Author name code: ishikawa ADS astronomy entries on 2022-09-14 =author:"Ishikawa, Ryohko" OR =author:"Ishikawa, Ryoko" OR =author:"Ishikawa, R." ------------------------------------------------------------------------ Title: Quiet Sun Center to Limb Variation of the Linear Polarization Observed by CLASP2 Across the Mg II h and k Lines Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.; Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto, T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi, L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu, T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De; Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán, J.; Carlsson, M.; Leenaarts, J. Bibcode: 2022ApJ...936...67R Altcode: 2022arXiv220701788R The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket mission was launched on 2019 April 11. CLASP2 measured the four Stokes parameters of the Mg II h and k spectral region around 2800 Å along a 200″ slit at three locations on the solar disk, achieving the first spatially and spectrally resolved observations of the solar polarization in this near-ultraviolet region. The focus of the work presented here is the center-to-limb variation of the linear polarization across these resonance lines, which is produced by the scattering of anisotropic radiation in the solar atmosphere. The linear polarization signals of the Mg II h and k lines are sensitive to the magnetic field from the low to the upper chromosphere through the Hanle and magneto-optical effects. We compare the observations to theoretical predictions from radiative transfer calculations in unmagnetized semiempirical models, arguing that magnetic fields and horizontal inhomogeneities are needed to explain the observed polarization signals and spatial variations. This comparison is an important step in both validating and refining our understanding of the physical origin of these polarization signatures, and also in paving the way toward future space telescopes for probing the magnetic fields of the solar upper atmosphere via ultraviolet spectropolarimetry. Title: CASPER: A mission to study the time-dependent evolution of the magnetic solar chromosphere and transition regions Authors: Orozco Suárez, D.; del Toro Iniesta, J. C.; Bailén, F. J.; López Jiménez, A.; Balaguez Jiménez, M.; Bellot Rubio, L. R.; Ishikawa, R.; Katsukawa, Y.; Kano, R.; Shimizu, T.; Trujillo Bueno, J.; Asensio Ramos, A.; del Pino Alemán, T. Bibcode: 2022ExA...tmp...26O Altcode: Our knowledge about the solar chromosphere and transition region (TR) has increased in the last decade thanks to the huge scientific return of space-borne observatories like SDO, IRIS, and Hinode, and suborbital rocket experiments like CLASP1, CLASP2, and Hi-C. However, the magnetic nature of those solar regions remain barely explored. The chromosphere and TR of the Sun harbor weak fields and are in a low ionization stage both having critical effects on their thermodynamic behavior. Relatively cold gas structures, such as spicules and prominences, are located in these two regions and display a dynamic evolution in high-resolution observations that static and instantaneous 3D-magnetohydrodynamic (MHD) models are not able to reproduce. The role of the chromosphere and TR as the necessary path to a (largely unexplained) very hot corona calls for the generation of observationally based, time-dependent models of these two layers that include essential, up to now disregarded, ingredients in the modeling such as the vector magnetic field. We believe that the community is convinced that the origin of both the heat and kinetic energy observed in the upper layers of the solar atmosphere is of magnetic origin, but reliable magnetic field measurements are missing. The access to sensitive polarimetric measurements in the ultraviolet wavelengths has been elusive until recently due to limitations in the available technology. We propose a low-risk and high-Technology Readiness Level (TRL) mission to explore the magnetism and dynamics of the solar chromosphere and TR. The mission baseline is a low-Earth, Sun-synchronous orbit at an altitude between 600 and 800 km. The proposed scientific payload consists of a 30 cm aperture telescope with a spectropolarimeter covering the hydrogen Ly-alpha and the Mg II h&k ultraviolet lines. The instrument shall record high-cadence, full spectropolarimetric observations of the solar upper atmosphere. Besides the answers to a fundamental solar problem the mission has a broader scientific return. For example, the time-dependent modeling of the chromospheres of stars harboring exoplanets is fundamental for estimating the planetary radiation environment. The mission is based on technologies that are mature enough for space and will provide scientific measurements that are not available by other means. Title: Empirical relations between the intensities of Lyman lines of H and He+ Authors: Gordino, M.; Auchère, F.; Vial, J. -C.; Bocchialini, K.; Hassler, D. M.; Bando, T.; Ishikawa, R.; Kano, R.; Kobayashi, K.; Narukage, N.; Trujillo Bueno, J.; Winebarger, A. Bibcode: 2022A&A...657A..86G Altcode: 2022arXiv220101519G Context. Empirical relations between major UV and extreme UV spectral lines are one of the inputs for models of chromospheric and coronal spectral radiances and irradiances. They are also needed for the interpretation of some of the observations of the Solar Orbiter mission.
Aims: We aim to determine an empirical relation between the intensities of the H I 121.6 nm and He II 30.4 nm Ly-α lines.
Methods: Images at 121.6 nm from the Chromospheric Lyman-Alpha Spectro Polarimeter (CLASP) and Multiple XUV Imager (MXUVI) sounding rockets were co-registered with simultaneous images at 30.4 nm from the EIT and AIA orbital telescopes in order to derive a spatially resolved relationship between the intensities.
Results: We have obtained a relationship between the H I 121.6 nm and He II 30.4 nm intensities that is valid for a wide range of solar features, intensities, and activity levels. Additional SUMER data have allowed the derivation of another relation between the H I 102.5 nm (Ly-β) and He II 30.4 nm lines for quiet-Sun regions. We combined these two relationships to obtain a Ly-α/Ly-β intensity ratio that is comparable to the few previously published results.
Conclusions: The relationship between the H I 121.6 nm and He II 30.4 nm lines is consistent with the one previously obtained using irradiance data. We have also observed that this relation is stable in time but that its accuracy depends on the spatial resolution of the observations. The derived Ly-α/Ly-β intensity ratio is also compatible with previous results. Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1 Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier; Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song, Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil, Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman, Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri Bibcode: 2021AGUFMSH52A..06M Altcode: Probing the magnetic nature of the Suns atmosphere requires measurement of the Stokes I, Q, U and V profiles of relevant spectral lines (of which Q, U and V encode the magnetic field information). Many of the magnetically sensitive lines formed in the chromosphere and transition region are in the ultraviolet spectrum, necessitating observations above the absorbing terrestrial atmosphere. The Chromospheric Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown successfully in April 2019, as a follow-on to the successful flight in September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP). Both projects were funded by NASAs Heliophysics Technology and Instrument Development for Science (H-TIDeS) program to develop and test a technique for observing the Sun in ultraviolet light, and for quantifying the polarization of that light. By demonstrating successful measurement and interpretation of the polarization in hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP and CLASP2 missions are vital first steps towards routine quantitative characterization of the local thermal and magnetic conditions in the solar chromosphere. In October of 2021, we re-flew the CLASP2 payload with a modified observing program to further demonstrate the maturity of the UV spectropolarimetry techniques, and readiness for development into a satellite observatory. During the reflight, called CLASP2.1, the spectrograph slit was scanned across an active region plage to acquire a two-dimensional map of Stokes V/I, to demonstrate the ability of UV spectropolarimetry to yield chromospheric magnetic fields over a large area. This presentation will display preliminary results from the flight of CLASP2.1. Title: 20 Years of Gender Equality Activities in Astronomical Society of Japan Authors: Bamba, Aya; Asai, Ayumi; Ishikawa, Ryohko; Sato, Kosuke; Nobukawa, Masayoshi; Nomura, Hideko; Furusawa, Hisanori; Machida, Mami Bibcode: 2021AstHe.114..688B Altcode: The female ratio in science field, including astronomy and astrophysics, is still low in Japan. We, the Astronomical Society of Japan, keep making efforts for the better gender balance. In this article, we summarize our survey results, how members' thinking changed within these 20 years from our questionnaire, the history and accomplishments of day-care system during annual meeting, other activities, and so on. Title: Mapping of Solar Magnetic Fields from the Photosphere to the Top of the Chromosphere with CLASP2 Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.; del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.; Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.; Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil, G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.; Asensio Ramos, A.; Carlsson, M.; Leenaarts, J. Bibcode: 2021AAS...23810603M Altcode: Coronal heating, chromospheric heating, and the heating & acceleration of the solar wind, are well-known problems in solar physics. Additionally, knowledge of the magnetic energy that powers solar flares and coronal mass ejections, important drivers of space weather, is handicapped by imperfect determination of the magnetic field in the sun's atmosphere. Extrapolation of photospheric magnetic measurements into the corona is fraught with difficulties and uncertainties, partly due to the vastly different plasma beta between the photosphere and the corona. Better results in understanding the coronal magnetic field should be derived from measurements of the magnetic field in the chromosphere. To that end, we are pursuing quantitative determination of the magnetic field in the chromosphere, where plasma beta transitions from greater than unity to less than unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown on a sounding rocket in April 2019, succeeded in measuring all four Stokes polarization parameters in UV spectral lines formed by singly ionized Magnesium and neutral Manganese. Because these ions produce spectral lines under different conditions, CLASP2 thus was able to quantify the magnetic field properties at multiple heights in the chromosphere simultaneously, as shown in the recent paper by Ishikawa et al. In this presentation we will report the findings of CLASP2, demonstrating the variation of magnetic fields along a track on the solar surface and as a function of height in the chromosphere; and we will illustrate what is next for the CLASP missions and the demonstration of UV spectropolarimetry in the solar chromosphere. Title: Mapping solar magnetic fields from the photosphere to the base of the corona Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán, Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère, Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage, Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge, Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.; Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán, Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit Bibcode: 2021SciA....7.8406I Altcode: 2021arXiv210301583I Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we report unprecedented spectropolarimetric observations of an active region plage and its surrounding enhanced network, showing circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We infer the longitudinal magnetic field from the photosphere to the very upper chromosphere. At the top of the plage chromosphere the field strengths reach more than 300 gauss, strongly correlated with the Mg II $k$ line core intensity and the electron pressure. This unique mapping shows how the magnetic field couples the different atmospheric layers and reveals the magnetic origin of the heating in the plage chromosphere. Title: Optical design of the Chromospheric LAyer Spectro-Polarimeter (CLASP2) Authors: Tsuzuki, Toshihiro; Ishikawa, Ryohko; Kano, Ryouhei; Narukage, Noriyuki; Song, Donguk; Yoshida, Masaki; Uraguchi, Fumihiro; Okamoto, Takenori J.; McKenzie, David; Kobayashi, Ken; Rachmeler, Laurel; Auchere, Frederic; Trujillo Bueno, Javier Bibcode: 2020SPIE11444E..6WT Altcode: Chromospheric LAyer Spectro-Polarimeter (CLASP2) was a sounding rocket experiment, which is a follow-up mission to the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP1) in 2015. To measure the magnetic fields in the upper solar atmosphere in a highly quantitative manner, CLASP2 changes the target wavelengths from the hydrogen Ly-α line (121.567 nm) to Mg II lines near 280 nm. We reused the main structure and most of the optical components in the CLASP1 instrument, which reduced the turnaround time and cost. We added a magnifying optical system to maintain the wavelength resolution, even at the longer wavelength of CLASP2. Here, we describe the optical design and performance of the CLASP2 instrument. Title: The Solar-C (EUVST) mission: the latest status Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu, Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto, Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki; Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren, Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca, Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William; Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic; Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise Bibcode: 2020SPIE11444E..0NS Altcode: Solar-C (EUVST) is the next Japanese solar physics mission to be developed with significant contributions from US and European countries. The mission carries an EUV imaging spectrometer with slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic Telescope) as the mission payload, to take a fundamental step towards answering how the plasma universe is created and evolves and how the Sun influences the Earth and other planets in our solar system. In April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA (Japan Aerospace Exploration Agency) has made the final down-selection for this mission as the 4th in the series of competitively chosen M-class mission to be launched with an Epsilon launch vehicle in mid 2020s. NASA (National Aeronautics and Space Administration) has selected this mission concept for Phase A concept study in September 2019 and is in the process leading to final selection. For European countries, the team has (or is in the process of confirming) confirmed endorsement for hardware contributions to the EUVST from the national agencies. A recent update to the mission instrumentation is to add a UV spectral irradiance monitor capability for EUVST calibration and scientific purpose. This presentation provides the latest status of the mission with an overall description of the mission concept emphasizing on key roles of the mission in heliophysics research from mid 2020s. Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) for sunrise III: system design and capability Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.; Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki, T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu, Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.; Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez, M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.; Riethmueller, T.; Gandorfer, A.; Lagg, A. Bibcode: 2020SPIE11447E..0YK Altcode: The Sunrise balloon-borne solar observatory carries a 1 m aperture optical telescope and provides us a unique platform to conduct continuous seeing-free observations at UV-visible-IR wavelengths from an altitude of higher than 35 km. For the next flight planned for 2022, the post-focus instrumentation is upgraded with new spectro- polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable of observing multiple spectral lines within the visible wavelength. A new spectro-polarimeter called the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is under development for observing near-IR wavelength ranges of around 770 nm and 850 nm. These wavelength ranges contain many spectral lines sensitive to solar magnetic fields and SCIP will be able to obtain magnetic and velocity structures in the solar atmosphere with a sufficient height resolution by combining spectro-polarimetric data of these lines. Polarimetric measurements are conducted using a rotating waveplate as a modulator and polarizing beam splitters in front of the cameras. The spatial and spectral resolutions are 0.2" and 2 105, respectively, and a polarimetric sensitivity of 0.03 % (1σ) is achieved within a 10 s integration time. To detect minute polarization signals with good precision, we carefully designed the opto-mechanical system, polarization optics and modulation, and onboard data processing. Title: Dynamics of the Convective Turbulence in the Solar Granulation Studied by the Spectral Line Broadening and Asymmetry Authors: Ishikawa, R.; Katsukawa, Y.; Oba, T.; Nakata, M.; Nagaoka, K.; Kobayashi, T. Bibcode: 2019AGUFMSH43E3385I Altcode: In the quiet region on the solar surface, turbulent convective motions of the granulation play an important role for creating small-scale magnetic structures as well as the energy injection into the upper atmosphere. The turbulent nature can be studied using spectral line profiles, especially line broadening, that contains information on the flow field smaller than the spatial resolution of an instrument. Doppler velocity gradient along a line-of-sight (LOS) is also a source of line broadening. However, the quantitative relation between velocity gradient and line broadening is not well understood. In this study, we perform bisector analyses using spectral profiles obtained with the Spectro-Polarimeter of Hinode Solar Optical Telescope to investigate how the line broadening and the bisector velocities are related with granulation flows. Our result indicates that the line broadening has a positive correlation with the LOS gradient of Doppler velocities. We found excessive line broadening in fading granules that cannot be explained only by the LOS velocity gradient, although the velocity gradient is enhanced in the course of fading granules. If we attribute the excessive line broadening to small-scale turbulent motions, the averaged turbulent velocity is 1.6 km/s. Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding Rocket Mission: First Results Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.; Rachmeler, L.; Kano, R.; Song, D.; Okamoto, J.; Kobayashi, K.; Yoshida, M. Bibcode: 2019AGUFMSH44A..06M Altcode: A major challenge for heliophysics is to decipher the magnetic structure of the chromosphere, because of its vital role in the transport of energy into the corona and solar wind. Routine satellite measurements of the chromospheric magnetic field will dramatically improve our understanding of the chromosphere and its connection to the rest of the solar atmosphere. Before such a satellite can be considered for flight, we must refine the measurement techniques by exploring emission lines with a range of magnetic sensitivities. In 2015, CLASP achieved the first measurement of linear polarization produced by scattering processes in a far UV resonance line (hydrogen Lyman­-α), and the first exploration of the magnetic field (via the Hanle effect) and geometrical complexity in quiet regions of the chromosphere/­corona transition region. These measurements are a first step towards routine quantitative characterization of the local thermal and magnetic conditions in this key layer of the solar atmosphere.

