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| Author | Catalina Morales-Yáñez, Zacharie Duputel, Luis Rivera | ||||
| Title | Impact of 3-D Earth structure on W-phase CMT parameters | Type | Journal | ||
| Year | 2020 | Publication | Geophysical Journal International | Abbreviated Journal | |
| Volume | 223 | Issue | 2 | Pages | 1432-1445 |
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Abstract  |
We investigate the impact of unmodelled 3-D structural heterogeneity on inverted W-phase source parameters. We generate a large data set of synthetic seismograms accounting for the Earths 3-D structure for 250 earthquakes globally distributed. The W-phase algorithm is then used to invert for earthquake CMT parameters, assuming a spherical Earth model. The impact of lateral heterogeneity is assessed by comparing inverted source parameters with those used to compute the 3-D synthetics. Results show that the 3-D structure mainly affects centroid location while the effect on the other source parameters remains small. Centroid mislocations present clear geographical patterns. In particular, W-phase solutions for earthquakes in South America are on average biased 17 km to the east of the actual centroid locations. This effect is significantly reduced using an azimuthally well balanced distribution of seismological stations. Source parameters are generally more impacted by mantle heterogeneity while the scalar moment of shallow earthquakes seems to be mainly impacted by the crustal structure. Shallow earthquakes present a variability of Mrθ and Mrϕ moment tensor elements, resulting both from the small amplitude and a larger uncertainty of the associated Green’s functions. | ||||
| Programme | 133 | ||||
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| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0956-540X | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 7890 | |||
| Permanent link to this record | |||||
| Author | Merieme Chadid, Chris Sneden and George Preston | ||||
| Title | Spectroscopic Comparison of Metal–Rich RRab Stars of theGalactic Field with Their Metal–Poor Counterparts | Type | Journal Article | ||
| Year | 2016 | Publication | Astrophysical journal | Abbreviated Journal | Astrophys. J. |
| Volume | 835 | Issue | 2 | Pages | 187 |
| Keywords | |||||
| Abstract |
We investigate atmospheric properties of 35 stable RRab stars that possess the full ranges of period, light amplitude, and metal abundance found in Galactic RR Lyrae stars. Our results are derived from several thousand echelle spectra obtained over several years with the du Pont telescope of Las Campanas Observatory. Radial velocities of metal lines and the Hα line were used to construct curves of radial velocity versus pulsation phase. From these we estimated radial velocity amplitudes for metal lines (formed near the photosphere) and Hα Doppler cores (formed at small optical depths). We also measured Hα emission fluxes when they appear during primary light rises. Spectra shifted to rest wavelengths, binned into small phase intervals, and co-added were used to perform model atmospheric and abundance analyses. The derived metallicities and those of some previous spectroscopic surveys were combined to produce a new calibration of the Layden abundance scale. We then divided our RRab sample into metal-rich (disk) and metal-poor (halo) groups at [Fe/H] = −1.0; the atmospheres of RRab families, so defined, differ with respect to (a) peak strength of Hα emission flux, (b) Hα radial velocity amplitude, (c) dynamical gravity, (d) stellar radius variation, (e) secondary acceleration during the photometric bump that precedes minimum light, and (f) duration of Hα line-doubling. We also detected Hα line-doubling during the | ||||
| Programme | 1096 | ||||
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| Address | |||||
| Corporate Author | Thesis | Bachelor's thesis | |||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0004-637X | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 6544 | |||
| Permanent link to this record | |||||
| Author | Michael Lockwood, Mathew J. Owens, Carl Haines, Luke Barnard, Christopher John Scott, Aude Chambodut, Kathryn A. McWilliams, Alan W. P. Thomson | ||||
| Title | Universal Time Variations in Space Weather | Type | Journal | ||
| Year | 2020 | Publication | Earth and space science open archive | Abbreviated Journal | |
| Volume | 12 | Issue | Pages | ||
| Keywords | |||||
| Abstract |
We introduce the inductive effects of polar cap motions towards and way from the Sun into magnetospheric electrodynamics and show how this explains observed Universal Time variations in hemispheric geomagnetic indices. The large (and growing) hemispheric asymmetry in the offsets of the geomagnetic (dip or eccentric dipole) poles from Earth’s rotational axis means that the effect is not cancelled out in global indices. By adding this effect to that of the Russell-McPherron effect on solar wind-magnetosphere coupling, that of ionospheric conductivities, and that of the solar wind dynamic pressure and dipole tilt on the near-Earth tail lobe field and cross-tail current sheet, we are able to model the persistent “equinoctial” time-of-day/time-of-year pattern (with additional net Universal time variations) observed in the an, as and am geomagnetic indices since 1959. We discuss the implications for the longitudinal dependence of the effects of extreme space weather events | ||||
