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.

Abstract: Internal temperature is an essential parameter for understanding ice sheet dynamics. Glaciological models provide estimations of temperature profiles over Antarctica and few boreholes are also available, but, at present, no measurement exists at the scale of the whole continent. The analysis of passive L-band observations from the Soil Moisture and Ocean Salinity (SMOS) satellite shows that, thanks to the high penetration depth (i.e. up to 1500?m), it is possible to infer information on in depth glaciological properties of the ice sheet including temperature. In this study, the temperature profile is retrieved from SMOS observations using jointly glaciological and emission models. The developed methodology is valid in the inner part of Antarctica where the ice sheet is almost stable (i.e. its velocity is limited to 10?m?yr?1). This analysis points out that in several cases, differences are observed between retrieved temperature profiles and those predicted by glaciological models. In particular, some geophysical parameters, namely the geothermal heat flux and the mean annual accumulation, need to be modified with respect to their prior values in order to simulate SMOS brightness temperatures. Results also clearly show that the reliability of the retrieved profile in depth decreases with increasing ice thickness due to the limited penetration of microwaves in the ice. The obtained results prove the capability of L band (1.4?GHz) passive microwave sensors for investigating the internal temperature of the ice-sheet.

Abstract: This work investigates the impact of Forbush decrease (FD) and ground-level enhancement (GLE) in the atmosphere, based on solar and galactic cosmic-ray models and the extensive air shower simulations. This approach gives the possibility to investigate both the dynamic behavior of neutron monitors (NM) (using response function) and the flight dose. The ambient dose equivalent during quiet solar activity and solar events (i.e., FDs and GLEs) were investigated for realistic flight plans issued from the Eurocontrol Demand Data Repository. The calculated ambient dose equivalents were compared with flight measurements in quiet solar conditions; comparisons are relevant and demonstrate the ability to estimate the dose level. The GLE model was validated for the GLEs 5 and 69 using the cosmic-ray variation recorded by NMs. The GLE model was applied to flight dose calculations. All of these results show that dose values vary drastically with the route path (latitude, longitude and altitude) and with the delay between the flight departure and the solar event occurrence. Doses induced by extreme GLE events were investigated specifically for London to New York flights, and resulting additional doses are a few hundred or 1,000 ?Sv, impacting significantly the annual effective dose. This highlights the importance of monitoring extreme solar events and using realistic semi-empirical and particle transport methods for reliable calculation of dose levels.