Nonetheless, Lyman­-α is only one of the magnetically sensitive spectral lines in the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by acquiring ground­breaking measurements in the Mg II h and k spectral lines near 280 nm, whose cores form about 100 km below the Lyman-­α core. These lines are sensitive to a larger range of field strengths than Lyman­-α, through both the Hanle and Zeeman effects. CLASP2 captures measurements of linear and circular polarization to enable the first determination of all 4 Stokes parameters in chromospheric UV radiation. Coupled with numerical modeling of the observed spectral line polarization (anisotropic radiation pumping with Hanle, Zeeman and magneto-­optical effects), CLASP2 is a pathfinder for determination of the magnetic field's strength and direction, as well as of the geometry of the plasma in the upper solar chromosphere.

CLASP2 was launched from White Sands Missile Range in April 2019. In this presentation, we will summarize the characteristics of the CLASP2 flight, the performance of the UV telescope and spectropolarimeter, and our preliminary findings. Title: Center-to-Limb Variation of the polarization of Mg II h & k lines as measured by CLASP2 Authors: Rachmeler, L.; McKenzie, D. E.; Ishikawa, R.; Kano, R.; Trujillo Bueno, J.; Kobayashi, K.; Song, D.; Yoshida, M.; Auchere, F.; Okamoto, J. Bibcode: 2019AGUFMSH11D3380R Altcode: The Chromospheric LAyer SpectroPolarimeter 2 (CLASP2) is a sounding rocket that was launched from White Sands Missile Range in April 2019. CLASP2 is a reflight of the CLASP instrument, and has been modified to observe the polarization of the Magnesium II h & k lines in the solar chromosphere. The instrument contains a slit-jaw context imager at Lyman Alpha (~121.6nm) and two spectropolarimetric cameras that capture Mg II h & k near 280nm. A rotating polarization modulation unit allows us to capture the full polarization state of Mg II h & k; the measured polarization signals are sensitive to the Hanle and the Zeeman magnetic effects, and magneto-optical effects. The center-to-limb variations (CLV) of the intensity of these lines has been measured, but the CLV of the polarization signals has only been investigated theoretically. The first flight of CLASP, which measured the linear polarization of the Lyman alpha line, found a surprising lack of CLV in the line core (Kano et al. 2017), which has important implications for the magnetic strength and geometrical complexity of the chromosphere-corona transition region (Trujillo Bueno et al. 2018). We present here initial results on the CLV of the Mg II polarization signals. Title: High-frequency Wave Propagation Along a Spicule Observed by CLASP Authors: Yoshida, Masaki; Suematsu, Yoshinori; Ishikawa, Ryohko; Okamoto, Takenori J.; Kubo, Masahito; Kano, Ryouhei; Narukage, Noriyuki; Bando, Takamasa; Winebarger, Amy R.; Kobayashi, Ken; Trujillo Bueno, Javier; Auchère, Frédéric Bibcode: 2019ApJ...887....2Y Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding rocket experiment, launched in 2015 September, observed the hydrogen Lyα line (121.6 nm) in an unprecedented high temporal cadence of 0.3 s. CLASP performed sit-and-stare observations of the quiet Sun near the limb for 5 minutes with a slit perpendicular to the limb and successfully captured an off-limb spicule evolving along the slit. The Lyα line is well suited for investigating how spicules affect the corona because it is sensitive to higher temperatures than other chromospheric lines, owing to its large optical thickness. We found high-frequency oscillations of the Doppler velocity with periods of 20-50 s and low-frequency oscillation of periods of ∼240 s on the spicule. From a wavelet analysis of the time sequence data of the Doppler velocity, in the early phase of the spicule evolution, we found that waves with a period of ∼30 s and a velocity amplitude of 2-3 km s-1 propagated upward along the spicule with a phase velocity of ∼470 km s-1. In contrast, in the later phase, possible downward and standing waves with smaller velocity amplitudes were also observed. The high-frequency waves observed in the early phase of the spicule evolution would be related with the dynamics and the formation of the spicules. Our analysis enabled us to identify the upward, downward, and standing waves along the spicule and to obtain the velocity amplitude of each wave directly from the Doppler velocity for the first time. We evaluated the energy flux by the upward-propagating waves along the spicule, and discussed the impact to the coronal heating. Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding Rocket Mission: First Results Authors: McKenzie, David Eugene; Ishikawa, Ryohko; Kano, Ryouhei; Rachmeler, Laurel; Trujillo Bueno, Javier; Kobayashi, Ken; Song, Donguk; Yoshida, Masaki; Auchere, Frederic; Okamoto, Takenori Bibcode: 2019AAS...23412601M Altcode: A major challenge for heliophysics is to decipher the magnetic structure of the chromosphere, because of its vital role in the transport of energy into the corona and solar wind. Routine satellite measurements of the chromospheric magnetic field will dramatically improve our understanding of the chromosphere and its connection to the rest of the solar atmosphere. Before such a satellite can be considered for flight, we must refine the measurement techniques by exploring emission lines with a range of magnetic sensitivities. In 2015, CLASP achieved the first measurement of linear polarization produced by scattering processes in a far UV resonance line (hydrogen Lyman-α), and the first exploration of the magnetic field (via the Hanle effect) and geometrical complexity in quiet regions of the chromosphere-corona transition region. These measurements are a first step towards routine quantitative characterization of the local thermal and magnetic conditions in this key layer of the solar atmosphere.

Nonetheless, Lyman-α is only one of the magnetically sensitive spectral lines in the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by acquiring ground-breaking measurements in the Mg II h and k spectral lines near 280 nm, whose cores form about 100 km below the Lyman-α core. These lines are sensitive to a larger range of field strengths than Lyman-α, through both the Hanle and Zeeman effects. CLASP2 will capture measurements of linear and circular polarization to enable the first determination of all 4 Stokes parameters in chromospheric UV radiation. Coupled with numerical modeling of the observed spectral line polarization (anisotropic radiation pumping with Hanle, Zeeman and magneto-optical effects), CLASP2 is a pathfinder for determination of the magnetic field's strength and direction, as well as of the geometry of the plasma in the upper solar chromosphere.

CLASP2 will launch from White Sands Missile Range in April 2019. In this presentation, we will summarize the characteristics of the CLASP2 flight, the performance of the UV telescope and spectropolarimeter, and our preliminary findings. Title: Lyman-α imaging polarimetry with the CLASP2 sounding rocket mission Authors: Kano, Ryouhei; Ishikawa, Ryohko; McKenzie, David Eugene; Trujillo Bueno, Javier; Song, Donguk; Yoshida, Masaki; Okamoto, Takenori; Rachmeler, Laurel; Kobayashi, Ken; Auchere, Frederic Bibcode: 2019AAS...23430216K Altcode: Ultraviolet polarimetry offers a unique opportunity to explore the upper solar chromosphere and the transition region (TR) to the million-degree corona. These outer atmospheric regions play a key role in the transfer of mass and energy from the solar photosphere to the corona. With a sounding rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), in September 2015 we succeeded in obtaining the first measurement of the linear polarization produced by scattering processes in the hydrogen Lyman-α line of the solar disk radiation. The analysis and interpretation of such spectro-polarimetric observation allowed us to obtain information on the geometrical complexity of the corrugated surface that delineates the TR, as well as on the magnetic field strength via the Hanle effect. At the same time, the CLASP slit-jaw (SJ) optics system, which is a Lyman-α filter imager characterized by a FWHM= 7 nm, allowed us to obtain broad-band Stokes-I and Q/I images over a large field of view. The obtained broad-band Q/I images are dominated by the scattering polarization signals of the Lyman-α wings, and not by the much weaker line-center signals where the Hanle effect operates. Recently, Alsina Ballester et al. (2019, ApJ, in press) showed that the scattering polarization signals of the Lyman-α wings are sensitive to chromospheric magnetic fields via the magneto-optical effects. Therefore, Lyman-α imaging polarimetry is of scientific interest also for magnetic-field investigations. On April 11, 2019, we performed another sounding rocket experiment, called the Chromospheric LAyer Spectro-Polarimeter (CLASP2). We used the same instrument after significant modifications in order to obtain spectro-polarimetric observations of a plage and a quiet region in the ionized magnesium lines around 280 nm (i.e., the Mg II h & k lines). At the same time, the CLASP2 SJ optics system allowed us to obtain broad-band Q/I and U/I images at the Lyman-α wavelength, in addition to the well-known SJ intensity images. In this presentation, we provide a first overview of the CLASP2 SJ data. Title: Modeling the Scattering Polarization of the Hydrogen Lyα Line Observed by CLASP in a Filament Channel Authors: Štěpán, J.; Trujillo Bueno, J.; Gunár, S.; Heinzel, P.; del Pino Alemán, T.; Kano, R.; Ishikawa, R.; Narukage, N.; Bando, T.; Winebarger, A.; Kobayashi, K.; Auchère, F. Bibcode: 2019ASPC..526..165S Altcode: The 400 arcsec spectrograph slit of CLASP crossed mainly quiet regions of the solar chromosphere, from the limb towards the solar disk center. Interestingly, in the CLASP slit-jaw images and in the SDO images of the He II line at 304 Å, we can identify a filament channel (FC) extending over more than 60 arcsec crossing the slit of the spectrograph. In order to interpret the peculiar spatial variation of the Q/I and U/I signals observed by CLASP in the hydrogen Lyα line (1216 Å), we perform multi-dimensional radiative transfer modeling in given filament models. In this contribution, we show the first results of the two-dimensional calculations we have carried out, with the aim of determining the filament thermal and magnetic structure by comparing the theoretical and the observed polarization signals. Our results suggest that the temperature gradients in the filament observed by CLASP are significantly larger than previously thought. Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchére, F.; Rachmeler, L. A.; Kubo, M.; Kobayashi, K.; Winebarger, A. R.; Bethge, C. W.; Narukage, N.; Kano, R.; Ishikawa, S.; de Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Štěpán, J.; del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A. Bibcode: 2019ASPC..526..361M Altcode: The hydrogen Lyman-α line at 121.6 nm and the Mg k line at 279.5 nm are especially relevant for deciphering the magnetic structure of the chromosphere since their line-center signals are formed in the chromosphere and transition region, with unique sensitivities to magnetic fields. We propose the Chromospheric LAyer Spectro-Polarimeter (CLASP2), to build upon the success of the first CLASP flight, which measured the linear polarization in H I Lyman-α. The existing CLASP instrument will be refitted to measure all four Stokes parameters in the 280 nm range, including variations due to the anisotropic radiation pumping, the Hanle effect, and the Zeeman effect. Title: Comparison of Scattering Polarization Signals Observed by CLASP: Possible Indication of the Hanle Effect Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.; Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa, Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.; Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso Sainz, R.; De Pomtieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R. Bibcode: 2019ASPC..526..305I Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP; Kano et al. 2012; Kobayashi et al. 2012; Kubo et al. 2014) observed, for the first time, the linear polarization produced by scattering processes in the hydrogen Lyman-α (121.57 nm) and Si III (120.56 nm) lines of the solar disk radiation. The complexity of the observed scattering polarization (i.e., conspicuous spatial variations in Q/I and U/I at spatial scales of 10″-20″ and the absence of center-to- limb variation at the Lyman-α center; see Kano et al. 2017) motivated us to search for possible hints of the operation of the Hanle effect by comparing: (a) the Lyman-α line center signal, for which the critical field strength (BH) for the onset of the Hanle effect is 53 G, (b) the Lyman-α wing, which is insensitive to the Hanle effect, and (c) the Si III line, whose BH = 290 G. We focus on four regions with different total unsigned photospheric magnetic fluxes (estimated from SDO/HMI observations), and compare the corresponding U/I spatial variations in the Lyman-α wing, Lyman-α center, and Si III line. The U/I signal in the Lyman-α wing shows an antisymmetric spatial distribution, which is caused by the presence of a bright structure in all the selected regions, regardless of the total unsigned photospheric magnetic flux. In an internetwork region, the Lyman-α center shows an antisymmetric spatial variation across the selected bright structure, but it does not show it in other more magnetized regions. In the Si III line, the spatial variation of U/I deviates from the above-mentioned antisymmetric shape as the total unsigned photospheric magnetic flux increases. We argue that a plausible explanation of this differential behavior is the operation of the Hanle effect.

