance parameters rather than cross sections allows more direct tests
of potentials used in the model and hence should offer greater insight
into possible improvements. In particular, an improved α+nucleus
potential is needed for applications in nuclear astrophysics. In
addition to providing a more direct test of the α+nucleus potential,
the α -width distributions show indications of nonstatistical effects.

---------------------------------------------------------
Title: Total solar irradiance variation during rapid sunspot growth
Authors: Zahid, H. J.; Hudson, H. S.; Frohlich, C.
2004cosp...35.2769Z Altcode: 2004cosp.meet.2769Z
Large sunspot areas correspond to dips in the total solar irradiance
(TSI), a phenomenon associated with the local suppression of convective
energy transport in the spot region. During the growth of a sunspot
other physics might conceivably affect the resulting correlation
between sunspot area and TSI. We study NOAA active region 8179, in
which large sunspots suddenly appeared near disk center, at a time
(March 1998) when few competing sunspots or plage regions were present
on the visible hemisphere. We find that the area/TSI correlation does
not significantly differ from the expected pattern of correlation,
a result consistent with the expected thermal conductivity of the
solar convection zone. In addition we have searched for a smaller-scale
effect by analyzing white-light images from MDI (the Michelson Doppler
Imager) on SOHO. A representative upper-limit energy consistent with
the images is on the order of 3 X 1031 ergs, assuming the time scale
of the actual spot area growth. This is the same order of magnitude
as the buoyant energy of the spot emergence even if it is shallow. We
suggest that detailed image analyses of sunspot growth may therefore
show "transient bright rings" at a detectable level.

---------------------------------------------------------
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.
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 Irradiance Variability
Authors: Fröhlich, Claus
2004GMS...141...97F Altcode:
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of more than
23 years. From measurements made by different space radiometers
(HF on NIMBUS 7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on
SOHO) a composite record of TSI can be compiled. This leads to a
reliable record of TSI with an overall precision of the order of
0.05 Wm-2. This time series is compared to an empirical
model based on sunspot darkening and brightening due to faculae and
network. Since early 1996 spectral measurements by filter-radiometers of
VIRGO provide continuous time series of spectral solar irradiance (SSI)
at 402, 500 and 862 nm. These time series are analyzed and compared
to TSI yielding information about the redistribution of energy within
the spectrum during changes of TSI.

---------------------------------------------------------
Title: ISS-SOLAR: Total (TSI) and Spectral (SSI) Irradiance
Measurements
Authors: Schmidtke, G.; Thuillier, G.; Fröhlich, C.
2004cosp...35.2503S Altcode: 2004cosp.meet.2503S
Related to the climatic aspects in atmospheric science the primary
objective of the ISS-SOLAR Mission on Columbus (to be launched in 2006)
is the quasi-continuous measurement of the solar irradiance variation
with highest possible accuracy. For this reason the total spectral range
will be recorded simultaneously for the first time from 3000-16 nm by
three sets of instruments: SOVIM(3) is combining two types of absolute
radiometers and three-channel filterradiometers. SOLSPEC(2) is composed
of three concave grating spectrometers with two monochromators, each,
covering the wavelength range from 3000-180 nm. SOL-ACES(1) has four
grazing incidence planar grating spectrometers plus two three-signal
ionization chambers with exchangeable band pass filters to determine
the absolute fluxes from 220-16 nm repeatedly during the mission. For
the TSI the absolute accuracy to be achieved is of the order of 0.1 %
and for the SSI from 1 % in the VIS, 2 % in the UV, 5 % in the FUV
to 10 % in the XUV spectral regions. The general requirements for the
TSI and SSI measurements and their conceptual realization within the
payload will be discussed with emphasis on instrumental realization
and calibration aspects.

---------------------------------------------------------
Title: Preface
Authors: Pap, Judit M.; Fox, Peter; Fröhlich, Claus; Hudson, Hugh S.;
Kuhn, Jeffrey; McCormack, John; North, Gerald; Sprigg, William; Wu,
S. T.
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: Measurements of the total and spectral solar irradiance:
what do we have and what will we get in future?
Authors: Thuillier, G.; Fröhlich, C.; Schmidtke, G.
2004cosp...35.1277T Altcode: 2004cosp.meet.1277T
Total and spectral solar irradiance (TSI and SSI) and their variability
play a key role as input to the Earth's and - in more general terms
- to all planetary atmospheres. Modeling of the properties of these
atmospheres in terms of composition, thermal structure and dynamics have
been significantly improved in recent years. Thus, the demand for more
accurate solar irradiance data has increased accordingly. On the other
hand, the solar physics community needs such data in order to improve
the understanding of the mechanisms leading to solar variability without
which no reliable long-term predictions are possible. The results from
8 years of the ESA/NASA SOHO mission and from the recently launched
US satellites TIMED and SORCE demonstrate the present state-of-the-art
capabilities for TSI and SSI. We summarize the present knowledge of TSI
and SSI together with estimates of the uncertainties involved. We show
also what the three instruments of SOLAR to be flown in 2006 on board
the International Space Station will contribute to the long-term record
with observations of TSI and the solar spectrum between 17 to 3000
nm. Moreover, in 2008 the data will be supplemented by TSI measurements
and some spectral channels of PICARD, a French microsatellite. As it
looks now, we will have overlapping measurements of total and spectral
solar irradiance - at least until about 2010 - which is very promising.

---------------------------------------------------------
Title: Solar irradiance variation during rapid sunspot growth
Authors: Zahid, H.; Frohlich, C.; Hudson, H.
2003AGUFMSH32A1102Z Altcode:
Large sunspot areas correspond to dips in the total solar irradiance
(TSI), a phenomenon associated with the local suppression of
convective energy transport in the spot region. Observations show
a strong correlation between spot area and TSI. During the growth
phase of a sunspot, though, other physics might conceivably affect
this correlation. In this study we analyze the growth phase of NOAA
active region 8179, in which large sunspots suddenly appeared near
disk center at a time when few competing sunspots or plage regions were
present on the visible hemisphere. The spot area of AR 8179 increased
by a factor of two in less than 12 hours on March 13, 1998. The study
makes use of the continuum images from SOHO/MDI and total-irradiance
data from SOHO/VIRGO. We find that the area/TSI correlation does
not significantly differ from the expected pattern of correlation,
a result consistent with high thermal conductivity even at small
depths below the photosphere. We have also searched for localized
irradiance variations (transient bright rings) associated with the
period of rapid growth. We discuss the significance of this lack of
irradiance signatures of spot formation.

---------------------------------------------------------
Title: Total Solar Irradiance Variability from 1978 to present
Authors: Fröhlich, C.
2003AGUFMSH31C..04F Altcode:
Since February 1996 VIRGO radiometers observe total solar irradiance
from SOHO at L1, allowing continuous and uninterrupted observations
of the Sun. Besides the 3-month gap during the SOHO vacation in
summer 1998 and a few other minor gaps the record covers more than
99% of the almost 8 years of operation. This allows a very detailed
assessment of the long-term behaviour of the two VIRGO radiometers,
PMO6V and DIARAD. The results of this analysis are presented and their
implications for other space radiometers discussed. With these data
and those from HF/NIMBUS7, ACRIM-I/SMM and ACRIM-II/UARS a composite
of total solar irradiance (TSI) is presented (updated and improved
from Fröhlich and Lean, 1998), which covers now almost three solar
cycles starting in November 1978, just before the maximum of solar
cycle 21. Radiometrically the composite is based on ACRIM-I and
ACRIM-II, with the latter shifted to the scale of ACRIM-I. During the
gap between ACRIM-I and II the results from the HF radiometer are
used. These data need to be corrected for a change which was first
detected by comparison with ERBS. The inclusion or omittance of this
change is the main reason for the discrepancy between this composite
and the one presented by Willson and Mordvinov (2003). The discussion
concentrates on this change and its determination by comparison of
HF with ERBS and a proxy model for interpolation between its 14-day
observations. Comparison of the composite with ERBS over the period
from 1984-2003 supports very strongly the validity and need of the HF
correction and confirms that TSI had no significant trend over the
last 25 years of observation from space. References: C. Fröhlich
and J. Lean, 1998, The Sun's Total Irradiance: Cycles and Trends in
the Past Two Decades and Associated Climate Change Uncertainties,
Geophys. Res. Let., 25, 4377--4380 R. C. Willson and A.~V. Mordvinov,
2003, Secular Total Solar Irradiance trend during solar cycles 21-23,
Geophys. Res. Let., 30, 1199--1202

---------------------------------------------------------
Title: Spectral Solar Irradiance Variability from {VIRGO} on {SOHO}:
1996 to present
Authors: Fröhlich, C.; Wachter, R.; Wehrli, C.
2003AGUFMSH12A1152F Altcode:
Since February 1996 VIRGO filterradiometers on SOHO monitor spectral
solar irradiance at 402, 500 and 862nm with a bandwidth of 5nm. SOHO's
vantage point at L1 allows uninterrupted observations of the Sun,
24 h a day and 365 days an year. Besides the 3-month gap during the
SOHO vacation in summer 1998 and a few other minor gaps the record
covers more than 99% of the period up to now of almost 8 years of
observations. The long-term behaviour of the operational channels is
dominated by instrumental degradation masking the solar variability
signature. However, comparisons with the back-up channels allows
to take off some of the instrumental long-term variation, and the
resulting time series can now provide reliable information about
variability with periods up to about 4--500 days. Time series with
the long-term variation removed and the corresponding periodogram
show many similarities between the three channels and total solar
irradiance. Details about the spectral redistribution during changes of
TSI are investigated by multivariate spectral analysis. Furthermore,
comparison of the spectral analysis of the cleaned 1-minute sampled
time series during solar minimum (1996/7) and maximum (2001/2)
allows to asses the variation of power with the activity cycle in a
range from about 30 nHz (about 1 year period) up to 8 mHz (5-minute
oscillations). The variability with activity of the three colours is
compared with the one of TSI.

---------------------------------------------------------
Title: Traceable radiometry underpinning terrestrial- and
helio-studies (TRUTHS)
Authors: Fox, N.; Aiken, J.; Barnett, J. J.; Briottet, X.; Carvell,
R.; Frohlich, C.; Groom, S. B.; Hagolle, O.; Haigh, J. D.; Kieffer,
H. H.; Lean, J.; Pollock, D. B.; Quinn, T.; Sandford, M. C. W.;
Schaepman, M.; Shine, K. P.; Schmutz, W. K.; Teillet, P. M.; Thome,
K. J.; Verstraete, M. M.; Zalewski, E.
2003AdSpR..32.2253F Altcode:
The Traceable Radiometry Underpinning Terrestrial- and Helio-
Studies (TRUTHS) mission offers a novel approach to the provision
of key scientific data with unprecedented radiometric accuracy
for Earth Observation (EO) and solar studies, which will also
establish well-calibrated reference targets/standards to support
other EO missions. This paper presents the TRUTHS mission and its
objectives. TRUTHS will be the first satellite mission to calibrate
its EO instrumentation directly to Sl in orbit, overcoming the usual
uncertainties associated with drifts of sensor gain and spectral shape
by using an electrical rather than an optical standard as the basis
of its calibration. The range of instruments flown as part of the
payload will also provide accurate input data to improve atmospheric
radiative transfer codes by anchoring boundary conditions, through
simultaneous measurements of aerosols, particulates and radiances
at various heights. Therefore, TRUTHS will significantly improve the
performance and accuracy of EO missions with broad global or operational
aims, as well as more dedicated missions. The provision of reference
standards will also improve synergy between missions by reducing
errors due to different calibration biases and offer cost reductions
for future missions by reducing the demands for on-board calibration
systems. Such improvements are important for the future success of
strategies such as Global Monitoring for Environment and Security (GMES)
and the implementation and monitoring of international treaties such
as the Kyoto Protocol. TRUTHS will achieve these aims by measuring
the geophysical variables of solar and lunar irradiance, together
with both polarised and unpolarised spectral radiance of the Moon,
Earth and its atmosphere. Published by Elsevier Ltd on behalf of COSPAR.

