Recent Solar Dynamic Observatory observations reveal that some coronal mass ejections (CMEs) consist of multi-temperature structures: a hot channel and a cool leading edge (LE). The channel first appears as a twisted loop and lies along the polarity inversion line; it then gradually develops into the less twisted semicircular structure during the impulsive phase of CME acceleration. In the meantime, the hot channel compresses the surrounding magnetic field and plasma, which successively stack into the CME leading front. Here, we study two well observed CMEs, which occurred on 2010 November 3 and 2011 March 8, respectively. We find that, the hot channel rises earlier than the first appearance of the CME leading front and the onset of the associated flare, and that the speed of the hot channel is always larger than that of the leading front. Further differential emission measure analysis shows that the channel often has significant emission at high temperatures. We thus conclude that the observed hot channel is likely to be magnetic flux rope that acts as a driver of the CME acceleration in the early phase.

“Extreme Ultraviolet (EUV) waves” are large-scale wavelike transients often associated with coronal mass ejections (CMEs). In this Letter, we present a possible detection of a fast-mode EUV wave associated with a mini-CME observed by the Solar Dynamics Observatory. On 2010 December 1, a small-scale EUV wave erupted near the disk center associated with a mini-CME, which showed all the low corona manifestations of a typical CME. The CME was triggered by the eruption of a mini-filament, with a typical length of about 30′′. Although the eruption was tiny, the wave had the appearance of an almost semicircular front and propagated at a uniform velocity of 220−250km s-1 with very little angular dependence. The CME lateral expansion was asymmetric with an inclination toward north, and the southern footprints of the CME loops hardly shifted. The lateral expansion resulted in deep long-duration dimmings, showing the CME extent. Our analysis confirms that the small-scale EUV wave is a true wave, interpreted as the fast-mode wave.

This review focuses on the so called three-part CMEs which essentially represent the standard picture of a CME eruption. It is shown how the multi-wavelength observations obtained in the last decade, especially those with high cadence, have validated the early models and contributed to their evolution. These observations cover a broad spectral range including the EUV, white-light, and radio domains.

Coronal “EIT wave” is a large-scale wavelike phenomenon propagating across the major part of the Sun. Debates are being continued regarding a more suitable name for it, its source driver, and its nature. “EIT waves” have been widely explained in terms of fast-mode waves, despite that the model contradicts with many observational features. Two-types of EUV waves were predicted 10 years ago. With the recent high-cadence observations, mainly from SDO/AIA telescope, more and more evidence has been revealed in favor of the two-wave model. In this paper, after summarizing different names used for EIT waves in the literature, we show how the community are getting close to reaching a consensus on the nature of EIT waves.

The origin of solar energetic particle (SEP) events is an issue for the understanding of particle acceleration and transport in astrophysics, as well as for space weather. We outline some recent studies addressing from the observational viewpoint the relationship between interacting and escaping particles, conditions for particle escape from the Sun, and the interplanetary magnetic field configurations where the particles propagate.

Magnetic Cloud Boundary Layer (MCBL) is formed by the interaction between a magnetic cloud ejected by the Sun and the ambient solar wind, which may be linked to the outer loops of an Interplanetary Coronal Mass Ejection (ICME) and often display the properties of magnetic reconnection. We study the relation between current sheets, turbulence, and magnetic reconnection at the leading edge of an ICME intercepted by the four Cluster spacecraft in the solar wind, upstream of the Earth’s bow shock, on 2005 January 21. We obtain the observational evidence of a fully-developed magnetic turbulence in the vicinity of two current sheets at the leading edge of ICME. Each current sheet shows the signatures of magnetic reconnections with oppositely propagating Alfven waves and jets. The current density of bifurcated current sheets is computed by the curlometer technique using multi-spacecraft data.

We focus our analysis on an event which occurred at the W-limb on May 30, 2003. The dynamical behavior of the filament, including damped oscillations, was investigated with the CDS and EIT (SoHO) experiments, as well as with Hα filtergrams (movies). The eruptive phase is analyzed taking into account the approximate phasing with other eruptive phenomena occurring at the same time or before, called homologous flares and eruptions.

In this presentation, we will summarize the progress in the observation and instrumentation for the measurement of solar magnetic field. And furthermore, some new Chinese projects in this aspect, such as the Space Solar Telescope, Chinese Giant Solar Telescope, etc., will be introduced too.

