Author name code: gabriel
ADS astronomy entries on 2022-09-14
author:"Gabriel, Alan H."
------------------------------------------------------------------------
Title: CamDavidsonPilon/lifelines: 0.26.0
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; JoseLlanes; Singaravelan, Karthikeyan; Besson, Lilian;
Sancho Peña, Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff;
Noorbakhsh, Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean;
Seabold, Skipper
Bibcode: 2021zndo...4816284D
Altcode:
0.26.0 - 2021-05-26 New features .BIC_ is now present on fitted
models. CoxPHFitter with spline baseline can accept pre-computed
knot locations. Left censoring fitting in KaplanMeierFitter is now
"expected". That is, predict always predicts the survival function (as
does every other model), confidence_interval_ is always the CI for the
survival function (as does every other model), and so on. In summary:
the API for estimates doesn't change depending on what your censoring
your dataset is. Bug fixes Fixed an annoying bug where at_risk-table
label's were not aligning properly when data spanned large ranges. See
merging PR for details. Fixed a bug in find_best_parametric_model
where the wrong BIC value was being computed. Fixed regression bug
when using an array as a penalizer in Cox models.
Title: CamDavidsonPilon/lifelines: v0.25.11
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Seabold, Skipper;
Golland, Dave
Bibcode: 2021zndo...4683730D
Altcode:
0.25.11 - 2021-04-06 A previous release (on Github) was missing correct
metadata and was deleted. Bug fixes Fix integer-valued categorical
variables in regression model predictions. numpy > 1.20 is allowed. Bug
fix in the elastic-net penalty for Cox models that wasn't weighting
the terms correctly.
Title: CamDavidsonPilon/lifelines: 0.25.10
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Seabold, Skipper;
Golland, Dave
Bibcode: 2021zndo...4579431D
Altcode:
0.25.10 - 2021-03-03 New features Better appearance when using a
single row to show in add_at_risk_table.
Title: CamDavidsonPilon/lifelines: v0.25.9
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Seabold, Skipper;
Golland, Dave
Bibcode: 2021zndo...4505728D
Altcode:
0.25.9 - 2021-02-04 Small bump in dependencies.
Title: CamDavidsonPilon/lifelines: v0.25.8
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Seabold, Skipper;
Golland, Dave
Bibcode: 2021zndo...4457577D
Altcode:
0.25.8 - 2021-01-22 Important: we dropped Patsy as our formula
framework, and adopted Formulaic. Will the latter is less mature than
Patsy, we feel the core capabilities are satisfactory and it provides
new opportunities. New features Parametric models with formulas are
able to be serialized now. a _scipy_callback function is available to
use in fitting algorithms.
Title: CamDavidsonPilon/lifelines: v0.25.7
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Reed, Sean; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Seabold, Skipper;
Golland, Dave
Bibcode: 2020zndo...4313838D
Altcode:
0.25.7 - 2020-12-09 API Changes Adding cumulative_hazard_at_times
to NelsonAalenFitter Bug fixes Fixed error in CoxPHFitter when
entry time == event time. Fixed formulas in AFT interval censoring
regression. Fixed concordance_index_ when no events observed Fixed
label being overwritten in ParametricUnivariate models
Title: CamDavidsonPilon/lifelines: v0.25.6
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Sean-Reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave;
Jlim13
Bibcode: 2020zndo...4136578D
Altcode:
0.25.6 - 2020-10-26 New features Parametric Cox models can now handle
left and interval censoring datasets. Bug fixes "improved" the output
of add_at_risk_counts by removing a call to plt.tight_layout() - this
works better when you are calling add_at_risk_counts on multiple axes,
but it is recommended you call plt.tight_layout() at the very end of
your script. Fix bug in KaplanMeierFitter's interval censoring where
max(lower bound) < min(upper bound).
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal.
Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing.
Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
Title: CamDavidsonPilon/lifelines: v0.25.5
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
sean-reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave;
jlim13
Bibcode: 2020zndo...4050560D
Altcode:
0.25.5 - 2020-09-23 API Changes check_assumptions now returns a
list of list of axes that can be manipulated Bug fixes fixed error
when using plot_partial_effects with categorical data in AFT models
improved warning when Hessian matrix contains NaNs. fixed performance
regression in interval censoring fitting in parametric models weights
wasn't being applied properly in NPMLE
Title: CamDavidsonPilon/lifelines: v0.25.4
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Sean-Reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave;
Jlim13
Bibcode: 2020zndo...4002777D
Altcode:
0.25.4 - 2020-08-26 New features New baseline estimator for Cox
models: piecewise Performance improvements for parametric models
log_likelihood_ratio_test() and print_summary() Better step-size
defaults for Cox model -> more robust convergence. Bug fixes fix
check_assumptions when using formulas.
Title: CamDavidsonPilon/lifelines: v0.25.3
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Sean-Reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Moncada-Torres, Arturo; Stark, Kyle; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; GrowthJeff; Noorbakhsh,
Javad; Begun, Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave;
Jlim13
Bibcode: 2020zndo...3998734D
Altcode:
0.25.3 - 2020-08-24 New features
survival_difference_at_fixed_point_in_time_test now accepts fitters
instead of raw data, meaning that you can use this function
on left, right or interval censored data. API Changes See note
on survival_difference_at_fixed_point_in_time_test above. Bug
fixes fix StatisticalResult printing in notebooks fix Python
error when calling plot_covariate_groups fix dtype mismatches in
plot_partial_effects_on_outcome.
Title: CamDavidsonPilon/lifelines: v0.24.16
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
sean-reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Stark, Kyle; Moncada-Torres, Arturo; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; Noorbakhsh, Javad; Begun,
Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave; jlim13; Flaxman,
Abraham
Bibcode: 2020zndo...3937749D
Altcode:
0.24.16 - 2020-07-09 New features improved algorithm choice for large
Dataframes for Cox models. Should see a significant performance boost.
Bug fixes fixed utils.median_survival_time not accepting Pandas Series.
Title: CamDavidsonPilon/lifelines: v0.24.15
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Sean-Reed; Kuhn, Ben; Zivich, Paul; Williamson, Mike; AbdealiJK;
Datta, Deepyaman; Fiore-Gartland, Andrew; Parij, Alex; WIlson, Daniel;
Gabriel; Moneda, Luis; Stark, Kyle; Moncada-Torres, Arturo; Gadgil,
Harsh; Jona; Singaravelan, Karthikeyan; Besson, Lilian; Sancho Peña,
Miguel; Anton, Steven; Klintberg, Andreas; Noorbakhsh, Javad; Begun,
Matthew; Kumar, Ravin; Hussey, Sean; Golland, Dave; Jlim13; Flaxman,
Abraham
Bibcode: 2020zndo...3934629D
Altcode:
0.24.15 - 2020-07-07 Bug fixes fixed an edge case in KaplanMeierFitter
where a really late entry would occur after all other population had
died. fixed plot in BreslowFlemingtonHarrisFitter fixed bug where
using conditional_after and times in CoxPHFitter("spline") prediction
methods would be ignored.
Title: CamDavidsonPilon/lifelines: v0.24.8
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Jacobson, Noah;
Zivich, Paul; Kuhn, Ben; Williamson, Mike; Sean-Reed; AbdealiJK;
Fiore-Gartland, Andrew; Datta, Deepyaman; Moneda, Luis; Gabriel;
WIlson, Daniel; Parij, Alex; Moncada-Torres, Arturo; Stark, Kyle;
Anton, Steven; Sancho Peña, Miguel; Besson, Lilian; Singaravelan,
Karthikeyan; Jona; Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar,
Ravin; Begun, Matthew; Noorbakhsh, Javad; Klintberg, Andreas; Rendeiro,
André F.; Flaxman, Abraham
Bibcode: 2020zndo...3833188D
Altcode:
0.24.8 New features Non parametric interval censoring is now available,
experimentally. Not all edge cases are fully checked, and some features
are missing. Try it under KaplanMeierFitter.fit_interval_censoring
Title: CamDavidsonPilon/lifelines: v0.23.9
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Williamson, Mike; AbdealiJK; Fiore-Gartland, Andrew;
Moneda, Luis; Gabriel; WIlson, Daniel; Parij, Alex; Stark, Kyle;
Anton, Steven; Sancho Peña, Miguel; Besson, Lilian; Jona; Gadgil,
Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh, Javad;
Klintberg, Andreas; Medvinsky, Dmitry; Zgonjanin, Denis; Katz, Daniel
S.; Chen, Daniel; Ahern, Christopher; Fournier, Chris; Moncada-Torres,
Arturo; Rendeiro, André F.
Bibcode: 2020zndo...3629409D
Altcode:
0.23.9 - 2020-01-28 Bug fixes fixed important error when
a parametric regression model would not assign the correct
labels to fitted parameters' variances. See more here:
https://github.com/CamDavidsonPilon/lifelines/issues/931. Users of
GeneralizedGammaRegressionFitter and any custom regression models
should update their code as soon as possible.
Title: CamDavidsonPilon/lifelines: v0.23.8
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Williamson, Mike; AbdealiJK; Fiore-Gartland, Andrew;
Moneda, Luis; Gabriel; WIlson, Daniel; Parij, Alex; Stark, Kyle;
Anton, Steven; Sancho Peña, Miguel; Besson, Lilian; Jona; Gadgil,
Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh, Javad;
Klintberg, Andreas; Medvinsky, Dmitry; Zgonjanin, Denis; Katz, Daniel
S.; Chen, Daniel; Ahern, Christopher; Fournier, Chris; Moncada-Torres,
Arturo; Rendeiro, André F.
Bibcode: 2020zndo...3620921D
Altcode:
Bug fixes fixed important error when a parametric regression model
would not assign the correct labels to fitted parameters. See more
here: https://github.com/CamDavidsonPilon/lifelines/issues/931. Users
of GeneralizedGammaRegressionFitter and any custom regression models
should update their code as soon as possible.
Title: CamDavidsonPilon/lifelines: v0.23.4
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Williamson, Mike; AbdealiJK; Fiore-Gartland, Andrew;
Moneda, Luis; Gabriel; WIlson, Daniel; Parij, Alex; Stark, Kyle;
Anton, Steven; Besson, Lilian; Jona; Gadgil, Harsh; Golland, Dave;
Hussey, Sean; Kumar, Ravin; Noorbakhsh, Javad; Klintberg, Andreas;
dhuynh; Medvinsky, Dmitry; Zgonjanin, Denis; Katz, Daniel S.; Chen,
Daniel; Ahern, Christopher; Fournier, Chris; Moncada-Torres, Arturo;
Rendeiro, André F.
Bibcode: 2019zndo...3576382D
Altcode:
Bugfix for PyPI
Title: CamDavidsonPilon/lifelines: v0.23.0
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; AbdealiJK; Moneda, Luis; Gabriel;
WIlson, Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson,
Lilian; Jona; Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar,
Ravin; Noorbakhsh, Javad; Klintberg, Andreas; Albrecht, Dylan; Dhuynh;
Medvinsky, Dmitry; Zgonjanin, Denis; Katz, Daniel S.; Chen, Daniel;
Ahern, Christopher; Fournier, Chris; Moncada-Torres, Arturo; Rendeiro,
André F.
Bibcode: 2019zndo...3544808D
Altcode:
0.23.0 New features new print_summary abstraction that allows HTML
printing in Jupyter notebooks! silenced some warnings. Bug fixes The
"comparison" value of some parametric univariate models wasn't standard,
so the null hypothesis p-value may have been wrong. This is now
fixed. fixed a NaN error in confidence intervals for KaplanMeierFitter
API Changes To align values across models, the column names for the
confidence intervals in parametric univariate models summary have
changed. Fixed typo in ParametricUnivariateFitter name. median_ has
been removed in favour of median_survival_time_. left_censorship in
fit has been removed in favour of fit_left_censoring.
Title: CamDavidsonPilon/lifelines: v0.22.4
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; Moneda, Luis; Gabriel; WIlson,
Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson, Lilian; Jona;
Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh,
Javad; Klintberg, Andreas; Ochoa, Eduardo; Albrecht, Dylan; dhuynh;
Medvinsky, Dmitry; Zgonjanin, Denis; Katz, Daniel S.; Chen, Daniel;
Ahern, Christopher; Fournier, Chris; Arturo; Rendeiro, André F.
Bibcode: 2019zndo...3386382D
Altcode:
0.22.4 - 2019-09-04 New features Some performance improvements
to regression models. lifelines will avoid penalizing the
intercept (aka bias) variables in regression models. new
utils.restricted_mean_survival_time that approximates the RMST
using numerical integration against survival functions. API changes
KaplanMeierFitter.survival_function_'s' index is no longer given the
name "timeline". Bug fixes Fixed issue where concordance_index would
never exit if NaNs in dataset.
Title: CamDavidsonPilon/lifelines: v0.22.0
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; Moneda, Luis; Gabriel; WIlson,
Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson, Lilian; Jona;
Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh,
Javad; Klintberg, Andreas; Martin, Eric; Ochoa, Eduardo; Albrecht,
Dylan; Dhuynh; Medvinsky, Dmitry; Zgonjanin, Denis; Chen, Daniel;
Ahern, Christopher; Fournier, Chris; Arturo; Rendeiro, André F.
Bibcode: 2019zndo...3267531D
Altcode:
New features Ability to create custom parametric regression models
by specifying the cumulative hazard. This enables new and extensions
of AFT models. percentile(p) method added to univariate models that
solves the equation p = S(t) for t for parametric univariate models,
the conditional_time_to_event_ is now exact instead of an approximation.
API changes In Cox models, the attribute hazards_ has been renamed
to params_. This aligns better with the other regression models,
and is more clear (what is a hazard anyways?) In Cox models, a new
hazard_ratios_ attribute is available which is the exponentiation of
params_. In regression models, the column names in confidence_intervals_
has changed to include the alpha value. In regression models, some
column names in .summary and .print_summary has changed to include
the alpha value. In regression models, some column names in .summary
and .print_summary includes confidence intervals for the exponential
of the value. Significant changes to internal AFT code. A change
to how fit_intercept works in AFT models. Previously one could set
fit_intercept to False and not have to set ancillary_df - now one must
specify a DataFrame. Bug fixes for parametric univariate models,
the conditional_time_to_event_ is now exact instead of an approximation.
Title: CamDavidsonPilon/lifelines: v0.21.3
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; Moneda, Luis; Gabriel; WIlson,
Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson, Lilian; Jona;
Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh,
Javad; Klintberg, Andreas; Kaluzka, Jakub; Slavitt, Isaac; Martin,
Eric; Ochoa, Eduardo; Albrecht, Dylan; Dhuynh; Zgonjanin, Denis;
Chen, Daniel; Fournier, Chris; Arturo; Rendeiro, André F.
Bibcode: 2019zndo...3240536D
Altcode:
0.21.3 - 2019-06-04 New features include in lifelines is a scikit-learn
adapter so lifeline's models can be used with scikit-learn's API. See
documentation here. CoxPHFitter.plot now accepts a hazard_ratios
(boolean) parameter that will plot the hazard ratios (and CIs) instead
of the log-hazard ratios. CoxPHFitter.check_assumptions now accepts
a columns parameter to specify only checking a subset of columns.
Bug fixes covariates_from_event_matrix handle nulls better
Title: CamDavidsonPilon/lifelines: v0.21.1
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; Moneda, Luis; Gabriel; WIlson,
Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson, Lilian; Jona;
Gadgil, Harsh; Golland, Dave; Hussey, Sean; Kumar, Ravin; Noorbakhsh,
Javad; Klintberg, Andreas; Kaluzka, Jakub; Slavitt, Isaac; Martin,
Eric; Ochoa, Eduardo; Albrecht, Dylan; Dhuynh; Zgonjanin, Denis;
Chen, Daniel; Fournier, Chris; Arturo; Rendeiro, André F.
Bibcode: 2019zndo...2652543D
Altcode:
0.21.1 - 2019-04-26 New features users can provided their
own start and stop column names in add_covariate_to_timeline
PiecewiseExponentialFitter now allows numpy arrays as breakpoints API
changes output of survival_table_from_events when collapsing rows to
intervals now removes the "aggregate" column multi-index. Bug fixes
fixed bug in CoxTimeVaryingFitter when ax is provided, thanks @j-i-l!
Title: CamDavidsonPilon/lifelines: v0.21.0
Authors: Davidson-Pilon, Cameron; Kalderstam, Jonas; Zivich, Paul;
Kuhn, Ben; Fiore-Gartland, Andrew; Moneda, Luis; Gabriel; WIlson,
Daniel; Parij, Alex; Stark, Kyle; Anton, Steven; Besson, Lilian;
Jona; Gadgil, Harsh; Golland, Dave; Hussey, Sean; Noorbakhsh, Javad;
Klintberg, Andreas; Rose, Jeff; Kaluzka, Jakub; Slavitt, Isaac;
Martin, Eric; Ochoa, Eduardo; Albrecht, Dylan; dhuynh; Zgonjanin,
Denis; Chen, Daniel; Fournier, Chris; Arturo; Rendeiro, André F.
Bibcode: 2019zndo...2638135D
Altcode:
0.21.0 New features weights is now a optional kwarg for parametric
univariate models. all univariate and multivariate parametric models
now have ability to handle left, right and interval censored data
(the former two being special cases of the latter). Users can use the
fit_right_censoring (which is an alias for fit), fit_left_censoring and
fit_interval_censoring. a new interval censored dataset is available
under lifelines.datasets.load_diabetes API changes left_censorship
on all univariate fitters has been deprecated. Please use the new api
model.fit_left_censoring(...). invert_y_axis in model.plot(... has been
removed. entries property in multivariate parametric models has a new
Series name: entry Bug fixes lifelines was silently converting any
NaNs in the event vector to True. An error is now thrown instead. Fixed
an error that didn't let users use Numpy arrays in prediction for
AFT models
Title: Detection of g modes in the asymptotic frequency range:
evidence for a rapidly rotating core
Authors: Ulrich, Roger K.; Fossat, Eric; Boumier, Patrick; Corbard,
Thierry; Provost, Janine; Salabert, David; Schmider, François-Xavier;
Gabriel, Alan; Grec, Gerard; Renaud, Catherine; Robillot, Jean-Maurice;
Roca Cortés, Teodoro; Turck-Chièze, Sylvaine
Bibcode: 2017SPD....4810906U
Altcode:
We present the identification of very low frequency g modes, in the
asymptotic regime, and two important parameters: the core rotation rate
and the asymptotic equidistant period spacing of these g modes. The
GOLF instrument on the SOHO space observatory has provided two
decades of full disk helioseismic data. The search for g modes in
GOLF measurements has been extremely difficult, due to solar and
instrumental noise. In the present study, the p modes of the GOLF
signal are analyzed differently, searching for possible collective
frequency modulations produced by periodic changes in the deep solar
structure. Such modulations provide access to only very low frequency
g modes, thus allowing statistical methods to take advantage of their
asymptotic properties. For oscillatory periods in the range between 9
and nearly 48 hours, almost 100 g modes of spherical harmonic degree
1 and more than 100 g modes of degree 2 are predicted. They are not
observed individually, but when combined, they unambiguously provide
their asymptotic period equidistance and rotational splittings,
in excellent agreement with the requirements of the asymptotic
approximations. P0, the g-mode period equidistance parameter, is
measured to be 34 min 01 s, with a 1 s uncertainty. The previously
unknown g-mode splittings have now been measured from a non synodic
reference with a very high accuracy, and they imply a mean weighted
rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting
in a rapid rotation frequency of 1644 ± 23 nHz (period of one week)
of the solar core itself, which is a factor 3:8 ± 0:1 faster than the
rotation of the radiative envelope.Acknowledgements. Ulrich is first
author on this abstract due to AAS rules, Fossat is the actual first
author. SOHO is a project of international collaboration between ESA and
NASA. We would like to acknowledge the support received continuously
during more than 3 decades from CNES. DS acknowledges the financial
support from the CNES GOLF grant and the Observatoire de la Côte
d’Azur for support during his stays. RKU acknowledges support from
NASA for his participation in this project and thanks John Bahcall
for enthusiastic encouragement for the g-mode search.
Title: Asymptotic g modes: Evidence for a rapid rotation of the
solar core
Authors: Fossat, E.; Boumier, P.; Corbard, T.; Provost, J.; Salabert,
D.; Schmider, F. X.; Gabriel, A. H.; Grec, G.; Renaud, C.; Robillot,
J. M.; Roca-Cortés, T.; Turck-Chièze, S.; Ulrich, R. K.; Lazrek, M.
Bibcode: 2017A&A...604A..40F
Altcode: 2017arXiv170800259F
Context. Over the past 40 years, helioseismology has been enormously
successful in the study of the solar interior. A shortcoming has
been the lack of a convincing detection of the solar g modes, which
are oscillations driven by gravity and are hidden in the deepest
part of the solar body - its hydrogen-burning core. The detection
of g modes is expected to dramatically improve our ability to model
this core, the rotational characteristics of which have, until now,
remained unknown.
Aims: We present the identification of very
low frequency g modes in the asymptotic regime and two important
parameters that have long been waited for: the core rotation rate,
and the asymptotic equidistant period spacing of these g modes.
Methods: The GOLF instrument on board the SOHO space observatory has
provided two decades of full-disk helioseismic data. The search for
g modes in GOLF measurements has been extremely difficult because of
solar and instrumental noise. In the present study, the p modes of the
GOLF signal are analyzed differently: we search for possible collective
frequency modulations that are produced by periodic changes in the
deep solar structure. Such modulations provide access to only very low
frequency g modes, thus allowing statistical methods to take advantage
of their asymptotic properties.
Results: For oscillatory
periods in the range between 9 and nearly 48 h, almost 100 g modes
of spherical harmonic degree 1 and more than 100 g modes of degree 2
are predicted. They are not observed individually, but when combined,
they unambiguously provide their asymptotic period equidistance and
rotational splittings, in excellent agreement with the requirements
of the asymptotic approximations. When the period equidistance has
been measured, all of the individual frequencies of each mode can
be determined. Previously, p-mode helioseismology allowed the g-mode
period equidistance parameter P0 to be bracketed inside a
narrow range, between approximately 34 and 35 min. Here, P0
is measured to be 34 min 01 s, with a 1 s uncertainty. The previously
unknown g-mode splittings have now been measured from a non-synodic
reference with very high accuracy, and they imply a mean weighted
rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting
in a rapid rotation frequency of 1644 ± 23 nHz (period of one week)
of the solar core itself, which is a factor 3.8 ± 0.1 faster than the
rotation of the radiative envelope.
Conclusions: The g modes
are known to be the keys to a better understanding of the structure
and dynamics of the solar core. Their detection with these precise
parameters will certainly stimulate a new era of research in this field.
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
Bibcode: 2016cosp...41E.607F
Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
Bibcode: 2016cosp...41E.681G
Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.
Title: Stratospheric Impact on the Onset of the Mesospheric Ice Season
Authors: Fiedler, J.; Baumgarten, G.; Berger, U.; Gabriel, A.; Latteck,
R.; Luebken, F. J.
Bibcode: 2014AGUFMSA44A..04F
Altcode:
Mesospheric ice layers, observed as noctilucent clouds (NLC) from
ground, are the visible manifestation of extreme conditions in the
polar summer mesopause region. Temperatures fall very low so that water
vapor can freeze condence, which at 69°N usually occurs beginning of
June. However, in 2013 the ALOMAR RMR lidar observed the first NLC on
21 May and the clouds reoccured during the following days. These were
the earliest detections since 20 years and indicated an about 10 days
earlier onset of the mesospheric ice season. This is supported by the
colocated MAARSY radar which showed the occurrence rates of polar
mesospheric summer echoes (PMSE) increasing faster than usual.The
exceptional case was accompanied by ∼6 K lower temperatures and
higher water vapor mixing ratios at NLC altitudes above ALOMAR from
end of April until beginning of June as measured by the MLS instrument
onboard the AURA satellite. Using MERRA reanalysis data we will show
that the zonal mean temperature as well as the dynamic conditions in
the Arctic middle atmosphere deviated in spring 2013 significantly
from the mean conditions of the last 20 years. The planetary wave
activity in the high latitude stratosphere was enhanced from 20 April
to beginning of May. The colder and wetter upper mesosphere in May
2013 is attributed to this unusual late planetary wave activity in
the stratosphere, introducing a strong upwelling in the mesosphere,
lower temperatures and an upward transport of water vapor, which
finally resulted into earlier existence conditions for mesospheric
ice particles. For the southern hemisphere a high correlation between
winter/summer transition in the stratosphere and onset of mesospheric
ice is known as intra-hemispheric coupling. We regard the processes
in the Arctic middle atmosphere in spring 2013 as a first evidence for
intra-hemispheric coupling in the northern hemisphere, extending from
the stratosphere into the mesopause region.
Title: Outflow Velocity Structure in the Upper Transition Region
and Corona
Authors: Gabriel, Alan; Abbo, Lucia
Bibcode: 2012SoPh..280..435G
Altcode: 2012SoPh..tmp..139G
Outflow velocity maps in the quiet Sun and coronal hole regions have
been observed with the EUV Imaging Spectrometer on Hinode over a range
of coronal and transition region temperatures, in order to correlate
the solar wind with effects due to the underlying supergranule network
and to coronal holes. The cell structure has been identified using
data from the Solar Dynamics Observatory: specifically, 1600 Å images
from the Advanced Imaging Assembly instrument and dopplergrams from
the Helioseismic and Magnetic Imager. We find that the expansion of
the velocity field with height through the upper transition region
and the corona follows the same general pattern that has been long
established for the emitted intensities. The outflow velocity field
expands laterally with height with the magnetic funnels, eventually
filling the space between the cell boundaries. Moreover, the detailed
structure of the outflow morphology, combined with the decrease of
velocity dispersion with increasing temperature, supports the concept
of local stochastic energy release at lower heights. This is consistent
with a reconnection process between emerging fields within the cell
and the funnels at the cell boundaries.
Title: The dependence of coronal velocities on sub-photospheric
magnetic and velocity fields
Authors: Gabriel, Alan; Abbo, Lucia
Bibcode: 2011sdmi.confE...3G
Altcode:
We examine the relationship between coronal outflow velocities derived
from Hinode/EIS spectra and the underlying photospheric supergranular
cell structure derived from SDO/HMI and SDO/AIA observations. We show to
what extent the spatial distribution of the outflow follows the expected
expansion in the corona of the photospheric magnetic field emergence.
