06/07/02
Lefebvre Sandrine	OCA/CERGA
Avenue Copernic	PNST-
06130	Grasse, France

Presentation 1 : Poster
Latitudinal variations : from the observations to the theory.
LEFEBVRE S. and ROZELOT J. P.
Since more than 25 years are gathered solar diameter measurements obtained from ground-based observatories that can be used to detect any temporal variations (not yet concluding, in phase or out of phase with the solar cycle according to the observation site) but also departures from the sphericity shown by latitudinal variations. This last feature seems know undoubted by comparison of all available data sets. Moreover a space experiment, known as PICARD, a CNES microsatellite expected to be launched by 2006-2007, will have as one of its main objectives the measurement of such latitudinal dependence. This mission is completed by a ground program composed of SODISM II, a replica of the space experiment, MISOLFA, a diurnal seeing monitor, and MIRESOL. The main goal of this last device is to study the contamination by spots and faculae at the limb, in order to sort diameters by classes of quiet Sun. We are currently elaborating a theory capable to explain the observed differential latitudinal distortions.

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