explanation      blue bibcodes open ADS page with paths to full text
Author name code: ishikawa
ADS astronomy entries on 2022-09-14
=author:"Ishikawa, Ryohko" OR =author:"Ishikawa, Ryoko" OR =author:"Ishikawa, R." 

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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.
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.

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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.
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.

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Title: Empirical relations between the intensities of Lyman lines
    of H and He<SUP>+</SUP>
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.
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. <BR /> 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. <BR
  /> 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. <BR /> 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. <BR /> 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.

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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
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.

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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
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.

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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.
2021AAS...23810603M    Altcode:
  Coronal heating, chromospheric heating, and the heating &amp;
  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.

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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
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 $h$ &amp; $k$ 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.

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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
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.

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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
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.

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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.
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.

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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.
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.

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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.
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. <P />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. <P />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.

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Title: Center-to-Limb Variation of the polarization of Mg II h &amp;
    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.
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 &amp; 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 &amp; k near 280nm. A rotating polarization
  modulation unit allows us to capture the full polarization state of
  Mg II h &amp; 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.

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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
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<SUP>-1</SUP> propagated upward along the spicule with a
  phase velocity of ∼470 km s<SUP>-1</SUP>. 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.

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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
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. <P />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. <P />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
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 &amp;
  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.
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.
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.
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 (B<SUB>H</SUB>) 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 B<SUB>H</SUB> = 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. <P />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.
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.
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
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
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
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 (&lt; 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
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 (&lt; 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
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<SUP>∘</SUP> instead of 90<SUP>∘</SUP> 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; &gt;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
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.
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
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 &lt;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
  (&lt;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 (&lt;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
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 &amp; k near 280 nm. This set of lines is sensitive to the upper
  chromospheric magnetic field via both the Hanle and the Zeeman effects.

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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.
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 &amp; k near 280 nm. This set of lines is sensitive to the upper
  chromospheric magnetic field via both the Hanle and the Zeeman effects.

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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.
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.

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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.
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.

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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.
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.

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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
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.
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.
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<SUP>-1</SUP>, 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.
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 3<SUP>rd</SUP> 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.
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
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
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.
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 [B<SUB>v</SUB>] and the horizontal [B<SUB>h</SUB>] 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 B<SUB>v</SUB> are bordered with areas of locally
  enhanced B<SUB>h</SUB>. This effect suggests a fountainlike spatial
  structure of the magnetic field near the B<SUB>v</SUB> 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.

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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.
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 &lt;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
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.
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). <P />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. <P />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. <P />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.
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
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&lt;2° and δ a&lt;10% as the instrument requirements. The
  spectro-polarimeter features a continuously rotating MgF<SUB>2</SUB>
  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. <P />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&lt;10% and Δ φ&lt;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). <P />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.
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.
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.
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
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
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
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
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.
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.
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 ( &gt; 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 ( &lt; 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.
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
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.
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 (10<SUP>15</SUP>-10<SUP>20</SUP>
  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 (&gt;=10<SUP>18</SUP> 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 (&lt;10<SUP>18</SUP> 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.
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. <P />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.
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.
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.
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
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
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 &lt; 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 Ly<SUB>α</SUB> 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.
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 Ly<SUB>α</SUB> 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 Ly<SUB>α</SUB> 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.
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
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
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 τ<SUB>500</SUB> ~ 0 at Δt = 0 s and around log
  τ<SUB>500</SUB> ~ -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<SUP>-1</SUP>, 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 × 10<SUP>17</SUP> 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.
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.
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 &amp; 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.
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.
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. <BR
  />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. <BR />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. <BR />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. <P />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.
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.
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<SUP>-1</SUP>. The apparent flows
  indicate a bias of about 0.2 km s<SUP>-1</SUP> 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.
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.
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. <BR />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. <BR />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. <BR
  />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.
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. <BR />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. <BR />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. <BR />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.
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. <P />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. <P />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.
2001aprs.conf..415W    Altcode:
  No abstract at ADS