Author name code: ichimoto
ADS astronomy entries on 2022-09-14
author:"Ichimoto, Kiyoshi"
------------------------------------------------------------------------
Title: Polarization calibration of the Tandem Etalon Magnetograph
of the Solar Magnetic Activity Research Telescope at Hida Observatory
Authors: Yamasaki, Daiki; Nagata, Shin'ichi; Ichimoto, Kiyoshi
Bibcode: 2022arXiv220810696Y
Altcode:
The Tandem Etalon Magnetograph (TEM) is one of the instruments of the
Solar Magnetic Activity Research Telescope of Hida Observatory. The
TEM is a partial disk (320" x240") filter magnetograph which scans
the wavelength around a Fe I line at 6303 angstrom and achieves
polarimetric sensitivity of < 5x10^-4 for each wavelength. To obtain
the polarimeter response matrix of the instrument, we have carried out
end-to-end polarization calibrations of the instrument. We have also
measured the polarization characteristics of the polarization beam
splitter (PBS), which is a crucial component of the instrument. As a
result of end-to-end calibration, we found significant spatial variation
in the response matrix across the field of view. From a laboratory test,
we found that 1% of the magnitude of a circular diattenuation of the
PBS was due to the retardation caused by the stress in the cube and
the linear diattenuation of the film. Although the spatial variation
across the field of view is more than ten times larger, to achieve the
polarimetric sensitivity of < 5x10^-4, this can be well explained by
the polarization characteristic of the PBS and corrected by using the
response matrix obtained in the end-to-end calibration. In addition, we
also obtained the daily variation of the polarization property of the
TEM. We found that the crosstalk from Stokes Q to V changes an amount
comparable to the tolerance through a day. In the present configuration,
we require a pixel-by-pixel calibration every 100 minutes to meet the
accuracy requirement.
Title: Universal Correlation between the Ejected Mass and Total
Flare Energy for Solar and Stellar Cold Plasma Ejection
Authors: Kotani, Yuji; Otsuji, Kenichi; Shibata, Kazunari; Asai,
Ayumi; Ichimoto, Kiyoshi; Ishii, Takako; Yamasaki, Daiki
Bibcode: 2022cosp...44.2450K
Altcode:
We often find spectral signatures of chromospheric plasma ejections
accompanied by flares in various spatial scales in the solar and stellar
atmospheres. Similar spectral signatures are found regardless of their
wide range of scale. However, no physical quantities such as mass and
energy have been estimated for flare energies covering over 10 orders
of magnitude until now. In this study, we analyzed the spectra of
cold plasma ejections associated with flares by performing H$\alpha$
imaging spectroscopy of the solar full-disk with SMART/SDDI. We
determined the ejected mass by cloud model fitting to the H$\alpha$
spectrum. We estimated flare energy by DEM analysis using SDO/AIA
for small-scale flares and by estimating the bolometric energy for
large-scale flares. In addition, we constructed a scaling law for
the total flare energy and the ejected mass and compared it with our
observation. The results are in good agreement with the scaling law for
small mass ejections with small flares in the quiet region for a coronal
field strength of 5 G and filament eruptions with flares for that of 5 -
50 G. We also compared it with the observations interpreted as stellar
filament eruptions, and found that they were roughly consistent with
the scaling law. These results suggest that cold plasma ejections with
flares taking place on the sun and stars in a wide range of the energy
scale are caused by a common mechanism.
Title: Sun-as-a-star analysis of H-alpha spectra for various active
events on the Sun
Authors: Otsu, Takato; Asai, Ayumi; Ichimoto, Kiyoshi; Namekata,
Kosuke; Ishii, Takako
Bibcode: 2022cosp...44.1380O
Altcode:
The surface of the Sun can be observed with high spatial resolution. On
the other hand, the surfaces of distant stars cannot be spatially
resolved. From this background, detailed data of the Sun have been
utilized for analysis of stellar data in recent years (e.g., Toriumi
et al. 2020, Namekata et al. 2021). For comparison with stellar data,
solar data are spatially integrated and such an analysis is called
Sun-as-a-star analysis. Namekata et al. (2021) carried out Sun-as-a-star
analysis of the H$\alpha$ spectra for solar flares accompanied by
filament eruptions in order to interpret the H$\alpha$ spectra for a
stellar flare. From a resemblance between them, the authors concluded
that a stellar filament eruption associated the detected stellar
flare. On the basis of Namekata et al. (2021), Sun-as-a-star analysis
of H$\alpha$ spectra is useful to investigate the motion of plasma on
a stellar surface. Therefore, it is important to study Sun-as-a-star
analysis of H$\alpha$ spectra for, in addition to flares, other various
active events on the Sun. Here we report a result of Sun-as-a-star
analysis of H$\alpha$ spectra for various solar active events,
namely, flares, filament eruptions, and prominence eruptions. We used
full-disk solar H$\alpha$ spectral data observed by SMART/SDDI at Hida
observatory, Kyoto University. SMART/SDDI can takes full-disk solar
images in the wavelengths from H$\alpha$ $-9.0$~{\AA} to H$\alpha$
$+9.0$~{\AA} with the spectral resolution of 0.25~{\AA} and the time
cadence of 12-16 sec (Ichimoto et al. 2017). All analyzed events show
brightening relative to pre-event and their changes in H$\alpha$
equivalent width are the same orders of $10^{-4}$~{\AA}. However,
there are different features in H$\alpha$ spectra depending on
causes of brightening: brightening near H$\alpha$ center with red
asymmetry and line broadening due to flares, brightening near H$\alpha$
center accompanied by shifted absorptions due to filament eruptions,
and shifted brightening due to prominence eruptions. These spectral
features can be used to diagnose the causes of brightening even though
the changes in the H$\alpha$ equivalent width are similar. Our result
can be helpful in studying various active events on stars.
Title: Sun-as-a-star Analysis of Hα Spectra of a Solar Flare Observed
by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening
Authors: Namekata, Kosuke; Ichimoto, Kiyoshi; Ishii, Takako T.;
Shibata, Kazunari
Bibcode: 2022ApJ...933..209N
Altcode: 2022arXiv220601395N
Stellar flares sometimes show red/blue asymmetries of the Hα
line, which can indicate chromospheric dynamics and prominence
activations. However, the origin of asymmetries is not completely
understood. For a deeper understanding of stellar data, we performed
a Sun-as-a-star analysis of Hα line profiles of an M4.2-class solar
flare showing dominant emissions from flare ribbons by using the
data of the Solar Dynamics Doppler Imager on board the Solar Magnetic
Activity Research Telescope at the Hida Observatory. Sun-as-a-star Hα
spectra of the flare show red asymmetry of up to ~95 km s-1
and line broadening of up to ~7.5 Å. The Sun-as-a-star Hα profiles
are consistent with spectra from flare regions with weak intensity, but
they take smaller redshift velocities and line widths by a factor of ~2
than those with strong intensity. The redshift velocities, as well as
line widths, peak out and decay more rapidly than the Hα equivalent
widths, which is consistent with the chromospheric condensation
model and spatially resolved flare spectra. This suggests that as
a result of superposition, the nature of chromospheric condensation
is observable even from stellar flare spectra. The time evolution of
redshift velocities is found to be similar to that of luminosities
of near-ultraviolet rays (1600 Å), while the time evolution of
line broadening is similar to that of optical white lights. These Hα
spectral behaviors in Sun-as-a-star view could be helpful to distinguish
whether the origin of Hα red asymmetry of stellar flares is a flare
ribbon or other phenomena.
Title: Detection of Filament Eruption from a Superflare on a
Solar-Type Star
Authors: Namekata, Kosuke; Maehara, Hiroyuki; Honda, Satoshi; Notsu,
Yuta; Okamoto, Soshi; Takahashi, Jun; Takayama, Masaki; Ohshima,
Tomohito; Saito, Tomoki; Katoh, Noriyuki; Tozuka, Miyako; Murata,
Katsuhiro; Ogawa, Futa; Niwano, Masafumi; Adachi, Ryo; Oeda, Motoki;
Shiraishi, Kazuki; Isogai, Keisuke; Seki, Daikichi; Ishii, Takako;
Ichimoto, Kiyoshi; Nogami, Daisaku; Shibata, Kazunari
Bibcode: 2021AGUFM.U43B..03N
Altcode:
Solar flares are often accompanied by filament/prominence eruptions,
sometimes leading to coronal mass ejections (CMEs) that directly affect
the Earth's environment. Very large flares called `superflares' are
found on some active solar-type (G-type main-sequence) stars (Maehara
et al. 2012, Nature), but the association of filament eruptions/CMEs
is unknown. Here we show that our optical spectroscopic observation of
the young solar-type star EK Draconis reveals the first evidence for
a stellar filament eruption associated with a superflare on solar-type
stars (Namekata et al. submitted). We monitored EK Draconis for about
30 nights with the TESS photometry and ground-based spectroscopy
onboard the Seimei Telescope (Japan) and Nayuta Telescope (Japan),
and finally detected a superflare with the TESS white-light and H-alpha
(Figure 1A). After the superflare with radiated energy of 2.0×1033 erg,
a blue-shifted hydrogen absorption component with a large velocity of
-510 km s-1 appeared (Figure 1B). The temporal changes in the spectra
greatly resemble those of the-Sun-as-a-star solar filament eruptions
observed by SMART telescope at Hida Observatory, indicating a common
process of solar and stellar filament eruptions. The comparison of this
eruption with solar filament eruptions in terms of the length scale and
velocity strongly suggests that this would eventually become a stellar
CME. The erupted filament mass of 1.1×1018 g is 10 times larger than
those of the largest solar CMEs. The huge filament eruption and an
associated CME on the young solar-type star provide the opportunity
to evaluate how they affect the environment of young exoplanets/young
Earth and stellar mass/angular-momentum evolution.
Title: Probable detection of an eruptive filament from a superflare
on a solar-type star
Authors: Namekata, Kosuke; Maehara, Hiroyuki; Honda, Satoshi; Notsu,
Yuta; Okamoto, Soshi; Takahashi, Jun; Takayama, Masaki; Ohshima,
Tomohito; Saito, Tomoki; Katoh, Noriyuki; Tozuka, Miyako; Murata,
Katsuhiro L.; Ogawa, Futa; Niwano, Masafumi; Adachi, Ryo; Oeda,
Motoki; Shiraishi, Kazuki; Isogai, Keisuke; Seki, Daikichi; Ishii,
Takako T.; Ichimoto, Kiyoshi; Nogami, Daisaku; Shibata, Kazunari
Bibcode: 2022NatAs...6..241N
Altcode: 2021NatAs...6..241N; 2021arXiv211204808N; 2021NatAs.tmp..246N
Solar flares are often accompanied by filament/prominence eruptions
(~104 K and ~1010−11 cm−3),
sometimes leading to coronal mass ejections that directly affect
the Earth's environment1,2. `Superflares' are found on
some active solar-type (G-type main-sequence) stars3-5,
but the filament eruption-coronal mass ejection association has
not been established. Here we show that our optical spectroscopic
observation of the young solar-type star EK Draconis reveals evidence
for a stellar filament eruption associated with a superflare. This
superflare emitted a radiated energy of 2.0 × 1033 erg,
and a blueshifted hydrogen absorption component with a high velocity of
−510 km s−1 was observed shortly afterwards. The temporal
changes in the spectra strongly resemble those of solar filament
eruptions. Comparing this eruption with solar filament eruptions in
terms of the length scale and velocity strongly suggests that a stellar
coronal mass ejection occurred. The erupted filament mass of 1.1 ×
1018 g is ten times larger than those of the largest solar
coronal mass ejections. The massive filament eruption and an associated
coronal mass ejection provide the opportunity to evaluate how they
affect the environment of young exoplanets/the young Earth6
and stellar mass/angular momentum evolution7.
Title: Investigation on the Evolution of the Nonpotential Magnetic
Field and the Onset Mechanism of the Successive M-class Solar Flares
in the Active Region NOAA 12673 Based on a Nonlinear Force-Free
Modeling
Authors: Yamasaki, Daiki; Inoue, Satoshi; Kusano, Kanya; Ishii,
Takako; Asai, Ayumi; Nagata, Shin'ichi; Ichimoto, Kiyoshi
Bibcode: 2021AGUFMSH23B..03Y
Altcode:
In September 2017, Active region (AR) NOAA 12673 has produced many
M-class and several X-class flares, one of which being an X9.3 flare,
which is recorded as the largest solar flare in solar cycle 24. Although
many M- and C-class flares have been observed before the occurrence
of the X-flares, the magnetic field structure before the flares and
the flare triggering mechanism have been not studied well. Therefore,
in this study, we reveal the magnetic field structure prior to the
flares and flare triggering mechanism, in particular, of M5.5 flare,
which is the largest M-class flare observed in AR 12673. In our study,
we analyzed the evolution of the three-dimensional magnetic field in AR
12673, using a time series of nonlinear force-free field extrapolations
of every 12 hours from 2017 September 4 00:00 UT to 6 00:00 UT. We
found that three magnetic flux ropes (MFRs) formed by September 4,
one of which produced the X9.3 flare on September 6. One MFR has
positive magnetic twist, which is a different sign from the other two
MFRs. Since the several M-class flares were observed when the time
profile of the magnetic flux of the MFR accumulating the positive
twist had a peak, we suggest that the formation of the MFR having the
positive twist is closely related to the occurrence of the M-class
flares, including an M5.5 flare. We further found a magnetic null in
the magnetic field surrounding the MFRs, which, in particular, locates
above the MFR having positive twist. By comparing with Atmospheric
Imaging Assembly 1600 angstrom images, we found that the footpoints
of the overlying field lines are anchored to the area where initial
brightening associated with the M5.5 flare was observed. Therefore,
we suggest that reconnection at the magnetic null possibly drove the
M5.5 flare. In addition, M4.2 flares was observed about 4.5 hours after
the onset of the M5.5 flare, and the initial brightenings and the flare
ribbons were observed in spatially similar location in AIA 1600 angstrom
in both flares. Interestingly, CME was only observed shortly after the
peak time of the M5.5 flare. In our presentation, we further discuss
the onset mechanism of the successive M-class flares and the cause of
the difference on the CME association in these two M-class flares.
Title: Space weather benchmarks on Japanese society
Authors: Ishii, Mamoru; Shiota, Daikou; Tao, Chihiro; Ebihara,
Yusuke; Fujiwara, Hitoshi; Ishii, Takako; Ichimoto, Kiyoshi; Kataoka,
Ryuho; Koga, Kiyokazu; Kubo, Yuki; Kusano, Kanya; Miyoshi, Yoshizumi;
Nagatsuma, Tsutomu; Nakamizo, Aoi; Nakamura, Masao; Nishioka, Michi;
Saito, Susumu; Sato, Tatsuhiko; Tsugawa, Takuya; Yoden, Shigeo
Bibcode: 2021EP&S...73..108I
Altcode:
We surveyed the relationship between the scale of space weather events
and their occurrence rate in Japan, and we discussed the social
impact of these phenomena during the Project for Solar-Terrestrial
Environment Prediction (PSTEP) in 2015-2019. The information was
compiled for domestic users of space weather forecasts for appropriate
preparedness against space weather disasters. This paper gives
a comprehensive summary of the survey, focusing on the fields of
electricity, satellite operations, communication and broadcasting,
satellite positioning usage, aviation, human space activity, and
daily life on the Earth's surface, using the cutting-edge knowledge
of space weather. Quantitative estimations of the economic impact
of space weather events on electricity supply and aviation are also
given. Some topics requiring future research, which were identified
during the survey are also described.
Title: PSTEP: project for solar-terrestrial environment prediction
Authors: Kusano, Kanya; Ichimoto, Kiyoshi; Ishii, Mamoru; Miyoshi,
Yoshizumi; Yoden, Shigeo; Akiyoshi, Hideharu; Asai, Ayumi; Ebihara,
Yusuke; Fujiwara, Hitoshi; Goto, Tada-Nori; Hanaoka, Yoichiro;
Hayakawa, Hisashi; Hosokawa, Keisuke; Hotta, Hideyuki; Hozumi,
Kornyanat; Imada, Shinsuke; Iwai, Kazumasa; Iyemori, Toshihiko; Jin,
Hidekatsu; Kataoka, Ryuho; Katoh, Yuto; Kikuchi, Takashi; Kubo, Yûki;
Kurita, Satoshi; Matsumoto, Haruhisa; Mitani, Takefumi; Miyahara,
Hiroko; Miyoshi, Yasunobu; Nagatsuma, Tsutomu; Nakamizo, Aoi; Nakamura,
Satoko; Nakata, Hiroyuki; Nishizuka, Naoto; Otsuka, Yuichi; Saito,
Shinji; Saito, Susumu; Sakurai, Takashi; Sato, Tatsuhiko; Shimizu,
Toshifumi; Shinagawa, Hiroyuki; Shiokawa, Kazuo; Shiota, Daikou;
Takashima, Takeshi; Tao, Chihiro; Toriumi, Shin; Ueno, Satoru;
Watanabe, Kyoko; Watari, Shinichi; Yashiro, Seiji; Yoshida, Kohei;
Yoshikawa, Akimasa
Bibcode: 2021EP&S...73..159K
Altcode:
Although solar activity may significantly impact the global environment
and socioeconomic systems, the mechanisms for solar eruptions and
the subsequent processes have not yet been fully understood. Thus,
modern society supported by advanced information systems is at risk
from severe space weather disturbances. Project for solar-terrestrial
environment prediction (PSTEP) was launched to improve this situation
through synergy between basic science research and operational
forecast. The PSTEP is a nationwide research collaboration in Japan
and was conducted from April 2015 to March 2020, supported by a
Grant-in-Aid for Scientific Research on Innovative Areas from the
Ministry of Education, Culture, Sports, Science and Technology of
Japan. By this project, we sought to answer the fundamental questions
concerning the solar-terrestrial environment and aimed to build a
next-generation space weather forecast system to prepare for severe
space weather disasters. The PSTEP consists of four research groups and
proposal-based research units. It has made a significant progress in
space weather research and operational forecasts, publishing over 500
refereed journal papers and organizing four international symposiums,
various workshops and seminars, and summer school for graduate students
at Rikubetsu in 2017. This paper is a summary report of the PSTEP and
describes the major research achievements it produced.
Title: Relationship between three-dimensional velocity of filament
eruptions and CME association
Authors: Seki, Daikichi; Otsuji, Kenichi; Ishii, Takako T.; Asai,
Ayumi; Ichimoto, Kiyoshi
Bibcode: 2021EP&S...73...58S
Altcode: 2021arXiv210204578S
It is widely recognised that filament disappearances or eruptions are
frequently associated with Coronal Mass Ejections (CMEs). Since CMEs
are a major source of disturbances of the space environment surrounding
the Earth, it is important to investigate these associations in detail
for the better prediction of CME occurrence. However, the proportion
of filament disappearances associated with CMEs is under debate. The
estimates range from ∼ 10 to ∼ 90% and could be affected by the
manners to select the events. In this study, we aim to reveal what
parameters control the association between filament eruptions and
CMEs. We analysed the relationships between CME associations and the
physical parameters of filaments including their length, maximum
ascending velocity, and direction of eruptions using 28 events of
filament eruptions observed in Hα . We found that the product of the
maximum radial velocity and the filament length is well correlated with
the CME occurrence. If the product is larger than 8.0 ×106
km2s-1, the filament will become a CME with a
probability of 93%, and if the product is smaller than this value,
it will not become a CME with a probability of 100%. We suggest a
kinetic-energy threshold above which filament eruptions are associated
with CMEs. Our findings also suggest the importance of measuring the
velocity vector of filament eruption in three-dimensional space for
the better prediction of CME occurrence.
Title: Special issue "Solar-terrestrial environment prediction:
toward the synergy of science and forecasting operation of space
weather and space climate"
Authors: Kusano, Kanya; Ishii, Mamoru; Berger, Tomas; Miyoshi,
Yoshizumi; Yoden, Shigeo; Liu, Huixin; Onsager, Terry; Ichimoto,
Kiyoshi
Bibcode: 2021EP&S...73..198K
Altcode:
No abstract at ADS
Title: Unusual enhancement of 30 MeV proton flux in an ICME
sheath region
Authors: Oka, Mitsuo; Obara, Takahiro; Nitta, Nariaki V.; Yashiro,
Seiji; Shiota, Daikou; Ichimoto, Kiyoshi
Bibcode: 2021EP&S...73...31O
Altcode:
In gradual Solar Energetic Particle (SEP) events, shock waves driven
by coronal mass ejections (CMEs) play a major role in accelerating
particles, and the energetic particle flux enhances substantially
when the shock front passes by the observer. Such enhancements are
historically referred to as Energetic Storm Particle (ESP) events,
but it remains unclear why ESP time profiles vary significantly from
event to event. In some cases, energetic protons are not even clearly
associated with shocks. Here, we report an unusual, short-duration
proton event detected on 5 June 2011 in the compressed sheath
region bounded by an interplanetary shock and the leading edge of the
interplanetary CME (or ICME) that was driving the shock. While < 10
MeV protons were detected already at the shock front, the higher-energy
(> 30 MeV) protons were detected about four hours after the shock
arrival, apparently correlated with a turbulent magnetic cavity embedded
in the ICME sheath region.