Title: Morphology, dynamics and plasma parameters of plumes and
inter-plume regions in solar coronal holes
Authors: Wilhelm, K.; Abbo, L.; Auchère, F.; Barbey, N.; Feng, L.;
Gabriel, A. H.; Giordano, S.; Imada, S.; Llebaria, A.; Matthaeus,
W. H.; Poletto, G.; Raouafi, N. -E.; Suess, S. T.; Teriaca, L.; Wang,
Y. -M.
Bibcode: 2011A&ARv..19...35W
Altcode: 2011arXiv1103.4481W
Coronal plumes, which extend from solar coronal holes (CH) into the high
corona and—possibly—into the solar wind (SW), can now continuously
be studied with modern telescopes and spectrometers on spacecraft,
in addition to investigations from the ground, in particular, during
total eclipses. Despite the large amount of data available on these
prominent features and related phenomena, many questions remained
unanswered as to their generation and relative contributions to
the high-speed streams emanating from CHs. An understanding of the
processes of plume formation and evolution requires a better knowledge
of the physical conditions at the base of CHs, in plumes and in the
surrounding inter-plume regions. More specifically, information is
needed on the magnetic field configuration, the electron densities
and temperatures, effective ion temperatures, non-thermal motions,
plume cross sections relative to the size of a CH, the plasma bulk
speeds, as well as any plume signatures in the SW. In spring 2007, the
authors proposed a study on `Structure and dynamics of coronal plumes
and inter-plume regions in solar coronal holes' to the International
Space Science Institute (ISSI) in Bern to clarify some of these aspects
by considering relevant observations and the extensive literature. This
review summarizes the results and conclusions of the study. Stereoscopic
observations allowed us to include three-dimensional reconstructions
of plumes. Multi-instrument investigations carried out during several
campaigns led to progress in some areas, such as plasma densities,
temperatures, plume structure and the relation to other solar phenomena,
but not all questions could be answered concerning the details of
plume generation process(es) and interaction with the SW.
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.
Bibcode: 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.
Title: The SDO data centre at IDOC/MEDOC in France
Authors: Parenti, Susanna; Bocchialini, Karine; Soubrie, Elie;
Auchere, Frederic; Ballans, Herv; Buchlin, Eric; Gabriel, Alan;
Mercier, Claude; Poulleau, Gilles; Vial, Jean-Claude
Bibcode: 2010cosp...38.2888P
Altcode: 2010cosp.meet.2888P
The IDOC/MEDOC centre at the Institut d'Astrophysique Spatiale (IAS,
Université Paris 11/CNRS) has a long experience in solar data archiving
and distribution, including almost 15 years of data from SOHO, STEREO
and TRACE. The center is now expanding its activity and becoming a
Pˆle Thématique Solaire of the CNES and INSU/CNRS. Part of the new
activities of the centre will be linked to the arrival of the enormous
volume of the new SDO data. The center will be one of the three European
centers to receive and redistribute the data to the community. It will
also be the only European site to permanently store about 10% of the
data (mainly from AIA). In continuity with its previous activities,
SDO data will be included in the data visualization tool FESTIVAL
and it will provide new services, like tools for the solar feature
identification (filaments, EUV intensity fluctuations). We will present
an overview of the facilities and activities of the centre in relation
to the SDO data.
Title: On the observations and possible interpretations of very long
period intensity oscillations of solar coronal loops
Authors: Solomon, Jacques; Auchere, Frederic; Bocchialini, Karine;
Gabriel, Alan; Tison, Emmanuelle
Bibcode: 2010cosp...38.2853S
Altcode: 2010cosp.meet.2853S
A comprehensive analysis of intensity oscillations in the Fe XII
line (19.5 nm) observed with EIT/SoHO in solar coronal loops during
solar cycle 23 (january 1997-september 2008) was performed. About
450 occurences of oscillations were obtained with periods ranging
between 3.4 and 13.6 hours and with durations up to about a
hundred hours. Interpratations in term of slow waves or of thermal
nonequilibrium were examined. However numerous inconsistencies arise
between current theories (in fact mostly expressed in terms of various
numerical simulations) and observations. Presently the lack of a direct
link between those very long oscillation periods and the characteristic
physical parameters of the loops (density, temperature, loop geometry)
hampers making progress in this major issue. This situation requires
an effort in a specific time analysis of the classical system of
equations of the problem: the question is examined from different
angles in relation to the data.
Title: Automatic detection and statistical analysis of intensity
oscillations in the solar corona with SDO
Authors: Auchere, Frederic; Bocchialini, Karine; Solomon, Jacques;
Gabriel, Alan; Tison, Emmanuelle
Bibcode: 2010cosp...38.2863A
Altcode: 2010cosp.meet.2863A
We present the generalization to SDO data of our automatic oscillation
detection algorithm. This technique was successfully tested using EIT
data on board SOHO at 19.5 nm from January 1997 to September 2008,
i.e almost the entire solar cycle 23. In the EIT data set we detected
400 oscillations whose periods range between 3.4 and 13.6 h with a
maximum around 6-7 hours. Most of the oscillations are localized in
coronal structures associated with active regions and last several
tens of hours. The AIA data will allow the detection of similar events
in several coronal temperature bands simultaneously, which will help
understand their physical nature.
Title: Study of Quiet Sun Through the Solar Atmosphere: From the
Chromosphere Up to Coronal Layers
Authors: Abbo, L.; Gabriel, A.; Harra, L.
Bibcode: 2009ASPC..415..389A
Altcode:
We analyze intensity maps over a range of temperatures covering the
chromosphere to the solar corona, near a polar coronal hole. Using
observations from EIS spectrometer on Hinode, we examine the width of
the network boundary as a function of temperature. Very preliminary
results show that there is a gradual increasing of the network boundary
width through the transition region up to coronal layers. Existing
observations are being studied and newer observation plans are currently
under way.
Title: The solar atmosphere as a driver for the corona
Authors: Gabriel, Alan H.
Bibcode: 2009lnu..confE..13G
Altcode:
No abstract at ADS
Title: The Structure and Origin of Solar Plumes: Network Plumes
Authors: Gabriel, A.; Bely-Dubau, F.; Tison, E.; Wilhelm, K.
Bibcode: 2009ApJ...700..551G
Altcode:
This study is based upon plumes seen close to the solar limb within
coronal holes in the emission from ions formed in the temperature region
of 1 MK, in particular, the band of Fe IX 171 Å from EIT on the Solar
and Heliospheric Observatory. It is shown, using geometric arguments,
that two distinct classes of structure contribute to apparently
similar plume observations. Quasi-cylindrical structures are anchored
in discrete regions of the solar surface (beam plumes), and faint
extended structures require integration along the line of sight (LOS)
in order to reproduce the observed brightness. This second category,
sometimes called "curtains," are ubiquitous within the polar holes and
are usually more abundant than the beam plumes, which depend more on
the enhanced magnetic structures detected at their footpoints. It is
here proposed that both phenomena are based on plasma structures in
which emerging magnetic loops interact with ambient monopolar fields,
involving reconnection. The important difference is in terms of physical
scale. It is proposed that curtains are composed of a large number
of microplumes, distributed along the LOS. The supergranule network
provides the required spatial structure. It is shown by modeling that
the observations can be reproduced if microplumes are concentrated
within some 5 Mm of the cell boundaries. For this reason, we propose to
call this second population "network plumes." The processes involved
could represent a major contribution to the heating mechanism of the
solar corona.
Title: Understanding structures at the base of the solar corona -
polar plumes
Authors: Gabriel, A. H.; Bely-Dubau, F.; Tison, E.; Abbo, L.
Bibcode: 2009IAUS..257..145G
Altcode:
Recent work on coronal polar plumes (Gabriel et al. 2003, 2005) has
aimed at determining the outflow velocity in plume and interplume
regions, using the Doppler dimming technique on oxygen VI observations
by SUMER and UVCS on SOHO. By comparing observations of SOHO/EIT with
plume modelling, we show that the major part of plumes is the result
of chance alignments along the line-of-sight of small enhancements in
intensity. This confirms the so-called curtain model. These plumes
can be attributed to reconnection activity along the boundaries of
supergranule cells. A second population of plumes has a lower abundance
and arises from surface bright points having a particular magnetic
configuration. New observations using the Hinode/EIS spectrometer are
in progress, with the aim of providing further insight for this model.
Title: Longitude-dependent decadal ozone changes and ozone trends
in boreal winter months during 1960-2000
Authors: Peters, D. H. W.; Gabriel, A.; Entzian, G.
Bibcode: 2008AnGeo..26.1275P
Altcode:
This study examines the longitude-dependent decadal changes and
trends of ozone for the boreal winter months during the period
of 1960-2000. These changes are caused primarily by changes in
the planetary wave structure in the upper troposphere and lower
stratosphere. The decadal changes and trends over 4 decades of
geopotential perturbations, defined as a deviation from the zonal mean,
are estimated by linear regression with time. The decadal changes in
longitude-dependent ozone were calculated with a simple transport
model of ozone based on the known planetary wave structure changes
and prescribed zonal mean ozone gradients. For December of the 1960s
and 1980s a statistically significant Rossby wave track appeared over
the North Atlantic and Europe with an anticyclonic disturbance over
the Eastern North Atlantic and Western Europe, flanked by cyclonic
disturbances. In the 1970s and 1990s statistically significant cyclonic
disturbances appeared over the Eastern North Atlantic and Europe,
surrounded by anticyclonic anomalies over Northern Africa, Central Asia
and Greenland. Similar patterns have been found for January. The Rossby
wave track over the North Atlantic and Europe is stronger in the 1980s
than in the 1960s. For February, the variability of the regression
patterns is higher. For January we found a strong alteration in the
modelled decadal changes in total ozone over Central and Northern
Europe, showing a decrease of about 15 DU in the 1960s and 1980s and
an increase of about 10 DU in the 1970s and 1990s. Over Central Europe
the positive geopotential height trend (increase of 2.3 m/yr) over 40
years is of the same order (about 100 m) as the increase in the 1980s
alone. This is important to recognize because it implies a total ozone
decrease over Europe of the order of 14 DU for the 1960-2000 period,
for January, if we use the standard change regression relation that
about a 10-m geopotential height increase at 300 hPa is related to
about a 1.4-DU total ozone decrease.
Title: Second Solar Orbiter Workshop - Concluding Remarks
Authors: Gabriel, A.
Bibcode: 2007ESASP.641E..50G
Altcode:
A number of personal impressions and reactions are presented at the
conclusion of this impressive second Solar Orbiter Workshop.
Title: g-mode search and the solar cycle
Authors: Gabriel, A.
Bibcode: 2006ESASP.624E.126G
Altcode: 2006soho...18E.126G
No abstract at ADS
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.
Bibcode: 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: Iron and Nickel in Ureilite Silicates - Chemistry and Isotopes
Authors: Gabriel, A.; Quitté, G.; Schönberg, R.; Schüßler, J.;
Pack, A.
Bibcode: 2006M&PSA..41.5326G
Altcode:
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.
Bibcode: 2006ESASP.617E...2A
Altcode: 2006soho...17E...2A
No abstract at ADS
Title: The effect of zonally asymmetric radiation perturbations in
the stratosphere on the coupling of atmospheric layers
Authors: Peters, D.; Gabriel, A.
Bibcode: 2006cosp...36.1628P
Altcode: 2006cosp.meet.1628P
The boreal decadal changes of zonally asymmetric total ozone during
the 60ies 70ies 80ies and 90ies of the last century showed a high
variability From a sensitivity study with different ozone distributions
of the lower stratosphere in the frame of the general circulation
model ECHAM4 we know that a positive feedback process appeared which
increased locally the radiative forcing of ozone by a factor of about
ten linked with a strong influence on the dynamics and the coupling
of the stratosphere and troposphere In this paper we report on a study
with the GCM MAECHAM5 to examine the effect of radiation perturbations
induced by zonally varying ozone in the whole stratosphere on the
dynamics of the stratosphere and related coupling with the troposphere
Especially the results reveal a shift in the polar vortex which induce
changes in the distribution of the process of Rossby wave breaking As
a further implication the jet induced generation of inertia gravity
waves will be discussed
Title: The Beleinos cornerstone: the Sun, the star close to Earth
Authors: Appourchaux, T.; Auchère, F.; Bocchialini, K.; Bonnet,
R. M.; Gabriel, A.; Vial, J. -C.
Bibcode: 2005ESASP.588..389A
Altcode: 2005tssc.conf..389A
No abstract at ADS
Title: Solar Wind Outflow in Polar Plumes from 1.05 to 2.4
Rsolar
Authors: Gabriel, A. H.; Abbo, L.; Bely-Dubau, F.; Llebaria, A.;
Antonucci, E.
Bibcode: 2005ApJ...635L.185G
Altcode:
An earlier publication (Paper I), which measured the outflow velocity in
solar plumes out to 1.35 Rsolar using the Doppler dimming
technique, has here been extended out to 2.4 Rsolar
by including observations from SOHO UVCS. It is shown that plume
outflow velocities, greater than interplumes at lower heights, have
lower acceleration and fall below interplume velocities at heights
greater than 1.6 Rsolar. This analysis resolves what has
been an apparent disagreement between previously published work. The
mass flow rate in plumes is shown to decrease with height, presumably
through mass transfer to the interplume regions.
Title: Global solar Doppler velocity determination with the GOLF/SoHO
instrument
Authors: García, R. A.; Turck-Chièze, S.; Boumier, P.; Robillot,
J. M.; Bertello, L.; Charra, J.; Dzitko, H.; Gabriel, A. H.;
Jiménez-Reyes, S. J.; Pallé, P. L.; Renaud, C.; Roca Cortés, T.;
Ulrich, R. K.
Bibcode: 2005A&A...442..385G
Altcode:
The Global Oscillation at Low Frequencies (GOLF) experiment is
a resonant scattering spectrophotometer on board the Solar and
Heliospheric Observatory (SoHO) mission, originally designed to measure
the disk-integrated solar oscillations of the Sun. This instrument was
designed in a relative photometric mode involving both wings of the
neutral sodium doublet (D1 at λ 5896 and D2 at
λ 5890 Å). However, a "one-wing" photometric mode has been selected
to ensure 100% continuity in the measurements after a problem in the
polarization mechanisms. Thus the velocity is obtained from only two
points on the same wing of the lines. This operating configuration
imposes tighter constraints on the stability of the instrument with a
higher sensitivity to instrumental variations. In this paper we discuss
the evolution of the instrument during the last 8 years in space and
the corrections applied to the measured counting rates due to known
instrumental effects. We also describe a scaling procedure to obtain
the variation of the Doppler velocity based on our knowledge of the
sodium profile slope and we compare it to previous velocity estimations.
Title: Erratum: ``Looking for Gravity-Mode Multiplets with the GOLF
Experiment aboard SOHO'' (ApJ,
604, 455 [2004])
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
Bibcode: 2004ApJ...608..610T
Altcode:
As a result of an error at the Press, the second panel of Figure 9
was repeated twice in the top row of the printed, black-and-white
version of this figure, and the first panel was omitted. This error
appears in the print edition and the PDF and postscript (PS) versions
available with the electronic edition of the journal, although the
panels of the color figure displayed in the electronic article itself
are correct. Please see below for the corrected print version of Figure
9. The Press sincerely regrets the error.
Title: Looking for Gravity-Mode Multiplets with the GOLF Experiment
aboard SOHO
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
Bibcode: 2004ApJ...604..455T
Altcode:
This paper is focused on the search for low-amplitude solar gravity
modes between 150 and 400 μHz, corresponding to low-degree, low-order
modes. It presents results based on an original strategy that looks
for multiplets instead of single peaks, taking into consideration
our knowledge of the solar interior from acoustic modes. Five years
of quasi-continuous measurements collected with the helioseismic GOLF
experiment aboard the SOHO spacecraft are analyzed. We use different
power spectrum estimators and calculate confidence levels for the
most significant peaks. This approach allows us to look for signals
with velocities down to 2 mm s-1, not far from the limit
of existing instruments aboard SOHO, amplitudes that have never been
investigated up to now. We apply the method to series of 1290 days,
beginning in 1996 April, near the solar cycle minimum. An automatic
detection algorithm lists those peaks and multiplets that have a
probability of more than 90% of not being pure noise. The detected
patterns are then followed in time, considering also series of 1768 and
2034 days, partly covering the solar cycle maximum. In the analyzed
frequency range, the probability of detection of the multiplets
does not increase with time as for very long lifetime modes. This is
partly due to the observational conditions after 1998 October and the
degradation of these observational conditions near the solar maximum,
since these modes have a ``mixed'' character and probably behave as
acoustic modes. Several structures retain our attention because of
the presence of persistent peaks along the whole time span. These
features may support the idea of an increase of the rotation in the
inner core. There are good arguments for thinking that complementary
observations up to the solar activity minimum in 2007 will be decisive
for drawing conclusions on the presence or absence of gravity modes
detected aboard the SOHO satellite.
Title: Outflow Velocities in Polar Coronal Holes
Authors: Gabriel, A. H.; Bely-Dubau, F.; Lemaire, P.; Antonucci, E.
Bibcode: 2004IAUS..219..635G
Altcode: 2003IAUS..219E.100G
It is well established that the fast solar wind originates during
the solar minimum from the polar coronal holes. The object is to
investigate this wind onset region to identify the solar structures
responsible. We report here the first measurements of outflow velocities
between 1.0 and 1.3 Ro in solar plumes using XUV spectral lines from
SUMER/SOHO and the Doppler dimming technique. In contrast to what has
been suggested by several other observers using SOHO data we conclude
that the wind velocity in plumes is greater than in the interplume
regions. This tendency diminishes with height so that it may vanish
or even reverse at greater distances. We show that one half of the
solar wind observed at 1 A.U. from Ulysses originates from the solar
plumes at 1.1 Ro. We are extending these observations to 4 Ro using the
UVCS/SOHO spectro-coronagraph to understand the connection with plumes
seen at greater distances. Initial indications suggest a change in the
physical nature of plumes around 2.0 Ro raising questions concerning
their relation to the frequently seen white-light plumes at large
distances. We explore the possible connection between polar plumes
the supergranule network and coronal heating in non-hole regions.
Title: Observation of, and temporal variations in, solar p-mode
multiplet frequency asymmetries at l= 2
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Thiery, S.; Boumier, P.; Gabriel, A. H.
Bibcode: 2003MNRAS.343..343C
Altcode:
The predominant contribution to the frequency splitting of low-l solar
p modes arises from the rotation of the solar interior and this lifts
the frequency degeneracy in l to give a symmetric pattern where the
observed (synodic) separation between adjacent m (i.e. for |Δm|= 1)
is ~400 nHz. Magnetic fields can also contribute to the splitting, but
they do so in such a way as to introduce asymmetries in the arrangement
of the components within each multiplet. In disc-integrated data this
effect may become apparent when l>= 2. Here, we attempt to extract
estimates of the frequency asymmetries at l= 2 from the analysis
of disc-integrated data collected by the ground-based Birmingham
Solar Oscillations Network (BiSON) and the GOLF instrument on board
the ESA/NASA SOHO satellite. Our analyses demonstrate that we have
evidence for there being non-zero asymmetries present (significance
~3-4σ) during an epoch coincident with high levels of surface
activity close to the maximum of solar cycle 23. The asymmetries are
indistinguishable from zero at minimum levels of activity near the cycle
22/23 boundary. We also compare the observed asymmetries with those
calculated from a model that is based upon the recent predictions of
Moreno-Insertis & Solanki. While the level of agreement between
the two is found to be reasonable, the observations suggest (though
with poor constraints placed upon this) that the influence on the
mode frequencies of high-latitude activity may not be as strong as in
the model.
Title: The Contribution of Polar Plumes to the Fast Solar Wind
Authors: Gabriel, A. H.; Bely-Dubau, F.; Lemaire, P.
Bibcode: 2003ApJ...589..623G
Altcode:
The Doppler dimming technique is used for the first time to
study ultraviolet polar plumes in the height range of 1.05-1.35
Rsolar, using observations from the spectrometer SUMER on
the Solar and Heliospheric Observatory. It is found that, contrary to
a number of published suggestions, outflow velocities in the plumes
exceed those in the interplume regions. Plume velocities are in excess
of 60 km s-1 and are approximately constant throughout
this height region. They tend to converge with the velocity of the
accelerating interplume material at some height above our region of
study. The analysis suggests that plume material makes a substantial
contribution to the total line of sight, favoring either a ``curtain''
model for plumes or a chance alignment of a number of elementary
cylindrical plumes. The intrinsic local density of plume material is
some 20%-50% in excess of the interplume regions. Estimation of the
total mass outflow indicates that approximately half of the fast solar
wind at 1.1 Rsolar arises from plumes, with the remainder
from interplume material. This result validates the published electron
temperature profile of David et al. for the fast wind onset, which
had been questioned over the suggestion that the flow velocity might
be negligible in solar plumes.
Title: The solar high-resolution imager - coronagraph LYOT mission
Authors: Vial, Jean-Claude; Song, Xueyan; Lemaire, Philippe; Gabriel,
Alan H.; Delaboudiniere, Jean-Pierre; Bocchialini, Karine; Koutchmy,
Serge L.; Lamy, Philippe L.; Mercier, Raymond; Ravet, Marie Francoise;
Auchere, Frederic
Bibcode: 2003SPIE.4853..479V
Altcode:
The LYOT (LYman Orbiting Telescope) solar mission is proposed to
be implemented on a micro-satellite of CNES (France) under phase A
study. It includes two main instruments, which image the solar disk
and the low corona up to 2.5 Ro in the H I Lyman-α line
at 121.6 nm. The spatial resolution is about 1” for the disk and
2.5” for corona. It also carries an EIT-type telescope in the He II
(30.4 nm) line. The coronagraph needs a super polished mirror at the
entrance pupil to minimize the light scattering. Gratings and optical
filters are used to select the Lyman-α wavelength. VUV cameras with
2048×2048 pixels record solar images up to every 10 seconds. The
satellite operates at a high telemetry rate (more then 100 kb/s,
after onboard data compression). The envisaged orbits are either
geostationary or heliosynchronous. Possible launch dates could be end
of 2006 - beginning of 2007.
Title: Searching for Resonances in the Presence of Cycle Variations
Authors: Gabriel, Alan
Bibcode: 2003IAUJD..12E..47G
Altcode:
The identification of new weak resonances against a broadband
background of convection noise is favoured by the analysis of longer
time-series. The signal to noise ratio is always improved by more data
but particularly so where the coherence time approaches or exceeds
the length of the series. On the other hand it is well known that the
frequencies of solar p-mode oscillations vary as a function of the solar
cycle. Many workers have made quantitative studies of this effect as
a function of activity frequency and degree. Such variations tend to
reduce the efficiency of many of the classical methods of searching for
signals in the presence of noise. The development of search techniques
which take into account the known or predicted cycle variation can
improve the detectability of certain low-frequency modes. If as some
theorists have suggested there exist activity cycle variations for solar
g-mode frequencies then such methods would be particularly applicable.
Title: The onset region of the fast solar wind
Authors: Gabriel, A.
Bibcode: 2003EAS.....9..227G
Altcode:
Over a range of spatial scales, the onset regions of the fast solar
wind are influenced or controlled by the structure of the local
magnetic fields. This is demonstrated for the large scale structures
that determine coronal holes, as well as for the supergranulation
network. It is likely that reconnexion effects in small-scale emerging
fields play a role in the initial accelerating mechanism. The role of
magnetic fields in outflowing solar plumes is at present less clear.
Title: Transition region dynamical components
Authors: Ben El Hadj, R.; Gabriel, A. H.; Bely-Dubau, F.
Bibcode: 2002ESASP.505..349B
Altcode: 2002solm.conf..349B; 2002IAUCo.188..349B
Certain coronal heating theories (e.g. Axford and McKenzie, 1993)
propose that small loops of new magnetic fields are born in cell
centers of supergranulation. They are carried by convection to the
network where they reconnect with network field. We are looking for
the observational evidence of this phenomenon. Firstly, we use the
differential emission measure (DEM) to identify the plasma associated to
these loops. For the first part of this analysis, we develop a numerical
technique, using CHIANTI spectroscopic database, to calculate the DEM
for given observed spectral intensities obtained by CDS. The method
requires an initial input model that is folded through spectral line
emissivities. This produces a set of predicted intensities that are then
compared with observed values. The DEM is then adjusted iteratively to
improve agreement between the observed and predicted intensities. The
question which remains, is that of the treatment of the cells alone
by separating them from the network. Indeed, cells and network have
different properties and should be treated separately. Cell-Network
separation is done using image analysis which avoids the errors produced
by the histogram method. We measure DEM in cells and network to be
able to deduce the loop emissions.
Title: A study of polar plumes during the solar activity minimum
Authors: Gabriel, A. H.; Bely-Dubau, F.
Bibcode: 2002ESASP.505..409G
Altcode: 2002IAUCo.188..409G; 2002solm.conf..409G
Understanding the nature of polar plumes is an important outstanding
question for coronal physics. The current best picture, that they
represent higher density, lower velocity plasma in a two-component
solar wind, is open to challenge and requires further definitive
research. We have studied the region up to 1.3 solar radii above the
limb, in a polar coronal hole during solar minimum. Observations with
SUMER of the oxygen VI doublet at 1032 Å are interpreted in terms of
the outflow velocity, using the Doppler dimming technique. Understanding
these structures can have an important influence on theories of heating
and acceleration of the fast solar wind and the structure of the local
magnetic field. Interpretation of an "interplume" region leads to flow
velocities ranging from 20 km/s at 1.1 Ro up to 46 km/s at 1.3 Ro. The
more intense regions, known as plumes, are difficult to understand,
due to uncertainties regarding their 3-dimensional structure.
Title: A search for solar g modes in the GOLF data
Authors: Gabriel, A. H.; Baudin, F.; Boumier, P.; García, R. A.;
Turck-Chièze, S.; Appourchaux, T.; Bertello, L.; Berthomieu, G.;
Charra, J.; Gough, D. O.; Pallé, P. L.; Provost, J.; Renaud, C.;
Robillot, J. -M.; Roca Cortés, T.; Thiery, S.; Ulrich, R. K.
Bibcode: 2002A&A...390.1119G
Altcode:
With over 5 years of GOLF data having some 90% continuity, a new
attempt has been made to search for possible solar g modes. Statistical
methods are used, based on the minimum of assumptions regarding the
solar physics; namely that mode line-widths are small compared with
the inverse of the observing time, and that modes are sought in the
frequency interval 150 to 400 mu Hz. A number of simulations are carried
out in order to understand the expected behaviour of a system consisting
principally of a solar noise continuum overlaid with some weak sharp
resonances. The method adopted is based on the FFT analysis of a time
series with zero-padding by a factor of 5. One prominent resonance at
284.666 mu Hz coincides with a previous tentative assignment as one
member of an n=1, l=1, p-mode multiplet. Components of two multiplets,
previously tentatively identified as possible g-mode candidates from
the GOLF data in 1998, continue to be found, although their statistical
significance is shown to be insufficient, within the present assumption
regarding the nature of the signal. An upper limit to the amplitude
of any g mode present is calculated using two different statistical
approaches, according to either the assumed absence (H0 hypothesis)
or the assumed presence (H1 hypothesis) of a signal. The former yields
a slightly lower limit of around 6 mm/s.
