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 &
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 $h$ & $k$ 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 &
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 & k
lines in the solar chromosphere. The instrument contains a slit-jaw
context imager at Lyman Alpha (~121.6nm) and two spectropolarimetric
cameras that capture Mg II h & k near 280nm. A rotating polarization
modulation unit allows us to capture the full polarization state of
Mg II h & k; the measured polarization signals are sensitive
to the Hanle and the Zeeman magnetic effects, and magneto-optical
effects. The center-to-limb variations (CLV) of the intensity of
these lines has been measured, but the CLV of the polarization signals
has only been investigated theoretically. The first flight of CLASP,
which measured the linear polarization of the Lyman alpha line, found
a surprising lack of CLV in the line core (Kano et al. 2017), which
has important implications for the magnetic strength and geometrical
complexity of the chromosphere-corona transition region (Trujillo Bueno
et al. 2018). We present here initial results on the CLV of the Mg II
polarization signals.
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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.
---------------------------------------------------------
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 &
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 (< 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 (< 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; >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 <1 minute
were discovered. In this paper, we focus on the active region within
the SJ field of view and investigate the relationship between short
(<30 s) temporal variations in the Lyα emission and the coronal
structures observed by Solar Dynamics Observatory/Atmospheric Imaging
Assembly (AIA). We compare the Lyα temporal variations at the coronal
loop footpoints observed in the AIA 211 Å (≈2 MK) and AIA 171 Å
(≈0.6 MK) channels with those in the regions with bright Lyα features
without a clear association with the coronal loop footpoints. We find
more short (<30 s) temporal variations in the Lyα intensity in the
footpoint regions. Those variations did not depend on the temperature
of the coronal loops. Therefore, the temporal variations in the Lyα
intensity at this timescale range could be related to the heating of
the coronal structures up to temperatures around the sensitivity peak
of 171 Å. No signature was found to support the scenario that these
Lyα intensity variations were related to the nanoflares. Waves or
jets from the lower layers (lower chromosphere or photosphere) are
possible causes for this phenomenon.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel; E McKenzie, David; Ishikawa, Ryohko;
Trujillo Bueno, Javier; Auchère, Frédéric; Kobayashi, Ken;
Winebarger, Amy; Bethge, Christian; Kano, Ryouhei; Kubo, Masahito;
Song, Donguk; Narukage, Noriyuki; Ishikawa, Shin-nosuke; De Pontieu,
Bart; Carlsson, Mats; Yoshida, Masaki; Belluzzi, Luca; Stepan, Jiri;
del Pino Alemná, Tanausú; Ballester, Ernest Alsina; Asensio Ramos,
Andres
2017SPD....4811010R Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.;
Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.;
Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.;
De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.;
del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
2017shin.confE..79R Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
---------------------------------------------------------
Title: Indication of the Hanle Effect by Comparing the Scattering
Polarization Observed by CLASP in the Lyα and Si III 120.65 nm Lines
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
2017ApJ...841...31I Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding
rocket experiment that has provided the first successful measurement
of the linear polarization produced by scattering processes in
the hydrogen Lyα line (121.57 nm) radiation of the solar disk. In
this paper, we report that the Si III line at 120.65 nm also shows
scattering polarization and we compare the scattering polarization
signals observed in the Lyα and Si III lines in order to search for
observational signatures of the Hanle effect. We focus on four selected
bright structures and investigate how the U/I spatial variations vary
between the Lyα wing, the Lyα core, and the Si III line as a function
of the total unsigned photospheric magnetic flux estimated from Solar
Dynamics Observatory/Helioseismic and Magnetic Imager observations. In
an internetwork region, the Lyα core shows an antisymmetric spatial
variation across the selected bright structure, but it does not show
it in other more magnetized regions. In the Si III line, the spatial
variation of U/I deviates from the above-mentioned antisymmetric
shape as the total unsigned photospheric magnetic flux increases. A
plausible explanation of this difference is the operation of the Hanle
effect. We argue that diagnostic techniques based on the scattering
polarization observed simultaneously in two spectral lines with very
different sensitivities to the Hanle effect, like Lyα and Si III,
are of great potential interest for exploring the magnetism of the
upper solar chromosphere and transition region.