Title: Small-scale Turbulent Motion of the Plasma in a Solar Filament
as the Precursor of Eruption
Authors: Seki, Daikichi; Otsuji, Kenichi; Isobe, Hiroaki; Del Zanna,
Giulio; Ishii, Takako T.; Sakaue, Takahito; Ichimoto, Kiyoshi;
Shibata, Kazunari
Bibcode: 2021ApJ...918...38S
Altcode: 2021arXiv210611875S
A filament, a dense cool plasma supported by the magnetic fields in
the solar corona, often becomes unstable and erupts. It is empirically
known that the filament often demonstrates some activations such
as a turbulent motion prior to eruption. In our previous study, we
analyzed the Doppler velocity of an Hα filament and found that the
standard deviation of the line-of-sight velocity distribution in a
filament, which indicates the increasing amplitude of the small-scale
motions, increased prior to the onset of the eruption. Here, we
present a further analysis on this filament eruption, which initiated
approximately at 03:40 UT on 2016 November 5 in the vicinity of NOAA
Active Region 12605. It includes a coronal line observation and the
extrapolation of the surrounding magnetic fields. We found that both
the spatially averaged microturbulence inside the filament and the
nearby coronal line emission increased 6 and 10 hr prior to eruption,
respectively. In this event, we did not find any significant changes
in the global potential field configuration preceding the eruption for
the past 2 days, which indicates that there is a case in which it is
difficult to predict the eruption only by tracking the extrapolated
global magnetic fields. In terms of space weather prediction, our
result on the turbulent motions in a filament could be used as the
useful precursor of a filament eruption.
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: Unusual enhancement of 30 MeV proton flux in an ICME sheath
region
Authors: Oka, Mitsuo; Obara, Takahiro; Nitta, Nariaki; Yashiro, Seiji;
Shiota, Daikou; Ichimoto, Kiyoshi
Bibcode: 2021EGUGA..23..421O
Altcode:
In gradual Solar Energetic Particle (SEP) events, shock waves driven
by coronal mass ejections (CMEs) play a major role in accelerating
particles, and the energetic particle flux enhances substantially
when the shock front passes by the observer. Such enhancements are
historically referred to as Energetic Storm Particle (ESP) events,
but it remains unclear why ESP time profiles vary significantly from
event to event. In some cases, energetic protons are not even clearly
associated with shocks. Here we report an unusual, short-duration proton
event detected on 5 June 2011 in the compressed sheath region bounded
by an interplanetary shock and the leading-edge of the interplanetary
CME (or ICME) that was driving the shock. While <10 MeV protons
were detected already at the shock front, the higher-energy (>30
MeV) protons were detected about four hours after the shock arrival,
apparently correlated with a turbulent magnetic cavity embedded in
the ICME sheath region.
Title: Detection of mass ejection from a superflare on a solar-type
star
Authors: Namekata, Kosuke; Maehara, Hiroyuki; Honda, Satoshi; Notsu,
Yuta; Okamoto, Soshi; Takahashi, Jun; Takayama, Masaki; Ohshima,
Tomohito; Saito, Tomoki; Katoh, Noriyuki; Tozuka, Miyako; Murata,
Katsuhiro; Ogawa, Futa; Niwano, Masafumi; Adachi, Ryo; Oeda, Motoki;
Shiraishi, Kazuki; Isogai, Keisuke; Ishii, Takako; Ichimoto, Kiyoshi;
Nogami, Daisaku; Shibata, Kazunari
Bibcode: 2021csss.confE.152N
Altcode:
Solar and stellar flares are caused by the sudden release of magnetic
energy on the surfaces. In the case of the Sun, mass ejections often
accompany solar flares and affect the Earth's environment. Active
solar-type stars (G-type main-sequence stars) sometimes show larger
`superflares' (Maehara et al. 2012) that may cause more huge mass
ejections than those of solar flares. The stellar mass ejections can
greatly affect the exoplanet habitability and the stellar mass evolution
(e.g. Airapetian et al. 2020). However, no observational indication
of mass ejection has been reported especially for solar-type stars.We
conducted spectroscopic monitoring observations of the active young
solar analog EK Dra (a famous zero-age main-sequence G-dwarf) by our
new 3.8-m Seimei telescope, simultaneously with TESS photometry. Our
time-resolved optical spectroscopic observation shows clear evidence for
a stellar mass ejection associated with a superflare on the solar-type
star (Namekata et al. submitted). After the superflare brightening
with the radiated energy of 2.0×1033 erg observed by TESS,
a blue-shifted H-alpha absorption component with a velocity of -510 km
s-1 appeared. The velocity gradually decayed in 2 hours and
the deceleration 0.34 km s-2 was consistent with the surface
gravity on EK Dra (0.30 ± 0.05 km s-2). The temporal changes
in the spectra greatly resemble that of a solar mass ejection observed
by the SMART telescope at Hida observatory. Moreover, the ejected
mass of 1.1×1018 g roughly corresponds to those predicted
from solar flare-energy/ejected-mass relation. These discoveries imply
that a huge stellar mass ejection occurs possibly in the same way as
solar ones. Our high-quality dataset can be helpful for future studies
to estimate its impacts on the young-planet atmosphere around young
solar-type stars as well as stellar mass/angular momentum evolution.
Title: Evolution of the Nonpotential Magnetic Field in the Solar
Active Region 12673 Based on a Nonlinear Force-free Modeling
Authors: Yamasaki, Daiki; Inoue, Satoshi; Nagata, Shin'ichi; Ichimoto,
Kiyoshi
Bibcode: 2021ApJ...908..132Y
Altcode: 2020arXiv201201008Y
Active region (AR) 12673 has produced many M-class and several X-class
flares, one of which being an X9.3 flare, which is recorded as the
largest solar flare in solar cycle 24. We studied the evolution of the
three-dimensional flare-productive magnetic field within AR 12673,
using a time series of nonlinear force-free field extrapolations of
every 12 hr from 2017 September 4 00:00 UT to 6 00:00 UT. Our analysis
found that three magnetic flux ropes (MFRs) formed by September 4,
one of which produced the X9.3 flare on September 6. One MFR has
positive magnetic twist, which is a different sign from the other two
MFRs. Since the temporal evolution of the magnetic flux of the MFR
accumulating the positive twist is consistent with the profile of the
GOES X-ray flux well observed from September 4 to 6, we suggest that
the formation of the MFR having the positive twist is closely related
to the occurrence of the M-class flares, including an M5.5 flare. We
further found a magnetic null in the magnetic field surrounding
the MFRs, in particular above the MFR having positive twist before
the M5.5 flare, which is the largest M-flare observed during this
period. By comparing with Atmospheric Imaging Assembly 1600 Å images,
we found that the footpoints of the overlying field lines are anchored
to the area where the brightening was initially observed. Therefore,
we suggest that reconnection induced by the torus instability of the
positively twisted MFR at the null possibly drove the M5.5 flare.
Title: First detection of stellar mass ejection from a superflare
on a solar-type star
Authors: Namekata, Kosuke; Ishii, Takako; Shibata, Kazunari; Ichimoto,
Kiyoshi; Honda, Satoshi; Maehara, Hiroyuki; Nogami, Daisaku; Notsu,
Yuta; Okamoto, Soshi
Bibcode: 2021cosp...43E1733N
Altcode:
Active solar-type stars sometimes show large `superflares' that may
cause huge mass ejections, greatly affecting the planetary environment
and the stellar mass evolution. However, no observational indication of
mass ejection has been reported especially for solar-type stars, and
furthermore, the signatures of mass ejections are very controversial
even for other kinds of magnetically active stars (e.g. cooler stars
and giant stars). We conducted a spectroscopic monitoring observations
of the active young solar-type star EK Draconis (EK Dra) by our new
3.8-m Seimei telescope, simultaneously with TESS satellite. Our
time-resolved optical spectroscopic observation shows the first,
conclusive evidence for a stellar mass ejection associated with a
superflare on the solar-type star. After the superflare brighntenings
with the radiated energy of $2.0\times10^{33}$ erg observed by TESS,
a blue-shifted H$\alpha$ absorption component with a velocity of
$-510$ km s$^{-1}$ appeared. The velocity gradually decayed in 1-2
hour and the deceleration 0.34 $km s$^{-2}$ was consistent with the
surface gravity on EK Dra (0.30 \pm 0.05 $km s$^{-2}$). The temporal
changes in the spectra greatly resemble that of solar mass ejections
observed by SMART telescope at Hida observatory. Moreover, the ejected
mass of $6.2\times10^{17}$ g corresponds to those predicted from solar
flare-energy/ejected-mass relation. These discoveries imply that a huge
stellar mass ejection did occur in the same way as solar ones, which
enables us to estimate its impacts on planets as well as mass/angular
momentum evolution.
Title: Statistical Analysis of the Relation between Coronal Mass
Ejections and Solar Energetic Particles
Authors: Kihara, K.; Nitta, N.; Yashiro, S.; Asai, A.; Ichimoto, K.
Bibcode: 2020AGUFMSH012..02K
Altcode:
To improve the forecasting capability of impactful solar energetic
particle (SEP) events, the relation between coronal mass ejections
(CMEs) and SEP events needs to be better understood. Here we present
a statistical study of SEP occurrences and timescales with respect
to the CME source locations and speeds, considering all 257 fast
(vCME ≥ 900 km/s) and wide (angular width ≥ 60°) CMEs
that occurred between December 2006 and October 2017. We associate
them with SEP events at energies above 10 MeV. Examination of the
source region of each CME reveals that CMEs more often accompany a
SEP event if they originate from the longitude of E20-W100 relative
to the observer. However, a SEP event could still be absent if the
CME is < 2000 km/s. For the associated CME-SEP pairs, we compute
three timescales for each of the SEP events, following Kahler (2005,
2013); namely the timescale of the onset (TO), the rise time (TR),
and the duration (TD). They are correlated with the longitude of
the CME source region relative to the footpoint of the Parker spiral
(ΔΦ) and vCME. The TO tends to be short for |ΔΦ| <
60° . This trend is weaker for TR and TD. The SEP timescales are only
weakly correlated with vCME. Positive correlations of both
TR and TD with vCME are seen in poorly connected (large
|ΔΦ|) events. Additionally, TO appears to be negatively correlated
with vCME for events with small |ΔΦ|.
Title: Estimation of Low-energy Cutoff of Non-thermal Electrons from
a Spectro-polarimetric Observation
Authors: Anan, T.; Yoneya, T.; Ichimoto, K.; Ueno, S.; Shiota, D.;
Nozawa, S.; Takasao, S.; Kawate, T.
Bibcode: 2020AGUFMSH0430015A
Altcode:
Low-energy cutoff of the non-thermal electron energy distribution
is crucial to derive the total non-thermal electron energy. A flare
kernel associated with a C4 class flare was observed in a spectral
window including the He I triplet 1083.0 nm and Si I 1082.7 nm with a
spectro-polarimeter on the Domeless Solar Telescope at Hida Observatory
on 2015 August 9. The observed Stokes profiles of the He I triplet in
the flare kernel are well reproduced through inversions considering
the Zeeman and the Paschen-Back effects with a three-slab model of
the flare kernel, in which two slabs which have upward and downward
velocities produce emissions and one slab produces an absorption. The
magnetic field strength inferred from the emission components of the
He I line is 1400 G, which is significantly stronger than 690 G that
is observed at the same location in the same line 6.5 hr before the
flare. In addition, the photospheric magnetic field vector derived from
the Si I10827 Å is similar to that of the flare kernel. To explain
this result, we suggest that the emission in the He I triplet during
the flare is produced in the deep layer, around which bombardment of
non-thermal electrons leads to the formation of a coronal temperature
plasma. Assuming a hydrogen column density at the location where the He
I emissions are formed, and a power-law index of non-thermal electron
energy distribution, we derived the low-energy cutoff of the non-thermal
electron as 20-30 keV independently from methods using hard X-ray data.
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: Development of new tunable filter for solar observation in
Hida observatory
Authors: Otsuji, Kenichi; Kimura, Gouichi; Nakatani, Yoshi-kazu;
Kaneda, Naoki; Ishii, Takako T.; Hagino, Masaoki; Ichimoto, Kiyoshi
Bibcode: 2020SPIE11447E..A5O
Altcode:
Solar Magnetic Activity Research Telescope (SMART) at Hida observatory
is in operational to monitor the solar activity. As a new solar Hα
observing instrument for SMART, we developed "Solar Dynamics Doppler
Imager (SDDI)", which can measure the three-dimensional motion of solar
eruptive phenomena. These eruptive events could be affective to the
earth magnetism and cause serious damage to our society. The purpose
of SMART/SDDI is monitoring and forecasting the geo-affective solar
eruptions. In this paper, we present the development of the tunable
filter "F40", the key component of SDDI. The features of TF40 are,
(1) fast tuning of observation wavelength, (2) narrow transmission
width and large free spectral range (FSR), (3) large field-of-view that
covers the entire solar disk with a 20 cm objective lens. TF40 has 7
stages of optical blocks. Each stage consists of a linear polarizer,
calcites, a quartz as half waveplate and a Liquid Crystal Variable
Retarder (LCVR), and has the periodic transmission profile with 0.05,
0.1, 0.2, 0.4, 0.8, 1.6 and 3.2 nm period at Hα line (656.2808 nm),
respectively. Combining the 7 stages, the 0.025 nm transmission
width and 3.2 nm FSR are achieved. Retardation of each LCVR and
its dependence on applied voltage and temperature were measured for
modeling its characteristics, with which we calculate the voltage
for desired retardation. Best-shaped transmission profile is obtained
by further adjustment of voltages of individual LCVRs using the real
solar light. We report the performance and current observing status
of the TF40.
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: Temperature analysis of solar prominences by multi-wavelength
observations
Authors: Okada, Sanetaka; Ichimoto, Kiyoshi; Machida, Aki; Tokuda,
Satomi; Huang, Yuwei; UeNo, Satoru
Bibcode: 2020PASJ...72...71O
Altcode: 2020PASJ..tmp..164O
The aim of this paper is to determine the kinetic temperature of
solar prominences from widths of emission lines with a careful
evaluation of its validity, and to investigate the spatial
distribution of the non-thermal velocity and the kinetic temperature
in prominences. Spectroscopic observations of prominences were carried
out using the Domeless Solar Telescope at the Hida observatory in four
emission lines, i.e., H $\alpha$ $656.3\:$ nm, H $\beta$ $486.1\:$
nm, Ca $^{+}$ IR $854.2\:$ nm, and Ca $^{+}$ K $393.4\:$ nm. We found
systematic differences in temperature and its spatial distributions in
prominences obtained from different pairs of spectral lines. The reason
for the difference is that the intrinsic widths of emission lines
determined by a single-slab model are different for optically thick
and thin lines, and can be attributed to the assumption of a Gaussian
profile of the non-thermal broadening in the single-slab model. With
numerical experiments, we found that the observed differences among
line pairs can be reproduced by a multi-slab model, in which each slab
has different non-thermal broadening and line-of-sight velocity. The
most accurate evaluation of the temperature is obtained with the
pair of H $\beta$ and Ca $^{+}$ IR in our selection. Based on these
results, we found the typical kinetic temperature of prominences to
be 8000&- $12000\:$ K, which is significantly higher than the
temperature determined by radiative balance and suggests the presence
of mechanical heating in prominences. Also suggested is the presence
of positive spatial correlation between non-thermal velocity and
temperature. We revisit past observational results on the prominence
temperature and discuss the reason for discrepancies among them.
Title: Statistical Analysis of the Relation between Coronal Mass
Ejections and Solar Energetic Particles
Authors: Kihara, Kosuke; Huang, Yuwei; Nishimura, Nobuhiko; Nitta,
Nariaki V.; Yashiro, Seiji; Ichimoto, Kiyoshi; Asai, Ayumi
Bibcode: 2020ApJ...900...75K
Altcode: 2020arXiv200708062K
To improve the forecasting capability of impactful solar energetic
particle (SEP) events, the relation between coronal mass ejections
(CMEs) and SEP events needs to be better understood. Here we present
a statistical study of SEP occurrences and timescales with respect
to the CME source locations and speeds, considering all 257 fast
(vCME ≥ 900 km s-1) and wide (angular width
≥60°) CMEs that occurred between 2006 December and 2017 October. We
associate them with SEP events at energies above 10 MeV. Examination of
the source region of each CME reveals that CMEs more often accompany a
SEP event if they originate from the longitude of E20-W100 relative to
the observer. However, an SEP event could still be absent if the CME is
<2000 km s-1. For the associated CME-SEP pairs, we compute
three timescales for each of the SEP events, namely the timescale of
the onset (TO), the rise time (TR), and the duration (TD). They are
correlated with the longitude of the CME source region relative to
the footpoint of the Parker spiral (ΔΦ) and vCME. The
TO tends to be short for $| {\rm{\Delta }}{\rm{\Phi }}| \ \lt $
60°. This trend is weaker for TR and TD. The SEP timescales are only
weakly correlated with vCME. Positive correlations of both
TR and TD with vCME are seen in poorly connected (large $|
{\rm{\Delta }}{\rm{\Phi }}| $ ) events. Additionally, TO appears to
be negatively correlated with vCME for events with small $|
{\rm{\Delta }}{\rm{\Phi }}| $ .
Title: SMART/SDDI Filament Disappearance Catalogue
Authors: Seki, Daikichi; Otsuji, Kenichi; Ishii, Takako T.; Hirose,
Kumi; Iju, Tomoya; UeNo, Satoru; Cabezas, Denis P.; Asai, Ayumi;
Isobe, Hiroaki; Ichimoto, Kiyoshi; Shibata, Kazunari
Bibcode: 2020arXiv200303454S
Altcode:
This paper describes a new SMART/SDDI Filament Disappearance Catalogue,
in which we listed almost all the filament disappearance events
that the Solar Dynamics Doppler Imager (SDDI) has observed since
its installation on the Solar Magnetic Activity Research Telescope
(SMART) in May 2016. Our aim is to build a database that can help
predict the occurrence and severity of coronal mass ejections
(CMEs). The catalogue contains miscellaneous information associated
with filament disappearance such as flare, CME, active region,
three-dimensional trajectory of erupting filaments, detection in
Interplanetary Scintillation (IPS), occurrence of interplanetary CME
(ICME) and Dst index. We also provide statistical information on the
catalogue data. The catalogue is available from the following website:
https://www.kwasan.kyoto-u.ac.jp/observation/event/sddi-catalogue/.
Title: SMART/SDDI Filament Disappearance Catalogue
Authors: Seki, D.; Otsuji, K.; Ishii, T.; Hirose, K.; Iju, T.; UeNo,
S.; Cabezas, D.; Asai, A.; Isobe, H.; Ichimoto, K.; Shibata, K.
Bibcode: 2019SunGe..14...95S
Altcode:
This paper describes a new "SMART/SDDI Filament Disappearance
Catalogue," in which we listed almost all the filament disappearance
events that the Solar Dynamics Doppler Imager (SDDI) has observed since
its installation on the Solar Magnetic Activity Research Telescope
(SMART) in May 2016. Our aim is to build a database that can help
predict the occurrence and severity of coronal mass ejections
(CMEs). The catalogue contains miscellaneous information associated
with filament disappearance such as flare, CME, active region,
three-dimensional trajectory of erupting filaments, detection in
Interplanetary Scintillation (IPS), occurrence of interplanetary CME
(ICME) and Dst index. We also provide statistical information on the
catalogue data. The catalogue is available from the following website:
https://www.kwasan.kyoto-u.ac.jp/observation/event/sddi-catalogue/.
Title: Dynamic Processes of the Moreton Wave on 2014 March 29
Authors: Cabezas, Denis P.; Asai, Ayumi; Ichimoto, Kiyoshi; Sakaue,
Takahito; UeNo, Satoru; Ishitsuka, José K.; Shibata, Kazunari
Bibcode: 2019ApJ...883...32C
Altcode: 2019arXiv190803534C
On 2014 March 29, an intense solar flare classified as X1.0 occurred
in active region 12017. Several associated phenomena accompanied this
event, among them a fast-filament eruption, large-scale propagating
disturbances in the corona and the chromosphere including a Moreton
wave, and a coronal mass ejection. This flare was successfully detected
in multiwavelength imaging in the Hα line by the Flare Monitoring
Telescope (FMT) at Ica University, Peru. We present a detailed study
of the Moreton wave associated with the flare in question. Special
attention is paid to the Doppler characteristics inferred from the
FMT wing (Hα ± 0.8 Å) observations, which are used to examine
the downward/upward motion of the plasma in the chromosphere. Our
findings reveal that the downward motion of the chromospheric material
at the front of the Moreton wave attains a maximum velocity of 4 km
s-1, whereas the propagation speed ranges between 640 and
859 km s-1. Furthermore, using the weak-shock approximation
in conjunction with the velocity amplitude of the chromospheric motion
induced by the Moreton wave, we derive the Mach number of the incident
shock in the corona. We also performed the temperature-emission measure
analysis of the coronal wave based on the Atmospheric Imaging Assembly
observations, which allowed us to derive the compression ratio, and to
estimate Alfvén and fast-mode Mach numbers on the order of 1.06-1.28
and 1.05-1.27. Considering these results and the magnetohydrodynamics
linear theory, we discuss the characteristics of the shock front and
the interaction with the chromospheric plasma.
Title: The influence of Hinode/SOT NFI instrumental effects on the
visibility of simulated prominence fine structures in Hα
Authors: Gunár, S.; Jurčák, J.; Ichimoto, K.
Bibcode: 2019A&A...629A.118G
Altcode:
Context. Models of entire prominences with their numerous fine
structures distributed within the prominence magnetic field use
approximate radiative transfer techniques to visualize the simulated
prominences. However, to accurately compare synthetic images of
prominences obtained in this way with observations and to precisely
analyze the visibility of even the faintest prominence features,
it is important to take into account the influence of instrumental
properties on the synthetic spectra and images.
Aims: In the
present work, we investigate how synthetic Hα images of simulated
prominences are impacted by the instrumental effects induced by the
Narrowband Filter Imager (NFI) of the Solar Optical Telescope (SOT)
onboard the Hinode satellite.
Methods: To process the synthetic
Hα images provided by 3D Whole-Prominence Fine Structure (WPFS) models
into SOT-like synthetic Hα images, we take into account the effects of
the integration over the theoretical narrow-band transmission profile
of NFI Lyot filter, the influence of the stray-light and point spread
function (PSF) of Hinode/SOT, and the observed noise level. This allows
us to compare the visibility of the prominence fine structures in the
SOT-like synthetic Hα images with the synthetic Hα line-center images
used by the 3D models and with a pair of Hinode/SOT NFI observations
of quiescent prominences.
