Small-scale jetlike features in penumbral chromospheres.

We observed fine-scale jetlike features, referred to as penumbral microjets, in chromospheres of sunspot penumbrae. The microjets were identified in image sequences of a sunspot taken through a Ca II H-line filter on the Solar Optical Telescope on board the Japanese solar physics satellite Hinode. The microjets' small width of 400 kilometers and short duration of less than 1 minute make them difficult to identify in existing observations. The microjets are possibly caused by magnetic reconnection in the complex magnetic configuration in penumbrae and have the potential to heat the corona above a sunspot.

Twisting motions of sunspot penumbral filaments.

The penumbra of a sunspot is composed of numerous thin, radially extended, bright and dark filaments carrying outward gas flows (the Evershed flow). Using high-resolution images obtained by the Solar Optical Telescope aboard the solar physics satellite Hinode, we discovered a number of penumbral bright filaments revealing twisting motions about their axes. These twisting motions are observed only in penumbrae located in the direction perpendicular to the symmetry line connecting the sunspot center and the solar disk center, and the direction of the twist (that is, lateral motions of intensity fluctuation across filaments) is always from limb side to disk-center side. Thus, the twisting feature is not an actual twist or turn of filaments but a manifestation of dynamics of penumbral filaments with three-dimensional radiative transfer effects.

Coronal transverse magnetohydrodynamic waves in a solar prominence.

Solar prominences are cool 10(4) kelvin plasma clouds supported in the surrounding 10(6) kelvin coronal plasma by as-yet-undetermined mechanisms. Observations from Hinode show fine-scale threadlike structures oscillating in the plane of the sky with periods of several minutes. We suggest that these represent Alfvén waves propagating on coronal magnetic field lines and that these may play a role in heating the corona.

Rotating waveplates as polarization modulators for Stokes polarimetry of the sun: evaluation of seeing-induced crosstalk errors.

A formalism for estimating the crosstalk error among Stokes I,Q,U,V introduced by seeing-induced image motion is presented. This formalism is applied to several modulation schemes for polarization involving rotating waveplates, and it is evaluated using an observed power spectrum of image motion obtained from the Vacuum Tower Telescope at the National Solar Observatory/Sunspot. It is shown that rotating waveplates offer an acceptable alternative for measurements of absorption line polarization of features observed on the solar disk, provided the detection can be carried out at video frame rates or faster.