The dissipative model of Solar Magnetic Cycle (SMC) is discussed. According to this conception, at the beginning of each odd 11-yr cycle, a large-scale dissipative magnetic structure is formed in the convective zone of the Sun, as a result of complex nonlinear interaction between magnetic field and turbulent plasma velocity field. During the 22-yr cycle, this large-scale magnetic structure evolves through the convective “envelope” and atmosphere of the Sun. Two main effects determine the process: i) diffusion of magnetic field and ii) $\omega$-effect: the conversion of poloidal magnetic field into toroidal one due to the differential rotation.

A major problem for predicting the onset of Solar Proton Events is the detection of the magnetic connection between the flare and the earth. If there is a magnetic connection, the particles accelerated by a large solar event may impact the earth and produce the onset of a solar energetic proton event. Current physical models cannot predict the onset of a SPE mainly because of the chaotic conditions within the IMF structure. Kiplinger (1995) reported a high correlation between the existence of 10 MeV protons at Earth and a characteristic pattern of X-ray spectral evolution for several associated flares. We propose a practical approach that tries to detect the time intervals of this correlation. Our assumption is that a high correlation betwewn X-ray and protons at Earth is an important symptom of a magnetic connection and may help to prevent Solar Proton Events.

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.

Supergranules are observed in the high photosphere as large convection eddies with horizontal diverging flows from the cell centre and subsiding flows at the cell borders.

Magnetohydrodynamic equilibria for a plasma in a gravitational field are investigated analytically. For equilibria with one ignorable spatial coordinate, the equations reduce to a single nonlinear elliptic partial differential equation for the magnetic potential A, known as the Grad-Shafranov equation. Specifying the arbitrary functions in the latter equation, one gets a nonlinear elliptic partial differential equation (the sinh Poisson equation). Analytical solutions of this equation are obtained for the case of an isothermal atmosphere in a uniform gravitational field. The solutions are obtained by using the tanh method, and are adequate for describing parallel filaments of diffuse, magnetized plasma suspended horizontally in equilibrium in a uniform gravitational field.

Using Big Bear Solar Observatory (BBSO) magnetograms and H${\alpha}$ images in a quiet region and a coronal hole, observed on 9 14 and 16, 2004, respectively, we have explored the magnetic flux emergence, disappearance and distribution in the two regions. The following results are obtained: (1) The evolution of magnetic flux in the quiet region is much faster than that in the coronal hole, as the flux appeared in the form of ephemeral regions in the quiet region is four times as large as that in the coronal hole, and the flux disappeared in the form of flux cancellation, three times as fast as in the coronal hole. (2) More magnetic elements with opposite polarities in the quiet region are connected by arch filaments. (3) The flux distribution of network and intranetwork (IN) elements is similar in both polarities in the quiet region. For network fields in the coronal hole, the number of negative elements is much more than that of positive elements. However for the IN fields, the number of positive elements is much more than that of negative elements. (4) In the coronal hole, the fraction of negative flux change obviously with different threshold flux density. 73% of the magnetic fields with flux density larger than 2 Gauss is negative polarity, and 95% of the magnetic fields is negative, if we only measure the fields with their flux density larger than 20 Gauss. These results display that in a coronal hole, stronger fields is occupied by one predominant polarity; however the majority of weaker fields, occupied by the other polarity.

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.

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.

This article is a study of a family of nonlinear force-free magnetic fields (FFMFs), in Cartesian geometry under assumption of translational symmetry, as simple models of the magnetic fields in the solar corona. For this configuration all the physical quantities are invariant under translations in a fixed direction to be the direction Oz of a Cartesian coordinate system. Two classes of exact analytic solutions for the steady state are obtained. These solutions may be helpful in understanding the physics involved in the transition from the low-confinement to the high-confinement mode in tokamaks. In particular, they can be employed for stability investigations, which would be of relevance to magnetic confinement systems. Further, the obtained solutions may have several applications in the study of solar photosphere, the solar corona, as well as astrophysical plasmas.

In this paper, we have presented high resolution magnetograms around sunspot at CaI $6102.7 \AA$ photospheric line and in $H\alpha$ chromospheric line.

