Using THEMIS vector magnetograms we measured vertical electric current density in the leading sunspot of NOAA 11127 active region during its disk passage. The current structures evolve versus time. MHD modelling allows us to explain the spiral pattern by torsion. We found observational visible counterparts in the SDO/AIA 335 A images. The field lines are visible as loops in the AIA images. When the torsion is increasing, a sigmoid is observed. In the present event observed on November 24th 2010, we find that reconnection is also necessary to explain their sigmoidal shape.

Recent observations of prominences obtained with high spatial and temporal resolution instruments, on board satellites (Hinode, SDO) as well as on the ground (SST) have provided very intriguing movies and open a new area for understanding the nature of prominences. The main topics are still debate: formation, dynamics, and characteristics of the plasma in the core and in the transition zone between the prominence and corona. We will review briefly the recent advances made in these topics, observationally as well as theoretically.

Vector magnetic fields of an active region filament are co-spatially and co-temporally mapped in photosphere and upper chromosphere, by using spectro-polarimetric observations made by Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A Zeeman-based ME inversion is performed on the full Stokes vectors of both the photospheric Si I 1082.7 nm and the chromospheric He I 1083.0 nm lines. We found that the strong magnetic fields, with the field strength of 600 − 800 G in the He I line formation height, are not uncommon among AR filaments. But such strong magnetic field is not always found in AR filaments.

Ground- and space-based observations have confirmed the presence of oscillatory motions in prominences and they have been interpreted in terms of magnetohydrodynamic (MHD) waves. This interpretation opens the door to perform prominence seismology, whose main aim is to determine physical parameters in magnetic and plasma structures (prominences) that are difficult to measure by direct means. Here, two prominence seismology applications are presented.

For space weather applications, it is important to understand filaments evolution and especially their eruptions associated with coronal mass ejections. In view of the cadence and continuity of SDO observations, AIA and HMI offer a unique tool for such a program. Because of the data volume and the requirement of short latency, only an automated detection can be worked out. We present a new method for the automated detection and tracking of filaments, based on the analysis of AIA 30.4 nm He ii images, with the capability to use also the magnetic field measured by HMI.

We reconstruct the three-dimensional geometry of erupting filaments using observations from different viewpoints. True kinematic evolution of different locations along the main bodies of filaments is investigated. For the erupting filament on 2009 September 26, the highest point is the fastest in the first half hour, and then the points at the low-latitude leg of the filament become the fastest. However, for the event on 2010 August 1, the highest location always has the largest velocity and acceleration during the eruption process. The propagation of EUV enhancements at the endpoints of the erupting filament is observed clearly, which is attributed to the successive down-flows along the different groups of thread-like structures of the filament. Both the two filaments show non-radial eruptions and move towards low-latitude region. Their latitudinal variation is greater than the longitudinal.

Images from the SWAP (Proba 2 mission) taken in the Fe IX/X coronal line emission are compared to simultaneous slitless flash spectra taken during the total solar eclipse of July, 11th 2010. Many faint low excitation emission lines together with the HeI and the HeII Paschen α (Pα) chromospheric lines are recorded in the regions of limb prominences observed in space. We consider a deep flash spectrum obtained by summing 80 individual spectra to show the intensity modulations of the continuum between HeI and HeII lines. Intensity depressions are observed around the prominences in both eclipse and SWAP images. The prominence cavities are interpreted as a relative depression of plasma density produced inside the corona surrounding the prominences, and some evidence of intense heating occuring in the region around the prominence is discussed.

The heating of the solar corona and the origin and acceleration of the solar wind are among the important unsolved problems of space plasma and solar physics. During the SOHO era, coronal holes as source regions of the fast solar wind have been investigated by using UV/EUV spectroscopic data observed with high-resolution spectrometers. At the base of the coronal hole, a detailed picture concerning the origin of the fast solar wind was first obtained by SUMER observations. For example, the Dopplergram deduced from the line profile of Ne VIII and other transition-region lines showed strong evidence that the wind originates in the chromospheric network and starts flowing out of the corona in magnetic funnels. Solar wind mass is suggested to be supplied through supergranule-scale magnetoconvection in the chromosphere and transition region. However, the spectral lines used in these studies are mainly obtained in the transition region and the behaviours of the nascent solar wind at higher temperatures have not yet been understood. Recent spectroscopic and imaging observations with instruments on Hinode and SDO provide further information about the coronal holes seen in EUV lines formed in the solar corona. Some interesting results, e.g., ubiquitous episodic outflow (jets) and enhanced emission in the blue wing of coronal line profiles, are found from the new observations. The purpose of this presentation is to review recent research progress on solar-wind source regions revealed by UV/EUV spectroscopic and imaging observations. Such observational studies and further interpretations of the data may provide crucial constraints and implications for future studies on both observations and theoretical models concerning coronal heating and acceleration of the nascent solar wind.

