Author name code: lites ADS astronomy entries on 2022-09-14 author:"Lites, Bruce William" ------------------------------------------------------------------------ Title: Measurements of Photospheric and Chromospheric Magnetic Fields Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca Bibcode: 2018smf..book...37L Altcode: No abstract at ADS Title: Measurements of Photospheric and Chromospheric Magnetic Fields Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca Bibcode: 2017SSRv..210...37L Altcode: 2015arXiv151006865L; 2015SSRv..tmp..115L The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space.

Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution. Title: Are Internetwork Magnetic Fields in the Solar Photosphere Horizontal or Vertical? Authors: Lites, B. W.; Rempel, M.; Borrero, J. M.; Danilovic, S. Bibcode: 2017ApJ...835...14L Altcode: Using many observations obtained during 2007 with the Spectro-Polarimeter of the Hinode Solar Optical Telescope, we explore the angular distribution of magnetic fields in the quiet internetwork regions of the solar photosphere. Our work follows from the insight of Stenflo, who examined only linear polarization signals in photospheric lines, thereby avoiding complications of the analysis arising from the differing responses to linear and circular polarization. We identify and isolate regions of a strong polarization signal that occupy only a few percent of the observed quiet Sun area yet contribute most to the net linear polarization signal. The center-to-limb variation of the orientation of linear polarization in these strong signal regions indicates that the associated magnetic fields have a dominant vertical orientation. In contrast, the great majority of the solar disk is occupied by much weaker linear polarization signals. The orientation of the linear polarization in these regions demonstrates that the field orientation is dominantly horizontal throughout the photosphere. We also apply our analysis to Stokes profiles synthesized from the numerical MHD simulations of Rempel as viewed at various oblique angles. The analysis of the synthetic data closely follows that of the observations, lending confidence to using the simulations as a guide for understanding the physical origins of the center-to-limb variation of linear polarization in the quiet Sun area. Title: Do the quiet sun magnetic fields vary with the solar cycle? Authors: Faurobert, Marianne; Ricort, Gilbert; Lites, Bruce Bibcode: 2015IAUS..305...22F Altcode: The quiet Sun observed in polarized light exhibits a rich and complex magnetic structuring which is still not fully resolved nor understood. The present work is intended to contribute to the debate about the origin of the quiet sun magnetic fields, in relation or not to the global solar dynamo. We present analysis of center-to-limb polarization measurements obtained with the SOT/SP spectropolarimeter onboard the Hinode satellite outside active regions, in 2007 and 2013, i.e. at a minimum and a maximum of the solar cycle, respectively. We compare the spatial fluctuation Fourier spectra of unsigned circular and linear polarization images after corrections for polarization bias and focus variations between the two data sets. The decay of active regions is clearly a source of magnetic fields in the quiet Sun. It leads to a global increase of the polarization fluctuation power spectrum in 2013 in the network. In the internetwork, we observe no variation of the polarization fluctuation power at mesogranular and granular scales, whereas it increases at sub-granular scales. We interpret these results in the following way. At the mesogranular and granular scales very efficient mechanisms of magnetic field removal are operating in the internetwork, that leads to a dissipation or a concentration of magnetic fields on smaller scales. So the cycle-invariant magnetic signal that we detect at mesogranular and granular scales must be continuously created by a dynamo mechanism which is independent of the solar cycle. Title: Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes Authors: Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, R.; Rempel, M. Bibcode: 2014A&A...572A..54B Altcode: 2014arXiv1409.3376B Milne-Eddington (M-E) inversion codes for the radiative transfer equation are the most widely used tools to infer the magnetic field from observations of the polarization signals in photospheric and chromospheric spectral lines. Unfortunately, a comprehensive comparison between the different M-E codes available to the solar physics community is still missing, and so is a physical interpretation of their inferences. In this contribution we offer a comparison between three of those codes (VFISV, ASP/HAO, and HeLIx+). These codes are used to invert synthetic Stokes profiles that were previously obtained from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD) simulations. The results of the inversion are compared with each other and with those from the MHD simulations. In the first case, the M-E codes retrieve values for the magnetic field strength, inclination and line-of-sight velocity that agree with each other within σB ≤ 35 (Gauss), σγ ≤ 1.2°, and σv ≤ 10 m s-1, respectively. Additionally, M-E inversion codes agree with the numerical simulations, when compared at a fixed optical depth, within σB ≤ 130 (Gauss), σγ ≤ 5°, and σv ≤ 320 m s-1. Finally, we show that employing generalized response functions to determine the height at which M-E codes measure physical parameters is more meaningful than comparing at a fixed geometrical height or optical depth. In this case the differences between M-E inferences and the 3D MHD simulations decrease to σB ≤ 90 (Gauss), σγ ≤ 3°, and σv ≤ 90 m s-1. Title: High-speed photospheric material flow observed at the polarity inversion line of a δ-type sunspot producing an X5.4 flare on 2012 March 7 Authors: Shimizu, Toshifumi; Lites, Bruce W.; Bamba, Yumi Bibcode: 2014PASJ...66S..14S Altcode: 2014arXiv1406.1617S; 2014PASJ..tmp..101S Solar flares abruptly release the free energy stored as a non-potential magnetic field in the corona and may be accompanied by eruptions of the coronal plasma. Formation of a non-potential magnetic field and the mechanisms for triggering the onset of flares are still poorly understood. In particular, photospheric dynamics observed near those polarity inversion lines that are sites of major flare production have not been well observed with high spatial resolution spectro-polarimetry. This paper reports on a remarkable high-speed material flow observed along the polarity inversion line located between flare ribbons at the main energy release side of an X5.4 flare on 2012 March 7. Observations were carried out by the spectro-polarimeter of the Solar Optical Telescope on board Hinode. The high-speed material flow was observed in the horizontally oriented magnetic field formed nearly parallel to the polarity inversion line. This flow persisted from at least six hours before the onset of the flare, and continued for at least several hours after the onset of the flare. Observations suggest that the observed material flow represents neither the emergence nor convergence of the magnetic flux. Rather, it may be considered to be material flow working both to increase the magnetic shear along the polarity inversion line and to develop magnetic structures favorable for the onset of the eruptive flare. Title: The solar cycle dependence of the weak internetwork flux Authors: Lites, Bruce W.; Centeno, Rebecca; McIntosh, Scott W. Bibcode: 2014PASJ...66S...4L Altcode: 2014PASJ..tmp..109L We examine data from the Hinode Observing Program 79 (the "HOP 79" irradiance program) as observed using the Hinode Solar Optical Telescope Spectro-Polarimeter for systematic changes in the weakest observable magnetic flux during the period 2008-2013. At moderate latitudes we find no evidence for systematic changes as a function of time and solar latitude in either the unsigned line-of-sight flux or in the measures of the transverse flux. However, in the polar regions, changes are apparent in the measure of signed magnetic flux corresponding to reversal of the polarity of the poles, changes that persist even for the weakest observed flux. Also evident in measures of the weakest signed flux are preferences for positive (negative) polarity at mid-north (mid-south) latitudes (20°-60°). Center-limb variations in various measures of the weak flux appear to be independent of the solar cycle. The results are consistent with the operation of a small-scale solar dynamo operating within and just below the solar photosphere, but the measures of the weakest signed flux still contain small signatures of the global solar cycle. Title: Unresolved Mixed Polarity Magnetic Fields at Flux Cancellation Site in Solar Photosphere at 0.''3 Spatial Resolution Authors: Kubo, Masahito; Chye Low, Boon; Lites, Bruce W. Bibcode: 2014ApJ...793L...9K Altcode: 2014arXiv1408.5796K This is a follow-up investigation of a magnetic flux cancellation event at a polarity inversion line (PIL) on the Sun observed with the spectropolarimeter on board Hinode. Anomalous circular polarization (Stokes V) profiles are observed in the photosphere along the PIL at the cancellation sites. Kubo et al. previously reported that the theoretically expected horizontal fields between the canceling opposite-polarity magnetic elements in this event are not detected at granular scales. We show that the observed anomalous Stokes V profiles are reproduced successfully by adding the nearly symmetric Stokes V profiles observed at pixels immediately adjacent to the PIL. This result suggests that these observed anomalous Stokes V profiles are not indications of a flux removal process, but are the result of either a mixture of unresolved, opposite-polarity magnetic elements or the unresolved width of the PIL, at an estimated resolution element of about 0.''3. The hitherto undetected flux removal process accounting for the larger-scale disappearance of magnetic flux during the observing period is likely to also fall below resolution. Title: The Interface Region Imaging Spectrograph (IRIS) Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.; Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou, C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman, C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish, D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.; Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons, R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.; Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.; Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.; Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski, W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.; Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.; Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.; Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson, M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu, K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora, J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.; Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N. Bibcode: 2014SoPh..289.2733D Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 - 0.4 arcsec spatial resolution, two-second temporal resolution, and 1 km s−1 velocity resolution over a field-of-view of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å, 1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw images in four different passbands (C II 1330, Si IV 1400, Mg II k 2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiative-MHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation. Title: The inference of the magnetic field vector in prominences Authors: Lites, Bruce W. Bibcode: 2014IAUS..300..101L Altcode: Prominences owe their existence to the presence of magnetic fields in the solar corona. The magnetic field determines their geometry and is crucial to their stability, energetics, and dynamics. This review summarizes techniques for measurement of the magnetic field vector in prominences. New techniques for inversions of full Stokes spectro-polarimetry, incorporating both the Zeeman and Hanle mechanisms for generation and modification of polarization, are now at the forefront. Also reviewed are measurements of the magnetic fields in the photosphere below prominences, and how they may be used to infer the field geometry in and surrounding the prominence itself. Title: Improved Search of Principal Component Analysis Databases for Spectro-polarimetric Inversion Authors: Casini, R.; Asensio Ramos, A.; Lites, B. W.; López Ariste, A. Bibcode: 2013ApJ...773..180C Altcode: 2013arXiv1307.0061C We describe a simple technique for the acceleration of spectro-polarimetric inversions based on principal component analysis (PCA) of Stokes profiles. This technique involves the indexing of the database models based on the sign of the projections (PCA coefficients) of the first few relevant orders of principal components of the four Stokes parameters. In this way, each model in the database can be attributed a distinctive binary number of 24n bits, where n is the number of PCA orders used for the indexing. Each of these binary numbers (indices) identifies a group of "compatible" models for the inversion of a given set of observed Stokes profiles sharing the same index. The complete set of the binary numbers so constructed evidently determines a partition of the database. The search of the database for the PCA inversion of spectro-polarimetric data can profit greatly from this indexing. In practical cases it becomes possible to approach the ideal acceleration factor of 24n as compared to the systematic search of a non-indexed database for a traditional PCA inversion. This indexing method relies on the existence of a physical meaning in the sign of the PCA coefficients of a model. For this reason, the presence of model ambiguities and of spectro-polarimetric noise in the observations limits in practice the number n of relevant PCA orders that can be used for the indexing. Title: The SP_PREP Data Preparation Package for the Hinode Spectro-Polarimeter Authors: Lites, B. W.; Ichimoto, K. Bibcode: 2013SoPh..283..601L Altcode: The Hinode/Spectro-Polarimeter (SP) is the first space-borne precision spectro-polarimeter for the study of solar phenomena. It is primarily intended for measuring the solar photospheric vector magnetic field at high spatial and spectral resolution. This objective requires that the data are calibrated and conditioned to a high degree of precision. We describe how the calibration package SP_PREP for the SP operates. Title: The Hinode Spectro-Polarimeter Authors: Lites, B. W.; Akin, D. L.; Card, G.; Cruz, T.; Duncan, D. W.; Edwards, C. G.; Elmore, D. F.; Hoffmann, C.; Katsukawa, Y.; Katz, N.; Kubo, M.; Ichimoto, K.; Shimizu, T.; Shine, R. A.; Streander, K. V.; Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S. Bibcode: 2013SoPh..283..579L Altcode: The joint Japan/US/UK Hinode mission includes the first large-aperture visible-light solar telescope flown in space. One component of the Focal Plane Package of that telescope is a precision spectro-polarimeter designed to measure full Stokes spectra with the intent of using those spectra to infer the magnetic-field vector at high precision in the solar photosphere. This article describes the characteristics of the flight hardware of the HinodeSpectro-Polarimeter, and summarizes its in-flight performance. Title: Granular-Scale Magnetic Flux Cancellations in the Photosphere Authors: Kubo, M.; Low, B. C.; Lites, B. W. Bibcode: 2012ASPC..454...41K Altcode: We find the unresolved flux removal process at the polarity inversion line formed by canceling opposite-polarity magnetic elements. Further details and results of this work can be seen in Kubo et al. (2010). Title: Is There Observational Evidence Indicating a Small-Scale Solar Dynamo? Authors: Lites, B. W. Bibcode: 2012ASPC..455....3L Altcode: Observations from the Hinode/SOT spectro-polarimeter are examined with the aim of identifying diagnostics for the presence (or absence) of a self-sustained small-scale turbulent dynamo in the upper solar convection zone. We examine 45 Hinode data sets obtained during 2007. We find much smaller net flux imbalance within regions of the quiet Sun having very weak flux compared to the imbalance averaged over each data set. Further, there is no correlation of the average net unsigned flux of regions having very weak flux relative to the average unsigned flux of the entire region. If internetwork fields were to arise from dispersal of flux from active regions, one would expect both measures to show significant correlation, so this analysis strongly supports the small-scale dynamo scenario. We also find that the average of the longitudinal apparent flux density increases slightly toward the limb for the very weakest observed flux elements. This behavior is likely the result of the dominance of horizontal fields higher in the photosphere. From data with very high signal-to-noise ratio, the distribution of magnetic field strength indicates that the magnetic energy of the quiet Sun is dominated by the small fraction of field elements having kG strengths. These strong-field elements are responsible for most of the imbalance of magnetic flux measured in each region, so it is suggested that they arise primarily from dispersal of flux from active regions, not from a small-scale dynamo. Title: Emergence of Twisted Flux in Prominence Observations Authors: Okamoto, T. J.; Tsuneta, S.; Berger, T. E.; Lites, B. W. Bibcode: 2012ASPC..455..123O Altcode: The emergence of twisted flux is a key process for supply of magnetic flux into the corona as well as solar dynamic activities such as sunspot formation and trigger of coronal mass ejections. In particular, there are numerous discussions about the role and necessity of twisted flux emergence for origin of prominences. However, the difficulty to measure vector magnetic fields has not allowed us to investigate the detailed relationship between emerging twisted flux and prominence. Hinode has changed the situation. The Spectro-Polarimeter aboard Hinode has high sensitivity to weaker magnetic fields of fine structures, and provides opportunities to detect weak horizontal magnetic fields. As a result, we have obtained signatures of twisted flux emergence associated with prominences: The observational features are "broadening and narrowing of a region dominated by horizontal magnetic field" and "rotating direction of horizontal field" on the photosphere. Moreover, the data show the interaction between the emerging twisted flux and granules, and that the flux rope has high intrinsic strength 650 G, while the flux density is as low as 100 G. Theoretical research with numerical simulation on the basis of these results is active. In addition, we investigate activities of a coronal cavity overlying a prominence on the limb, and suggest the existence of twisted flux rope to explain the activities of prominence and the coronal cavity comprehensively. Here we introduce both these observational and theoretical results, and discuss the details about emerging twisted flux. Title: Hinode Observations Suggesting the Presence of a Local Small-scale Turbulent Dynamo Authors: Lites, B. W. Bibcode: 2011ApJ...737...52L Altcode: Analysis of observations from the Hinode/Solar Optical Telescope spectropolarimeter (SP) yields results that are consistent with the operation of a small-scale turbulent dynamo in the upper solar convection zone. Examination of 45 Hinode data sets obtained in 2007 reveals only a very small correlation of the net polarity imbalance of the regions of the quiet Sun having very weak flux, relative to the polarity imbalance averaged over each data set. Further, there is no correlation of the average net unsigned flux of those regions of weakest flux with the average unsigned flux of each region studied. Positive correlations, especially of the net unsigned flux, should exist if the internetwork fields were to arise from dispersal of flux from active regions, so the absence of significant correlations supports the small-scale dynamo (SSD) scenario. Considering only regions of weakest flux, the net longitudinal flux increases slightly toward the limb, probably as the result of the dominance of horizontal fields higher in the photosphere. Inferred distributions of magnetic field strength as derived from inversions of Stokes profiles indicate that the magnetic energy of the quiet Sun observed at the resolution of the Hinode SP is dominated by the small fraction of field elements having kilo-Gauss strengths. Because these strong-field elements carry most of the imbalance of magnetic flux measured in each region, they likely arise primarily from dispersal of flux from active regions, rather than from an SSD. Title: Temporal Relation Between the Disappearance of Penumbral Fine-scale Structure and Evershed Flow Authors: Kubo, M.; Ichimoto, K.; Lites, B. W.; Shine, R. A. Bibcode: 2011ApJ...731...84K Altcode: 2011arXiv1102.1137K We investigate the temporal relation between the Evershed flow, dot-like bright features (penumbral grain), the complex magnetic field structure, and dark lanes (dark core) along bright filaments in a sunspot penumbra. We use a time series of high spatial resolution photospheric intensity, vector magnetic field maps, and Doppler velocity maps obtained with the Solar Optical Telescope aboard the Hinode spacecraft. We conclude that the appearance and disappearance of the Evershed flow and penumbra grains occur at nearly the same time and are associated with changes of the inclination angle of the magnetic field from vertical to more horizontal. This supports the idea that Evershed flow is a result of thermal convection in the inclined field lines. The dark core of the bright penumbral filament also appears coincidental with the Evershed flow. However, the dark-cored bright filament survives at least for 10-20 minutes after the disappearance of the Evershed flow. The heat input into the bright filament continues even after the end of heat transfer by the Evershed flow. This suggests that local heating along the bright filament is important for maintaining its brightness, in addition to heat transfer by the Evershed flow. Title: The Sunrise Mission Authors: Barthol, P.; Gandorfer, A.; Solanki, S. K.; Schüssler, M.; Chares, B.; Curdt, W.; Deutsch, W.; Feller, A.; Germerott, D.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.; Meller, R.; Müller, R.; Riethmüller, T. L.; Tomasch, G.; Knölker, M.; Lites, B. W.; Card, G.; Elmore, D.; Fox, J.; Lecinski, A.; Nelson, P.; Summers, R.; Watt, A.; Martínez Pillet, V.; Bonet, J. A.; Schmidt, W.; Berkefeld, T.; Title, A. M.; Domingo, V.; Gasent Blesa, J. L.; del Toro Iniesta, J. C.; López Jiménez, A.; Álvarez-Herrero, A.; Sabau-Graziati, L.; Widani, C.; Haberler, P.; Härtel, K.; Kampf, D.; Levin, T.; Pérez Grande, I.; Sanz-Andrés, A.; Schmidt, E. Bibcode: 2011SoPh..268....1B Altcode: 2010arXiv1009.2689B; 2010SoPh..tmp..224B The first science flight of the balloon-borne Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is discussed. Title: Observations of solar scattering polarization at high spatial resolution Authors: Snik, F.; de Wijn, A. G.; Ichimoto, K.; Fischer, C. E.; Keller, C. U.; Lites, B. W. Bibcode: 2010A&A...519A..18S Altcode: 2010arXiv1005.5042S Context. The weak, turbulent magnetic fields that supposedly permeate most of the solar photosphere are difficult to observe, because the Zeeman effect is virtually blind to them. The Hanle effect, acting on the scattering polarization in suitable lines, can in principle be used as a diagnostic for these fields. However, the prediction that the majority of the weak, turbulent field resides in intergranular lanes also poses significant challenges to scattering polarization observations because high spatial resolution is usually difficult to attain.
Aims: We aim to measure the difference in scattering polarization between granules and intergranules. We present the respective center-to-limb variations, which may serve as input for future models.
Methods: We perform full Stokes filter polarimetry at different solar limb positions with the CN band filter of the Hinode-SOT Broadband Filter Imager, which represents the first scattering polarization observations with sufficient spatial resolution to discern the granulation. Hinode-SOT offers unprecedented spatial resolution in combination with high polarimetric sensitivity. The CN band is known to have a significant scattering polarization signal, and is sensitive to the Hanle effect. We extend the instrumental polarization calibration routine to the observing wavelength, and correct for various systematic effects.
Results: The scattering polarization for granules (i.e., regions brighter than the median intensity of non-magnetic pixels) is significantly larger than for intergranules. We derive that the intergranules (i.e., the remaining non-magnetic pixels) exhibit (9.8±3.0)% less scattering polarization for 0.2 < μ ≤ 0.3, although systematic effects cannot be completely excluded.
Conclusions: These observations constrain MHD models in combination with (polarized) radiative transfer in terms of CN band line formation, radiation anisotropy, and magnetic fields. Title: Emergence of Helical Flux and the Formation of an Active Region Filament Channel Authors: Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K. Bibcode: 2010ApJ...718..474L Altcode: We present comprehensive observations of the formation and evolution of a filament channel within NOAA Active Region (AR) 10978 from Hinode/Solar Optical Telescope and TRACE. We employ sequences of Hinode spectro-polarimeter maps of the AR, accompanying Hinode Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode Broadband Filter Instrument filtergrams in the Ca II H line and G-band, Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 Å image sequences. The development of the channel resembles qualitatively that presented by Okamoto et al. in that many indicators point to the emergence of a pre-existing sub-surface magnetic flux rope. The consolidation of the filament channel into a coherent structure takes place rapidly during the course of a few hours, and the filament form then gradually shrinks in width over the following two days. Particular to this filament channel is the observation of a segment along its length of horizontal, weak (500 G) flux that, unlike the rest of the filament channel, is not immediately flanked by strong vertical plage fields of opposite polarity on each side of the filament. Because this isolated horizontal field is observed in photospheric lines, we infer that it is unlikely that the channel formed as a result of reconnection in the corona, but the low values of inferred magnetic fill fraction along the entire length of the filament channel suggest that the bulk of the field resides somewhat above the low photosphere. Correlation tracking of granulation in the G band presents no evidence for either systematic flows toward the channel or systematic shear flows along it. The absence of these flows, along with other indications of these data from multiple sources, reinforces (but does not conclusively demonstrate) the picture of an emerging flux rope as the origin of this AR filament channel. Title: Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. I. Turbulent Upflow Plumes Authors: Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine, Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya; Suematsu, Yoshinori; Shimizu, Toshifumi Bibcode: 2010ApJ...716.1288B Altcode: Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) "arches" or "bubbles" that "inflate" from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex "roll-up" of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) "optical flow" code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s-1, which is supersonic for a ~10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s-1. Typical lifetimes range from 300 to 1000 s (~5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km2 s-1 reaching maximum projected areas from 2 to 15 Mm2. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images is negative and ranges from -10% for smaller flows to -50% for larger flows. Passive scalar "cork movies" derived from NAVE measurements show that prominence plasma is entrained by the upflows, helping to counter the ubiquitous downflow streams in the prominence. Plume formation shows no clear temporal periodicity. However, it is common to find "active cavities" beneath prominences that can spawn many upflows in succession before going dormant. The mean flow recurrence time in these active locations is roughly 300-500 s (5-8 minutes). Locations remain active on timescales of tens of minutes up to several hours. Using a column density ratio measurement and reasonable assumptions on plume and prominence geometries, we estimate that the mass density in the dark cavities is at most 20% of the visible prominence density, implying that a single large plume could supply up to 1% of the mass of a typical quiescent prominence. We hypothesize that the plumes are generated from a Rayleigh-Taylor instability taking place on the boundary between the buoyant cavities and the overlying prominence. Characteristics, such as plume size and frequency, may be modulated by the strength and direction of the cavity magnetic field relative to the prominence magnetic field. We conclude that buoyant plumes are a source of quiescent prominence mass as well as a mechanism by which prominence plasma is advected upward, countering constant gravitational drainage. Title: Granular-scale Magnetic Flux Cancellations in the Photosphere Authors: Kubo, M.; Low, B. C.; Lites, B. W. Bibcode: 2010ApJ...712.1321K Altcode: 2010arXiv1003.2863K We investigate the evolution of five granular-scale magnetic flux cancellations just outside the moat region of a sunspot by using accurate spectropolarimetric measurements and G-band images with the Solar Optical Telescope (SOT) aboard Hinode. The opposite-polarity magnetic elements approach a junction of the intergranular lanes and then collide with each other there. The intergranular junction has strong redshifts, darker intensities than the regular intergranular lanes, and surface converging flows. This clearly confirms that the converging and downward convective motions are essential for the approaching process of the opposite-polarity magnetic elements. However, the motion of the approaching magnetic elements does not always match with their surrounding surface flow patterns in our observations. This suggests that, in addition to the surface flows, subsurface downward convective motions and subsurface magnetic connectivities are important for understanding the approach and collision of the opposite-polarity elements observed in the photosphere. We find that the horizontal magnetic field appears between the canceling opposite-polarity elements in only one event. The horizontal fields are observed along the intergranular lanes with Doppler redshifts. This cancellation is most probably a result of the submergence (retraction) of low-lying photospheric magnetic flux. In the other four events, the horizontal field is not observed between the opposite-polarity elements at any time when they approach and cancel each other. These approaching magnetic elements are more concentrated rather than gradually diffused, and they have nearly vertical fields even while they are in contact each other. We thus infer that the actual flux cancellations are highly time-dependent events at scales less than a pixel of Hinode SOT (about 200 km) near the solar surface. Title: Scattering Polarization in the Fe I 630 nm Emission Lines at the Extreme Limb of the Sun Authors: Lites, B. W.; Casini, R.; Manso Sainz, R.; Jurčák, J.; Ichimoto, K.; Ishikawa, R.; Okamoto, T. J.; Tsuneta, S.; Bellot Rubio, L. Bibcode: 2010ApJ...713..450L Altcode: Spectro-polarimetric observations with the Solar Optical Telescope onboard Hinode reveal the emission spectrum of the Fe I 630 nm lines at the solar limb. The emission shell extends for less than 1'' thereby making it extremely difficult to detect from ground-based observatories viewing the limb through the Earth's atmosphere. The linear polarization signal is clearly due to scattering and it is predominantly oriented in the radial direction. Using a comprehensive atomic model of iron, we are able to interpret qualitatively the observed signals, including the radial orientation of the linear polarization. The Hanle effect causes the linear polarization of the Fe I 630 nm lines to be sensitive to magnetic fields between ~0.1 G and ~40 G, and also to be sensitive to the field's topology for stronger fields. The overall degree of observed polarization can be reproduced by randomly oriented horizontal magnetic fields of strength ≈2 G. The discovery of their scattering polarization signals thus opens a new diagnostic opportunity for these lines. Title: Emerging flux as the source of downflows in the chromosphere Authors: Lites, B. W. Bibcode: 2010MmSAI..81..792L Altcode: Downward flowing plasma is a common signature of Doppler diagnostics in spectral lines forming in the chromosphere. Examples of such are the foot points of arch filament systems associated with emerging flux and the inverse Evershed flow in and around the penumbrae of sunspots. This contribution puts forth the hypothesis that these downward flows, at least those occurring in and around active regions, trace their origin to the ubiquitous emergence of magnetic flux. In this scenario, the buoyantly rising, emerging flux carries mass upward from lower levels, then drains downward along magnetic lines of force to produce the observed downflow signatures in the chromosphere and below. The hypothesis is discussed and illustrated by chromospheric observations of sunspots and filaments. Title: Granular scale magnetic flux cancellations . Authors: Kubo, M.; Low, B. C.; Lites, B. W. Bibcode: 2010MmSAI..81..790K Altcode: We summarize the evolution of granular-scale ``magnetic-flux cancellation'' as observed with Hinode/SOT. Further details and results of this work are given in \citet{Kubo2009}. Title: Unresolved Magnetic Flux Removal Process in the Photosphere Authors: Kubo, Masahito; Chye Low, Boon; Lites, Bruce Bibcode: 2010cosp...38.2828K Altcode: 2010cosp.meet.2828K The mutual loss of magnetic flux due to the apparent collision of opposite-polarity magnetic elements is called "magnetic flux cancellation" as a descriptive term. The flux cancellation is essential to understand the dissipation of magnetic flux from the solar surface. An Ω-loop submerging below the surface or a U-loop rising through the photosphere is the usual idea to explain the magnetic flux cancellation. Magnetic reconnection may be crucial for the forma-tion of these loops, especially for the submerging -loop. In fact, chromospheric and coronal activities are often observed at the cancellation sites. We investigate the evolution of 5 cancel-lation events of the opposite-polarity magnetic elements at granular scales by using accurate spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We find that the horizontal magnetic field, which is expected in both submerging Ω-loop model and emerging U-loop model, does not appear between the canceling magnetic elements in 4 of the 5 events. The approaching magnetic elements in these events are more concentrated rather than gradually diffused, and they have nearly vertical fields even while they are in contact each other. We thus imply that the actual flux cancellation is highly time dependent event near the solar surface at scales less than a pixel of Hinode/SOT (about 200 km). At the polarity inversion line formed by the canceling magnetic elements, highly asymmetric Stokes-V profiles are observed. We confirm that such asymmetric profile can be made by the sum of the profiles at the opposite-polarity magnetic elements next to the polarity inversion line. This means that the approaching bipolar flux tubes still keep their nature within the pixel where they come in contact with each other, and thus supports the unresolved flux removal process within the pixel at the polarity inversion line. Title: Hinode's SP and G-band Co-Alignment Authors: Centeno, R.; Lites, B.; de Wijn, A. G.; Elmore, D. Bibcode: 2009ASPC..415..323C Altcode: 2009arXiv0902.0027C We analyze the co-alignment between Hinode's BFI-Gband images and simultaneous SP maps with the aim of characterizing the general off-sets between them and the second order non-linear effects in SP's slit scanning mechanism. We provide calibration functions and parameters to correct for the nominal pixel scales and positioning Title: Statistics of Convective Collapse Events in the Photosphere and Chromosphere Observed with the HINODE SOT Authors: Fischer, C. E.; de Wijn, A. G.; Centeno, R.; Lites, B. W.; Keller, C. U. Bibcode: 2009ASPC..415..127F Altcode: Convective collapse, a theoretically predicted process that intensifies existing weak magnetic fields in the solar atmosphere, was first directly observed in a single event by Nagata et al. (2008) using the high resolution Solar Optical Telescope (SOT) of the Hinode satellite. Using the same space telescope, we observed 49 such events and present a statistical analysis of convective collapse events. Our data sets consist of high resolution time series of polarimetric spectral scans of two iron lines formed in the lower photosphere and filter images in Mg I b2 and Ca II H. We were thus able to study the implication of convective collapse events on the high photospheric and the chromospheric layers. The physical parameters from the full Stokes profiles were obtained with the MERLIN Milne-Eddington inversion code. For each of the 49 events we determined the duration, maximum photospheric downflow, and field strength increase. We found event durations of about 10 minutes and field strengths of up to 1.65 kG. Title: Magnetic Flux Budget in a Decaying Active Region Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K. Bibcode: 2009ASPC..415..359K Altcode: We investigate the sunspot decay process in terms of the magnetic flux budget of a decaying sunspot. This article is based on results in Kubo et al. 2008. Please see this paper for further details. Title: Is Flux Submergence an Essential Aspect of Flux Emergence? Authors: Lites, B. W.; Frank, Z.; Shine, R. A.; Title, A. M.; Ichimoto, K. Bibcode: 2009ASPC..415..172L Altcode: High resolution Hinode Spectro-Polarimeter observations permit one to examine the detailed structure of the magnetic field vector in emerging flux regions. We find the field to have a concave-upward geometry on the smallest scales observed (0.3 arcsec), indicating the presence of U-loops at the sites of approaching and canceling opposite polarities. This structure suggests that reconnection is taking place at or below the surface, allowing the emerging flux to rid itself of its considerable mass burden. Supersonic down flows are often observed adjacent to, but not coincident with, the sites of canceling flux. We propose that these are the sites that drain the mass contained in the buoyantly-rising flux elements. The observations then suggest a process of sub-surface reconnection producing O-loops that then are forced to descend with the intergranular convective down flows, thus making flux submergence important to the larger scale flux emergence process. Title: The Second Hinode Science Meeting: Beyond Discovery-Toward Understanding Authors: Lites, B.; Cheung, M.; Magara, T.; Mariska, J.; Reeves, K. Bibcode: 2009ASPC..415.....L Altcode: No abstract at ADS Title: Granular Scale Magnetic Flux Cancellations as Observed with the Hinode/SOT Authors: Kubo, M.; Low, B.; Lites, B. W. Bibcode: 2009AGUFMSH53B..05K Altcode: The mutual loss of magnetic flux due to the apparent collision of opposite-polarity magnetic elements is called ``magnetic flux cancellation'' as a descriptive term. The flux cancellation is essential to understand the dissipation of magnetic flux from the solar surface. We investigate the evolution of 5 granular-scale flux cancellations just outside the moat region of a sunspot by using accurate spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We find that the opposite-polarity magnetic elements approach a junction of the intergranular lanes and then they collide with each other there. The intergranular junction has Doppler red shifts, darker intensities than the regular intergranular lanes, and surface converging flows. We also find that the horizontal magnetic field appears between the canceling elements in only one event. The horizontal fields are observed along the intergranular lanes with red shifts. This cancellation is most probably a result of the submergence of low-lying photospheric magnetic flux. In the other 4 events, the horizontal field is not observed between the opposite-polarity magnetic elements at any time when they approach and cancel each other. These canceling elements have nearly vertical fields even while they are in contact each other. These events are more interesting because in the usual idea of the submergence of a low lying Ω-loop or the buoyant rise of a U-loop, the appearance of a horizontal field is the observational signature of the loop top (or bottom) passing across the photosphere. Our observational results suggest the possibility that the actual flux cancellation is highly time dependent events near the solar surface at scales less than a pixel of Hinode/SOT (about 200 km). Observations with a spatial resolution higher than Hinode/SOT are essential to reveal physical process of the dissipation of magnetic flux on the Sun. Title: A new perspective on quiet Sun magnetism Authors: Lites, Bruce William Bibcode: 2009ScChG..52.1660L Altcode: The Hinode mission has provided us with a new, quantitative view of the magnetism of the quiet Sun. It has revealed that the quiet internetwork areas are blanketed by horizontal fields that appear at first sight to have more flux than the vertical fields resolved on the same 0.3″ size scale. These measurements point to the possibility that the horizontal fields might be the primary source of the “hidden turbulent flux” of the quiet Sun anticipated from Hanle effect depolarization. In this paper, evidence is presented suggesting that the “seething” horizontal fields observed by Harvey in 2007 and the horizontal fields revealed by Hinode are the same phenomenon. Because the seething fields appear to be of uniform fluctuation over the whole disk, the phenomenon is most likely not associated with the dynamo source of solar activity. Thus, the small-scale “hidden turbulent flux” lends support to the notion of a local solar dynamo acting on granular sizes and time scales. Title: Statistics of convective collapse events in the photosphere and chromosphere observed with the Hinode SOT Authors: Fischer, C. E.; de Wijn, A. G.; Centeno, R.; Lites, B. W.; Keller, C. U. Bibcode: 2009A&A...504..583F Altcode: 2009arXiv0906.2308F Convective collapse, a theoretically predicted process that intensifies existing weak magnetic fields in the solar atmosphere, was first directly observed in a single event by Nagata et al. (2008, ApJ, 677, L145) using the high resolution Solar Optical Telescope (SOT) of the Hinode satellite. Using the same space telescope, we observed 49 such events and present a statistical analysis of convective collapse events. Our data sets consist of high resolution time series of polarimetric spectral scans of two iron lines formed in the lower photosphere and filter images in Mg I b{2} and Ca II H, spectral lines that are formed in the high photosphere and the lower chromosphere, respectively. We were thus able to study the implication of convective collapse events on the high photospheric and the chromospheric layers. We found that in all cases, the event was accompanied by a continuum bright point and nearly always by a brightening in the Ca II H images. The magnesium dopplergram exhibits a strong downflow in about three quarters of the events that took place within the field of view of the magnesium dopplergram. The physical parameters from the full Stokes profiles were obtained with the MERLIN Milne-Eddington inversion code. For each of the 49 events we determined the duration, maximum photospheric downflow, field strength increase and size. We found event durations of about 10 min, magnetic element radii of about 0.43 arcsec and 0.35 arcsec, before and after the event, respectively, and field strengths of up to 1.65 kG. Title: Magnetic Flux Budget of a Decaying Sunspot Authors: Kubo, Masahito; Lites, Bruce W.; Shimizu, Toshifumi; Ichimoto, Kiyoshi Bibcode: 2009shin.confE...9K Altcode: Numerous small magnetic elements called moving magnetic features (MMFs) are generally observed in the moat region that surrounds a sunspot. We attempt to address a basic question how much magnetic flux is carried away from a sunspot by MMFs and is subsequently removed from the photosphere. This is essential for understanding decay of sunspots and distribution of magnetic flux on the Sun. We estimate the magnetic flux budget in a decaying sunspot and its surrounding moat region by using a time series of the spatial distribution of vector magnetic fields in the photosphere. Spectropolarimetric measurements with the Solar Optical Telescope aboard the Hinode satellite allow us, for the first time, to know an accurate flux change without any effects of atmospheric seeing. The amount of magnetic flux that decreases in the sunspot and (inner) moat region is very similar to magnetic flux transported to the outer boundary of the moat region. The flux loss rates 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 MMFs, and then the transported flux is removed from the photosphere by apparent collisions of opposite-polarity magnetic elements (called Title: A New View of Fine Scale Dynamics and Magnetism of Sunspots Revealed by Hinode/SOT Authors: Ichimoto, K.; Suematsu, Y.; Katsukawa, Y.; Tsuneta, S.; Shimojo, M.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Berger, T.; Title, A. M.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Nagata, S. Bibcode: 2009ASPC..405..167I Altcode: The Solar Optical Telescope on-board Hinode is providing a new view of the fine scale dynamics in sunspots with its high spatial resolution and unprecedented image stability. We present three features related to the Evershed flow each of which raises a new puzzle in sunspot dynamics; i.e., twisting appearance of penumbral filaments, the source and sink of individual Evershed flow channels, and the net circular polarization in penumbrae with its spatial relation to the Evershed flow channels. Title: Has Hinode Revealed the Missing Turbulent Flux of the Quiet Sun? Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S. Bibcode: 2009ASPC..405..173L Altcode: The Hinode Spectro-Polarimeter has revealed the presence of surprisingly strong horizontal magnetic fields nearly everywhere in the quiet solar atmosphere. These horizontal fields, along with measures of the vertical fields, may be the signature of the ``hidden turbulent flux'' of the quiet Sun. The measured horizontal fields average at least to 55 Gauss: nearly 5 times that of the measured longitudinal apparent flux density. The nature of these fields are reviewed, and discussed in the light of recent magneto-convection numerical simulations of the quiet Sun. Title: Nonlinear Force-Free Magnetic Field Modeling of AR 10953: A Critical Assessment Authors: De Rosa, Marc L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; Amari, T.; Canou, A.; McTiernan, J. M.; Régnier, S.; Thalmann, J. K.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M. C. M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T. Bibcode: 2009SPD....40.3102D Altcode: Nonlinear force-free field (NLFFF) modeling seeks to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have failed to arrive at consistent solutions when applied to (thus far, two) cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not available). One issue is that NLFFF models require consistent, force-free vector magnetic boundary data, and vector magnetogram data sampling the photosphere do not satisfy this requirement. Consequently, several problems have arisen that are believed to affect such modeling efforts. We use AR 10953 to illustrate these problems, namely: (1) some of the far-reaching, current-carrying connections are exterior to the observational field of view, (2) the solution algorithms do not (yet) incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is needed to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models. Title: Hinode Observation of the Magnetic Fields in a Sunspot Light Bridge Accompanied by Long-Lasting Chromospheric Plasma Ejections Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Kubo, Masahito; Lites, Bruce W.; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Tsuneta, Saku; Nagata, Shin'ichi; Shine, Richard A.; Tarbell, Theodore D. Bibcode: 2009ApJ...696L..66S Altcode: We present high-resolution magnetic field measurements of a sunspot light bridge (LB) that produced chromospheric plasma ejections intermittently and recurrently for more than 1 day. The observations were carried out with the Hinode Solar Optical Telescope on 2007 April 29 and 30. The spectro-polarimeter reveals obliquely oriented magnetic fields with vertical electric current density higher than 100 mA m-2 along the LB. The observations suggest that current-carrying highly twisted magnetic flux tubes are trapped below a cusp-shaped magnetic structure along the LB. The presence of trapped current-carrying flux tubes is essential for causing long-lasting chromospheric plasma ejections at the interface with pre-existing vertically oriented umbral fields. A bidirectional jet was clearly detected, suggesting magnetic reconnections occurring at very low altitudes, slightly above the height where the vector magnetic fields are measured. Moreover, we found another strong vertical electric current on the interface between the current-carrying flux tube and pre-existing umbral field, which might be a direct detection of the currents flowing in the current sheet formed at the magnetic reconnection sites. Title: A Critical Assessment of Nonlinear Force-Free Field Modeling of the Solar Corona for Active Region 10953 Authors: De Rosa, Marc L.; Schrijver, Carolus J.; Barnes, Graham; Leka, K. D.; Lites, Bruce W.; Aschwanden, Markus J.; Amari, Tahar; Canou, Aurélien; McTiernan, James M.; Régnier, Stéphane; Thalmann, Julia K.; Valori, Gherardo; Wheatland, Michael S.; Wiegelmann, Thomas; Cheung, Mark C. M.; Conlon, Paul A.; Fuhrmann, Marcel; Inhester, Bernd; Tadesse, Tilaye Bibcode: 2009ApJ...696.1780D Altcode: 2009arXiv0902.1007D Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics, and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically constructed Sun-like test cases, but they are less successful in application to real solar data. Different NLFFF models have been found to have markedly different field line configurations and to provide widely varying estimates of the magnetic free energy in the coronal volume, when applied to solar data. NLFFF models require consistent, force-free vector magnetic boundary data. However, vector magnetogram observations sampling the photosphere, which is dynamic and contains significant Lorentz and buoyancy forces, do not satisfy this requirement, thus creating several major problems for force-free coronal modeling efforts. In this paper, we discuss NLFFF modeling of NOAA Active Region 10953 using Hinode/SOT-SP, Hinode/XRT, STEREO/SECCHI-EUVI, and SOHO/MDI observations, and in the process illustrate three such issues we judge to be critical to the success of NLFFF modeling: (1) vector magnetic field data covering larger areas are needed so that more electric currents associated with the full active regions of interest are measured, (2) the modeling algorithms need a way to accommodate the various uncertainties in the boundary data, and (3) a more realistic physical model is needed to approximate the photosphere-to-corona interface in order to better transform the forced photospheric magnetograms into adequate approximations of nearly force-free fields at the base of the corona. We make recommendations for future modeling efforts to overcome these as yet unsolved problems. Title: Magnetic Flux Budget of a Decaying Sunspot Authors: Kubo, Masahito; Lites, B. W.; Shimizu, T.; Ichimoto, K. Bibcode: 2009SPD....40.0905K Altcode: We estimate how much magnetic flux is lost in a decaying sunspot and how much magnetic flux is carried away from the sunspot through its surrounding moat region. A time series of spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode allows us, for the first time, to investigate an accurate flux change without any effects of atmospheric seeing. The amount of magnetic flux that decreases in the sunspot and moat region is almost equal to that of magnetic flux transported to the outer boundary of the moat region. The flux loss rates 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 moat boundary. Title: Direct Imaging of Fine Structure in the Chromosphere of a Sunspot Umbra Authors: Socas-Navarro, H.; McIntosh, S. W.; Centeno, R.; de Wijn, A. G.; Lites, B. W. Bibcode: 2009ApJ...696.1683S Altcode: 2008arXiv0810.0597S High-resolution imaging observations from the Hinode spacecraft in the Ca II 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 (0farcs22). 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 data set move with horizontal propagation speeds of 30 km s-1. 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 reveal 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. Title: Prominence Formation Associated with an Emerging Helical Flux Rope Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo, Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M. Bibcode: 2009ApJ...697..913O Altcode: 2009arXiv0904.0007O The formation and evolution process and magnetic configuration of solar prominences remain unclear. In order to study the formation process of prominences, we examine continuous observations of a prominence in NOAA AR 10953 with the Solar Optical Telescope on the Hinode satellite. As reported in our previous Letter, we find a signature suggesting that a helical flux rope emerges from below the photosphere under a pre-existing prominence. Here we investigate more detailed properties and photospheric indications of the emerging helical flux rope, and discuss their relationship to the formation of the prominence. Our main conclusions are: (1) a dark region with absence of strong vertical magnetic fields broadens and then narrows in Ca II H-line filtergrams. This phenomenon is consistent with the emergence of the helical flux rope as photospheric counterparts. The size of the flux rope is roughly 30,000 km long and 10,000 km wide. The width is larger than that of the prominence. (2) No shear motion or converging flows are detected, but we find diverging flows such as mesogranules along the polarity inversion line. The presence of mesogranules may be related to the emergence of the helical flux rope. (3) The emerging helical flux rope reconnects with magnetic fields of the pre-existing prominence to stabilize the prominence for the next several days. We thus conjecture that prominence coronal magnetic fields emerge in the form of helical flux ropes that contribute to the formation and maintenance of the prominence. Title: Emergence of Helical Flux and the Formation of an Active Region Filament Channel Authors: Lites, Bruce W. Bibcode: 2009SPD....40.0910L Altcode: We present comprehensive observations from Hinode/SOT and TRACE of the formation and evolution of a filament channel within NOAA Active Region 10978. We employ sequences of Hinode spectro-polarimeter maps of the active region, accompaning Hinode NFI magnetograms in the Na I D1 line, Hinode BFI filtergrams in the Ca II H-line and G-band, and TRACE Fe IX 171 [[Unable to Display Character: &#506]] image sequences. The development of the channel resembles qualitatively that presented by Okamoto et al. (2008,2009) in that many indicators that point to the emergence of a pre-existing sub-surface flux rope. The formation takes place rapidly in the course of a few hours, and the filament channel gradually shrinks over the following two days. Particular to this filament channel is the observation of a segment of horizontal, weak (500 Gauss) flux that is not flanked by stronger field, opposite polarity flux. Because this isolated horizontal field is observed in photospheric lines, we infer that it is unlikely that the channel formed as a result of reconnection in the higher layers of the atmosphere. Furthermore, correlation tracking of granulation in the G-band presents no evidence for either systematic flows toward the channel or systematic shear flows along it. The absence of these flows reinforces the picture of an emerging flux rope as the origin of this filament channel. Title: The Topology and Behavior of Magnetic Fields Emerging at the Solar Photosphere Authors: Lites, B. W. Bibcode: 2009SSRv..144..197L Altcode: 2008SSRv..tmp..156L The nature of flux emerging through the surface layers of the Sun is examined in the light of new high-resolution magnetic field observations from the Hinode space mission. The combination of vector magnetic field data and visible-light imaging from Hinode support the hypothesis that active region filaments are created as a result of an emerging, twisted flux system. The observations do not present strong evidence for an alternate hypothesis: that the filaments form as a result of localized shear flows at the photospheric level. Examination of the vector magnetic field at very small scales in emerging flux regions suggests that reconnection at the photospheric level and below, followed by submergence of flux, is a likely and essential part of the flux emergence process. The reconnection and flux submergence are driven by granular convection. Title: The Topology and Behavior of Magnetic Fields Emerging at the Solar Photosphere Authors: Lites, B. W. Bibcode: 2009odsm.book..197L Altcode: The nature of flux emerging through the surface layers of the Sun is examined in the light of new high-resolution magnetic field observations from the Hinode space mission. The combination of vector magnetic field data and visible-light imaging from Hinode support the hypothesis that active region filaments are created as a result of an emerging, twisted flux system. The observations do not present strong evidence for an alternate hypothesis: that the filaments form as a result of localized shear flows at the photospheric level. Examination of the vector magnetic field at very small scales in emerging flux regions suggests that reconnection at the photospheric level and below, followed by submergence of flux, is a likely and essential part of the flux emergence process. The reconnection and flux submergence are driven by granular convection. Title: Observations and Nonlinear Force-Free Field Modeling of Active Region 10953 Authors: Su, Yingna; van Ballegooijen, Adriaan; Lites, Bruce W.; Deluca, Edward E.; Golub, Leon; Grigis, Paolo C.; Huang, Guangli; Ji, Haisheng Bibcode: 2009ApJ...691..105S Altcode: We present multiwavelength observations of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. We also explore nonlinear force-free field (NLFFF) modeling of this region prior to the C8.5 flare on May 2, using magnetograph data from SOHO/MDI and Hinode/SOT. A series of NLFFF models are constructed using the flux-rope insertion method. By comparing the modeled field lines with multiple X-ray loops observed by Hinode/XRT, we find that the axial flux of the flux rope in the best-fit models is (7± 2)× 1020 Mx, while the poloidal flux has a wider range of (0.1-10)× 1010 Mx cm-1. The axial flux in the best-fit model is well below the upper limit (~15× 1020 Mx) for stable force-free configurations, which is consistent with the fact that no successful full filament eruption occurred in this active region. From multiwavelength observations of the C8.5 flare, we find that the X-ray brightenings (in both RHESSI and XRT) appeared about 20 minutes earlier than the EUV brightenings seen in TRACE 171 Å images and filament activations seen in MLSO Hα images. This is interpreted as an indication that the X-ray emission may be caused by direct coronal heating due to reconnection, and the energy transported down to the chromosphere may be too low to produce EUV brightenings. This flare started from nearly unsheared flare loop, unlike most two-ribbon flares that begin with highly sheared footpoint brightenings. By comparing with our NLFFF model, we find that the early flare loop is located above the flux rope that has a sharp boundary. We suggest that this flare started near the outer edge of the flux rope, not at the inner side or at the bottom as in the standard two-ribbon flare model. Title: The Scientific Ballooning Program Authors: Israel, Martin; Boggs, Steven; Cherry, Michael; Devlin, Mark; Grindlay, Jonathan; Lites, Bruce; Ormes, Jonathan; Young, Eliot; Tueller, Jack; Mitchell, John Bibcode: 2009astro2010P..24I Altcode: No abstract at ADS Title: Nonlinear Force-Free Magnetic Field Modeling of the Solar Corona: A Critical Assessment Authors: De Rosa, M. L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; McTiernan, J. M.; Régnier, S.; Thalmann, J.