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Frey, M. M., J. Savarino, S. Morin, and J. Erbland. (2009). A chemical fingerprint of surface UV in the 20th century firn record of nitrate stable isotopes at Dome C, East Antarctica,.
Abstract: EGU General Assembly, poster, Abstract EGU2009-8637
Programme: 1011
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Morin, S., J. Savarino, M. M. Frey, and J. Erbland. (2009). Atmospheric photochemistry of ozone, nitrogen oxides and nitrate from an isotopic viewpoint (Vol. Invited introductory lecture).
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Fort Jérôme, Warren P. Porter and David Grémillet. (2009). Thermodynamic modelling predicts energetic bottleneck for seabirds wintering in the northwest Atlantic.
Abstract: Seabird Group 10th International Conference
Programme: 388
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Fotzé M., Bernard A., Durand J., Chambodut A. and Schot J.J. (2007). New acquisition systems in French austral magnetic observatories.
Abstract: Poster at XIV Assembly of IUUG, Pérouges, 2-13 July 2007
Programme: 905
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Schott J.J. (2007). Progresses and challenges in magnetic observatory operation.
Abstract: The description of the recent progresses in ground based magnetic observatory operation encompasses
several aspects: instrumentation, acquisition, accuracy estimation, data processing, data transmission, opening of new observatories. In the present state of the art, manual absolute measurements remain the most accurate way of controlling the base lines of the magnetometers, whatever their type. Their obvious drawback is that the observatories have to be operated by a trained observer. This condition may be difficult to fulfil in remote areas. In addition, economic pressure may result in a reduction of the observer staffs. Efforts are made for several years towards more automatization of the absolute measurements. Two recently proposed solutions (Rasson and Van Loo, one one hand, Auster et al. on the other hand) will be discussed. Both solutions, however, still need the presence of an observer. The most elegant way of solving the problem would be to imagine continuous recording absolute magnetometers. An idea, originally proposed by Alldredge (1960) led to the development of the DIDD instrument (Hegymegi, Krmendi). Although many improvements were brought to the successive versions, it still requires manual base line controls. In addition, the instrumental reference frame is not easy to determine. More recently, a new concept was implemented, based upon the modulation of the signal of an optical pumping magnetometer by two orthogonal coils (Gavrand et al.,2001 ). Although it should be more stable than the DIDD system, similar problems arise with the orientation of the instrument. Numerical acquisition, based upon some kind of data logger, is now the standard, the typical reference being the Intermagnet network. Currently, concerns focus on resolution, sampling rate and time stamp. These issues become particularly crucial with the solicitation for moving towards subminute – typically one second- sampling rates. Worldwide synchronized one second data (in addition properly filtered) acquisition and dissemination will probably be a big challenge for the next future. Even data processing and accuracy estimation for the current one minute sampling rate have not yet reached their mature estate. Efforts have still to be made towards a more homogeneous processing protocol and accuracy estimation based upon safe statistical methods. The last issue includes sensor orientation and calibration aspects. Various calibration methods are regularly suggested but the sensor orientation
problem is probably underestimated. Finally, we will evoke the efforts made towards a more homogeneous worldwide distribution of ground-based observatories with a particular emphasis on observatories opened or planned in remote areas. However, it is obvious that due to the poor distribution of emerged lands, this endeavor will remain limited. Extending the netword to ocean bottom observatories could be an exciting challenge for the next future, although technically difficult and financially demanding.
Programme: 139
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Hamoudi M., Lesur V.,Chambodut A.,Thébault E., Quesnel Y. and Mandea M. (2007). Spectral Analysis of the Global Lithospheric Magnetic Anomaly Field derived from Airborne, shipborne, and satellite Data.
Abstract: Several candidate grids were submitted for evaluation in the framework of the World Digital Magnetic
Anomaly Map (WDMAM) project. A standard way of evaluating the final grids is to compare them with
original gridded data in order to verify that the geomagnetic information have been properly secured
during the final stage of the processing. Nevertheless, the original data and grids used for the WDMAM have themselves heterogeneous qualities and resolutions and the lack of metadata information about the raw data makes it difficult to assess the consistency and the resolution of the magnetic anomalies everywhere.In this paper, we use the Geoforschungszentrum MAgnetic Anomaly Map (GAMMA)
candidate grid as an input to derive a spherical harmonic model to degree and order 500 .The harmonic decomposition allows to analyze the global magnetic spectrum of the map. The results are then compared to local wavelet spectral analysis of the grid in order to find out the effective spectral content of the WDMAM and to obtain some constrains on the source depths and Curie isotherm determination. This extra information will prove useful for more cautious geological interpretations based on the WDMAM grid.
Programme: 139
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Minchev B., Chambodut A., Holschneider M. and Mandea M. (2007). Global magnetic field modelling using local multipolar expansions.
Abstract: EGU, April 2007, Vienne (AT).
Programme: 139
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Chambodut A., Hamoudi M., Thebault E. & Lesur V. (2008). Spectral analysis of the World Digital Magnetic Anomaly Map.
Abstract: EGU, April 2008, Vienna, Austria.
Programme: 139
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W. Lyatsky, G. V. Khanazov, S. Lyatskaya, D. Di Mauro, S. Lepidi, L. Cafarella, A. Chambodut, J.-J. Schott. (2009). Polar magnetic indices : a new key to correlate magnetic variations in the Earth's hemisphere.
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.
Programme: 139
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Masson, S., Klein, K.-L., Buetikofer, R., Flueckiger, E., Kurt, V., Yushkov B. & Krucker, S. (2009). Acceleration of Relativistic Protons during the 20 January 2005 Flare and CME. SOLAR PHYSICS, 257, 305.
Abstract: The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far. We perform a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event of 20 January 2005. The intensity – time profile of the relativistic protons derived from the neutron monitor data indicates two successive peaks. We show that microwave, hard X-ray, and ! -ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion-decay ! rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures of particle acceleration in the corona within !1R" above the photosphere, revealed by hard X-ray and microwave emissions of low intensity and by the renewed radio emission of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration in the corona.
Programme: 227
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