Observed Variations of the Solar Diameter in 1998/2000

摘要: The results from 9112 independent measurements of the solar diameter, made between years 1998 and 2000, at Observatorio Nacional Rio de Janeiro station, are examined. After removal isolated observations correction systematic effects, series presents a well-defined normal distribution with standard deviation 566 milli-arc-seconds (mas). east west results, which were taken under quite different atmospheric instrumental conditions, have been treated separately smoothed correlate level 80%. figure as charted these data diverges perfect sphere by mid-heliolatitude depletion 50 mas, an overall flatness, to effect polar radius being shorter than equatorial 13±4 mas. Finally, significant periodic variation around 515 days is found for observed amplitude 60