---------------------------------------------------------
Title: Solar irradiance variations
Authors: Fröhlich, C.
2003ESASP.535..183F Altcode: 2003iscs.symp..183F
Since November 1978 a set of total solar irradiance (TSI) measurements
from space is available, yielding a time series of nearly 25 years. From
measurements made by different space radiometers (HF on NIMBUS 7, ACRIM
I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite recored of
TSI can be constructed. This leads to a reliable record of TSI with
an overall precision of the order of ±0.1 Wm-2 over the
25 years. Within this uncertainty no significant secular trend of TSI
can be detected. This contrasts the results of the ACRIM composite
which does show a significant trend. This difference is analyzed in
detail and it can be demonstrated that the assumptions for the ACRIM
composite are incorrect. The variability of TSI over the last cycle
is characterized by analyzing the statistics of the time series and
the behaviour of the power spectrum. Moreover, the composite TSI is
compared to a proxy model based on sunspot darkening and brightening due
to faculae and network, both in terms of time series and in frequency
space. Since early 1996 spectral measurements by filter-radiometers of
VIRGO provide continuous time series of spectral solar irradiance (SSI)
at 402, 500 and 862 nm. These time series are analyzed and compared to
TSI providing detailed information about the redistribution of energy
within the spectrum during changes of TSI.

---------------------------------------------------------
Title: A Small Institute with a Heart as Big as the Sun
Authors: Fröhlich, Claus
2002ESASP1261...97F Altcode: 2002ses..book...97F
No abstract at ADS

---------------------------------------------------------
Title: Solar irradiance variability and climate
Authors: Fröhlich, C.; Lean, J.
2002AN....323..203F Altcode:
Since November 1978 a complete set of total solar irradiance (TSI)
measurements from space is available, yielding a time series of
more than 23 years. From measurements made by different space-based
radiometers (HF on NIMBUS 7, ACRIM I on SMM, ACRIM II on UARS
and VIRGO on SOHO) a composite record of TSI is compiled with an
overall precision of order 0.05 Wm-2 and a secular trend
uncertainty of +/-3 ppm/year. This time series is compared with an
empirical model of irradiance variability based on sunspot darkening
and brightening due to faculae and network. From this comparison the
model is calibrated and used to estimate possible changes of TSI in the
past, using historical proxies of solar activity. For this purpose,
stellar observations provide information about the possible range of
solar variability over the last millennium when changes of Earth's
climate are well documented. Together, the paleo solar and climate
data enable a discussion of the extent of global climate change that
can be explained by a variable Sun.

---------------------------------------------------------
Title: Estimation of the ozone and temperature sensitivity to the
variation of spectral solar flux
Authors: Rozanov, E.; Egorova, T.; Fröhlich, C.; Haberreiter, M.;
Peter, T.; Schmutz, W.
2002ESASP.508..181R Altcode: 2002soho...11..181R
We have applied a 1-D steady-state radiative-convective model
with interactive photochemistry to estimate the sensitivity of
temperature and ozone mixing ratio to the observed variability of
the extraterrestrial spectral solar irradiance. We have carried out
several runs using the spectral solar flux for minimum and maximum solar
activity conditions. The results show that the ozone and temperature
in the stratosphere are mostly sensitive to the solar flux variations
in the spectral area between 200 and 220 nm, where they positively
correlate with solar flux intensity. In the upper stratosphere and
mesosphere the effects of the solar flux variability in the Lyman-α
line and Schumann-Runge band are found to be very important. The
obtained results have an implication for the optimal choice of
wavelength to be measured from a satellite and for the understanding
of what kind of radiation code should be used in a GCM aimed to study
solar-climate connections.

---------------------------------------------------------
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.
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
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: ISCS Working Group1 Activities
Authors: Pap, J.; Frohlich, C.
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: Long-term solar irradiance variations: results and perspectives
Authors: Pap, J.; Fleck, B.; Frohlich, C.; Jones, H.; Kuhn, J.;
Schmutz, W.
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: Total solar irradiance variations since 1978
Authors: Fröhlich, Claus
2002AdSpR..29.1409F Altcode:
A composite record of solar total irradiance compiled from measurements
made by five independent space-based radiometers since 1978 is the
basis for an evaluation of the influence of solar activity on total
solar irradiance. An empirical model that parameterizes the combined
influences of dark sunspots and bright faculae features on solar
irradiance is able to explain more than 95% of the variance. After
removing the magnetic influence with the model, the remaining 'quiet
sun' shows no trend over the whole period, indicating that the sun has
not changed over the past two solar cycles. The inclusion of p-mode
frequency changes in the model does not explain more than already
expained by the magnetic parameters.

---------------------------------------------------------
Title: Preface
Authors: Fröhlich, Claus; Pap, Judit M.
2002AdSpR..29.1879F Altcode:
No abstract at ADS

---------------------------------------------------------
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
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: SIM3D: Solar Irradiance Monitor-3D-view
Authors: Schmutz, W.; Fröhlich, C.; Rüedi, I.; Roth, H.; Wehrli,
Ch.; Wyss, J.
2001ESASP.493..447S Altcode: 2001sefs.work..447S
No abstract at ADS

---------------------------------------------------------
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.
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: Low-Order p Modes From Virgo Irradiance Data
Authors: Finsterle, W.; Fröhlich, C.
2001SoPh..200..393F Altcode:
Several candidates for low-order p modes (n ≤ 5) and possibly
g modes were found by applying mode-detection techniques such
as multivariate spectral regression analysis and time-frequency
analysis to the VIRGO full-disc solar irradiance data. Three out of
the candidates for low-order p modes could be confirmed by significant
peaks in the un-treated power spectra in good agreement with theoretical
predictions. The frequency of a fourth candidate for a low-order p mode
lies some 2.8 μHz below the predicted frequency. The candidates found
for g modes are less reliable, since none of them could be confirmed
neither by significant peaks in the un-treated power spectra nor by
the detection of multiplets.

---------------------------------------------------------
Title: VIRGO Radiometry and Total Solar Irradiance 1996-2000 Revised
Authors: Fröhlich, C.; Finsterle, W.
2001IAUS..203..105F Altcode:
Total solar irradiance (TSI) observations show a very short solar
minimum in early 1996. The increase of TSI starts well before those
of other activity parameters such as the magnetic field or the MgII
index. Thus the onset of solar cycle 23 seems to be quite different
from the last one in 1987. Models based on PSI and MgII-Index are
unable to explain this behaviour whereas they accounted for over 90%
of the variance over the period of the minimum in the 1985-87 time
frame followed by the increase into cycle 22. Possible explanations
for this behaviour are proposed.

---------------------------------------------------------
Title: Dependence on azimuthal order of the amplitudes of low-degree
p modes
Authors: Fröhlich, C.; Appourchaux, T.; Gough, D. O.
2001ESASP.464..629F Altcode: 2001soho...10..629F
The m-dependence of the amplitudes of the multiplets of low-degree p
modes contains information about the latitudinal distribution of the
power in the excitation of the oscillations. We present estimates of
those amplitudes from 4 years of VIRGO/LOI observations. Variation of
the excitation with magnetic activity is studied.

---------------------------------------------------------
Title: Using Precise Solar Limb Shape Measurements to Study the
Solar Cycle
Authors: Kuhn, J. R.; Floyd, L.; Fröhlich, C.; Pap, J. M.
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: Observations of Irradiance Variations
Authors: Fröhlich, Claus
2000SSRv...94...15F Altcode:
Since November 1978 a complete set of total solar irradiance (TSI)
measurements from space is available, yielding a time series of 21
years. From measurements made by different space radiometers (HF
on NIMBUS-7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO)
a composite record of TSI can be compiled. The corrections which are
needed for each radiometer, mainly to compensate for degradation, but
also for operational influences are described. ACRIM I (1980-1989) and
ACRIM II (1992-1995) are taken as reference because their degradation
was monitored by inflight comparisons with spare radiometers; since 1996
VIRGO is used as reference. The scale of ACRIM II is adjusted to ACRIM I
by comparison with NIMBUS-7 and ERBE. The reliability of this adjustment
depends strongly on the stability of the HF and ERBE radiometer during
the period of the gap between the ACRIMs which is discussed in detail
together with an assessment of the overall precision of the composite.

---------------------------------------------------------
Title: Observational Upper Limits to Low-Degree Solar g-Modes
Authors: Appourchaux, T.; Fröhlich, C.; Andersen, B.; Berthomieu, G.;
Chaplin, W. J.; Elsworth, Y.; Finsterle, W.; Gough, D. O.; Hoeksema,
J. T.; Isaak, G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.;
Sekii, T.; Toutain, T.
2000ApJ...538..401A Altcode:
Observations made by the Michelson Doppler Imager (MDI) and Variability
of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and
Heliospheric Observatory (SOHO) and by the ground-based Birmingham
Solar Oscillations Network (BiSON) and Global Oscillations Network
Group (GONG) have been used in a concerted effort to search for solar
gravity oscillations. All spectra are dominated by solar noise in the
frequency region from 100 to 1000 μHz, where g-modes are expected to be
found. Several methods have been used in an effort to extract any g-mode
signal present. These include (1) the correlation of data-both full-disk
and imaged (with different spatial-mask properties)-collected over
different time intervals from the same instrument, (2) the correlation
of near-contemporaneous data from different instruments, and (3) the
extraction-through the application of complex filtering techniques-of
the coherent part of data collected at different heights in the solar
atmosphere. The detection limit is set by the loss of coherence
caused by the temporal evolution and the motion (e.g., rotation)
of superficial structures. Although we cannot identify any g-mode
signature, we have nevertheless set a firm upper limit to the amplitudes
of the modes: at 200 μHz, they are below 10 mm s-1 in
velocity, and below 0.5 parts per million in intensity. The velocity
limit corresponds very approximately to a peak-to-peak vertical
displacement of δR/Rsolar=2.3×10-8 at the
solar surface. These levels which are much lower than prior claims,
are consistent with theoretical predictions.

