سخنرانی علمی : اختر فیزیک (فیزیک خورشید)
سخنران : پروفسور سرژ کوچمی ، انسیتوی اختر فیزیک پاریس - یکشنبه 2 آذر ساعت 10 صبح
During the last decades, considerable efforts have been devoted to the analysis of possible climatic effects of the irregular activity cycles of the Sun, through solar forcing effects. Why such interest and how to reach this goal? Long term variations of the Solar Diameter could indeed be a significant factor; more than 1.5 century long efforts will be summarized leading to the question of the solar diameter variations. The absolute value of the solar diameter is still measured at Ground-based and in Space, without a definite answer and without improving the canonic value visually deduced at the end of the 19th century. Using the Moon as a cosmic etalon, many attempts were made at past Solar Total eclipses. We show how indeed the solar edge is not even well known and/or understood; the result of an experiment aimed at looking at the spectrum of the edge of the Sun is evaluated for different distances near the extreme-limb. The importance of faint low FIP lines and other emission lines is discussed. Finally the calibration of the relief of the Moon is an ultimate limitation at eclipses that is not yet reached and similarities exist with the calibration of instrumental effects in large telescopes. We emphasize the importance of including the amount of stray-light and of the smearing for correcting the best observed photometric very high resolution data, including those deduced fr0m Space.