Author name code: katsukawa
ADS astronomy entries on 2022-09-14
author:"Katsukawa, Yukio"
------------------------------------------------------------------------
Title: Development of Fast and Precise Scan Mirror Mechanism for an
Airborne Solar Telescope
Authors: Oba, Takayoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Kubo,
Masahito; Kawabata, Yusuke; Hara, Hirohisa; Uraguchi, Fumihiro;
Tsuzuki, Toshihiro; Tamura, Tomonori; Shinoda, Kazuya; Kodeki,
Kazuhide; Fukushima, Kazuhiko; Morales Fernández, José Miguel;
Sánchez Gómez, Antonio; Balaguer Jimenéz, María; Hernández
Expósito, David; Gandorfer, Achim
Bibcode: 2022arXiv220713864O
Altcode:
We developed a scan mirror mechanism (SMM) that enable a slit-based
spectrometer or spectropolarimeter to precisely and quickly map
an astronomical object. The SMM, designed to be installed in the
optical path preceding the entrance slit, tilts a folding mirror
and then moves the reflected image laterally on the slit plane,
thereby feeding a different one-dimensional image to be dispersed by
the spectroscopic equipment. In general, the SMM is required to scan
quickly and broadly while precisely placing the slit position across
the field-of-view (FOV). These performances are highly in demand for
near-future observations, such as studies on the magnetohydrodynamics of
the photosphere and the chromosphere. Our SMM implements a closed-loop
control system by installing electromagnetic actuators and gap-based
capacitance sensors. Our optical test measurements confirmed that the
SMM fulfils the following performance criteria: i) supreme scan-step
uniformity (linearity of 0.08%) across the wide scan range (${\pm}$1005
arcsec), ii) high stability (3${\sigma}$ = 0.1 arcsec), where the
angles are expressed in mechanical angle, and iii) fast stepping speed
(26 ms). The excellent capability of the SMM will be demonstrated
soon in actual use by installing the mechanism for a near-infrared
spectropolarimeter onboard the balloon-borne solar observatory for
the third launch, Sunrise III.
Title: Polarimetric calibration of the Sunrise UV Spectropolarimeter
and Imager
Authors: Iglesias, F. A.; Feller, A.; Gandorfer, A.; Lagg, A.;
Riethmüller, T. L.; Solanki, S. K.; Katsukawa, Y.; Kubo, M.;
Zucarelli, G.; Sanchez, M.; Sunrise Team
Bibcode: 2022BAAA...63..305I
Altcode:
Sunrise is an optical observatory mounted in a stratospheric balloon,
developed to study magnetic fields in the solar atmosphere with very
high resolution. In its third flight, Sunrise carry the Sunrise UV
Spectropolarimeter and Imager (SUSI), that operates in the 313-430 nm
range, covering thousands of spectral lines not accessible from the
ground and thus largely unexplored. SUSI does not include a polarimetric
calibration unit on board. We report about the development status of
SUSI and the preliminary results of its calibration.
Title: Unipolar versus Bipolar Internetwork Flux Appearance
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, L. R.; Del
Toro Iniesta, Jose Carlos; Cheung, Mark; Orozco Suárez, David
Bibcode: 2022cosp...44.2513G
Altcode:
Small-scale internetwork (IN) magnetic fields are considered to be
the main building blocks of the quiet Sun magnetism. It is therefore
of paramount importance to understand how these fields are generated
on the solar surface. To shed new light on this open question,
we studied the appearance modes and spatio-temporal evolution of
individual IN magnetic elements inside one supergranular cell. For
that purpose, we employed a high-resolution, high-sensitivity,
long-duration Hinode/NFI magnetogram sequence. From identification
of flux patches and magnetofrictional simulations, we show that there
are two distinct populations of IN flux concentrations: unipolar and
bipolar features. Bipolar features tend to be bigger, live longer
and carry more flux than unipolar features. About $70$% of the total
instantaneous IN flux detected inside the supergranule is in the form
of bipoles. Both types of flux concentrations are uniformly distributed
over the solar surface. However, bipolar features appear (randomly
oriented) at a faster rate than unipolar features (68 as opposed to
55~Mx~cm$^{-2}$~day$^{-1}$). Our results lend support to the idea that
bipolar features may be the signature of local dynamo action, while
unipolar features seem to be formed by coalescence of background flux.
Title: CASPER: A mission to study the time-dependent evolution of
the magnetic solar chromosphere and transition regions
Authors: Orozco Suárez, D.; del Toro Iniesta, J. C.; Bailén, F. J.;
López Jiménez, A.; Balaguez Jiménez, M.; Bellot Rubio, L. R.;
Ishikawa, R.; Katsukawa, Y.; Kano, R.; Shimizu, T.; Trujillo Bueno,
J.; Asensio Ramos, A.; del Pino Alemán, T.
Bibcode: 2022ExA...tmp...26O
Altcode:
Our knowledge about the solar chromosphere and transition region (TR)
has increased in the last decade thanks to the huge scientific return
of space-borne observatories like SDO, IRIS, and Hinode, and suborbital
rocket experiments like CLASP1, CLASP2, and Hi-C. However, the magnetic
nature of those solar regions remain barely explored. The chromosphere
and TR of the Sun harbor weak fields and are in a low ionization stage
both having critical effects on their thermodynamic behavior. Relatively
cold gas structures, such as spicules and prominences, are located in
these two regions and display a dynamic evolution in high-resolution
observations that static and instantaneous 3D-magnetohydrodynamic (MHD)
models are not able to reproduce. The role of the chromosphere and TR
as the necessary path to a (largely unexplained) very hot corona calls
for the generation of observationally based, time-dependent models
of these two layers that include essential, up to now disregarded,
ingredients in the modeling such as the vector magnetic field. We
believe that the community is convinced that the origin of both the
heat and kinetic energy observed in the upper layers of the solar
atmosphere is of magnetic origin, but reliable magnetic field
measurements are missing. The access to sensitive polarimetric
measurements in the ultraviolet wavelengths has been elusive until
recently due to limitations in the available technology. We propose a
low-risk and high-Technology Readiness Level (TRL) mission to explore
the magnetism and dynamics of the solar chromosphere and TR. The mission
baseline is a low-Earth, Sun-synchronous orbit at an altitude between
600 and 800 km. The proposed scientific payload consists of a 30 cm
aperture telescope with a spectropolarimeter covering the hydrogen
Ly-alpha and the Mg II h&k ultraviolet lines. The instrument shall
record high-cadence, full spectropolarimetric observations of the
solar upper atmosphere. Besides the answers to a fundamental solar
problem the mission has a broader scientific return. For example,
the time-dependent modeling of the chromospheres of stars harboring
exoplanets is fundamental for estimating the planetary radiation
environment. The mission is based on technologies that are mature
enough for space and will provide scientific measurements that are
not available by other means.
Title: The Solar Internetwork. III. Unipolar versus Bipolar Flux
Appearance
Authors: Gošić, M.; Bellot Rubio, L. R.; Cheung, M. C. M.; Orozco
Suárez, D.; Katsukawa, Y.; del Toro Iniesta, J. C.
Bibcode: 2022ApJ...925..188G
Altcode: 2021arXiv211103208G
Small-scale internetwork (IN) magnetic fields are considered to be the
main building blocks of quiet Sun magnetism. For this reason, it is
crucial to understand how they appear on the solar surface. Here,
we employ a high-resolution, high-sensitivity, long-duration
Hinode/NFI magnetogram sequence to analyze the appearance modes and
spatiotemporal evolution of individual IN magnetic elements inside a
supergranular cell at the disk center. From identification of flux
patches and magnetofrictional simulations, we show that there are
two distinct populations of IN flux concentrations: unipolar and
bipolar features. Bipolar features tend to be bigger and stronger
than unipolar features. They also live longer and carry more flux
per feature. Both types of flux concentrations appear uniformly over
the solar surface. However, we argue that bipolar features truly
represent the emergence of new flux on the solar surface, while
unipolar features seem to be formed by the coalescence of background
flux. Magnetic bipoles appear at a faster rate than unipolar features
(68 as opposed to 55 Mx cm-2 day-1), and provide
about 70% of the total instantaneous IN flux detected in the interior
of the supergranule.
Title: Multi-scale deep learning for estimating horizontal velocity
fields on the solar surface
Authors: Ishikawa, Ryohtaroh T.; Nakata, Motoki; Katsukawa, Yukio;
Masada, Youhei; Riethmüller, Tino L.
Bibcode: 2022A&A...658A.142I
Altcode: 2021arXiv211112518I
Context. The dynamics in the photosphere is governed by the multi-scale
turbulent convection termed as granulation and supergranulation. It is
important to derive three-dimensional velocity vectors to understand the
nature of the turbulent convection and to evaluate the vertical Poynting
flux toward the upper atmosphere. The line-of-sight component of the
velocity can be obtained by observing the Doppler shifts. However,
it is difficult to obtain the velocity component perpendicular to the
line of sight, which corresponds to the horizontal velocity in disk
center observations.
Aims: We present a new method based on a
deep neural network that can estimate the horizontal velocity from
the spatial and temporal variations of the intensity and vertical
velocity. We suggest a new measure for examining the performance of
the method.
Methods: We developed a convolutional neural network
model with a multi-scale deep learning architecture. The method consists
of multiple convolutional kernels with various sizes of receptive
fields, and performs convolution for spatial and temporal axes. The
network is trained with data from three different numerical simulations
of turbulent convection. Furthermore, we introduced a novel coherence
spectrum to assess the horizontal velocity fields that were derived for
each spatial scale.
Results: The multi-scale deep learning method
successfully predicts the horizontal velocities for each convection
simulation in terms of the global correlation coefficient, which is
often used to evaluate the prediction accuracy of the methods. The
coherence spectrum reveals the strong dependence of the correlation
coefficients on the spatial scales. Although the coherence spectra
are higher than 0.9 for large-scale structures, they drastically
decrease to less than 0.3 for small-scale structures, wherein the
global correlation coefficient indicates a high value of approximately
0.95. By comparing the results of the three convection simulations, we
determined that this decrease in the coherence spectrum occurs around
the energy injection scales, which are characterized by the peak of
the power spectra of the vertical velocities.
Conclusions: The
accuracy for the small-scale structures is not guaranteed solely by
the global correlation coefficient. To improve the accuracy on small
scales, it is important to improve the loss function for enhancing
the small-scale structures and to utilize other physical quantities
related to the nonlinear cascade of convective eddies as input data.
Title: Diagnostic capabilities of spectropolarimetric observations for
understanding solar phenomena. I. Zeeman-sensitive photospheric lines
Authors: Quintero Noda, C.; Barklem, P. S.; Gafeira, R.; Ruiz Cobo,
B.; Collados, M.; Carlsson, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Uitenbroek, H.; Katsukawa, Y.
Bibcode: 2021A&A...652A.161Q
Altcode: 2021arXiv210605084Q
Future ground-based telescopes will expand our capabilities for
simultaneous multi-line polarimetric observations in a wide range of
wavelengths, from the near-ultraviolet to the near-infrared. This
creates a strong demand to compare candidate spectral lines to
establish a guideline of the lines that are most appropriate for each
observation target. We focused in this first work on Zeeman-sensitive
photospheric lines in the visible and infrared. We first examined their
polarisation signals and response functions using a 1D semi-empirical
atmosphere. Then we studied the spatial distribution of the line core
intensity and linear and circular polarisation signals using a realistic
3D numerical simulation. We ran inversions of synthetic profiles, and
we compared the heights at which we obtain a high correlation between
the input and the inferred atmosphere. We also used this opportunity
to revisit the atomic information we have on these lines and computed
the broadening cross-sections due to collisions with neutral hydrogen
atoms for all the studied spectral lines. The results reveal that
four spectral lines stand out from the rest for quiet-Sun and network
conditions: Fe I 5250.2, 6302, 8468, and 15 648 Å. The first three
form higher in the atmosphere, and the last line is mainly sensitive to
the atmospheric parameters at the bottom of the photosphere. However,
as they reach different heights, we strongly recommend using at least
one of the first three candidates together with the Fe I 15 648 Å line
to optimise our capabilities for inferring the thermal and magnetic
properties of the lower atmosphere.
Title: Instrumental design of the Solar Observing Satellite:
solar-C_EUVST
Authors: Suematsu, Yoshinori; Shimizu, Toshifumi; Hara, Hirohisa;
Kawate, Tomoko; Katsukawa, Yukio; Ichimoto, Kiyoshi; Imada, Shinsuke
Bibcode: 2021SPIE11852E..3KS
Altcode:
The EUV High-Throughput Spectroscopic Telescope (EUVST) of Solar-C
mission is a revolutionary spectrometer that is designed to provide
high-quality and high cadence spectroscopic data covering a wide
temperature range of the chromosphere to flaring corona to investigate
the energetics and dynamics of the solar atmosphere. The EUVST consists
of only two imaging optical components; a 28-cm clear aperture off-axis
parabolic primary mirror and a two-split ellipsoidal grating without a
blocking filter for visible light before the primary mirror to achieve
unprecedented high spatial and temporal resolution in EUV-UV imaging
spectroscopic observations. For this reason, about 53 W of sunlight
is absorbed by the multilayer coating on the mirror. We present an
instrumental design of the telescope, particularly, primary mirror
assembly which enables slit-scan observations for imaging spectroscopy,
an image stabilizing tip-tilt control, and a focus adjustment on
orbit, together with an optomechanical design of the primary mirror
and its supporting system which gives optically tolerant wavefront
error against a large temperature increase due to an absorption of
visible and IR lights.
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
Title: A HAWAII-2RG infrared camera operated under fast readout mode
for solar polarimetry
Authors: Hanaoka, Yoichiro; Katsukawa, Yukio; Morita, Satoshi; Kamata,
Yukiko; Ishizuka, Noriyoshi
Bibcode: 2020EP&S...72..181H
Altcode:
Polarimetry is a crucial method to investigate solar magnetic
fields. From the viewpoint of space weather, the magnetic field
in solar filaments, which occasionally erupt and develop into
interplanetary flux ropes, is of particular interest. To measure
the magnetic field in filaments, high-performance polarimetry in
the near-infrared wavelengths employing a high-speed, large-format
detector is required; however, so far, this has been difficult to be
realized. Thus, the development of a new infrared camera for advanced
solar polarimetry has been started, employing a HAWAII-2RG (H2RG)
array by Teledyne, which has 2048 ×2048 pixels, focusing on the
wavelengths in the range of 1.0 -1.6 μ m . We solved the problem
of the difficult operation of the H2RGs under "fast readout mode"
synchronizing with high-speed polarization modulation by introducing a
"MACIE" (Markury ASIC Control and Interface Electronics) interface card
and new assembly codes provided by Markury Scientific. This enables
polarization measurements with high frame-rates, such as 29-117 frames
per seconds, using a H2RG. We conducted experimental observations of
the Sun and confirmed the high polarimetric performance of the camera.
Title: SUNRISE Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: Scan mirror mechanism
Authors: Oba, Takayoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Kubo,
Masahito; Uraguchi, Fumihiro; Tsuzuki, Toshihiro; Tamura, Tomonori;
Shinoda, Kazuya; Kodeki, Kazuhide; Fukushima, Kazuhiko; Gandorfer,
Achim; del Toro Iniesta, Jose Carlos
Bibcode: 2020SPIE11445E..4FO
Altcode:
The SUNRISE Chromospheric Infrared spectroPolarimeter (SCIP) is a
balloon-borne long-slit spectrograph for SUNRISE III to precisely
measure magnetic fields in the solar atmosphere. The scan mirror
mechanism (SMM) is installed in the optical path to the entrance slit
of the SCIP to move solar images focused on the slit for 2-dimensional
mapping. The SMM is required to have (1) the tilt stability better
than 0.035″ (3σ) on the sky angle for the diffraction-limited
spatial resolution of 0.2″, (2) step response shorter than 32 msec
for rapid scanning observations, and (3) good linearity (i.e. step
uniformity) over the entire field-of-view (60″x60″). To achieve
these performances, we have developed a flight-model mechanism
and its electronics, in which the mirror tilt is controlled by
electromagnetic actuators with a closed-loop feedback logic with
tilt angles from gap-based capacitance sensors. Several optical
measurements on the optical bench verified that the mechanism meets
the requirements. In particular, the tilt stability achives better
than 0.012″ (3σ). Thermal cycling and thermal vacuum tests have
been completed to demonstrate the performance in the vacuum and the
operational temperature range expected in the balloon flight. We
found a small temperature dependence in the step uniformity and this
dependence will be corrected to have 2-demensional maps with the
sub-arcsec spatial accuracy in the data post-processing.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: optical design and performance
Authors: Tsuzuki, Toshihiro; Katsukawa, Yukio; Uraguchi, Fumihiro;
Hara, Hirohisa; Kubo, Masahito; Nodomi, Yoshifumi; Suematsu, Yoshinori;
Kawabata, Yusuke; Shimizu, Toshifumi; Gandorfer, Achim; Feller, Alex;
Grauf, Bianca; Solanki, Sami; Carlos del Toro Iniesta, Jose
Bibcode: 2020SPIE11447E..AJT
Altcode:
The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is a
near-IR spectro-polarimeter instrument newly designed for Sunrise III,
which is a balloon-borne solar observatory equipped with a 1 m optical
telescope. To acquire high-quality 3D magnetic and velocity fields,
SCIP selects the two wavelength bands centered at 850 nm and 770 nm,
which contain many spectrum lines that are highly sensitive to magnetic
fields permeating the photosphere and chromosphere. To achieve high
spatial and spectral resolution (0.21 arcsec and 2 × 105),
SCIP optics adopt a quasi-Littrow configuration based on an echelle
grating and two high-order aspheric mirrors. Using different diffraction
orders of the echelle grating, dichroic beam splitter, and polarizing
beam-splitters, SCIP can obtain s- and p-polarization signals in the
two wavelength bands simultaneously within a relatively small space. We
established the wavefront error budget based on tolerance analysis,
surface figure errors, alignment errors, and environmental changes. In
addition, we performed stray light analysis, and designed light traps
and baffles needed to suppress unwanted reflections and diffraction
by the grating. In this paper, we present the details of this optical
system and its performance.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: polarization modulation unit
Authors: Kubo, Masahito; Shimizu, Toshifumi; Katsukawa, Yukio;
Kawabata, Yusuke; Anan, Tetsu; Ichimoto, Kiyoshi; Shinoda, Kazuya;
Tamura, Tomonori; Nodomi, Yoshifumi; Nakayama, Satoshi; Yamada, Takuya;
Tajima, Takao; Nakata, Shimpei; Nakajima, Yoshihito; Okutani, Kousei;
Feller, Alex; del Toro Iniesta, Jose Carlos
Bibcode: 2020SPIE11447E..A3K
Altcode:
Polarization measurements of the solar chromospheric lines at
high precision are key to present and future solar telescopes for
understanding magnetic field structures in the chromosphere. The
Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) for Sunrise
III is a spectropolarimeter with a polarimetric precision of 0.03 %
(1 σ). The key to high-precision polarization measurements using
SCIP is a polarization modulation unit that rotates a waveplate
continuously at a constant speed. The rotating mechanism is a DC
brushless motor originally developed for a future space mission, and
its control logic was originally developed for the sounding rocket
experiment CLASP. Because of our requirement on a speed of rotation
(0.512 s/rotation) that was 10 times faster than that of CLASP, we
optimized the control logic for the required faster rotation. Fast
polarization modulation is essential for investigating the fine-scale
magnetic field structures related to the dynamical chromospheric
phenomena. We have verified that the rotation performance can achieve
the polarization precision of 0.03 % (1 σ) required by SCIP and such
a significant rotation performance is maintained under thermal vacuum
conditions by simulating the environment of the Sunrise III balloon
flight. The waveplate was designed as a pair of two birefringent
plates made of quartz and sapphire to achieve a constant retardation
in a wide wavelength range. We have confirmed that the retardation
is almost constant in the 770 nm and 850nm wavelength bands of SCIP
under the operational temperature conditions.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for SUNRISE III: opto-mechanical analysis and design
Authors: Uraguchi, Fumihiro; Tsuzuki, Toshihiro; Katsukawa, Yukio;
Hara, Hirohisa; Iwamura, Satoru; Kubo, Masahito; Nodomi, Yoshifumi;
Suematsu, Yoshinori; Kawabata, Yusuke; Shimizu, Toshifumi; Gandorfer,
Achim; del Toro Iniesta, Jose Carlos
Bibcode: 2020SPIE11447E..ABU
Altcode:
The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is a
near-IR spectro-polarimeter instrument newly designed for Sunrise III,
a balloon-borne solar observatory with a 1-m diameter telescope. In
order to achieve the strict requirements the SCIP wavefront error, it is
necessary to quantify the errors due to environmen- tal effects such as
gravity and temperature variation under the observation conditions. We
therefore conducted an integrated opto-mechanical analysis incorporating
mechanical and thermal disturbances into a finite element model of
the entire SCIP structure to acquire the nodal displacements of each
optical element, then fed them back to the optical analysis software
in the form of rigid body motion and surface deformation fitted by
polynomials. This method allowed us to determine the error factors
having a significant influence on optical performance. For example,
no significant wavefront degradation was associated with the structural
mountings because the optical element mounts were well designed based
on quasi-kinematic constraints. In contrast, we found that the main
factor affecting wavefront degradation was the rigid body motions of
the optical elements, which must be mini- mized within the allowable
level. Based on these results, we constructed the optical bench using a
sandwich panel as the optical bench consisting of an aluminum-honeycomb
core and carbon fiber reinforced plastic skins with a high stiffness
and low coefficient of thermal expansion. We then confirmed that the
new opto-mechanical model achieved the wavefront error requirement. In
this paper, we report the details of this integrated opto-mechanical
analysis, including the wavefront error budgeting and the design of
the opto-mechanics.
Title: The SUNRISE UV Spectropolarimeter and imager for SUNRISE III
Authors: Feller, Alex; Gandorfer, Achim; Iglesias, Francisco A.;
Lagg, Andreas; Riethmüller, Tino L.; Solanki, Sami K.; Katsukawa,
Yukio; Kubo, Masahito
Bibcode: 2020SPIE11447E..AKF
Altcode:
Sunrise is a balloon-borne solar observatory dedicated to the
investigation of key processes of the magnetic field and the plasma
flows in the lower solar atmosphere. The observatory operates in
the stratosphere at an altitude of around 37 km in order to avoid
image degradation due to turbulence in the Earth's atmosphere and to
access the UV range. The third science flight of Sunrise will carry new
instrumentation which samples the solar spectrum over a broad wavelength
domain from the UV to the near IR and covers an extended height range in
the solar atmosphere. A key feature of the Sunrise UV Spectropolarimeter
and Imager (SUSI) operating between 309 nm and 417 nm, is its capability
to simultaneously record a large number of spectral lines. By combining
the spectral and polarization information of many individual lines
with different formation heights and sensitivities, the accuracy and
the height resolution of the inferred atmospheric parameters can be
significantly increased. The spectral bands of SUSI are selected one
at a time by rotating a diffraction grating with respect to a fixed
polarimetry unit. The spatial and spectral field of view on the 2k x
2k cameras is 59" and 2.0 - 2.3 nm, respectively. A further innovation
is the numerical restoration of the spectrograph scans by means of
synchronized 2D context imaging, a technique that has recently produced
impressive results at ground-based solar observatories.
Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
Bibcode: 2020SPIE11444E..0NS
Altcode:
Solar-C (EUVST) is the next Japanese solar physics mission to
be developed with significant contributions from US and European
countries. The mission carries an EUV imaging spectrometer with
slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
Telescope) as the mission payload, to take a fundamental step towards
answering how the plasma universe is created and evolves and how the
Sun influences the Earth and other planets in our solar system. In
April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
(Japan Aerospace Exploration Agency) has made the final down-selection
for this mission as the 4th in the series of competitively chosen
M-class mission to be launched with an Epsilon launch vehicle in mid
2020s. NASA (National Aeronautics and Space Administration) has selected
this mission concept for Phase A concept study in September 2019 and
is in the process leading to final selection. For European countries,
the team has (or is in the process of confirming) confirmed endorsement
for hardware contributions to the EUVST from the national agencies. A
recent update to the mission instrumentation is to add a UV spectral
irradiance monitor capability for EUVST calibration and scientific
purpose. This presentation provides the latest status of the mission
with an overall description of the mission concept emphasizing on key
roles of the mission in heliophysics research from mid 2020s.
Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP)
for sunrise III: system design and capability
Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.;
Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki,
T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu,
Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.;
Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez,
M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.;
Riethmueller, T.; Gandorfer, A.; Lagg, A.
Bibcode: 2020SPIE11447E..0YK
Altcode:
The Sunrise balloon-borne solar observatory carries a 1 m aperture
optical telescope and provides us a unique platform to conduct
continuous seeing-free observations at UV-visible-IR wavelengths from
an altitude of higher than 35 km. For the next flight planned for
2022, the post-focus instrumentation is upgraded with new spectro-
polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas
the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable
of observing multiple spectral lines within the visible wavelength. A
new spectro-polarimeter called the Sunrise Chromospheric Infrared
spectroPolarimeter (SCIP) is under development for observing near-IR
wavelength ranges of around 770 nm and 850 nm. These wavelength ranges
contain many spectral lines sensitive to solar magnetic fields and
SCIP will be able to obtain magnetic and velocity structures in the
solar atmosphere with a sufficient height resolution by combining
spectro-polarimetric data of these lines. Polarimetric measurements are
conducted using a rotating waveplate as a modulator and polarizing beam
splitters in front of the cameras. The spatial and spectral resolutions
are 0.2" and 2 105, respectively, and a polarimetric sensitivity of
0.03 % (1σ) is achieved within a 10 s integration time. To detect
minute polarization signals with good precision, we carefully designed
the opto-mechanical system, polarization optics and modulation, and
onboard data processing.
Title: Current Status of the Solar-C_EUVST Mission
Authors: Imada, S.; Shimizu, T.; Kawate, T.; Toriumi, S.; Katsukawa,
Y.; Kubo, M.; Hara, H.; Suematsu, Y.; Ichimoto, K.; Watanabe, T.;
Watanabe, K.; Yokoyama, T.; Warren, H.; Long, D.; Harra, L. K.;
Teriaca, L.
Bibcode: 2020AGUFMSH056..05I
Altcode:
Solar-C_EUVST (EUV High-Throughput Spectroscopic Telescope) is designed
to comprehensively understand the energy and mass transfer from the
solar surface to the solar corona and interplanetary space, and to
investigate the elementary processes that take place universally
in cosmic plasmas. As 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, the proposed mission
is designed to comprehensively understand how mass and energy are
transferred throughout the solar atmosphere. Understanding the solar
atmosphere, which connects to the heliosphere via radiation, the solar
wind and coronal mass ejections, and energetic particles is pivotal
for establishing the conditions for life and habitability in the solar
system. The two primary science objectives for Solar-C_EUVST are :
I) Understand how fundamental processes lead to the formation of the
solar atmosphere and the solar wind, II) Understand how the solar
atmosphere becomes unstable, releasing the energy that drives solar
flares and eruptions. Solar-C_EUVST will, A) seamlessly observe all
the temperature regimes of the solar atmosphere from the chromosphere
to the corona at the same time, B) resolve elemental structures of the
solar atmosphere with high spatial resolution and cadence to track their
evolution, and C) obtain spectroscopic information on the dynamics of
elementary processes taking place in the solar atmosphere. In this
talk, we will first discuss the science target of the Solar-C_EUVST,
and then discuss the current status of the Solar-C_EUVST mission.
Title: Thermal design of the Solar-C (EUVST) telescope
Authors: Suematsu, Yoshinori; Shimizu, Toshifumi; Hara, Hirohisa;
Kawate, Tomoko; Katsukawa, Yukio; Ichimoto, Kiyoshi; Imada, Shinsuke;
Nagae, Kazuhiro; Yamazaki, Atsumu; Hattori, Tomoya
Bibcode: 2020SPIE11444E..3KS
Altcode:
The EUV High-Throughput Spectroscopic Telescope (EUVST) of Solar-C
mission consists of only two imaging optical components; a 28-cm clear
aperture off-axis parabolic primary mirror and a two-split ellipsoidal
grating without a blocking filter for visible light before the primary
mirror to achieve unprecedented high spatial and temporal resolution in
EUV-UV imaging spectroscopic observations. For this reason, about 60
W of sunlight is absorbed by the multilayer coating on the mirror. We
report a thermal design of telescope in which the temperature of the
primary mirror bonding part and underlying tip-tilt and slit-scanning
mechanisms is well lower than a glass transition temperature of adhesive
(about 60°C) and thermal deformation of the primary mirror is small,
although it is non-negligibly small.
Title: A sensitivity analysis of the updated optical design for
EUVST on the Solar-C mission
Authors: Kawate, Tomoko; Tsuzuki, Toshihiro; Shimizu, Toshifumi;
Imada, Shinsuke; Katsukawa, Yukio; Hara, Hirohisa; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Hattori, Tomoya; Narasaki, Shota; Warren, Harry P.;
Teriaca, Luca; Korendyke, Clarence M.; Brown, Charles M.; Auchere,
Frederic
Bibcode: 2020SPIE11444E..3JK
Altcode:
The EUV high-throughput spectroscopic telescope (EUVST) onboard the
Solar-C mission has the high spatial (0.4'') resolution over a wide
wavelength range in the vacuum ultraviolet. To achieve high spatial
resolution under a design constraint given by the JAXA Epsilon launch
vehicle, we further update the optical design to secure margins
needed to realize 0.4'' spatial resolution over a field of view of
100''×100''. To estimate the error budgets of spatial and spectral
resolutions due to installation and fabrication errors, we perform a
sensitivity analysis for the position and orientation of each optical
element and for the grating parameters by ray tracing with the Zemax
software. We obtain point spread functions (PSF) for rays from 9
fields and at 9 wavelengths on each detector by changing each parameter
slightly. A full width at half maximum (FWHM) of the PSF is derived at
each field and wavelength position as a function of the perturbation
of each optical parameter. Assuming a mount system of each optical
element and an error of each optical parameter, we estimate spatial
and spectral resolutions by taking installation and fabrication errors
into account. The results of the sensitivity analysis suggest that
budgets of the total of optical design and the assembly errors account
for 15% and 5.8% of our budgets of the spatial resolution in the long
wavelength and short wavelength bands, respectively. On the other hand,
the grating fabrication errors give a large degradation of spatial and
spectral resolutions, and investigations of compensators are needed
to relax the fabrication tolerance of the grating surface parameters.
Title: Temporal and Spatial Scales in Coronal Rain Revealed by UV
Imaging and Spectroscopic Observations
Authors: Ishikawa, Ryohtaroh T.; Katsukawa, Yukio; Antolin, Patrick;
Toriumi, Shin
Bibcode: 2020SoPh..295...53I
Altcode: 2020arXiv200313214I
Coronal rain corresponds to cool and dense clumps in the corona
accreting towards the solar surface; it is often observed above solar
active regions. These clumps are generally thought to be produced by
a thermal instability in the corona and their lifetime is limited by
the time they take to reach the chromosphere. Although the rain usually
fragments into smaller clumps while falling down, their specific spatial
and temporal scales remain unclear. In addition, the observational
signatures of the impact of the rain with the chromosphere have not been
clarified yet. In this study, we investigate the time evolution of the
velocity and intensity of coronal rain above a sunspot by analyzing
coronal images obtained by the Atmospheric Imaging Assembly (AIA)
onboard the Solar Dynamics Observatory (SDO) as well as the slit-jaw
images (SJIs) and spectral data taken by the Interface Region Imaging
Spectrograph (IRIS) satellite. We identify dark and bright threads
moving towards the umbra in AIA images and in SJIs, respectively,
and co-spatial chromospheric intensity enhancements and redshifts in
three IRIS spectral lines, Mg II k 2796 Å, Si IV 1394 Å, and C II
1336 Å. The intensity enhancements and coronal rain redshifts occur
almost concurrently in all the three lines, which clearly demonstrates
the causal relationship with coronal rain. Furthermore, we detect bursty
intensity variation with a time scale shorter than 1 minute in Mg II k,
Si IV, and C II, indicating that a length scale of rain clumps is about
2.7 Mm if we multiply the typical time scale of the busty intensity
variation at 30 sec by the rain velocity at 90 kms−1. Such
rapid enhancements in the IRIS lines are excited within a time lag
of 5.6 sec limited by the temporal resolution. These temporal and
spatial scales may reflect the physical processes responsible for
the rain morphology, and are suggestive of instabilities such as the
Kelvin-Helmholtz instability.
Title: Study of the Dynamics of Convective Turbulence in the Solar
Granulation by Spectral Line Broadening and Asymmetry
Authors: Ishikawa, Ryohtaroh T.; Katsukawa, Yukio; Oba, Takayoshi;
Nakata, Motoki; Nagaoka, Kenichi; Kobayashi, Tatsuya
Bibcode: 2020ApJ...890..138I
Altcode: 2020arXiv200104632I
In quiet regions on the solar surface, turbulent convective motions
of granulation play an important role in creating small-scale
magnetic structures, as well as in energy injection into the upper
atmosphere. The turbulent nature of granulation can be studied using
spectral line profiles, especially line broadening, which contain
information on the flow field smaller than the spatial resolution of
an instrument. Moreover, the Doppler velocity gradient along a line of
sight (LOS) causes line broadening as well. However, the quantitative
relationship between velocity gradient and line broadening has not
been understood well. In this study, we perform bisector analyses
using the spectral profiles obtained using the spectropolarimeter of
the Hinode/Solar Optical Telescope to investigate the relationship of
line broadening and bisector velocities with the granulation flows. The
results indicate that line broadening has a positive correlation with
the Doppler velocity gradients along the LOS. 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 process of fading. If this excessive line broadening is attributed
to small-scale turbulent motions, the averaged turbulent velocity is
obtained as 0.9 km s-1.
Title: Dynamics of the Convective Turbulence in the Solar Granulation
Studied by the Spectral Line Broadening and Asymmetry
Authors: Ishikawa, R.; Katsukawa, Y.; Oba, T.; Nakata, M.; Nagaoka,
K.; Kobayashi, T.
Bibcode: 2019AGUFMSH43E3385I
Altcode:
In the quiet region on the solar surface, turbulent convective motions
of the granulation play an important role for creating small-scale
magnetic structures as well as the energy injection into the upper
atmosphere. The turbulent nature can be studied using spectral line
profiles, especially line broadening, that contains information on the
flow field smaller than the spatial resolution of an instrument. Doppler
velocity gradient along a line-of-sight (LOS) is also a source of
line broadening. However, the quantitative relation between velocity
gradient and line broadening is not well understood. In this study,
we perform bisector analyses using spectral profiles obtained with the
Spectro-Polarimeter of Hinode Solar Optical Telescope to investigate
how the line broadening and the bisector velocities are related with
granulation flows. Our result indicates that the line broadening has a
positive correlation with the LOS gradient of Doppler velocities. We
found excessive line broadening in fading granules that cannot be
explained only by the LOS velocity gradient, although the velocity
gradient is enhanced in the course of fading granules. If we attribute
the excessive line broadening to small-scale turbulent motions, the
averaged turbulent velocity is 1.6 km/s.
Title: Development of Solar-C_EUVST structural design
Authors: Suematsu, Yoshinori; Shimizu, Toshifumi; Hara, Hirohisa;
Katsukawa, Yukio; Kawate, Tomoko; Ichimoto, Kiyoshi; Imada, Shinsuke
Bibcode: 2019SPIE11118E..1OS
Altcode:
The Solar-C_EUVST is a mission designed to provide high-quality solar
spectroscopic data covering a wide temperature range of the chromosphere
to flaring corona. To fulfill a high throughput requirement, the
instrument consists of only two optical components; a 28-cm primary
mirror and a segmented toroidal grating which have high reflective
coatings in EUV-UV range. We present a mission payload structural
design which accommodates long focal length optical components and
a launcher condition/launch environment (JAXA Epsilon). We also
present a mechanical design of primary mirror assembly which enables
slit-scan observations, an image stabilizing tip-tilt control, and a
focus adjustment on orbit, together with an optomechanical design of
the primary mirror and its supporting system which gives optically
tolerant wavefront error against a large temperature increase due to
an absorption of visible and IR lights.
Title: Concept study of Solar-C_EUVST optical design
Authors: Kawate, Tomoko; Shimizu, Toshifumi; Imada, Shinsuke; Tsuzuki,
Toshihiro; Katsukawa, Yukio; Hara, Hirohisa; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Warren, Harry; Teriaca, Luca; Korendyke, Clarence
M.; Brown, Charles
Bibcode: 2019SPIE11118E..1NK
Altcode:
The main characteristics of Solar-C_EUVST are the high temporal and
high spatial resolutions over a wide temperature coverage. In order
to realize the instrument for meeting these scientific requirements
under size constraints given by the JAXA Epsilon vehicle, we examined
four-dimensional optical parameter space of possible solutions of
geometrical optical parameters such as mirror diameter, focal length,
grating magnification, and so on. As a result, we have identified
the solution space that meets the EUVST science objectives and rocket
envelope requirements. A single solution was selected and used to define
the initial optical parameters for the concept study of the baseline
architecture for defining the mission concept. For this solution, we
optimized the grating and geometrical parameters by ray tracing of the
Zemax software. Consequently, we found an optics system that fulfills
the requirement for a 0.4" angular resolution over a field of view of
100" (including margins) covering spectral ranges of 170-215, 463-542,
557-637, 690-850, 925-1085, and 1115-1275 A. This design achieves an
effective area 10 times larger than the Extreme-ultraviolet Imaging
Spectrometer onboard the Hinode satellite, and will provide seamless
observations of 4.2-7.2 log(K) plasmas for the first time. Tolerance
analyses were performed based on the optical design, and the moving
range and step resolution of focus mechanisms were identified. In
the presentation, we describe the derivation of the solution space,
optimization of the optical parameters, and show the results of ray
tracing and tolerance analyses.
Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
Bibcode: 2019SPIE11118E..07S
Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
Title: Development of an Infrared Camera Using a Hawaii-2RG Detector
for Solar Polarimetry.
Authors: Hanaoka, Y.; Katsukawa, Y.; Morita, S.; Kamata, Y.;
Ishizuka, N.
Bibcode: 2019spw..confE...9H
Altcode:
No abstract at ADS
Title: Design of all-reflective space-borne 1-m aperture solar
optical telescope
Authors: Suematsu, Y.; Hara, H.; Katsukawa, Y.; Kano, R.; Shimizu,
T.; Ichimoto, K.
Bibcode: 2019SPIE11180E..0RS
Altcode:
A 1-m aperture optical telescope is planned for a future Japanese solar
mission. The telescope is designed to provide high spatial resolution
data of solar lower atmosphere from the photosphere to the uppermost
chromosphere with enhanced spectroscopic and spectro-polarimetric
capabilities covering a wide wavelength region from UV to near IR where
many useful spectral lines and continua exist for physical diagnosis of
the solar magnetized atmosphere. We designed an allreflective telescope
to fulfill the scientific and engineering requirements. From a thermal
view point, a Gregorian telescope is the most suitable. To avoid
chromatic aberration, a tri-aspheric-mirror collimator coupling to
the Gregorian was designed to give a diffraction-limited performance
over the FOV by allowing a field curvature. The field curvature can
be compensated by an off-axis Ritchey Chretien reimaging optics at an
entrance of focal plane instrument, which has an opposite sign in the
field curvature to the Gregorian. We also briefly studied structural
design of all-reflective 1-m aperture solar optical telescope for the
space solar mission.
Title: Chromospheric polarimetry through multiline observations of
the 850 nm spectral region III: Chromospheric jets driven by twisted
magnetic fields
Authors: Quintero Noda, C.; Iijima, H.; Katsukawa, Y.; Shimizu,
T.; Carlsson, M.; de la Cruz Rodríguez, J.; Ruiz Cobo, B.; Orozco
Suárez, D.; Oba, T.; Anan, T.; Kubo, M.; Kawabata, Y.; Ichimoto,
K.; Suematsu, Y.
Bibcode: 2019MNRAS.486.4203Q
Altcode: 2019MNRAS.tmp.1081N; 2019arXiv190409151Q
We investigate the diagnostic potential of the spectral lines at 850
nm for understanding the magnetism of the lower atmosphere. For that
purpose, we use a newly developed 3D simulation of a chromospheric
jet to check the sensitivity of the spectral lines to this phenomenon
as well as our ability to infer the atmospheric information through
spectropolarimetric inversions of noisy synthetic data. We start
comparing the benefits of inverting the entire spectrum at 850 nm versus
only the Ca II 8542 Å spectral line. We found a better match of the
input atmosphere for the former case, mainly at lower heights. However,
the results at higher layers were not accurate. After several tests,
we determined that we need to weight more the chromospheric lines
than the photospheric ones in the computation of the goodness of the
fit. The new inversion configuration allows us to obtain better fits and
consequently more accurate physical parameters. Therefore, to extract
the most from multiline inversions, a proper set of weights needs to
be estimated. Besides that, we conclude again that the lines at 850
nm, or a similar arrangement with Ca II 8542 Å plus Zeeman-sensitive
photospheric lines, pose the best-observing configuration for examining
the thermal and magnetic properties of the lower solar atmosphere.
Title: Comparison of Scattering Polarization Signals Observed by
CLASP: Possible Indication of the Hanle Effect
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pomtieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
Bibcode: 2019ASPC..526..305I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP; Kano et
al. 2012; Kobayashi et al. 2012; Kubo et al. 2014) observed, for the
first time, the linear polarization produced by scattering processes
in the hydrogen Lyman-α (121.57 nm) and Si III (120.56 nm) lines of
the solar disk radiation. The complexity of the observed scattering
polarization (i.e., conspicuous spatial variations in Q/I and U/I
at spatial scales of 10″-20″ and the absence of center-to- limb
variation at the Lyman-α center; see Kano et al. 2017) motivated us
to search for possible hints of the operation of the Hanle effect by
comparing: (a) the Lyman-α line center signal, for which the critical
field strength (BH) for the onset of the Hanle effect is
53 G, (b) the Lyman-α wing, which is insensitive to the Hanle effect,
and (c) the Si III line, whose BH = 290 G. We focus on four
regions with different total unsigned photospheric magnetic fluxes
(estimated from SDO/HMI observations), and compare the corresponding
U/I spatial variations in the Lyman-α wing, Lyman-α center, and Si III
line. The U/I signal in the Lyman-α wing shows an antisymmetric spatial
distribution, which is caused by the presence of a bright structure in
all the selected regions, regardless of the total unsigned photospheric
magnetic flux. In an internetwork region, the Lyman-α center shows an
antisymmetric spatial variation across the selected bright structure,
but it does not show it in other more magnetized regions. In the Si III
line, the spatial variation of U/I deviates from the above-mentioned
antisymmetric shape as the total unsigned photospheric magnetic flux
increases. We argue that a plausible explanation of this differential
behavior is the operation of the Hanle effect. This work, presented
in an oral contribution at this Workshop, has been published on The
Astrophysical Journal (Ishikawa et al. 2017).
Title: Observations of photospheric magnetic structure below a dark
filament using the Hinode Spectro-Polarimeter
Authors: Yokoyama, Takaaki; Katsukawa, Yukio; Shimojo, Masumi
Bibcode: 2019PASJ...71...46Y
Altcode: 2019arXiv190110695Y; 2019PASJ..tmp...26Y
The structure of the photospheric vector magnetic field below a
dark filament on the Sun is studied using the observations of the
Spectro-Polarimeter attached to the Solar Optical Telescope onboard
Hinode. Special attention is paid to discriminating between two
suggested models, a flux rope or a bent arcade. "Inverse polarity"
orientation is possible below the filament in a flux rope, whereas
"normal polarity" can appear in both models. We study a filament in the
active region NOAA 10930, which appeared on the solar disk during 2006
December. The transverse field perpendicular to the line of sight has a
direction almost parallel to the filament spine with a shear angle of
30°, the orientation of which includes the 180° ambiguity. To know
whether it is in the normal orientation or in the inverse one, the
center-to-limb variation is used for the solution under the assumption
that the filament does not drastically change its magnetic structure
during the passage. When the filament is near the east limb, we found
that the line-of-site magnetic component below the filament is positive,
while it is negative near the west limb.This change of sign indicates
that the horizontal photospheric field perpendicular to the polarity
inversion line beneath the filament has an "inverse-polarity", which
indicates a flux-rope structure of the filament supporting field.
Title: Study of the polarization produced by the Zeeman effect in
the solar Mg I b lines
Authors: Quintero Noda, C.; Uitenbroek, H.; Carlsson, M.; Orozco
Suárez, D.; Katsukawa, Y.; Shimizu, T.; Ruiz Cobo, B.; Kubo, M.; Oba,
T.; Kawabata, Y.; Hasegawa, T.; Ichimoto, K.; Anan, T.; Suematsu, Y.
Bibcode: 2018MNRAS.481.5675Q
Altcode: 2018arXiv181001067Q; 2018MNRAS.tmp.2566Q
The next generation of solar observatories aim to understand the
magnetism of the solar chromosphere. Therefore, it is crucial to
understand the polarimetric signatures of chromospheric spectral
lines. For this purpose, we here examine the suitability of the three
Fraunhofer Mg I b1, b2, and b4 lines
at 5183.6, 5172.7, and 5167.3 Å, respectively. We start by describing
a simplified atomic model of only six levels and three line transitions
for computing the atomic populations of the 3p-4s (multiplet number
2) levels involved in the Mg I b line transitions assuming non-local
thermodynamic conditions and considering only the Zeeman effect using
the field-free approximation. We test this simplified atom against
more complex ones finding that, although there are differences in the
computed profiles, they are small compared with the advantages provided
by the simple atom in terms of speed and robustness. After comparing
the three Mg I lines, we conclude that the most capable one is the
b2 line as b1 forms at similar heights and always
shows weaker polarization signals, while b4 is severely
blended with photospheric lines. We also compare Mg I b2
with the K I D1 and Ca II 8542 Å lines finding that the
former is sensitive to the atmospheric parameters at heights that
are in between those covered by the latter two lines. This makes Mg I
b2 an excellent candidate for future multiline observations
that aim to seamlessly infer the thermal and magnetic properties of
different features in the lower solar atmosphere.
Title: Solar Ultraviolet Bursts
Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.;
Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal
J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria
S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark
C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr
Bibcode: 2018SSRv..214..120Y
Altcode: 2018arXiv180505850Y
The term "ultraviolet (UV) burst" is introduced to describe small,
intense, transient brightenings in ultraviolet images of solar active
regions. We inventorize their properties and provide a definition
based on image sequences in transition-region lines. Coronal signatures
are rare, and most bursts are associated with small-scale, canceling
opposite-polarity fields in the photosphere that occur in emerging flux
regions, moving magnetic features in sunspot moats, and sunspot light
bridges. We also compare UV bursts with similar transition-region
phenomena found previously in solar ultraviolet spectrometry and
with similar phenomena at optical wavelengths, in particular Ellerman
bombs. Akin to the latter, UV bursts are probably small-scale magnetic
reconnection events occurring in the low atmosphere, at photospheric
and/or chromospheric heights. Their intense emission in lines with
optically thin formation gives unique diagnostic opportunities
for studying the physics of magnetic reconnection in the low solar
atmosphere. This paper is a review report from an International Space
Science Institute team that met in 2016-2017.
Title: CLASP Constraints on the Magnetization and Geometrical
Complexity of the Chromosphere-Corona Transition Region
Authors: Trujillo Bueno, J.; Štěpán, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Ishikawa,
R.; Kano, R.; Winebarger, A.; Auchère, F.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
Bibcode: 2018ApJ...866L..15T
Altcode: 2018arXiv180908865T
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
suborbital rocket experiment that on 2015 September 3 measured
the linear polarization produced by scattering processes in the
hydrogen Lyα line of the solar disk radiation. The line-center
photons of this spectral line radiation mostly stem from the
chromosphere-corona transition region (TR). These unprecedented
spectropolarimetric observations revealed an interesting surprise,
namely that there is practically no center-to-limb variation (CLV) in
the Q/I line-center signals. Using an analytical model, we first show
that the geometric complexity of the corrugated surface that delineates
the TR has a crucial impact on the CLV of the Q/I and U/I line-center
signals. Second, we introduce a statistical description of the solar
atmosphere based on a 3D model derived from a state-of-the-art radiation
magnetohydrodynamic simulation. Each realization of the statistical
ensemble is a 3D model characterized by a given degree of magnetization
and corrugation of the TR, and for each such realization we solve the
full 3D radiative transfer problem taking into account the impact
of the CLASP instrument degradation on the calculated polarization
signals. Finally, we apply the statistical inference method presented
in a previous paper to show that the TR of the 3D model that produces
the best agreement with the CLASP observations has a relatively weak
magnetic field and a relatively high degree of corrugation. We emphasize
that a suitable way to validate or refute numerical models of the upper
solar chromosphere is by confronting calculations and observations
of the scattering polarization in ultraviolet lines sensitive to the
Hanle effect.
Title: A Statistical Inference Method for Interpreting the CLASP
Observations
Authors: Štěpán, J.; Trujillo Bueno, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Kano, R.;
Winebarger, A.; Auchère, F.; Ishikawa, R.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
Bibcode: 2018ApJ...865...48S
Altcode: 2018arXiv180802725S
On 2015 September 3, the Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) successfully measured the linear polarization produced by
scattering processes in the hydrogen Lyα line of the solar disk
radiation, revealing conspicuous spatial variations in the Q/I and U/I
signals. Via the Hanle effect, the line-center Q/I and U/I amplitudes
encode information on the magnetic field of the chromosphere-corona
transition region, but they are also sensitive to the three-dimensional
structure of this corrugated interface region. With the help of a simple
line-formation model, here we propose a statistical inference method
for interpreting the Lyα line-center polarization observed by CLASP.
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for the SUNRISE balloon-borne solar observatory
Authors: Suematsu, Yoshinori; Katsukawa, Yukio; Hara, Hirohisa;
Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Barthol,
Peter; Riethmueller, Tino; Gandorfer, Achim; Feller, Alex; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Kano, Ryouhei; Ishikawa,
Shin-nosuke; Ishikawa, Ryohko; Tsuzuki, Toshihiro; Uraguchi, Fumihiro;
Quintero Noda, Carlos; Tamura, Tomonori; Oba, Takayoshi; Kawabata,
Yusuke; Nagata, Shinichi; Anan, Tetsu; Cobos Carrascosa, Juan Pedro;
Lopez Jimenez, Antonio Carlos; Balaguer Jimenez, Maria; Solanki, Sami
Bibcode: 2018cosp...42E3285S
Altcode:
The SUNRISE balloon-borne solar observatory carries a 1 m aperture
optical telescope, and allows us to perform seeing-free continuous
observations at visible-IR wavelengths from an altitude higher than
35 km. In the past two flights, in 2009 and 2013, observations mainly
focused on fine structures of photospheric magnetic fields. For the
third flight planned for 2021, we are developing a new instrument
for conducting spectro-polarimetry of spectral lines formed over a
larger height range in the solar atmosphere from the photosphere to
the chromosphere. Targets of the spectro-polarimetric observation
are (1) to determine 3D magnetic structure from the photosphere to
the chromosphere, (2) to trace MHD waves from the photosphere to the
chromosphere, and (3) to reveal the mechanism driving chromospheric
jets, by measuring height- and time-dependent velocities and magnetic
fields. To achieve these goals, a spectro-polarimeter called SCIP
(Sunrise Chromospheric Infrared spectroPolarimeter) is designed to
observe near-infrared spectrum lines sensitive to solar magnetic
fields. The spatial and spectral resolutions are 0.2 arcsec and
200,000, respectively, while 0.03% polarimetric sensitivity is
achieved within a 10 sec integration time. The optical system employs
an Echelle grating and off-axis aspheric mirrors to observe the two
wavelength ranges centered at 850 nm and 770 nm simultaneously by
two cameras. Polarimetric measurements are performed using a rotating
waveplate and polarization beam-splitters in front of the cameras. For
detecting minute polarization signals with good precision, we carefully
assess the temperature dependence of polarization optics, and make
the opto-structural design that minimizes the thermal deformation
of the spectrograph optics. Another key technique is to attain good
(better than 30 msec) synchronization among the rotating phase of
the waveplate, read-out timing of cameras, and step timing of a
slit-scanning mirror. On-board accumulation and data processing are
also critical because we cannot store all the raw data read-out from the
cameras. We demonstrate that we can reduce the data down to almost 10%
with loss-less image compression and without sacrificing polarimetric
information in the data. The SCIP instrument is developed by internal
collaboration among Japanese institutes including Japan Aerospace
Exploration Agency (JAXA), the Spanish Sunrise consortium, and the
German Max Planck Institute for Solar System Research (MPS) with a
leadership of the National Astronomical Observatory of Japan (NAOJ).
Title: Current State of UV Spectro-Polarimetry and its Future
Direction
Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara,
Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito;
Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi,
. Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier;
Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts,
Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke;
Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel;
Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan,
Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey,
Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David;
Rachmeler, Laurel; Bethge, Christian
Bibcode: 2018cosp...42E1564I
Altcode:
To obtain quantitative information on the magnetic field in low beta
regions (i.e., upper chromosphere and above) has been increasingly
important to understand the energetic phenomena of the outer
solar atmosphere such as flare, coronal heating, and the solar wind
acceleration. In the UV range, there are abundant spectral lines that
originate in the upper chromosphere and transition region. However,
the Zeeman effect in these spectral lines does not give rise to easily
measurable polarization signals because of the weak magnetic field
strength and the larger Doppler broadening compared with the Zeeman
effect. Instead, the Hanle effect in UV lines is expected to be a
suitable diagnostic tool of the magnetic field in the upper atmospheric
layers. To investigate the validity of UV spectro-polarimetry and
the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP), which is a NASA sounding- rocket experiment, was launched at
White Sands in US on September 3, 2015. During its 5 minutes ballistic
flight, it successfully performed spectro-polarimetric observations
of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly
high polarization sensitivity of 0.1% in this wavelength range. CLASP
observed the linear polarization produced by scattering process in VUV
lines for the first time and detected the polarization signals which
indicate the operation of the Hanle effect. Following the success
of CLASP, we are confident that UV spectro-polarimetry is the way
to proceed, and we are planning the second flight of CLASP (CLASP2:
Chromospheric LAyer SpectroPolarimeter 2). For this second flight we
will carry out spectro-polarimetry in the Mg II h and k lines around
280 nm, with minimum modifications of the CLASP1 instrument. The linear
polarization in the Mg II k line is induced by scattering processes and
the Hanle effect, being sensitive to magnetic field strengths of 5 to 50
G. In addition, the circular polarizations in the Mg II h and k lines
induced by the Zeeman effect can be measurable in at least plage and
active regions. The combination of the Hanle and Zeeman effects could
help us to more reliably infer the magnetic fields of the upper solar
chromosphere. CLASP2 was selected for flight and is being developed for
launch in the spring of 2019.Based on these sounding rocket experiments
(CLASP1 and 2), we aim at establishing the strategy and refining the
instrument concept for future space missions to explore the enigmatic
atmospheric layers via UV spectro-polarimetry.
Title: Getting Ready for the Third Science Flight of SUNRISE
Authors: Barthol, Peter; Katsukawa, Yukio; Lagg, Andreas; Solanki,
Sami K.; Kubo, Masahito; Riethmueller, Tino; Martínez Pillet,
Valentin; Gandorfer, Achim; Feller, Alex; Berkefeld, . Thomas; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Bernasconi, Pietro;
Álvarez-Herrero, Alberto; Quintero Noda, Carlos
Bibcode: 2018cosp...42E.215B
Altcode:
SUNRISE is a balloon-borne, stratospheric solar observatory dedicated
to the investigation of the structure and dynamics of the Sun's
magnetic field and its interaction with convective plasma flows and
waves. The previous science flights of SUNRISE in 2009 and 2013 have
led to many new scientific results, so far described in around 90
refereed publications. This success has shown the huge potential of the
SUNRISE concept and the recovery of the largely intact payload offers
the opportunity for a third flight.The scientific instrumentation of
SUNRISE 3 will have extended capabilities in particular to measure
magnetic fields, plasma velocities and temperatures with increased
sensitivity and over a larger height range in the solar atmosphere, from
the convectively dominated photosphere up to the still poorly understood
chromosphere. The latter is the key interaction region between magnetic
field, waves and radiation and plays a central role in transporting
energy to the outer layers of the solar atmosphere including the
corona.SUNRISE 3 will carry 2 new grating-based spectro-polarimeters
with slit-scanning and context imaging with slitjaw cameras. The
SUNRISE UV Spectro-polarimeter and Imager (SUSI) will explore the rich
near-UV range between 300 nm and 430 nm which is poorly accessible
from the ground. The SUNRISE Chromospheric Infrared spectro-Polarimeter
(SCIP) will sample 2 spectral windows in the near-infrared, containing
many spectral lines highly sensitive to magnetic fields at different
formation heights. In addition to the two new instruments the Imaging
Magnetograph eXperiment (IMaX), an etalon-based tunable filtergraph and
spectro-polarimeter flown on both previous missions, will be upgraded
to IMaX+, enhancing its cadence and giving access to 2 spectral lines
in the visible spectral range. All three instruments will allow
investigating both the photosphere and the chromosphere and will
ideally complement each other in terms of sensitivity, height coverage
and resolution.A new gondola with a sophisticated attitude control
system including roll damping will provide improved pointing/tracking
performance. Upgraded image stabilization with higher bandwidth will
further reduce residual jitter, maximizing the quality of the science
data.SUNRISE 3 is a joint project of the German Max-Planck-Institut für
Sonnensystemforschung together with the Spanish SUNRISE consortium, the
Johns Hopkins University Applied Physics Laboratory, USA, the German
Kiepenheuer Institut für Sonnenphysik, the National Astronomical
Observatory of Japan and the Japan Aerospace eXploraion Agency (JAXA).
Title: Wavefront error measurements and alignment of CLASP2 telescope
with a dual-band pass cold mirror coated primary mirror
Authors: Yoshida, Masaki; Song, Donguk; Ishikawa, Ryoko; Kano, Ryouhei;
Katsukawa, Yukio; Suematsu, Yoshinori; Narukage, Noriyuki; Kubo,
Masahito; Shinoda, Kazuya; Okamoto, Takenori J.; McKenzie, David E.;
Rachmeler, Laurel A.; Auchère, Frédéric; Trujillo Bueno, Javier
Bibcode: 2018SPIE10699E..30Y
Altcode:
"Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding
rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP)" that succeeded in observing for the first time the linear
polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is
scheduled to be launched in 2019. In CLASP2, we will carry out full
Stokes-vector spectropolarimetric observations in the Mg ii h and k
lines near 280 nm with the spectro-polarimeter (SP), while imaging
observations in the Lyman-α line will be conducted with the slitjaw
optics (SJ). For the wavelength selection of CLASP2, the primary
mirror of the telescope uses a new dual-band pass cold mirror coating
targeting both at 121.6 nm and 280 nm. Therefore, we have to perform
again the alignment of the telescope after the installation of the
recoated primary mirror. Before unmounting the primary mirror from
the telescope structure, we measured the wave-front error (WFE) of the
telescope. The measured WFE map was consistent with what we had before
the CLASP flight, clearly indicating that the telescope alignment has
been maintained even after the flight. After the re-coated primary
mirror was installed the WFE was measured, and coma aberration was
found to be larger. Finally, the secondary mirror shim adjustments
were carried out based on the WFE measurements. In CLASP2 telescope,
we improved a fitting method of WFE map (applying 8th terms circular
Zernike polynomial fitting instead of 37th terms circular Zernike
fitting) and the improved method enables to achieve better performance
than CLASP telescope. Indeed, WFE map obtained after the final shim
adjustment indicated that the required specification (< 5.5 μm
RMS spot radius) that is more stringent than CLASP telescope was met.
Title: Solar polarimetry in the K I D2 line : A novel
possibility for a stratospheric balloon
Authors: Quintero Noda, C.; Villanueva, G. L.; Katsukawa, Y.; Solanki,
S. K.; Orozco Suárez, D.; Ruiz Cobo, B.; Shimizu, T.; Oba, T.; Kubo,
M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2018A&A...610A..79Q
Altcode: 2018arXiv180101655Q
Of the two solar lines, K I D1 and D2, almost
all attention so far has been devoted to the D1 line, as
D2 is severely affected by an O2 atmospheric
band. This, however, makes the latter appealing for balloon and space
observations from above (most of) the Earth's atmosphere. We estimate
the residual effect of the O2 band on the K I D2
line at altitudes typical for stratospheric balloons. Our aim is to
study the feasibility of observing the 770 nm window. Specifically,
this paper serves as a preparation for the third flight of the Sunrise
balloon-borne observatory. The results indicate that the absorption
by O2 is still present, albeit much weaker, at the expected
balloon altitude. We applied the obtained O2 transmittance
to K I D2 synthetic polarimetric spectra and found that in
the absence of line-of-sight motions, the residual O2 has
a negligible effect on the K I D2 line. On the other hand,
for Doppler-shifted K I D2 data, the residual O2
might alter the shape of the Stokes profiles. However, the residual
O2 absorption is sufficiently weak at stratospheric levels
that it can be divided out if appropriate measurements are made,
something that is impossible at ground level. Therefore, for the
first time with Sunrise III, we will be able to perform polarimetric
observations of the K I D2 line and, consequently, we will
have improved access to the thermodynamics and magnetic properties of
the upper photosphere from observations of the K I lines.
Title: From Hinode to the Next-Generation Solar Observation Missions
Authors: Ichimoto, Kiyoshi; Hara, Hirohisa; Katsukawa, Yukio;
Ishikawa, Ryoko
Bibcode: 2018ASSL..449..231I
Altcode:
No abstract at ADS
Title: Penumbral Microjets in Sunspot Chromospheres: Evidence of
Magnetic Reconnection
Authors: Katsukawa, Yukio
Bibcode: 2018ASSL..449..201K
Altcode:
No abstract at ADS
Title: Pointing stability of Hinode and requirements for the next
Solar mission Solar-C
Authors: Katsukawa, Y.; Masada, Y.; Shimizu, T.; Sakai, S.; Ichimoto,
K.
Bibcode: 2017SPIE10565E..28K
Altcode:
It is essential to achieve fine pointing stability in a space mission
aiming for high resolutional observations. In a future Japanese
solar mission SOLAR-C, which is a successor of the HINODE (SOLAR-B)
mission, we set targets of angular resolution better than 0.1 arcsec
in the visible light and better than 0.2 - 0.5 arcsec in EUV and
X-rays. These resolutions are twice to five times better than those of
corresponding instruments onboard HINODE. To identify critical items
to achieve the requirements of the pointing stability in SOLAR-C, we
assessed in-flight performance of the pointing stability of HINODE that
achieved the highest pointing stability in Japanese space missions. We
realized that one of the critical items that have to be improved in
SOLAR-C is performance of the attitude stability near the upper limit
of the frequency range of the attitude control system. The stability
of 0.1 arcsec (3σ) is required in the EUV and X-ray telescopes
of SOLAR-C while the HINODE performance is slightly worse than the
requirement. The visible light telescope of HINODE is equipped with
an image stabilization system inside the telescope, which achieved
the stability of 0.03 arcsec (3σ) by suppressing the attitude jitter
in the frequency range lower than 10 Hz. For further improvement, it
is expected to suppress disturbances induced by resonance between the
telescope structures and disturbances of momentum wheels and mechanical
gyros in the frequency range higher than 100 Hz.
Title: Instrument design and on-orbit performance of the solar
optical telescope aboard hinode (Solar-B)
Authors: Suematsu, Yoshinori; Ichimoto, Kiyoshi; Katsukawa, Yukio;
Tsuneta, Saku; Shimizu, Toshifumi
Bibcode: 2017SPIE10566E..2ZS
Altcode:
The Solar Optical Telescope (SOT) aboard Solar-B satellite (Hinode)
is designed to perform high-precision photometric and polarimetric
observations of the solar lower atmosphere in visible light spectra
(388-668 nm) with a spatial resolution of 0.2 to 0.3 arcsec. The
SOT consists of two components; the optical telescope assembly (OTA)
consisting of a 50-cm aperture Gregorian telescope with a collimating
lens unit and an active tip-tilt mirror for an image-stabilization and
an accompanying focal plane package (FPP) housing two filtergraphs and a
spectro-polarimeter. Since its first-light observation on 25 Oct. 2006,
the image-stabilization system has been working with performance
better than 0.01 arcsec rms and the SOT has been continuously
providing unprecedented solar data of high spatial resolution. Since
the opto-mechanical and -thermal performance of the OTA is crucial
to attain unprecedented high-quality solar observations, we here
describe in detail the instrument design and on-orbit diffraction-limit
performance of the OTA, the largest state-of-the-art solar telescope
yet flown in space.
Title: Instrument design of 1.5-m aperture solar optical telescope
for the Solar-C Mission
Authors: Suematsu, Yoshinori; Katsukawa, Yukio; Shimizu, Toshifumi;
Ichimoto, Kiyoshi
Bibcode: 2017SPIE10564E..0TS
Altcode:
A 1.5 m aperture optical telescope is planned for the next Japanese
solar mission SOLAR-C as one of major three observing instruments. The
optical telescope is designed to provide high-angular-resolution
investigation of lower atmosphere from the photosphere to the uppermost
chromosphere with enhanced spectroscopic and spectropolarimetric
capability covering a wide wavelength region from 280 nm to 1100
nm. The opto-mechanical and -thermal performance of the telescope is
crucial to attain high-quality solar observations and we present a
study of optical and structural design of the large aperture space
solar telescope, together with conceptual design of its accompanying
focal plane instruments: wide-band and narrow-band filtergraphs and
a spectro-polarimeter for high spatial and temporal observations in
the solar photospheric and chromospheric lines useful for sounding
physical condition of dynamical phenomena.
Title: Chromospheric polarimetry through multiline observations of
the 850-nm spectral region - II. A magnetic flux tube scenario
Authors: Quintero Noda, C.; Kato, Y.; Katsukawa, Y.; Oba, T.; de la
Cruz Rodríguez, J.; Carlsson, M.; Shimizu, T.; Orozco Suárez, D.;
Ruiz Cobo, B.; Kubo, M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2017MNRAS.472..727Q
Altcode: 2017arXiv170801333Q
In this publication, we continue the work started in Quintero Noda et
al., examining this time a numerical simulation of a magnetic flux
tube concentration. Our goal is to study if the physical phenomena
that take place in it, in particular, the magnetic pumping, leaves
a specific imprint on the examined spectral lines. We find that the
profiles from the interior of the flux tube are periodically doppler
shifted following an oscillation pattern that is also reflected in
the amplitude of the circular polarization signals. In addition, we
analyse the properties of the Stokes profiles at the edges of the flux
tube discovering the presence of linear polarization signals for the Ca
II lines, although they are weak with an amplitude around 0.5 per cent
of the continuum intensity. Finally, we compute the response functions
to perturbations in the longitudinal field, and we estimate the field
strength using the weak-field approximation. Our results indicate
that the height of formation of the spectral lines changes during the
magnetic pumping process, which makes the interpretation of the inferred
magnetic field strength and its evolution more difficult. These results
complement those from previous works, demonstrating the capabilities and
limitations of the 850-nm spectrum for chromospheric Zeeman polarimetry
in a very dynamic and complex atmosphere.
Title: Optical and thermal design of 1.5-m aperture solar UV visible
and IR observing telescope for Solar-C mission
Authors: Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.;
Horiuchi, T.; Matsumoto, Y.; Takeyama, N.
Bibcode: 2017SPIE10565E..0RS
Altcode:
The next Japanese solar mission, SOLAR-C, which has been envisaged
after successful science operation of Hinode (SOLAR-B) mission, is
perusing two plans: plan-A and plan-B, and under extensive study from
science objectives as well as engineering point of view. The plan-A
aims at performing out-of-ecliptic observations for investigating, with
helioseismic approach, internal structure and dynamo mechanisms of the
Sun. It also explores polar regions where fast solar wind is believed
to originate. A baseline orbit for plan-A is a circular orbit of 1 AU
distance from the Sun with its inclination at around or greater than
40 degrees. The plan-B aims to study small-scale plasma processes and
structures in the solar atmosphere which attract researchers' growing
interest, followed by many Hinode discoveries [1], for understanding
fully dynamism and magnetic nature of the atmosphere. With plan-B,
high-angular-resolution investigation of the entire solar atmosphere
(from the photosphere to the corona, including their interface layers,
i.e., chromosphere and transition region) is to be performed with
enhanced spectroscopic and spectro-polarimetric capability as compared
with Hinode, together with enhanced sensitivity towards ultra-violet
wavelengths. The orbit of plan-B is either a solar synchronous polar
orbit of altitude around 600 km or a geosynchronous orbit to ensure
continuous solar observations. After the decision of any one of the
two plans, the SOLAR-C will be proposed for launch in mid-2010s. In
this paper, we will present a basic design of one of major planned
instrumental payload for the plan-B: the Solar Ultra-violet Visible
and near IR observing Telescope (hereafter referred to as SUVIT). The
basic concept in designing the SUVIT is to utilize as much as possible
a heritage of successful telescope of the Solar Optical Telescope
(SOT) aboard Hinode [2]. Major differences of SUVIT from SOT are
the three times larger aperture of 1.5 m, which enables to collect
one order of magnitude more photons than SOT, relatively shorter
telescope length of 2.8 m to accommodate a launcher's nosecone size
for possible dual-satellite-launch configuration, and much wider
observing wavelength from UV (down to 250 nm) through near IR (up
to 1100 nm). The large aperture is essentially important to attain
scientific goals of the plan-B, especially for accurate diagnostics of
the dynamic solar chromosphere as revealed by Hinode, although this
make it difficult to design the telescope because of ten times more
solar heat load introduced into the telescope. The SUVIT consists of
two optically separable components; the telescope assembly (TA) and
an accompanying focal plane package equipped with filtergraphs and
spectrographs. Opto-mechanical and -thermal performance of the TA is
crucial to attain high-quality solar observations and here we present
a status of feasible study in its optical and thermal designing for
diffraction-limited performance at visible wavelength in a reasonably
wide field of view.
Title: Solar polarimetry through the K I lines at 770 nm
Authors: Quintero Noda, C.; Uitenbroek, H.; Katsukawa, Y.; Shimizu,
T.; Oba, T.; Carlsson, M.; Orozco Suárez, D.; Ruiz Cobo, B.; Kubo,
M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2017MNRAS.470.1453Q
Altcode: 2017arXiv170510002Q
We characterize the K I D1 & D2 lines in
order to determine whether they could complement the 850 nm window,
containing the Ca II infrared triplet lines and several Zeeman sensitive
photospheric lines, that was studied previously. We investigate the
effect of partial redistribution on the intensity profiles, their
sensitivity to changes in different atmospheric parameters, and
the spatial distribution of Zeeman polarization signals employing a
realistic magnetohydrodynamic simulation. The results show that these
lines form in the upper photosphere at around 500 km, and that they
are sensitive to the line-of-sight velocity and magnetic field strength
at heights where neither the photospheric lines nor the Ca II infrared
lines are. However, at the same time, we found that their sensitivity
to the temperature essentially comes from the photosphere. Then, we
conclude that the K I lines provide a complement to the lines in the
850 nm window for the determination of atmospheric parameters in the
upper photosphere, especially for the line-of-sight velocity and the
magnetic field.
Title: CLASP/SJ Observations of Rapid Time Variations in the Lyα
Emission in a Solar Active Region
Authors: Ishikawa, Shin-nosuke; Kubo, Masahito; Katsukawa, Yukio;
Kano, Ryouhei; Narukage, Noriyuki; Ishikawa, Ryohko; Bando, Takamasa;
Winebarger, Amy; Kobayashi, Ken; Trujillo Bueno, Javier; Auchère,
Frédéric
Bibcode: 2017ApJ...846..127I
Altcode:
The Chromospheric Lyα SpectroPolarimeter (CLASP) is a sounding
rocket experiment launched on 2015 September 3 to investigate the
solar chromosphere and transition region. The slit-jaw (SJ) optical
system captured Lyα images with a high time cadence of 0.6 s. From
the CLASP/SJ observations, many variations in the solar chromosphere
and transition region emission with a timescale of <1 minute
were discovered. In this paper, we focus on the active region within
the SJ field of view and investigate the relationship between short
(<30 s) temporal variations in the Lyα emission and the coronal
structures observed by Solar Dynamics Observatory/Atmospheric Imaging
Assembly (AIA). We compare the Lyα temporal variations at the coronal
loop footpoints observed in the AIA 211 Å (≈2 MK) and AIA 171 Å
(≈0.6 MK) channels with those in the regions with bright Lyα features
without a clear association with the coronal loop footpoints. We find
more short (<30 s) temporal variations in the Lyα intensity in the
footpoint regions. Those variations did not depend on the temperature
of the coronal loops. Therefore, the temporal variations in the Lyα
intensity at this timescale range could be related to the heating of
the coronal structures up to temperatures around the sensitivity peak
of 171 Å. No signature was found to support the scenario that these
Lyα intensity variations were related to the nanoflares. Waves or
jets from the lower layers (lower chromosphere or photosphere) are
possible causes for this phenomenon.
Title: Indication of the Hanle Effect by Comparing the Scattering
Polarization Observed by CLASP in the Lyα and Si III 120.65 nm Lines
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
Bibcode: 2017ApJ...841...31I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding
rocket experiment that has provided the first successful measurement
of the linear polarization produced by scattering processes in
the hydrogen Lyα line (121.57 nm) radiation of the solar disk. In
this paper, we report that the Si III line at 120.65 nm also shows
scattering polarization and we compare the scattering polarization
signals observed in the Lyα and Si III lines in order to search for
observational signatures of the Hanle effect. We focus on four selected
bright structures and investigate how the U/I spatial variations vary
between the Lyα wing, the Lyα core, and the Si III line as a function
of the total unsigned photospheric magnetic flux estimated from Solar
Dynamics Observatory/Helioseismic and Magnetic Imager observations. In
an internetwork region, the Lyα core shows an antisymmetric spatial
variation across the selected bright structure, but it does not show
it in other more magnetized regions. In the Si III line, the spatial
variation of U/I deviates from the above-mentioned antisymmetric
shape as the total unsigned photospheric magnetic flux increases. A
plausible explanation of this difference is the operation of the Hanle
effect. We argue that diagnostic techniques based on the scattering
polarization observed simultaneously in two spectral lines with very
different sensitivities to the Hanle effect, like Lyα and Si III,
are of great potential interest for exploring the magnetism of the
upper solar chromosphere and transition region.
Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV
Range. Part II: In-Flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.;
Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
Bibcode: 2017SoPh..292...57G
Altcode:
The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding
rocket instrument designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm). The instrument
was successfully launched on 3 September 2015 and observations were
conducted at the solar disc center and close to the limb during the
five-minutes flight. In this article, the disc center observations are
used to provide an in-flight calibration of the instrument spurious
polarization. The derived in-flight spurious polarization is consistent
with the spurious polarization levels determined during the pre-flight
calibration and a statistical analysis of the polarization fluctuations
from solar origin is conducted to ensure a 0.014% precision on the
spurious polarization. The combination of the pre-flight and the
in-flight polarization calibrations provides a complete picture of
the instrument response matrix, and a proper error transfer method
is used to confirm the achieved polarization accuracy. As a result,
the unprecedented 0.1% polarization accuracy of the instrument in the
vacuum ultraviolet is ensured by the polarization calibration.
Title: Discovery of Scattering Polarization in the Hydrogen Lyα
Line of the Solar Disk Radiation
Authors: Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchère, F.;
Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.;
Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu,
T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.;
Štěpán, J.; Asensio Ramos, A.; Manso Sainz, R.; Champey, P.;
Cirtain, J.; De Pontieu, B.; Casini, R.; Carlsson, M.
Bibcode: 2017ApJ...839L..10K
Altcode: 2017arXiv170403228K
There is a thin transition region (TR) in the solar atmosphere where
the temperature rises from 10,000 K in the chromosphere to millions
of degrees in the corona. Little is known about the mechanisms that
dominate this enigmatic region other than the magnetic field plays a
key role. The magnetism of the TR can only be detected by polarimetric
measurements of a few ultraviolet (UV) spectral lines, the Lyα line
of neutral hydrogen at 121.6 nm (the strongest line of the solar UV
spectrum) being of particular interest given its sensitivity to the
Hanle effect (the magnetic-field-induced modification of the scattering
line polarization). We report the discovery of linear polarization
produced by scattering processes in the Lyα line, obtained with
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) rocket
experiment. The Stokes profiles observed by CLASP in quiet regions of
the solar disk show that the Q/I and U/I linear polarization signals are
of the order of 0.1% in the line core and up to a few percent in the
nearby wings, and that both have conspicuous spatial variations with
scales of ∼10 arcsec. These observations help constrain theoretical
models of the chromosphere-corona TR and extrapolations of the
magnetic field from photospheric magnetograms. In fact, the observed
spatial variation from disk to limb of polarization at the line core
and wings already challenge the predictions from three-dimensional
magnetohydrodynamical models of the upper solar chromosphere.
Title: High-Reflectivity Coatings for a Vacuum Ultraviolet
Spectropolarimeter
Authors: Narukage, Noriyuki; Kubo, Masahito; Ishikawa, Ryohko;
Ishikawa, Shin-nosuke; Katsukawa, Yukio; Kobiki, Toshihiko; Giono,
Gabriel; Kano, Ryouhei; Bando, Takamasa; Tsuneta, Saku; Auchère,
Frédéric; Kobayashi, Ken; Winebarger, Amy; McCandless, Jim; Chen,
Jianrong; Choi, Joanne
Bibcode: 2017SoPh..292...40N
Altcode:
Precise polarization measurements in the vacuum ultraviolet (VUV)
region are expected to be a new tool for inferring the magnetic fields
in the upper atmosphere of the Sun. High-reflectivity coatings are key
elements to achieving high-throughput optics for precise polarization
measurements. We fabricated three types of high-reflectivity coatings
for a solar spectropolarimeter in the hydrogen Lyman-α (Lyα ; 121.567
nm) region and evaluated their performance. The first high-reflectivity
mirror coating offers a reflectivity of more than 80 % in Lyα
optics. The second is a reflective narrow-band filter coating that has
a peak reflectivity of 57 % in Lyα , whereas its reflectivity in the
visible light range is lower than 1/10 of the peak reflectivity (∼5
% on average). This coating can be used to easily realize a visible
light rejection system, which is indispensable for a solar telescope,
while maintaining high throughput in the Lyα line. The third is a
high-efficiency reflective polarizing coating that almost exclusively
reflects an s-polarized beam at its Brewster angle of 68° with a
reflectivity of 55 %. This coating achieves both high polarizing power
and high throughput. These coatings contributed to the high-throughput
solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.
Title: Chromospheric polarimetry through multiline observations of
the 850-nm spectral region
Authors: Quintero Noda, C.; Shimizu, T.; Katsukawa, Y.; de la Cruz
Rodríguez, J.; Carlsson, M.; Anan, T.; Oba, T.; Ichimoto, K.;
Suematsu, Y.
Bibcode: 2017MNRAS.464.4534Q
Altcode: 2016arXiv161006651Q
Future solar missions and ground-based telescopes aim to understand the
magnetism of the solar chromosphere. We performed a supporting study in
Quintero Noda et al. focused on the infrared Ca II 8542 Å line and we
concluded that it is one of the best candidates because it is sensitive
to a large range of atmospheric heights, from the photosphere to the
middle chromosphere. However, we believe that it is worth trying to
improve the results produced by this line observing additional spectral
lines. In that regard, we examined the neighbourhood solar spectrum
looking for spectral lines which could increase the sensitivity to
the atmospheric parameters. Interestingly, we discovered several
photospheric lines which greatly improve the photospheric sensitivity
to the magnetic field vector. Moreover, they are located close to a
second chromospheric line which also belongs to the Ca II infrared
triplet, I.e. the Ca II 8498 Å line, and enhances the sensitivity to
the atmospheric parameters at chromospheric layers. We conclude that the
lines in the vicinity of the Ca II 8542 Å line not only increase its
sensitivity to the atmospheric parameters at all layers, but also they
constitute an excellent spectral window for chromospheric polarimetry.
Title: Various Local Heating Events in the Earliest Phase of Flux
Emergence
Authors: Toriumi, Shin; Katsukawa, Yukio; Cheung, Mark C. M.
Bibcode: 2017ApJ...836...63T
Altcode: 2017arXiv170101446T
Emerging flux regions (EFRs) are known to exhibit various sporadic
local heating events in the lower atmosphere. To investigate the
characteristics of these events, especially to link the photospheric
magnetic fields and atmospheric dynamics, we analyze Hinode, Interface
Region Imaging Spectrograph (IRIS), and Solar Dynamics Observatory
data of a new EFR in NOAA AR 12401. Out of 151 bright points (BPs)
identified in Hinode/SOT Ca images, 29 are overlapped by an SOT/SP
scan. Seven BPs in the EFR center possess mixed-polarity magnetic
backgrounds in the photosphere. Their IRIS UV spectra (e.g., Si IV
1402.8 Å) are strongly enhanced and red- or blueshifted, with tails
reaching +/- 150 {km} {{{s}}}-1, which is highly suggestive
of bi-directional jets; each brightening lasts for 10-15 minutes,
leaving flare-like light curves. Most of this group show bald patches,
the U-shaped photospheric magnetic loops. Another 10 BPs are found in
unipolar regions at the EFR edges. They are generally weaker in UV
intensities and exhibit systematic redshifts with Doppler speeds up
to 40 {km} {{{s}}}-1, which could exceed the local sound
speed in the transition region. Both types of BPs show signs of strong
temperature increase in the low chromosphere. These observational
results support the physical picture that heating events in the EFR
center are due to magnetic reconnection within cancelling undular
fields like Ellerman bombs, while the peripheral heating events are
due to shocks or strong compressions caused by fast downflows along
the overlying arch filament system.
Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1 % Polarization Sensitivity in the VUV
Range. Part I: Pre-flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.
Bibcode: 2016SoPh..291.3831G
Altcode: 2016SoPh..tmp..177G
The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) is a sounding
rocket experiment designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm) and requires
a 0.1 % polarization sensitivity, which is unprecedented for a
spectropolarimeter in the vacuum UV (VUV) spectral range.
Title: Discovery of Ubiquitous Fast-Propagating Intensity Disturbances
by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP)
Authors: Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Kano, R.; Bando,
T.; Narukage, N.; Ishikawa, R.; Hara, H.; Giono, G.; Tsuneta, S.;
Ishikawa, S.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.;
Cirtain, J.; Champey, P.; Auchère, F.; Trujillo Bueno, J.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
Bibcode: 2016ApJ...832..141K
Altcode:
High-cadence observations by the slit-jaw (SJ) optics system of the
sounding rocket experiment known as the Chromospheric Lyman Alpha
Spectropolarimeter (CLASP) reveal ubiquitous intensity disturbances
that recurrently propagate in either the chromosphere or the transition
region or both at a speed much higher than the speed of sound. The
CLASP/SJ instrument provides a time series of two-dimensional images
taken with broadband filters centered on the Lyα line at a 0.6 s
cadence. The multiple fast-propagating intensity disturbances appear in
the quiet Sun and in an active region, and they are clearly detected in
at least 20 areas in a field of view of 527″ × 527″ during the 5
minute observing time. The apparent speeds of the intensity disturbances
range from 150 to 350 km s-1, and they are comparable
to the local Alfvén speed in the transition region. The intensity
disturbances tend to propagate along bright elongated structures away
from areas with strong photospheric magnetic fields. This suggests
that the observed fast-propagating intensity disturbances are related
to the magnetic canopy structures. The maximum distance traveled by
the intensity disturbances is about 10″, and the widths are a few
arcseconds, which are almost determined by a pixel size of 1.″03. The
timescale of each intensity pulse is shorter than 30 s. One possible
explanation for the fast-propagating intensity disturbances observed
by CLASP is magnetohydrodynamic fast-mode waves.
Title: Analysis of a spatially deconvolved solar pore
Authors: Quintero Noda, C.; Shimizu, T.; Ruiz Cobo, B.; Suematsu,
Y.; Katsukawa, Y.; Ichimoto, K.
Bibcode: 2016MNRAS.460.1476Q
Altcode: 2016arXiv160501796Q; 2016MNRAS.tmp..847Q
Solar pores are active regions with large magnetic field strengths
and apparent simple magnetic configurations. Their properties
resemble the ones found for the sunspot umbra although pores do
not show penumbra. Therefore, solar pores present themselves as an
intriguing phenomenon that is not completely understood. We examine
in this work a solar pore observed with Hinode/SP using two state
of the art techniques. The first one is the spatial deconvolution
of the spectropolarimetric data that allows removing the stray
light contamination induced by the spatial point spread function
of the telescope. The second one is the inversion of the Stokes
profiles assuming local thermodynamic equilibrium that let us to
infer the atmospheric physical parameters. After applying these
techniques, we found that the spatial deconvolution method does not
introduce artefacts, even at the edges of the magnetic structure,
where large horizontal gradients are detected on the atmospheric
parameters. Moreover, we also describe the physical properties of
the magnetic structure at different heights finding that, in the
inner part of the solar pore, the temperature is lower than outside,
the magnetic field strength is larger than 2 kG and unipolar, and
the line-of-sight velocity is almost null. At neighbouring pixels,
we found low magnetic field strengths of same polarity and strong
downward motions that only occur at the low photosphere, below the
continuum optical depth log τ = -1. Finally, we studied the spatial
relation between different atmospheric parameters at different heights
corroborating the physical properties described before.
Title: Optical alignment of the Chromospheric Lyman-Alpha
Spectro-Polarimeter using sophisticated methods to minimize activities
under vacuum
Authors: Giono, G.; Katsukawa, Y.; Ishikawa, R.; Narukage, N.;
Kano, R.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.
Bibcode: 2016SPIE.9905E..3DG
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
sounding-rocket instrument developed at the National Astronomical
Observatory of Japan (NAOJ) as a part of an international
collaboration. The instrument main scientific goal is to achieve
polarization measurement of the Lyman-α line at 121.56 nm emitted from
the solar upper-chromosphere and transition region with an unprecedented
0.1% accuracy. The optics are composed of a Cassegrain telescope
coated with a "cold mirror" coating optimized for UV reflection and
a dual-channel spectrograph allowing for simultaneous observation of
the two orthogonal states of polarization. Although the polarization
sensitivity is the most important aspect of the instrument, the spatial
and spectral resolutions of the instrument are also crucial to observe
the chromospheric features and resolve the Ly-α profiles. A precise
alignment of the optics is required to ensure the resolutions, but
experiments under vacuum conditions are needed since Ly-α is absorbed
by air, making the alignment experiments difficult. To bypass this
issue, we developed methods to align the telescope and the spectrograph
separately in visible light. We explain these methods and present
the results for the optical alignment of the CLASP telescope and
spectrograph. We then discuss the combined performances of both parts
to derive the expected resolutions of the instrument, and compare them
with the flight observations performed on September 3rd 2015.
Title: Development of a near-infrared detector and a fiber-optic
integral field unit for a space solar observatory SOLAR-C
Authors: Katsukawa, Yukio; Kamata, Yukiko; Anan, Tetsu; Hara,
Hirohisa; Suematsu, Yoshinori; Bando, Takamasa; Ichimoto, Kiyoshi;
Shimizu, Toshifumi
Bibcode: 2016SPIE.9904E..5IK
Altcode:
We are developing a high sensitivity and fast readout near-infrared
(NIR) detector and an integral field unit (IFU) for making
spectro-polarimetric observations of rapidly varying chromospheric
spectrum lines, such as He I 1083 nm and Ca II 854 nm, in the
next space-based solar mission SOLAR-C. We made tests of a 1.7 μm
cutoff H2RG detector with the SIDECAR ASIC for the application in
SOLAR-C. It's important to verify its perfor- mance in the temperature
condition around -100 °C, which is hotter than the typical temperature
environment used for a NIR detector. We built a system for testing the
detector between -70 °C and -140 °C. We verified linearity, read-out
noise, and dark current in both the slow and fast readout modes. We
found the detector has to be cooled down lower than -100 °C because
of significant increase of the number of hot pixels in the hotter
environment. The compact and polarization maintenance IFU was designed
using fiber-optic ribbons consisting of rectangular cores which exhibit
good polarization maintenance. A Silicone adhesive DC-SE9187L was used
to hold the fragile fiber-optic ribbons in a metal housing. Polarization
maintenance property was confirmed though polarization calibration
as well as temperature control are required to suppress polarization
crosstalk and to achieve the polarization accuracy in SOLAR-C.
Title: Spectropolarimetric capabilities of Ca II 8542 Å line
Authors: Quintero Noda, C.; Shimizu, T.; de la Cruz Rodríguez, J.;
Katsukawa, Y.; Ichimoto, K.; Anan, T.; Suematsu, Y.
Bibcode: 2016MNRAS.459.3363Q
Altcode: 2016MNRAS.tmp..667Q; 2016arXiv160404957Q
The next generation of space- and ground-based solar missions aim
to study the magnetic properties of the solar chromosphere using the
infrared Ca II lines and the He I 10830 Å line. The former seem to be
the best candidates to study the stratification of magnetic fields in
the solar chromosphere and their relation to the other thermodynamical
properties underlying the chromospheric plasma. The purpose of this
work is to provide a detailed analysis of the diagnostic capabilities
of the Ca II 8542 Å line, anticipating forthcoming observational
facilities. We study the sensitivity of the Ca II 8542 Å line
to perturbations applied to the physical parameters of reference
semi-empirical 1D model atmospheres using response functions and we
make use of 3D magnetohydrodynamics simulations to examine the expected
polarization signals for moderate magnetic field strengths. Our results
indicate that the Ca II 8542 Å line is mostly sensitive to the layers
enclosed in the range log τ = [0, -5.5], under the physical conditions
that are present in our model atmospheres. In addition, the simulated
magnetic flux tube generates strong longitudinal signals in its centre
and moderate transversal signals, due to the vertical expansion of
magnetic field lines, in its edge. Thus, observing the Ca II 8542 Å
line we will be able to infer the 3D geometry of moderate magnetic
field regions.
Title: Flux appearance and disappearance rates in the solar
internetwork
Authors: Gosic, Milan; Bellot Rubio, Luis; Del Toro Iniesta, Jose
Carlos; Orozco Suarez, David; Katsukawa, Yukio
Bibcode: 2016SPD....4740105G
Altcode:
The solar internetwork contains weak and highly dynamic magnetic
fields that are essential to understanding the solar magnetism at small
spatial and temporal scales. Therefore, it is important to determine
how these fields are maintained on the solar surface. Using unique
Hinode observations, we follow the evolution of individual magnetic
elements in the interior of two supergranular cells at the disk
center. From up to 38 hr of continuous measurements, we show that
magnetic flux appears in internetwork regions at a rate of 120±3
Mx cm-2 day-1 (3.7±0.4 × 1024 Mx
day-1 over the entire solar surface). Flux disappears from
the internetwork at a rate of 125±6 Mx cm-2 day-1
(3.9±0.5 × 1024 Mx day-1) through fading of
magnetic elements, cancellation between opposite-polarity features,
and interactions with network patches, which converts internetwork
elements into network features. The removal of flux from supergranules
occurs mainly through fading and interactions with network, at nearly
the same rate of about 50 Mx cm-2 day-1. Our
results demonstrate that the sources and sinks of internetwork magnetic
flux are well balanced, reflecting the steady-state nature of the quiet
Sun. Using the instantaneous flux appearance and disappearance rates,
we successfully reproduce, for the first time, the temporal evolution
of the total unsigned flux in the interior of supergranular cells.
Title: Spectro-polarimetric observation in UV with CLASP to probe
the chromosphere and transition region
Authors: Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère,
Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi,
Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori;
Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi;
Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto;
Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi,
Luca; Carlsson, Mats
Bibcode: 2016SPD....4710107K
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA
sounding-rocket experiment that was performed in White Sands in
the US on September 3, 2015. During its 5-minute ballistic flight,
CLASP successfully made the first spectro-polarimetric observation in
the Lyman-alpha line (121.57 nm) originating in the chromosphere and
transition region. Since the Lyman-alpha polarization is sensitive
to magnetic field of 10-100 G by the Hanle effect, we aim to infer
the magnetic field information in such upper solar atmosphere with
this experiment.The obtained CLASP data showed that the Lyman-alpha
scattering polarization is about a few percent in the wings and
the order of 0.1% in the core near the solar limb, as it had been
theoretically predicted, and that both polarization signals have a
conspicuous spatio-temporal variability. CLASP also observed another
upper-chromospheric line, Si III (120.65 nm), whose critical field
strength for the Hanle effect is 290 G, and showed a measurable
scattering polarization of a few % in this line. The polarization
properties of the Si III line could facilitate the interpretation of
the scattering polarization observed in the Lyman-alpha line.In this
presentation, we would like to show how the upper chromosphere and
transition region are seen in the polarization of these UV lines and
discuss the possible source of these complicated polarization signals.
Title: The Solar Internetwork. II. Flux Appearance and Disappearance
Rates
Authors: Gošić, M.; Bellot Rubio, L. R.; del Toro Iniesta, J. C.;
Orozco Suárez, D.; Katsukawa, Y.
Bibcode: 2016ApJ...820...35G
Altcode: 2016arXiv160205892G
Small-scale internetwork magnetic fields are important ingredients of
the quiet Sun. In this paper we analyze how they appear and disappear
on the solar surface. Using high resolution Hinode magnetograms,
we follow the evolution of individual magnetic elements in the
interior of two supergranular cells at the disk center. From up to
38 hr of continuous measurements, we show that magnetic flux appears
in internetwork regions at a rate of 120 ± 3 Mx cm-2
day-1 (3.7 ± 0.4 × 1024 Mx day-1
over the entire solar surface). Flux disappears from the internetwork
at a rate of 125 ± 6 Mx cm-2 day-1 (3.9
± 0.5 × 1024 Mx day-1) through fading of
magnetic elements, cancelation between opposite-polarity features,
and interactions with network patches, which converts internetwork
elements into network features. Most of the flux is lost through
fading and interactions with the network, at nearly the same rate of
about 50 Mx cm-2 day-1. Our results demonstrate
that the sources and sinks of internetwork magnetic flux are well
balanced. Using the instantaneous flux appearance and disappearance
rates, we successfully reproduce the time evolution of the total
unsigned flux in the two supergranular cells.
Title: Light Bridge in a Developing Active Region. II. Numerical
Simulation of Flux Emergence and Light Bridge Formation
Authors: Toriumi, Shin; Cheung, Mark C. M.; Katsukawa, Yukio
Bibcode: 2015ApJ...811..138T
Altcode: 2015arXiv150900205T
Light bridges, the bright structure dividing umbrae in sunspot regions,
show various activity events. In Paper I, we reported on an analysis
of multi-wavelength observations of a light bridge in a developing
active region (AR) and concluded that the activity events are caused
by magnetic reconnection driven by magnetconvective evolution. The
aim of this second paper is to investigate the detailed magnetic and
velocity structures and the formation mechanism of light bridges. For
this purpose, we analyze numerical simulation data from a radiative
magnetohydrodynamics model of an emerging AR. We find that a weakly
magnetized plasma upflow in the near-surface layers of the convection
zone is entrained between the emerging magnetic bundles that appear
as pores at the solar surface. This convective upflow continuously
transports horizontal fields to the surface layer and creates a light
bridge structure. Due to the magnetic shear between the horizontal
fields of the bridge and the vertical fields of the ambient pores,
an elongated cusp-shaped current layer is formed above the bridge,
which may be favorable for magnetic reconnection. The striking
correspondence between the observational results of Paper I and the
numerical results of this paper provides a consistent physical picture
of light bridges. The dynamic activity phenomena occur as a natural
result of the bridge formation and its convective nature, which has
much in common with those of umbral dots and penumbral filaments.
Title: Light Bridge in a Developing Active Region. I. Observation
of Light Bridge and its Dynamic Activity Phenomena
Authors: Toriumi, Shin; Katsukawa, Yukio; Cheung, Mark C. M.
Bibcode: 2015ApJ...811..137T
Altcode: 2015arXiv150900183T
Light bridges, the bright structures that divide the umbra of sunspots
and pores into smaller pieces, are known to produce a wide variety
of activity events in solar active regions (ARs). It is also known
that the light bridges appear in the assembling process of nascent
sunspots. The ultimate goal of this series of papers is to reveal
the nature of light bridges in developing ARs and the occurrence of
activity events associated with the light bridge structures from
both observational and numerical approaches. In this first paper,
exploiting the observational data obtained by Hinode, the Interface
Region Imaging Spectrograph, and the Solar Dynamics Observatory, we
investigate the detailed structure of the light bridge in NOAA AR 11974
and its dynamic activity phenomena. As a result, we find that the light
bridge has a weak, horizontal magnetic field, which is transported from
the interior by a large-scale convective upflow and is surrounded by
strong, vertical fields of adjacent pores. In the chromosphere above the
bridge, a transient brightening occurs repeatedly and intermittently,
followed by a recurrent dark surge ejection into higher altitudes. Our
analysis indicates that the brightening is the plasma heating due
to magnetic reconnection at lower altitudes, while the dark surge is
the cool, dense plasma ejected from the reconnection region. From the
observational results, we conclude that the dynamic activity observed
in a light bridge structure such as chromospheric brightenings and dark
surge ejections are driven by magnetoconvective evolution within the
light bridge and its interaction with the surrounding magnetic fields.
Title: CLASP: A UV Spectropolarimeter on a Sounding Rocket for
Probing theChromosphere-Corona Transition Regio
Authors: Ishikawa, Ryohko; Kano, Ryouhei; Winebarger, Amy; Auchere,
Frederic; Trujillo Bueno, Javier; Bando, Takamasa; Narukage,
Noriyuki; Kobayashi, Ken; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Giono, Gabriel; Tsuneta, Saku; Hara, Hirohisa; Suematsu,
Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Ichimoto, Kiyoshi;
Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Manso Sainz,
Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca
Bibcode: 2015IAUGA..2254536I
Altcode:
The wish to understand the energetic phenomena of the outer solar
atmosphere makes it increasingly important to achieve quantitative
information on the magnetic field in the chromosphere-corona
transition region. To this end, we need to measure and model the
linear polarization produced by scattering processes and the Hanle
effect in strong UV resonance lines, such as the hydrogen Lyman-alpha
line. A team consisting of Japan, USA, Spain, France, and Norway has
been developing a sounding rocket experiment called the Chromospheric
Lyman-alpha Spectro-Polarimeter (CLASP). The aim is to detect the
scattering polarization produced by anisotropic radiation pumping in
the hydrogen Lyman-alpha line (121.6 nm), and via the Hanle effect to
try to constrain the magnetic field vector in the upper chromosphere
and transition region. In this talk, we will present an overview
of our CLASP mission, its scientific objectives, ground tests made,
and the latest information on the launch planned for the Summer of 2015.
Title: The Solar Internetwork. I. Contribution to the Network
Magnetic Flux
Authors: Gošić, M.; Bellot Rubio, L. R.; Orozco Suárez, D.;
Katsukawa, Y.; del Toro Iniesta, J. C.
Bibcode: 2014ApJ...797...49G
Altcode: 2014arXiv1408.2369G
The magnetic network (NE) observed on the solar surface harbors a
sizable fraction of the total quiet Sun flux. However, its origin and
maintenance are not well known. Here we investigate the contribution
of internetwork (IN) magnetic fields to the NE flux. IN fields permeate
the interior of supergranular cells and show large emergence rates. We
use long-duration sequences of magnetograms acquired by Hinode and
an automatic feature tracking algorithm to follow the evolution of NE
and IN flux elements. We find that 14% of the quiet Sun (QS) flux is
in the form of IN fields with little temporal variations. IN elements
interact with NE patches and modify the flux budget of the NE either
by adding flux (through merging processes) or by removing it (through
cancellation events). Mergings appear to be dominant, so the net flux
contribution of the IN is positive. The observed rate of flux transfer
to the NE is 1.5 × 1024 Mx day-1 over the entire
solar surface. Thus, the IN supplies as much flux as is present in the
NE in only 9-13 hr. Taking into account that not all the transferred
flux is incorporated into the NE, we find that the IN would be able
to replace the entire NE flux in approximately 18-24 hr. This renders
the IN the most important contributor to the NE, challenging the view
that ephemeral regions are the main source of flux in the QS. About 40%
of the total IN flux eventually ends up in the NE.
Title: Precision VUV Spectro-Polarimetry for Solar Chromospheric
Magnetic Field Measurements
Authors: Ishikawa, R.; Bando, T.; Hara, H.; Ishikawa, S.; Kano, R.;
Kubo, M.; Katsukawa, Y.; Kobiki, T.; Narukage, N.; Suematsu, Y.;
Tsuneta, S.; Aoki, K.; Miyagawa, K.; Ichimoto, K.; Kobayashi, K.;
Auchère, F.; Clasp Team
Bibcode: 2014ASPC..489..319I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV
spectro-polarimeter optimized for measuring the linear polarization
of the Lyman-α line (121.6 nm) to be launched in 2015 with NASA's
sounding rocket (Ishikawa et al. 2011; Narukage et al. 2011; Kano et
al. 2012; Kobayashi et al. 2012). With this experiment, we aim to (1)
observe the scattering polarization in the Lyman-α line, (2) detect
the Hanle effect, and (3) assess the magnetic fields in the upper
chromosphere and transition region for the first time. The polarization
measurement error consists of scale error δ a (error in amplitude
of linear polarization), azimuth error Δφ (error in the direction
of linear polarization), and spurious polarization ɛ (false linear
polarization signals). The error ɛ should be suppressed below 0.1%
in the Lyman-α core (121.567 nm ±0.02 nm), and 0.5% in the Lyman-α
wing (121.567 nm ±0.05 nm), based on our scientific requirements shown
in Table 2 of Kubo et al. (2014). From scientific justification, we
adopt Δ φ<2° and δ a<10% as the instrument requirements. The
spectro-polarimeter features a continuously rotating MgF2
waveplate (Ishikawa et al. 2013), a dual-beam spectrograph with a
spherical grating working also as a beam splitter, and two polarization
analyzers (Bridou et al. 2011), which are mounted at 90 degree from
each other to measure two orthogonal polarization simultaneously. For
the optical layout of the CLASP instrument, see Figure 3 in Kubo et
al. (2014). Considering the continuous rotation of the half-waveplate,
the modulation efficiency is 0.64 both for Stokes Q and U. All the raw
data are returned and demodulation (successive addition or subtraction
of images) is done on the ground. We control the CLASP polarization
performance in the following three steps. First, we evaluate the
throughput and polarization properties of each optical component in
the Lyman-α line, using the Ultraviolet Synchrotron ORbital Radiation
Facility (UVSOR) at the Institute for Molecular Science. The second
step is polarization calibration of the spectro-polarimeter after
alignment. Since the spurious polarization caused by the axisymmetric
telescope is estimated to be negligibly small because of the symmetry
(Ishikawa et al. 2014), we do not perform end-to-end polarization
calibration. As the final step, before the scientific observation near
the limb, we make a short observation at the Sun center and verify
the polarization sensitivity, because the scattering polarization
is expected to be close to zero at the Sun center due to symmetric
geometry. In order to clarify whether we will be able to achieve the
required polarization sensitivity and accuracy via these steps, we
exercise polarization error budget, by investigating all the possible
causes and their magnitudes of polarization errors, all of which are not
necessarily verified by the polarization calibration. Based on these
error budgets, we conclude that a polarization sensitivity of 0.1% in
the line core, δ a<10% and Δ φ<2° can be achieved combined
with the polarization calibration of the spectro-polarimeter and the
onboard calibration at the Sun center(refer to Ishikawa et al. 2014,
for the detail). We are currently conducting verification tests
of the flight components and development of the UV light source for
the polarization calibration. From 2014 spring, we will begin the
integration, alignment, and calibration. We will update the error
budgets throughout the course of these tests.
Title: A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP)
Authors: Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.;
Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.;
Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway,
T.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchère,
F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; Asensio Ramos,
A.; Štěpán, J.; Carlsson, M.
Bibcode: 2014ASPC..489..307K
Altcode:
A sounding-rocket experiment called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is presently under development to measure
the linear polarization profiles in the hydrogen Lyman-alpha (Lyα)
line at 121.567 nm. CLASP is a vacuum-UV (VUV) spectropolarimeter to aim
for first detection of the linear polarizations caused by scattering
processes and the Hanle effect in the Lyα line with high accuracy
(0.1%). This is a fist step for exploration of magnetic fields in
the upper chromosphere and transition region of the Sun. Accurate
measurements of the linear polarization signals caused by scattering
processes and the Hanle effect in strong UV lines like Lyα are
essential to explore with future solar telescopes the strength
and structures of the magnetic field in the upper chromosphere and
transition region of the Sun. The CLASP proposal has been accepted by
NASA in 2012, and the flight is planned in 2015.
Title: Large aperture solar optical telescope and instruments for
the SOLAR-C mission
Authors: Suematsu, Y.; Katsukawa, Y.; Hara, H.; Kano, R.; Shimizu,
T.; Ichimoto, K.
Bibcode: 2014SPIE.9143E..1PS
Altcode:
A large aperture solar optical telescope and its instruments
for the SOLAR-C mission are under study to provide the critical
physical parameters in the lower solar atmosphere and to resolve the
mechanism of magnetic dynamic events happening there and in the upper
atmosphere as well. For the precise magnetic field measurements and
high angular resolution in wide wavelength region, covering FOV of 3
arcmin x3 arcmin, an entrance aperture of 1.4 m Gregorian telescope is
proposed. Filtergraphs are designed to realize high resolution imaging
and pseudo 2D spectro-polarimetry in several magnetic sensitive lines of
both photosphere and chromosphere. A full stokes polarimetry is carried
out at three magnetic sensitive lines with a four-slit spectrograph
of 2D image scanning mechanism. We present a progress in optical and
structural design of SOLAR-C large aperture optical telescope and its
observing instruments which fulfill science requirements.
Title: Polarization properties of a birefringent fiber optic image
slicer for diffraction-limited dual-beam spectropolarimetry
Authors: Schad, Thomas; Lin, Haosheng; Ichimoto, Kiyoshi; Katsukawa,
Yukio
Bibcode: 2014SPIE.9147E..6ES
Altcode:
The birefringent fiber optic image slicer design, or BiFOIS,
adapts integral field spectroscopy methods to the special needs of
high-sensitivity, spatially-resolved spectropolarimetry. In solar
astronomy these methods are of particular importance, as dynamic
magnetism lies at the heart of various multi-scaled phenomena in the
solar atmosphere. While integral field units (IFU) based on fiber
optics have been in continual development for some time, standard
stock multimode fibers do not typically preserve polarization. The
importance of a birefringent fiber optic IFU design stems from the
need for dual-beam spatio-temporal polarimetric modulation to correct
for spurious polarization signals induced either by platform jitter or
atmospheric seeing. Here we characterize the polarization response of a
second generation BiFOIS IFU designed for solar spectropolarimetry. The
unit provides 60 × 64 spatial imaging pixels in a densely-packed,
high filling factor configuration. Particular attention is placed on
the spatial uniformity of the IFU polarization response. Calibrated
first-light solar observations are also presented to demonstrate the
performance of the device in a real application.
Title: Current progress of optical alignment procedure of CLASP's
Lyman-alpha polarimetry instrument
Authors: Giono, G.; Ishikawa, R.; Katsukawa, Y.; Bando, T.; Kano, R.;
Suematsu, Y.; Narukage, N.; Sakao, Taro; Kobayashi, K.; Auchère, F.
Bibcode: 2014SPIE.9144E..3EG
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
sounding-rocket instrument currently under development at the
National Astronomical Observatory of Japan (NAOJ) as a part of an
international collaboration. CLASP's optics are composed of a Cassegrain
telescope and a spectro-polarimeter which are designed to achieve an
unprecedentedly accurate polarization measurement of the Ly-α line
at 121.6nm emitted from the solar upper-chromosphere and transition
region. CLASP's first flight is scheduled for August 2015. Reaching
such accuracy requires a careful alignment of the optical elements
to optimize the image quality at 121.6 nm. However Ly-α is absorbed
by air and therefore the optics alignment has to be done under vacuum
condition which makes any experiment difficult. To bypass this issue,
we proposed to align the telescope and the spectrograph separately
in visible light. Hence we present our alignment procedure for both
telescope and spectro-polarimeter. We will explain details about the
telescope preliminary alignment before mirrors coating, which was done
in April 2014, present the telescope combined optical performance
and compare them to CLASP tolerance. Then we will present details
about an experiment designed to confirm our alignment procedure for
the CLASP spectro-polarimeter. We will discuss the resulting image
quality achieved during this experiment and the lessons learned.
Title: Reconnection in the solar magnetic fields beyond HINODE
Authors: Katsukawa, Yukio
Bibcode: 2014cosp...40E1427K
Altcode:
HINODE has revealed that magnetic reconnection plays an important
role in energy conversion process not only in the corona but
also in the chromosphere which is a relatively dense and plasma
beta = 1 atmospheric layer located between the photosphere and the
corona. Lots of small-scale jets are identified in the chromosphere
and they are expected to be driven not only by Lorentz force, but
also through strong influence of gas pressures and generation of MHD
waves. HINODE has indicated pervasive MHD waves in the chromosphere,
but there is little observations showing how such waves are generated
by the reconnection and how the waves drive flows and heating. Their
possible influence to the coronal heating is also an important
problem. For tackling them, our strong demand is to obtain detailed
diagnostic capability of plasma parameters as well as magnetic fields
by spectroscopic and spectro-polarimetric measurements with high
spatial resolution. IRIS (Interface Region Imaging Spectrograph)
has just started its observations since 2013, and is now providing
spectroscopic data of the chromosphere with unprecedented spatial
and temporal resolution. For remotely sensing magnetic fields in the
solar atmosphere, precise measurements of polarization signals are
highly demanded which is going to be attempted in a sounding-rocket
experiment CLASP (Chromospheric Lyman-Alpha SpectroPolarimeter) and
the next solar physics satellite SOLAR-C.
Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP)
Authors: Kano, Ryouhei; Katsukawa, Yukio; Kubo, Masahito; Auchere,
Frederic; Ishikawa, Ryohko; Kobayashi, Ken; Narukage, Noriyuki;
Trujillo Bueno, Javier; Bando, Takamasa; Ishikawa, Shin-nosuke
Bibcode: 2014cosp...40E1383K
Altcode:
In the solar chromosphere, magneto-hydrodynamic waves and super-sonic
jets ubiquitously happen as revealed by the Japanese solar satellite
Hinode. Now, we understand that the solar chromosphere is not a simple
intermediate layer smoothly connecting the photosphere and corona,
but a site where those dynamics may play an important role in the
chromospheric and coronal heating. Such discoveries imply that the
next frontier in solar physics lies in simultaneous observations
between the dynamics and magnetic structures in the chromosphere and
transition region, where the gas-dominant photosphere changes to the
magnetic-dominant corona. Therefore, we promote the Chromospheric
Lyman-Alpha SpectroPolarimeter (CLASP), which is a NASA's sounding
rocket experiment scheduled in 2015 for aiming to infer the magnetic
field information in the solar chromosphere and transition region. CLASP
makes precise measurement (0.1%) of the polarization profile of the
Lyman-alpha line, and aims to make the first ever measurement of the
Hanle effect polarization caused by magnetic fields in the upper solar
atmosphere. It is also a pathfinder to establish a new measurement
tool for chromospheric and transition-region magnetic fields, and to
make progress on chromospheric studies in future missions.
