Showing papers by "Bruce W. Lites published in 2008"

The Solar Optical Telescope for the Hinode Mission: An Overview

Abstract: The Solar Optical Telescope (SOT) aboard the Hinode satellite (formerly called Solar-B) consists of the Optical Telescope Assembly (OTA) and the Focal Plane Package (FPP). The OTA is a 50-cm diffraction-limited Gregorian telescope, and the FPP includes the narrowband filtergraph (NFI) and the broadband filtergraph (BFI), plus the Stokes Spectro-Polarimeter (SP). The SOT provides unprecedented high-resolution photometric and vector magnetic images of the photosphere and chromosphere with a very stable point spread function and is equipped with an image-stabilization system with performance better than 0.01 arcsec rms. Together with the other two instruments on Hinode (the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS)), the SOT is poised to address many fundamental questions about solar magnetohydrodynamics. This paper provides an overview; the details of the instrument are presented in a series of companion papers.

The Horizontal Magnetic Flux of the Quiet-Sun Internetwork as Observed with the Hinode Spectro-Polarimeter

Abstract: Observations of very quiet Sun using the Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft reveal that the quiet internetwork regions are pervaded by horizontal magnetic flux. The spatial average horizontal apparent flux density derived from wavelength-integrated measures of Zeeman-induced linear polarization is -->BTapp = 55 Mx cm −2, as compared to the corresponding average vertical apparent flux density of -->| BLapp| = 11 Mx cm −2. Distributions of apparent flux density are presented. Magnetic fields are organized on mesogranular scales, with both horizontal and vertical fields showing voids of reduced flux density of a few granules spatial extent. The vertical fields are concentrated in the intergranular lanes, whereas the stronger horizontal fields are somewhat separated spatially from the vertical fields and occur most commonly at the edges of the bright granules. High-S/N observations from disk center to the limb help to constrain possible causes of the apparent imbalance between -->| BLapp| and -->BTapp, with unresolved structures of linear dimension on the surface smaller by at least a factor of 2 relative to the SOT/SP angular resolution being one likely cause of this discrepancy. Other scenarios for explaining this imbalance are discussed. The horizontal fields are likely the source of the seething fields of the quiet Sun discovered by Harvey et al. The horizontal fields may also contribute to the hidden turbulent flux suggested by studies involving Hanle effect depolarization of scattered radiation.

Polarization Calibration of the Solar Optical Telescope onboard Hinode

Abstract: The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector magnetic fields on the Sun through precise spectropolarimetry of solar spectral lines with a spatial resolution of 0.2 – 0.3 arcsec. A photometric accuracy of 10−3 is achieved and, after the polarization calibration, any artificial polarization from crosstalk among Stokes parameters is required to be suppressed below the level of the statistical noise over the SOT’s field of view. This goal was achieved by the highly optimized design of the SOT as a polarimeter, extensive analyses and testing of optical elements, and an end-to-end calibration test of the entire system. In this paper we review both the approach adopted to realize the high-precision polarimeter of the SOT and its final polarization characteristics.

Nonlinear Force‐free Field Modeling of a Solar Active Region around the Time of a Major Flare and Coronal Mass Ejection

Abstract: Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and are powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of preexisting atmospheric magnetic flux subject to surface plasma flows or whether these currents are associated with the emergence of flux from within the solar convective zone. We address this problem by applying state-of-the-art nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA AR 10930 around the time of a powerful X3.4 flare. We compute 14 NLFFF models with four different codes and a variety of boundary conditions. We find that the model fields differ markedly in geometry, energy content, and force-freeness. We discuss the relative merits of these models in a general critique of present abilities to model the coronal magnetic field based on surface vector field measurements. For our application in particular, we find a fair agreement of the best-fit model field with the observed coronal configuration, and argue (1) that strong electrical currents emerge together with magnetic flux preceding the flare, (2) that these currents are carried in an ensemble of thin strands, (3) that the global pattern of these currents and of field lines are compatible with a large-scale twisted flux rope topology, and (4) that the ~1032 erg change in energy associated with the coronal electrical currents suffices to power the flare and its associated coronal mass ejection.

