After constructing a number of simple antennas for solar work at Nancay field station, during the second half of the 1950s and through into the 1960s radio astronomers from the Paris Observatory (Meudon) erected five different innovative multi-element arrays. Three of these operated at 169 MHz, a fourth at 408 MHz and the fifth array at 9,300 MHz. While all of these radio telescopes were used for solar research, one of the 169 MHz arrays was used mainly for galactic and extra-galactic research. In this paper we discuss these arrays and summarise the science that was achieved with them during this important period in the development of French radio astronomy.

This paper will review the input of 65 years of radio observations to our understanding of solar and solar–terrestrial physics. It is focussed on the radio observations of phenomena linked to solar activity in the period going from the first discovery of the radio emissions to present days. We shall present first an overview of solar radio physics focussed on the active Sun and on the premices of solar–terrestrial relationships from the discovery to the 1980s. We shall then discuss the input of radioastronomy both at metric/decimetric wavelengths and at centimetric/millimetric and submillimetric wavelengths to our understanding of flares. We shall also review some of the radio, X-ray and white-light signatures bringing new evidence for reconnection and current sheets in eruptive events. The input of radio images (obtained with a high temporal cadence) to the understanding of the initiation and fast development in the low corona of coronal mass ejections (CMEs) as well as the radio observations of shocks in the corona and in the interplanetary medium will be reviewed. The input of radio observations to our knowledge of the interplanetary magnetic structures (ICMEs) will be summarized; we shall show how radio observations linked to the propagation of electron beams allow to identify small scale structures in the heliosphere and to trace the connection between the Sun and interplanetary structures as far as 4AU. We shall also describe how the radio observations bring useful information on the relationship and connections between the energetic electrons in the corona and the electrons measured in-situ. The input of radio observations on the forecasting of the arrival time of shocks at the Earth as well as on Space Weather studies will be described. In the last section, we shall summarize the key results that have contributed to transform our knowledge of solar activity and its link with the interplanetary medium. In conclusion, we shall indicate the instrumental radio developments at Earth and in space, which are from our point of view, necessary for the future of solar and interplanetary physics.

In this paper, we present a tutorial review which was presented at the first Advanced School on Space Environment (ASSE 2004). We first describe the basics of radioastronomy definitions, and discuss radiation processes relevant to solar radio emissions like plasma emission, free–free bremsstrählung and gyromagnetic emissions. We illustrate these fundamentals by describing recent solar radio observations and the constraints they bring on different solar physical parameters. We focus on solar radio emissions from the quiet sun, active regions and during explosive events known as solar flares, and how the latter can bring quantitative informations on the particles responsible for the emission. Finally, particular attention is paid to new radio diagnostics obtained at very high frequencies in the millimeter/submillimeter range, as well as to radio emissions relevant to Space Weather studies.

We report the discovery of a new radio feature associated with coronal mass ejection (CME) events. The feature is a low-frequency (<1 MHz), relatively wide (~300 kHz) continuum that appears just after the main phase of the eruptive event, lasts for several hours, and exhibits a slow negative frequency drift. So far, we have identified this radio signature in a handful of CME events and suspect it might be a common occurrence. The radio continuum starts almost simultaneously with the commonly observed decimetric type IV stationary continuum (also called flare continuum), but the two seem unrelated. The emission mechanism, whether plasma emission or gyroresonance, is unclear at the moment. On the basis of our preliminary analysis, we interpret this radio continuum as the lateral interaction of the CME with magnetic structures. Another possibility is that this continuum traces the reconfiguration of large-scale loop systems, such as streamers. In other words, it could be the large-scale counterpart of the post-CME arcades seen over active region neutral lines after big CME events. This Letter aims to bring attention to this feature and attract more research into its nature.