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T. Bibcode: 2008AGUFMSH41A1604D Altcode: Nonlinear force-free field (NLFFF) modeling promises to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have so far failed to arrive at consistent solutions when applied to cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not been available). It is our view that the lack of robust results indicates an endemic problem with the NLFFF modeling process, and that this process will likely continue to fail until (1) more of the far-reaching, current-carrying connections are within the observational field of view, (2) the solution algorithms incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is found to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models. Title: Erratum: "Magnetic Flux Loss and Flux Transport in a Decaying Active Region" (ApJ, 686, 1447 [2008]) Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K. Bibcode: 2008ApJ...689.1456K Altcode: No abstract at ADS Title: The Magnetic Landscape of the Sun's Polar Region Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.; Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo, M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title, A. M. Bibcode: 2008ApJ...688.1374T Altcode: 2008arXiv0807.4631T 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 Alfvén waves that accelerate the solar wind. Title: Magnetic Flux Loss and Flux Transport in a Decaying Active Region Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K. Bibcode: 2008ApJ...686.1447K Altcode: 2008arXiv0807.4340K 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. Title: Magnetic Fields of the Quiet Sun: A New Quantitative Perspective From Hinode Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S. Bibcode: 2008ASPC..397...17L Altcode: This article summarizes results of studies presented in two papers already published: Lites et al. (2007a); Lites et al. (2007b). Please see these for further details. Title: On-orbit Performance of the Solar Optical Telescope aboard Hinode Authors: Ichimoto, K.; Katsukawa, Y.; Tarbell, T.; Shine, R. A.; Hoffmann, C.; Berger, T.; Cruz, T.; Suematsu, Y.; Tsuneta, S.; Shimizu, T.; Lites, B. W. Bibcode: 2008ASPC..397....5I Altcode: 2008arXiv0804.3248I On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode is described with some attention to its unpredicted aspects. In general, SOT reveals an excellent performance and has been providing outstanding data. Some unexpected features exist, however, in behaviours 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 Dopplergrams and magnetograms are now available. October and March, when the orbit of satellite becomes nearly perpendicular to the direction towards the Sun, provide a favourable condition for continuous runs of the narrow-band filter imager. Title: Evolution of Magnetic Fields at the Boundary of the Penumbra Authors: Kubo, M.; Ichimoto, K.; Shimizu, T.; Lites, B. W.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Tarbell, T.; Shine, R. A.; Title, A. M. Bibcode: 2008ASPC..397...79K Altcode: The formation of moving magnetic features (MMFs) separating from the penumbra were successfully observed with the Solar Optical Telescope (SOT) aboard the Hinode satellite. We find that bright features in the outer penumbra are located at the penumbral spines, which have magnetic fields more vertical than the surroundings, or located at the MMFs separating from the spines. This suggests that convection in the outer penumbra is related to the disintegration of the sunspot. Title: Hinode Observations of Magnetic Elements in Internetwork Areas Authors: de Wijn, A. G.; Lites, B. W.; Berger, T. E.; Frank, Z. A.; Tarbell, T. D.; Ishikawa, R. Bibcode: 2008ApJ...684.1469D Altcode: 2008arXiv0806.0345D 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. Title: Erratum: The Analysis of Penumbral Fine Structure Using an Advanced Inversion Technique Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta, Saku Bibcode: 2008PASJ...60..933J Altcode: In the article [PASJ 59, S601-S606 (2007)], the word ''CSIC'' was omitted from the affiliation of Dr. Luis Bellot Rubio. The correct affiliation is : 2Instituto de Astrofísica de Andalucía (CSIC), Apdo. de Correos 3004, 18080 Granada, Spain Title: Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode SOT Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu, Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata, S.; Tsuneta, S. Bibcode: 2008ApJ...681.1677K Altcode: 2008arXiv0806.0415K 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. Title: Polarization Calibration of the Solar Optical Telescope onboard Hinode Authors: Ichimoto, K.; Lites, B.; Elmore, D.; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.; Shimizu, T.; Shine, R.; Tarbell, T.; Title, A.; Kiyohara, J.; Shinoda, K.; Card, G.; Lecinski, A.; Streander, K.; Nakagiri, M.; Miyashita, M.; Noguchi, M.; Hoffmann, C.; Cruz, T. Bibcode: 2008SoPh..249..233I Altcode: 2008SoPh..tmp...69I 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. Title: The Solar Optical Telescope for the Hinode Mission: An Overview Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Otsubo, M.; Shimizu, T.; Suematsu, Y.; Nakagiri, M.; Noguchi, M.; Tarbell, T.; Title, A.; Shine, R.; Rosenberg, W.; Hoffmann, C.; Jurcevich, B.; Kushner, G.; Levay, M.; Lites, B.; Elmore, D.; Matsushita, T.; Kawaguchi, N.; Saito, H.; Mikami, I.; Hill, L. D.; Owens, J. K. Bibcode: 2008SoPh..249..167T Altcode: 2008SoPh..tmp...74T; 2007arXiv0711.1715T 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. Title: Frequent Occurrence of High-Speed Local Mass Downflows on the Solar Surface Authors: Shimizu, T.; Lites, B. W.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Tsuneta, S.; Nagata, S.; Kubo, M.; Shine, R. A.; Tarbell, T. D. Bibcode: 2008ApJ...680.1467S Altcode: 2008arXiv0804.1167S 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. Title: Cooperative Observation of Ellerman Bombs between the Solar Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope Authors: Matsumoto, Takuma; Kitai, Reizaburo; Shibata, Kazunari; Nagata, Shin'ichi; Otsuji, Kenichi; Nakamura, Tahei; Watanabe, Hiroko; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M. Bibcode: 2008PASJ...60..577M Altcode: High-resolution CaIIH broad-band filter images of NOAA10933 on 2007 January 5 were obtained by the Solar Optical Telescope aboard the Hinode satellite. Many small-scale (∼1") 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 Hα images taken by the Domeless Solar Telescope at Hida observatory. The sub-arcsec structures of two EBs seen in CaIIH were studied in detail. Our observation showed the following two aspects: (1) The CaIIH bright points identified with EBs were associated with the bipolar magnetic field structures, as reported by previous studies. (2)The structure of the CaIIH bright points turned out to consist of the following two parts: a central elongated bright core (0.7" × 0.5") located along the magnetic neutral line and a diffuse halo (1.2"×1.8"). Title: Emergence of a helical flux rope and prominence formation Authors: Okamoto, T. J.; Tsuneta, S.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Berger, T. E.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Shibata, K.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M. Bibcode: 2008AGUSMSP43B..06O Altcode: We report a discovery about emergence of a helical flux rope. The episode may be related to the formation and evolution of an active region prominence. Statistical studies by previous authors indicate that numerous prominences have the inverse-polarity configuration suggesting the helical magnetic configurations. There are two theoretical models about formation of such a coronal helical magnetic field in association with prominences: flux rope model and sheared-arcade model. We have so far no clear observational evidence to support either model. In order to find a clue about the formation of the prominence, we had continuous observations of NOAA AR 10953 with the SOT during 2007 April 28 to May 9. A prominence was located over the polarity inversion line 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 new features: (1) The abutting opposite-polarity regions on the two sides along the polarity inversion line 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 polarity inversion line 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 emerges from below the photosphere into the corona along the polarity inversion line under the prominence. We suggest that this supply of a helical magnetic flux possibly into the corona is related to formation and maintenance of active-region prominences. Title: Photospheric Signature of Penumbral Microjets Authors: Katsukawa, Y.; Jurcak, J.; Ichimoto, K.; Suemtasu, Y.; Tsuneta, S.; Shimizu, T.; Berger, T. E.; Shine, R. A.; Tarbell, T. D.; Lites, B. W. Bibcode: 2008AGUSMSP53A..03K Altcode: HINODE Solar Optical Telescope (SOT) discovered ubiquitous occurrence of fine-scale jetlike activities in penumbral chromospheres, which are referred to as penumbral microjets. The microjets' small width of 400 km and short duration of less than 1 min make them difficult to identify in existing ground-based observations. The apparent rise velocity is faster than 50km/s and is roughly comparable to the Alfven speed in the sunspot chromosphere. These properties of penumbral microjets suggest that magnetic reconnection in uncombed magnetic field configuration is the most possible cause of penumbral microjets. In order to understand magnetic configuration associated with penumbral microjets and prove the chromospheric magnetic reconnection hypothesis, we investigated relationship between penumbral microjets seen in CaIIH images and photospheric magnetic fields measured by the HINODE spectro-polarimeter. We found the inclination angles of penumbral microjets measured in CaII H images are roughly consistent with inclination angles of relatively vertical magnetic field component in uncombed magnetic field configuration. In addition, strong and transient downflows are observed in the photosphere near the boundary of a horizontal flux tube associated with a penumbral microjet. The size of the downflow region is about 300km, which is close to the width of penumbral microjets seen in CaII H images. The downflow velocity of several km/s might be a result of an outflow of chromospheric magnetic reconnection and suffer deceleration due to the higher density in the photosphere. Title: Non-Linear Force-Free Field Modeling of a Solar Active Region Around the Time of a Major Flare and Coronal Mass Ejection Authors: De Rosa, M. L.; Schrijver, C. J.; Metcalf, T. R.; Barnes, G.; Lites, B.; Tarbell, T.; McTiernan, J.; Valori, G.; Wiegelmann, T.; Wheatland, M.; Amari, T.; Aulanier, G.; Démoulin, P.; Fuhrmann, M.; Kusano, K.; Régnier, S.; Thalmann, J. Bibcode: 2008AGUSMSP31A..06D Altcode: Solar flares and coronal mass ejections are associated with rapid changes in coronal magnetic field connectivity and are powered by the partial dissipation of electrical currents that run through the solar corona. A critical unanswered question is whether the currents involved are induced by the advection along the photosphere of pre-existing atmospheric magnetic flux, or whether these currents are associated with newly emergent flux. We address this problem by applying nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA Active Region 10930 around the time of a powerful X3.4 flare in December 2006. We compute 14 NLFFF models using 4 different codes having a variety of boundary conditions. We find that the model fields differ markedly in geometry, energy content, and force-freeness. We do find 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. We discuss the relative merits of these models in a general critique of our present abilities to model the coronal magnetic field based on surface vector field measurements. Title: Evershed Flows as an Integral Part of Penumbral Formation and its Fine Structure Authors: Ryutova, M.; Berger, T.; Lites, B.; Title, A.; Frank, Z. Bibcode: 2008AGUSMSP41B..07R Altcode: Observations of Evershed flows with the Solar Optical Telescope (SOT) on Hinode (Ichimito, Shine, Lites, et al. 2008, PASJ, 59, S593) showed that penumbral flows have small scale structures and much more complex properties than those of a simple outflow of material with unique direction and appearence. We address this problem and show that the flow properties are directly connected to the observed properties of penumbral filaments and are an integral part of penumbral development during sunspot formation. In our recent model (Ryutova, Berger, & Title, 2008, ApJ, 676, April), based on the observations that sunspot has a filamentary structure and consists of a dense conglomerate of non-collinear interlaced flux tubes, the penumbra is formed due to an on-going reconnection processes that leads to branching out of the peripheral flux tubes from the "trunk". As flux tubes have different parameters, branching occurs at different heights and with different inclinations, thus forming an "uncombed" penumbra. Each elemental act of reconnection generates an inevitable twist in the post-reconnection filaments that acquire a screw pinch configuration. This explains the remarkable dynamic stability of penumbral filaments and their observed properties, such as presence of dark cores, wrapping and spinning of filaments around each other, bright footpoints, etc. Here we show that propagation of twist along current carrying helical flux tubes is accompanied by plasma flows that may have diverse properties depending on the location of interacting flux tubes, their inclination and pitch. We apply the model to observations taken with the SOT instrument, which includes spectro-polarimetric data, and perform quantitative analysis. Title: Sources and Sinks of the Evershed Flow Authors: Shine, R. A.; Title, A. M.; Ichimoto, K.; Lites, B. Bibcode: 2008AGUSMSP31A..01S Altcode: Extending the work of Ichimoto et al (2007), we investigate the sources and sinks of the Evershed flow in sunspot penumbra using data from the Solar Optical Telescope (SOT) instruments on the Hinode satellite. We use spectral maps taken with the Spectro-Polarimeter (SP) that provide detailed snapshots of the large sunspot in AR 10930 over a range of viewing angles as it rotated across the solar disk in December 2006. These are supplemented by images taken with the Filtergraph (FG) instrument that show the dynamics of the structures. AR 10930 has some large sunspots showing sources and sinks within the penumbra as well as near the inner and outer boundaries. There are also regions of contact between penumbra of two sunspots (of opposite magnetic polarity) that show stronger horizontal flows and downdrafts than seen elsewhere in the penumbras. The relationship between Evershed "clouds" showing quasi-periodic variations in the spatially averaged Evershed flow and the penumbral fine structures is also investigated. This work was supported by NASA contract NNM07AA01C. Title: Disintegration of Magnetic Flux in Decaying Sunspots as Observed with the Hinode/SOT Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu, Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata, S.; Tsuneta, S. Bibcode: 2008AGUSMSP31B..01K Altcode: 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 having fields that are stronger and more vertical than their surroundings). These granules that appear in the outer penumbra often merge with bright features inside the penumbra that move with spines as they elongate toward the moat region. This suggests that convective motions around the penumbral outer boundary are related to 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 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. Title: Evidence of magnetic field wrapping around penumbral filaments Authors: Borrero, J. M.; Lites, B. W.; Solanki, S. K. Bibcode: 2008A&A...481L..13B Altcode: 2007arXiv0712.2548B 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. Title: Formation of Solar Magnetic Flux Tubes with Kilogauss Field Strength Induced by Convective Instability Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama, Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.; Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco Suárez, David Bibcode: 2008ApJ...677L.145N Altcode: 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. Title: Transient horizontal magnetic fields in solar plage regions Authors: Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M. Bibcode: 2008A&A...481L..25I Altcode: 2008arXiv0802.1769I 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. Title: Net circular polarization of sunspots in high spatial resolution Authors: Ichimoto, K.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Lites, B. W.; Kubo, M.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata, S. Bibcode: 2008A&A...481L...9I Altcode: 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 (Δγ-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 Δγ-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. Title: Nonlinear Force-free Field Modeling of a Solar Active Region around the Time of a Major Flare and Coronal Mass Ejection Authors: Schrijver, C. J.; DeRosa, M. L.; Metcalf, T.; Barnes, G.; Lites, B.; Tarbell, T.; McTiernan, J.; Valori, G.; Wiegelmann, T.; Wheatland, M. S.; Amari, T.; Aulanier, G.; Démoulin, P.; Fuhrmann, M.; Kusano, K.; Régnier, S.; Thalmann, J. K. Bibcode: 2008ApJ...675.1637S Altcode: 2007arXiv0712.0023S 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. Title: Hinode SOT Observations of Solar Quiescent Prominence Dynamics Authors: Berger, Thomas E.; Shine, Richard A.; Slater, Gregory L.; Tarbell, Theodore D.; Title, Alan M.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Suematsu, Yoshinori; Tsuneta, Saku; Lites, Bruce W.; Shimizu, Toshifumi Bibcode: 2008ApJ...676L..89B Altcode: 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. Title: Emergence of a Helical Flux Rope under an Active Region Prominence Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo, Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M. Bibcode: 2008ApJ...673L.215O Altcode: 2008arXiv0801.1956O 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. Title: The Horizontal Magnetic Flux of the Quiet-Sun Internetwork as Observed with the Hinode Spectro-Polarimeter Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S. Bibcode: 2008ApJ...672.1237L Altcode: 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. Title: Hinode Observations of Flux Emergence in Quiet and Active Regions Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S. Bibcode: 2008ASPC..383...71L Altcode: We review briefly the observational understanding of emergence of flux in both the quiet Sun and active regions in the light of first results from the joint Japan/US/UK Hinode mission. That spacecraft is now providing us with our first continuous, high resolution measurements of the photospheric vector magnetic field, along with high resolution observations of the thermal and dynamic properties of the chromosphere and corona. This review is intended to present a few very early results and to highlight the potential for discovery offered by this extraordinary new mission. The discovery of ubiquitous horizontal magnetic flux in the quiet internetwork regions is presented. Title: Mangetic field properties at the footpoints of solar microflares (active-region transient brightenings) Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.; Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu, Y.; Tarbell, T.; Title, A.; Tsuneta, S. Bibcode: 2007AGUFMSH52C..06S Altcode: Solar active regions produce numerous numbers of small-scale explosive energy releases, i.e., microflares, which are captured by imaging observations in soft X-rays as transient brightenings of small-scale coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT) onboard the Hinode satellite, we can investigate finer structure of the brightening X-ray sources in more details than we did with Yohkoh data. One of important questions on microflares is what causes microflares. The simultaneous visible-light observations by the Solar Optical Telescope (SOT) allow us to explore magnetic activities and magnetic field configuration at the photospheric footpoints of brightening loops, giving key observations to investigate the question. For our investigations of corona-photosphere magnetic coupling, we have established co-alignment between SOT and XRT with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in press). It turns out that Ca II H observations are very useful to identify the exact positions of footpoints of X-ray transient brightening loops. Small "Kernels" are sometimes observed in Ca II H and they may be signature of highly accelerated non-thermal particles impinging on chromosphere. As already shown in Shimizu et al.(2002), frequent transient brightenings are observed at the locations where emerging activities are on going. However, another type of brightening triggering mechanism should exist to explain some observed multiple-loop brightenings. In the multiple-loop brightenings, multiple loops are magnetically in parallel with each other and no apparent magnetic activities, such as emerging and canceling, are observed at and near the footpoints. This paper will present SOT observations of some microflares observed with XRT. Title: Small-Scale Jetlike Features in Penumbral Chromospheres Authors: Katsukawa, Y.; Berger, T. E.; Ichimoto, K.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.; Tsuneta, S. Bibcode: 2007Sci...318.1594K Altcode: 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. Title: Magnetic and Doppler Observations of the Photosphere and Low Chromosphere with the Solar Optical Telescope on Hinode Authors: Tarbell, T. D.; Lites, B. W.; Shine, R. A.; Ichimoto, K. Bibcode: 2007AGUFMSH53A1064T Altcode: We present magnetic field and Doppler shift measurements in the Mg I b line at 517.3 nm obtained with the Solar Optical Telescope's Narrowband Filter Imager on Hinode. The line core forms in the low chromosphere, and the wings where the measurements are made probably form around the temperature minimum. Stokes IQUV images in the red and blue wings are combined to make movies of longitudinal magnetograms and Dopplergrams. The direction of the transverse field component is also measurable in strong field concentrations. These are compared with very accurate photospheric magnetic measurements in Fe I 630.2 nm from the Spectro-Polarimeter. This comparison calibrates the filter longitudinal magnetograms in flux density and shows changes in field geometry with height. The Doppler measurements are calibrated using wavelength scans through the Mg line profile. A number of emerging and canceling magnetic features were observed in AR 10961 during its disk passage in late June and early July. Since these were made during the Hinode eclipse season, the observations have somewhat lower spatial resolution than usual (0.32 arcsecond pixels), but the uniformity and sensitivity are excellent. Intermittent upflows seen between canceling magnetic features are interpreted in terms of reconnection outflows. Strong, persistent downflows are seen adjacent to but not on flux concentrations outside of sunspots and pores. In the sunspot, running penumbral waves are clearly visible, and steady downflows are observed over the light bridges. Hinode is a Japanese mission developed and launched by ISAS/ JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in cooperation with ESA and NSC (Norway). Title: Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection Authors: Shibata, Kazunari; Nakamura, Tahei; Matsumoto, Takuma; Otsuji, Kenichi; Okamoto, Takenori J.; Nishizuka, Naoto; Kawate, Tomoko; Watanabe, Hiroko; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo; Nozawa, Satoshi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Berger, Thomas E.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M. Bibcode: 2007Sci...318.1591S Altcode: 2008arXiv0810.3974S The heating of the solar chromosphere and corona is a long-standing puzzle in solar physics. Hinode observations show the ubiquitous presence of chromospheric anemone jets outside sunspots in active regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their velocity is 10 to 20 kilometers per second. These small jets have an inverted Y-shape, similar to the shape of x-ray anemone jets in the corona. These features imply that magnetic reconnection similar to that in the corona is occurring at a much smaller spatial scale throughout the chromosphere and suggest that the heating of the solar chromosphere and corona may be related to small-scale ubiquitous reconnection. Title: Twisting Motions of Sunspot Penumbral Filaments Authors: Ichimoto, K.; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Lites, B. W.; Kubo, M.; Nagata, S. Bibcode: 2007Sci...318.1597I Altcode: 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. Title: Hinode observations reveal boundary layers of magnetic elements in the solar photosphere Authors: Rezaei, R.; Steiner, O.; Wedemeyer-Böhm, S.; Schlichenmaier, R.; Schmidt, W.; Lites, B. W. Bibcode: 2007A&A...476L..33R Altcode: 2007arXiv0711.0408R Aims:We study the structure of the magnetic elements in network-cell interiors.
Methods: A quiet Sun area close to the disc centre was observed with the spectro-polarimeter of the Solar Optical Telescope on board the Hinode space mission, which yielded the best spatial resolution ever achieved in polarimetric data of the Fe I 630 nm line pair. For comparison and interpretation, we synthesize a similar data set from a three-dimensional magneto-hydrodynamic simulation.
Results: We find several examples of magnetic elements, either roundish (tube) or elongated (sheet), which show a central area of negative Stokes-V area asymmetry framed or surrounded by a peripheral area with larger positive asymmetry. This pattern was predicted some eight years ago on the basis of numerical simulations. Here, we observationally confirm its existence for the first time.
Conclusions: We gather convincing evidence that this pattern of Stokes-V area asymmetry is caused by the funnel-shaped boundary of magnetic elements that separates the flux concentration from the weak-field environment. On this basis, we conclude that electric current sheets induced by such magnetic boundary layers are common in the photosphere. Title: Hinode SOT observations of plume upflows and cascading downflows in quiescent solar prominences Authors: Berger, T.; Shine, R.; Slater, G.; Tarbell, T.; Title, A.; Lites, B.; Tsuneta, S.; Okamoto, T. J.; Ichimoto, K.; Katsukawa, Y.; Sekii, T.; Suematsu, Y.; Shimizu, T. Bibcode: 2007AGUFMSH53A1065B Altcode: We present several Hinode SOT filtergram movies of quiescent solar prominences that show newly discovered "plume-like" upflows and cascading "waterfall-like" downflows that persist for the entire multi-hour duration of the observations. The flow speeds are on the order of 10 km/sec with typical widths of 400-700 km. Preliminary calculations show that if the upflows are buoyancy driven, the associated thermal perturbation is on the order of 10,000 K, sufficient to explain the dark appearance of the upflows in the interference filter passbands. In addition we observe rotational vortices and body oscillations within the prominences. These new observations challenge current magnetostatic models of solar prominences by showing that prominence plasmas are in constant motion, often in directions perpendicular to the magnetic field lines proposed by the models. TRACE, Hinode/EIS, and Hinode/XRT observations are used to investigate the differential topology of the flows across temperature regimes. Title: Coronal Transverse Magnetohydrodynamic Waves in a Solar Prominence Authors: Okamoto, T. J.; Tsuneta, S.; Berger, T. E.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shibata, K.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M. Bibcode: 2007Sci...318.1577O Altcode: 2008arXiv0801.1958O Solar prominences are cool 104 kelvin plasma clouds supported in the surrounding 106 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. Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of Hinode Measurements Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M. Bibcode: 2007ApJ...670L..61O Altcode: 2007arXiv0710.1405O We analyze Fe I 630 nm observations of the quiet Sun at disk center taken with the spectropolarimeter of the Solar Optical Telescope aboard the Hinode satellite. A significant fraction of the scanned area, including granules, turns out to be covered by magnetic fields. We derive field strength and inclination probability density functions from a Milne-Eddington inversion of the observed Stokes profiles. They show that the internetwork consists of very inclined, hG fields. As expected, network areas exhibit a predominance of kG field concentrations. The high spatial resolution of Hinode's spectropolarimetric measurements brings to an agreement the results obtained from the analysis of visible and near-infrared lines. Title: Center-to-Limb Variation of Stokes V Asymmetries in Solar Pores Observed with the Hinode Spectro-Polarimeter Authors: Morinaga, Shuji; Nagata, Shin'ichi; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Sakurai, Takashi Bibcode: 2007PASJ...59S.613M Altcode: Here we present spectro-polarimetric measurements of several pores and the surrounding regions taken with the Solar Optical Telescope aboard Hinode at various viewing angles. We analyzed the Stokes V area asymmetry, and confirmed that it is depressed at the center of the pores, while it shows large positive values (a blue lobe larger than a red lobe) in the surrounding area; this is consistent with a previous report. In addition to this ring of positive asymmetry, we found regions of alternating positive and negative area asymmetries when weak V regions were observed near the solar limb. The positive asymmetry occurs on the disk-center side and the negative asymmetry on the limb side of the magnetic concentrations. These center-to-limb variations of the Stokes V area asymmetry can be interpreted as being a systematic inflow of plasma into the magnetic concentrations from their surroundings. Title: Initial Results on Line-of-Sight Field Calibrations of SP/NFI Data Taken by SOT/Hinode Authors: Chae, Jongchul; Moon, Yong-Jae; Park, Young-Deuk; Ichimoto, Kiyoshi; Sakurai, Takashi; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi; Yokoyama, Takaaki Bibcode: 2007PASJ...59S.619C Altcode: We present initial results on the line-of-sight field calibration of the two kinds of Stokes I and V data taken by the Solar Optical Telescope on the satellite Hinode: spectral profiles of Stokes I and V parameters recorded on the Spectro-polarimeter (SP), and monochromatic images of the same parameters recorded on the Narrow-band Filter Imager (NFI). By applying the center-of-gravity method to the SP data of AR10930 taken on 2006 December 11, we determined the line-of-sight field at every location in the active region. As a result, we found that the line-of-sight field strength ranges up to 2kG in plages, even without taking into account the filling factor, and up to 3.5kG or higher values inside the umbra of the major sunspot. We calibrated the NFI data in reference to the field determined from the SP data. In regions outside the sunspots and the penumbral regions, we adopted a linear relation, B|| = βV / I, between the circular polarization, V / I, and the line-of-sight field strength, B||, and obtained β = 23.5kG in regions outside the sunspots, and β = 12.0kG in penumbral regions. In umbral regions of sunspots, a first-order polynomial was adopted to model the reversal of the polarization signal over the field strength. Title: Response of the Solar Atmosphere to Magnetic Flux Emergence from Hinode Observations Authors: Li, Hui; Sakurai, Takashi; Ichimito, Kiyoshi; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi; Kotoku, Jun; Shibasaki, Kiyoto; Saar, Steven H.; Bobra, Monica Bibcode: 2007PASJ...59S.643L Altcode: No abstract at ADS Title: Initial Helioseismic Observations by Hinode/SOT Authors: Sekii, Takashi; Kosovichev, Alexander G.; Zhao, Junwei; Tsuneta, Saku; Shibahashi, Hiromoto; Berger, Thomas E.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M. Bibcode: 2007PASJ...59S.637S Altcode: 2007arXiv0709.1806S Results from initial helioseismic observations by the Solar Optical Telescope on-board Hinode are reported. It has been demonstrated that intensity oscillation data from the Broadband Filter Imager can be used for various helioseismic analyses. The k - ω power spectra, as well as the corresponding time-distance cross-correlation function, which promise high-resolution time-distance analysis below the 6-Mm travelling distance, were obtained for G-band and CaII-H data. Subsurface supergranular patterns were observed from our first time-distance analysis. The results show that the solar oscillation spectrum is extended to much higher frequencies and wavenumbers, and the time-distance diagram is extended to much shorter travel distances and times than were observed before, thus revealing great potential for high-resolution helioseismic observations from Hinode. Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux and the ``Hidden Turbulent Magnetic Flux'' Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger, Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu, Yoshinori; Shimizu, Toshifumi Bibcode: 2007PASJ...59S.571L Altcode: We present observations of magnetic fields of the very quiet Sun near disk center using the Spectro-Polarimeter of the Solar Optical Telescope aboard the Hinode satellite. These observations reveal for the first time the ubiquitous presence of horizontal magnetic fields in the internetwork regions. The horizontal fields are spatially distinct from the vertical fields, demonstrating that they are not arising mainly from buffeting of vertical flux tubes by the granular convection. The horizontal component has an average ``apparent flux density'' of 55Mxcm-2 (assuming the horizontal field structures are spatially resolved), in contrast to the average apparent vertical flux density of 11Mxcm-2. The vertical fields reside mainly in the intergranular lanes, whereas the horizontal fields occur mainly over the bright granules, with a preference to be near the outside edge of the bright granules. The large apparent imbalance of vertical and horizontal flux densities is discussed, and several scenarios are presented to explain this imbalance. Title: Strategy for the Inversion of Hinode Spectropolarimetric Measurements in the Quiet Sun Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi; Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M. Bibcode: 2007PASJ...59S.837O Altcode: 2007arXiv0709.2033O In this paper we propose an inversion strategy for the analysis of spectropolarimetric measurements taken by Hinode in the quiet Sun. The Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records the Stokes spectra of the FeI line pair at 630.2nm with unprecendented angular resolution, high spectral resolution, and high sensitivity. We discuss the need to consider a local stray-light contamination to account for the effects of telescope diffraction. The strategy is applied to observations of a wide quiet Sun area at disk center. Using these data we examine the influence of noise and initial guess models in the inversion results. Our analysis yields the distributions of magnetic field strengths and stray-light factors. They show that quiet Sun internetwork regions consist mainly of hG fields with stray-light contamination of about 0.8. Title: Hinode Observations of a Vector Magnetic Field Change Associated with a Flare on 2006 December 13 Authors: Kubo, Masahito; Yokoyama, Takaaki; Katsukawa, Yukio; Lites, Bruce; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Nagata, Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.; Elmore David Bibcode: 2007PASJ...59S.779K Altcode: 2007arXiv0709.2397K Continuous observations of the flare productive active region 10930 were successfully carried out with the Solar Optical Telescope aboard the Hinode spacecraft during 2006 December 6 to 19. We focused on the evolution of photospheric magnetic fields in this active region, and the magnetic field properties at the site of the X3.4 class flare, using a time series of vector field maps with high spatial resolution. The X3.4 class flare occurred on 2006 December 13 at the apparent collision site between the large, opposite polarity umbrae. Elongated magnetic structures with alternatingly positive and negative polarities resulting from flux emergence appeared one day before the flare in the collision site penumbra. Subsequently, the polarity inversion line at the collision site became very complicated. The number of bright loops in CaII H increased during the formation of these elongated magnetic structures. Flare ribbons and bright loops evolved along the polarity inversion line and one footpoint of the bright loop was located in a region having a large departure of the field azimuth angle with respect to its surroundings. SOT observations with high spatial resolution and high polarization precision revealed temporal change in the fine structure of magnetic fields at the flare site: some parts of the complicated polarity inversion line then disappeared, and in those regions the azimuth angle of the photospheric magnetic field changed by about 90°, becoming more spatially uniform within the collision site. Title: The Analysis of Penumbral Fine Structure Using an Advanced Inversion Technique Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta, Saku Bibcode: 2007PASJ...59S.601J Altcode: 2007arXiv0707.1560J We present a method to study the penumbral fine structure using data obtained by the spectropolarimeter on board Hinode. For the first time, the penumbral filaments can be considered as being resolved in spectropolarimetric measurements. This enables us to use inversion codes with only one-component model atmospheres, and thus to assign the obtained stratifications of the plasma parameters directly to the penumbral fine structure. This approach was applied to the limb-side part of the penumbra in the active region NOAA10923. Preliminary results show a clear dependence of the plasma parameters on the continuum intensity in the inner penumbra, i.e., a weaker and horizontal magnetic field along with an increased line-of-sight velocity are found in the low layers of the bright filaments. The results in the mid penumbra are ambiguous, and future analyses are necessary to unveil the magnetic field structure and other plasma parameters there. Title: Fine-Scale Structures of the Evershed Effect Observed by the Solar Optical Telescope aboard Hinode Authors: Ichimoto, Kiyoshi; Shine, Richard A.; Lites, Bruce; Kubo, Masahito; Shimizu, Toshifumi; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Tarbell, Theodore D.; Title, Alan M.; Nagata, Shin'ichi; Yokoyama, Takaaki; Shimojo, Masumi Bibcode: 2007PASJ...59S.593I Altcode: The small-scale structure of the Evershed effect is being studied using data obtained by the Spectropolarimeter and the Broadband Filter Imager of the Solar Optical Telescope aboard Hinode. We find that the Evershed flow starts at the leading edge of inwardly migrating bright penumbral grains, and turns to nearly a horizontal flow preferentially in the dark lanes of the penumbra. A number of small elongated regions that have an upward motion of ∼ 1kms-1 are found in the deep photosphere distributed over the penumbra. They are cospatial with bright grains and have relatively horizontal magnetic fields. A number of patches having a strong downward motion associated with the opposite magnetic polarity from the sunspot are also found in the mid and outer penumbra. They could be identified as foot points of the Evershed flow channels, though the identification of individual pairs is not straightforward. Our results provide strong support for some recent findings from ground-based high-resolution observations, and are in general agreement with the well-known picture of the uncombed structure of the penumbra, in which the penumbrae consist of rising flux tubes carrying nearly horizontal Evershed flows embedded in more vertical background magnetic fields. Title: Flare Ribbons Observed with G-band and FeI 6302Å, Filters of the Solar Optical Telescope on Board Hinode Authors: Isobe, Hiroaki; Kubo, Masahito; Minoshima, Takashi; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tarbell, Theodore D.; Tsuneta, Saku; Berger, Thomas E.; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Title, Alan M. Bibcode: 2007PASJ...59S.807I Altcode: 2007arXiv0711.3946I The Solar Optical Telescope (SOT) on board the Hinode satellite observed an X3.4 class flare on 2006 December 13. A typical two-ribbon structure was observed, not only in the chromospheric CaII H line, but also in the G-band and FeI 6302Å line. The high-resolution, seeing-free images achieved by SOT revealed, for the first time, sub-arcsec fine structures of the ``white light'' flare. The G-band flare ribbons on sunspot umbrae showed a sharp leading edge, followed by a diffuse inside, as well as a previously known core-halo structure. The underlying structures, such as umbral dots, penumbral filaments, and granules, were visible in the flare ribbons. Assuming that the sharp leading edge was directly heated by a particle beam and the diffuse parts were heated by radiative back-warming, we estimated the depth of the diffuse flare emission using an intensity profile of the flare ribbon. We found that the depth of the diffuse emission was about 100km or less from the height of the source of radiative back-warming. The flare ribbons were also visible in the Stokes-V images of FeI 6302Å, as a transient polarity reversal. This is probably related to a ``magnetic transient'' reported in the literature. The intensity increase in Stokes-I images indicates that the FeI 6302Å line was significantly deformed by the flare, which may cause such a magnetic transient. Title: Small-Scale Magnetic-Flux Emergence Observed with Hinode Solar Optical Telescope Authors: Otsuji, Kenichi; Shibata, Kazunari; Kitai, Reizaburo; Ueno, Satoru; Nagata, Shin'ichi; Matsumoto, Takuma; Nakamura, Tahei; Watanabe, Hiroko; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Lites, Bruce; Shine, Richard A.; Title Alan M. Bibcode: 2007PASJ...59S.649O Altcode: 2007arXiv0709.3207O We observed small-scale magnetic-flux emergence in a sunspot moat region by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We analyzed filtergram images observed at wavelengths of Fe 6302Å, G band, and CaII H. In Stokes I images of Fe 6302Å, emerging magnetic flux was recognized as dark lanes. In the G band, they showed to be their shapes almost the same as in Stokes I images. These magnetic fluxes appeared as dark filaments in CaII H images. Stokes V images of Fe 6302Å showed pairs of opposite polarities at footpoints of each filament. These magnetic concentrations were identified to correspond to bright points in G band/CaII H images. From an analysis of time-sliced diagrams, we derived the following properties of emerging flux, which are consistent with those of previous studies: (1) Two footpoints separate each other at a speed of 4.2kms-1 during the initial phase of evolution, and decrease to about 1kms-1 10minutes later. (2) CaII H filaments appear almost simultaneously with the formation of dark lanes in Stokes I in an observational cadence of 2minutes. (3) The lifetime of the dark lanes in the Stokes I and G band is 8minutes, while that of Ca filament is 12minutes. An interesting phenomena was observed, that an emerging flux tube expanded laterally in the photosphere with a speed of 3.8kms-1. A discussion on the horizontal expansion of the flux tube is given with refernce to previous simulation studies. Title: Observations of Sunspot Oscillations in G Band and CaII H Line with Solar Optical Telescope on Hinode Authors: Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.; Shibahashi, Hiromoto; Tsuneta, Saku; Ichimoto, Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M. Bibcode: 2007PASJ...59S.631N Altcode: 2007arXiv0709.0569N Exploiting high-resolution observations made by the Solar Optical Telescope on board Hinode, we investigate the spatial distribution of the power spectral density of the oscillatory signal in and around the active region NOAA 10935. The G-band data show that in the umbra the oscillatory power is suppressed in all frequency ranges. On the other hand, in CaII H intensity maps oscillations in the umbra, so-called umbral flashes, are clearly seen with the power peaking around 5.5mHz. The CaII H power distribution shows the enhanced elements with the spatial scale of the umbral flashes over most of the umbra, but there is a region with suppressed power at the center of the umbra. The origin and property of this node-like feature remain unexplained. Title: Hinode SP Vector Magnetogram of AR10930 and Its Cross-Comparison with MDI Authors: Moon, Yong-Jae; Kim, Yeon-Han; Park, Young-Deuk; Ichimoto, Kiyoshi; Sakurai, Takashi; Chae, Jongchul; Cho, Kyung Suk; Bong, Suchan; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimojo, Masumi; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi; Yokoyama, Takaaki Bibcode: 2007PASJ...59S.625M Altcode: We present one Hinode Spectropolarimeter (SP) magnetogram of AR 10930 that produced several major flares. The inversion from Stokes profiles to magnetic field vectors was made using the standard Milne-Eddington code. We successfully applied the Uniform Shear Method for resolving the 180° ambiguity to the magnetogram. The inversion gave very strong magnetic field strengths (near 4500 gauss) for a small portion of area in the umbra. Considering that the observed V-profile of 6301.5Å was well-fitted as well as a direct estimation of the Zeeman splitting results in 4300-4600 gauss, we think that the field strengths should not be far from the actual value. A cross-comparison of the Hinode SP and SOHO MDI high resolution flux densities shows that the MDI flux density could be significantly underestimated by about a factor of two. In addition, it has a serious negative correlation (the so-called Zeeman saturation effect) with the Hinode SP flux density for umbral regions. Finally, we could successfully obtain a recalibrated MDI magnetogram that has been corrected for the Zeeman saturation effect using not only a pair of MDI intensity and magnetogram data simultaneously observed, but also the relationship from the cross-comparison between the Hinode SP and MDI flux densities. Title: Formation Process of a Light Bridge Revealed with the Hinode Solar Optical Telescope Authors: Katsukawa, Yukio; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi; Kubo, Masahito; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta, Saku Bibcode: 2007PASJ...59S.577K Altcode: 2007arXiv0709.2527K The Solar Optical Telescope (SOT) on-board Hinode successfully and continuously observed the formation process of a light bridge in a matured sunspot of the NOAA active region 10923 for several days with high spatial resolution. During its formation, many umbral dots were observed to be emerging from the leading edges of penumbral filaments, and rapidly intruding into the umbra. The precursor of the light bridge formation was also identified as a relatively slow inward motion of the umbral dots, which emerged not near the penumbra, but inside the umbra. The spectro-polarimeter on SOT provided physical conditions in the photosphere around the umbral dots and the light bridges. We found that the light bridges and the umbral dots had significantly weaker magnetic fields associated with upflows relative to the core of the umbra, which implies that there was hot gas with weak field strength penetrating from the subphotosphere to near the visible surface inside those structures. There needs to be a mechanism to drive the inward motion of the hot gas along the light bridges. We suggest that the emergence and the inward motion are triggered by a buoyant penumbral flux tube as well as subphotospheric flow crossing the sunspot. Title: Umbral Fine Structures in Sunspots Observed with Hinode Solar Optical Telescope Authors: Kitai, Reizaburo; Watanabe, Hiroko; Nakamura, Tahei; Otsuji, Ken-ichi; Matsumoto, Takuma; UeNo, Satoru; Nagata, Shin'ichi; Shibata, Kazunari; Muller, Richard; Ichimoto, Kiyoshi; Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Shimizu, Toshifumi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.; Lites, Bruce Bibcode: 2007PASJ...59S.585K Altcode: 2007arXiv0711.3266K A high resolution imaging observation of a sunspot umbra was made with the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the blue and green continua were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components, and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution, and morphological evolution. The brightness of UDs is confirmed to depend on the brightness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of the space observation, we could for the first time follow the temporal behavior of these events. The derived properties of the internal structure of the umbra are discussed from the viewpoint of magnetoconvection in a strong magnetic field. Title: Formation of Moving Magnetic Features and Penumbral Magnetic Fields with Hinode/SOT Authors: Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Nagata, Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.; Frank, Zoe A.; Lites, Bruce; Elmore, David Bibcode: 2007PASJ...59S.607K Altcode: 2007arXiv0709.1853K Vector magnetic fields of moving magnetic features (MMFs) were well observed with the Solar Optical Telescope (SOT) aboard the Hinode satellite. We focused on the evolution of three MMFs with the SOT in this study. We found that an MMF having relatively vertical fields with the same polarity as the sunspot was detached from the penumbra around the granules appearing in the outer penumbra. This suggests that granular motions in the outer penumbra are responsible for disintegration of the sunspot. Two MMFs with polarity opposite to the sunspot are located around the outer edge of horizontal fields extending from the penumbra. This is evidence that the MMFs with polarity opposite to the sunspot are the prolongation of penumbral horizontal fields. Redshifts larger than the sonic velocity in the photosphere are detected for some of the MMFs with polarity opposite to the sunspot. Title: Summary Review: Science with the SOT Authors: Lites, B. W. Bibcode: 2007ASPC..369..579L Altcode: This workshop highlights the ongoing maturation of numerical modeling and simulations that are increasingly useful in interpretation of observations. A few examples of presentations that underscore this theme are briefly discussed. Next, a brief advocacy of the advantages of close coordination of Solar-B and ground-based observations is presented. Finally, three controversial hypotheses are presented in order to stimulate discussion within our community. Title: Estimate on SOT Light Level in Flight with Throughput Measurements in SOT Sun Tests Authors: Shimizu, T.; Kubo, M.; Tarbell, T. D.; Berger, T. E.; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Miyashita, M.; Noguchi, M.; Nakagiri, M.; Tsuneta, S.; Elmore, D. F.; Lites, B. W. Bibcode: 2007ASPC..369...51S Altcode: The SOT (Solar Optical Telescope, e.g., Shimizu 2004) optical system consists of 50cm-aperture optical telescope (OTA) and focal plane instrument (FPP). The solar light into the telescope penetrates through many optical elements located in OTA and FPP before illuminating CCDs. Natural solar light was fed to the integrated SOT in sun tests for verifying various optical aspects including the confirmation of photon throughput. CCD exposures provide the number of photons accumulated in an exposure duration with a clean-room test condition. To estimate the absolute intensity of the solar light at the telescope entrance in the clean-room test condition, we developed a pinhole-PSD sensor for simultaneous monitoring the solar light outside the clean room and measured the transmission of light through two flat mirrors of the heliostat and clean-room entrance window glass as a function of wavelength. The PSD sensor was pre-calibrated with continuous monitoring the solar light in a day long under a clear constant sky condition, determining the earth atmospheric attenuation and the PSD output for the solar light on orbit. These throughput measurements have provided an estimate on photon throughput for the SOT flight model. The results confirm suitable number of photons without saturation for proper CCD exposures in flight. Title: Performance Characteristics of the Solar-B Spectro-Polarimeter Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.; Hoffmann, C. M.; Tarbell, T. D.; Title, A. M.; Shine, R. A.; Ichimoto, K.; Tsuneta, S.; Shimizu, T.; Suematsu, Y. Bibcode: 2007ASPC..369...55L Altcode: The Focal Plane Package (FPP) of the Solar Optical Telescope (SOT) includes the first precision Spectro-Polarimeter (SP) for solar space observations. The FPP/SP will provide high precision measures of the vector magnetic field in the solar photosphere. Here we present some as-built performance specifications for the entire system of telescope + polarimeter. The FPP-SP system represents significant gains in several aspects over existing spectro-polarimetric systems; notably, angular resolution, polarimetric accuracy, spectral purity, and most importantly, temporal continuity of stable, high angular resolution. In this short summary of the poster, a few of the performance characteristics of the SP are presented. Title: Calibration of the SOT Polarization Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.; Noguchi, M.; Nakagiri, M.; Miyashita, M.; Tsuneta, S.; Tarbell, T. D.; Shine, R. A.; Hoffmann, C. M.; Cruz, T.; Lites, B. W.; Elmore, D. F. Bibcode: 2007ASPC..369...39I Altcode: Calibration of SOT polarization property was performed using natural sunlight and well calibrated sheet polarizer (linear and circular) placed on the entrance of the telescope. The polarimeter response matrices were determined for the spectropolarimeter (SP) and the narrowband filter imager (NFI), and it is shown that they are well behave as predicted and constant over the field of view. The crosstalk between I,Q,U,V will be suppressed to the negligible level at the photometric accuracy of 10^{-3} after the calibration with the obtained matrices. The sensitivity of SOT on linear and circular polarizations at each wavelength observed by NFI are also obtained. Title: Vector Spectropolarimetry of Dark-cored Penumbral Filaments with Hinode Authors: Bellot Rubio, L. R.; Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.; del Toro Iniesta, J. C. Bibcode: 2007ApJ...668L..91B Altcode: 2007arXiv0708.2791B We present spectropolarimetric measurements of dark-cored penumbral filaments taken with Hinode at a resolution of 0.3". Our observations demonstrate that dark-cored filaments are more prominent in polarized light than in continuum intensity. Far from disk center, the Stokes profiles emerging from these structures are very asymmetric and show evidence for magnetic fields of different inclinations along the line of sight, together with strong Evershed flows of at least 6-7 km s-1. In sunspots closer to disk center, dark-cored penumbral filaments exhibit regular Stokes profiles with little asymmetries due to the vanishing line-of-sight component of the horizontal Evershed flow. An inversion of the observed spectra indicates that the magnetic field is weaker and more inclined in the dark cores as compared with the surrounding bright structures. This is compatible with the idea that dark-cored filaments are the manifestation of flux tubes carrying hot Evershed flows. Title: Emergence of Small-Scale Magnetic Loops in the Quiet-Sun Internetwork Authors: Centeno, R.; Socas-Navarro, H.; Lites, B.; Kubo, M.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.; Katsukawa, Y.; Suematsu, Y.; Shimizu, T.; Nagata, S. Bibcode: 2007ApJ...666L.137C Altcode: 2007arXiv0708.0844C We study the emergence of magnetic flux at very small spatial scales (less than 2") in the quiet-Sun internetwork. To this aim, a time series of spectropolarimetric maps was taken at disk center using the instrument SP/SOT on board Hinode. The LTE inversion of the full Stokes vector measured in the Fe I 6301 and 6302 Å lines allows us to retrieve the magnetic flux and topology in the region of study. In the example presented here, the magnetic flux emerges within a granular structure. The horizontal magnetic field appears prior to any significant amount of vertical field. As time goes on, the traces of the horizontal field disappear, while the vertical dipoles drift-carried by the plasma motions-toward the surrounding intergranular lanes. These events take place within typical granulation timescales. Title: Variation of the Stokes-V area asymmetry across magnetic elements Authors: Rezaei, R.; Steiner, O.; Wedemeyer-Böhm, S.; Schlichenmaier, R.; Lites, B. W. Bibcode: 2007AN....328..706R Altcode: No abstract at ADS Title: Magnetic Patches in Internetwork Quiet Sun Authors: De Wijn, Alfred; Lites, B.; Berger, T.; Shine, R.; Title, A.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Hinode Team Bibcode: 2007AAS...210.9412D Altcode: 2007BAAS...39Q.219D We study strong flux elements in the quiet sun in the context of the nature of quiet-sun magnetism, its coupling to chromospheric, transition-region and coronal fields, and the nature of a local turbulent dynamo. Strong, kilogauss flux elements show up intermittently as small bright points in G-band and Ca II H images. Although bright points have been extensively studied in the magnetic network, internetwork magnetism has only come under scrutiny in recent years. A full spectrum of field strengths seems to be ubiquitously present in the internetwork at small spatial scales, with the stronger elements residing in intergranular lanes. De Wijn et al. (2005) found that bright points in quiet sun internetwork areas appear recurrently with varying intensity and horizontal motion within long-lived patches that outline cell patterns on mesogranular scales. They estimate that the "magnetic patches" have a mean lifetime of nine hours, much longer than granular timescales. We use multi-hour sequences of G-band and Ca II H images as well as magnetograms recorded by the Hinode satellite to follow up on their results. The larger field of view, the longer sequences, the addition of magnetograms, and the absence of atmospheric seeing allows us to better constrain the patch lifetime, to provide much improved statistics on IBP lifetime, to compare IBPs to network bright points, and to study field polarity of IBPs in patches and between nearby patches.

