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Do Rosario Valentin. (2020). Ecological, biological and physiological effects of climate change on insect species. Master 1 EFCE, Université de Rennes 1 (Encadrement : D. Renault).
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Chelsea Ward. (2020). Examining the effect of experimentally induced stress and the stress response on eye region surface temperature in wild king penguins (Aptenodytes patagonicus) (supervisors P Bize and A Lewden).
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Moynard Fanny. (2020). L’exposition des insectes aux insecticides accroît-elle leur sensibilité au réchauffement climatique? Master 1 EFCE, Université de Rennes 1 (Encadrement: D. Renault).
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Eymar-Dauphin Pauline. (2020). Réponses des plantes aquatiques des Iles Kerguelen à l’intensification des contraintes thermiques de leur habitat. Approche par les hypervolumes. Master 2 ECOMONT, Université de Savoie Mont-Blanc (encadrement : A.-K. Bittebiere).
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Korbinian Sager, Christian Boehm, Laura Ermert, Lion Krischer, Andreas Fichtner. (2020). Global-Scale Full-Waveform Ambient Noise Inversion (Vol. 125).
Abstract: We present the first application of full-waveform ambient noise inversion to observed correlation functions that jointly constrains 3-D Earth structure and heterogeneous noise sources. For this, we model and interpret ambient noise correlations as recordings of correlation wavefields, which completely eliminates the limiting assumptions of Green's function retrieval, such as equipartitioning and homogeneous random noise sources. Our method accounts for seismic wave propagation physics in 3-D heterogeneous and attenuating media and also for the heterogeneous and nonstationary nature of the ambient noise field. Designed as a proof of concept, the study considers long periods from 100 to 300 s, thus focusing on the Earth's hum. Treating correlations as self-consistent observables allows us to make separate measurements on the causal and acausal branches of correlation functions, without any need to choose one of them or form the average. We validate our approach by assessing the quality of the obtained models and by comparing them to previous studies. This work is a step toward the establishment of full-waveform ambient noise inversion as a tomographic technique with the goal to go beyond ambient noise tomography based on Green's function retrieval.
Keywords: computational seismology full-waveform inversion global tomography interferometry seismic noise
Programme: 133
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F. Pitout, A. Marchaudon, K. J. Trattner, J. Berchem, H. Laakso, C. P. Escoubet. (2020). Simultaneous Polar and Cluster Observations in the Northern and Southern Middle-Altitude Polar Cusps Around Equinox (Vol. 125).
Abstract: We present an event of simultaneous observations of the northern and southern middle-altitude polar cusps by the Polar spacecraft and Cluster fleet that occurred on 23 September 2004. We examine the possible asymmetries in the fields and plasma parameters, although the proximity of the equinox should limit these asymmetries. Ion sensors reveal two dispersions in both cusps, and data analysis leads to the conclusion that those dispersions are due to pulsed reconnection at a single X-line, which runs along the subsolar magnetopause. While the electromagnetic and particle energy fluxes injected in both cusp are globally very similar, we report significant differences in ion dispersions, width of the low-latitude boundary layer, and peak convection velocities. We ascribe these differences to the dipole tilt that introduces an asymmetry in the magnetosheath flow at the exterior cusps.
Keywords: dayside magnetosphere hemispheric asymmetry polar cusp
Programme: 312
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Léo Bosse, Jean Lilensten, Nicolas Gillet, Sylvain Rochat, Alain Delboulbé, Stephane Curaba, Alain Roux, Yves Magnard, Magnar G. Johnsen, Unni-Pia Løvhaug, Pierre-Olivier Amblard, Nicolas Le Bihan, Maxime Nabon, Hanane Marif, Frédérique Auriol, Camille Noûs. (2020). On the nightglow polarisation for space weather exploration (Vol. 10).
Abstract: We present here observations of the polarisation of four auroral lines in the auroral oval and in the polar cusp using a new ground polarimeter called Petit Cru. Our results confirm the already known polarisation of the red line, and show for the first time that the three other lines observed here (namely 557.7 nm, 391.4 nm and 427.8 nm) are polarised as well up to a few percent. We show that in several circumstances, this polarisation is linked to the local magnetic activity and to the state of the ionosphere through the electron density measured with EISCAT. However, we also show that the contribution of light pollution from nearby cities via scattering can not be ignored and can play an important role in polarisation measurements. This series of observations questions the geophysical origin of the polarisation. It also leaves open its relation to the magnetic field orientation and to the state of both the upper atmosphere and the troposphere.
Keywords: polarisation / aurora
Programme: 1026
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Crouzet N., Guillot T., Abe L., Mékarnia D., Agabi K., Bresson Y., Bailet C., Mauclert N., Heras A., Ferruit P., Triaud A., Lagrange A., Schmider ., Giardino G., Isaak K., Kohley R., Michalik D., Foing B., Pilbratt G., Stankov A., Gondoin P., Birkmann S., O'Rourke L. (2020). Two-colour photometry to search for transiting exoplanets with ASTEP at Dome C, Antarctica.
Abstract: Dome C in Antarctica provides exceptional conditions for photometry thanks to the continuous night during the Antarctic winter, a high clear sky fraction, low wind speeds, and a cold and dry atmosphere. The ASTEP project (Antarctic Search for Transiting ExoPlanets) aims at detecting and characterising transiting exoplanets and qualifying this site for photometry in the visible. The main instrument, a 40 cm telescope, has been designed to perform high precision photometry under the extreme conditions of the Antarctic winter and has operated at the Concordia station since 2010. It will be upgraded with two new cameras and a new camera box in order to provide simultaneous two-colour photometry and substantially increase its throughput. The new setup will be operational for the winter campaign 2021 and will allow us to discover transiting exoplanets orbiting bright stars in particular low mass exoplanets, temperate exoplanets, exoplanets around young stars, and to refine the ephemerides of exoplanets discovered by the TESS mission. These observations will provide targets for first characterisation with the CHEOPS mission and atmospheric studies with the JWST and ARIEL missions. In this talk, I will describe the science goals and the upgrade of the ASTEP telescope.
Programme: 1066
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E. Aristidi, A. Agabi, L. Abe, E. Fossat, A. Ziad, D. Mékarnia. (2020). Dome C coherence time statistics from DIMM data (Vol. 496).
Abstract: We present a reanalysis of several years of DIMM data at the site of Dome C, Antarctica, to provide measurements of the coherence time $\tau0$. Statistics and seasonal behaviour of $\tau0$ are given at two heights above the ground, 3m and 8m, for the wavelength $\lambda=500$nm. We found an annual median value of $2.9$ms at the height of 8m. A few measurements could also be obtained at the height of 20m and give a median value of 6ms during the period June--September. For the first time, we provide measurements of $\tau0$ in daytime during the summer, which appears to show the same time dependence as the seeing with a sharp maximum at 5pm local time. Exceptional values of $\tau0$ above 10ms are met at this particular moment. The continuous slow variations of turbulence conditions during the day offers a natural test bed for a solar adaptive optics system.
Keywords: Astrophysics – Instrumentation and Methods for Astrophysics
Programme: 1066
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Crouzet N., et al. (2020). Towards a two-colour photometer at Dome C, Antartica.
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