---------------------------------------------------------
Title: Solar Variability and Climate
Authors: Friis-Christensen, E.; Fröhlich, C.; Haigh, J. D.;
Schüssler, M.; Von Steiger, R.
2000svc..book.....F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Total Solar Irradiance from VIRGO on SOHO
Authors: Fröhlich, C.; Finsterle, W.
2000ESASP.463..665F Altcode: 2000sctc.proc..665F
No abstract at ADS

---------------------------------------------------------
Title: Influence of snow and clouds on erythemal UV radiation:
Analysis of Swiss measurements and comparison with models
Authors: Renaud, Anne; Staehelin, Johannes; Fröhlich, Claus;
Philipona, Rolf; Heimo, Alain
2000JGR...105.4961R Altcode:
Global, direct and diffuse measurements of erythemal UV radiation with
UV-Biometer and radiative transfer calculations are used to estimate the
influences of (1) a snow-covered surface, (2) an overcast sky, and (3)
a joined snow-covered surface and overcast sky at Davos (1610 m asl,
Swiss Alps). The influence of total ozone, zenith angle, and aerosol
are first investigated. The influence of surface albedo and clouds are
then estimated as a function of the zenith angle after normalization
of the data to a fixed ozone amount. If the ground is covered with
snow on clear-sky days at Davos, erythemal irradiance increases by
15 to 25% due to multiple reflections between the surface and the
atmosphere. This relative increase may reach 80% on overcast days. The
highly significant dependence of the albedo on solar elevation is most
probably due to inhomogeneities in the surrounding terrain leading to
a strong non-Lambertian behavior. The impact of clouds on radiation is
highly variable: on overcast days with a snow free surface, erythemal
UV radiation at Davos is reduced to a level ranging between 8% (very
thick cloud cover) and 70% (thin cloud layer) relative to the radiation
under clear-sky conditions.

---------------------------------------------------------
Title: Observations of Irradiance Variations
Authors: Fröhlich, Claus
2000svc..book...15F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Total Solar and Spectral Irradiance Measured in France during
a Stratospheric Balloon Flight
Authors: Anklin, M.; Wehrli, C.; Fröhlich, C.; Pepe, F.
1999ESASP.437..537A Altcode: 1999erbp.conf..537A
No abstract at ADS

---------------------------------------------------------
Title: Spectral and Total Solar Irradiance Measurements on Board
the International Space Station
Authors: Thuillier, G.; Fröhlich, C.; Schmidtke, G.
1999ESASP.433..605T Altcode: 1999uiss.conf..605T
No abstract at ADS

---------------------------------------------------------
Title: Total solar irradiance variations
Authors: Pap, J. M.; Fröhlich, C.
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: What do VIRGO results tell about the solar interior and
atmosphere
Authors: Fröhlich, Claus
1999AdSpR..24..157F Altcode:
The more than two years of observations from VIRGO (Variability
of solar IRradiance and Gravity Oscillations) yield a unique data
set covering the activity minimum and the rising part of solar cycle
23. This allows not only to determine the influence of varying activity
on the solar oscillation frequencies and amplitudes, but also to study
the relationship between oscillations and irradiance variability.

---------------------------------------------------------
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
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 &amp;
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: PICARD: simultaneous measurements of the solar diameter,
differential rotation, solar constant and their variations
Authors: Damé, Luc; Hersé, Michel; Thuillier, Gérard; Appourchaux,
Thierry; Crommelynck, Dominique; Dewitte, Steven; Joukoff, Alexandre;
Fröhlich, Claus; Laclare, Francis; Delmas, Christian; Boumier, Patrick
1999AdSpR..24..205D Altcode:
PICARD is a CNES micro-satellite mission due for flight by the end
of 2002, named after the name of a French astronomer who first
observed with consistency the solar diameter changes during the
Maunder minimum in the 16th century. It consists of two instruments
measuring (i) the solar diameter and differential rotation, and (ii)
the total solar irradiance. These quantities are fundamental for the
understanding of the solar-Terrestrial relations, e.g. the influence
of the Sun on the Earth's climate, and of the internal structure
of the Sun. The continuous - or nearly continuous - viewing of the
Sun from an appropriate orbit, the 5 minutes sampling rate and the
very low noise measurements, will allow g-modes detection and precise
diameter measurements besides accurately establishing the relationship
between irradiance and diameter changes. Providing an absolute measure
of the solar diameter to 1 milliarcsecond, PICARD is the first step
towards instruments capable of accurate and perennial measurements,
for the centuries to come, of the solar-terrestrial influence. The
objectives of the mission, instrument capabilities, observing modes
and performances are described.

---------------------------------------------------------
Title: Preface
Authors: Fröhlich, Claus; Foing, Bernard
1999AdSpR..24..135F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Sun's total irradiance: Cycles, trends and related climate
change uncertainties since 1976
Authors: Fröhlich, Claus; Lean, Judith
1998GeoRL..25.4377F Altcode:
A composite record of the Sun's total irradiance compiled from
measurements made by five independent space-based radiometers since 1978
exhibits a prominent 11-year cycle with similar levels during 1986 and
1996, the two most recent minimum epochs of solar activity. This finding
contradicts recent assertions of a 0.04% irradiance increase from the
1986 to 1996 solar minima and suggests that solar radiative output
trends contributed little of the 0.2°C increase in the global mean
surface temperature in the past decade. Nor does our 18-year composite
irradiance record support a recent upward irradiance trend inferred
from solar cycle length, a parameter used to imply a close linkage in
the present century between solar variability and climate change.

---------------------------------------------------------
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
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: Asymmetry and Frequencies of Low-Degree p-Modes and the
Structure of the Sun's Core
Authors: Toutain, T.; Appourchaux, T.; Fröhlich, C.; Kosovichev,
A. G.; Nigam, R.; Scherrer, P. H.
1998ApJ...506L.147T Altcode:
An accurate determination of the frequencies of low-degree solar
p-modes is an important task of helioseismology. Using 679 days of
solar oscillation data observed in Doppler velocity and continuum
intensity from two Solar and Heliospheric Observatory instruments
(the Michelson Doppler Imager and the SunPhotoMeter), we show that
fitting the spectra with Lorentzian profiles leads to systematic
differences between intensity and velocity frequencies as large as
0.1 μHz for angular degrees l=0, 1, and 2 because of the opposite
asymmetry between intensity and velocity. We use a physics-based
asymmetrical line shape to fit p-mode lines, and we demonstrate
that their asymmetry is statistically significant and that frequency
differences are considerably reduced. These measurements provide more
accurate estimates of the solar eigenfrequencies. We discuss inferences
of the structure of the solar core.

---------------------------------------------------------
Title: A model of solar total and spectral irradiance variations
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y. C.; Froehlich, C.;
Wehrli, Ch.
1998A&A...335..709F Altcode:
We model solar spectral irradiance variations under the assumption
that they are produced by sunspots and faculae alone. The model is
based on three components, i.e. quiet Sun, assumed to be temporally
invariant, sunspots and faculae whose temporal variations are mimicked
using time series of sunspot areas and Mg II core-to-wing ratios. The
detailed flux spectrum for each component is employed. The results
are compared to spectral irradiance measurements at 402 nm, 500 nm
and 862 nm obtained between February 22 and December 31, 1996 by
the three-channel sunphotometers (SPM) which are part of the VIRGO
package onboard SOHO. Our model shows a good correlation with the
measured variations of the three colour channels and of the total
irradiance. Since it also successfully reproduces changes in the UV
spectral irradiance, irradiance variations and observed variations
of the faculae-to-spots filling factor ratio since 1978, our model
supports earlier suggestions that a large part of the solar irradiance
variations is caused by magnetic fields at the solar surface. Finally,
we use the model to test whether the difference between the magnitude
of solar and stellar brightness variations reported by Lockwood et
al. (1992) is due to the particular filters they use for their stellar
observations. Our results suggest that this effect can explain only
a small part of the discrepancy.

---------------------------------------------------------
Title: Foreword
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998SSRv...85...11F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Assessment of Degradation of VIRGO Radiometers on Board SOHO
Authors: Anklin, M.; Frohlich, C.; Finsterle, W.; Crommelynck, D. A.;
Dewitte, S.
1998Metro..35..685A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line Asymmetry of VIRGO and MDI Low-Degree p Modes
Authors: Toutain, T.; Appourchaux, T.; Frohlich, C.; Kosovichev, A.;
Rakesh, N.; Scherrer, P.
1998ESASP.418..973T Altcode: 1998soho....6..973T
Using continuous time series of 610 days of velocity (MDI, LOI-proxy)
and intensity (VIRGO, SPM and LOI) we show that Lorentzian profiles as
a model of low-degree p-mode line leads to systematic differences in
the determination of intensity and velocity mode frequencies. These
differences, as large as 0.1 muHz for degrees l = 0, 1, 2 and 3,
are frequency-dependent. The use of a physics-based asymmetrical line
shape (Rakesh et al., 1998) to fit the same lines has allowed us to
significantly reduce differences in the frequency determination. P-mode
lines in velocity exhibit a significant negative asymmetry (excess
of power in the left wing) whereas p-modes lines in intensity have a
positive asymmetry (excess of power in the right wing). The magnitude
and sign of this asymmetry are directly related to the location of
the source of p-mode excitation and to the correlation between mode
and solar noise.

---------------------------------------------------------
Title: Solar Composition and Its Evolution -- From Core to Corona
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998sce..conf.....F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Total Solar Irradiance: Present Knowledge and Future Needs
Authors: Fröhlich, C.; Lean, J.
1998ESASP.417..239F Altcode: 1998cesh.conf..239F
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.
1998ESASP.417..267P Altcode: 1998cesh.conf..267P
No abstract at ADS

---------------------------------------------------------
Title: Solar irradiance variations during Solar Cycle 22 from ACRIM
II, SOVA and VIRGO Radiometry
Authors: Froehlich, C.; Anklin, M.; Crommelynck, D.; Finsterle, W.;
Willson, R. C.
1998IAUS..185...89F Altcode:
The radiometers on UARS (ACRIM II), on EURECA (SOVA) and on SOHO
(VIRGO) cover the solar irradiance from the maximum cyle 22 to the
minimum. Results from the comparison of the 3 experiments will be
presented together with a discussion of the variability during the cycle
with special emphasis on the amplitude of the cycle variation. This
result will also be compared with the previous cycle.

---------------------------------------------------------
Title: Time Dependence of Solar Noise Observed with VIRGO
Authors: Andersen, Bo; Leifsen, Torben; Appourchaux, Thierry; Frohlich,
Claus; Jiménez, Antonio; Wehrli, Christoph
1998ESASP.418...83A Altcode: 1998soho....6...83A
The effect of non- and quasiperiodic solar surface structures dominate
the power spectra of solar irradiance and radiance over a broad range
of time scales. Only in the p-mode region above about 2 mHz and in the
rotationally dominated region below about 3 μ Hz there seems to be
narrow stationary peaks. The solar background signal, or solar noise has
clear large scale quasi-stationary structures that seems to be closely
correlated to the combination of timescales and contrasts of the solar
surface sources. The dominant sources are the solar granulation and
supergranulation. The solar noise determines the detection limit in
the search for g-modes. Thus an increased understanding of it may be
helpfull in this search. In addition this understanding will be usefull
to determine the properities of stellar small scale surface structures
from the data from future asteroseismology space missions. In this
study we use the VIRGO data to study the time variation of the solar
noise with timescales from about one day to about one year.

