Seasonal variation in the solar diurnal tide and its possible influence on the atmospheric sodium layer

In a paper published 12 years ago, we showed that the height of the atmospheric sodium layer at our location is about 1 km lower in November than at any other time of the year. We also showed that the decrease in height of the sodium layer was accompanied by an increase in the intensity of the OI 557.7 nm and OH(9,4) band airglow emissions. At that time we suggested that this behavior could be the result of large scale convective transport in the MLT region. We have now had the opportunity to compare the diurnal variations of the sodium layer and airglow emissions with the tidal winds measured by meteor radar over the past 5 years. We find that the amplitude of the diurnal tide is much smaller in November than at other times of the year. Since most of the sodium measurements and all of the airglow observations are for night-time conditions only, a change in the amplitude of the 24-h tide could strongly influence the average measured sodium and airglow parameters. It is shown that the observed changes in the tidal winds are qualitatively consistent with the sodium measurements, but the amplitude of the observed height change is much greater than would be expected from the tidal winds.     

ALTEA: anomalous long term effects in astronauts. A probe on the influence of cosmic radiation and microgravity on the central nervous system during long flights.

The ALTEA project participates to the quest for increasing the safety of manned space flights. It addresses the problems related to possible functional damage to neural cells and circuits due to particle radiation in space environment. Specifically it aims at studying the functionality of the astronauts' Central Nervous Systems (CNS) during long space flights and relating it to the peculiar environments in space, with a particular focus on the particle flux impinging in the head. The project is a large international and multidisciplinary collaboration. Competences in particle physics, neurophysiology, psychophysiology, electronics, space environment, data analyses will work together to construct the fully integrated vision electrophysiology and particle analyser system which is the core device of the project: an helmet-shaped multi-sensor device that will measure concurrently the dynamics of the functional status of the visual system and passage of each particle through the brain within a pre-determined energy window. ALTEA is scheduled to fly in the International Space Station in late 2002. One part of the multi-sensor device, one of the advanced silicon telescopes, will be launched in the ISS in early 2002 and serve as test for the final device and as discriminating dosimeter for the particle fluences within the ISS.