Futher, more the longitudinal magnetic field difference in two wings(red and blue)around central line in photosphere and chromosphere has been studied.

Hasan et al. (2005) have recently presented 2-D dynamical calculations on wave propagation in in the magnetic network of the Sun. The latter is idealized as consisting of non-potential flux tubes in the quiet solar chromosphere. It is of interest to understand how the nature of wave propagation is influenced by the choice of initial equilibrium configuration of the magnetic field. We examine this by comparing the earlier calculations with those when the network is modelled as a potential structure. Our calculations demonstrate that the nature of the wave propagation is significantly different, particularly the transport of energy which for the potential case, occurs more isotropically than for the non-potential configuration.

Using one-minute cadence vector magnetograms of BBSO, we analyze the temporal behavior of the derived vertical electric currents associated with two solar flares on July 26, 2002. One is an M1.0 flare occurred in AR10044, while the other is an M8.7 flare in the adjacent AR 10039. We find that the temporal behaviors of electric currents are very different. For the M1.0 flare, the current density drops rapidly near the flaring neutral line; while for the M8.7 flare, the current density rapidly increases.

Based upon the similar time profiles of the hard x-ray and microwave emissions on 21 April 2002 flare-CME event, we argue that: (1) in the impulsive phase of the flare, the fast loop-loop reconnection triggered the quasi periodic magnetic energy release and particle acceleration with duration of the order of minute, (2) in the extended phase of the flare (01:40-01:50UT), the quasi period reconnection in current sheet produced the impulsive energetic electrons injection and modulated the microwave emissions with duration of 10-30 s, (3) the current driven instability enhances the magnetic energy releasing rate and scatters the energetic electrons, which may be used to explain the power index of the hard X-ray and microwave emissions.

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.

Latitudinal structure with four zones: two sub polar and two equatorial with 22-year period of polarity change is clearly demonstrated. The auto-correlation of the magnetic field has been calculated for all latitudes from 75 N to 75 S to study its temporal variability on a short and on a long term scale. The meridional drift of the magnetic field with 2–3 years periodicities has been clearly evidenced in the both hemispheres.

From Yohkoh and SoHO observations, the magnetic reconnection is considered as a main energy release mechanism of the solar active phenomena. In this study, we try to reproduce GOES X-ray light curves (1–8 $\AA$) of solar flares using a model incorporating the radiative and conductive cooling and the magnetic reconnection heating.

Using time-dependent resistive magnetohydrodynamic simulations, we study a flux rope eruption caused by magnetic reconnection with implication in coexistent flare-CME events. Without the resistance the flux rope system presents a double catastrophe. We use the first catastrophic state as the initial condition, in which an isolated flux rope coexists with two current sheets: a vertical one below and a transverse one above the flux rope. The flux rope erupts when reconnection starts in the current sheets, and the flux rope dynamics depends on the reconnection sequence in the two current sheets. We obtain three cases: reconnection occurs (1) simultaneously in the two current sheets, (2) first in the transverse one and then in the vertical, and (3) in an order opposite to case 2. Such a model exhibits characteristics of both magnetic breakout model for CME initiation and standard flare model. We argue that both breakout-like and tether-cutting reconnections may be important for CME eruptions.

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).

The propagation of surface and body linear MHD modes in a twisted magnetic flux tube embedded in a magnetically twisted plasma environment is considered. The dispersion relation for surface and body modes is derived assuming constant external twisted field. Analytic approximate solutions to the dispersion equation are found for the long and short wave length cases.

It was found, that in case the twisted component of the magnetic field in the environment of the flux tube is constant the index of Bessel functions $\nu$ in the corresponding dispersion relation is not integer. In the particular case of a homogen magnetic twist the total pressure is found to be constant across the boundary of the flux tube.

In this paper, we apply the general theory of Arnold (1965, 1966) and Moffatt et al. (1997). We search sufficient conditions for the linear stability of steady three-dimensional incompressible gravitating flows in ideal magnetohydrodynamics (MHD). The results suggest that the solar and the stellar convection zones must be sensitive to the density stratification.