This work, presented in an oral contribution at this Workshop, has been published on The Astrophysical Journal (Ishikawa et al. 2017). Title: CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region Authors: Trujillo Bueno, J.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Ishikawa, R.; Kano, R.; Winebarger, A.; Auchère, F.; Narukage, N.; Kobayashi, K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M. Bibcode: 2018ApJ...866L..15T Altcode: 2018arXiv180908865T The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a suborbital rocket experiment that on 2015 September 3 measured the linear polarization produced by scattering processes in the hydrogen Lyα line of the solar disk radiation. The line-center photons of this spectral line radiation mostly stem from the chromosphere-corona transition region (TR). These unprecedented spectropolarimetric observations revealed an interesting surprise, namely that there is practically no center-to-limb variation (CLV) in the Q/I line-center signals. Using an analytical model, we first show that the geometric complexity of the corrugated surface that delineates the TR has a crucial impact on the CLV of the Q/I and U/I line-center signals. Second, we introduce a statistical description of the solar atmosphere based on a 3D model derived from a state-of-the-art radiation magnetohydrodynamic simulation. Each realization of the statistical ensemble is a 3D model characterized by a given degree of magnetization and corrugation of the TR, and for each such realization we solve the full 3D radiative transfer problem taking into account the impact of the CLASP instrument degradation on the calculated polarization signals. Finally, we apply the statistical inference method presented in a previous paper to show that the TR of the 3D model that produces the best agreement with the CLASP observations has a relatively weak magnetic field and a relatively high degree of corrugation. We emphasize that a suitable way to validate or refute numerical models of the upper solar chromosphere is by confronting calculations and observations of the scattering polarization in ultraviolet lines sensitive to the Hanle effect. Title: A Statistical Inference Method for Interpreting the CLASP Observations Authors: Štěpán, J.; Trujillo Bueno, J.; Belluzzi, L.; Asensio Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Kano, R.; Winebarger, A.; Auchère, F.; Ishikawa, R.; Narukage, N.; Kobayashi, K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M. Bibcode: 2018ApJ...865...48S Altcode: 2018arXiv180802725S On 2015 September 3, the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) successfully measured the linear polarization produced by scattering processes in the hydrogen Lyα line of the solar disk radiation, revealing conspicuous spatial variations in the Q/I and U/I signals. Via the Hanle effect, the line-center Q/I and U/I amplitudes encode information on the magnetic field of the chromosphere-corona transition region, but they are also sensitive to the three-dimensional structure of this corrugated interface region. With the help of a simple line-formation model, here we propose a statistical inference method for interpreting the Lyα line-center polarization observed by CLASP. Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) for the SUNRISE balloon-borne solar observatory Authors: Suematsu, Yoshinori; Katsukawa, Yukio; Hara, Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Barthol, Peter; Riethmueller, Tino; Gandorfer, Achim; Feller, Alex; Orozco Suárez, David; Del Toro Iniesta, Jose Carlos; Kano, Ryouhei; Ishikawa, Shin-nosuke; Ishikawa, Ryohko; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Quintero Noda, Carlos; Tamura, Tomonori; Oba, Takayoshi; Kawabata, Yusuke; Nagata, Shinichi; Anan, Tetsu; Cobos Carrascosa, Juan Pedro; Lopez Jimenez, Antonio Carlos; Balaguer Jimenez, Maria; Solanki, Sami Bibcode: 2018cosp...42E3285S Altcode: The SUNRISE balloon-borne solar observatory carries a 1 m aperture optical telescope, and allows us to perform seeing-free continuous observations at visible-IR wavelengths from an altitude higher than 35 km. In the past two flights, in 2009 and 2013, observations mainly focused on fine structures of photospheric magnetic fields. For the third flight planned for 2021, we are developing a new instrument for conducting spectro-polarimetry of spectral lines formed over a larger height range in the solar atmosphere from the photosphere to the chromosphere. Targets of the spectro-polarimetric observation are (1) to determine 3D magnetic structure from the photosphere to the chromosphere, (2) to trace MHD waves from the photosphere to the chromosphere, and (3) to reveal the mechanism driving chromospheric jets, by measuring height- and time-dependent velocities and magnetic fields. To achieve these goals, a spectro-polarimeter called SCIP (Sunrise Chromospheric Infrared spectroPolarimeter) is designed to observe near-infrared spectrum lines sensitive to solar magnetic fields. The spatial and spectral resolutions are 0.2 arcsec and 200,000, respectively, while 0.03% polarimetric sensitivity is achieved within a 10 sec integration time. The optical system employs an Echelle grating and off-axis aspheric mirrors to observe the two wavelength ranges centered at 850 nm and 770 nm simultaneously by two cameras. Polarimetric measurements are performed using a rotating waveplate and polarization beam-splitters in front of the cameras. For detecting minute polarization signals with good precision, we carefully assess the temperature dependence of polarization optics, and make the opto-structural design that minimizes the thermal deformation of the spectrograph optics. Another key technique is to attain good (better than 30 msec) synchronization among the rotating phase of the waveplate, read-out timing of cameras, and step timing of a slit-scanning mirror. On-board accumulation and data processing are also critical because we cannot store all the raw data read-out from the cameras. We demonstrate that we can reduce the data down to almost 10% with loss-less image compression and without sacrificing polarimetric information in the data. The SCIP instrument is developed by internal collaboration among Japanese institutes including Japan Aerospace Exploration Agency (JAXA), the Spanish Sunrise consortium, and the German Max Planck Institute for Solar System Research (MPS) with a leadership of the National Astronomical Observatory of Japan (NAOJ). Title: Current State of UV Spectro-Polarimetry and its Future Direction Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara, Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi, . Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier; Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts, Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke; Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel; Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan, Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey, Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David; Rachmeler, Laurel; Bethge, Christian Bibcode: 2018cosp...42E1564I Altcode: To obtain quantitative information on the magnetic field in low beta regions (i.e., upper chromosphere and above) has been increasingly important to understand the energetic phenomena of the outer solar atmosphere such as flare, coronal heating, and the solar wind acceleration. In the UV range, there are abundant spectral lines that originate in the upper chromosphere and transition region. However, the Zeeman effect in these spectral lines does not give rise to easily measurable polarization signals because of the weak magnetic field strength and the larger Doppler broadening compared with the Zeeman effect. Instead, the Hanle effect in UV lines is expected to be a suitable diagnostic tool of the magnetic field in the upper atmospheric layers. To investigate the validity of UV spectro-polarimetry and the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), which is a NASA sounding- rocket experiment, was launched at White Sands in US on September 3, 2015. During its 5 minutes ballistic flight, it successfully performed spectro-polarimetric observations of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly high polarization sensitivity of 0.1% in this wavelength range. CLASP observed the linear polarization produced by scattering process in VUV lines for the first time and detected the polarization signals which indicate the operation of the Hanle effect. Following the success of CLASP, we are confident that UV spectro-polarimetry is the way to proceed, and we are planning the second flight of CLASP (CLASP2: Chromospheric LAyer SpectroPolarimeter 2). For this second flight we will carry out spectro-polarimetry in the Mg II h and k lines around 280 nm, with minimum modifications of the CLASP1 instrument. The linear polarization in the Mg II k line is induced by scattering processes and the Hanle effect, being sensitive to magnetic field strengths of 5 to 50 G. In addition, the circular polarizations in the Mg II h and k lines induced by the Zeeman effect can be measurable in at least plage and active regions. The combination of the Hanle and Zeeman effects could help us to more reliably infer the magnetic fields of the upper solar chromosphere. CLASP2 was selected for flight and is being developed for launch in the spring of 2019.Based on these sounding rocket experiments (CLASP1 and 2), we aim at establishing the strategy and refining the instrument concept for future space missions to explore the enigmatic atmospheric layers via UV spectro-polarimetry. Title: Wavefront error measurements and alignment of CLASP2 telescope with a dual-band pass cold mirror coated primary mirror Authors: Yoshida, Masaki; Song, Donguk; Ishikawa, Ryoko; Kano, Ryouhei; Katsukawa, Yukio; Suematsu, Yoshinori; Narukage, Noriyuki; Kubo, Masahito; Shinoda, Kazuya; Okamoto, Takenori J.; McKenzie, David E.; Rachmeler, Laurel A.; Auchère, Frédéric; Trujillo Bueno, Javier Bibcode: 2018SPIE10699E..30Y Altcode: "Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)" that succeeded in observing for the first time the linear polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is scheduled to be launched in 2019. In CLASP2, we will carry out full Stokes-vector spectropolarimetric observations in the Mg ii h and k lines near 280 nm with the spectro-polarimeter (SP), while imaging observations in the Lyman-α line will be conducted with the slitjaw optics (SJ). For the wavelength selection of CLASP2, the primary mirror of the telescope uses a new dual-band pass cold mirror coating targeting both at 121.6 nm and 280 nm. Therefore, we have to perform again the alignment of the telescope after the installation of the recoated primary mirror. Before unmounting the primary mirror from the telescope structure, we measured the wave-front error (WFE) of the telescope. The measured WFE map was consistent with what we had before the CLASP flight, clearly indicating that the telescope alignment has been maintained even after the flight. After the re-coated primary mirror was installed the WFE was measured, and coma aberration was found to be larger. Finally, the secondary mirror shim adjustments were carried out based on the WFE measurements. In CLASP2 telescope, we improved a fitting method of WFE map (applying 8th terms circular Zernike polynomial fitting instead of 37th terms circular Zernike fitting) and the improved method enables to achieve better performance than CLASP telescope. Indeed, WFE map obtained after the final shim adjustment indicated that the required specification (< 5.5 μm RMS spot radius) that is more stringent than CLASP telescope was met. Title: Optical alignment of the high-precision UV spectro-polarimeter (CLASP2) Authors: Song, Donguk; Ishikawa, Ryohko; Kano, Ryouhei; Yoshida, Masaki; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Shinoda, Kazuya; Hara, Hirohisa; Okamoto, Takenori J.; Auchère, Frédéric; McKenzie, David E.; Rachmeler, Laurel A.; Trujillo Bueno, Javier Bibcode: 2018SPIE10699E..2WS Altcode: Chromospheric LAyer Spectro-Polarimeter (CLASP2) is our next sounding rocket experiment after the success of Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP1). CLASP2 is scheduled to launch in 2019, and aims to achieve high precision measurements (< 0.1 %) of the linear and circular polarizations in the Mg ii h and k lines near the 280 nm, whose line cores originate in the upper solar chromosphere. The CLASP2 spectro-polarimeter follows very successful design concept of the CLASP1 instrument with the minimal modification. A new grating was fabricated with the same radius of curvature as the CLASP1 grating, but with a different ruling density. This allows us to essentially reuse the CLASP1 mechanical structures and layout of the optics. However, because the observing wavelength of CLASP2 is twice longer than that of CLASP1, a magnifier optical system was newly added in front of the cameras to double the focal length of CLASP2 and to maintain the same wavelength resolution as CLASP1 (0.01 nm). Meanwhile, a careful optical alignment of the spectro-polarimeter is required to reach the 0.01 nm wavelength resolution. Therefore, we established an efficient alignment procedure for the CLASP2 spectro-polarimeter based on an experience of CLASP1. Here, we explain in detail the methods for achieving the optical alignment of the CLASP2 spectro-polarimeter and discuss our results by comparing with the performance requirements. Title: Influence of the Atmospheric Model on Hanle Diagnostics Authors: Ishikawa, Ryohko; Uitenbroek, Han; Goto, Motoshi; Iida, Yusuke; Tsuneta, Saku Bibcode: 2018SoPh..293...74I Altcode: We clarify the uncertainty in the inferred magnetic field vector via the Hanle diagnostics of the hydrogen Lyman-α line when the stratification of the underlying atmosphere is unknown. We calculate the anisotropy of the radiation field with plane-parallel semi-empirical models under the nonlocal thermal equilibrium condition and derive linear polarization signals for all possible parameters of magnetic field vectors based on an analytical solution of the atomic polarization and Hanle effect. We find that the semi-empirical models of the inter-network region (FAL-A) and network region (FAL-F) show similar degrees of anisotropy in the radiation field, and this similarity results in an acceptable inversion error (e.g., ∼40 G instead of 50 G in field strength and ∼100∘ instead of 90∘ in inclination) when FAL-A and FAL-F are swapped. However, the semi-empirical models of FAL-C (averaged quiet-Sun model including both inter-network and network regions) and FAL-P (plage regions) yield an atomic polarization that deviates from all other models, which makes it difficult to precisely determine the magnetic field vector if the correct atmospheric model is not known (e.g., the inversion error is much larger than 40% of the field strength; >70 G instead of 50 G). These results clearly demonstrate that the choice of model atmosphere is important for Hanle diagnostics. As is well known, one way to constrain the average atmospheric stratification is to measure the center-to-limb variation of the linear polarization signals. The dependence of the center-to-limb variations on the atmospheric model is also presented in this paper. Title: From Hinode to the Next-Generation Solar Observation Missions Authors: Ichimoto, Kiyoshi; Hara, Hirohisa; Katsukawa, Yukio; Ishikawa, Ryoko Bibcode: 2018ASSL..449..231I Altcode: No abstract at ADS Title: Comparison of Solar Fine Structure Observed Simultaneously in Lyα and Mg II h Authors: Schmit, D.; Sukhorukov, A. V.; De Pontieu, B.; Leenaarts, J.; Bethge, C.; Winebarger, A.; Auchère, F.; Bando, T.; Ishikawa, R.; Kano, R.; Kobayashi, K.; Narukage, N.; Trujillo Bueno, J. Bibcode: 2017ApJ...847..141S Altcode: 2017arXiv170900035S The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the Sun in H I Lyα during a suborbital rocket flight on 2015 September 3. The Interface Region Imaging Telescope (IRIS) coordinated with the CLASP observations and recorded nearly simultaneous and co-spatial observations in the Mg II h and k lines. The Mg II h and Lyα lines are important transitions, energetically