| Programme | 139 | ||||
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| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 8464 | |||
| Permanent link to this record | |||||
| Author | C. Goyens, S. Marty, E. Leymarie, D. Antoine, M. Babin, S. Bélanger | ||||
| Title | High Angular Resolution Measurements of the Anisotropy of Reflectance of Sea Ice and Snow | Type | Journal | ||
| Year | 2018 | Publication | Earth and Space Science | Abbreviated Journal | |
| Volume | 5 | Issue | 1 | Pages | 30-47 |
| Keywords | Arctic bidirectional reflectance reflectance anisotropy remote sensing snow and ice albedo spectroradiometry | ||||
| Abstract |
We introduce a new method to determine the anisotropy of reflectance of sea ice and snow at spatial scales from 1 m2 to 80 m2 using a multispectral circular fish-eye radiance camera (CE600). The CE600 allows measuring radiance simultaneously in all directions of a hemisphere at a 1° angular resolution. The spectral characteristics of the reflectance and its dependency on illumination conditions obtained from the camera are compared to those obtained with a hyperspectral field spectroradiometer manufactured by Analytical Spectral Device, Inc. (ASD). Results confirm the potential of the CE600, with the suggested measurement setup and data processing, to measure commensurable sea ice and snow hemispherical-directional reflectance factor, HDRF, values. Compared to the ASD, the reflectance anisotropy measured with the CE600 provides much higher resolution in terms of directional reflectance (N = 16,020). The hyperangular resolution allows detecting features that were overlooked using the ASD due to its limited number of measurement angles (N = 25). This data set of HDRF further documents variations in the anisotropy of the reflectance of snow and ice with the geometry of observation and illumination conditions and its spectral and spatial scale dependency. Finally, in order to reproduce the hyperangular CE600 reflectance measurements over the entire 400–900 nm spectral range, a regression-based method is proposed to combine the ASD and CE600 measurements. Results confirm that both instruments may be used in synergy to construct a hyperangular and hyperspectral snow and ice reflectance anisotropy data set. | ||||
| Programme | 1164 | ||||
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| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2333-5084 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 8134 | |||
| Permanent link to this record | |||||
| Author | Parrenin, F.; Rémy, F.; Ritz, C.; Siegert, M.J.; Jouzel, J. | ||||
| Title | New modeling of the Vostok ice flow line and implication for the glaciological chronology of the Vostok ice core | Type | Journal Article | ||
| Year | 2004 | Publication | Journal of geophysical research-atmospheres | Abbreviated Journal | J. Geophys. Res. |
| Volume | 109 | Issue | Pages | ||
| Keywords | glaciology; paleoclimatology; Antarctica; inverse theory; 1827 Hydrology: Glaciology; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 3260 Mathematical Geophysics: Inverse theory; 9310 Information Related to Geographic Region: Antarctica | ||||
| Abstract |
We have used new spaceborne (elevation) and airborne (ice thickness) data to constrain a 2D1/2 model of snow accumulation and ice flow along the Ridge B-Vostok station ice flow line (East Antarctica). We show that new evaluations of the ice flow line geometry (from the surface elevation), ice thickness (from low-frequency radar data), and basal melting and sliding change significantly the chronology of the Vostok ice core. This new Vostok dating model reconciles orbital and glaciological timescales and is in good agreement with the Dome Fuji glaciological timescale. At the same time, the new model shows significantly older ages than the previous GT4 timescale for the last glacial part, being thus in better agreement with the GRIP and GISP2 chronologies. | ||||
| Programme | 355 | ||||
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| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | American Geophysical Union | Place of Publication | Editor | ||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0148-0227 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | IPEV @ Thierry.Lemaire @ | Serial | 5618 | ||
| Permanent link to this record | |||||
| Author | Bulat S., Alekhina I A Blot M., Petit J.R., De Angelis M., Wagenbach D. Lipenkov V.Y., | ||||
| Title | DNA signature of thermophilic bacteria from the aged accretion ice of Lake Vostok, Antarctica: implications for searching for life in extreme icy environments | Type | Journal Article | ||
| Year | 2004 | Publication | International journal of astrobiology | Abbreviated Journal | |
| Volume | 3 | Issue | 1 | Pages | 1-12 |
| Keywords | |||||
| Abstract |