X-ray solar coronal jets are short–duration, fast, well collimated plasma brightenings occurring in the solar corona. To explain and understand the processes driving the jets, one must be able to model an explosive release of free energy. Magnetic reconnection is believed to play a key role in the generation of these energetic bursting events. The model of jets that we have been developing is based on a magnetic field constructed by embedding a vertical magnetic dipole in a uniform open magnetic field. In this study, we investigate the influence of the inclination of the open field on the properties of the jet using numerical simulations. We will show that the inclination of the open field is of critical importance for the properties of the jet such as the energy released. We conclude that the characteristics of the open field at the time of observations are a central criterion that must be taken into account and reported on in observational studies.

We present a tomographic reconstruction of polar plumes as observed in the Extreme Ultraviolet in January 2010. Plumes are elusive structures visible in polar coronal holes that may play an important role in the acceleration of the solar wind. However, despite numerous observations, little is irrefutably known about them. Because of line of sight effects, even their geometry is subject to debate. Are they genuine cylindrical features of the corona or are they only chance alignments along the line of sight? Tomography provides a means to reconstruct the volume of an optically thin object from a set of observations taken from different vantage points. In the case of the Sun, these are typically obtained by using a solar rotation worth of images, which limits the ability to reconstruct short lived structures. We present here a tomographic inversion of the solar corona obtained using only 6 days of data. This is achieved by using simultaneously three space telescopes (EUVI/STEREO and SWAP/PROBA2) in a very specific orbital configuration. The result is the shortest possible tomographic snapshot of polar plumes. The 3D reconstruction shows both quasi-cylindrical plumes and a network pattern that can mimic them by line of sight superimpositions. This suggests that the controversy on plume geometry is due to the coexistence of both types of structures.

We present results from quiet sun observations in the metric range. Solar images where obtained through rotational aperture synthesis at a number of frequencies, using the Nançay radioheliograph in its latest version, from 2004 to 2011. The main morphology is described, and compared to the magnetic field topology. We also measured on-disk spectra, of the average sun and of coronal holes, and equatorial and polar limb profiles. From these measurements, simple temperature/density atmospheric models are derived and briefly discussed.

The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed

This short reviewing article is intended to introduce a possibly existing relevance for three important macroscopic behaviors of solar flares. The behaviors include the contraction of flare loops (implosion), the rapid change of magnetic fields and seismic waves during flares. We show that the phenomena basically reflects a process of rapid restructuring of sheared magnetic field by a release of free magnetic energy. The contraction and rapid magnetic changes might be the direct consequences of the restructuring. Also the flattening of magnetic loops caused by the contraction in the corona will impart momentum down to the photosphere even to the solar interior. Part of the energy transported by the downward momentum can account for seismic waves. All phenomena, putting together, show that the magnetic reconnection process during the early impulsive phase is quite different from during the gradual phase and plays a dominant role in powering solar flares.

By giving three different definitions of peak flux(original peak flux, corrected peak flux, and scaled peak flux), we analyze the frequency distributions of 14057 flares recorded by GOES from 2000 to 2005. We find a significant result that the frequency distribution of the scaled peak flux for all the sample flares can be approximated by a perfect power-law function with an index of 2.18, without any usually deviating from the power-law at the lower fluxes.

Chromospheric evaporation suggests the mass upflows from chromosphere to corona after the electron heating at the chromosphere during the solar flares. It takes place at the rising phase, and has a typical timescale about 100 s and a typical speed about 300–400 km s-1. Such characteristics are well observed as the blueshift at the spectral lines. By the way, the facts of the high-frequency cutoff negatively drifting on the radio dynamic spectra and the hard X-ray footpoint source motions along the loop legs are also thought to be the signatures of the chromosphere evaporation. In this paper, we show the observational evidences of the chromospheric evaporation at radio, EUV and X-ray emissions.