and diagnostically, in the chromosphere. The canonical solar atmosphere model predicts that these lines form in close proximity to each other and so we expect that the line profiles will exhibit similar variability. In this analysis, we present these coordinated observations and discuss how the two profiles compare over a region of quiet Sun at viewing angles that approach the limb. In addition to the observations, we synthesize both line profiles using a 3D radiation-MHD simulation. In the observations, we find that the peak width and the peak intensities are well correlated between the lines. For the simulation, we do not find the same relationship. We have attempted to mitigate the instrumental differences between IRIS and CLASP and to reproduce the instrumental factors in the synthetic profiles. The model indicates that formation heights of the lines differ in a somewhat regular fashion related to magnetic geometry. This variation explains to some degree the lack of correlation, observed and synthesized, between Mg II and Lyα. Our analysis will aid in the definition of future observatories that aim to link dynamics in the chromosphere and transition region. Title: CLASP/SJ Observations of Rapid Time Variations in the Lyα Emission in a Solar Active Region Authors: Ishikawa, Shin-nosuke; Kubo, Masahito; Katsukawa, Yukio; Kano, Ryouhei; Narukage, Noriyuki; Ishikawa, Ryohko; Bando, Takamasa; Winebarger, Amy; Kobayashi, Ken; Trujillo Bueno, Javier; Auchère, Frédéric Bibcode: 2017ApJ...846..127I Altcode: The Chromospheric Lyα SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on 2015 September 3 to investigate the solar chromosphere and transition region. The slit-jaw (SJ) optical system captured Lyα images with a high time cadence of 0.6 s. From the CLASP/SJ observations, many variations in the solar chromosphere and transition region emission with a timescale of <1 minute were discovered. In this paper, we focus on the active region within the SJ field of view and investigate the relationship between short (<30 s) temporal variations in the Lyα emission and the coronal structures observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). We compare the Lyα temporal variations at the coronal loop footpoints observed in the AIA 211 Å (≈2 MK) and AIA 171 Å (≈0.6 MK) channels with those in the regions with bright Lyα features without a clear association with the coronal loop footpoints. We find more short (<30 s) temporal variations in the Lyα intensity in the footpoint regions. Those variations did not depend on the temperature of the coronal loops. Therefore, the temporal variations in the Lyα intensity at this timescale range could be related to the heating of the coronal structures up to temperatures around the sensitivity peak of 171 Å. No signature was found to support the scenario that these Lyα intensity variations were related to the nanoflares. Waves or jets from the lower layers (lower chromosphere or photosphere) are possible causes for this phenomenon. Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter Authors: Rachmeler, Laurel; E McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier; Auchère, Frédéric; Kobayashi, Ken; Winebarger, Amy; Bethge, Christian; Kano, Ryouhei; Kubo, Masahito; Song, Donguk; Narukage, Noriyuki; Ishikawa, Shin-nosuke; De Pontieu, Bart; Carlsson, Mats; Yoshida, Masaki; Belluzzi, Luca; Stepan, Jiri; del Pino Alemná, Tanausú; Ballester, Ernest Alsina; Asensio Ramos, Andres Bibcode: 2017SPD....4811010R Altcode: We present the instrument, science case, and timeline of the CLASP2 sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha Spectro-Polarimeter) sounding rocket flight in 2015 resulted in the first-ever linear polarization measurements of solar hydrogen Lyman-alpha line, which is sensitive to the Hanle effect and can be used to constrain the magnetic field and geometric complexity of the upper chromosphere. Ly-alpha is one of several upper chromospheric lines that contain magnetic information. In the spring of 2019, we will re-fly the modified CLASP telescope to measure the full Stokes profile of Mg II h & k near 280 nm. This set of lines is sensitive to the upper chromospheric magnetic field via both the Hanle and the Zeeman effects. Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.; Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.; Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.; De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.; del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A. Bibcode: 2017shin.confE..79R Altcode: We present the instrument, science case, and timeline of the CLASP2 sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha Spectro-Polarimeter) sounding rocket flight in 2015 resulted in the first-ever linear polarization measurements of solar hydrogen Lyman-alpha line, which is sensitive to the Hanle effect and can be used to constrain the magnetic field and geometric complexity of the upper chromosphere. Ly-alpha is one of several upper chromospheric lines that contain magnetic information. In the spring of 2019, we will re-fly the modified CLASP telescope to measure the full Stokes profile of Mg II h & k near 280 nm. This set of lines is sensitive to the upper chromospheric magnetic field via both the Hanle and the Zeeman effects. Title: Indication of the Hanle Effect by Comparing the Scattering Polarization Observed by CLASP in the Lyα and Si III 120.65 nm Lines Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.; Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa, Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.; Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R. Bibcode: 2017ApJ...841...31I Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding rocket experiment that has provided the first successful measurement of the linear polarization produced by scattering processes in the hydrogen Lyα line (121.57 nm) radiation of the solar disk. In this paper, we report that the Si III line at 120.65 nm also shows scattering polarization and we compare the scattering polarization signals observed in the Lyα and Si III lines in order to search for observational signatures of the Hanle effect. We focus on four selected bright structures and investigate how the U/I spatial variations vary between the Lyα wing, the Lyα core, and the Si III line as a function of the total unsigned photospheric magnetic flux estimated from Solar Dynamics Observatory/Helioseismic and Magnetic Imager observations. In an internetwork region, the Lyα core shows an antisymmetric spatial variation across the selected bright structure, but it does not show it in other more magnetized regions. In the Si III line, the spatial variation of U/I deviates from the above-mentioned antisymmetric shape as the total unsigned photospheric magnetic flux increases. A plausible explanation of this difference is the operation of the Hanle effect. We argue that diagnostic techniques based on the scattering polarization observed simultaneously in two spectral lines with very different sensitivities to the Hanle effect, like Lyα and Si III, are of great potential interest for exploring the magnetism of the upper solar chromosphere and transition region. Title: Polarization Calibration of the Chromospheric Lyman-Alpha SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV Range. Part II: In-Flight Calibration Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.; Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M. Bibcode: 2017SoPh..292...57G Altcode: The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding rocket instrument designed to measure for the first time the linear polarization of the hydrogen Lyman-α line (121.6 nm). The instrument was successfully launched on 3 September 2015 and observations were conducted at the solar disc center and close to the limb during the five-minutes flight. In this article, the disc center observations are used to provide an in-flight calibration of the instrument spurious polarization. The derived in-flight spurious polarization is consistent with the spurious polarization levels determined during the pre-flight calibration and a statistical analysis of the polarization fluctuations from solar origin is conducted to ensure a 0.014% precision on the spurious polarization. The combination of the pre-flight and the in-flight polarization calibrations provides a complete picture of the instrument response matrix, and a proper error transfer method is used to confirm the achieved polarization accuracy. As a result, the unprecedented 0.1% polarization accuracy of the instrument in the vacuum ultraviolet is ensured by the polarization calibration. Title: Discovery of Scattering Polarization in the Hydrogen Lyα Line of the Solar Disk Radiation Authors: Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchère, F.; Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.; Štěpán, J.; Asensio Ramos, A.; Manso Sainz, R.; Champey, P.; Cirtain, J.; De Pontieu, B.; Casini, R.; Carlsson, M. Bibcode: 2017ApJ...839L..10K Altcode: 2017arXiv170403228K There is a thin transition region (TR) in the solar atmosphere where the temperature rises from 10,000 K in the chromosphere to millions of degrees in the corona. Little is known about the mechanisms that dominate this enigmatic region other than the magnetic field plays a key role. The magnetism of the TR can only be detected by polarimetric measurements of a few ultraviolet (UV) spectral lines, the Lyα line of neutral hydrogen at 121.6 nm (the strongest line of the solar UV spectrum) being of particular interest given its sensitivity to the Hanle effect (the magnetic-field-induced modification of the scattering line polarization). We report the discovery of linear polarization produced by scattering processes in the Lyα line, obtained with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) rocket experiment. The Stokes profiles observed by CLASP in quiet regions of the solar disk show that the Q/I and U/I linear polarization signals are of the order of 0.1% in the line core and up to a few percent in the nearby wings, and that both have conspicuous spatial variations with scales of ∼10 arcsec. These observations help constrain theoretical models of the chromosphere-corona TR and extrapolations of the magnetic field from photospheric magnetograms. In fact, the observed spatial variation from disk to limb of polarization at the line core and wings already challenge the predictions from three-dimensional magnetohydrodynamical models of the upper solar chromosphere. Title: High-Reflectivity Coatings for a Vacuum Ultraviolet Spectropolarimeter Authors: Narukage, Noriyuki; Kubo, Masahito; Ishikawa, Ryohko; Ishikawa, Shin-nosuke; Katsukawa, Yukio; Kobiki, Toshihiko; Giono, Gabriel; Kano, Ryouhei; Bando, Takamasa; Tsuneta, Saku; Auchère, Frédéric; Kobayashi, Ken; Winebarger, Amy; McCandless, Jim; Chen, Jianrong; Choi, Joanne Bibcode: 2017SoPh..292...40N Altcode: Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-α (Lyα ; 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Lyα optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Lyα , whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (∼5 % on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Lyα line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015. Title: Polarization Calibration of the Chromospheric Lyman-Alpha SpectroPolarimeter for a 0.1 % Polarization Sensitivity in the VUV Range. Part I: Pre-flight Calibration Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J. Bibcode: 2016SoPh..291.3831G Altcode: 2016SoPh..tmp..177G The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) is a sounding rocket experiment designed to measure for the first time the linear polarization of the hydrogen Lyman-α line (121.6 nm) and requires a 0.1 % polarization sensitivity, which is unprecedented for a spectropolarimeter in the vacuum UV (VUV) spectral range. Title: Discovery of Ubiquitous Fast-Propagating Intensity Disturbances by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP) Authors: Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Kano, R.; Bando, T.; Narukage, N.; Ishikawa, R.; Hara, H.; Giono, G.; Tsuneta, S.; Ishikawa, S.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.; Auchère, F.; Trujillo Bueno, J.; Asensio Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M. Bibcode: 2016ApJ...832..141K Altcode: High-cadence observations by the slit-jaw (SJ) optics system of the sounding rocket experiment known as the Chromospheric Lyman Alpha Spectropolarimeter (CLASP) reveal ubiquitous intensity disturbances that recurrently propagate in either the chromosphere or the transition region or both at a speed much higher than the speed of sound. The CLASP/SJ instrument provides a time series of two-dimensional images taken with broadband filters centered on the Lyα line at a 0.6 s cadence. The multiple fast-propagating intensity disturbances appear in the quiet Sun and in an active region, and they are clearly detected in at least 20 areas in a field of view of 527″ × 527″ during the 5 minute observing time. The apparent speeds of the intensity disturbances range from 150 to 350 km s-1, and they are comparable to the local Alfvén speed in the transition region. The intensity disturbances tend to propagate along bright elongated structures away from areas with strong photospheric magnetic fields. This suggests that the observed fast-propagating intensity disturbances are related to the magnetic canopy structures. The maximum distance traveled by the intensity disturbances is about 10″, and the widths are a few arcseconds, which are almost determined by a pixel size of 1.″03. The timescale of each intensity pulse is shorter than 30 s. One possible explanation for the fast-propagating intensity disturbances observed by CLASP is magnetohydrodynamic fast-mode waves. Title: Optical alignment of the Chromospheric Lyman-Alpha Spectro-Polarimeter using sophisticated methods to minimize activities under vacuum Authors: Giono, G.; Katsukawa, Y.; Ishikawa, R.; Narukage, N.; Kano, R.