Hinode SOT Observations of Solar Quiescent Prominence Dynamics

Abstract: We report findings from multihour 0.2'' resolution movies of solar quiescent prominences (QPs) observed with the Solar Optical Telescope (SOT) on the Hinode satellite. The observations verify previous findings of filamentary downflows and vortices in QPs. SOT observations also verify large-scale transverse oscillations in QPs, with periods of 20-40 minutes and amplitudes of 2-5 Mm. The upward propagation speed of several waves is found to be ~10 km s-1, comparable to the sound speed of a 10,000 K plasma, implying that the waves are magnetoacoustic in origin. Most significantly, Hinode SOT observations reveal that dark, episodic upflows are common in QPs. The upflows are 170-700 km in width, exhibit turbulent flow, and rise with approximately constant speeds of ~20 km s-1 from the base of the prominence to heights of ~10-20 Mm. The upflows are visible in both the Ca II H-line and Hα bandpasses of SOT. The new flows are seen in about half of the QPs observed by SOT to date. The dark upflows resemble buoyant starting plumes in both their velocity profile and flow structure. We discuss thermal and magnetic mechanisms as possible causes of the plumes.

The Magnetic Landscape of the Sun's Polar Region

Abstract: We present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field strengths as strong as 1 kG scattered in latitude between 70° and 90°. They all have the same polarity, consistent with the global polarity of the polar region. The field vectors are observed to diverge from the centers of the flux elements, consistent with a view of magnetic fields that are expanding and fanning out with height. The polar region is also found to have ubiquitous horizontal fields. The polar regions are the source of the fast solar wind, which is channeled along unipolar coronal magnetic fields whose photospheric source is evidently rooted in the strong-field, vertical patches of flux. We conjecture that vertical flux tubes with large expansion around the photospheric-coronal boundary serve as efficient chimneys for Alfven waves that accelerate the solar wind.

Magnetic Landscape of Sun's Polar Region

Abstract: We present the magnetic landscape of the polar region of the Sun that is unprecedented in terms of high spatial resolution, large field of view, and polarimetric precision. These observations were carried out with the Solar Optical Telescope aboard \emph{Hinode}. Using a Milne-Eddington inversion, we found many vertically-oriented magnetic flux tubes with field strength as strong as 1 kG that are scattered in latitude between 70-90 degree. They all have the same polarity, consistent with the global polarity of the polar region. The field vectors were observed to diverge from the center of the flux elements, consistent with a view of magnetic fields that expand and fan out with height. The polar region is also covered with ubiquitous horizontal fields. The polar regions are the source of the fast solar wind channelled along unipolar coronal magnetic fields whose photospheric source is evidently rooted in the strong field, vertical patches of flux. We conjecture that vertical flux tubes with large expansion around the photosphere-corona boundary serve as efficient chimneys for Alfven waves that accelerate the solar wind.

Emergence of a Helical Flux Rope under an Active Region Prominence

Abstract: Continuous observations were obtained of NOAA AR 10953 with the Solar Optical Telescope (SOT) on board the Hinode satellite from 2007 April 28 to May 9. A prominence was located over the polarity inversion line (PIL) to the southeast of the main sunspot. These observations provided us with a time series of vector magnetic fields on the photosphere under the prominence. We found four features: (1) The abutting opposite-polarity regions on the two sides along the PIL first grew laterally in size and then narrowed. (2) These abutting regions contained vertically weak but horizontally strong magnetic fields. (3) The orientations of the horizontal magnetic fields along the PIL on the photosphere gradually changed with time from a normal-polarity configuration to an inverse-polarity one. (4) The horizontal magnetic field region was blueshifted. These indicate that helical flux rope was emerging from below the photosphere into the corona along the PIL under the preexisting prominence. We suggest that this supply of a helical magnetic flux to the corona is associated with evolution and maintenance of active region prominences.

Formation of Solar Magnetic Flux Tubes with Kilogauss Field Strength Induced by Convective Instability

Abstract: Convective instability has been a mechanism used to explain the formation of solar photospheric flux tubes with kG field strength. However, the turbulence of the Earth's atmosphere has prevented ground-based observers from examining the hypothesis with precise polarimetric measurement on the subarcsecond scale flux tubes. Here we discuss observational evidence of this scenario based on observations with the Solar Optical Telescope (SOT) aboard Hinode. The cooling of an equipartition field strength flux tube precedes a transient downflow reaching 6 km s−1 and the intensification of the field strength to 2 kG. These observations agree very well with the theoretical predictions.