Title: Dynamical components of northern hemispheric zonal mean total
ozone changes during 1979-93
Authors: Gabriel, A.; Schmitz, G.
Bibcode: 2002GeoRL..29.1675G
Altcode: 2002GeoRL..29n..20G
In this work, we examine the influence of northern hemispheric
large-scale eddy fluxes on the zonal mean total ozone changes. For this
purpose, zonal means of the eddy fluxes of the period 1979-93 were
introduced into a dynamically-chemically coupled two-dimensional
circulation model, based on a diffusivity approach for the
quasi-geostrophic potential vorticity, the potential temperature and
the chemical tracers. The model calculations show that the eddy fluxes
induce regular interannual ozone variations with a period of about
3-3.5 years in the northern midlatitudes, and, for the pre-Pinatubo
time period 1979-91, a decadal decline in the northern hemispheric
total ozone that amounts to about 50% of the observed trend.
Title: Transition Region Dynamical Components
Authors: Ben El Hadj, R.; Gabriel, A. H.
Bibcode: 2002sf2a.conf..123B
Altcode:
Certain coronal heating theories (eg. Axford and Mc Kenzie, 1993)
propose that small loops of new magnetic fields are born in cell centers
of supergranulation. They are carried by convection to the network where
they reconnect with network field, liberating magnetic energy. We are
looking for observational evidence for this phenomenon. We use the
differential emission measure (DEM) analysis to identify the plasma
associated with these loops.It is reasonable to suppose that their
DEM contribution will be of a diffrent form in the cells that in the
network where they are destroyed.For first part of this analysis, we
develop a numerical technique, using CHIANTI spectroscopic database, to
calculate the DEM from our observed spectral intensities. The question
which remains, is that of the treatment of the cells alone by separating
them from the network. For this we use image analysis techniques wich
avoids errors introduced by the use of histogram method.We measure
DEM in cells and network to be able to deduce the loops.
Title: Cycle effects on low-degree p-modes: results from GOLF
Authors: Boumier, P.; Lochard, J.; Thiery, S.; Baudin, F.; Gabriel,
A. H.; Grec, G.; Renaud, C.
Bibcode: 2002ESASP.508...67B
Altcode: 2002soho...11...67B
We present updated results on the low-degree p-mode parameters changes
with solar activity: frequency, spectral width, rotational splittings
and spectral asymmetry.
Title: Low-degreep modes: results from GOLF
Authors: Boumier, P.; Lochard, J.; Baudin, F.; Gabriel, A. H.; Grec,
G.; Renaud, C.
Bibcode: 2002sf2a.conf..127B
Altcode:
We present updated results on the low-degree p-mode parameters changes
with solar activity: frequency, spectral width, rotational splittings
and spectral asymmetry.
Title: The determination of coronal hole outflow velocities below
1.5 R0 using the "Doppler Dimming" technique with the
SUMER instrument on SOHO
Authors: Gabriel, A. H.; Bely-Dubau, F.; David, C.
Bibcode: 2002ESASP.477..343G
Altcode: 2002scsw.conf..343G
This paper presents an attempt to evaluate the use below 1.5
R0 of the Doppler Dimming method, pioneered by the
UVCS/SOHO team, who use it at larger radial distances. Following
Noci et al. (1987), the theoretical model for this process has been
reevaluated, incorporating some of the more recent atomic and solar
data. The model is applied to data from SUMER that was recorded above
the limb in a classical polar coronal hole, during the solar minimum
in May 1996. This 2-dimensional raster is capable of resolving the
solar plumes. The interpretation is shown to be critically dependent
on the assumed density and spatial homogeneity.
Title: Preface
Authors: Gabriel, Alan; Bely-Dubau, Françoise
Bibcode: 2002AdSpR..30..431G
Altcode:
No abstract at ADS
Title: Application of Fano profiles to asymmetric resonances in
helioseismology
Authors: Gabriel, A. H.; Connerade, J. -P.; Thiery, S.; Boumier, P.
Bibcode: 2001A&A...380..745G
Altcode:
Parallels are drawn between the asymmetric resonance profiles observed
in global helioseismology and the Fano theory for autoionisation
profiles in atomic spectroscopy. We show that the underlying physics of
the interaction of a discrete resonance with a correlated continuum
is common to both systems. The approximate formula normally used
for fitting to profiles in helioseismology is essentially similar to
that developed for atomic spectroscopy by Fano. We propose that the
two systems are in reality equivalent. This proposition enables us to
understand better which resonances in helioseismology will be correlated
with each other and with which solar background ``continua". We also
question whether the two interacting influences of excitation sources
and correlated solar background, are really separate independent
processes.
Title: A critical review of the remote-sensing instrumentation
envisaged for the Solar Orbiter mission
Authors: Gabriel, Alan
Bibcode: 2001ESASP.493..135G
Altcode: 2001sefs.work..135G
This review is based in part on the model payload conceived within the
ESA preliminary study, but also on the various modifications proposed
at the workshop, together with some very constructive discussions that
we have heard. There is an impression that the optical payload concepts,
already pushing at the limits of the available spacecraft resources, may
also be underestimating technical difficulties associated in particular
with the high thermal flux expected. A suggested programme for the next
stage includes a review of these technical difficulties, together with
an effort to obtain rapid agreement on a number of system-level choices,
concerned with communications aspects and pointing strategy. This will
enable the payload concepts to be carried forward to a more advanced
level of definition.
Title: Solar Neutrino Emission Deduced from a Seismic Model
Authors: Turck-Chièze, S.; Couvidat, S.; Kosovichev, A. G.; Gabriel,
A. H.; Berthomieu, G.; Brun, A. S.; Christensen-Dalsgaard, J.; García,
R. A.; Gough, D. O.; Provost, J.; Roca-Cortes, T.; Roxburgh, I. W.;
Ulrich, R. K.
Bibcode: 2001ApJ...555L..69T
Altcode:
Three helioseismic instruments on the Solar and Heliospheric Observatory
have observed the Sun almost continuously since early 1996. This
has led to detailed study of the biases induced by the instruments
that measure intensity or Doppler velocity variation. Photospheric
turbulence hardly influences the tiny signature of conditions in the
energy-generating core in the low-order modes, which are therefore very
informative. We use sound-speed and density profiles inferred from GOLF
and MDI data including these modes, together with recent improvements
to stellar model computations, to build a spherically symmetric
seismically adjusted model in agreement with the observations. The
model is in hydrostatic and thermal balance and produces the present
observed luminosity. In constructing the model, we adopt the best
physics available, although we adjust some fundamental ingredients,
well within the commonly estimated errors, such as the p-p reaction
rate (+1%) and the heavy-element abundance (+3.5%); we also examine the
sensitivity of the density profile to the nuclear reaction rates. Then,
we deduce the corresponding emitted neutrino fluxes and consequently
demonstrate that it is unlikely that the deficit of the neutrino fluxes
measured on Earth can be explained by a spherically symmetric classical
model without neutrino flavor transitions. Finally, we discuss the
limitations of our results and future developments.
Title: g-mode: a new generation of helioseismic instrument
Authors: Turck-Chièze, S.; Robillot, J. M.; Dzitko, H.; Boumier, P.;
Decaudin, M.; Gabriel, A.; Garcia, R. A.; Gree, G.; Pallé, P. L.;
Renaud, C.; Schmitt, D.
Bibcode: 2001ESASP.464..331T
Altcode: 2001soho...10..331T
The GOLF team pushes a new concept of instrument devoted to the search
of gravity modes and low order low frequency p modes in order to improve
our knowledge of the deep solar interior. The instrumental concept
is to measure the Doppler shift together with the time evolution of
the D1 sodium line using a 15 point resonance spectrometer. A sodium
vapor resonance cell placed in a static magnetic field varying along
the longitudinal axis is used to sample simultaneously 8 points on
each wing of the line. New Active Pixel Sensor detectors will be
specifically designed for this instrument. A low spatial resolution
of the Sun is also under study in this concept. First ground-based
observations with this instrument are scheduled for 2001/2002 at
Tenerife. The space concept of this instrument is under study in France
as an R&T (Research and Technology) study sponsored by CNES, the
French Space Agency. After some determining validation tests, this
kind of instrument might be placed onboard either a micro satellite
or a satellite dedicated to the study of the Sun.
Title: Frequency evolution with activity cycle in GOLF data:
dependence on m
Authors: Thiery, S.; Boumier, P.; Gabriel, A. H.; GOLF Team
Bibcode: 2001ESASP.464..119T
Altcode: 2001soho...10..119T
We present here new results on the low degree p-mode frequency shifts
with solar activity. This analysis based on GOLF observations aims to
look for an m-dependence of the frequency shifts, already observed for
intermediate degree modes but only predicted for low degree. We show
that the l=2 zonal modes display shifts which are distinct from the
l=2 sectoral modes. This introduces an asymmetry in the pattern of the
multiplet which has to be taken into account in the fitting processes.
Title: A brief status report on the GOLF programme
Authors: Gabriel, A. H.; GOLF Team
Bibcode: 2001ESASP.464..307G
Altcode: 2001soho...10..307G
GOLF has recorded a time-series of integrated Sun velocity oscillations
covering 805 days on the solar blue-wing, followed by over 700 days on
the red wing, with a remarkable continuity for both series, separated by
a gap of some 200 days, due to the temporary loss of SOHO. We discuss
how the sub-series can be combined to provide a coherent series of
around 1500 days of data. Some of the data analysis activities are
reviewed, including the fitting of asymmetric resonance profiles and
the search for low-frequency p-modes and g-modes. The g-mode situation
remains uncertain, with some possible "candidates" and with an upper
velocity limit of less than 10 mm/s. Some recent studies are summarised
on the correlated solar noise and on the effect of solar activity on
the multiplet separation patterns. The GOLF instrument is continuing
operations, with no apparent signs of serious deterioration, indicating
a possibility of extending the present series by many years.
Title: p-mode profile asymmetry in GOLF data: variation with altitude
Authors: Thiery, S.; Boumier, P.; Gabriel, A. H.; Henney, C. J.;
GOLF Team
Bibcode: 2001ESASP.464..681T
Altcode: 2001soho...10..681T
We present here new results on the asymmetry of low degree p-mode
profiles using GOLF and MDI data. The GOLF p-mode profiles asymmetry
is found to be higher after the recovery of SOHO than it was before,
whereas MDI profiles remained roughly the same. A complementary study of
the phase difference between MDI and GOLF signals allows us to explain
this behaviour. This study confirms the hypothesis of the influence
of a correlated noise in GOLF data, and shows the dependency of this
correlated noise with the observation altitude. The percentage of
correlated noise in GOLF data is computed.
Title: Analysis of low frequency signal with the GOLF experiment:
methodology and results
Authors: García, R. A.; Bertello, L.; Turck-Chièze, S.; Couvidat,
S.; Gabriel, A. H.; Henney, C. J.; Régulo, C.; Robillot, J. M.;
Roca Cortés, T.; Ulrich, R. K.; Varadi, F.
Bibcode: 2001ESASP.464..473G
Altcode: 2001soho...10..473G
Four years of GOLF velocity time series have been used to study the
low frequency part of the solar spectrum below 1.5 mHz. This paper
discusses the methods already developed for the research of the
low-degree low-order acoustic modes by Garcia et al. (2000) and for
the gravity modes by Turck-Chieze et al. (2000). These methods are
based on our knowledge of the general theoretical properties of the p
and g modes that lead us to determine the statistical significance of
the structures (multiplets) present in the GOLF spectrum in terms of
p- and g-mode candidates. In addition to the search of single peaks,
we try to detect multiplets (l = 1, 2 and 3) which allows us to lower
the detection threshold while keeping the same confidence level. We
will concentrate the discussion on the limits of this search that only
takes into account those peaks above a selected statistical threshold
giving an estimation of the possible uncertainties due to the solar
noise and the nature of the solar resonances.
Title: Sensitivity of the GOLF signal to combined solar velocity
and intensity variations
Authors: Ulrich, R. K.; García, R. A.; Robillot, J. -M.;
Turck-Chièze, S.; Bertello, L.; Charra, J.; Dzitko, H.; Gabriel,
A. H.; Roca Cortés, T.
Bibcode: 2000A&A...364..799U
Altcode:
The GOLF instrument provides a stable and continuous measurement of
the intensity of spatially integrated sunlight in one wing of the
sodium D lines. Because the detected radiation results from atomic
scattering, the GOLF signal can be traced to an atomic reference
wavelength. The planned operations were to involve a form of relative
photometry through the use of measurements on both the blue and red
wings of the solar D lines of neutral sodium. However, due to the
occasional malfunction of the polarization subsystem a ``one wing
photometric mode" operational alternative has been selected in order
to ensure achievement of a 100% duty cycle. In this case, the signal
observed consists of two photometric measurements at only one wing
of each line of the sodium doublet separated by gx0.43 picometers
(pm). The sodium cell system in GOLF combines photons scattered at
three different wavelengths: one at D_1 and two at D_2. This paper
developes a formalism to describe this system in terms of the solar
spectral line profiles. A method of converting the one wing data to an
effective velocity scale is presented. The method is applied to the
nearly continuous 804 day sequence received from the GOLF instrument
prior to the loss of telecommunications with SOHO on 24-June-1998. The
resulting time sequence is part of the GOLF archive and can be made
available to investigators. This publication describes some properties
of this time series.
Title: Comparison of Frequencies and Rotational Splittings of Solar
Acoustic Modes of Low Angular Degree from Simultaneous MDI and
GOLF Observations
Authors: Bertello, L.; Henney, C. J.; Ulrich, R. K.; Varadi, F.;
Kosovichev, A. G.; Scherrer, P. H.; Roca Cortés, T.; Thiery, S.;
Boumier, P.; Gabriel, A. H.; Turck-Chièze, S.
Bibcode: 2000ApJ...535.1066B
Altcode:
During the years 1996 through 1998 the Michelson Doppler Imager (MDI)
and the Global Oscillations at Low Frequency (GOLF) experiments on the
Solar and Heliospheric Observatory (SOHO) mission have provided unique
and nearly uninterrupted sequences of helioseismic observations. This
paper describes the analysis carried out on power spectra from 759
days of calibrated disk-averaged velocity signals provided by these two
experiments. The period investigated in this work is from 1996 May 25
to 1998 June 22. We report the results of frequency determination of
low-degree (l<=3) acoustic modes in the frequency range between 1.4
mHz and 3.7 mHz. Rotational splittings are also measured for nonradial
modes up to 3.0 mHz. The power spectrum estimation of the signals
is performed using classical Fourier analysis and the line-profile
parameters of the modes are determined by means of a maximum likelihood
method. All parameters have been estimated using both symmetrical and
asymmetrical line profile-fitting formula. The line asymmetry parameter
of all modes with frequency higher than 2.0 mHz is systematically
negative and independent of l. This result is consistent with the
fact that both MDI and GOLF data sets investigated in this paper are
predominantly velocity signals, in agreement with previous results. A
comparison of the results between the symmetric and asymmetric fits
shows that there is a systematic shift in the frequencies for modes
above 2.0 mHz. Below this frequency, the line width of the modes
is very small and the time base of the data does not provide enough
statistics to reveal an asymmetry. In general, the results show that
frequency and rotational splitting values obtained from both the
MDI and GOLF signals are in excellent agreement, and no significant
differences exist between the two data sets within the accuracy of the
measurements. Our results are consistent with a uniform rotation of
the solar core at the rate of about 435 nHz and show only very small
deviations of the core structure from the standard solar model.
Title: Structure of the Solar Core: Effect of Asymmetry of Peak
Profiles
Authors: Basu, S.; Turck-Chièze, S.; Berthomieu, G.; Brun, A. S.;
Corbard, T.; Gonczi, G.; Christensen-Dalsgaard, J.; Provost, J.;
Thiery, S.; Gabriel, A. H.; Boumier, P.
Bibcode: 2000ApJ...535.1078B
Altcode: 2000astro.ph..1208B
Recent studies have established that peaks in solar oscillation
power spectra are not Lorentzian in shape but have a distinct
asymmetry. Fitting a symmetric Lorentzian profile to the peaks,
therefore, produces a shift in frequency of the modes. Accurate
determination of low-frequency modes is essential to infer the structure
of the solar core by inversion of the mode frequencies. In this paper
we investigate how the changes in frequencies of low-degree modes
obtained by fitting symmetric and asymmetric peak profiles change the
inferred properties of the solar core. We use data obtained by the
Global Oscillations at Low Frequencies (GOLF) project on board the
SOHO spacecraft. Two different solar models and inversion procedures
are used to invert the data in order to determine the sound speed in
the solar core. We find that for a given set of modes no significant
difference in the inferred sound speed results from taking asymmetry
into account when fitting the low-degree modes.
Title: Analysis of asymmetric p-mode profiles in GOLF data
Authors: Thiery, S.; Boumier, P.; Gabriel, A. H.; Bertello, L.;
Lazrek, M.; García, R. A.; Grec, G.; Robillot, J. M.; Roca Cortés,
T.; Turck-Chièze, S.; Ulrich, R. K.
Bibcode: 2000A&A...355..743T
Altcode:
We show here evidence for the necessity of an asymmetric form in
modelling the profile of an acoustic mode in the power spectral
density. The analysis was performed on a 805-day series of GOLF data
(l=0 to 3). The assumptions used for the fits are discussed and their
consequences quantified, in particular for the optimum choice of the
fitting spectral window. Values are given for the bias on the mode
parameters (frequency, width, splitting) when using a Lorentzian
fit. The bias depends on the degree l and on the frequency, and when
taken into account leads to variations in the mode parameters with
degree more consistent with theoretical expectations.
Title: Reply and Comment
Authors: Gabriel, A.
Bibcode: 1999ESASP.446...21G
Altcode: 1999soho....8...21G
No abstract at ADS
Title: Working Group 4: Wind Acceleration Processes
Authors: Wurz, P.; Gabriel, A.
Bibcode: 1999ESASP.446...87W
Altcode: 1999soho....8...87W
No abstract at ADS
Title: The Coarse Versus The Fine Structure Of The Quiet-Sun
Chromospheric And Transition Region Network
Authors: Patsourakos, Spyridwn; Vial, J. -C.; Gabriel, A. -H.;
Bellamine, N.
Bibcode: 1999ESASP.446..537P
Altcode: 1999soho....8..537P
The chromospheric and transition region network is believed to be
the basic channel of energy and momentum that heats the corona and
accelerates the solar wind. While at spatial scales of one supergranular
cell the network appears to be more or less homogeneous, at smaller
scales it possesses a finer structure. We present here observations
made with the CDS and SUMER spectrometers on SOHO pursuing the
investigation of the coarse and the fine structure of the quiet-Sun
network. A two-dimensional autocorrelation method allowed us to
deduce the temperature-variation of network's width, while well-chosen
density-sensitive line-ratios permitted to determine its filling factor
at different temperatures. A discussion on possible implications of our
results for steady-state energy and momentum balance for the quiet-Sun
is included.
Title: Transition-Region Network Boundaries in the Quiet Sun: Width
Variation with Temperature as Observed with CDS on SOHO
Authors: Patsourakos, S.; Vial, J. -C.; Gabriel, A. H.; Bellamine, N.
Bibcode: 1999ApJ...522..540P
Altcode:
We report here the results of a study of the temperature variation
of the network boundary thicknesses in the quiet-Sun transition
region. A Fourier-based two-dimensional autocorrelation method has
been applied to 240''×240'' rasters obtained in
several transition-region lines by the CDS spectrometer on SOHO. The
quantitative variation of the network boundary width with temperature
has been obtained for the first time in a full two-dimensional field. It
appears that network boundaries have an almost constant width up to
a temperature of about 105.4 K and then fan out rapidly at
coronal temperatures. This expansion of the transition-region network
boundaries with temperature is found to be quantitatively in agreement
with earlier theoretical models of the transition region.
Title: The integrated magnetic field of the Sun as seen by GOLF on
board SOHO
Authors: García, R. A.; Boumier, P.; Charra, J.; Foglizzo, T.;
Gabriel, A. H.; Grec, G.; Régulo, C.; Robillot, J. M.; Turck-Chièze,
S.; Ulrich, R. K.
Bibcode: 1999A&A...346..626G
Altcode:
An objective of the GOLF experiment (Global Oscillations at Low
Frequencies) on-board the SOHO (Solar and Heliospheric Observatory)
space mission was to measure the line-of-sight component of the
disk-averaged magnetic field of the Sun. In this paper, a theoretical
study of this observable is presented. The newly developed techniques
are tested using simulated data series based on the observation of this
experiment, and the sensitivity of GOLF to magnetic measurements is
calculated. An average solar mean magnetic field of 0.120 +/- 0.002
G has been found corresponding to the minimum of solar activity by
analyzing 26 days of full GOLF data. The power spectrum of this field
is calculated and the main characteristics {are} described.
Title: Solar oscillations: time analysis of the GOLF p-mode signal
Authors: Renaud, C.; Grec, G.; Boumier, P.; Gabriel, A. H.; Robillot,
J. M.; Roca Cortés, T.; Turck-Chièze, S.; Ulrich, R. K.
Bibcode: 1999A&A...345.1019R
Altcode:
We determine the intrinsic phase lag of the GOLF data for the solar
p-mode velocity deduced either from one of the narrow band photometers
working alternatively on blue and red wing of the sodium lines. The
timing of the ``blue wing'' velocity coming from the current GOLF data
is given in respect to the ground-based observations. The phase lag for
the ``blue'' velocity is 6 s in advance relatively to a velocity coming
from a differential device. For individual p modes, the phase lag from
the ``blue'' velocity to the ``red'' velocity are not in opposition of
phase, as expected in a very simple solar model, but differs from 8(o)
to 18(o) from the opposition, depending on the degree and the radial
order of the acoustic mode. The measurement of the differential lag
between the blue and red wings of the D lines may open a new way to
monitor the temperature oscillations with the optical depth.
Title: Results from the GOLF instrument on SOHO
Authors: Gabriel, A. H.; Turck-Chièze, S.; García, R. A.; Pallé,
P. L.; Boumier, P.; Thiery, S.; Baudin, F.; Grec, G.; Ulrich, R. K.;
Bertello, L.; Roca Cortés, T.; Robillot, J. -M.
Bibcode: 1999AdSpR..24..147G
Altcode:
An 800 day series of GOLF velocity data, with uniquely high continuity
and stability, offers the best ever signal to noise ratio obtained
in global Sun observations. Following meticulous efforts to provide
reliable calibration, these data have been used for measurements of
frequencies, line-widths and power in the p-modes, which are used
for inversion to give the internal sound speed, for comparison with
theoretical models. A search for g-modes is at present inconclusive, but
has yielded two possible candidate frequencies. The analysis available
today is regarded as preliminary and more complete methods are currently
in hand. With the resumption of routine observations following the
SOHO recovery, it is hoped that the data can be considerably extended,
enabling changes with the solar cycle to be explored, as well as an
extended g-mode search.
Title: On the nature of the current GOLF p-mode signal
Authors: Pallé, P. L.; Régulo, C.; Roca Cortés, T.; García, R. A.;
Jiménez, A.; Boumier, P.; Gabriel, A.; Grec, G.; Robillot, J. M.;
Turck-Chièze, S.; Ulrich, R. K.; SOI Team
Bibcode: 1999A&A...341..625P
Altcode:
The GOLF experiment on board SOHO is designed to measure global
oscillations of the disk-integrated sunlight with high sensitivity and
with long term stability. The GOLF data is thus ideally suited for
both the study of the p-mode spectrum and to address the search for
gravity modes. Due to their occasional malfunction the project decided
to stop the rotating polarizing elements at an optimum place in order to
maintain a precise sequence of measurements with the highest possible
duty cycle. This action means that subsequently GOLF only measures two
monochromatic intensities {I}_b(+) and {I}_b(-) on the blue wing of
the sodium doublet. In this work we investigate the nature of these
signals separately and in combinations. Our method is to study the
temporal relative phase relations between the low degree (l <=
3) p-mode signals derived from data sets obtained from simultaneous
observations, both from other SOHO instruments (GOLF and SOI) and from
Mark- I, the Tenerife station of the ground-based BiSON network. It
is found that these signals are ``almost'' pure velocity signals. A
simple model indicates that a contamination of a pure intensity-like
signal of 14% amplitude would fully explain the true nature of the
current GOLF signal. Moreover, it is found that the ratios, defined
for other instruments (Mark-I, SOI and, by extension BiSON and IRIS),
also have exactly the same nature as the GOLF ratio.
Title: SOHO After 30 Months: A Personal View
Authors: Gabriel, A. H.
Bibcode: 1999SSRv...87..123G
Altcode:
No abstract at ADS
Title: Observations of Coronal Structures Above an Active Region by
EIT and Implications for Coronal Energy Deposition
Authors: Neupert, W. M.; Newmark, J.; Delaboudinière, J. -P.;
Thompson, B. J.; Catura, R. C.; Moses, J. D.; Gurman, J. B.;
Portier-Fozzani, F.; Gabriel, A. H.; Artzner, G.; Clette, F.; Cugnon,
P.; Maucherat, A. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Dere,
K. P.; Howard, R. A.; Michels, D. J.; Freeland, S.; Lemen, J. R.;
Stern, R. A.
Bibcode: 1998SoPh..183..305N
Altcode:
Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO
have been used to evaluate temperature and density as a function of
position in two largescale features in the corona observed in the
temperature range of 1.0-2.0 MK. Such observations permit estimates
of longitudinal temperature gradients (if present) in the corona and,
consequently, estimates of thermal conduction and radiative losses
as a function of position in the features. We examine two relatively
cool features as recorded in EIT's Fe ix/x (171 Å) and Fe xii (195 Å)
bands in a decaying active region. The first is a long-lived loop-like
feature with one leg, ending in the active region, much more prominent
than one or more distant footpoints assumed to be rooted in regions of
weakly enhanced field. The other is a near-radial feature, observed
at the West limb, which may be either the base of a very high loop
or the base of a helmet streamer. We evaluate energy requirements to
support a steady-state energy balance in these features and find in
both instances that downward thermal conductive losses (at heights
above the transition region) are inadequate to support local radiative
losses, which are the predominant loss mechanism. The requirement that a
coronal energy deposition rate proportional to the square of the ambient
electron density (or pressure) is present in these cool coronal features
provides an additional constraint on coronal heating mechanisms.