Title: Coronal rain observed with IRIS
Authors: Antolin, Patrick; Katsukawa, Yukio; De Pontieu, Bart; Kleint,
Lucia; Pereira, Tiago
Bibcode: 2014cosp...40E.105A
Altcode:
New IRIS observations in upper chromospheric and TR lines show abundance
of coronal rain in active regions. The wide range of spectral lines in
which it is observed together with co-observations in cool chromospheric
lines with SOT and SST show clearly that coronal rain has a broad
multi-thermal character. This picture agrees well with the thermal
instability scenario in which the plasma cools down catastrophically
from coronal temperatures. A statistical analysis of the line widths
in the rain provides estimates of the non-thermal line broadening and
temperature. Mainly, we find Gaussian-like distributions of non-thermal
line broadening between 0 and 17 km/s with a peak at 7 km/s and a small
upper tail spanning up to 25 km/s. We also report on short-lived heating
events in umbrae and penumbrae at the end of thermally unstable coronal
loops. Bursts of high redshifts up to 200 km/s in TR lines are found,
accompanied by milder blue shifts. The bright dots sometimes display
coherent structure into a "string of pearls" with striking similarity
to flare ribbons, suggesting a strong heating correlation between the
loops. We discuss these results within the coronal rain scenario.
Title: Flux emergence in the solar internetwork and its contribution
to the network
Authors: Gosic, Milan; Katsukawa, Yukio; Orozco Suarez, David; Bellot
Rubio, L. R.
Bibcode: 2014cosp...40E1055G
Altcode:
Network and internetwork magnetic fields are believed to play a
crucial role in the energy budget of the solar atmosphere. Therefore,
it is essential to understand how they are maintained on the
solar surface. Using high resolution Hinode/NFI magnetograms at
disk center, we automatically follow quiet Sun magnetic elements
from their appearance to disappearance. From up to 40 hours of
continuous measurements, we derive the flux emergence rate in the
solar internetwork to be around 40 Mx cm(-2) day(-1) . We show
that internetwork fields appearing in the interior of individual
supergranular cells contribute flux to the surrounding network at
a rate of 2×10(19) Mx h(-1) . In only 10-20 hours, internetwork
elements can transfer as much flux as resides in network features,
establishing them as the most important source of flux for the network
and the quiet Sun flux budget.
Title: UV spectropolarimeter design for precise polarization
measurement and its application to the CLASP for exploration of
magnetic fields in solar atmosphere
Authors: Narukage, Noriyuki; Katsukawa, Yukio; Hara, Hirohisa; Kubo,
Masahito; Auchere, Frederic; Ishikawa, Ryohko; Kano, Ryouhei; Bando,
Takamasa; Ishikawa, Shin-nosuke; Suematsu, Yoshinori; Tsuneta, Saku
Bibcode: 2014cosp...40E2232N
Altcode:
In order to measure the magnetic field in the region where the
hot plasma from 10 (4) K to 10 (6) K is occupied, e.g., for solar
atmosphere, the polarimetric measurements in ultra violet (UV)
with 0.1% accuracy are required. In this paper, we propose a new
UV spectropolarimeter design with 0.1% sensitivity in polarization
measurement. This spectropolarimeter has two devices for the 0.1%
accuracy. First, all optical components except the waveplate are the
reflective type ones that can be equipped with the high reflectivity
coating for the high throughput. Secondly, it equips the optically
symmetric dual channels to measure the orthogonal linear polarization
state simultaneously, using a concave diffraction grating as both the
spectral dispersion element and the beam splitter. These two devices
make the spurious polarizations caused by the photon noise, by the
intensity variation of the observation target, and, by the instrument
itself, enough small to achieve the 0.1% accuracy in polarization
measurement. The spectropolarimeter thus designed is currently under
fabrication for the sounding rocket project of Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP) that aims at the direct measurement of the
magnetic fields in solar atmosphere with Lyman-alpha line (121.6 nm)
for the first time.
Title: Spectral Signatures of Penumbral Transients
Authors: Reardon, K.; Tritschler, A.; Katsukawa, Y.
Bibcode: 2013ApJ...779..143R
Altcode:
In this work we investigate the properties of penumbral transients
observed in the upper photospheric and chromospheric region above a
sunspot penumbra using two-dimensional spectroscopic observations
of the Ca II 854.21 nm line with a 5 s cadence. In our 30 minutes
of observations, we identify several penumbral-micro jets (PMJs)
with cotemporal observations from Dunn Solar Telescope/IBIS and
Hinode/SOT. We find that the line profiles of these PMJ events
show emission in the two wings of the line (±0.05 nm), but
little modification of the line core. These are reminiscent of
the line profiles of Ellerman bombs observed in plage and network
regions. Furthermore, we find evidence that some PMJ events have a
precursor phase starting 1 minute prior to the main brightening that
might indicate initial heating of the plasma prior to an acoustic or
bow shock event. With the IBIS data, we also find several other types
of transient brightenings with timescales of less than 1 minute that
are not clearly seen in the Hinode/SOT data. The spectral profiles and
other characteristics of these events are significantly different from
those of PMJs. The different appearances of all these transients are
an indicator of the general complexity of the chromospheric magnetic
field and underscore the highly dynamic behavior above sunspots. It
also highlights the care that is needed in interpreting broadband
filter images of chromospheric lines, which may conceal very different
spectral profiles, and the underlying physical mechanisms at work.
Title: FISS Observations of Vertical Motion of Plasma in Tiny Pores
Authors: Cho, K. -S.; Bong, S. -C.; Chae, J.; Kim, Y. -H.; Park,
Y. -D.; Katsukawa, Y.
Bibcode: 2013SoPh..288...23C
Altcode:
Pores can be exploited for the understanding of the interaction
between small-scale vertical magnetic field and the surrounding
convective motions as well as the transport of mechanical energy into
the chromosphere along the magnetic field. For better understanding of
the physics of pores, we investigate tiny pores in a new emerging
active region (AR11117) that were observed on 26 October 2010
by the Solar Optical Telescope (SOT) on board Hinode and the Fast
Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope
(NST). The pores are compared with nearby small magnetic concentrations
(SMCs), which have similar magnetic flux as the pores but do not
appear dark. Magnetic flux density and Doppler velocities in the
photosphere are estimated by applying the center-of-gravity method to
the Hinode/Spectro-Polarimeter data. The line-of-sight motions in the
lower chromosphere are determined by applying the bisector method to
the wings of the Hα and the Ca II 8542 Å line simultaneously taken
by the FISS. The coordinated observation reveals that the pores are
filled with plasma which moves down slowly and are surrounded by
stronger downflow in the photosphere. In the lower chromosphere, we
found that the plasma flows upwards inside the pores while the plasma
in the SMCs is always moving down. Our inspection of the Ca II 8542 Å
line from the wing to the core shows that the upflow in the pores slows
down with height and turns into downflow in the upper chromosphere
while the downflow in the SMCs gains its speed. Our results are in
agreement with the numerical studies which suggest that rapid cooling
of the interior of the pores drives a strong downflow, which collides
with the dense lower layer below and rebounds into an upflow.
Title: Chromospheric Lyman Alpha SpectroPolarimeter: CLASP
Authors: Kobayashi, Ken; Kano, R.; Trujillo Bueno, J.; Winebarger,
A. R.; Cirtain, J. W.; Bando, T.; De Pontieu, B.; Ishikawa, R.;
Katsukawa, Y.; Kubo, M.; Narukage, N.; Sakao, T.; Tsuneta, S.;
Auchère, F.; Asensio Ramos, A.; Belluzzi, L.; Carlsson, M.; Casini,
R.; Hara, H.; Ichimoto, K.; Manso Sainz, R.; Shimizu, T.; Stepan,
J.; Suematsu, Y.; Holloway, T.
Bibcode: 2013SPD....44..142K
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV
spectropolarimeter optimized for measuring the linear polarization of
the Lyman-alpha line (121.6 nm). The Lyman-alpha line is predicted to
show linear polarization caused by atomic scattering in the chromosphere
and modified by the magnetic field through the Hanle effect. The
Hanle effect is sensitive to weaker magnetic fields than Zeeman
effect, and is not canceled by opposing fields, making it sensitive
to tangled or unresolved magnetic field structures. These factors make
the Hanle effect a valuable tool for probing the magnetic field in the
chromosphere above the quiet sun. To meet this goal, CLASP is designed
to measure linear polarization with 0.1% polarization sensitivity
at 0.01 nm spectral resolution and 10" spatial resolution. CLASP is
scheduled to be launched in 2015.
Title: The Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Akin, D. L.; Card, G.; Cruz, T.; Duncan, D. W.;
Edwards, C. G.; Elmore, D. F.; Hoffmann, C.; Katsukawa, Y.; Katz, N.;
Kubo, M.; Ichimoto, K.; Shimizu, T.; Shine, R. A.; Streander, K. V.;
Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S.
Bibcode: 2013SoPh..283..579L
Altcode:
The joint Japan/US/UK Hinode mission includes the first large-aperture
visible-light solar telescope flown in space. One component of the
Focal Plane Package of that telescope is a precision spectro-polarimeter
designed to measure full Stokes spectra with the intent of using those
spectra to infer the magnetic-field vector at high precision in the
solar photosphere. This article describes the characteristics of the
flight hardware of the HinodeSpectro-Polarimeter, and summarizes its
in-flight performance.
Title: Next space solar observatory SOLAR-C: mission instruments
and science objectives
Authors: Katsukawa, Y.; Watanabe, T.; Hara, H.; Ichimoto, K.; Kubo,
M.; Kusano, K.; Sakao, T.; Shimizu, T.; Suematsu, Y.; Tsuneta, S.
Bibcode: 2012IAUSS...6E.207K
Altcode:
SOLAR-C, the fourth space solar mission in Japan, is under study with a
launch target of fiscal year 2018. A key concept of the mission is to
view the photosphere, chromosphere, and corona as one system coupled
by magnetic fields along with resolving the size scale of fundamental
physical processes connecting these atmospheric layers. It is especially
important to study magnetic structure in the chromosphere as an
interface layer between the photosphere and the corona. The SOLAR-C
satellite is equipped with three telescopes, the Solar UV-Visible-IR
Telescope (SUVIT), the EUV/FUV High Throughput Spectroscopic Telescope
(EUVS/LEMUR), and the X-ray Imaging Telescope (XIT). Observations
with SUVIT of photospheric and chromospheric magnetic fields make it
possible to infer three dimensional magnetic structure extending from
the photosphere to the chromosphere and corona.This helps to identify
magnetic structures causing magnetic reconnection, and clarify how
waves are propagated, reflected, and dissipated. Phenomena indicative
of or byproducts of magnetic reconnection, such as flows and shocks,
are to be captured by SUVIT and by spectroscopic observations using
EUVS/LEMUR, while XIT observes rapid changes in temperature distribution
of plasma heated by shock waves.
Title: Instrument Design of the Large Aperture Solar UV Visible and
IR Observing Telescope (SUVIT) for the SOLAR-C Mission
Authors: Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.;
Takeyama, N.
Bibcode: 2012ASPC..463..439S
Altcode:
We present an instrumental design of one major solar observation payload
planned for the SOLAR-C mission: the Solar Ultra-violet Visible and
near IR observing Telescope (SUVIT). The SUVIT is designed to provide
high-angular-resolution investigation of the lower solar atmosphere,
from the photosphere to the uppermost chromosphere, with enhanced
spectroscopic and spectro-polarimetric capability in wide wavelength
regions from 280 nm (Mg II h&k lines) to 1100 nm (He I 1083 nm
line) with 1.5 m class aperture and filtergraphic and spectrographic
instruments.
Title: Science and Instrument Design of 1.5-m Aperture Solar Optical
Telescope for the SOLAR-C Mission
Authors: Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.; Shimizu, T.
Bibcode: 2012IAUSS...6E.208S
Altcode:
We present science cases and a design of one of major instruments for
SOLAR-C mission; 1.5-m-class aperture solar ultra-violet visible and
near IR observing Telescope (SUVIT). The SOLAR-C mission aims at fully
understanding dynamism and magnetic nature of the solar atmosphere by
observing small-scale plasma processes and structures. The SUVIT is
designed to provide high-angular-resolution investigation of lower
atmosphere from the photosphere to the uppermost chromosphere with
enhanced spectroscopic and spectro-polarimetric capability covering
a wide wavelength region from 280 nm (Mg II h&k) to 1100 nm (He
I 1083 nm), using focal plane instruments: wide-band and narrow-band
filtergraphs and a spectrograph for high-precision spectro-polarimetry
in the solar photospheric and chromospheric lines. We will discuss
about instrument design to realize the science cases.
Title: Requirements for the Analysis of Quiet-Sun Internetwork
Magnetic Elements with EST and ATST
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Katsukawa, Y.
Bibcode: 2012ASPC..463...57O
Altcode: 2012arXiv1203.2185O
The quiet-Sun internetwork is permeated by weak and highly inclined
magnetic fields whose physical properties, dynamics, and magnetic
interactions are not fully understood. High spatial resolution
magnetograms show them as discrete magnetic elements that appear/emerge
and disappear/cancel continuously over the quiet Sun surface. The
4-m European Solar Telescope (EST) and the Advanced Technology
Solar Telescope (ATST) will obtain two-dimensional, high cadence,
high precision polarimetric measurements at the diffraction limit
(30 km). Here, we compile the basic requirements for the observation
of internetwork fields with EST and ATST (field of view, cadence,
instrument configuration, etc.). More specifically, we concentrate
on the field-of-view requirements. To set them we analyze the proper
motion of internetwork magnetic elements across the solar surface. We
use 13 hours of magnetograms taken with the Hinode satellite to
identify and track thousands of internetwork magnetic element in an
isolated supergranular cell. We calculate the velocity components of
each element and the mean distance they travel. The results show that,
on average, magnetic elements in the interior of supergranular cells
move toward the network. The radial velocity is observed to depend on
the distance to the center of the supergranule. Internetwork magnetic
elements travel 4″ on average. These results suggest that ATST and
EST should cover, at least, one supergranular cell to obtain a complete
picture of the quiet Sun internetwork.
Title: The Connection between Internetwork Magnetic Elements and
Supergranular Flows
Authors: Orozco Suárez, D.; Katsukawa, Y.; Bellot Rubio, L. R.
Bibcode: 2012ApJ...758L..38O
Altcode:
The advection of internetwork magnetic elements by supergranular
convective flows is investigated using high spatial resolution, high
cadence, and high signal-to-noise ratio Na I D1 magnetograms obtained
with the Hinode satellite. The observations show that magnetic elements
appear everywhere across the quiet Sun surface. We calculate the proper
motion of these magnetic elements with the aid of a feature tracking
algorithm. The results indicate that magnetic elements appearing in
the interior of supergranules tend to drift toward the supergranular
boundaries with a non-constant velocity. The azimuthally averaged
radial velocities of the magnetic elements and of the supergranular
flow, calculated from a local correlation tracking technique applied
to Dopplergrams, are very similar. This suggests that, in the long
term, surface magnetic elements are advected by supergranular flows,
although on short timescales their very chaotic motions are driven
mostly by granular flows and other processes.
Title: Power Spectra of Velocities and Magnetic Fields on the Solar
Surface and their Dependence on the Unsigned Magnetic Flux Density
Authors: Katsukawa, Y.; Orozco Suárez, D.
Bibcode: 2012ApJ...758..139K
Altcode: 2012arXiv1209.0548K
We have performed power spectral analysis of surface temperatures,
velocities, and magnetic fields, using spectropolarimetric data taken
with the Hinode Solar Optical Telescope. When we make power spectra in
a field of view covering the supergranular scale, kinetic and thermal
power spectra have a prominent peak at the granular scale while the
magnetic power spectra have a broadly distributed power over various
spatial scales with weak peaks at both the granular and supergranular
scales. To study the power spectra separately in internetwork and
network regions, power spectra are derived in small subregions extracted
from the field of view. We examine slopes of the power spectra using
power-law indices, and compare them with the unsigned magnetic flux
density averaged in the subregions. The thermal and kinetic spectra
are steeper than the magnetic ones at the subgranular scale in the
internetwork regions, and the power-law indices differ by about 2. The
power-law indices of the magnetic power spectra are close to or smaller
than -1 at that scale, which suggests the total magnetic energy mainly
comes from either the granular scale magnetic structures or both the
granular scale and smaller ones contributing evenly. The slopes of the
thermal and kinetic power spectra become less steep with increasing
unsigned flux density in the network regions. The power-law indices
of all the thermal, kinetic, and magnetic power spectra become similar
when the unsigned flux density is larger than 200 Mx cm-2.
Title: Design of large aperture solar optical telescope for the
SOLAR-C mission
Authors: Suematsu, Y.; Katsukawa, Y.; Hara, H.; Shimizu, T.;
Ichimoto, K.
Bibcode: 2012SPIE.8442E..25S
Altcode:
A large aperture optical telescope is planned for the next Japanese
solar mission SOLAR-C as one of major three observing instruments. The
optical telescope is designed to provide high-angular-resolution
investigation of lower atmosphere from the photosphere to the uppermost
chromosphere with enhanced spectroscopic and spectro-polarimetric
capability covering a wide wavelength region from 280 nm to 1100
nm. The opto-mechanical and -thermal performance of the telescope is
crucial to attain high-quality solar observations and we present a
study of optical and structural design of the large aperture space
solar telescope, together with conceptual design of its accompanying
focal plane instruments: wide-band and narrow-band filtergraphs and
a spectro-polarimeter for high spatial and temporal observations in
the solar photospheric and chromospheric lines useful for sounding
physical condition of dynamical phenomena.
Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP)
Authors: Kano, Ryouhei; Bando, Takamasa; Narukage, Noriyuki; Ishikawa,
Ryoko; Tsuneta, Saku; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Hara, Hirohisa; Shimizu, Toshifumi; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Sakao, Taro; Goto, Motoshi; Kato, Yoshiaki; Imada,
Shinsuke; Kobayashi, Ken; Holloway, Todd; Winebarger, Amy; Cirtain,
Jonathan; De Pontieu, Bart; Casini, Roberto; Trujillo Bueno, Javier;
Štepán, Jiří; Manso Sainz, Rafael; Belluzzi, Luca; Asensio Ramos,
Andres; Auchère, Frédéric; Carlsson, Mats
Bibcode: 2012SPIE.8443E..4FK
Altcode:
One of the biggest challenges in heliophysics is to decipher the
magnetic structure of the solar chromosphere. The importance of
measuring the chromospheric magnetic field is due to both the key role
the chromosphere plays in energizing and structuring the outer solar
atmosphere and the inability of extrapolation of photospheric fields to
adequately describe this key boundary region. Over the last few years,
significant progress has been made in the spectral line formation
of UV lines as well as the MHD modeling of the solar atmosphere. It
is found that the Hanle effect in the Lyman-alpha line (121.567 nm)
is a most promising diagnostic tool for weaker magnetic fields in
the chromosphere and transition region. Based on this groundbreaking
research, we propose the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP) to NASA as a sounding rocket experiment, for making the first
measurement of the linear polarization produced by scattering processes
and the Hanle effect in the Lyman-alpha line (121.567 nm), and making
the first exploration of the magnetic field in the upper chromosphere
and transition region of the Sun. The CLASP instrument consists
of a Cassegrain telescope, a rotating 1/2-wave plate, a dual-beam
spectrograph assembly with a grating working as a beam splitter, and
an identical pair of reflective polarization analyzers each equipped
with a CCD camera. We propose to launch CLASP in December 2014.
Title: Persistent Circulating Motion in a Sunspot Umbra
Authors: Katsukawa, Y.; Kitai, R.; Watanabe, H.
Bibcode: 2012ASPC..454..213K
Altcode:
We studied temporal evolution of flow patterns inside an umbra
using the local correlation tracking algorithm applied to long-term
filtergram data of a matured sunspot taken with the Hinode Solar
Optical Telescope. We found not only inward migration of umbral dots
in a peripheral region of the umbra but also a circulating motion in
a central region of the umbra. The circulating motion was persistently
observed for at least 3 days. The observation suggests that there are
magnetic and flow structures below a sunspot maintaining the motion
of umbral dots.
Title: The SOLAR-C Mission: Plan B Payload Concept
Authors: Shimizu, T.; Sakao, T.; Katsukawa, Y.; Group, J. S. W.
Bibcode: 2012ASPC..454..449S
Altcode:
The telescope concepts for the SOLAR-C Plan B mission as of the time of
the Hinode-3 meeting were briefly presented for having comments from
the international solar physics community. The telescope candidates
are 1) near IR-visible-UV telescope with 1.5m aperture and enhanced
spectro-polarimetric capability, 2) UV/EUV high throughput spectrometer,
and 3) next generation X-ray telescope.
Title: Evolution of internetwork magnetic fields inside supergranular
cells
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, Luis; Orozco
Suarez, David
Bibcode: 2012cosp...39..657G
Altcode: 2012cosp.meet..657G
To understand the formation of small-scale magnetic fields in the quiet
Sun and their contribution to the solar activity, it is essential to
investigate the properties of internetwork magnetic fields. Using
Hinode/NFI magnetograms of very high sensitivity (7 Mx/cm^{2}),
spatial resolution (0.16 arcsec/pixel), and cadence (90 s), we
follow the evolution of magnetic fields inside of a supergranular
cell located at disk center. In 5 hours of continuous measurements
covering an area of 20.8 × 23.2 arcsec^{2}, we manually track 2415
magnetic elements from appearance to disappearance and derive their
physical properties. The average values of the magnetic flux, effective
diameter, lifetime, and horizontal velocity are 3 × 10^{17} Mx, 0.5 Mm,
17 min, and 2 km/s, respectively. We also investigate how the physical
parameters of the individual elements vary as a function of time,
flux, and spatial position. Using this unique data set, we determine
with unprecedented accuracy the flux emergence and disappearance rate
in the solar internetwork.
Title: The Chromospheric Lyman-Alpha SpectroPolarimeter: CLASP
Authors: Kobayashi, K.; Kano, R.; Trujillo-Bueno, J.; Asensio Ramos,
A.; Bando, T.; Belluzzi, L.; Carlsson, M.; De Pontieu, R. C. B.; Hara,
H.; Ichimoto, K.; Ishikawa, R.; Katsukawa, Y.; Kubo, M.; Manso Sainz,
R.; Narukage, N.; Sakao, T.; Stepan, J.; Suematsu, Y.; Tsuneta, S.;
Watanabe, H.; Winebarger, A.
Bibcode: 2012ASPC..456..233K
Altcode:
The magnetic field plays a crucial role in the chromosphere and the
transition region, and our poor empirical knowledge of the magnetic
field in the upper chromosphere and transition region is a major
impediment to advancing the understanding of the solar atmosphere. The
Hanle effect promises to be a valuable alternative to Zeeman effect
as a method of measuring the magnetic field in the chromosphere and
transition region; it is sensitive to weaker magnetic fields, and
also sensitive to tangled, unresolved field structures. CLASP
is a sounding rocket experiment that aims to observe the Hanle effect
polarization of the Lyman α (1215.67Å) line in the solar chromosphere
and transition region, and prove the usefulness of this technique in
placing constraints on the magnetic field strength and orientation
in the low plasma-β region of the solar atmosphere. The Ly-α line
has been chosen because it is a chromospheric/transition-region line,
and because the Hanle effect polarization of this line is predicted to
be sensitive to 10-250 Gauss, encompassing the range of interest. The
CLASP instrument is designed to measure linear polarization in the
Ly-α line with a polarization sensitivity of 0.1%. The instrument is
currently funded for development. The optical design of the instrument
has been finalized, and an extensive series of component-level tests
are underway to validate the design.
Title: On the Distribution of Quiet-Sun Magnetic Fields at Different
Heliocentric Angles
Authors: Orozco Suárez, D.; Katsukawa, Y.
Bibcode: 2012ApJ...746..182O
Altcode:
This paper presents results from the analysis of high signal-to-noise
ratio spectropolarimetric data taken at four heliocentric angles in
quiet-Sun internetwork regions with the Hinode satellite. First, we
find that the total circular and total linear polarization signals vary
with heliocentric angle, at least for fields with large polarization
signals. We also report changes on the Stokes V amplitude asymmetry
histograms with viewing angle for fields weaker than 200 G. Then,
we subject the data to a Milne-Eddington inversion and analyze
the variation of the field vector probability density functions
with heliocentric angle. Weak, highly inclined fields permeate
the internetwork at all heliocentric distances. For fields weaker
than 200 G, the distributions of field inclinations peak at 90°
and do not vary with viewing angle. The inclination distributions
change for fields stronger than 200 G. We argue that the shape of
the inclination distribution for weak fields partly results from the
presence of coherent, loop-like magnetic features at all heliocentric
distances and not from tangled fields within the field of view. We also
find that the average magnetic field strength is about 180 G (for 75%
of the pixels) and is constant with heliocentric angle. The average
vertical and horizontal magnetic field components are 70 and 150 G. The
latter (former) is slightly greater (smaller) near the limb. Finally,
the ratio between the horizontal and vertical components of the fields
ranges from ~1 for strong fields to ~3.5 for weak fields, suggesting
that the magnetic field vector is not isotropically distributed within
the field of view.
Title: The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP)j
Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Bando, T.;
Belluzzi, L.; Casini, R.; Carlsson, M.; Cirtain, J. W.; De Pontieu,
B.; Hara, H.; Ichimoto, K.; Ishikawa, R.; Kano, R.; Katsukawa, Y.;
Kim, T.; Kubo, M.; Manso Sainz, R.; Narukage, N.; Asensio Ramos,
A.; Robinson, B.; Sakao, T.; Shimizu, T.; Stepan, J.; Suematsu, Y.;
Watanabe, H.; West, E.; Winebarger, A. R.
Bibcode: 2011AGUFM.P14C..05K
Altcode:
We present an overview of the Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP) program. CLASP is a proposed sounding rocket
experiment currently under development as collaboration between Japan,
USA and Spain. The aim is to achieve the first measurement of magnetic
field in the upper chromosphere and transition region of the Sun
through the detection and measurement of Hanle effect polarization
of the Lyman alpha line. The Hanle effect (i.e. the magnetic field
induced modification of the linear polarization due to scattering
processes in spectral lines) is believed to be a powerful tool for
measuring the magnetic field in the upper chromosphere, as it is more
sensitive to weaker magnetic fields than the Zeeman effect, and also
sensitive to magnetic fields tangled at spatial scales too small to be
resolved. The Lyman-alpha (121.567 nm) line has been chosen because
it is a chromospheric/transition-region line, and because the Hanle
effect polarization of the Lyman-alpha line is predicted to be sensitive
to 10-250 Gauss, encompassing the range of interest. Hanle effect is
predicted to be observable as linear polarization or depolarization,
depending on the geometry, with a fractional polarization amplitude
varying between 0.1% and 1% depending on the strength and orientation of
the magnetic field. This quantification of the chromospheric magnetic
field requires a highly sensitive polarization measurement. The
CLASP instrument consists of a large aperture (287 mm) Cassegrain
telescope mated to a polarizing beamsplitter and a matched pair
of grating spectrographs. The polarizing beamsplitter consists
of a continuously rotating waveplate and a linear beamsplitter,
allowing simultaneous measurement of orthogonal polarizations and
in-flight self-calibration. Development of the instrument is underway,
and prototypes of all optical components have been tested using a
synchrotron beamline. The experiment is proposed for flight in 2014.
Title: Magnetic Field Diagnostics with the HINODE Spectro-Polarimeter
Authors: Katsukawa, Y.; Hinode Sot Team
Bibcode: 2011AGUFMSH33C..01K
Altcode:
After HINODE started its observations in 2006, the Spectro-Polarimeter
(SP) aboard Hinode has provided unique data for studies of photospheric
magnetic fields. Advantages of the HINODE SP is that we can get
full polarimetric and spectroscopic information on Zeeman-sensitive
photospheric lines as well as stable image quality whose angular
resolution is 0.3 arcsec. It allows us to carry out detailed studies on
magentic and flow structures of sunspot fine structures (e.g. umbral
dots, light bridges, and penumbral filaments) and properties of the
quiet Sun magnetic fields, which has provided insights on how magnetic
flux interacts with convective flows in the photosphere. Vector field
maps generated through a Stokes inversion technique are accurate
enough to track development of magnetic shear toward the onset of a
flare, and are also useful to carry out the nonlinear force-free field
(NLFFF) extrapolation. The weakness of the HINODE SP observations is
a limited field-of-view and temporal coverage because of the scanning
instrument. This is why complementary observations with SDO/HMI and
SOLIS are important in the current increasing solar activity.
Title: Focal plane instrument for the Solar UV-Vis-IR Telescope
aboard SOLAR-C
Authors: Katsukawa, Yukio; Suematsu, Yoshinori; Shimizu, Toshifumi;
Ichimoto, Kiyoshi; Takeyama, Norihide
Bibcode: 2011SPIE.8148E..0EK
Altcode: 2011SPIE.8148E..13K
It is presented the conceptual design of a focal plane instrument for
the Solar UV-Vis-IR Telescope (SUVIT) aboard the next Japanese solar
mission SOLAR-C. A primary purpose of the telescope is to achieve
precise as well as high resolution spectroscopic and polarimetric
measurements of the solar chromosphere with a big aperture of 1.5 m,
which is expected to make a significant progress in understanding basic
MHD processes in the solar atmosphere. The focal plane instrument
consists of two packages: A filtergraph package is to get not only
monochromatic images but also Dopplergrams and magnetograms using a
tunable narrow-band filter and interference filters. A spectrograph
package is to perform accurate spectro-polarimetric observations for
measuring chromospheric magnetic fields, and is employing a Littrow-type
spectrograph. The most challenging aspect in the instrument design is
wide wavelength coverage from 280 nm to 1.1 μm to observe multiple
chromospheric lines, which is to be realized with a lens unit including
fluoride glasses. A high-speed camera for correlation tracking of
granular motion is also implemented in one of the packages for an
image stabilization system, which is essential to achieve high spatial
resolution and high polarimetric accuracy.
Title: Overview of Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP)
Authors: Narukage, Noriyuki; Tsuneta, Saku; Bando, Takamasa; Kano,
Ryouhei; Kubo, Masahito; Ishikawa, Ryoko; Hara, Hirohisa; Suematsu,
Yoshinori; Katsukawa, Yukio; Watanabe, Hiroko; Ichimoto, Kiyoshi;
Sakao, Taro; Shimizu, Toshifumi; Kobayashi, Ken; Robinson, Brian; Kim,
Tony; Winebarger, Amy; West, Edward; Cirtain, Jonathan; De Pontieu,
Bart; Casini, Roberto; Trujillo Bueno, Javier; Stepan, Jiri; Manso
Sainz, Rafael; Belluzzi, Luca; Asensio Ramos, Andres; Carlsson, Mats
Bibcode: 2011SPIE.8148E..0HN
Altcode: 2011SPIE.8148E..16N
The solar chromosphere is an important boundary, through which all of
the plasma, magnetic fields and energy in the corona and solar wind
are supplied. Since the Zeeman splitting is typically smaller than
the Doppler line broadening in the chromosphere and transition region,
it is not effective to explore weak magnetic fields. However, this is
not the case for the Hanle effect, when we have an instrument with
high polarization sensitivity (~ 0.1%). "Chromospheric Lyman- Alpha
SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect
linear polarization produced by the Hanle effect in Lyman-alpha line
(121.567 nm) and to make the first direct measurement of magnetic
fields in the upper chromosphere and lower transition region. To
achieve the high sensitivity of ~ 0.1% within a rocket flight (5
minutes) in Lyman-alpha line, which is easily absorbed by materials,
we design the optical system mainly with reflections. The CLASP
consists of a classical Cassegrain telescope, a polarimeter and a
spectrometer. The polarimeter consists of a rotating 1/2-wave plate
and two reflecting polarization analyzers. One of the analyzer also
works as a polarization beam splitter to give us two orthogonal linear
polarizations simultaneously. The CLASP is planned to be launched in
2014 summer.
Title: Short telescope design of 1.5-m aperture solar UV visible
and IR telescope aboard Solar-C
Authors: Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.;
Horiuchi, T.; Matsumoto, Y.; Takeyama, N.
Bibcode: 2011SPIE.8148E..0DS
Altcode: 2011SPIE.8148E..12S
We present an optical and thermal design of one of major instrumental
payload planned for SOLAR-C mission/Plan-B (high resolution
spectroscopic option): the telescope assembly of Solar Ultra-violet
Visible and near IR observing Telescope (SUVIT). To accommodate a
launcher's nosecone size, a wide observing wavelength coverage from UV
(down to 280 nm) through near IR (up to 1100 nm), and an 0.1 arcsec
resolution in the field of 200 arcsec diameter, a short telescope
design was made for a 1.5 m aperture solar Gregorian telescope with
the compact design of three-mirror collimator unit.
Title: Modeling and verification of the diffraction-limited visible
light telescope aboard the solar observing satellite HINODE
Authors: Katsukawa, Y.; Suematsu, Y.; Tsuneta, S.; Ichimoto, K.;
Shimizu, T.
Bibcode: 2011SPIE.8336E..0FK
Altcode: 2011SPIE.8336E..14K
HINODE, Japanese for "sunrise", is a spacecraft dedicated for
observations of the Sun, and was launched in 2006 to study the Sun's
magnetic fields and how their explosive energies propagate through the
different atmospheric layers. The spacecraft carries the Solar Optical
Telescope (SOT), which has a 50 cm diameter clear aperture and provides
a continuous series of diffraction-limited visible light images from
space. The telescope was developed through international collaboration
between Japan and US. In order to achieve the diffraction-limited
performance, thermal and structural modeling of the telescope was
extensively used in its development phase to predict how the optical
performance changes dependent on the thermal condition in orbit. Not
only the modeling, we devoted many efforts to verify the optical
performance in ground tests before the launch. The verification in
the ground tests helped us to find many issues, such as temperature
dependent focus shifts, which were not identified only through the
thermal-structural modeling. Another critical issue was micro-vibrations
induced by internal disturbances of mechanical gyroscopes and momentum
wheels for attitude control of the spacecraft. Because the structural
modeling was not accurate enough to predict how much the image quality
was degraded by the micro-vibrations, we measured their transmission
in a spacecraft-level test.
Title: Tiny Pores Observed by New Solar Telescope and Hinode
Authors: Cho, KyungSuk; Bong, S.; Chae, J.; Kim, Y.; Park, Y.; Ahn,
K.; Katsukawa, Y.
Bibcode: 2011SPD....42.1903C
Altcode: 2011BAAS..43S.1903C
Seoul National University and Korea Astronomy and Space Science
Institute installed Fast Imaging Solar Spectrograph (FISS) in the
Cude room of the 1.6 m New Solar Telescope (NST) at Big Bear Solar
Observatory on May 14, 2010. FISS is a unique system that can do
imaging of H-alpha and Ca II 8542 band simultaneously, which is quite
suitable for studying of dynamics of chromosphere. To investigate the
relationship between the photospheric and low-chromospheric motions at
the pore region, we took a coordinate observation with NST/FISS and
Hinode/SOT for new emerging active region (AR11117) on October 26,
2010. In the observed region, we could find two tiny pores and two
small magnetic concentrations (SMCs), which have similar magnetic
flux with the pores but do not look dark. Magnetic flux density and
Doppler velocities at the photosphere are estimated by applying the
center-of-gravity (COG) method to the HINODE/spectropolarimeter (SP)
data. The line-of-sight motions above the photosphere are determined
by adopting the bisector method to the wing spectra of Ha and CaII
8542 lines. As results, we found the followings. (1)There are upflow
motion on the pores and downflow motion on the SMCs. (2)Towards the
CaII 8542 line center, upflow motion decrease and turn to downward
motion in pores, while the speed of down flow motion increases in
the SMCs. (3)There is oscillating motion above pores and the SMCs,
and this motion keep its pattern along the height. (4) As height
increase, there is a general tendency of the speed shift to downward
on pores and the SMCs. In this poster, we will present preliminary
understanding of the coupling of pore dynamics between the photosphere
and the low-chromosphere.
Title: Chromospheric Diagnostics in the Next Japanese Solar Mission
SOLAR-C
Authors: Katsukawa, Y.; Solar-C Working Groups
Bibcode: 2011ASPC..437..281K
Altcode:
The SOLAR-C working group (WG) was established in 2007 to investigate
scientific and technical feasibility for the next Japanese solar
mission SOLAR-C whose earliest launch window is 2018. There are two
conceptual options in SOLAR-C. Option-A is a mission for out-of-ecliptic
observations of the solar polar regions to understand dynamics
in the high latitude regions of the Sun, and internal structures
and dynamo mechanism. The other option, option-B, is a mission for
high-resolutional spectroscopic and polarimetric observations of the
solar atmosphere with advanced telescopes. In option-B of SOLAR-C,
strong emphasis is on measuring chromospheric magnetic fields with a
precise spectropolarimetric instrument thanks to a large aperture of
1 to 1.5 m, which is important to understand mechanisms responsible
for transfer and dissipation of magnetic energies through the solar
atmosphere.