We have used 16S ribosomal genes to estimate the bacterial contents of Lake Vostok accretion ice samples at 3551 m and 3607 m, both containing sediment inclusions and formed 20000–15000 yr ago. Decontamination proved to be a critical issue, and we used stringent ice chemistry-based procedures and comprehensive biological controls in order to restrain contamination. As a result, up to now we have only recognized one 16S rDNA bacterial phylotype with confident relevance to the lake environment. It was found in one sample at 3607 m depth and represents the extant thermophilic facultative chemolithoautotroph Hydrogenophilus thermoluteolus of beta-Proteobacteria, and until now had only been found in hot springs. No confident findings were detected in the sample at 3551 m, and all other phylotypes revealed (a total of 16 phylotypes, 336 clones including controls) are presumed to be contaminants. It seems that the Lake Vostok accretion ice is actually microbe-free, indicating that the water body should also be hosting a highly sparse life. The message of thermophilic bacteria suggests that a geothermal system exists beneath the cold water body of Lake Vostok, what is supported by the geological setting, the long-term seismotectonic evidence from 4He degassing and the ‘18O shift’ of the Vostok accretion ice. The seismotectonic activity that seems to operate in deep faults beneath the lake could sustain thermophilic chemolithoautotrophic microbial communities. Such a primary production scenario for Lake Vostok may have relevance for icy planets and the approaches used for estimating microbial contents in accretion ice are clearly relevant for searching for extraterrestrial life. | ||||
| Programme | 355 | ||||
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| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 2604 | |||
| Permanent link to this record | |||||
| Author | Thébault, E.; Mandea, M.; Schott, J.J. | ||||
| Title | Modeling the lithospheric magnetic field over France by means of revised spherical cap harmonic analysis (R-SCHA) | Type | Journal Article | ||
| Year | 2006 | Publication | Journal of geophysical research-atmospheres | Abbreviated Journal | J. Geophys. Res. |
| Volume | 111 | Issue | Pages | ||
| Keywords | regional modeling; France; magnetic field; 1517 Geomagnetism and Paleomagnetism: Magnetic anomalies: modeling and interpretation; 1545 Geomagnetism and Paleomagnetism: Spatial variations: all harmonics and anomalies; 0545 Computational Geophysics: Modeling | ||||
| Abstract |
We have recently proposed the revised spherical cap harmonic analysis (R-SCHA) modeling technique. The new mathematical functions represent faithfully the spatial variations of potential fields in a restricted area. In this paper, we tackle the inverse problem and outline the efficiency of the new basis functions with respect to real magnetic data. Processing simultaneously repeat stations, observatory, aeromagnetic, and CHAMP satellite data provides our first vector lithospheric field model over France, which extends from surface to 500 km of altitude. The magnetic field is represented with a minimum horizontal spatial representation of 40 km at the mean Earth radius. The magnetic lithospheric map consistency is confirmed with a comparison to known geological features. The model variation with altitude also suggests that the major French magnetic anomaly, the Paris basin anomaly, is produced by a deep-rooted geological structure. These results demonstrate the superiority of regional modeling over global modeling for delineating small-scale details in the lithospheric field. In view of forthcoming satellite missions, like Swarm, the revised spherical cap harmonic analysis method will help to accurately represent the lithospheric field for more detailed geological interpretations. | ||||
| Programme | 905;139 | ||||
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| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | American Geophysical Union | Place of Publication | Editor | ||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0148-0227 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | IPEV @ Thierry.Lemaire @ | Serial | 5617 | ||
| Permanent link to this record | |||||
| Author | W. Lyatsky, G. V. Khanazov, S. Lyatskaya, D. Di Mauro, S. Lepidi, L. Cafarella, A. Chambodut, J.-J. Schott | ||||
| Title | Polar magnetic indices : a new key to correlate magnetic variations in the Earth's hemisphere | Type | Conference - International - Poster | ||
| Year | 2009 | Publication | Abbreviated Journal | ||
| Volume | IAGA 11th Scientific Assembly, 23-30 August 2009 | Issue | Pages | ||
| Keywords | |||||
| Abstract |
We have presented here the results of a statistical study of two polar magnetic indices, computed from data from two near-pole geomagnetic observatories: Thule in the northern hemisphere and new, Concordia (Dome C) observatory near the southern geomagnetic pole in Antarctica. We found that:
The northern PMn and southern PMs polar magnetic indices show a good correlation with the solar wind/IMF parameters (the average correlation coefficient is ~ 0.87). Meanwhile, the southern PMs index shows a significantly better correlation than the northern PMn index, which demonstrates that the new Concordia observatory may play an important role in improving the Space Weather prediction. The obtained results also show a high correlation between these two polar magnetic indices: the average correlation coefficient for this period was ~0.9 while for equinoctial months it increased up to 0.94-0.96. Using the polar magnetic indices in two hemispheres may also significantly improve the prediction of other parameters, including the auroral electrojet AL index which shows substorm activity. Using the polar magnetic indices in two hemispheres allows us to predict the auroral electrojet AL index with a very high reliability (the correlation coefficient between predicted and actual AL indices is ~0.9, while for the equinoctial months the correlation coefficient was ~0.92). The results of this study show an important role which is played by the magnetic disturbances in both polar ionospheres in developing the global magnetic activity, and the necessity to account for the magnetic disturbances in both ionospheres for improving the Space Weather prediction in the Geospace environment. |
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| Programme | 905 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 5745 | |||
| Permanent link to this record | |||||
| Author | W. Lyatsky, G. V. Khanazov, S. Lyatskaya, D. Di Mauro, S. Lepidi, L. Cafarella, A. Chambodut, J.-J. Schott | ||||
| Title | Polar magnetic indices : a new key to correlate magnetic variations in the Earth's hemisphere | Type | Conference - International - Poster | ||
| Year | 2009 | Publication | Abbreviated Journal | ||
| Volume | Issue | Pages | |||
| Keywords | |||||
| Abstract |
We have presented here the results of a statistical study of two polar magnetic indices, computed from data from two near-pole geomagnetic observatories: Thule in the northern hemisphere and new, Concordia (Dome C) observatory near the southern geomagnetic pole in Antarctica. We found that:
The northern PMn and southern PMs polar magnetic indices show a good correlation with the solar wind/IMF parameters (the average correlation coefficient is ~ 0.87). Meanwhile, the southern PMs index shows a significantly better correlation than the northern PMn index, which demonstrates that the new Concordia observatory may play an important role in improving the Space Weather prediction. The obtained results also show a high correlation between these two polar magnetic indices: the average correlation coefficient for this period was ~0.9 while for equinoctial months it increased up to 0.94-0.96. Using the polar magnetic indices in two hemispheres may also significantly improve the prediction of other parameters, including the auroral electrojet AL index which shows substorm activity. Using the polar magnetic indices in two hemispheres allows us to predict the auroral electrojet AL index with a very high reliability (the correlation coefficient between predicted and actual AL indices is ~0.9, while for the equinoctial months the correlation coefficient was ~0.92). The results of this study show an important role which is played by the magnetic disturbances in both polar ionospheres in developing the global magnetic activity, and the necessity to account for the magnetic disturbances in both ionospheres for improving the Space Weather prediction in the Geospace environment. |
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| Programme | 139 | ||||
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| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 5861 | |||
| Permanent link to this record | |||||
| Author | Butler Rhett, Tsuboi Seiji, | ||||
| Title | Antipodal seismic observations of temporal and global variation at Earth's inner-outer core boundary | Type | Journal Article | ||
| Year | 2010 | Publication | Geophysical Research Letters | Abbreviated Journal | |
| Volume | 37 | Issue | 11 | Pages | L11301- |
| Keywords | antipode, Earth, core, 7207 Core, 7203 Body waves, 8115 Core processes, | ||||
| Abstract |
We have found two pairs of earthquake doublets closely located antipodally on one diametral axis between Tonga-Algeria, and several other events on other axes. These doublets show significant correlation, and exhibit seismic phases traversing the Core that cannot be explained by a standard radial Earth model such as PREM. The antipodal waveform data are highly variable between axes. The observed variability of the waveforms indicates global variations in the structure above and below the Inner-Outer Core boundary region. We have found evidence for a regional low-velocity zone at the base of the Outer Core, corresponding with a decadal temporal variation (0.55 s) in seismic energy traversing the top of the Inner Core. We propose an antipodal seismic array to constrain and to provide further progress for the study of the Inner and Outer Core.
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| Programme | 133 | ||||
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| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1944-8007 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 448 | |||
| Permanent link to this record | |||||