Title: Time-correlation of the solar p-mode velocity signal from GOLF
Authors: Gabriel, M.; Grec, G.; Renaud, C.; Gabriel, A. H.; Robillot,
J. M.; Roca Cortes, T.; Turck-Chieze, S.; Ulrich, R. K.
Bibcode: 1998A&A...338.1109G
Altcode:
Since the launch of SOHO, the Solar Heliospheric Orbital Observatory,
the helioseismic observations are nearly uninterrupted. The GOLF
instrument (A. Gabriel et al., 1997) measures the mean velocity
integrated over the disk. The autocorrelation function of this velocity
shows two main features: Firstly, the initial decrease of the peak
amplitudes is much faster than expected from the width of the most
powerful lines and %!second secondly it does not %!go decrease to
zero for large times. These two features have been studied using the
model of stochastically excited oscillators.The second one can also be
understood on the basis of a completely general discussion. We show
that the fast initial decrease of the peak amplitudes results from
the departure of the mode frequencies from the values predicted by
the first order asymptotic theory (the modes are not equidistant) and
that the damping time of the modes has only a small influence. The non
vanishing amplitudes at large times result either from the presence of a
periodic non-stochastic component in the signal or from the stochastic
nature of the excitation. Further tests have shown that the second
possibility is the right one. This result gives a new argument in
favor of the stochastic excitation of solar p-modes. The use of the
ACF also suggests a new method to study line profiles which has been
tested for radial modes and Lorentz profiles.
Title: High-Frequency Peaks in the Power Spectrum of Solar Velocity
Observations from the GOLF Experiment
Authors: García, R. A.; Pallé, P. L.; Turck-Chièze, S.; Osaki,
Y.; Shibahashi, H.; Jefferies, S. M.; Boumier, P.; Gabriel, A. H.;
Grec, G.; Robillot, J. M.; Roca Cortés, T.; Ulrich, R. K.
Bibcode: 1998ApJ...504L..51G
Altcode:
The power spectrum of more than 630 days of full-disk solar velocity
data, provided by the GOLF spectrophotometer aboard the Solar and
Heliospheric Observatory, has revealed the presence of modelike
structure well beyond the acoustic cutoff frequency for the solar
atmosphere (νac~5.4 mHz). Similar data produced by
full-disk instruments deployed in Earth-based networks (BiSON and
IRIS) had not shown any peak structure above νac: this
is probably due to the higher levels of noise that are inherent in
Earth-based experiments. We show that the observed peak structure
(νac<=ν<=7.5 mHz) can be explained by a simple
two-wave interference model if the high-frequency waves are partially
reflected at the back side of the Sun.
Title: Measurement of the electron temperature gradient in a solar
coronal hole
Authors: David, C.; Gabriel, A. H.; Bely-Dubau, F.; Fludra, A.;
Lemaire, P.; Wilhelm, K.
Bibcode: 1998A&A...336L..90D
Altcode:
It has long been established that the high speed solar wind streams
observed at 1 A.U. originate from the coronal hole regions of the
Sun. Theoretical modelling of the acceleration mechanism depends
critically on the value of the maximum of temperature existing close
to the Sun. Measurements of the temperature in coronal holes prior
to SOHO are unreliable. The very low luminosity leads to extreme
observational difficulties, in particular due to light scattering in
the instrument telescopes. Using the two SOHO spectrometers CDS and
SUMER, electron temperatures have now been measured as a function of
height above the limb in a polar coronal hole. Temperatures of around
0.8 MK are found close to the limb, rising to a maximum of less than
1 MK at 1.15 R_sun, then falling to around 0.4 MK at 1.3 R_sun. With
these low temperatures, the classical Parker mechanism cannot alone
explain the high wind velocities, which must therefore be due to the
direct transfer of momentum from MHD waves to the ambient plasma.
Title: The Solar Corona Above Polar Coronal Holes as Seen by SUMER
on SOHO
Authors: Wilhelm, Klaus; Marsch, Eckart; Dwivedi, Bhola N.; Hassler,
Donald M.; Lemaire, Philippe; Gabriel, Alan H.; Huber, Martin C. E.
Bibcode: 1998ApJ...500.1023W
Altcode:
In order to address two of the principal scientific objectives of the
Solar and Heliospheric Observatory (SOHO), studies of the heating
mechanisms of the solar corona and the acceleration processes of
the solar wind, we deduce electron temperatures, densities, and
ion velocities in plumes and interplume regions of polar coronal
holes using ultraviolet observations from SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) on SOHO. SUMER allows us to study
the inner corona up to a distance of about 430,000 km above the
limb, or r = 1.6 R⊙ (solar radius) from the center
of the disk. We find the electron temperatures, Te,
to be less than 800,000 K in a plume in the range from r = 1.03 to
1.60 R⊙, decreasing with height to ~330,000 K. Near
an interplume lane, the electron temperature is also low, but stays
between 750,000 and 880,000 K in the same height interval. Doppler
widths of O VI lines in plumes are narrower (ΔλD ~
150 mÅ, v1/E ~ 43 km s-1) than in interplume
lanes (~190 mÅ, ~55 km s-1). The thermal and turbulent
ion speeds, v1/E, of Si7+ reach values up to
~80 km s-1 in the darkest regions outside plumes above the
coronal hole. This corresponds to a kinetic ion temperature of 1 ×
107 K. A limit of ~18 km s-1 for the bulk speed
in plumes below r = 1.2 R⊙ is deduced from O VI line shift
measurements and consideration of the three-dimensional plume geometry
(differential line-of-sight velocities <=3 km s-1),
whereas differential line-of-sight velocities of Mg8+
ions up to 34 km s-1 can be seen in dark regions.
Title: Are solar acoustic modes correlated?
Authors: Foglizzo, T.; Garcia, R. A.; Boumier, P.; Charra, J.; Gabriel,
A. H.; Grec, G.; Robillot, J. M.; Roca Cortes, T.; Turck-Chieze, S.;
Ulrich, R. K.
Bibcode: 1998A&A...330..341F
Altcode: 1997astro.ph..9095F
We have studied the statistical properties of the energy of individual
acoustic modes, extracted from 310 days of GOLF data near the solar
minimum. The exponential distribution of the energy of each mode is
clearly seen. The modes are found to be uncorrelated with a partial
0.6% accuracy, thus supporting the hypothesis of stochastic excitation
by the solar convection. Nevertheless, the same analysis performed on
the same modes just before the solar maximum, using IPHIR data, rejects
the hypothesis of no correlation at a 99.3% confidence level. A simple
model suggests that 31.3partialm 9.4% of the energy of each mode is
coherent among the modes studied in IPHIR data, correponding to a mean
correlation of 10.7partialm 5.9%.
Title: Stability Study of the GOLF Blue Wing Working Cycle
Authors: Robillot, J. M.; Turck-Chieze, S.; Garcia, R. A.; Boumier,
P.; Charra, J.; Ulrich, R. K.; Gabriel, A.; Grec, G.; Roca Cortes, T.
Bibcode: 1998ESASP.418..317R
Altcode: 1998soho....6..317R
The GOLF experiment is a resonant scattering spectrophotometer in
flight on board the SOHO mission, originally designed to measure the
intensity of the solar radiation at 4 selected positions within the
sodium doublet (D1 at λ 5896 and D2 at λ 5890 AA). Each position was
determined by a modulated magnetic field and a combination of rotating
polarizers (see Gabriel et al. 1995, 1997 for a full description of the
instrument). Due to occasional malfunctions of the polarizing element
that allows to switch between the two wings of the solar profile,
it was decided to stop the mechanism in a safety position. Thus,
only two monochromatic intensities, Ib+ and
Ib- are measured but a duty cycle close to 100 %
is achieved. After more than two years of blue wing measurements we
show the long term stability of the GOLF experiment and we discuss
their impact on the new derived velocity.
Title: GOLF: Status and Future Prospects
Authors: Gabriel, A. H.
Bibcode: 1998ESASP.418...11G
Altcode: 1998soho....6...11G
No abstract at ADS
Title: VIRGO on SOHO: Status and Future Prospects
Authors: Fröhlich, C.; Scherrer, P.; MDI Team; Virgo Team; Gabriel,
A.; GOLF Team
Bibcode: 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: Space based astronomy: ISO, AGN, radiopulsars and the
Sun. Proceedings. E1.3, E1.4, E1.5 and E2.3 Symposia of COSPAR
Scientific Commission E which were held during the Thirty-first
COSPAR Scientific Assembly, Birmingham (UK), 14 - 21 July 1996.
Authors: Walker, H. J.; Welsh, W. F.; Caraveo, P. A.; Gabriel, A. H.
Bibcode: 1998AdSpR..21.....W
Altcode:
The symposia themes reflected in the papers included: calibration
and performance of the Long Wavelength Spectrometer (LWS) and Short
Wavelength Spectrometer (SWS), ISOPHOT observations of dust around main
sequence and evolved stars, AGN variability, particularly double-peaked
emission lines as signatures of accretion disks in AGN, the "AGN Watch"
and variability in blazars. An overview of the radio studies of pulsars
was also given.
Title: Preface
Authors: Gabriel, A.
Bibcode: 1998AdSpR..21..261G
Altcode:
No abstract at ADS
Title: Search for g-mode Frequencies in the GOLF Oscillations Spectrum
Authors: Gabriel, A. H.; GOLF Team
Bibcode: 1998ESASP.418...61G
Altcode: 1998soho....6...61G
The GOLF instrument, as its name implies, was designed in order to
optimise the possibility of measuring low frequencies, in the range of
the g-modes and the lower p-modes. The high stability of the instrument,
combined with a continuity of data close too 100 % has contributed
to providing a velocity time series in which the instrumental noise
is indeed extremely low. However, in the region of the expected
g-modes, global oscillations compete with a quite significant solar
velocity background, due to the non-global convective movements in the
photosphere. With now 2 years of high-quality data, the GOLF team is
employing several different techniques to search for these modes. The
upper limit to possible g-mode power is being pushed continually lower,
as the techniques are refined. An identification of g-mode frequencies
would yeild a highly sensitive probe for the properties of the core,
in contrast to the p-modes for which extremely precise frequencies are
required for the inversion. The poster presents the current status of
the g-mode search, together with the results available at the time of
the meeting.
Title: First Results on it P Modes from GOLF Experiment
Authors: Lazrek, M.; Baudin, F.; Bertello, L.; Boumier, P.; Charra,
J.; Fierry-Fraillon, D.; Fossat, E.; Gabriel, A. H.; García, R. A.;
Gelly, B.; Gouiffes, C.; Grec, G.; Pallé, P. L.; Pérez Hernández,
F.; Régulo, C.; Renaud, C.; Robillot, J. -M.; Roca Cortés, T.;
Turck-Chièze, S.; Ulrich, R. K.
Bibcode: 1997SoPh..175..227L
Altcode:
The GOLF experiment on the SOHO mission aims to study the internal
structure of the Sun by measuring the spectrum of global oscillations
in the frequency range 10-7 to 10-2 Hz. Here
we present the results of the analysis of the first 8 months of
data. Special emphasis is put into the frequency determination of the p
modes, as well as the splitting in the multiplets due to rotation. For
both, we show that the improvement in S/N level with respect to the
ground-based networks and other experiments is essential in achieving
a very low-degree frequency table with small errors ∼ 2 parts in
10-5). On the other hand, the splitting found seems to favour
a solar core which does not rotate slower than its surface. The line
widths do agree with theoretical expectations and other observations.
Title: EIT Observations of the Extreme Ultraviolet Sun
Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner,
G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.;
Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard,
R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus,
P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.;
Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark,
J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.;
Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R.
Bibcode: 1997SoPh..175..571M
Altcode:
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO
spacecraft has been operational since 2 January 1996. EIT observes
the Sun over a 45 x 45 arc min field of view in four emission line
groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination
of the instrument flatfield, the instrument scattering function, and
the instrument aging were necessary for the reduction and analysis
of the data. The observed structures and their evolution in each
of the four EUV bandpasses are characteristic of the peak emission
temperature of the line(s) chosen for that bandpass. Reports on the
initial results of a variety of analysis projects demonstrate the range
of investigations now underway: EIT provides new observations of the
corona in the temperature range of 1 to 2 MK. Temperature studies of
the large-scale coronal features extend previous coronagraph work
with low-noise temperature maps. Temperatures of radial, extended,
plume-like structures in both the polar coronal hole and in a low
latitude decaying active region were found to be cooler than the
surrounding material. Active region loops were investigated in detail
and found to be isothermal for the low loops but hottest at the loop
tops for the large loops.
Title: First View of the Solar Core from GOLF Acoustic Modes
Authors: Turck-Chièze, S.; Basu, S.; Brun, A. S.;
Christensen-Dalsgaard, J.; Eff-Darwich, A.; Lopes, I.; Pérez
Hernández, F.; Berthomieu, G.; Provost, J.; Ulrich, R. K.; Baudin,
F.; Boumier, P.; Charra, J.; Gabriel, A. H.; Garcia, R. A.; Grec,
G.; Renaud, C.; Robillot, J. M.; Roca Cortés, T.
Bibcode: 1997SoPh..175..247T
Altcode:
After 8 months of nearly continuous measurements the GOLF instrument,
aboard SOHO, has detected acoustic mode frequencies of more than 100
modes, extending from 1.4 mHz to 4.9 mHz. In this paper, we compare
these results with the best available predictions coming from solar
models. To verify the quality of the data, we examine the asymptotic
seismic parameters; this confirms the improvements achieved in solar
models during the last decade.
Title: Performance and Early Results from the GOLF Instrument Flown
on the SOHO Mission
Authors: Gabriel, A. H.; Charra, J.; Grec, G.; Robillot, J. -M.;
Roca Cortés, T.; Turck-Chièze, S.; Ulrich, R.; Basu, S.; Baudin,
F.; Bertello, L.; Boumier, P.; Charra, M.; Christensen-Dalsgaard, J.;
Decaudin, M.; Dzitko, H.; Foglizzo, T.; Fossat, E.; García, R. A.;
Herreros, J. M.; Lazrek, M.; Pallé, P. L.; Pétrou, N.; Renaud, C.;
Régulo, C.
Bibcode: 1997SoPh..175..207G
Altcode:
GOLF in-flight commissioning and calibration was carried out during the
first four months, most of which represented the cruise phase of SOHO
towards its final L1 orbit. The initial performance of GOLF is shown
to be within the design specification, for the entire instrument as
well as for the separate sub-systems. Malfunctioning of the polarising
mechanisms after 3 to 4 months operation has led to the adoption of an
unplanned operating sequence in which these mechanisms are no longer
used. This mode, which measures only the blue wing of the solar sodium
lines, detracts little from the detection and frequency measurements of
global oscillations, but does make more difficult the absolute velocity
calibration, which is currently of the order of 20%. Data continuity
in the new mode is extremely high and the instrument is producing
exceptionally noise-free p-mode spectra. The data set is particularly
well suited to the study of effects due to the excitation mechanism
of the modes, leading to temporal variations in their amplitudes. The
g modes have not yet been detected in this limited data set. In the
present mode of operation, there are no indications of any degradation
which would limit the use of GOLF for up to 6 years or more.
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.;
Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier,
F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.;
Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.;
Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.;
Llebaria, A.; Schwenn, R.; Simnett, G. M.
Bibcode: 1997SoPh..175..601D
Altcode:
We present the first observations of the initiation of a coronal mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
experiment on SOHO show that the CME began in a small volume and was
initially associated with slow motions of prominence material and a
small brightening at one end of the prominence. Shortly afterward,
the prominence was accelerated to about 100 km s-1 and
was preceded by a bright loop-like structure, which surrounded an
emission void, that traveled out into the corona at a velocity of
200-400 km s-1. These three components, the prominence,
the dark void, and the bright loops are typical of CMEs when seen at
distance in the corona and here are shown to be present at the earliest
stages of the CME. The event was later observed to traverse the LASCO
coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest
is the fact that this large-scale event, spanning as much as 70 deg in
latitude, originated in a volume with dimensions of roughly 35" (2.5
x 104 km). Further, a disturbance that propagated across
the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the
west limb.
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.
Bibcode: 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: Observations of Coronal Features by EIT above an Active Region
by EIT and Implications for Coronal Heating
Authors: Neupert, W. M.; Newmark, J.; Thompson, B. J.; Catura, R.;
Moses, J. D.; Portier-Fozzani, F.; Delaboudiniere, J. P.; Gabriel, A.;
Artzner, G.; Clette, F.; Cugnon, P.; Maucherat, A.; Defise, J. M.;
Jamar, C.; Rochus, P.; Howard, R.; Michels, D.; Dere, K.; Freeland,
S.; Lemen, J.; Stern, R.; Gurman, J.
Bibcode: 1997SPD....28.0115N
Altcode: 1997BAAS...29..881N
The EUV Imaging Telescope (EIT) on the SOHO provides the capability
for multi-wavelength imaging of the corona in four spectral bands,
centered at 171, 195, 284, and 304 Angstroms, using multilayer telescope
technology. These bands encompass coronal temperatures from 1 MK
to 2.5 MK as well as the upper chromosphere, at about 60,000 K. In
particular, nearly simultaneous imaging in the 171 and 195 Angstrom
bands, the former including major Fe IX and Fe X emission lines, the
latter including a strong Fe XII line, provides a capability to infer
the morphology and characteristics of the corona at temperatures of
1.0 - 1.7 MK. We have examined the corona in this temperature range
over an active region observed from SOHO from May - September, 1996 and
find that low-lying loops (below a density scale height of 75,000 km,
characteristic of Fe X) vary little in brightness and temperature along
their length. For features extending to greater heights, however, both
brightness gradients and temperature gradients are observed. Preliminary
analysis of the observations when the region was on the West limb
on September 30 indicates a small positive temperature gradient of
approximately 0.5 K/km in one loop system that extended above 100,000
km. On the other hand, a nearly radial feature extending to the edge of
the EIT FOV was isothermal or had at most a slight negative temperature
gradient. Such measurements may have application to the modeling of
coronal loops and streamers and the processes of coronal heating and
solar wind acceleration.
Title: Measurement of Above-Limb Coronal Intensities
Authors: David, C.; Gabriel, A. H.; Bely-Dubau, F.
Bibcode: 1997ESASP.404..313D
Altcode: 1997cswn.conf..313D
No abstract at ADS
Title: Imaging the solar corona in the EUV
Authors: Delaboudiniere, J. -P.; Stern, R. A.; Maucherat, A.;
Portier-Fozzani, F.; Neupert, W. M.; Gurman, J. B.; Catura, R. C.;
Lemen, J. R.; Shing, L.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.;
Michels, D. J.; Moses, J. D.; Au, B.; Dere, K. P.; Howard, R. A.;
Kreplin, R.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.;
Marioge, J. P.; Clette, F.; Cugnon, P.; van Dessel, E. L.
Bibcode: 1997AdSpR..20.2231D
Altcode:
The SOHO (SOlar and Heliospheric Observatory) satellite was launched on
December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point
on February 14th 1996, it began to continuously observe the Sun. As
one of the instruments onboard SOHO, the EIT (Extreme ultraviolet
Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The
He II filter at 304 A˚ images the chromosphere and the base of the
transition region at a temperature of 5 - 8 x 10^4 K; the Fe IX-X
filter at 171 A˚ images the corona at a temperature of ~ 1.3 x 10^6 K;
the Fe XII filter at 195 A˚ images the quiet corona outside coronal
holes at a temperature of ~ 1.6 x 10^6 K; and the Fe XV filter at 284
A˚ images active regions with a temperature of ~ 2.0 x 10^6 K. About
5000 images have been obtained up to the present. In this paper,
we describe also some aspects of the telescope and the detector
performance for application in the observations. Images and movies
of all the wavelengths allow a look at different phenomena present in
the Sun's corona, and in particular, magnetic field reconnection.
Title: First Results of the SUMER Telescope and Spectrometer on SOHO -
I. Spectra and Spectroradiometry
Authors: Wilhelm, K.; Lemaire, P.; Curdt, W.; Schühle, U.; Marsch, E.;
Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Huber,
M. C. E.; Vial, J. -C.; Kühne, M.; Siegmund, O. H. W.; Gabriel, A.;
Timothy, J. G.; Grewing, M.; Feldman, U.; Hollandt, J.; Brekke, P.
Bibcode: 1997SoPh..170...75W
Altcode:
SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation
instrument on the Solar and Heliospheric Observatory (SOHO) - observed
its first light on January 24, 1996, and subsequently obtained a
detailed spectrum with detector B in the wavelength range from 660
to 1490 Å (in first order) inside and above the limb in the north
polar coronal hole. Using detector A of the instrument, this range
was later extended to 1610 Å. The second-order spectra of detectors
A and B cover 330 to 805 Å and are superimposed on the first-order
spectra. Many more features and areas of the Sun and their spectra
have been observed since, including coronal holes, polar plumes and
active regions. The atoms and ions emitting this radiation exist at
temperatures below 2 × 106 K and are thus ideally suited
to investigate the solar transition region where the temperature
increases from chromospheric to coronal values. SUMER can also be
operated in a manner such that it makes images or spectroheliograms
of different sizes in selected spectral lines. A detailed line profile
with spectral resolution elements between 22 and 45 mÅ is produced for
each line at each spatial location along the slit. From the line width,
intensity and wavelength position we are able to deduce temperature,
density, and velocity of the emitting atoms and ions for each emission
line and spatial element in the spectroheliogram. Because of the high
spectral resolution and low noise of SUMER, we have been able to detect
faint lines not previously observed and, in addition, to determine
their spectral profiles. SUMER has already recorded over 2000 extreme
ultraviolet emission lines and many identifications have been made on
the disk and in the corona.
Title: Performance and first results from the GOLF instrument on SoHO
Authors: Gabriel, A. H.; Charra, J.; Grec, G.; Robillot, J. -M.; Roca
Cortés, T.; Turck-Chièze, S.; Ulrich, R.; Baudin, F.; Bertello,
L.; Boumier, P.; Decaudin, M.; Dzitko, H.; Foglizzo, T.; Fossat, E.;
García, R. A.; Herreros, J. M.; Lazrek, M.; Pallé, P. L.; Pétrou,
N.; Renaud, C.; Régulo, C.
Bibcode: 1997IAUS..181...53G
Altcode:
No abstract at ADS
Title: Temperature Structure in Coronal Holes
Authors: David, C.; Gabriel, A. H.; Bely-Dubau, F.
Bibcode: 1997ESASP.404..319D
Altcode: 1997cswn.conf..319D
No abstract at ADS
Title: Actual Status and Early Results from GOLF Experiment on-board
SOHO
Authors: Roca Cortes, T.; Gabriel, A. H.; Charra, J.; Grec, G.; Ulrich,
R. K.; Turck-Chieze, S.; Robillot, J. M.; Boumier, P.; Regulo, C.;
Baudin, F.; Lazrek, M.; Garcia, R. A.; Palle, P. L.; GOLF Team
Bibcode: 1997ASPC..118..249R
Altcode: 1997fasp.conf..249R
GOLF is a resonant scattering spectrophotomer which is flying onboard
SOHO. The first four months were dedicated to the commissioning
and calibration of the instrument which led to the conclusion of
a performance within design specification at system and subsystem
levels. However, mal-functioning of the polarising mechanisms at the end
of this period led to the adoption of an unplanned operating sequence in
which the mechanisms are no longer used. This photometric mode, which
measures at two points on the blue wing of the solar sodium lines, has
very little effect on the possibility of reaching the first objective
of the mission: measuring the solar spectrum of normal modes. However,
the precise calibration procedure to transform the actual measurements
into velocity is not trivial. The actual operating mode allows the
obtention of continuous data without interruptions which is producing
exceptionally noise-free p-mode spectra. Although this spectrum is
being studied, the data accumulated do not allow a positive detection
of the g-mode spectrum yet. On the other hand, the present mode of
operation do not show any indication of degradation which could limit
its use for up to 6 years or more of operation.
Title: First Results of the SUMER Telescope and Spectrometer on SOHO -
II. Imagery and Data Management
Authors: Lemaire, P.; Wilhelm, K.; Curdt, W.; SchÜle, U.; Marsch,
E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial,
J. C.; KÜhne, M.; Huber, M. C. E.; Siegmund, O. H. W.; Gabriel, A.;
Timothy, J. G.; Grewing, M.
Bibcode: 1997SoPh..170..105L
Altcode:
SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not
only an extreme ultraviolet (EUV) spectrometer capable of obtaining
detailed spectra in the range from 500 to 1610 Å, but, using the
telescope mechanisms, it also provides monochromatic images over
the full solar disk and beyond, into the corona, with high spatial
resolution. We report on some aspects of the observation programmes
that have already led us to a new view of many aspects of the Sun,
including quiet Sun, chromospheric and transition region network,
coronal hole, polar plume, prominence and active region studies. After
an introduction, where we compare the SUMER imaging capabilities to
previous experiments in our wavelength range, we describe the results
of tests performed in order to characterize and optimize the telescope
under operational conditions. We find the spatial resolution to be
1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along
the slit. Resolution and sensitivity are adequate to provide details
on the structure, physical properties, and evolution of several solar
features which we then present. Finally some information is given on
the data availability and the data management system.
Title: Dedication to Bruce Patchett
Authors: Gabriel, A.
Bibcode: 1997ESASP.404....3G
Altcode: 1997cswn.conf....3G
No abstract at ADS
Title: Extreme ultraviolet observations of the solar corona: first
results from the coronal diagnostic spectrometer on SOHO
Authors: Harrison, R. A.; Fludra, A.; Sawyer, E. C.; Culhane, J. L.;
Norman, K.; Poland, A. I.; Thompson, W. T.; Kjeldseth-Moe, O.;
Aschenbach, B.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.
Bibcode: 1997AdSpR..20.2239H
Altcode:
We present first results from the Coronal Diagnostic Spectrometer (CDS)
aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is
a double spectrometer operating in the 151-785 A˚ range. This region
of the solar spectrum is rich in emission lines from trace elements
in the solar atmosphere, which can be used to derive diagnostic
information on coronal and transition region plasma. Early spectra are
presented and well identified lines are listed. In addition, examples
of images in selected wavelength ranges are shown, for a prominence,
a loop system and a bright point, demonstrating well the power of such
extreme ultraviolet observations.
Title: GOLF results: today's view on the solar modes
Authors: Grec, C.; Turck-Chièze, S.; Lazrek, M.; Roca Cortés, T.;
Bertello, L.; Baudin, F.; Boumier, P.; Charra, J.; Fierry-Fraillon,
D.; Fossat, E.; Gabriel, A. H.; Garcia, R. A.; Gelly, B.; Gouiffes,
C.; Régulo, C.; Renaud, C.; Robillot, J. M.; Ulrich, R. K.