Results: The comparison between
the SOT-like synthetic Hα images and the synthetic Hα line-center
images shows that all large and small-scale features are very similar
in both visualizations and that the same very faint prominence fine
structures can be discerned in both. This demonstrates that the
computationally efficient Hα line-center visualization technique
can be reliably used for the purpose of visualization of complex 3D
prominence models. In addition, the qualitative comparison between the
SOT-like synthetic images and prominence observations shows that the
3D WPFS models can reproduce large-scale prominence features rather
well. However, the distribution of the prominence fine structures
is significantly more diffuse in the observations than in the models
and the diffuse intensity areas surrounding the observed prominences
are also not present in the synthetic images. We also found that the
maximum intensities reached in the models are about twice as high as
those present in the observations-an indication that the mass-loading
assumed in the present 3D WPFS models might be too large.
Title: ngGONG: The Next Generation GONG - A New Solar Synoptic
Observational Network
Authors: Hill, Frank; Hammel, Heidi; Martinez-Pillet, Valentin; de
Wijn, A.; Gosain, S.; Burkepile, J.; Henney, C. J.; McAteer, J.; Bain,
H. M.; Manchester, W.; Lin, H.; Roth, M.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2019BAAS...51g..74H
Altcode: 2019astro2020U..74H
The white paper describes a next-generation GONG, a ground-based
geographically distributed network of instrumentation to continually
observe the Sun. This would provide data for solar magnetic field
research and space weather forecasting, and would extend the time
coverage of helioseismology.
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: Polarization Calibration of the Solar Magnetic Activity
Research Telescope(SMART)-T4
Authors: Yamasaki, D.; Nagata, S.; Ichimoto, K.
Bibcode: 2019spw..confE...6Y
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: Small-scale motions in solar filaments as the precursors
of eruptions
Authors: Seki, Daikichi; Otsuji, Kenichi; Isobe, Hiroaki; Ishii,
Takako T.; Ichimoto, Kiyoshi; Shibata, Kazunari
Bibcode: 2019PASJ...71...56S
Altcode: 2019arXiv190208718S; 2019PASJ..tmp...48S
Filaments, the dense cooler plasma floating in the solar corona
supported by magnetic fields, generally exhibit certain activations
before they erupt. In our previous study (Seki et al. 2017, ApJ, 843,
L24), we observed that the standard deviation of the line-of-sight (LOS)
velocities of the small-scale motions in a filament increased prior
to its eruption. However, because that study only analyzed one event,
it is unclear whether such an increase in the standard deviation of
LOS velocities is common in filament eruptions. In this study, 12
filaments that vanished in Hα line center images were analyzed in
a manner similar to the one in our previous work; these included two
quiescent filaments, four active region filaments, and six intermediate
filaments. We verified that in all the 12 events, the standard deviation
of the LOS velocities increased before the filaments vanished. Moreover,
we observed that the quiescent filaments had approximately 10 times
longer duration of an increase in the standard deviation than the
other types of filaments. We concluded that the standard deviation
of the LOS velocities of the small-scale motions in a filament can
potentially be used as a precursor of a filament eruption.
Title: Synoptic Studies of the Sun as a Key to Understanding Stellar
Astrospheres
Authors: Martinez Pillet, Valentin; Hill, Frank; Hammel, Heidi B.;
de Wijn, Alfred G.; Gosain, Sanjay; Burkepile, Joan; Henney, Carl;
McAteer, R. T. James; Bain, Hazel; Manchester, Ward; Lin, Haosheng;
Roth, Markus; Ichimoto, Kiyoshi; Suematsu, Yoshinori
Bibcode: 2019BAAS...51c.110M
Altcode: 2019astro2020T.110M; 2019arXiv190306944M
Ground-based solar observations provide key contextual data (i.e., the
"big picture") to produce a complete description of the only astrosphere
we can study in situ: our Sun's heliosphere. This white paper outlines
the current paradigm for ground-based solar synoptic observations,
and indicates those areas that will benefit from focused attention.
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: Chapter 5.3 - Spectropolarimetry and Magnetic Structures
Authors: Ichimoto, Kiyoshi
Bibcode: 2019sgsp.book..185I
Altcode:
Spectropolarimetry is a powerful tool used to diagnose magnetic
fields in the solar atmosphere. Zeeman and Hanlé effects provide the
foundation for retrieving information about the magnetic field from
the polarization observed in spectral lines. We described the basic
concepts of spectropolarimetry in current solar observations and present
an overview of the nature of magnetic fields in the photosphere and
chromosphere and in prominences. We discuss structures such as sunspots
and small-scale photospheric magnetic flux tubes and their distribution.
Title: Developments of a multi-wavelength spectro-polarimeter on
the Domeless Solar Telescope at Hida Observatory
Authors: Anan, Tetsu; Huang, Yu-Wei; Nakatani, Yoshikazu; Ichimoto,
Kiyoshi; UeNo, Satoru; Kimura, Goichi; Ninomiya, Shota; Okada,
Sanetaka; Kaneda, Naoki
Bibcode: 2018PASJ...70..102A
Altcode: 2018arXiv180302094A; 2018PASJ..tmp...66A
To obtain full Stokes spectra in multi-wavelength windows
simultaneously, we developed a new spectro-polarimeter on the Domeless
Solar Telescope at Hida Observatory. The new polarimeter consists of
a 60 cm aperture vacuum telescope on an altazimuth mounting, an image
rotator, a high-dispersion spectrograph, and a polarization modulator
and an analyzer composed of a continuously rotating waveplate with
a retardation that is nearly constant at around 127° in 500-1100
nm. There are also a polarizing beam splitter located close behind
the focus of the telescope, fast and large format CMOS cameras, and
an infrared camera. A slit spectrograph allows us to obtain spectra in
as many wavelength windows as the number of cameras. We characterized
the instrumental polarization of the entire system and established a
polarization calibration procedure. The cross-talks among the Stokes Q,
U, and V have been evaluated to be about 0.06%-1.2%, depending on the
degree of the intrinsic polarizations. In a typical observing setup,
a sensitivity of 0.03% can be achieved in 20-60 seconds for 500-1100
nm. The new polarimeter is expected to provide a powerful tool for
diagnosing the 3D magnetic field and other vector physical quantities
in the solar atmosphere.
Title: Observational study on the fine structure and dynamics of a
solar jet. II. Energy release process revealed by spectral analysis
Authors: Sakaue, Takahito; Tei, Akiko; Asai, Ayumi; Ueno, Satoru;
Ichimoto, Kiyoshi; Shibata, Kazunari
Bibcode: 2018PASJ...70...99S
Altcode: 2017arXiv171008441S; 2018PASJ..tmp....6S
We report on a solar jet phenomenon associated with the C5.4 class
flare on 2014 November 11. The data of the jet was provided by the Solar
Dynamics Observatory, the X-Ray Telescope (XRT) aboard Hinode, and the
Interface Region Imaging Spectrograph and Domeless Solar Telescope (DST)
at Hida Observatory, Kyoto University. These plentiful data enabled
us to present this series of papers to discuss all the processes of
the observed phenomena, including energy storage, event trigger,
and energy release. In this paper, we focus on the energy release
process of the observed jet, and mainly describe our spectral analysis
on the Hα data of DST to investigate the internal structure of the
Hα jet and its temporal evolution. This analysis reveals that in the
physical quantity distributions of the Hα jet, such as line-of-sight
velocity and optical thickness, there is a significant gradient in
the direction crossing the jet. We interpret this internal structure
as the consequence of the migration of the energy release site, based
on the idea of ubiquitous reconnection. Moreover, by measuring the
horizontal flow of the fine structures in the jet, we succeeded in
deriving the three-dimensional velocity field and the line-of-sight
acceleration field of the Hα jet. The analysis result indicates that
part of the ejecta in the Hα jet experienced additional acceleration
after it had been ejected from the lower atmosphere. This secondary
acceleration was found to occur in the vicinity of the intersection
between the trajectories of the Hα jet and the X-ray jet observed by
Hinode/XRT. We propose that a fundamental cause of this phenomenon is
magnetic reconnection involving the plasmoid in the observed jet.
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: Space Weather Prediction from the Ground: Case of CHAIN
Authors: Seki, Daikichi; Ueno, Satoru; Isobe, Hiroaki; Otsuji, Kenichi;
Cabezas, Denis P.; Ichimoto, Kiyoshi; Shibata, Kazunari; Chain Team
Bibcode: 2018SunGe..13..157S
Altcode:
In this article, we insist on the importance and the challenges of the
prediction of solar eruptive phenomena including flares, coronal mass
ejections (CME), and filament eruptions fully based on the ground-based
telescopes. It is true that satellites' data are indispensable for the
space weather prediction, but they are vulnerable to the space weather
effects. Therefore, the ground-based telescopes can be complementary
to them from the viewpoint of space weather prediction. From this
view point, one possible new flare prediction method that makes use of
H-alpha, red wings, and blue wings images obtained by the SDDI/SMART,
the ground-based telescope at Hida Observatory, is presented. And
in order to show the possibility for the actual operation based on
that method, the recent progress of CHAIN project, the international
observation network, is mentioned in terms of their outcomes and
capacity buildings.
Title: Blue-wing enhancement of the chromospheric Mg II h and k
lines in a solar flare
Authors: Tei, Akiko; Sakaue, Takahito; Okamoto, Takenori J.; Kawate,
Tomoko; Heinzel, Petr; UeNo, Satoru; Asai, Ayumi; Ichimoto, Kiyoshi;
Shibata, Kazunari
Bibcode: 2018PASJ...70..100T
Altcode: 2018PASJ..tmp...61T; 2018arXiv180305237T
We performed coordinated observations of AR 12205, which showed a
C-class flare on 2014 November 11, with the Interface Region Imaging
Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida
Observatory. Using spectral data in the Si IV 1403 Å, C II 1335 Å,
and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542 Å, and
Hα lines from DST, we investigated a moving flare kernel during the
flare. In the Mg II h line, the leading edge of the flare kernel showed
an intensity enhancement in the blue wing and a smaller intensity of the
blue-side peak (h2v) than that of the red-side one (h2r). The blueshift
lasted for 9-48 s with a typical speed of 10.1 ± 2.6 km s-1,
which was followed by a high intensity and a large redshift with a speed
of up to 51 km s-1 detected in the Mg II h line. The large
redshift was a common property for all six lines, but the blueshift
prior to it was found only in the Mg II lines. Cloud modeling of the
Mg II h line suggests that the blue-wing enhancement with such a peak
difference could have been caused by a chromospheric-temperature (cool)
upflow. We discuss a scenario in which an upflow of cool plasma is
lifted up by expanding hot plasma owing to the deep penetration of
non-thermal electrons into the chromosphere. Furthermore, we found
that the blueshift persisted without any subsequent redshift in the
leading edge of the flare kernel during its decaying phase. The cause
of such a long-lasting blueshift is also discussed.
Title: Measurement of vector magnetic field in a flare kernel with
a spectropolarimetric observation in He I 10830 Å
Authors: Anan, Tetsu; Yoneya, Takurou; Ichimoto, Kiyoshi; UeNo, Satoru;
Shiota, Daikou; Nozawa, Satoshi; Takasao, Shinsuke; Kawate, Tomoko
Bibcode: 2018PASJ...70..101A
Altcode: 2018arXiv180806821A; 2018PASJ..tmp..113A
A flare kernel associated with a C4 class flare was observed in a
spectral window including the He I triplet 10830 Å and Si I 10827
Å with a spectropolarimeter on the Domeless Solar Telescope at
Hida Observatory on 2015 August 9. The observed Stokes profiles of
the He I triplet in the flare kernel in its post-maximum phase are
well reproduced through inversions considering the Zeeman and the
Paschen-Back effects with a three-slab model of the flare kernel,
in which two slabs which have upward and downward velocities produce
emissions and one slab produces an absorption. The magnetic field
strength inferred from the emission components of the He I line is 1400
G, which is significantly stronger than 690 G that is observed at the
same location in the same line 6.5 hr before the flare. In addition,
the photospheric magnetic field vector derived from the Si I10827 Å is
similar to that of the flare kernel. To explain this result, we suggest
that the emission in the He I triplet during the flare is produced in
the deep layer, around which bombardment of non-thermal electrons leads
to the formation of a coronal temperature plasma. Assuming a hydrogen
column density at the location where the He I emissions are formed,
and a power-law index of non-thermal electron energy distribution, we
derived the low-energy cutoff of the non-thermal electron as 20-30 keV,
which is consistent with that inferred from hard X-ray data obtained
by RHESSI.
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: Formation of an Active Region Filament Driven By a Series
of Jets
Authors: Wang, Jincheng; Yan, Xiaoli; Qu, Zhongquan; UeNo, Satoru;
Ichimoto, Kiyoshi; Deng, Linhua; Cao, Wenda; Liu, Zhong
Bibcode: 2018ApJ...863..180W
Altcode: 2018arXiv180700992W
We present a formation process of a filament in active region NOAA
12574 during the period from 2016 August 11 to 12. Combining the
observations of the Global Oscillation Network Group Hα, the Hida
spectrum, and the Solar Dynamics Observatory/AIA 304 Å, the formation
process of the filament is studied. It is found that cool material (T
∼ 104 K) is ejected by a series of jets originating from
the western footpoint of the filament. Simultaneously, the magnetic flux
emerged from the photosphere in the vicinity of the western footpoint of
the filament. These observations suggest that cool material in the low
atmosphere can be directly injected into the upper atmosphere and the
jets are triggered by the magnetic reconnection between pre-existing
magnetic fields and new emerging magnetic fields. A detailed study of
a jet at 18:02 UT on August 11 with GST/BBSO TiO observations revealed
that some dark threads appeared in the vicinity of the western footpoint
after the jet and the projection velocity of plasma along the filament
axis was about 162.6 ± 5.4 km s-1. Using these observations
of the Domeless Solar Telescope/Hida, we find that the injected plasma
by a jet at 00:42 UT on August 12 was rotating. Therefore, we conclude
that the jets not only supplied the material for the filament, but also
injected the helicity into the filament simultaneously. Comparing the
quantity of mass injection by the jets with the mass of the filament,
we conclude that the estimated mass loading by the jets is sufficient
to account for the mass in the filament.
Title: Does the solar granulation change with the activity cycle?
Authors: Muller, R.; Hanslmeier, A.; Utz, D.; Ichimoto, K.
Bibcode: 2018A&A...616A..87M
Altcode:
Context. Knowledge of the variation of the solar granulation properties
(contrast and scale) with the 11-yr activity cycle is useful for a
better understanding of the interaction between magnetic field and
convection at global or local scales. A varying granulation may also
contribute to irradiance variations and affect the p-mode damping
rates and lifetimes.
Aims: HINODE/SOT blue continuum images
taken in the frame of the synoptic program at the disk center on a
daily basis between November 2006 and February 2016 are used. This
period covers the minimum of activity between cycles 23 and 24 and the
maximum of cycle 24.
Methods: The sharpness of a significant
number of images was reduced because of instrumental aberrations or
inaccurate focusing. Only the sharpest images were selected for this
investigation.
Results: To be detectable with HINODE/SOT images,
the variation of the granulation contrast and of the granulation scale
at the disk center should have been larger than 3%. As it is not the
case, it is concluded that they varied by less than 3% through the
weak cycle 24.
Title: Space Weather Prediction from the Ground: Case of CHAIN
Authors: Seki, Daikichi; Ueno, Satoru; Isobe, Hiroaki; Otsuji, Kenichi;
Cabezas, Denis P.; Ichimoto, Kiyoshi; Shibata, Kazunari; CHAIN team
Bibcode: 2018arXiv180806295S
Altcode:
In this article, we insist on the importance and the challenges of the
prediction of solar eruptive phenomena including flares, coronal mass
ejections (CME), and filament eruptions fully based on the ground-based
telescopes. It is true that satellites' data are indispensable for the
space weather prediction, but they are vulnerable to the space weather
effects. Therefore, the ground-based telescopes can be complementary
to them from the viewpoint of space weather prediction. From this
view point, one possible new flare prediction method that makes use of
H-alpha, red wings, and blue wings images obtained by the SDDI/SMART,
the ground-based telescope at Hida Observatory, is presented. And
in order to show the possibility for the actual operation based on
that method, the recent progress of CHAIN project, the international
observation network, is mentioned in terms of their outcomes and
capacity buildings.
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: Parallel processing of solar image restoration with phase
diversity technique
Authors: Suzuki, Takahiro; Miura, Noriaki; Kuwamura, Susumu; Oya,
Shin; Ueno, Satoru; Nakatani, Yoshikazu; Ichimoto, Kiyoshi
Bibcode: 2018SPIE10703E..32S
Altcode:
We aim at improving solar images partially compensated by Adaptive
Optics (AO) or Ground-Layer (GL) AO using a phase diversity (PD)
method. To reduce computational time in the PD execution, we develop
a computer cluster system that enables restoration of several images
in parallel. We set a PD-observational system downstream of an AO
system in the Hida Observatory in Japan. Driving the AO system, we
recorded focused and defocused solar images. They were segmented to
partial images, and then were restored by the PD method. We show the
results of solar image restoration, and also demonstrate the reduction
of processing time by the computer cluster.
Title: Blue wing enhancement of the chromospheric Mg II h and k
lines in a solar flare
Authors: Tei, Akiko; Shibata, Kazunari; Asai, Ayumi; Ichimoto,
Kiyoshi; Heinzel, Petr; Ueno, Satoru; Okamoto, Joten; Sakaue, Takahito;
Kawate, Tomoko
Bibcode: 2018cosp...42E3350T
Altcode:
We performed coordinated observations of NOAA AR 12205, which produced
a C-class flare on 2014 November 11, with the Interface Region Imaging
Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida
Observatory.Using spectral data in the Si IV 1403 Å, C II 1335 Å,
and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542 Å,
and Hα lines from DST, we investigated the temporal and spatial
evolution around a moving flare kernel.In the Mg II h line, the leading
edge of the kernel showed intensity enhancement in the blue wing and
difference between the blue-side peak and red-side one (I_{h2v} <
I_{h2r}).Then, the drastic change of the intensity in the red wing
occurred.The blueshift lasted for 9-48 s with a speed of 10.1 ± 2.6
km s^{-1} and it was followed by the strong redshift with a speed of
up to 51 km s^{-1} detected in the Mg II h line.The strong redshift
was a common property for all six lines but the blueshift prior to it
was found only in the Mg II lines.A cloud modeling of the Mg II h line
suggests that the blue wing enhancement with such peak difference can
be caused by a chromospheric-temperature (cool) upflow.We discuss a
scenario in which an upflow of cool plasma is lifted up by expanding
(hot) plasma owing to the deep penetration of non-thermal electrons
into the chromosphere.In addition, at the leading edge of the final
flare footpoints, the blueshift persisted in the Mg II h line, which
was not followed by any large redshift and intensity enhancement.Such
long-lasting blueshift can be explained by cool upflow caused by small
energy flux into the lower atmosphere.
Title: Experiments of GLAO using the domeless solar telescope of
the Hida Observatory
Authors: Miura, Noriaki; Suzuki, Takahiro; Takahashi, Shinya; Kuwamura,
Susumu; Baba, Naoshi; Oya, Shin; Ueno, Satoru; Nakatani, Yoshikazu;
Ichimoto, Kiyoshi
Bibcode: 2018SPIE10703E..36M
Altcode:
We report experiments of solar ground-layer (GL) adaptive optics
(AO) using the 60cm domeless solar telescope of the Hida Observatory,
Japan. We developed an averaging-type GL wavefront sensor and confirmed
that it properly worked in computer simulations. We set the wavefront
sensor behind a conventional AO system and modified AO software so as
to drive a deformable mirror using the GL sensor. We conducted solar
observations with the GLAO system in September, 2017. It worked to
improve observational images over wide fields.
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: 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: Observational study on the fine structure and dynamics of a
solar jet. I. Energy build-up process around a satellite spot
Authors: Sakaue, Takahito; Tei, Akiko; Asai, Ayumi; Ueno, Satoru;
Ichimoto, Kiyoshi; Shibata, Kazunari
Bibcode: 2017PASJ...69...80S
Altcode: 2017arXiv170701262S
We report on a solar jet phenomenon associated with successive flares
on 2014 November 10. These explosive events were involved with the
satellite spots' emergence around a δ-type sunspot in the decaying
active region NOAA 12205. The data for this jet were provided by the
Solar Dynamics Observatory, the X-Ray Telescope aboard Hinode, and the
Interface Region Imaging Spectrograph and Domeless Solar Telescope
at Hida Observatory, Kyoto University. These abundant data enabled
us to present this series of papers to discuss the entire process of
the observed phenomena, including the energy storage, event trigger,
and energy release. In this paper, we focus on the energy build-up and
trigger phases, by analyzing the photospheric horizontal flow field
around the active region by an optical flow method. The analysis shows
the following results: (1) The observed explosive phenomena involved
three satellite spots, the magnetic fluxes of which successively
reconnected with their pre-existing ambient fields; (2) All of these
satellite spots emerged in the moat region of a pivotal δ-type
sunspot, especially near its convergent boundary with the neighboring
supergranules or moat regions of adjacent sunspots; (3) Around the
jet ejection site, the positive polarities of the satellite spot and
adjacent emerging flux encountered the global magnetic field with a
negative polarity in the moat region of the pivotal δ-type sunspot,
and thus the polarity inversion line was formed along the convergent
boundary of the photospheric horizontal flow channels.
