Large scale eruption events in the solar atmosphere can generate global waves, i.e. waves which propagate over distances comparable to the solar radius. In the low solar corona, global waves observed by SOHO/EIT, generated by coronal mass ejections or flares are usually referred to as EIT waves. Since EIT waves carry information about their environment, they can be used for diagnostics of, e.g. the local and global magnetic field. This contribution presents theoretical models for finding values of magnetic field in the quiet Sun and coronal loops, and explores the physical connection between local and global solar coronal events (e.g. flares and coronal loop oscillations).

Based on the concept that the CMEs are the results of coronal magnetic restructuring or reconfiguring, we analyze the December 18, 2000 event by using Nançay Radioheliograph (NRH) images and combining the multi-spatial scale observations. We investigated the onset, duration and position of the radio emissions in relation to EUV dimming and the inferred CME onset, with the purpose to estimate the spatial and temporal scales of the coronal restructuring, thus, to understand the physics of the initiation and development of the CME.

We explain the generation of the large-scale unipolar magnetic field regions (global magnetic regions) by the same dynamo action as for the generation of the sunspots and the polar faculae butterfly diagrams as given by Callebaut (2006). The previous global magnetic regions through meridional circulation now serve as the main seed fields (flux-transport dynamo for the global field regions), possibly supplemented by leftovers from the sunspots and some weak fields generated at the tachocline.

In this paper we have used the general theory of Arnold (1965,1966) and Vladimirov et al. (1997) to obtain sufficient conditions for linear stability of steady MHD flows of an ideal three-dimensional compressible gravitating flows.

Everybody understands what is meant by an eclipse: a body that covers another one. However, the general audience and the students in particular do not know exactly “What the relative positions of the Earth, the Sun and the Moon have to be in order for an eclipse to take place?”

You can read a newspaper or watch TV and observe that the information about an eclipse is not correct. In my country, it was stated, in a very important newspaper, that “the solar eclipse will take place tomorrow because there will be a Full Moon”.

Teaching this topic in schools or in educational sessions in observatories, it is a good idea to introduce a simple model that maintains the proportion between the diameters and distances of these three bodies. This contribution will introduce this model, showing their applications in the playgrounds of the school, for sunny days or in the classroom for cloudy days.

The last decade observations revealed the essential variations of energy balance take place in the pre-flare active regions at all atmospheric levels and they are caused by both evolution of AR and processes associated with flare activity. We present the multi-wavelength study of the solar flare jointly with the preceding event. The combined investigation is perspective for the mechanism understanding of the energy storage, trigger and release during the solar flares. A special attention was given to signatures of energetic particle beam effect on chromosphere according to H$\alpha$ and CaII K intensity changes. Combination of data from ground based instruments and space observatories (TRACE, MDI, RHESSI) will allow us to track processes taking place in a wide range of solar atmosphere layers - from the temperature minimum region to the corona. The obtained results are discussed.

Based on the neutron monitor counting rate profiles, soft X-ray emission from GOES, Yohkoh/HXT, RHESSI/HXT, ACE/SIS, and SOHO/LASCO CME catalog, the relationship between the onset time of solar cycle 23 Ground Level Enhancements(GLEs) and solar activity are analyzed. It was found that the correlation between the onset time of GLEs and flare maximum is better than that of the onset time of metric type II radio burst and CME. Average value of the ratio of Fe/O is about 2.65 times of coronal value in the range 30 – 40 MeV/n for all events. If considering the parent flare sites, the situation of proton acceleration in flares, and transport effect from flare sites (if it located in poorly-connected region) to well-connected region, several GLEs onset time are roughly at the peak time of the X-ray.

Utilizing SOHO/MDI data of two active regions (ARs 08398 & 10373), we identify and trace the whole lifetimes of 26 positive and 68 negative unipolar Moving Magnetic Features (MMFs). The statistical properties of several kinematic and magnetic quantities are studied.