Bibcode: 1997IAUS..181...91G
Altcode:
No abstract at ADS
Title: First Results from EIT
Authors: Clette, F.; Delaboudiniere, J. -P.; Artzner, G. E.; Brunaud,
J.; Gabriel, A. H.; Hochedez, J. -F.; Millier, F.; Song, X. Y.; Au, B.;
Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.;
Defise, J. -M.; Jamar, C.; Rochus, P.; Chauvineau, J. -P.; Marioge,
J. -P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman,
J. B.; Neupert, W. M.; Maucherat, A.; Cugnon, P.; van Dessel, E. L.
Bibcode: 1997ASPC..118..268C
Altcode: 1997fasp.conf..268C
The Extreme-UV Imaging telescope has already produced more than 15000
wide-field images of the corona and transition region, on the disk
and up to 1.5R_⊙ above the limb, with a pixel size of 2.6\arcsec. By
using four different emission lines, it provides the global temperature
distribution in the quiet corona, in the range 0.5 to 3*E(6) K. Its
excellent sensitivity and wide dynamic range allow unprecedented views
of low emission features, even inside coronal holes. Those so-called
``quiet'' regions actually display a wide range of dynamical phenomena,
in particular at small spatial scales and at time scales going down
to only a few seconds, as revealed by all EIT time sequences of
full- or partial-field images. The initial results presented here
demonstrate the importance of this wide-field imaging experiment for
a good coordination between SOHO and ground-based solar telescopes,
as well as for science planning.
Title: Temporal characteristics of solar p-modes.
Authors: Baudin, F.; Gabriel, A.; Gibert, D.; Palle, P. L.; Regulo, C.
Bibcode: 1996A&A...311.1024B
Altcode:
A method for ``time/frequency'' analysis is shortly described, with
a discussion of its limitations in time and frequency resolution,
and in sensitivity to noise in the signal. This is then applied to
observational data. The data used are the luminosity measurements of
the IPHIR experiment, and the velocity measurements performed at the
Observatorio del Teide. The application to these two contemporary data
sets confirms the reliability of the method and provides additional
proof that the observed variation with time is not an effect of
noise. The long and continuous data set allows to extract information
on the temporal behaviour of low degree solar p-modes. The power
of the modes is shown to vary strongly over a time-scale of a few
days. These estimates are direct measurements from power variations,
unlike those deduced from width measured in Fourier spectra. The
temporal behaviour of several modes are compared, mainly showing
independent behaviour, but also giving some indications of weak
correlations between neighbouring modes.
Title: Observations of the South coronal hole from EIT and YOHKOH
Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern,
R.; Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel, A.;
Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr,
O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert,
W.; Einfalt, E.; Newmark, J.
Bibcode: 1996AAS...188.0206H
Altcode: 1996BAAS...28..821H
The Extreme ultraviolet Imaging Telescope (EIT) on board the
SOHO spacecraft is capable of studying solar transition region,
chomospheric and coronal plasmas over bandpasses optimized for He II
304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 - 1.0 MK),
Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 - 2.5
MK) with 2.5 arcsecond spatial resolution. This telescope in concert
with the Yohkoh/SXT instrument allows us to simultaneously observe
solar structures at temperatures ranging from less than 0.1MK in the
transition region to over 3MK in the solar corona. EIT has had several
opportunities to observe the South coronal hole with high spatial and
temporal resolution. We compare observations from EIT and SXT with
an eye towards correlating temporal variations over the range of
wavelengths, activity of polar crown filament systems and relating
large-scale morphology of the X-ray corona to the transition region
in He II.
Title: There's No Such Thing as the Quiet Sun: EUV Movies from SOHO
Authors: Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel,
A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr,
O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert,
W.; Einfalt, E.; Newmark, J.
Bibcode: 1996AAS...188.3718G
Altcode: 1996BAAS...28..880G
We present unique time series of high-resolution solar images from the
normal-incidence Extreme ultraviolet Imaging Telescope (EIT) on board
the SOHO spacecraft. With a pixel scale of 2.6 arc sec and a detector
dynamic range of > 10(4) , the EIT can be used to study the dynamics
of chromospheric and coronal features in multilayer bandpasses optimized
for He II 304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 -
1.0 MK), Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 -
2.5 MK). Among the most striking features of the digital movies we will
display are: the dynamic nature of small-scale loop features in the
polar coronal holes, the constant activity of the polar crown filament
systems, the locations of the bases of polar plumes, the presence
of dark (scattering) filament material in the coronal emission line
images, and the evolution of a unique, linear, dark feature in a young
active region. The latter feature is suggestive of the ``coronal void''
observed in the electron scattering corona by Macqueen et al./ (1983).
Title: Observations of the south coronal hole from EIT and Yohkoh.
Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern,
R.; Gurman, J. B.; Delaboudinière, J. P.; Artzner, G.; Gabriel,
A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; St. Cyr,
O. C.; Neupert, W.; Einfalt, E.; Newmark, J.
Bibcode: 1996BAAS...28Q.821H
Altcode:
No abstract at ADS
Title: Studies of Solar Wind Onset in Coronal Holes Planned for SOHO
Authors: Gabriel, A. H.; Bely-Debau, F.; David, C.
Bibcode: 1996mpsa.conf..499G
Altcode: 1996IAUCo.153..499G
No abstract at ADS
Title: Global Oscillations at Low Frequency from the SOHO Mission
(GOLF)
Authors: Gabriel, A. H.; Grec, G.; Charra, J.; Robillot, J. -M.; Roca
Cortés, T.; Turck-Chièze, S.; Bocchia, R.; Boumier, P.; Cantin, M.;
Cespédes, E.; Cougrand, B.; Crétolle, J.; Damé, L.; Decaudin, M.;
Delache, P.; Denis, N.; Duc, R.; Dzitko, H.; Fossat, E.; Fourmond,
J. -J.; García, R. A.; Gough, D.; Grivel, C.; Herreros, J. M.;
Lagardère, H.; Moalic, J. -P.; Pallé, P. L.; Pétrou, N.; Sanchez,
M.; Ulrich, R.; van der Raay, H. B.
Bibcode: 1995SoPh..162...61G
Altcode:
The GOLF experiment on the SOHO mission aims to study the internal
structure of the sun by measuring the spectrum of global oscillations in
the frequency range 10−7 to 10−2 Hz. Bothp
andg mode oscillations will be investigated, with the emphasis on
the low order long period waves which penetrate the solar core. The
instrument employs an extension to space of the proven ground-based
technique for measuring the mean line-of-sight velocity of the viewed
solar surface. By avoiding the atmospheric disturbances experienced
from the ground, and choosing a non-eclipsing orbit, GOLF aims to
improve the instrumental sensitivity limit by an order of magnitude
to 1 mm s−1 over 20 days for frequencies higher than
2.10−4 Hz. A sodium vapour resonance cell is used in
a longitudinal magnetic field to sample the two wings of the solar
absorption line. The addition of a small modulating field component
enables the slope of the wings to be measured. This provides not only
an internal calibration of the instrument sensitivity, but also offers a
further possibility to recognise, and correct for, the solar background
signal produced by the effects of solar magnetically active regions. The
use of an additional rotating polariser enables measurement of the
mean solar line-of-sight magnetic field, as a secondary objective.
Title: The Coronal Diagnostic Spectrometer for the Solar and
Heliospheric Observatory
Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise,
A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang,
J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards,
A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al
Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas,
P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe,
O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger,
H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.;
Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I.
Bibcode: 1995SoPh..162..233H
Altcode:
The Coronal Diagnostic Spectrometer is designed to probe the solar
atmosphere through the detection of spectral emission lines in the
extreme ultraviolet wavelength range 150 - 800 å. By observing
the intensities of selected lines and line profiles, we may derive
temperature, density, flow and abundance information for the plasmas
in the solar atmosphere. Spatial and temporal resolutions of down to
a few arcseconds and seconds, respectively, allow such studies to be
made within the fine-scale structure of the solar corona. Futhermore,
coverage of large wavelength bands provides the capability for
simultaneously observing the properties of plasmas across the wide
temperature ranges of the solar atmosphere.
Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schühle, U.; Lemaire,
P.; Gabriel, A.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan,
S. D.; Poland, A. I.; Thomas, R. J.; Kühne, M.; Timothy, J. G.;
Hassler, D. M.; Siegmund, O. H. W.
Bibcode: 1995SoPh..162..189W
Altcode:
The instrument SUMER - Solar Ultraviolet Measurements of Emitted
Radiation is designed to investigate structures and associated dynamical
processes occurring in the solar atmosphere, from the chromosphere
through the transition region to the inner corona, over a temperature
range from 104 to 2 × 106K and above. These
observations will permit detailed spectroscopic diagnostics of plasma
densities and temperatures in many solar features, and will support
penetrating studies of underlying physical processes, including plasma
flows, turbulence and wave motions, diffusion transport processes,
events associated with solar magnetic activity, atmospheric heating,
and solar wind acceleration in the inner corona. Specifically, SUMER
will measure profiles and intensities of EUV lines; determine Doppler
shifts and line broadenings with high accuracy; provide stigmatic
images of the Sun in the EUV with high spatial, spectral, and temporal
resolution; and obtain monochromatic maps of the full Sun and the inner
corona or selected areas thereof. SUMER will be flown on the Solar
and Heliospheric Observatory (SOHO), scheduled for launch in November,
1995. This paper has been written to familiarize solar physicists with
SUMER and to demonstrate some command procedures for achieving certain
scientific observations.
Title: EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission
Authors: Delaboudinière, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel,
A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.;
Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise,
J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.;
Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.;
Neupert, W. M.; Maucherat, A.; Clette, F.; Cugnon, P.; Van Dessel,
E. L.
Bibcode: 1995SoPh..162..291D
Altcode:
The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field
images of the corona and transition region on the solar disc and up to
1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated
optics will select spectral emission lines from Fe IX (171 å), Fe
XII (195 å), Fe XV (284 å), and He II (304 å) to provide sensitive
temperature diagnostics in the range from 6 × 104 K to 3
× 106 K. The telescope has a 45 x 45 arcmin field of view
and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial
resolution. The EIT will probe the coronal plasma on a global scale,
as well as the underlying cooler and turbulent atmosphere, providing
the basis for comparative analyses with observations from both the
ground and other SOHO instruments. This paper presents details of the
EIT instrumentation, its performance and operating modes.
Title: Some design and performance features of SUMER: solar
ultraviolet measurements of emitted radiation
Authors: Wilhelm, Klaus; Curdt, W.; Marsh, E.; Schuehle, Udo H.;
Lemaire, Philippe; Gabriel, Alan H.; Vial, J. -C.; Grewing, Michael;
Huber, Martin C.; Jordan, S. D.; Poland, Arthur I.; Thomas, Roger J.;
Kuehne, Mikhael; Timothy, J. Gethyn; Hassler, Donald M.; Siegmund,
Oswald H.
Bibcode: 1995SPIE.2517....2W
Altcode:
The instrument SUMER (solar ultraviolet measurements of emitted
radiation) is designed to investigate structures and associated
dynamical processes occurring in the solar atmosphere from the
chromosphere through the transition region to the inner corona, over a
temperature range from 104 to 2 multiplied by 106
K and above. The observations will be performed, on board SOHO (solar
and heliospheric observatory) scheduled for launch in November 1995,
by a scanning, normal-incidence telescope/spectrometer system in
the wavelength range from 500 to 1610 angstrom. Spatial resolution
requirements compatible with the pointing stability of SOHO are less
than 1000 km corresponding to about 1-arcsec angular resolution. Doppler
observations of EUV line shifts and broadenings should permit solar
plasma velocity measurements down to 1 km s-1. We report
here on some specific features of this instrument related to its
pointing as well as its spatial and spectral resolution capabilities.
Title: Spacelab 2 measurement of the solar coronal helium abundance
Authors: Gabriel, A. H.; Culhane, J. L.; Patchett, B. E.; Breeveld,
E. R.; Lang, J.; Parkinson, J. H.; Payne, J.; Norman, K.
Bibcode: 1995AdSpR..15g..63G
Altcode: 1995AdSpR..15...63G
The abundance of helium relative to hydrogen has been measured with
the ``Coronal Helium Abundance Spacelab Experiment'' (CHASE) from the
space shuttle Challenger in 1985. Previous solar measurements have
proved difficult due to the temperature-sensitivity of the electron
excitation rates for the observed lines. In this approach scattered
Lyman Alpha (Lyalpha) radiation of helium and hydrogen formed in
the corona were measured with a grazing-incidence spectrometer and
compared with the intensity of the illuminating flux from the solar
chromosphere. The abundance ratio by number of atoms was found to be
0.070 with an uncertainty of 0.011. Scattered light in the telescope
is the main source of error.
Title: Temporal Behaviour of Solar P-Modes of Low Degree L
Authors: Baudin, F.; Gabriel, A.; Gibert, D.; Pallé, P.; Régulo, C.
Bibcode: 1995ESASP.376b.323B
Altcode: 1995help.confP.323B; 1995soho....2..323B
No abstract at ADS
Title: Corot: a Space Project Devoted to the Study of Convection
and Rotation in Stars
Authors: Catala, C.; Auvergne, M.; Baglin, A.; Bonneau, F.; Magnan,
A.; Vuillemin, A.; Goupil, M. J.; Michel, E.; Boumier, P.; Dzitko,
H.; Gabriel, A.; Gautier, D.; Lemaire, P.; Mangeney, A.; Mosser, B.;
Turck-Chiéze, S.; Zahn, J. P.
Bibcode: 1995ESASP.376b.549C
Altcode: 1995soho....2..549C; 1995help.confP.549C
No abstract at ADS
Title: Global Oscillations at Low Frequency from the SOHO Mission
(golf)
Authors: Gabriel, A.; GOLF Team
Bibcode: 1995ESASP.376a..77G
Altcode: 1995heli.conf...77G; 1995soho....1...77G
The GOLF experiment on the SOHO mission aims to study the internal
structure of the Sun by measuring the spectrum of global oscillations in
the frequency range between 10-7 and 10-2Hz. Both
p and g mode oscillations will be investigated, with the emphasis on
the low order long period waves which penetrate the solar core. By
avoiding the atmospheric disturbances experienced from the ground, and
choosing a non-eclipsing orbit, GOLF aims to improve the instrumental
sensitivity limit by an order of magnitude to 1 mm s-1
over 20 days for frequencies higher than 2×10-4Hz. A
sodium vapour resonance cell is used in a longitudinal magnetic field
to sample the two wings of the solar absorption line. The addition
of a small modulating field component enables the slope of the wings
to be measured. This provides not only an internal calibration of
the instrument sensitivity, but also offers a further possibility
to recognise, and correct for, the solar background signal produced
by the effects of solar magnetically active regions. The use of an
additional rotating polariser enables measurement of the mean solar
line-of-sight magnetic field, as a secondary objective. A description
is given of the plans for reduction and analysis of the data.
Title: COROT: A Proposal to Study Stellar Convection and Internal
Rotation
Authors: Catala, C.; Mangeney, A.; Gautier, D.; Auvergne, M.; Baglin,
A.; Goupil, M. J.; Michel, E.; Zahn, J. P.; Magnan, A.; Vuillemin,
A.; Boumier, P.; Gabriel, A.; Lemaire, P.; Turck-Chieze, S.; Dzitko,
H.; Mosser, B.; Bonneau, F.
Bibcode: 1995ASPC...76..426C
Altcode: 1995gong.conf..426C
No abstract at ADS
Title: Time/frequency analysis of solar p-modes
Authors: Baudin, F.; Gabriel, A.; Gibert, D.
Bibcode: 1994A&A...285L..29B
Altcode:
A time/frequency analysis method is applied firstly to simulated
solar data in order to demonstrate its suitability for the analysis
of solar p-modes. It is then applied to real data, using the 6 months
uninterrupted set of luminosity measurements from IPHIR, which is
particularly suited on account of its continuity. The method yields
very interesting results: strong short-term variations of energy
in individual modes, independent behaviour of the modes and of the
components of a single mode. The information provided by this method
is relevant to the understanding of the mechanisms which drive solar
p-modes.
Title: The solar corona. Proceedings. Symposium E1 of the COSPAR
29. Plenary Meeting, Washington, DC (USA), 28 Aug - 5 Sep 1992.
Authors: Gabriel, A. H.
Bibcode: 1994AdSpR..14d....G
Altcode: 1994AdSpR..14Q....G
The Symposium emphasised aspects of the corona which are always present,
i.e. the so-called quiet corona, although a number of contributions
were received relating to activity and transient phenomena. Physical
properties studied include velocity fields, abundance variations and
MHD waves. Efforts to understand or predict the coronal properties in
terms of energy and momentum balance were presented.
Title: Introduction
Authors: Gabriel, Alan
Bibcode: 1994AdSpR..14d...1G
Altcode: 1994AdSpR..14....1G
No abstract at ADS
Title: 'SUMER' - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber,
M. C. E.; Jordan, S. D.; Kuhne, M.; Lemaire, P.; Marsch, E.; Poland,
A. I.; Schuhle, U.; Thomas, R. J.; Timothy, J. G.; Vial, J. -C.
Bibcode: 1994scs..conf..619W
Altcode: 1994IAUCo.144..619W
SUMER is designed for the investigations of plasma flow characteristics,
turbulence and wave motions, plasma densities and temperatures,
structures and events associated with solar magnetic activity in the
chromosphere, the transition zone and the corona. The spatial and
spectral resolution capabilities of the instrument are considered in
some detail, and a new detector concept is introduced.
Title: Some Problems in Understanding the Solar Corona (Introductory
Review)
Authors: Gabriel, A. H.
Bibcode: 1994scs..conf....1G
Altcode: 1994IAUCo.144....1G
No abstract at ADS
Title: A new method for helioseismic data analysis
Authors: Baudin, F.; Gabriel, A.; Gibert, D.
Bibcode: 1993A&A...276L...1B
Altcode:
Following a description of the "homomorphic deconvolution" and its aims,
we apply it to synthetic data to verify its application, and then
to real data. The data used is the 6 month set of solar luminosity
measurements from IPHIR . The method seems to be as efficient as
expected, showing "cleaning" 0 the spectra, advantage which will make
possible more accurate studies 0 the characteristics of the solar
acoustic modes.
Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel,
A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.;
Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G.
Bibcode: 1993BAAS...25.1192W
Altcode:
No abstract at ADS
Title: SOHO overview and preparation for operations.
Authors: Gabriel, A. H.
Bibcode: 1992ESASP.348....5G
Altcode: 1992cscl.work....5G
An overview is given of the particular scientific qualities
of the SOHO mission. The operations phase will need to take
account of the importance of coordinated observations between many
instruments. Feedback from quick-look data evaluation into the daily
planning cycle is an essential requirement for the success. Much
work remains in planning detailed scientific sequences for joint
observations.
Title: Solar corona synoptic observations from SOHO with an Extreme
Ultraviolet Imaging Telescope.
Authors: Delaboudinière, J. P.; Gabriel, A. H.; Artzner, G. E.;
Dere, K.; Howard, R.; Michels, D.; Catura, R.; Lemen, J.; Stern, R.;
Gurman, J.; Neupert, W.; Cugnon, P.; Koeckelenbergh, A.; van Dessel,
E. L.; Jamar, C.; Maucherat, A.
Bibcode: 1992ESASP.348...21D
Altcode: 1992cscl.work...21D
The major scientific objective of the EUV Imaging Telescope (EIT)
is to study the evolution of coronal structure over a wide range
of spatial and temporal scales and temperatures. A second strategic
objective is to provide full disk synoptic maps of the global corona
to aid in unifying SOHO (Solar and Heliospheric Observatory)/Cluster
investigations. EIT will also provide images to support the planning
of detailed spectroscopic investigations by the CDS (Coronal Diagnostic
Spectrometer) and SUMER spectrometers in SOHO. EIT observations will be
made in four narrow spectral bands, centered at 171 A (Fe 9), 195 A(Fe
12), 284 A (Fe 15), and 304 A (He 2) representing restricted temperature
domains within a wide temperature range from 40,000 to 3,000,000
K. The results will be images of the solar atmosphere from the upper
chromosphere and transition region to the active region corona. These
maps, made at appropriate time intervals, will be used to study the fine
structures in the solar corona and to relate their dynamic properties
to the underlying chromosphere and photosphere. Dynamic events in the
inner corona will be related to white light transients in the outer
corona, and observations of the internal structure of coronal holes
will be used to investigate origins of the solar wind.
Title: SUMER: temperatures, densities, and velocities in the outer
solar atmosphere.
Authors: Lemaire, P.; Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel,
A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuehne, M.;
Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy,
J. G.; Vial, J. C.
Bibcode: 1992ESASP.348...13L
Altcode: 1992cscl.work...13L
The SUMER instrumentation, that will be mounted on the SOHO spacecraft,
is in development under MPAE leadership. It has some capability
to improve the solar angular resolution and the spectral resolution
already obtained in the far UV to the extreme UV, corresponding to the
temperature range between 104 and a few 106K. The
authors give some insights into the SUMER spectrometer that is developed
to study the dynamics and to infer temperatures and densities of the
low corona and the chromosphere-corona transition zone in using the
50 - 160 nm wavelength range. First, they recall the SUMER scientific
goals and the technics used. Then, after a brief description of the
instrumentation the expected performances are described. The way the
observations can be conducted is emphasized and it is shown how SUMER
is operated in coordination with other SOHO instrumentations and in
cooperation with ground-based observations.
Title: "SUMER" - Solar Ultraviolet Measurements of Emitted Radiation.
Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.;
Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kühne, M.; Lemaire, P.;
Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy,
J. G.; Vial, J. C.
Bibcode: 1992eocm.rept..225W
Altcode:
The experiment Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) is designed for the investigations of plasma flow
characteristics, turbulence and wave motions, plasma densities
and temperatures, structures and events associated with solar
magnetic activity in the chromosphere, the transition zone and the
corona. Specifically, SUMER will measure profiles and intensities
of extreme ultraviolet (EUV) lines emitted in the solar atmosphere
ranging from the upper chromosphere to the lower corona; determine line
broadenings, spectral positions and Doppler shifts with high accuracy;
provide stigmatic images of selected areas of the Sun in the EUV with
high spatial, temporal and spectral resolution and obtain full images of
the Sun and the inner corona in selectable EUV lines, corresponding to a
temperature range from 104 to more than 1.8×106K.
Title: Spectroscopic Diagnostics
Authors: Gabriel, A.
Bibcode: 1992ASIC..373..261G
Altcode: 1992sla..conf..261G
No abstract at ADS
Title: Soft X-Ray Instrumentation
Authors: Gabriel, A.
Bibcode: 1992ASIC..373..423G
Altcode: 1992sla..conf..423G
No abstract at ADS
Title: SUMER - Solar ultraviolet measurements of emitted radiation
Authors: Wilhelm, K.; Axford, W. I.; Gurdt, W.; Marsch, E.; Richter,
A. K.; Grewing, M.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Huber,
M. C. E.
Bibcode: 1992sws..coll..129W
Altcode:
The SUMER (solar ultraviolet measurements of emitted radiation)
experiment is described. It will study flows, turbulent motions, waves,
temperatures and densities of the plasma in the upper atmosphere of
the Sun. Structures and events associated with solar magnetic activity
will be observed on various spatial and temporal scales. This will
contribute to the understanding of coronal heating processes and the
solar wind expansion. The instrument will take images of the Sun in EUV
(extreme ultraviolet) light with high resolution in space, wavelength
and time. The spatial resolution and spectral resolving power of the
instrument are described. Spectral shifts can be determined with
subpixel accuracy. The wavelength range extends from 500 to 1600
angstroms. The integration time can be as short as one second. Line
profiles, shifts and broadenings are studied. Ratios of temperature
and density sensitive EUV emission lines are established.
Title: The Solar Corona
Authors: Gabriel, A.
Bibcode: 1992ASIC..373..277G
Altcode: 1992sla..conf..277G
No abstract at ADS
Title: The O VII Soft X-Ray Spectrum and Its Application to Hot
Plasmas in Astrophysics
Authors: Gabriel, A. H.; Bely-Dubau, F.; Faucher, P.; Acton, L. W.
Bibcode: 1991ApJ...378..438G
Altcode:
The paper presents a revised theory and atomic model for the line
intensities emitted by O VII, taking into account all of the processes
responsible for the emission. This is used to provide a revision of the
density measurements made for solar active regions and during flares, as
well as an attempt to understand the spectrum of the Puppis A supernova
remnant. In order to explain the strange intensity ratios observed
from Puppis A, previous authors have proposed an interpretation based
upon a high-temperature thermal plasma in a nonequilibrium ionization
state. An alternative model is presented here, based upon the assumed
presence of a proportion of fast, nonthermal electrons imbedded in an
otherwise thermal plasma at a temperature below 10 to the 6th K. This
can adequately explain the observations without the necessity of
invoking departures from the ionization balance.
Title: Global oscillations at low frequency from the SOHO mission
(GOLF)
Authors: Gabriel, A. H.; GOLF Team
Bibcode: 1991AdSpR..11d.103G
Altcode: 1991AdSpR..11..103G
The GOLF experiment on the SOHO mission will study the internal
structure of the sun by measuring the spectrum of global oscillations in
the frequency range 10-7 to 6 10-3 Hz. Both p and
g mode oscillations will be investigated, with the emphasis on the low
order long period waves which penetrate the solar core. The instrument
employs an extension to space of the proven ground-based technique for
measuring the mean line-of-sight velocity of the viewed solar surface. A
sodium vapour resonance filter is used in a longitudinal magnetic field
to sample the two wings of the solar absorption line. The addition
of a small modulating field component enables the slope of the wings
to be measured. This provides not only an internal calibration of the
instrument sensitivity, but also opens the possibility to recognise,
and correct for, the solar background signal produced by the effects of
solar magnetically active regions. The use of an additional rotating
polariser enables also measurement of the mean solar line-of sight
magnetic field. (see final Section)
Title: Diagnostic methods for the inner corona
Authors: Gabriel, A. H.
Bibcode: 1991AdSpR..11a.253G
Altcode: 1991AdSpR..11..253G
In this review we discuss in general terms the relationship between
some current ideas on the heating of the corona, the onset of the
solar wind, and the observational possibilities which exist for making
significant measurements over the next few years. The essentially
two-component corona provides different challenges in the open- and
closed-field regions. The launch in 1995 of the SOHO mission offers
the most extensive of a number of new observational techniques which
will become available.
Title: Interpretation of X-ray spectra from solar flares
Authors: Gabriel, A. H.; Bely-Dubau, F.; Millier, F.
Bibcode: 1991AdSpR..11a.323G
Altcode: 1991AdSpR..11..323G
A technique developed for analysing the SMM X-ray spectra has been
adapted to the interpretation of high resolution cooled germanium
flare spectra. It is shown that these can be fitted equally well by
simple all thermal or non-thermal distributions, and that the data
set is insufficient to determine the non-thermal nature of the flare.
Title: Que peut-on apprendre sur le soleil à partir de SOHO.
Authors: Bely-Dubau, F.; Gabriel, A. H.
