Solar Electromagnetic Radiation Study For Solar Cycle 22

Measurements of solar irradiance, both bolometric and at various wavelengths, over the last two decades have established conclusively that the solar energy flux varies on a wide range of time scales, from minutes to the 11-year solar cycle. The major question is how the solar variability influences the terrestrial climate. The Solar Electromagnetic Radiation Study for Solar Cycle 22 (SOLERS22) is an international research program operating under the auspices of the Solar-Terrestrial Energy Program (STEP) Working Group 1: `The Sun as a Source of Energy and Disturbances'. STEP is sponsored by the Scientific Committee of Solar-Terrestrial Physics (SCOSTEP) of the International Council of Scientific Unions (ICSU). The main goal of the SOLERS22 1996 Workshop was to bring the international research community together to review the most recent results obtained from observations, theoretical interpretation, empirical and physical models of the variations in the solar energy flux and their possible impact on climate studies. These questions are essential for researchers and graduate students in solar-terrestrial physics.

The IAU Colloquium No. 143 "The Sun as a Variable Star: Solar and Stellar Irradiance Variations" was held on June 20 - 25, 1993 at the Clarion Harvest House, Boulder, Colorado, USA. The main objective of this Colloquium was to review the most recent results on the observations, theoretical interpreta tions, and empirical and physical models of the variations observed in solar and stellar irradiances. A special emphasis of the Colloquium was to discuss the results gained on the climatic impact of solar irradiance variability. The study of changes in solar and stellar irradiances has been of high interest for a long time. Determining the absolute value of the luminosity of stars with different ages is a crucial question for the theory of stellar evolu tion and energy production of stellar interiors. Observations of the temporal changes of solar and stellar irradiances - in the entire spectral band and at different wavelengths - provide an additional tool for studying the physical processes below the photosphere and in the solar- stellar atmospheres. Since the Sun's radiative output is the main driver of the physical processes with in the Earth's atmosphere, the study of irradiance changes is an extremely important issue for climatic studies as well. Climatic models show that small, but persistent changes in solar irradiance may influence the Earth's climate.

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

The message of sunspots from the interior of the Sun to the Earth's climate When Galileo was summoned before the Inquisition on April 12, 1633, the main accusations laid against him concerned the doubts he expressed about Aristotle's theory of the universe. Aristotle's idea was that the Earth was the centre of the cosmos and that all of the stars, including the Sun, turned around it. Moreover, for Aristotle and the world of the Inquisitors, the Sun was a perfect celestial body. Now, Galileo had discovered spots on the Sun. These spots were seen as imperfections, and not just surface markings, but coming from within the Sun. Worse yet, they revolved around the Sun. All this supported the newfangled theory of Copernicus, and undermined a system of thought that had reigned supreme for centuries. Man of science that he was, and a prudent Catholic too, Galileo strived all his life to prove that Copernicus' astronomical concept was compatible with the word of the Bible. He proposed that there were not two truths but a single divine truth. It was just expressed in two different languages : there was the language of the common people, with its imprecision and inconsistencies, but intuitively understandable by everyone; and then there was the precise language of science with its strict regard for observation, which only a chosen few can grasp [L. Geymonat. 1992].

The worldwide community of solar-terrestrial scientists has embarked on an exciting and intellectually rewarding project - to understand quantitatively the linkage from the Sun through the interplanetary medium and into the depths of our surrounding geospace. The variety and complexity of the physical processes involved in these linkages have stood as a challenge to mankind's understanding for centuries. Through a concerted global effort, the Solar-Terrestrial Energy Program (STEP) has begun to use remarkable new observational tools and modelling capabilities to achieve an unprecedented comprehension of our solar-terrestrial system. STEP has been designed to study the flow of energy starting from the Sun, tracking that energy as it progressed through the interplanetary medium into the magnetosphere-ionosphere system and ultimately through the thermosphere and middle atmosphere to regions adjacent to the Earth's surface. This volume contains a selection of articles presented at the first major STEP Symposium on The Initial Results from the STEP Facilities and Theory Campaigns, and represents the state-of-the-art in the comprehension of solar-terrestrial environments.

The present Proceedings contain a selection of papers and posters con- tributions presented at the Improved Quality of Service in Ionospheric Tele- communications Systems Planning and Operation (IITS) -COST 251 Workshop 1998 on "Procedures and testing of the models for ionospheric telecommuni- cations applications" in INTA-El Arenosillo, Mazagón-Moguer-Huelva, Spain. As usual the Reports of the Session Chairperson have been included as far as they were made available.