Title: Temporal downflows in a penumbra
Authors: Jurčák, J.; Katsukawa, Y.
Bibcode: 2010A&A...524A..21J
Altcode:
Aims: We analyze temporal downflow patches that are located
in a penumbra and have the same polarity of the magnetic field as
a sunspot umbra.
Methods: The repetitive 2'' wide raster
scans of penumbral regions that are taken with one minute cadence by
the Hinode spectropolarimeter are used to detect the line-of-sight
velocities in the penumbra from enhanced signals in the wings of
Stokes V profiles. The lifetimes and positions within penumbra of the
identified downflow patches are investigated. The plasma properties
of the downflow patches are determined using the inversions of the
observed Stokes profiles.
Results: The temporal downflows
have lifetimes of up to fourteen minutes. Some of them are related
to the disappearance or weakening of nearby upflow regions or to the
chromospheric brightenings. The downflows take place in regions with
stronger and more vertical magnetic fields than the upflow regions.
Title: A new type of small-scale downflow patches in sunspot penumbrae
Authors: Katsukawa, Y.; Jurčák, J.
Bibcode: 2010A&A...524A..20K
Altcode: 2010arXiv1007.1702K
Context. Magnetic and flow structures in a sunspot penumbra are created
by strong interplay between inclined magnetic fields and photospheric
convection. They exhibit a complex nature that cannot always be
explained by the well-known Evershed flow.
Aims: A sunspot
penumbra is observationally examined to reveal properties of small-scale
flow structures and their relationship to the filamentary magnetic
structures and the Evershed flow. We also study how the photospheric
dynamics are related to chromospheric activities.
Methods: This
study is based on data analysis of spectro-polarimetric observations of
photospheric Fe I lines with the Solar Optical Telescope aboard Hinode
in a sunspot penumbra at different heliocentric angles. Vector magnetic
fields and velocities are derived using the spectro-polarimetric
data and a Stokes inversion technique. An observation with a Ca II H
filtergram co-spatial and co-temporal with the spectro-polarimetric
one is also used to study possible chromospheric responses.
Results: We find small patches with downflows in the photospheric
layers. The downflow patches have a size of 0.5'' or smaller and
a different geometrical configuration from the Evershed flow. The
downflow velocity is about 1 km s-1 in the lower photspheric
layers and is almost zero in the upper layers. Some of the downflow
patches are associated with brightenings seen in Ca II H images.
Conclusions: The downflows are possible observational signatures
of downward flows driven by magnetic reconnection in the interlaced
magnetic field configuration, where upward flows make brightenings in
the chromosphere. Another possibility is that they are concentrated
downward flows of overturning magnetoconvection.
Title: Quiescent Prominence Dynamics Observed with the Hinode Solar
Optical Telescope. I. Turbulent Upflow Plumes
Authors: Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine,
Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto,
Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya;
Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2010ApJ...716.1288B
Altcode:
Hinode/Solar Optical Telescope (SOT) observations reveal two new
dynamic modes in quiescent solar prominences: large-scale (20-50 Mm)
"arches" or "bubbles" that "inflate" from below into prominences, and
smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are
related in that they are always dark in visible-light spectral bands,
they rise through the bright prominence emission with approximately
constant speeds, and the small-scale upflows are sometimes observed to
emanate from the top of the larger bubbles. Here we present detailed
kinematic measurements of the small-scale turbulent upflows seen in
several prominences in the SOT database. The dark upflows typically
initiate vertically from 5 to 10 Mm wide dark cavities between the
bottom of the prominence and the top of the chromospheric spicule
layer. Small perturbations on the order of 1 Mm or less in size
grow on the upper boundaries of cavities to generate plumes up to
4-6 Mm across at their largest widths. All plumes develop highly
turbulent profiles, including occasional Kelvin-Helmholtz vortex
"roll-up" of the leading edge. The flows typically rise 10-15 Mm before
decelerating to equilibrium. We measure the flowfield characteristics
with a manual tracing method and with the Nonlinear Affine Velocity
Estimator (NAVE) "optical flow" code to derive velocity, acceleration,
lifetime, and height data for several representative plumes. Maximum
initial speeds are in the range of 20-30 km s-1, which
is supersonic for a ~10,000 K plasma. The plumes decelerate in the
final few Mm of their trajectories resulting in mean ascent speeds
of 13-17 km s-1. Typical lifetimes range from 300 to 1000
s (~5-15 minutes). The area growth rate of the plumes (observed as
two-dimensional objects in the plane of the sky) is initially linear
and ranges from 20,000 to 30,000 km2 s-1 reaching
maximum projected areas from 2 to 15 Mm2. Maximum contrast of
the dark flows relative to the bright prominence plasma in SOT images
is negative and ranges from -10% for smaller flows to -50% for larger
flows. Passive scalar "cork movies" derived from NAVE measurements show
that prominence plasma is entrained by the upflows, helping to counter
the ubiquitous downflow streams in the prominence. Plume formation
shows no clear temporal periodicity. However, it is common to find
"active cavities" beneath prominences that can spawn many upflows in
succession before going dormant. The mean flow recurrence time in these
active locations is roughly 300-500 s (5-8 minutes). Locations remain
active on timescales of tens of minutes up to several hours. Using a
column density ratio measurement and reasonable assumptions on plume
and prominence geometries, we estimate that the mass density in the
dark cavities is at most 20% of the visible prominence density, implying
that a single large plume could supply up to 1% of the mass of a typical
quiescent prominence. We hypothesize that the plumes are generated from
a Rayleigh-Taylor instability taking place on the boundary between
the buoyant cavities and the overlying prominence. Characteristics,
such as plume size and frequency, may be modulated by the strength
and direction of the cavity magnetic field relative to the prominence
magnetic field. We conclude that buoyant plumes are a source of
quiescent prominence mass as well as a mechanism by which prominence
plasma is advected upward, countering constant gravitational drainage.
Title: Magnetic Structure of Umbral Dots with SOT SP
Authors: Watanabe, H.; Kitai, R.; Ichimoto, K.; Katsukawa, Y.
Bibcode: 2009ASPC..415..378W
Altcode:
High resolution and seeing-free spectroscopic observations of a decaying
sunspot were done with the Solar Optical Telescope aboard Hinode
satellite. We report the magnetic structure and Doppler velocity fields
around umbral dots (UDs), based on the Milne-Eddington inversion of the
two iron absorption lines at 6302 Å. The histograms of magnetic
field strength (B), inclination angle (i), and Doppler velocity (v)
of UDs showed a center-to-limb variation. Observed at the disk center,
UDs had (i) slightly smaller field strength (ΔB = -17 Gauss) and
(ii) relative blue shifts (Δv =28 m s-1) compared to their
surroundings. When the sunspot approached to the limb, UDs and their
surroundings showed almost no difference in the magnetic and Doppler
values. This center-to-limb variation can be understood by the formation
height difference in a cusp-shaped magnetized atmosphere around UDs,
due to the weakly magnetized hot gas intrusion. In addition, some UDs
showed oscillatory light curves with multiple peaks around 10 min,
which may indicate the presence of the oscillatory convection.
Title: Downflow Patches in a Penumbra Observed with the Hinode
Spectro-Polarimeter
Authors: Katsukawa, Y.; Jurčák, J.
Bibcode: 2009ASPC..415..117K
Altcode:
We here present a new observational signature of dynamics in a sunspot
penumbra. The dynamics are observed as a small patch of downflows
distributed sparsely in a center-side penumbra, and not observed in
a limb-side penumbra. The distribution suggests that the downflow is
aligned to magnetic field lines relatively vertical to the surface. The
flow might be related to dissipation of magnetic energies in a penumbra.
Title: Supersonic Continuation of the Evershed Flow Outside a Sunspot
as Observed with Hinode
Authors: Martínez Pillet, V.; Katsukawa, Y.; Puschmann, K. G.;
Ruiz Cobo, B.
Bibcode: 2009ApJ...701L..79M
Altcode: 2009arXiv0907.3835M
We report on the discovery of mostly horizontal field channels just
outside sunspot penumbrae (in the so-called "moat" region) that are
seen to sustain supersonic flows (line-of-sight component of 6 km
s-1). The spectral signature of these supersonic flows
corresponds to circular polarization profiles with an additional,
satellite, third lobe of the same sign as the parent sunspot' Stokes
V blue lobe, for both downflows and upflows. This is consistent with
an outward directed flow that we interpret as the continuation of the
magnetized Evershed flow outside sunspots at supersonic speeds. In
Stokes Q and U, a clear signature of a transverse field connecting
the two flow streams is observed. Such an easily detectable spectral
signature should allow for a clear identification of these horizontal
field channels in other spectropolarimetric sunspot data. For the spot
analyzed in this paper, a total of five channels with this spectral
signature have been unambiguously found.
Title: A New View of Fine Scale Dynamics and Magnetism of Sunspots
Revealed by Hinode/SOT
Authors: Ichimoto, K.; Suematsu, Y.; Katsukawa, Y.; Tsuneta, S.;
Shimojo, M.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Berger, T.;
Title, A. M.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Nagata, S.
Bibcode: 2009ASPC..405..167I
Altcode:
The Solar Optical Telescope on-board Hinode is providing a new view of
the fine scale dynamics in sunspots with its high spatial resolution and
unprecedented image stability. We present three features related to the
Evershed flow each of which raises a new puzzle in sunspot dynamics;
i.e., twisting appearance of penumbral filaments, the source and sink
of individual Evershed flow channels, and the net circular polarization
in penumbrae with its spatial relation to the Evershed flow channels.
Title: Has Hinode Revealed the Missing Turbulent Flux of the
Quiet Sun?
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2009ASPC..405..173L
Altcode:
The Hinode Spectro-Polarimeter has revealed the presence of surprisingly
strong horizontal magnetic fields nearly everywhere in the quiet
solar atmosphere. These horizontal fields, along with measures of the
vertical fields, may be the signature of the ``hidden turbulent flux''
of the quiet Sun. The measured horizontal fields average at least to
55 Gauss: nearly 5 times that of the measured longitudinal apparent
flux density. The nature of these fields are reviewed, and discussed
in the light of recent magneto-convection numerical simulations of
the quiet Sun.
Title: Hinode Observation of the Magnetic Fields in a Sunspot Light
Bridge Accompanied by Long-Lasting Chromospheric Plasma Ejections
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Kubo, Masahito; Lites,
Bruce W.; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Tsuneta, Saku;
Nagata, Shin'ichi; Shine, Richard A.; Tarbell, Theodore D.
Bibcode: 2009ApJ...696L..66S
Altcode:
We present high-resolution magnetic field measurements of a sunspot
light bridge (LB) that produced chromospheric plasma ejections
intermittently and recurrently for more than 1 day. The observations
were carried out with the Hinode Solar Optical Telescope on 2007
April 29 and 30. The spectro-polarimeter reveals obliquely oriented
magnetic fields with vertical electric current density higher than
100 mA m-2 along the LB. The observations suggest that
current-carrying highly twisted magnetic flux tubes are trapped below
a cusp-shaped magnetic structure along the LB. The presence of trapped
current-carrying flux tubes is essential for causing long-lasting
chromospheric plasma ejections at the interface with pre-existing
vertically oriented umbral fields. A bidirectional jet was clearly
detected, suggesting magnetic reconnections occurring at very low
altitudes, slightly above the height where the vector magnetic fields
are measured. Moreover, we found another strong vertical electric
current on the interface between the current-carrying flux tube
and pre-existing umbral field, which might be a direct detection
of the currents flowing in the current sheet formed at the magnetic
reconnection sites.
Title: Prominence Formation Associated with an Emerging Helical
Flux Rope
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2009ApJ...697..913O
Altcode: 2009arXiv0904.0007O
The formation and evolution process and magnetic configuration of
solar prominences remain unclear. In order to study the formation
process of prominences, we examine continuous observations of a
prominence in NOAA AR 10953 with the Solar Optical Telescope on
the Hinode satellite. As reported in our previous Letter, we find
a signature suggesting that a helical flux rope emerges from below
the photosphere under a pre-existing prominence. Here we investigate
more detailed properties and photospheric indications of the emerging
helical flux rope, and discuss their relationship to the formation of
the prominence. Our main conclusions are: (1) a dark region with absence
of strong vertical magnetic fields broadens and then narrows in Ca II
H-line filtergrams. This phenomenon is consistent with the emergence
of the helical flux rope as photospheric counterparts. The size of the
flux rope is roughly 30,000 km long and 10,000 km wide. The width is
larger than that of the prominence. (2) No shear motion or converging
flows are detected, but we find diverging flows such as mesogranules
along the polarity inversion line. The presence of mesogranules may
be related to the emergence of the helical flux rope. (3) The emerging
helical flux rope reconnects with magnetic fields of the pre-existing
prominence to stabilize the prominence for the next several days. We
thus conjecture that prominence coronal magnetic fields emerge in
the form of helical flux ropes that contribute to the formation and
maintenance of the prominence.
Title: Magnetic Structure of Umbral Dots Observed with the Hinode
Solar Optical Telescope
Authors: Watanabe, Hiroko; Kitai, Reizaburo; Ichimoto, Kiyoshi;
Katsukawa, Yukio
Bibcode: 2009PASJ...61..193W
Altcode: 2008arXiv0811.1074W
A high-resolution, seeing-free spectroscopic observation of a decaying
sunspot was made with the Solar Optical Telescope aboard the Hinode
satellite. The target was NOAA 10944, located in the west side of the
solar surface from 2007 March 2 to March 4. The umbra included many
umbral dots (UDs) with a size of ∼300 km in continuum light. We report
on the magnetic structures and Doppler velocity fields around UDs, based
on the Milne-Eddington inversions of the two iron absorption lines at
6302Å. Histograms of the magnetic field strength (B), inclination angle
(i), and Doppler velocity (v) of UDs showed a center-to-limb variation;
observed at the disk center, the UDs had (i) slightly smaller field
strength (ΔB = -17Gauss) and (ii) relative blue shifts (Δv = 28m
s-1) compared to their surroundings. When the sunspot
got close to the limb, UDs and their surroundings showed almost no
difference in the magnetic and Doppler values. This center-to-limb
variation can be understood by the formation height difference in
a cusp-shaped magnetized atmosphere around UDs, due to the weakly
magnetized hot gas intrusion. In addition, some UDs showed the
oscillatory light curves with multiple peaks separated around 10min,
which may indicate the presence of the oscillatory convection. We
discuss our results within the frameworks of two theoretical models:
the monolithic model (Schüssler & Vögler 2006, ApJ, 641, L73)
and the field-free intrusion model (Spruit & Scharmer 2006, A&A,
447, 343).
Title: The Magnetic Landscape of the Sun's Polar Region
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.;
Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo,
M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008ApJ...688.1374T
Altcode: 2008arXiv0807.4631T
We present observations of the magnetic landscape of the polar region
of the Sun that are unprecedented in terms of spatial resolution,
field of view, and polarimetric precision. They were carried out with
the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington
inversion, we find many vertically oriented magnetic flux tubes
with field strengths as strong as 1 kG scattered in latitude between
70° and 90°. They all have the same polarity, consistent with the
global polarity of the polar region. The field vectors are observed to
diverge from the centers of the flux elements, consistent with a view
of magnetic fields that are expanding and fanning out with height. The
polar region is also found to have ubiquitous horizontal fields. The
polar regions are the source of the fast solar wind, which is channeled
along unipolar coronal magnetic fields whose photospheric source is
evidently rooted in the strong-field, vertical patches of flux. We
conjecture that vertical flux tubes with large expansion around the
photospheric-coronal boundary serve as efficient chimneys for Alfvén
waves that accelerate the solar wind.
Title: Magnetic flux cancellation associated with a recurring solar
jet observed with Hinode, RHESSI, and STEREO/EUVI
Authors: Chifor, C.; Isobe, H.; Mason, H. E.; Hannah, I. G.; Young,
P. R.; Del Zanna, G.; Krucker, S.; Ichimoto, K.; Katsukawa, Y.;
Yokoyama, T.
Bibcode: 2008A&A...491..279C
Altcode:
Aims: We study the physical properties of a recurring solar active
region jet observed in X-rays and extreme-ultraviolet (EUV).
Methods: Multi-wavelength data from all three instruments on
board Hinode were analysed. X-ray imaging and spectroscopy of the
microflaring emission associated with the jets was performed with the
Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). Associated
EUV jets were observed with the Sun Earth Connection Coronal and
Heliospheric Investigation (SECCHI)/Extreme Ultraviolet Imager
(EUVI) on board STEREO.
Results: We found a correlation between
recurring magnetic flux cancellation close to a pore, the X-ray jet
emission, and associated Ca II H ribbon brightenings. We estimated the
lower limit for the decrease in magnetic energy associated with the
X-ray jet emission at 3 × 1029 erg. The recurring plasma
ejection was observed simultaneously at EUV and X-ray temperatures,
associated with type III radio bursts and microflaring activity at the
jet footpoint.
Conclusions: The recurring jet (EUV and X-ray)
emissions can be attributed to chromospheric evaporation flows due to
recurring coronal magnetic reconnection. In this process, the estimated
minimum loss in the magnetic energy is sufficient to account for the
total energy required to launch the jet. Movie of Fig. 3 is only
available in electronic form via http://www.aanda.org
Title: Magnetic Fields of the Quiet Sun: A New Quantitative
Perspective From Hinode
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..397...17L
Altcode:
This article summarizes results of studies presented in two papers
already published: Lites et al. (2007a); Lites et al. (2007b). Please
see these for further details.
Title: On-orbit Performance of the Solar Optical Telescope aboard
Hinode
Authors: Ichimoto, K.; Katsukawa, Y.; Tarbell, T.; Shine, R. A.;
Hoffmann, C.; Berger, T.; Cruz, T.; Suematsu, Y.; Tsuneta, S.; Shimizu,
T.; Lites, B. W.
Bibcode: 2008ASPC..397....5I
Altcode: 2008arXiv0804.3248I
On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode
is described with some attention to its unpredicted aspects. In general,
SOT reveals an excellent performance and has been providing outstanding
data. Some unexpected features exist, however, in behaviours of the
focus position, throughput and structural stability. Most of them are
recovered by the daily operation i.e., frequent focus adjustment,
careful heater setting and corrections in data analysis. The
tunable filter contains air bubbles which degrade the data quality
significantly. Schemes for tuning the filter without disturbing the
bubbles have been developed and tested, and some useful procedures
to obtain Dopplergrams and magnetograms are now available. October
and March, when the orbit of satellite becomes nearly perpendicular
to the direction towards the Sun, provide a favourable condition for
continuous runs of the narrow-band filter imager.
Title: Evolution of Magnetic Field and Flow in NOAA 10930 Obtained
by Hinode Observations
Authors: Magara, T.; Katsukawa, Y.; Ichimoto, K.; Tsuneta, S.;
Yokoyama, T.; Nagata, S.; Inoue, S.
Bibcode: 2008ASPC..397..135M
Altcode:
We here present an initial result of investigations into the evolution
of NOAA 10930 obtained by the Solar Optical Telescope on board
Hinode. The fine-scale G-band images associated with three components of
the magnetic field provide useful information on the characteristics
of this active region. We derived three phases characterizing the
evolution of magnetic field toward producing an X-class flare. We
also study the nature of a rapid flow found in this active region by
investigating the configuration of the magnetic field and flow.
Title: High Resolution Observations of Spicules with Hinode/SOT
Authors: Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Shimizu, T.;
Okamoto, T.; Tsuneta, S.; Tarbell, T.; Shine, R. A.
Bibcode: 2008ASPC..397...27S
Altcode:
High time cadence unprecedented images at the limb with Ca II H line
filtergraph from the Solar Optical Telescope (SOT) aboard Hinode
have revealed that a spicule consists of highly dynamic multi-threads
(typically twin) as thin as a few tenths of an arcsecond, and shows
prominent lateral movement or oscillation with rotation on its axis
during its life. This multi-thread structure and lateral motion indicate
that the spicules can be driven by magnetic reconnection at unresolved
spatial scales at their footpoints.
Title: Evolution of Magnetic Fields at the Boundary of the Penumbra
Authors: Kubo, M.; Ichimoto, K.; Shimizu, T.; Lites, B. W.; Tsuneta,
S.; Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Tarbell, T.; Shine,
R. A.; Title, A. M.
Bibcode: 2008ASPC..397...79K
Altcode:
The formation of moving magnetic features (MMFs) separating from the
penumbra were successfully observed with the Solar Optical Telescope
(SOT) aboard the Hinode satellite. We find that bright features in
the outer penumbra are located at the penumbral spines, which have
magnetic fields more vertical than the surroundings, or located at the
MMFs separating from the spines. This suggests that convection in the
outer penumbra is related to the disintegration of the sunspot.
Title: The Properties of Penumbral Microjets - Inclinations and
Possible Potospheric Response
Authors: Jurcak, J.; Katsukawa, Y.
Bibcode: 2008ESPM...12.2.25J
Altcode:
The dependence of penumbral microjets inclination on the position
within penumbra is investigated using the Ca II images taken with Hinode
SOT. The penumbral microjet inclination is increasing towards the outer
edge of the penumbra; from 35 deg at the umbra-penumbra boundary up
to 70 deg at the penumbra/quiet sun boundary. The comparison with the
inclination of photospheric magnetic field suggest that the penumbral
microjet follows the opening magnetic field lines of a vertical flux
tube that creates the sunspot. Another data set of Ca II images with
simultaneous SP measurements is used to study the possible relation
between the penumbral microjets and the downflows observed in middle
of the centre-side penumbra. Some of these downflow patches can be
associated with the Ca II brightenings and might correspond to the
reconnection outflow. As is retrieved from the Stokes inversion, the
downflow preferentially take place in the lower photosphere and this
may provide a constraint on a reconnection site.
Title: The properties of penumbral microjets inclination
Authors: Jurčák, J.; Katsukawa, Y.
Bibcode: 2008A&A...488L..33J
Altcode: 2008arXiv0808.0757J
Aims: We investigate the dependence of penumbral microjets inclination
on the position within penumbra.
Methods: The high cadence
observations taken on 10 November 2006 with the Hinode satellite
through the Ca II H and G-band filters were analysed to determine the
inclination of penumbral microjets. The results were then compared with
the inclination of the magnetic field determined through the inversion
of the spectropolarimetric observations of the same region.
Results: The penumbral microjet inclination is increasing towards
the outer edge of the penumbra. The results suggest that the penumbral
microjet follows the opening magnetic field lines of a vertical flux
tube that creates the sunspot.
Title: Balloon-Borne Hard X-Ray Spectrometer Using CdTe Detectors
Authors: Kobayashi, K.; Tsuneta, S.; Tamura, T.; Kumagai, K.;
Katsukawa, Y.; Kubo, M.; Sakamoto, Y.; Kohara, N.; Yamagami, T.;
Saito, Y.; Mori, K.
Bibcode: 2008SoPh..250..431K
Altcode: 2008SoPh..tmp..132K
Spectroscopic observation of solar flares in the hard X-ray energy
range, particularly the 20 ∼ 100 keV region, is an invaluable tool
for investigating the flare mechanism. This paper describes the design
and performance of a balloon-borne hard X-ray spectrometer using CdTe
detectors developed for solar flare observation. The instrument is a
small balloon payload (gondola weight 70 kg) with sixteen 10×10×0.5
mm CdTe detectors, designed for a 1-day flight at 41 km altitude. It
observes in an energy range of 20−120 keV and has an energy resolution
of 3 keV at 60 keV. The second flight on 24 May 2002 succeeded in
observing a class M1.1 flare.
Title: Erratum: The Analysis of Penumbral Fine Structure Using an
Advanced Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2008PASJ...60..933J
Altcode:
In the article [PASJ 59, S601-S606 (2007)], the word ''CSIC'' was
omitted from the affiliation of Dr. Luis Bellot Rubio. The correct
affiliation is : 2Instituto de Astrofísica de Andalucía
(CSIC), Apdo. de Correos 3004, 18080 Granada, Spain
Title: Giant Chromospheric Anemone Jet Observed with Hinode and
Comparison with Magnetohydrodynamic Simulations: Evidence of
Propagating Alfvén Waves and Magnetic Reconnection
Authors: Nishizuka, N.; Shimizu, M.; Nakamura, T.; Otsuji, K.; Okamoto,
T. J.; Katsukawa, Y.; Shibata, K.
Bibcode: 2008ApJ...683L..83N
Altcode: 2008arXiv0810.3384N
Hinode discovered a beautiful giant jet with both cool and hot
components at the solar limb on 2007 February 9. Simultaneous
observations by the Hinode SOT, XRT, and TRACE 195 Å satellites
revealed that hot (~5 × 106 K) and cool (~104
K) jets were located side by side and that the hot jet preceded the
associated cool jet (~1-2 minutes). A current-sheet-like structure
was seen in optical (Ca II H), EUV (195 Å), and soft X-ray emissions,
suggesting that magnetic reconnection is occurring in the transition
region or upper chromosphere. Alfvén waves were also observed with
Hinode SOT. These propagated along the jet at velocities of ~200
km s-1 with amplitudes (transverse velocity) of ~5-15 km
s-1 and a period of ~200 s. We performed two-dimensional MHD
simulation of the jets on the basis of the emerging flux-reconnection
model, by extending Yokoyama and Shibata's model. We extended the model
with a more realistic initial condition (~106 K corona) and
compared our model with multiwavelength observations. The improvement
of the coronal temperature and density in the simulation model allowed
for the first time the reproduction of the structure and evolution of
both the cool and hot jets quantitatively, supporting the magnetic
reconnection model. The generation and the propagation of Alfvén
waves are also reproduced self-consistently in the simulation model.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008ApJ...681.1677K
Altcode: 2008arXiv0806.0415K
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features that have fields that are stronger and more vertical
than those of their surroundings). These granules that appear in the
outer penumbra often merge with bright features inside the penumbra
that move with the spines as they elongate toward the moat region. This
suggests that convective motions around the penumbral outer boundary are
related to the disintegration of magnetic flux in the sunspot. We also
find that dark penumbral filaments frequently elongate into the moat
region in the vicinity of MMFs that detach from penumbral spines. Such
elongating dark penumbral filaments correspond to nearly horizontal
fields extending from the penumbra. Pairs of MMFs with positive and
negative polarities are sometimes observed along the elongating dark
penumbral filaments. This strongly supports the notion that such
elongating dark penumbral filaments have magnetic fields with a "sea
serpent"-like structure. Evershed flows, which are associated with the
penumbral horizontal fields, may be related to the detachment of the
MMFs from the penumbral spines, as well as to the formation of the MMFs
along the dark penumbral filaments that elongate into the moat region.
Title: Polarization Calibration of the Solar Optical Telescope
onboard Hinode
Authors: Ichimoto, K.; Lites, B.; Elmore, D.; Suematsu, Y.; Tsuneta,
S.; Katsukawa, Y.; Shimizu, T.; Shine, R.; Tarbell, T.; Title, A.;
Kiyohara, J.; Shinoda, K.; Card, G.; Lecinski, A.; Streander, K.;
Nakagiri, M.; Miyashita, M.; Noguchi, M.; Hoffmann, C.; Cruz, T.
Bibcode: 2008SoPh..249..233I
Altcode: 2008SoPh..tmp...69I
The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector
magnetic fields on the Sun through precise spectropolarimetry of
solar spectral lines with a spatial resolution of 0.2 - 0.3 arcsec. A
photometric accuracy of 10−3 is achieved and, after the
polarization calibration, any artificial polarization from crosstalk
among Stokes parameters is required to be suppressed below the level
of the statistical noise over the SOT's field of view. This goal was
achieved by the highly optimized design of the SOT as a polarimeter,
extensive analyses and testing of optical elements, and an end-to-end
calibration test of the entire system. In this paper we review both
the approach adopted to realize the high-precision polarimeter of the
SOT and its final polarization characteristics.
Title: Formation Process of a Light Bridge Revealed with Hinode SOT
Authors: Katsukawa, Yukio
Bibcode: 2008AstHe.101..318K
Altcode:
The Solar Optical Telescope (SOT) on-board Hinode has enabled to
continously observe fine features created by magnetic fields on the
solar surface, and is expected to shed light on longstanding puzzles
on a sunspot. Here presented is an observational study on formation
process of a light bridge. A light bridge is a photospheric structure
dividing a sunspot umbra into two parts, and provides implications on
how strong magnetic flux in a sunspot is broken up by convection.
Title: The Solar Optical Telescope for the Hinode Mission: An Overview
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Otsubo,
M.; Shimizu, T.; Suematsu, Y.; Nakagiri, M.; Noguchi, M.; Tarbell,
T.; Title, A.; Shine, R.; Rosenberg, W.; Hoffmann, C.; Jurcevich,
B.; Kushner, G.; Levay, M.; Lites, B.; Elmore, D.; Matsushita, T.;
Kawaguchi, N.; Saito, H.; Mikami, I.; Hill, L. D.; Owens, J. K.
Bibcode: 2008SoPh..249..167T
Altcode: 2008SoPh..tmp...74T; 2007arXiv0711.1715T
The Solar Optical Telescope (SOT) aboard the Hinode satellite
(formerly called Solar-B) consists of the Optical Telescope Assembly
(OTA) and the Focal Plane Package (FPP). The OTA is a 50-cm
diffraction-limited Gregorian telescope, and the FPP includes the
narrowband filtergraph (NFI) and the broadband filtergraph (BFI), plus
the Stokes Spectro-Polarimeter (SP). The SOT provides unprecedented
high-resolution photometric and vector magnetic images of the
photosphere and chromosphere with a very stable point spread function
and is equipped with an image-stabilization system with performance
better than 0.01 arcsec rms. Together with the other two instruments
on Hinode (the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer
(EIS)), the SOT is poised to address many fundamental questions about
solar magnetohydrodynamics. This paper provides an overview; the
details of the instrument are presented in a series of companion papers.
Title: Frequent Occurrence of High-Speed Local Mass Downflows on
the Solar Surface
Authors: Shimizu, T.; Lites, B. W.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Nagata, S.; Kubo, M.; Shine, R. A.; Tarbell,
T. D.
Bibcode: 2008ApJ...680.1467S
Altcode: 2008arXiv0804.1167S
We report on new spectropolarimetric measurements with simultaneous
filter imaging observation, revealing the frequent appearance of
polarization signals indicating high-speed, probably supersonic,
downflows that are associated with at least three different
configurations of magnetic fields in the solar photosphere. The
observations were carried out with the Solar Optical Telescope on
board the Hinode satellite. High-speed downflows are excited when a
moving magnetic feature is newly formed near the penumbral boundary of
sunspots. Also, a new type of downflows is identified at the edge of
sunspot umbra that lack accompanying penumbral structures. These may
be triggered by the interaction of magnetic fields swept by convection
with well-concentrated magnetic flux. Another class of high-speed
downflows are observed in quiet Sun and sunspot moat regions. These are
closely related to the formation of small concentrated magnetic flux
patches. High-speed downflows of all types are transient time-dependent
mass motions. These findings suggest that the excitation of supersonic
mass flows are one of the key observational features of the dynamical
evolution occurring in magnetic-field fine structures on the solar
surface.
Title: Cooperative Observation of Ellerman Bombs between the Solar
Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope
Authors: Matsumoto, Takuma; Kitai, Reizaburo; Shibata, Kazunari;
Nagata, Shin'ichi; Otsuji, Kenichi; Nakamura, Tahei; Watanabe, Hiroko;
Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Lites, Bruce W.;
Shine, Richard A.; Title, Alan M.
Bibcode: 2008PASJ...60..577M
Altcode:
High-resolution CaIIH broad-band filter images of NOAA10933 on 2007
January 5 were obtained by the Solar Optical Telescope aboard the Hinode
satellite. Many small-scale (∼1") bright points were observed outside
the sunspot and inside the emerging flux region. We identified some of
these bright points with Ellerman bombs (EBs) by using Hα images taken
by the Domeless Solar Telescope at Hida observatory. The sub-arcsec
structures of two EBs seen in CaIIH were studied in detail. Our
observation showed the following two aspects: (1) The CaIIH bright
points identified with EBs were associated with the bipolar magnetic
field structures, as reported by previous studies. (2)The structure
of the CaIIH bright points turned out to consist of the following two
parts: a central elongated bright core (0.7" × 0.5") located along
the magnetic neutral line and a diffuse halo (1.2"×1.8").
Title: The Solar Optical Telescope of Solar-B ( Hinode): The Optical
Telescope Assembly
Authors: Suematsu, Y.; Tsuneta, S.; Ichimoto, K.; Shimizu, T.; Otsubo,
M.; Katsukawa, Y.; Nakagiri, M.; Noguchi, M.; Tamura, T.; Kato, Y.;
Hara, H.; Kubo, M.; Mikami, I.; Saito, H.; Matsushita, T.; Kawaguchi,
N.; Nakaoji, T.; Nagae, K.; Shimada, S.; Takeyama, N.; Yamamuro, T.
Bibcode: 2008SoPh..249..197S
Altcode: 2008SoPh..tmp...26S
The Solar Optical Telescope (SOT) aboard the Solar-B satellite (Hinode)
is designed to perform high-precision photometric and polarimetric
observations of the Sun in visible light spectra (388 - 668 nm)
with a spatial resolution of 0.2 - 0.3 arcsec. The SOT consists of
two optically separable components: the Optical Telescope Assembly
(OTA), consisting of a 50-cm aperture Gregorian with a collimating lens
unit and an active tip-tilt mirror, and an accompanying Focal Plane
Package (FPP), housing two filtergraphs and a spectro-polarimeter. The
optomechanical and optothermal performance of the OTA is crucial to
attain unprecedented high-quality solar observations. We describe in
detail the instrument design and expected stable diffraction-limited
on-orbit performance of the OTA, the largest state-of-the-art solar
telescope yet flown in space.
Title: The intensity contrast of solar granulation: comparing Hinode
SP results with MHD simulations
Authors: Danilovic, S.; Gandorfer, A.; Lagg, A.; Schüssler, M.;
Solanki, S. K.; Vögler, A.; Katsukawa, Y.; Tsuneta, S.
Bibcode: 2008A&A...484L..17D
Altcode: 2008arXiv0804.4230D
Context: The contrast of granulation is an important quantity
characterizing solar surface convection.
Aims: We compare the
intensity contrast at 630 nm, observed using the Spectro-Polarimeter
(SP) aboard the Hinode satellite, with the 3D radiative MHD simulations
of Vögler & Schüssler (2007, A&A, 465, L43).
Methods:
A synthetic image from the simulation is degraded using a theoretical
point-spread function of the optical system, and by considering other
important effects.
Results: The telescope aperture and the
obscuration by the secondary mirror and its attachment spider, reduce
the simulated contrast from 14.4% to 8.5%. A slight effective defocus
of the instrument brings the simulated contrast down to 7.5%, close to
the observed value of 7.0%.
Conclusions: A proper consideration
of the effects of the optical system and a slight defocus, lead to
sufficient degradation of the synthetic image from the MHD simulation,
such that the contrast reaches almost the observed value. The remaining
small discrepancy can be ascribed to straylight and slight imperfections
of the instrument, which are difficult to model. Hence, Hinode SP data
are consistent with a granulation contrast which is predicted by 3D
radiation MHD simulations.
Title: Moat Flow in the Vicinity of Sunspots for Various Penumbral
Configurations
Authors: Vargas Domínguez, S.; Rouppe van der Voort, L.; Bonet,
J. A.; Martínez Pillet, V.; Van Noort, M.; Katsukawa, Y.
Bibcode: 2008ApJ...679..900V
Altcode: 2008arXiv0802.1457V
High-resolution time series of sunspots have been obtained with
the Swedish 1 m Solar Telescope between 2003 and 2006 at different
locations on the solar disk. Proper motions in seven different active
regions have been studied. The analysis was performed by applying local
correlation tracking to every series of sunspots, each of them more than
40 minutes long. The sunspots' shapes include a different variety of
penumbral configurations. We report on the systematic behavior of the
large-scale outflows surrounding the sunspots, commonly known as moat
flows, that are essentially present only when preceded by a penumbra
not tangential but perpendicular to the sunspot border. We present
one case for which this rule appears not to be confirmed. We speculate
that the magnetic neutral line, which is located in the vicinity of the
anomalous region, might be responsible for blocking the outflow. These
new results confirm the systematic and strong relation between the
moat flows and the existence of penumbrae. A comparative statistical
study between moats and standard granulation is also performed.