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J. Bibcode: 2016SPIE.9905E..3DG Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument developed at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. The instrument main scientific goal is to achieve polarization measurement of the Lyman-α line at 121.56 nm emitted from the solar upper-chromosphere and transition region with an unprecedented 0.1% accuracy. The optics are composed of a Cassegrain telescope coated with a "cold mirror" coating optimized for UV reflection and a dual-channel spectrograph allowing for simultaneous observation of the two orthogonal states of polarization. Although the polarization sensitivity is the most important aspect of the instrument, the spatial and spectral resolutions of the instrument are also crucial to observe the chromospheric features and resolve the Ly-α profiles. A precise alignment of the optics is required to ensure the resolutions, but experiments under vacuum conditions are needed since Ly-α is absorbed by air, making the alignment experiments difficult. To bypass this issue, we developed methods to align the telescope and the spectrograph separately in visible light. We explain these methods and present the results for the optical alignment of the CLASP telescope and spectrograph. We then discuss the combined performances of both parts to derive the expected resolutions of the instrument, and compare them with the flight observations performed on September 3rd 2015. Title: Chromospheric LAyer SpectroPolarimeter (CLASP2) Authors: Narukage, Noriyuki; McKenzie, David E.; Ishikawa, Ryoko; Trujillo-Bueno, Javier; De Pontieu, Bart; Kubo, Masahito; Ishikawa, Shin-nosuke; Kano, Ryouhei; Suematsu, Yoshinori; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Cirtain, Jonathan W.; Winebarger, Amy R.; Asensio Ramos, Andres; del Pino Aleman, Tanausu; Štępán, Jiri; Belluzzi, Luca; Larruquert, Juan Ignacio; Auchère, Frédéric; Leenaarts, Jorrit; Carlsson, Mattias J. L. Bibcode: 2016SPIE.9905E..08N Altcode: The sounding rocket Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) was launched on September 3rd, 2015, and successfully detected (with a polarization accuracy of 0.1 %) the linear polarization signals (Stokes Q and U) that scattering processes were predicted to produce in the hydrogen Lyman-alpha line (Lyα 121.567 nm). Via the Hanle effect, this unique data set may provide novel information about the magnetic structure and energetics in the upper solar chromosphere. The CLASP instrument was safely recovered without any damage and we have recently proposed to dedicate its second flight to observe the four Stokes profiles in the spectral region of the Mg II h and k lines around 280 nm; in these lines the polarization signals result from scattering processes and the Hanle and Zeeman effects. Here we describe the modifications needed to develop this new instrument called the "Chromospheric LAyer SpectroPolarimeter" (CLASP2). Title: In-flight performance of the polarization modulator in the CLASP rocket experiment Authors: Ishikawa, Shin-nosuke; Shimizu, Toshifumi; Kano, Ryohei; Bando, Takamasa; Ishikawa, Ryoko; Giono, Gabriel; Beabout, Dyana L.; Beabout, Brent L.; Nakayama, Satoshi; Tajima, Takao Bibcode: 2016SPIE.9905E..2UI Altcode: We developed a polarization modulation unit (PMU), a motor system to rotate a waveplate continuously. In polarization measurements, the continuous rotating waveplate is an important element as well as a polarization analyzer to record the incident polarization in a time series of camera exposures. The control logic of PMU was originally developed for the next Japanese solar observation satellite SOLAR-C by the SOLAR-C working group. We applied this PMU for the Chromospheric Lyman-alpha SpectroPolarimeter (CLASP). CLASP is a sounding rocket experiment to observe the linear polarization of the Lyman-alpha emission (121.6 nm vacuum ultraviolet) from the upper chromosphere and transition region of the Sun with a high polarization sensitivity of 0.1 % for the first time and investigate their vector magnetic field by the Hanle effect. The driver circuit was developed to optimize the rotation for the CLASP waveplate (12.5 rotations per minute). Rotation non- uniformity of the waveplate causes error in the polarization degree (i.e. scale error) and crosstalk between Stokes components. We confirmed that PMU has superior rotation uniformity in the ground test and the scale error and crosstalk of Stokes Q and U are less than 0.01 %. After PMU was attached to the CLASP instrument, we performed vibration tests and confirmed all PMU functions performance including rotation uniformity did not change. CLASP was successfully launched on September 3, 2015, and PMU functioned well as designed. PMU achieved a good rotation uniformity, and the high precision polarization measurement of CLASP was successfully achieved. Title: Spectro-polarimetric observation in UV with CLASP to probe the chromosphere and transition region Authors: Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère, Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi, Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi; Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto; Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca; Carlsson, Mats Bibcode: 2016SPD....4710107K Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA sounding-rocket experiment that was performed in White Sands in the US on September 3, 2015. During its 5-minute ballistic flight, CLASP successfully made the first spectro-polarimetric observation in the Lyman-alpha line (121.57 nm) originating in the chromosphere and transition region. Since the Lyman-alpha polarization is sensitive to magnetic field of 10-100 G by the Hanle effect, we aim to infer the magnetic field information in such upper solar atmosphere with this experiment.The obtained CLASP data showed that the Lyman-alpha scattering polarization is about a few percent in the wings and the order of 0.1% in the core near the solar limb, as it had been theoretically predicted, and that both polarization signals have a conspicuous spatio-temporal variability. CLASP also observed another upper-chromospheric line, Si III (120.65 nm), whose critical field strength for the Hanle effect is 290 G, and showed a measurable scattering polarization of a few % in this line. The polarization properties of the Si III line could facilitate the interpretation of the scattering polarization observed in the Lyman-alpha line.In this presentation, we would like to show how the upper chromosphere and transition region are seen in the polarization of these UV lines and discuss the possible source of these complicated polarization signals. Title: Development of Active Regions: Flows, Magnetic-Field Patterns and Bordering Effect Authors: Getling, A. V.; Ishikawa, R.; Buchnev, A. A. Bibcode: 2016SoPh..291..371G Altcode: 2016SoPh..tmp....9G; 2015arXiv150601848G A qualitative analysis is given of the data on the full magnetic and velocity vector fields in a growing sunspot group, recorded nearly simultaneously with the Solar Optical Telescope on the Hinode satellite. Observations of a young bipolar subregion developing within AR 11313 were carried out on 9 - 10 October 2011. Our aim was to form an idea about the consistency of the observed pattern with the well-known rising-tube model of the formation of bipolar active regions and sunspot groups. We find from our magnetograms that the distributions of the vertical [Bv] and the horizontal [Bh] component of the magnetic field over the area of the magnetic subregion are spatially well correlated; in contrast, the rise of a flux-tube loop would result in a qualitatively different pattern, with the maxima of the two magnetic-field components spatially separated: the vertical field would be the strongest where either spot emerges, while the maximum horizontal-field strengths would be reached in between them. A specific feature, which we call the bordering effect, is revealed: some local extrema of Bv are bordered with areas of locally enhanced Bh. This effect suggests a fountainlike spatial structure of the magnetic field near the Bv extrema, which is also hardly compatible with the emergence of a flux-tube loop. The vertical-velocity field in the area of the developing active subregion does not exhibit any upflow on the scale of the whole subregion, which should be related to the rising-tube process. Thus, our observational data can hardly be interpreted in the framework of the rising-tube model. Title: Development of a Precise Polarization Modulator for UV Spectropolarimetry Authors: Ishikawa, S.; Shimizu, T.; Kano, R.; Bando, T.; Ishikawa, R.; Giono, G.; Tsuneta, S.; Nakayama, S.; Tajima, T. Bibcode: 2015SoPh..290.3081I Altcode: 2015arXiv150905716I; 2015SoPh..tmp..120I We developed a polarization modulation unit (PMU) to rotate a waveplate continuously in order to observe solar magnetic fields by spectropolarimetry. The non-uniformity of the PMU rotation may cause errors in the measurement of the degree of linear polarization (scale error) and its angle (crosstalk between Stokes-Q and -U ), although it does not cause an artificial linear polarization signal (spurious polarization). We rotated a waveplate with the PMU to obtain a polarization modulation curve and estimated the scale error and crosstalk caused by the rotation non-uniformity. The estimated scale error and crosstalk were <0.01 % for both. This PMU will be used as a waveplate motor for the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) rocket experiment. We confirm that the PMU performs and functions sufficiently well for CLASP. Title: CLASP: A UV Spectropolarimeter on a Sounding Rocket for Probing theChromosphere-Corona Transition Regio Authors: Ishikawa, Ryohko; Kano, Ryouhei; Winebarger, Amy; Auchere, Frederic; Trujillo Bueno, Javier; Bando, Takamasa; Narukage, Noriyuki; Kobayashi, Ken; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-nosuke; Giono, Gabriel; Tsuneta, Saku; Hara, Hirohisa; Suematsu, Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Ichimoto, Kiyoshi; Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca Bibcode: 2015IAUGA..2254536I Altcode: The wish to understand the energetic phenomena of the outer solar atmosphere makes it increasingly important to achieve quantitative information on the magnetic field in the chromosphere-corona transition region. To this end, we need to measure and model the linear polarization produced by scattering processes and the Hanle effect in strong UV resonance lines, such as the hydrogen Lyman-alpha line. A team consisting of Japan, USA, Spain, France, and Norway has been developing a sounding rocket experiment called the Chromospheric Lyman-alpha Spectro-Polarimeter (CLASP). The aim is to detect the scattering polarization produced by anisotropic radiation pumping in the hydrogen Lyman-alpha line (121.6 nm), and via the Hanle effect to try to constrain the magnetic field vector in the upper chromosphere and transition region. In this talk, we will present an overview of our CLASP mission, its scientific objectives, ground tests made, and the latest information on the launch planned for the Summer of 2015. Title: Doubts about the crucial role of the rising-tube mechanism in the formation of sunspot groups Authors: Getling, A. V.; Ishikawa, R.; Buchnev, A. A. Bibcode: 2015AdSpR..55..862G Altcode: 2014arXiv1401.8077G Some preliminary processing results are presented for a dataset obtained with the Solar Optical Telescope on the Hinode satellite. The idea of the project is to record, nearly simultaneously, the full velocity and magnetic-field vectors in growing active regions and sunspot groups at a photospheric level. Our ultimate aim is to elaborate observational criteria to distinguish between the manifestations of two mechanisms of sunspot-group formation - the rising of an Ω -shaped flux tube of a strong magnetic field and the in situ amplification and structuring of magnetic field by convection (the convective mechanism is briefly described).

Observations of a young bipolar subregion developing within AR 11313 were carried out on 9-10 October 2011. During each 2-h observational session, 5576-Å filtergrams and Dopplergrams were obtained at a time cadence of 2 min, and one or two 32-min-long spectropolarimetric fast-mode scans were done. Based on the series of filtergrams, the trajectories of corks are computed, using a technique similar to but more reliable than local correlation tracking (LCT), and compared with the magnetic maps. At this stage of the investigation, only the vertical magnetic field and the horizontal flows are used for a qualitative analysis.

According to our preliminary findings, the velocity pattern in the growing active region has nothing to do with a spreading flow on the scale of the entire bipolar region, which could be expected if a tube of strong magnetic field emerged. No violent spreading flows on the scale of the entire growing magnetic region can be identified. Instead, normal mesogranular and supergranular flows are preserved. Signs of small-scale structuring of the magnetic field can be detected in the area where new spots develop, and signs of the presence of separatrices between the magnetic polarities can be found, such that the surface flows converge to but not diverge from these separatrix curves. The observed scenario of evolution seems to agree with Bumba's inference that the development of an active region does not entail the destruction of the existing convective-velocity field. The convective mechanism appears to be better compatible with observations than the rising-tube mechanism.

In the umbras of the well-developed sunspots, flows converging to the umbra centres are revealed. Spreading streams are present around these spots. Title: Strategy for Realizing High-Precision VUV Spectro-Polarimeter Authors: Ishikawa, R.; Narukage, N.; Kubo, M.; Ishikawa, S.; Kano, R.; Tsuneta, S. Bibcode: 2014SoPh..289.4727I Altcode: 2014SoPh..tmp..116I Spectro-polarimetric observations in the vacuum ultraviolet (VUV) range are currently the only means to measure magnetic fields in the upper chromosphere and transition region of the solar atmosphere. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) aims to measure linear polarization at the hydrogen Lyman-α line (121.6 nm). This measurement requires a polarization sensitivity better than 0.1 %, which is unprecedented in the VUV range. We here present a strategy with which to realize such high-precision spectro-polarimetry. This involves the optimization of instrument design, testing of optical components, extensive analyses of polarization errors, polarization calibration of the instrument, and calibration with onboard data. We expect that this strategy will aid the development of other advanced high-precision polarimeters in the UV as well as in other wavelength ranges. Title: Precision VUV Spectro-Polarimetry for Solar Chromospheric Magnetic Field Measurements Authors: Ishikawa, R.; Bando, T.; Hara, H.; Ishikawa, S.; Kano, R.; Kubo, M.; Katsukawa, Y.; Kobiki, T.; Narukage, N.; Suematsu, Y.; Tsuneta, S.; Aoki, K.; Miyagawa, K.; Ichimoto, K.; Kobayashi, K.; Auchère, F.; Clasp Team Bibcode: 2014ASPC..489..319I Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV spectro-polarimeter optimized for measuring the linear polarization of the Lyman-α line (121.6 nm) to be launched in 2015 with NASA's sounding rocket (Ishikawa et al. 2011; Narukage et al. 2011; Kano et al. 2012; Kobayashi et al. 2012). With this experiment, we aim to (1) observe the scattering polarization in the Lyman-α line, (2) detect the Hanle effect, and (3) assess the magnetic fields in the upper chromosphere and transition region for the first time. The polarization measurement error consists of scale error δ a (error in amplitude of linear polarization), azimuth error Δφ (error in the direction of linear polarization), and spurious polarization ɛ (false linear polarization signals). The error ɛ should be suppressed below 0.1% in the Lyman-α core (121.567 nm ±0.02 nm), and 0.5% in the Lyman-α wing (121.567 nm ±0.05 nm), based on our scientific requirements shown in Table 2 of Kubo et al. (2014). From scientific justification, we adopt Δ φ<2° and δ a<10% as the instrument requirements. The spectro-polarimeter features a continuously rotating MgF2 waveplate (Ishikawa et al. 2013), a dual-beam spectrograph with a spherical grating working also as a beam splitter, and two polarization analyzers (Bridou et al. 2011), which are mounted at 90 degree from each other to measure two orthogonal polarization simultaneously. For the optical layout of the CLASP instrument, see Figure 3 in Kubo et al. (2014). Considering the continuous rotation of the half-waveplate, the modulation efficiency is 0.64 both for Stokes Q and U. All the raw data are returned and demodulation (successive addition or subtraction of images) is done on the ground.

We control the CLASP polarization performance in the following three steps. First, we evaluate the throughput and polarization properties of each optical component in the Lyman-α line, using the Ultraviolet Synchrotron ORbital Radiation Facility (UVSOR) at the Institute for Molecular Science. The second step is polarization calibration of the spectro-polarimeter after alignment. Since the spurious polarization caused by the axisymmetric telescope is estimated to be negligibly small because of the symmetry (Ishikawa et al. 2014), we do not perform end-to-end polarization calibration. As the final step, before the scientific observation near the limb, we make a short observation at the Sun center and verify the polarization sensitivity, because the scattering polarization is expected to be close to zero at the Sun center due to symmetric geometry. In order to clarify whether we will be able to achieve the required polarization sensitivity and accuracy via these steps, we exercise polarization error budget, by investigating all the possible causes and their magnitudes of polarization errors, all of which are not necessarily verified by the polarization calibration. Based on these error budgets, we conclude that a polarization sensitivity of 0.1% in the line core, δ a<10% and Δ φ<2° can be achieved combined with the polarization calibration of the spectro-polarimeter and the onboard calibration at the Sun center(refer to Ishikawa et al. 2014, for the detail).