---------------------------------------------------------
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.
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: Statistical Properties of the Amplitude Modulation of Solar
p-Modes
Authors: Andersen, Bo; Aarset, Magne; Leifsen, Torben; Appourchaux,
Thierry; Frohlich, Claus; Hoeksema, J. T.; Jiménez, Antonio; Toutain,
Thierry
1998ESASP.418..897A Altcode: 1998soho....6..897A
The low degree solar p-modes show amplitude modulation at all observable
timescales. For some modes a large fraction of this modulation seems
to be correlated to the solar rotation. For other modes there seems
to be little or no deterministic component in the modulation. Only
intermittent correlation between the modulation of different modes
have been observed. This is to be expected if the excitation of modes
is completely stochastic. None of the observational methods observe the
modes directly. In different ways they all observe the solar atmospheres
response to the modes. This implies that the modes may be modulated by
this response. By studying the statistical properties of the different
observed modes we attempt to discriminate between variations in the
modes themselves and the atmospheric response. In this work we study the
statistical properties of the mode amplitude variations for radial order
p-modes observed with the VIRGO and SOI/MDI instruments on SOHO. The
time scales studied span the region from 0.2 μ Hz to 15 muHz. Here,
we are modelling the amplitude modulation, utilising the concepts of
state space models, as a stochastic process and study the properties
of this model as function of radial order and line width of the modes.

---------------------------------------------------------
Title: Characterization of Solar Noise in Irradiance from VIRGO
Authors: Anklin, Martin; Frohlich, Claus; Wehrli, Christopf; Finsterle,
Wolfgang
1998ESASP.418...91A Altcode: 1998soho....6...91A
Power spectral analysis of measurements of total and spectral solar
irradiance show a similar general behavior for periods between
two minutes to 50 days as found by Frohlich et al. (1997) with a
much shorter time series. While the time series are extended, low
frequencies become accessible and the influence of the increasing
solar activity can be studied. Furthermore, the temporal variation of
the influence of supergranulation, mesogranulation, and granulation is
investigated. With multivariate spectral analysis the contribution of
three spectral channels, blue, green and red, to the variance of the
total channel are determined. The difference in gain of the spectral
channels is investigated for the frequency range corresponding to
magnetic activity or to convection in the range from supergranulation
to granulation. Moreover, the temporal variations of the contribution
of each channel to the total is studied.

---------------------------------------------------------
Title: VIRGO on SOHO: Status and Future Prospects
Authors: Fröhlich, C.; Scherrer, P.; MDI Team; Virgo Team; Gabriel,
A.; GOLF Team
1998ESASP.418....7F Altcode: 1998soho....6....7F
After two years of nearly uninterrupted operation, the Michelson
Doppler Imager (MDI) instrument has produced many unique data sets
that are being used to address a wide variety of topics in solar
physics. The more than two years of observations from VIRGO (Variability
of solar IRradiance and Gravity Oscillations) yield a unique data set
covering the activity minimum and the rising part of cycle 23. This
allows not only to determine the influence of varying activity on the
solar oscillation frequencies and amplitudes, but also to study the
relationship between oscillations and irradiance variability. Over
2 years of GOLF data with nearly 100% continuity are yielding the
highest ever signal to noise quality, enabling precise measurements of
the frequencies, linewidths and power in the p-modes. The precision
available for the inversion of the frequencies in terms of sound
speed in the solar interior is no longer limited by the quality of the
time-series itself, but rather by questions concerning the most correct
method of fitting the observed spectrum. Unique measurements from the
GOLF p-mode signals include the high-frequency global structure above
the acoustic cut-off and the measurement of the global average magnetic
field of the Sun. Several different techniques are being employed in
searching for the g-mode signals in the GOLF spectrum.

---------------------------------------------------------
Title: Solar Total Irradiance Variations
Authors: Lean, Judith; Frohlich, Claus
1998ASPC..140..281L Altcode: 1998ssp..conf..281L
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.
1998ESASP.418..951P Altcode: 1998soho....6..951P
No abstract at ADS

---------------------------------------------------------
Title: Modelling Spectral Irradiance Variations obtained by VIRGO
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y.; Frohlich, C.;
Wehrli, Ch.
1998ASPC..140..311F Altcode: 1998ssp..conf..311F
No abstract at ADS

---------------------------------------------------------
Title: Observational Upper Limits for Low-Degree Solar g-modes
Authors: Fröhlich, C.; Finsterle, W.; Andersen, B.; Appourchaux, T.;
Chaplin, W. J.; Elsworth, Y.; D. O. Gough; Hoeksema, J. T.; Isaak,
G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.; Sekii, T.;
Toutain, T.
1998ESASP.418...67F Altcode: 1998soho....6...67F
No abstract at ADS

---------------------------------------------------------
Title: Amplitude modulation of radial p-modes from Virgo
Authors: Leifsen, T.; Andersen, B. N.; Appourchaux, T.; Frohlich,
C.; Jimenez, A.; Toutain, T.; Wehrli, C.
1998IAUS..185..113L Altcode:
We present results from wavelet analysis of more than one year of
data from the VIRGO Sun Photometers (SPM) and the VIRGO Luminosity
Oscillation Imager (LOI) onboard the SOHO spacecraft. The temporal
behaviour of p-modes with l=0--2 is presented. The analysis of
the l=0 modes show a modulation of the mode amplitudes with the
solar rotation. This result is quite surprising as the l=0 modes
should not be sensitive to the solar rotation. Possible effects of
varying solar activity on the modulation of the mode amplitudes is
investigated. The effect of the modulation on the fitting of mode lines
and determination of the mode frequencies is also studied. Wavelet
analysis has a fundamental limitation in the ability to achieve
simultaneous high frequency and time resolution. In order to be able
to study the rotationally split components of the l=1 modes with good
time resolution, we apply a spatial filtering technique on the LOI
data to separate the different components.

---------------------------------------------------------
Title: Solar Electromagnetic Radiation Study for Solar Cycle 22
Authors: Pap, J. M.; Frohlich, C.; Ulrich, R. K.
1998sers.conf.....P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Total Solar Irradiance Monitoring Programs
Authors: Fröhlich, Claus
1998sers.conf..391F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar composition and its evolution - from core to
corona. Proceedings. ISSI (International Space Science Institute)
Workshop, Bern (Switzerland), 26 - 30 Jan 1998.
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998SSRv...85.....F Altcode:
The following topics were dealt with: solar composition, solar
evolution, the solar interior, helioseismology, photosphere,
chromosphere, solar corona, solar wind, the Sun as a Sun-like star.

---------------------------------------------------------
Title: Comparative Studies of Low-Order and Low-Degree Solar p Modes
Authors: Appourchaux, T.; Andersen, B.; Chaplin, W.; Elsworth, Y.;
Finsterle, W.; Frohlich, C.; Gough, D.; Hoeksema, J. T.; Isaak, G.;
Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.; Toutain, T.
1998ESASP.418...95A Altcode: 1998soho....6...95A
The amplitudes of solar p-modes decrease steeply with decreasing
radial order below about 17. The background solar signal (solar noise)
in general increases steadily with decreasing frequency. For the
irradiance and radiance measurements with VIRGO or SOI/MDI on SOHO this
combination makes it difficult to detect low degree modes below about
1.8 mHz. The solar noise as observed in velocity with SOI/MDI or the
ground based BISON network is significantly lower in this region than
in intensity measurements. This allows low degree modes to be observed
close to 1 mHz. We present results of detection and charaterization
of the lowest order observable p-modes both in velocity and intensity
measurements. Where applicable the properties of the modes observed
with the two methods are compared.

---------------------------------------------------------
Title: The Effect of Amplitude Modulation on Asymmetries of Solar
p-Modes
Authors: Andersen, Bo; Leifsen, Torben; Appourchaux, Thierry; Frohlich,
Claus; Hoeksema, J. T.; Toutain, Thierry
1998ESASP.418..893A Altcode: 1998soho....6..893A
The low degree solar p-modes show an asymmetry in their line profiles
that both depend on the observational technique and on the radial
order of the modes. Typically the modes determined from observations
with Doppler shift methods show an asymmetry towards lower frequency
while the opposite is the case for modes determined from irradiance and
radiance observations. The difference in asymmetry is probably caused by
near surface effects. If the modes are fitted with symmetric functions
this leads to a systematic shift in the frequency determinations for
the two data sets. This may lead to systematic differences in the
inversions based on the different frequencies. All the mode amplitudes
show significant time variation. The typical centroid frequency also
varies with timescales from a few days to the solar cycle. These
variations may set absolute limits to the observable accuracy of the
frequency determination. These time modulations may influence the
observed line profiles and thus the frequency determinations. Here we
present results of the effect on the mode asymmetry of the amplitude
modulation of low degree modes observed with VIRGO and SOI/MDI. The
range in timescales is from a few days to a few solar rotations.

---------------------------------------------------------
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.
1997ESASP.415..477P Altcode: 1997cpsh.conf..477P
No abstract at ADS

---------------------------------------------------------
Title: Total Solar Irradiance Variations: The Construction of a
Composite and its Comparison with Models
Authors: Fröhlich, C.; Lean, J.
1997ESASP.415..227F Altcode: 1997cpsh.conf..227F
No abstract at ADS

---------------------------------------------------------
Title: Wavelength Dependence of Solar Irradiance Variability from
VIRGO Onboard SOHO
Authors: Wehrli, C.; Fröhlich, C.; Anklin, M.; Fligge, M.; SOlanki,
S. K.; Unruh, Y.
1997ESASP.415..497W Altcode: 1997cpsh.conf..497W
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.
1997ESASP.415..469D Altcode: 1997cpsh.conf..469D
No abstract at ADS

---------------------------------------------------------
Title: Assessment of Degradation of VIRGO Radiometers Onboard SOHO
Authors: Anklin, M.; Fröhlich, C.; Finsterle, W.; Wehrli, C.;
Crommelynck, D. A.
1997ESASP.415..459A Altcode: 1997cpsh.conf..459A
No abstract at ADS

---------------------------------------------------------
Title: In-Flight Performance of the Virgo Solar Irradiance Instruments
on SOHO
Authors: Fröhlich, Claus; Crommelynck, Dominique A.; Wehrli,
Christoph; Anklin, Martin; Dewitte, Steven; Fichot, Alain; Finsterle,
Wolfgang; Jiménez, Antonio; Chevalier, André; Roth, Hansjörg
1997SoPh..175..267F Altcode:
The in-flight performance of the total and spectral irradiance
instruments within VIRGO (Variability of solar IRradiance and Gravity
Oscillations) on the ESA/NASA Mission SOHO (SOlar and Heliospheric
Observatory) is in most aspects better than expected. The behaviour
during the first year of operation of the two types of radiometers and
the sunphotometers together with a description of their data evaluation
procedures is presented.