Bibcode: 1991sed..conf..301B
Altcode:
Contents: (1) Introduction. (2) Concept de la mission SOHO. (3)
Héliosismologie. (4) Atmosphère solaire à grande echelle. (5)
Structure fine de l'atmosphère solaire. (6) Observations
complémentaires à SOHO.
Title: Interpretation of Multi-channel X-ray Intensities from
Solar Flares
Authors: Gabriel, A. H.; Bely-Dubau, F.; Millier, F.
Bibcode: 1991LNP...387..184G
Altcode: 1991fpsa.conf..184G
We investigate the analysis of muti-channel X-ray spectral intensities
in terms of the electron energy distribution in the flare. This is
related to the identification of thermal and non-thermal, as well as
possible super-hot components. The observations studied are from SMM
and from a balloon-borne instrument of Lin et al (1971). It is shown
that the observations can be tilted by a wide range of different
plasma conditions, making it necessary to constrain the range of
models considered. This problem cannot be solved by improving the
spectral resolution of the continuum channels. However, the addition
of spectral line intensities from the hot plasma, as in Solar-A,
is very important in reducing the ambiguity.
Title: European Photon Imaging Camera (EPIC) for X-ray astronomy.
Authors: Bignami, G. F.; Villa, G. E.; Boella, G.; Bonelli, G.;
Caraveo, P.; Chiappetti, L.; Quadrini, M. E.; Di Cocco, G.; Trifoglio,
M.; Ubertini, P.; Peres, G.; Sciortino, S.; Serio, S.; Vaiana, G.;
Rothenflug, R.; Vigroux, L.; Koch, L.; Rio, Y.; Pigot, C.; Cretolle,
J.; Gabriel, A.; Foing, B.; Atteia, J. L.; Roques, J. P.; Bräuninger,
H.; Pietsch, W.; Predehl, P.; Reppin, C.; Struder, L.; Trümper, J.;
Lutz, G.; Kendziorra, E.; Staubert, R.; Holland, A. D.; Cole, R. E.;
Wells, A.; Pounds, K.; Lumb, D. A.; Pye, J.; Turner, M. J. L.; Goodall,
C. V.; Ponman, T. J.; Skinner, G. K.; Willmore, A. P.
Bibcode: 1990SPIE.1344..144B
Altcode: 1990exrg.conf..144B
ESA has selected the final payload for its "Cornerstone" mission
in X-Ray astronomy with multiple mirrors (XMM), to be flown in the
late nineties in the context of the "Horizon 2000" long term science
plan. EPIC represents the main instrument of the mission, to include
three CCD arrays in the focal planes of the three telescopes of the
spacecraft. They will be dedicated to source imaging, photometry,
spectroscopy and timing. The goals of EPIC are described.
Title: Extreme ultraviolet imaging telescope on board the Solar
Heliospheric Observatory
Authors: Delaboudiniere, Jean-Pierre; Gabriel, Alan H.; Artzner,
Guy E.; Millier, F.; Michels, Donald J.; Dere, Kenneth P.; Howard,
Russell A.; Kreplin, Robert W.; Catura, Richard C.; Stern, Robert A.;
Lemen, James R.; Neupert, Werner M.; Gurman, Joseph B.; Cugnon, P.;
Koeckelenbergh, A.; van Dessel, E. L.; Jamar, Claude A.; Maucherat,
Andre J.; Chauvineau, Jean-Pierre; Marioge, Jean-Paul
Bibcode: 1989SPIE.1160..518D
Altcode: 1989xeoa.conf..518D
The design of the multibandpass Extreme-Ultraviolet Imaging Telescope
designed for 1996 launch on board the Solar Heliospheric Observatory
is described. The telescope will observe simultaneously distinct
temperature ranges in the solar corona, defined by well chosen emission
lines. Images in four narrow bandpasses at wavelengths ranging from 17
to 31 nm will be obtained using normal-incidence multilayered optics
deposited on quadrants of a Ritchey-Chretien telescope. Results are
presented on the performances measured on a 2/3 scale mock-up. The
bandpasses could be adjusted to better than 1 percent in wavelength.
Title: Flare Energy Release and Deposition
Authors: Holman, G.; Benka, S.; de La Beaujardiere, J.; Dulk, G.;
Gabriel, A.; Henoux, J. C.; Hiei, E.; Kane, S.; Klein, L.; Kuin, P.;
Larosa, T.; MacKinnon, A.; McClements, K.; Moses, D.; Ramaty, R.;
Tromans, N.; Vilmer, N.
Bibcode: 1989tnti.conf....3H
Altcode:
No abstract at ADS
Title: SUMER - Solar ultraviolet measurements of emitted radiation.
Authors: Curdt, W.; Wilhelm, K.; Axford, W. I.; Marsch, E.; Richter,
A. K.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber,
M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Timothy, J. G.
Bibcode: 1989AGAb....2...14C
Altcode: 1989amt..conf...14C
No abstract at ADS
Title: Impulsive phase transport.
Authors: Canfield, R. C.; Bely-Dubau, E.; Brown, J. C.; Dulk, G. A.;
Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose,
D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.;
Tanaka, K.; Zirin, H.
Bibcode: 1989epos.conf..225C
Altcode:
The work of this group was concerned with how the energy released
in a solar flare is transported through the solar atmosphere before
escaping in the form of radiant and mechanical energy.
Title: GOLF: Global Oscillations at Low Frequencies for the SOHO
mission
Authors: Gabriel, A. H.; Bocchia, R.; Bonnet, R. M.; Cesarsky, C.;
Christensen-Dalsgaard, J.; Dame, L.; Delache, Ph.; Deubner, F. L.;
Foing, B.; Fossat, E.
Bibcode: 1988sohi.rept...13G
Altcode:
The GOLF (global oscillations at low frequencies) SOHO (solar
heliospheric observatory) mission is described. It aims to study
the internal structure of the Sun by measuring the spectrum of free
global oscillations. GOLF will measure both p and g mode oscillations,
with emphasis on low order long period waves which penetrate the
solar core. The instrument aims to measure frequencies between 10-7
and 6 10-3 Hz, with a sensitivity of 1 mm/s. The method involves an
extension to space of the ground based technique for measuring the mean
line-of-sight velocity of the solar surface. A sodium vapor resonance
scattering filter is used in a longitudinal magnetic field to sample the
two wings of the solar absorption line. The use of a modulating magnetic
field provides a continuous internal calibration of the sensitivity. By
adding an additional rotating polarizer, measurements are also made
of the average solar magnetic field. Efforts are made to correct the
data for the spurious effects caused by solar magnetic active regions.
Title: CDS: The Coronal Diagnostic Spectrometer
Authors: Patchett, B. E.; Harrison, R. A.; Sawyer, E. C.; Aschenbach,
B.; Culhane, J. L.; Doschek, G. A.; Gabriel, A. H.; Huber, M. C. E.;
Jordan, C.; Kjeldseth-Moe, O.
Bibcode: 1988sohi.rept...39P
Altcode:
The prime objective of the Coronal Diagnostic Spectrometer (CDS) is to
obtain intensity ratios of selected extreme-ultraviolet line pairs, with
spatial and temporal scales appropriate to the fine-scale features of
the solar atmosphere. This will be done simultaneously across a large
portion of the solar atmosphere. From this, density and temperature
information will be derived which coupled with a modest capability for
the detection of flows will be used to study the energy and mass balance
of the atmosphere. Understanding the heating of the solar corona and the
acceleration of the solar wind are the ultimate goals of this research.
Title: SUMER: Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.;
Grewing, M.; Huber, M. C. E.; Jordan, M. C. E.; Lemaire, P.; Marsch,
E.; Poland, A. I.
Bibcode: 1988sohi.rept...31W
Altcode:
The SUMER (solar ultraviolet measurements of emitted radiation)
experiment is described. It will study flows, turbulent motions, waves,
temperatures and densities of the plasma in the upper atmosphere of
the Sun. Structures and events associated with solar magnetic activity
will be observed on various spatial and temporal scales. This will
contribute to the understanding of coronal heating processes and the
solar wind expansion. The instrument will take images of the Sun in EUV
(extreme ultra violet) light with high resolution in space, wavelength
and time. The spatial resolution and spectral resolving power of the
instrument are described. Spectral shifts can be determined with
subpixel accuracy. The wavelength range extends from 500 to 1600
angstroms. The integration time can be as short as one second. Line
profiles, shifts and broadenings are studied. Ratios of temperature
and density sensitive EUV emission lines are established.
Title: EIT: Solar corona synoptic observations from SOHO with an
Extreme-ultraviolet Imaging Telescope
Authors: Delaboudiniere, J. P.; Gabriel, A. H.; Artzner, G. E.;
Michels, D. J.; Dere, K. P.; Howard, R. A.; Catura, R.; Stern, R.;
Lemen, J.; Neupert, W.
Bibcode: 1988sohi.rept...43D
Altcode:
The Extreme-ultraviolet Imaging Telescope (EIT) of SOHO (solar and
heliospheric observatory) will provide full disk images in emission
lines formed at temperatures that map solar structures ranging from
the chromospheric network to the hot magnetically confined plasma in
the corona. Images in four narrow bandpasses will be obtained using
normal incidence multilayered optics deposited on quadrants of a
Ritchey-Chretien telescope. The EIT is capable of providing a uniform
one arc second resolution over its entire 50 by 50 arc min field of
view. Data from the EIT will be extremely valuable for identifying
and interpreting the spatial and temperature fine structures of the
solar atmosphere. Temporal analysis will provide information on the
stability of these structures and identify dynamical processes. EIT
images, issued daily, will provide the global corona context for aid
in unifying the investigations and in forming the observing plans for
SOHO coronal instruments.
Title: The diagnostics of astrophysical plasmas, using the oxygen
VII soft X-ray lines.
Authors: Gabriel, A. H.; Bely-Dubau, F.; Faucher, P.; Acton, L. W.
Bibcode: 1988JPhys..49..235G
Altcode: 1988IAUCo.102..235G
The authors present a revised theory and atomic model for the line
intensities emitted by O VII, taking into account all of the processes
responsible for the emission. This is used to provide a revision of
the density measurements made during solar flares, as well as in an
attempt to understand the spectrum of the Puppis A supernova remnant.
Title: Localization of chromospheric evaporation in solar flares,
by the analysis of X-ray spectra.
Authors: Gabriel, A. H.; Millier, F.; Lizambert, N.
Bibcode: 1988JPhys..49..325G
Altcode: 1988IAUCo.102..325G
Analysis of solar flares using the data from the Bent Crystal
Spectrometer on the SMM solar flare satellite, shows a thermal
plasma which expands vertically at a velocity of up to 350 km
s-1. This plasma, at a temperature of the order of
25×106K is observed in the line radiation of He-like Ca
XIX. Its velocity is determined by measuring the blue shift of the
resonance line "w", whereas its intensity is expressed relatively to
that of the stationary component. The authors analyse the variations
of velocity and relative intensity of the evaporating plasma as a
function of its location on the solar disc for 33 flares during the
year 1980. The results are compared with the values expected from two
alternative models.
Title: CHASE Observations of the Solar Corona
Authors: Breeveld, E. R.; Culhane, J. L.; Norman, K.; Parkinson,
J. H.; Gabriel, A. H.; Lang, J.; Patchett, B. E.; Payne, J.
Bibcode: 1988ApL&C..27..155B
Altcode:
The Coronal Helium Abundance Spacelab Experiment (CHASE) was undertaken
to make a precision measurement which could have significant
cosmological implications. The CHASE UV-spectrometer was flown
successfully on the Spacelab 2 mission. Observations of many spectral
lines were made including the Lyman-alpha lines of hydrogen at 121.6
nm and of ionized helium at 30.4 nm both on the solar disk where the
lines are excited, and in the corona, where the lines are formed by
resonance scattering of the disk radiation. When the instrument scatter
function has been measured, these observations will enable the solar
helium abundance to be measured.
Title: The Solar Corona
Authors: Gabriel, A. H.
Bibcode: 1988ASIC..249...79G
Altcode: 1988htpa.conf...79G
No abstract at ADS
Title: Calcium ionization balance and argon/calcium abundance in
solar flares
Authors: Antonucci, E.; Marocchi, D.; Gabriel, A. H.; Doschek, G. A.
Bibcode: 1987A&A...188..159A
Altcode:
An earlier analysis of solar flare calcium spectra from XRP and P78-1
aimed at measuring the calcium ionization balance resulted in an
ambiguity due to a line blend between the calcium q line and an Ar
XVII line. In the present work the calcium line 'r' is included in
the analysis in order to resolve this problem. It is shown that the
correct calcium ionization balance is that indicated in the earlier
paper as corresponding to an argon/calcium abundance ratio of 0.2. The
argon/calcium abundance ratio in the group of solar flares studied
is shown to be 0.2 + or - 0.2. It is further argued that while the
abundance of heavy elements may be enhanced in energetic flare events,
this enhancement is less for argon than for calcium, leading to an
argon/calcium ratio smaller than that present in the quiet sun.
Title: Ionization balance for iron XXV, XXIV and XXIII derived from
solar flare X-ray spectra
Authors: Antonucci, E.; Dodero, M. A.; Gabriel, A. H.; Tanaka, K.;
Dubau, J.
Bibcode: 1987A&A...180..263A
Altcode:
An analysis has been carried out using over 300 spectra of solar
flares from both the XRP instrument on SMM and the SOX instrument on
Hinotori. The helium-like iron and associated dielectronic satellite
spectra were used in order to derive a revised ionization balance for
Fe XXIV/Fe XXV. This is found to lie between the theoretical curves
based upon ECIP ionization rates, and those using Lotz formalism, with
a tendency to be closer to the former. An extension of the analysis
to include Fe XXIII is subject to a somewhat larger uncertainty in
the interpretation. However it indicates a similar effect for this
ion. Using all three ions, a revised ionization balance for iron
is presented.
Title: The X-ray spectroscopy cornerstone mission.
Authors: Bely-Dubau, F.; Gabriel, A. H.; Predehl, Peter; Schmitt,
J.; Stewart, Gordon; Truemper, J.; Wells, Alan; White, Nicolas E.
Bibcode: 1987ESASP.268..117B
Altcode:
The high throughput X-ray astronomical spectroscopy observatory,
called the X-ray Multi-Mirror mission (XMM) is an array of telescopes
providing the required sensitivity to perform detailed spectral
diagnostics on many classes of objects, particularly those with low
surface brightness. Such investigations are important for studying the
evolution of large and small scale structures of the Universe. The
XMM also allows simultaneous observations of spatial, spectral,
and temporal properties of many classes of astronomical targets, and
unambiguous physical interpretation of the observed phenomena. The
XMM is Europe's cornerstone mission in X-ray astronomy and complements
NASA's AXAF mission, which pursues ultimate imaging capability as its
main objective.
Title: Impulsive Phase Observations and Their Interpretation
Authors: Canfield, R. C.; Bely-Dumau, E.; Brown, J. C.; Dulk, G. A.;
Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose,
D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.;
Tanaka, K.; Zirin, H.
Bibcode: 1986epos.conf..3.4C
Altcode: 1986epos.confC...4C
No abstract at ADS
Title: Theoretical Studies of Transport Processes
Authors: Canfield, R. C.; Bely-Dumau, E.; Brown, J. C.; Dulk, G. A.;
Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose,
D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.;
Tanaka, K.; Zirin, H.
Bibcode: 1986epos.conf.3.34C
Altcode: 1986epos.confBC.34C
No abstract at ADS
Title: Impulsive phase transport
Authors: Canfield, Richard C.; Bely-Dubau, Francoise; Brown, John C.;
Dulk, George A.; Emslie, A. Gordon; Enome, Shinzo; Gabriel, Alan H.;
Kundu, Mukul R.; Melrose, Donald; Neidig, Donald F.
Bibcode: 1986epos.conf..3.1C
Altcode: 1986epos.confC...1C
The transport of nonthermal electrons is explored. The thick-target
electron beam model, in which electrons are presumed to be accelerated
in the corona and typically thermalized primarily in the chromosphere
and photosphere, is supported by observations throughout the
electromagnetic spectrum. At the highest energies, the anisotropy
of gamma-ray emission above 10 MeV clearly indicates that these
photons are emitted by anisotropically-directed particles. The timing
of this high-energy gamma-radiation with respect to lower-energy
hard X-radiation implies that the energetic particles have short
life-times. For collisional energy loss, this means that they are
stopped in the chromosphere or below. Stereoscopic (two-spacecraft)
observations at hard X-ray energies (up to 350 keV) imply that these
lower-energy (but certainly nonthermal) electrons are also stopped deep
in the chromosphere. Hard X-ray images show that, in spatially resolved
flares whose radiation consists of impulsive bursts, the impulsive
phase starts with X-radiation that comes mostly from the foot-points
of coronal loops whose coronal component is outlined by microwaves.
Title: Early results from the CHASE experiment flown on Spacelab 2.
Authors: Gabriel, A. H.; Patchett, B. E.; Lang, J.; Culhane, J. L.;
Norman, K.; Parkinson, J. H.
Bibcode: 1986JBIS...39..207G
Altcode:
The Coronal Helium Abundance Spacelab Experiment (CHASE), flown on
the Space Shuttle as part of the Spacelab 2 payload on July 29, 1985,
was designed to measure the abundance of helium relative to hydrogen;
a measure of this quantity is an important verification of models
of the birth of the universe. In addition to this primary objective,
the instrument was used to study the properties of the corona. CHASE
instrumentation and operation are described, and preliminary data are
examined. The instrument consists of a grazing incidence spectrometer
covering the wavelength range of 150 A to 1350 A, illuminated by a
grazing incidence telescope of 28 cm focal length; the spectrometer
module incorporated the mechanism control electronics, detector
preamplifiers, high voltage supplies and a sensor to indicate the
offset from the sun center. Spectral lines are indicated schematically,
and it is noted that there is no problem separating the He II line from
the nearby Si XI line. Mapping of large areas of the sun revealed that
at low temperature, two bright points are apparent, whereas at high
temperature, these coalesce to form a single bright patch in the center.
Title: Impulsive phase transport.
Authors: Canfield, R. C.; Bely-Dubau, E.; Brown, J. C.; Dulk, G. A.;
Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose,
D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.;
Tanaka, K.; Zirin, H.
Bibcode: 1986NASCP2439....3C
Altcode:
Contents: 1. Introduction: motivation for transport studies, historical
perspective, overview of the chapter. 2. Impulsive phase observations
and their interpretation: gamma-ray emission above 10 MeV, hard
X-ray and microwave morphology, combined soft and hard X-ray spectra,
iron Kα emission, ultraviolet and hard X-ray emission, white light
emission, Hα emission. 3. Theoretical studies of transport processes:
electron beams and reverse currents, proton transport, radiative energy
transport by amplified decimetric waves. 4. Summary.
Title: Chase observations from spacelab 2 - the chase team
Authors: Parkinson, John H.; Gabriel, Alan H.
Bibcode: 1986AdSpR...6h.243P
Altcode: 1986AdSpR...6..243P
The Coronal Helium Abundance Spacelab Experiment (CHASE) was designed
and built in the UK by groups at the Rutherford Appleton Laboratory
and at the Mullard Space Science Laboratory. The main objective of the
experiment was to improve the measurement of the abundance of helium
in the Sun, which currently is uncertain by a factor of approximately
three. Since most of this helium must be of primordial origin, being
formed within a few minutes of the big bang, such a measurement would
also have significant cosmological implications. The instrument
consisted of a grazing incidence telescope feeding a 1200 lines
mm-1 diffraction grating. Parts of the dispersed spectrum
were then observed around the Rowland circle with channel electron
multipliers and a channel multiplier array plate. During the flight,
good observations were made of the Lyman-α lines of hydrogen at 1216 A
and of ionised helium at 304 A, both in the corona, where the lines are
formed by resonance scattering, and on the solar disc where excitation
of the lines is much more complex. The spectrometer was also able
to observe many other transition region and coronal lines in ions of O,
S and Fe. Images in these lines clearly show how the magnetic fields
in active regions constrain the material in arch-shaped loops with
the hot material towards the top. Present Address: Laboratoire
de Phsique Stellaire et Planetaire, 91370 Verrietes-les-Buisson, France.
Title: Interpretation of the oxygen VII soft X-ray spectrum from
the Puppis-A supernova remnant.
Authors: Gabriel, A. H.; Acton, L. W.; Bely-Dubau, F.; Faucher, P.
Bibcode: 1985ESASP.239..137G
Altcode: 1985cxrs.work..137G
The soft X-ray line spectrum from Puppis-A recorded with the
Einstein observatory shows line ratios different from those
anticipated. Previous interpretations were based upon high temperatures
>5×106K and departures from ionization equilibrium. It
is shown that an alternative model can fit the observations, in which
1% of fast electrons are present in an otherwise thermal plasma at 1
to 2×106K. This plasma can be in steady-state ionization
balance.
Title: Origin of the Solar Wind
Authors: Gabriel, A.; Schwenn, R.
Bibcode: 1985ESASP.235..231G
Altcode: 1985fmsh.work..231G
No abstract at ADS
Title: Initial Phase of Chromospheric Evaporation in a Solar Flare
Authors: Antonucci, E.; Dennis, B. R.; Gabriel, A. H.; Simnett, G. M.
Bibcode: 1985SoPh...96..129A
Altcode:
In this paper we discuss the initial phase of chromospheric evaporation
during a solar flare observed with instruments on the Solar Maximum
Mission on May 21, 1980 at 20:53 UT. Images of the flaring region
taken with the Hard X-Ray Imaging Spectrometer in the energy bands from
3.5 to 8 keV and from 16 to 30 keV show that early in the event both
the soft and hard X-ray emissions are localized near the footpoints,
while they are weaker from the rest of the flaring loop system. This
implies that there is no evidence for heating taking place at the
top of the loops, but energy is deposited mainly at their base. The
spectral analysis of the soft X-ray emission detected with the Bent
Crystal Spectrometer evidences an initial phase of the flare, before
the impulsive increase in hard X-ray emission, during which most of
the thermal plasma at 107 K was moving toward the observer
with a mean velocity of about 80 km s-1. At this time
the plasma was highly turbulent. In a second phase, in coincidence
with the impulsive rise in hard X-ray emission during the major
burst, high-velocity (370 km s-1) upward motions were
observed. At this time, soft X-rays were still predominantly emitted
near the loop footpoints. The energy deposition in the chromosphere by
electrons accelerated in the flare region to energies above 25 keV,
at the onset of the high-velocity upflows, was of the order of 4 ×
1010 erg s-1 cm-2. These observations
provide further support for interpreting the plasma upflows as the
mechanism responsible for the formation of the soft X-ray flare,
identified with chromospheric evaporation. Early in the flare soft
X-rays are mainly from evaporating material close to the footpoints,
while the magnetically confined coronal region is at lower density. The
site where upflows originate is identified with the base of the loop
system. Moreover, we can conclude that evaporation occurred in two
regimes: an initial slow evaporation, observed as a motion of most of
the thermal plasma, followed by a high-speed evaporation lasting as
long as the soft X-ray emission of the flare was increasing, that is
as long as plasma accumulation was observed in corona.
Title: Report of IAU Commission 14: Atomic and molecular data
(Données atomiques et moléculaires).
Authors: Gabriel, A. H.
Bibcode: 1985IAUTA..19..121G
Altcode:
No abstract at ADS
Title: The energetics of chromospheric evaporation in solar flares
Authors: Antonucci, E.; Gabriel, A. H.; Dennis, B. R.
Bibcode: 1984ApJ...287..917A
Altcode:
The Solar Maximum Mission (SMM) spacecraft has provided high time
resolution observational data regarding the soft X-ray emission from
solar-flare plasma during 1980. The present investigation is concerned
with the characteristics of a soft X-ray flare and the energetics of
the impulsive phase on the basis of the data collected with the aid of
two of the instruments on board the SMM, taking into account the Hard
X-ray Burst Spectrometer (HXRBS) and the Bent Crystal Spectrometer
(BCS). Attention is given to an analysis of soft X-ray flare spectra,
the relative motion of the soft X-ray sources, the phenomenology of
the soft X-ray flare, energy and mass transport during the impulsive
phase, and energy deposition in the chromosphere during evaporation.
Title: Solar Maximum Mission results on the energetics of the
impulsive phase of solar flares.
Authors: Antonucci, E.; Gabriel, A. H.
Bibcode: 1984ESASP.220..279A
Altcode: 1984ESPM....4..279A
The presence of chromospheric material evaporating in response
to localized heating to coronal temperatures is inferrred from the
observations of systematic plasma upflows during the rise of the soft
X-ray emission in solar flares.
Title: Solar research at RAL (Rutherford Appleton Laboratory).
Authors: Gabriel, A. H.
Bibcode: 1984JBIS...37..317G
Altcode:
The role of the Rutherford Appleton Laboratory in space-based
solar observations is surveyed. The reasons for studying the sun
are reviewed; the history of observations and the value of space
observations are discussed; and some problem areas are characterized:
coronal heating, the onset of the solar wind, solar flares, and global
solar oscillations. RAL solar projects at present include the X-ray
polychromator experiment on the Solar Maximum Mission and the Coronal
Helium Abundance Spacelab Experiment to be flown on the second Spacelab
mission in March, 1985. Future prospects center on the proposed ESA
Solar and Heliospheric Observatory.
Title: Oscillations in Extreme Ultraviolet Emission Lines during a
Loop Brightening
Authors: Antonucci, E.; Gabriel, A. H.; Patchett, B. E.
Bibcode: 1984SoPh...93...85A
Altcode:
Oscillations in the emission in the ultraviolet lines of CII, OIV, and
Mg X, detected by the Harvard College Observatory EUV spectroheliometer
on Skylab are observed on August 7, 1973, during a loop brightening. The
intensity of the EUV lines varies with a period of 141 s during the
time of enhanced intensity of the coronal loop, lasting 10 min. The
periodic oscillation is not only localized in the loop region but
extends over a larger area of the active region, maintaining the same
phase. We suggest that the intensity fluctuation of the EUV lines is
caused by small-amplitude waves, propagating in the plasma confined
in the magnetic loop and that size of the loop might be important in
determining its perferential heating in the active region.
Title: Derivation of ionization balance for calcium XVIII/XIX using
XRP solar X-ray data
Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.;
Faucher, P.; Jordan, C.; Veck, N.
Bibcode: 1984A&A...133..239A
Altcode:
Spectra of calcium from solar flares are used in an attempt to derive
an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption
inherent in this derivation is shown not to introduce errors, by
modelling a number of hypothetical nonisothermal plasmas. The unresolved
blend of calcium and argon lines prevents a definitive determination of
the results, owing to uncertainties in the ratio of abundances of these
elements. The resulting ionization balance curves are presented as a
function of the solar argon/calcium abundance ratio. The theoretical
ionization balance of Doyle and Raymond is consistent with the data. To
within the expected accuracy of the atomic theories, there is no reason
to assume that the flare plasma is other than close to steady-state
ionization balance.