Hinode is an international project supported by JAXA, NASA, PPARC and ESA. We are grateful to the Hinode team for all their efforts in the design, build and operation of the mission. Title: Hinode/SOT Observation of Fine Structure of the Evershed Flow Authors: Ichimoto, Kiyoshi; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.; Shimojo, M.; Kubo, M.; Shimizu, T.; Shine, R.; Tarbell, T.; Title, A.; Lites, B.; Elmore, D.; Yokoyama, T.; Nagaka, S. Bibcode: 2007AAS...210.9408I Altcode: 2007BAAS...39..218I Small scale structure of the Evershed effect was studied using the Spectropolarimeter (SP) and Broadband Filter Imager (BFI) of SOT aboard Hinode. SP maps and high cadence continuum images of BFI coverting entire sunspots are used to investigate the spatial distribution of the flow field, brightness and magnetic fields. It is revealed that the Evershed flow starts at the front edge of inwardly migrating penumbral grains with an upward velocity component and turns to nearly holizontal flow preferentially in dark lanes (or dark core of filaments) of the penumbra. Our results are in general agreement with the well known uncombed penumbral concept in which the Evershed flow takes place in nearly holizontal field channels. We discovered a number of tiny elongated regions in deep photosphere in which there is an obvious upward motion of 1-1.5km/s distributing over the penumbra.

They could be identified as the 'foot points' of the individual Evershed flow channels. Cross-correlation among the flow speed, intensity, magnetic field strength and inclination, and distribution of string down flows in and around the penumbra will also be discussed. Title: Magnetic Flux Emergence In The Quiet Sun Photosphere Authors: Centeno, Rebecca; Lites, B.; Socas-Navarro, H.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.; Katsukawa, Y.; Suematsu, Y.; Kubo, M.; Shimizu, T. Bibcode: 2007AAS...210.9406C Altcode: 2007BAAS...39..218C We study the emergence of magnetic flux at very small spacial scales (less than 1 arcsec) in the quiet Sun internetwork. To this aim, several time series of spectropolarimetric maps were taken at disk center using the instrument SP/SOT on board Hinode. The LTE inversion of the full Stokes vector measured in the Fe I 6301 and 6302 lines will allow us to retrieve the magnetic flux and topology in the region of study. We find that the magnetic flux emerges typically within the granular structures. In many cases, the horizontal magnetic field appears prior to any significant amount of vertical field. As time goes on, the traces of the horizontal field dissapear while the the vertical dipoles drift -carried by the plasma motions- towards the surrounding intergranular lanes. Sometimes they stay trapped there for a while but they eventually either disappear by disgregation/cancelation or agregate to other magnetic field concentrations giving rise to larger flux elements. The time scale of these events is of the order of 10-20 minutes. Title: Formation of Moving Magnetic Features and Penumbral Magnetic Fields Authors: Kubo, Masahito; Ichimoto, K.; Shimizu, T.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Lites, B. W.; Frank, Z.; Tarbell, T. D.; Shine, R. A.; Title, A. M. Bibcode: 2007AAS...210.9410K Altcode: 2007BAAS...39..218K We investigate the formation process of Moving Magnetic Features (MMFs) observed with Hinode/SOT. Moving magnetic features are small magnetic elements moving outward in the moat region surrounding mature sunspots. We derive vector magnetic fields of MMFs around simple sunspots near the disk center. Most of MMFs with polarity opposite to the sunspot have large redshift around the penumbral outer boundary. We find that some of them have Doppler velocities of about 10 km/s and such large Doppler motion is observed only in the Stokes V profile. The Stokes Q and U profiles in the same pixel do not have any significant Doppler motions. Horizontal magnetic fields of the penumbra frequently extend to the moat region and the MMFs having horizontal fields with polarity same as the sunspot are formed. The MMFs with polarity opposite to the sunspot appear around the outer edge of the extending penumbral fields. We also find penumbral spines, which have more vertical magnetic fields than the surroundings, branch off at their outer edge and MMFs having relatively vertical fields with polarity same as the sunspot are detached from the outer edge of the branch. The branch of penumbral spine is formed when granular cells in the moat region go into the penumbra. Title: Ubiquitous Horizontal Magnetic Fields in the Quiet Solar Photosphere as Revealed by HINODE Meaurements Authors: Lites, Bruce W.; Socas Navarro, H.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Kubo, M.; Shimizu, T.; Nagata, S.; Hinode Team Bibcode: 2007AAS...210.6303L Altcode: 2007BAAS...39..171L Measurements with the HINODE Spectro-Polarimeter (SP) of the quiet Sun allow characterization of the weak, mixed-polarity magnetic flux at the highest angular resolution to date (0.3"), and with good polarimetric sensitivity(0.025% relative to the continuum). The image stabilization of the HINODE spacecraft allows long integrations with degradation of the image quality only by the evolution of the solar granulation. From the Stokes V profile measurements we find an average solar "Apparent Flux Density" of 14 Mx cm-2, with significant Stokes V signals at every position on the disk at all times. However, there are patches of meso-granular size (5-15") where the flux is very weak. At this high sensitivity, transverse fields produce measurable Stokes Q,U linear polarization signals over a majority of the area, with apparent transverse flux densities in the internetwork significantly larger than the corresponding longitudinal flux densities. When viewed at the center of the solar disk, the Stokes V signals (longitudinal fields) show a preference for occurrence in the intergranular lanes, and the Q,U signals occur preferably over the granule interiors, but neither association is exclusive.

Hinode is an international project supported by JAXA, NASA, PPARC and ESA. We are grateful to the Hinode team for all their efforts in the design, build and operation of the mission. Title: Attempt to detect Aflven waves with Solar Optical Telescope aboard Hinode Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Shimizu, T.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.; Tarbell, T.; Title, A. Bibcode: 2007AAS...210.9428T Altcode: 2007BAAS...39..222T Flux tube on the sun may carry linear and torsional Alfven waves generated by photospheric motion. Photospheric motion of 2 km/s would provide magnetic fluctuation of 40G for 1KG tube and for the Alfven speed of 50km/s. This may be close to the detection limit of the Stokes Q and U signals for flux tubes located in the sun center. However, for flux tubes located near the limb, the fluctuation would be seen in the Stokes V signal, and can be detectable.

We also may be able to confirm the 90 degree phase shift between magnetic fluctuation and velocity fluctuation, which is easier to observe for flux tubes near the limb. Detection of waves would be important in terms of coronal heating and solar wind acceleration. An attempt to detect waves along flux tubes will be reported. Title: Is Coronal X-ray Emission Energized By Electric Currents? Authors: Ishibashi, Kazunori; Metcalf, T.; Lites, B. Bibcode: 2007AAS...210.9421I Altcode: 2007BAAS...39..220I We examine the spatial correlation between coronal X-ray emission observed with the Hinode X-Ray Telescope and electric currents observed with the Hinode Solar Optical Telescope Spectro-polarimeter. We determine to what extent the X-ray brightness is correlated with electric current density and hence to what extent the hot corona is energized by electric currents which flow through the photosphere. We will also consider whether the currents reach the corona to heat the coronal plasma or whether they predominantly close below the corona.

Hinode is an international project supported by JAXA, NASA, PPARC and ESA. We are grateful to the Hinode team for all their efforts in the design, development and operation of the mission. Title: Discovery Of Cool Cloud-like Structures In The Corona With Hinode Solar Optical Telescope Authors: Okamoto, Takenori; Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Nagata, S.; Shibata, K.; Tarbell, T.; Shine, R.; Berger, T.; Lites, B.; Myers, D. Bibcode: 2007AAS...210.9426O Altcode: 2007BAAS...39..221O A solar observation satellite Hinode (Japanese for sun rise) was launched in September 2006.Hinode carried 3 advanced solar telescopes, visible light telescope, EUV imaging spectrometer, and X-ray telescope to simultaneously observe the photosphere, chromosphere, transition region, and corona. In the performance verification phase of the Hinode spacecraft with its telescopes, we observed an active region AR10921 near the west limb of the solar disk on November 9 2006. At this point, we planned to observe spicules on the limb with a broadband filter dedicated to Ca II H line (3968A). Ca II-H emission line (3968A) comes from plasma with temperature of approx. 10(4) K, which is much lower than the coronal temperature of 10(6-7) K. In addition to spectacular spicules, we find a large cloud-like structure located 10,000-20,000 km above the limb. The cloud has a very complex fine structure with dominant horizontal thread-like structure. Some features are moving horizontally and also have clear vertical oscillatory motions. The periods and amplitudes of these oscillations are 130-250 seconds and 200-850 km, respectively. The vertical oscillatory motion sometimes has a coherence length as long as 16,000 km. We conclude that from various observational features this vertical oscillation is a signature of Alfven waves propagating along the horizontal magnetic fields. We will discuss their origin and implications. Title: Discovery Of Small-scale Horizontal Magnetic Structures On The Solar Photosphere Authors: Ishikawa, Ryohko; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Ishobe, H.; Tarbell, T.; Lites, B. W.; Title, A. Bibcode: 2007AAS...210.9404I Altcode: 2007BAAS...39..217I We discover two different types of episodes on the appearance of horizontal magnetic fields with Solar Optical Telescope aboard Hinode.

The first episode is an emergence of strong thin horizontal magnetic fields associated with separating vertical components on both ends. Its size is about two granules. We also detect strong area asymmetry of the environment Stokes Vprofile for the bout 8 minutes before the first emergence of the horizontal component. One of the footpoints has very strong downflows (several km/s), while the region with strong linear polarization signal has small blue shift, indicating an upward-moving horizontal flux.

The second episode appears to be more ubiquitous. Linear polarization signals appear inside granules (not in inter-granules). Their size is smaller than granules, and lifetime is longer than several minutes. We will summarize the nature of the two types of the horizontal magnetic fluxes, and discuss their origin. Title: Hinode/SOT Observations of Sunspot Penumbral Dynamics and Evolution Authors: Shine, Richard A.; Hagenaar, M.; Tarbell, T.; Title, A.; Lites, B.; Ichimoto, K.; Tsuneta, S.; Katsakawa, Y.; Suematsu, Y.; Nagata, S.; Kubo, M.; Shimizu, T. Bibcode: 2007AAS...210.9407S Altcode: 2007BAAS...39..218S The Solar Optical Telescope (SOT) on the Hinode satellite (launched October 2006) has obtained long and nearly continuous time series of several large sunspots including those in NOAA AR's 10923, 10925, and 10930. Here we use high resolution movies taken primarily with the broad band Ca II (396.8nm) and G band (430.5nm) channels and magnetograms taken with the 630.2nm narrow band channel to study the details and short term evolution of penumbral fine structures as well as the long term evolution of the sunspots. We compute flow maps and use space/time slices to track motions of Evershed clouds, penumbral grains, and visualize oscillations. The data contain examples of penumbral formation and disintegration including "orphan" penumbra (i.e., penumbra without an obvious umbra). There is also an interesting instance of "colliding" penumbra in AR 10930 as two sunspots of opposite polarity converged. The zone of apparent shear was associated with several flares.

This work was supported by NASA contract NNM07AA01C Title: Magnetic Landscape Of Solar Polar Region With Solar Optical Telescope Aboard Hinode Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Shimizu, T.; Katsukawa, Y.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.; Tarbell, T.; Title, A. Bibcode: 2007AAS...210.9405T Altcode: 2007BAAS...39..218T Solar polar region is the final destination for remnant magnetic fields due to meridional flow and granular diffusion, and is very important for the global solar dynamo. Hinode satellite carried out high-resolution spectro-polarimetric observations for the Northern pole on 2006 November 22 as a part of its performance verification program. We find ubiquitous isolated (positive and negative) patches in the Stokes V map (i.e. fields horizontal to local surface) all over the Arctic circle. The Q (vertical to local surface) map indicates scattered vertical flux tubes, which have bipolar feature in the U and V maps. This suggests canopy-like structure of the strong isolated flux tubes. This will be compared with equatorial landscape with similar distance from the sun center. Strong flux tube and weaker ubiquitous horizontal fields as represented by Stokes V would have implication to the current understanding of the global and local dynamo. Title: A suite of community tools for spectro-polarimetric analysis . Authors: Lites, B.; Casini, R.; Garcia, J.; Socas-Navarro, H. Bibcode: 2007MmSAI..78..148L Altcode: The National Center for Atmospheric Research (NCAR) has undertaken a 3-year initiative to develop the Community Spectro-polarimetric Analysis Center (CSAC). The goal of this effort is to provide the community with standardized tools for extracting the solar magnetic field vector and related atmospheric parameters from spectro-polarimetric observations. The emphasis will be to develop portable, efficient, and well-documented procedures for analysis of data from the many new and upcoming observational facilities, both ground- and space-based. The initial focus of CSAC will be the development of robust methods for inversion of Stokes spectral data, starting with a standard Milne-Eddington inversion that has been the workhorse for analysis of data from e.g. the Advanced Stokes Polarimeter. Upon completion of that code, the program will move to more sophisticated methods that embrace more realistic and detailed models of the solar atmosphere. Very fast methods for inversion (neural networks or pattern recognition techniques, for example) are also candidates. Finally, the CSAC is intended to eventually provide standardized methods for resolution of the 180-degree field azimuth ambiguity, and for visualization of the resulting magnetic field vector maps. CSAC is formulated as a community effort, and as such will receive guidance and input from the community. Title: Polarimetric Observations of the Formation of a G-Band Bright Point Authors: Beck, C.; Schmidt, W.; Bellot Rubio, L. R.; Schlichenmaier, R.; Sütterlin, P.; Lites, B. W. Bibcode: 2006ASPC..358...72B Altcode: We investigate the kinematic and magnetic properties of G-band bright points in the moat of a regular sunspot. The analysis is based on vector polarimetric measurements made at the German Vacuum Tower Telescope in visible (630 nm) and infrared (1565 nm) spectral lines, complemented by high-resolution filtergrams in the G-band at 430.6 nm and the core of the Ca II H line at 396.7 nm from the Dutch Open Telescope. The spectro-polarimetric data has been inverted to derive the magnetic field properties of the observed region. We witness the formation of a G-band bright point from a patch of diffuse flux with an initial field strength of 0.4 kG. The magnetic field strength increases to 0.9 kG in the course of several minutes, accompanied by a downflow of magnetized plasma. A few minutes after the field intensification, a G-band bright point is seen at the location of the flux concentration. The formation of the bright point shows the signatures of convective collapse. Title: Spectral Line Selection for HMI Authors: Norton, A. A.; Pietarila Graham, J. D.; Ulrich, R. K.; Schou, J.; Tomczyk, S.; Liu, Y.; Lites, B. W.; López Ariste, A.; Bush, R. I.; Socas-Navarro, H.; Scherrer, P. H. Bibcode: 2006ASPC..358..193N Altcode: We present information on two spectral lines, Fe I 6173 Å and Ni I 6768 Å, that were candidates for use in the Helioseismic and Magnetic Imager (HMI) instrument. Both Fe I and Ni I profiles have clean continuum and no blends that threaten performance. The higher Landé factor of Fe I means its operational velocity range in regions of strong magnetic field is smaller than for Ne I. Fe I performs better than Ni I for vector magnetic field retrieval. Inversion results show that Fe I consistently determines field strength and flux more accurately than the Ni I line. Inversions show inclination and azimuthal errors are recovered to ≈2° above 600 Mx/cm2 for Fe I and above 1000 Mx/cm2 for Ni I. The Fe I line was recommended, and ultimately chosen, for use in HMI. Title: Spectral Line Selection for HMI: A Comparison of Fe I 6173 Å and Ni I 6768 Å Authors: Norton, A. A.; Graham, J. Pietarila; Ulrich, R. K.; Schou, J.; Tomczyk, S.; Liu, Y.; Lites, B. W.; Ariste, A. López; Bush, R. I.; Socas-Navarro, H.; Scherrer, P. H. Bibcode: 2006SoPh..239...69N Altcode: 2006SoPh..tmp...88N; 2006astro.ph..8124N We present a study of two spectral lines, Fe I 6173 Å and Ni I 6768 Å, that were candidates to be used in the Helioseismic and Magnetic Imager (HMI) for observing Doppler velocity and the vector magnetic field. The line profiles were studied using the Mt. Wilson Observatory, the Advanced Stokes Polarimeter and the Kitt Peak-McMath Pierce telescope and one-meter Fourier transform spectrometer atlas. Both Fe I and Ni I profiles have clean continua and no blends that threaten instrument performance. The Fe I line is 2% deeper, 15% narrower, and has a 6% smaller equivalent width than the Ni I line. The potential of each spectral line to recover pre-assigned solar conditions is tested using a least-squares minimization technique to fit Milne-Eddington models to tens of thousands of line profiles that have been sampled at five spectral positions across the line. Overall, the Fe I line has a better performance than the Ni I line for vector-magnetic-field retrieval. Specifically, the Fe I line is able to determine field strength, longitudinal and transverse flux four times more accurately than the Ni I line in active regions. Inclination and azimuthal angles can be recovered to ≈2° above 600 Mx cm−2 for Fe I and above 1000 Mx cm−2 for Ni I. Therefore, the Fe I line better determines the magnetic-field orientation in plage, whereas both lines provide good orientation determination in penumbrae and umbrae. We selected the Fe I spectral line for use in HMI due to its better performance for magnetic diagnostics while not sacrificing velocity information. The one exception to the better performance of the Fe I line arises when high field strengths combine with high velocities to move the spectral line beyond the effective sampling range. The higher geff of Fe I means that its useful range of velocity values in regions of strong magnetic field is smaller than Ni I. Title: Magnetic Field Diagnostic Capability of Solar-B/SOT: Filtergraph Instrument Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.; Tsuneta, S.; Tarbell, T. D.; Shine, R. A.; Hoffmann, C. M.; Title, A. M.; Lites, B. W.; Elmore, D. F.; Streander, K. V. Bibcode: 2006ASPC..358..189I Altcode: The Narrowband Filter Instrument (NFI) of the Solar Optical Telescope onboard Solar-B provides 2D magnetograms/Dopplergrams with a tunable Lyot filter (width ∼ 0.1 Å) in 6 selected wavelength bands, and spatial sampling of 0.08 arcsec/px. The Zeeman-effect sensitivity of NFI and the detection limits of weak magnetic fields are evaluated for 2 photospheric and 3 chromospheric lines. Magnetic-field retrievability from the NFI observables is studied using synthetic Stokes profiles of Fe I 5250 Å. We find that, with optimized wavelength sampling at 4 positions, the inferred magnetic field is sufficiently accurate under the hypothesis of constant magnetic field and velocity along the LOS. Title: Solar Polarization 4 Authors: Casini, R.; Lites, B. W. Bibcode: 2006ASPC..358.....C Altcode: No abstract at ADS Title: The Diffraction Limited Spectro-Polarimeter Authors: Sankarasubramanian, K.; Lites, B.; Gullixson, C.; Elmore, D.; Hegwer, S.; Streander, K.; Rimmele, T.; Fletcher, S.; Gregory, S.; Sigwarth, M. Bibcode: 2006ASPC..358..201S Altcode: The Diffraction Limited Spectro-Polarimeter (DLSP) is a collaboration between the National Solar Observatory (NSO) and the High Altitude Observatory (HAO)