---------------------------------------------------------
Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV
Range. Part II: In-Flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.;
Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
2017SoPh..292...57G Altcode:
The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding
rocket instrument designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm). The instrument
was successfully launched on 3 September 2015 and observations were
conducted at the solar disc center and close to the limb during the
five-minutes flight. In this article, the disc center observations are
used to provide an in-flight calibration of the instrument spurious
polarization. The derived in-flight spurious polarization is consistent
with the spurious polarization levels determined during the pre-flight
calibration and a statistical analysis of the polarization fluctuations
from solar origin is conducted to ensure a 0.014% precision on the
spurious polarization. The combination of the pre-flight and the
in-flight polarization calibrations provides a complete picture of
the instrument response matrix, and a proper error transfer method
is used to confirm the achieved polarization accuracy. As a result,
the unprecedented 0.1% polarization accuracy of the instrument in the
vacuum ultraviolet is ensured by the polarization calibration.
---------------------------------------------------------
Title: Discovery of Scattering Polarization in the Hydrogen Lyα
Line of the Solar Disk Radiation
Authors: Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchère, F.;
Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.;
Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu,
T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.;
Štěpán, J.; Asensio Ramos, A.; Manso Sainz, R.; Champey, P.;
Cirtain, J.; De Pontieu, B.; Casini, R.; Carlsson, M.
2017ApJ...839L..10K Altcode: 2017arXiv170403228K
There is a thin transition region (TR) in the solar atmosphere where
the temperature rises from 10,000 K in the chromosphere to millions
of degrees in the corona. Little is known about the mechanisms that
dominate this enigmatic region other than the magnetic field plays a
key role. The magnetism of the TR can only be detected by polarimetric
measurements of a few ultraviolet (UV) spectral lines, the Lyα line
of neutral hydrogen at 121.6 nm (the strongest line of the solar UV
spectrum) being of particular interest given its sensitivity to the
Hanle effect (the magnetic-field-induced modification of the scattering
line polarization). We report the discovery of linear polarization
produced by scattering processes in the Lyα line, obtained with
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) rocket
experiment. The Stokes profiles observed by CLASP in quiet regions of
the solar disk show that the Q/I and U/I linear polarization signals are
of the order of 0.1% in the line core and up to a few percent in the
nearby wings, and that both have conspicuous spatial variations with
scales of ∼10 arcsec. These observations help constrain theoretical
models of the chromosphere-corona TR and extrapolations of the
magnetic field from photospheric magnetograms. In fact, the observed
spatial variation from disk to limb of polarization at the line core
and wings already challenge the predictions from three-dimensional
magnetohydrodynamical models of the upper solar chromosphere.
---------------------------------------------------------
Title: High-Reflectivity Coatings for a Vacuum Ultraviolet
Spectropolarimeter
Authors: Narukage, Noriyuki; Kubo, Masahito; Ishikawa, Ryohko;
Ishikawa, Shin-nosuke; Katsukawa, Yukio; Kobiki, Toshihiko; Giono,
Gabriel; Kano, Ryouhei; Bando, Takamasa; Tsuneta, Saku; Auchère,
Frédéric; Kobayashi, Ken; Winebarger, Amy; McCandless, Jim; Chen,
Jianrong; Choi, Joanne
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.
---------------------------------------------------------
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 <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<2° and δ a<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<10% and Δ φ<2° can be achieved combined
with the polarization calibration of the spectro-polarimeter and the
onboard calibration at the Sun center(refer to Ishikawa et al. 2014,
for the detail). <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 ( > 10^18 Mx) have the same polarity, while
smaller patches have a fair balance of both polarities. The polarity
of the polar region as a whole is consequently determined only by the
large magnetic concentrations. A clear decrease in the net flux of
the polar region is detected in the slow rising phase of the current
solar cycle. The decrease is more rapid in the north polar region than
in the south. The decrease in the net flux is caused by a decrease in
the number and size of the large flux concentrations as well as the
appearance of patches with opposite polarity at lower latitudes. In
contrast, we do not see temporal change in the magnetic flux associated
with the smaller patches ( < 10^18 Mx) and that of the horizontal
magnetic fields during the years 2008--2012.
---------------------------------------------------------
Title: Properties of transient horizontal magnetic fields and their
implication to the origin of the quiet-Sun magnetism
Authors: Ishikawa, R.
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 (>=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 (<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 < 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 & 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