To explain the origin of hard X-ray emission, we suggest the internal shocks could be created in the reconnection jet and accelerate the energetic particles in the solar flares. We examine its possibility by performing 2D resistive MHD simulations. We use very small very small grid to resolve the diffusion region and remove the effect of numerical noise. As the results, the current sheet becomes thin by tearing instability, and collapses to Sweet-Parker sheet. It becomes unstable again so that the secondary teaing instability occurs. Immediately after the plasmoid ejection, anomalous resistivity sets in and Petschek-like reconnection starts. During the Petschek reconnection, many plasmoids are created by the secondary tearing instability and ejected along the current sheet. The multiple fast shocks are created in the current sheet. We suggest that the internal shocks shown in this paper are possible sites for the particle acceleration in the solar flares.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

After briefly summarizing the outstanding achievements and new tendencies witnessed in recent years in the studies of magnetic fields of solar active regions (ARs), we focus on the current understanding on flux appearance and disappearance. On flux appearance, the moving magnetic features (MMFs) stand still as a mystery in solar physics, although the emergence of magnetic flux in the bipolar form are fairly understood. However, the possibly sympathetic flux emergence of several ARs and the appearance of active longitudes or hot spots are poorly understood. The only confirmed model of flux disappearance is the observed flux cancellation. Detailed analysis of the alignments of transverse magnetic fields and the history of magnetic flux evolution suggest that flux cancellation is more likely to be the magnetic reconnection in the lower solar atmosphere. Magnetic and current helicity provide new diagnosis in understanding flux emergence and disappearance, and constrains the energy process in solar activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Many records of climatic and environmental changes based on various proxy data exhibit distinct cyclicities that have been attributed to extraterrestrial forcing such as changes in solar activity. To study the long-term changes of solar activity, different data sets of solar activity, both indirect data (the Schove series) and proxy data (cosmogenic isotopes) were analyzed. Both sets of solar activity clearly show centennial and millennial changes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Long-term behaviour of the interplanetary magnetic field is compared with that of the quadrupole harmonic of the solar axisymmetric magnetic field. Substantial correlation between them is found both on the time scale of 22-yr cycle and on the shorter time scale of several years.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Transits of Venus occur in pairs 8 yr apart, the pairs separated by intervals of either 112 or 130 yr, because of the pattern of approximate orbital resonances. Transits of Mercury show a different pattern, partly because of the more eccentric orbit, and also because the structure of the approximate resonances is different. The near-resonance in Venus' axial rotation strongly suggests a tidal link with the Earth.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Integral Field Spectroscopy provides a powerful new tool for disentangling the complex structure of Active Galactic Nuclei—allowing 2D mapping of the distribution, kinematics and excitation of ionized gas and of stellar velocity profiles and populations. Such comprehensive datasets are likely to reveal important clues about the physics of the narrow line region, interactions with the host galaxy and central dynamical forces. Here we present observations of the central regions of NGC1068, obtained using the visible-wavelength GMOS-IFU at Gemini North and NGC4151, taken with a prototype near-infrared fibre IFU at the UK Infrared Telescope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The propagation of cosmological ionization fronts during the reionization of the universe is strongly influenced by small-scale ($\sim$ kpc) gas inhomogeneities caused by structure formation. In this paper we study this important effect by performing detailed radiative-hydrodynamic simulations of photoevaporation of cosmological minihalos (MHs) and incorporating the results into a semi-analytical model of reionization, which also includes the effect of mean intergalactic medium (IGM) clumping and the nonlinear clustering of minihalos. We find that small-scale structures have a significant effect on the process of reionization, slowing it down and extending it in time. This can help in understanding the recent observations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, which point to an early and extended reionization epoch.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We collected X-ray and optical images for a X-ray flux-limited, complete sample of 93 active galactic nuclei (AGNs) at z<0.1, selected from the ROSAT Bright Survey. By modeling the host galaxy and the central AGN, we decompose the optical emission into nuclear, bulge and disk components. We cross-correlated our sample with the NVSS and FIRST radio catalogs, and, due to their limited sky coverage, 53 matches were found. We find that the nuclear optical luminosity, thought to be associated with the accretion disk surrounding the active black hole, correlates with the X-ray luminosity, the radio luminosity, and the black hole mass.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html