On August 9, 2011, there was an X6.9 flare event occurred near the west limb of solar disk. From the observation obtained by the spectrometer of the Chinese Solar Broadband Radio Spectrometer in Huairou (SBRS/Huairou) around the flare, we find that this powerful flare has only a short-duration microwave burst of about only 5 minutes, and during the short-duration microwave burst, there are several kinds of fine structures on the spectrogram. These fine structures include very short-period pulsations, millisecond spike bursts, and type III bursts. The most interesting is that almost all of the pulses of very short-period pulsation (VSP) are structured by clusters of millisecond timescales of spike bursts or type III bursts. And there exists three different kinds of frequency drift rates in the VSP: the frequency drift rates with absolute value of about 55–130 MHz s-1) in the pulse groups, the frequency drift rates with absolute value of about 2.91–16.9 GHz s-1) on each individual pulse, and the frequency drift rates with absolute value of about 15–25 GHz s-1) at each individual spike burst or type III burst.

Observations of jet- like phenomena near the solar limb are reported for a long time, first in Hα (Secchi observations of spicules in the 1870 ies), and after, from eclipse high resolution coronal images taken in white-light (1920–1973) as spiky structures. EUV jets were reported in the 70 ies from rocket and space-borne CIV filtergrams and finally X-EUV jets were reported from SXT observations of Yohkoh and from EIT and CDS SoHO observations. There is now little doubt that they are of magnetic origin although no magnetic field measurements exist for these regions and thermo-dynamical models are still work out. New observations of both spicules and jets with the SOT/SXT of Hinode were subjected to an analysis showing the influence of the null point(s) of the magnetic field. The collective behavior of the H CaII SOT(Hinode) time sequences of processed with the Madmax operator images of limb spicules show the torsional effects which were partly suggested before from the interpretation of high resolution limb spectra taken on Russian coronagraphs and the VTT at SacPeak. 100 s and shorter period waves are recorded. We propose a reconnection process occurring at the top of an emerging twisted flux tube for explaining some peculiarities of the spicular eruptions and possibly, as a viable mechanism for explaining the SXR jet eruptions. The result of a numerical 3D modeling illustrates this erupting mechanism although the behavior of the magneto-plasma structure near a null point, as shown by coronal filtergrams, does not necessary imply reconnections, especially the case of jets making a long coronal ray we observed in white-light with Lasco C2.

An analysis of the temporal properties of a group of spikes in the solar flares is presented recorded by the 1–2 GHz spectrometer of National Astronomical observatories of China (NAOC) on 27 October 2003. The time profile of each single spike was fitted and analyzed. In particular, we determine the e-folding rise and decay times corresponding to the ascending and decaying parts of the time profile, respectively. Several important correlations have studied and compared with the results in earlier literature, i.e. those between duration and frequency, e-folding rise time and decay time, e-folding decay time and duration, and e-folding decay time and peak flux. Plasma temperatures of source region are also estimated and the possible decaying mechanism is discussed.

We develop mathematical models describing plasma heating in the corona by heat fluxes from a super-hot (T \hbox{$ \stackrel{>}{_\sim}}$\mathit{T}\stackrel{\mathit{>}}{{}_{\mathrm{~}}}{\mathrm{10}}^{\mathrm{8}}$ 108 K) reconnecting current layer in solar flares. The effect of collisional relaxation is shown to be important in these conditions. Taking this effect into account, we have computed the electron-temperature distributions in the vicinity of the current layer, differential and integral emission measures of the heated plasma, the intensities of spectral lines Fe XXVI (1.78 and 1.51 Å) and Ni XXVII (1.59 Å). The theoretical results are compared with observations.

This presentation displays several well-known CME models and the related theories, figuring out both advantages and disadvantages of each model through looking at aspects that fit and do not fit observations. It is also aim to enhance the mutual understanding between observers and modelers, helping modelers to improve their models by putting more realistic constrains on the models and helping observers to get detailed physics behind the observations. Therefore, the models and observations are connected to one another such that what the modelers may expect and what the observers can tell.