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International audience; A critical problem in determining the climate impact of solar radiative forcing on decadal time scales is the paucity of properly calibrated observations. Total irradiance observations started in the 1980s only, and their long-term trend is still subject to debate. Reconstructions further back into the past mostly rely on the sunspot number, which suffers from being only loosely connected to the radiative output of the Sun. However, radio observations in the centimetric range have been made since the early 1950s at several wavelengths, and with highly stable receivers, thus providing a unique record of past solar activity. So far only the 10.7 cm has been routinely used, whereas the other wavelengths have been almost totally ignored. We have collected these daily radio observations at five wavelengths (3.2 to 30 cm) into a single composite dataset. By using blind source separation, we are able to decompose the variability on time scales of months, and below, into three components; these can be readily ascribed to thermal bremsstrahlung, and to gyroresonant emissions. We find that the 30 cm radio flux is a better proxy for the specification of the upper atmosphere than the better known 10.7 cm flux, presumably because it has a stronger bremsstrahlung contribution. This is confirmed by comparing the modelled and the observed neutral density of the thermosphere, using the DTM2012 drag temperature model. When considering long-term variations, we find tiny but significant differences between the various wavelengths, which allow us to constrain the variability of the solar UV forcing since the early 1950s. Particular attention will be given here to the possible existence of long-term trends and their relevance to climate studies.

The Nançay Radioheliograph, upgraded in 1996, is specifically devoted to the study of the sporadic activity of the Sun, in the metric and decimetric radio band. Low contrast structures of the quiet Sun are also studied, using an aperture synthesis method.I present the first results of the aperture synthesis method designed for the new instrument, focusing on the radio counterpart of solar filaments, never described in this radio band. These observations agree with the presence of a coronal cavity surrounding filaments, which is observable directly on the disk.Finally, I present three cases of filament eruptions allowing, for the first time, the observation of thermal counterparts of filaments eruptions and CME initions on the disk. This work was supported by multi-wavelengths observations performed by the SOHO spacecraft, and especially by the EIT and LASCO instruments., Le Radiohéliographe de Nançay, rénové en 1996, est un instrument dédié à l'étude de l'activité sporadique de la couronne solaire, dans le domaine métrique et décimétrique. Les structures calmes de la couronne peuvent être également observées par l'utilisation de la synthèse d'ouverture, qui autorise la cartographie de structures à faible contraste.Je présente dans cette thèse les premiers résultats de synthèse d'ouverture pour l'instrument rénové, en m'intéressant tout particulièrement à la contrepartie radio des filaments solaires, jamais étudiée auparavant dans cette gamme de longueur d'onde. Je montre que les observations sont explicables par la présence d'une cavité coronale autour des filaments, et que la radio permet son observation directe sur le disque.Je décris enfin trois cas de Disparitions Brusques de filament montrant, pour la première fois en radio, les stades initiaux du développement d'éruptions de filaments et de CMEs sur le disque, sous l'aspect des émissions thermiques. Ce travail s'appuie fortement sur les observations multi longueurs d'onde, rendues possibles par l'existence du satellite SOHO sur toute la période, et notamment son télescope EIT, et son coronographe LASCO.

The Nançay Radioheliograph, upgraded in 1996, is specifically devoted to the study of the sporadic activity of the Sun, in the metric and decimetric radio band. Low contrast structures of the quiet Sun are also studied, using an aperture synthesis method.I present the first results of the aperture synthesis method designed for the new instrument, focusing on the radio counterpart of solar filaments, never described in this radio band. These observations agree with the presence of a coronal cavity surrounding filaments, which is observable directly on the disk.Finally, I present three cases of filament eruptions allowing, for the first time, the observation of thermal counterparts of filaments eruptions and CME initions on the disk. This work was supported by multi-wavelengths observations performed by the SOHO spacecraft, and especially by the EIT and LASCO instruments.; Le Radiohéliographe de Nançay, rénové en 1996, est un instrument dédié à l'étude de l'activité sporadique de la couronne solaire, dans le domaine métrique et décimétrique. Les structures calmes de la couronne peuvent être également observées par l'utilisation de la synthèse d'ouverture, qui autorise la cartographie de structures à faible contraste.Je présente dans cette thèse les premiers résultats de synthèse d'ouverture pour l'instrument rénové, en m'intéressant tout particulièrement à la contrepartie radio des filaments solaires, jamais étudiée auparavant dans cette gamme de longueur d'onde. Je montre que les observations sont explicables par la présence d'une cavité coronale autour des filaments, et que la radio permet son observation directe sur le disque.Je décris enfin trois cas de Disparitions Brusques de filament montrant, pour la première fois en radio, les stades initiaux du développement d'éruptions de filaments et de CMEs sur le disque, sous l'aspect des émissions thermiques. Ce travail s'appuie fortement sur les observations multi longueurs d'onde, rendues possibles par l'existence du satellite SOHO sur toute la période, et notamment son télescope EIT, et son coronographe LASCO.

On November 4th, 2015 secondary air traffic control radar was strongly disturbed in Sweden and some other European countries. The disturbances occurred when the radar antennas were pointing at the Sun. In this paper, we show that the disturbances coincided with the time of peaks of an exceptionally strong (∼105 Solar Flux Units) solar radio burst in a relatively narrow frequency range around 1 GHz. This indicates that this radio burst is the most probable space weather candidate for explaining the radar disturbances. The dynamic radio spectrum shows that the high flux densities are not due to synchrotron emission of energetic electrons, but to coherent emission processes, which produce a large variety of rapidly varying short bursts (such as pulsations, fiber bursts, and zebra patterns). The radio burst occurs outside the impulsive phase of the associated flare, about 30 min after the soft X-ray peak, and it is temporarily associated with fast evolving activity occurring in strong solar magnetic fields. While the relationship with strong magnetic fields and the coherent spectral nature of the radio burst provide hints towards the physical processes which generate such disturbances, we have so far no means to forecast them. Well-calibrated monitoring instruments of whole Sun radio fluxes covering the UHF band could at least provide a real-time identification of the origin of such disturbances, which reports in the literature show to also affect GPS signal reception., Journal of Space Weather and Space Climate, 8