The formation of jets such as dynamic fibrils, mottles, and spicules in the solar chromosphere is one of the most important, but also most poorly understood, phenomena of the Sun's magnetized outer atmosphere. We use extremely high resolution observations from the Swedish 1 m Solar Telescope combined with advanced numerical modeling to show that in active regions these jets are a natural consequence of upwardly propagating slow-mode magnetoacoustic shocks. These shocks form when waves generated by convective flows and global p-mode oscillations in the lower lying photosphere leak upward into the magnetized chromosphere. We find excellent agreement between observed and simulated jet velocities, decelerations, lifetimes, and lengths. Our findings suggest that previous observations of quiet-Sun spicules and mottles may also be interpreted in light of a shockdriven mechanism.

We discuss penumbral fine structure in a small part of a pore, observed with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST), close to its diffraction limit of 0.16 arcsec. Milne-Eddington inversions applied to these Stokes data reveal large variations of field strength and inclination angle over dark-cored penumbral intrusions and a dark-cored light bridge. The mid-outer part of this penumbra structure shows 0.3 arcsec wide spines, separated by 1.6 arcsec (1200 km) and associated with 30 deg inclination variations. Between these spines, there are no small-scale magnetic structures that easily can be be identified with individual flux tubes. A structure with nearly 10 deg more vertical and weaker magnetic field is seen midways between two spines. This structure is co-spatial with the brightest penumbral filament, possibly indicating the location of a convective upflow from below.Comment: Accepted for publication in ApJL 17 Oct 2008. One Figure adde

We present unprecedented high resolution Hα observations, obtained with the Swedish 1-m Solar Telescope, that, for the first time, spatially and temporally resolve dynamic fibrils in active regions on the Sun. These jet-like features are similar to mottles or spicules in quiet Sun. We find that most of these fibrils follow almost perfect parabolic paths in their ascent and descent. We measure the properties of the parabolic paths taken by 257 fibrils, and present an overview of the deceleration, maximum velocity, maximum length and duration, as well as their widths and the thickness of a bright ring that often occurs above dynamic fibrils. We find that the observed deceleration of the projected path is typically only a fraction of solar gravity, and incompatible with a ballistic path at solar gravity. We report on significant differences of fibril properties between those occurring above a dense plage region, and those above a less dense plage region where the magnetic field seems more inclined from the vertical. We compare these findings to advanced numerical 2D radiative MHD simulations, and find that fibrils are most likely formed by chromospheric shock waves that occur when convective flows and global oscillations leak into the chromosphere along the field lines of magnetic flux concentrations. Detailed comparison of observed and simulated fibril properties shows striking similarities of the values for deceleration, maximum velocity, maximum length and duration. We compare our results with observations of mottles and find that a similar mechanism is most likely at work in the quiet Sun.