to provide a stable instrument for precision measurements of solar vector magnetic fields at high angular resolution. The DLSP is integrated with the new high-order Adaptive Optics (HOAO) system at the Dunn Solar Telescope (DST) and provides Stokes spectra of the Fe I 630 nm lines approaching the 0.2 arcs3c diffraction limit of the DST. It is configured as a fixed, well-calibrated instrument that may be used simultaneously with G-band (1 nm bandpass) and a Ca K imagers (0.1 nm bandpass). The 2K×2K G-band imager allows fast frame selection and includes a burst mode for speckle imaging. The setup of DLSP and its imagers require only about 10 min of preparation before start of observations. This fixed setup facilitates standardized data reduction. The DLSP permits observations with 0.09 arcsec sampling in high resolution mode. In wide-field mode, the 0.27 arcsec sampling allows one to map regions about 3 arcmin on a side. The achieved continuum S/N is 500 (1500) in high resolution (wide-field) mode for a 4 s integration. It is possible to achieve higher S/N by integrating longer. Data reduction routines are now available in IDL for post-observation processing, and parallel analysis routines in FORTRAN 77 are being developed to allow ``on-the-fly'' data reduction and inversion. Title: An Overview of Existing Algorithms for Resolving the 180° Ambiguity in Vector Magnetic Fields: Quantitative Tests with Synthetic Data Authors: Metcalf, Thomas R.; Leka, K. D.; Barnes, Graham; Lites, Bruce W.; Georgoulis, Manolis K.; Pevtsov, A. A.; Balasubramaniam, K. S.; Gary, G. Allen; Jing, Ju; Li, Jing; Liu, Y.; Wang, H. N.; Abramenko, Valentyna; Yurchyshyn, Vasyl; Moon, Y. -J. Bibcode: 2006SoPh..237..267M Altcode: 2006SoPh..tmp...14M We report here on the present state-of-the-art in algorithms used for resolving the 180° ambiguity in solar vector magnetic field measurements. With present observations and techniques, some assumption must be made about the solar magnetic field in order to resolve this ambiguity. Our focus is the application of numerous existing algorithms to test data for which the correct answer is known. In this context, we compare the algorithms quantitatively and seek to understand where each succeeds, where it fails, and why. We have considered five basic approaches: comparing the observed field to a reference field or direction, minimizing the vertical gradient of the magnetic pressure, minimizing the vertical current density, minimizing some approximation to the total current density, and minimizing some approximation to the field's divergence. Of the automated methods requiring no human intervention, those which minimize the square of the vertical current density in conjunction with an approximation for the vanishing divergence of the magnetic field show the most promise. Title: SUNRISE: high resolution UV/VIS observations of the Sun from the stratosphere Authors: Gandorfer, A. M.; Solanki, S. K.; Barthol, P.; Lites, B. W.; Martínez Pillet, V.; Schmidt, W.; Soltau, D.; Title, A. M. Bibcode: 2006SPIE.6267E..0SG Altcode: 2006SPIE.6267E..25G SUNRISE is an international project for the development, construction, and operation of a balloon-borne solar telescope with an aperture of 1 m, working in the UV/VIS spectral domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide near diffraction-limited images of the photosphere and chromosphere with an unpredecented resolution down to 35 km on the solar surface at wavelengths around 220 nm. The focal-plane instrumentation consists of a polarization sensitive spectrograph, a Fabry-Perot filter magnetograph, and a phase-diverse filter imager working in the near UV. The first stratospheric long-duration balloon flight of SUNRISE is planned in Summer 2009 from the swedish ESRANGE station. SUNRISE is a joint project of the german Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut fur Sonnenphysik (KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder, USA, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, USA, and the spanish IMaX consortium. In this paper we will present an actual update on the mission and give a brief description of its scientific and technological aspects. Title: Spectro-Polarimetric Observations and Non-Lte Modeling of Ellerman Bombs Authors: Socas-Navarro, Hector; Pillet, Valentín Martínez; Elmore, David; Pietarila, Anna; Lites, Bruce W.; Sainz, Rafael Manso Bibcode: 2006SoPh..235...75S Altcode: 2005astro.ph..8667S Ellerman bombs are bright emission features observed in the wings of Hα, usually in the vicinity of magnetic concentrations. Here we show that they can also be detected in the Ca II infrared triplet lines, which are easier to interpret and therefore allow for more detailed diagnostics. We present full Stokes observations of the 849.8 and 854.2 nm lines acquired with the new spectro-polarimeter SPINOR. The data show no significant linear polarization at the level of 3 × 10−4. The circular polarization profiles exhibit measureable signals with a very intricate pattern of peaks. A non-LTE analysis of the spectral profiles emerging from these features reveals the presence of strong downflows (∼10 {km s−1}) in a hot layer between the upper photosphere and the lower chromosphere. Title: Spinor: Visible and Infrared Spectro-Polarimetry at the National Solar Observatory Authors: Socas-Navarro, Hector; Elmore, David; Pietarila, Anna; Darnell, Anthony; Lites, Bruce W.; Tomczyk, Steven; Hegwer, Steven Bibcode: 2006SoPh..235...55S Altcode: 2005astro.ph..8685S The Spectro-Polarimeter for Infrared and Optical Regions (SPINOR) is a new spectro-polarimeter that will serve as a facility instrument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic polarimetry over a very broad range of wavelengths, from 430 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.). Title: On the fine structure of sunspot penumbrae. III. The vertical extension of penumbral filaments Authors: Borrero, J. M.; Solanki, S. K.; Lagg, A.; Socas-Navarro, H.; Lites, B. Bibcode: 2006A&A...450..383B Altcode: 2005astro.ph.10586B In this paper we study the fine structure of the penumbra as inferred from the uncombed model (flux tube embedded in a magnetic surrounding) when applied to penumbral spectropolarimetric data from the neutral iron lines at 6300 Å. The inversion infers very similar radial dependences in the physical quantities (LOS velocity, magnetic field strength etc.) as those obtained from the inversion of the Fe I 1.56 μm lines. In addition, the large Stokes V area asymmetry exhibited by the visible lines helps to constrain the size of the penumbral flux tubes. As we demonstrate here, the uncombed model is able to reproduce the area asymmetry with striking accuracy, returning flux tubes as thick as 100-300 kilometers in the vertical direction, in good agreement with previous investigations. Title: A Detailed Analysis of an Ephemeral Region . Authors: Guglielmino, S. L.; Martínez Pillet, V.; Ruiz Cobo, B.; Zuccarello, F.; Lites, B. W. Bibcode: 2006MSAIS...9..103G Altcode: In order to improve the understanding of the process of emergence of magnetic flux on the solar surface, we studied the temporal evolution of an ephemeral region using \emph{Advanced Stokes Polarimeter} data. We adopted two different approaches: first, we used a Milne-Eddington inversion to obtain mean parameters of the emerging bipole magnetic configuration. Then, we considered the full radiative transfer equation, and we studied the trend of all the previous parameters as a function of the optical depth tau . We pointed out peculiar flows, such as an initial upflow of 1.5 ;textrm {km s}-1 where the zenith angle is essentially horizontal, and downflows decreasing in time in footpoints, characterized by a vertical field. These results seem to confirm the emerging bipole topology, due to magnetic flux tube emergence. The results obtained with this inversion confirm the structure found with Milne-Eddington code. However we found regions in which the presence of two distinct magnetic components is highly significant. It also seems very interesting the trend of the temperature with optical depth: the plasma temperature appears to grow up in the high photosphere above the emerging bipole. Title: SUNRISE: high-resolution UV/VIS observations of the Sun from the stratosphere Authors: Solanki, S. K.; Barthol, P.; Gandorfer, A.; Schüssler, M.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M. Bibcode: 2006cosp...36.2416S Altcode: 2006cosp.meet.2416S SUNRISE is a balloon-borne solar telescope with an aperture of 1m working in the UV VIS optical domain The main scientific goal of SUNRISE is to study the structure and dynamics of the magnetic field in the atmosphere of the Sun at high spatial resolution SUNRISE will provide diffraction-limited images of the photosphere and chromosphere with an unprecedented resolution down to 35km at wavelengths around 220nm Focal-plane instruments are a UV filter imager a Fabry-Perot filter magnetograph and a spectrograph polarimeter Stratospheric long-duration balloon flights of SUNRISE over the North Atlantic and or Antarctica are planned SUNRISE is a joint project of the Max-Planck-Institut fuer Sonnensystemforschung MPS Katlenburg-Lindau with the Kiepenheuer-Institut fuer Sonnenphysik KIS Freiburg the High-Altitude Observatory HAO Boulder the Lockheed-Martin Solar and Astrophysics Lab LMSAL Palo Alto and the spanish IMaX consortium The presentation will give an overview about the mission and a description of the instrumentation now at the beginning of the hardware construction phase Title: Measurements of solar magnetic fields Authors: Lites, B. W. Bibcode: 2006cosp...36.3626L Altcode: 2006cosp.meet.3626L Over the past decade precision spectro-polarimetry of the sun has resulted in highly quantitative measurements of the magnetic field vector in the solar photosphere These successes have revealed new understanding of how magnetic fields emerge and interact with convection to produce the variability of the sun s radiation across the spectrum and led to the development of many new observational capabilities both ground- and space-based In anticipation of the revolutionary data these instruments will provide this review highlights possible scientific advances that can be anticipated within the next few years including magneto-convection in the presence of weak and strong fields structure and evolution of sunspots and measurement of magnetic fields above the photosphere Title: Magnetic Flux Ropes in the Solar Photosphere: The Vector Magnetic Field under Active Region Filaments Authors: Lites, B. W. Bibcode: 2005ApJ...622.1275L Altcode: This study is an observational search for evidence of prominence-associated magnetic flux ropes at the photospheric level in plage regions away from sunspots. Although there are a few cases of supposed flux rope geometry in the photosphere of complex sunspot regions (notably ``δ sunspots''), such cases appear to be fairly rare and therefore do not contribute significantly to the suspected emergence of magnetic helicity in active regions leading to the common eruption of coronal mass ejections. In the present study, the Advanced Stokes Polarimeter (ASP) at the Dunn Solar Telescope of the National Solar Observatory was used to measure simultaneously the evolution of the photospheric vector magnetic field and the structure of the chromosphere as seen in the Hα line. The high angular resolution of these vector field measurements coupled with the high polarimetric precision of the ASP has allowed the possible identification of flux rope (concave up) geometry in the photosphere below some narrow (and supposedly low-lying) active region filaments. Two cases of such occurrence are presented in detail. These results indicate that flux ropes may be rather common in normal (i.e., non-δ sunspot) active regions. Further observations should shed some light on origin of these flux ropes as either emerging from the solar interior or generated in the solar atmosphere as a consequence of driven magnetic footpoint motion and reconnection. Title: Full Stokes Spectropolarimetry of Hα in Prominences Authors: López Ariste, A.; Casini, R.; Paletou, F.; Tomczyk, S.; Lites, B. W.; Semel, M.; Landi Degl'Innocenti, E.; Trujillo Bueno, J.; Balasubramaniam, K. S. Bibcode: 2005ApJ...621L.145L Altcode: We report on spectropolarimetric observations of Hα in prominences made with the Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires and the High Altitude Observatory/Advanced Stokes Polarimeter. Stokes Q and U show the expected profile shape from resonance scattering polarization and the Hanle effect. In contrast, most of the time, Stokes V does not show the antisymmetric profile shape typical of the Zeeman effect but a profile that indicates the presence of strong atomic orientation in the hydrogen levels, to an extent that cannot be explained by invoking the alignment-to-orientation transfer mechanism induced by the prominence magnetic field. We found that the largest signal amplitudes of Stokes V (comparable to that of Stokes Q and U) could be produced by a process of selective absorption of circularly polarized radiation from the photosphere, which requires that the prominence be in the vicinity of an active region. Although recent observations of active region filaments indicate such a selective absorption mechanism as a plausible explanation of the anomalous signals observed, the particular set of conditions that must be met suggest that a different explanation may be required to explain the almost ubiquitous symmetric V signal observed in Hα prominences. Therefore, we speculate that an alternative mechanism inducing strong atomic orientation at the observed level could be due to the presence of electric fields inducing an electric Hanle effect on Hα. Although we are still working toward a careful modeling of this effect, including both electric and magnetic fields, we present some preliminary considerations that seem to support this possibility. Title: Wavelet Phase Coherence Analysis: Application to a Quiet-Sun Magnetic Element Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Lites, Bruce W.; Judge, Philip G.; Mathioudakis, Mihalis; Keenan, Francis P. Bibcode: 2004ApJ...617..623B Altcode: A new application of wavelet analysis is presented that utilizes the inherent phase information residing within the complex Morlet transform. The technique is applied to a weak solar magnetic network region, and the temporal variation of phase difference between TRACE 1700 Å and SOHO/SUMER C II 1037 Å intensities is shown. We present, for the first time in an astrophysical setting, the application of wavelet phase coherence, including a comparison between two methods of testing real wavelet phase coherence against that of noise. The example highlights the advantage of wavelet analysis over more classical techniques, such as Fourier analysis, and the effectiveness of the former to identify wave packets of similar frequencies but with differing phase relations is emphasized. Using cotemporal, ground-based Advanced Stokes Polarimeter measurements, changes in the observed phase differences are shown to result from alterations in the magnetic topology. Title: Observational Evidence for Small-Scale Mixture of Weak and Strong Fields in the Quiet Sun Authors: Socas-Navarro, H.; Lites, B. W. Bibcode: 2004ApJ...616..587S Altcode: 2004astro.ph.10562S Three different maps of the quiet Sun, observed with the Advanced Stokes Polarimeter (ASP) and the Diffraction-Limited Stokes Polarimeter (DLSP), show evidence of strong (~=1700 G) and weak (<500 G) fields coexisting within the resolution element at both network and internetwork locations. The angular resolution of the observations is of 1" (ASP) and 0.6" (DLSP). Even at the higher DLSP resolution, a significant fraction of the network magnetic patches harbor a mixture of strong and weak fields. Internetwork elements that exhibit kG fields when analyzed with a single-component atmosphere are also shown to harbor considerable amounts of weak fields. Only those patches for which a single-component analysis yields weak fields do not show this mixture of field strengths. Finally, there is a larger fractional area of weak fields in the convective upflows than in the downflows. Title: SUNRISE: high-resolution UV/VIS observations of the Sun from the stratosphere Authors: Gandorfer, Achim M.; Solanki, Sami K.; Schüssler, Manfred; Curdt, Werner; Lites, Bruce W.; Martínez Pillet, Valentin; Schmidt, Wolfgang; Title, Alan M. Bibcode: 2004SPIE.5489..732G Altcode: SUNRISE is a balloon-borne solar telescope with an aperture of 1m, working in the UV/VIS optical domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide diffraction-limited images of the photosphere and chromosphere with an unpredecented resolution down to 35km at wavelengths around 220nm. Focal-plane instruments are a spectrograph/polarimeter, a Fabry-Perot filter magnetograph, and a filter imager. The first stratospheric long-duration balloon flight of SUNRISE over Antarctica is planned in winter 2006/2007. SUNRISE is a joint project of the Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofisica de Canarias, La Laguna, Tenerife. In this paper we will present an overview on the mission and give a description of the instrumentation, now, at the beginning of the hardware construction phase. Title: Characterization of Magnetic Flux in the Quiet Sun. II. The Internetwork Fields at High Angular Resolution Authors: Lites, B. W.; Socas-Navarro, H. Bibcode: 2004ApJ...613..600L Altcode: This paper presents high-resolution (0.6") spectropolarimetric observations of very quiet solar regions. We make determinations of the magnetic flux density, intrinsic field strength, and magnetic filling factor in these regions. Our results confirm other previous works in that most of the internetwork flux is in the form of intrinsically strong fields. However, in contrast to other recent observations, we do not find a significant increase in the amount of unsigned magnetic flux relative to that measured at an angular resolution of 1", nor do we find that most internetwork lanes are populated by strong flux. We discuss possible causes for this disparity. The lack of additional flux with increased resolution may be used to set constrains on the typical spatial scales at which mixed polarities occur (smaller than ~=0.6"). Title: Magnetic Properties of the Solar Internetwork Authors: Socas-Navarro, H.; Martínez Pillet, V.; Lites, B. W. Bibcode: 2004ApJ...611.1139S Altcode: Advanced Stokes Polarimeter observations are used to study the weakest polarization signals observed in the quiet photosphere with flux densities in the range of 1.5-50 Mx cm-2, which are found in internetwork regions. Our analysis allows us to reach an unprecedented spectropolarimetric sensitivity at the cost of sacrificing spatial resolution. We find evidence for intrinsically different fields in granules and lanes and characterize the average properties of the weakest observable flux concentrations. The magnetic signals observed suggest a strong coupling between magnetic fields and convective flows. Upflows bring up weak fields (equipartition or weaker) to the surface, with stronger upflows carrying larger amounts of flux. The circular polarization profiles observed in the granular regions display a very strongly asymmetric shape, which contrasts with the less asymmetric profiles observed in the downflowing regions. At downflowing locations with speeds of 0.5 km s-1, both weak and strong fields can be found. However, when the downflow speed increases (up to about 1 km s-1) both the mean flux and the intrinsic field strength show a tendency to increase. The asymmetry of the circular polarization profiles also shows a clear trend as a function of magnetic flux density. Low-flux regions display the negative area asymmetry one naturally expects for field strengths decreasing with height embedded in a downflowing environment. As we move to stronger flux density locations, the well-known positive area asymmetry develops and reaches even higher values than those typically found in network regions. These results may have important implications for our understanding of the coupling between magnetic fields and convective processes that pervade the solar photosphere. Title: Evaluation of Seeing-Induced Cross Talk in Tip-Tilt-Corrected Solar Polarimetry Authors: Judge, Philip G.; Elmore, David F.; Lites, Bruce W.; Keller, Christoph U.; Rimmele, Thomas Bibcode: 2004ApOpt..43.3817J Altcode: We reanalyze the effects of atmosphere-induced image motions on the measurement of solar polarized light using a formalism developed by Lites. Our reanalysis is prompted by the advent of adaptive optics (AO) systems that reduce image motion and higher-order aberrations, by the availability of liquid crystals as modulation devices, and by the need to understand how best to design polarimeters for future telescopes such as the Advanced Technology Solar Telescope. In this first attempt to understand the major issues, we analyze the influence of residual image motion (tip-tilt) corrections of operational AO systems on the cross talk between Stokes parameters and present results for several polarization analysis schemes. Higher-order wave-front corrections are left for future research. We also restrict our discussion to the solar photosphere, which limits several important parameters of interest, using some recent magnetoconvection simulations. Title: Three-Dimensional Structure of the Active Region Photosphere as Revealed by High Angular Resolution Authors: Lites, B. W.; Scharmer, G. B.; Berger, T. E.; Title, A. M. Bibcode: 2004SoPh..221...65L Altcode: Blue continuum images of active regions at ∼ 60° from the center of the solar disk obtained with the new Swedish 1-m Solar Telescope reveal heretofore unreported structure of the magnetized solar atmosphere. Perhaps the most striking aspect of these images is that, at an angular resolution of 0.12″, they show clearly the three-dimensional structure of the photosphere. In particular, the Wilson depression of the dark floors of pores is readily apparent. Conversely, the segmented structure of light bridges running through sunspots and pores reveal that light bridges are raised above the dark surroundings. The geometry of light bridges permits estimates of the height of their central (slightly darker) ridge: typically in the range 200-450 km. These images also clearly show that facular brightenings outside of sunspots and pores occur on the disk-center side of those granules just limbward of intergranular lanes that presumably harbor the associated plage magnetic flux. In many cases the brightening extends 0.5″ or more over those granules. Furthermore, a very thin, darker lane is often found just centerward of the facular brightening. We speculate that this feature is the signature of cool down flows that surround flux tubes in dynamical models. These newly recognized observational aspects of photospheric magnetic fields should provide valuable constraints for MHD models of the magnetized photosphere, and examination of those models as viewed from oblique angles is encouraged. Title: Diffraction Limited Spectro-Polarimetry at the Dunn Solar Telescope Authors: Sankarasubramanian, K.; Rimmele, T. R.; Lites, B. W. Bibcode: 2004AAS...204.2006S Altcode: 2004BAAS...36..686S The Diffraction Limited Spectro-Polarimeter (DLSP) is a collaborative project between the National Solar Observatory (NSO) and the High-Altitude Observatory (HAO). This new instrument, along with the high-order Adaptive Optics (AO-76) system (which is being developed at the NSO) has been used to measure magnetic fields on the solar photosphere at the highest spatial resolution (0.2 arcsec which is the diffraction limit of the DST at the 630.0nm wavelength). A few preliminary results obtained from the first observing run with this instrument are,

(1) The fine structures present inside the sunspot umbra (like the umbral dots) show upflows and reduced field strengths compared to the surrounding umbra.

(2) The sizes of these umbral fine structures goes down to the diffraction limit of the DST (about 0.2 arcsec). This result confirms that the instrument did achieve its full capability.

(3) There are small-scale convective up and down flows in the light bridges. The strength of these flow is about a km/sec. The field strengths are smaller in these regions compared to the surrounding umbra. At some places in the light bridges, the field strengths are as small as half of the umbral field strength.