We argue that millimeter continuum observations promise to be an important diagnostic of chromospheric dynamics and the appropriate wavelengths to look for dynamic signatures are in the range 0.8–5.0 mm. We have analyzed the millimeter intensity spectrum expected from the dynamic model of the solar non-magnetic atmosphere of Carlsson & Stein (1992, 1995, 1997, 2002, hereafter CS) together with the interferometric observations of the quiet Sun obtained at a wavelength of 3.5 mm with the Berkeley-Illinois-Maryland Array. Model radio emission at millimeter wavelengths is found to be extremely sensitive to dynamic processes in the chromosphere, if these are spatially and temporally resolved. The estimated millimeter brightness temperatures are time-dependent, following changes in the atmospheric parameters, and result in clear signatures of waves with a period of 180 s seen in the radio intensity as a function of time. At the same time, the interferometric observations of the internetwork regions reveal significant oscillations with amplitudes of 50–150 K in the frequency range 1.5–8 mHz. We give an estimate of the influence of the limited available spatial resolution of observations on the comparison with the predictions of dynamic models. We are able to establish a correspondence between the CS model predictions and the observational data if we assume that the horizontal coherence length of the oscillations is on the order of 1 arcsec.

Magnetic field topology at the CME source regions is considered to play a role in CME initiation processes. We use observational data and Potential Field Source Surface model to investigate the magnetic field topology over CME productive quiescent filaments. We found both bipolar topology and quadrupolar topology at CME source regions, but bipolar topology is more common overall and in each year. The total occurrence ratio between bipolar and quadrupolar topology is about 3:1 with our 80 events. On the rising phase of the solar cycle, there is mostly bipolar topology, but on the declining phase, there is a mixture of both bipolar and quadrupolar topology.

One of the observational facts about sunspots is that magnetic field strength of sunspots varies in narrow interval $\approx$ from 1 to 4–5 kG. Why sunspot equilibrium is stable only under these values? To answer this question, we propose the energetic model of sunspot, which involves the gravitational energy of the system. Formation of a sunspot is followed by redistribution of gas density along the vertical: cooled plasma flows down, inside the “magnetic funnel”, from above the sunspot to the “low boundary of magnetic flux tube”, i.e. to the region where the magnetic field of sunspot decreases abruptly with depth. Theoretical model gives the interval of stable sunspot equilibria exactly between 0.8–1.0 and 4–6 kG, which suites the observations. The “depth of sunspot” turns to be about 2–4 Mm – this fact now is approved by helioseismology. Also, the long-term (T$\,{>}\,$20 min) eigen oscillations of sunspot, as a whole, are studied. These oscillations were measured by different methods, being observed as quasi periodical vertical displacements of the body of sunspot followed by variations of its radius and magnetic field strength.

We analyze time series scans of the solar limb performed by the spectrometer SUMER on-board the SoHO satellite. The analyzed dataset consists of observations obtained in the C III 977 Å line. After applying the standard SUMER data reduction procedure, we perform a one line Gaussian fit to the profiles to obtain different parameters for each pixel within the scans. Studying the variations of the line width from the disk to the limb and off-limb we find that it increases off-limb and shows a peak at $\sim15\prime\prime above the limb. We suggest that this increase is due to the random directions of several spicules found along the line of sight.

A kinetic analysis is performed here considering close relationship between plasma jets in the solar corona and a consequent acceleration of electrons. Solar jets are formed when a plasma stream is shooted out from a reconnection site. In some cases these jets are temporally and spatially associated with type III radio bursts, the latter being the radio signatures of nonthermal electron beam propagation through the corona. This theoretical work on jet associated type III burst argue the possibility of regarding the plasma jet as a trigger mechanism for electron energization (heating or/and acceleration). While the jet propagates in the solar corona, it creates wave-like disturbances in the background plasma, that are in general unstable. Further on we are interested in how a test electron will behave in such (electrostatic) wave field. The settings for the jet and the test electron are done under typical coronal conditions.

The manuscript presents a review of the results obtained by the author from fast sequential H-alpha filtergrams taken for a quiescent filament together with similar results of other authors. The revealed structure clearly shows that the foot elements of the filament are surrounded by a fishbone-like plage area (magnetic region). Some parts of the filament exist at the boundary of large supergranular cells of about 40′′ in diameter. It seems that the filament is formed due to mixing of magnetic elements of different polarities.