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: Temporal Evolution and Spatial Distribution of White-light
Flare Kernels in a Solar Flare
Authors: Kawate, Tomoko; Ishii, Takako; Nakatani, Yoshikazu; Ichimoto,
Kiyoshi; Asai, Ayumi; Morita, Satoshi; Masuda, Satoshi
Bibcode: 2017SPD....4810002K
Altcode:
On 2011 September 6, we observed an X2.1-class flare in continuum
and Hα with a frame rate of about 30 Hz. After processing images
of the event by using a speckle-masking image reconstruction, we
identified white-light (WL) flare ribbons on opposite sides of the
magnetic neutral line. We derive the light curve decay times of the
WL flare kernels at each resolution element by assuming that the
kernels consist of one or two components that decay exponentially,
starting from the peak time. As a result, 42% of the pixels have two
decay-time components with average decay times of 15.6 and 587 s,
whereas the average decay time is 254 s for WL kernels with only one
decay-time component. The peak intensities of the shorter decay-time
component exhibit good spatial correlation with the WL intensity,
whereas the peak intensities of the long decay-time components tend
to be larger in the early phase of the flare at the inner part of
the flare ribbons, close to the magnetic neutral line. The average
intensity of the longer decay-time components is 1.78 times higher than
that of the shorter decay-time components. If the shorter decay time is
determined by either the chromospheric cooling time or the nonthermal
ionization timescale and the longer decay time is attributed to the
coronal cooling time, this result suggests that WL sources from both
regions appear in 42% of the WL kernels and that WL emission of the
coronal origin is sometimes stronger than that of chromospheric origin.
Title: Differences between Doppler velocities of ions and neutral
atoms in a solar prominence
Authors: Anan, T.; Ichimoto, K.; Hillier, A.
Bibcode: 2017A&A...601A.103A
Altcode: 2017arXiv170302132A
Context. In astrophysical systems with partially ionized plasma,
the motion of ions is governed by the magnetic field while the
neutral particles can only feel the magnetic field's Lorentz force
indirectly through collisions with ions. The drift in the velocity
between ionized and neutral species plays a key role in modifying
important physical processes such as magnetic reconnection, damping
of magnetohydrodynamic waves, transport of angular momentum in plasma
through the magnetic field, and heating.
Aims: This paper
aims to investigate the differences between Doppler velocities of
calcium ions and neutral hydrogen in a solar prominence to look for
velocity differences between the neutral and ionized species.
Methods: We simultaneously observed spectra of a prominence over an
active region in H I 397 nm, H I 434 nm, Ca II 397 nm, and Ca II
854 nm using a high dispersion spectrograph of the Domeless Solar
Telescope at Hida observatory. We compared the Doppler velocities,
derived from the shift of the peak of the spectral lines presumably
emitted from optically-thin plasma.
Results: There are instances
when the difference in velocities between neutral atoms and ions is
significant, for example 1433 events ( 3% of sets of compared profiles)
with a difference in velocity between neutral hydrogen atoms and
calcium ions greater than 3σ of the measurement error. However, we
also found significant differences between the Doppler velocities of
two spectral lines emitted from the same species, and the probability
density functions of velocity difference between the same species is not
significantly different from those between neutral atoms and ions.
Conclusions: We interpreted the difference of Doppler velocities as
being a result of the motions of different components in the prominence
along the line of sight, rather than the decoupling of neutral atoms
from plasma. The movie attached to Fig. 1 is available at http://www.aanda.org
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: A New Solar Imaging System for Observing High-Speed Eruptions:
Solar Dynamics Doppler Imager (SDDI)
Authors: Ichimoto, Kiyoshi; Ishii, Takako T.; Otsuji, Kenichi; Kimura,
Goichi; Nakatani, Yoshikazu; Kaneda, Naoki; Nagata, Shin'Ichi; UeNo,
Satoru; Hirose, Kumi; Cabezas, Denis; Morita, Satoshi
Bibcode: 2017SoPh..292...63I
Altcode:
A new solar imaging system was installed at Hida Observatory to
observe the dynamics of flares and filament eruptions. The system (Solar
Dynamics Doppler Imager; SDDI) takes full-disk solar images with a field
of view of 2520 arcsec×2520 arcsec at multiple wavelengths around
the H α line at 6562 Å. Regular operation was started in May 2016,
in which images at 73 wavelength positions spanning from H α −9 Å
to H α +9 Å are obtained every 15 seconds. The large dynamic range
of the line-of-sight velocity measurements (±400 kms−1)
allows us to determine the real motions of erupting filaments in
3D space. It is expected that SDDI provides unprecedented datasets
to study the relation between the kinematics of filament eruptions
and coronal mass ejections (CME), and to contribute to the real-time
prediction of the occurrence of CMEs that cause a significant impact
on the space environment of the Earth.
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: Investigating prominence turbulence with Hinode SOT
Dopplergrams
Authors: Hillier, A.; Matsumoto, T.; Ichimoto, K.
Bibcode: 2017A&A...597A.111H
Altcode: 2016arXiv161008281H
Quiescent prominences host a diverse range of flows, including
Rayleigh-Taylor instability driven upflows and impulsive downflows,
and so it is no surprise that turbulent motions also exist. As
prominences are believed to have a mean horizontal guide field,
investigating any turbulence they host could shed light on the
nature of magnetohydrodynamic (MHD) turbulence in a wide range of
astrophysical systems. In this paper we have investigated the nature
of the turbulent prominence motions using structure function analysis
on the velocity increments estimated from Hα Dopplergrams constructed
with observational data from Hinode Solar Optical Telescope (SOT). The
probability density function of the velocity increments shows that as
we look at increasingly small spatial separations the distribution
displays greater departure from a reference Gaussian distribution,
hinting at intermittency in the velocity field. Analysis of the
even order structure functions for both the horizontal and vertical
separations showed the existence of two distinct regions displaying
different exponents of the power law with the break in the power
law at approximately 2000 km. We hypothesise this to be a result
of internal turbulence excited in the prominence by the dynamic
flows of the system found at this spatial scale. We found that the
scaling exponents of the pth order structure functions for these
two regions generally followed the p/ 2 (smaller scales) and p/ 4
(larger scales) laws that are the same as those predicted for weak MHD
turbulence and Kraichnan-Iroshnikov turbulence respectively. However,
the existence of the p/ 4 scaling at larger scales than the p/ 2
scaling is inconsistent with the increasing nonlinearity expected
in MHD turbulence. We also found that as we went to higher order
structure functions, the dependence of the scaling exponent on the
order p is nonlinear implying that intermittency may be playing an
important role in the turbulent cascade. Estimating the heating from
the turbulent energy dissipation showed that this turbulence would be
very inefficient at heating the prominence plasma, but that the mass
diffusion through turbulence driven reconnection was of the order
of 1010 cm2 s-1. This is of similar
order to that of the expected value of the ambipolar diffusion and a
few orders of magnitude greater than Ohmic diffusion for a quiescent
prominence. The movie associated to Fig. 4 is available at http://www.aanda.org
Title: Temporal Evolution and Spatial Distribution of White-light
Flare Kernels in a Solar Flare
Authors: Kawate, T.; Ishii, T. T.; Nakatani, Y.; Ichimoto, K.; Asai,
A.; Morita, S.; Masuda, S.
Bibcode: 2016ApJ...833...50K
Altcode: 2016arXiv161004328K
On 2011 September 6, we observed an X2.1-class flare in continuum
and Hα with a frame rate of about 30 Hz. After processing images
of the event by using a speckle-masking image reconstruction, we
identified white-light (WL) flare ribbons on opposite sides of the
magnetic neutral line. We derive the light curve decay times of the
WL flare kernels at each resolution element by assuming that the
kernels consist of one or two components that decay exponentially,
starting from the peak time. As a result, 42% of the pixels have two
decay-time components with average decay times of 15.6 and 587 s,
whereas the average decay time is 254 s for WL kernels with only one
decay-time component. The peak intensities of the shorter decay-time
component exhibit good spatial correlation with the WL intensity,
whereas the peak intensities of the long decay-time components tend
to be larger in the early phase of the flare at the inner part of
the flare ribbons, close to the magnetic neutral line. The average
intensity of the longer decay-time components is 1.78 times higher than
that of the shorter decay-time components. If the shorter decay time is
determined by either the chromospheric cooling time or the nonthermal
ionization timescale and the longer decay time is attributed to the
coronal cooling time, this result suggests that WL sources from both
regions appear in 42% of the WL kernels and that WL emission of the
coronal origin is sometimes stronger than that of chromospheric origin.
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: Status of Hida solar adaptive optics system and experiment
of tomographic wavefront sensing
Authors: Miura, Noriaki; Oh-ishi, Akira; Kuwamura, Susumu; Baba,
Naoshi; Hanaoka, Yoichiro; Ueno, Satoru; Nakatani, Yoshikazu;
Ichimoto, Kiyoshi
Bibcode: 2016SPIE.9909E..2NM
Altcode:
An adaptive optics (AO) system is developed for the 60cm domeless
solar telescope of the Hida Observatory, Japan. Its performances are
analyzed by the computer simulations, and improved by replacing the
Zernike polynomials by Karhunen-Loève functions. Also, a tomographic
wavefront sensor is developed for a ground-layer AO system. From test
data acquired at the Hida observatory, wavefront-phase maps both in
the ground-layer and in an upper layer are successfully derived.
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: Spectro-polarimetric observation in UV with CLASP to probe
the chromosphere and transition region
Authors: Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère,
Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi,
Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori;
Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi;
Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto;
Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi,
Luca; Carlsson, Mats
Bibcode: 2016SPD....4710107K
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA
sounding-rocket experiment that was performed in White Sands in
the US on September 3, 2015. During its 5-minute ballistic flight,
CLASP successfully made the first spectro-polarimetric observation in
the Lyman-alpha line (121.57 nm) originating in the chromosphere and
transition region. Since the Lyman-alpha polarization is sensitive
to magnetic field of 10-100 G by the Hanle effect, we aim to infer
the magnetic field information in such upper solar atmosphere with
this experiment.The obtained CLASP data showed that the Lyman-alpha
scattering polarization is about a few percent in the wings and
the order of 0.1% in the core near the solar limb, as it had been
theoretically predicted, and that both polarization signals have a
conspicuous spatio-temporal variability. CLASP also observed another
upper-chromospheric line, Si III (120.65 nm), whose critical field
strength for the Hanle effect is 290 G, and showed a measurable
scattering polarization of a few % in this line. The polarization
properties of the Si III line could facilitate the interpretation of
the scattering polarization observed in the Lyman-alpha line.In this
presentation, we would like to show how the upper chromosphere and
transition region are seen in the polarization of these UV lines and
discuss the possible source of these complicated polarization signals.
Title: Development of the Universal Tunable Filter and High-resolution
Imaging Observation with the Fuxian Solar Observatory
Authors: Hagino, M.; Ichimoto, K.; Ueno, S.; Kimura, G.; Otsuji, K.;
Kitai, R.; Zhong, L.; Xu, Z.; Shinoda, K.; Hara, H.; Suematsu, Y.;
Shimizu, T.
Bibcode: 2016ASPC..504..103H
Altcode:
We have developed a new narrow-band universal tunable filter to perform
imaging spectroscopy of the solar chromosphere. The development stage
of the filter has been almost finished and we shifted to the scientific
observation phase by using large grand-based telescopes. Using the
filter, a series of high-resolution images were obtained with the 1m
vacuum solar telescope at the Fuxian Solar Observatory. We succeeded in
observing several flares and fine structures of the chromospheric layer.
Title: Roles of Ground-based Solar Observations of Hida Observatory
toward the Solar-C Era
Authors: Ueno, S.; Shibata, K.; Ichimoto, K.; Nagata, S.; Dorotovič,
I.; Shahamatnia, E.; Ribeiro, R. A.; Fonseca, J. M.
Bibcode: 2016ASPC..504..309U
Altcode:
For the realization of the Solar-C satellite, discussions about
scientific themes and preliminary observations are internationally
carried out now. At Hida Observatory of Kyoto University, we will play
the following roles toward the Solar-C era by utilizing the Domeless
Solar Telescope (DST) and the international solar chromospherirc
full-disk observation network (CHAIN project) that includes the
Solar Magnetic Activity Research Telescope (SMART) with international
collaborations, for example, such as the development of image-analysis
software by UNINOVA (Portugal) and so on.
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: A Real Source of a Stealth CME - Energetics of a Filament
Eruption and Giant Arcade Formation
Authors: Asai, Ayumi; Ishii, Takako T.; Otsuji, Kenichi; Ichimoto,
Kiyoshi; Shibata, Kazunari
Bibcode: 2015IAUGA..2255125A
Altcode:
Various active phenomena occurring on the solar surface are sources
of disturbances in the solar-terrestrial environment. It is, however,
sometimes said that solar flares, the most energetic explosions in the
active phenome on the sun, are not crucially important for space weather
researches, but coronal mass ejections (CMEs) are more significant. This
is because not all flares are associated with CMEs, and therefore, not
geo-effective, and because geo-effective CMEs sometimes occur without
any notable active phenomena (such as flares) on the sun. The latter
is sometimes called as a “stealth CME” event. However, for even
such cases, we often see filament eruptions in H-alpha observations
and formations of giant arcade in X-ray and/or extreme ultraviolet
(EUV) observations.The geomagnetic storm with the Dst index of -105
nT that occurred on October 8, 2012 was such a stealth event. We,
on the other hand, recognize formation of an X-ray giant arcade and
activation of an H-alpha filament on October 5, 2012. We examined the
velocity field of the filament by using the H-alpha wing data obtained
with SMART telescope at Hida Observatory, Kyoto University. We also
derived the temperature and the volume emission measure by using the
X-ray and EUV data obtained by Hinode/XRT and SDO/AIA. We discuss the
energetics of this event on the solar surface
Title: Coupling of the magnetic field and gas flows inferred from
the net circular polarization in a sunspot penumbra
Authors: Shaltout, Abdelrazek M. K.; Ichimoto, Kiyoshi
Bibcode: 2015PASJ...67...27S
Altcode:
We analyze penumbral fine structure using high-resolution
spectropolarimetric data obtained by the Solar Optical Telescope on
board the Hinode satellite. The spatial correlation between the net
circular polarization (NCP) and Evershed flow is investigated in
detail. Here we obtain that negative NCP structures are correlated
with the Evershed flow channels in the limb-side penumbra, and that
negative NCP or depressions of positive NCP are associated with the
Evershed flow channels in the disk center-side of the penumbra for a
negative-polarity sunspot in NOAA 10923. The positive NCP dominant in
the disk center-side penumbra is essentially attributed to interflow
channels instead of Evershed flow channels. The stratification of
magnetic field and velocity are investigated by using SIR-JUMP inversion
with a one-component atmosphere, and the NCP of spectral lines in
the limb-side and disk center-side of the penumbra is successfully
reproduced. The inversion results show that an increased Evershed
flow is associated with a strong magnetic field located in the deep
photosphere. Our result does not match with the simple two-component
penumbral models in which the penumbra consists of Evershed flow
and interflow channels and the global NCP is attributed only to the
Evershed flow channels.
Title: Simultaneous Transverse Oscillations of a Prominence and a
Filament and Longitudinal Oscillation of Another Filament Induced
by a Single Shock Wave
Authors: Shen, Yuandeng; Liu, Ying D.; Chen, P. F.; Ichimoto, Kiyoshi
Bibcode: 2014ApJ...795..130S
Altcode: 2014arXiv1409.1304S
We present the first stereoscopic and Doppler observations of
simultaneous transverse oscillations of a prominence and a filament and
longitudinal oscillation of another filament launched by a single shock
wave. Using Hα Doppler observations, we derive the three-dimensional
oscillation velocities at different heights along the prominence
axis. The results indicate that the prominence has a larger oscillation
amplitude and damping time at higher altitude, but the periods at
different heights are the same (i.e., 13.5 minutes). This suggests that
the prominence oscillates like a linear vertical rigid body with one
end anchored on the Sun. One of the filaments shows weak transverse
oscillation after the passing of the shock, which is possibly due to
the low altitude of the filament and the weakening (due to reflection)
of the shock wave before the interaction. Large-amplitude longitudinal
oscillation is observed in the other filament after the passing of
the shock wave. The velocity amplitude and period are about 26.8 km
s-1 and 80.3 minutes, respectively. We propose that the
orientation of a filament or prominence relative to the normal vector
of the incoming shock should be an important factor for launching
transverse or longitudinal filament oscillations. In addition, the
restoring forces of the transverse prominence are most likely due
to the coupling of gravity and magnetic tension of the supporting
magnetic field, while that for the longitudinal filament oscillation
is probably the resultant force of gravity and magnetic pressure.
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: Magnetic and Electric Field Diagnostics of Chromospheric Jets
by Spectropolarimetric Observations of the HI Paschen Lines
Authors: Anan, T.; Casini, R.; Ichimoto, K.
Bibcode: 2014ASPC..489...67A
Altcode:
In order to study the magnetic and electric fields of chromospheric
jets, we observed the full Stokes spectra of the Paschen series of
neutral hydrogen in active region jets that took place at the solar limb
on May 5, 2012. For the observations, we used the spectropolarimeter
of the Domeless Solar Telescope at Hida observatory, Japan. Inversion
of the Stokes spectra taking into account the effect of magnetic
field on the energy structure and polarization of the hydrogen
levels (including the Hanle effect and level-crossing effects)
elucidates the magnetic field approximately aligned with the visible
structure of the jets. In addition to the magnetic field, the energy
structure and the polarization of the hydrogen levels is sensitive
to electric field through the Stark effect, electric Hanle effect
(analogous effect with the Hanle effect by magnetic field), and the
level-crossing effects. Since, we found no definitive evidence of the
polarization produced by the effect of electric field in the observed
Stokes profiles, we derived upper limits of electric field felt by
neutral atom moving across the magnetic field, and conclude that the
velocity of the neutral atom perpendicular to the magnetic field was
below several percents of the velocity bulk plasma motion.
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: Feasibility study of an image slicer for future space
application
Authors: Calcines, A.; Ichimoto, K.
Bibcode: 2014SPIE.9143E..4CC
Altcode:
This communication presents the feasibility study of an image slicer for
future space missions, especially for the integral field unit (IFU) of
the SUVIT (Solar UV-Visible-IR telescope) spectro-polarimeter on board
the Japanese-led solar space mission Solar-C as a backup option. The
MuSICa (Multi-Slit Image slicer based on collimator-Camera) image
slicer concept, originally developed for the European Solar Telescope,
has been adapted to the SUVIT requirements. The IFU will reorganizes
a 2-D field of view of 10 x 10 arcsec2 into three slits of
0.18 arcsec width by 185.12 arcsec length using flat slicer mirrors
of 100 μm width. The layout of MuSICa for Solar-C is telecentric and
offers an optical quality limited by diffraction. The entrance for the
SUVIT spectro-polarimeter is composed by the three IFU slits and one
ordinal long slit to study, using high resolution spectro-polarimetry,
the solar atmosphere (Photosphere and Chromosphere) within a spectral
range between 520 nm (optionally 280 nm) and 1,100 nm.
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: Development of a universal tunable filter for future solar
observations
Authors: Hagino, M.; Ichimoto, K.; Kimura, G.; Nakatani, Y.; Kawate,
T.; Shinoda, K.; Suematsu, Y.; Hara, H.; Shimizu, T.
Bibcode: 2014SPIE.9151E..5VH
Altcode:
We have developed a new narrowband tunable filter to perform imaging
spectroscopy of the solar chromosphere. Using Liquid Crystal Variable
Retarders (LCVRs) as the tuning elements for wavelength, wide-band
polarizers and super achromatic half-wave plates, it is possible to make
high speed tuning (about 0.1Sec), to exclude mechanical drives (and oil
tank), and to cover a wide wavelength range (510-100nm). This filter
builds up with seven stages each consisting of a pair of calcites,
LCVR, half-wave plates and linear polarizer. The full width at half
maximum (FWHM) of the filter transmission is about 0.025nm at 656.3nm.We
demonstrate that the concept of the universal tunable filter using the
LCVR's as tuning elements is highly promising for future application
to space mission and ground based observations.
Title: Small-scale chromospheric jets above a sunspot light bridge
Authors: Louis, Rohan E.; Beck, Christian; Ichimoto, Kiyoshi
Bibcode: 2014A&A...567A..96L
Altcode: 2014arXiv1406.0103L
Context. The chromosphere above sunspot umbrae and penumbrae shows
several different types of fast dynamic events such as running
penumbral waves, umbral flashes, and penumbral microjets.
Aims:
The aim of this paper is to identify the physical driver responsible
for the dynamic and small-scale chromospheric jets above a sunspot
light bridge.
Methods: High-resolution broadband filtergrams
of active region NOAA 11271 in Ca ii H and G band were obtained with
the Solar Optical Telescope on board Hinode. We identified the jets in
the Ca ii H images using a semi-automatic routine and determined their
length and orientation. We applied local correlation tracking (LCT)
to the G-band images to obtain the photospheric horizontal velocity
field. The magnetic field topology was derived from a Milne-Eddington
inversion of a simultaneous scan with the Spectropolarimeter.
Results: The chromospheric jets consist of a bright, triangular-shaped
blob that lies on the light bridge, while the apex of this blob extends
into a spike-like structure that is bright against the dark umbral
background. Most of the jets have apparent lengths of less than 1000
km and about 30% of the jets have lengths between 1000-1600 km. The
jets are oriented within ±35° to the normal of the spine of the light
bridge. Most of them are clustered near the central part of the light
bridge within a 2'' area. The jets are seen to move rapidly along the
light bridge and many of them cannot be identified in successive images
taken with a 2 min cadence. The jets are primarily located on one side
of the light bridge and are directed into the umbral core. The Stokes
profiles at or close to the location of the blobs on the LB exhibit
both a significant net circular polarization and multiple components,
including opposite-polarity lobes. The magnetic field diverges from the
light bridge towards the umbral cores that it separates. The LCT reveals
that in the photosphere there is a predominantly uni-directional flow
with speeds of 100-150 m s-1 along the light bridge. This
unidirectional flow is interrupted by a patch of weak or very small
motions on the light bridge which also moves along the light bridge.
