Context. Jets of plasma are frequently observed in the solar corona. A self-similar recurrent behavior is observed in a fraction of them. Aims. Jets are thought to be a consequence of magnetic reconnection; however, the physics involved is not fully understood. Therefore, we study some jet observations with unprecedented temporal and spatial resolutions. Methods. The extreme-ultraviolet (EUV) jets were observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board SDO measured the vector magnetic field, from which we derive the magnetic flux evolution, the photospheric velocity field, and the vertical electric current evolution. The magnetic configuration before the jets is derived by the nonlinear force-free field extrapolation. Results. Three EUV jets recurred in about one hour on 17 September 2010 in the following magnetic polarity of active region 11106. We derive that the jets are above a pair of parasitic magnetic bipoles that are continuously driven by photospheric diverging flows. The interaction drove the buildup of electric currents, which we observed as elongated patterns at the photospheric level. For the first time, the high temporal cadence of the HMI allows the evolution of such small currents to be followed. In the jet region, we found that the integrated absolute current peaks repetitively in phase with the 171 Å flux evolution. The current buildup and its decay are both fast, about ten minutes each, and the current maximum precedes the 171 Å also by about ten minutes. Then, the HMI temporal cadence is marginally fast enough to detect such changes. Conclusions. The photospheric current pattern of the jets is found to be associated with the quasi-separatrix layers deduced from the magnetic extrapolation. From previous theoretical results, the observed diverging flows are expected to continuously build such currents. We conclude that the magnetic reconnection occurs periodically, in the current layer created between the emerging bipoles and the large-scale active region field. The periodic magnetic reconnection induced the observed recurrent coronal jets and the decrease of the vertical electric current magnitude.

The interaction between emerging magnetic flux and the pre-existing ambient field has become a "hot" topic for both numerical simulations and high-resolution observations of the solar atmosphere. The appearance of brightenings and surges during episodes of flux emergence is believed to be a signature of magnetic reconnection processes. We present an analysis of a small-scale flux emergence event in NOAA 10971, observed simultaneously with the Swedish 1-m Solar Telescope on La Palma and the Hinode satellite during a joint campaign in September 2007. Extremely high-resolution G-band, Hα, and Ca II H filtergrams, Fe I and Na I magnetograms, EUV raster scans, and Xray images show that the emerging region was associated with chromospheric, transition region and coronal brightenings, as well as with chromospheric surges. We suggest that these features were caused by magnetic reconnection at low altitude in the atmosphere. To support this idea, we perform potential and linear force-free field extrapolations using the FROMAGE service. The extrapolations show that the emergence site is cospatial with a 3D null point, from which a spine originates. This magnetic configuration and the overall orientation of the field lines above the emerging flux region are compatible with the structures observed in the different atmospheric layers, and remain stable against variations of the force-free field parameter. Our analysis supports the predictions of recent 3D numerical simulations that energetic phenomena may result from the interaction between emerging flux and the pre-existing chromospheric and coronal field.

Aims. Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures bright in G-band. Methods. The G-band filtergrams together with magnetograms and dopplergrams were taken for a plage region covered by abnormal granules as well as ubiquitous G-band bright points, using the Swedish 1-m Solar Telescope (SST) under very good seeing conditions. Results. High magnetic flux density regions are not necessarily associated with G-band bright points. We refer to the observed extended areas with high magnetic flux density as magnetic islands to separate them from magnetic elements. We discover that Gband bright points tend to be located near the boundary of such magnetic islands. The concentration of G-band bright points decreases with inward distance from the boundary of the magnetic islands. Moreover, G-band bright points are preferentially located where magnetic flux density is higher, given the same distance from the boundary. There are some bright points located far inside the magnetic islands. Such bright points have higher minimum magnetic flux density at the larger inward distance from the boundary. Convective velocity is apparently reduced for such high magnetic flux density regions regardless of whether they are populated by G-band bright points or not. The magnetic islands are surrounded by downflows. Conclusions. These results suggest that high magnetic flux density, as well as efficient heat transport from the sides or beneath, are required to make magnetic elements bright in G-band.Key words. Sun: magnetic fields -Sun: faculae, plages -convection IntroductionMagnetic fields on the Sun have various spatial and time scales. Sunspots have the largest scale size (∼10 4−5 km) with long lifetimes (∼1 month) and very high contrast, while magnetic elements often observed in the Fraunhofer G-band (the CN band, the wing of Ca H and K, and continuum) are the smallest resolved structures, and are believed to be building blocks of active regions and the quiet Sun magnetic network. In the 1970s, filigree structures in the intergranular lanes and faculae observed at the solar limb were reported (Dunn & Zirker 1973;Mehltretter 1974), and these small bright points were believed to be a manifestation of elemental magnetic fields (Spruit 1976(Spruit , 1977. Beckers & Schröter (1968) originally observed small magnetic features called magnetic knots with magnetic field strength between 1000−2000 G. Recent high-resolution observations have been able to resolve these magnetic knots into smaller magnetic elements. The question of how such small structures with strong magnetic flux density and with short lifetime exist is one of the central issues in solar magnetohydrodynamics. Direct magnetic observations of the magnetic elements are, however, diffic...

Vortex-type motions have been measured by tracking bright points in high-resolution observations of the solar photosphere. These small-scale motions are thought to be determinant in the evolution of magnetic footpoints and their interaction with plasma and therefore likely to play a role in heating the upper solar atmosphere by twisting magnetic flux tubes. We report the observation of magnetic concentrations being dragged towards the center of a convective vortex motion in the solar photosphere from highresolution ground-based and space-borne data. We describe this event by analyzing a series of images at different solar atmospheric layers. By computing horizontal proper motions, we detect a vortex whose center appears to be the draining point for the magnetic concentrations detected in magnetograms and well-correlated with the locations of bright points seen in G-band and CN images.

High-resolution observations of a quiet-Sun internetwork region taken with the Solar 1-m Swedish Telescope in La Palma are analysed. We determine the location of small-scale vortex motions in the solar photospheric region by computing the horizontal proper motions of smallscale structures on time-series of images. These plasma convectively driven swirl motions are associated to (1) downdrafts (that have been commonly explained as corresponding to sites where the plasma is cooled down and hence returned to the interior below the visible photospheric level) and (2) horizontal velocity vectors converging on a central point. The sink cores are proved to be the final destination of passive floats tracing plasma flows towards the centre of each vortex. We establish the occurrence of these events to be 1.4 × 10 −3 and 1.6 × 10 −3 vortices Mm −2 min −1 , respectively, for the two time-series analysed here.