In our recent Letter (A. Vourlidas et al. [ApJ, 656, L105 (2007)], hereafter Paper I), we determined the azimuth and elevation of our radio source with a direction-finding algorithm (Paper I, Fig. 4) assuming that the source emission dominates over the galactic background. This is generally true for type III emissions that are mainly used for these analyses. However, this condition does not necessarily hold for weaker emissions such as the broadband continuum source in our Letter. As the source intensity decreases to near the Galactic background level, the source direction shifts toward the direction of the Galactic center. It is therefore important to subtract the background before deriving source directions, which we did not do in Paper I. This correction has now been applied to the WIND WAVES data reported in Figure 4 of Paper I. As a result, there is no more significant drift in the source elevation or azimuth. The radio continuum source remains along the ecliptic plane as do other radio bursts observed in association with this coronal mass ejection (CME) event. This correction does not significantly alter our proposed scenarios for the origin of the broadband source. The emission could still arise from electrons injected in nearby structures originating from interactions between the expanding CME and closed coronal loops or from the closing down of previously opened loops. Our velocity estimations are also unaffected by the corrections on the source location. They still suggest that the continuum propagates too slowly to be the CME shock. However, we must point out that M. J. Reiner, M. L. Kaiser, & J.-L. Bougeret (ApJ, 663 1369 [2007]) modeled this event as a type II source deriving an initial speed of 3000 km s , a strong deceleration of 41 ms lasting for about 15 hr, followed by an almost constant propagation 2

On 2001 April 15, the Nancay radioheliograph observed fast-moving, expanding loops in images taken in the wavelength range between 164 and 432 MHz. We were able to follow the progression of the radio loops, starting from a few tenths to more than 1 R-circle dot above the solar limb, with a time cadence of order seconds. The loops seen in radio agree very well with the features of the coronal mass ejection (CME) seen later, more than 2.5 R-circle dot above the limb, in white-light images by the Large Angle Spectrometric Coronagraph (LASCO) experiment on board the Solar and Heliospheric Observatory (SOHO) spacecraft. The event is well associated with an energetic electron event seen by the Electron, Proton, and Alpha Monitor (EPAM) experiment on board the Advanced Composition Explorer (ACE) spacecraft. A detailed transport model for the electrons shows that, not only the inferred onset at the Sun, but also the duration of the particle release, are similar for the radio loop and the in situ electron event detected near the Earth.

The Sun is a radio emitter in a large spectral domain from submillimeter to kilometer wavelengths. Observations at different wavelengths sample different heights in the solar atmosphere, with longer wavelengths referring to higher heights above the photosphere. This review focuses on a few topics related to the physics of the Sun-Earth system. Section 2 summarizes the general context of radio wave propagation and radio emissions. The limits of the shortest and longest wavelengths that can be observed from ground are fixed, respectively, by the transparency of the Earth's atmosphere and by the frequency cutoff of the ionosphere. Satellite observations extend the observable radio spectrum. Radio emissions result from thermal and nonthermal mechanisms. Section 3 summarizes the radio thermal observations of the Sun. The thermal emission is produced by thermal bremsstrahlung and also by gyro resonance emission of the electrons in the presence of a magnetic field (mainly in the microwave domain). Thermal emissions originate from regions with distinct physical parameters, and their detection will depend on the observing frequency. The different classes of radio bursts are presented in Sect. 4. They have distinct spectral characteristics and can last from a fraction of second to several hours; this section focuses more particularly on radio bursts that are produced by accelerated electron beams propagating along the magnetic field or by shocks. The impact on technologies of solar radio bursts is briefly discussed in Sect. 5. Observations of radio bursts reveal various forms of activity and acceleration processes that are associated sometimes to large-scale eruptive phenomena that include flares, filament eruptions, Coronal Mass Ejections (CMEs), and shocks. CMEs are the most spectacular large-scale manifestations occurring at the Sun. Radio observations of CME events are presented in Sect. 5. It is shown that radio imaging and spectral observations provide signatures on the initial steps and development of CMEs. The last section concludes that radio observations offer significant insights to understand solar activity, its link with the interplanetary medium, and the consequence on the Sun-Earth system.