Title: Emergence of a helical flux rope and prominence formation
Authors: Okamoto, T. J.; Tsuneta, S.; Lites, B. W.; Kubo, M.; Yokoyama,
T.; Berger, T. E.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Shibata,
K.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008AGUSMSP43B..06O
Altcode:
We report a discovery about emergence of a helical flux rope. The
episode may be related to the formation and evolution of an active
region prominence. Statistical studies by previous authors indicate that
numerous prominences have the inverse-polarity configuration suggesting
the helical magnetic configurations. There are two theoretical
models about formation of such a coronal helical magnetic field in
association with prominences: flux rope model and sheared-arcade
model. We have so far no clear observational evidence to support
either model. In order to find a clue about the formation of the
prominence, we had continuous observations of NOAA AR 10953 with the
SOT during 2007 April 28 to May 9. A prominence was located over the
polarity inversion line in the south-east of the main sunspot. These
observations provided us with a time series of vector magnetic fields
on the photosphere under the prominence. We found four new features:
(1) The abutting opposite-polarity regions on the two sides along
the polarity inversion line first grew laterally in size and then
narrowed. (2) These abutting regions contained vertically-weak,
but horizontally-strong magnetic fields. (3) The orientations of
the horizontal magnetic fields along the polarity inversion line on
the photosphere gradually changed with time from a normal- polarity
configuration to an inverse-polarity one. (4) The horizontal-magnetic
field region was blueshifted. These indicate that helical flux rope
emerges from below the photosphere into the corona along the polarity
inversion line under the prominence. We suggest that this supply of a
helical magnetic flux possibly into the corona is related to formation
and maintenance of active-region prominences.
Title: Photospheric Signature of Penumbral Microjets
Authors: Katsukawa, Y.; Jurcak, J.; Ichimoto, K.; Suemtasu, Y.;
Tsuneta, S.; Shimizu, T.; Berger, T. E.; Shine, R. A.; Tarbell, T. D.;
Lites, B. W.
Bibcode: 2008AGUSMSP53A..03K
Altcode:
HINODE Solar Optical Telescope (SOT) discovered ubiquitous occurrence
of fine-scale jetlike activities in penumbral chromospheres, which
are referred to as penumbral microjets. The microjets' small width
of 400 km and short duration of less than 1 min make them difficult
to identify in existing ground-based observations. The apparent
rise velocity is faster than 50km/s and is roughly comparable to
the Alfven speed in the sunspot chromosphere. These properties of
penumbral microjets suggest that magnetic reconnection in uncombed
magnetic field configuration is the most possible cause of penumbral
microjets. In order to understand magnetic configuration associated with
penumbral microjets and prove the chromospheric magnetic reconnection
hypothesis, we investigated relationship between penumbral microjets
seen in CaIIH images and photospheric magnetic fields measured by
the HINODE spectro-polarimeter. We found the inclination angles of
penumbral microjets measured in CaII H images are roughly consistent
with inclination angles of relatively vertical magnetic field
component in uncombed magnetic field configuration. In addition,
strong and transient downflows are observed in the photosphere near
the boundary of a horizontal flux tube associated with a penumbral
microjet. The size of the downflow region is about 300km, which is
close to the width of penumbral microjets seen in CaII H images. The
downflow velocity of several km/s might be a result of an outflow of
chromospheric magnetic reconnection and suffer deceleration due to
the higher density in the photosphere.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode/SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008AGUSMSP31B..01K
Altcode:
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features having fields that are stronger and more vertical
than their surroundings). These granules that appear in the outer
penumbra often merge with bright features inside the penumbra that move
with spines as they elongate toward the moat region. This suggests that
convective motions around the penumbral outer boundary are related to
disintegration of magnetic flux in the sunspot. We also find that dark
penumbral filaments frequently elongate into the moat region in the
vicinity of MMFs that detach from penumbral spines. Such elongating
dark penumbral filaments correspond to nearly horizontal fields
extending from the penumbra. Pairs of MMFs with positive and negative
polarities are sometimes observed along the elongating dark penumbral
filaments. This strongly supports the notion that such elongating dark
penumbral filaments have magnetic fields with a "sea serpent"-like
structure. Evershed flows, which are associated with the penumbral
horizontal fields, may be related to detachment of the MMFs from the
penumbral spines, as well as to the formation of the MMFs along the
dark penumbral filaments that elongate into the moat region.
Title: Formation of Solar Magnetic Flux Tubes with Kilogauss Field
Strength Induced by Convective Instability
Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama,
Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.;
Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco
Suárez, David
Bibcode: 2008ApJ...677L.145N
Altcode:
Convective instability has been a mechanism used to explain
the formation of solar photospheric flux tubes with kG field
strength. However, the turbulence of the Earth's atmosphere has
prevented ground-based observers from examining the hypothesis
with precise polarimetric measurement on the subarcsecond scale
flux tubes. Here we discuss observational evidence of this scenario
based on observations with the Solar Optical Telescope (SOT) aboard
Hinode. The cooling of an equipartition field strength flux tube
precedes a transient downflow reaching 6 km s-1 and the
intensification of the field strength to 2 kG. These observations
agree very well with the theoretical predictions.
Title: Transient horizontal magnetic fields in solar plage regions
Authors: Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2008A&A...481L..25I
Altcode: 2008arXiv0802.1769I
Aims:We report the discovery of isolated, small-scale emerging
magnetic fields in a plage region with the Solar Optical Telescope
aboard Hinode.
Methods: Spectro-polarimetric observations were
carried out with a cadence of 34 s for the plage region located near
disc center. The vector magnetic fields are inferred by Milne-Eddington
inversion.
Results: The observations reveal widespread occurrence
of transient, spatially isolated horizontal magnetic fields. The
lateral extent of the horizontal magnetic fields is comparable to
the size of photospheric granules. These horizontal magnetic fields
seem to be tossed about by upflows and downflows of the granular
convection. We also report an event that appears to be driven by the
magnetic buoyancy instability. We refer to buoyancy-driven emergence
as type 1 and convection-driven emergence as type 2. Although both
events have magnetic field strengths of about 600 G, the filling
factor of type 1 is a factor of two larger than that of type 2.
Conclusions: Our finding suggests that the granular convection in
the plage regions is characterized by a high rate of occurrence of
granular-sized transient horizontal fields.
Title: Suppression of convection around small magnetic concentrations
Authors: Morinaga, S.; Sakurai, T.; Ichimoto, K.; Yokoyama, T.;
Shimojo, M.; Katsukawa, Y.
Bibcode: 2008A&A...481L..29M
Altcode:
Aims: It is well known that convective motions in the photosphere are
suppressed by magnetic fields. However, it has been difficult to study
the interaction between convection and small magnetic features, such
as G-band bright points (GBPs) or pores with polarimetric measurements,
because of the available spatial resolution (~1´´). This situation is
changed by the advent of the Spectro-Polarimeter (SP) aboard the Hinode
satellite, which has 0.3 arcsec spatial resolution.
Methods:
We analyzed the pore and its surrounding region in NOAA 10940 near the
disk center. We obtained the field strength and filling factor through
the Milne-Eddington inversion of the Stokes profiles. We also derived
the line-of-sight velocity by the shift of the line core. Using these
physical parameters, we investigated the physical conditions needed to
suppress the convection.
Results: We found that the convection
is suppressed, not by the strength of the magnetic field itself,
but by high concentration of magnetic flux tubes. We also found that
GBPs and pores are distinguished in terms of the filling factor (f);
f ≃ 0.6 for GBPs and f=0.8-0.9 for pores.
Title: Net circular polarization of sunspots in high spatial
resolution
Authors: Ichimoto, K.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.;
Shimizu, T.; Lites, B. W.; Kubo, M.; Tarbell, T. D.; Shine, R. A.;
Title, A. M.; Nagata, S.
Bibcode: 2008A&A...481L...9I
Altcode:
Context: Net circular polarization (NCP) of spectral lines in
sunspots has been most successfully explained by the presense of
discontinuities in the magnetic field inclination and flow velocity
along the line-of-sight in the geometry of the embedded flux tube model
of penumbrae (Δγ-effect).
Aims: The fine scale structure of
NCP in a sunspot is examined with special attention paid to spatial
relations of the Evershed flow to confirm the validity of the present
interpretation of the NCP of sunspots.
Methods: High resolution
spectro-polarimetric data of a positive-polarity sunspot obtained
by the Solar Optical Telescope aboard Hinode are analysed.
Results: A positive NCP is associated with the Evershed flow
channels in both limb-side and disk center-side penumbrae and with
upflows in the penumbra at disk center. The negative NCP in the disk
center-side penumbra is generated in inter-Evershed flow channels.
Conclusions: The first result is apparently inconsistent with the
current explanation of NCP with the Δγ-effect but rather suggests a
positive correlation between the magnetic field strength and the flow
velocity as the cause of the NCP. The second result serves as strong
evidence for the presence of gas flows in inter-Evershed flow channels.
Title: Hinode SOT Observations of Solar Quiescent Prominence Dynamics
Authors: Berger, Thomas E.; Shine, Richard A.; Slater, Gregory L.;
Tarbell, Theodore D.; Title, Alan M.; Okamoto, Takenori J.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Suematsu, Yoshinori; Tsuneta, Saku; Lites,
Bruce W.; Shimizu, Toshifumi
Bibcode: 2008ApJ...676L..89B
Altcode:
We report findings from multihour 0.2'' resolution movies of
solar quiescent prominences (QPs) observed with the Solar Optical
Telescope (SOT) on the Hinode satellite. The observations verify
previous findings of filamentary downflows and vortices in QPs. SOT
observations also verify large-scale transverse oscillations in QPs,
with periods of 20-40 minutes and amplitudes of 2-5 Mm. The upward
propagation speed of several waves is found to be ~10 km s-1,
comparable to the sound speed of a 10,000 K plasma, implying that
the waves are magnetoacoustic in origin. Most significantly, Hinode
SOT observations reveal that dark, episodic upflows are common in
QPs. The upflows are 170-700 km in width, exhibit turbulent flow,
and rise with approximately constant speeds of ~20 km s-1
from the base of the prominence to heights of ~10-20 Mm. The upflows
are visible in both the Ca II H-line and Hα bandpasses of SOT. The new
flows are seen in about half of the QPs observed by SOT to date. The
dark upflows resemble buoyant starting plumes in both their velocity
profile and flow structure. We discuss thermal and magnetic mechanisms
as possible causes of the plumes.
Title: Emergence of a Helical Flux Rope under an Active Region
Prominence
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2008ApJ...673L.215O
Altcode: 2008arXiv0801.1956O
Continuous observations were obtained of NOAA AR 10953 with the Solar
Optical Telescope (SOT) on board the Hinode satellite from 2007 April
28 to May 9. A prominence was located over the polarity inversion
line (PIL) to the southeast of the main sunspot. These observations
provided us with a time series of vector magnetic fields on the
photosphere under the prominence. We found four features: (1) The
abutting opposite-polarity regions on the two sides along the PIL first
grew laterally in size and then narrowed. (2) These abutting regions
contained vertically weak but horizontally strong magnetic fields. (3)
The orientations of the horizontal magnetic fields along the PIL on
the photosphere gradually changed with time from a normal-polarity
configuration to an inverse-polarity one. (4) The horizontal magnetic
field region was blueshifted. These indicate that helical flux rope
was emerging from below the photosphere into the corona along the PIL
under the preexisting prominence. We suggest that this supply of a
helical magnetic flux to the corona is associated with evolution and
maintenance of active region prominences.
Title: The Horizontal Magnetic Flux of the Quiet-Sun Internetwork
as Observed with the Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ApJ...672.1237L
Altcode:
Observations of very quiet Sun using the Solar Optical
Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft
reveal that the quiet internetwork regions are pervaded by horizontal
magnetic flux. The spatial average horizontal apparent flux density
derived from wavelength-integrated measures of Zeeman-induced linear
polarization is BTapp = 55 Mx cm -2, as
compared to the corresponding average vertical apparent flux density of
| BLapp| = 11 Mx cm -2. Distributions
of apparent flux density are presented. Magnetic fields are organized on
mesogranular scales, with both horizontal and vertical fields showing
"voids" of reduced flux density of a few granules spatial extent. The
vertical fields are concentrated in the intergranular lanes, whereas the
stronger horizontal fields are somewhat separated spatially from the
vertical fields and occur most commonly at the edges of the bright
granules. High-S/N observations from disk center to the limb help
to constrain possible causes of the apparent imbalance between |
BLapp| and BTapp, with
unresolved structures of linear dimension on the surface smaller by at
least a factor of 2 relative to the SOT/SP angular resolution being one
likely cause of this discrepancy. Other scenarios for explaining this
imbalance are discussed. The horizontal fields are likely the source of
the "seething" fields of the quiet Sun discovered by Harvey et al. The
horizontal fields may also contribute to the "hidden" turbulent flux
suggested by studies involving Hanle effect depolarization of scattered
radiation.
Title: Giant chromospheric jet observed with Hinode and magnetic
reconnection model
Authors: Nishizuka, Naoto; Shimizu, Masaki; Nakamura, Tahei; Otsuji,
Kenichi; Okamoto, Takenori; Shibata, Kazunari; Katsukawa, Yukio
Bibcode: 2008cosp...37.2239N
Altcode: 2008cosp.meet.2239N
Heating of the solar chromosphere and corona is one of the long-standing
puzzles in astronomy and also a key to understand the Sun-Earth
connection through solar wind and EUV/X-ray radiation. A solar space
telescope mission Hinode revealed that solar chromosphere is much more
dynamic than had been thought and is full of tiny jets, which may be
a key to resolve the puzzle of chromospheric and coronalheating. It
has long been observed that H-alpha jets called surges often occur in
the chromosphere. They have been believed to be produced by magnetic
reconnection, which is an energy conversion mechanism from magnetic
energy into thermal and kinetic energies of plasma when anti-parallel
magnetic fields encounter and reconnect with each other. Hinode's
new chromospheric observations (with Calcium II H broad band filter)
revealed that jets are ubiquitous in the chromosphere and some of the
jets show evidence of magnetic reconnection. However, there have not
been simultaneous observations of the chromospheric jets at X-ray,
EUV, and Optical (at Calcium II H line) wavelengths until now. Here
we report first multi-wavelength observations of a chromospheric
jet with Solar Optical Telescope (SOT) and X-Ray Telescope (XRT)
on board Hinode and TRACE 195A filter. With its unprecedented high
quality instruments at both optical and X-rays, Hinode discovered a
beautiful, giant jet with both cool (104 K) and hot (5x106 K) components
at the solar limb. TRACE satellite also observed the same jet with
EUV telescope and revealed the existence of both hot (106 K) and cool
(unknown temperature) components. These data set are probably the best
multi-wavelength observations of solar jets until now. We also performed
magnetohydrodynamic simulation of the jet based on the reconnection
model and found that it can explain various observational facts very
well. It has often been argued that some of solar jets are produced by
magnetic reconnection, but previous observations had a limitation on
spatial and temporal resolutions and temperature coverage. Using these
new data and twodimensional magnetohydrodynamic simulations of the jet,
we showed, for the first time, how hot and cool jets are heated and
accelerated during the reconnection, including associated generation of
Alfvén waves. This jet formation dynamics would show a proto-tyep of
reconnection e model of solar jets and can be applied for other small
jets discovered by Hinode, which might heat the chromosphere and corona.
Title: Hinode Observations of Flux Emergence in Quiet and Active
Regions
Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger,
T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.;
Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..383...71L
Altcode:
We review briefly the observational understanding of emergence of
flux in both the quiet Sun and active regions in the light of first
results from the joint Japan/US/UK Hinode mission. That spacecraft
is now providing us with our first continuous, high resolution
measurements of the photospheric vector magnetic field, along with
high resolution observations of the thermal and dynamic properties
of the chromosphere and corona. This review is intended to present a
few very early results and to highlight the potential for discovery
offered by this extraordinary new mission. The discovery of ubiquitous
horizontal magnetic flux in the quiet internetwork regions is presented.
Title: Photospheric activities inside sunspots and their relationship
with heating of the upper atmosphere
Authors: Katsukawa, Yukio
Bibcode: 2008cosp...37.1466K
Altcode: 2008cosp.meet.1466K
HINODE Solar Optical Telescope (SOT) allows us to see photospheric
magnetic structures and their temporal evolution with stable and
uniform image quality. A sunspot especially provides us with a unique
site to understand interaction between very stong magnetic fields and
convective flows, and exhibits various kinds of magnetic activties:
Continual inward migration of leading edges of penumbral filaments,
emergence of umbral dots in a peripheral region of an umbra, formation
of a light bridge, and rapid motion of umbral dots associated with
the formation of a light bridge, etc. Chromospheric activities are
also observed directly associated with these photospheric magnetic
activities. Penumbral microjets, which are newly discoverd by HINODE as
thin and transient jetlike activities in the penumbral chromospheres,
are mostly found near a leading edge of penumbral filaments migrating
inward to an umbra. Surges are sometimes observed above a light
bridge. It is still an open question how these photospheric and
chromospheric activities influence the corona. Motion of umbral dots are
observed not only in a peripherial region of an umbra but in deep insdie
an umbra. The proper motion of central umbral dots is about 0.1 - 0.5
km/s, which is slower than that of the peripheral ones. If the motion
of the umbral dots takes along magnetic field lines, it should provide
substantial amount of Poynting flux to the upper atmosphere by shaking
very strong magnetic field lines inside sunspots even with such a slow
velocity. Nevertheless, the corona above a sunspot umbra is generally
dark in X-rays, which implys no significant heating there. The observed
motion of the umbral dots does not necessarily mean the motion of
magnetic field lines, but can be the motion of the hot gas penetrating
into the strongly magnetized atmosphere from the subphotosphere along
a fiele-free gap, which might explain less heating above sunspot umbrae.
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
Bibcode: 2007AGUFMSH52C..06S
Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
Title: Small-Scale Jetlike Features in Penumbral Chromospheres
Authors: Katsukawa, Y.; Berger, T. E.; Ichimoto, K.; Lites, B. W.;
Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.;
Title, A. M.; Tsuneta, S.
Bibcode: 2007Sci...318.1594K
Altcode:
We observed fine-scale jetlike features, referred to as penumbral
microjets, in chromospheres of sunspot penumbrae. The microjets
were identified in image sequences of a sunspot taken through a Ca II
H-line filter on the Solar Optical Telescope on board the Japanese solar
physics satellite Hinode. The microjets’ small width of 400 kilometers
and short duration of less than 1 minute make them difficult to identify
in existing observations. The microjets are possibly caused by magnetic
reconnection in the complex magnetic configuration in penumbrae and
have the potential to heat the corona above a sunspot.
Title: Chromospheric Alfvénic Waves Strong Enough to Power the
Solar Wind
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Schrijver, C. J.; Title, A. M.; Shine, R. A.;
Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.;
Nagata, S.
Bibcode: 2007Sci...318.1574D
Altcode:
Alfvén waves have been invoked as a possible mechanism for the heating
of the Sun's outer atmosphere, or corona, to millions of degrees and
for the acceleration of the solar wind to hundreds of kilometers per
second. However, Alfvén waves of sufficient strength have not been
unambiguously observed in the solar atmosphere. We used images of
high temporal and spatial resolution obtained with the Solar Optical
Telescope onboard the Japanese Hinode satellite to reveal that the
chromosphere, the region sandwiched between the solar surface and
the corona, is permeated by Alfvén waves with strong amplitudes on
the order of 10 to 25 kilometers per second and periods of 100 to
500 seconds. Estimates of the energy flux carried by these waves and
comparisons with advanced radiative magnetohydrodynamic simulations
indicate that such Alfvén waves are energetic enough to accelerate
the solar wind and possibly to heat the quiet corona.
Title: Chromospheric Anemone Jets as Evidence of Ubiquitous
Reconnection
Authors: Shibata, Kazunari; Nakamura, Tahei; Matsumoto, Takuma; Otsuji,
Kenichi; Okamoto, Takenori J.; Nishizuka, Naoto; Kawate, Tomoko;
Watanabe, Hiroko; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo;
Nozawa, Satoshi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi;
Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Berger,
Thomas E.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M.
Bibcode: 2007Sci...318.1591S
Altcode: 2008arXiv0810.3974S
The heating of the solar chromosphere and corona is a long-standing
puzzle in solar physics. Hinode observations show the ubiquitous
presence of chromospheric anemone jets outside sunspots in active
regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers
long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their
velocity is 10 to 20 kilometers per second. These small jets have an
inverted Y-shape, similar to the shape of x-ray anemone jets in the
corona. These features imply that magnetic reconnection similar to that
in the corona is occurring at a much smaller spatial scale throughout
the chromosphere and suggest that the heating of the solar chromosphere
and corona may be related to small-scale ubiquitous reconnection.
Title: Twisting Motions of Sunspot Penumbral Filaments
Authors: Ichimoto, K.; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Lites, B. W.;
Kubo, M.; Nagata, S.
Bibcode: 2007Sci...318.1597I
Altcode:
The penumbra of a sunspot is composed of numerous thin, radially
extended, bright and dark filaments carrying outward gas flows
(the Evershed flow). Using high-resolution images obtained by the
Solar Optical Telescope aboard the solar physics satellite Hinode, we
discovered a number of penumbral bright filaments revealing twisting
motions about their axes. These twisting motions are observed only
in penumbrae located in the direction perpendicular to the symmetry
line connecting the sunspot center and the solar disk center, and
the direction of the twist (that is, lateral motions of intensity
fluctuation across filaments) is always from limb side to disk-center
side. Thus, the twisting feature is not an actual twist or turn of
filaments but a manifestation of dynamics of penumbral filaments with
three-dimensional radiative transfer effects.
Title: Continuous Plasma Outflows from the Edge of a Solar Active
Region as a Possible Source of Solar Wind
Authors: Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku,
Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.;
Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito;
Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay
A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto;
Shimizu, Toshifumi; Nakatani, Ichiro
Bibcode: 2007Sci...318.1585S
Altcode:
The Sun continuously expels a huge amount of ionized material into
interplanetary space as the solar wind. Despite its influence on the
heliospheric environment, the origin of the solar wind has yet to
be well identified. In this paper, we report Hinode X-ray Telescope
observations of a solar active region. At the edge of the active region,
located adjacent to a coronal hole, a pattern of continuous outflow of
soft-x-ray emitting plasmas was identified emanating along apparently
open magnetic field lines and into the upper corona. Estimates of
temperature and density for the outflowing plasmas suggest a mass
loss rate that amounts to ~1/4 of the total mass loss rate of the
solar wind. These outflows may be indicative of one of the solar wind
sources at the Sun.
Title: Hinode SOT observations of plume upflows and cascading
downflows in quiescent solar prominences
Authors: Berger, T.; Shine, R.; Slater, G.; Tarbell, T.; Title, A.;
Lites, B.; Tsuneta, S.; Okamoto, T. J.; Ichimoto, K.; Katsukawa, Y.;
Sekii, T.; Suematsu, Y.; Shimizu, T.
Bibcode: 2007AGUFMSH53A1065B
Altcode:
We present several Hinode SOT filtergram movies of quiescent solar
prominences that show newly discovered "plume-like" upflows and
cascading "waterfall-like" downflows that persist for the entire
multi-hour duration of the observations. The flow speeds are on the
order of 10 km/sec with typical widths of 400-700 km. Preliminary
calculations show that if the upflows are buoyancy driven, the
associated thermal perturbation is on the order of 10,000 K, sufficient
to explain the dark appearance of the upflows in the interference
filter passbands. In addition we observe rotational vortices and
body oscillations within the prominences. These new observations
challenge current magnetostatic models of solar prominences by showing
that prominence plasmas are in constant motion, often in directions
perpendicular to the magnetic field lines proposed by the models. TRACE,
Hinode/EIS, and Hinode/XRT observations are used to investigate the
differential topology of the flows across temperature regimes.
Title: Coronal Transverse Magnetohydrodynamic Waves in a Solar
Prominence
Authors: Okamoto, T. J.; Tsuneta, S.; Berger, T. E.; Ichimoto, K.;
Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shibata, K.; Shimizu, T.;
Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2007Sci...318.1577O
Altcode: 2008arXiv0801.1958O
Solar prominences are cool 104 kelvin plasma clouds
supported in the surrounding 106 kelvin coronal plasma by
as-yet-undetermined mechanisms. Observations from Hinode show fine-scale
threadlike structures oscillating in the plane of the sky with periods
of several minutes. We suggest that these represent Alfvén waves
propagating on coronal magnetic field lines and that these may play
a role in heating the corona.
Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of
Hinode Measurements
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata,
S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2007ApJ...670L..61O
Altcode: 2007arXiv0710.1405O
We analyze Fe I 630 nm observations of the quiet Sun at disk center
taken with the spectropolarimeter of the Solar Optical Telescope aboard
the Hinode satellite. A significant fraction of the scanned area,
including granules, turns out to be covered by magnetic fields. We
derive field strength and inclination probability density functions from
a Milne-Eddington inversion of the observed Stokes profiles. They show
that the internetwork consists of very inclined, hG fields. As expected,
network areas exhibit a predominance of kG field concentrations. The
high spatial resolution of Hinode's spectropolarimetric measurements
brings to an agreement the results obtained from the analysis of
visible and near-infrared lines.
Title: Center-to-Limb Variation of Stokes V Asymmetries in Solar
Pores Observed with the Hinode Spectro-Polarimeter
Authors: Morinaga, Shuji; Nagata, Shin'ichi; Ichimoto, Kiyoshi;
Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu,
Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.;
Lites, Bruce; Kubo, Masahito; Sakurai, Takashi
Bibcode: 2007PASJ...59S.613M
Altcode:
Here we present spectro-polarimetric measurements of several pores
and the surrounding regions taken with the Solar Optical Telescope
aboard Hinode at various viewing angles. We analyzed the Stokes V
area asymmetry, and confirmed that it is depressed at the center of
the pores, while it shows large positive values (a blue lobe larger
than a red lobe) in the surrounding area; this is consistent with a
previous report. In addition to this ring of positive asymmetry, we
found regions of alternating positive and negative area asymmetries
when weak V regions were observed near the solar limb. The positive
asymmetry occurs on the disk-center side and the negative asymmetry
on the limb side of the magnetic concentrations. These center-to-limb
variations of the Stokes V area asymmetry can be interpreted as being
a systematic inflow of plasma into the magnetic concentrations from
their surroundings.
Title: Initial Results on Line-of-Sight Field Calibrations of SP/NFI
Data Taken by SOT/Hinode
Authors: Chae, Jongchul; Moon, Yong-Jae; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell,
Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata,
Shin'ichi; Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.619C
Altcode:
We present initial results on the line-of-sight field calibration
of the two kinds of Stokes I and V data taken by the Solar Optical
Telescope on the satellite Hinode: spectral profiles of Stokes I and V
parameters recorded on the Spectro-polarimeter (SP), and monochromatic
images of the same parameters recorded on the Narrow-band Filter Imager
(NFI). By applying the center-of-gravity method to the SP data of
AR10930 taken on 2006 December 11, we determined the line-of-sight field
at every location in the active region. As a result, we found that the
line-of-sight field strength ranges up to 2kG in plages, even without
taking into account the filling factor, and up to 3.5kG or higher values
inside the umbra of the major sunspot. We calibrated the NFI data in
reference to the field determined from the SP data. In regions outside
the sunspots and the penumbral regions, we adopted a linear relation,
B|| = βV / I, between the circular polarization, V / I,
and the line-of-sight field strength, B||, and obtained β =
23.5kG in regions outside the sunspots, and β = 12.0kG in penumbral
regions. In umbral regions of sunspots, a first-order polynomial was
adopted to model the reversal of the polarization signal over the
field strength.
Title: Response of the Solar Atmosphere to Magnetic Flux Emergence
from Hinode Observations
Authors: Li, Hui; Sakurai, Takashi; Ichimito, Kiyoshi; Suematsu,
Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine,
Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo,
Masahito; Nagata, Shin'ichi; Kotoku, Jun; Shibasaki, Kiyoto; Saar,
Steven H.; Bobra, Monica
Bibcode: 2007PASJ...59S.643L
Altcode:
No abstract at ADS
Title: Initial Helioseismic Observations by Hinode/SOT
Authors: Sekii, Takashi; Kosovichev, Alexander G.; Zhao, Junwei;
Tsuneta, Saku; Shibahashi, Hiromoto; Berger, Thomas E.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2007PASJ...59S.637S
Altcode: 2007arXiv0709.1806S
Results from initial helioseismic observations by the Solar Optical
Telescope on-board Hinode are reported. It has been demonstrated
that intensity oscillation data from the Broadband Filter Imager
can be used for various helioseismic analyses. The k - ω power
spectra, as well as the corresponding time-distance cross-correlation
function, which promise high-resolution time-distance analysis below
the 6-Mm travelling distance, were obtained for G-band and CaII-H
data. Subsurface supergranular patterns were observed from our first
time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and
the time-distance diagram is extended to much shorter travel distances
and times than were observed before, thus revealing great potential
for high-resolution helioseismic observations from Hinode.
Title: Magnetic Feature and Morphological Study of X-Ray Bright
Points with Hinode
Authors: Kotoku, Jun'ichi; Kano, Ryouhei; Tsuneta, Saku; Katsukawa,
Yukio; Shimizu, Toshifumi; Sakao, Taro; Shibazaki, Kiyoto; Deluca,
Edward E.; Korreck, Kelly E.; Golub, Leon; Bobra, Monica
Bibcode: 2007PASJ...59S.735K
Altcode:
We observed X-ray bright points (XBPs) in a quiet region of the Sun
with the X-Ray Telescope (XRT) aboard the Hinode satellite on 2006
December 19. XRT's high-resolution X-ray images revealed many XBPs with
complicated structure and evolving dramatically with time. Almost all
of the dynamic eruptions in the quiet region were composed of XBPs,
and they had either loop or multiloop shapes, as is observed in larger
flares. Brightening XBPs had strong magnetic fields with opposite
polarities near their footpoints. While we have found a possible
example of associated magnetic cancellation, other XBPs brighten and
fade without any associated movement of the photospheric magnetic field.
Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux
and the ``Hidden Turbulent Magnetic Flux''
Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger,
Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title,
Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu,
Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.571L
Altcode:
We present observations of magnetic fields of the very quiet Sun
near disk center using the Spectro-Polarimeter of the Solar Optical
Telescope aboard the Hinode satellite. These observations reveal for
the first time the ubiquitous presence of horizontal magnetic fields in
the internetwork regions. The horizontal fields are spatially distinct
from the vertical fields, demonstrating that they are not arising mainly
from buffeting of vertical flux tubes by the granular convection. The
horizontal component has an average ``apparent flux density'' of
55Mxcm-2 (assuming the horizontal field structures are
spatially resolved), in contrast to the average apparent vertical flux
density of 11Mxcm-2. The vertical fields reside mainly in
the intergranular lanes, whereas the horizontal fields occur mainly
over the bright granules, with a preference to be near the outside
edge of the bright granules. The large apparent imbalance of vertical
and horizontal flux densities is discussed, and several scenarios are
presented to explain this imbalance.
Title: Strategy for the Inversion of Hinode Spectropolarimetric
Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.837O
Altcode: 2007arXiv0709.2033O
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by Hinode in the quiet Sun. The
Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We
discuss the need to consider a local stray-light contamination to
account for the effects of telescope diffraction. The strategy is
applied to observations of a wide quiet Sun area at disk center. Using
these data we examine the influence of noise and initial guess models
in the inversion results. Our analysis yields the distributions of
magnetic field strengths and stray-light factors. They show that quiet
Sun internetwork regions consist mainly of hG fields with stray-light
contamination of about 0.8.
Title: Hinode Calibration for Precise Image Co-Alignment between
SOT and XRT (2006 November-2007 April)
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Matsuzaki, Keiichi;
Ichimoto, Kiyoshi; Kano, Ryohei; Deluca, Edward E.; Lundquist,
Loraine L.; Weber, Mark; Tarbell, Theodore D.; Shine, Richard A.;
Sôma, Mitsuru; Tsuneta, Saku; Sakao, Taro; Minesugi, Kenji
Bibcode: 2007PASJ...59S.845S
Altcode: 2007arXiv0709.4098S
To understand the physical mechanisms for activity and heating in
the solar atmosphere, the magnetic coupling from the photosphere
to the corona is an important piece of information from the Hinode
observations, and therefore precise positional alignment is required
among the data acquired by different telescopes. The Hinode spacecraft
and its onboard telescopes were developed to allow us to investigate
magnetic coupling with co-alignment accuracy better than 1". Using
the Mercury transit observed on 2006 November 8 and co-alignment
measurements regularly performed on a weekly basis, we have determined
the information necessary for precise image co-alignment, and have
confirmed that co-alignment better than 1" can be realized between
Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our
baseline co-alignment method. This paper presents results from the
calibration for precise co-alignment of CCD images from SOT and XRT.
Title: Hinode Observations of a Vector Magnetic Field Change
Associated with a Flare on 2006 December 13
Authors: Kubo, Masahito; Yokoyama, Takaaki; Katsukawa, Yukio; Lites,
Bruce; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Nagata, Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.;
Title, Alan M.; Elmore David
Bibcode: 2007PASJ...59S.779K
Altcode: 2007arXiv0709.2397K
Continuous observations of the flare productive active region 10930
were successfully carried out with the Solar Optical Telescope aboard
the Hinode spacecraft during 2006 December 6 to 19. We focused on the
evolution of photospheric magnetic fields in this active region, and the
magnetic field properties at the site of the X3.4 class flare, using
a time series of vector field maps with high spatial resolution. The
X3.4 class flare occurred on 2006 December 13 at the apparent
collision site between the large, opposite polarity umbrae. Elongated
magnetic structures with alternatingly positive and negative polarities
resulting from flux emergence appeared one day before the flare in the
collision site penumbra. Subsequently, the polarity inversion line
at the collision site became very complicated. The number of bright
loops in CaII H increased during the formation of these elongated
magnetic structures. Flare ribbons and bright loops evolved along
the polarity inversion line and one footpoint of the bright loop was
located in a region having a large departure of the field azimuth angle
with respect to its surroundings. SOT observations with high spatial
resolution and high polarization precision revealed temporal change in
the fine structure of magnetic fields at the flare site: some parts of
the complicated polarity inversion line then disappeared, and in those
regions the azimuth angle of the photospheric magnetic field changed by
about 90°, becoming more spatially uniform within the collision site.
Title: The Analysis of Penumbral Fine Structure Using an Advanced
Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2007PASJ...59S.601J
Altcode: 2007arXiv0707.1560J
We present a method to study the penumbral fine structure using data
obtained by the spectropolarimeter on board Hinode. For the first
time, the penumbral filaments can be considered as being resolved in
spectropolarimetric measurements. This enables us to use inversion
codes with only one-component model atmospheres, and thus to assign
the obtained stratifications of the plasma parameters directly to the
penumbral fine structure. This approach was applied to the limb-side
part of the penumbra in the active region NOAA10923. Preliminary results
show a clear dependence of the plasma parameters on the continuum
intensity in the inner penumbra, i.e., a weaker and horizontal magnetic
field along with an increased line-of-sight velocity are found in the
low layers of the bright filaments. The results in the mid penumbra
are ambiguous, and future analyses are necessary to unveil the magnetic
field structure and other plasma parameters there.
Title: Fine-Scale Structures of the Evershed Effect Observed by the
Solar Optical Telescope aboard Hinode
Authors: Ichimoto, Kiyoshi; Shine, Richard A.; Lites, Bruce; Kubo,
Masahito; Shimizu, Toshifumi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Tarbell, Theodore D.; Title, Alan M.; Nagata,
Shin'ichi; Yokoyama, Takaaki; Shimojo, Masumi
Bibcode: 2007PASJ...59S.593I
Altcode:
The small-scale structure of the Evershed effect is being studied
using data obtained by the Spectropolarimeter and the Broadband Filter
Imager of the Solar Optical Telescope aboard Hinode. We find that the
Evershed flow starts at the leading edge of inwardly migrating bright
penumbral grains, and turns to nearly a horizontal flow preferentially
in the dark lanes of the penumbra. A number of small elongated regions
that have an upward motion of ∼ 1kms-1 are found in the
deep photosphere distributed over the penumbra. They are cospatial
with bright grains and have relatively horizontal magnetic fields. A
number of patches having a strong downward motion associated with the
opposite magnetic polarity from the sunspot are also found in the mid
and outer penumbra. They could be identified as foot points of the
Evershed flow channels, though the identification of individual pairs
is not straightforward. Our results provide strong support for some
recent findings from ground-based high-resolution observations, and
are in general agreement with the well-known picture of the uncombed
structure of the penumbra, in which the penumbrae consist of rising
flux tubes carrying nearly horizontal Evershed flows embedded in more
vertical background magnetic fields.
Title: Flare Ribbons Observed with G-band and FeI 6302Å, Filters
of the Solar Optical Telescope on Board Hinode
Authors: Isobe, Hiroaki; Kubo, Masahito; Minoshima, Takashi; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Tarbell, Theodore D.; Tsuneta, Saku; Berger,
Thomas E.; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Title, Alan M.
Bibcode: 2007PASJ...59S.807I
Altcode: 2007arXiv0711.3946I
The Solar Optical Telescope (SOT) on board the Hinode satellite observed
an X3.4 class flare on 2006 December 13. A typical two-ribbon structure
was observed, not only in the chromospheric CaII H line, but also in
the G-band and FeI 6302Å line. The high-resolution, seeing-free images
achieved by SOT revealed, for the first time, sub-arcsec fine structures
of the ``white light'' flare. The G-band flare ribbons on sunspot
umbrae showed a sharp leading edge, followed by a diffuse inside,
as well as a previously known core-halo structure. The underlying
structures, such as umbral dots, penumbral filaments, and granules,
were visible in the flare ribbons. Assuming that the sharp leading
edge was directly heated by a particle beam and the diffuse parts were
heated by radiative back-warming, we estimated the depth of the diffuse
flare emission using an intensity profile of the flare ribbon. We found
that the depth of the diffuse emission was about 100km or less from
the height of the source of radiative back-warming. The flare ribbons
were also visible in the Stokes-V images of FeI 6302Å, as a transient
polarity reversal. This is probably related to a ``magnetic transient''
reported in the literature. The intensity increase in Stokes-I images
indicates that the FeI 6302Å line was significantly deformed by the
flare, which may cause such a magnetic transient.