We are currently conducting verification tests of the flight components and development of the UV light source for the polarization calibration. From 2014 spring, we will begin the integration, alignment, and calibration. We will update the error budgets throughout the course of these tests. Title: A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) Authors: Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.; Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway, T.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchère, F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; Asensio Ramos, A.; Štěpán, J.; Carlsson, M. Bibcode: 2014ASPC..489..307K Altcode: A sounding-rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is presently under development to measure the linear polarization profiles in the hydrogen Lyman-alpha (Lyα) line at 121.567 nm. CLASP is a vacuum-UV (VUV) spectropolarimeter to aim for first detection of the linear polarizations caused by scattering processes and the Hanle effect in the Lyα line with high accuracy (0.1%). This is a fist step for exploration of magnetic fields in the upper chromosphere and transition region of the Sun. Accurate measurements of the linear polarization signals caused by scattering processes and the Hanle effect in strong UV lines like Lyα are essential to explore with future solar telescopes the strength and structures of the magnetic field in the upper chromosphere and transition region of the Sun. The CLASP proposal has been accepted by NASA in 2012, and the flight is planned in 2015. Title: Current progress of optical alignment procedure of CLASP's Lyman-alpha polarimetry instrument Authors: Giono, G.; Ishikawa, R.; Katsukawa, Y.; Bando, T.; Kano, R.; Suematsu, Y.; Narukage, N.; Sakao, Taro; Kobayashi, K.; Auchère, F. Bibcode: 2014SPIE.9144E..3EG Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument currently under development at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. CLASP's optics are composed of a Cassegrain telescope and a spectro-polarimeter which are designed to achieve an unprecedentedly accurate polarization measurement of the Ly-α line at 121.6nm emitted from the solar upper-chromosphere and transition region. CLASP's first flight is scheduled for August 2015. Reaching such accuracy requires a careful alignment of the optical elements to optimize the image quality at 121.6 nm. However Ly-α is absorbed by air and therefore the optics alignment has to be done under vacuum condition which makes any experiment difficult. To bypass this issue, we proposed to align the telescope and the spectrograph separately in visible light. Hence we present our alignment procedure for both telescope and spectro-polarimeter. We will explain details about the telescope preliminary alignment before mirrors coating, which was done in April 2014, present the telescope combined optical performance and compare them to CLASP tolerance. Then we will present details about an experiment designed to confirm our alignment procedure for the CLASP spectro-polarimeter. We will discuss the resulting image quality achieved during this experiment and the lessons learned. Title: On the Inversion of the Scattering Polarization and the Hanle Effect Signals in the Hydrogen Lyα Line Authors: Ishikawa, R.; Asensio Ramos, A.; Belluzzi, L.; Manso Sainz, R.; Štěpán, J.; Trujillo Bueno, J.; Goto, M.; Tsuneta, S. Bibcode: 2014ApJ...787..159I Altcode: 2014arXiv1404.0786I Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio β is lower than unity, are essential for understanding the thermal structure and dynamical activity of the solar atmosphere. Recent developments in the theory and numerical modeling of polarization in spectral lines have suggested that information on the magnetic field of the chromosphere-corona transition region could be obtained by measuring the linear polarization of the solar disk radiation at the core of the hydrogen Lyα line at 121.6 nm, which is produced by scattering processes and the Hanle effect. The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) sounding rocket experiment aims to measure the intensity (Stokes I) and the linear polarization profiles (Q/I and U/I) of the hydrogen Lyα line. In this paper, we clarify the information that the Hanle effect can provide by applying a Stokes inversion technique based on a database search. The database contains all theoretical Q/I and U/I profiles calculated in a one-dimensional semi-empirical model of the solar atmosphere for all possible values of the strength, inclination, and azimuth of the magnetic field vector, though this atmospheric region is highly inhomogeneous and dynamic. We focus on understanding the sensitivity of the inversion results to the noise and spectral resolution of the synthetic observations as well as the ambiguities and limitation inherent to the Hanle effect when only the hydrogen Lyα is used. We conclude that spectropolarimetric observations with CLASP can indeed be a suitable diagnostic tool for probing the magnetism of the transition region, especially when complemented with information on the magnetic field azimuth that can be obtained from other instruments. Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP) Authors: Kano, Ryouhei; Katsukawa, Yukio; Kubo, Masahito; Auchere, Frederic; Ishikawa, Ryohko; Kobayashi, Ken; Narukage, Noriyuki; Trujillo Bueno, Javier; Bando, Takamasa; Ishikawa, Shin-nosuke Bibcode: 2014cosp...40E1383K Altcode: In the solar chromosphere, magneto-hydrodynamic waves and super-sonic jets ubiquitously happen as revealed by the Japanese solar satellite Hinode. Now, we understand that the solar chromosphere is not a simple intermediate layer smoothly connecting the photosphere and corona, but a site where those dynamics may play an important role in the chromospheric and coronal heating. Such discoveries imply that the next frontier in solar physics lies in simultaneous observations between the dynamics and magnetic structures in the chromosphere and transition region, where the gas-dominant photosphere changes to the magnetic-dominant corona. Therefore, we promote the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which is a NASA's sounding rocket experiment scheduled in 2015 for aiming to infer the magnetic field information in the solar chromosphere and transition region. CLASP makes precise measurement (0.1%) of the polarization profile of the Lyman-alpha line, and aims to make the first ever measurement of the Hanle effect polarization caused by magnetic fields in the upper solar atmosphere. It is also a pathfinder to establish a new measurement tool for chromospheric and transition-region magnetic fields, and to make progress on chromospheric studies in future missions. Title: Formation of sunspot groups: Do we see manifestations of the rising-tube mechanism? Authors: Getling, Alexander; Ishikawa, Ryohko; Buchnev, Aleksei Bibcode: 2014cosp...40E.974G Altcode: A comparison is made between the expected manifestations of two mechanisms suggested to account for the formation of local photospheric magnetic fields, viz., the rising of an Omega-shaped flux tube of a strong magnetic field and the emph{in situ} amplification and structuring of magnetic field by convection. The ultimate aim of the study is to elaborate observational criteria to find out which mechanism controls the process in any given case. To this end, the full velocity and magnetic-field vectors in growing active regions and sunspot groups at a photospheric level were recorded nearly simultaneously. Observations of a young bipolar subregion developing within AR 11313 were carried out on 9-10 October 2011, with the Solar Optical Telescope on the emph{Hinode} satellite, which yielded 5576-Å filtergrams and Dopplergrams and also spectropolarimetric records of the magnetic-field vector. To determine the tangential-velocity field, a technique similar to but more reliable than local correlation tracking (LCT) was applied to the series of filtergrams, and the trajectories of corks were computed. According to our preliminary findings, the velocity pattern in the growing active region cannot be described as a spreading flow on the scale of the entire bipolar region, which could be expected if a tube of strong magnetic field emerged. Instead, normal mesogranular and supergranular flows are observed in agreement with Bumba’s inference that the development of an active region does not entail the destruction of the existing convective-velocity field. Between the magnetic polarities, curves can be found to which the surface flows converge rather than diverging from them under the action of a rising tube. The convective mechanism appears to be better compatible with observations than the rising-tube mechanism. In the umbras of the well-developed sunspots, flows converging to the umbra centres are revealed. Spreading streams are present around these spots. 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). This work was supported by the Russian Foundation for Basic Research (project no. 12-02-00792-a). Title: UV spectropolarimeter design for precise polarization measurement and its application to the CLASP for exploration of magnetic fields in solar atmosphere Authors: Narukage, Noriyuki; Katsukawa, Yukio; Hara, Hirohisa; Kubo, Masahito; Auchere, Frederic; Ishikawa, Ryohko; Kano, Ryouhei; Bando, Takamasa; Ishikawa, Shin-nosuke; Suematsu, Yoshinori; Tsuneta, Saku Bibcode: 2014cosp...40E2232N Altcode: In order to measure the magnetic field in the region where the hot plasma from 10 (4) K to 10 (6) K is occupied, e.g., for solar atmosphere, the polarimetric measurements in ultra violet (UV) with 0.1% accuracy are required. In this paper, we propose a new UV spectropolarimeter design with 0.1% sensitivity in polarization measurement. This spectropolarimeter has two devices for the 0.1% accuracy. First, all optical components except the waveplate are the reflective type ones that can be equipped with the high reflectivity coating for the high throughput. Secondly, it equips the optically symmetric dual channels to measure the orthogonal linear polarization state simultaneously, using a concave diffraction grating as both the spectral dispersion element and the beam splitter. These two devices make the spurious polarizations caused by the photon noise, by the intensity variation of the observation target, and, by the instrument itself, enough small to achieve the 0.1% accuracy in polarization measurement. The spectropolarimeter thus designed is currently under fabrication for the sounding rocket project of Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) that aims at the direct measurement of the magnetic fields in solar atmosphere with Lyman-alpha line (121.6 nm) for the first time. Title: Origin of quiet-Sun magnetic fields revealed with Hinode Authors: Ishikawa, Ryohko Bibcode: 2013IAUS..294..143I Altcode: Quiet-Sun magnetic fields are enigmatic in terms of their properties, and their origin is not well understood. One likely possibility is that they are a consequence of interactions with turbulent convective motions of various temporal and spatial scales. Here we investigate the relationship between small-scale magnetic fields and various convection flows. We demonstrate that in addition to granulation and supergranulation, mesogranulation also plays an important role in structuring quiet-Sun magnetic fields. We also study the vector magnetic fields in the quiet Sun, and propose that emerging granular-scale bipolar loops are major sources of the quiet-Sun magnetic fields. Title: Chromospheric Lyman Alpha SpectroPolarimeter: CLASP Authors: Kobayashi, Ken; Kano, R.; Trujillo Bueno, J.; Winebarger, A. R.; Cirtain, J. W.; Bando, T.; De Pontieu, B.; Ishikawa, R.; Katsukawa, Y.; Kubo, M.; Narukage, N.; Sakao, T.; Tsuneta, S.; Auchère, F.; Asensio Ramos, A.; Belluzzi, L.; Carlsson, M.; Casini, R.; Hara, H.; Ichimoto, K.; Manso Sainz, R.; Shimizu, T.; Stepan, J.; Suematsu, Y.; Holloway, T. Bibcode: 2013SPD....44..142K Altcode: The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV spectropolarimeter optimized for measuring the linear polarization of the Lyman-alpha line (121.6 nm). The Lyman-alpha line is predicted to show linear polarization caused by atomic scattering in the chromosphere and modified by the magnetic field through the Hanle effect. The Hanle effect is sensitive to weaker magnetic fields than Zeeman effect, and is not canceled by opposing fields, making it sensitive to tangled or unresolved magnetic field structures. These factors make the Hanle effect a valuable tool for probing the magnetic field in the chromosphere above the quiet sun. To meet this goal, CLASP is designed to measure linear polarization with 0.1% polarization sensitivity at 0.01 nm spectral resolution and 10" spatial resolution. CLASP is scheduled to be launched in 2015. Title: Polar Field Reversal Observations with Hinode Authors: Shiota, D.; Tsuneta, S.; Shimojo, M.; Sako, N.; Orozco Suarez, D.; Ishikawa, R. Bibcode: 2012AGUFMSH13C2274S Altcode: We have been monitoring yearly variation in the Sun's polar magnetic fields with the Solar Optical Telescope aboard Hinode to record their evolution and expected reversal near the solar maximum. All magnetic patches in the magnetic flux maps are automatically identified to obtain the number density and magnetic flux density as a function of the total magnetic flux per patch. The detected magnetic flux per patch ranges over four orders of magnitude (10^15 -- 10^20 Mx). The higher end of the magnetic flux in the polar regions is about one order of magnitude larger than that of the quiet Sun, and nearly that of pores. Almost all large patches ( > 10^18 Mx) have the same polarity, while smaller patches have a fair balance of both polarities. The polarity of the polar region as a whole is consequently determined only by the large magnetic concentrations. A clear decrease in the net flux of the polar region is detected in the slow rising phase of the current solar cycle. The decrease is more rapid in the north polar region than in the south. The decrease in the net flux is caused by a decrease in the number and size of the large flux concentrations as well as the appearance of patches with opposite polarity at lower latitudes. In contrast, we do not see temporal change in the magnetic flux associated with the smaller patches ( < 10^18 Mx) and that of the horizontal magnetic fields during the years 2008--2012. Title: Properties of transient horizontal magnetic fields and their implication to the origin of the quiet-Sun magnetism Authors: Ishikawa, R. Bibcode: 2012IAUSS...6E.103I Altcode: Recent spectropolarimetric observations with high spatial resolution and high polarization sensitivity have provided us with new insight to better understand the quiet-Sun magnetism. This talk is concerned with the ubiquitous transient horizontal magnetic fields in the quiet-Sun, as revealed by the Solar Optical Telescope (SOT) on board Hinode satellite. These horizontal magnetic fields are smaller than the granules, and transient with the lifetime of 1-10 min. The field strength of these magnetic fields is essentially smaller than the equi-paritition field strength corresponding to the granular convective motions. The properties of these magnetic fields are common between the quiet and weak plage regions. These observational consequences would suggest that the local dynamo process driven by the granular convective motions generates these horizontal magnetic fields. Furthermore, the continuous observations from the space enable us to study the relationship between these small-scale magnetic fields and large-scale convections such as the meso- and supergranulations, and lead us to discuss the origin of the quiet Sun magnetism as a whole. We also estimate the magnetic energy flux carried by these horizontal magnetic fields based on the statistical data, and find that the total magnetic energy is comparable to the total chromospheric and coronal energy loss. This enhances the importance of the magnetic fields measurements in the chromosphere. Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP) Authors: Kano, Ryouhei; Bando, Takamasa; Narukage, Noriyuki; Ishikawa, Ryoko; Tsuneta, Saku; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-nosuke; Hara, Hirohisa; Shimizu, Toshifumi; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Sakao, Taro; Goto, Motoshi; Kato, Yoshiaki; Imada, Shinsuke; Kobayashi, Ken; Holloway, Todd; Winebarger, Amy; Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Trujillo Bueno, Javier; Štepán, Jiří; Manso Sainz, Rafael; Belluzzi, Luca; Asensio Ramos, Andres; Auchère, Frédéric; Carlsson, Mats Bibcode: 2012SPIE.8443E..4FK Altcode: One of the biggest challenges in heliophysics is to decipher the magnetic structure of the solar chromosphere. The importance of measuring the chromospheric magnetic field is due to both the key role the chromosphere plays in energizing and structuring the outer solar atmosphere and the inability of extrapolation of photospheric fields to adequately describe this key boundary region. Over the last few years, significant progress has been made in the spectral line formation of UV lines as well as the MHD modeling of the solar atmosphere. It is found that the Hanle effect in the Lyman-alpha line (121.567 nm) is a most promising diagnostic tool for weaker magnetic fields in the chromosphere and transition region. Based on this groundbreaking research, we propose the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) to NASA as a sounding rocket experiment, for making the first measurement of the linear polarization produced by scattering processes and the Hanle effect in the Lyman-alpha line (121.567 nm), and making the first exploration of the magnetic field in the upper chromosphere and transition region of the Sun. The CLASP instrument consists of a Cassegrain telescope, a rotating 1/2-wave plate, a dual-beam spectrograph assembly with a grating working as a beam splitter, and an identical pair of reflective polarization analyzers each equipped with a CCD camera. We propose to launch CLASP in December 2014. Title: Polar Field Reversal Observations with Hinode Authors: Shiota, D.; Tsuneta, S.; Shimojo, M.; Sako, N.; Orozco Suárez, D.; Ishikawa, R. Bibcode: 2012ApJ...753..157S Altcode: 2012arXiv1205.2154S We have been monitoring yearly variation in the Sun's polar magnetic fields with the Solar Optical Telescope aboard Hinode to record their evolution and expected reversal near the solar maximum. All magnetic patches in the magnetic flux maps are automatically identified to obtain the number density and magnetic flux density as a function of the total magnetic flux per patch. The detected magnetic flux per patch ranges over four orders of magnitude (1015-1020 Mx). The higher end of the magnetic flux in the polar regions is about one order of magnitude larger than that of the quiet Sun, and nearly that of pores. Almost all large patches (>=1018 Mx) have the same polarity, while smaller patches have a fair balance of both polarities. The polarity of the polar region as a whole is consequently determined only by the large magnetic concentrations. A clear decrease in the net flux of the polar region is detected in the slow rising phase of the current solar cycle. The decrease is more rapid in the north polar region than in the south. The decrease in the net flux is caused by a decrease in the number and size of the large flux concentrations as well as the appearance of patches with opposite polarity at lower latitudes. In contrast, we do not see temporal change in the magnetic flux associated with the smaller patches (<1018 Mx) and that of the horizontal magnetic fields during the years 2008-2012. Title: The Chromospheric Lyman-Alpha SpectroPolarimeter: CLASP Authors: Kobayashi, K.; Kano, R.; Trujillo-Bueno, J.; Asensio Ramos, A.; Bando, T.; Belluzzi, L.; Carlsson, M.; De Pontieu, R. C. B.; Hara, H.; Ichimoto, K.; Ishikawa, R.; Katsukawa, Y.; Kubo, M.; Manso Sainz, R.; Narukage, N.; Sakao, T.; Stepan, J.; Suematsu, Y.; Tsuneta, S.; Watanabe, H.; Winebarger, A. Bibcode: 2012ASPC..456..233K Altcode: The magnetic field plays a crucial role in the chromosphere and the transition region, and our poor empirical knowledge of the magnetic field in the upper chromosphere and transition region is a major impediment to advancing the understanding of the solar atmosphere. The Hanle effect promises to be a valuable alternative to Zeeman effect as a method of measuring the magnetic field in the chromosphere and transition region; it is sensitive to weaker magnetic fields, and also sensitive to tangled, unresolved field structures.