(4) There are small-scale upflows in the inner penumbra of the observed sunspot. These regions coincide with the inner foot-point of the bright penumbral filaments as seen in the continuum intensity map. Some of these upflow regions also show a reduced field strength. Title: The Diffraction Limited Spectro-Polarimeter: a new instrument for high-resolution solar polarimetry Authors: Sankarasubramanian, K.; Gullixson, Craig; Hegwer, Stephen; Rimmele, Thomas R.; Gregory, Scott; Spence, Tony; Fletcher, Stephen; Richards, Kit; Rousset, Emilie; Lites, Bruce; Elmore, David; Streander, Kim; Sigwarth, Michael Bibcode: 2004SPIE.5171..207S Altcode: The National Solar Observatory in collaboration with the High-Altitude Observatory is developing a new solar polarimeter, the Diffraction Limited Spectro-Polarimeter. In conjunction with a new high-order adaptive optics system at the NSO Dunn Solar Telescope, the DLSP design facilitates very high angular resolution observations of solar vector magnetic fields. This project is being carried out in two phases. As a follow-on to the successful completion of the first phase, the ongoing DLSP Phase II implements a high QE CCD camera system, a ferro-electric liquid crystal modulator, and a new opto-mechanical system for polarization calibration. This paper documents in detail the development of the modulator system and its performance, and presents preliminary results from an engineering run carried out in combination with the new NSO high-order AO system. Title: Oscillatory Signatures above Quiet Sun Magnetic Elements Authors: Bloomfield, D. S.; McAteer, R. T. J.; Lites, B. W.; Judge, P. G.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2004ESASP.547...51B Altcode: 2004soho...13...51B A new application of wavelet analysis is presented. The data used are part of Joint Observing Proposal 72 between SoHO and TRACE, obtained on 1998 May 16 with accompanying groundbased data taken with the Dunn Solar Telescope at Sacramento Peak, New Mexico. A weak magnetic network region is studied and the temporal variation of phase difference between TRACE 1700 Å and SoHO/SUMER C II intensities is shown. The example clearly highlights the advantages of wavelet analysis over more classical techniques such as Fourier analysis, where the effectiveness of the technique to identify wavepackets with differing phase difference relations is emphasised. Title: The evoluton of vector magnetic fields in an emerging flux region Authors: Kubo, Masahito; Shimizu, Toshifumi; Tsuneta, Saku; Lites, B. W. Bibcode: 2004naoj.book...41K Altcode: No abstract at ADS Title: Magnetic maps of prominences Authors: Casini, R.; Lopez Ariste, A.; Tomczyk, S.; Lites, B. Bibcode: 2003AGUFMSH42D..05C Altcode: We present the first magnetic maps of a prominence obtained by applying our PCA inversion approach to prominence spectropolarimetric data in the He I D3 line. Our results indicate the presence of organized structures in the prominence plasma embedded in magnetic field that are significantly larger than average (50 G and higher). We reaffirm the need for a Hanle-based diagnostics of prominence magnetism using full Stokes spectropolarimetry, and the importance of improved, multi-line observations, ideally involving both He I D3 and 10830. Title: Magnetic Maps of Prominences from Full Stokes Analysis of the He I D3 Line Authors: Casini, R.; López Ariste, A.; Tomczyk, S.; Lites, B. W. Bibcode: 2003ApJ...598L..67C Altcode: We present the first magnetic maps of a prominence, derived from inversion of spectropolarimetric data in He I D3 using the principal component analysis of all four Stokes profiles. This prominence, along with several others, was observed in 2002 May using the Dunn Solar Telescope of the National Solar Observatory/Sacramento Peak Observatory, equipped with the High Altitude Observatory Advanced Stokes Polarimeter. The use of an unocculted instrument allowed us to map the prominence magnetic fields down to the chromospheric limb. Our analysis indicates that the average magnetic field in prominences is mostly horizontal and varies between 10 and 20 G, thus confirming previous findings. However, our maps show that fields significantly stronger than average, even as large as 60 or 70 G, can often be found in clearly organized plasma structures of the prominence. Title: The Evolution of Vector Magnetic Fields in an Emerging Flux Region Authors: Kubo, M.; Shimizu, T.; Lites, B. W. Bibcode: 2003ApJ...595..465K Altcode: Collaborative observations of NOAA Active Region 9231 were carried out during 9 days in 2000 November using the Advanced Stokes Polarimeter (ASP), Yohkoh/SXT, TRACE, and SOHO/MDI, in order to record the evolution of the photospheric magnetic field and its related coronal response. During this period an emerging flux region (EFR) appeared in the photosphere near the well-developed leading sunspot of this region, and subsequently bright bundles of coronal loops formed between the main concentrations of opposite magnetic polarity. The structure of the photospheric field comprising the EFR is classified into three regions: (1) the main bipolar magnetic flux of the EFR; (2) two small, rapidly emerging bipoles within the EFR; and (3) the remainder of the EFR excluding the other two regions. Two small, rapidly emerging bipoles are observed within a few hours of their first appearance at the photosphere. Examination of the vector magnetic field, its filling factor, and Doppler motion within the EFR shows that the young emerging magnetic field is nearly horizontal, the intrinsic field strength is weaker than that of the surrounding magnetic field (~500 G), and the weak field has a high filling factor (>80%) and upward motion (<1 km s-1). At both ends of the horizontal field structure we find that the magnetic field strength increases to about 1500 G and the filling factor drops to about 40% as the magnetic field becomes vertical in orientation during its first 12 hr. This field strength is typical of the field within the main bipolar magnetic flux, but the filling factor increases to 80% during the following 2 days. The process for organizing magnetic field configuration including convective collapse and flux concentration provides one possible explanation of the evolution of the field strength and the filling factor in the EFR. In addition, aymmetric surface distributions of magnetic field inclination were observed in the horizontal magnetic field area in the EFR. These asymmetric distributions were also observed in the small, young, emerging bipoles. This may mean that the magnetic field of the EFR is affected by the preexisting magnetic environment surrounding the EFR and that the emerging magnetic loops are deformed before or at the time they reach the photospheric level. Title: SUNRISE: Balloon-borne High-Resolution Observation of the Sun Authors: Solanki, S. K.; Curdt, W.; Gandorfer, A.; Schüssler, M.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.; Sunrise Team Bibcode: 2003ANS...324..113S Altcode: 2003ANS...324..P20S No abstract at ADS Title: Weak-Field Magnetogram Calibration using Advanced Stokes Polarimeter Flux Density Maps - II. SOHO/MDI Full-Disk Mode Calibration Authors: Berger, T. E.; Lites, B. W. Bibcode: 2003SoPh..213..213B Altcode: Cotemporal Ni i 676.8 nm full-disk magnetograms from the Michelson Doppler Interferometer (MDI) instrument on SOHO and the Advanced Stokes Polarimeter (ASP) are quantitatively compared using observations of active region AR 8218, a large negative polarity sunspot group observed at S20 W22 on 13 May 1998. MDI produces flux density estimates based on a polarized line center-of-gravity algorithm using moderate spectral resolution filtergrams with approximately 4 arc sec angular resolution. The magnetograms are formed by an on-board image processor and sent to the ground where they are calibrated using an empirical model to produce flux density maps. The ASP uses high spectral resolution Stokes polarimetric observations to produce very high precision vector magnetic field maps at angular resolution values on the order of 1 arc sec in good seeing. We use ASP inversion results to create a reference ASP `longitudinal magnetic flux density map' with which to calibrate the MDI full-disk magnetograms. The magnetograms from each instrument are scaled to a common reference frame and co-aligned with an accuracy of about 1.6 arc sec. Regions of invalid data, poor field-of-view overlap, and sunspots are masked out in order to calibrate MDI predominately on the relatively vertical `weak-field' plage magnetic elements. Pixel-to-pixel statistical comparisons are used to determine an MDI magnetogram linear calibration relative to reference ASP flux density values. We find that the current Level-1.5 MDI full-disk calibration gives flux density values lower on average by a factor of 0.64±0.013 compared to the ASP reference in active region plage. In sunspot regions (penumbra and umbra) the factor is 0.69±0.007. Title: SUNRISE: a balloon-borne telescope for high resolution solar observations in the visible and UV Authors: Solanki, Sami K.; Gandorfer, Achim M.; Schuessler, Manfred; Curdt, W.; Lites, Bruce W.; Martinez-Pillet, Valentin; Schmidt, Wolfgang; Title, Alan M. Bibcode: 2003SPIE.4853..129S Altcode: Sunrise is a light-weight solar telescope with a 1 m aperture for spectro-polarimetric observations of the solar atmosphere. The telescope is planned to be operated during a series of long-duration balloon flights in order to obtain time series of spectra and images at the diffraction-limit and to study the UV spectral region down to ~200 nm, which is not accessible from the ground. The central aim of Sunrise is to understand the structure and dynamics of the magnetic field in the solar atmosphere. Through its interaction with the convective flow field, the magnetic field in the solar photosphere develops intense field concentrations on scales below 100 km, which are crucial for the dynamics and energetics of the whole solar atmosphere. In addition, Sunrise aims to provide information on the structure and dynamics of the solar chromosphere and on the physics of solar irradiance changes. Sunrise is a joint project of the Max-Planck-Institut fuer Aeronomie (MPAe), Katlenburg-Lindau, with the Kiepenheuer-Institut fuer Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofi sica de Canarias, La Laguna, Tenerife. In addition, there are close contacts with associated scientists from a variety of institutes. Title: Diffraction limited spectro-polarimeter - Phase I Authors: Sankarasubramanian, Kasiviswanathan; Elmore, David F.; Lites, Bruce W.; Sigwarth, Michael; Rimmele, Thomas R.; Hegwer, Steven L.; Gregory, Scott; Streander, Kim V.; Wilkins, Lawrence M.; Richards, K.; Berst, C. Bibcode: 2003SPIE.4843..414S Altcode: A diffraction limited spectro-polarimeter is under construction at the National Solar Observatory in collaboration with the High Altitude Observatory. The scientific objective of the project is to measure the magnetic fields on the Sun up to the diffraction limit of the Dunn Solar Telescope. The same instrument would also measure the magnetic field of large sunspots or sunspot groups with reasonable spatial resolution. This requires a flexible image scale which cannot be obtained with the current Advanced Stokes Polarimeter (ASP) without loosing 50% of the light. The new spectro-polarimeter is designed in such a way that the image scale can be changed without loosing much light. It can work either in high-spatial resolution mode (0.09 arcsec per pixel) with a small field of view (FOV: 65 arcsec) or in large FOV mode (163 arcsec) with low-spatial resolution (0.25 arcsec per pixel). The phase-I of this project is to design and build the spectrograph with flexible image scale. Using the existing modulation, calibration optics of the ASP and the ASP control and data acquisition system with ASP-CHILL camera, the spectrograph was tested for its performance. This paper will concentrate on the performance of the spectrograph and will discuss some preliminary results obtained with the test runs. Title: POLIS: A spectropolarimeter for the VTT and for GREGOR Authors: Schmidt, W.; Beck, C.; Kentischer, T.; Elmore, D.; Lites, B. Bibcode: 2003AN....324..300S Altcode: The polarimetric Littrow Spectrograph POLIS is designed for vector polarimetry at high angular and spectral resolution. It measures the magnetic field simultaneously in the photosphere and the chromosphere of the sun. Both branches of the polarimetry unit are dual beam systems with a single rotating modulator for both wavelengths and polarizing beam splitters in front of each CCD camera. POLIS has been installed at the VTT on Tenerife and has seen First Light on 17 May 2002. A modified version of POLIS will be developed for the balloon mission Sunrise. That version will have UV capabilities down to 200 nm. Title: First Results from the HAO/NSO Diffraction-Limited Spectro-Polarimeter Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.; Sankarasubramanian, K.; Rimmele, T. R.; Sigwarth, M. Bibcode: 2003ASPC..307..324L Altcode: No abstract at ADS Title: The Helioseismic and Magnetic Imager (HMI) on SDO: Full Vector Magnetography with a Filtergraph Polarimeter Authors: Graham, J. D.; Norton, A.; López Ariste, A.; Lites, B.; Socas-Navarro, H.; Tomczyk, S. Bibcode: 2003ASPC..307..131G Altcode: No abstract at ADS Title: Estimating the Effects of JPEG Compression and Radiation on the Accuracy of Vector Magnetic Fields Measurements for Solar-B Authors: Lites, B.; Shine, R. A.; López Ariste, A.; Tarbell, T. D. Bibcode: 2002AGUFMSH52A0471L Altcode: The Japanese Solar-B satellite, currently scheduled for launch in September 2005, includes a spectro-polarimeter (SP) to precisely measure the full Stokes polarization vector (I,Q,U,V) in the Fe I lines at 6302Å. These will be processed to produce vector magnetograms of the solar surface using algorithms based on those for the Advanced Stokes Polarimeter (ASP) as described in Skumanich, et al, 1997, ApJ Suppl 110. Accumulations of the raw images into time averaged I,Q,U,V images will be done on board and the results will be 12 bit JPEG compressed to make the best use of the available telemetry. Hence a single radiation hit in a raw image affects the entire time average at that point. Also, radiation spikes affect JPEG compression performance. Because of concerns about these effects, we simulated them separately and in combination using ASP data and radiation level measurements from the TRACE satellite. Like TRACE, Solar-B will fly in a high inclination, sun synchronous orbit and be exposed to radiation from the polar radiation belts as well as the SAA. Since the SP detector will be better shielded than that on TRACE, we hope that these will be an over estimate of the effects. The results from the simulations are very encouraging. We find that for active region magnetic fields we can use JPEG to compress the data volume by more than a factor of 10 without compromising the accuracy of the inferred magnetic field vector. The radiation in the polar regions has little effect and even the much stronger SAA radiation causes average perturbations that are less than the formal errors for sunspot fields and about twice the formal errors for plage fields. However, very weak field measurements will benefit from less lossy compression and periods of low radiation. Of course, the very strong radiation hits always produce artifacts. Compression performance is affected only slightly so it will not be necessary to avoid observations in the SAA because of excessive telemetry usage. This work was supported by NASA contract NAS8-01002. Title: Sunrise: a 1-m balloon borne solar telescope Authors: Solanki, S. K.; Schüssler, M.; Curdt, W.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.; Sunrise Team Bibcode: 2002ESASP.505...27S Altcode: 2002solm.conf...27S; 2002IAUCo.188...27S Sunrise is a light-weight solar telescope with a 1 m aperture for spectro-polarimetric observations of the solar atmosphere. The telescope is planned to be operated during a series of long-duration balloon flights in order to obtain time series of spectra and images at the diffraction-limit and to study the UV spectral region down to ≅200 nm, which is not accessible from the ground. The central aim of Sunrise is to understand the structure and dynamics of the magnetic field in the solar atmosphere. Interacting with the convective flow field, the magnetic field in the solar photosphere develops intense field concentrations on scales below 100 km, which are crucial for the dynamics and energetics of the whole solar atmosphere. In addition, Sunrise aims to provide information on the structure and dynamics of the solar chromosphere and on the physics of solar irradiance changes. Title: Intensity tracers of the magnetic field: pitfalls and opportunities Authors: Lites, B. W.; Berger, T. E. Bibcode: 2002ESASP.505...57L Altcode: 2002solm.conf...57L; 2002IAUCo.188...57L Magnetic fields are the main source of structuring of the solar atmosphere. Stokes I images at various wavelengths reflect this structure at the monochromatic heights of formation of the intensity. In the photosphere intensity tracers identify the location and evolution of kiloGauss flux tubes. In the chromosphere and above Stokes I images may be used to identify the direction of the magnetic lines of force, and may be used to establish the connectivity of the field inferred from photospheric vector magnetograms. In some circumstances the intensity diagnostics of the field may be misleading. Some of these "pitfalls" are discussed. Title: Weak-Field Magnetogram Calibration using Advanced Stokes Polarimeter Flux-Density Maps - I. Solar Optical Universal Polarimeter Calibration Authors: Berger, T. E.; Lites, B. W. Bibcode: 2002SoPh..208..181B Altcode: Cotemporal Fe i 630.2 nm magnetograms from the Solar Optical Universal Polarimeter (SOUP) filter and the Advanced Stokes Polarimeter (ASP) are quantitatively compared using observations of active region AR 8218, a large negative polarity sunspot group observed at S20 W22 on 13 May 1998. The SOUP instrument produces Stokes V/I `filter magnetograms' with wide field of view and spatial resolution below 0.5 arc sec in good seeing, but low spectral resolution. In contrast, the ASP uses high spectral resolution to produce very high-precision vector magnetic field maps at spatial resolution values on the order of 1 arc sec in good seeing. We use ASP inversion results to create an ASP `longitudinal magnetic flux-density map' with which to calibrate the less precise SOUP magnetograms. The magnetograms from each instrument are co-aligned with an accuracy of about 1 arc sec. Regions of invalid data, poor field-of-view overlap, and sunspots are masked out in order to calibrate SOUP predominately on the relatively vertical `weak-field' plage magnetic elements. Pixel-to-pixel statistical comparisons are used to determine the SOUP magnetogram linear calibration constant relative to ASP flux-density values. We compare three distinct methods of scaling the ASP and SOUP data to a common reference frame in order to explore filling factor effects. The recommended SOUP calibration constant is 17 000 ± 550 Mx cm−2 per polarization percent in plage regions. We find a distinct polarity asymmetry in SOUP response relative to the ASP, apparently due to a spatial resolution effect in the ASP data: the smaller, less numerous, minority polarity structures in the plage region are preferentially blended with the majority polarity structures. The blending occurs to a lesser degree in the high-resolution SOUP magnetogram thus leading to an apparent increase in SOUP sensitivity to the minority polarity structures relative to the ASP. One implication of this effect is that in mixed polarity regions on the Sun, lower spatial resolution magnetograms may significantly underestimate minority polarity flux levels, thus leading to apparent flux imbalances in the data. Title: Converging Flows in the Penumbra of a δ Sunspot Authors: Lites, B. W.; Socas-Navarro, H.; Skumanich, A.; Shimizu, T. Bibcode: 2002ApJ...575.1131L Altcode: Doppler velocities in the penumbra of a δ-configuration sunspot observed near the limb indicate flows that converge upon the line separating locally positive and negative polarity magnetic field (the polarity inversion line). These flows persist for many hours. Observations of this region with the Advanced Stokes Polarimeter (ASP) reveal a convex vector field geometry with magnetic lines of force arching upward from positive polarity, then downward to negative polarity. The straightforward interpretation of the combined Doppler velocity and vector field information leads to an untenable physical situation: were flows directed from both footpoints toward the tops of arched magnetic lines of force, mass would rapidly load the tops of the arches. However, there is no observational evidence of the dynamics that such a loading would require. To better understand this apparent contradiction, we perform two-component analyses of the observed Stokes spectral profiles in the vicinity of the polarity inversion line, in order to extract information about unresolved structure of the magnetic field and its associated flows. Fits to the observed profiles, obtained by use of two different inversion techniques, suggest strongly that, as in penumbrae of simple sunspots, the field geometry in the convergence zone is ``fluted.'' However, unlike in simple sunspots, which have only an outward-directed Evershed flow in the more horizontal of the field components, at each spatial point our analysis reveals flows in the two components that are oppositely directed. We interpret these observations as indicative of an interleaved system of field lines in the vicinity of the polarity reversal, whereby the convergent streams are able to slip past one another and return downward into the solar interior. Title: The upcoming new world of sunspot observations from space Authors: Lites, B. W. Bibcode: 2002AN....323..277L Altcode: Several space missions are in planning, or actually in preparation for launch, that will provide tremendous advances in observational capability for angular resolution, polarimetric precision, wavelength coverage, and continuity of observation. These missions, including Solar-B, Sunrise, Solar Dynamics Observatory, and Solar Orbiter, will lay the observational framework for confronting many outstanding questions regarding sunspots: their formation, evolution, and dissipation; and their consequences for other solar phenomena. These four missions are briefly reviewed in the context of their importance to the physics of the sunspot phenomenon. Title: Characterization of Magnetic Flux in the Quiet Sun Authors: Lites, B. W. Bibcode: 2002ApJ...573..431L Altcode: Observations of the quiet Sun observed with the Advanced Stokes Polarimeter are used to explore the distribution of apparent flux density (Bapp) and size scales of internetwork regions. For a typical disk-center quiet-Sun observation with excellent seeing (at a quantifiable angular resolution of 1"), average |Bapp| of 18.6 and 10.7 Mx cm-2 are found for the entire quiet region map and the internetwork region (2 σ noise <|Bapp|<40Mxcm-2), respectively. The weak internetwork flux appears to consist of two components: the spatially concentrated ``granular'' internetwork fields and a more diffuse, weaker component that has a characteristic size scale of a few arcseconds. Most of the internetwork area is occupied by measurable fields: 69% of the area has apparent flux density greater than 4.5 Mx cm-2 (3 σ), or 84% with flux density greater than 3.0 Mx cm-2 (2 σ). If the results of Hanle depolarization measurements are accepted, the internetwork flux detected here must be close (within a factor of 2-3) to being spatially resolved and must be intrinsically weak (10-30 G). Examination of Stokes polarimetry in quiet regions away from disk center indicates that the central cores of network flux, as indicated by high-polarization signals, do not have a high degree of mixed polarity. In contrast, regions immediately surrounding the network elements have stronger linear polarization than would be expected from locally vertical fields, indicating a high degree of mixed polarity. This mixed polarity may be the result of the continual ``sweeping'' of mixed polarity internetwork flux toward the network boundaries. When a quiet region has a significant imbalance of flux of opposite polarities, the internetwork imbalance is of the same sign and typically 1/3 that of the network. The smaller imbalance in the internetwork suggests that a local dynamo produces most of the internetwork flux. Title: The Solar Internetowrk Magnetic Fields Authors: Socas-Navarro, H.; Lites, B. W. Bibcode: 2002AAS...200.5516S Altcode: 2002BAAS...34R.950S The properties of solar photospheric inter-network fields are studied using observations from the Advanced Stokes Polarimeter. By averaging over large areas of the observed map we are able to bring down the noise level to approximately 10-5 and determine typical magnetic properties of granules and intergranular lanes outside the magnetic network. Title: Inference of Solar Vector Magnetic Fields with Filtergraph Instruments Authors: Graham, J. D.; Lites, B. W.; López Ariste, A.; Norton, A.; Socas-Navarro, H.; Tomczyk, S. Bibcode: 2002AAS...200.5611G Altcode: 2002BAAS...34..736G We investigate the diagnostic potential of polarimetric measurements with filtergraph instruments. Numerical simulations are used to explore the possibility of inferring the magnetic field vector, its filling factor, and the thermodynamics of model atmospheres when only a few wavelength measurements are available. The simulations assume the magnetic sun to be represented by Milne-Eddington (ME) atmospheres. The results indicate that two wavelength measurements are insufficient to reliably determine the magnetic parameters, regardless of whether magnetograph techniques or least-squares fitting inversions are used. However, as few as four measurements analyzed with the inversion technique provide enough information to retrieve the intrinsic magnetic field with an accuracy better than 10 generated by more general models and ASP data passed through a simulated filtergraph. Title: New Polarization Diagnostics for the Solar Atmosphere Authors: Casini, R.; López Ariste, A.; Tomczyk, S.; Lites, B. Bibcode: 2002AAS...200.3403C Altcode: 2002BAAS...34..690C We present relatively new diagnostics of ``weak" magnetic fields in the solar atmosphere. The first diagnostic is suggested by recent advances in the inversion of Stokes profiles of lines formed by resonance scattering in the weakly magnetized plasma of prominences (Hanle effect and level-crossing; 0 to 100 G). Use of pattern recognition techniques (PCA) in this field has marked a sensible progress with respect to previous diagnostic procedures. The second diagnostic is the modelling of hyperfine structured (HFS) lines that can be observed in the spectrum of the quiet photosphere. This allows to investigate relatively weak photospheric fields (200 G to 1000 G), in which regime the HFS induces peculiar signatures in the Stokes profiles, including the appearance of subcomponents and net circular polarization. The third diagnostic is suggested by interesting polarization properties of the Na I D1 line formed by resonance scattering: the atomic polarization in the upper level of D1, which is responsible of a characteristic antisymmetric (i.e., V-like) signature in the core of Stokes Q, is rapidly suppressed for B > 10 G, irrespective of the magnetic field direction. A common denominator of these three diagnostics is their sensitivity to the actual strength of the magnetic field, instead of the magnetic flux within the resolution element. Another common aspect is that all require (or would profit from) high polarization sensitivity, which will be one of the strengths of ATST. For the diagnostics of prominence magnetic fields, the possibility of multiline spectropolarimetry could be decisive. Simultaneous observations of He I D3 (5876A) and 10830A, or of He I D3 and the Na I D lines (all within a 20A spectral range!), would increase the inversion accuracy of PCA. The high spatial resolution capabilities of ATST would be advantageous mostly to diagnose weak photospheric fields, already at the present time. Because of the complexity of radiative transfer in complicated structures like prominences, high spatial resolution in these structures is not the highest priority. However, we hope that when ATST will become operative, this complicated problem will have been attacked succesfully. Title: The sunrise international balloon program for high resolution solar physics Authors: Lites, B. Bibcode: 2002cosp...34E1321L Altcode: 2002cosp.meetE1321L The Sunrise program is an international effort to fly a large aperture (1-m) diffractionlimited solar telescope on a long-duration Antarctic balloon in order to investigate the detailed physics of solar magnetism and solar variability at very small scales. Instrumentation will include imaging and spectrographic polarimeters to yield quantitative measures of the solar vector magnetic field, and broad-band imaging down to 200 nm with the capability of post-observation phase diversity wavefront correction to image the Sun with the highest angular resolution yet (35 km at the solar surface). The program is a cooperation among United States, Germany, and Spain, with the US portion funded by NASA. The first science flight from Antarctica is expected in 2006. Title: Dynamics of the solar chromosphere. III. Ultraviolet brightness oscillations from TRACE Authors: Krijger, J. M.; Rutten, R. J.; Lites, B. W.; Straus, Th.; Shine, R. A.; Tarbell, T. D. Bibcode: 2001A&A...379.1052K Altcode: We analyze oscillations in the solar atmosphere using image sequences from the Transition Region and Coronal Explorer (TRACE) in three ultraviolet passbands which sample the upper solar photosphere and low chromosphere. We exploit the absence of atmospheric seeing in TRACE data to furnish comprehensive Fourier diagnostics (amplitude maps, phase-difference spectra, spatio-temporal decomposition) for quiet-Sun network and internetwork areas with excellent sampling statistics. Comparison displays from the ground-based Ca Ii H spectrometry that was numerically reproduced by Carlsson & Stein are added to link our results to the acoustic shock dynamics in this simulation. The TRACE image sequences confirm the dichotomy in oscillatory behaviour between network and internetwork and show upward propagation above the cutoff frequency, the onset of acoustic shock formation in the upper photosphere, phase-difference contrast between pseudo-mode ridges and the interridge background, enhanced three-minute modulation aureoles around network patches, a persistent low-intensity background pattern largely made up of internal gravity waves, ubiquitous magnetic flashers, and low-lying magnetic canopies with much low-frequency modulation. The spatio-temporal occurrence pattern of internetwork grains is found to be dominated by acoustic and gravity wave interference. We find no sign of the high-frequency sound waves that have been proposed to heat the quiet chromosphere, but such measurement is hampered by non-simultaneous imaging in different passbands. We also find no signature of particular low-frequency fluxtube waves that have been proposed to heat the network. However, internal gravity waves may play a role in their excitation. Title: Precision spectro-polarimeter for high-resolution observations of solar magnetic fields Authors: Lites, Bruce W.; Elmore, David F.; Streander, Kim V.; Akin, David L.; Berger, Tom; Duncan, Dexter W.; Edwards, Chris G.; Francis, Barbara; Hoffmann, Chris; Katz, Noah; Levay, Michael; Mathur, Dnyanesh; Rosenberg, William A.; Sleight, Ericka; Tarbell, Theodore D.; Title, Alan M.; Torgerson, Darrel Bibcode: 2001SPIE.4498...73L Altcode: As a Japanese National space mission with international collaboration, Solar-B (2005 launch) will carry a spectro- polarimeter (SP) to be operated in visible light to obtain the first high angular resolution, precision measurements of solar vector magnetic fields from space. The SP is part of the Focal Plane Package (FPP) fed by a diffraction-limited 50-cm optical telescope. The SP will be operated exclusively at the photospheric 630 nm Fe I lines. It features a rotating, low-order crystalline quartz retarder for polarization modulation and a reflecting Littrow spectrograph design that is shortened by using diffraction from the 12micrometers wide slit to fill the grating. Polarization analysis is accomplished by a modified Savart plate beam splitter. A custom CCD detector with two active areas, one for each beam from the beam splitter, allows continuous high duty-cycle sampling of polarization. The spectrograph slit will sample a 0.16 x 164 arcsec2 rectangle of the solar image, which may be scanned across the slit by up to +/- 160 arcsec in order to build up vector magnetic field maps of the solar photosphere. Along with simultaneous, co-spatial imaging and polarimetry with the filter imagers of the FPP, the SP will provide a precise view of active and quiet solar magnetic fields that control the structure, dynamics, and energetics of the upper solar atmosphere. Title: High-resolution solar polarimetry with Sunrise Authors: Schmidt, W.; Solanki, S. K.; Lites, B. W.; Title, A. M.; Martínez Pillet, V. Bibcode: 2001AN....322..363S Altcode: Sunrise is a solar telescope with an aperture of 1 m, and is dedicated for spectropolarimetric measurements in the visible and the near UV. The total wavelength range is 200 to 1000 nm for narrowband imaging and diagnostic spectroscopy. Sunrise is planned as a stratospheric long-duration balloon mission with a first flight in 2006 Title: Pattern recognition techniques and the measurement of solar magnetic fields Authors: Lopez Ariste, Arturo; Rees, David E.; Socas-Navarro, Hector; Lites, Bruce W. Bibcode: 2001SPIE.4477...96L Altcode: Measuring vector magnetic fields in the solar atmosphere using the profiles of the Stokes parameters of polarized spectral lines split by the Zeeman effect is known as Stokes Inversion. This inverse problem is usually solved by least-squares fitting of the Stokes profiles. However least-squares inversion is too slow for the new generation of solar instruments (THEMIS, SOLIS, Solar-B, ...) which will produce an ever-growing flood of spectral data. The solar community urgently requires a new approach capable of handling this information explosion, preferably in real-time. We have successfully applied pattern recognition and machine learning techniques to tackle this problem. For example, we have developed PCA-inversion, a database search technique based on Principal Component Analysis of the Stokes profiles. Search is fast because it is carried out in low dimensional PCA feature space, rather than the high dimensional space of the spectral signals. Such a data compression approach has been widely used for search and retrieval in many areas of data mining. PCA-inversion is the basis of a new inversion code called FATIMA (Fast Analysis Technique for the Inversion of Magnetic Atmospheres). Tests on data from HAO's Advanced Stokes Polarimeter show that FATIMA isover two orders of magnitude faster than least squares inversion. Initial tests on an alternative code (DIANNE - Direct Inversion based on Artificial Neural NEtworks) show great promise of achieving real-time performance. In this paper we present the latest achievements of FATIMA and DIANNE, two powerful examples of how pattern recognition techniques can revolutionize data analysis in astronomy. Title: Visible-light observations and high-resolution polarimetry Authors: Lites, Bruce W. Bibcode: 2001ESASP.493....3L Altcode: 2001sefs.work....3L The polarimetric imager on Solar Orbiter will follow the realization of significant space- and ground-based programs for high resolution solar polarimetry in the coming decade. In this review I attempt to identify the scientific potential of Solar Orbiter within the context of anticipated observational capability and scientific understanding ten years from now. The unique contribution of Solar Orbiter is its high resolution imaging from an angular perspective well-removed from that of the Earth. When combined with simultaneous high resolution polarimetry from the perspective of the Earth, Solar Orbiter will provide stereoscopic observations of the fine structure in the solar photospheric magnetic field which will likely reveal the detailed structure on a physical height scale, rather than an optical depth scale. Furthermore, the observations will provide the velocity field components in a plane, rather than along just one line-of-sight. These advances promise tight observational constraints for fundamental processes such as convective collapse, generation and propagation of MHD waves in flux tubes, ultra fine-scale magnetic flux of the quiet Sun internetwork. At some phase of its orbit, the Orbiter will also provide the unique capability to follow the development of solar activity through a large fraction of a complete solar rotation; a capability that should illuminate the processes responsible for active region decay. Finally, the perspective views of Solar Orbiter may permit measurements of vector magnetic fields in the chromosphere without resorting to linear polarimetry. Title: Sunspot Bright Rings: Evidence from Case Studies Authors: Rast, M. P.; Meisner, R. W.; Lites, B. W.; Fox, P. A.; White, O. R. Bibcode: 2001ApJ...557..864R Altcode: We present evidence, from both the Precision Solar Photometric Telescope and the Advanced Stokes Polarimeter, for a ring of enhanced continuum intensity surrounding large isolated sunspots. We do not attempt to evaluate the frequency of the phenomenon based on a large sample of spots but instead concentrate on illustrative best-case examples. The rings are about 0.5%-1.0% brighter in red and blue continuum (10 K warmer) than the surrounding photosphere and extend about one sunspot radius outward from the outer penumbral boundary. Most of the excess radiation is not directly associated with the strongest regions of Ca II K emission surrounding the spots or with measurable vertical magnetic field when such measurements are available. Moreover, the temporal evolution of the Ca II K and continuum emission in the ring differ, with the continuum intensity evolving on a shorter timescale. This suggests a convective origin for the bright ring, although a role for weaker, more diffuse magnetic fields cannot be ruled out. While we have inferred that only about 10% of the radiant energy missing from the sunspot is emitted through the bright ring, even this small enhancement may be significant to our understanding of subsurface sunspot structure and energy transport. Title: Fast Inversion of Spectral Lines Using Principal Components Analysis. II. Inversion of Real Stokes Data Authors: Socas-Navarro, H.; López Ariste, A.; Lites, B. W. Bibcode: 2001ApJ...553..949S Altcode: The principal components analysis (PCA) technique is used to develop an extremely fast and stable Stokes inversion code, suitable for application to large data sets from instruments that operate under standard conditions. This paper provides some tips on reducing the dimensionality of the problem, which are then used to develop a practical implementation of PCA for the automatic analysis of Stokes profiles. The resulting code is tested using real spectropolarimetric observations of the pair of Fe I lines at 6302 Å at a sunspot. Title: Intercomparison of SOUP, ASP, LPSP, and MDI magnetograms Authors: Berger, T.; Lites, B.; Martinez-Pillet, V.; Tarbell, T.; Title, A. Bibcode: 2001AGUSM..SP51B12B Altcode: We compare simultaneous magnetograms of a solar active region taken by the Advanced Stokes Polarimeter (ASP) and the Solar Optical Universal Polimeter (SOUP) in 1998. In addition we compare magnetograms taken by the La Palma Stokes Polarimeter (LPSP), the Michelson Doppler Imager (MDI) on SOHO, and the SOUP instrument in 2000. The SOUP instrument on the Swedish Vacuum Solar Telescope (SVST) attains the highest spatial resolution but has the least understood calibration; the ASP on the Dunn Solar Telescope (DST) at Sacramento Peak attains the highest magnetic field precision. The goal of the program is to better quantify the SOUP magnetograms and thereby study magnetic element dynamics in the photosphere with higher precision. Title: Optical Tomography of a Sunspot. II. Vector Magnetic Field and Temperature Stratification Authors: Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martínez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 2001ApJ...547.1130W Altcode: An observational determination of the three-dimensional magnetic and thermal structure of a sunspot is presented. It has been obtained through the application of the SIR inversion technique (Stokes Inversion based on Response functions) on a low-noise, full Stokes profile two-dimensional map of the sunspot as observed with the Advanced Stokes Polarimeter. As a result of the inversion, maps of the magnetic field strength, B, zenith angle, γ, azimuth, χ, and temperature, T, over 25 layers at given optical depths (i.e., an optical tomography) are obtained, of which those between logτ5=0 and logτ5=-2.8 are considered to provide accurate information on the physical parameters. All over the penumbra γ increases with depth, while B is larger at the bottom layers of the inner penumbra (as in the umbra) but larger at the top layers of the outer penumbra (as in the canopy). The corrugation of the penumbral magnetic field already observed by other authors has been confirmed by our different inversion technique. Such a corrugation is especially evident in the zenith angle maps of the intermediate layers, featuring the presence of the so-called spines that we further characterize: spines are warmer and have a less inclined magnetic field than the spaces between them and tend to have a smaller gradient of γ with optical depth over the entire penumbra, but with a field strength which is locally stronger in the middle penumbra and locally weaker in the outer penumbra and beyond in the canopy. In the lower layers of these external parts of the sunspot, most of the field lines are seen to return to the solar surface, a result that is closely connected with the Evershed effect (e.g., Westendorp et al., the third paper in this series). The Stokes V net area asymmetry map as well as the average B, γ, and T radial distributions (and that of the line-of-sight velocities; see the third paper in this series) show a border between an inner and an outer penumbra with different three-dimensional structure. We suggest that it is in this middle zone where most of a new family of penumbral flux tubes (some of them with Evershed flow) emerge interlaced (both horizontally and vertically) among themselves and with the ``background'' magnetic field of the penumbra. The interlacing along the line of sight is witnessed by the indication of many points in the outer penumbra showing rapid transitions with height between two structures, one with very weak and inclined magnetic field at the bottom of the photosphere and the other with a stronger and less inclined magnetic field. Over the whole penumbra, and at all optical layers, a constant but weak deviation from radiality of some 5° is detected for the azimuth of the vector magnetic field, which may be in agreement with former detections but which is not significantly higher than the size of the errors for this parameter. Title: An Observational Manifestation of Magnetoatmospheric Waves in Internetwork Regions of the Chromosphere and Transition Region Authors: McIntosh, S. W.; Bogdan, T. J.; Cally, P. S.; Carlsson, M.; Hansteen, V. H.; Judge, P. G.; Lites, B. W.; Peter, H.; Rosenthal, C. S.; Tarbell, T. D. Bibcode: 2001ApJ...548L.237M Altcode: We discuss an observational signature of magnetoatmospheric waves in the chromosphere and transition region away from network magnetic fields. We demonstrate that when the observed quantity, line or continuum emission, is formed under high-β conditions, where β is the ratio of the plasma and magnetic pressures, we see fluctuations in intensity and line-of-sight (LOS) Doppler velocity consistent with the passage of the magnetoatmospheric waves. Conversely, if the observations form under low-β conditions, the intensity fluctuation is suppressed, but we retain the LOS Doppler velocity fluctuations. We speculate that mode conversion in the β~1 region is responsible for this change in the observational manifestation of the magnetoatmospheric waves. Title: Converging Flows in the Penumbra of a δ-Sunspot Authors: Lites, B. W.; Socas-Navarro, H.; Skumanich, A.; Shimizu, T. Bibcode: 2001ASPC..248..143L Altcode: 2001mfah.conf..143L No abstract at ADS Title: Convergent Flows in the Penumbra of a δ-Sunspot Authors: Lites, B. W.; Socas-Navarro, H. Bibcode: 2001ASPC..236..329L Altcode: 2001aspt.conf..329L No abstract at ADS Title: Space-Based Instrumentation for Inference of the Solar Magnetic Field Authors: Lites, B. W. Bibcode: 2001ASPC..248..553L Altcode: 2001mfah.conf..553L No abstract at ADS Title: A new Stokes Polarimeter for the Dunn Solar Telescope Authors: Sigwarth, M.; Berst, C.; Gregory, S.; Hegwer, S.; Richards, K.; Rimmele, T.; Wilkins, L.; Lites, B. W.; Elmore, D. F.; Streander, K. V. Bibcode: 2001ASPC..236...57S Altcode: 2001aspt.conf...57S No abstract at ADS Title: The Solar-B Spectro-Polarimeter Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V. Bibcode: 2001ASPC..236...33L Altcode: 2001aspt.conf...33L No abstract at ADS Title: POLIS: Simultaneous Measurement of Photospheric and Chromospheric Magnetic Field Authors: Schmidt, W.; Kentischer, T. J.; Bruls, J.; Lites, B. W. Bibcode: 2001ASPC..236...49S Altcode: 2001aspt.conf...49S No abstract at ADS Title: High-resolution Solar Polarimetry with Sunrise Authors: Schmidt, W.; Solanki, S. K.; Schüssler, M.; Curdt, W.; Lites, B. W.; Title, A. M.; Martinez Pillet, V. Bibcode: 2001AGM....18S1001S Altcode: Sunrise is a 1m balloon-borne solar telescope. It is equipped with a spectrograph polarimeter which combines vector-polarimetry in the visible with diagnostic spectroscopy in the visible and the UV, down to 200 nm. The instrumentation includes a filter-magnetograph and a medium-band filtergraph. The wavelength bands of the latter include the CH-band (430.6 nm) and a UV continuum at 205 nm. Diffraction limited resolution in the UV will be achieved by employing a phase diversity technique. The main telescope is based on a lightweight silicon-carbide mirror, developed within the Solar Lite program. During the long-duration flight at Antarctica, foreseen for late 2005, Sunrise will continuously observe the sun for a period of about ten days, with constant image quality across the full field of view. In-flight alignment of the telescope optics will be controlled by a wavefront sensor. The main goal of Sunrise is to understand the structure and dynamics of the magnetic field in the atmosphere of the sun. To this end, Sunrise will observe small magnetic flux concentrations with dimensions of less than 70 km with high polarimetric accuracy. At the same time, Sunrise will provide diffraction-limited filtergrams of the photosphere and chromosphere with a resolution down to 35 km at a wavelength of 200 nm. Title: Calibration procedure for the polarimetric instrument for Solar Eclipse-98 Authors: Elmore, David F.; Card, G. L.; Lecinski, A. R.; Lites, Bruce W.; Streander, Kim V.; Tomczyk, Steven Bibcode: 2000SPIE.4139..370E Altcode: We describe a ground-based eclipse instrument for measuring solar coronal polarization brightness and intensity, and the calibration procedures for this instrument. We present coronal measurements from the February 26, 1998 total solar eclipse observed at Curacao, N.A.. The instrument employs a liquid crystal variable retarder for analysis of coronal broad band linear polarization and collects data on an array detector spanning a 6.5 solar radius field of view. Polarization calibration of the liquid crystal variable retarder utilizes the tangential orientation of coronal polarization to calculate retardance values. Title: Solar Magnetic Field: Inference by Polarimetry Authors: Lites, B. Bibcode: 2000eaa..bookE2402L Altcode: Most solar structure and phenomena occurring in the solar atmosphere arise from the presence of magnetic fields. This article describes techniques for remote sensing of the solar magnetic field, primarily via analysis of the polarization it imparts to the radiation emitted by the Sun.... Title: The Solar-B Focal Plane Package Authors: Berger, T. E.; Title, A. M.; Tarbell, T. D.; Lites, B. W.; Elmore, D. F. Bibcode: 2000SPD....31.0292B Altcode: 2000BAAS...32..827B Solar-B is a Japanese national space science mission of the Institute of Space and Astronautical Sciences (ISAS) with participation from US and UK research groups. The satellite consists of a 50-cm optical telescope and Focal Plane Package (FPP) designed for high resolution photospheric and chromospheric imaging and spectro-polarimetry as well as two coronal instruments: the X-Ray Telescope (XRT) and the Extreme-ultraviolet Imaging Spectrometer (EIS). Solar-B will be launched into a Sun-synchronous orbit in August of 2004. A team of Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), High Altitude Observatory, and ISAS personnel are designing the FPP instrument. It consists of a narrow-band tunable birefringent filter system, a wide band interference filter system, and a spectro-polarimeter system for very high sensitivity Stokes polarimetry, all of which will be fabricated at LMSAL. We describe the main science goals of the FPP as well as the current instrument design and performance characteristics. This work is supported by NASA contract NAS8-00014 (Solar-B FPP). Title: Physical Properties of the Solar Magnetic Photosphere under the MISMA Hypothesis. II. Network and Internetwork Fields at the Disk Center Authors: Sánchez Almeida, J.; Lites, B. W. Bibcode: 2000ApJ...532.1215S Altcode: This paper is the second in a series that models photospheric magnetic structures in terms of atmospheres having optically thin fluctuations of magnetic field and thermodynamic state (the MISMA hypothesis). We apply an inversion procedure to the polarization of Fe I λ6301.5 and Fe I λ6302.5 observed in network and internetwork regions with the Advanced Stokes Polarimeter. Some 5200 independent spectra, comprising mildly asymmetric to very abnormal Stokes profiles, were reproduced by a single type of model atmosphere. It has three components, two that are magnetized and one that is not. A large fraction among the field strengths we measure are in the kG regime, but simulations suggest that the polarization of the observed Fe I lines weakens below detectable levels for fields substantially smaller than the observed ones. Synthesis of Stokes profiles of the IR Fe I λ15648.5 line in MISMAs reveals the opposite behavior, i.e., an increase of polarization for sub-kG fields. The highly transparent MISMAs inferred from observations are significantly brighter in the continuum than an unmagnetized atmosphere. The mass of the magnetic structures tends to be at rest, although a minor fraction undergoes strong downflows. Downflows are also present in the nonmagnetic environment. A significant number of fitted Stokes profiles require opposite magnetic polarities within the same resolution element. The occurrence of mixed polarities increases with weakening degree of polarization, such that 25% of the weakest signals require mixed polarity. The weak polarization signals account for most of the total (unsigned) magnetic flux of the observed region. By extrapolation, this indicates that a significant fraction of photospheric magnetic flux remains undetected. The MISMA framework provides a unified and physically consistent scenario for interpretation of quiet Sun magnetism. Moreover, it is the only one available at present that is able to fit the abnormal Stokes profiles as revealed by the new generation of sensitive Stokes polarimeters. Title: Remote sensing of solar magnetic fields Authors: Lites, Bruce W. Bibcode: 2000RvGeo..38....1L Altcode: New techniques for remote sensing of solar magnetic fields now provide measures of the magnetic field vector within the solar atmosphere with high angular resolution and high precision. These measurements have enabled a much improved physical understanding of magnetic processes and phenomena in the solar atmosphere, processes that drive the variability of the Sun's radiative and particulate output. The new techniques are reviewed here in the context of the scientific advances they have fostered. Emphasis is given to techniques for inferring the field vector. The quantitative nature of the information needed to explore the solar phenomena sharply constrains the needed precision and angular resolution of the observations. These requirements are reviewed here, along with an assessment of how future improvements in observing capabilities will address these requirements. One may also attribute much of the recent advance in our understanding of solar magnetic fields to ongoing progress in techniques for analysis of the polarization measurements that underlie solar magnetometry. The status and prospects of analysis techniques are also reviewed. Title: Dynamics of polar plumes observed at the 1998 February 26 eclipse Authors: Lites, B. W.; Card, G.; Elmore, D. F.; Holzer, T.; Lecinski, A.; Streander, K. V.; Tomczyk, S.; Gurman, J. B. Bibcode: 1999SoPh..190..185L Altcode: This paper presents first observations of dynamics of the white-light solar corona detected during the few minutes of totality of a solar eclipse. Perturbations of a polar plume associated with an embedded `jet' structure observed simultaneously at 195 Å with the EUV Imaging Telescope (EIT) aboard the SOHO spacecraft lead to estimates of the electron density fluctuations accompanying the jet: ±15%. The morphological behavior of the jet, its apparent upward propagation speed of ≈200 km s−1, and the inferred density perturbations suggest that the jet is led by a weak, outward-propagating shock resulting from the injection of material at high velocity at the base of the corona. Smaller perturbations of the white-light corona are apparent at many other locations, sustaining hope that propagating Alfvén waves may be measurable in the solar corona. Density perturbations associated with the jet follow from empirical electron density models of the polar inter-plume and plume regions, as derived from the ground-based eclipse measurements of coronal polarization brightness. These models indicate polar plume densities 4-6 times that of the interplume low corona. Title: Bright rings around sunspots Authors: Rast, M. P.; Fox, P. A.; Lin, H.; Lites, B. W.; Meisner, R. W.; White, O. R. Bibcode: 1999Natur.401..678R Altcode: There are two possible explanations for why sunspots are dark: the partial suppression by the sunspot magnetic fields of convective energy transport from the underlying layers, or the removal of energy from the sunspot by enhanced hydromagnetic wave radiation. Both processes would reduce the energy emitted radiatively. The first explanation is currently favoured, and predicts that the blocked energy should show up as a bright ring around the spot, with the actual brightness of the ring sensitive to details of solar convective transport and sunspot structure. Previous searches for these bright rings were inconclusive because of the presence of bright, vertical magnetic flux tubes near the spots, and a lack of sufficient precision in the observations. Here we report high-photometric-precision observations of bright rings around eight sunspots. The rings are about 10K warmer than the surrounding photosphere and extend at least one sunspot radius out from the penumbra. About 10% of the radiative energy missing from the sunspots is emitted through the bright rings. We also report observations of a second set of sunspots, for which simultaneous magnetic field measurements demonstrate that the rings are not associated with vertical flux tubes. Title: Dynamics of the Solar Chromosphere. II. Ca II H2V and K2V Grains versus Internetwork Fields Authors: Lites, B. W.; Rutten, R. J.; Berger, T. E. Bibcode: 1999ApJ...517.1013L Altcode: We use the Advanced Stokes Polarimeter at the NSO/Sacramento Peak Vacuum Tower Telescope to search for spatio-temporal correlations between enhanced magnetic fields in the quiet solar internetwork photosphere and the occurrence of Ca II H2V grains in the overlying chromosphere. We address the question of whether the shocks that produce the latter are caused by magnetism-related processes, or whether they are of purely hydrodynamic nature. The observations presented here are the first in which sensitive Stokes polarimetry is combined synchronously with high-resolution Ca II H spectrometry. We pay particular attention to the nature and significance of weak polarization signals from the internetwork domain, obtaining a robust estimate of our magnetographic noise level at an apparent flux density of only 3 Mx cm-2. For the quiet Sun internetwork area analyzed here, we find no direct correlation between the presence of magnetic features with apparent flux density above this limit and the occurrence of H2V brightenings. This result contradicts the one-to-one correspondence claimed by Sivaraman & Livingston. We also find no correspondence between H2V grains and the horizontal-field internetwork features discovered by Lites et al. Title: The Solar-B Solar Optical Telescope Focal Plane Package Authors: Levay, M.; Berger, T.; Rosenberg, W.; Tarbell, T.; Title, A.; Bogdan, T.; Elmore, D.; Lites, B. Bibcode: 1999AAS...194.7610L Altcode: 1999BAAS...31R.957L The primary goal of the Solar-B mission is to understand the physical processes responsible for dynamics and heating of the outer solar atmosphere. The Focal Plane Package (FPP) instrument for the 50-cm Solar Optical Telescope provides precise measurements of the vector magnetic field, vertical and horizontal flows, and thermal conditions in the photosphere and low chromosphere with spatial resolution as high as 0.16 arcsec and a field-of-view as large as 320 x 160 arcsec. The FPP can measure continuously and at high cadence to follow the evolution of solar features. The FPP consists of broad ( 8 Angstroms) and narrow ( 100 m Angstroms) filters and a spectro-polarimeter that provides precise polarimetry with high spectral resolution ( 25 m Angstroms). A correlation tracker and tip-tilt mirror ensure that all focal planes are stable to better than 0.01 arcsec. A major design consideration of the FPP is cooperative science operations with the other Solar-B instruments. Solar-B is a Japanese mission with US and UK partners; S. Tsuneta is the PI of the Solar Optical Telescope and A. Title the US PI of the FPP. It is scheduled to launch in Japanese FY 2004. Title: Internetwork Grains with TRACE Authors: Rutten, R. J.; de Pontieu, B.; Lites, B. Bibcode: 1999ASPC..183..383R Altcode: 1999hrsp.conf..383R No abstract at ADS Title: Dynamics of the Quiet Solar Chromosphere Authors: Rutten, R. J.; Lites, B. W.; Berger, T. E.; Shine, R. A. Bibcode: 1999ASPC..158..249R Altcode: 1999ssa..conf..249R No abstract at ADS Title: Vector magnetic fields of emerging solar flux. I. Properties at the site of emergence Authors: Lites, B. W.; Skumanich, A.; Martinez Pillet, V. Bibcode: 1998A&A...333.1053L Altcode: Several small emerging bipolar regions have been observed with the Advanced Stokes Polarimeter (ASP), including extensive time series measurements of one small region. Both new and previously recognized properties of the actual site of first emergence, where the magnetic field is nearly horizontal to the surface, are revealed by these observations. They provide the most complete and accurate observational description to date of newly emerging vector magnetic fields. We find that: 1) the strength of the magnetic field at the site of the emergence (where the vector field is nearly parallel to the solar surface) ranges from about 200 to 600 G, 2) as individual flux elements migrate rapidly away from the emergence zone, they attain kiloGauss strengths only after becoming oriented nearly vertically, 3) the emergence zone is dotted by small, transient, upward rising ( ~ 1 km s(-1) ) horizontal magnetic elements as indicated by the Doppler shift of the polarized spectral profiles, 4) the leading polarity flux coalesces immediately into a compact region which forms a pore, but the emerging following polarity flux is spatially much less compact, 5) some ``moving magnetic features'' having the same magnetic polarity as the growing pore, but on the opposite side of the pore from the emergence zone, coalesce with the pore during the observation period, and 6) the observations suggest a low canopy of weak horizontal magnetic fields arches over the emergence zone. These observations support a widely accepted picture of emerging bipolar flux: the buoyantly rising flux transports mass from the photosphere into the chromosphere, where it then may drain downward along arched magnetic loops. The observed formation of a pore suggests that emergence of subsurface structure, not organized flows near the surface, is largely responsible for the apparent coalescence of sunspots from more diffuse fields viewed at the solar surface. These observations neither confirm nor refute the operation of convective collapse of flux tubes. Title: Velocity and Magnetic Field Fluctuations in the Photosphere of a Sunspot Authors: Lites, Bruce W.; Thomas, John H.; Bogdan, Thomas J.; Cally, Paul S. Bibcode: 1998ApJ...497..464L Altcode: We use a data set of exceptionally high quality to measure oscillations of Doppler velocity, intensity, and the vector magnetic field at photospheric heights in a sunspot. Based on the full Stokes inversion of the line profiles of Fe I 630.15 and 630.25 nm, in the sunspot umbra we find upper limits of 4 G (root mean square [rms]) for the amplitude of 5 minute oscillations in magnetic field strength and 0.09d (rms) for the corresponding oscillations of the inclination of the magnetic field to the line of sight. Our measured magnitude of the oscillation in magnetic field strength is considerably lower than that found in 1997 by Horn, Staude, & Landgraf. Moreover, we find it likely that our measured magnetic field oscillation is at least partly due to instrumental and inversion cross talk between the velocity and magnetic signals, so that the actual magnetic field strength fluctuations are even weaker than 4 G. In support of this we show, on the basis of the eigenmodes of oscillation in a theoretical model of the sunspot umbra, that magnetic field variations of at most 0.5 G are all that is to be expected. The theoretical model also provides an explanation of the shift of power peaks in Doppler velocity to the 3 minute band in chromospheric umbral oscillations, as a natural consequence of the drastic change in character of the eigenmodes of oscillation between frequencies of about 4.5 and 5.0 mHz due to increased tunneling through the acoustic cutoff-frequency barrier. Using measurements of the phase of velocity oscillations above the acoustic cutoff frequency, we determine the relative velocity response height in the umbra of four different photospheric spectral lines from the phase differences between velocities in these lines, assuming that the oscillations propagate vertically at the local sound speed. In spacetime maps of fluctuations in continuum intensity, Doppler velocity, magnetic field strength, and field inclination, we see distinct features that migrate radially inward from the inner penumbra all the way to the center of the umbra, at speeds of a few tenths of a kilometer per second. These moving features are probably a signature of the convective interchange of magnetic flux tubes in the sunspot, although we failed to find any strong correlation among the features in the different quantities, indicating that these features have not been fully resolved. Title: Optical Tomography of a Sunspot. I. Comparison between Two Inversion Techniques Authors: Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martínez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1998ApJ...494..453W Altcode: A quantitative comparison between the Milne-Eddington (ME) inversion technique implemented by Skumanich & Lites and the SIR (Stokes Inversion based on Response Functions) proposed by Ruiz Cobo & del Toro Iniesta is presented. Numerical experiments are carried out to explore the capabilities and limitations of both diagnostic techniques. Such experiments consist of inversions of Stokes profiles previously synthesized in ``realistic'' solar atmospheric models. The results show that the ME inversion provides accurate, line-of-sight (LOS) averaged values for the input stratification of the vector magnetic field. Its greater speed compared to SIR makes it useful for quick analysis of large quantities of data (such as those currently provided by modern spectropolarimeters) if one is only interested in LOS-averaged quantities. However, the higher order description of the atmosphere used by SIR (which acknowledges variation of the thermal, dynamic, and magnetic parameters through the photosphere) allows retrieval of the stratification of all these parameters to good accuracy. This is so even in the presence of discontinuities such as those foreseen in magnetic canopies of sunspots. The trade-offs between thermodynamic and magnetic parameters observed in some ME inversions are reduced considerably in the case of SIR inversions because of the more realistic treatment of the thermodynamics in this analysis. Notably, both allow one to extract quantitative inferences of fairly weak magnetic fields (below 500 G), even when they are applied to Zeeman-sensitive lines in the visible spectrum; i.e., well below the commonly accepted limit of 500 G. The thermodynamic parameters resulting from the ME inversion are understood theoretically in terms of the generalized response functions introduced by Ruiz Cobo & del Toro Iniesta and through the concept of height of formation for inferred values proposed by Sánchez Almeida, Ruiz Cobo, & del Toro Iniesta.