Title: Small-Scale Magnetic-Flux Emergence Observed with Hinode
Solar Optical Telescope
Authors: Otsuji, Kenichi; Shibata, Kazunari; Kitai, Reizaburo; Ueno,
Satoru; Nagata, Shin'ichi; Matsumoto, Takuma; Nakamura, Tahei;
Watanabe, Hiroko; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto,
Kiyoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.;
Lites, Bruce; Shine, Richard A.; Title Alan M.
Bibcode: 2007PASJ...59S.649O
Altcode: 2007arXiv0709.3207O
We observed small-scale magnetic-flux emergence in a sunspot moat region
by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We
analyzed filtergram images observed at wavelengths of Fe 6302Å, G band,
and CaII H. In Stokes I images of Fe 6302Å, emerging magnetic flux was
recognized as dark lanes. In the G band, they showed to be their shapes
almost the same as in Stokes I images. These magnetic fluxes appeared
as dark filaments in CaII H images. Stokes V images of Fe 6302Å showed
pairs of opposite polarities at footpoints of each filament. These
magnetic concentrations were identified to correspond to bright points
in G band/CaII H images. From an analysis of time-sliced diagrams, we
derived the following properties of emerging flux, which are consistent
with those of previous studies: (1) Two footpoints separate each other
at a speed of 4.2kms-1 during the initial phase of evolution,
and decrease to about 1kms-1 10minutes later. (2) CaII H
filaments appear almost simultaneously with the formation of dark lanes
in Stokes I in an observational cadence of 2minutes. (3) The lifetime
of the dark lanes in the Stokes I and G band is 8minutes, while that
of Ca filament is 12minutes. An interesting phenomena was observed,
that an emerging flux tube expanded laterally in the photosphere with a
speed of 3.8kms-1. A discussion on the horizontal expansion
of the flux tube is given with refernce to previous simulation studies.
Title: Observations of Sunspot Oscillations in G Band and CaII H
Line with Solar Optical Telescope on Hinode
Authors: Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.;
Shibahashi, Hiromoto; Tsuneta, Saku; Ichimoto, Kiyoshi; Katsukawa,
Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.631N
Altcode: 2007arXiv0709.0569N
Exploiting high-resolution observations made by the Solar Optical
Telescope on board Hinode, we investigate the spatial distribution
of the power spectral density of the oscillatory signal in and around
the active region NOAA 10935. The G-band data show that in the umbra
the oscillatory power is suppressed in all frequency ranges. On
the other hand, in CaII H intensity maps oscillations in the umbra,
so-called umbral flashes, are clearly seen with the power peaking around
5.5mHz. The CaII H power distribution shows the enhanced elements with
the spatial scale of the umbral flashes over most of the umbra, but
there is a region with suppressed power at the center of the umbra. The
origin and property of this node-like feature remain unexplained.
Title: Hinode SP Vector Magnetogram of AR10930 and Its
Cross-Comparison with MDI
Authors: Moon, Yong-Jae; Kim, Yeon-Han; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Chae, Jongchul; Cho, Kyung Suk; Bong,
Suchan; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimojo,
Masumi; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.;
Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi;
Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.625M
Altcode:
We present one Hinode Spectropolarimeter (SP) magnetogram of AR 10930
that produced several major flares. The inversion from Stokes profiles
to magnetic field vectors was made using the standard Milne-Eddington
code. We successfully applied the Uniform Shear Method for resolving
the 180° ambiguity to the magnetogram. The inversion gave very strong
magnetic field strengths (near 4500 gauss) for a small portion of area
in the umbra. Considering that the observed V-profile of 6301.5Å was
well-fitted as well as a direct estimation of the Zeeman splitting
results in 4300-4600 gauss, we think that the field strengths
should not be far from the actual value. A cross-comparison of the
Hinode SP and SOHO MDI high resolution flux densities shows that the
MDI flux density could be significantly underestimated by about a
factor of two. In addition, it has a serious negative correlation
(the so-called Zeeman saturation effect) with the Hinode SP flux
density for umbral regions. Finally, we could successfully obtain
a recalibrated MDI magnetogram that has been corrected for the
Zeeman saturation effect using not only a pair of MDI intensity and
magnetogram data simultaneously observed, but also the relationship
from the cross-comparison between the Hinode SP and MDI flux densities.
Title: Formation Process of a Light Bridge Revealed with the Hinode
Solar Optical Telescope
Authors: Katsukawa, Yukio; Yokoyama, Takaaki; Berger, Thomas E.;
Ichimoto, Kiyoshi; Kubo, Masahito; Lites, Bruce; Nagata, Shin'ichi;
Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell,
Theodore D.; Title, Alan M.; Tsuneta, Saku
Bibcode: 2007PASJ...59S.577K
Altcode: 2007arXiv0709.2527K
The Solar Optical Telescope (SOT) on-board Hinode successfully and
continuously observed the formation process of a light bridge in a
matured sunspot of the NOAA active region 10923 for several days with
high spatial resolution. During its formation, many umbral dots were
observed to be emerging from the leading edges of penumbral filaments,
and rapidly intruding into the umbra. The precursor of the light bridge
formation was also identified as a relatively slow inward motion of
the umbral dots, which emerged not near the penumbra, but inside the
umbra. The spectro-polarimeter on SOT provided physical conditions in
the photosphere around the umbral dots and the light bridges. We found
that the light bridges and the umbral dots had significantly weaker
magnetic fields associated with upflows relative to the core of the
umbra, which implies that there was hot gas with weak field strength
penetrating from the subphotosphere to near the visible surface inside
those structures. There needs to be a mechanism to drive the inward
motion of the hot gas along the light bridges. We suggest that the
emergence and the inward motion are triggered by a buoyant penumbral
flux tube as well as subphotospheric flow crossing the sunspot.
Title: Umbral Fine Structures in Sunspots Observed with Hinode Solar
Optical Telescope
Authors: Kitai, Reizaburo; Watanabe, Hiroko; Nakamura, Tahei; Otsuji,
Ken-ichi; Matsumoto, Takuma; UeNo, Satoru; Nagata, Shin'ichi; Shibata,
Kazunari; Muller, Richard; Ichimoto, Kiyoshi; Tsuneta, Saku; Suematsu,
Yoshinori; Katsukawa, Yukio; Shimizu, Toshifumi; Tarbell, Theodore D.;
Shine, Richard A.; Title, Alan M.; Lites, Bruce
Bibcode: 2007PASJ...59S.585K
Altcode: 2007arXiv0711.3266K
A high resolution imaging observation of a sunspot umbra was made with
the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the
blue and green continua were taken during three consecutive days. The
umbra consisted of a dark core region, several diffuse components,
and numerous umbral dots. We derived basic properties of umbral dots
(UDs), especially their temperatures, lifetimes, proper motions,
spatial distribution, and morphological evolution. The brightness
of UDs is confirmed to depend on the brightness of their surrounding
background. Several UDs show fission and fusion. Thanks to the stable
condition of the space observation, we could for the first time follow
the temporal behavior of these events. The derived properties of the
internal structure of the umbra are discussed from the viewpoint of
magnetoconvection in a strong magnetic field.
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.699H
Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
Title: Can High Frequency Acoustic Waves Heat the Quiet Sun
Chromosphere?
Authors: Carlsson, Mats; Hansteen, Viggo H.; de Pontieu, Bart;
McIntosh, Scott; Tarbell, Theodore D.; Shine, Dick; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Shimizu,
Toshifumi; Nagata, Shin'ichi
Bibcode: 2007PASJ...59S.663C
Altcode: 2007arXiv0709.3462C
We use Hinode/SOT Ca II H-line and blue continuum broadband observations
to study the presence and power of high frequency acoustic waves at
high spatial resolution. We find that there is no dominant power at
small spatial scales; the integrated power using the full resolution of
Hinode (0.05'' pixels, 0.16'' resolution) is larger than the power in
the data degraded to 0.5'' pixels (TRACE pixel size) by only a factor
of 1.2. At 20 mHz the ratio is 1.6. Combining this result with the
estimates of the acoustic flux based on TRACE data of Fossum &
Carlsson (2006), we conclude that the total energy flux in acoustic
waves of frequency 5-40 mHz entering the internetwork chromosphere of
the quiet Sun is less than 800 W m$^{-2}$, inadequate to balance the
radiative losses in a static chromosphere by a factor of five.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields with Hinode/SOT
Authors: Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Nagata,
Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.;
Frank, Zoe A.; Lites, Bruce; Elmore, David
Bibcode: 2007PASJ...59S.607K
Altcode: 2007arXiv0709.1853K
Vector magnetic fields of moving magnetic features (MMFs) were well
observed with the Solar Optical Telescope (SOT) aboard the Hinode
satellite. We focused on the evolution of three MMFs with the SOT in
this study. We found that an MMF having relatively vertical fields
with the same polarity as the sunspot was detached from the penumbra
around the granules appearing in the outer penumbra. This suggests
that granular motions in the outer penumbra are responsible for
disintegration of the sunspot. Two MMFs with polarity opposite to
the sunspot are located around the outer edge of horizontal fields
extending from the penumbra. This is evidence that the MMFs with
polarity opposite to the sunspot are the prolongation of penumbral
horizontal fields. Redshifts larger than the sonic velocity in the
photosphere are detected for some of the MMFs with polarity opposite
to the sunspot.
Title: A Tale of Two Spicules: The Impact of Spicules on the Magnetic
Chromosphere
Authors: de Pontieu, Bart; McIntosh, Scott; Hansteen, Viggo H.;
Carlsson, Mats; Schrijver, Carolus J.; Tarbell, Theodore D.; Title,
Alan M.; Shine, Richard A.; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Nagata,
Shin'ichi
Bibcode: 2007PASJ...59S.655D
Altcode: 2007arXiv0710.2934D
We use high-resolution observations of the Sun in CaIIH (3968Å)
from the Solar Optical Telescope on Hinode to show that there are
at least two types of spicules that dominate the structure of the
magnetic solar chromosphere. Both types are tied to the relentless
magnetoconvective driving in the photosphere, but have very different
dynamic properties. ``Type-I'' spicules are driven by shock waves
that form when global oscillations and convective flows leak into
the upper atmosphere along magnetic field lines on 3--7minute
timescales. ``Type-II'' spicules are much more dynamic: they form
rapidly (in ∼ 10s), are very thin (≤ 200 km wide), have lifetimes
of 10-150s (at any one height), and seem to be rapidly heated to
(at least) transition region temperatures, sending material through
the chromosphere at speeds of order 50--150kms-1. The
properties of Type II spicules suggest a formation process that is
a consequence of magnetic reconnection, typically in the vicinity
of magnetic flux concentrations in plage and network. Both types of
spicules are observed to carry Alfvén waves with significant amplitudes
of order 20kms-1.
Title: Estimate on SOT Light Level in Flight with Throughput
Measurements in SOT Sun Tests
Authors: Shimizu, T.; Kubo, M.; Tarbell, T. D.; Berger, T. E.;
Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Miyashita, M.; Noguchi,
M.; Nakagiri, M.; Tsuneta, S.; Elmore, D. F.; Lites, B. W.
Bibcode: 2007ASPC..369...51S
Altcode:
The SOT (Solar Optical Telescope, e.g., Shimizu 2004) optical
system consists of 50cm-aperture optical telescope (OTA) and focal
plane instrument (FPP). The solar light into the telescope penetrates
through many optical elements located in OTA and FPP before illuminating
CCDs. Natural solar light was fed to the integrated SOT in sun tests for
verifying various optical aspects including the confirmation of photon
throughput. CCD exposures provide the number of photons accumulated
in an exposure duration with a clean-room test condition. To estimate
the absolute intensity of the solar light at the telescope entrance
in the clean-room test condition, we developed a pinhole-PSD sensor
for simultaneous monitoring the solar light outside the clean room
and measured the transmission of light through two flat mirrors of
the heliostat and clean-room entrance window glass as a function of
wavelength. The PSD sensor was pre-calibrated with continuous monitoring
the solar light in a day long under a clear constant sky condition,
determining the earth atmospheric attenuation and the PSD output for
the solar light on orbit. These throughput measurements have provided
an estimate on photon throughput for the SOT flight model. The results
confirm suitable number of photons without saturation for proper CCD
exposures in flight.
Title: Supersonic Downflows in the Photosphere Discovered in Sunspot
Moat Regions
Authors: Shimizu, T.; Martinez-Pillet, V.; Collados, M.; Ruiz-Cobo,
B.; Centeno, R.; Beck, C.; Katsukawa, Y.
Bibcode: 2007ASPC..369..113S
Altcode:
This paper reports on our new findings from the International
Time Program observations at the Canaries islands, Spain, in July
2005. We have found small-scale photospheric events with extremely
red-shifted Stokes V signals in sunspot moat regions. A preliminary
estimate of the physical conditions for an observed Stokes V profile
indicates the presence of a downward motion with a supersonic speed
in the order of 10 km/s. With the currently evaluated observational
information, we interprete the supersonic flows as downward motion from
magnetic reconnection occurring at the upper chromosphere or lower
photosphere. With coordinated observations of the Solar-B onboard
telescopes, Stokes measurements by the SOT spectro-polarimeter would
give new information for further understanding the nature of these
events with strongly red-shifted Stokes V, and for discussing the
physical conditions involving in possible magnetic reconnections in
the lower solar atmosphere.
Title: Calibration of the SOT Polarization
Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.;
Noguchi, M.; Nakagiri, M.; Miyashita, M.; Tsuneta, S.; Tarbell, T. D.;
Shine, R. A.; Hoffmann, C. M.; Cruz, T.; Lites, B. W.; Elmore, D. F.
Bibcode: 2007ASPC..369...39I
Altcode:
Calibration of SOT polarization property was performed using natural
sunlight and well calibrated sheet polarizer (linear and circular)
placed on the entrance of the telescope. The polarimeter response
matrices were determined for the spectropolarimeter (SP) and the
narrowband filter imager (NFI), and it is shown that they are well
behave as predicted and constant over the field of view. The crosstalk
between I,Q,U,V will be suppressed to the negligible level at the
photometric accuracy of 10^{-3} after the calibration with the obtained
matrices. The sensitivity of SOT on linear and circular polarizations
at each wavelength observed by NFI are also obtained.
Title: Calibration of SOT Dopplergrams
Authors: Katsukawa, Y.; Ichimoto, K.; Sekii, T.; Suematsu, Y.; Tsuneta,
S.; Shine, R. A.; Tarbell, T. D.
Bibcode: 2007ASPC..369...43K
Altcode:
Narrow-band Filter Imager on SOT provides Dopplergrams (DGs) which
are images of Doppler (line- of-sight) velocities. Observations with
DGs are critically important in studies of photospheric dynamics and
helioseismology. The primary photospheric line used for DGs is Fe I 5576
Å which is a line insensitive to Zeeman effect. We made a calibration
function for the 5576 Å DGs to get actual Doppler velocities from
velocity indexes using an atlas spectrum and simulated transmission
profiles for the tunable filter (TF) on SOT. Using data sets taken
in the natural sun-light test, we quantitatively evaluated accuracy
of the DGs by comparing the rotational speed of the Sun measured
with DGs with the expected one. There was a little systematic error
in the velocity obtained by SOT, but the error was less than 20 %
of the predicted velocities.
Title: Examinations of the Relative Alignment of the Instruments
on SOT
Authors: Okamoto, T. J.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T. D.
Bibcode: 2007ASPC..369...47O
Altcode:
We report the results of the examination about the relative alignment
among the instruments on SOT. We employ a test data set obtained in the
natural sun-light test in May 2005, which has had a grid pattern over
the entire FOV. SOT has the filtergraph (FG) and the spectro-polarimeter
(SP). The FG consists of six broadband filter imagers (BFI) and six
narrowband filter imagers (NFI). We examined the displacements among
the images taken with different filters to an accuracy of better than
0.1 pixel corresponding to 0.02''. It is important to know relative
displacements and plate scales of these instruments for accurate
alignment of observational data. We note that the values measured in
our work are relative and it is needed to decide the absolute values
with another way.
Title: Vector Spectropolarimetry of Dark-cored Penumbral Filaments
with Hinode
Authors: Bellot Rubio, L. R.; Tsuneta, S.; Ichimoto, K.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.; del Toro Iniesta, J. C.
Bibcode: 2007ApJ...668L..91B
Altcode: 2007arXiv0708.2791B
We present spectropolarimetric measurements of dark-cored penumbral
filaments taken with Hinode at a resolution of 0.3". Our observations
demonstrate that dark-cored filaments are more prominent in polarized
light than in continuum intensity. Far from disk center, the Stokes
profiles emerging from these structures are very asymmetric and show
evidence for magnetic fields of different inclinations along the
line of sight, together with strong Evershed flows of at least 6-7 km
s-1. In sunspots closer to disk center, dark-cored penumbral
filaments exhibit regular Stokes profiles with little asymmetries due
to the vanishing line-of-sight component of the horizontal Evershed
flow. An inversion of the observed spectra indicates that the magnetic
field is weaker and more inclined in the dark cores as compared with
the surrounding bright structures. This is compatible with the idea
that dark-cored filaments are the manifestation of flux tubes carrying
hot Evershed flows.
Title: Observational Analysis of the Relation between Coronal Loop
Heating and Photospheric Magnetic Fields
Authors: Katsukawa, Y.
Bibcode: 2007ASPC..369..287K
Altcode:
The solar corona and the photosphere are linked through magnetic
field lines, and heating energy is supposed to be supplied from the
footpoints of each coronal loop along magnetic field lines. Thus it is
important to examine properties of photospheric magnetic fields at the
footpoints of the coronal loops in order to understand heating of the
coronal loops. We performed simultaneous observations of photospheric
magnetic properties and coronal loop structures using the ground based
telescopes and Transition Region And Coronal Explorer (TRACE). Footpoint
locations were identified in the TRACE images, and the structure in
the photosphere was examined by Advanced Stokes Polarimeter (ASP) or
Dutch Open Telescope (DOT). Most of the coronal loops emanating from
a sunspot had their footpoints around the boundary between the umbra
and the penumbra. Furthermore, bright loops were revealed to have
their footpoints at the locations where there was highly interlaced
magnetic configuration. We observed fragmentation of an umbra and
formation of a light bridge in decaying sunspots, and found possible
association between such phenomena in the decaying spots and the coronal
loops. These observational results suggest that spatial fluctuation
of magnetic fields forms current sheets at the base of the corona,
resulting in heating of the coronal loops.
Title: Relationships between magnetic foot points and G-band bright
structures
Authors: Ishikawa, R.; Tsuneta, S.; Kitakoshi, Y.; Katsukawa, Y.;
Bonet, J. A.; Vargas Domínguez, S.; Rouppe van der Voort, L. H. M.;
Sakamoto, Y.; Ebisuzaki, T.
Bibcode: 2007A&A...472..911I
Altcode: 2008arXiv0802.1765I
Aims:Magnetic elements are thought to be described by flux tube models,
and are well reproduced by MHD simulations. However, these simulations
are only partially constrained by observations. We observationally
investigate the relationship between G-band bright points and magnetic
structures to clarify conditions, which make magnetic structures
bright in G-band.
Methods: The G-band filtergrams together with
magnetograms and dopplergrams were taken for a plage region covered
by abnormal granules as well as ubiquitous G-band bright points,
using the Swedish 1-m Solar Telescope (SST) under very good seeing
conditions.
Results: High magnetic flux density regions are
not necessarily associated with G-band bright points. We refer to the
observed extended areas with high magnetic flux density as magnetic
islands to separate them from magnetic elements. We discover that G-band
bright points tend to be located near the boundary of such magnetic
islands. The concentration of G-band bright points decreases with inward
distance from the boundary of the magnetic islands. Moreover, G-band
bright points are preferentially located where magnetic flux density is
higher, given the same distance from the boundary. There are some bright
points located far inside the magnetic islands. Such bright points have
higher minimum magnetic flux density at the larger inward distance from
the boundary. Convective velocity is apparently reduced for such high
magnetic flux density regions regardless of whether they are populated
by G-band bright points or not. The magnetic islands are surrounded by
downflows.
Conclusions: These results suggest that high magnetic
flux density, as well as efficient heat transport from the sides or
beneath, are required to make magnetic elements bright in G-band.
Title: Emergence of Small-Scale Magnetic Loops in the Quiet-Sun
Internetwork
Authors: Centeno, R.; Socas-Navarro, H.; Lites, B.; Kubo, M.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2007ApJ...666L.137C
Altcode: 2007arXiv0708.0844C
We study the emergence of magnetic flux at very small spatial
scales (less than 2") in the quiet-Sun internetwork. To this aim,
a time series of spectropolarimetric maps was taken at disk center
using the instrument SP/SOT on board Hinode. The LTE inversion of
the full Stokes vector measured in the Fe I 6301 and 6302 Å lines
allows us to retrieve the magnetic flux and topology in the region
of study. In the example presented here, the magnetic flux emerges
within a granular structure. The horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field disappear, while the vertical dipoles
drift-carried by the plasma motions-toward the surrounding intergranular
lanes. These events take place within typical granulation timescales.
Title: Chromospheric Micro-jets Discovered Above Sunspot Penumbrae
Authors: Katsukawa, Yukio; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Shimizu, T.; Kubo, M.; Nagata, S.; Berger, T.; Tarbell, T.; Shine,
R.; Title, A.
Bibcode: 2007AAS...210.9413K
Altcode: 2007BAAS...39..219K
The Solar Optical Telescope (SOT) aboard HINODE allows us to observe
dynamical activities in the solar photosphere and the chromosphere
with high and stable image quality of 0.2 arcseconds. This superior
performance of SOT provides new findings of fine-scale transient
activities occurring in the chromosphere. In this paper, we report
discovery of fine-scale jet-like phenomena ubiquitously observed
above sunspot penumbrae. The jets are identified in image sequences
of a sunspot taken through a Ca II H line filter at 3968A. The Ca II
H line is sensitive to about 10^4 K plasma in the chromosphere. Their length is typically between 3000 and 10000km, and their
width is smaller than 500km. It is notable that their lifetime
is shorter than 1 minute. Those small spatial and temporal scale
possibly makes it difficult to identify the phenomena in existing
ground-based observations. The jets are easily identified when a
sunspot is located far from the disk center, and motion of the bright
features suggests that mass is erupted from lower chromosphere to upper
atmosphere. Velocities of the motion are estimated to be 50 to 100 km/s
from their lateral motion of intensity patterns. The velocities are much
faster than sound speeds in the chromosphere. A possible cause of such
high-speed jets is magnetic reconnection at the lower chromosphere
resulted from fluted magnetic configuration in penumbrae which is
suggested by vector magnetic field measurements in the photosphere.
Title: Hinode Data Calibration For Precise Image Co-alignment:
XRT vs. SOT
Authors: Shimizu, Toshifumi; DeLuca, E. E.; Lundquist, L.; Sakao,
T.; Kubo, M.; Narukage, N.; Kano, R.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T.; Shine, D.; Hinode Team
Bibcode: 2007AAS...210.9417S
Altcode: 2007BAAS...39Q.220S
From late October in 2006, Hinode solar optical telescope (SOT) has
started to produce series of 0.2-0.3 arcsec visible-light images,
revealing dynamical behaviors of solar magnetic fields on the
solar surface. Simultaneously, Hinode X-ray telescope (XRT) has been
providing 1 arcsec resolution X-ray images of the solar corona, giving
the location of heating and dynamics occuring in the corona. Precise
image co-alignment of SOT data on XRT data with sub-arcsec accuracy is
required to provide new information regarding connecting the corona to
the photosphere. This presentation will give an introduction of Hinode
between-telescopes' image co-alignment to SPD participants. For active
region observations with sunspots, sunspots can be used as fiducial to
co-align the data from the two telescopes each other. Satellite jitter
in order of 1 arcsec or less is included in the series of XRT data,
whereas image stabilization system (correlation tracker) removes the
satellite jitter from the series of SOT images. Telescope pointings show
orbital variation in order of a few arcsec, which can be well predicted
from Hinode orbit information. Modeling co-alignment is under study
and it is the only precise method for quiet Sun and limb observations.
Title: Magnetic Patches in Internetwork Quiet Sun
Authors: De Wijn, Alfred; Lites, B.; Berger, T.; Shine, R.; Title,
A.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Hinode Team
Bibcode: 2007AAS...210.9412D
Altcode: 2007BAAS...39Q.219D
We study strong flux elements in the quiet sun in the context of
the nature of quiet-sun magnetism, its coupling to chromospheric,
transition-region and coronal fields, and the nature of a local
turbulent dynamo. Strong, kilogauss flux elements show up intermittently
as small bright points in G-band and Ca II H images. Although
bright points have been extensively studied in the magnetic network,
internetwork magnetism has only come under scrutiny in recent years. A
full spectrum of field strengths seems to be ubiquitously present in
the internetwork at small spatial scales, with the stronger elements
residing in intergranular lanes. De Wijn et al. (2005) found that bright
points in quiet sun internetwork areas appear recurrently with varying
intensity and horizontal motion within long-lived patches that outline
cell patterns on mesogranular scales. They estimate that the "magnetic
patches" have a mean lifetime of nine hours, much longer than granular
timescales. We use multi-hour sequences of G-band and Ca II H images
as well as magnetograms recorded by the Hinode satellite to follow up
on their results. The larger field of view, the longer sequences, the
addition of magnetograms, and the absence of atmospheric seeing allows
us to better constrain the patch lifetime, to provide much improved
statistics on IBP lifetime, to compare IBPs to network bright points,
and to study field polarity of IBPs in patches and between nearby
patches. Hinode is an international project supported by JAXA,
NASA, PPARC and ESA. We are grateful to the Hinode team for all their
efforts in the design, build and operation of the mission.
Title: Hinode/SOT Observations Of Apparent "Thermal Plume" Motions
In A Solar Prominence
Authors: Berger, Thomas; Tarbell, T.; Slater, G.; Tsuneta, S.;
Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Shimizu, T.; Kubo, M.;
Nagata, S.
Bibcode: 2007AAS...210.9433B
Altcode: 2007BAAS...39..222B
We present 396.8 nm Ca II H-line observations of a large
hedgerow, or "sheet", prominence seen on the solar western limb
on 30-November-2006. The 16 second cadence observations show dark
channels rising vertically at speeds of approximately 10 km/sec to
heights of about 15 Mm above the limb. Many of the motions end in
vortical overturning near the top of the sheet . Bright downflows of
similar speed are also seen within the sheet, often in association
with a dark channel that has risen to the top of the sheet. The dark
channels are suggestive of hot material rising in thermal plumes
within the prominence sheet. Similarly, the bright material motions
appear to be density enhanced regions of turbulent downflow. Current
models of sheet prominences do not include the observed dynamics. In
these models, the prominence plasma is in a low-beta state and is
constrained to move only along magnetic field lines. However the
motions observed here are extremely complex, implying either that the
magnetic field lines are undergoing turbulent motion, thus tangling
and reconnecting constantly, or that the plasma is not constrained
by the field and is in a high-beta convective state. We measure the
motion of several representative "plumes" and downflows, estimate the
density and temperature of the prominence plasma, and suggest several
avenues for further investigation. This work was supported by
NASA under the Hinode/SOT contract NNM07AA01C.
Title: High Resolution Observation of Spicules in Ca II H with
Hinode/SOT
Authors: Suematsu, Yoshinori; Katsukawa, Y.; Ichimoto, K.; Tsuneta, S.;
Okamoto, T.; Nagata, S.; Shimizu, T.; Tarbell, T.; Shine, R.; Title, A.
Bibcode: 2007AAS...210.9411S
Altcode: 2007BAAS...39..219S
High cadence observation with a Ca II H broadband filtergraph
(passband of 0.25 nm) of the Solar Optical Telescope (SOT) aboard
HINODE has revealed dynamical nature of solar limb spicules. Thanks to a
diffraction-limited and low-scattered light property of the instrument,
we can track the detailed evolution of individual spicules for the first
time with a spatial resolution of 0.2 arcsec. The spicules in Ca II
H are typically several arcsec tall and have multi-thread structure;
each threads are a few tenth of arcsec wide. It should be stressed
that most spicules do not show a simple up-and-down motion along a
rigid path line. They start with bright structure emanating from Ca II
H bright region, get widen and diffused with time and ascent, showing
expansion with lateral or even helical motion in tall events. Small and
short lived spicules tend to fade out after ascent. We will present
new findings of spicule dynamics in different magnetic environments
and discuss about long standing controversy of its motion and evolution.
Title: Hinode/SOT Observation of Fine Structure of the Evershed Flow
Authors: Ichimoto, Kiyoshi; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimojo, M.; Kubo, M.; Shimizu, T.; Shine, R.; Tarbell, T.; Title,
A.; Lites, B.; Elmore, D.; Yokoyama, T.; Nagaka, S.
Bibcode: 2007AAS...210.9408I
Altcode: 2007BAAS...39..218I
Small scale structure of the Evershed effect was studied using the
Spectropolarimeter (SP) and Broadband Filter Imager (BFI) of SOT aboard
Hinode. SP maps and high cadence continuum images of BFI coverting
entire sunspots are used to investigate the spatial distribution of
the flow field, brightness and magnetic fields. It is revealed that the
Evershed flow starts at the front edge of inwardly migrating penumbral
grains with an upward velocity component and turns to nearly holizontal
flow preferentially in dark lanes (or dark core of filaments) of the
penumbra. Our results are in general agreement with the well known
uncombed penumbral concept in which the Evershed flow takes place
in nearly holizontal field channels. We discovered a number of tiny
elongated regions in deep photosphere in which there is an obvious
upward motion of 1-1.5km/s distributing over the penumbra. They
could be identified as the 'foot points' of the individual Evershed
flow channels. Cross-correlation among the flow speed, intensity,
magnetic field strength and inclination, and distribution of string
down flows in and around the penumbra will also be discussed.
Title: On the Moat-Penumbra Relation
Authors: Vargas Domínguez, S.; Bonet, J. A.; Martínez Pillet, V.;
Katsukawa, Y.; Kitakoshi, Y.; Rouppe van der Voort, L.
Bibcode: 2007ApJ...660L.165V
Altcode: 2007astro.ph..2713V
Proper motions in a sunspot group with a δ-configuration and close to
the solar disk center have been studied by employing local correlation
tracking techniques. The analysis is based on a more than 1 hr time
series of G-band images. Radial outflows with a mean speed of 0.67
km s-1 have been detected around the spots, the well-known
sunspots moats. However, these outflows are not found in those umbral
core sides without penumbra. Moreover, moat flows are only found
in those sides of penumbrae located in the direction marked by the
penumbral filaments. Penumbral sides perpendicular to them show no
moat flow. These results strongly suggest a relation between the
moat flow and the well-known, filament-aligned Evershed flow. The
standard picture of a moat flow originating from a blocking of the
upward propagation of heat is discussed in some detail.
Title: Continuous Upflow of Plasmas at the Edge of an Active Region
as Revealed by the X-ray Telescope (XRT) aboard Hinode
Authors: Sakao, Taro; Kano, R.; Narukage, N.; Kotoku, J.; Bando, T.;
DeLuca, E. E.; Lundquist, L. L.; Golub, L.; Kubo, M.; Katsukawa, Y.;
Tsuneta, S.; Hara, H.; Matsuzaki, K.; Shimojo, M.; Shibasaki, K.;
Shimizu, T.; Nakatani, I.
Bibcode: 2007AAS...210.7205S
Altcode: 2007BAAS...39Q.179S
We present X-ray imaging observations with Hinode X-Ray Telescope (XRT)
of an active region NOAA AR 10942 made in the period of 20-22 February
2007. A prominent feature that drew our particular attention is that
there revealed continuous upflow of soft-X-ray-emitting plasmas along
apparently-open field lines towards the outer corona emanating from the
edge of the active region. The field lines are originated from
an ensamble of small spots of following polarity, and are located at
a border between the active region and an adjacent equatorial coronal
hole(s) located to the east. The upflow was observed to be continuous
throughout the three days of observation intervals with projected
velocity of 140 km/s, accompanied with undulating motion of the field
lines. We assert that these upflowing plasmas would be a possible
source of slow solar wind material, which supports a foresighted
notion which grew out of interplanetary scintillation observations
that slow solar wind most likely has its origin in the vicinity of
active regions with large flux expansion (Kojima et al. 1999). A
preliminaty analysis indicates that the temperature of the upflowing
material near the base of the field lines is 1.3 MK with number density
of 2 × 109 /cm3. Assuming that all the material
is to escape to the interplanetary space, this leads to a mass loss
rate of 2 × 1011 g/s which amounts to a good fraction of
the total mass loss rate for solar wind. It is noteworthy that, even
apart from this unique upflow, we see continuous (up)flows of plasmas
anywhere around (surrounding) the active region. Details of the
upflow will be presented and their possible implication to slow solar
wind discussed.
Title: Magnetic Flux Emergence In The Quiet Sun Photosphere
Authors: Centeno, Rebecca; Lites, B.; Socas-Navarro, H.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9406C
Altcode: 2007BAAS...39..218C
We study the emergence of magnetic flux at very small spacial scales
(less than 1 arcsec) in the quiet Sun internetwork. To this aim, several
time series of spectropolarimetric maps were taken at disk center using
the instrument SP/SOT on board Hinode. The LTE inversion of the full
Stokes vector measured in the Fe I 6301 and 6302 lines will allow us
to retrieve the magnetic flux and topology in the region of study. We
find that the magnetic flux emerges typically within the granular
structures. In many cases, the horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field dissapear while the the vertical
dipoles drift -carried by the plasma motions- towards the surrounding
intergranular lanes. Sometimes they stay trapped there for a while
but they eventually either disappear by disgregation/cancelation
or agregate to other magnetic field concentrations giving rise to
larger flux elements. The time scale of these events is of the order
of 10-20 minutes.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields
Authors: Kubo, Masahito; Ichimoto, K.; Shimizu, T.; Tsuneta, S.;
Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Lites, B. W.; Frank, Z.;
Tarbell, T. D.; Shine, R. A.; Title, A. M.
Bibcode: 2007AAS...210.9410K
Altcode: 2007BAAS...39..218K
We investigate the formation process of Moving Magnetic Features
(MMFs) observed with Hinode/SOT. Moving magnetic features are small
magnetic elements moving outward in the moat region surrounding
mature sunspots. We derive vector magnetic fields of MMFs around
simple sunspots near the disk center. Most of MMFs with polarity
opposite to the sunspot have large redshift around the penumbral outer
boundary. We find that some of them have Doppler velocities of about
10 km/s and such large Doppler motion is observed only in the Stokes
V profile. The Stokes Q and U profiles in the same pixel do not have
any significant Doppler motions. Horizontal magnetic fields of the
penumbra frequently extend to the moat region and the MMFs having
horizontal fields with polarity same as the sunspot are formed. The
MMFs with polarity opposite to the sunspot appear around the outer
edge of the extending penumbral fields. We also find penumbral spines,
which have more vertical magnetic fields than the surroundings, branch
off at their outer edge and MMFs having relatively vertical fields
with polarity same as the sunspot are detached from the outer edge
of the branch. The branch of penumbral spine is formed when granular
cells in the moat region go into the penumbra.
Title: Ubiquitous Horizontal Magnetic Fields in the Quiet Solar
Photosphere as Revealed by HINODE Meaurements
Authors: Lites, Bruce W.; Socas Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Kubo, M.; Shimizu, T.; Nagata, S.;
Hinode Team
Bibcode: 2007AAS...210.6303L
Altcode: 2007BAAS...39..171L
Measurements with the HINODE Spectro-Polarimeter (SP) of the quiet
Sun allow characterization of the weak, mixed-polarity magnetic
flux at the highest angular resolution to date (0.3"), and with good
polarimetric sensitivity(0.025% relative to the continuum). The image
stabilization of the HINODE spacecraft allows long integrations with
degradation of the image quality only by the evolution of the solar
granulation. From the Stokes V profile measurements we find an average
solar "Apparent Flux Density" of 14 Mx cm-2, with significant Stokes V
signals at every position on the disk at all times. However, there are
patches of meso-granular size (5-15") where the flux is very weak. At
this high sensitivity, transverse fields produce measurable Stokes
Q,U linear polarization signals over a majority of the area, with
apparent transverse flux densities in the internetwork significantly
larger than the corresponding longitudinal flux densities. When viewed
at the center of the solar disk, the Stokes V signals (longitudinal
fields) show a preference for occurrence in the intergranular lanes,
and the Q,U signals occur preferably over the granule interiors,
but neither association is exclusive. Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful to the
Hinode team for all their efforts in the design, build and operation
of the mission.