Title: Combined analysis of soft and hard X-ray spectra from flares
Authors: Gabriel, A. H.; Bely-Dubau, E.; Sherman, J. C.; Orwig, L. E.;
Schrijver, J.
Bibcode: 1984AdSpR...4g.221G
Altcode: 1984AdSpR...4..221G
A method has been developed for interpreting the combined data set
from the BCS, HXIS and HXRBS instruments on the SMM. The observations
are fitted to a model including thermal and non-thermal electron
components. Analysis of the flare of 1980 June 29, 18.22 UT shows
the way in which these components vary through the impulsive and
gradual phases.
Title: Soft X-ray spectral diagnostics from flares
Authors: Bely-Dubau, F.; Gabriel, A. H.
Bibcode: 1984MmSAI..55..685B
Altcode:
The X-ray data on the emissions in the 1-25 A range, prominent in
the spectrum of hot (1-50 x 10 to the sixth K) plasma were obtained
by the Bent Crystal Spectrometer component of the X-ray Polychromator
experiment on the NASA Solar Maximum Mission Satellite. The experimental
observations made on solar flares and theoretical treatment are
presented in reference to emission line intensities, dielectronic
satellite spectra, measurement of electron density, differential
emission measure, and transient and nonthermal effects.
Title: Results from the X-ray polychromator on SMM
Authors: Culhane, J. L.; Acton, L. W.; Gabriel, A. H.
Bibcode: 1984MmSAI..55..673C
Altcode:
Observations of the soft X-ray emitting plasma by means of the
X-Ray Polychromator (XRP) on the Solar Maximum Mission satellite are
described. The scientific advances achieved by use of the XRP are
in the areas of: (1) flare morphology, (2) spectroscopy and plasma
diagnostics, (3) chromospheric evaporation and the physics of flare
loops, (4) studies of the microwave emission mechanisms of active
regions, (5) the fluorescent excitation of Fe II K-alpha radiation,
(6) measurement of variations of calcium abundance for X-ray plasmas,
and (7) soft X-ray observations of spray transients. The findings in
each of these areas are discussed.
Title: Derivation of the Ionization Balance for Iron Xxiv/xxv and
Xxiii/xxiv Using Solar X-Ray Data
Authors: Antonucci, E.; Dodero, M. A.; Gabriel, A. H.; Tanaka, K.
Bibcode: 1984uxsa.coll...13A
Altcode: 1984uxsa.conf...13A; 1984IAUCo..86...13A
No abstract at ADS
Title: Non-thermal and non-equilibrium effects in soft X-ray flare
spectra
Authors: Gabriel, A. H.; Antonucci, E.; Steenman-Clark, L.
Bibcode: 1983SoPh...86...59G
Altcode:
Processes leading to the excitation of soft X-ray line spectra are
discussed in relation to their thermal or non-thermal nature. Through
analysis of calcium spectra from the XRP experiment on SMM, it is
shown that the ionization balance during the gradual phase of flares is
effectively in the steady-state. A search of suitable complex flares
with multiple impulsive features has shown indications of soft X-ray
line intensity anomalies, consistent with the presence of a non-thermal
electron component.
Title: Book Review: Astronomy and astrophysics, sub-vol. a: Methods,
constants, solar system. K. SCHAIFERS and H. H. VOIGT (editors):
Landolt-Bornstein group VI, vol. 2 Springer, Berlin 1981. xviii +
305 pp. $237.50.
Authors: Gabriel, A. H.
Bibcode: 1983P&SS...31..141G
Altcode:
No abstract at ADS
Title: Dielectronic satellite spectra for highly-charged helium-like
ions. VII - Calcium spectra: Theory and comparison with SMM
observations
Authors: Bely-Dubau, F.; Faucher, P.; Steenman-Clark, L.; Dubau, J.;
Loulergue, M.; Gabriel, A. H.; Antonucci, E.; Volonte, S.; Rapley,
C. G.
Bibcode: 1982MNRAS.201.1155B
Altcode:
The atomic theory, developed in earlier papers in this series for
iron, has been applied to the spectra from calcium. This includes
the production of satellite lines by dielectronic recombination and
inner-shell excitation, as well as the production of helium-like spectra
by excitation, radiative and dielectronic recombination and through
cascades. Two methods are described for fitting observed spectra,
to determine the plasma physical parameters. The results are applied
to the observations from the soft X-ray Polychromator of the flare on
1980 May 21. The good agreement between computed and observed spectra
gives support to the accuracy of the theory presented. Analysis of
the time variations shows that the flare is close to steady-state
ionization balance throughout.
Title: Impulsive Phase of Flares in Soft X-Ray Emission
Authors: Antonucci, E.; Gabriel, A. H.; Acton, L. W.; Culhane, J. L.;
Doyle, J. G.; Leibacher, J. W.; Machado, M. E.; Orwig, L. E.; Rapley,
C. G.
Bibcode: 1982SoPh...78..107A
Altcode:
Observations using the Bent Crystal Spectrometer instrument on the
Solar Maximum Mission show that turbulence and blue-shifted motions
are characteristic of the soft X-ray plasma during the impulsive phase
of flares, and are coincident with the hard X-ray bursts observed
by the Hard X-ray Burst Spectrometer. A method for analysing the
Ca XIX and Fe XXV spectra characteristic of the impulsive phase
is presented. Non-thermal widths and blue-shifted components in the
spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent
velocities exceeding 100 km s-1 and upward motions of
300-400 km s-1.
Title: Solar flare X-ray spectra from the Solar Maximum Mission Flat
Crystal Spectrometer
Authors: Phillips, K. J. H.; Fawcett, B. C.; Kent, B. J.; Gabriel,
A. H.; Leibacher, J. W.; Wolfson, C. J.; Acton, L. W.; Parkinson,
J. H.; Culhane, J. L.; Mason, H. E.
Bibcode: 1982ApJ...256..774P
Altcode:
High-resolution solar X-ray spectra obtained with the Flat Crystal
Spectrometer aboard the Solar Maximum Mission from two solar flares and
a nonflaring active region are analyzed. The 1-22 A region was observed
during the flare on 1980 August 25, while smaller spectral regions were
repeatedly covered during the 1980 November 5 flare. Voigt profiles
were fitted to spectral lines to derive accurate wavelengths and to
resolve blends. During the August 25 flare, 205 lines were found in
the range 5.68-18.97 A, identifications being provided for all but 40
(mostly weak) lines. Upper limits to flare densities are derived from
various line ratios, the hotter (about 10 to the 7th K) ions giving an
electron density of less than 10 to the 12th per cu cm for the August
25 flare. Other observed line ratios (e.g., in Fe XVII and Mg XII)
indicate a need for revisions in theoretical calculations.
Title: Observations of a POST Flare Radio Burst in X-Rays
Authors: Svestka, Z.; Hoyng, P.; van Tend, W.; Boelee, A.; de Jager,
C.; Stewart, R. T.; Acton, L. W.; Bruner, E. C.; Gabriel, A. H.;
Rapley, C. G.; de Jager, C.; LaFleur, H.; Nelson, G.; Simnett, G. M.;
van Beek, H. F.; Wagner, W. J.
Bibcode: 1982SoPh...75..305S
Altcode:
More than six hours after the two-ribbon flare of 21 May 1980, the
hard X-ray spectrometer aboard the SMM imaged an extensive arch above
the flare region which proved to be the lowest part of a stationary
post-flare noise storm recorded at the same time at Culgoora. The X-ray
arch extended over 3 or more arc minutes to a projected distance of
95 000 km, and its real altitude was most probably between 110 000
and 180 000 km. The mean electron density in the cloud was close to
109 cm−3 and its temperature stayed for many
hours at a fairly constant value of about 6.5 × 106 K. The
bent crystal spectrometer aboard the SMM confirms that the arch emission
was basically thermal. Variations in brightness and energy spectrum at
one of the supposed footpoints of the arch seem to correlate in time
with radio brightness suggesting that suprathermal particles from
the radio noise regions dumped in variable quantities into the low
corona and transition layer; these particles may have contributed to
the population of the arch, after being trapped and thermalized. The
arch extended along the H∥ = 0 line thus apparently
hindering any upward movement of the upper loops reconnected in the
flare process. There is evidence from Culgoora that this obstacle may
have been present above the flare since 15-30 min after its onset.
Title: Dielectronic satellite spectra for highly charged helium-like
ions. VI - Iron spectra with improved inner-shell and helium-like
excitation rates
Authors: Bely-Dubau, F.; Faucher, P.; Dubau, J.; Gabriel, A. H.
Bibcode: 1982MNRAS.198..239B
Altcode:
The atomic theory developed through earlier papers in this series is
extended in order to improve the understanding of iron solar flare
spectra in the region 1.85-1.88 Å. The new work concerns impact
excitation by distorted wave theory for the inner- shell Fe xxiv
transitions and the 1 S2 - 1 s 2l transitions in Fe XXV. In
addition, rates are evaluated for contributions to the Fe XXV lines
from cascade, radiative recombination, dielectronic recombination,
and inner-shell ionization of Fe XXIV. The results will be applicable
to any plasma with a density below 1015 cm-3,
and are therefore of use in Tokamak devices as well as in astrophysics.
Title: Solar physics
Authors: Gabriel, A. H.; Mason, H. E.
Bibcode: 1982aacp....1..345G
Altcode:
A review is presented of the two major aspects of the interaction
between atomic and solar physics. The first aspect is related to the way
in which the various atomic collision processes determine the physical
behavior of the plasma, and, thereby, the physical properties of the
sun. The second aspect is concerned with diagnostics, taking into
account the way in which the spectra emitted are determined by the
atomic processes occurring in the observed plasma. Aspects of solar
physics involving atomic collisions are examined, giving attention to
radial structure, active regions, solar flares, element abundances,
and spectroscopic diagnostics. Questions of impact excitation are
considered along with ionization and recombination, absolute spectral
intensities, and radiation effects.
Title: Solar Physics
Authors: Gabriel, Alan H.; Mason, Helen E.
Bibcode: 1982aacp....1..346G
Altcode:
No abstract at ADS
Title: The Coronal Helium Abundance Experiment on SPACELAB-2
Authors: Patchett, B. E.; Norman, K.; Gabriel, A. H.; Culhane, J. L.
Bibcode: 1981SSRv...29..431P
Altcode:
The Coronal Helium Abundance Spacelab Experiment, (CHASE), basically
consists of a grazing incidence telescope and spectrometer sensitive
over the range 150 1335 Å. Whilst aimed primarily at deriving the solar
helium abundance from measurements of coronal resonance scattering,
its specification has been extended in order to provide a more general
purpose solar XUV facility. The instrument will be flown on the Spacelab
2 Mission, currently scheduled for launch in November 1984.
Title: Observations of transitions of hydrogen-like Fe XXVI in solar
flare spectra
Authors: Parmar, A. N.; Culhane, J. L.; Rapley, C. G.; Antonucci,
E.; Gabriel, A. H.; Loulergue, M.
Bibcode: 1981MNRAS.197P..29P
Altcode:
Observations of solar flare spectra over the wavelength range
1.769-1.796 A with the Bent Crystal Spectrometer on the NASA
Solar Maximum Mission satellite are presented. The 2P3/2, 2P1/2
and associated satellite transitions of Fe XXVI are identified,
their intensities and widths estimated and the results compared with
theoretical predictions. For two spectra, which include the isolated n
= 2 satellite features, the observations can be reproduced by plasma
temperatures of 24,000,000 and 28,400,000 K. Linewidth measurements
show evidence for nonthermal velocities of up to 150 km/s. Emission
measures derived from the Fe XXVI observations are compared with those
from lower temperature Ca XIX and Fe XXV measurements and an emission
measure decreasing with temperature is found.
Title: Book-Review - the Sun and the Heliosphere
Authors: Massey, H.; Gabriel, A. H.; Elliot, H.; Marlborough, J. M.
Bibcode: 1981Obs...101..187M
Altcode:
No abstract at ADS
Title: Dielectronic satellite spectra for hydrogen-like iron in low
density plasmas
Authors: Dubau, J.; Loulergue, M.; Gabriel, A. H.; Steenman-Clark,
L.; Volonte, S.
Bibcode: 1981MNRAS.195..705D
Altcode:
Wavelengths and intensities of dielectronic satellite lines of the type
1snl-2pnl have been calculated for n equals 2, 3 and 4 in iron. These
are compared with previous calculations for n equals 2. The effect of
cascades from higher satellite levels is shown to be negligible. An
approximation is used to scale for all n greater than 4, in order
to produce the total satellite spectrum, including the contribution
to the apparent resonance line intensity. A technique is proposed
for using this spectrum to measure the electron temperature in the
source. An estimate is made of the dielectronic recombination rate,
which is compared with the result of earlier semi-empirical formulae.
Title: Solar Flare Plasmas
Authors: Gabriel, A. H.
Bibcode: 1981RSPTA.300..497G
Altcode:
The solar flare is discussed in terms of its three phases: energy
storage, energy release, and dissipation. Some of the problems
associated with theoretical modelling are considered, together with
the limitations imposed by current observations. New measurements to
be made by the N.A.S.A. Solar Maximum Mission satellite are expected
to advance significantly our understanding of the flare mechanism.
Title: X-ray line widths and coronal heating
Authors: Acton, L. W.; Wolfson, C. J.; Joki, E. G.; Culhane, J. L.;
Rapley, C. G.; Bentley, R. D.; Gabriel, A. H.; Phillips, K. J. H.;
Hayes, R. W.; Antonucci, E.
Bibcode: 1981ApJ...244L.137A
Altcode:
Preliminary results of spectroscopy and imaging of a solar active region
and flare plasma in soft X-ray emission lines are presented. Observed
X-ray line widths in a nonflaring active region are broader than the
Doppler width corresponding to the local electron temperature. An
analysis of 41 soft X-ray flares within a single active region reveals
a preference for flares to occur at locations that already show
enhanced X-ray emission and to favor magnetic complexity over high
gradient. However, flares do not appear to be directly responsible
for the heating and X-ray production of the active regions.
Title: Observations of the limb solar flare on 1980 April 30 with
the SMM X-ray polychromator
Authors: Gabriel, A. H.; Phillips, K. J. H.; Acton, L. W.; Wolfson,
C. J.; Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Kayat, M. A.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.147G
Altcode:
No abstract at ADS
Title: X-ray spectra of solar flares obtained with a high-resolution
bent crystal spectrometer
Authors: Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Gabriel,
A. H.; Phillips, K. J.; Acton, L. W.; Wolfson, C. J.; Catura, R. C.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.141C
Altcode:
Preliminary results obtained for three solar flares with the bent
crystal spectrometer on the SMM are presented. Resonance and satellite
lines of Ca XIX and XVIII and Fe XXV and XXIV are observed together
with the Fe XXVI Lyman-alpha line. Plasma properties are deduced from
line ratios and evidence is presented for changes of line widths
coincident with the occurrence of a hard X-ray impulsive burst. Fe
K-alpha spectra from a disk center and a limb flare agree with the
predictions of a fluorescence excitation model. However, a transient
Fe K-alpha burst observed in a third flare may be explained by the
collisional ionization of cool iron by energetic electrons.
Title: Book Review - the Sun and the Heliosphere
Authors: Massey, H.; Gabriel, A. H.; Elliot, H.; Axford, W. I.
Bibcode: 1981SSRv...28R.114M
Altcode:
No abstract at ADS
Title: Solar maximum mission experiment: Early results from the soft
X-ray polychromator experiment
Authors: Gabriel, A. H.; Antonucci, E.; Phillips, K. J. H.; Culhane,
J. L.; Bentley, R. D.; Parmar, A. N.; Rapley, C. G.; Acton, L. W.;
Leibacher, J. W.; Wolfson, C. J.; Strong, K. T.; Jordan, C.
Bibcode: 1981AdSpR...1m.267G
Altcode: 1981AdSpR...1Q.267G
The X-Ray Polychromator experiment has been in operation on the
SMM satellite for over three months. It is observing flares and
active regions in the wavelength range 1Å to 23Å using a number
of different modes. These include polychromatic imaging, high
resolution line profiles, high dispersion spectra, and light curves
with high time-resolution. Data are described together with some of
the preliminary analysis and interpretation.
Title: Solar Maximum Mission experiment: early results from the soft
X-ray polychromator experiment.
Authors: Gabriel, A. H.; Culhane, J. L.; Acton, L. W.; Antonucci,
E.; Bentley, R. D.; Jordan, C.; Leibacher, J. W.; Parmar, A. N.;
Phillips, K. J. H.; Rapley, C. G.; Wolfson, C. J.; Strong, K. T.
Bibcode: 1981hea..conf..267G
Altcode:
No abstract at ADS
Title: Solar Flare Diagnostics Using the Solar Maximum Mission
Authors: Gabriel, A. H.
Bibcode: 1981ecap.conf...50G
Altcode:
No abstract at ADS
Title: Soft X-ray Emission During the Impulsive Phase of a Flare
Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.
Bibcode: 1980BAAS...12..900A
Altcode:
No abstract at ADS
Title: Interpretation of the Ca XIX, Fe XXV and Fe XXVI BCS Spectra
Authors: Gabriel, A. H.; Antonucci, E.; Dubau, J.
Bibcode: 1980BAAS...12..912G
Altcode:
No abstract at ADS
Title: Detailed ultraviolet observations of the quasar 3C 273 with
the IUE.
Authors: Ulrich, M. H.; Boksenberg, A.; Bromage, G.; Carswell, R.;
Elvius, A.; Gabriel, A.; Gondhalekar, P. M.; Lind, J.; Lindegren,
L.; Longair, M. S.; Penston, M. V.; Perryman, M. A. C.; Pettini, M.;
Perola, G. C.; Rees, M.; Sciama, D.; Snijders, M. A. J.; Tanzi, E.;
Tarenghi, M.; Wilson, R.
Bibcode: 1980MNRAS.192..561U
Altcode:
The paper analyzes the nine spectra of the quasar 3C 273 obtained with
the International Ultraviolet Explorer in order to combine them and
to obtain a high signal-to-noise spectrum between 1100 and 3300 A. An
analysis was then made of the emission line intensity ratios and of
the continuous energy distribution; evidence was found for thermal
contribution to the ultraviolet continuum. The ultraviolet spectrum
of 3C 273 shows eight absorption lines at zero redshift due to the
intervening material of our galaxy; the C IV lambda absorption is much
stronger in the spectrum of 3C 273 than in the spectra of halo stars,
showing that a hot gaseous component exists in the outer regions of
the halo of the galaxy.
Title: The ultraviolet spectrum of the anomalous EUV-source halo
star HD 192273.
Authors: Bromage, G. E.; Gabriel, A. H.; Sciama, D. W.
Bibcode: 1980ESASP.157..353B
Altcode: 1980IUE2n......353B; 1980iue..conf..353B
The proposed EUV source HD 192273 was observed with International
Ultraviolet Explorer at both low and high resolution. Results
of an analysis of the stellar and interstellar spectrum are
presented. Strengths of interstellar absorption lines give a value
for the column density of neutral hydrogen atoms, NH =
2.0 + or - 0.5 x 10 to the 20th power cm sq, making the proposed EUV
identification untenable. The star appears to be a normal B2 V star
with eB-V = 0.04 but an approximate distance of 0.5 kpc
was derived from the IUE data and this leaves the star 4 magnitudes
too faint for Be V.
Title: The ultraviolet spectrum of the anomalous EUV-source halo
star HD 192273.
Authors: Bromage, G. E.; Gabriel, A. H.; Sciama, D. W.
Bibcode: 1980ESASP.157...23B
Altcode: 1980IUE2n.......23B
No abstract at ADS
Title: The Distribution of Interstellar CIV in the Galaxy
Authors: Bromage, G.; Gabriel, A. H.; Sciama, D. W.
Bibcode: 1980ESASP.157...21B
Altcode: 1980iue..conf...21B
No abstract at ADS
Title: The distribution of interstellar C IV in the galaxy.
Authors: Bromage, G. E.; Gabriel, A. H.; Sciama, D. W.
Bibcode: 1980ESASP.157..345B
Altcode: 1980iue..conf..345B; 1980IUE2n......345B; 1980IUE2E.R....345B
Some high dispersion spectra of 13 halo and disc stars were reduced and
column densities of C IV presented. The galactic distribution of C IV
is discussed and, combining the data with other published measurements,
a mean exponential scale height of 3 + 2 -1 kpc and disk space density
no = 8.5 x 10 to the minus 9th power cu cm are derived. The
results were compared with Copernicus O VI data. Strengths and profiles
of Si IV, C IV and N V from International Ultraviolet Explorer data
were also compared for a few representative lines of sight. N V/O VI
ratios imply log T 5.5, while SI IV/C IV (including the value for the
whole halo towards 3C 273) require 4.80 less than Log T less than 4.95.
Title: Observations of NGC 4151 with IUE.
Authors: Boksenberg, A.; Bromage, G.; Clavel, J.; Elvius, A.; Gabriel,
A.; Gondhalekar, P.; Jordan, C.; Lind, J.; Lindegren, L.; Longair,
M.; Penston, M. V.; Perola, G.; Perryman, M.; Pettini, M.; Rees, M.;
Sciama, D.; Snijders, M.; Tanzi, E.; Tarenghi, M.; Ulrich, M. H.;
Wilson, R.
Bibcode: 1980ESASP.157D..67B
Altcode:
No abstract at ADS
Title: Search for flare non-thermal electrons in iron and calcium
BCS spectra
Authors: Kayat, M. A.; Gabriel, A. H.; Phillips, K. J. H.
Bibcode: 1980BAAS...12Q.533K
Altcode:
No abstract at ADS
Title: The soft X-ray polychromator for the Solar Maximum Mission.
Authors: Acton, L. W.; Culhane, J. L.; Gabriel, A. H.; Bentley,
R. D.; Bowles, J. A.; Firth, J. G.; Finch, M. L.; Gilbreth, C. W.;
Guttridge, P.; Hayes, R. W.; Joki, E. G.; Jones, B. B.; Kent, B. J.;
Leibacher, J. W.; Nobles, R. A.; Patrick, T. J.; Phillips, K. J. H.;
Rapley, C. G.; Sheather, P. H.; Sherman, J. C.; Stark, J. P.; Springer,
L. A.; Turner, R. F.; Wolfson, C. J.
Bibcode: 1980SoPh...65...53A
Altcode:
The 1.4-22.4 Å range of the soft X-ray spectrum includes a multitude
of emission lines which are important for the diagnosis of plasmas
in the 1.5-50 million degree temperature range. In particular, the
hydrogen and helium-like ions of all abundant solar elements with Z
> 7 have their primary transitions in this region and these are
especially useful for solar flare and active region studies. The soft
X-ray polychromator (XRP) is a high resolution experiment working
in this spectral region. The XRP consists of two instruments with
a common control, data handling and power system. The bent crystal
spectrometer is designed for high time resolution studies in lines of Fe
I-Fe XXVI and Ca XIX. The flat crystal scanning spectrometer provides
for 7 channel polychromatic mapping of flares and active regions in
the resonance lines of O VIII, Ne IX, Mg XI, Si XIII, S XV, Ca XIX,
and Fe XXV with 14″ spatial resolution. In its spectral scanning
mode it covers essentially the entire 1.4-22.5 Å region.
Title: Impulsive phase of solar flares
Authors: Kane, S. R.; Crannell, C. J.; Datlowe, D.; Feldman, U.;
Gabriel, A.; Hudson, H. S.; Kundu, M. R.; Maetzler, C.; Neidig, D.;
Petrosian, V.
Bibcode: 1980sfsl.work..187K
Altcode: 1980sofl.symp..187K
The present understanding of the impulsive phase of a solar flare,
characterized by short-duration bursts of impulsive hard X-ray,
EUV, optical and radio emission indicating the release of energetic
electrons is reviewed. Observations of the spectral distribution
of impulsive hard X-ray bursts and of Type III and radio continuum
bursts are presented and interpreted in terms of energetic electron
distributions, and impulsive EUV, XUV, soft X-ray and optical
observations, which provide a lower limit to total energy release
during the impulsive phase, are discussed. The role of energetic
electrons in exciting the hard X-ray, EUV and microwave emissions is
considered, and thin-target, thick-target, partial-precipitation and
thermal models of impulsive phase electron acceleration are evaluated
in light of the observations. It is noted that available data do
not allow discrimination between a thermal or a nonthermal electron
distribution, on which depends the proportion of flare energy supplied
by the energetic electrons, and that data favors models which permit
at least partial electron precipitation. Future observational and
theoretical work is indicated.
Title: Dielectronic satellite spectra for highly charged helium-like
ions. V - Effect of total satellite contribution on the solar flare
iron spectra
Authors: Bely-Dubau, F.; Gabriel, A. H.; Volonte, S.
Bibcode: 1979MNRAS.189..801B
Altcode:
For satellites of the type 1s2nl-1s 2pnl in Fe XXIV,
wavelengths and intensities have been calculated for n = 4. Together
with previous calculations for n = 2 and 3, these enable the wavelengths
and decay rates to be scaled for higher values of n. The series up
to n = 11 for satellites of the resonance line 1s2 1s2p
1P1, and up to n = 16 for satellites of the inter-
combination line 1s2-ls 2p 3P1, have
been derived. This leads to a good estimate for the contribution of
satellites to the apparent wavelength shift, width, and intensity of the
resonance line, and thus to a value of the correction factor a needed
for deriving electron temperature from satellite! resonance line ratios,
as described in Papers I and II in this series. Also obtained, from the
sum of all the satellites, is a new value for the major contribution (
90 per cent) to the total dielectronic recombination rate. At typical
flare temperatures of 20 × 106 K, this is greater by a
factor of two than values obtained from earlier semi-empirical formulae.
Title: Dielectronic satellite spectra for highly charged helium-like
ions - IV. Iron satellite lines as a measure of non-thermal electron
energy distributions.
Authors: Gabriel, A. H.; Phillips, K. J. H.
Bibcode: 1979MNRAS.189..319G
Altcode:
The intensities of two satellite lines 1s2 nl-1s 2pnl with n
= 2 and 3 relative to the Fe XXV resonance line 1s2-1s 2p are
considered. The intensities of these three lines are described by
a single temperature only if the emitting plasma has a Maxwellian
distribution of electrons. Analysis of the measured relative line
intensities is proposed as a means of detecting departures from
Maxwellian distributions, such as occur in solar flares. No data yet
exist with the required quality to which the method may be applied,
but an illustration is provided by two flares in which nonthermal
electrons are present, and expected line ratios are deduced from these.
Title: High dielectronic satellite lines in solar flare spectra
Authors: Steenman-Clark, L.; Bely-Dubau, F.; Faucher, P.; Dubau, J.;
Loulergue, M.; Gabriel, A. H.; Volonte, S.