Conclusions: The dynamic short-lived chromospheric jets above the LB
seem to be guided by the magnetic field lines. Reconnection events are
a likely trigger for such phenomenon since they occur at locations where
the magnetic field changes orientation sharply and where we also observe
isolated patches of opposite-polarity magnetic components. We find no
clear relation between the jets and the photospheric flow pattern.
Title: Development of a new solar adaptive optics system at the
Hida Observatory
Authors: Miura, Noriaki; Oh-ishi, Ayumu; Aoki, Shotaro; Mogaki, Hikaru;
Kuwamura, Susumu; Baba, Naoshi; Hanaoka, Yoichiro; Yamaguchi, Masashi;
Ueno, Satoru; Nakatani, Yoshikazu; Ichimoto, Kiyoshi
Bibcode: 2014SPIE.9148E..31M
Altcode:
We are developing a new adaptive optics (AO) system for the 60cm
domeless solar telescope of the Hida Observatory, Japan. The system has
a deformable mirror with 97 piezo-actuators, a Shack-Hartmann wavefront
sensor with a 10×10-microlens array and standard personal computers. We
conducted solar observations in September, 2013, and confirmed that our
AO system cancelled image-shifts so that the deviations were within
the resolution of the telescope. We report the detailed performances
of our new AO system.
Title: The SUVIT Instrument on the Solar-C Mission
Authors: Tarbell, Theodore D.; Ichimoto, Kiyoshi
Bibcode: 2014AAS...22412363T
Altcode:
Solar-C is a new space mission being proposed to JAXA, with significant
contributions anticipated from NASA, ESA, and EU countries. The main
scientific objectives are to: reveal the mechanisms for heating and
dynamics of the chromosphere and corona and acceleration of the solar
wind; determine the physical origin of the large-scale explosions
and eruptions that drive short-term solar, heliospheric, and geospace
variability; use the solar atmosphere as a laboratory for understanding
fundamental physical processes; make unprecedented observations
of the polar magnetic fields. The unique approaches of Solar-C to
achieve these goals are to: determine the properties and evolution of
the 3-dimensional magnetic field, especially on small spatial scales,
and for the first time observed in the crucial low beta plasma region;
observe all the temperature regimes of the atmosphere seamlessly at
the highest spatial resolution ever achieved; observe at high cadence
the prevailing dynamics in all regions of the atmosphere; determine
physical properties from high resolution spectroscopic measurements
throughout the atmosphere and into the solar wind. The powerful suite
of instruments onboard Solar-C will be sensitive to temperatures from
the photosphere 5500 K) to solar flares 20 MK) with no temperature
gap, with spatial resolution at all temperatures of 0.3″ or less
(0.1″ in the lower atmosphere) and at high cadence. The purpose of
the Solar UV-Visible-IR Telescope (SUVIT) is to obtain chromospheric
velocity, temperature, density and magnetic field diagnostics
over as wide arange of heights as possible, through high cadence
spectral line profiles and vector spectro-polarimetry. SUVIT is a
meter-class telescope currently under study at 1.4m in order to obtain
sufficientresolution and S/N. SUVIT has two complementary focal plane
packages, the Filtergraph that makes high cadence imaging observations
with the highest spatial resolution and the Spectro-polarimeter that
makes precise spectro-polarimetric observations. With their powerful
sets of spectral lines, FG and SP collect physical measurements from
the lower photosphere to upper chromosphere with much better spatial
and temporal resolution than Hinode SOT.
Title: Diagnosis of Magnetic and Electric Fields of Chromospheric
Jets through Spectropolarimetric Observations of H I Paschen Lines
Authors: Anan, T.; Casini, R.; Ichimoto, K.
Bibcode: 2014ApJ...786...94A
Altcode: 2014arXiv1402.4903A
Magnetic fields govern the plasma dynamics in the outer layers
of the solar atmosphere, and electric fields acting on neutral
atoms that move across the magnetic field enable us to study the
dynamical coupling between neutrals and ions in the plasma. In order
to measure the magnetic and electric fields of chromospheric jets,
the full Stokes spectra of the Paschen series of neutral hydrogen
in a surge and in some active region jets that took place at the
solar limb were observed on 2012 May 5, using the spectropolarimeter
of the Domeless Solar Telescope at Hida observatory, Japan. First,
we inverted the Stokes spectra taking into account only the effect of
magnetic fields on the energy structure and polarization of the hydrogen
levels. Having found no definitive evidence of the effects of electric
fields in the observed Stokes profiles, we then estimated an upper
bound for these fields by calculating the polarization degree under
the magnetic field configuration derived in the first step, with the
additional presence of a perpendicular (Lorentz type) electric field
of varying strength. The inferred direction of the magnetic field on
the plane of the sky approximately aligns to the active region jets
and the surge, with magnetic field strengths in the range 10 G <
B < 640 G for the surge. Using magnetic field strengths of 70, 200,
and 600 G, we obtained upper limits for possible electric fields of
0.04, 0.3, and 0.8 V cm-1, respectively. This upper bound
is conservative, since in our modeling we neglected the possible
contribution of collisional depolarization. Because the velocity of
neutral atoms of hydrogen moving across the magnetic field derived
from these upper limits of the Lorentz electric field is far below
the bulk velocity of the plasma perpendicular to the magnetic field
as measured by the Doppler shift, we conclude that the neutral atoms
must be highly frozen to the magnetic field in the surge.
Title: A Chain of Winking (Oscillating) Filaments Triggered by an
Invisible Extreme-ultraviolet Wave
Authors: Shen, Yuandeng; Ichimoto, Kiyoshi; Ishii, Takako T.; Tian,
Zhanjun; Zhao, Ruijuan; Shibata, Kazunari
Bibcode: 2014ApJ...786..151S
Altcode: 2014arXiv1403.7705S
Winking (oscillating) filaments have been observed for many
years. However, observations of successive winking filaments in
one event have not yet been reported. In this paper, we present the
observations of a chain of winking filaments and a subsequent jet that
are observed right after the X2.1 flare in AR11283. The event also
produced an extreme-ultraviolet (EUV) wave that has two components: an
upward dome-like wave (850 km s-1) and a lateral surface
wave (554 km s-1) that was very weak (or invisible)
in imaging observations. By analyzing the temporal and spatial
relationships between the oscillating filaments and the EUV waves,
we propose that all the winking filaments and the jet were triggered
by the weak (or invisible) lateral surface EUV wave. The oscillation
of the filaments last for two or three cycles, and their periods,
Doppler velocity amplitudes, and damping times are 11-22 minutes,
6-14 km s-1, and 25-60 minutes, respectively. We further
estimate the radial component magnetic field and the maximum kinetic
energy of the filaments, and they are 5-10 G and ~1019 J,
respectively. The estimated maximum kinetic energy is comparable to the
minimum energy of ordinary EUV waves, suggesting that EUV waves can
efficiently launch filament oscillations on their path. Based on our
analysis results, we conclude that the EUV wave is a good agent for
triggering and connecting successive but separated solar activities
in the solar atmosphere, and it is also important for producing solar
sympathetic eruptions.
Title: The Tandem Etalon Magnetograph of the Solar Magnetic Activity
Research Telescope (SMART) at Hida Observatory
Authors: Nagata, Shin'ichi; Morita, Satoshi; Ichimoto, Kiyoshi;
Nishida, Keisuke; Nakatani, Yoshikazu; Kimura, Goichi; Kaneda, Naoki;
Kitai, Reizaburou; UeNo, Satoru; Ishii, Takako T.
Bibcode: 2014PASJ...66...45N
Altcode:
The imaging photospheric magnetograph using tandem Fabry-Perot filters
is newly installed in the Solar Magnetic Activity Research Telescope
(SMART) of Hida Observatory, Kyoto University. The instrument,
Tandem Etalon Magnetograph (TEM), consists of a rotating wave plate,
tandem Fabry-Perot filters which scan the Fe I 6302.5 Å line with
∼ 130 mÅ bandwidth, a polarizing beam splitter, and two CCD cameras
simultaneously taking orthogonally polarized light with a frame rate
of 30 frames per second. We have confirmed that the Stokes vector map
deduced from 20 s integration achieves a polarimetric sensitivity of
∼ 5 × 10-4 for all polarization states at one wavelength,
which is higher than is achieved with a space instrument such as the
Spectro-Polarimeter aboard Hinode or the Helioseismic and Magnetic
Imager aboard the Solar Dynamic Observatory (SDO). We expect the
complementary observations by SMART/TEM, Hinode, and SDO can shed new
light on the trigger and energy storage mechanism of solar flares.
Title: International Collaboration and Academic Exchange of the
CHAIN Project in this Three Years (Period)
Authors: Ueno, Satoru; Shibata, Kazunari; Morita, Satoshi; Kimura,
Goichi; Asai, Ayumi; Kitai, Reizaburo; Ichimoto, Kiyoshi; Nagata,
Shin'ichi; Ishii, Takako; Nakatani, Yoshikazu; Masashi, Yamaguchi;
et al.
Bibcode: 2014SunGe...9...97U
Altcode:
We will introduce contents of international collaboration and
academic exchange of the CHAIN project in recent three years (ISWI
period). After April of 2010, we have not obtained any enough budget
for new instruments. Therefore, we have not been able to install new
Flare Monitoring Telescopes (FMT) in new countries, such as Algeria. On
the other hand, however, we have continued international academic
exchange through scientific and educational collaboration with mainly
Peru, such as data-analysis training, holding scientific workshops
etc. Additionally, in this year, King Saudi University of Saudi Arabia
and CRAAG of Algeria have planned to build a new FMT in their university
by their own budget. Therefore, we have started some collaboration in
the field of technical advices of instruments and scientific themes
etc. Moreover, Pakistan Space and Upper Atmosphere Research Commission
(SUPARCO) also offered us participation in the CHAIN-project. We would
like to continue to consider the possibility of academic collaboration
with such new positive developing nations, too.
Title: Within the International Collaboration CHAIN: a Summary of
Events Observed with Flare Monitoring Telescope (FMT) in Peru
Authors: Ishitsuka, J.; Asai, A.; Morita, S.; Terrazas, R.; Cabezas,
D.; Gutierrez, V.; Martinez, L.; Buleje, Y.; Loayza, R.; Nakamura,
N.; Takasao, S.; Yoshinaga, Y.; Hillier, A.; Otsuji, K.; Shibata, K.;
Ishitsuka, M.; Ueno, S.; Kitai, R.; Ishii, T.; Ichimoto, K.; Nagata,
S.; Narukage, N.
Bibcode: 2014SunGe...9...85I
Altcode:
In 2008 we inaugurated the new Solar Observatory in collaboration with
Faculty of Sciences of San Luis Gonzaga de Ica National University,
300 km south of Lima. In March of 2010 a Flare Monitoring Telescope
of Hida Observatory of Kyoto University arrived to Ica, part of CHAIN
Project (Continuous H-alpha Imaging Network). In October of the same
year we hosted the First FMT Workshop in Ica, then in July of 2011 the
Second FMT Workshop was opened. Since that we are focused on two events
registered by FMT in Peru to publish results. FMT is a good tool to
introduce young people from universities into scientific knowledge;
it is good also for education in Solar Physics and outreach. Details
of this successful collaboration will be explained in this presentation.
Title: Multi-Wavelength Observations of Large Amplitude Prominence
Oscillations
Authors: Shen, Yuandeng; Shibata, Kazunari; Ichimoto, Kiyoshi; Liu, Yu
Bibcode: 2014cosp...40E3016S
Altcode:
Multi-Wavelength observations of large amplitude prominence oscillations
are important in diagnosing the physical property and eruption
mechanism of prominences, as well as their ambient coronal magnetic
fields. Such studies has led to a new discipline dubbed ‘’Prominence
Seismology’’. However, up to the present, high-resolution and
multi-wavelength observations of large amplitude oscillations are very
scarce. Using high-resolution spectroscopic Halpha observations taken
by the Solar Magnetic Activity Research Telescope (SMART) and the
Solar Dynamics Observatory, we studied a series of intriguing large
amplitude prominence (filament) oscillation events. We find that large
amplitude horizontal and vertical prominence oscillations are often
launched by large-scale shock waves associated with remote flares,
while large amplitude longitudinal prominence oscillations are often
associated with nearby micro jets or flare activities. Sometimes,
longitudinal oscillations can also be launched by large-scale
shocks. With the spectroscopic observations taken by the SMART, we can
measure the Doppler velocity and even the three-dimensional velocity
of the oscillations, with the so-called ``Clould Model’’. The
oscillation period, amplitude, and damping time are also determined
from the Halpha observations. These prominence parameters are used to
estimate the magnetic fields of the prominence and the surrounding
corona using the method of prominence seismology. Other property of
large amplitude oscillation prominences such as restoring forces and
damping mechanisms are also discussed in our study.
Title: Properties of sunspot penumbral grains observed with Hinode
Authors: Zhang, Y.; Ichimoto, K.
Bibcode: 2013A&A...560A..77Z
Altcode:
Context. Penumbral grains (PGs) are small-scale (subarcsec) bright
features found in the bright penumbral filament in the outer parts of
sunspots.
Aims: We aim to study properties of PGs at the blue
continuum (4504 Å) and the G-band (4305 Å) by using simultaneous
seeing free data obtained by Broadband Filter Imager (BFI) on board
Hinode.
Methods: We use an automatic identification and tracking
algorithm to identify PGs, which were observed in a period of 170 min in
the blue continuum and 88 min in the G-band.
Results: Our results
indicate that 776 PGs were identified in the blue continuum, and 413
PGs were identified in the G-band,. A statistical study reveals that
about 55% of PGs move toward the umbra, about 13-19% of PGs move toward
the surrounding granulation, and the rest are relatively static. The
inward moving PGs are mostly located in the inner penumbra (up to
0.6 of the distance from the umbra to the photosphere) and outward
moving PGs are located in the outer penumbra. In the blue continuum
(and G band), the average lifetime, speed, and brightness of inward
moving PGs are 14.7 (13.5) min, 0.71 (0.70) km s-1 and 0.89
(0.88) of the quiet Sun. For outward moving PGs, the average lifetime,
speed and brightness are 8.0 (7.0) min, 0.93 (0.65) km s-1
and 0.99 (0.98) of the quiet Sun. For PGs that are relatively static,
the average lifetime and brightness are 7.6 (6.0) min and 0.94 (0.91)
of the quiet Sun. Moreover, our observational results show that the
correlation between the temporal evolutions of the speed and brightness
is complex.
Title: Emission Height and Temperature Distribution of White-light
Emission Observed by Hinode/SOT from the 2012 January 27 X-class
Solar Flare
Authors: Watanabe, Kyoko; Shimizu, Toshifumi; Masuda, Satoshi;
Ichimoto, Kiyoshi; Ohno, Masanori
Bibcode: 2013ApJ...776..123W
Altcode: 2013arXiv1308.5059W
White-light emissions were observed from an X1.7 class solar flare on
2012 January 27, using three continuum bands (red, green, and blue) of
the Solar Optical Telescope on board the Hinode satellite. This event
occurred near the solar limb, and so differences in the locations of the
various emissions are consistent with differences in heights above the
photosphere of the various emission sources. Under this interpretation,
our observations are consistent with the white-light emissions occurring
at the lowest levels of where the Ca II H emission occurs. Moreover, the
centers of the source regions of the red, green, and blue wavelengths
of the white-light emissions are significantly displaced from each
other, suggesting that those respective emissions are emanating from
progressively lower heights in the solar atmosphere. The temperature
distribution was also calculated from the white-light data, and we found
the lower-layer emission to have a higher temperature. This indicates
that high-energy particles penetrated down to near the photosphere,
and deposited heat into the ambient lower layers of the atmosphere.
Title: Solar scintillation detection and ranging (SCIDAR) technique
for measuring turbulent-layer heights
Authors: Miura, Noriaki; Oh-ishi, Ayumu; Shionoya, Shingo; Watanabe,
Koji; Kuwamura, Susumu; Baba, Naoshi; Ueno, Satoru; Ichimoto, Kiyoshi
Bibcode: 2013MNRAS.434.1205M
Altcode: 2013MNRAS.tmp.1834M
A solar SCIDAR (scintillation detection and ranging) technique is
proposed for measuring the heights of turbulent layers using the Sun
itself, instead of the binary stars used in night-time SCIDAR. A
formula for the technique is derived under various assumptions:
uniform intensity distributions on the solar surface and sparse
speckle distributions on the image plane. It indicates that the
cross-correlation of scintillation shadows yields peaks at positions
corresponding to layer heights, although the shapes of peaks are
blurred by both an extended seeing disc and a finite-sized field
stop. A knife-edge effect caused by field stops in an observational
system is also described, which yields another peak at the centre of
the correlation plane. Observations were conducted using a solar SCIDAR
system developed at the Hida Observatory in Japan. In many results,
peaks on correlation planes demonstrated a contrast high enough for
them to be distinguished from the background. Most of the distances to
turbulent layers derived from the scintillation peaks were found to
be between 2.5 and 3.5 km. Use of a high-performance adaptive-optics
system upstream of the SCIDAR system is suggested in order to provide
better results.
Title: Diffraction, Refraction, and Reflection of an
Extreme-ultraviolet Wave Observed during Its Interactions with Remote
Active Regions
Authors: Shen, Yuandeng; Liu, Yu; Su, Jiangtao; Li, Hui; Zhao, Ruijuan;
Tian, Zhanjun; Ichimoto, Kiyoshi; Shibata, Kazunari
Bibcode: 2013ApJ...773L..33S
Altcode: 2013arXiv1307.6098S
We present observations of the diffraction, refraction, and reflection
of a global extreme-ultraviolet (EUV) wave propagating in the solar
corona. These intriguing phenomena are observed when the wave interacts
with two remote active regions, and together they exhibit properties
of an EUV wave. When the wave approached AR11465, it became weaker
and finally disappeared in the active region, but a few minutes
later a new wavefront appeared behind the active region, and it was
not concentric with the incoming wave. In addition, a reflected wave
was also simultaneously observed on the wave incoming side. When the
wave approached AR11459, it transmitted through the active region
directly and without reflection. The formation of the new wavefront
and the transmission could be explained with diffraction and refraction
effects, respectively. We propose that the different behaviors observed
during the interactions may be caused by different speed gradients at
the boundaries of the two active regions. We find that the EUV wave
formed ahead of a group of expanding loops a few minutes after the
start of the loops' expansion, which represents the initiation of
the associated coronal mass ejection (CME). Based on these results,
we conclude that the EUV wave should be a nonlinear magnetosonic wave
or shock driven by the associated CME, which propagated faster than
the ambient fast mode speed and gradually slowed down to an ordinary
linear wave. Our observations support the hybrid model that includes
both fast wave and slow non-wave components.
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 SP_PREP Data Preparation Package for the Hinode
Spectro-Polarimeter
Authors: Lites, B. W.; Ichimoto, K.
Bibcode: 2013SoPh..283..601L
Altcode:
The Hinode/Spectro-Polarimeter (SP) is the first space-borne precision
spectro-polarimeter for the study of solar phenomena. It is primarily
intended for measuring the solar photospheric vector magnetic field at
high spatial and spectral resolution. This objective requires that the
data are calibrated and conditioned to a high degree of precision. We
describe how the calibration package SP_PREP for the SP operates.
Title: The Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Akin, D. L.; Card, G.; Cruz, T.; Duncan, D. W.;
Edwards, C. G.; Elmore, D. F.; Hoffmann, C.; Katsukawa, Y.; Katz, N.;
Kubo, M.; Ichimoto, K.; Shimizu, T.; Shine, R. A.; Streander, K. V.;
Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S.
Bibcode: 2013SoPh..283..579L
Altcode:
The joint Japan/US/UK Hinode mission includes the first large-aperture
visible-light solar telescope flown in space. One component of the
Focal Plane Package of that telescope is a precision spectro-polarimeter
designed to measure full Stokes spectra with the intent of using those
spectra to infer the magnetic-field vector at high precision in the
solar photosphere. This article describes the characteristics of the
flight hardware of the HinodeSpectro-Polarimeter, and summarizes its
in-flight performance.
Title: High-Speed Imaging System for Solar-Flare Research at Hida
Observatory
Authors: Ishii, Takako T.; Kawate, Tomoko; Nakatani, Yoshikazu;
Morita, Satoshi; Ichimoto, Kiyoshi; Masuda, Satoshi
Bibcode: 2013PASJ...65...39I
Altcode:
A high-speed imaging system for observing solar flares in the
continuum and Hα wavelengths was installed on a φ 25 cm telescope
of the Solar Magnetic Activity Research Telescope (SMART) at Hida
observatory of Kyoto University. The aim of this system is to diagnose
the spatio-temporal evolution of high-energy particles in solar flares
by capturing the explosive evolution of chromospheric and photospheric
flare kernels. The system acquires flare images covering a field of view
of 344" × 258" with a spatial sampling of 0.215" pixel-1
and a frame rate of 25 frames s-1 . Initial data, including
two white-light flares, demonstrate the diffraction-limited performance
of the system. Observations have been in regular operation since
2011 November. The system is expected to provide a data set that is
highly complementary with Hinode/SOT, SDO/AIA, and other ground-based
instruments for upcoming solar-flare research.
Title: The abundance of silicon in the solar atmosphere
Authors: Shaltout, A. M. K.; Beheary, M. M.; Bakry, A.; Ichimoto, K.
Bibcode: 2013MNRAS.430.2979S
Altcode: 2013MNRAS.tmp..777S
High-resolution solar spectra were used to determine the silicon
abundance (ɛSi) content by comparison with Si line synthesis
relying on realistic hydrodynamical simulations of the solar surface
convection, as 3D inhomogeneous model of the solar photosphere. Based
on a set of 19 Si I and 2 Si II lines, with accurate transition
probabilities as well as accurate observational data available,
the solar photospheric Si abundance has been determined to be log
ɛSi(3D) = 7.53 ± 0.07. Here we derive the photospheric
silicon abundance taking into account non-LTE effects based on 1D solar
model, the non-LTE abundance value we find is log ɛSi
(1D) = 7.52 ± 0.08. The photospheric Si abundance agrees well with
the results of Asplund and more recently published by Asplund et
al. relative to previous 3D-based abundances, the consistency given
that the quoted errors here are (±0.07 dex).