Title: Attempt to detect Aflven waves with Solar Optical Telescope
aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.;
Shimizu, T.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9428T
Altcode: 2007BAAS...39..222T
Flux tube on the sun may carry linear and torsional Alfven waves
generated by photospheric motion. Photospheric motion of 2 km/s would
provide magnetic fluctuation of 40G for 1KG tube and for the Alfven
speed of 50km/s. This may be close to the detection limit of the Stokes
Q and U signals for flux tubes located in the sun center. However,
for flux tubes located near the limb, the fluctuation would be seen in
the Stokes V signal, and can be detectable. We also may be able
to confirm the 90 degree phase shift between magnetic fluctuation and
velocity fluctuation, which is easier to observe for flux tubes near
the limb. Detection of waves would be important in terms of coronal
heating and solar wind acceleration. An attempt to detect waves along
flux tubes will be reported.
Title: Discovery Of Cool Cloud-like Structures In The Corona With
Hinode Solar Optical Telescope
Authors: Okamoto, Takenori; Tsuneta, S.; Katsukawa, Y.; Ichimoto,
K.; Suematsu, Y.; Shimizu, T.; Nagata, S.; Shibata, K.; Tarbell, T.;
Shine, R.; Berger, T.; Lites, B.; Myers, D.
Bibcode: 2007AAS...210.9426O
Altcode: 2007BAAS...39..221O
A solar observation satellite Hinode (Japanese for sun rise) was
launched in September 2006.Hinode carried 3 advanced solar telescopes,
visible light telescope, EUV imaging spectrometer, and X-ray telescope
to simultaneously observe the photosphere, chromosphere, transition
region, and corona. In the performance verification phase of the Hinode
spacecraft with its telescopes, we observed an active region AR10921
near the west limb of the solar disk on November 9 2006. At this point,
we planned to observe spicules on the limb with a broadband filter
dedicated to Ca II H line (3968A). Ca II-H emission line (3968A) comes
from plasma with temperature of approx. 10(4) K, which is much lower
than the coronal temperature of 10(6-7) K. In addition to spectacular
spicules, we find a large cloud-like structure located 10,000-20,000
km above the limb. The cloud has a very complex fine structure with
dominant horizontal thread-like structure. Some features are moving
horizontally and also have clear vertical oscillatory motions. The
periods and amplitudes of these oscillations are 130-250 seconds and
200-850 km, respectively. The vertical oscillatory motion sometimes
has a coherence length as long as 16,000 km. We conclude that from
various observational features this vertical oscillation is a signature
of Alfven waves propagating along the horizontal magnetic fields. We
will discuss their origin and implications.
Title: Discovery Of Small-scale Horizontal Magnetic Structures On
The Solar Photosphere
Authors: Ishikawa, Ryohko; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Katsukawa, Y.; Nagata, S.; Ishobe, H.; Tarbell, T.; Lites, B. W.;
Title, A.
Bibcode: 2007AAS...210.9404I
Altcode: 2007BAAS...39..217I
We discover two different types of episodes on the appearance
of horizontal magnetic fields with Solar Optical Telescope aboard
Hinode. The first episode is an emergence of strong thin horizontal
magnetic fields associated with separating vertical components on
both ends. Its size is about two granules. We also detect strong area
asymmetry of the environment Stokes Vprofile for the bout 8 minutes
before the first emergence of the horizontal component. One of the
footpoints has very strong downflows (several km/s), while the region
with strong linear polarization signal has small blue shift, indicating
an upward-moving horizontal flux. The second episode appears to be
more ubiquitous. Linear polarization signals appear inside granules (not
in inter-granules). Their size is smaller than granules, and lifetime
is longer than several minutes. We will summarize the nature of the
two types of the horizontal magnetic fluxes, and discuss their origin.
Title: Optical Performance of the Solar Optical Telescope aboard
HINODE
Authors: Suematsu, Yoshinori; Ichimoto, K.; Katsukawa, Y.; Otsubo,
M.; Tsuneta, S.; Nakagiri, M.; Noguchi, M.; Tamura, T.; Kato, Y.;
Hara, H.; Miyashita, M.; Shimizu, T.; Kubo, M.; Sakamoto, Y.
Bibcode: 2007AAS...210.9402S
Altcode: 2007BAAS...39Q.217S
The Solar Optical Telescope (SOT) carried by HINODE was designed
to perform a high-precision polarimetric observation of the Sun
in visible light spectra with a spatial resolution of 0.2 - 0.3
arcseconds. The SOT is a sophistcated instrument and consists of two
separate optical parts; the Optical Telescope Assembly (OTA) which is
50 cm aperture Gregorian telescope feeding the light into following
observing instruments which is called the focal plane package (FPP)
made of two filtergraphs and a spectro-polarimeter. The performance
of the OTA is important because a spatial resolution and its temporal
stability is mainly determined by this component. To keep the OTA in
moderate temperature and optical thermal deformation small, it equipped
newly designed components such as a heat dump and a secondary field stop
aluminum mirror with high reflectivity silver coating and a temperature
low-sensitive apochromatic collimataing lens unit with a UV/IR cut
coating on the first surface. In addition, the SOT has an active image
stabilization system consisting of correlation tracker, tip-tilt mirror
and its controller against satellite pointing jitter. It was confirmed
that this system freezes residual motion to the 0.01 arcsecond level
on orbit. The image of sub-arcsecond G-band (430.5 nm) bright points
clearly indicates that the SOT achieves the diffraction-limit on orbit;
this is also confirmed using a phase diversity method. In this paper,
we describe details of the design and on-orbit performance of the OTA.
Title: Magnetic Landscape Of Solar Polar Region With Solar Optical
Telescope Aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Shimizu, T.;
Katsukawa, Y.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9405T
Altcode: 2007BAAS...39..218T
Solar polar region is the final destination for remnant magnetic
fields due to meridional flow and granular diffusion, and is very
important for the global solar dynamo. Hinode satellite carried out
high-resolution spectro-polarimetric observations for the Northern
pole on 2006 November 22 as a part of its performance verification
program. We find ubiquitous isolated (positive and negative) patches
in the Stokes V map (i.e. fields horizontal to local surface) all over
the Arctic circle. The Q (vertical to local surface) map indicates
scattered vertical flux tubes, which have bipolar feature in the U and
V maps. This suggests canopy-like structure of the strong isolated flux
tubes. This will be compared with equatorial landscape with similar
distance from the sun center. Strong flux tube and weaker ubiquitous
horizontal fields as represented by Stokes V would have implication
to the current understanding of the global and local dynamo.
Title: Evidence Of An Association Between The Presence Of Penumbrae
And Strong Radial Outflows In Sunspots
Authors: Santiago, Vargas Domínguez; Bonet, J. A.; Martinez Pillet,
V.; Katsukawa, Y.
Bibcode: 2007ESASP.641E..87S
Altcode:
Time series of high-resolution images of the complex ac-tive region NOAA
10786 are studied. The observations were performed in G-band (430.5 nm)
and in the nearby continuum (463.3 nm), on July 9, 2005 at the Swedish
1-meter Solar Telecope (SST) in La Palma. Granular proper motions in the
surroundings of the sunspots have been quantified. A large-scale radial
outflow in the velocity range 0.3 - 1 km s-1 has been measured around
the sunspots by using local correlation tracking techniques. However,
this outflow is not found in those regions around the sunspots with
no penumbral structure. This result evidences an association between
penumbrae and the existence of strong horizontal outflows (the moat)
in sunspots.
Title: Magnetic Field Diagnostic Capability of Solar-B/SOT:
Filtergraph Instrument
Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.;
Tsuneta, S.; Tarbell, T. D.; Shine, R. A.; Hoffmann, C. M.; Title,
A. M.; Lites, B. W.; Elmore, D. F.; Streander, K. V.
Bibcode: 2006ASPC..358..189I
Altcode:
The Narrowband Filter Instrument (NFI) of the Solar Optical Telescope
onboard Solar-B provides 2D magnetograms/Dopplergrams with a tunable
Lyot filter (width ∼ 0.1 Å) in 6 selected wavelength bands, and
spatial sampling of 0.08 arcsec/px. The Zeeman-effect sensitivity of
NFI and the detection limits of weak magnetic fields are evaluated for
2 photospheric and 3 chromospheric lines. Magnetic-field retrievability
from the NFI observables is studied using synthetic Stokes profiles
of Fe I 5250 Å. We find that, with optimized wavelength sampling at 4
positions, the inferred magnetic field is sufficiently accurate under
the hypothesis of constant magnetic field and velocity along the LOS.
Title: Evidence of an association between the presence of penumbrae
and strong radial outflows in sunspots
Authors: Vargas Domínguez, S.; Bonet, J. A.; Martinez Pillet, V.;
Katsukawa, Y.
Bibcode: 2006astro.ph.11500V
Altcode:
Time series of high-resolution images of the complex active region NOAA
10786 are studied. The observations were performed in G-band (430.5 nm)
and in the nearby continuum (463.3 nm), on July 9, 2005 at the Swedish
1-meter Solar Telecope (SST) in La Palma. Granular proper motions in the
surroundings of the sunspots have been quantified. A large-scale radial
outflow in the velocity range 0.3 - 1 km s^[-1] has been measured around
the sunspots by using local correlation tracking techniques. However,
this outflow is not found in those regions around the sunspots with
no penumbral structure. This result evidences an association between
penumbrae and the existence of strong horizontal outflows (the moat)
in sunspots.
Title: Hard X-Ray Spectral Observation of a High-Temperature
Thermal Flare
Authors: Kobayashi, Ken; Tsuneta, Saku; Tamura, Tomonori; Kumagai,
Kazuyoshi; Katsukawa, Yukio; Kubo, Masahito; Sakamoto, Yasushi;
Kohara, Naoki; Yamagami, Takamasa; Saito, Yoshitaka
Bibcode: 2006ApJ...648.1239K
Altcode:
We report on the analysis of a thermal flare observed by a newly
developed balloon-borne hard X-ray spectrometer. This instrument uses
CdTe detectors and can observe the 20-120 keV hard X-ray range, with
3.0 keV energy resolution at 60 keV. During the 2002 May 24 flight,
it successfully observed a class M1.1 flare. This flare observation
shows no detectable flux above 35 keV, and its spectrum is consistent
with a superhot thermal source with the temperature varying from 44
to 20 MK. Partial observation of the flare by the RHESSI satellite is
consistent with this result. The Nobeyama Radio Polarimeters (NORP)
observation of this flare shows no detectable polarization. The NORP
light curves show impulsive features at 3.75 GHz that can be explained
as thermal gyrosynchrotron emission, and this flux is consistent with
observed X-ray spectra if a magnetic field of 275 G is assumed. Slower
varying features seen in the NORP data are consistent with the
lower temperature (``hot'') thermal source of 10-15 MK seen in soft
X-rays. We conclude that this flare shows no observable signature of
nonthermal electrons, and all observed features are consistent with
a purely thermal event. This serves as a strong indication that a
nonthermal electron beam is not always the dominant energy source of
plasma heating in solar flares.
Title: Dynamical Properties of Photospheric Flux Tubes at the
Footpoints of Hot and Cool Coronal Loops
Authors: Nagata, Shin'ichi; Bellot Rubio, Luis R.; Katsukawa, Yukio
Bibcode: 2006ApJ...638..539N
Altcode:
The dynamical properties of photospheric flux tubes at the footpoints
of hot (T>2 MK) and cool (T=1-2 MK) coronal loops in active region
plages are investigated by analyzing the Stokes V profile parameters of
Fe I λ6302. We show that the footpoints of both hot and cool loops are
located at the periphery of small magnetic concentrations, such as pores
and azimuth centers, having a field strength of 1-1.8 kG and a spatial
size of 2"-5". The footpoints of cool loops seem to be associated with
more densely packed and higher field strength pores and azimuth centers
than those of hot loops. Enhanced Stokes V asymmetries, redshifted
zero-crossing velocities, and small magnetic filling factors are found
at the footpoints of both types of loops, as compared with outside
the footpoints. However, the largest asymmetries and more redshifted
zero-crossing velocities are observed at the footpoints of hot loops,
where the filling factor is smaller than at the footpoints of cool
loops. The differences between the profiles emerging from the footpoints
of hot and cool coronal loops suggest that heating of the coronal loops
could be related to the dynamical properties of photospheric flux tubes.
Title: Probing coronal heating with variability of solar X-ray
emission
Authors: Vekstein, G.; Jain, R.; Katsukawa, Y.; Tsuneta, S.
Bibcode: 2006cosp...36...65V
Altcode: 2006cosp.meet...65V
If the mechanism responsible for creating hot solar corona is a
magnetic one the resulting coronal heating events are likely to be
highly fragmented in space and in time This makes the nanoflare
heating scenario where both these features are at the heart of
the concept a strong candidate The major problem is to find out
how to test this theory while individual nanoflares remain beyond
observational recognition Here we discuss a possibility of probing
nanoflares with variability of the coronal X-ray emission We present
results of the numerical simulation of X-ray coronal loops that mimics
a sporadic nature of the nanoflare heating The aim is to investigate
how an imposed power-law energy spectrum of heating events nanoflares
translates into fluctuations in the intensity of the X-ray emission
which can be detected observationally as X-ray and EUV brightenings
These theoretical predictions are compared with a recently reported
analysis of observed fluctuations of the solar X-ray emission and
we discuss their implications on the deduced energy and spectrum of
nanoflares A future study envisaged with the upcoming Solar-B mission
is also discussed
Title: Magnetic Properties at Footpoints of Hot and Cool Loops
Authors: Katsukawa, Yukio; Tsuneta, Saku
Bibcode: 2005ApJ...621..498K
Altcode:
Observations of the solar corona with Yohkoh, the Solar and Heliospheric
Observatory, and the Transition Region and Coronal Explorer (TRACE)
have revealed that individual coronal loops of active regions have their
own temperatures from 1 to 5 MK. The hot (2-5 MK) Soft X-Ray Telescope
(SXT) loops appear to require more heating energy than the cool (1-2 MK)
EUV loops. We investigate the photospheric magnetic signature for the
hot and cool loops with the Advanced Stokes Polarimeter. In contrast to
the cool loops, the hot loops observed with the SXT are usually diffuse,
resulting in ambiguous identification of their footpoint locations. We
use TRACE ``moss'' structure, which we confirm is low-lying EUV emission
at the footpoints of the hot loops. Footpoints of both loops have
magnetic fields whose strength is 1.2-1.3 kG, and the orientation is
almost vertical to the surface. A significant difference is discovered
in the magnetic filling factor, which is defined by the fraction of
a pixel filled with a magnetized atmosphere. The footpoints of the
hot loops have a lower filling factor than the footpoints of the cool
loops. We suggest that braiding of coronal magnetic fields is more
efficient at the footpoints of the hot loops than at the footpoints
of the cool loops as a result of the combination of the lower filling
factor and higher horizontal velocity.
Title: Completion of Solar-B/Optical Telescope flight model
Authors: Suematsu, Yoshinori; Ichimoto, Kiyosi; Shimizu, Toshifumi;
Otsubo, Masashi; Nakagiri, Masao; Noguchi, Motokazu; Tamura, Tomonori;
Katsukawa, Yukio; Kato, Yoshihiro; Hara, Hirohisa; Miyashita, Masakuni;
Tsuneta, Saku; Kubo, Masahito; Sakamoto, Yasushi
Bibcode: 2005ARAOJ...7...52S
Altcode:
No abstract at ADS
Title: Observation of solar flare hard X-ray spectra using CdTe
detectors
Authors: Kobayashi, Ken; Tsuneta, Saku; Tamura, Tomonori; Kumagai,
Kazuyoshi; Katsukawa, Yukio; Kubo, Masahito; Sakamoto, Yasushi;
Kohara, Naoki; Yamagami, Takamasa; Saito, Yoshitaka; Mori, Kunishiro;
Kato, Genzo
Bibcode: 2005naoj.book...33K
Altcode:
No abstract at ADS
Title: Solar-B/Optical Telescope flight model is coming up
Authors: Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Otsubo, Masashi; Nakagiri, Masao; Noguchi, Motokazu; Tamura, Tomonori;
Kato, Yoshihiro; Hara, Hirohisa; Miyashita, Masakuni; Tsuneta, Saku;
Katsukawa, Yukio; Kubo, Masahito; Sakamoto, Yasushi
Bibcode: 2005naoj.book....4S
Altcode:
No abstract at ADS
Title: Magnetic properties at the footpoints of hot and cool loops
Authors: Katsukawa, Yukio; Tsuneta, Saku
Bibcode: 2005naoj.book...27K
Altcode:
No abstract at ADS
Title: The first build-up of the Solar-B flight models
Authors: Hara, Hirohisa; Ichimoto, Kiyoshi; Otsubo, Masashi; Katsukawa,
Yukio; Kato, Yoshihiro; Kano, Ryohei; Kumagai, Kazuyoshi; Shibasaki,
Kiyoto; Shimizu, Toshifumi; Shimojo, Masumi; Suematsu, Yoshinori;
Tamura, Tomonori; Tsuneta, Saku; Noguchi, Motokazu; Nakagiri, Masao;
Miyashita, Masakuni; Watanabe, Tesuya; Kosuchi, Takeo; Sakao, Taro;
Matsuzaki, Keiichi; Kitakoshi, Yasunori; Kubo, Masahito; Sakamoto,
Yasushi
Bibcode: 2005ARAOJ...7...46H
Altcode:
No abstract at ADS
Title: Hard X-Ray Spectral Observation of a High-Temperature
Thermal Flare
Authors: Kobayashi, K.; Katsukawa, Y.; Kubo, M.; Sakamoto, Y.; Kohara,
N.; Tsuneta, S.; Tamura, T.; Kumagai, K.; Yamagami, T.; Saito, Y.
Bibcode: 2004ASPC..325..353K
Altcode:
No abstract at ADS
Title: Multi-Temperature Corona and the Photospheric Magnetic Fields
Authors: Katsukawa, Y.; Tsuneta, S.
Bibcode: 2004ASPC..325..281K
Altcode:
No abstract at ADS
Title: Coronal Heating with Sweet-Parker Picoflares
Authors: Tsuneta, S.; Katsukawa, Y.
Bibcode: 2004ASPC..325..289T
Altcode:
Katsukawa & Tsuneta (2001) found an excess fluctuation in soft
X-rays coming from active regions, and proposed that the fluctuation
was attributed to ubiquitous tiny bursts. They estimated the energy
range of individual bursts to be 1020--1022
erg. There appears to be a big desert, the void in which no burst
occurs for 3--6 orders of magnitudes in energy from the pico-flare
range to the observed micro-flare range, indicating that a separate
physical mechanism is responsible for the picoflares. We propose that
the picoflares are due to Sweet-Parker reconnection, which is presumably
easier to occur than the Petschek reconnection responsible for larger
flares. We point out the critical importance of the simultaneous
observations with SolarB X-ray/EUV and visible-light telescopes.
Title: Nanoflares and Coronal X-Ray Variability
Authors: Jain, R.; Katsukawa, Y.; Tsuneta, S.; Vekstein, G.
Bibcode: 2004ASPC..325..271J
Altcode:
A possibility of probing nanoflares with variability in the coronal
X-ray emission is discussed. We present results of numerical simulation
of X-ray coronal loops by using a Monte Carlo code, which mimics a
sporadic nature of the nanoflare heating. The aim is to investigate how
the imposed power-law energy spectrum of heating events (nanoflares)
translates into fluctuations in the intensity of the X-ray emission,
which can be detected observationally as X-ray and EUV brightenings. It
was found that probability distribution of these fluctuations is
very sensitive to the power-law index α of the energy spectrum of
nanoflares. If α > 3, intensity fluctuations have a noise-like
nature with a Gaussian distribution originating from interference of
many small nanoflares. For spectral indices 2 < α ≤ 3, histograms
of the intensity deviation from the mean value show positive skewness
indicating significant role of bigger events. Comparison of these
results with the analysis of small fluctuations of coronal X-ray
intensity observed with Yohkoh SXT telescope yields an estimate of
1023 erg for the energy of nanoflares in the active region.
Title: The Solar Optical Telescope onboard the Solar-B
Authors: Ichimoto, Kiyoshi; Tsuneta, Saku; Suematsu, Yoshinori;
Shimizu, Toshifumi; Otsubo, Masashi; Kato, Yoshihiro; Noguchi,
Motokazu; Nakagiri, Masao; Tamura, Tomonori; Katsukawa, Yukio; Kubo,
Masahito; Sakamoto, Yasushi; Hara, Hirohisa; Minesugi, Kenji; Ohnishi,
Akira; Saito, Hideo; Kawaguchi, Noboru; Matsushita, Tadashi; Nakaoji,
Toshitaka; Nagae, Kazuhiro; Sakamoto, Joji; Hasuyama, Yoshihiro;
Mikami, Izumi; Miyawaki, Keizo; Sakurai, Yasushi; Kaido, Nobuaki;
Horiuchi, Toshihida; Shimada, Sadanori; Inoue, Toshio; Mitsutake,
Masaaki; Yoshida, Norimasa; Takahara, Osamu; Takeyama, Norihide;
Suzuki, Masaharu; Abe, Shunichi
Bibcode: 2004SPIE.5487.1142I
Altcode:
The solar optical telescope onboard the Solar-B is aimed to perform a
high precision polarization measurements of the solar spectral lines
in visible wavelengths to obtain, for the first time, continuous
sets of high spatial resolution (~0.2arcsec) and high accuracy
vector-magnetic-field map of the sun for studying the mechanisms
driving the fascinating activity phenomena occurring in the solar
atmosphere. The optical telescope assembly (OTA) is a diffraction
limited, aplanatic Gregorian telescope with an aperture of Φ500mm. With
a collimating lens unit and an active folding mirror, the OTA provides
a pointing-stabilized parallel beam to the focal plane package (FPP)
with a field of view of about 360x200arcsec. In this paper we identify
the key technical issues of OTA for achieving the mission goal and
describe the basic concepts in its optical, mechanical and thermal
designs. The strategy to verify the in-orbit performance of the
telescope is also discussed.
Title: Heating of the solar corona and fine magnetic structure in
the photosphere
Authors: Katsukawa, Yukio
Bibcode: 2004AstHe..97..571K
Altcode: 2004AstHe..97..571N
It is important to investigate magnetic connection between the
photosphere and the corona for understanding the heating mechanism
of the solar corona. We investigate what magnetic signature in
the photosphere is responsible for the difference in the coronal
temperature, and find that number density of fine magnetic elements
(magnetic filling factor) is significantly correlated with the heating
rate of the corona. This result suggests that motion of the magnetic
elements in the photosphere plays an important role in the heating of
the corona. The Solar-B satellite, which will be launched in 2006,
will provide an opportunity to perform direct investigation of the
correlation between the photospheric motion of fine magnetic elements
and the coronal heating.
Title: Observation of solar flare hard X-ray spectra using CdTe
detectors
Authors: Kobayashi, K.; Tsuneta, S.; Tamura, T.; Kumagai, K.;
Katsukawa, Y.; Kubo, M.; Sakamoto, Y.; Kohara, N.; Yamagami, T.;
Saito, Y.; Mori, K.
Bibcode: 2004AdSpR..33.1786K
Altcode:
We present the design and initial flight results of a balloon-borne
hard X-ray spectrometer for observing solar flares. The instrument
is designed for quantitative observation of nonthermal and thermal
components of solar flare hard X-ray emission, and has an energy range
of 15-120 keV and an energy resolution of 3 keV. The instrument is
a small (gondola weight 70 kg) system equipped with sixteen 10 ×
10 × 0.5 mm CdTe detectors, and designed for a 1-day flight at 41
km altitude. Detector temperature of -15 °C was achieved through
radiative cooling alone. Pre-flight tests confirmed that all detectors
exceeded the target 3 keV resolution. No flares were observed during
the 2001 flight, but the second flight on May 24, 2002 succeeded
in observing a class M1.1 flare. Preliminary analysis indicates the
observed spectrum is consistent with a purely thermal plasma at an
unusually high temperature of 47 mK.
Title: Observation of solar flare hard X-ray spectra using CdTe
detectors
Authors: Kobayashi, Ken; Tsuneta, Saku; Tamura, Tomonori; Kumagai,
Kazuyoshi; Katsukawa, Yukio; Kubo, Masahito; Sakamoto, Yasushi;
Kohara, Naoki; Yamagami, Takamasa; Saito, Yoshitaka; Mori, Kunishiro;
Kato, Genzo
Bibcode: 2004naoj.book...38K
Altcode:
No abstract at ADS
Title: What determines the coronal heating rate in the photosphere?
Authors: Katsukawa, Y.; Tsuneta, S.
Bibcode: 2004cosp...35.2233K
Altcode: 2004cosp.meet.2233K
Observations of the solar corona with Yohkoh/SXT, SOHO/EIT and TRACE
have revealed that individual loops of active region corona have their
own temperatures from 1 MK to 5 MK. The most significant difference
between hot (2 - 5 MK) SXT loops and cool (1 - 2 MK) EUV ones is that
heat input to maintain the hot loops is about one order of magnitude
larger than that for the cool loops. We investigate the photospheric
magnetic signature for the hot and cool loops with the Advanced Stokes
Polarimeter (ASP) to clarify what makes such a large difference in the
heat input. Footpoints of both loops have magnetic fields whose strength
is 1.2 - 1.3 kG and the orientation is almost vertical to the surface. A
significant difference is discovered in the magnetic filling factor,
which is defined by the fraction of a pixel filled with a magnetized
atmosphere. The footpoints of the hot loops have significantly lower
filling factor than the footpoints of the cool loops. If we interpret
the lower filing factor as multiple granular magnetic elements in
an ASP pixel, those elemental magnetic footpoints combined with
photospheric motion would provide enhanced coronal heating, leading
to the hot loops. Solar-B and STEREO will provide an opportunity to
perform direct investigation of the correlation between the photospheric
motion of magnetic elements and the coronal temperature.
Title: Thermo-optical testing of the solar optical telescope of
the Solar-B
Authors: Ichimoto, Kiyoshi; Nakagiri, Masao; Suematsu, Yoshinori;
Tamura, Tomonori; Tsuneta, Saku; Noguchi, Motokazu; Kato, Yoshihiro;
Otsubo, Seiji; Katsukawa, Yukio; Kubo, Masahito
Bibcode: 2004naoj.book....6I
Altcode:
No abstract at ADS
Title: Spatial and Temporal Extent of Solar Nanoflares and Their
Energy Range
Authors: Katsukawa, Yukio
Bibcode: 2003PASJ...55.1025K
Altcode:
Coronal X-ray emission observed with the Yohkoh Soft X-ray Telescope
(SXT) fluctuates with an amplitude larger than the Poisson photon
noise, as shown in our previous paper (Katsukawa, Tsuneta 2001, ApJ,
557, 343). This fluctuation is attributed to small energy events
(``nanoflares'') that cannot be identified as individual bursts. We
present here a detailed analysis of the fluctuation, particularly
concerning the spatial and temporal extents of the fluctuating
sources. A macro-pixel analysis of the intensity fluctuation reveals
that the spatial extent of the fluctuation is a few pixels of
SXT. The scale size may be due to the point-spread function of SXT,
and/or indicates the intrinsic size of the fluctuating source. An
auto-correlation analysis gives a loose upper limit of the time scale,
1 minute. Taking into account the spatial and temporal scales, the
energy of nanoflares estimated in the previous paper is updated to be
1022 to 1022 erg.
Title: Development and flight performance of the sun sensor for
balloon observation
Authors: Tamura, Tomonori; Kobayashi, Ken; Tsuneta, Saku; Kubo,
Masahito; Katsukawa, Yukio
Bibcode: 2003RNAOJ...6..117T
Altcode:
We developed a sun-sensor for the balloon mission to observe solar
flare hard X-ray spectra using CdTe detectors. The sensor utilizes a
position-sensitive detector (PSD) with a pinhole, and has 60 degrees ×
60 degrees field-of-view with a 1 degree resolution. The sun-sensor
operated nominally during the two flights. We report the design,
ground calibration, and flight performance.
Title: Balloon-borne hard x-ray spectrometer for flare observations
Authors: Kobayashi, Ken; Tsuneta, Saku; Tamura, Tomonori; Kumagai,
Kazuyoshi; Katsukawa, Yukio; Kubo, Masahito; Yamagami, Takamasa;
Saito, Yoshitaka
Bibcode: 2003SPIE.4851.1009K
Altcode:
We present the design and initial flight results of a balloon-borne
hard X-ray detector system for observing high-resolution spectra of
solar flares. The instrument is designed to achieve a 3 keV energy
resolution over the energy range of 15-120 keV. The instrument uses
sixteen 10×10×0.5mm cadmium telluride (CdTe) detectors with indium
electrodes that act as Schottky barriers. Pre-flight tests confirmed
that all detectors exceeded the target 3 keV resolution. The detector
system is designed to optimize radiative cooling in order to achieve
the operating temperature of 0°C without refrigeration mechanisms. The
first flight took place on August 29, 2001 and while no major flares
were observed, the instrument operation was verified and a detector
temperature of -13° C was achieved. The second flight took place on
May 24, 1974 and during the 8 hours of level flight at an altitude of
41km, we succeeded in observing a class M1.1 solar flare.
Title: Development of the Solar-B spacecraft
Authors: Tsuneta, Saku; Ichimoto, Kiyoshi; Suematsu, Yoshinori;
Shimizu, Toshifumi; Hara, Hirohisa; Kano, Ryohei; Nagata, Shin'ichi;
Tamura, Tomonori; Nakagiri, Masao; Noguchi, Motokazu; Kato, Yoshihiro;
Watanabe, Tetsuya; Hanaoka, Yoichiro; Sawa, Masaki; Otsubo, Masashi;
Kosugi, Takeo; Yamada, Takahiro; Sakao, Taro; Matsuzaki, Keiichi;
Minesugi, Kenji; Onishi, Akira; Katsukawa, Yukio; Kobayashi, Ken;
Kubo, Masahito
Bibcode: 2003naoj.book....3T
Altcode:
No abstract at ADS
Title: Development of Solar-B solar optical telescope
Authors: Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Nagata, Shin'ichi; Tamura, Tomonori; Tsuneta, Saku; Noguchi, Motokazu;
Kato, Yoshihiro; Nakagiri, Masao; Otsubo, Masashi; Hanaoka, Yoichiro;
Katsukawa, Yukio; Kobayashi, Ken; Kubo, Masahito
Bibcode: 2003naoj.book....5S
Altcode:
No abstract at ADS
Title: Small fluctuation of coronal X-ray intensity: possibility of
nanoflare heating
Authors: Katsukawa, Yukio; Tsuneta, Saku
Bibcode: 2003naoj.book...41K
Altcode:
No abstract at ADS
Title: Balloon-Borne Hard X-ray Spectrometer for Flare Observations
Authors: Kobayashi, K.; Tsuneta, S.; Tamura, T.; Kumagai, K.;
Katsukawa, Y.; Kubo, S.; Yamagami, T.; Saitoh, Y.
Bibcode: 2002mwoc.conf..429K
Altcode:
We present an overview of a balloon-borne hard X-ray detector system
designed for high spectral resolution observation of solar flares. The
goal is to achieve a 3-keV energy resolution over an energy range of
15--100 keV, to observe both non-thermal and thermal components of the
solar flare hard X-ray emission. We achieve this by using an array of
16 CdTe detectors, each with a 10 times 10 times 0.5 mm size. These
detectors use an Indium electrode on one side which act as a Shottky
barrier, reducing leak current and improving energy resolution compared
to conventional CdTe detectors. The detectors are passively shielded by
2 mm of lead. The detectors are installed in a pressurized enclosure to
prevent coronal discharge. In order to maximize passive cooling, thermal
shields are installed around the detector housing to block sunlight and
infrared emission from the ground. Thermal math models indicate that
the detectors will be cooled to below 0circC. The signal
from the 16 detectors are processed by independent preamplifiers and
amplifiers, and a custom-designed 16 channel multichannel analyzer
acquires the signal and constructs 16 independent spectra. These are
read every 0.56 seconds and transmitted by telemetry. A 0.14 second
resolution counter is used to correct for dead time. The instrument
is currently undergoing testing and calibration, and first flight is
scheduled for September 2001 from an ISAS (Institute of Space and
Astronautical Science) facility in Sanriku, Japan. The flight will
last one day at an altitude of 42 km.
Title: Small Fluctuations of Coronal X-ray Intensity: A Signature
of Nanoflares
Authors: Katsukawa, Y.; Tsuneta, A.
Bibcode: 2002mwoc.conf...61K
Altcode:
If small energy events (nanoflares) contribute to the heating of the
solar corona, they may be too small to be recognized as independent
events. We analyze fluctuation of X-ray intensity observed with Soft
X-Ray Telescope (SXT) aboard Yohkoh satellite to detect the tiny events
which may occur in the solar corona. When we create a simple histogram
of the X-Ray intensity fluctuation around mean intensity, we find that
the histogram consists of a central Gaussian component and a wing
component. The Gaussian component corresponds to random fluctuation
around the mean X-ray intensity. The width of this component becomes
broader with increasing intensity, and is larger than the width of
the predicted photon noise distribution. We suggest that nanoflares
produce the observed fluctuation of the X-ray intensity. We derive
the analytical expression for the intensity fluctuation to estimate
the individual energy of nanoflares from the observed intensity
fluctuation. The intensity fluctuation can be related with the mean
X-ray intensity, the energy of nanoflares, and the time scale of
individual nanoflares. By comparing the observed fluctuation with the
analytical expression, we are able to estimate the individual energy
of nanoflares. The estimated energy ranges from 1020 to
1023 ergs. The observed fluctuation corresponds to an energy
much smaller than previously predicted energy. It is estimated that if
the energy of nanoflares is 1021 ergs, then these nanoflares
must occur at a rate of 105 s-1 in a single active
region (sim 1020 cm2) to supply the required
energy (~ 5 times 107 ergs cm-2s-1)
to maintain the solar corona.
Title: Observation of solar flare hard x-ray spectra using CdTe
detectors
Authors: Kobayashi, K.; Tsuneta, S.; Tamura, T.; Kumagai, K.;
Katsukawa, Y.; Kubo, M.; Sakamoto, Y.; Yamagami, T.; Saito, Y.;
Mori, K.
Bibcode: 2002cosp...34E1971K
Altcode: 2002cosp.meetE1971K
We present the design and flight results of a balloon-borne hard
X-ray detector system for observing high-resolution spectra of solar
flares. The instrument is designed to achieve a 3 keV energy resolution
over the energy range of 15-120 keV. The instrument uses sixteen 10 ×
10 × 0.5 mm cadmium telluride (CdTe) detectors with indium electrodes
that act as Schottky barriers to minimize leak current and allow a high
bias voltage. Pre-flight tests confirmed that all detectors exceeded
the target 3 keV resolution. The pressurized detector vessel uses
a low-density (0.1 g/cm^2) CFRP/Rohacell window. The detectors are
passively shielded by 2 mm of lead, and field of view is constrained
with a graded-Z collimator. The vertical angle of the detectors are
fixed at 45 degrees, and the azimuth angle of the entire gondola
is controlled using a signal from a sun position sensor. Specially
developed electronics accumulate a 128 channel spectrum for each
detector, which is read through telemetry every 0.54 seconds. These
detectors need to be cooled down to 0 degrees C for optimal performance;
due to weight constraints this was achieved purely by radiative cooling,
using the detector enclosure surface as a radiator and by placing
shields that minimize radiative heat input from the sun and earth while
maximizing heat loss to the sky. The first flight of the instrument
took place on August 29, 2001 and while no major flares were observed,
we succeeded in detecting a small brightening (microflare). Detector
temperature of -13 degrees C was achieved, and all systems performed
as expected. The instrument was recovered successfully after the flight
and a second flight is planned for May 2002.
Title: Small Fluctuation of Coronal X-Ray Intensity and a Signature
of Nanoflares
Authors: Katsukawa, Yukio; Tsuneta, Saku
Bibcode: 2001ApJ...557..343K
Altcode:
If small energy events (nanoflares) contribute to the heating of the
solar corona, they may be too small to be recognized as independent
events. We create a simple histogram of the X-ray intensity fluctuation
around the mean intensity and find that the histogram consists of a
central Gaussian component and a wing component. The Gaussian component
corresponds to random fluctuation around the mean intensity. The width
of this component becomes broader with increasing intensity and is
larger than the predicted photon noise distribution. We suggest that
nanoflares produce the observed fluctuation of the X-ray intensity. The
energy of nanoflares is estimated to be less than 1022 ergs
to explain the observed fluctuation for active regions. It is estimated
that if the energy of nanoflares is 1020 ergs, then these
nanoflares must occur at a rate of 106 s-1 in a
single active region (~1020 cm2) to supply the
required energy (~5×107 ergs cm-2 s-1)
to maintain the corona.
Title: Scaling Laws for a Nanoflare-Heated Solar Corona
Authors: Vekstein, G.; Katsukawa, Y.
Bibcode: 2000ApJ...541.1096V
Altcode:
The concept that the solar corona is heated by numerous small flarelike
events dubbed ``nanoflares'' is considered. The hot corona is viewed as
an ensemble of high-temperature elemental magnetic filaments created
within the coronal magnetic field by randomly distributed impulsive
heating events. It is shown that such an approach allows us to predict
various signatures of X-ray coronal loops without specifying the
details of the heating process. In particular, the dependence of the
temperature, filling factor, and emission measure on the length of
the loop and strength of the coronal magnetic field is derived. The
obtained scaling laws fit reasonably with observational data.