Bibcode: 1979JPhys..40....1S
Altcode:
Resonance lines of highly ionized H and He-like ions and their
associated satellite lines are used to determine the electron
temperature and the transient state of the plasma in solar flares. The
intensity ratio of the satellite lines 1s(2)nl-1s2pl to the resonance
line 1s(2)-1s2p has been calculated for the n equals 2, 3 and 4 shells
of Fe XXIV. The results have enabled the identification of many lines
in the only available high resolution solar flare iron spectrum and
give a good estimate of the spectral intensity in the resonance line
by evaluating the contribution due to the blending of the satellites
with n not less than 3.
Title: Dielectronic satellite spectra for highly charged helium-like
ions - III. Calculations of n = 3 solar flare iron lines.
Authors: Bely-Dubau, F.; Gabriel, A. H.; Volonte, S.
Bibcode: 1979MNRAS.186..405B
Altcode:
New calculations have been carried out in a multiconfiguration
intermediate coupling scheme for dielectronic satellite spectra in Fe
XXIV of the type 1s2nl-1s 2p nl, for n = 2 and 3. These
are for application to solar flare spectra. The n = 2 result is
consistent with previous calculations. Satellites with n = 3 enable (a)
features in the observed spectra to be identified and explained, (b)
a correction to be made to the intensity of the Fe XXV resonance line,
and (c) provide part of the data for an estimate of the contribution
of satellites with n ≥ 3 to the overall dielectronic recombination
process. The computed spectra are compared with the solar flare spectra
of Grineva et al. (1973). The results are discussed in terms of plasma
diagnostic techniques, and the further theoretical work required to
complete our understanding of these spectra. This is important for
the interpretation of future planned observations of solar flare iron
lines in the soft X-ray region.
Title: Ultraviolet Observations of the Quasar 3C273 and Detection
of a Hot Gaseous Component in the Galactic Halo
Authors: Ulrich, M. H.; Boksenberg, A.; Bromage, G.; Carswell, R.;
Elvius, A.; Gabriel, A.; Gondhalekar, P. M.; Lind, J.; Lindegren,
L.; Longair, M. S.; Penston, M. V.; Perryman, M. A. C.; Pettini, M.;
Perola, G. C.; Rees, M.; Sciama, D.; Snijders, M. A. J.; Tanzi, E.;
Tarenghi, M.; Wilson, R.
Bibcode: 1979IUE1.symp..145U
Altcode:
No abstract at ADS
Title: Observations of the ultraviolet spectrum of the variable
Seyfert galaxy NGC4151
Authors: Baldwin, J.; Boksenberg, A.; Bromage, G.; Carswell, R.;
Elvius, A.; Gabriel, A.; Gondhalekar, P. M.; Jordan, C.; Lind, J.;
Lindegren, L.; Longair, M. S.; Penston, M. V.; Perola, G. C.; Perryman,
M. A. C.; Pettini, M.; Rees, M.; Snijders, M. A. J.; Tanzi, E. G.;
Tarenghi, M.; Ulrich, M. H.; Wilson, R.
Bibcode: 1979IUE1.symp..126B
Altcode:
High-resolution UV spectra of NGC 4151 from the IUE satellite are
presented and discussed. The Lyman-alpha emission line is narrow and
asymmetrical - there are two absorption systems. One is narrow and
probably represents the outer parts of NGC 4151. The other is broad,
primarily from material nearer to the nucleus. C IV 1550 A emission is
broad, with absorption between velocities of -100 and -1100 km/sec. The
absorbing clouds cover at least 80 percent of the emission region. Due
to the doublet nature of the line, alternative explanations are possible
for the details of the C IV absorption profile. Two such alternatives
are discussed.
Title: Preliminary studies of electromagnetic sounding of cometary
nuclei
Authors: Gabriel, A.; Warne, L.; Bednarczyk, S.; Elachi, C.
Bibcode: 1978STIN...7834022G
Altcode:
The internal structure of a comet could be determined with a spacecraft
borne electromagnetic sounder. A dielectric profile of the comet
could be produced in direct analogy with terrestrial glacier and ice
sheet sounding experiments. This profile would allow the detection
of a rocky core or ice layers if they exist, just as layers in the
ice and the bedrock interface have been clearly observed through
the Greenland ice sheet. It would also provide a gross estimate of
the amount of dust in the icy region. Models for the response of the
nucleus and cometary plasma to electromagnetic sounding are developed
and used to derive experimental parameters. A point system design was
completed. Preliminary engineering study results indicate that the
sounder is well within the bounds of current space technology.
Title: A focussing iron line crystal spectrometer for Spacelab.
Authors: Catura, R. C.; Culhane, J. L.; Gabriel, A. H.; Rapley, C. G.;
Walker, A. B. C., Jr.; Woodgate, B. E.
Bibcode: 1978nisa.symp..271C
Altcode: 1978nisa.conf..271C
No abstract at ADS
Title: The upper chromosphere and corona. Observations and
interpretation
Authors: Gabriel, A. H.
Bibcode: 1977MmSAI..48..559G
Altcode:
No abstract at ADS
Title: A focussing iron line crystal spectrometer for Spacelab
Authors: Catura, R. C.; Culhane, J. L.; Rapley, C. G.; Gabriel, A. H.;
Walker, A. B. C., Jr.; Woodgate, B. E.
Bibcode: 1977cosp.meetS....C
Altcode:
A crystal spectrometer system is described which employs conical
focusing of 12 curved LiF crystal panels to minimize the detector
size and reduce the background counting rate. The wavelength range
from 1.70 to 1.98 A is covered, including the resonance lines of
Fe XXV and Fe XXVI as well as the Fe I K-alpha line and absorption
edge. Operation of the spectrometer is discussed, noting that diffracted
X-rays are registered in one-dimensional position-sensitive detectors
and that the arrival position of a photon in a detector is related
to its wavelength due to the fixed curvature of the crystal panels
in the dispersion plane. Some characteristics of the multianode
position-sensitive detectors are reviewed along with the crystal
arrangement and mounting. The instrument sensitivity is evaluated in
relation to the strengths of 6.7-keV emission features detected by
the Ariel 5 and OSO 8 proportional-counter spectrometers.
Title: Why measure astrophysical X-ray spectra?
Authors: Gabriel, A. H.
Bibcode: 1977Natur.267..410G
Altcode:
CRAIG and Brown1 advise caution against some of the
limitations of X-ray astronomy, and emphasise the need to take
theoretical considerations into account before planning expensive
experiments. Their remarks must be taken seriously by those involved
in space experiments, but their statements represent only one extreme
viewpoint on this complex problem.
Title: Radiation Processes in High-Energy Astrophysical Plasmas.
Authors: Gabriel, A. H.
Bibcode: 1977uxsa.collE...8G
Altcode: 1977IAUCo..43.....G
No abstract at ADS
Title: Structure of the Quiet Chromosphere and Corona
Authors: Gabriel, A. H.
Bibcode: 1977ebhs.coll..375G
Altcode: 1977IAUCo..36..375G
No abstract at ADS
Title: High Dielectronic Satellite Lines in Solar Flare Iron Spectra.
Authors: Bely-Debau, F.; Gabriel, A. H.; Volonté, S.
Bibcode: 1977uxsa.coll...45B
Altcode: 1977IAUCo..43...45B
No abstract at ADS
Title: A Magnetic Model of the Solar Transition Region
Authors: Gabriel, A. H.
Bibcode: 1976RSPTA.281..339G
Altcode: 1976RSLPT.281..339G
A two-dimensional model of the chromosphere and corona has been
constructed. This is based upon the magnetic flux concentrations which
occur at the boundaries of the supergranule convection cells. The
expansion of the magnetic flux is determined by the vertical extent
of the convecting plasma. The distribution of atmospheric material
is consistent both with observed spectral intensities and with energy
balance requirements. The model predicts a primary transition region
which is confined to an area about 10' ' wide overlying the
supergranule boundaries. A secondary transition region which is much
thinner covers the cell centres. The predictions are fully consistent
with recent ultraviolet observations.
Title: A discussion on the physics of the solar atmosphere. held
1975 January 14 and 15.
Authors: Massey, H.; Sweet, P. A.; Gabriel, A. H.
Bibcode: 1976RSPTA.281..293M
Altcode:
No abstract at ADS
Title: High Resolution X-Ray Spectra of the Sun: Discussion
Authors: Brown, J. C.; Parkinson, J. H.; Gabriel, A. H.
Bibcode: 1976RSPTA.281..382B
Altcode:
No abstract at ADS
Title: Analysis of EUV observations of regions of the quiet and
active corona at the time of the 1970 March 7 eclipse.
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1975MNRAS.173..397G
Altcode:
A series of EUV spectra were obtained from a rocket flight during
the 1970 March 7 total solar eclipse. The intensities of permitted
and forbidden emission lines in both quiet and active regions have
been analyzed. The densities and temperatures have been derived as a
function of position in the active region. In a given line-of-sight
the density increases with increasing temperature and overall the
central, low, parts of the active region contain more material at
the higher temperatures than do the more extensive loop systems. The
populations of the excited levels of the forbidden lines have been
calculated using currently available atomic data. It appears that
these and known excitation processes significantly underestimate the
excited level populations. The populations used have therefore been
normalized by using a quiet region of the corona as a diagnosed plasma.
Title: Dielectronic satellite spectra for highly- charged helium-like
ions-11. Improved calculations
Authors: Bhalla, C. P.; Gabriel, A. H.; Presnyakov, L. P.
Bibcode: 1975MNRAS.172..359B
Altcode:
Earlier calculations on the intensities of dielectronic satellite
spectra for helium-like ion resonance lines (Gabriel) have now been
revised. The revision is based upon new and improved calculations for
the rates of autoionization of the levels responsible, and of their
production rate by direct inner-shell excitation. The new theory makes
some significant alterations in the interpretation of the intensities
of observed lines from solar and laboratory plasmas, in particular
in relation to the extent to which the ionization departs from the
steady-state distribution. Recent improved observations of solar active
regions and flares and high temperature laboratory plasmas are compared
with the calculated spectra.
Title: Further measurements of emission line profiles in the solar
ultraviolet spectrum.
Authors: Boland, B. C.; Dyer, E. P.; Firth, J. G.; Gabriel, A. H.;
Jones, B. B.; Jordan, C.; McWhirter, R. W. P.; Monk, P.; Turner, R. F.
Bibcode: 1975MNRAS.171..697B
Altcode:
A further flight of a high resolution echelle spectrograph has been
carried out on a Skylark rocket to measure solar line profiles in
the region 1400-2200 A. Improvements in reflective coatings and better
thermal stability resulted in an increase in both the number and quality
of profiles recorded. Microdensitometer traces for 37 emission lines are
presented. Analysis of the profiles leads to a nonthermal mechanical
velocity component which increases with temperature over the range
6,000 to 100,000 K, always remaining subsonic. Interpretations are
considered in terms of a progressive mechanical energy flux to the
corona. These include acoustic and MHD modes for both spherically
symmetric and network models of the atmosphere.
Title: Solar physics research at the Appleton Laboratory, Culham
Authors: Gabriel, A. H.
Bibcode: 1975cesra...5..102G
Altcode:
No abstract at ADS
Title: Solar physics research at the Appleton Laboratory, Culham.
Authors: Gabriel, A. H.
Bibcode: 1975MmArc.105..102G
Altcode:
No abstract at ADS
Title: Observations of the solar spectrum in the re.-ion 150 A to
870 A emitted from the disk and above the limb
Authors: Firth, J. G.; Freeman, F. F.; Gabriel, A. H.; Jones, B. B.;
Jordan, C.; Negus, C. R.; Shenton, D. B.; Turner, R. F.
Bibcode: 1974MNRAS.166..543F
Altcode:
Photographic spectra have been obtained in the grazing-incidence
region from a position on the quiet solar disk and from a region
just above the visible limb. The payload, which was launched on a
Sun-stabilized Skylark rocket, contained three grazing-incidence
spectrographs, each illuminated by a two-component grazing-incidence
telescope mirror. One of these, which was viewing the limb spectrum,
was fitted with a fine-alignment servo system to stabilize the image. A
careful intensity calibration will enable the data to be analysed in
terms of limbldisk intensity ratios, and absolute intensities. The
present paper presents a full identification of the spectra, which
includes a number of intersystem transitions, notably in iron ions.
Title: Analysis of EUV Observations of a Coronal Active Region Made
during the 7 March 1970 Eclipse (presented by C. Jordan)
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1974IAUS...57...93G
Altcode:
No abstract at ADS
Title: Highly charged ions in astrophysics.
Authors: Gabriel, A. H.
Bibcode: 1974PhyS....9..300G
Altcode:
No abstract at ADS
Title: A Magnetic Model of the Chromosphere-Corona Transition Region
Authors: Gabriel, A. H.
Bibcode: 1974IAUS...56..295G
Altcode:
No abstract at ADS
Title: Highly Charged Ions in Astrophysics
Authors: Gabriel, A. H.
Bibcode: 1974PhyS....9..306G
Altcode:
The study of highly ionized atoms in astrophysical sources is reviewed
with particular reference to the spectroscopy of the sun. The range
of spectroscopic observations is surveyed in terms of the general
properties of the solar atmosphere. Such spectra contain important
information on the physical properties of the emitting regions. Some of
the methods are described by which spectral intensities can be related,
through the processes of ionization recombination and excitation,
to the temperature and density structure of the source.
Title: The Temperature Dependence of Line Ratios of Helium-Like Ions
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1973ApJ...186..327G
Altcode:
In a recent paper Blumenthal et a!. have suggested that the
use of helium-like intercombination to forbidden line ratios to
measure electron densities is complicated by an important electron-
temperature dependence of the ratios. It is shown here that their
theory uses an incorrect treatment of dielectronic recombination and
that the temperature dependence is in fact smaller. It is concluded
that significant observations of ratios which vary by more than I 10
percent can safely be attributed to electron density effects. Recent
observations, in particular those of Acton et a!. of O vii, show
variations of only 15 percent. Although Acton et a!. consider that
their data support the temperature dependence predicted by Blumenthal
et a!., they can equally well agree with a much lower temperature
dependence. However, the accuracy of the observations to date is
not sufficient to show a definite dependence on temperature. Subject
headings: atomic processes - atmospheres, solar
Title: The sixteenth Herstmonceux conference, 1972 April 5 - 6. Cosmic
X-ray sources.
Authors: Pounds, K. A.; Miley, G. K.; Murdin, P.; Webster, B. L.;
Pacini, F.; Pringle, J. E.; Jackson, J. C.; Morrison, L. V.; Culhane,
J. L.; Sciama, D. W.; Fabian, A. C.; Brown, J. C.; Gabriel, A. H.;
Bingham, R. G.; Lategan, A. H.; Pagel, B. E. J.
Bibcode: 1972Obs....92..193P
Altcode:
No abstract at ADS
Title: Dielectronic Satellite Spectra in the Soft X-Ray Region
(invited Paper)
Authors: Gabriel, A. H.
Bibcode: 1972SSRv...13..655G
Altcode: 1972IAUCo..14..655G
Satellite lines, situated on the long wavelength side of the helium-like
ion resonance line, can be observed in highly-ionized ions both in
laboratory sources and from the Sun. Although seen for more than 30
years, these lines have only recently been classified in detail as
inner-shell transitions in lithium-like ions. Laboratory experiments
have shown that under steady-state conditions these satellites are
produced by dielectronic recombination, although in transient ionizing
plasmas direct inner-shell excitation can be important. Detailed
calculations have been carried out for high Z ions up to copper, and
the results can be compared with solar flare spectra in iron. Such
comparisons allow both the electron temperature and the transient state
of the plasma to be determined. Laboratory spectra from such high-Z
ions are different in appearance, and may be dominated by processes
resulting from the transient ionizing state of the plasma.
Title: Preface
Authors: Gabriel, A. H.
Bibcode: 1972SSRv...13D...3G
Altcode:
No abstract at ADS
Title: Dielectronic satellite spectra for highly-charged helium-like
ionlines
Authors: Gabriel, A. H.
Bibcode: 1972MNRAS.160...99G
Altcode:
Calculations have been carried out in intermediate coupling of the
wavelengths and intensities of the satellite lines situated on the
long wavelength side of the helium4ike ion resonance lines, recently
observed from solar flares. Earlier calculations up to aluminium have
been extended up to iron and copper. For the intensities, the important
processes are primarily dielectronic recombination, but also direct
inner-shell excitation. Comparisons have been made with spectra from
solar flares and active regions, and from low-inductance laboratory
sparks. Computed wavelengths in iron are found to agree with these to
better than A. Comparison of the intensities allows the determination
of both the electron temperature and the transient ionizing state of
the plasma. The laboratory plasma spectra are found to be in an extreme
transient ionizing condition, and are thus significantly different from
solar spectra. in the cases studied, solar active regions were found
to be moderately ionizing, while the flare spectra were recombining.
Title: Ultraviolet and X-ray Spectroscopy of Astrophysical and
Laboratory Plasmas.
Authors: Gabriel, A. H.
Bibcode: 1972SSRv...13.....G
Altcode: 1972IAUCo..14.....G
No abstract at ADS
Title: Ultraviolet and X-ray spectroscopy of astrophysical and
laboratory plasmas. IAU Colloquium No. 14, held at Utrecht 24 -
26 August, 1971.
Authors: Gabriel, A. H.
Bibcode: 1972SSRv...13..489G
Altcode:
No abstract at ADS
Title: Spectral Intensities from Helium-Like Ions
Authors: Gabriel, A. H.
Bibcode: 1972ama..conf..311G
Altcode:
No abstract at ADS
Title: Measurements on the Lyman Alpha Corona (Papers presented at
the Proceedings of the International Symposium on the 1970 Solar
Eclipse, held in Seattle, U. S. A. , 18-21 June, 1971.)
Authors: Gabriel, A. H.
Bibcode: 1971SoPh...21..392G
Altcode:
As a result of a collaborative rocket experiment carried out during
the solar eclipse on 7 March, 1970, measurements have been made
of the brightness of Lyman α from the corona, at heights between
5 × 104 and 5 × 105 km above the limb. The
emission is shown to occur primarily through the resonance scattering
of chromospheric Lyman α from the residual neutral hydrogen in the
corona. Both the absolute value and radial fall-off of the brightness
agree well with calculations based on solar density models. The Lyman
α emission has similar variations around the limb to the white light
corona, showing in particular an equatorial enhancement.
Title: Rocket Observations of the Ultraviolet Solar Spectrum during
the Total Eclipse of 1970 March 7
Authors: Gabriel, A. H.; Garton, W. R. S.; Goldberg, L.; Jones,
T. J. L.; Jordan, Carole; Morgan, F. J.; Nicholls, R. W.; Parkinson,
W. J.; Paxton, H. J. B.; Reeves, E. M.; Shenton, C. B.; Speer, R. J.;
Wilson, R.
Bibcode: 1971ApJ...169..595G
Altcode:
A sequence of thirty-five ultraviolet photographic spectra of the
Sun has been obtained in the wavelength region 850-2190 A, as a
function of time during the eclipse. These cover the range from before
second contact until midtotality, with a spatial resolution of the
order 2 arc sec. A general description of the experiment and data is
given. Twenty-five new coronal lines have been seen, the majority of
which have been identified as new forbidden transitions. The La corona
is observed out to over 1.5 R0, and a quantitative interpretation
is presented. Analyses of other features-e.g., prominences,
quiet-atmosphere structure, and coronal condensations-are continuing.
Title: Helium-Like Ion Forbidden Line Emission, and Solar Active
Regions
Authors: Freeman, F. F.; Gabriel, A. H.; Jones, B. B.; Jordan, Carole
Bibcode: 1971RSPTA.270..127F
Altcode:
A theory has been developed for interpreting the intensity of the
1s2 1S-1s2s 3S forbidden line in
helium-like ions in terms of electron density at the source. In a
recent soft X-ray rocket experiment, this transition has been observed
simultaneously from C V, N VI and O VII. New values for the forbidden
transition probabilities are derived in a semi-empirical manner using
this data. The new values lead to derived solar densities in active
regions of between 1011 and 1013 cm-3.
Title: Some Problems Relating to Solar Line Identification
Authors: Gabriel, A. H.
Bibcode: 1971HiA.....2..486G
Altcode:
No abstract at ADS
Title: A discussion on solar studies with special reference to space
observations. British National Committee on Space Research.
Authors: Massey, H.; Allen, C. W.; Gabriel, A. H.; Pagel, B. E. J.;
Wilson, R.
Bibcode: 1971RSPTA.270.....M
Altcode:
No abstract at ADS
Title: Some problems relating to solar line identification.
Authors: Gabriel, A. H.
Bibcode: 1971adiu.conf..486G
Altcode:
No abstract at ADS
Title: Helium-like ion forbidden line emission from the sun
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1970PhLA...32..166G
Altcode:
A recent theory for interpreting relative line intensities from
helium-like ions is re-examined in the light of newer data. New
semi-empirical values for the transition probability 1s2
1S - 1s2s 3S, are proposed, which lead to higher
measured electron densities.
Title: Plasma light sources.
Authors: Gabriel, A. H.
Bibcode: 1970bfs..conf..157G
Altcode:
No abstract at ADS
Title: Long Wavelength Satellites to the He-like Ion Resonance Lines
in the Laboratory and in the Sun
Authors: Gabriel, A. H.; Jordan, Carole
Bibcode: 1969Natur.221..947G
Altcode:
SATELLITE lines, situated on the long wavelength side of the
He-like resonance lines in laboratory plasmas, are classified here
as transitions in highly excited Li-like ions. We also show that
intense features in the solar X-ray spectrum, of similar appearance,
are of different origin, and these are classified as the forbidden
ls2 1S0-ls2s 3S1
line of the He-like ion.
Title: Interpretation of solar helium-like ion line intensities
Authors: Gabriel, A. H.; Jordan, Carole
Bibcode: 1969MNRAS.145..241G
Altcode:
Recent identification of the line from helium-like ions in the
solar soft X-ray spectrum, followed by calculation of its transition
probability, enables an analysis of the observations to be carried
out, based on intensities of the three lines 21P I1S, I1S, and 23S
11S. The relative collision rates to the excited levels and the
electron densities in the emitting regions have been determined,
subject to the limitation of available observations. Densities of 3 x
io cm- are found from lines formed over the quiet corona, but values of
between I0 and 1011 cm-3 are found from lines emitted in active regions,
and the highest electron densities occur in the hottest regions.
Title: Spectroscopic Observations of Dielectronic Recombination in
Helium-Like Ions
Authors: Gabriel, A. H.; Jordan, C.; Paget, T. M.
Bibcode: 1969peac.conf..558G
Altcode:
No abstract at ADS
Title: Solar Iron Lines at 182 Å
Authors: Fawcett, B. C.; Gabriel, A. H.; Jordan, C.
Bibcode: 1968ApJ...152L.119F
Altcode:
No abstract at ADS
Title: Identification of the Solar Spectrum in the Region 60-170 Å
Authors: Gabriel, A. H.; Fawcett, B. C.
Bibcode: 1965Natur.206..808G
Altcode:
A GROUP of intense unidentified lines in the solar spectrum in the
range 170-220 Å was first recognized in a laboratory source by
Fawcett et al.1, who compared solar spectra photographed
by Tousey2 with spectra from Zeta, and indicated that iron
was the probable source element. There followed work from a number of
laboratories3-5, all confirming that iron was the element
responsible. More recently, Gabriel, Fawcett and Jordan6
have obtained classifications for many of the lines in this group, which
is due chiefly to FeIX to FeXIV. This work also provided information
on the corresponding isoelectronic sequences through to nickel.
Title: Classification of Iron Lines in the Spectrum of the Sun and
Zeta in the Range 167 Å to 220 Å
Authors: Gabriel, A. H.; Fawcett, B. C.
Bibcode: 1965Natur.206..390G
Altcode:
A NUMBER of teams1-3 using rocket or satellite-borne
spectrometers have made observations of a group of intense unidentified
emission lines in the solar spectrum between 167 Å and 220 Å. The
origin and classification of these lines have aroused considerable
interest in a number of laboratories. The lines were first reported from
laboratory sources by Fawcett et al.4, who produced them
in the Zeta discharge at Harwell. There were strong indications that
iron from the walls of the discharge vessel was responsible. Further
evidence for iron was provided by Elton et al.5 and House,
Deutsehmann and Sawyer6, who produced the same lines by
adding iron to θ-pinch discharges. Fawcett and Gabriel7
at Culham showed that the lines could be produced in various iron
sparks, and also produced similar systems of intense lines from all
elements in the period from calcium to nickel. From the wave number
variation in these elements, they were able to state that 3p-3d
transitions were responsible. By studying the intensity variation with
exciting energy they obtained a correlation with ions between FeIX and
FeXIII. Alexander, Feldman and Fraenkel8 observed some of
these lines in several sparks of different types, and assigned degrees
of ionization as FeVII to FeX. Neupert9 has made an attempt
to assign ionization states by correlating the intensities from the
Sun with periods of solar activity, and proposed ions between FeX and
FeXIV. Zirin10 in an analysis of solar data2
has tentatively classified three lines in this spectral region as
FeXIII lines.
Title: New Spectra of the Iron Transition Elements of Astrophysical
Interest.
Authors: Fawcett, B. C.; Gabriel, A. H.
Bibcode: 1965ApJ...141..343F
Altcode:
A group of intense lines between 170 and 220 A has been observed in
the Zeta Discharge, and found to coincide with intense unidentified
lines previously observed in the solar spectrum Using high-current and
high-voltage sparks, these lines have again been produced and shown to
be due to iron Similar groups of lines have been produced and measured
from of the elements from calcium to nickel Over 300 new lines are
listed in the wavelength range 400-100 A. Two possible mechanisms for
the production of these lines are considered.
Title: Observations of the Zeta Spectrum in the Wave-length Range
16 Å-400 Å
Authors: Fawcett, B. C.; Gabriel, A. H.; Griffin, W. G.; Jones, B. B.;
Wilson, R.
Bibcode: 1963Natur.200.1303F
Altcode:
SPECTROSCOPIC studies of Zeta1 are now being carried
out in the important wave-length region below 400 Å. Previous
investigations in the vacuum ultra-violet have been mainly confined to
the region between 400 Å and 2000 Å using a variety of vacuum grating
spectrometers with both photographic and photoelectric detectors. Thus,
spectral line identifications have been made by Butt et al.1,
and Fawcett et al.2. Measurement and interpretation of
the temporal variation of spectral line intensities have been made
by Burton and Wilson3, and Hobbs et al.4, and
measurement of the Doppler profiles of spectral lines has been made by
Jones and Wilson5. More recently, observations have been
made by Heroux6,7, who measured the relative intensities
of spectral lines in order to determine the electron temperature,
using a grazing incidence rocket monochromator8.