The large-scale magnetic field of the Sun and solar-type stars is probably generated near the interface of the radiative core and the convection zone. One of the well-known difficulties of interface-type and other dynamo models is to explain the latitudinal distribution of magnetic fields as observed on the Sun. In this contribution new results of numerical MHD simulations of transport coefficients of magnetic fields in the rapid rotation regime, relevant for the base of the solar convection zone, are presented that may contribute to explaining the latitudinal distribution of magnetic fields observed on the Sun. A brief outlook on further numerical simulations of transport coefficients and their relevance for mean-field dynamo theory is given.

A suggested method is proposed to forecast the general features of the 11- year solar activity principle cycle. It is based upon the count of lengths and durations of spotless events, prevailing in the preceding minimum of the coming new cycle. The method has been successfully applied to predict the strengths and time of rises for the $22^{nd}$ and $23^{rd}$ 11-year cycles. The proposed precursor technique is further developed to make preliminary prediction of the maximum relative sunspot number and the time of rise of the $24^{th}$ 11-year cycle. The predicted values of these parameters are found to be $90.7\pm9.2$ and $4.6 \pm1.2$ year respectively. In addition, neural, Fuzzy neural and genetic algorithms have been also applied for the confirmation of the predicted results. A comparison with the early predictions used by other methods is given.

Major properties of the solar atmosphere and wind are not understood. The energy distribution of the solar atmosphere perturbations, over nearly ten orders of magnitude in energy, is close (within one order of magnitude) to a power-law of index -2, even though there is no agreement on the detailed shape. There is no agreed explanation of the origin of the solar wind, either, nor of the fact that the total wind energy flux is independent of speed, latitude, and phase of solar cycle, with an average base flux of 70 W/m$^2$ – a figure that is similar for a number of other cool stellar winds, and is close to the total observed energy flux of solar atmosphere perturbations. A major theoretical difficulty is that both coronal heating and wind production depend fundamentally on the heat flux, and the solar atmosphere is not collisional enough for classical transport theory to hold. Heat transport thus behaves non classically and the particle velocity distributions may have significant high energy tails, which should dramatically affect coronal heating and solar wind acceleration, in a way that is outside the scope of standard MHD.

Fourier local correlation tracking (FLCT) was applied to time series of the normal magnetic field in vector magnetograms of NOAA AR 8210, from 17:13–21:29 UT on 1998 May 1, to derive photospheric flows. These flows, combined with both the observed horizontal magnetic field and an inferred horizontal potential magnetic field, can be used to derive the flux of free magnetic energy across the photosphere. Here, we present the formalism used, as well as a map of the time-averaged free energy flux. Over the time interval covered by the magnetograms, ${\sim} 10^{31}\,$erg of free magnetic energy flowed upward across the photosphere, a significant fraction of the energy typically released in large flares coronal mass ejections (CMEs). A flare and coronal mass ejection began at 22:30 UT. We acknowledge the kind support of AFOSR's MURI program.

We report on a complex study of a typical large W-limb CME event occurring on December 2, 2003 in the vicinity of AR 0508. It is associated with a prominence eruption which has been observed with the Pic du Midi Ha flux coronagraph as well as in EUV by both the SOHO/EIT and the Coronas/SPIRIT space telescopes. The eruption started with the emergence of a fast expanding loop between 9 and 10 UT, followed by a heating and an acceleration of the erupted material and resulted in three-part CME observed by LASCO after 10:50 UT. A temporal analysis of the prominence motion and the EUV dimming light curve have shown that both the frontal structure and the core of a CME were initiated simultaneously with the peak of the X-ray C7.2 flare. The total mass of the prominence including the H$\alpha$ filament and EUV filament channel is close to the mass of the core but significantly less than the total CME mass.

Here we present an analysis of microwave emission spectra from flare-productive active regions (FPAR). For that we used regular observations in a wide frequency range with high spectral resolution and polarization sensitivity made with the RATAN-600 radio telescope. The multi-frequency observations make possible to detect small changes of magnetic field structures at different heights of the solar atmosphere. Observations with RATAN-600 and other large radio heliographs revealed an existence of narrow-band irregularities in the circular polarization spectra of FPARs radio emission. The new receiver complex, recently installed at RATAN-600, significantly improves its technical capabilities for the FPARs further study. Now it provides 1% (or 100 MHz) resolution in the frequency range from 6 GHz to 18 GHz in simultaneous registration. We present some observational results obtained with this new equipment.