Title: Thermal Structure of Coronal Loops as Seen with Norikura
Coronagraph
Authors: Krishna Prasad, S.; Singh, Jagdev; Ichimoto, K.
Bibcode: 2013ApJ...765L..46K
Altcode: 2013arXiv1302.5905K
The thermal structure of a coronal loop, both along and across
the loop, is vital in determining the exact plasma heating
mechanism. High-resolution spectroscopic observations of the
off-limb corona were made using the 25 cm Norikura coronagraph,
located at Norikura, Japan. Observations on a number of days were
made simultaneously in four forbidden iron emission lines, namely,
the [Fe XI] 7892 Å line, the [Fe XIII] 10747 Å and 10798 Å lines,
and the [Fe XIV] 5303 Å line and on some days made only in the [Fe
XI] 7892 Å and [Fe X] 6374 Å lines. Using temperature sensitive
emission line ratios [Fe XIV] 5303 Å/[Fe XIII] 10747 Å and [Fe XI]
7892 Å/[Fe X] 6374 Å, we compute the electron temperatures along
18 different loop structures observed on different days. We find a
significant negative temperature gradient in all of the structures
observed in Fe XIV and Fe XIII and a positive temperature gradient in
the structures observed in Fe XI and Fe X. Combining these results with
the previous investigations by Singh and his collaborators, we infer
that the loop tops, in general, appear hotter when observed in colder
lines and colder when observed in relatively hotter lines as compared
to their coronal foot points. We suggest that this contrasting trend
observed in the temperature variation along the loop structures can be
explained by a gradual interaction of different temperature plasma. The
exact mechanism responsible for this interaction must be investigated
further and has the potential to constrain loop heating models.
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: Emission Height and Temperature Distribution of White-Light
Emission from the 2011 January 27 Flare Observed by Hinode/SOT
Authors: Watanabe, K.; Shimizu, T.; Masuda, S.; Ichimoto, K.
Bibcode: 2012AGUFMSH52B..03W
Altcode:
White light flares are flares that show an emission enhancement in
the visible continuum. White-light emissions are well correlated
with hard X-ray and radio emissions in time profile and emission
location. This seems to imply that the origin of white-light emission
is accelerated particles, in particular non-thermal elections. However,
this is hard to understand in terms of the expected respective emission
heights. Theoretically, white-light emissions are generated near the
photosphere, but non-thermal electrons of energy ~50-100 keV should
deposit their energy in the lower chromosphere, more than 500 km
above the photosphere. Thus there should be ~500 km difference in
the white-light and X-ray emission heights, which seems at odds with
the observations. We investigate this question with observations
of a near-limb X1.7 flare of 27 January 2012, using three continuum
bands (red, green, and blue) of the Hinode Solar Optical Telescope
(SOT). The near-limb location allowed us to determine the heights of the
emissions. We found the white-light emissions to be located low down,
apparently at the photosphere, with the Ca II H emission originating
from higher up. We also calculated the temperature distribution from the
three white-light continuum bands, and found the lower layer to have
higher temperature. These findings suggest that high energy particles
penetrate to near the photosphere, heating the ambient atmosphere from
very low (near photospheric) layers.
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: Developments of the wideband spectropolarimeter of the Domeless
Solar Telescope at Hida Observatory
Authors: Anan, Tetsu; Ichimoto, Kiyoshi; Oi, Akihito; Kimura, Goichi;
Nakatani, Yoshikazu; Ueno, Satoru
Bibcode: 2012SPIE.8446E..1CA
Altcode:
We developed a new universal spectropolarimeter on the Domeless Solar
Telescope at Hida Observatory to realize precise spectropolarimetric
observations in a wide range of wavelength in visible and near
infrared. The system aims to open a new window of plasma diagnostics by
using Zeeman effect, Hanle effect, Stark effect, and impact polarization
to measure the external magnetic field, electric field, and anisotropies
in atomic excitation in solar atmosphere. The polarimeter consists of a
60 cm aperture vacuum telescope, a high dispersion vacuum spectrograph,
polarization modulator and analyser composed of a continuously rotating
waveplate whose retardation is constant in 400 - 1100 nm and Wallaston
prisms located closely behind the focus of the telescope, and a fast
and high sensitive CCD camera or a infrared camera. The duration for
this polarimeter's achieving photometric accuracy of 10-3
is 30 - 60 s. Instrumental polarization of the telescope is calibrated
by using a remotely controllable turret accommodating linear polarizer
attached at the entrance window of the telescope to induce well known
polarized light into the telescope. Thus a Mueller matrix model of the
telescope is established to compensate the instrumental polarization
included in observed data within the required accuracy.
Title: Statistical Analysis of Doppler Velocity Field and Magnetic
Structure around Cancellations in the Quiet Sun
Authors: Iida, Y.; Yokoyama, T.; Ichimoto, K.
Bibcode: 2012ASPC..454...43I
Altcode:
The cancellation is a convergence and a disappearance of the
two opposite polarities and is thought as a main process of the
flux disappearance in the photosphere. We investigate the spatial
structures and time evolutions of Doppler velocity field around
the cancellations in the quiet Sun by using Filtergram (FG) onboard
Hinode. We found the characteristic redshifts in 7 cancellations, blue
shifts in 2 cancellations, and no characteristic Doppler velocity in
3 events. It is found that the stable downflow is coincident with the
flux decrease. These results suggest that the Omega-loop submergence
is a dominant scenario in the cancellation of the quiet Sun.
Title: Spicule Dynamics over Plage Region
Authors: Anan, T.; Kitai, R.; Hillier, A.; Kawate, T.; Ichimoto, K.;
Shibata, K.
Bibcode: 2012ASPC..454...91A
Altcode:
We have studied spicular jets over a plage region and derived their
dynamic characteristics using Hinode Solar Optical Telescope (SOT)
high-resolution Ca II H images. We have identified 169 spicules over
the target plage. This sample size permits us to derive statistically
reliable results regarding spicular dynamics. The properties of plage
spicules can be summarized as follows: (1) In a plage area, we clearly
identify spicular jet features. (2) They are shorter in length than
the quiet-region limb spicules, and follow ballistic motion under
constant deceleration. (3) The majority (80%) of the plage spicules
show a full rise and retreat (which we call ‘parabolic’ spicules),
while 10% of them fade out without a complete retreat phase(which we
call ‘fade out’ spicules). (4) The deceleration of the spicule is
proportional to the velocity of ejection (i.e. the initial velocity).
Title: Chromospheric Anemone Jets Observed with Hinode/SOT and Hida
Ca II Spectroheliograph
Authors: Morita, S.; Shibata, K.; Ueno, S.; Ichimoto, K.; Kitai, R.;
Otsuji, K.
Bibcode: 2012ASPC..454...95M
Altcode:
We present the first simultaneous observations of chromospheric
“anemone” jets in active regions with the Ca II H broadband
filetergram on the Hinode/SOT and with the Ca II K spetroheliogram on
the Domeless Solar Telescope (DST) at the Hida Observatory. During
coordinated observation period, 9 chromospheric anemone jets were
simultaneously observed with the two instruments. These observations
revealed: (1) the jets are generated in the low chromosphere because
these cannot be seen in Ca II K3, (2) these jets are
associated with mixed polarity regions which are either small emerging
flux regions or moving magnetic features, (3) the Ca II K line often
show red or blue asymmetry in K2/K1 component;
the footpoint of the jets associated with emerging flux regions often
show red asymmetry (2-16 km s-1), while the one with moving
magnetic features show blue asymmetry (∼5 km s-1). The
magnetic cancellations were observed at the footpoint of the jets. The
canceling rates are of order of 1016 Mx s-1, and
the resulting magnetic energy release rate (1.1-10)×1024 erg
s-1, with the total energy release (1-13)×1026
erg for the duration of the magnetic cancellations, ∼130 s. These
are comparable to the estimated total energy, ∼1026 erg,
in a single chromospheric anemone jet.
Title: Coupling of the magnetic field and gas flows in sunspot
penumbra inferred from the Hinode/SOT observation
Authors: Ichimoto, Kiyoshi; Shaltout, Abdelrazek Mohammed
Bibcode: 2012cosp...39..789I
Altcode: 2012cosp.meet..789I
Sunspot penumbrae has been an enigmatic region that consists of fine
scale filamentary structures harboring conspicuous gas flows known as
the Evershed flow in the base of photosphere and the inverse-Evershed
flow in higher layer. Recent high resolution observations including
those by Hinode/SOT revealed that the penumbral magnetic field is
highly fluctuating in its strength and inclination in space, and the
geometry is called as interlocking comb structure. There is a strong
coupling of the magnetic field and gas flow, i.e., many observational
aspects suggest the origin of the sunspot penumbra as the vigorous
thermal-convection of plasma under the inclined strong magnetic field
of sunspots. However the relation between the magnetic field and gas
flow is still an open issue to be settled. A number of observational
and theoretical works suggest that the convective hot gas with a large
flow speed is associated with a weak field. In this paper, we present an
evidence of contradictory relation, i.e., a positive correlation between
the field strength and flow velocity in photosphere. The geometry of
the inverse-Evershed flow in conjunction with the interlocking magnetic
field structure of penumbra is another issue that is not understood. We
present an insight on the relation between the magnetic field structure
and the inverse-Evershed flow based on the SOT/SP observations.
Title: Solar adaptive optics at the Hida Observatory: latest
achievements of current system and design of new system
Authors: Miura, Noriaki; Miyazaki, Jun'ichi; Kuwamura, Susumu; Baba,
Naoshi; Hanaoka, Yoichiro; Yamaguchi, Masashi; Ueno, Satoru; Nakatani,
Yoshikazu; Nagata, Shin'ichi; Kitai, Reizaburou; Ichimoto, Kiyoshi;
Takami, Hideki
Bibcode: 2012SPIE.8447E..4DM
Altcode:
Solar adaptive optics (AO) systems are developed at the 60cm
domeless solar telescope in the Hida Observatory, Japan. An AO
system currently used has a deformable mirror with high-speed 97
electromagnetic actuators and a Shack- Hartmann wavefront sensor with a
10x10-microlens array and 4000fps-CMOS camera. Its control frequency is
about 1100-1400 Hz, and hence the -3dB cutoff frequency of the system
is theoretically above 100 Hz. In parallel to developing the system,
a new full-scaled AO system is designed to be applicable to various
observations, such as highdispersion spectroscopy and simultaneous
wide-range spectroscopy. The new system will work as classical AO at
first. The details of the current system, observational results using
it, and the design of the new AO system are described.
Title: Properties of Umbral Dots from Stray Light Corrected Hinode
Filtergrams
Authors: Louis, Rohan E.; Mathew, Shibu K.; Bellot Rubio, Luis R.;
Ichimoto, Kiyoshi; Ravindra, B.; Raja Bayanna, A.
Bibcode: 2012ApJ...752..109L
Altcode: 2012arXiv1204.4088L
High-resolution blue continuum filtergrams from Hinode are employed
to study the umbral fine structure of a regular unipolar sunspot. The
removal of scattered light from the images increases the rms contrast
by a factor of 1.45 on average. Improvement in image contrast renders
identification of short filamentary structures resembling penumbrae
that are well separated from the umbra-penumbra boundary and comprise
bright filaments/grains flanking dark filaments. Such fine structures
were recently detected from ground-based telescopes and have now been
observed with Hinode. A multi-level tracking algorithm was used to
identify umbral dots (UDs) in both the uncorrected and corrected images
and to track them in time. The distribution of the values describing
the photometric and geometric properties of UDs is more easily affected
by the presence of stray light while it is less severe in the case
of kinematic properties. Statistically, UDs exhibit a peak intensity,
effective diameter, lifetime, horizontal speed, and a trajectory length
of 0.29I QS, 272 km, 8.4 minutes, 0.45 km s-1,
and 221 km, respectively. The 2 hr 20 minute time sequence depicts
several locations where UDs tend to appear and disappear repeatedly
with various time intervals. The correction for scattered light in the
Hinode filtergrams facilitates photometry of umbral fine structure,
which can be related to results obtained from larger telescopes and
numerical simulations.
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: Precursor of Sunspot Penumbral Formation Discovered with
Hinode SOT Observation
Authors: Shimizu, T.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2012ASPC..456...43S
Altcode:
We newly found a precursory signature of sunspot penumbral formation
in Ca II H images. The precursor is a dark annular zone (width 3"-5")
around the umbra (pore), which was formed soon after the pore formation
and existed until the penumbral formation. The penumbra was developed
as if to fill the annular zone. Pre-existing ambient magnetic field
islands were moved to be distributed at the outer edge of the annular
zone and did not come into the zone. The observations indicate that
the annular zone is different from sunspot moat flow region and that
the zone is visible only in chromospheric Ca II H images, not in
photospheric G-band images. We conclude that the annular zone reflects
the formation of a magnetic canopy overlying the region surrounding
the umbra at the chromospheric level, much before the formation of the
penumbra at the photospheric level. We can predict the region and size
of the penumbra, by looking at the appearance of dark zone around pores.
Title: Precursor of Sunspot Penumbral Formation Discovered with
Hinode Solar Optical Telescope Observations
Authors: Shimizu, Toshifumi; Ichimoto, Kiyoshi; Suematsu, Yoshinori
Bibcode: 2012ApJ...747L..18S
Altcode: 2012arXiv1202.1025S
We present observations of a precursory signature that would be helpful
for understanding the formation process of sunspot penumbrae. The Hinode
Solar Optical Telescope successfully captured the entire evolution of a
sunspot from the pore to a large well-developed sunspot with penumbra
in an emerging flux region appearing in NOAA Active Region 11039. We
found an annular zone (width 3''-5'') surrounding the umbra (pore)
in Ca II H images before the penumbra formed around the umbra. The
penumbra developed as if to fill the annular zone. The annular zone
shows weak magnetogram signals, meaning less magnetic flux or highly
inclined fields there. Pre-existing ambient magnetic field islands were
distributed at the outer edge of the annular zone and did not come into
the zone. There are no strong systematic flow patterns in the zone,
but we occasionally observed small magnetic flux patches streaming
out. The observations indicate that the annular zone is different from
the sunspot moat flow region and that it represents the structure in the
chromosphere. We conclude that the annular zone reflects the formation
of a magnetic canopy overlying the region surrounding the umbra at the
chromospheric level, long before the formation of the penumbra at the
photospheric level. The magnetic field structure in the chromosphere
needs to be considered in the formation process of the penumbrae.
Title: First Simultaneous Observation of an Hα Moreton Wave, EUV
Wave, and Filament/Prominence Oscillations
Authors: Asai, Ayumi; Ishii, Takako T.; Isobe, Hiroaki; Kitai,
Reizaburo; Ichimoto, Kiyoshi; UeNo, Satoru; Nagata, Shin'ichi; Morita,
Satoshi; Nishida, Keisuke; Shiota, Daikou; Oi, Akihito; Akioka, Maki;
Shibata, Kazunari
Bibcode: 2012ApJ...745L..18A
Altcode: 2011arXiv1112.5915A
We report on the first simultaneous observation of an Hα Moreton wave,
the corresponding EUV fast coronal waves, and a slow and bright EUV
wave (typical EIT wave). We observed a Moreton wave, associated with
an X6.9 flare that occurred on 2011 August 9 at the active region
NOAA 11263, in the Hα images taken by the Solar Magnetic Activity
Research Telescope at Hida Observatory of Kyoto University. In the
EUV images obtained by the Atmospheric Imaging Assembly on board the
Solar Dynamic Observatory we found not only the corresponding EUV fast
"bright" coronal wave, but also the EUV fast "faint" wave that is not
associated with the Hα Moreton wave. We also found a slow EUV wave,
which corresponds to a typical EIT wave. Furthermore, we observed,
for the first time, the oscillations of a prominence and a filament,
simultaneously, both in the Hα and EUV images. To trigger the
oscillations by the flare-associated coronal disturbance, we expect
a coronal wave as fast as the fast-mode MHD wave with the velocity of
about 570-800 km s-1. These velocities are consistent with
those of the observed Moreton wave and the EUV fast coronal wave.
Title: A Study on Red Asymmetry of Hα Flare Ribbons Using a
Narrowband Filtergram in the 2001 April 10 Solar Flare
Authors: Asai, Ayumi; Ichimoto, Kiyoshi; Kita, Reizaburo; Kurokawa,
Hiroki; Shibata, Kazunari
Bibcode: 2012PASJ...64...20A
Altcode: 2011arXiv1112.5912A
We report on a detailed examination of the ``red asymmetry'' of the
Hα emission line seen during the 2001 April 10 solar flare by using
a narrowband filtergram. We investigated the temporal evolution and
the spatial distribution of the red asymmetry by using Hα data taken
with the 60-cm Domeless Solar Telescope at Hida Observatory, Kyoto
University. We confirmed that the red asymmetry clearly appeared all
over the flare ribbons, and the strong red asymmetry is located on the
outer narrow edges of the flare ribbons, with a width of about 1.5"-3.0"
(1000-2000 km), where strong energy releases occur. Moreover, we found
that the red asymmetry, which also gives a measure of the Doppler
shift of the Hα emission line, concentrates on a certain value,
not depending on the intensity of the Hα kernels. This implies not
only that the temporal evolutions of the red asymmetry and those of
the intensity are not synchronous in each flare kernel, but also that
the peak asymmetry (or velocity of the chromospheric condensation)
of individual kernel is not a strong function of their peak intensity.
Title: Ly-alpha polarimeter design for CLASP rocket experiment
Authors: Kubo, M.; Watanabe, H.; Narukage, N.; Ishikawa, R.; Bando,
T.; Kano, R.; Tsuneta, S.; Kobayashi, K.; Ichimoto, K.; Trujillo Bueno,
J.; Song, D.
Bibcode: 2011AGUFM.P11F1627K
Altcode:
A sounding-rocket program called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is proposed to be launched in the Summer
of 2014. CLASP will observe the upper solar chromosphere in Ly-alpha
(121.567 nm), aiming to detect the linear polarization signal produced
by scattering processes and the Hanle effect for the first time. The
CLASP needs a rotating half-waveplate and a polarization analyzer
working at the Ly-alpha wavelength to measure the linear polarization
signal. We select Magnesium Fluoride (MgF2) as a material of the
optical components because of its birefringent property and high
transparency at UV wavelength. We have confirmed that the reflection
at the Brewster's Angle of MgF2 plate is a good polarization analyzer
for the Ly-alpha line by deriving its ordinary refractive index and
extinction coefficient along the ordinary and extraordinary axes. These
optical parameters are calculated with a least-square fitting in such a
way that the reflectance and transmittance satisfy the Kramers-Kronig
relation. The reflectance and transmittance against oblique incident
angles for the s-polarized and the p-polarized light are measured
using the synchrotron beamline at the Ultraviolet Synchrotron Orbital
Radiation Facility (UVSOR). We have also measured a retardation of
a zeroth-order waveplate made of MgF2. The thickness difference of
the waveplate is 14.57 um.This waveplate works as a half-waveplate at
121.74 nm. From this measurement, we estimate that a waveplate with
the thickness difference of 15.71 um will work as a half-waveplate
at the Ly-alpha wavelength. We have developed a rotating waveplate -
polarization analyzer system called a prototype of CLASP polarimeter,
and input the perfect Stokes Q and U signals. The modulation patterns
that are consistent with the theoretical prediction are successfully
obtained in both cases.
Title: The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP)j
Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Bando, T.;
Belluzzi, L.; Casini, R.; Carlsson, M.; Cirtain, J. W.; De Pontieu,
B.; Hara, H.; Ichimoto, K.; Ishikawa, R.; Kano, R.; Katsukawa, Y.;
Kim, T.; Kubo, M.; Manso Sainz, R.; Narukage, N.; Asensio Ramos,
A.; Robinson, B.; Sakao, T.; Shimizu, T.; Stepan, J.; Suematsu, Y.;
Watanabe, H.; West, E.; Winebarger, A. R.
Bibcode: 2011AGUFM.P14C..05K
Altcode:
We present an overview of the Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP) program. CLASP is a proposed sounding rocket
experiment currently under development as collaboration between Japan,
USA and Spain. The aim is to achieve the first measurement of magnetic
field in the upper chromosphere and transition region of the Sun
through the detection and measurement of Hanle effect polarization
of the Lyman alpha line. The Hanle effect (i.e. the magnetic field
induced modification of the linear polarization due to scattering
processes in spectral lines) is believed to be a powerful tool for
measuring the magnetic field in the upper chromosphere, as it is more
sensitive to weaker magnetic fields than the Zeeman effect, and also
sensitive to magnetic fields tangled at spatial scales too small to be
resolved. The Lyman-alpha (121.567 nm) line has been chosen because
it is a chromospheric/transition-region line, and because the Hanle
effect polarization of the Lyman-alpha line is predicted to be sensitive
to 10-250 Gauss, encompassing the range of interest. Hanle effect is
predicted to be observable as linear polarization or depolarization,
depending on the geometry, with a fractional polarization amplitude
varying between 0.1% and 1% depending on the strength and orientation of
the magnetic field. This quantification of the chromospheric magnetic
field requires a highly sensitive polarization measurement. The
CLASP instrument consists of a large aperture (287 mm) Cassegrain
telescope mated to a polarizing beamsplitter and a matched pair
of grating spectrographs. The polarizing beamsplitter consists
of a continuously rotating waveplate and a linear beamsplitter,
allowing simultaneous measurement of orthogonal polarizations and
in-flight self-calibration. Development of the instrument is underway,
and prototypes of all optical components have been tested using a
synchrotron beamline. The experiment is proposed for flight in 2014.