---------------------------------------------------------
Title: Tri-Phonic Helioseismology: Comparison of Solar P Modes
Observed by the Helioseismology Instruments Aboard SOHO
Authors: Toutain, T.; Appourchaux, T.; Baudin, F.; Fröhlich, C.;
Gabriel, A.; Scherrer, P.; Andersen, B. N.; Bogart, R.; Bush, R.;
Finsterle, W.; García, R. A.; Grec, G.; Henney, C. J.; Hoeksema,
J. T.; Jiménez, A.; Kosovichev, A.; Roca Cortés, T.; Turck-Chièze,
S.; Ulrich, R.; Wehrli, C.
1997SoPh..175..311T Altcode:
The three helioseismology instruments aboard SOHO observe solar p modes
in velocity (GOLF and MDI) and in intensity (VIRGO and MDI). Time series
of two months duration are compared and confirm that the instruments
indeed observe the same Sun to a high degree of precision. Power
spectra of 108 days are compared showing systematic differences between
mode frequencies measured in intensity and in velocity. Data coverage
exceeds 97% for all the instruments during this interval. The weighted
mean differences (V-I) are −0.1 µHz for l=0, and −0.16 µHz for
l=1. The source of this systematic difference may be due to an asymmetry
effect that is stronger for modes seen in intensity. Wavelet analysis
is also used to compare the shape of the forcing functions. In these
data sets nearly all of the variations in mode amplitude are of solar
origin. Some implications for structure inversions are discussed.

---------------------------------------------------------
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.
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: 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.
1997IAUS..181...67F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: In-Flight Performance of the Virgo Luminosity Oscillations
Imager Aboard SOHO
Authors: Appourchaux, Thierry; Andersen, Bo N.; Fröhlich, Claus;
Jiménez, Antonio; Telljohann, Udo; Wehrli, Christoph
1997SoPh..170...27A Altcode:
The Luminosity Oscillations Imager (LOI) is a part of the VIRGO
instrument aboard the Solar and Heliospheric Observatory (SOHO). The
scientific objective of the LOI experiment is to identify and
characterize pressure and internal gravity oscillations of the Sun by
observing the radiance variations. The LOI is a low-resolution imager
with 12 pixels, for the measurement of the radiance distribution
over the solar disk at 500 nm. The low resolution capability of the
instrument allows the identification of individual azimuthal orders
for l = 0 to 7, without suffering the mixing that affects integrated
solar disk instruments. The performance, calibrations and instrumental
effects of the LOI are described together with the procedures for
extracting the solar p modes.

---------------------------------------------------------
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
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: 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.
1996SSRv...76..354P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The history of thge SOHO mission.
Authors: Huber, M. C. E.; Bonnet, R. M.; Dale, D. C.; Arduini, M.;
Fröhlich, C.; Domingo, V.; Whitcomb, G.
1996ESABu..86...25H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Space degradation of SOVA sunphotometers on EURECA.
Authors: Wehrli, C.; Fröhlich, C.; Romero, J.
1996Metro..32..653W Altcode:
Two sunphotometers with three channels at 862 nm, 500 nm and 335 nm were
operated in space for eleven months on board the European Retrievable
Carrier (EURECA). Both instruments experienced substantial losses of
sensitivity, although the second instrument was exposed 100 times less
than the first one. After retrieval of EURECA, the instruments were
examined and optically tested. Contamination and degradation of optical
components were found, but only small changes in spectral bandpasses.

---------------------------------------------------------
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.
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: Results of solar spectral irradiance measurements by SOVA2
on EURECA
Authors: Wehrli, Ch.; Frohlich, C.; Romero, J.
1995AdSpR..16h..25W Altcode: 1995AdSpR..16...25W
The solar irradiance has been measured at 3 wavelengths (335, 500
and 862nm) by the experiment SOVA2 from the European Retrievable
Carrier (EURECA). The dataset, corrected for instrumental effects
and degradation, is examined for solar variability on timescales from
minutes to days.

---------------------------------------------------------
Title: The European retrievable carrier (EURECA) as an observing
platform from a user's point of view
Authors: Wehrli, Ch.; Frohlich, C.; Romero, J.
1995AdSpR..16g..51W Altcode: 1995AdSpR..16...51W
The operational environment of EURECA as experienced by the SOVA2
experiment is presented. This experiment has independently measured
the solar pointing with a high resolution sun sensor and monitored
several temperatures as ancillary parameters to be used in evaluation
of the scientific measurements. Results of these measurements are
presented and experience with the novel telemetry / telecommand and
data retrieval system is commented.

---------------------------------------------------------
Title: Solar total irradiance variability measured by SOVA-2 on
board EURECA
Authors: Romero, J.; Frohlich, C.; Wehrli, Ch.
1995AdSpR..16h..29R Altcode: 1995AdSpR..16...29R
During its 9 months of operation, the experiment SOVA-2 (Solar Constant
and Variability) on board the European Retrievable Carrier (EURECA)
has measured the total solar irradiance with two radiometers of the
type PMO6-R. The solar variability has been investigated by bivariate
spectral analysis of the irradiance and the Photometric Sunspot Index
(PSI) to account for the sunspot blocking and after removal of the
spot influence with the MgII-Index as proxy for the contribution of
faculae and other bright magnetic elements.

---------------------------------------------------------
Title: Low Frequency Helioseismology
Authors: Fröhlich, C.; Andersen, B. N.
1995ESASP.376a.137F Altcode: 1995heli.conf..137F; 1995soho....1..137F
The main objective of low frequency helioseismology is the search
for solar g-modes which allows sounding of the core close to the
center. The analyses have been based on ground-based observations by
the Crimean Astrophysical Observatory, Stanford University, SCLERA,
Birmingham University, Instituto Astrofisica de Canarias and on
irradiance observations by ACRIM on the US Solar Maximum Mission
satellite and IPHIR on the Russian PHOBOS mission. The most intriguing
observation from the ground is the 160 minutes oscillation. Its
interpretation is still controversial and even the solar origin is
questioned. Interpretation of the observed spectra in the range from 45
- 140 μHz is mostly based on asymptotic theory, but the results do not
show consistent evidence that g-modes have been unambiguously detected.

---------------------------------------------------------
Title: Virgo: Expriment for Helioseismology and Solar Irradiance
Monitoring
Authors: Fröhlich, C.; Andersen, B. N.
1995ESASP.376a..83F Altcode: 1995soho....1...83F; 1995heli.conf...83F
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
nm. 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: VIRGO - the Solar Monitor Experiment on SOHO
Authors: Appourchaux, T.; Domingo, V.; Frohlich, C.; Romero, J.;
Wehrli, C.; Andersen, B. N.; Berthomieu, G.; Delache, P.; Crommelynck,
D.; Jimenez, A.; Roca Cortes, T.; Jones, A. R.
1995ASPC...76..408A Altcode: 1995gong.conf..408A
No abstract at ADS

---------------------------------------------------------
Title: Preface
Authors: Pap, Judit M.; Fröhlich, Claus; Hudson, Hugh S.; Tobiska,
W. Kent
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.
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: The sun as a variable star: Solar and stellar irradiance
variations
Authors: Pap, Judit M.; Froehlich, Claus; Hudson, Hugh S.; Tobiska,
W. Kent
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: 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.
1994svsp.coll.....P Altcode: 1994IAUCo.143P....P
No abstract at ADS

---------------------------------------------------------
Title: Irradiance Observations of the Sun
Authors: Frohlich, C.
1994svsp.coll...28F Altcode: 1994IAUCo.143P..28F
No abstract at ADS

---------------------------------------------------------
Title: Relationship between solar activity and luminosity
Authors: Fröhlich, Claus
1993AdSpR..13i.429F Altcode: 1993AdSpR..13..429F
Measurements of the solar constant - the total irradiance at mean
Sun-Earth distance - during the last 12 years from satellites show
variations over time scales from minutes to years and decades. The most
important variance is in the range from days to several months and is
related to the photospheric features of solar activity: decreasing
the irradiance during the appearance of sunspots, and increasing it
by faculae and the bright magnetic network. Modulation by the 11-year
activity cycle is now observed conclusively with the irradiance being
higher during solar maximum. All these variations can be explained - at
least qualitatively - by their manifestation on the photosphere. Whether
the short term variations are luminosity changes cannot be deduced from
irradiance observations. For the solar cycle variation the situation
is different: simultaneous changes of the solar p-mode frequencies are
observed and both effects can be explained qualitatively by the same
mechanism. This suggests that the solar cycle related irradiance change
can be interpreted as a global phenomenon and is the manifestation of
a change in luminosity. Longer term variations can be inferred from
stellar observations and the possibility for a solar origin of the
little ice-age during the Maunder minimum are explored.

---------------------------------------------------------
Title: Prisma - the First Space Mission to See Inside the Stars
Authors: Appourchaux, T.; Gough, D. O.; Catala, C.; Frandsen, S.;
Frohlich, C.; Hoyng, P.; Jones, A.; Lemaire, P.; Tondello, G.; Weiss,
W. W.
1993ASPC...42..411A Altcode: 1993gong.conf..411A
No abstract at ADS

---------------------------------------------------------
Title: PRISMA: Probing Stars from Core to Corona
Authors: Appourchaux, T.; Catala, C.; Catalano, S.; Fransden, S.;
Fröhlich, C.; Gough, D. O.; Hoyng, P.; Jones, A.; Lemaire, P.;
Tondello, G.; Weiss, W.
1993ASSL..183..505A Altcode: 1993pssc.symp..505A
No abstract at ADS

---------------------------------------------------------
Title: Results from IPHIR as guideline for asteroseismology
Authors: Toutain, T.; Fröhlich, C.
1993ASPC...40..713T Altcode: 1993ist..proc..713T; 1993IAUCo.137..713T
No abstract at ADS

---------------------------------------------------------
Title: PRISMA: a new space mission for stellar physics.
Authors: Appourchaux, T.; Gough, D.; Hyoyng, P.; Catala, C.; Frandsen,
S.; Froehlich, C.; Jones, A.; Lemaire, P.; Tondello, G.; Weiss, W. W.
1993ASPC...40..812A Altcode: 1993ist..proc..812A; 1993IAUCo.137..812A
This paper mainly focuses on the scientific objectives that can be
achieved with a new space mission of the European Space Agency -
PRISMA (Probing Rotation and Interior of Stars: Microvariability
and Activity). The scientific objectives can be classified into
three areas of interest: (1) Stellar structure and evolution. (2)
Stellar atmospheres and magnetic fields. (3) Stellar dynamics and
stellar dynamos.

