ROZELOT , Jean-Pierre

The Pic du Midi Turret-Dome, known as ''Lunette Jean Rösch'' or LJR (''lunette'' for refractor in French), was scientifically active during five decades between 1960 and 2010. It was dedicated to high spatial resolution observations in solar astronomy. We review fifty years of advances in solar instrumentation and solar physics made by this...

Shrinking or expansion of the solar shape and irradiance variations are ultimately related to solar activity. We give here a review on existing ground-based or space solar radius measurements, extending the concept to shape changes. We show how helioseismology results allow us to look at the variations below the surface, where changes are not...

Early attempts to find how solar activity can influence the Earth's climate involved comparison of many physical processes, such as dynamo mechanism, magnetic reconnection and eruptive activity, irradiance, open flux and particles variations, global atmospheric chemistry and dynamics.. . . However, such direct links seem to be weak even if the...

The perihelion advance of the orbit of Mercury has long been one of the observational cornerstones for testing General Relativity (G.R.). The main goal of this paper is to discuss how, presently, observational and theoretical constraints may challenge Einstein's theory of gravitation characterized by $\beta =\gamma =1$. To achieve this purpose,...

Rotation, and more precisely differential rotation, have a major impact on the internal dynamics of stars (and the Sun) and induce many instabilities driving the transport of angular momentum. In the present paper we shall consider the effects on the shape of shellular layers, and to first order, these concerning the apparent oblateness. The...

Regular measurements of the Sun's diameter have been obtained by means of solar astrolabes for several decades. However, the variations found from those measurements are still very controversial, and the results implying changes in the solar radius are not conclusive. Since the quality of the measurements cannot be doubted, it is necessary to...

We consider a binary system composed of a pulsar and a massive, fast rotating, highly distorted main sequence star of mass M, spin angular momentum $\mathbf S $ , dimensionless mass quadrupole moment $J_2$ , equatorial and polar radii $R_\text {e},~R_\text {p}$ , flattening $\nu \doteq (R_\text {e}-R_\text {p})/R_\text {e}$ , and ellipticity...

Rotation, and more precisely differential rotation, has a major impact on the internal dynamics of stars (and the Sun) and induces many instabilities driving the transport of angular momentum. In this chapter we shall consider these effects on the shape of shelllular layers, and to first order, those concerning the apparent oblateness. Thanks...

We hereby present a review on solar oblateness measurements. By emphasizing historical data, we illustrate how the discordance between experimental results can lead to substantial improvements in the building of new technical apparatus as well as to the emergence of new ideas to develop new theories. We stress out the need to get accurate data...

The long term solar activity dependencies of ionospheric F1 and F2 regions' critical frequencies (f0F1 and f0F2) are analyzed for the last four solar cycles (1976-2015). We show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (f0F1) peaks...