IKHLEF , R.

In this work we study in details the influence of pure astronomical refraction on solar metrological measurements made from ground-based full disc imagery and provide the tools for correcting the measurements and estimating the associated uncertainties. For a given standard atmospheric model, we first use both analytical and numerical methods...

The Franco-Algerian Monitor of Solar Images (MISOLFA) was developped in order to study the effect of optical turbulence on diameter measurements from ground-based solar observations. Some first results obtained with MISOLFA are presented.

The potential relationship between solar activity and changes in solar diameter remains the subject of debate and requires both models and measurements with sufficient precision over long periods of time. Using the PICARD instruments, we carried out precise measurements of variations in solar diameter during the rising phase of solar cycle 24....

Context. In 2015, the International Astronomical Union (IAU) passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined a new value of the nominal solar radius (R N = 695 700 km) that is different from the canonical value used until now (695 990 km). The nominal solar...

For the past thirty years, modern ground-based time-series of the solar radius have shown different apparent variations according to different instruments. The origins of these variations may result from the observer, the instrument, the atmosphere, or the Sun. Solar radius measurements have been made for a very long time and in different ways....

PICARD is a space mission launched in June 2010 to study mainly the geometry of the Sun. The PICARD mission has a ground program consisting mostly in four instruments based at the Calern Observatory (Obser-vatoire de la Côte d'Azur). They allow recording simultaneous solar images and various atmospheric data from ground. The ground instruments...

For the last thirty years, ground time series of the solar radius have shown different variations according to different instruments. The origin of these variations may be found in the observer, the instrument, the atmosphere and the Sun. These time series show inconsistencies and conflicting results, which likely originate from instrumental...