The present comparison and verification of the reliability of inversion methods is a natural first step toward the ongoing analysis of the three-dimensional magnetic structure of a sunspot. By using SIR (with ME results for initialization) on maps of a whole sunspot observed by the Advanced Stokes Polarimeter, we obtain maps at different optical layers (i.e., an optical tomography) of the temperature, vector magnetic field, and LOS velocity. Such a tomography will appear in subsequent papers of the present series. To illustrate fits to the observed Stokes profiles, we show here actual inversion results for three points observed within a sunspot: one within the umbra, another from the outermost parts of the penumbra, and a third from the magnetic canopy surrounding the sunspot. Title: The Seismology of Sunspots: A Comparison of Time-Distance and Frequency-Wavenumber Methods Authors: Bogdan, T. J.; Braun, D. C.; Lites, B. W.; Thomas, John H. Bibcode: 1998ApJ...492..379B Altcode: A pair of formulae are developed that relate the absorption coefficient and partial-wave phase shift concepts of frequency-wavenumber local helioseismology to the center-annulus cross-correlation function of time-distance helioseismology, under the general circumstances that both induced and spontaneous sunspot oscillations may be present. These formulae show that spontaneous emission of p-modes by magnetic and Reynolds stresses within the spot and the mode mixing between incoming and outgoing p-modes affect only the outgoing center-annulus cross-correlation time τ+, and they caution that real or spurious phase lags of the umbral oscillation signal lead to differences in the incoming and outgoing correlation times, resulting in τ- ≠ τ+. The application of these methods to actual helioseismic data obtained by the Global Oscillation Network Group (GONG) project is carried out in order to provide a tangible illustration of how time-distance and frequency-wavenumber ideas can profitably be combined to yield deeper insight into the seismic probing of sunspots.

By using the helioseismic GONG data in conjunction with concurrent observations of Doppler velocities and vector magnetic fields obtained by the High Altitude Observatory/National Solar Observatory (HAO/NSO) Advanced Stokes Polarimeter (ASP) for the 1995 October disk passage of active region NOAA 7912, we demonstrate that the inferred GONG umbral signal actually originates from the umbra-penumbra boundary about 6 Mm distant from the center of the spot. Further, the ASP observations show that the 5 minute oscillations at the umbra-penumbra boundary lag behind those in the center of the umbra by approximately 1 minute, which is precisely the difference between the incoming and outgoing correlation times for NOAA 7912 recently determined by Braun. This remarkable result underscores the perils of using umbral oscillations in time-distance helioseismology, and it calls into question previous claims that correlation time differences constitute direct evidence for the existence of a steady downflow in and around sunspots. Taken together, the observational and theoretical evidence suggest that the p-mode forcing of the spot leads to the generation of upwardly propagating slow magnetoatmospheric waves. These waves are in turn responsible for the decreased amplitudes of the outwardly propagating p-modes in the surrounding quiet Sun, and the dispersion in their travel times between the hidden subsurface layer where they are forced and the overlying level where the Doppler signals originate leads to the observed phase lag between the umbral and penumbral oscillations and the corresponding correlation time differences.

This work utilizes data obtained by the Global Oscillations Network Group (GONG) project, managed by the National Solar Observatory, a Division of the National Optical Astronomy Observatories, which is operated by AURA, Inc., under a cooperative agreement with the National Science Foundation. Title: Vector Magnetic Fields of Emerging Solar Flux Authors: Martínez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1998ESASP.417..259M Altcode: 1998cesh.conf..259M No abstract at ADS Title: Evidence for a downward mass flux in the penumbral region of a sunspot Authors: Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martinez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1997Natur.389...47W Altcode: No abstract at ADS Title: The Vector Magnetic Field, Evershed Flow and Intensity in a Sunspot Authors: Stanchfield, D. C. H.; Thomas, J. H.; Lites, B. W. Bibcode: 1997ASNYN...5b..14S Altcode: No abstract at ADS Title: Flux Emergence and Prominences: a New Scenario for 3-DIMENSIONAL Field Geometry Based on Observations with the Advanced Stokes Polarimeter Authors: Lites, B. W.; Low, B. C. Bibcode: 1997SoPh..174...91L Altcode: This paper presents an interpretation of the evolution of the vector magnetic field at the photosphere based on measurements of the advanced Stokes polarimeter, along with chromospheric Hα from the Lockheed instrument operating on La Palma and X-ray images of the corona from Yohkoh. These measurements are consistent with the emergence of a nearly closed magnetic structure from the solar interior into the corona. The highly non-potential field topology inferred from the data suggests that strong field-aligned currents exist in the emergent magnetic structure as it buoyantly rises through the photosphere. Material trapped in this closed structure is pulled upward to later condense into a prominence. By analogy of this small active region evolution with the observed properties of large quiescent prominences, we speculate that this process might also be operative on a much larger scale. A 3-dimensional magnetostatic model is presented which has many topological features in common with the observations. Title: The Vector Magnetic Field and Evershed Flow in a Sunspot Authors: Stanchfield, D. C. H.; Thomas, J. H.; Lites, B. W. Bibcode: 1997ASNYN...5b..12S Altcode: No abstract at ADS Title: The Calibration of the Advanced Stokes Polarimeter Authors: Skumanich, A.; Lites, B. W.; Martínez Pillet, V.; Seagraves, P. Bibcode: 1997ApJS..110..357S Altcode: We describe and apply the methods that have been developed to calibrate the Advanced Stokes Polarimeter and to compensate for the polarization effects introduced by the Vacuum Tower Telescope at the National Solar Observatory/Sunspot. A seven-parameter model of the telescope is fitted to data obtained at a variety of mirror angles using observations of both the center of the solar disk and that point within a sunspot umbra at which the magnetic field is oriented as close to the line of sight as possible. The response matrix of the polarimeter itself is determined by the use of polarizing calibration optics that modify the polarization state of the beam exiting the telescope but before entering the polarimeter. A global least-squares solution is obtained simultaneously for the response matrix and the telescope parameters. A detailed gain-correction procedure is described that reduces the multiplicative gain errors in the spectral images to typically less than 1%. We have successfully recovered net-linear polarization profiles with peak amplitudes of 1 × 10-3Ic against an instrumentally produced background polarization of ~=1-5 × 10-2Ic. Net-polarization signals smaller than ~=3 × 10-4Ic are lost, even with sufficient averaging, in a background due to photometric and other calibration errors. Title: The Solar-B Mission Authors: Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila, Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon; Harvey, John; Hathaway, David; Hudson, Hugh; Moore, Ronald; Lites, Bruce; Rust, David; Strong, Keith; Title, Alan Bibcode: 1997STIN...9721329A Altcode: Solar-B, the next ISAS mission (with major NASA participation), is designed to address the fundamental question of how magnetic fields interact with plasma to produce solar variability. The mission has a number of unique capabilities that will enable it to answer the outstanding questions of solar magnetism. First, by escaping atmospheric seeing, it will deliver continuous observations of the solar surface with unprecedented spatial resolution. Second, Solar-B will deliver the first accurate measurements of all three components of the photospheric magnetic field. Solar-B will measure both the magnetic energy driving the photosphere and simultaneously its effects in the corona. Solar-B offers unique programmatic opportunities to NASA. It will continue an effective collaboration with our most reliable international partner. It will deliver images and data that will have strong public outreach potential. Finally, the science of Solar-B is clearly related to the themes of origins and plasma astrophysics, and contributes directly to the national space weather and global change programs. Title: Velocity and Magnetic Field Fluctuations in the Photosphere of a Sunspot Authors: Thomas, J. H.; Lites, B. W.; Bogdan, T. J. Bibcode: 1997SPD....28.0236T Altcode: 1997BAAS...29..899T We use a data set of exceptionally high quality, obtained with the HAO/NSO Advanced Stokes Polarimeter, to measure oscillations of Doppler velocity, intensity, and the vector magnetic field at photospheric heights in a sunspot. We find an upper limit of 4 G (rms) for 5-min oscillations in magnetic field strength in the umbra, based on the full Stokes inversion of the line profiles of Fe I 6301.5 and 6302.5. This magnitude of the oscillation in field strength is considerably lower than that found recently by Horn, Staude, and Landgraf (1997). We show, on the basis of the eigenmodes of oscillation in a simple theoretical model of the sunspot umbra, that magnetic field variations of order 1 G are all that is to be expected. Using measurements of velocity oscillations above the acoustic cutoff frequency, we determine the relative heights of formation in the umbra of four different photospheric spectral lines from the phase differences between velocities in these lines, assuming the oscillations propagate vertically at the local sound speed. In space-time maps of fluctuations in continuum intensity, Doppler velocity, magnetic field strength, and field inclination we see distinct features that migrate radially inward from the inner penumbra all the way to the center of the umbra. These moving features are probably a signature of the convective interchange of magnetic flux tubes in the sunspot, although we failed to find any strong correlation among the features in the different quantities, indicating that these features have not been fully resolved. Title: The Seismology of Sunspots: A Comparison of Time-Distance and Frequency-Wavenumber Methods Authors: Bogdan, T. J.; Braun, D. C.; Lites, B. W.; Thomas, J. H. Bibcode: 1997SPD....28.0210B Altcode: 1997BAAS...29..894B A pair of formulae are developed which relate the absorption coefficient and partial wave phase-shift concepts of frequency-wavenumber local helioseismology to the center- annulus cross correlation function of time-distance helioseismology, under the general circumstances that both induced and spontaneous sunspot oscillations may be present. These formulae caution that real or spurious phase lags of the umbral oscillation signal lead to differences in the incoming and outgoing correlation times for sunspots, as first observed by Duvall et al. (1996, Nature, 379, 430) and recently confirmed by Braun (1997, ApJ, submitted). By using helioseismic data obtained by the GONG project in conjunction with concurrent observations of Doppler velocities and magnetic fields obtained by the HAO/NSO Advanced Stokes Polarimeter for the October 1995 disk passage of active region NOAA 7912, we demonstrate that the inferred GONG umbral oscillation signal actually originates from the umbra-penumbra boundary some 6 Mm distant from the center of the spot. Further, the ASP observations show that the 5-min oscillations at the umbra-penumbra boundary lag those in the center of the umbra by approximately 1 min, which is precisely the difference between the incoming and outgoing cross correlation times for NOAA 7912 recently determined by Braun. The evidence suggests that p-mode forcing of the spot results in the generation of upward propagating slow MAG waves. These waves are responsible for the absorption of the p-modes, and the dispersion in their travel times between the subsurface layer where they are forced and the overlying level where the Doppler signals originate leads to the observed phase lag between the umbral and penumbral oscillations, and the corresponding correlation time differences. Title: The Vector Magnetic Field, Evershed Flow, and Intensity in a Sunspot Authors: Stanchfield, Donald C. H., II; Thomas, John H.; Lites, Bruce W. Bibcode: 1997ApJ...477..485S Altcode: We present results of simultaneous observations of the vector magnetic field, Evershed flow, and intensity pattern in a nearly axisymmetric sunspot, made with the Advanced Stokes Polarimeter at the Vacuum Tower Telescope at NSO (Sacramento Peak). The vector magnetic field is determined from the Stokes profiles of the magnetically sensitive lines Fe I 630.15 and 630.25 nm, and Doppler velocities and intensities are measured in several lines including the weak C I 538.03 nm line, formed in the deepest layers of the atmosphere. The strength of the magnetic field decreases with increasing zenith angle (angle of inclination to the local vertical), and this decrease is nearly linear over most of the range of values in the sunspot. Magnetic field strength and continuum intensity are inversely related in the sunspot in a manner similar to the characteristic nonlinear relationship found by Kopp & Rabin in the infrared line Fe I 1564.9 nm. A different relationship is found between magnetic field strength and core intensity (in Fe I 630.25 nm), however, with the curve doubling back to give two distinct values of field strength at the same core intensity in the penumbra--the higher and lower field strengths corresponding to the inner and outer penumbra, respectively. In the penumbra the magnetic field pattern consists of spokelike extensions of stronger, more vertical magnetic field separated by regions of weaker, nearly horizontal magnetic field, as found by Degenhardt & Wiehr and Lites et al. The penumbral magnetic field extends outward beyond the outer continuum boundary of the sunspot, forming a canopy at the height of formation of Fe I 630.25 nm. Our results for the Evershed flow confirm the discovery by Rimmele that this flow is generally confined to narrow, elevated channels in the penumbra. In the Fe I 630.25 nm line and other strong photospheric lines we see isolated, radially elongated channels of Evershed flow crossing the outer penumbra. These flow channels lie in regions of the penumbra where the magnetic field is very nearly horizontal. In the weak C I 538.03 nm line (formed at a height h = 40 km) the flow pattern shows small, isolated patches of upflow, lying at the inner end of the Fe I flow channels where the magnetic field is more inclined to the horizontal. These patches presumably correspond to the upstream footpoints of the arched magnetic flux tubes carrying the Evershed flow. For some of the flow channels we find isolated patches of strong downflow in the C I line just outside the penumbra that might correspond to the downstream footpoints of these flux tubes. There is a weak association between the Evershed flow channels and the dark filaments seen in continuum intensity in the penumbra, but a much stronger association between the flow and the dark filaments seen in core intensity measured in the same spectral line. Title: Active Region Magnetic Fields. I. Plage Fields Authors: Martínez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1997ApJ...474..810M Altcode: We present observations taken with the Advanced Stokes Polarimeter (ASP) in active-region plages and study the frequency distribution of the magnetic field strength (B), inclination with respect to vertical (γ), azimuthal orientation (χ), and filling factor (f). The most common values at disk center are B = 1400 G, γ < 10°, no preferred east-west orientation, and f = 15%. At disk center, there is a component of weak (<1000 G), more horizontal fields that corresponds to arching field lines connecting footpoints of different polarities. The center-to-limb variation (CLV) of the field strength shows that, close to the limb (μ = 0.3), the field strength is reduced to 800 G from its disk-center value. This can be interpreted as a gradient of B with height in solar plages of around -3 G km-1. From this CLV study, we also deduce that magnetic field lines remain vertical for the entire range of heights involved. A similar analysis is performed for structures found in active regions that show a continuous distribution of azimuths (resembling sunspots) but that do not have a darkening in continuum. These ``azimuth centers'' show slightly larger values of B than normal plages, in particular at their magnetic center. Filling factors are also larger on average for these structures.

The velocities in the magnetic component of active regions have been studied for both averaged Stokes profiles over the entire active region and for the spatially resolved data. The averaged profiles (more representative of high filling factor regions) do not show any significant mean velocities. However, the spatial average of Doppler velocities derived from the spatially resolved profiles (i.e., unweighted by filling factor) show a net redshift at disk center of 200 m s-1. The spatially resolved velocities show a strong dependence on filling factor. Both mean velocities and standard deviations are reduced when the filling factor increases. This is interpreted as a reduction of the p-mode amplitude within the magnetic component. Strong evidence for velocities transverse to the magnetic field lines has been found. Typical rms values are between 200 and 300 m s-1, depending on the filling factor. The possible importance of these transverse motions for the dynamics of the upper atmospheric layers is discussed.

The asymmetries of the Stokes profiles and their CLV have been studied. The averaged Stokes V profiles show amplitude and area asymmetries that are positive at disk center and become negative at the limb. Both asymmetries, and for the two Fe I lines, are maximized away from disk center. The spatially resolved amplitude asymmetries show a clear dependence on filling factor: the larger the filling factor, the smaller the amplitude asymmetry. On the other hand, the area asymmetry is almost independent of the filling factor. The only observed dependence is the existence of negative area-asymmetry profiles at disk center for filling factors smaller than 0.2. Around 20% of the observed points in a given plage have negative area asymmetry. The amplitude asymmetry of Stokes V is, on the other hand, always positive. The amplitude asymmetries of the linear polarization profiles are observed to have the same sign as the Stokes V profiles. Similarly, the same CLV variation of the linear polarization amplitude asymmetries as for Stokes V has been found. The scenarios in which this similarity can exist are studied in some detail. Title: Inversion Techniques Applied to Sunspot Spectropolarimetric Data Authors: Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martinez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1997ASPC..118..197W Altcode: 1997fasp.conf..197W Two inversion techniques are compared: the Unno-Rachkov\-sky fitting method (UR) and the Stokes Inversion based on Response functions (SIR). Results with synthetic profiles in sunspot model atmospheres and real data show that whilst UR is well suited for recovering a constant vec B, SIR enables us to know the run with depth of vec B and the line of sight velocity together with the temperature stratification. Title: Optical Tomography of a Sunspot: Preliminary Results Authors: Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martinez Pillet, V.; Lites, B. W.; Skumanich, A. Bibcode: 1997ASPC..118..202W Altcode: 1997fasp.conf..202W Preliminary results of the inversion of spectropolarimetric maps of a sunspot observed with the Advanced Stokes Polarimeter (ASP) are presented. The method used, Stokes Inversion based on Response functions (SIR), does not assume constancy of the different parameters with depth, thus enabling us to embark on an analysis of the information at different layers in continuum optical depth (i.e. optical tomography), of a sunspot's photosphere. Maps of the vector magnetic field and other physical quantities like temperature or line-of-sight velocity at several optical depths show a new and promising view of the structure of a sunspot, casting light on long standing debates as those over penumbral `corrugated' fields (spines), superpenumbral canopies, return flux, or the nature of the Evershed effect. Title: Line Asymmetries and the Microstructure of Photospheric Magnetic Fields Authors: Sanchez Almeida, J.; Landi Degl'Innocenti, E.; Martinez Pillet, V.; Lites, B. W. Bibcode: 1996ApJ...466..537S Altcode: A systematic structuring of magnetic fields over scales much smaller than the mean free path of photospheric photons may be responsible for the observed asymmetrical Stokes profiles. We explore this possibility by deriving the radiative transfer equation for microstructured magnetic atmospheres (the MISMA approximation). This equation is subsequently employed to show that very schematic MISMA scenarios for the penumbrae of sunspots, plage and network regions, and internetwork regions produce Stokes profiles that have the observed asymmetries. The details of these model atmospheres are of secondary importance, but the ease of generating the type of observed asymmetries with MISMAs is significant, so the existence of MISMAs deserves serious consideration. Should such microstructures exist, the techniques currently employed to infer properties of the solar photosphere need to be revised. MISMAs are also of concern for the physics of the photosphere itself. These two topics are briefly discussed. Title: Magnetic Flux Emergence Observed with the Advanced Stokes Polarimeter Authors: Lites, B.; Martinez Pillet, V. Bibcode: 1996AAS...188.3313L Altcode: 1996BAAS...28Q.870L We have carried out quantitative observations of the vector magnetic field during the emergence of three small bipolar active regions in June, 1992, July 1993, and September 1994 using the Advanced Stokes Polarimeter (ASP). The region of horizontal magnetic field at the actual site of emergence is always characterized by low magnetic field strength (i.e. considerably less than 1000 Gauss). We find a strong relationship between field strength and inclination in these regions. This suggests that 1) flux emerging from below the photosphere does not coalesce into strong flux tubes until it reaches the photosphere, becomes nearly vertical as a result of magnetic buoyancy, and is then acted upon by convective collapse, and 2) the field strength of flux rising through the convection zone may be in rough equipartition with the fluid motions. We find the flux emergence zone to be characterized by highly variable (both spatially and temporally) fill factors for the magnetic field, suggesting that the flux below the surface is filamentary, that it rises rapidly through the photosphere to form a magnetic canopy above the emergence region. Sequences of Hα on- and off-band images obtained with the ASP reveal the accompanying development of the arch-filament system, and suggest that the material within the Hα structures is supplied by a siphon flow as evidenced by apparent chromospheric red shifts on the sides of the loops closest to a large pore, and blue shifts where the fields anchor in plage regions. Proper motions of the magnetic flux images throughout a day's observation indicate the presence of a persistent vortex flow on a small scale (a few arcseconds). The National Center for Atmospheric Research is sponsored by the National Science Foundation. Title: Vector Magnetic Fields and the Evershed Flow in Sunspots Authors: Stanchfield, D. C. H., II; Thomas, J. H.; Lites, B. W. Bibcode: 1996AAS...188.3507S Altcode: 1996BAAS...28..872S We present results of simultaneous observations of the vector magnetic field and the Evershed effect in two sunspots, made with the Advanced Stokes Polarimeter at the Vacuum Tower Telescope at NSO (Sacramento Peak). The vector magnetic field is determined from the Stokes profiles of the magnetically sensitive line Fe I 630.25, and Doppler velocities are measured in several lines including the weak C I 538.03 line, formed in the deepest layers of the atmosphere. In addition to maps of the vector magnetic field and the line-of-sight Doppler velocity, we present maps of the true flow speed assuming that the flow is everywhere aligned with the magnetic field. The results confirm the recent discovery by Rimmele (1995), that the Evershed flow is generally confined to narrow, elevated channels in the penumbra. In the Fe I 537.96 line (formed at a height of about 230 km) we see isolated, radially elongated channels of Evershed flow in the outer penumbra. These flow channels lie in regions of the penumbra where the magnetic field is most nearly horizontal. In the C I line (formed at a height of about 40 km) the flow pattern shows small, isolated patches of upflow lying at the inner end of the Fe I flow channels, where the magnetic field is more highly inclined to the horizontal. These patches presumably correspond to the upstream footpoints of the arched magnetic flux tubes carrying the Evershed flow. In some cases, along a radial line extending outward from a flow channel, we find isolated patches of downflow in the C I line just outside the penumbra, with magnetic field inclination slightly beyond the horizontal (i.e., magnetic field diving beneath the surface). These patches might well correspond to the downstream footpoints of these flux tubes. Title: Small-Scale Horizontal Magnetic Fields in the Solar Photosphere Authors: Lites, B. W.; Leka, K. D.; Skumanich, A.; Martinez Pillet, V.; Shimizu, T. Bibcode: 1996ApJ...460.1019L Altcode: We present recent observations of quiet regions near the center of the solar disk using the Advanced Stokes Polarimeter. These observations reveal a component of the solar magnetic field heretofore unobserved: isolated, small-scale (typically 1"-2" or smaller), predominantly horizontal magnetic flux structures in the solar photosphere. These features occur in isolation of the well-known, nearly vertical flux concentrations usually seen in the photospheric "network." Hence we ascribe this horizontal flux to the photospheric "internetwork." They reveal themselves by the distinct signature of the Stokes Q and U polarization profiles, which are symmetric about the line center. The polarization signals are weak, with peak amplitudes typically ∼0.1%-0.2% of the continuum intensity in the resolved spectral profiles, but they are well above the noise level of these observations (≍0.05%). Such magnetic fields are weak (significantly less than 1000 G) and largely horizontal owing to the absence, or near absence, of accompanying Stokes V polarization when observed at the center of the solar disk. These horizontal field elements are often associated with blueshifted Stokes line profiles, and they often occur between regions of opposite polarity (but weak) Stokes V profiles. The horizontal elements are short-lived, typically lasting ∼5 minutes. Our observations suggest that we are viewing the emergence of small, concentrated loops of flux, carried upward either by granular convection or magnetic buoyancy. Even though these entities show weak field strengths, they also seem to be fairly common, implying that they could carry the order of 1024 Mx of magnetic flux to the surface on a daily basis. However, further observational study is needed to identify the specific nature of this phenomenon. Title: Performance Characteristics of the Advanced Stokes Polarimeter Authors: Lites, B. W. Bibcode: 1996SoPh..163..223L Altcode: Recently Zirin (1995) published a response to our paper of last year (Lites, Martínez Pillet, and Skumanich, 1994), in which we quantified some limitations of vector magnetometry by the use of a generic filter magnetograph. Zirin's Letter makes specific reference to the Advanced Stokes Polarimeter (ASP), and in so doing he makes incorrect statements regarding the performance characteristics of the ASP. The intent of this paper is to rectify those erroneous representations and to clarify several other issues raised by Zirin which might give the reader of his Letter an incorrect picture of the ASP. Title: SPLIT: a large spectro-polarimetric space instrument for solar observations. Authors: Schmidt, W.; Kentischer, T.; Title, A. M.; Lites, B. W. Bibcode: 1996AGAb...12...88S Altcode: No abstract at ADS Title: Partial Redistribution in Multilevel Atoms. I. Method and Application to the Solar Hydrogen Line Formation Authors: Hubeny, I.; Lites, B. W. Bibcode: 1995ApJ...455..376H Altcode: We present a robust method for solution of multilevel non-LTE line transfer problems including the effects of partial frequency redistribution (PRD). This method allows the self-consistent solution for redistribution of scattered line photons simultaneously in multiple transitions of a model atom, including the effects of resonant Raman scattering ("cross-redistribution") among lines sharing common upper levels. The method is incorporated into the framework of the widely used non-LTE complete redistribution code MULTI. We have applied this method to the problem of transfer in hydrogen lines in a plane-parallel solar model atmosphere, including cross-redistribution between the Hα and Lβ, using general redistribution functions for the Lα and Lβ lines which are not restricted by the impact approximation. The convergence properties of this method are demonstrated to be comparable to that of the equivalent complete redistribution problem. In this solar model, PRD in the Lα line produces the dominant influence on the level populations. It changes considerably the populations of the excited states of hydrogen, as well as the proton number density, in the middle and upper chromosphere, owing to modification of the Lα wing radiation.

The population of the hydrogen ground state undergoes only modest changes, however. The influence of cross-redistribution and PRD in Lβ has a much smaller influence on the level populations but a considerable influence on the wing intensity of the Lβ line. Title: The Possible Ascent of a Closed Magnetic System through the Photosphere Authors: Lites, B. W.; Low, B. C.; Martinez Pillet, V.; Seagraves, P.; Skumanich, A.; Frank, Z. A.; Shine, R. A.; Tsuneta, S. Bibcode: 1995ApJ...446..877L Altcode: We present a comprehensive interpretation of the evolution of a small magnetic region observed during its entire disk passage. The vector magnetic field measurements from the Advanced Stokes Polarimeter, along with Hα and magnetogram measurements from the Lockheed SOUP instrument operating at the Swedish Solar Observatory on La Palma, and soft X-ray images from the Yohkoh satellite support the hypothesis that we have observed the passage of a nearly closed magnetic system through the photosphere into the corona. The observations suggest that as the magnetic flux begins to emerge into the photosphere it shows a rather simple geometry, but it subsequently develops a small δ-sunspot configuration with a highly sheared vector field along the polarity inversion line running through it. At that stage, the vector field is consistent with a concave upward magnetic topology, indicative of strong electric currents above the photosphere. An Hα prominence is found above this inversion line when the δ-sunspot is fully formed. These observed features and the sequence of events are interpreted in terms of a nearly closed magnetic system that rises through the photosphere into the corona as a result of magnetic buoyancy. The magnetic system persists in the corona well after the dark δ-sunspot has disappeared in the photosphere We suggest that this coronal structure is in quasi-static equilibrium with its buoyancy partially countered by the weight of the plasma trapped at the bottom of closed magnetic loops. The plausibility of such a scenario is demonstrated by a three-dimensional magnetostatic model of the emergence of a closed, spheroidal magnetic system in the corona, in which the Lorentz force arising from cross-field currents is balanced by the gravitational and pressure forces. This theoretical model carries many features in common with the observed morphology of our active region. Title: Horizontal Internetwork Magnetic Fields Observed with the Advanced Stokes Polarimeter Authors: Lites, B. W.; Martìnez Pillet, V. Bibcode: 1995SPD....26..204L Altcode: 1995BAAS...27..951L No abstract at ADS Title: Small scale horizontal magnetic fields in the solar photosphere Authors: Leka, K. D.; Lites, B. W.; Skumanich, A.; Martínez Pillet, V.; Shimizu, T. Bibcode: 1995IAUS..176P.120L Altcode: No abstract at ADS Title: A Quantitative Comparison of Vector Magnetic Field Measurement and Analysis Techniques Authors: Lites, B. W.; Martinez Pillet, V.; Skumanich, A. Bibcode: 1994SoPh..155....1L Altcode: We make a quantitative comparison between spectral vs filter measurement and analysis techniques for extraction of solar vector magnetic fields from polarimetric data using as a basis the accurately calibrated, high angular resolution Stokes profile data from the Advanced Stokes Polarimeter. It is shown that filter-based measurements deliver qualitative images of the field alignment for sunspots that are visually similar to images derived from the more detailed analysis of the Stokes profiles. However, quantitative comparison with least-squares fits to the full Stokes profiles show that both the strength of the field predicted by the filter-based analysis and its orientation contain substantial errors. These errors are largest for plage regions outside of sunspots, where the field strengths are inferred to be only a fraction of their true values, and errors in the orientation of 40-50° are common. Within sunspots, errors of 20° are commonplace. The greatest source of these errors is the inability of the filter-based measurements to account for the small fill fraction of magnetic fields or, equivalently, scattered light in the instrument, which reduce the degree of polarization. The uncertainties of the full profile fitting methods are also discussed, along with the errors introduced by coarser wavelength sampling of the observed Stokes profiles. The least-squares fitting procedure operates best when the profiles are sampled at least as frequently as one Doppler width of the line. Title: Evidence for Supersonic Downflows in the Photosphere of a Delta Sunspot Authors: Martinez Pillet, V.; Lites, B. W.; Skumanich, A.; Degenhardt, D. Bibcode: 1994ApJ...425L.113M Altcode: 1994ApJ...425L.113P We present polarization profiles observed with the High Altitude Observatory/National Solar Observatory (HAO/NSO) Advanced Stokes Polarimeter (ASP) that demonstrate, in a model-independent way, the presence of strong downflows close to the neutral line of a delta sunspot (a spot with both polarities contained within the same penumbra). The flows are as large as 14 km/s, a velocity that, at photospheric levels, strongly suggests the presence of supersonic compressive fluid flows in a region only 100-200 km above the visible surface. These velocities are probably the largest ever reported at photospheric levels. The region containing the downflows is large enough (about 2 sec on a side) to be resolved, although it is likely to contain fine structure at or below our spatial resolution. The origin of these flows is discussed in terms of the funneling of material through an isolated magnetic nozzle in an otherwise closed magnetic system which is rising through the surface. Title: Vector spectropolarimetry with the Advanced Stokes Polarimeter (ASP) for quantitative solar magnetometry Authors: Skumanich, A.; Lites, B. W.; Martínez Pillet, V. Bibcode: 1994ASIC..433...99S Altcode: No abstract at ADS Title: Magnetic Configuration of a Short-Lived Delta SPOT Authors: Martinez Pillet, V.; Lites, B. W.; Skumanich, A. P.; Seagraves, P. Bibcode: 1994ASPC...68..244M Altcode: 1994sare.conf..244M No abstract at ADS Title: Chromospheric oscillations Authors: Lites, B. W.; Rutten, R. J.; Thomas, J. H. Bibcode: 1994ASIC..433..159L Altcode: No abstract at ADS Title: Physical conditions in magnetic elements of different polarities surrounding sunspots Authors: Martínez Pillet, V.; Lites, B. W.; Skumanich, A. P.; Elmore, D. F.; Seagraves, P. Bibcode: 1994smf..conf..219M Altcode: No abstract at ADS Title: The dynamics of magnetic regions in the quiet chromosphere Authors: Lites, B. Bibcode: 1994chdy.conf....1L Altcode: No abstract at ADS Title: Material Flows in Sunspots Authors: Degenhardt, D.; Lites, B. W. Bibcode: 1994smf..conf..185D Altcode: No abstract at ADS Title: Vector field structure of a small sunspot Authors: Skumanich, A.; Lites, B. W. Bibcode: 1994smf..conf..200S Altcode: No abstract at ADS Title: The structure of umbral fluxtubes. Authors: Degenhardt, D.; Lites, B. W. Bibcode: 1994IAUS..154..465D Altcode: Subsurface filamentation of sunspot magnetic fields has been postulated as a source of the visible small-scale structure of sunspot umbrae. The authors examine this possibility by investigating the magnetohydrodynamic structure of thin, vertical magnetized gas columns embedded in sunspot umbrae. Steady-state magnetohydrodynamic equations are solved numerically. The geometric shape of the steady flow solution is a gas column converging with height. The authors discuss the relationship of their results to observed properties of umbral brightenings (umbral dots). They show that, even if there is a large difference in magnetic field strength between the dot and the ambient medium in deeper layers, the field strengths are nearly equal in the observable layers, a result required by the observations. They also show that either high temperatures at the lower boundary of the dots or strong upflows are needed in order to produce bright continuum structures. Title: Stokes Profile Analysis and Vector Magnetic Fields. VI. Fine Scale Structure of a Sunspot Authors: Lites, B. W.; Elmore, D. F.; Seagraves, P.; Skumanich, A. P. Bibcode: 1993ApJ...418..928L Altcode: The vector magnetic field structure of a small, symmetric sunspot observed very close to disk center has been explored using data from the High Altitude Observatory/National Solar Observatory Advanced Stokes Polarimeter (ASP). This instrument provides, for the first time, quantitative information on sunspot photospheric vector magnetic fields with high angular resolution, as derived from full Stokes profiles of the Zeeman-sensitive Fe I line pair at 630 nm. We find the following. (1) The penumbra contains narrow, radial "spines" of more intense magnetic field more vertically oriented than their surroundings; (2) the magnetic field diverges azimuthally away from the spine axes, as it should for a more intense intrusion of field embedded in a gravitational stratified atmosphere; (3) there are dark protrusions out from the umbra which traverse much of the penumbra and which are characterized by more vertical magnetic field; (4) the observed structure of the magnetic field in both the umbra and penumbra is stable over the 30 minute duration of our observing sequence; (5) we do not find a tight correlation of field inclination with intensity in the penumbra; (6) at the outer edge of the penumbra, the field penetrates the photosphere at an average angle of about 70° from the vertical; (7) outside of the penumbra the sunspot field forms a canopy which is directly observed by our technique; (8) outside of, but close to the sunspot, there are small magnetic features of mixed polarity that are rather highly inclined to the vertical, presumably as influenced by the sunspot canopy; (9) away from the sunspot, the isolated magnetic elements have nearly vertical orientation. These observations suggest that magnetic buoyancy, in addition to thermal buoyancy, plays an important role in maintaining the observed structure in sunspot penumbra. Title: The Magnetohydrodynamics of Umbral Flux Tubes. II. Spectroscopic Properties Authors: Degenhardt, Detlev; Lites, Bruce W. Bibcode: 1993ApJ...416..875D Altcode: We apply a recently developed magnetohydrodynamic model for flux tube systems within sunspot umbrae for a range of model parameters appropriate to umbral dots. The results are used to generate synthetic observations of umbral dots, which we then compare to recent observational data taken from the literature.

Below the umbral surface, our umbral flux tube models are characterized by (1) reduced (but nonzero) field strength relative to the surrounding umbra, (2) a relative temperature enhancement, and (3) an assumed upflow which advects heat toward the surface, thus making the dot brighter than its surroundings. In this paper we vary the free parameters which characterize our model to explore the range of physical conditions within umbral dots as admitted by our model. We find that the equivalent width of lines of Fe I and Fe ii within the umbral flux tubes, relative to the surrounding umbra, provides specific quantitative constraints for selection among parameters specified at the lower boundary of our models. Available observations do not clearly delimit line strengths; however, empirical models based on recent observations by Sobotka et al. suggest that our models with strong upflow (15 m s-1) and modest temperature enhancement relative to the surrounding umbra at 100 km below the visible surface best characterize umbral dots.