CLASP is a sounding rocket experiment that aims to observe the Hanle effect polarization of the Lyman α (1215.67Å) line in the solar chromosphere and transition region, and prove the usefulness of this technique in placing constraints on the magnetic field strength and orientation in the low plasma-β region of the solar atmosphere. The Ly-α line has been chosen because it is a chromospheric/transition-region line, and because the Hanle effect polarization of this line is predicted to be sensitive to 10-250 Gauss, encompassing the range of interest. The CLASP instrument is designed to measure linear polarization in the Ly-α line with a polarization sensitivity of 0.1%. The instrument is currently funded for development. The optical design of the instrument has been finalized, and an extensive series of component-level tests are underway to validate the design. Title: Ly-alpha polarimeter design for CLASP rocket experiment Authors: Kubo, M.; Watanabe, H.; Narukage, N.; Ishikawa, R.; Bando, T.; Kano, R.; Tsuneta, S.; Kobayashi, K.; Ichimoto, K.; Trujillo Bueno, J.; Song, D. Bibcode: 2011AGUFM.P11F1627K Altcode: A sounding-rocket program called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is proposed to be launched in the Summer of 2014. CLASP will observe the upper solar chromosphere in Ly-alpha (121.567 nm), aiming to detect the linear polarization signal produced by scattering processes and the Hanle effect for the first time. The CLASP needs a rotating half-waveplate and a polarization analyzer working at the Ly-alpha wavelength to measure the linear polarization signal. We select Magnesium Fluoride (MgF2) as a material of the optical components because of its birefringent property and high transparency at UV wavelength. We have confirmed that the reflection at the Brewster's Angle of MgF2 plate is a good polarization analyzer for the Ly-alpha line by deriving its ordinary refractive index and extinction coefficient along the ordinary and extraordinary axes. These optical parameters are calculated with a least-square fitting in such a way that the reflectance and transmittance satisfy the Kramers-Kronig relation. The reflectance and transmittance against oblique incident angles for the s-polarized and the p-polarized light are measured using the synchrotron beamline at the Ultraviolet Synchrotron Orbital Radiation Facility (UVSOR). We have also measured a retardation of a zeroth-order waveplate made of MgF2. The thickness difference of the waveplate is 14.57 um.This waveplate works as a half-waveplate at 121.74 nm. From this measurement, we estimate that a waveplate with the thickness difference of 15.71 um will work as a half-waveplate at the Ly-alpha wavelength. We have developed a rotating waveplate - polarization analyzer system called a prototype of CLASP polarimeter, and input the perfect Stokes Q and U signals. The modulation patterns that are consistent with the theoretical prediction are successfully obtained in both cases. Title: The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP)j Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Bando, T.; Belluzzi, L.; Casini, R.; Carlsson, M.; Cirtain, J. W.; De Pontieu, B.; Hara, H.; Ichimoto, K.; Ishikawa, R.; Kano, R.; Katsukawa, Y.; Kim, T.; Kubo, M.; Manso Sainz, R.; Narukage, N.; Asensio Ramos, A.; Robinson, B.; Sakao, T.; Shimizu, T.; Stepan, J.; Suematsu, Y.; Watanabe, H.; West, E.; Winebarger, A. R. Bibcode: 2011AGUFM.P14C..05K Altcode: We present an overview of the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) program. CLASP is a proposed sounding rocket experiment currently under development as collaboration between Japan, USA and Spain. The aim is to achieve the first measurement of magnetic field in the upper chromosphere and transition region of the Sun through the detection and measurement of Hanle effect polarization of the Lyman alpha line. The Hanle effect (i.e. the magnetic field induced modification of the linear polarization due to scattering processes in spectral lines) is believed to be a powerful tool for measuring the magnetic field in the upper chromosphere, as it is more sensitive to weaker magnetic fields than the Zeeman effect, and also sensitive to magnetic fields tangled at spatial scales too small to be resolved. The Lyman-alpha (121.567 nm) line has been chosen because it is a chromospheric/transition-region line, and because the Hanle effect polarization of the Lyman-alpha line is predicted to be sensitive to 10-250 Gauss, encompassing the range of interest. Hanle effect is predicted to be observable as linear polarization or depolarization, depending on the geometry, with a fractional polarization amplitude varying between 0.1% and 1% depending on the strength and orientation of the magnetic field. This quantification of the chromospheric magnetic field requires a highly sensitive polarization measurement. The CLASP instrument consists of a large aperture (287 mm) Cassegrain telescope mated to a polarizing beamsplitter and a matched pair of grating spectrographs. The polarizing beamsplitter consists of a continuously rotating waveplate and a linear beamsplitter, allowing simultaneous measurement of orthogonal polarizations and in-flight self-calibration. Development of the instrument is underway, and prototypes of all optical components have been tested using a synchrotron beamline. The experiment is proposed for flight in 2014. Title: Ly-alpha polarimeter design for CLASP rocket experiment Authors: Watanabe, H.; Narukage, N.; Kubo, M.; Ishikawa, R.; Bando, T.; Kano, R.; Tsuneta, S.; Kobayashi, K.; Ichimoto, K.; Trujillo-Bueno, J. Bibcode: 2011SPIE.8148E..0TW Altcode: 2011SPIE.8148E..25W; 2014arXiv1407.4577W A sounding-rocket program called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is proposed to be launched in the summer of 2014. CLASP will observe the solar chromosphere in Ly-alpha (121.567 nm), aiming to detect the linear polarization signal produced by scattering processes and the Hanle effect for the first time. The polarimeter of CLASP consists of a rotating half-waveplate, a beam splitter, and a polarization analyzer. Magnesium Fluoride (MgF2) is used for these optical components, because MgF2 exhibits birefringent property and high transparency at ultraviolet wavelength. The development and comprehensive testing program of the optical components of the polarimeter is underway using the synchrotron beamline at the Ultraviolet Synchrotron Orbital Radiation Facility (UVSOR). The first objective is deriving the optical constants of MgF2 by the measurement of the reflectance and transmittance against oblique incident angles for the s-polarized and the p-polarized light. The ordinary refractive index and extinction coefficient along the ordinary and extraordinary axes are derived with a least-square fitting in such a way that the reflectance and transmittance satisfy the Kramers-Krönig relation. The reflection at the Brewster's Angle of MgF2 plate is confirmed to become a good polarization analyzer at Ly-alpha. The second objective is the retardation measurement of a zeroth-order waveplate made of MgF2. The retardation of a waveplate is determined by observing the modulation amplitude that comes out of a waveplate and a polarization analyzer. We tested a waveplate with the thickness difference of 14.57 um. The 14.57 um waveplate worked as a half-waveplate at 121.74 nm. We derived that a waveplate with the thickness difference of 15.71 um will work as a half-waveplate at Ly-alpha wavelength. We developed a prototype of CLASP polarimeter using the MgF2 half-waveplate and polarization analyzers, and succeeded in obtaining the modulation patterns that are consistent with the theoretical prediction. We confirm that the performance of the prototype is optimized for measuring linear polarization signal with the least effect of the crosstalk from the circular polarization. Title: Overview of Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) Authors: Narukage, Noriyuki; Tsuneta, Saku; Bando, Takamasa; Kano, Ryouhei; Kubo, Masahito; Ishikawa, Ryoko; Hara, Hirohisa; Suematsu, Yoshinori; Katsukawa, Yukio; Watanabe, Hiroko; Ichimoto, Kiyoshi; Sakao, Taro; Shimizu, Toshifumi; Kobayashi, Ken; Robinson, Brian; Kim, Tony; Winebarger, Amy; West, Edward; Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Trujillo Bueno, Javier; Stepan, Jiri; Manso Sainz, Rafael; Belluzzi, Luca; Asensio Ramos, Andres; Carlsson, Mats Bibcode: 2011SPIE.8148E..0HN Altcode: 2011SPIE.8148E..16N The solar chromosphere is an important boundary, through which all of the plasma, magnetic fields and energy in the corona and solar wind are supplied. Since the Zeeman splitting is typically smaller than the Doppler line broadening in the chromosphere and transition region, it is not effective to explore weak magnetic fields. However, this is not the case for the Hanle effect, when we have an instrument with high polarization sensitivity (~ 0.1%). "Chromospheric Lyman- Alpha SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect linear polarization produced by the Hanle effect in Lyman-alpha line (121.567 nm) and to make the first direct measurement of magnetic fields in the upper chromosphere and lower transition region. To achieve the high sensitivity of ~ 0.1% within a rocket flight (5 minutes) in Lyman-alpha line, which is easily absorbed by materials, we design the optical system mainly with reflections. The CLASP consists of a classical Cassegrain telescope, a polarimeter and a spectrometer. The polarimeter consists of a rotating 1/2-wave plate and two reflecting polarization analyzers. One of the analyzer also works as a polarization beam splitter to give us two orthogonal linear polarizations simultaneously. The CLASP is planned to be launched in 2014 summer. Title: The Relationship between Vertical and Horizontal Magnetic Fields in the Quiet Sun Authors: Ishikawa, Ryohko; Tsuneta, Saku Bibcode: 2011ApJ...735...74I Altcode: 2011arXiv1103.5556I Vertical magnetic fields have been known for decades to exist in the internetwork region of the Sun, while the properties of horizontal magnetic fields have only recently been extensively investigated with Hinode. Vertical and horizontal magnetic fields in the internetwork region are considered to be separate entities and have thus far not been investigated in a unified way. We discover a clear positional association between the vertical and horizontal magnetic fields in the internetwork region with Hinode. Essentially, all of the horizontal magnetic patches are associated with the vertical magnetic patches. Alternatively, half of the vertical magnetic patches accommodate the horizontal magnetic patches. These horizontal patches are located around the borders of the vertical patches. The intrinsic magnetic field strength as obtained with the Stokes V line ratio inside the horizontal patches is weak, and is in the subequipartition field regime (B < 700 G), while the field strength outside the horizontal patches ranges from weak to strong (kG) fields. Vertical magnetic patches are known to be concentrated on mesogranular and supergranular boundaries, while the horizontal magnetic patches are found only on mesogranular boundaries. These observations provide us with new information on the origin of the vertical and horizontal internetwork magnetic fields, in a unified way. We conjecture that internetwork magnetic fields are formed by the emergence of small-scale flux tubes with bipolar footpoints, and the vertical magnetic fields of the footpoints are intensified to kG fields due to convective collapse. Resultant strong vertical fields are advected by the supergranular flow, and eventually form the network fields. Title: A Sounding Rocket Experiment for Spectropolarimetric Observations with the Lyα Line at 121.6 nm (CLASP) Authors: Ishikawa, R.; Bando, T.; Fujimura, D.; Hara, H.; Kano, R.; Kobiki, T.; Narukage, N.; Tsuneta, S.; Ueda, K.; Wantanabe, H.; Kobayashi, K.; Trujillo Bueno, J.; Manso Sainz, R.; Stepan, J.; de Pontieu, B.; Carlsson, M.; Casini, R. Bibcode: 2011ASPC..437..287I Altcode: A team consisting of Japan, USA, Spain, and Norway is developing a high-throughput Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which is proposed to fly with a NASA sounding rocket in 2014. CLASP will explore the magnetism of the upper solar chromosphere and transition region via the Hanle effect of the Lyα line for the first time. This experiment requires spectropolarimetric observations with high polarimetric sensitivity (∼0.1%) and wavelength resolution (0.1 Å). The final spatial resolution (slit width) is being discussed taking into account the required high signal-to-noise ratio. We have demonstrated the performance of the Lyα polarimeter by extensively using the Ultraviolet Synchrotron ORbital Radiation Facility (UVSOR) at the Institute for Molecular Sciences. In this contribution, we report these measurements at UVSOR together with the current status of the CLASP project. Title: The Chromospheric Lyman Alpha SpectroPolarimeter (CLASP) Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Cirtain, J. W.; Bando, T.; Kano, R.; Hara, H.; Fujimura, D.; Ueda, K.; Ishikawa, R.; Watanabe, H.; Ichimoto, K.; Sakao, T.; de Pontieu, B.; Carlsson, M.; Casini, R. Bibcode: 2010AGUFMSH11B1632K Altcode: Magnetic fields in the solar chromosphere play a key role in the energy transfer and dynamics of the solar atmosphere. Yet a direct observation of the chromospheric magnetic field remains one of the greatest challenges in solar physics. While some advances have been made for observing the Zeeman effect in strong chromospheric