Title: High speed imaging system in continuum and H-alpha at the Hida
observatory for the study of high energy particles in solar flares
Authors: Ichimoto, K.; Kawate, T.; Yoshikazu, N.; Ishii, T.; Nagata,
S.; Asai, A.; Masuda, S.; Kusano, K.; Yamamoto, T. T.; Minoshima,
T.; Yokoyama, T.; Watanabe, K.
Bibcode: 2011AGUFMSH41A1914I
Altcode:
Non-thermal particles are the fundamental ingredient of solar flares
that carry the bulk energy released from the coronal magnetic fields
and cause subsequent heating of the solar atmosphere to produce the
radiation of wide range of electro-magnetic waves. The observations of
hard X-ray and radio emissions suggest a rapid change of population of
high energy particles with a time scale of sub-second. Flare kernels
observed in visible lights, ex., H-alpha and continuum, show drastic
evolutions in space and time during the rising phase of solar flares,
and thought to be representing the locations of the precipitation of
high energy particles into the chromosphere. Therefore the observations
of flare kernels with high spatial and temporal resolutions provide
valuable diagnosis of the distribution of high energy particles together
with the information of connectivity of coronal magnetic fields. We
developed a new high speed imaging system on a 25cm diameter telescope
of the Solar Magnetic Activity Research Telescope (SMART) at the Hida
observatory of Kyoto University. Images in H-alpha (width~3A) and
continuum (6547A, width~10A) are recorded simultaneously with two CCD
cameras with a spatial sampling of 0.2 arcsec/pix, field coverage of
344 arcsec x 258 arcsec, and a frame rate of 30fr/sec. Observation is
conducted continuously by focusing a targeted active region every day,
while only data sets that capture flare events are permanently stored
for further analysis. The spatial and temporal evolutions of flare
kernels thus obtained are combined with photospheric vector magnetic
field taken by the SMART, SOT/Hinode and HMI/SDO, radio data by NoRH,
hard X-ray image by RHESSI, and X-ray / UV images by SXT/Hinode
and AIA/SDO to identify the instantaneous locations of high energy
particles injection in the corona. In this paper we will present an
overview of the observing system and its initial results. This work
was carried out by the joint research program of the Solar-Terrestorial
Environment Laboratory, Nagoya University.
Title: Center-to-Limb Variation of Microwave Emissions from
Thermal-Rich and Thermal-Poor Solar Flares
Authors: Kawate, T.; Asai, A.; Ichimoto, K.
Bibcode: 2011AGUFMSH41A1913K
Altcode:
Non-thermal microwave emissions observed in the impulsive phase of
solar flares are produced by the gyrosynchrotron mechanism, which
depends on a number of physical parameters such as electron energy
spectra, their pitch angle distribution, magnetic field strength,
angle between line of sight and the magnetic field (viewing angle),
and the number of electrons. Therefore, it is difficult to determine
those physical parameters uniquely only from the observed quantities
of individual microwave burst. Statistical analysis of microwave
bursts by using a number of flare events provide us a way to find
mutual relationships between different quantities, and thus are useful
to restrict the possible domain of those physical quantities of the
microwave source. The pitch angle distribution of accelerated electrons
is of a crucial importance for the problem of particle acceleration in
solar flares. A clue to know the pitch angle distribution of accelerated
particles could be obtained from the center-to-limb variations of
observed microwave emissions, since relativistic electrons trapped in
flare loops emit the microwaves to the direction of their velocity, and
the viewing angle effect, i.e., center-to-limb variation of the flare
emission, can be related to the pitch angle distribution of accelerated
electrons. A statistical analysis of microwave flare events is performed
by using the event list of Nobeyama Radioheliograph in 1996-2009. We
examine center-to-limb variations of17GHz and 34GHz flux by dividing
the flare events into different groups with respect to the 'thermal
plasma richness' (ratio of the peak flux of soft X-ray to non-thermal
microwave emissions) and the duration of microwave bursts. It is
found that peak flux of 17 and 34GHz tend to be higher toward the
limb for thermal-rich flares with short durations. We propose that
the thermal-rich flares, which are supposed to be associated with an
efficient precipitation of high energy particles into the chromosphere,
have a pitch angle distribution of non-thermal electrons with a higher
population along the flare loop.
Title: Center-to-Limb Variation of Radio Emissions from Thermal-Rich
and Thermal-Poor Solar Flares
Authors: Kawate, Tomoko; Asai, Ayumi; Ichimoto, Kiyoshi
Bibcode: 2011PASJ...63.1251K
Altcode: 2011arXiv1107.1905K
A statistical analysis of radio flare events was conducted by using
the event list of Nobeyama Radioheliograph in the years 1996-2009. We
examined center-to-limb variations of 17 GHz and 34 GHz fluxes by
dividing the flare events into different groups according to the
``thermal plasma richness'' (ratio of the peak flux of soft X-ray to
nonthermal radio emissions) and the duration of radio bursts. It was
found that the peak flux at 17 and 34 GHz tended to be higher toward
the limb for thermal-rich flares with short durations. We propose that
the thermal-rich flares, which are supposed to be associated with an
efficient precipitation of high-energy particles into the chromosphere,
have a pitch-angle distribution of nonthermal electrons with a higher
population along the flare loop.
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: Ly-alpha polarimeter design for CLASP rocket experiment
Authors: Watanabe, H.; Narukage, N.; Kubo, M.; Ishikawa, R.; Bando, T.;
Kano, R.; Tsuneta, S.; Kobayashi, K.; Ichimoto, K.; Trujillo-Bueno, J.
Bibcode: 2011SPIE.8148E..0TW
Altcode: 2011SPIE.8148E..25W; 2014arXiv1407.4577W
A sounding-rocket program called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is proposed to be launched in the summer of
2014. CLASP will observe the solar chromosphere in Ly-alpha (121.567
nm), aiming to detect the linear polarization signal produced by
scattering processes and the Hanle effect for the first time. The
polarimeter of CLASP consists of a rotating half-waveplate, a beam
splitter, and a polarization analyzer. Magnesium Fluoride (MgF2) is
used for these optical components, because MgF2 exhibits birefringent
property and high transparency at ultraviolet wavelength. The
development and comprehensive testing program of the optical components
of the polarimeter is underway using the synchrotron beamline at the
Ultraviolet Synchrotron Orbital Radiation Facility (UVSOR). The first
objective is deriving the optical constants of MgF2 by the measurement
of the reflectance and transmittance against oblique incident angles
for the s-polarized and the p-polarized light. The ordinary refractive
index and extinction coefficient along the ordinary and extraordinary
axes are derived with a least-square fitting in such a way that the
reflectance and transmittance satisfy the Kramers-Krönig relation. The
reflection at the Brewster's Angle of MgF2 plate is confirmed to become
a good polarization analyzer at Ly-alpha. The second objective is the
retardation measurement of a zeroth-order waveplate made of MgF2. The
retardation of a waveplate is determined by observing the modulation
amplitude that comes out of a waveplate and a polarization analyzer. We
tested a waveplate with the thickness difference of 14.57 um. The 14.57
um waveplate worked as a half-waveplate at 121.74 nm. We derived that
a waveplate with the thickness difference of 15.71 um will work as a
half-waveplate at Ly-alpha wavelength. We developed a prototype of CLASP
polarimeter using the MgF2 half-waveplate and polarization analyzers,
and succeeded in obtaining the modulation patterns that are consistent
with the theoretical prediction. We confirm that the performance of
the prototype is optimized for measuring linear polarization signal
with the least effect of the crosstalk from the circular polarization.
Title: Statistical Study on the Nature of Solar-Flux Emergence
Authors: Otsuji, Kenichi; Kitai, Reizaburo; Ichimoto, Kiyoshi;
Shibata, Kazunari
Bibcode: 2011PASJ...63.1047O
Altcode: 2011arXiv1106.1955O
We studied 101 flux emergence events ranging from small ephemeral
regions to large emerging flux regions that were observed with the
Hinode Solar Optical Telescope filtergram. We investigated how the
total magnetic flux of the emergence event controls the nature of
emergence. To determine the modes of emergences, horizontal velocity
fields of the global motion of the magnetic patches in the flux emerging
sites were measured by local correlation tracking. Between two main
polarities of the large emerging flux regions with more than around 2
× 1019 Mx, there were converging flows of anti-polarity
magnetic patches. On the other hand, small ephemeral regions showed
no converging flow, but a simple diverging pattern. When we looked
into the detailed features in the emerging sites, irrespective of
the total flux and the spatial size, all of the emergence events
were observed to consist of single or multiple elementary emergence
unit(s). The typical size of unitary emergence is 4 Mm, and consistent
with simulation results. From a statistical study of the flux emergence
events, the maximum spatial distance between two main polarities, the
magnetic flux growth rate and the mean separation speed were found
to follow the power-law functions of the total magnetic flux with
indices of 0.27, 0.57, and -0.16, respectively. From a discussion on
the observed power-law relations, we obtained a physical view of solar
flux emergence, in which the emerging magnetic fields float and evolve
while balancing to the surrounding turbulent atmosphere.
Title: Overview of Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP)
Authors: Narukage, Noriyuki; Tsuneta, Saku; Bando, Takamasa; Kano,
Ryouhei; Kubo, Masahito; Ishikawa, Ryoko; Hara, Hirohisa; Suematsu,
Yoshinori; Katsukawa, Yukio; Watanabe, Hiroko; Ichimoto, Kiyoshi;
Sakao, Taro; Shimizu, Toshifumi; Kobayashi, Ken; Robinson, Brian; Kim,
Tony; Winebarger, Amy; West, Edward; Cirtain, Jonathan; De Pontieu,
Bart; Casini, Roberto; Trujillo Bueno, Javier; Stepan, Jiri; Manso
Sainz, Rafael; Belluzzi, Luca; Asensio Ramos, Andres; Carlsson, Mats
Bibcode: 2011SPIE.8148E..0HN
Altcode: 2011SPIE.8148E..16N
The solar chromosphere is an important boundary, through which all of
the plasma, magnetic fields and energy in the corona and solar wind
are supplied. Since the Zeeman splitting is typically smaller than
the Doppler line broadening in the chromosphere and transition region,
it is not effective to explore weak magnetic fields. However, this is
not the case for the Hanle effect, when we have an instrument with
high polarization sensitivity (~ 0.1%). "Chromospheric Lyman- Alpha
SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect
linear polarization produced by the Hanle effect in Lyman-alpha line
(121.567 nm) and to make the first direct measurement of magnetic
fields in the upper chromosphere and lower transition region. To
achieve the high sensitivity of ~ 0.1% within a rocket flight (5
minutes) in Lyman-alpha line, which is easily absorbed by materials,
we design the optical system mainly with reflections. The CLASP
consists of a classical Cassegrain telescope, a polarimeter and a
spectrometer. The polarimeter consists of a rotating 1/2-wave plate
and two reflecting polarization analyzers. One of the analyzer also
works as a polarization beam splitter to give us two orthogonal linear
polarizations simultaneously. The CLASP is planned to be launched in
2014 summer.
Title: The SOLAR-C mission: current status
Authors: Shimizu, Toshifumi; Tsuneta, Saku; Hara, Hirohisa; Ichimoto,
Kiyoshi; Kusano, Kanya; Sakao, Taro; Sekii, Takashi; Suematsu,
Yoshinori; Watanabe, Tetsuya
Bibcode: 2011SPIE.8148E..0BS
Altcode: 2011SPIE.8148E..10S
Two mission concepts (plan A: out-of-ecliptic mission and plan B:
high resolution spectroscopic mission) have been studied for the next
Japanese-led solar mission Solar-C, which will follow the scientific
success of the Hinode mission. The both mission concepts are concluded
as equally important and attractive for the promotion of space solar
physics. In the meantime we also had to make efforts for prioritizing
the two options, in order to proceed to next stage of requesting the
launch of Solar-C mission at the earliest opportunity. This paper
briefly describes the two mission concepts and the current status
on our efforts for prioritizing the two options. More details are
also described for the plan B option as the first-priority Solar-C
mission. The latest report from the Solar-C mission concept studies
was documented as "Interim Report on the Solar-C Mission Concept."
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: Seeing measurements using the solar limb - I. Comparison of
evaluation methods for the Differential Image Motion Monitor
Authors: Kawate, T.; Hanaoka, Y.; Ichimoto, K.; Miura, N.
Bibcode: 2011MNRAS.416.2154K
Altcode: 2011MNRAS.tmp.1125K
Differential Image Motion Monitors (DIMMs) are used not only for stellar
observations but also for solar observations with the limb as the target
to evaluate the seeing. In stellar observations, the differential image
motions along and perpendicular to the DIMM baseline are consistently
employed to evaluate Fried's parameter. However this is not the case
for solar-limb observations, in which we can measure the image motion
only perpendicular to the limb. Therefore the validity of the methods
so far proposed to calculate Fried's parameter from a DIMM using
the solar limb is still open to examination. We have focused on this
problem and carried out DIMM observations of the solar limb using a
Shack-Hartmann wavefront sensor of the Domeless Solar Telescope at
Hida Observatory. Pairs of apertures in the Shack-Hartmann sensor
act as multiple DIMMs that have different baselines in distance and
orientation. We calculated Fried's parameters based on three evaluating
methods (those of Sarazin & Roddier, Sasiela and Conan et al.) and
found that the method of Sarazin & Roddier gives a consistent
value of Fried's parameter over the set of multiple DIMMs.
Title: Magnetic Structure of Sunspots
Authors: Borrero, Juan M.; Ichimoto, Kiyoshi
Bibcode: 2011LRSP....8....4B
Altcode: 2011arXiv1109.4412B
In this review we give an overview about the current state-of-knowledge
of the magnetic field in sunspots from an observational point of
view. We start by offering a brief description of tools that are most
commonly employed to infer the magnetic field in the solar atmosphere
with emphasis in the photosphere of sunspots. We then address separately
the global and local magnetic structure of sunspots, focusing on the
implications of the current observations for the different sunspots
models, energy transport mechanisms, extrapolations of the magnetic
field towards the corona, and other issues.
Title: Temporal Relation Between the Disappearance of Penumbral
Fine-scale Structure and Evershed Flow
Authors: Kubo, M.; Ichimoto, K.; Lites, B. W.; Shine, R. A.
Bibcode: 2011ApJ...731...84K
Altcode: 2011arXiv1102.1137K
We investigate the temporal relation between the Evershed flow,
dot-like bright features (penumbral grain), the complex magnetic
field structure, and dark lanes (dark core) along bright filaments in
a sunspot penumbra. We use a time series of high spatial resolution
photospheric intensity, vector magnetic field maps, and Doppler velocity
maps obtained with the Solar Optical Telescope aboard the Hinode
spacecraft. We conclude that the appearance and disappearance of the
Evershed flow and penumbra grains occur at nearly the same time and are
associated with changes of the inclination angle of the magnetic field
from vertical to more horizontal. This supports the idea that Evershed
flow is a result of thermal convection in the inclined field lines. The
dark core of the bright penumbral filament also appears coincidental
with the Evershed flow. However, the dark-cored bright filament
survives at least for 10-20 minutes after the disappearance of the
Evershed flow. The heat input into the bright filament continues even
after the end of heat transfer by the Evershed flow. This suggests that
local heating along the bright filament is important for maintaining
its brightness, in addition to heat transfer by the Evershed flow.
Title: Quantitative Comparison between the Polarization Data
Taken with the Solar Flare Telescope and with the Hinode SOT
Spectro-Polarimeter
Authors: Hagino, M.; Hanaoka, Y.; Sakurai, T.; Ichimoto, K.
Bibcode: 2011ASPC..437..359H
Altcode:
The aim of this study is to establish the method to derive correct
vector magnetic fields from imaging polarimetry data taken with the
Solar Flare Telescope of the National Astronomical Observatory of
Japan. We compared our imaging polarimetry data taken during 2006
December with the spectro-polarimetry data taken with the Hinode
Solar Optical Telescope. While the polarization signals obtained with
the two instruments are basically consistent to each other, we found
some systematic differences between them, particularly in transverse
magnetic field vectors.
Title: Developments of the Multi-wavelength Polarimeter of the
Domeless Solar Telescope at the Hida Observatory
Authors: Anan, T.; Ichimoto, K.; Ueno, S.; Kimura, G.; Nakatani, Y.;
Kaneda, N.; Hagino, M.; Suzuki, I.
Bibcode: 2011ASPC..437..365A
Altcode:
A new universal spectropolarimeter is developed on the Domeless
Solar Telescope (DST) at the Hida Observatory to realize precise
spectropolarimetric observations in a wide range of wavelengths in
visible and near infrared. The system aims to open a new window of
plasma diagnostics by using Zeeman effect, Hanle effect, Stark effect
and impact polarization for measuring the chromospheric magnetic
fields, electric fields and unisotropically accelerated particles in
the solar atmosphere. The new system consists of a 60 cm aperture
vacuum telescope, a high dispersion vacuum spectrograph, polarization
modulator/analyser composed of a rotating waveplate and a Wallaston
prism located after the entrance slit of the spectrograph, and a fast
and large format CCD camera. Spectral images in both orthogonal
polarizations are taken simultaneously with a frame rate of ∼20 Hz
while the waveplate rotates continuously in a rate of 1 rev./sec. Thus
a high signal to noise ratio can be achieved in a short time. To
calibrate the instrumental polarization of the telescope a remotely
controllable turret accommodating linear polarizers is attached at the
entrance window of the telescope to induce a well known polarization
into the telescope. A Muellar matrix model of the telescope to correct
the obtained data is under examination.
Title: The Chromospheric Lyman Alpha SpectroPolarimeter (CLASP)
Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Cirtain,
J. W.; Bando, T.; Kano, R.; Hara, H.; Fujimura, D.; Ueda, K.; Ishikawa,
R.; Watanabe, H.; Ichimoto, K.; Sakao, T.; de Pontieu, B.; Carlsson,
M.; Casini, R.
Bibcode: 2010AGUFMSH11B1632K
Altcode:
Magnetic fields in the solar chromosphere play a key role in the
energy transfer and dynamics of the solar atmosphere. Yet a direct
observation of the chromospheric magnetic field remains one of the
greatest challenges in solar physics. While some advances have been
made for observing the Zeeman effect in strong chromospheric lines,
the effect is small and difficult to detect outside sunspots. The
Hanle effect offers a promising alternative; it is sensitive to weaker
magnetic fields (e.g., 5-500 G for Ly-Alpha), and while its magnitude
saturates at stronger magnetic fields, the linear polarization signals
remain sensitive to the magnetic field orientation. The Hanle effect
is not only limited to off-limb observations. Because the chromosphere
is illuminated by an anisotropic radiation field, the Ly-Alpha line is
predicted to show linear polarization for on-disk, near-limb regions,
and magnetic field is predicted to cause a measurable depolarization. At
disk center, the Ly-Alpha radiation is predicted to be negligible
in the absence of magnetic field, and linearly polarized to an order
of 0.3% in the presence of an inclined magnetic field. The proposed
CLASP sounding rocket instrument is designed to detect 0.3% linear
polarization of the Ly-Alpha line at 1.5 arcsecond spatial resolution
(0.7’’ pixel size) and 10 pm spectral resolution. The instrument
consists of a 30 cm aperture Cassegrain telescope and a dual-beam
spectropolarimeter. The telescope employs a ``cold mirror’’ design
that uses multilayer coatings to reflect only the target wavelength
range into the spectropolarimeter. The polarization analyzer consists of
a rotating waveplate and a polarizing beamsplitter that comprises MgF2
plates placed at Brewster’s Angle. Each output beam of the polarizing
beamsplitter, representing two orthogonal linear polarizations, is
dispersed and focused using a separate spherical varied-line-space
grating, and imaged with a separate 512x512 CCD camera. Prototypes
of key optical components have been fabricated and tested. Instrument
design is being finalized, and the experiment will be proposed for a
2014 flight aboard a NASA sounding rocket.
Title: Observations of solar scattering polarization at high spatial
resolution
Authors: Snik, F.; de Wijn, A. G.; Ichimoto, K.; Fischer, C. E.;
Keller, C. U.; Lites, B. W.
Bibcode: 2010A&A...519A..18S
Altcode: 2010arXiv1005.5042S
Context. The weak, turbulent magnetic fields that supposedly
permeate most of the solar photosphere are difficult to observe,
because the Zeeman effect is virtually blind to them. The Hanle
effect, acting on the scattering polarization in suitable lines,
can in principle be used as a diagnostic for these fields. However,
the prediction that the majority of the weak, turbulent field resides
in intergranular lanes also poses significant challenges to scattering
polarization observations because high spatial resolution is usually
difficult to attain.
Aims: We aim to measure the difference
in scattering polarization between granules and intergranules. We
present the respective center-to-limb variations, which may serve as
input for future models.
Methods: We perform full Stokes filter
polarimetry at different solar limb positions with the CN band filter
of the Hinode-SOT Broadband Filter Imager, which represents the first
scattering polarization observations with sufficient spatial resolution
to discern the granulation. Hinode-SOT offers unprecedented spatial
resolution in combination with high polarimetric sensitivity. The CN
band is known to have a significant scattering polarization signal,
and is sensitive to the Hanle effect. We extend the instrumental
polarization calibration routine to the observing wavelength,
and correct for various systematic effects.
Results: The
scattering polarization for granules (i.e., regions brighter than
the median intensity of non-magnetic pixels) is significantly larger
than for intergranules. We derive that the intergranules (i.e., the
remaining non-magnetic pixels) exhibit (9.8±3.0)% less scattering
polarization for 0.2 < μ ≤ 0.3, although systematic effects cannot
be completely excluded.
Conclusions: These observations constrain
MHD models in combination with (polarized) radiative transfer in terms
of CN band line formation, radiation anisotropy, and magnetic fields.