A new multi-wavelength solar telescope, Optical and Near-infrared Solar Eruption Tracer (ONSET), is constructed by Nanjing University, being run in cooperation with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows: He I 10830 Å, Hα and white-light at 3600 Å or 4250 Å. Full-disk or partial solar images with a field of 10 arcmin at three wavelengths can be obtained nearly simultaneously. It is designed to trace solar eruptions with high spatial and temporal resolutions. This telescope has been installed at a new solar observing site near the Fuxian Lake, Yunnan Province. The site is located at E102N24, with an altitude of 1722 m. The seeing is stable and very nice. We give a brief description of the scientific objectives and the basic structure of ONSET. Some preliminary results are also shown.

We propose to use an aperture shaped as a cat’s eye for high contrast imaging of the solar corona. The high angular resolution is recovered in the long direction of the rectilinear aperture. A rotation of the diaphragm in front of the telescope and a tomographic-like post processing will be necessary for a complete 2D imaging of the corona.

The Dome C high plateau is unique for coronagraphic observations: sky brightness is reduced, water vapour is low, seeing is excellent and continuity of observations on several weeks is possible. ESCAPE (the Extreme Solar Coronagraphy Antarctic Program Experiment) will perform 2-dimensional spectroscopy of the forbidden line of FeXIV at 530.285 nm: precise line profile analysis will allow the diagnostic of the nature of waves by simultaneous measurements of velocities and intensities in the corona. ESCAPE is proposed to Institut Paul-Emile Victor (IPEV) for a campaign in 2012–2013 at Dome C/Concordia since all subsystems are available in particular thanks to an ESA STARTIGER 2010 R&D “Toward a New Generation of Formation Flying Coronagraph”. Using state-of-the-art technologies developed for Space missions (a Three Mirrors Anastigmat telescope, the TMA, a 4 stages Liquid Crystal Tunable-filter Polarimeter, the LCTP) allows us to propose an automated Coronal Green Line full-field Polarimeter for unique observations (waves nature and intensity to address coronal heating) with the best possible performances on Earth and for preparing and testing the technologies for the next steps in Space. No other site would allow such coronagraphic performances (the sky brightness is a factor 2 to 4 better than in Hawaï) and with high spatial resolution (better than an arcsec is possible).

We have installed a small telescope to monitor the sky brightness around the sun at the French-Italian station Concordia at Dome C in Antarctica. Previous campaigns have been performed with the same instrument at Haleakala in Hawai and Sunspot in New Mexico. We compare here the results of the first year of the campaign at Dome C (2008) to the purest sky observed at Haleakala. We show that Dome C is an outstanding site for coronal observations. Compared to Haleaka, it appears to be more transparent, and to contain less aerosols. Its water vapour content is also significantly smaller. These results still have to be confirmed by the analysis of the 2009 and 2010 data.

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.

We present the Mirror Advanced technology Coronagraph (MAC) as a new generation solar telescope to be put at suitable high altitude coronal sites in order to resolve modern problems of solar physics, like the origin of the heating of the chromosphere and of the corona, the analysis of the mesospheric layers of the solar atmosphere and the effects of shearing the photospheric magnetic fields on the dynamics of the upper coronal layers.

Measurements of the power spectrum of the seeing in the range 0.001–1 Hz have been performed in order to understand the criticity of the transits method for solar diameter monitoring.

Imaging spectropolarimetry is a powerful tool in solar physics. Multichannel Subtractive Double Pass (MSDP) spectrographs can produce simultaneous 2D images in a number of wavelengths covering several line profiles with the following advantages:

- Contrary to long slit spectroscopy, the spatial resolution can reach the diffraction limit.

- Contrary to narrow band filters, full line profiles are recorded at the same time without any image motion and differential seeing effect.

MSDP spectrographs use an entrance window instead of the usual long slit. A new generation MSDP using slicers made of mirrors instead of prisms is proposed for the future 4 m class European Solar Telescope. We describe the beam slicer prototype S4I (Spectral Sampling with Slicer for Solar Instrumentation) that will be tested soon at the 14 m spectrograph of the Meudon Solar Tower.

We introduce a new method to perform high resolution astrometry of the solar diameter from the ground, through the observations of eclipses. A discussion of the solar diameter and its variations is linked to the Limb Darkening Function (LDF) using the luminosity evolution of a Baily’s Bead and the profile of the lunar limb available from satellite data. The inflexion point of the LDF is defined as the solar limb. The method proposed is applied for the videos of the eclipse in January, 15, 2010 recorded by Richard Nugent in Uganda and Andreas Tegtmeier in India. An upper limit for the inflexion point position has been set for that eclipse.

The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement of the solar diameter with the Venus transit of 5/6 June 2012 with an unprecedented accuracy, and with absolute calibration given by the ephemerides.