Transient horizontal magnetic fields in solar plage regions

Abstract: Aims. We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Methods. Spectro-polarimetric observations were carried out with a cadence of 34 s for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. Results. The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type 1 and convection-driven emergence as type 2. Although both events have magnetic field strengths of about 600 G, the filling factor of type 1 is a factor of two larger than that of type 2. Conclusions. Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.

Hinode Observations of Magnetic Elements in Internetwork Areas

Abstract: We use sequences of images and magnetograms from Hinode to study magnetic elements in internetwork parts of the quiet solar photosphere. Visual inspection shows the existence of many long-lived (several hours) structures that interact frequently and may migrate over distances of ~7 Mm over a period of a few hours. About a fifth of the elements have an associated bright point in G-band or Ca II H intensity. We apply a hysteresis-based algorithm to identify elements. The algorithm is able to track elements for about 10 minutes on average. Elements intermittently drop below the detection limit, although the associated flux apparently persists and often reappears some time later. We infer proper motions of elements from their successive positions and find that they obey a Gaussian distribution with an rms of 1.57 ± 0.08 km s−1. The apparent flows indicate a bias of about 0.2 km s−1 toward the network boundary. Elements of negative polarity show a higher bias than elements of positive polarity, perhaps as a result of the dominant positive polarity of the network in the field of view or because of increased mobility due to their smaller size. A preference for motions in X is likely explained by higher supergranular flow in that direction. We search for emerging bipoles by grouping elements of opposite polarity that appear close together in space and time. We find no evidence supporting Joy's law at arcsecond scales.

Transient horizontal magnetic fields in solar plage regions

Abstract: We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Spectro-polarimetric observations were carried out with a cadence of 34 seconds for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type1 and convection-driven emergence as type2. Although both events have magnetic field strengths of about 600 G, the filling factor of type1 is a factor of two larger than that of type2. Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.

Cooperative Observation of Ellerman Bombs between the Solar Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope

Abstract: High-resolution Ca II H broad-band filter images of NOAA 10933 on 2007 January 5 were obtained by the Solar Optical Telescope aboard the Hinode satellite. Many small-scale ( 100) bright points were observed outside the sunspot and inside the emerging flux region. We identified some of these bright points with Ellerman bombs (EBs) by using H images taken by the Domeless Solar Telescope at Hida observatory. The sub-arcsec structures of two EBs seen in Ca II H were studied in detail. Our observation showed the following two aspects: (1) The Ca II H bright points identified with EBs were associated with the bipolar magnetic field structures, as reported by previous studies. (2) The structure of the Ca II H bright points turned out to consist of the following two parts: a central elongated bright core (0:007 0:005) located along the magnetic neutral line and a diffuse halo (1:002 1:008).

Frequent Occurrence of High-Speed Local Mass Downflows on the Solar Surface

Abstract: We report on new spectropolarimetric measurements with simultaneous filter imaging observation, revealing the frequent appearance of polarization signals indicating high-speed, probably supersonic, downflows that are associated with at least three different configurations of magnetic fields in the solar photosphere. The observations were carried out with the Solar Optical Telescope on board the Hinode satellite. High-speed downflows are excited when a moving magnetic feature is newly formed near the penumbral boundary of sunspots. Also, a new type of downflows is identified at the edge of sunspot umbra that lack accompanying penumbral structures. These may be triggered by the interaction of magnetic fields swept by convection with well-concentrated magnetic flux. Another class of high-speed downflows are observed in quiet Sun and sunspot moat regions. These are closely related to the formation of small concentrated magnetic flux patches. High-speed downflows of all types are transient time-dependent mass motions. These findings suggest that the excitation of supersonic mass flows are one of the key observational features of the dynamical evolution occurring in magnetic-field fine structures on the solar surface.

Evidence of magnetic field wrapping around penumbral filaments

Abstract: We employ high-spatial resolution spectropolarimetric observations from the Solar Optical Telescope on-board the Hinode spacecraft to investigate the fine structure of the penumbral magnetic fields. The Stokes vector of two neutral iron lines at 630 nm is inverted at every spatial pixel to retrieve the depth-dependence of the magnetic field vector, line-of-sight velocity and thermodynamic parameters. We show that the azimuthal angle of the magnetic field vector has opposite sign on both sides above the penumbral filaments. This is consistent with the wrapping of an inclined field around the horizontal filaments. The wrapping effect is stronger for filaments with larger horizontal extensions. In addition, we find that the external magnetic field can penetrate into the intraspines, leading to non-radial magnetic fields inside them. These findings shed some light on the controversial small-scale structure of the sunspot penumbra.