---------------------------------------------------------
Title: Multi-Variate Spectral Analysis of Short-Term Irradiance
Variations
Authors: Pap, J. M.; Frohlich, C.
1992sers.conf...62P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Irradiance Variability
Authors: Frohlich, C.
1992sers.conf....1F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Characteristics of solar p-modes - Results from the IPHIR
experiment
Authors: Toutain, T.; Froehlich, C.
1992A&A...257..287T Altcode:
Solar p-modes were observed in irradiance during more than 160 days
by the IPHIR experiment on the USSR PHOBOS Mission in 1988. They
are characterized by their frequency, splitting, linewidth, and
amplitudes, determined by fitting Lorentzians to the lines. Because
of the long uninterrupted time series the frequencies are probably
the most accurate available at present. They are compared with results
from other observations and theoretical models. Very good agreement is
observed with a recent standard model, MHD-S2, of Christensen-Dalsgaard
(1991), for both the absolute frequencies (less than 3 micro-Hz) and the
difference delta (02) = nu(n,0) - nu(n-1,2) (less than 0.15 micro-Hz),
which means that the standard solar model is a good approximation to
the real sun and that the solution to the 'Neutrino Puzzle' has to be
sought from particle physics. From the splittings of the l = 1 and 2
modes the rotation of the core (0.0 - 0.2) is inferred to about 4.6
times the surface rate. The damping of p-modes is determined from the
linewidths; lifetimes between 24 and 2 days are found for n = 16...26.

---------------------------------------------------------
Title: Rotation of the Sun's Core
Authors: Goode, Philip R.; Frohlich, Claus; Toutain, Thierry
1992ASPC...27..282G Altcode: 1992socy.work..282G
No abstract at ADS

---------------------------------------------------------
Title: Multi-Variate Spectral Analysis of Solar Irradiance Variations
Authors: Pap, J. M.; Frohlich, C.
1991BAAS...23Q1069P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The helioseismology experiment on the Phobos planetary
mission. Preliminary results
Authors: Frohlich, C.; Bonnet, R. M.; Bruns, A. V.; Vial, J. C.;
Delaboudiniere, J. P.; Domingo, V.; Kollath, Z.; Kotov, V. A.;
Rachkovskii, D. N.; Wehrli, Ch.; Toulain, T.; Shumko, S. M.
1991BCrAO..83...18F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar Variations (SOVA) experiment in the EURECA space
platform
Authors: Crommelynck, D.; Domingo, V.; Fröhlich, C.
1991AdSpR..11d..83C Altcode: 1991AdSpR..11Q..83C
The Solar Variations (SOVA) experiment aboard EURECA will measure the
total and spectral irradiance of the Sun, and their variations. Aims
of the experiment are: - to study the short term (hours to months)
variations of the solar irradiance for the investigation of the
mechanisms of energy redistribution in the convection zone, - to study
periodic fluctuations, with periods between a few minutes and several
hours, for helioseismology and, - to measure the absolute value of the
solar constant to determine its long term variations when compared
with previous and future measurements. Two absolute active cavity
radiometers of different design will measure independently the value
of the total solar irradiance, one relative radiometer will measure
the variations of the total solar irradiance and five photometers
will measure the variations of the spectral irradiance in 5-nm wide
wavelength bands centred at 335, 480, 500, 546 and 865 nm. The European
Retrievable Carrier (Eureca), is an ESA space platform that will be
placed in orbit around the Earth by the NASA Shuttle in October 1991,
and will be recovered after 6 months of operation.

---------------------------------------------------------
Title: Phase difference between irradiance and velocity in low degree
solar p-modes
Authors: Schrijver, C. J.; Jiménez, A.; Domingo, V.; Fröhlich, C.
1991AdSpR..11d..77S Altcode: 1991AdSpR..11Q..77S
We derive phase differences between irradiance and full-disk velocity
variations for l=0, 1, and 2 modes with order ranging from 11 up to 30
(1.8-4.3mHz). We use irradiance measurements from the IPHIR instrument
flown on the PHOBOS mission to Mars during the second half of 1988,
and simultaneous velocity measurements obtained at Tenerife. The
IPHIR instrument measures broad-band irradiance fluctuations and the
derived phase differences are therefore typical of the deep layers of
the photosphere. We select three one week intervals from the 155 day
observing interval of PHOBOS 2 for which simultaneous good quality
velocity data are available. We find a smooth variation of the phase
difference between irradiance at 500nm (5nm FWHM) and velocity from
about 70° at 1.8mHz to 145° at 2.5mHz, while it remains roughly
constant at 145° degrees up to at least 3.5mHz, and possibly up to
4.3mHz. We also show that the phase differences between the green
(500nm) and red (865nm) channels does not differ significantly from
zero below 3mHz, while a small difference of about 10° may exist at
higher frequencies.

---------------------------------------------------------
Title: Solar gravity modes.
Authors: Hill, H.; Froehlich, C.; Gabriel, M.; Kotov, V. A.
1991sia..book..562H Altcode:
The internal gravity modes, or g-modes, of the Sun may be important
both in affecting the internal structure of the Sun and in furnishing a
diagnostic probe of the solar interior. The internal structure could be
altered by core mixing due to unstable g-modes or by nonlinear effects
due to large-amplitude g-modes located in the core. On the other hand,
small-amplitude g-modes operating in the linear regime offer the
possibility of studying in detail the present state of internal solar
structure such as the internal rotation rate, the Brunt-Väisälä
frequency, the speed of sound and the mean molecular weight. In all
of these roles, the solar g-modes may be important. The g-modes may
be a contributor to the solar neutrino paradox and/or they may be a
source of information leading to a more complete understanding of the
physics responsible for the paradox. The observational work on solar
g-modes does not exclude any of these possibilities at this time.

---------------------------------------------------------
Title: The helioseismological experiment at the Phobos interplanetary
station - Preliminary results
Authors: Froehlich, C.; Bonnet, R. M.; Bruns, A. V.; Vial, J. C.;
Delaboudiniere, J. P.; Domingo, V.; Kollath, Z.; Kotov, V. A.;
Rachkovskii, D. N.; Wehrli, Ch.
1991IzKry..83...22F Altcode:
Preliminary results obtained from IPHIR (Interplanetary Helioseismology
by Irradiance Measurements), a solar irradiance experiment on board
the Soviet planetary mission Phobos-2, are presented. During the
spacecraft's flight to Mars, the instrument gathered valuable data on
tiny variations of solar irradiance over the course of six months. The
data clearly show 5-min oscillations with relative amplitudes of about
10 exp -5 and with a well-defined pattern of discrete peaks in the
power spectrum. The data of the red channel (it exhibited the lowest
degradation of sensitivity over time) reveal remarkable temporal changes
of amplitudes of discrete peaks within a period range of about 5 min,
but with excellent frequency stability.

---------------------------------------------------------
Title: Solar Irradiance Variability from Modern Measurements
Authors: Froehlich, C.; Foukal, P. V.; Hickey, J. R.; Hudson, H. S.;
Willson, R. C.
1991suti.conf...11F Altcode:
Direct measurements from satellites of the solar 'constant' (the total
irradiance at mean sun-earth distance) during more than ten years
show variations over time scales from minutes to years and decades. At
high frequencies, solar oscillations contribute to the variance. The
most important influences are related to solar activity: during the
passage of active regions on the solar disk (sunspots and faculae)
changes of a few 0.1 percent lasting for several days are observed. The
effects of spots can be well reproduced by the projected sunspot index,
whereas the influence of faculae have to be modeled from proxy data
like the Ca-K plage index or the He I index. Long-term trends are
detected which are connected to the 11-yr solar activity cycle.

---------------------------------------------------------
Title: Helioseismology with the IPHIR instrument on the
U.S.S.R. Phobos mission
Authors: Froehlich, C.; Toutain, Th.; Schrijver, C. J.
1991AdSpR..11d..69F Altcode: 1991AdSpR..11...69F
We analyze the solar irradiance data gathered by the IPHIR experiment
on the USSR planetary mission to Phobos during 160 days of the cruise
phase to Mars of PHOBOS II, launched on 12 July 1988. We use two methods
to `clean' the data from the unexpected effects caused by the variable
pointing. Both methods yield spectra of the green and red passbands in
the range of the solar 5-minute p-mode oscillations with a very high
signal-to-noise ratio. The consistency of the four spectra demonstrates
the effectiveness of the `cleaning' and allows to determine highly
accurate p-mode frequencies. For the low-frequency analysis another,
independent method is applied which produces reasonable power spectra in
the range from 0.1 to 200 μHz. Interesting features of the medium-term
variability of the solar spectral irradiance are revealed. No evidence
was found for solar g modes, possibly because the solar or the pointing
noise prevents their disclosure.

---------------------------------------------------------
Title: Line shape and temporal variation of p-modes from IPHIR data
Authors: Toutain, T.; Froehlich, C.
1991AdSpR..11d.213T Altcode: 1991AdSpR..11R.213T
The p-mode linewidths, obtained with the data of the space experiment
IPHIR, are performed with a likelihood technique, taking into account
the χ2 statistics of the power spectrum. A smoothed daily
power is also performed for each mode of the IPHIR p-mode spectrum.

---------------------------------------------------------
Title: Irradiance variability of the Sun.
Authors: Froehlich, Claus
1990NASCP3086..269F Altcode: 1990cisv.nasa..269F
Direct measurements of the solar constant - the total irradiance at
mean Sun-Earth distance - during the last ten years from satellite
show variations over time scales from minutes to years and decades. At
high frequencies the spectral power is determined by granulation,
super- and mesogranulation. In the 5-minute range, moreover, it is
dominated by power from the solar p-mode oscillations. Their power
and frequencies change with time yielding information about changes
in the convection zone. Towards periods of several hours the power is
steadily increasing and may be partly due to solar gravity modes. The
most important variance is in the range from days to several months and
is related to the photospheric features of solar activity: decreasing
the irradiance during the appearance of sunspots, and increasing it by
faculae and the magnetic network. Long-term modulation by the 11-year
activity cycle are observed conclusively with the irradiance being
higher during solar maximum. All these variations can be explained -
at least qualitatively - by their manifestation on the photosphere. For
the long-term changes the simultaneous changes of the frequencies
of solar p-mode oscillations suggest a more global origin of the
variations. Indeed, it seems that the observed irradiance modulation
is a true luminosity change with the magnetic cycle of the Sun.

---------------------------------------------------------
Title: Solar Brightness Oscillations - PHOBOS-2 Observations
Authors: Bruns, A. V.; Bonnet, R.; Delaboudinier, J. P.; Frohlich,
C.; Shumko, S. M.
1990SvAL...16..140B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Results of the Phobos-2 study of solar brightness oscillations
Authors: Bruns, A. V.; Bonnet, R.; Delaboudinier, J. P.; Frohlich,
C.; Shumko, S. M.
1990PAZh...16..330B Altcode:
Phobos-2 observations indicate that the variations in the power spectrum
of 5-min oscillations of the sun appear independently for each of the
modes and have the character of 4-5-hour amplitude bursts. In general,
the power spectrum lines reveal both quiet and active periods. The
quiet periods are characterized by a brightness burst amplitude of
(1.5-2) x 10 to the -7th and have a lifetime from about 10 hours to a
few days. The active spectrum consists of a single burst or a sequence
of bursts with an amplitude 30-50 times higher and lasting from a few
hours to one day.