We show that, even though the flow velocity is large well above the photospheric surface of our model umbral flux tubes, the line-of-sight component of velocity as inferred from the zero crossing of the Stokes V profile is (in general) smaller than 0.5 km s-1. Likewise, the amplitude asymmetry of the Stokes V profiles arising from our models are correspondingly quite weak (<3%). Title: Dynamics of the Solar Chromosphere. I. Long-Period Network Oscillations Authors: Lites, B. W.; Rutten, R. J.; Kalkofen, W. Bibcode: 1993ApJ...414..345L Altcode: We analyze differences in solar oscillations between the chromospheric network and internetwork regions from a 1 hr sequence of spectrograms of a quiet region near disk center. The spectrograms contain Ca II H, Ca I 422.7 nm, and various Fe I blends in the Ca II H wing. They permit vertical tracing of oscillations throughout the photosphere and into the low chromosphere. We find that the rms amplitude of Ca II H line center Doppler fluctuations is about 1.5 km/s for both network and internetwork, but that the character of the oscillations differs markedly in these two regions. Within internetwork areas the chromospheric velocity power spectrum is dominated by oscillations with frequencies at and above the acoustic cutoff frequency. They are well correlated with the oscillations in the underlying photosphere, but they are much reduced in the network. In contrast, the network Ca II H line center velocity and intensity power spectra are dominated by low-frequency oscillations with periods of 5-20 min. Their signature is much clearer in our Ca II H line center measurements than in previously used diagnostics which are contaminated by signals from deeper layers. We find that these long-period oscillations are not correlated with underlying photospheric disturbances, and we discuss their nature. Title: The Morphology of Flare Phenomena, Magnetic Fields, and Electric Currents in Active Regions. I. Introduction and Methods Authors: Canfield, Richard C.; de La Beaujardiere, J. -F.; Fan, Yuhong; Leka, K. D.; McClymont, A. N.; Metcalf, Thomas R.; Mickey, Donald L.; Wuelser, Jean-Pierre; Lites, Bruce W. Bibcode: 1993ApJ...411..362C Altcode: Electric current systems in solar active regions and their spatial relationship to sites of electron precipitation and high-pressure in flares were studied with the purpose of providing observational evidence for or against the flare models commonly discussed in the literature. The paper describes the instrumentation, the data used, and the data analysis methods, as well as improvements made upon earlier studies. Several flare models are overviewed, and the predictions yielded by each model for the relationships of flares to the vertical current systems are discussed. Title: A Magnetograph Comparison Workshop Authors: Jones, H.; Bogart, R.; Canfield, R.; Chapman, G.; Henney, C.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet, V.; Rabin, D.; Ulrich, R.; Walton, S. Bibcode: 1993BAAS...25.1216J Altcode: No abstract at ADS Title: Some challenging problems of the structured and dynamical solar atmosphere. Authors: Lites, B. W. Bibcode: 1993ESASP1157...11L Altcode: 1993srfs.book...11L Several current but long-standing problems of the solar photosphere are briefly presented, along with some suggestions which may help resolved them in the future. Particular emphasis is given to phenomena and processes involving the solar magnetic field. These problems may best be addressed in the future by means of carefully coordinated ground- and space-based observations. Title: Intercomparison of Seven Magnetographs Authors: Walton, S. R.; Bogart, R. S.; Chapman, G. A.; Henney, C.; Jones, H.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet, V.; Rabin, D. Bibcode: 1993BAAS...25.1205W Altcode: No abstract at ADS Title: The Absorption of p-Modes by Sunspots: Variations with Degree and Order Authors: Bogdan, Thomas J.; Brown, Timothy M.; Lites, Bruce W.; Thomas, John H. Bibcode: 1993ApJ...406..723B Altcode: A spherical harmonic decomposition of the p-modes into inward and outward propagating waves is employed to investigate the absorption of solar p-modes by an isolated sunspot. The absorption coefficient (averaged over frequency and azimuthal order) is found to increase with increasing horizontal wavenumber k over the range 0-0.8/Mm. For larger horizontal wavenumbers, in the range 0.8-1.5/Mm, the absorption coefficient decreases with increasing k. The absorption along each individual p-mode ridge tends to peak at an intermediate value of the spherical harmonic degree in the range 200-400. The highest absorption is found along the p(1) ridge, and the absorption decreases with increasing radial order. Title: The polarization properties of Fe ii 614.9 nm Authors: Lites, Bruce W. Bibcode: 1993SoPh..143..229L Altcode: The anomalous Zeeman splitting of the FeII line at 614.9 nm results in four unusual properties of the polarization signature of this line in the presence of magnetic fields: the absence of linear polarization, no magneto-optical effect, the independence of intensity at line center from the inclination of the field, and a depolarizing self-absorption. The origin of these properties is illustrated in terms of the transfer of line radiation in an idealized solar atmosphere. Title: The Magnetohydrodynamics of Umbral Flux Tubes. I. Theoretical Model Authors: Degenhardt, Detlev; Lites, Bruce W. Bibcode: 1993ApJ...404..383D Altcode: The MHD consequences of thin vertical gas columns embedded in sunspot umbrae are investigated in order to elucidate the nature of umbral fine structure, specifically, umbral dots, from a theoretical perspective. Both these gas columns and the surrounding umbral stratification are permeated by a magnetic field, the field strength of the column being weaker than that of the ambient medium. The steady-state MHD equations are solved numerically in the thin flux tube approximation. The geometry of the flux tube, which in all cases is a rapidly converging column with increasing height in the atmosphere, is determined. At heights representing the observable layers of the umbra, the strengths of the magnetic fields inside and outside of the umbral flux tube approach a common value. It is shown that either high temperatures at the lower boundary of the umbral flux tubes or strong upflows are needed in order to produce bright continuum structures. Title: Early Results from HAO/NSO Advanced Stokes Polarimeter Authors: Lites, B. W.; Elmore, D. F.; Tomczyk, S.; Seagraves, P.; Skumanich, A.; Streander, K. V. Bibcode: 1993ASPC...46..173L Altcode: 1993mvfs.conf..173L; 1993IAUCo.141..173L No abstract at ADS Title: Oscillations of the Magnetic Network Authors: Lites, B. W.; Rutten, R. J.; Kalkofen, W. Bibcode: 1993ASPC...46..530L Altcode: 1993mvfs.conf..530L; 1993IAUCo.141..530L No abstract at ADS Title: Asymmetric Stokes Q, U and V Line Profiles Observed in Sunspots Authors: Sanchez Almeida, J.; Lites, B. W. Bibcode: 1993ASPC...46..177S Altcode: 1993mvfs.conf..177S; 1993IAUCo.141..177S No abstract at ADS Title: The Advanced Stokes Polarimeter - A new instrument for solar magnetic field research Authors: Elmore, D. F.; Lites, B. W.; Tomczyk, S.; Skumanich, A. P.; Dunn, R. B.; Schuenke, J. A.; Streander, K. V.; Leach, T. W.; Chambellan, C. W.; Hull, H. K. Bibcode: 1992SPIE.1746...22E Altcode: A new Stokes polarimeter for high spatial resolution quantitative measurement of magnetic fields at multiple heights in the solar atmosphere has been constructed by the National Center for Atmospheric Research and the National Solar Observatory. The instrument uses the Vacuum Tower Telescope at Sunspot, New Mexico, and its existing horizontal spectrograph, universal birefringment filter, and image motion stabilization system. The polarimeter uses a rotating retarder polarization modulator with polarization calibration optics. Multiple paired CCDs are used for detection followed by video processing to produce spatial maps of the full state of polarization in restricted regions of the solar spectrum. Two spectral regions encompassing lines sensitive to the Zeeman effect, which form in the photosphere and low chromosphere, are recorded simultaneously. Significant developments include: construction of the new telescope post focus optical arrangement, creation of a polarization model for the telescope, construction of high-speed, low-noise solid state cameras, and construction of computer hardware for receiving and processing high-rate 12-bit digital data. Title: Observation and Interpretation of the Asymmetric Stokes Q, U, and V Line Profiles in Sunspots Authors: Sanchez Almeida, J.; Lites, B. W. Bibcode: 1992ApJ...398..359S Altcode: We present a first approach to systematic characterization and interpretation of observed asymmetries of Stokes profiles as a function of spatial position within sunspots. Spatial maps of the full Stokes profiles of Fe I 6302.5 A gathered in large sunspots using the HAO Stokes II instrument reveal asymmetries that vary systematically across large sunspots observed during 1980. We use the inversion technique by Landolfi to extract the velocity gradients along the line of sight (LOS) which give rise to these asymmetries. The gradients derived from full Stokes profiles are in agreement with previous characterizations of the Evershed flow derived from Stokes I profiles alone (i.e., a flow increasing with depth in the atmosphere). By coupling this semiempirical gradient of velocity with a magnetic field inclination varying along the LOS, the synthesized profiles are able to mimic basic observed features of the broad-band circular polarization present in our data and observed previously by others. This characterization has magnetic field lines which become progressively more horizontal with depth in the penumbra. Title: Localized Sources of Propagating Acoustic Waves in the Solar Photosphere Authors: Brown, Timothy M.; Bogdan, Thomas J.; Lites, Bruce W.; Thomas, John H. Bibcode: 1992ApJ...394L..65B Altcode: A time series of Doppler measurements of the solar photosphere with moderate spatial resolution is described which covers a portion of the solar disk surrounding a small sunspot group. At temporal frequencies above 5.5 mHz, the Doppler field probes the spatial and temporal distribution of regions that emit acoustic energy. In the frequency range between 5.5 and 7.5 mHz, inclusive, a small fraction of the surface area emits a disproportionate amount of acoustic energy. The regions with excess emission are characterized by a patchy structure at spatial scales of a few arcseconds and by association (but not exact co-location) with regions having substantial magnetic field strength. These observations bear on the conjecture that most of the acoustic energy driving solar p-modes is created in localized regions occupying a small fraction of the solar surface area. Title: The Advanced Stokes Polarimeter: A New Instrument for Solar Magnetic Field Research Authors: Tomczyk, S.; Elmore, D. F.; Lites, B. W.; Dunn, R. B.; Skumanich, A.; Schuenke, J. A.; Streander, K. V.; Leach, T. W.; Chambellan, C. W.; Lacey, L. B. Bibcode: 1992AAS...180.5108T Altcode: 1992BAAS...24..814T A new Stokes polarimeter for high spatial resolution quantitative measurement of magnetic fields at multiple heights in the solar atmosphere has been constructed by the National Center for Atmospheric Research and the National Solar Observatory. The instrument has become operational at the Vacuum Tower Telescope at Sunspot, New Mexico and uses its existing horizontal spectrograph, universal birefringent filter, and image motion stabilization system. To these optical systems we have added a rotating wave plate polarimeter and polarization calibration optics. Multiple CCDs are used for detection followed by video processing in order to produce polarization maps of solar regions from several spectrum lines simultaneously. Significant developments include: a) construction of the new VTT post focus optical arrangement, b) creation of a polarization model for the VTT, c) construction of high speed, low noise CCD cameras, and d) construction of computer hardware for receiving and processing high rate 12-bit digital data. Title: Stokes Inversion in the Presence of Canopy-Like Structures and Unresolved Flux-Tubes Authors: Skumanich, A.; Grossmann-Doerth, U.; Lites, B. W. Bibcode: 1992AAS...180.1203S Altcode: 1992BAAS...24Q.748S The issue of the Stokes polarization signature of canopy-like structures and the inversion of the resulting Stokes profiles is considered for a self-consistent flux tube (sheet) model. It is found that when the `canopy' and its attendant current sheet have an optical thickness at line center tau_0 <= 5, the intensity and net polarization profiles become decoupled. An effective inversion strategy is to reduce or eliminate the role of the intensity parameter. The Milne-Eddington (ME) analytic inversion in current use is easily adapted for this purpose. It is found that the use of a magnetic fill factor allows for an approximate compensation for the presence of a field discontinuity along the line of sight but a more accurate procedure is to restrict the inversion to the net polarization profiles. In the case of sufficiently thin canopies the ME inversion, when reduced to the Sears form, yields fields within ~ 100 G of the true field. When the Stokes profiles are averaged over the flux sheet to simulate the effects of limited angular resolution, the fill factor strategy yields an accurate measure of both the axial field and the width of the flux sheet at tau_0 =~ 1 for observing angles <= 35(deg) to the normal. For larger angles, opacity shielding occurs and reduced fields are derived. Title: Very high spatial resolution two-dimensional solar spectroscopy with video CCDs Authors: Johanneson, A.; Bida, T.; Lites, B.; Scharmer, G. B. Bibcode: 1992A&A...258..572J Altcode: We have developed techniques for recording and reducing spectra of solar fine structure with complete coverage of two-dimensional areas at very high spatial resolution and with a minimum of seeing-induced distortions. These new techniques permit one, for the first time, to place the quantitative measures of atmospheric structure that are afforded only by detailed spectral measurements into their proper context. The techniques comprise the simultaneous acquisition of digital spectra and slit-jaw images at video rates as the solar scene sweeps rapidly by the spectrograph slit. During data processing the slit-jaw images are used to monitor rigid and differential image motion during the scan, allowing measured spectrum properties to be remapped spatially. The resulting quality of maps of measured properties from the spectra is close to that of the best filtergrams. We present the techniques and show maps from scans over pores and small sunspots obtained at a resolution approaching 1/3 arcsec in the spectral region of the magnetically sensitive Fe I lines at 630.15 and 630.25 nm. The maps shown are of continuum intensity and calibrated Doppler velocity. More extensive spectral inversion of these spectra to yield the strength of the magnetic field and other parameters is now underway, and the results of that analysis will be presented in a following paper. Title: First Results from the Advanced Stokes Polarimeter Authors: Lites, B. W.; Dunn, R. B.; Elmore, D. F.; Tomczyk, S.; Skumanich, A.; Streander, K. V. Bibcode: 1992AAS...180.1201L Altcode: 1992BAAS...24..747L The Advanced Stokes Polarimeter (ASP) is a collaborative program between the High Altitude Observatory (HAO) and the National Solar Observatory (NSO) to investigate the physics of solar active regions though quantitative measurements of vector magnetic fields. First scientific results from the ASP were obtained during an observing run in March, 1992, when high resolution Stokes profile maps of active regions were obtained under good seeing conditions. The ASP measures simultaneously the full Stokes profiles in photospheric Fe I lines near 630 nm and in the temperature minimum/low chromospheric Mg I b-lines at 517 nm. We present scans of an isolated small sunspot near disk center, and we discuss the fine structure of the vector field within this sunspot and in the magnetic elements surrounding it. Observations of a complex active region near the east limb will also be presented. This active region produced a flare during the observational sequence. Title: Sunspot Oscillations - Observations and Implications Authors: Lites, B. W. Bibcode: 1992ASIC..375..261L Altcode: 1992sto..work..261L This review summarizes the current state of observational knowledge of oscillations within sunspots. Three classes of oscillations are discussed: (1) oscillations measured in the photosphere of sunspot umbrae which are dominated by the apparent response of the umbral photosphere to the 5-minute p-mode oscillations, (2) the energetic oscillations in the umbral chromosphere, and (3) oscillations observed in the penumbral chromosphere. Observational results are critically examined. The theory of sunspot oscillations is discussed in light of the observations, and new observational tests are proposed. Title: Phase Delays in the Vertical Propagation of Waves in the Solar Atmosphere Authors: Chipman, E. G.; Lites, B. W. Bibcode: 1991BAAS...23R1389C Altcode: No abstract at ADS Title: High-Resolution Spectra of Solar Magnetic Features. II. Magnetic Fields of Umbral Brightenings Authors: Lites, Bruce W.; Bida, Thomas A.; Johannesson, A.; Scharmer, G. B. Bibcode: 1991ApJ...373..683L Altcode: The spectra of Fe I and Fe II Zeeman-sensitive lines enhanced by video processing of CCD images are considered. The magnetic-field variation within umbras is obtained from the nearly complete Zeeman splitting of the Stokes I profile. It is shown that small brightenings within umbrae have magnetic fields nearly equal to or slightly smaller than that of the darker surroundings; these features are also nearly at rest with respect to their surroundings. It is noted that the absence of significant motions in umbral dots implies that radiation transports most of the energy at and immediately below the surface. The small size of the dots implies that, if convective plumes transport energy below the surface of sunspot umbrae, they should have both a lateral extent and a depth of their upper boundary comparable to or smaller than the size of the dot. Title: Long-Period Oscillations of the Chromospheric Network Authors: Lites, B. W.; Kalkofen, W.; Rutten, R. J. Bibcode: 1991BAAS...23.1050L Altcode: No abstract at ADS Title: LEST Progress Authors: Lites, B. Bibcode: 1991BAAS...23.1034L Altcode: No abstract at ADS Title: The derivation of vector magnetic fields from Stokes profiles: derivative versus least squares fitting techniques. Authors: Metcalf, T. R.; Canfield, R. C.; Mickey, D. L.; Lites, B. W. Bibcode: 1991sopo.work..376M Altcode: The authors present a comparison of solar magnetic fields calculated using the weak field equations of Jefferies, Lites, and Skumanich and the least squares fitting method of Skumanich and Lites. The two calculations used Fe I 6302 data from June, 1985, and are found to agree quite well up to at least 1200 G. Title: Fringes in polarizing optical elements. Authors: Lites, B. W. Bibcode: 1991sopo.work..166L Altcode: A Muller Matrix description is developed for expressing the effects of spectral fringes (channel spectra) arising from polarizing optical elements in astronomical polarimeters. This description allows one to derive the effects of fringes in a straightforward manner. The formalism is applied to the case of the rotating linear retarder that will be used in the Advanced Stokes Polarimeter (ASP). It is shown that, through proper calibration of the ASP polarimeter on a pixel-by-pixel basis, the effects of spectral fringing should not be troublesome, but these effects may be more troublesome in polarimeters which demand higher polarization accuracy. Title: Sensitivity to polarization: how can we measure weak vector magnetic fields at high angular resolution? Authors: Lites, B. W. Bibcode: 1991sopo.work..173L Altcode: The difficulties of using ground-based instrumentation to measure weak vector magnetic fields in the photosphere through polarization measurements of high precision in the visible spectrum are discussed. Title: Velocity gradients across a flaring neutral line from Stokes II measurements. Authors: Skumanich, A.; Lites, B. Bibcode: 1991sopo.work..307S Altcode: The pattern of profile reversals formed due to incomplete cancellation of the Stokes net circular polarization parameter, V, when the resolution element contains the magnetic neutral line (in the observer's frame) represents a sensitive diagnostic of the line-of-sight velocity difference between the opposite polarity regions. Typical V profile patterns found in such circumstances with the HAO/SPO Stokes II polarimeter are illustrated. Resulting velocity differences are estimated both by analytic decomposition of a specific neutral line profile and by composition of profiles from elements on opposite sides of the neutral line. Pre- and post-flare Stokes II observations of Hale Active Region ≠16604 are under such analysis. Title: The orbiting solar laboratory Authors: Lites, B. W. Bibcode: 1991AdSpR..11e.181L Altcode: 1991AdSpR..11..181L The Orbiting Solar Laboratory (OSL) is an unmanned NASA space mission which will place a relatively large aperture (1.0 m) solar telescope for optical and near-ultraviolet wavelengths into a slowly precessing polar orbit, such that the spacecraft will see continuous illumination by sunlight for about 260 days per year. Focal-plane instrumentation for this telescope will produce images and spectra from 220-1000 nm with an angular resolution of about 0.13 arcsec at 500 nm. Polarization analysis will allow detailed studies of solar magnetic fields at high resolution. The spacecraft will also carry co-observing instruments to observe at ultraviolet and X-ray wavelengths with sub-arcsecond resolution. The long duration of this mission will permit thorough study of many solar phenomena whose physical behavior is rooted in small-scale dynamical processes. Complemented by a new generation of ground-based solar instrumentation, OSL will revolutionize our observational understanding of MHD processes in the solar atmosphere. The OSL mission now holds the position as the only 1992 new-start candidate in the current NASA five-year strategic plan. Based on a 1992 startup, OSL is scheduled for launch in 1997.