Magnetic flux loss and flux transport in a decaying active region

Abstract: We estimate the temporal change of magnetic flux normal to the solar surface in a decaying active region by using a time series of the spatial distribution of vector magnetic fields in the photosphere The vector magnetic fields are derived from full spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode We compare a magnetic flux loss rate to a flux transport rate in a decaying sunspot and its surrounding moat region The amount of magnetic flux that decreases in the sunspot and moat region is very similar to magnetic flux transported to the outer boundary of the moat region The flux loss rates [(dF/dt)loss] of magnetic elements with positive and negative polarities balance each other around the outer boundary of the moat region These results suggest that most of the magnetic flux in the sunspot is transported to the outer boundary of the moat region as moving magnetic features, and then removed from the photosphere by flux cancellation around the outer boundary of the moat region

Net circular polarization of sunspots in high spatial resolution

Abstract: Context Net circular polarization (NCP) of spectral lines in sunspots has been most successfully explained by the presense of discontinuities in the magnetic field inclination and flow velocity along the line-of-sight in the geometry of the embedded flux tube model of penumbrae (∆γ-effect) Aims The fine scale structure of NCP in a sunspot is examined with special attention paid to spatial relations of the Evershed flow to confirm the validity of the present interpretation of the NCP of sunspots Methods High resolution spectro-polarimetric data of a positive-polarity sunspot obtained by the Solar Optical Telescope aboard Hinode are analysed Results A positive NCP is associated with the Evershed flow channels in both limb-side and disk center-side penumbrae and with upflows in the penumbra at disk center The negative NCP in the disk center-side penumbra is generated in inter-Evershed flow channels Conclusions The first result is apparently inconsistent with the current explanation of NCP with the ∆γ-effect but rather suggests a positive correlation between the magnetic field strength and the flow velocity as the cause of the NCP The second result serves as strong evidence for the presence of gas flows in inter-Evershed flow channels

Magnetic Flux Loss and Flux Transport in a Decaying Active Region

Abstract: We estimate the temporal change of magnetic flux perpendicular to the solar surface in a decaying active region by using a time series of the spatial distribution of vector magnetic fields in the photosphere. The vector magnetic fields are derived from full spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We compare a magnetic flux loss rate to a flux transport rate in a decaying sunspot and its surrounding moat region. The amount of magnetic flux that decreases in the sunspot and moat region is very similar to magnetic flux transported to the outer boundary of the moat region. The flux loss rates [$(dF/dt)_{loss}$] of magnetic elements with positive and negative polarities are balanced each other around the outer boundary of the moat region. These results suggest that most of the magnetic flux in the sunspot is transported to the outer boundary of the moat region as moving magnetic features, and then removed from the photosphere by flux cancellation around the outer boundary of the moat region.

Coronal transverse magnetohydrodynamic waves in a solar prominence

Abstract: 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 \emph{Hinode} show fine-scale threadlike structures oscillating in the plane of the sky with periods of several minutes. We suggest these transverse magnetohydrodynamic waves may represent Alfv\'en waves propagating on coronal magnetic field lines and these may play a role in heating the corona.

Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode SOT

Abstract: Continuous observations of sunspot penumbrae with the Solar Optical Telescope aboard Hinode clearly show that the outer boundary of the penumbra fluctuates around its averaged position. The penumbral outer boundary moves inward when granules appear in the outer penumbra. We discover that such granules appear one after another while moving magnetic features (MMFs) are separating from the penumbral "spines" (penumbral features that have fields that are stronger and more vertical than those of their surroundings). These granules that appear in the outer penumbra often merge with bright features inside the penumbra that move with the spines as they elongate toward the moat region. This suggests that convective motions around the penumbral outer boundary are related to the disintegration of magnetic flux in the sunspot. We also find that dark penumbral filaments frequently elongate into the moat region in the vicinity of MMFs that detach from penumbral spines. Such elongating dark penumbral filaments correspond to nearly horizontal fields extending from the penumbra. Pairs of MMFs with positive and negative polarities are sometimes observed along the elongating dark penumbral filaments. This strongly supports the notion that such elongating dark penumbral filaments have magnetic fields with a "sea serpent"-like structure. Evershed flows, which are associated with the penumbral horizontal fields, may be related to the detachment of the MMFs from the penumbral spines, as well as to the formation of the MMFs along the dark penumbral filaments that elongate into the moat region.

Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode/SOT

Abstract: Continuous observations of sunspot penumbrae with the Solar Optical Telescope aboard Hinode clearly show that the outer boundary of the penumbra fluctuates around its averaged position. The penumbral outer boundary moves inward when granules appear in the outer penumbra. We discover that such granules appear one after another while moving magnetic features (MMFs) are separating from the penumbral "spines" (penumbral features that have fields that are stronger and more vertical than those of their surroundings). These granules that appear in the outer penumbra often merge with bright features inside the penumbra that move with the spines as they elongate toward the moat region. This suggests that convective motions around the penumbral outer boundary are related to the disintegration of magnetic flux in the sunspot. We also find that dark penumbral filaments frequently elongate into the moat region in the vicinity of MMFs that detach from penumbral spines. Such elongating dark penumbral filaments correspond to nearly horizontal fields extending from the penumbra. Pairs of MMFs with positive and negative polarities are sometimes observed along the elongating dark penumbral filaments. This strongly supports the notion that such elongating dark penumbral filaments have magnetic fields with a "sea serpent"-like structure. Evershed flows, which are associated with the penumbral horizontal fields, may be related to the detachment of the MMFs from the penumbral spines, as well as to the formation of the MMFs along the dark penumbral filaments that elongate into the moat region.

Emergence of a Helical Flux Rope Under an Active Region Prominence

Abstract: Continuous observations were obtained of active region 10953 with the Solar Optical Telescope (SOT) on board the \emph{Hinode} satellite during 2007 April 28 to May 9. A prominence was located over the polarity inversion line (PIL) in the south-east of the main sunspot. These observations provided us with a time series of vector magnetic fields on the photosphere under the prominence. We found four features: (1) The abutting opposite-polarity regions on the two sides along the PIL first grew laterally in size and then narrowed. (2) These abutting regions contained vertically-weak, but horizontally-strong magnetic fields. (3) The orientations of the horizontal magnetic fields along the PIL on the photosphere gradually changed with time from a normal-polarity configuration to a inverse-polarity one. (4) The horizontal-magnetic field region was blueshifted. These indicate that helical flux rope was emerging from below the photosphere into the corona along the PIL under the pre-existing prominence. We suggest that this supply of a helical magnetic flux into the corona is associated with evolution and maintenance of active-region prominences.

Hinode Observations of Magnetic Elements in Internetwork Areas

Abstract: We use sequences of images and magnetograms from Hinode to study magnetic elements in internetwork parts of the quiet solar photosphere. Visual inspection shows the existence of many long-lived (several hours) structures that interact frequently, and may migrate over distances ~7 Mm over a period of a few hours. About a fifth of the elements have an associated bright point in G-band or Ca II H intensity. We apply a hysteresis-based algorithm to identify elements. The algorithm is able to track elements for about 10 min on average. Elements intermittently drop below the detection limit, though the associated flux apparently persists and often reappears some time later. We infer proper motions of elements from their successive positions, and find that they obey a Gaussian distribution with an rms of 1.57+-0.08 km/s. The apparent flows indicate a bias of about 0.2 km/s toward the network boundary. Elements of negative polarity show a higher bias than elements of positive polarity, perhaps as a result of to the dominant positive polarity of the network in the field of view, or because of increased mobility due to their smaller size. A preference for motions in X is likely explained by higher supergranular flow in that direction. We search for emerging bipoles by grouping elements of opposite polarity that appear close together in space and time. We find no evidence supporting Joy's law at arcsecond scales.