---------------------------------------------------------
Title: p-Mode Analysis of the IPHIR Data
Authors: Fröhlich, Claus; Toutain, Thierry
1990LNP...367..215F Altcode: 1990psss.conf..215F
The results of the IPHIR experiment on the USSR planetary mission to
Phobos presented here are from data gathered during 160 days of the
cruise phase of PHOBOS II to Mars, launched on 12 July 1988. The long
uninterrupted observation produces a spectrum of the solar p-mode
oscillations in the 5-minute range with a very high signal-to-noise
ratio. Frequency and line shape determination is limited by the lifetime
of the modes and the noise from stochastic excitation. The temporal
variation of the amplitudes of l = 0... 2 is discussed.

---------------------------------------------------------
Title: Search for g-Modes in the IPHIR Data
Authors: Fröhlich, Claus
1990LNP...367..221F Altcode: 1990psss.conf..221F
The results of the IPHIR experiment on the USSR planetary mission
to Phobos presented here are from data gathered during 160 days of
the cruise phase of PHOBOS II to Mars, launched on 12 July 1988. The
search for g-modes is based on a cross-spectral analysis of the low
frequency spectrum from IPHIR (20 to 120 µHz) with theoretical g-mode
spectra. These spectra are calculated using a second order asymptotic
theory for the frequencies and a visibility function for the amplitudes
which depends on degree and frequency; the basic period spacing of the
g-modes and the rotational rate are varied in the ranges 26 &lt; P 0
&lt; 45 minutes and 0.4 &lt; v R &lt; 2.0 µHz respectively. Comparison
with artificial noise spectra indicates that the solar g-modes —
if they exist — are buried in solar noise with an upper limit for
their amplitudes of the order of 1.3 ppm at 20 µHz. More sophisticated
methods to extract a possible g-mode signal from noise are proposed.

---------------------------------------------------------
Title: Solar irradiance variability.
Authors: Fröhlich, C.
1989AtmRe..23..379F Altcode:
The solar "constant" varies over time scales from minutes to years
and decades. From direct measurements of the solar "constant" during
the last 10 years, one indeed becomes aware of substantial changes
on time scales longer than days. The most important influences seem
to be related to solar activity. It is indicated that global effects
not related to the solar activity produce irradiance variations, which
may be modulated by the same mechanism as that producing solar activity.

---------------------------------------------------------
Title: Multi-spectral analysis of total solar irradiance variations
Authors: Froehlich, C.; Pap, J.
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: VIRGO: The solar monitor experiment on SOHO.
Authors: Froehlich, C.; Andersen, Bo Nyborg; Berthomieu, G.;
Crommelynck, D.; Delache, Philippe; Domingo, V.; Jimenez, A.; Jones,
A. R.; Roca Cortés, Teodoro; Wehrli, Ch.
1988ESASP.286..371F Altcode: 1988ssls.rept..371F
The VIRGO Experiment (Variability of solar Irradiance and Gravity
Oscillations) contains two types of active cavity radiometers for
monitoring of the solar "constant", two three channel sunphotometers
(SPM) for the measurement of spectral irradiance at 335, 500 and 865 nm
and a low resolution imager (LOI) with 12 pixels. The main scientific
objective is probing the solar interior by helioseismology with p-
and g-mode solar oscillations determined from spectral irradiance
(SPM) and radiance (LOI) variations on time scales of minutes to
the mission time. Moreover, the measurements of the variability of
the solar "constant" and spectral irradiance over periods of days to
the mission time will yield information about the convection zone, as
will the comparison of the amplitudes and phases of the oscillations
as manifested in irradiance and radiance (from VIRGO) and velocity
(from GOLF and SOI).

---------------------------------------------------------
Title: IPHIR: The helioseismology experiment on the PHOBOS mission.
Authors: Fröhlich, C.; Bonnet, R. M.; Bruns, A. V.; Delaboudinière,
J. P.; Domingo, V.; Kotov, V. A.; Kollath, Z.; Rashkovsky, D. N.;
Toutain, T.; Vial, J. C.; Wehrli, C.
1988ESASP.286..359F Altcode: 1988ssls.rept..359F
IPHIR (InterPlanetary Helioseismology by IRradiance measurements) is
a solar irradiance experiment on the USSR planetary mission PHOBOS to
Mars and its satellite Phobos. The experiment is a cooperative effort
of PMOD/WRC, LPSP, SSD/ESA, KrAO and CRIP. The sensor is a three channel
sunphotometer (SPM) which measures the solar spectral irradiance at 335,
500 and 865 nm with a precision of better than 1 ppm. A two axis solar
sensor (TASS) is added to monitor the moderate solar pointing of the
spacecraft. A microprocessor based data processing unit controls the
sensor operation, acquires the data, and performs the data compression
for the transmission at a mean rate of 1 bit/s. The two spacecrafts
have been launched on July 7th and 12th, 1988. The experiment on
PHOBOS I gathered data during 45 days before the S/C was lost, the
one on PHOBOS II is still operating. The data recovery is excellent
with virtually 100% coverage. Although the signal is disturbed by the
pointing of the spacecraft the results of a preliminary analysis in
the range of the 5-minutes oscillations demonstrate the improvement
achievable due to the fact that the time series is truly continuous
and the instrumental and sampling noise is very low.

---------------------------------------------------------
Title: VIRGO: The solar monitor experiment on SOHO
Authors: Froehlich, C.; Andersen, B. N.; Berthomieu, G.; Crommelynck,
D.; Delache, Ph.; Domingo, V.; Jimenez, A.; Jones, A. R.; Roca Cortes,
T.; Wehrli, Ch.
1988sohi.rept...19F Altcode:
The Variability of solar IRradiance and Gravity Oscillations (VIRGO)
experiment contains two types of active cavity radiometers for
monitoring of the solar constant, two three channel sunphotometers for
the measurement of spectral irradiance at 335, 500 and 865 nm and a
low resolution imager with 12 pixels. The main scientific objective
is probing the solar interior by helioseismology with p and g mode
solar oscillations determined from spectral irradiance and radiance
variations on time scales of minutes to the mission time. Information
about the convection zone is thus obtained. The comparison of the
amplitudes and phases of the oscillations as manifested in irradiance
and radiance (from VIRGO) and velocity as measured by the GOLF (global
oscillations at low frequencies) experiment are also used in analyzing
the convection zone.

---------------------------------------------------------
Title: Solar Gravity Modes from Acrim/smm Irradiance Data
Authors: Frohlich, C.
1988IAUS..123...83F Altcode:
The power spectra of the time series of 270 days in 1980 and of 240 days
in 1984 are analysed using a statistical method for the determination
of the basic g-mode period separation T0 and the rotational
frequency νR. The results of the analysis of both time
series in the frequency range from 10 to 40 μHz are best fitted by a
T0 of 29.85 minutes. The angular velocity in the center of
the Sun inferred from the rotational splitting of the g-modes amounts to
6.6×10-6per sec, which is 2.3 times the photospheric rate.

---------------------------------------------------------
Title: Correlation of solar irradiance variability with evolution
of activity
Authors: Pap, J.; Froehlich, C.
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: Solar oscillations and helioseismology from ACRIM/SMM
irradiance data.
Authors: Fröhlich, C.
1987nep..conf..397F Altcode:
An introduction to solar oscillations, their properties and diagnostic
potential, and a review of our present knowledge is presented. The solar
irradiance data from the ACRIM (Active Cavity Radiometer for Irradiance
Monitoring) solar constant experiment on board the Solar Maximum
Mission satellite (SMM) are used to search for solar gravity modes,
which yield a direct information on the structure of the solar core.

---------------------------------------------------------
Title: Variability of the solar "constant" on time scales of minutes
to years.
Authors: Froehlich, C.
1987JGR....92..796F Altcode:
The power of the irradiance variability spectrum from about 70 nHz
(150 days) to 5 mHz (3.3 min) can be divided into three major domains
with the following characteristics: (1) From 70 nHz to 2 μHz (5.8 -
150 days) the spectrum is dominated by solar activity, the power of
which changes during the course of the solar cycle by up to 1 order of
magnitude. (2) From 2 to 20 μHz (14 hours to 5.8 days) the spectrum
follows a 1/ν2 law, which may be due to g modes. (3) From
20 μHz to 5 mHz (14 hours to 3.3 min) the spectrum follows a 1/ν
law, with a broad peak around 5 min which is due to p modes yielding
amplitudes of several ppm. As to the long-term changes, trends of
the order of 0.02% per year seem to exist. The question whether the
up and down trends with a peak around 1980 belong to an oscillatory
modulation of the solar output can only be answered in the future.

---------------------------------------------------------
Title: Solar oscillations and helioseismology from ACRIM/SMM
irradiance data
Authors: Fröhlich, C.
1987nep..conf..395F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-Term Downward Trend in Total Solar Irradiance
Authors: Willson, R. C.; Hudson, H. S.; Frohlich, C.; Brusa, R. W.
1986Sci...234.1114W Altcode:
The first 5 years (from 1980 to 1985) of total solar irradiance
observations by the first Active Cavity Radiometer Irradiance Monitor
(ACRIM I) experiment on board the Solar Maximum Mission spacecraft show
a clearly defined downward trend of -0.019% per year. The existence
of this trend has been confirmed by the internal self-calibrations of
ACRIM I, by independent measurements from sounding rockets and balloons,
and by observations from the Nimbus-7 spacecraft. The trend appears
to be due to unpredicted variations of solar luminosity on time scales
of years, and it may be related to solar cycle magnetic activity.

---------------------------------------------------------
Title: Internal Structure of the Sun
Authors: Frohlich, C.; Gough, D.
1985ESASP.235..241F Altcode: 1985fmsh.work..241F
No abstract at ADS

---------------------------------------------------------
Title: Solar gravity modes from ACRIM/SMM irradiance data.
Authors: Frohlich, C.; Delache, P.
1984sses.nasa..183F Altcode: 1984sss..conf..183F
The record of 280 days of continuous data of the ACRIM radiometer
on board the Solar Maximum Mission satellite is analysed in the
frequency range from 10 to 80 μHz. Gravity modes of degree one and
two with orders from about 10 to several hundreds can be localized. A
statistical method to determine the fundamental period T0
and the rate of rotation νR as seen by rotational splitting
is described and the results for 33.5 &lt; T0 &lt; 45.5
minutes and 0.4 &lt; νR &lt; 2.0 μHz presented. They
indicate a rather high T0 and it cannot be excluded that
it is above the upper limit analysed.