We revisit the impulsive beamlike particle events detected in situ from 1997 to 2000 by the Electron, Proton, and Alpha Monitor (EPAM) experiment on the Advanced Composition Explorer spacecraft. We study in detail a subset of events for which there are radio coronal observations from the Nancay Radioheliograph. EPAM measures electrons in the energy range from 40 to 300 keV over a wide range of look directions and with better than 1 minute time resolution, while the Nancay radioheliograph provides images of the solar corona at five different frequencies with time cadence of eight images per second and per frequency. The radio images are complemented with spectral information from a series of radiospectrographs over a wide frequency range (from dm to km wavelengths), white-light coronagraphic images from the Large Angle Spectroscopic Coronagraph (LASCO) on the the Solar and Heliospheric Observatory (SOHO) spacecraft, and EUV images from the Extreme Ultraviolet Imaging Telescope (EIT), also on SOHO. We separate the particle events according to their associated radio emissions in the meter to decameter wavelengths, in radio-simple (only type III bursts) and radio-complex (also type II bursts and/or continua). The electron events in the radio-simple category have rather short durations, are very weak, and show essentially no delay between the onset of type III emission and the inferred release time for the energetic electrons. The electron events in the radio-complex category present variable delays between the onset of type III emission and the inferred release time for the energetic electrons. The inferred release time for the particles in the radio-complex category always coincides with the onset or major changes in the complex radio emissions; this good association suggests that the coronal processes involved in the radio emissions are at the origin of the electron acceleration. The timing and spectral characteristics of the radio emissions, when compared with the properties of the particles seen at EPAM, and the white-light information from LASCO, strongly support an acceleration process in the corona, at variable heights and below the leading edge of the associated coronal mass ejection. The coronal restructuring put in evidence by the radio signatures is the simplest explanation for the origin of those energetic particles.

The solar origin of 40 interplanetary disturbances observed in the vicinity of the Earth between January 1997 and June 1998 is investigated in this paper. Analysis starts with the establishment of a list of Interplanetary Mass Ejections or ICMEs (magnetic clouds, flux ropes and ejecta) and of Interplanetary Shocks measured at WIND for the period for which we had previously investigated the coupling of the interplanetary medium with the terrestrial ionospheric response. A search for associated coronal mass ejections (CMEs) observed by LASCO/SOHO is then performed, starting from an estimation of the transit time of the inter-planetary perturbation from the Sun to the Earth, assumed to be achieved at a constant speed (i.e. the speed measured at 1 AU). EIT/SOHO and Nançay Radioheliograph (NRH) observations are also used as proxies in this identification for the cases when LASCO observations do not allow one to firmly establish the association. The last part of the analysis concerns the identification of the solar source of the CMEs, performed using a large set of solar observations from X-ray to radio wavelengths. In the present study, this association is based on a careful examination of many data sets (EIT, NRH and H images and not on the use of catalogs and of Solar Geophysical Data reports). An association between inter-planetary disturbances and LASCO/CMEs or proxies on the disk is found for 36 interplanetary events. For 32 events, the solar source of activity can also be identified. A large proportion of cases is found to be associated with a flare signature in an active region, not excluding of course the involvement of a filament. Conclusions are finally drawn on the propagation of the disturbances in the interplanetary medium, the preferential association of disturbances detected close to the Earth’s orbit with halos or wide CMEs and the location on the solar disk of solar sources of the interplanetary disturbances during that period.Key words. Interplanetary physics (interplanetary shocks); solar physics, astrophysics and astronomy (flares and mass ejections)

This review is concerned to study of sun at frequencies lower than 1.4 GHz. Emphasis is made on results which illustrate the topics in which GMRT could play a major role. Coordinated studies including spectral and imaging radio observations are important for research in solar physics. Joint observations between the Giant Meter Radio Telescope (GMRT) with radio instruments located in the same longitude range are encouraged. This review inludes three distinct topics: Electron beams and radio observations- Radio signatures of Coronal Mass Ejections- Radio signatures of coronal and interplanetary shocks.

When radio waves propagate through a irregular medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena, which include intensity scintillation. The observed scattering can be interpreted to gain information about the random medium and such inversion studies are valuable when the accessibility of the medium becomes difficult. This paper briefly describes the intensity scintillation of celestial radio sources caused by the turbulence in the solar wind and summarizes the salient features of the method employed in mapping the structure of disturbances leaving the Sun out to ∼1 AU.