Frequent Occurrence of High-speed Local Mass Downflows on the Solar Surface

Abstract: We report on new spectro-polarimetric measurements with simultaneous filter imaging observation, revealing the frequent appearance of polarization signals indicating high-speed, probably supersonic, downflows that are associated with at least three different configurations of magnetic fields in the solar photosphere. The observations were carried out with the Solar Optical Telescope onboard the {\em Hinode} satellite. High speed downflows are excited when a moving magnetic feature is newly formed near the penumbral boundary of sunspots. Also, a new type of downflows is identified at the edge of sunspot umbra that lack accompanying penumbral structures. These may be triggered by the interaction of magnetic fields sweeped by convection with well-concentrated magnetic flux. Another class of high speed downflows are observed in quiet sun and sunspot moat regions. These are closely related to the formation of small concentrated magnetic flux patches. High speed downflows of all types are transient time-dependent mass motions. These findings suggest that the excitation of supersonic mass flows are one of the key observational features of the dynamical evolution occurring in magnetic-field fine structures on the solar surface.

Direct Imaging of Fine Structure in the Chromosphere of a Sunspot Umbra

Abstract: High-resolution imaging observations from the Hinode spacecraft in the CaII H line are employed to study the dynamics of the chromosphere above a sunspot. We find that umbral flashes and other brightenings produced by the oscillation are extremely rich in fine structure, even beyond the resolving limit of our observations (0.22"). The umbra is tremendously dynamic, to the point that our time cadence of 20 s does not suffice to resolve the fast lateral (probably apparent) motion of the emission source. Some bright elements in our dataset move with horizontal propagation speeds of 30 km/s. We have detected filamentary structures inside the umbra (some of which have a horizontal extension of ~1500 km) which, to our best knowledge, had not been reported before. The power spectra of the intensity fluctuations reveals a few distinct areas with different properties within the umbra that seem to correspond with the umbral cores that form it. Inside each one of these areas the dominant frequencies of the oscillation are coherent, but they vary considerably from one core to another.

Motivation and Initial Results from SPINOR in the Near Infrared

Abstract: SPINOR is a new spectro-polarimeter that will serve as a facility in- strument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic operation over a very broad range of wave- lengths, from ∼400 up to 1600 nm, allowing for the simultaneous observation of several visible and infrared spectral regions with full Stokes polarimetry. Another key feature of the design is its flexibility to observe virtually any combination of spectral lines, limited only by practical considerations (e.g., the number of detectors available, space on the optical bench, etc). SPINOR is scheduled for commissioning by the end of 2005. In this paper we report on the current status of the project and present actual observations of active regions in the Ca II infrared triplet and the He I multiplet at 1083 nm.

On-orbit Performance of the Solar Optical Telescope aboard Hinode

Abstract: On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode is described with some attentions on its unpredicted aspects. In general, SOT revealed an excellent performance and has been providing outstanding data. Some unexpected features exist, however, in behaviors of the focus position, throughput and structural stability. Most of them are recovered by the daily operation i.e., frequent focus adjustment, careful heater setting and corrections in data analysis. The tunable filter contains air bubbles which degrade the data quality significantly. Schemes for tuning the filter without disturbing the bubbles have been developed and tested, and some useful procedures to obtain Dopplergram and magnetogram are now available. October and March when the orbit of satellite becomes nearly perpendicular to the direction towards the sun provide a favorable condition for continuous runs of the narrow-band filter imager.

Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode SOT

Abstract: Continuous observations of sunspot penumbrae with the Solar Optical Telescope aboard \textit{Hinode} clearly show that the outer boundary of the penumbra fluctuates around its averaged position. The penumbral outer boundary moves inward when granules appear in the outer penumbra. We discover that such granules appear one after another while moving magnetic features (MMFs) are separating from the penumbral ``spines'' (penumbral features that have stronger and more vertical fields than those of their surroundings). These granules that appear in the outer penumbra often merge with bright features inside the penumbra that move with the spines as they elongate toward the moat region. This suggests that convective motions around the penumbral outer boundary are related to the disintegration of magnetic flux in the sunspot. We also find that dark penumbral filaments frequently elongate into the moat region in the vicinity of MMFs that detach from penumbral spines. Such elongating dark penumbral filaments correspond to nearly horizontal fields extending from the penumbra. Pairs of MMFs with positive and negative polarities are sometimes observed along the elongating dark penumbral filaments. This strongly supports the notion that such elongating dark penumbral filaments have magnetic fields with a ``sea serpent''-like structure. Evershed flows, which are associated with the penumbral horizontal fields, may be related to the detachment of the MMFs from the penumbral spines, as well as to the formation of the MMFs along the dark penumbral filaments that elongate into the moat region.