---------------------------------------------------------
Title: Global solar oscillations in irradiance and velocity:
a comparison.
Authors: Frohlich, C.; Vanderraay, H. B.
1984ESASP.220...17F Altcode: 1984ESPM....4...17F
The results of 7 hours of solar spectral irradiance measurements from
a stratospheric balloon (1983) are analysed for frequencies between 1
ad 5 mHz. Several significant peaks of up to 6 ppm in the red (778 nm)
and of up to 15 ppm in the blue (380 nm) can be identified as 5-minute
p-mode oscillations of the Sun. From bivariate time series analysis a
more or less constant relative phase close to zero and an amplitude
ratio between 1.5 and 3.2 with a maximum around 3 mHz is found. By
comparing the spectra with velocity measurements a phase difference
between the velocity and irradiance signals of 120 to 180° is found
and amplitude ratios of 15 and 50 ppm/m s-1 for the red
and blue respectively.

---------------------------------------------------------
Title: Solar gravity modes from ACRIM/SMM irradiance data
Authors: Froehlich, C.; Delache, P.
1984MmSAI..55...99F Altcode:
The record of 280 days of continuous data of the ACRIM radiometer
on board the Solar Maximum Mission satellite is analyzed in the
frequency range 2-80 microhertz. Gravity modes of degree one and two
with orders from about 10 to several hundred can be localized. Due
to the complexity of the spectrum of the enormous number of lines
in a given frequency interval, the individual identification is very
difficult. A statistical method to determine the fundamental period
and the rate of rotation as seen by rotational splitting is described,
and the results compared with other determinations.

---------------------------------------------------------
Title: The solar and heliospheric observatory, SOHO - A phase-A
project of the European space agency
Authors: Malinovsky-Arduini, M.; Froehlich, C.
1984AdSpR...4g.383M Altcode: 1984AdSpR...4..383M
The Solar and Heliospheric Observatory is designed to address basic
questions concerning the Sun and Heliosphere. In this paper our
present understanding of coronal heating, solar wind generation and
solar oscillations is described. The proposed model SOHO instrument
payload is outlined and it is shown how it would contribute to our
understanding in the above three fields.

---------------------------------------------------------
Title: Approaches to radiation guidelines for space travel
Authors: Froehlich, C.; Eddy, J. A.
1984AdSpR...4h.121F Altcode: 1984AdSpR...4..121F
There are obvious risks in space travel that have loomed larger
than any risk from radiation. Nevertheless, NASA has maintained
a radiation program that has involved maintenance of records of
radiation exposure, and planning so that the astronauts' exposures
are kept as low as possible, and not just within the current
guidelines. These guidelines are being reexamined currently by NCRP
Committee 75 because new information is available, for example, risk
estimates for radiation-induced cancer and about the effects of HZE
particles. Furthermore, no estimates of risk or recommendations were
made for women in 1970 and must now be considered. The current
career limit is 400 rem to the blood forming organs. The appropriateness
of this limit and its basis are being examined as well as the limits
for specific organs. There is now considerably more information about
age-dependency for radiation effects and this will be taken into
account. In 1973 a committee of the National Research Council made a
separate study of HZE particle effects and it was concluded that the
attendant risks did not pose a hazard for low inclination near-earth
orbit missions. Since that time work has been carried out on the
so-called microlesions caused by HZE particles and on the relative
carcinogic effect of heavy ions, including iron. A remaining question
is whether the fluence of HZE particles could reach levels of concern
in missions under consideration. Finally, it is the intention of the
committee to indicate clearly the areas requiring further research.

---------------------------------------------------------
Title: Solar variability for periods of days to months
Authors: Froehlich, C.
1984AdSpR...4h.117F Altcode: 1984AdSpR...4..117F
The time series of total solar irradiance determinations from ACRIM
on the Solar Maximum Mission satellite (SMM) of 270 days and from
the ERB experiment on NIMBUS 7 of 1445 days are analysed for periods
greater than a few days. Comparison of the spectra of both with the
spectrum of projected sunspot area over the corresponding time periods
show high coherence for periods of 7 to about 25 days and for periods
longer than about 30 to 35 days. In the vicinity and at the 27-day
rotational period of the Sun, however, the coherence between sunspot
area and irradiance is small, although both spectra show significant
power at and around this period. This means that there is a signal
in the irradiance which cannot be due to the sunspot area and the
assumption of a straight forward sunspot blocking seems to be over
simplified. This irradiance signal at 27 days has an amplitude of
about +/-0.012 per cent and is an enhancement.

---------------------------------------------------------
Title: Solar radiometry from high-altitude balloons
Authors: Brusa, R. W.; Froehlich, C.; Wehrli, C.
1983ESASP.183..429B Altcode: 1983erbp.conf..429B
A balloon experiment was devised to determine the solar constant and
the spectral solar irradiance at selected wavelengths. New methods of
characterization substantially improved the state of the art of absolute
radiometers and sunphotometers. The solar constant was determined during
flights in 1979 and 1980 as 1366.2 and 1367.8 W m-2. A time
series analysis of the sunphotometer data showed several peaks in the 5
minutes range. The high coherence with simultaneous measurements from
the SMM satellite indicates the solar origin of the peaks, which are
likely to be low degree p-mode oscillations of the Sun.

---------------------------------------------------------
Title: Determination of aerosol optical depth from ground measurements
Authors: Fröhlich, C.
1982AdSpR...2e.139F Altcode: 1982AdSpR...2..139F
The methods used to determine the aerosol optical depth as a function
of wavelength are briefly described and discussed. Some results from
the operational network of the World Meteorological Organization and
other, more research oriented studies, are reviewed and critically
analysed to assess the reliability and accuracy of such determinations
and their value as ground truth measurements for space applications.

---------------------------------------------------------
Title: Solar radiometry: Total irradiance measurements
Authors: Froehlich, C.
1982AdSpR...2d.191F Altcode: 1982AdSpR...2..191F
The operating principles of modern absolute radiometers are discussed
and the methods of their characterization, that is the accurate
determination of the uncertainties, are described. In view of this
analysis, the results of the solar constant determinations of the
last 6 years are reviewed and an estimate of their uncertainties
given. Procedures for the strategy of future experiments are
recommended.

---------------------------------------------------------
Title: The variability of the solar output
Authors: Frohlich, C.
1981NASCP2191...37F Altcode: 1981vsc..conf...37F
A review of solar constant determinations and measurements of its
spectral distribution is presented. For the period from 1966 to 1980
a mean value of 1367 Wm-2 was determined. Within the corresponding
uncertainty, no significant change of both the integral value and
the spectral distribution can be detected. However, short term solar
variations and their spectral dependence were deduced from measurements
during four hours on June 20, 1980 from 34 km altitude with amplitudes
of + or - 500 ppm at 368 nm, of 200 ppm at 500 nm and + or - 150 ppm
at 778 nm. Comparison with simultaneous total irradiance data of the
Solar Maximum Mission (SMM) shows a high correlation which indicates
the solar origin. The power spectrum shows a weak peak at about 3.2 mHz,
which corresponds to the frequency of the 5 minutes solar oscillation.

---------------------------------------------------------
Title: Solar Radiation and its Variation in Time
Authors: Froehlich, C.; Brusa, R. W.
1981SoPh...74..209F Altcode:
In order to assess the variability of the solar radiation, the record of
determinations of the total and spectral solar irradiance of the last 15
years is analysed. Although the datapoints for the period before 1969
suggest a slight decrease, the uncertainties of these determinations
are too large to render this statement significant. Together with the
results of the following period (1969-1980) which show that within
the uncertainty no change is detectable, it can be concluded, that
the solar constant has not changed during the last 15 years. The
same result is found from the spectral distribution record, though
not as conclusive as for the solar constant, due to the much larger
uncertainties of the spectral data.

---------------------------------------------------------
Title: New determination of Rayleigh scattering in the terrestrial
atmosphere
Authors: Froehlich, C.; Shaw, G. E.
1980ApOpt..19.1773F Altcode:
New Rayleigh-scattering optical thickness values for the
terrestrial atmosphere in the 260-1500-nm wavelength range have been
calculated using updated data on atmospheric optical parameters. The
calculations include molecular scattering from water vapor and take
into account varying atmospheric composition with altitude. The new
Rayleigh-scattering coefficients average 4.5% lower than those listed
by Penndorf in 1955.

---------------------------------------------------------
Title: Field measurements of penetrator seismic coupling in sediments
and volcanic rocks
Authors: Nakamura, Y.; Latham, G. V.; Frohlich, C.; Blanchard, M. B.;
Murphy, J. P.
1979STIN...7921977N Altcode:
Field experiments were conducted to determine how well a seismometer
installed using a penetrator would be coupled to the ground. A dry-lake
bed and a lava bed were chosen as test sites to represent geological
environments of two widely different material properties. At each site,
two half-scale penetrators were fired into the ground, a three-component
geophone assembly was mounted to the aft end of each penetrator,
and dummy penetrators were at various distances to generate seismic
signals. These signals were detected by the penetrator-mounted geophone
assembly and by a reference geophone assembly buried or anchored to
surface rock and 1-m from the penetrator. The recorded signals were
digitized, and cross-spectral analyses were performed to compare the
observed signals in terms of power spectral density ratio, coherence,
and phase difference. The analyses indicate that seismometers deployed
by penetrators will be as well coupled to the ground as are seismometers
installed by conventional methods for the frequency range of interest
in earthquake seismology.

---------------------------------------------------------
Title: Contemporary Measures of the Solar Constant
Authors: Fröhlich, C.
1977soiv.conf...93F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar Constant: A Critical Review
Authors: Fröhlich, C.
1977raat.conf..589F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 1. Upper mantle structure beneath the Fiji plateau: Seismic
observations of second P-arrivals from the olivine spinel phase
transition zone. 2: Strainmeter and tiltmeter measurements from the
Tonga Island arc. 3: The case for four-component strainmeters
Authors: Frohlich, C. A.
1976PhDT........22F Altcode:
Large and impulsive second P-arrivals (4-12 second after the intial
P-arrivals) from intermediate depth earthquakes located in the New
Hebrides island arc are observed at distances of 7 deg. to 14 deg. on
the records produced by short-period seismographs in Fiji. This
conclusion is consistent with: (1) the observed onset distance of the
travel time cusp, (2) the change with distance of Delta t (the time
difference between the first and second P-arrivals), (3) the change
of Delta t with the depth of the events, (4) the slowness of the first
and second P-arrivals, and finally, (5) comparisons with the predicted
arrival times from other published velocity models which contain a rapid
P-velocity increase in the upper mantle. A four-component quartz tube
strainmeter with capacitance transducers was installed in a surface
site on the small coral island of Tongatapu in Tonga and 30 days of
data was analyzed. Semidiurnal lunar tidal strains with peak-to-peak
amplitudes were observed on all components.

---------------------------------------------------------
Title: Measurement of the Solar Constant, A Critical Review
Authors: Fröhlich, C.; Brusa, R. W.
1975scea.conf..111F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The relation between the IPS now in use and Smithsonian scale
1913, Angstrom scale and Absolute scale
Authors: Frohlich, C.
1973srmi.symp...61F Altcode:
Radiation scales used as references for meteorological radiation
measurements are discussed. Specific radiation scales included are:
the Angstrom scale, the Smithsonian scale, the Absolute scale, and the
International Pyrheliometer Scale. The relations between the radiation
scales are stated along with the estimated mean differences between
the scales.