Monday 11 October 2010 à 11h00 (Salle de confĂ©rence du bât. 17)
M. A. Mosalam SHALTOUT (National Research Institute of Astronomy and Geophysics, Helwan - Cairo - Egypt)
It is proved from the last 22 years observations of the total solar irradiance (TSI) from space by artificial satellites, that TSI shows negative correlation with the solar activity (sunspots, flares, and 10.7cm Radio emissions) from day to day, but shows positive correlations with the same activity from year to year (on the base of the annual average for each of them). Also, the solar constant, which estimated from ground stations for beam solar radiations observations during the 20th century indicate coincidence with the phases of the 11- year cycles.
It is known from sunspot observations (250 years) , and from C14 analysis, that there are another long-term cycles for the solar activity larger than 11-year cycle. The variability of the total solar irradiance affecting on the climate, and the Nile flooding, where there is a periodicities in the Nile flooding similar to that of solar activity, from the analysis of about 1300 years of the Nile level observations at Cairo. The secular variations of the Nile levels, regularly measured from the 7th to 15th century A.D., clearly correlate with the solar variations, which suggests evidence for solar influence on the climatic changes in the East African tropics.
The civilization of the ancient Egyptian was highly correlated with the Nile flooding , where the river Nile was and still is, the source of the life in the Valley and Delta inside high dry desert area.
The study depends on long-time historical data for Carbon 14 (more than five thousand years), and chronical scanning for all the elements of the ancient Egyptian civilization starting from the first dynasty to the twenty sixth dynasty. The result shows coincidence between the ancient Egyptian civilization and solar activity. For example, the period of pyramids building, which is one of the Brilliant periods, is corresponding to maximum solar activity, where the periods of occupation of Egypt by Foreign Peoples corresponding to minimum solar activity. The decline of the Kingdoms in ancient Egypt and occurrence of the intermediate periods are generally explained by very low Nile floods and prolonged droughts followed by severe famines and the destruction of the political structure. The study clarifies the role of solar activity on the climatic change, and the humankind history.
Tuesday 28 September 2010 à 11h00 (Salle de confĂ©rence du bât. 17)
Ian Waite (University of Southern Queensland, Toowoomba, Australia)
The Semel Polarimeter, developed by Meir Semel from LESIA, has been in use as a visitor instrument on the Australian Astronomical Telescope for the past 20 years to map the magnetic fields around various types of stars to produce a wealth of scientific results. Magnetic fields play a crucial role in the evolution of these stars. The key questions that we are currently investigating are “How do young stars actually generate magnetic fields and at what stage do these stars begin to produce solar-like magnetic cycles?”. Using the technique of Zeeman Doppler imaging we have mapped the magnetic field topology of a small number of young Sun-like stars at multiple epochs. This presentation outlines recent results from these observations and discusses implications for magnetic field generation and its evolution as these stars attempt to undergo magnetic reversals prior to the onset of the more familiar solar-like cycles.
Co-author: Stephen Marsden(University of Southern Queensland & James Cook University)