lines, the effect is small and difficult to detect outside sunspots. The Hanle effect offers a promising alternative; it is sensitive to weaker magnetic fields (e.g., 5-500 G for Ly-Alpha), and while its magnitude saturates at stronger magnetic fields, the linear polarization signals remain sensitive to the magnetic field orientation. The Hanle effect is not only limited to off-limb observations. Because the chromosphere is illuminated by an anisotropic radiation field, the Ly-Alpha line is predicted to show linear polarization for on-disk, near-limb regions, and magnetic field is predicted to cause a measurable depolarization. At disk center, the Ly-Alpha radiation is predicted to be negligible in the absence of magnetic field, and linearly polarized to an order of 0.3% in the presence of an inclined magnetic field. The proposed CLASP sounding rocket instrument is designed to detect 0.3% linear polarization of the Ly-Alpha line at 1.5 arcsecond spatial resolution (0.7’’ pixel size) and 10 pm spectral resolution. The instrument consists of a 30 cm aperture Cassegrain telescope and a dual-beam spectropolarimeter. The telescope employs a ``cold mirror’’ design that uses multilayer coatings to reflect only the target wavelength range into the spectropolarimeter. The polarization analyzer consists of a rotating waveplate and a polarizing beamsplitter that comprises MgF2 plates placed at Brewster’s Angle. Each output beam of the polarizing beamsplitter, representing two orthogonal linear polarizations, is dispersed and focused using a separate spherical varied-line-space grating, and imaged with a separate 512x512 CCD camera. Prototypes of key optical components have been fabricated and tested. Instrument design is being finalized, and the experiment will be proposed for a 2014 flight aboard a NASA sounding rocket. Title: Spatial and Temporal Distributions of Transient Horizontal Magnetic Fields with Deep Exposure Authors: Ishikawa, Ryohko; Tsuneta, Saku Bibcode: 2010ApJ...718L.171I Altcode: 2011arXiv1103.5812I We obtained a long-exposure vector magnetogram of the quiet Sun photosphere at the disk center with a wide field of view of 51'' × 82''. The observation was performed at Fe I 525.0 nm with the shutterless mode of the Narrow Band Filter Imager of the Solar Optical Telescope (SOT) on board the Hinode satellite. We summed the linear polarization (LP) maps taken with a time cadence of 60 s for 2 hr to obtain a map with as long of an exposure as possible. The polarization sensitivity would be more than 4.6 (21.2 in exposure time) times the standard observation with the SOT Spectropolarimeter. The LP map shows a cellular structure with a typical scale of 5''-10''. We find that the enhanced LP signals essentially consist of the isolated sporadic transient horizontal magnetic fields (THMFs) with a lifetime of 1-10 minutes and are not contributed by long-duration weak horizontal magnetic fields. The cellular structure coincides in position with the negative divergence of the horizontal flow field, i.e., mesogranular boundaries with downflows. Azimuth distribution appears to be random for the scale size of the mesogranules. Some pixels have two separate appearances of THMFs, and the measured time intervals are consistent with the random appearance. THMFs tend to appear at the mesogranular boundaries, but appear randomly in time. We discuss the origin of THMFs based on these observations. Title: Three-Dimensional View of Transient Horizontal Magnetic Fields in the Photosphere Authors: Ishikawa, Ryohko; Tsuneta, Saku; Jurčák, Jan Bibcode: 2010ApJ...713.1310I Altcode: 2010arXiv1003.1376I We infer the three-dimensional magnetic structure of a transient horizontal magnetic field (THMF) during its evolution through the photosphere using SIRGAUS inversion code. The SIRGAUS code is a modified version of SIR (Stokes Inversion based on Response function), and allows for retrieval of information on the magnetic and thermodynamic parameters of the flux tube embedded in the atmosphere from the observed Stokes profiles. Spectropolarimetric observations of the quiet Sun at the disk center were performed with the Solar Optical Telescope on board Hinode with Fe I 630.2 nm lines. Using repetitive scans with a cadence of 130 s, we first detect the horizontal field that appears inside a granule, near its edge. On the second scan, vertical fields with positive and negative polarities appear at both ends of the horizontal field. Then, the horizontal field disappears leaving the bipolar vertical magnetic fields. The results from the inversion of the Stokes spectra clearly point to the existence of a flux tube with magnetic field strength of ~400 G rising through the line-forming layer of the Fe I 630.2 nm lines. The flux tube is located at around log τ500 ~ 0 at Δt = 0 s and around log τ500 ~ -1.7 at Δt = 130 s. At Δt = 260 s, the horizontal part is already above the line-forming region of the analyzed lines. The observed Doppler velocity is maximally 3 km s-1, consistent with the upward motion of the structure as retrieved from the SIRGAUS code. The vertical size of the tube is smaller than the thickness of the line-forming layer. The THMF has a clear Ω-shaped loop structure with the apex located near the edge of a granular cell. The magnetic flux carried by this THMF is estimated to be 3.1 × 1017 Mx. 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: Internetwork Horizontal Magnetic Fields in the Quiet Sun Chromosphere: Results from a Joint Hinode/VTT Study Authors: Lagg, A.; Ishikawa, R.; Merenda, L.; Wiegelmann, T.; Tsuneta, S.; Solanki, S. K. Bibcode: 2009ASPC..415..327L Altcode: We present results from a joint Hinode/VTT campaign (May 2008). Spectropolarimetric data of a quiet Sun super-granular network cell at a heliocentric angle of 28° in the He I 10830 Å line were analyzed using an inversion code incorporating Hanle and Zeeman effects (HeLIx^+) to retrieve magnetic field strength and direction in the upper chromosphere. Simultaneously recorded Hinode SOT/SP data reveal the photospheric magnetic field morphology, clearly showing magnetic flux concentrations in the internetwork. The photospheric magnetic field maps are used to feed potential field extrapolations similar to the work by Schrijver & Title (2003). The extrapolated magnetic field structure is compared with the magnetic field configuration resulting from the He 10830 inversions. These inversions also reveal horizontal magnetic structures extending over a length of up to 20 Mm above the internetwork, indicative of the presence of a magnetic canopy. The photospheric magnetic flux concentrations in the internetwork are obviously not sufficiently strong to prevent the formation of a canopy at chromospheric heights. Title: Properties of Transient Horizontal Magnetic Fields Authors: Ishikawa, R.; Tsuneta, S. Bibcode: 2009ASPC..415..132I Altcode: We present statistical properties of the transient horizontal magnetic field (THMF) observed by the spectropolarimeter (SP) aboard Hinode. The topics to be reported here include (1) locations of their appearance and disappearance in terms of granular structure, (2) size and lifetime distribution, (3) spatial relationship between vertical and horizontal magnetic fields, (4) azimuth orientation of the horizontal field vector, (5) PDF (probability distribution function) of the intrinsic magnetic field strength. An extensive statistical survey reveals numbers of so far unknown unique and remarkable properties of THMFs, leading us to conclude that a local dynamo processes is responsible for THMFs. Title: Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun Authors: Ishikawa, R.; Tsuneta, S. Bibcode: 2009A&A...495..607I Altcode: 2008arXiv0812.1631I Aims: The properties of transient horizontal magnetic fields (THMFs) in both plage and quiet Sun regions are obtained and compared.
Methods: Spectro-polarimetric observations with the Solar Optical Telescope (SOT) on the Hinode satellite were carried out with a cadence of about 30 s for both plage and quiet regions located near the disk center. We selected THMFs that have net linear polarization (LP) higher than 0.22%, and an area larger than or equal to 3 pixels, and compared their occurrence rates and distribution of magnetic field azimuth. We obtained probability density functions (PDFs) of magnetic field strength and inclination for both regions.
Results: The occurrence rate in the plage region is the same as for the quiet Sun. The vertical magnetic flux in the plage region is ~8 times more than in the quiet Sun. There is essentially no preferred orientation for the THMFs in either region; however, THMFs in the plage region with higher LP have a preferred direction consistent with that of the plage-region's large-scale vertical field pattern. PDFs show that there is no difference in the distribution of field strength of horizontal fields between the quiet Sun and the plage regions when we avoid the persistent vertical flux concentrations for the plage region.
Conclusions: The similarity between the PDFs and the occurrence rates in plage and quiet regions suggests that a local dynamo process due to the granular motion may generate THMFs all over the Sun. The preferred orientation for higher LP in the plage indicates that the THMFs may be somewhat influenced by the larger-scale magnetic field pattern of the plage.

A movie is only available in electronic form at http://www.aanda.org Title: New Form of Emerging Magnetic Fields in Plage Regions Authors: Ishikawa, R.; Tsuneta, S. Bibcode: 2008ASPC..397...21I Altcode: Using the Solar Optical Telescope aboard Hinode we have discovered a new form of emerging magnetic fields. In this article we briefly outline our results and their possible implications. 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: Properties of transient horizontal magnetic field and its implication to a local dynamo process Authors: Ishikawa, R.; Tsuneta, S. Bibcode: 2008AGUSMSP23A..01I Altcode: Hinode discovered granular-sized "transient horizontal magnetic fields" (THMFs) on the photosphere. They are ubiquitous in a plage region as well as in the quiet Sun, and they attract a lot of attention due to their apparent unique properties. Spectro-polarimetric observations with the Solar Optical Telescope (SOT) are analyzed to compare the properties of THMFs in both plage and quiet Sun regions near solar disc center. The distribution of magnetic field strengths inferred from Milne-Eddington inversions of the data are remarkably similar. A majority of the THMFs have field strengths smaller than the equipartition field strength for average local convective flow. The occurrence rate in plage is only two times that in the quiet Sun, while the vertical magnetic flux in the plage region is 8 times larger than in the quiet Sun. The similarity in the field strength distributions and the occurrence rates suggests that a common local dynamo process generates THMFs all over the sun. THMFs in the plage region selected for their higher degree of linear polarization appear to have preferred direction which is consistent with that of the plage-region's large-scale vertical field pattern. This fact and the slightly higher occurrence rate in the plage suggest that the THMFs are influenced by the larger-scale magnetic field pattern of the plage. These unique properties of the horizontal magnetic fields are presented. We also plan to clarify a connection between the horizontal magnetic fields and chromospheric activities. 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: Relationships between magnetic foot points and G-band bright structures Authors: Ishikawa, R.; Tsuneta, S.; Kitakoshi, Y.; Katsukawa, Y.; Bonet, J. A.; Vargas Domínguez, S.; Rouppe van der Voort, L. H. M.; Sakamoto, Y.; Ebisuzaki, T. Bibcode: 2007A&A...472..911I Altcode: 2008arXiv0802.1765I Aims:Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures bright in G-band.
Methods: The G-band filtergrams together with magnetograms and dopplergrams were taken for a plage region covered by abnormal granules as well as ubiquitous G-band bright points, using the Swedish 1-m Solar Telescope (SST) under very good seeing conditions.
Results: High magnetic flux density regions are not necessarily associated with G-band bright points. We refer to the observed extended areas with high magnetic flux density as magnetic islands to separate them from magnetic elements. We discover that G-band bright points tend to be located near the boundary of such magnetic islands. The concentration of G-band bright points decreases with inward distance from the boundary of the magnetic islands. Moreover, G-band bright points are preferentially located where magnetic flux density is higher, given the same distance from the boundary. There are some bright points located far inside the magnetic islands. Such bright points have higher minimum magnetic flux density at the larger inward distance from the boundary. Convective velocity is apparently reduced for such high magnetic flux density regions regardless of whether they are populated by G-band bright points or not. The magnetic islands are surrounded by downflows.
Conclusions: These results suggest that high magnetic flux density, as well as efficient heat transport from the sides or beneath, are required to make magnetic elements bright in G-band. 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: Measurement of Specific Absorption Rates Caused by Hand-Held Amateur Radio Communication Devices Authors: Watanabe, S.; Akiyama, Y.; Ishikawa, R.; Asou, H.; Yamanaka, Y. Bibcode: 2001aprs.conf..415W Altcode: No abstract at ADS