The National Center for Atmospheric Research is sponsored by the National Science Foundation. Title: Preliminary results from the HAO/NSO Advanced Stokes Polarimeter prototype observing run. Authors: Lites, B. W.; Elmore, D.; Murphy, G.; Skumanich, A.; Tomczyk, S.; Dunn, R. B. Bibcode: 1991sopo.work....3L Altcode: A prototype version of the Advanced Stokes Polarimeter was operated at the Sunspot Vacuum Tower Telescope of the National Solar Observatory in May und June, 1990. Although the prototype instrument does not have the capability of the final instrument to be deployed in 1991, it nonetheless provided high spatial resolution Stokes profiles observations of a small symmetric sunspot. Analysis of these observations shows that the magnetic field at the outer edge of the penumbra of this sunspot is highly inclined with respect to the local normal (γ = 70 - 80°), in agreement with previous Stokes II measurements of larger sunspots. In addition, the axial field and flux distribution was found to be nearly identical to that of the previous Stokes II measurement. Title: High-Resolution Spectra of Solar Magnetic Features. I. Analysis of Penumbral Fine Structure Authors: Lites, B. W.; Scharmer, G. B.; Skumanich, A. Bibcode: 1990ApJ...355..329L Altcode: The Swedish Vacuum Telescope on La Palma was used to obtain spectra of the magnetic-sensitive Fe I 630.25 nm line under conditions of exceptional angular resolution (0.32 arcsec) and high spectral resolution (FWHM 2.5 pm). Simultaneous 0.02 s CCD exposures of both the spectrum and the slit-jaw image effectively 'freeze' the atmospheric seeing motions and permit unambiguous identification of the spectra of the various penumbral structures. These spectra reveal the magnetic field strength in penumbral filaments through an intensity fit of the Zeeman splitting of this line. The observations show that: (1) the field strength varies from about 2100 G near the umbra-penumbra boundary to about 900 G at the outer edge of the penumbra, (2) the observed fluctuation of penumbral magnetic field is much less dramatic than the fluctuation in intensity, (3) there is a suggestion of a rapid change in field inclination between some light and dark filaments near the edge of the penumbra, and (4) there is no obvious correlation between Doppler shift (in part due to the Evershed flow) and filament intensity. Title: High Resolution Spectroscopy of Penumbral Fine Structure Authors: Bida, T.; Lites, B. W.; Johannesson, A.; Scharmer, G. Bibcode: 1990BAAS...22..880B Altcode: No abstract at ADS Title: Stokes Profile Analysis and Vector Magnetic Fields. V. The Magnetic Field Structure of Large Sunspots Observed with Stokes II Authors: Lites, B. W.; Skumanich, A. Bibcode: 1990ApJ...348..747L Altcode: Results are presented on the analysis of Stokes II polarimeter data on four large sunspots during 1980, yielding the vector magnetic field structure and thermodynamic parameters of these sunspots. It is found that the magnetic field occupies significant fractions of the area in both light and dark penumbral filaments, and that the intrinsic field does not fall below 600 G, either in the sunspot or in the surrounding plage areas, and is typically 700-800 G at the outer edge of the penumbra. The radial variation of the vector field in these sunspots does not agree with the return-flux models of Fla et al. (1982). The variation of the poloidal field strength and inclination with distance from the center of the symmetric sunspots exhibits little nonpotential character and is well represented by the potential field of a buried dipole. Title: High resolution spectra of umbral fine structure from the Swedish solar observatory at La Palma Authors: Lites, B. W.; Scharmer, G. Bibcode: 1989hsrs.conf..286L Altcode: No abstract at ADS Title: The Advanced Stokes Polarimeter Authors: Lites, B. W.; Skumanich, A. Bibcode: 1989hsrs.conf..389L Altcode: No abstract at ADS Title: Transfer of Line Radiation in a Magnetic Field Authors: Jefferies, John; Lites, Bruce W.; Skumanich, A. Bibcode: 1989ApJ...343..920J Altcode: Using a classical approach, the transfer equations are derived for spectral-line radiation in a medium which is permeated by a magnetic field. Consideration is given to solutions of these equations for the 'weak-field' case, when the Zeeman splitting is a fraction of the Doppler width, and the range of validity of such solutions. Some approximate expressions allow a simple inference of the vector-field characteristics directly from the line profiles. Title: The HAO/NSO Advanced Stokes Polarimeter Authors: Lites, B. W.; Elmore, D. F. Bibcode: 1989BAAS...21..863L Altcode: No abstract at ADS Title: The Magnetic Field Strength of Umbral Dots Authors: Lites, B. W.; Bida, T. A.; Scharmer, G. B. Bibcode: 1989BAAS...21..854L Altcode: No abstract at ADS Title: Constraints Imposed by Very High Resolution Spectra and Images on Theoretical Simulations of Granular Convection Authors: Lites, B. W.; Nordlund, Å.; Scharmer, G. B. Bibcode: 1989ASIC..263..349L Altcode: 1989ssg..conf..349L No abstract at ADS Title: Photoelectric Observations of Chromospheric Sunspot Oscillations. V. Penumbral Oscillations Authors: Lites, Bruce W. Bibcode: 1988ApJ...334.1054L Altcode: This paper presents a new analysis of observations of penumbral magneto-atmospheric oscillations in which both the spatial and temporal behavior are measured simultaneously in two spectral lines (Fe I λ5434 and Ca II λ8498) formed at widely separated heights in the atmosphere. The spatial distribution of the amplitude of oscillation indicates that the velocity perturbations are aligned with the magnetic field (1) in the inner penumbra at photospheric heights, and (2) in the outer penumbra at chromospheric heights. In the outer penumbra, it is found that the p-modes with their usual frequencies around ν = 3 mHz are the dominant feature of the oscillatory spectrum at photospheric heights, but oscillations of much lower frequencies are dominant in the chromosphere. Title: Stokes Profile Analysis and Vector Magnetic Fields. IV. Synthesis and Inversion of the Chromospheric MG i B Lines Authors: Lites, B. W.; Skumanich, A.; Rees, D. E.; Murphy, G. A. Bibcode: 1988ApJ...330..493L Altcode: An analytic solution to the transfer equations for polarized radiation which allows for departures from LTE in the overall excitation of a chromospheric line is discussed, and a method of least-squares inversion is applied to profiles of Mg I b lines at 5172.7 and 5183.6 A observed in December 1978. An analytic form expressing the source function dependence on line-center optical depth leads to a generalization of an existing least-squares procedure which is found to be effective in recovering the magnetic field from simulated Stokes profiles under specified conditions. Reasonable magnetic field values are obtained if a macroturbulent profile smearing of 1-2 km/s is used and if the profiles are corrected for scattered light. Title: High Resolution Observations of Penubral Magnetic Fields Authors: Lites, B. W.; Scharmer, G. B. Bibcode: 1988BAAS...20..681L Altcode: No abstract at ADS Title: Sunspot Seismology Authors: Thomas, J. H.; Lites, B. W.; Abdelatif, T. E. Bibcode: 1988IAUS..123..181T Altcode: The 5 minute oscillations in a sunspot umbra are the response of the sunspot to forcing by the 5 minute p-modes in the surrounding convection zone (Thomas 1981). This interaction of solar p-modes with a sunspot can be used to probe the structure of a sunspot beneath the visible surface of the Sun (Thomas, Cram, and Nye 1982). Here the authors report briefly the results of both an observational study and a simple theoretical analysis of this interaction. Title: Stokes Profile Analysis and Vector Magnetic Fields. I. Inversion of Photospheric Lines Authors: Skumanich, A.; Lites, B. W. Bibcode: 1987ApJ...322..473S Altcode: The authors consider improvements to the Auer, Heasley, and House method for the analytic inversion of Stokes profiles via nonlinear least squares. In the application of this method to actual sunspot observations, the authors have found that its simplifications often yield erroneous solutions or nonconvergent behavior. By including damping wings and magneto-optical birefringence and by decoupling the intensity profile from the three-vector polarization profile in the analysis, the authors develop a more robust inversion method that provides a more reliable and accurate estimate of sunspot vector magnetic fields without significant loss of economy. Title: The Polarization Properties of Model Sunspots: The Broad-Band Polarization Signature of the Schlueter-Temesvary Representation Authors: Skumanich, A.; Lites, B. W. Bibcode: 1987ApJ...322..483S Altcode: The properties and diagnostic content of integrated-over-wavelength Zeeman-induced polarization in spectral lines formed in sunspots are investigated. The net circular polarization (NCP) generated by a continuously varying velocity field parallel to a constant magnetic field with arbitrary inclination is shown to follow the algebraic expression for the step-velocity model of Auer and Heasley (1978). Although application of the analysis to parameters representative of sunspots fails to yield the observed broadband NCP radius pattern, the introduction of magnetic field gradients and magnetooptical birefringence is found to result in a pattern similar to that observed. Title: Rotating waveplates as polarization modulators for Stokes polarimetry of the sun: evaluation of seeing-induced crosstalk errors Authors: Lites, Bruce W. Bibcode: 1987ApOpt..26.3838L Altcode: 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. Title: Stokes Profile Analysis and Vector Magnetic Fields. III. Extended Temperature Minima of Sunspot Umbrae as Inferred from Stokes Profiles of MG i lambda 4571 Authors: Lites, B. W.; Skumanich, A.; Rees, D. E.; Murphy, G. A.; Carlsson, M. Bibcode: 1987ApJ...318..930L Altcode: Observed Stokes profiles of Mg I 4571 A are analyzed as a diagnostic of the magnetic field and thermal structure at the temperature minimum of sunspot umbrae. Multilevel non-LTE transfer calculations of the Mg I-II-III excitation and ionization balance in model umbral atmospheres show: (1) Mg I to be far less ionized in sunspot umbrae than in the quiet sun, leading to greatly enhanced opacity in 4571 A, and (2) LTE excitation of 4571 A. Existing umbral models predict emission cores of the Stokes I profile due to the chromospheric temperature rise. This feature is not present in observed umbral profiles. Moreover, such an emission reversal causes similar anomalous features in the Stokes Q, U, V profiles, which are also not observed. Umbral atmospheres with extended temperature minima are suggested. Implications for chromospheric heating mechanisms and the utility of this line for solar vector magnetic field measurements are discussed. Title: Synthesis and Inversion of the Chromospheric Mg I ????-Line Stokes Profiles Authors: Murphy, G. A.; Rees, D. E.; Lites, B. W.; Skumanich, A. Bibcode: 1987BAAS...19..938M Altcode: No abstract at ADS Title: The Vector Magnetic Field Structure of Large Sunspots Observed with Stokes II Authors: Lites, B. W.; Skumanich, A.; Lundgren, S. Bibcode: 1987BAAS...19..945L Altcode: No abstract at ADS Title: Simultaneous Measurements of Sunspot Umbral Oscillations in the Photosphere, Chromosphere, and Transition Region Authors: Thomas, John H.; Lites, Bruce W.; Gurman, Joseph B.; Ladd, Edwin F. Bibcode: 1987ApJ...312..457T Altcode: Measurements of umbral oscillations in a sunspot were made simultaneously from space (with the SMM/UVSP instrument) in the C IV transition-region line and from the ground (with the tower telescope at NSO/sunspot) in spectral lines formed in the photosphere and chromosphere. The power spectra of velocity and intensity variations show multiple peaks in the 3 min band (4.5-10 mHz). A strong oscillation at 5.5 mHz is coherent between the chromosphere and transition region. Another strong oscillation mode at 7.5 mHz is coherent between the photosphere and transition region and appears to have a node in the chromosphere. The rms velocity in the 3 min band is a little over 12 km/sec in both the chromosphere and transition region, but the kinetic energy density is lower in the transition region (by a factor of 10 or more) due to the lower mass density there. These measurements of amplitude and phase of the waves at different heights provided a new, independent method of testing or fitting models of the vertical temperature distribution in the umbral chromosphere and transition regions. Title: Rotating waveplates as polarization modulators for Stokes polarimetryof the sun: evaluation of seeing-induced crosstalk errors. Authors: Lites, B. W. Bibcode: 1987LFTR...23.....L Altcode: No abstract at ADS Title: On the need for a large aperture solar telescope for quantitative studies of vector magnetic fields. Authors: Lites, B. W. Bibcode: 1987LFTR...22.....L Altcode: It is demonstrated that quantitative measures of the solar vector magnetic field demand at once high spatial resolution, high spectral resolution, and simultaneous wavelength coverage of line profiles. These requirements dictate a large aperture telescope in order to achieve the necessary photon flux. Title: The Interaction of Solar p-Modes with a Sunspot. I. Observations Authors: Abdelatif, Toufik E.; Lites, Bruce W.; Thomas, John H. Bibcode: 1986ApJ...311.1015A Altcode: Time series of velocity maps of two isolated sunspots and their surroundings were recorded in the Fe I line and the umbral line Ti I. Both 3 and 5 min umbral oscillations were detected at photospheric heights. The 5 min oscillations have reduced amplitude in the umbra, which appears to act as a filter in transmitting selected frequencies in the power spectrum of 5 min p-mode oscillations of the surrounding convection zone. The k-omicron power spectrum of the umbral oscillations shows this selective transmission and also shows a shift of power to longer horizontal wavelengths. This behavior is exhibited by a simple theoretical model of the interaction of p-modes with a sunspot. The 3 min umbral oscillations are concentrated in the dark central part of the umbra. In both sunspots, the kinetic energy density of the 3 min umbral oscillation in the photosphere is much greater than the corresponding kinetic energy density at chromospheric heights measured in other sunspots. Title: Radiative Transfer Diagnostics: Understanding Multilevel Transfer Calculations. I. Analysis of the Full Statistical Equilibrium Equations Authors: Skumanich, Andrew; Lites, Bruce W. Bibcode: 1986ApJ...310..419S Altcode: The sensitivity analysis method of Skumanich and Lites (1985), which makes it possible to decompose the equivalent two-level parameters of a non-LTE transition problem into their most significant excitation (source) and deexcitation (sink) terms, is reviewed and extended. In the method, the statistical equilibrium (SE) equations are solved numerically for the explicit upper and lower level occupations of a particular transition under various combinations of perturbations of atomic rates, both collisional and radiative, about an exact numerical solution. The sensitivity analysis is applied to the formation of the hydrogen spectrum in a representative model of the solar atmosphere. Although the numerical method is not a means of avoiding the direct algebraic solution of the SE equations, it reduces the burden of identifying the most significant terms along the (N-1)-factorial terms that occur in such a solution. Title: Sunspot Umbral Oscillations in the Photosphere, Chromosphere, and Transition Region Authors: Thomas, J. H.; Lites, B. W.; Gurman, J. B.; Ladd, E. F. Bibcode: 1986BAAS...18..678T Altcode: No abstract at ADS Title: Extended Temperature Minima of Sunspot Umbrae Authors: Lites, B. W.; Skumanich, A.; Rees, D. E.; Murphy, G. A.; Carlsson, M. Bibcode: 1986BAAS...18..662L Altcode: No abstract at ADS Title: Photoelectric Observations of Chromospheric Sunspot Oscillations. IV. The CA II H Lines and He i lambda 10830 Authors: Lites, B. W. Bibcode: 1986ApJ...301.1005L Altcode: Simultaneous observations of profiles of He I λ10830 and the Ca II H line in sunspot umbrae have been made with the Tower telescope, echelle spectrograph, and multidiode array at the National Solar Observatory/Sunspot. These observations reveal the nature of fluid motions in the upper chromosphere during the cycle of umbral oscillations. Time sequences of profiles show that the chromospheric He I line is in weak absorption during all phases of the umbral oscillations, and that it undergoes periodic Doppler shifts of high amplitude (up to 11 km s-1). The amplitudes and waveforms of the Doppler shifts in the He I line indicate that the oscillations are frequently nonlinear (i.e., forming shocks) and therefore contribute to the heating of the upper umbral chromosphere. Title: Photoelectric Observations of Chromospheric Sunspot Oscillations. III. Spatial Distribution of Power and Frequency in Umbrae Authors: Lites, B. W. Bibcode: 1986ApJ...301..992L Altcode: On the basis of analyses of the spatial distribution of oscillation power and frequency of data from Lites (1984), the multiple peaks frequently observed in average power spectra are noted to be due to the presence of cospatial modes with different frequencies. Changes in these modes' amplitudes and frequencies with time and place within an umbra appear to arise from an interference of modes in the driving force in the photosphere. High oscillatory power regions in the 3-min band are uncorrelated with high oscillatory power regions in the 5-min band within the umbrae, suggesting that the 5-min oscillations in the photosphere do not drive the 3-min chromospheric oscillations. These results are used to develop a consistent view of the umbral oscillation mechanism: attention is given to a photospheric resonator for fast magnetoatmospheric waves, driving the chromospheric resonator through nonlinear wave interaction. Title: The visible helium spectrum of a white-light flare. Authors: Lites, B. W.; Meidig, D. F.; Trujillo Bueno, J. Bibcode: 1986lasf.conf..101L Altcode: 1986lasf.symp..101L Emission lines of neutral and ionized helium at visible wavelengths are measured in the white-light flare of 24 April 1981. These intensities, along with accompanying profiles, are presented for the purpose of providing an observational basis for future radiative transfer models of white-light flares. Absolute intensities, both peak and integrated, are given for 14 lines of He I, and for the He II line at 4686 Å. The authors compare intensities of these lines in the white-light emitting region to intensities measured in a flare kernel that does not show significant continuum emission. From this, they infer that the white light emission arises from material at chromospheric temperatures, and not from temperatures greater than about 20,000K. A search for Stark-enhanced forbidden neighbors to the allowed He I lines in this disk flare was unsuccessful. Title: Future Directions for the Theory of Radiative Transfer in Chromospheric Structures Authors: Lites, B. W. Bibcode: 1985tphr.conf..273L Altcode: No abstract at ADS Title: Sunspot umbral oscillations in the photosphere and low chromosphere Authors: Lites, B. W.; Thomas, J. H. Bibcode: 1985ApJ...294..682L Altcode: In the present simultaneous measurement of sunspot umbrae velocity oscillations in one spectral line formed in the low photosphere, and in another formed in the low chromosphere, just above the temperature minimum, the velocity power spectrum in each is found to exhibit both 5-min and 3-min oscillations, with the kinetic energy of the latter being at least 5 times greater in the low photosphere than in the low chromosphere. The 3-min umbral oscillation has the character of a coherent, vertically standing wave in the photosphere. These results imply a photospheric, rather than chromospheric, resonant origin for the fundamental 3-min umbral oscillation. A negative phase difference at frequencies around 2 mHz suggests the presence of gravity waves in the umbra. Title: Steady flows in active regions observed with the HeI 10830 Å line Authors: Lites, B. W.; Keil, S. L.; Scharmer, G. B.; Wyller, A. A. Bibcode: 1985SoPh...97...35L Altcode: We show that the He I 10830 A line gives reliable Doppler shift measurements in the upper chromosphere above active regions. Persistent flow patterns in active regions observed near the solar limb show features previously noted in Dopplergrams using the CIV transition region ultraviolet emission line. Unlike the CIV measurements, however, the He I absorption shows a strong correlation with the line-of-sight velocity images in certain regions of some active regions. Title: The effect of line damping, magneto-optics and parasitic light on the derivation of sunspot vector magnetic fields Authors: Skumanich, A.; Lites, B. W. Bibcode: 1985svmf.nasa..341S Altcode: The least square fitting of Stokes observations of sunspots using a Milne-Eddington-Unno model appears to lead, in many circumstances, to various inconsistencies such as anomalously large doppler widths and, hence, small magnetic fields which are significantly below those inferred solely from the Zeeman splitting in the intensity profile. It is found that the introduction of additional physics into the model such as the inclusion of damping wings and magneto-optic birefrigence significantly improves the fit to Stokes parameters. Model fits excluding the intensity profile, i.e., of both magnitude as well as spectral shape of the polarization parameters alone, suggest that parasitic light in the intensity profile may also be a source of inconsistencies. The consequences of the physical changes on the vector properties of the field derived from the Fe I lambda 6173 line for the 17 November 1975 spot as well as on the thermodynamic state are discussed. A Doppler width delta lambda (D) - 25mA is bound to be consistent with a low spot temperature and microturbulence, and a damping constant of a = 0.2. Title: The inference of vector magnetic fields from polarization measurements with limited spectral resolution Authors: Lites, B. W.; Skumanich, A. Bibcode: 1985svmf.nasa..342L Altcode: A method is presented for recovery of the vector magnetic field and thermodynamic parameters from polarization measurement of photospheric line profiles measured with filtergraphs. The method includes magneto-optic effects and may be utilized on data sampled at arbitrary wavelengths within the line profile. The accuracy of this method is explored through inversion of synthetic Stokes profiles subjected to varying levels of random noise, instrumental wave-length resolution, and line profile sampling. The level of error introduced by the systematic effect of profile sampling over a finite fraction of the 5 minute oscillation cycle is also investigated. The results presented here are intended to guide instrumental design and observational procedure. Title: Least squares inversion of Stokes profiles in the presence of velocity gradients Authors: Skumanich, A.; Rees, D. E.; Lites, B. W. Bibcode: 1985svmf.nasa..306S Altcode: The Auer, Heasley and House Stokes inversion procedure in use at High Altitude Observatory is based on the analytic solution of the equation of transfer for polarized light where the representation of the thermodynamic and magnetic structure of the atmosphere is assumed to have a high degree of invariance, namely, a Milne-Eddington (ME) structure with a constant magnetic field. In the presence of invariance breaking gradients the resultant Stokes profiles are represented only approximately, if at all, by analytic forms. The accuracy of the inversion parameters and their significance as measures of actual structure are explored for the ME and the Landman-Finn sunspot models under the effects of velocity gradients. The resulting field parameters are good to a few percent and prove to be insensitive to the errors committed by the use of a ME-representation, but the resulting ME parameters yield a less precise measure of thermal structure. Title: Umbral Oscillations: Correlation of Amplitudes Between Two Chromospheric Heights Authors: Lites, B. W. Bibcode: 1985BAAS...17R.631L Altcode: No abstract at ADS Title: Sunspot Umbral Oscillations in the Photosphere and Low Chromosphere Authors: Thomas, J. H.; Lites, B. W. Bibcode: 1985BAAS...17..631T Altcode: No abstract at ADS Title: Description and operation of CHISQMO, INVRTS, VOIGEN, VOIGTV, SMEAR, RUFF, AND POSCAR in the Stokes Analysis Program Authors: Lites, B. W.; Skumanich, A. Bibcode: 1985STIN...8530991L Altcode: Some details of the computer program used to carry out the least-squares inversion of polarization profiles obtained with the HAO (High Altitude Observatory) Stokes Polarimeters I and II are documented. Improvements to the computer code originated by Auer, Heasley, and House (1977) include: magneto-optical effects, line damping, scattered light correction, instrumental broadening, and allowing the line center position to be a free parameter. The entire program has not been documented here, since various aspects of the program are still being revised and improved. Title: On The Broad-Band Circular Polarization Signature of Sunspots Authors: Skumanich, A.; Lites, B. W. Bibcode: 1985BAAS...17R.631S Altcode: No abstract at ADS Title: Steady flows in active regions observed with the He I 10830 Å line. Authors: Lites, B. W.; Keil, S. L.; Scharmer, G. B.; Wyller, A. A. Bibcode: 1985cdm..proc..287L Altcode: No abstract at ADS Title: Least squares inversion of Stokes profiles in the presence of velocity gradients. Authors: Skumanich, A.; Rees, D. E.; Lites, B. W. Bibcode: 1985NASCP2374..306S Altcode: The authors study the performance of the least squares fit when applied to theoretical profiles calculated with a realistic model of a sunspot. The model has gradients in all physical parameters including magnetic and velocity fields. This numerical experiment allows one to assess the physical significance of the Milne-Eddington and mean field parameters provided by the inversion. Observed Stokes profiles invariably have asymmetric distortions due to velocity gradients in the solar atmosphere. The inversion method symmetrizes the profiles prior to fitting and it is important to know how this affects the inference on the magnetic vector. Title: Chromospheric diagnostics and modelling; Proceedings of the Conference, Sunspot, NM, August 13-16, 1984 Authors: Lites, B. W. Bibcode: 1985cdm..proc.....L Altcode: The conference presents papers on the observed structure of the chromosphere, recent thermal models and modeling techniques, chromospheric magnetic field structure, chromospheric heating and dynamics, and new and proposed observational diagnostics. Attention is focused on HRTS observations of the solar chromosphere and transition zone, an interpretation of H-alpha observations of chromospheric fine structure, an inhomogeneous model of the chromosphere, Ca II K resonance line polarization, magnetic canopies and models of the solar chromosphere, and mechanisms for chromospheric heating. Other topics include the dynamical behavior of a theoretical chromosphere model, Alfvenic heating of the chromosphere and corona, cool plasma at the base of the solar chromosphere revealed by infrared bands of carbon monoxide, and Ayres' bifurcated solar model. Title: Radiative transfer diagnostics: Understanding multi-level transfer calculations. Authors: Skumanich, A.; Lites, B. W. Bibcode: 1985ASIC..152..175S Altcode: 1985pssl.proc..175S The authors present a method of interpreting the solution to a multi-level, multi-transition non-LTE transfer problem. The method respresents the solutions in terms of equivalent two-level forms with a scattering and a source term. The resulting individual quenching probability, i.e. the difference of the scattering albedo from one, and source term are then decomposed by a perturbation method into their principal dependence on collisional and/or radiative rates. The method is illustrated by considering the excitation and ionization of hydrogen in the VAL 3C model of the quiet sun chromosphere. Title: The inference of vector magnetic fields from polarization measurements with limited spectral resolution. Authors: Lites, B. W.; Skumanich, A. Bibcode: 1985NASCP2374..342L Altcode: The authors present a method for recovery of the vector magnetic field and thermodynamic parameters from polarization measurements of photospheric line profiles measured with filtergraphs. Title: The effect of line damping, magneto-optics and parasitic light on thederivation of sunspot vector magnetic fields. Authors: Skumanich, A.; Lites, B. W. Bibcode: 1985NASCP2374..341S Altcode: No abstract at ADS Title: Future directions for the theory of radiative transfer in chromospheric structures. Authors: Lites, B. W. Bibcode: 1985MPARp.212..273L Altcode: The treatment of the theory of radiative transfer as applied to both modelling of the chromosphere and analysis of chromospheric spectra is reviewed. Topics for continued research are discussed, with emphasis on understanding the physics of the chromospheric phenomenon. Special attention is paid to theoretical developments that may be clarified by observations gathered by the Solar Optical Telescope. Title: Observational aspects of sunspot oscillations. Authors: Lites, B. W. Bibcode: 1984ESASP.220..207L Altcode: 1984ESPM....4..207L Several new observational results of oscillations in sunspots are presented. Observations of umbral oscillations in Ca II H and He I 10830 Å show that they have high amplitude in the upper chromosphere. The umbral oscillations have several co-spatial frequency modes. Title: The H− equilibrium using coupled rate equations for H−, H, H+, H2, and H2+ Authors: Lites, B. W.; Mihalas, D. Bibcode: 1984SoPh...93...23L Altcode: We formulate rate equations for the reaction network coupling H, H−, H+, H2, and H2+. We attempt to systematize the notation, and to write the equations in a form suitable for modern computational methods of handling the coupled rate equations and radiative transfer equations, for both dynamical and static atmospheres. We have accounted for more processes than are generally considered in most current work; some of these may have an impact on the equilibrium of H− (hence its opacity) and on charge conservation (hence the proton density) in the atmospheres of solar-type stars. Title: Photoelectric observations of chromospheric sunspot oscillations. II - Propagation characteristics Authors: Lites, B. W. Bibcode: 1984ApJ...277..874L Altcode: Measurements of oscillations in umbrae and penumbrae using the line pairs (Ca II lambda 8498 - lambda 8542) and (Fe I lambda 5434 - Ca II lambda 8498) are presented for seven sunspots and 11 observing runs. In the umbral chromosphere, the observations reported here, taken with other measurements of umbral oscillations, suggest that the oscillations are upward propagating acoustic (or slow mode) disturbances, and that they become nonlinear and develop into shock waves in the upper layers. They cause a significant increase in the radiative output of the umbral chromosphere, indicating the possibility of nonthermal heating at these levels. On the basis of this picture, umbral chromospheres have a greater physical extent in height than predicted by umbral models with coronal pressures greater than those found in the quiet sun. Oscillations are present in the outer regions of penumbrae with frequencies and phase relationships that suggest the possibility of magneto-gravity waves. Title: The Color Temperature of a Sunspot Penumbra Authors: Lites, B. W. Bibcode: 1984SoPh...90....1L Altcode: The new Multi-Diode Array and the recently modified Universal Birefringent Filter were used at the Vacuum Tower Telescope at the Sacramento Peak National Observatory to measure the continuum color temperature of a sunspot penumbra between 428.4 and 667.6 nm. The results show that the color temperatures within the penumbral structures closely follow a measure of the wavelength average of the brightness temperature. These observations suggest that, if the dark penumbral filaments overlie a normal quiet photosphere, they are opaque to the radiation from below. Title: Oscillations in a Sunspot and the Surrounding Photosphere Authors: Abdelatif, T. E.; Lites, B. W.; Thomas, J. H. Bibcode: 1984ssdp.conf..141A Altcode: Velocity oscillations at photospheric heights in a sunspot and its surroundings have been measured. The average temporal power spectrum of oscillations in the sunspot umbra shows the five-minute oscillations splitting into several distinct modes and also shows the existence of the three-minute umbral oscillation at photospheric heights, with greater kinetic energy density than in the chromosphere. Title: A Diagnostic for the Distribution of Medium to Small-Scale Chromospheric Motions Authors: Lites, B. W. Bibcode: 1984ssdp.conf..157L Altcode: The shapes of the line cores of self-reversed optically-thick chromospheric lines provide a sensitive measure of chromospheric macro- and microturbulence. Title: An Estimation of the Fluctuations in the Extreme Limb of the Sun Authors: Lites, B. W. Bibcode: 1983SoPh...85..193L Altcode: Detailed computations of synthetic solar limb curves are carried out for the purpose of estimating the effects of inhomogeneities in the solar atmosphere upon the observed limb position. Methods of determining the limb position given a solar limb curve are compared. The method of finding the locus of a fixed intensity level with respect to the average disk-center intensity at a given wavelength seems to be the most tractable definition to use on noise free data. It is found that limb fluctuations due to the solar 5-min p-mode oscillations produce a fluctuation in the limb height of about 6 km (0.008 arc sec) rms. Limb fluctuations due to granulation and chromospheric structure are much smaller. The wavelength dependence of the solar H− opacity causes the height of the limb to increase by about 35 km between 400 and 850 nm, thus leading to a `limb reddening' at the extreme limb of the Sun. Title: Oscillations in Sunspots and the Surrounding Photosphere Authors: Abdelatif, T.; Lites, B. W.; Thomas, J. H. Bibcode: 1983BAAS...15R.719A Altcode: No abstract at ADS Title: A model of a sunspot chromosphere based on OSO 8 observations Authors: Lites, B. W.; Skumanich, A. Bibcode: 1982ApJS...49..293L Altcode: OSO 8 spectrometer observations of the H I, Mg II, and Ca II resonance lines of a large quiet sunspot during November 16-17, 1975, along with a C IV line of that event obtained by a ground-based spectrometer, are analyzed together with near-simultaneous ground-based Stokes measurements to yield an umbral chromosphere and transition region model. Features of this model include a chromosphere that is effectively thin in the resonance lines of H I and Mg II, while being saturated in Ca II, and an upper chromospheric structure similar to that of quiet-sun models. The similarity of the upper chromosphere of the sunspot umbra to the quiet-sun chromosphere suggests that the intense magnetic field plays only a passive role in the chromospheric heating mechanism, and the observations cited indicate that solar-type stars with large areas of ordered magnetic flux would not necessarily exhibit extremely active chromosphere. Title: The vertical propagation of waves in the solar atmosphere. II Phase delays in the quiet chromosphere and cell-network distinctions Authors: Lites, B. W.; Chipman, E. G.; White, O. R. Bibcode: 1982ApJ...253..367L Altcode: The differences in the phase of the velocity oscillations between a pair of chromospheric Ca II lines was measured using the Vacuum Tower Telescope at the Sacramento Peak Observatory. The observed phase differences indicate that the acoustic modes are trapped or envanescent, rather than propagating, in the chromosphere. Systematic distinctions are found in the phase delays between quiet network and cell interior regions for both intensity and velocity oscillations in photospheric and chromospheric lines. The theory of linear perturbations in an isothermal atmosphere is invoked to interpret these differences. From this analysis it is found that one or more of the following explanations is possible: (1) the radiative damping is more effective in the network than in the cell interior; (2) the network features exclude oscillations of large horizontal wavenumber; or (3) the scale height of the chromosphere is larger in the network than in the cell interior. Title: Photoelectric observations of propagating sunspot oscillations Authors: Lites, B. W.; White, O. R.; Packman, D. Bibcode: 1982ApJ...253..386L Altcode: Repeated intensity and velocity images of a large, isolated sunspot in both the chromospheric Ca II 8542 A and photospheric Fe I 5576 line were performed. It is shown by means of a movie of the digital data for the chromospheric line that a relationship exists between the propagating umbral disturbances and the running penumbral waves. Power spectra of the oscillations show a sharp peak at a period of about 170 sec in both the velocity and intensity signals, and the oscillations at any point in the sunspot are found to be very regular. The phase relationship between the velocity and the intensity of the chromospheric oscillations contrasts with that for the quiet sun. The mechanical energy flux carried by the observed umbral disturbances does not appear to be a significant contributor to the overall energy budget of the sunspot or the surrounding active region. Title: Transition-Zone Observations of Rapid Flare Events as Observed by OSO-8 Authors: Lites, B. W. Bibcode: 1981SoPh...71..329L Altcode: The rapid dissipation of flare energy has been observed in the transition-zone line of C IV at 1548.2 Å using the University of Colorado spectrometer aboard OSO-8. Impulsive brightenings have been resolved with characteristic risetimes as low as 3.5 s. One event is analyzed in detail, in which it is inferred that the electron density is greater than 2 × 1011 cm−3 at T = 60 000 K, and that the flare energy is deposited at a rate of 2 ergs cm−3 s−1 or greater. The temporal behavior of the intensity at the center of the C IV line is consistent with a non-equilibrium ionization of C III through C V. If this event is a result of the multiple tearing mode instability as the primary energy release mechanism, then the observations indicate a pre-flare magnetic field of about 175 G. Title: A Search for Microwave Counterparts of Umbral Flashes Authors: McConnell, D.; Kundu, M. R.; Schmahl, E. J.; Lites, B. Bibcode: 1981BAAS...13..858M Altcode: No abstract at ADS Title: Observation of Vertical Phase Delays of Chromospheric Oscillations Above Sunspot Umbrae Authors: Lites, B. W. Bibcode: 1981BAAS...13..909L Altcode: No abstract at ADS Title: OSO-8 Observations of the Impulsive Phase of Solar Flares in the Transition Zone and Corona Authors: Lites, B. W.; Bruner, E. C., Jr.; Wolfson, C. J. Bibcode: 1981SoPh...69..373L Altcode: Several solar flares have been observed from their onset in C IV λ 1548.2 and 1-8 Å X-rays using instruments aboard OSO-8. In addition, microwave and Hα flare patrol data have been obtained for this study. The impulsive brightening in C IV is frequently accompanied by redshifts, interpreted as downflows, of the order of 80 km s-1. The maximum soft X-ray intensity usually arrives several minutes after the maximum C IV intensity. The most energetic C IV event studied shows a small blueshift just before reaching maximum intensity, and estimates of the mass flux associated with this upflow through the transition-zone are consistent with the increase of mass in the coronal loops as observed in soft X-rays. This event had no observable microwave burst, suggesting that electron beams did not play a major role in the chromospheric and transition-zone excitation. Lastly, our observations suggest that the frequent occurrence of violent dynamical processes at the onset of the flare are associated with the initial energy release mechanism. Title: An empirical view of the chromospheric temperature structure above a sunspot umbra Authors: Lites, B. W.; Skumanich, A. Bibcode: 1981phss.conf..152L Altcode: OSO-8 observations of the chromospheric and transition region emission lines are used to develop a temperature-based model of the chromosphere above a sunspot. The data base included observations of Lyman-alpha, Lyman-beta, the resonance lines of singly-ionized Mg, and the resonance lines of singly-ionized Ca. Details of the line profiles are provided, and features of the derived plateau model of the chromosphere are discussed. Weak reversals and broad wings in the observed Ca II lines were accounted for by assuming a 5 km/sec broadening, thus implying greater significance for the Ca II/Mg II, K/H, and k/h intensity ratios than details of the line profile shapes. The L-alpha and L-beta intensities are noted to constrain the upper chromosphere and transition region pressure to lower values than in the average quiet solar corona. Title: Steady Flows in the Chromosphere and Transition-Zone above Active Regions as Observed by OSO-8 Authors: Lites, B. W. Bibcode: 1980SoPh...68..327L Altcode: Two years of data from the University of Colorado ultraviolet spectrometer aboard OSO-8 were searched for steady line-of-sight flows in the chromosphere and transition-zone above active regions. The most conspicuous pattern that emerges from this data set is that many sunspots show persistent blueshifts of transition-zone lines indicating velocities of about 20 km s−1 with respect to the surrounding plage areas. The data show much smaller shifts in ultraviolet emission lines arising from the chromosphere: the shifts are frequently to the blue, but sometimes redshifts do occur. Plage areas often show a redshift of the transition-zone lines relative to the surrounding quiet areas, and a strong gradient of the vertical component of the velocity is evident in many plages. One area of persistent blueshift was observed in the transition-zone above an active region filament. The energy requirement of these steady flows over sunspots is discussed. Title: On the formation of Fe II lines in stellar spectra. I. Solar spatial intensity variation of lambda 3969.4. Authors: Cram, L. E.; Rutten, R. J.; Lites, B. W. Bibcode: 1980ApJ...241..374C Altcode: High-spatial-resolution solar observations of the weak Fe II lambda 3969.4 line are employed to study non-local thermodynamic equilibrium effects in Fe II line formation. This line is superposed on the wing of the Ca II H line, which raises its height of formation. The line shows extraordinary spatial intensity variations, including emission features whose contrast increases toward the limb. Observed profiles of the Fe II resonance lines in the UV are used to define formation parameters in a 15-level atomic model computation, which shows that Fe II subordinate lines are generally formed out of local thermodynamic equilibrium as a result of pumping by UV line-wing photons from the deep photosphere. For the lambda 3969.4 line, this pumping results in large sensitivity to the atmospheric structure in layers deeper than the layer of formation of the H-wing background intensity. The absence of intense emission cores in the Fe II resonance lines, the effects of partially coherent scattering, and the effects of chromospheric and photospheric inhomogeneities are discussed. It is found that emission of lambda 3969.4 provides a diagnostic of the inhomogeneous structure of the deep photosphere, for the sun and for late-type stars. Title: Photoelectric Observations of Propagating Sunspot Oscillations Authors: Lites, B. W.; White, O. R.; Packman, D. Bibcode: 1980BAAS...12..897L Altcode: No abstract at ADS Title: OSO-8 Observations of the Sunspot Chromosphere Authors: Skumanich, A.; Lites, B. W. Bibcode: 1980BAAS...12..896S Altcode: No abstract at ADS Title: Impulsive EUV bursts observed in C iv with OSO-8 Authors: Athay, R. G.; White, O. R.; Lites, B. W.; Bruner, E. C., Jr. Bibcode: 1980SoPh...66..357A Altcode: Time sequences of profiles of the λ1548 line of C IV containing 51 EUV bursts observed in or near active regions are analyzed to determine the brightness, Doppler shift and line broadening characteristics of the bursts. The bursts have mean lifetimes of approximately 150s, and mean increases in brightness at burst maximum of four-fold as observed with a field of view of 2″ × 20″. Mean burst diameters are estimated to be 3″, or smaller. All but three of the bursts show Doppler shifts with velocities sometimes exceeding 75 km s−1; 31 are dominated by red shifts and 17 are dominated by blue shifts. Approximately half of the latter group have red-shifted precursors. We interpret the bursts as prominence material, such as surges and coronal rain, moving through the field of view of the spectrometer. Title: Transition-Zone Observations of Rapid Flare Events As Observed by OSO-8 Authors: Lites, B. W. Bibcode: 1980BAAS...12..479L Altcode: No abstract at ADS Title: Line formation in the solar chromosphere. II - an optically thick region of the chromosphere-corona transition region observed with OSO 8 Authors: Lites, B. W.; Hansen, E. R.; Shine, R. A. Bibcode: 1980ApJ...236..280L Altcode: The University of Colorado ultraviolet spectrometer aboard the Orbiting Solar Observatory 8(OSO 8) has measured self-reversed profiles of the resonance line of C IV lamda 1548.2 at the limb passage of an active region. The degree of the self-reversal together with the absolute intensity of the line profile determine the electron density in the active region at 10 to the 10th/cu cm at temperatures where the C IV line is formed. The nonthermal component of the broadening velocity is no more than 14km/s, and the physical thickness of an equivalent plane-parallel slab in hydrostatic equilibrium that would give rise to the observed line profiles is about 430 km. Title: The chromosphere and transition region Authors: Canfield, R. C.; Brown, J. C.; Craig, I. J. D.; Brueckner, G. E.; Cook, J. W.; Doschek, G. A.; Emslie, A. G.; Machado, M. E.; Henoux, J. -C.; Lites, B. W. Bibcode: 1980sfsl.work..231C Altcode: 1980sofl.symp..231C The physical processes occurring as a result of the transfer of energy and momentum from the primary solar flare energy release site in the corona to the underlying chromosphere and transition region during the course of the flare are investigated through a comparison of theoretical models and observational data. Static, dynamic and hydrodynamic models of the lower-temperature chromospheric flare are reviewed. The roles of thermal conduction, radiation, fast particles and mass motion in chromosphere-corona interactions are analyzed on the basis of Skylab UV, EUV and X-ray data, and empirical and synthetic models of the chromospheric and upper photospheric responses to flares are developed. The canonical model of chromospheric heating during flares as a result of primary energy release elsewhere is found to be justified in the chromosphere as a whole, although not entirely as the temperature minimum, and a simplified model of horizontal chromospheric flare structure based on results obtained is presented. Title: Transition region chromospheric models of 24 UMa based on IUE ultraviolet spectrograms. Authors: Simon, T.; Stencel, R. E.; Lites, B. W. Bibcode: 1980PASP...92R.550S Altcode: No abstract at ADS Title: Diagnostic Use of Feii H and K Wing Emission Lines Authors: Cram, L. E.; Rutten, R. J.; Lites, B. W. Bibcode: 1980LNP...114..102C Altcode: 1980IAUCo..51..102C; 1980sttu.coll..102C No abstract at ADS Title: The vertical propagation of waves in the solar atmosphere. I. Observations of phase delay. Authors: Lites, B. W.; Chipman, E. G. Bibcode: 1979ApJ...231..570L Altcode: The Sacramento Peak Observatory Tower Vacuum Telescope, echelle spectrograph, and diode array were used to simultaneously measure velocities and intensities in three spectral lines and the continuum. According to our contribution function calculations, these wavelengths are formed at heights from the low photosphere to the chromosphere. The phase velocities of the intensity and velocity oscillations between the various heights, and the phase relations between intensity and velocity at one height were determined as a function of frequency in the range 0-11.1 mHz. The oscillations are found to be predominantly evanescent in nature for frequencies less than 4 mHz and propagating upward at higher frequencies, with phase velocities approaching the sound speed at approximately 6 mHz. We calculated the upward mechanical flux in the observed waves at two atmospheric heights by an integration in frequency, and we show that in the chromosphere the propagated power is centered at 6 mHz but is still much too small to heat the overlying atmosphere. Title: A semiempirical model of the upper flare chromosphere. Authors: Lites, B. W.; Cook, J. W. Bibcode: 1979ApJ...228..598L Altcode: Ultraviolet spectra of the August 9, 1973, flare taken with the NRL S082B spectrograph aboard ATM/Skylab have been analyzed to derive a semiempirical model of the flare chromosphere between 5500 and 100,000 K. The hydrogen radiative transfer is solved to obtain a self-consistent set of physical conditions within the flare atmosphere, from which line profiles and continua of the ions C I, C II, C III, and C IV are synthesized and compared with the observations. The model exhibits a rapid rise in the temperature at a column mass of 0.0003 g/sq cm. There is some evidence for much of the C III line emission's arising from flare kernels not exceeding 3 arcsec in size, and the C IV line profiles indicate the possibility of nonequilibrium excitation. Title: Frequency Shift of Solar Oscillations in a Flaring Region Authors: Illing, R. M. E.; Lites, B. W. Bibcode: 1979BAAS...11..398I Altcode: No abstract at ADS Title: Mass motions in impulsive flarelike brightenings as observed by OSO 8. Authors: Bruner, E. C., Jr.; Lites, B. W. Bibcode: 1979ApJ...228..322B Altcode: C IV 1548-A line profiles obtained with the University of Colorado spectrometer aboard OSO 8 reveal transient, redshifted brightenings in the chromosphere-corona transition region above active regions and sunspots. In these events the intensity rises by factors of up to 5 in less than the profile sampling interval of 27 sec. These events indicate that the emitting material is moving downward at velocities of up to 30 km/sec. The increase in line intensity and the amount of motion are consistent with the interpretation of these events as pressure waves propagating down magnetic flux loops. Title: Overlapping emission peaks in the solar C I multiplet at lambda 1560 and lambda 1657. Authors: Shine, R. A.; Lites, B. W.; Chipman, E. G. Bibcode: 1978ApJ...224..247S Altcode: Observations of the C I multiplets at 1560 and 1657 A made with the University of Colorado spectrometer on the OSO 8 satellite are presented and compared with computed profiles for the Vernazza-Avrett-Loeser solar atmosphere. These are optically thick emission lines formed in the solar chromosphere that show the central reversals typical of such lines. In each multiplet there is an interesting case of overlapping emission peaks which shows that such peaks do not constructively combine but instead weaken. This behavior is easily understood and reproduced with an optically thick, non-LTE mode of formation for these lines and is not consistent with an optically thin mechanism. We also find that the shapes of these blends are very sensitive to the magnitude of the nonthermal microvelocities. Title: Line formation in the solar chromosphere. I. The C II resonance lines observed with OSO 8. Authors: Lites, B. W.; Shine, R. A.; Chipman, E. G. Bibcode: 1978ApJ...222..333L Altcode: The temperature structure of the upper chromosphere is investigated using center-to-limb measurements of the C II resonance lines at 1335 A from the University of Colorado spectrometer aboard OSO 8. Spectrum synthesis of these lines shows them to be extremely sensitive to the temperature and the physical extent of the 20,000 K plateau proposed by Vernazza et al (1973). Hydrostatic equilibrium models of the quiet chromosphere are computed to obtain theoretical spectra of the Lyman lines and continuum as well as the center-to-limb behavior of the C II lines. Good agreement is found with observations for a plateau at 16,500 K with about 25% more material than that of Vernazza et al. Title: OSO-8 Measurements of Rapid Downflow in the Transition Zone During the Impulsive Phase of Solar Flares. Authors: Lites, B. W.; Bruner, E. C.; Hansen, E. R. Bibcode: 1978BAAS...10..441L Altcode: No abstract at ADS Title: Observations of Phase Delays and the Vertical Propagation of Waves in the Solar Atmosphere. Authors: Lites, B. W.; Chipman, E. G. Bibcode: 1978BAAS...10..415L Altcode: No abstract at ADS Title: Ultraviolet brightenings in active regions as observed from OSO-8. Authors: Lites, B. W.; Hansen, E. R. Bibcode: 1977SoPh...55..347L Altcode: Repeated raster images of solar active regions taken at the line centers of the Si IV and C IV resonance lines using the University of Colorado (CU) ultraviolet spectrometer aboard OSO-8 reveal dramatic transient brightenings of up to factors of 10. These brightenings last several minutes and frequently show a repetitive character. Inspection of simultaneous Hα flare patrol records show that these transition zone events are often associated with subflare-like brightenings in the chromosphere. These observations indicate that direct excitation or heating of material already at transition zone temperatures caused by non-thermal particle streams is inadequate to explain the degree of brightening of these lines. The measurements suggest that some process that enhances density of material at ∼105 K is occurring during these events. Title: Center-to-Limb Profiles and Spatial Variations of SiII and FeII Lines in the Solar EUV. Authors: Shine, R. A.; Lites, B. W. Bibcode: 1977BAAS....9R.325S Altcode: No abstract at ADS Title: Transient Brightenings in Transition Zone Lines. Authors: Bruner, E. C., Jr.; Lites, B. W. Bibcode: 1977BAAS....9Q.323B Altcode: No abstract at ADS Title: Preliminary results from the Orbiting Solar Observatory 8: transition-zone dynamics over a sunspot. Authors: Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman, G. J.; Shine, R. A.; Athay, R. G.; White, O. R. Bibcode: 1976ApJ...210L..97B Altcode: No abstract at ADS Title: Preliminary results from the Orbiting Solar Observatory 8: velocities in the solar chromosphere observed in the Si II lambda 1816 line. Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites, B. W.; Rottman, G. J.; Athay, R. G.; White, O. R. Bibcode: 1976ApJ...210L.103C Altcode: No abstract at ADS Title: Preliminary results from the Orbiting Solar Observatory 8: observations of optically thin lines. Authors: Shine, R. A.; Roussel-Dupre, D.; Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman, G. J.; Athay, R. G.; White, O. R. Bibcode: 1976ApJ...210L.107S Altcode: The University of Colorado spectrometer aboard OSO 8 has measured the high temperature C IV resonance lines (at 1548 and 1551 A) and the Si IV resonance lines (at 1393 and 1402 A) formed in the solar chromosphere-corona transition region. Preliminary results include studies of mean profiles, a comparison of cell and network profiles, and the behavior of the lines at the extreme solar limb. Title: Preliminary results from the Orbiting Solar Observatory 8: persistent velocity fields in the chromosphere and transition region. Authors: Lites, B. W.; Bruner, E. C., Jr.; Chipman, E. G.; Shine, R. A.; Rottman, G. J.; White, O. R.; Athay, R. G. Bibcode: 1976ApJ...210L.111L Altcode: No abstract at ADS Title: Analysis of OSO-8 Measurements of the Center-to-Limb Behavior of Solar CII Line Profiles. Authors: Lites, B. W.; Shine, R. A. Bibcode: 1976BAAS....8..501L Altcode: No abstract at ADS Title: Periodic Fluctuations in the Solar Transition Zone Authors: Bruner, E. C., Jr.; Chipman, E. G.; Shine, R. A.; Lites, B. W.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.; White, O. R. Bibcode: 1976BAAS....8Q.313B Altcode: No abstract at ADS Title: Model Calculations of Chromospheric Lines Observed by OSO-8 Authors: Shine, R. A.; Lites, B. W.; Chipman, E. G.; Rousel-Dupree, D.; Bruner, E. C., Jr.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.; White, O. R. Bibcode: 1976BAAS....8..331S Altcode: No abstract at ADS Title: Velocities in the Solar Chromosphere Observed in the CII λ1336 Line Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites, B. W.; Rottman, G. J.; Orrall, F. Q.; White, O. R.; Athay, R. G. Bibcode: 1976BAAS....8..312C Altcode: No abstract at ADS Title: OSO-8 Observations of Mean Vertical Motions in the Solar Transition Region Authors: Roussel-Dupree, D. C.; Shine, R. A.; Chipman, E. G.; Bruner, E. C., Jr.; Lites, B. W.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.; White, O. R. Bibcode: 1976BAAS....8..312R Altcode: No abstract at ADS Title: Short Period Chromospheric Oscillations Observed with OSO-8 Authors: Athay, R. G.; White, O. R.; Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Shine, R. A.; Orrall, F. Q. Bibcode: 1976BAAS....8..312A Altcode: No abstract at ADS Title: Supergranulation Velocity Fields Observed in the Solar Transition Region with OSO-8 Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.; Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Shine, R. A.; Orrall, F. Q.; Athay, R. G.; White, O. R. Bibcode: 1976BAAS....8..311N Altcode: No abstract at ADS Title: Repetitive Brightenings in Active Region Transition Zone Lines as Observed with OSO-8 Authors: Lites, B. W.; Hansen, E. R.; Shine, R. A.; Chipman, E. G.; Bruner, E. C., Jr.; Orrall, F. Q.; Athay, R. G.; White, O. R.; Rottman, G. J. Bibcode: 1976BAAS....8Q.331L Altcode: No abstract at ADS Title: High Resolution Spectroscopy From Orbiting Solar Observatory VIII: Transition Zone Dynamics Over a Sunspot Authors: Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman, G. J.; Shine, R. A.; Athay, R. G.; White, O. R. Bibcode: 1975BAAS....7..522B Altcode: No abstract at ADS Title: Persistent Velocity Fields in the Middle Chromosphere Authors: Lites, B. W.; Bruner, E. C., Jr.; Chipman, E. G.; Shine, R. A.; Rottman, G. J.; White, O. R.; Athay, R. G. Bibcode: 1975BAAS....7..522L Altcode: No abstract at ADS Title: Velocities in the Solar Chromosphere Observed in the Si II λ1816 Line Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites, B. W.; Rottman, G. J.; White, O. R.; Athay, R. G. Bibcode: 1975BAAS....7..522C Altcode: No abstract at ADS Title: OSO-8 Observations of Optically Thin Lines Authors: Shine, R. A.; Rousell-Dupree, D.; Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman, G. J.; Athay, R. G.; White, O. R. Bibcode: 1975BAAS....7Q.552S Altcode: No abstract at ADS Title: The Solar Fen 2L 3969. 4 Disk Emission Line Authors: Lites, B. W. Bibcode: 1974A&A....33..363L Altcode: Summary. The recent identification by Engvold and Halvorsen (1973) of the solar Fe II emission feature at 3969.40 is confirmed through line profile synthesis from kinetic equilibrium computations. In sharp contrast to the photospheric origin of the emission in rare earth lines in the H and K line wings, the Fe ii line emission appears to be of chromospheric origin. It is suggested that this line could be used as another indicator of conditions in the low chromosphere, for example in plage regions near the limb. Key words: solar emission lines - chromosphere - solar iron Title: Fe I line formation in solar-type giants and dwarfs. Authors: Lites, B. W.; Cowley, C. R. Bibcode: 1974A&A....31..361L Altcode: Summary. The formation of Fe ilines is investigated in stellar models of solar Teff but surface gravities ranging fr6m log g =4 to log g =2. The results of these kinetic equilibrium computations demonstrate that the departures from LTE in the Fe I lines generally cause only small differences from equivalent widths computed under the LTE assumption. Thus one does not expect large errors in iron abundance determinations to arise in stars of these types from the neglect of departures from LTE. The Fe I line formation in stars of extremely low metal abundances indicates that departures from LTE in the Fe i-Fe ii ionization balance could cause an iron abundance based upon the Saha equilibrium to underestimate the true abundance by a maximum of about 40 %. This study provides no evidence that departures from LTE in Fe I lines could account for the increase in measured microturbulence from solartype dwarf to supergiant stars as determined by curveof-growth studies. However, moderate strength Fe I lines may be strongly affected by damping, and the failure to recognize this may lead to overestimates in curve-of-growth microturbulences. Key words: stellar iron abundances - line formation Title: The Influence of Blends upon the Formation of Spectral Lines Authors: Lites, B. W. Bibcode: 1974A&A....30..297L Altcode: Summary. The effect of blending of normal stellar absorption lines is investigated in order to determine the error introduced when such blending is neglected in line transfer calculations. Solutions of the radiative transfer equations in some typical blended solar absorption lines demonstrate that, in cases where the line under consideration has only weaker blends confined to wavelengths outside the immediate line core, the neglect of the blending in the radiative transfer computations is indeed a valid approximation. Key words: radiative transfer - line formation - blends Title: The Solar Neutral Iron Spectrum. II: Profile Synthesis of Representative Fe I Fraunhofer Lines Authors: Lites, Bruce W. Bibcode: 1973SoPh...32..283L Altcode: The profiles of eighteen neutral iron lines of varying strengths were synthesized from disk center to the limb using source functions from detailed statistical equilibrium calculations. Emphasis is placed upon the analysis of the strong Fe I lines between 3500 Å and 4500 Å which are formed at and below the region of the initial temperature rise in the chromosphere. The major results are as follows: (1) We find an iron abundance of 1.5 × 1−5 relative to hydrogen (7.2 on a logarithmic scale with hydrogen equal to 12) that is independent of the assumed microturbulence model since it is based upon the far wing profiles of the strong lines. The far wings are formed in the photosphere where both the ionization and excitation equilibria are in detailed balance, so this abundance is directly comparable to other LTE abundances. (2) The strong line cores indicate that the chromospheric electron densities in the region of the initial temperature rise are similar to those derived by Henze (1969) from eclipse observations; i.e. higher than the HSRA model (Gingerich et al., 1971) by factors of two to five. We present (3) an anisotropic (angle-dependent) microturbulent velocity model, and (4) a mean macroturbulent velocity that aids in fitting the line cores. The formation of the two Fe I lines λ5232.95 and λ5250.21 is also discussed. Title: The Solar Neutral Iron Spectrum. I: Measurement of Solar Fe I Line Profiles from Center to Limb Authors: Lites, Bruce W.; Brault, J. W. Bibcode: 1973SoPh...30..283L Altcode: Mean profiles of eighteen neutral iron lines of varying strengths were measured at selected positions from the center of the solar disk to the limb. These profiles were obtained by rapid photoelectric scanning of the spectrum with a double-pass spectrometer. The Fe I lines selected are representative of most of the stronger low-lying transitions in the neutral iron atom. In addition to the iron lines, this observational program includes center-to-limb measurements of three Ti II lines and of the Ca I resonance line λ4226.7. The line profiles are presented here in graphical form after correction for instrumental effects and normalization to the local disk center continuum. Title: F i Ionization and Excitation Equilibrium in the Solar Atmosphere Authors: Athay, R. Grant; Lites, B. W. Bibcode: 1972ApJ...176..809A Altcode: Computations for a 15-level model Fe I atom in the solar atmosphere indicate that many of the Fe I spectral lines are strongly influenced by departures from LTE. The strong lines originating from the ground term and low-lying metastable terms have a strong chromospheric contribution. Although for many of the lines the source functions saturate to the Planck function near the temperature minimum (τ_5000 ≈ 10-4) and lower, the ionization equilibrium does not saturate to the Saha condition until τ_5000 > 3 × 10-3. The low-lying levels in Fe I reach maximum absolute populations near τ_5000 = 3 × 10-3, and lines originating from these levels tend to be formed at atmospheric depths where τ_5000; ≤ 3 × 10-3. For high-excitation levels in Fe I, departures of the line source function from the Planck function extend deeper into the photosphere and may influence abundances derived from lines originating from these high lying levels. From the weakness of the principal Fe II lines in the far-ultraviolet (λ2599, in particular) relative to lines of Si II and Mg II it is suggested that the Fe II f-values of Corliss and Bozman are too high by a factor of the order of 10+2. Fe I photoionization from the lowest levels may be a significant source of opacity in the region 1600-2000 Å. Title: A First Order Analysis of Variations of the Limb Darkening and the Shapes for Solar Fraunhofer Lilnes Authors: Athay, R. G.; Lites, B. W.; White, O. R.; Brault, J. W. Bibcode: 1972SoPh...24...18A Altcode: New center-to-limb measurements in FeI lines show changes in both the line profiles and the limb darkening curves that appear to be characteristic of many other solar lines. Here we seek the constraints placed on the atmospheric model by these effects. We find that in addition to a depth varying source function we must also allow the ratio of the continuous absorption coefficient to the total absorption coefficient to pass through a minimum in the mid-photosphere. Such an effect is consistent with inward increases of the Doppler width and damping constant in the upper photosphere and an inward increase of the ionization for both iron and hydrogen in the low photosphere. Title: FeI Ionization and Excitation Equilibrium in the Solar Atmosphere. Authors: Lites, B. W.; Athay, R. G. Bibcode: 1972BAAS....4..212L Altcode: No abstract at ADS Title: Observation and Analysis of the Solar Neutral Iron Spectrum. Authors: Lites, Bruce William Bibcode: 1972PhDT.........7L Altcode: No abstract at ADS Title: Hα Doppler Brightening and Lyman-α Doppler Dimming in Moving Hα Prominences Authors: Hyder, Charles L.; Lites, Bruce W. Bibcode: 1970SoPh...14..147H Altcode: We consider the effect that coherent motion has on the observed brightness of moving clouds above the photosphere. We find that steady state clouds (constant Ne and Te) that are moving perpendicular to the line of sight will appear brighter in Hα for speeds between 8 and 100 km/sec and dimmer for speeds greater than 135 km/sec. The brightening and dimming are due to apparent Doppler shifts of the respective Hα absorption and the Lyman-α emission profiles `seen' by the absorption profile of the moving cloud.