A pinhole camera has the advantage of undistorted field of view. Its imaging capability is limited by random (diffraction and atmospheric seeing) and systematic (penumbra) effects. The Pinhole Solar Monitor, PSM, measures the solar angular diameter by timing meridian transits. Meridian transits have been videorecorded with UTC synchronization at the pinhole gnomon of Santa Maria degli Angeli church in Rome. The tarature of this Clementine Gnomon is outlined with its accuracy as PSM. On the Moon an array of such PSM equipped with 1000 lines for parallel transits can monitor 0.1” variations of solar diameter.

A brief overview of upcoming total solar eclipses in 2008–2010 is presented. Global maps illustrate the geographic region of visibility for each eclipse. In addition, preliminary weather prospects are discussed.

It was performed a study of the North-South asymmetry of the magnetic field distribution by comparison of the temporal behavior of long and short term variabilities of the photospheric field at the same latitudes in opposit hemispheres using WSO data sets covered the interval from 1976 to 2005.

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.

Time-distance helioseismology and data from SOHO/MDI are used for obtaining 3D images of subsurface sound-speed perturbations and maps of plasma flows, associated with emerging magnetic flux and flaring activity of large active regions in October 2003. The results reveal extremely complicated dynamical processes in the upper convection zone and indicate that subsurface shear flows may play an important role in magnetic energy release in solar flares. Strong X-class flares generated impulsive seismic waves (“sunquakes”), traveling through surrounding sunspots, thus providing new insight into the interaction of seismic waves with magnetic fields.

Spectropolarimetric methods used at the Sayan Solar Observatory for measuring magnetic field strengths are described. The spectropolarimeter consists of a polarization splitter and a ferroelectric liquid crystal (FLC) modulator, allowing for several longitudinal H measurement modes. The report discusses advantages and disadvantages of modulation-based and modulationless measurements using ordinary slow CCD cameras. In some cases combined variants appear to be preferable.

Within the framework of the two-layer model the expression for the reflection coefficients of Alfven (torsion) waves propagated from the chromosphere into the corona have been obtained. As a result of reflection the energetic losses of waves with a period less than several tens of seconds are about 70%. This shows evidence in favor of the essential contribution of Alfven waves with a period of 10–40 s to coronal heating of the Sun.

The main aim of this research is to make direct comparison between the basic structure and dynamics of the photospheric magnetic field, solar wind and geomagnetic characteristics without using theoretical assumptions. The heliospheric and geomagnetic data are found to be divided into two groups characterized by their response to the variability of the latitudinal structures of the photospheric field on short and on long time scales.

The problem of isotropization of energetic protons in the $H_\alpha$ emitting region during flare energy release is considered. It has been shown that absence of the linear polarization of $H_\alpha$ emission in some events can be caused by excitation of small scale Alfven waves by anisotropic protons. Consequences of the proposed model are discussed.

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.

We extrapolated observed photospheric magnetic field before the 3B/X1.2 flare occurred in NOAA 10486 on 2003 October 26. Two magnetic null points exist above the active region, which have no crucial role in triggering the flare, even though enhanced TRACE EUV/UV emission was observed before the main flare due to magnetic reconnection near the lower-altitude null point. We conclude that this flare results from the loss of equilibrium due to persistent flux emergence and photospheric motion, and strong shear. The accompanying fast CME with velocity of $\sim$ 800 km $s^{-1}$ shows quick mass pickup and energy increase in the low corona. Its kinetic energy is always larger than its potential energy.

After summarizing the geometric relationship of the RHESSI flare X-ray sources with the TRACE flare loops, and the motion modes of RHESSI flare X-ray sources, we concentrate on the newly discovered downward motion of flare looptop X-ray source. In particular, we present a new argument for the flare loop shrinkage during the impulsive phase: TRACE 195 Å loop shrinkage. The temporal behavior of 195 Å loop shrinkage and its magnitude are consistent with that revealed from the RHESSI X-ray sources. Further study shows that the TRACE 195 Å loop shrinkage is in the form of oscillation, with a period of about 150 s and an amplitude of about 300 km. We discuss this oscillatory shrinkage with respect to a numerical simulation of reconnection model.

The solar magnetic field that extends through the chromosphere is thought to expand through the transition region into the corona. The strong flux concentrations are located within the boundaries of supergranular convection cells. These boundaries form network lanes, observed in emission lines as bright lanes with varying width throughout the solar atmosphere. These network field concentrations are surrounded by mixed-polarity magnetic field with a scale of the granule diameter, as suggested by observations. We use potential magnetic field extrapolations on synthetic magnetograms to study the magnetic network topology and the effects of background magnetic field on the network expansion through the solar atmosphere. We find that the background magnetic field has a considerable effect on the ratio of network area over field of view. Furthermore we find that the expansion of the network boundaries with height deviate significantly from well-assumed funnel model expansion.

I first review: a) the current state of knowledge of ion acceleration in solar flares; b) the physics of positron production and annihilation; and c) recent RHESSI data on solar flare annihilation radiation. I then show how the modeling of the positron production and annihilation in the chromosphere, coupled with the newly available high-resolution data on the 511 keV annihilation line, can have important physical implications w. r. t. the models: a) information on the temperature and density of the chromosphere; b) constraints on some of the physical characteristics of the flare and to some extent on the acceleration process.

Although I do mention past instruments (SMM and Yohkoh), this review focuses on the RHESSI satellite, considering the quantum leap it has constituted in the quality of the data it is providing and consequently the constraints it can place on models (of ion acceleration, annihilation environment, etc.).

The solar magnetism, its origin, and its impact on the earth are of primary interest for solar physicists. The understanding of the solar dynamo in the convection zone and the coupling of the magnetic fields up to the corona and the heliosphere calls for synoptic as well as for high spatial resolution observations of the Sun. Understanding the interactions between radiative and magneto-convective processes at the interface between the solar interior and the atmosphere requires spectro-polarimetric observations at high spatial and spectral resolution with high polarimetric accuracy. Thus large-aperture telescopes are needed to resolve the small scales and to collect enough photons to study the evolution of the magnetic processes. For assembling the mosaic of the solar dynamo and its magnetic coupling out to the heliosphere, large scale properties and hence synoptic observations play a crucial role. I present my personal perspective of the prospects in ground-based solar physics, and comment on the planned and upcoming new facilities including SOLIS, GREGOR, NST, SUNRISE, and ATST, as well as ALMA and FASR, but also mention the upcoming space missions HMI@SDO and SOLAR-B.

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.

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.

The performance of the solar cell is influenced by the spectral solar distribution. The silicon solar cell spectral response does not totally coincide with the solar spectrum. In the case of sun light exposure at outdoor conditions, the shapes of the cell spectral response curves are slightly different than that of under simulated light exposure. This paper is interested in studying the effect of variation of solar radiation during the partial eclipse on the output short circuit current and open circuit voltage of the monocrystalline and amorphous silicon solar cells. Also, the spectral cell behaveiour in terms of the solar eclipse was investigated. The ultimate goal is to explain some of an interesting natural phenomenon by using the solar cell spectral response.

We review what we have learnt about flares and prominences using multi-wavelength observations in the perspective of testing theoretical models.

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.