Title: Temporal Evolution of a Rapidly-Moving Umbral Dot
Authors: Watanabe, Hiroko; Tritschler, Alexandra; Kitai, Reizaburo;
Ichimoto, Kiyoshi
Bibcode: 2010SoPh..266....5W
Altcode: 2010SoPh..tmp..147W
We performed two-dimensional spectroscopic observations of the preceding
sunspot of NOAA 10905 located off disk center (S8 E36, μ≈0.81) by
using the Interferometric BI-dimensional Spectrometer (IBIS) operated
at the Dunn Solar Telescope (DST) of the National Solar Observatory,
New Mexico. The magnetically insensitive Fe I line at 709.04 nm
was scanned in wavelength repetitively at an interval of 37 s to
calculate sequences of maps of the line-wing and line-core intensity,
and the line-of-sight Doppler velocity at different line depths (3%
to 80%). Visual inspection of movies based on speckle reconstructions
computed from simultaneous broadband data and the local continuum
intensity at 709.04 nm revealed an umbral dot (UD) intruding rapidly
from the umbral boundary to the center of the umbra. The apparent
motion of this object was particularly fast (1.3 km s−1)
when compared to typical UDs. The lifetime and size of the UD was 8.7
min and 240 km, respectively. The rapid UD was visible even in the
line-core intensity map of Fe I 709.04 nm and was accompanied by a
persistent blueshift of about 0.06 km s−1.
Title: Observations of Chromospheric Anemone Jets with Hinode Ca II
Broadband Filtergraph and Hida Ca II Spectroheliograph
Authors: Morita, Satoshi; Shibata, Kazunari; UeNo, Satoru; Ichimoto,
Kiyoshi; Kitai, Reizaburo; Otsuji, Ken-ichi
Bibcode: 2010PASJ...62..901M
Altcode: 2010arXiv1002.2143M
We present the first simultaneous observations of chromospheric
"anemone" jets in solar active regions with Hinode SOT Ca II H
broadband filetergram and Ca II K spetroheliogram on the Domeless
Solar Telescope (DST) at Hida Observatory. During the coordinated
observation, 9 chromospheric anemone jets were simultaneously observed
with the two instruments. These observations revealed three important
features, i.e.: (1) the jets are generated in the lower chromosphere,
(2) the length and lifetime of the jets are 0.4-5 Mm and 40-320 sec,
(3) the apparent velocity of the jets with Hinode SOT are 3-24 km/s,
while Ca II K3 component at the jets show blueshifts (in 5 events) in
the range of 2- 6 km/s. The chromospheric anemone jets are associated
with mixed polarity regions which are either small emerging flux regions
or moving magnetic features. It is found that the Ca II K line often
show red or blue asymmetry in K2/K1 component: the footpoint of the
jets associated with emerging flux regions often show redshift (2-16
km/s), while the one with moving magnetic features show blueshift
(around 5 km/s). Detailed analysis of magnetic evolution of the jet
foaming regions revealed that the reconnection rate (or canceling
rate) of the total magnetic flux at the footpoint of the jets are of
order of 10^{16} Mx/s, and the resulting magnetic energy release rate
(1.1-10) x 10^{24} erg/s, with the total energy release (1-13) x 10^{26}
erg for the duration of the magnetic cancellations, 130s. These are
comparable to the estimated total energy, 10^{26} erg, in a single
chromospheric anemone jet. An observation-based physical model of the
jet is presented. The relation between chromospheric anemone jets and
Ellerman bombs is discussed.
Title: Internal Fine Structure of Ellerman Bombs
Authors: Hashimoto, Yuki; Kitai, Reizaburo; Ichimoto, Kiyoshi; Ueno,
Satoru; Nagata, Shin'ichi; Ishii, Takako T.; Hagino, Masaoki; Komori,
Hiroyuki; Nishida, Keisuke; Matsumoto, Takuma; Otsuji, Kenichi;
Nakamura, Tahei; Kawate, Tomoko; Watanabe, Hiroko; Shibata, Kazunari
Bibcode: 2010PASJ...62..879H
Altcode:
We conducted coordinated observations of Ellerman bombs (EBs) between
Hinode Satellite and Hida Observatory (HOP12). CaII H broad-band
filter images of NOAA 10966 on 2007 August 9 and 10 were obtained
with the Solar Optical Telescope (SOT) aboard the Hinode Satellite,
and many bright points were observed. We identified a total of 4
bright points as EBs, and studied the temporal variation of their
morphological fine structures and spectroscopic characteristics. With
high-resolution CaII H images of SOT, we found that the EBs, thus far
thought of as single bright features, are composed of a few of fine
subcomponents. Also, by using Stokes I/V filtergrams with Hinode/SOT,
and CaII H spectroheliograms with Hida/Domeless Solar Telescope (DST),
our observation showed: (1) The mean duration, the mean width, the
mean length, and the mean aspect ratio of the subcomponents were
390 s, 170 km, 450 km, and 2.7, respectively. (2) Subcomponents
started to appear on the magnetic neutral lines, and extended their
lengths from the original locations. (3) When the CaII H line of EBs
showed the characteristic blue asymmetry, they are associated with the
appearance or re-brightening of subcomponents. Summarizing our results,
we obtained an observational view that elementary magnetic reconnections
take place one by one successively and intermittently in EBs, and that
their manifestation is the fine subcomponents of the EB phenomena.
Title: Spicule Dynamics over a Plage Region
Authors: Anan, Tetsu; Kitai, Reizaburo; Kawate, Tomoko; Matsumoto,
Takuma; Ichimoto, Kiyoshi; Shibata, Kazunari; Hillier, Andrew; Otsuji,
Kenichi; Watanabe, Hiroko; Ueno, Satoru; Nagata, Shin'ichi; Ishii,
Takako T.; Komori, Hiroyuki; Nishida, Keisuke; Nakamura, Tahei; Isobe,
Hiroaki; Hagino, Masaoki
Bibcode: 2010PASJ...62..871A
Altcode: 2010arXiv1002.2288A
We studied spicular jets over a plage area and derived their
dynamic characteristics using Hinode Solar Optical Telescope (SOT)
high-resolution images. A target plage region was near to the west limb
of the solar disk. This location permitted us to study the dynamics
of spicular jets without any overlapping effect of spicular structures
along the line of sight. In this work, to increase the ease with which
we could identify spicules on the disk, we applied the image processing
method `MadMax' developed by Koutchmy et al. (1989). It enhances fine,
slender structures (like jets), over a diffuse background. We identified
169 spicules over the target plage. This sample permited us to derive
statistically reliable results regarding spicular dynamics. The
properties of plage spicules can be summarized as follows: (1) In a
plage area, we clearly identified spicular jet features. (2) They were
shorter in length than the quiet region limb spicules, and followed a
ballistic motion under constant deceleration. (3) The majority (80%)
of the plage spicules showed a cycle of rise and retreat, while 10% of
them faded out without a complete retreat phase. (4) The deceleration
of the spicule was proportional to the velocity of ejection (i.e.,
the initial velocity).
Title: CaII K Spectral Study of an Emerging Flux Region using the
Domeless Solar Telescope in Hida Observatory
Authors: Otsuji, Kenichi; Kitai, Reizaburo; Matsumoto, Takuma;
Ichimoto, Kiyoshi; Ueno, Satoru; Nagata, Shin'ichi; Isobe, Hiroaki;
Shibata, Kazunari
Bibcode: 2010PASJ...62..893O
Altcode: 2010arXiv1005.2025O
A cooperative observation with Hida Observatory and the Hinode
satellite was performed on an emerging flux region. Successive CaII
K spectro-heliograms of the emerging flux region were taken by the
Domeless Solar Telescope of Hida Observatory. Hinode observed the
emerging flux region with CaII H and FeI Stokes IQUV filtergrams. In
this study, detailed dynamics and the temporal evolution of the
magnetic flux emergence was studied observationally. The event was first
detected in the photospheric magnetic field signals; 3 minutes later,
a horizontal expansion of the dark area was detected. Then, 7 minutes
later than the horizontal expansion, the emerging loops were detected
with a maximal rise speed of 2.1 km s-1 at chromospheric
heights. The observed dynamics of the emerging magnetic flux from the
photosphere to the upper chromosphere was very consistent with the
results of previous simulation studies. A gradual rising phase of flux
tubes with a weak magnetic strength was confirmed by our observation.
Title: Optical setup and wavefront sensor for solar adaptive optics
at the Domeless Solar Telescope, Hida Observatory
Authors: Miura, Noriaki; Yokoyama, Fumihito; Nefu, Maoto; Kuwamura,
Susumu; Baba, Naoshi; Hanaoka, Yoichiro; Ueno, Satoru; Nakatani,
Yoshikazu; Nagata, Shin'ichi; Kitai, Reizaburou; Ichimoto, Kiyoshi;
Takami, Hideki
Bibcode: 2010SPIE.7736E..54M
Altcode: 2010SPIE.7736E.172M
A solar adaptive optics system for a high-dispersion spectrograph is
developed at the 60 cm domeless solar telescope of the Hida Observatory
in Japan. Details of its optical setup are described for implementing
a scanning slit spectroscopy with wavefront correction. A wavefront
sensor used in the system is specified and a technique of reducing
computational cost in wavefront sensing is also described. In solar
observations, the improvement of contrast in images obtained with the
adaptive optics system was demonstrated when a sunspot was used as a
target of wavefront sensing.
Title: Continuous H-alpha Imaging Network Project (CHAIN) with Ground-
based Solar Telescopes for Space Weather Research
Authors: Ueno, S.; Shibata, K.; Ichimoto, K.; Kitai, R.; Nagata, S.;
Kimura, G.; Nakatani, Y.
Bibcode: 2010AfrSk..14...17U
Altcode:
No abstract at ADS
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: G-band and Hard X-ray Emissions of the 2006 December 14 Flare
Observed by Hinode/SOT and Rhessi
Authors: Watanabe, Kyoko; Krucker, Säm; Hudson, Hugh; Shimizu,
Toshifumi; Masuda, Satoshi; Ichimoto, Kiyoshi
Bibcode: 2010ApJ...715..651W
Altcode: 2010arXiv1004.4259W
We report on G-band emission observed by the Solar Optical Telescope on
board the Hinode satellite in association with the X1.5-class flare on
2006 December 14. The G-band enhancements originate from the footpoints
of flaring coronal magnetic loops, coinciding with nonthermal hard
X-ray bremsstrahlung sources observed by the Reuven Ramaty High Energy
Solar Spectroscopic Imager. At the available 2 minute cadence, the
G-band and hard X-ray intensities are furthermore well correlated in
time. Assuming that the G-band enhancements are continuum emission from
a blackbody, we derived the total radiative losses of the white-light
flare (white-light power). If the G-band enhancements additionally have
a contribution from lines, the derived values are overestimates. We
compare the white-light power with the power in hard X-ray producing
electrons using the thick-target assumption. Independent of the cutoff
energy of the accelerated electron spectrum, the white-light power and
the power of accelerated electrons are roughly proportional. Using
the observed upper limit of ~30 keV for the cutoff energy, the hard
X-ray producing electrons provide at least a factor of 2 more power
than needed to produce the white-light emission. For electrons above
40 keV, the powers roughly match for all four of the time intervals
available during the impulsive phase. Hence, the flare-accelerated
electrons contain enough energy to produce the white-light flare
emissions. The observed correlation in time, space, and power strongly
suggests that electron acceleration and white-light production in solar
flares are closely related. However, the results also call attention
to the inconsistency in apparent source heights of the hard X-ray
(chromosphere) and white-light (upper photosphere) sources.
Title: Scattering Polarization in the Fe I 630 nm Emission Lines at
the Extreme Limb of the Sun
Authors: Lites, B. W.; Casini, R.; Manso Sainz, R.; Jurčák, J.;
Ichimoto, K.; Ishikawa, R.; Okamoto, T. J.; Tsuneta, S.; Bellot
Rubio, L.
Bibcode: 2010ApJ...713..450L
Altcode:
Spectro-polarimetric observations with the Solar Optical Telescope
onboard Hinode reveal the emission spectrum of the Fe I 630 nm lines
at the solar limb. The emission shell extends for less than 1'' thereby
making it extremely difficult to detect from ground-based observatories
viewing the limb through the Earth's atmosphere. The linear polarization
signal is clearly due to scattering and it is predominantly oriented
in the radial direction. Using a comprehensive atomic model of
iron, we are able to interpret qualitatively the observed signals,
including the radial orientation of the linear polarization. The Hanle
effect causes the linear polarization of the Fe I 630 nm lines to be
sensitive to magnetic fields between ~0.1 G and ~40 G, and also to
be sensitive to the field's topology for stronger fields. The overall
degree of observed polarization can be reproduced by randomly oriented
horizontal magnetic fields of strength ≈2 G. The discovery of their
scattering polarization signals thus opens a new diagnostic opportunity
for these lines.
Title: Vector Magnetic Fields and Doppler Velocity Structures Around
a Cancellation Site in the Quiet Sun
Authors: Iida, Y.; Yokoyama, T.; Ichimoto, K.
Bibcode: 2010ApJ...713..325I
Altcode:
A cancellation is thought to be a basic process of the photospheric
magnetic field and plays an important role in magnetic flux budget and
in various solar activities. There are two major theoretical scenarios
for this phenomena, the "U-loop emergence" and the "Ω-loop submergence"
models. It is important to clarify which is the dominant process during
the cancellation for the estimation of the solar magnetic flux transport
through the surface. We study the vector magnetic field and velocity
structures around a quiet-Sun cancellation by using the Solar Optical
Telescope on board the Hinode satellite. Transverse magnetic field
connecting the canceling magnetic features and strong long-lasting
Doppler redshift signal are found. The transverse field is observed in
the first spectropolarimetric observation after the occurrence of the
cancellation while the redshift is clearly delayed to the cancellation
by 20 minutes. These results indicate that the observed cancellation
is an "Ω-loop submergence."
Title: Magnetic Fields and Velocity Structures around a Cancellation
Site
Authors: Iida, Y.; Yokoyama, T.; Ichimoto, K.
Bibcode: 2010arXiv1002.4274I
Altcode:
A cancellation is thought to be a basic process of the photospheric
magnetic field and plays an important role in magnetic flux budget and
in various solar activities. There are two major theoretical scenarios
for this phenomena, i.e. the "U-loop emergence" and the Omega-loop
submergence models. It is important to clarify which is the dominant
process during the cancellation for the estimation of the solar magnetic
flux transport through the surface. We study the vector magnetic field
and velocity structures around a quiet Sun cancellation by using the
Solar Optical Telescope on board Hinode satellite. Transverse magnetic
field connecting the canceling magnetic features and strong long-lasting
Doppler red-shift signal are found. The transverse field is observed in
the first spectropolarimetric observation after the occurrence of the
cancellation while the red-shift clearly delayed to the cancellation
by 20 minutes. These results indicate that the observed cancellation
is an Omega-loop submergence.
Title: Characteristic Dependence of Umbral Dots on thier Magnetic
Structure
Authors: Watanabe, Hiroko; Kitai, Reizaburo; Ichimoto, Kiyoshi
Bibcode: 2010cosp...38.2933W
Altcode: 2010cosp.meet.2933W
Umbral dots (UDs) were observed in a stable sunspot in NOAA 10944 by
the Hinode Solar Optical Telescope on 2007 March 1. The observation
program consisted of blue continuum images and spectropolarimetric
profiles of Fe I 630 nm line. An automatic detection algorithm for UDs
was applied to the 2 hr continuous blue continuum images, and using
the obtained data, the lifetime, size, and proper motion of UDs were
calculated. The magnetic structure of the sunspot was derived through
the inversion of the spectropolarimetric profiles. We calculated the
correlations between UD's parameters (size, lifetime, occurrence rate,
proper motion) and magnetic fields (field strength, inclination,
azimuth), and obtained the following results. (1) Both the lifetime
and size of UDs are almost constant regardless of the magnetic field
strength at their emergence site. (2) The speed of UDs increases as
the field inclination angle at their emergence site gets larger. (3)
The direction of movement of UDs is nearly parallel to the direction of
the horizontal component of magnetic field in the region with strongly
inclined field, while UDs in the region with weakly inclined field show
virtually no proper motion. Our results describe the basic properties
of magnetoconvection in sunspots.
Title: Diagnosis of accelerated electrons in solar flare with radio
observation
Authors: Kawate, Tomoko; Asai, Ayumi; Ichimoto, Kiyoshi
Bibcode: 2010cosp...38.2982K
Altcode: 2010cosp.meet.2982K
Many problems still remain in particle acceleration in solar flare;
energy release site, particle acceleration mechanism, ratio of
nonthermal energy to whole released energy, maximum energy of particles,
energy spectrum of accelerated particles, spatial and temporal scale
of acceleration, difference of accelerated condition between ions
and electrons, etc. In this study, we discuss the characteristics of
accelerated electrons using statistical results of multi-wavelength
observations, mainly radio and hard X-ray data with non-thermal
emission process. The data we analyze are from Nobeyama Radioheliograph
(17GHz intensity and polarization, 34GHz intensity), RHESSI space
telescope (X-ray, gamma-ray), SOHO space telescope (magnetic field
in photosphere, EUV line emission), TRACE space telescope (UV, EUV)
and from optical data of ground-based telescopes. Our aim is to impose
some restrictions on the models of particle acceleration. To achieve
this, we examine pitch angle distribution of accelerated electrons. We
analyze practically in the following way. First, we pick up several
flare events observed with Nobeyama Radioheliograph at different
locations on the sun. Second, we identify the structure of flare
loops from EUV and magnetic field distributions in the photosphere
for each event. Third, we examine the radio flux, its polarization
and the position of the radio source in the flare loops, especially
focusing on their variations with the viewing angle to the magnetic
field by referring to the geometry of the flare loop and the location
of the flare on the sun. Finally, we compare the obtained properties
of the radio sources with the emission mechanisms of gyro-synchrotron
radiation to extract information of the pitch angle anisotropy.
Title: Fine scale dynamics of the Evershed flow
Authors: Ichimoto, Kiyoshi
Bibcode: 2010cosp...38.2934I
Altcode: 2010cosp.meet.2934I
Evershed flow is one of the most distinguished gas motion observed
on the solar surface; the flow takes place systematically in sunspot
penumbra whenever they present. Under low resolution observations,
it looks a stationary horizontal out flow with a speed of 1 2km/s. The
nature and origin of the Evershed flow, however, has been a longstanding
mystery since its discovery in 1909. The Solar Optical Telescope
(SOT) aboard Hinode revealed the fine scale structure of the penumbra
and brought a significant progress on our understanding of the
Evershed effect; The Evershed flow is confined in narrow channels
with nearly horizontal magnetic fields embedded in deep layer of
penumbral atmosphere. Individual flow channels are associated with
tiny upflow of hot gas (source) at the inner end and down flow (sink)
at the outer end. It is a dynamic phenomenon with the flow velocity
exceeding the sound speed in the photosphere at the outer ends of the
flow channels. SOT also discovered the 'twisting' motions of penumbral
filaments which could be attributed to the manifestation of overturning
convection. These observational results suggest that the Evershed flow
is explained as a natural consequence of thermal convection taking place
under strong, inclined magnetic fields of sunspot penumbra. There remain
unsolved issues, however, i.e., What is the mechanism that drives the
supersonic flow at the outer edge of the penumbra? What is the real
origin of the twisting motion of the penumbral filaments? What is the
origin of the enigmatic net circular polarization in penumbra? In this
presentation, we focus on the dynamic (i.e., non-stationary) aspects
of the Evershed flow found in fine scale features, and address the
basic properties of the driving force of the Evershed flow.
Title: The Evershed Effect with SOT/Hinode
Authors: Ichimoto, K.
Bibcode: 2010ASSP...19..186I
Altcode: 2009arXiv0903.2605I; 2010mcia.conf..186I
The Solar Optical Telescope onboard Hinode revealed the fine-scale
structure of the Evershed flow and its relation to the filamentary
structures of the sunspot penumbra. The Evershed flow is confined in
narrow channels with nearly horizontal magnetic fields embedded in
a deep layer of the penumbral atmosphere. It is a dynamic phenomenon
with flow velocity close to the photospheric sound speed. Individual
flow channels are associated with tiny upflows of hot gas (sources)
at the inner end and downflows (sinks) at the outer end. SOT/Hinode
also discovered "twisting" motions of penumbral filaments, which may be
attributed to the convective nature of the Evershed flow. The Evershed
effect may be understood as a natural consequence of thermal convection
under a strong, inclined magnetic field. Current penumbral models are
discussed in the lights of these new Hinode observations.
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: On the origin of reverse polarity patches found by Hinode in
sunspot penumbrae
Authors: Sánchez Almeida, J.; Ichimoto, K.
Bibcode: 2009A&A...508..963S
Altcode: 2009arXiv0909.3232S
Context: The topology of penumbral magnetic fields is poorly known. The
satellite Hinode has recently revealed penumbral structures of a
magnetic polarity that is opposite to the main sunspot polarity. They
may be direct confirmation that magnetic field lines and mass flows
return to the solar interior throughout the penumbra, a configuration
previously inferred from interpretation of observed Stokes profile
asymmetries.
Aims: We try to point out the relationship
between the reverse polarity features found by Hinode, and the
model Micro-Structured Magnetic Atmospheres (MISMAs) proposed for
sunspots.
Methods: The work is based on synthesis and inversion
of sunspot Stokes profiles.
Results: Existing model MISMAs
produce strongly redshifted reverse polarity structures as found
by Hinode. Ad hoc model MISMAs also explain the asymmetric Stokes
profiles observed by Hinode. The same modeling may be consistent with
magnetograms of dark cored penumbral filaments if the dark cores are
associated with the reverse polarity. This hypothetical relationship
can only be identified in the far red wings of the spectral lines.
Conclusions: The reverse polarity patches may result from aligned
magnetic field lines and mass flows that bend over and return to the
solar interior throughout the penumbra.
Title: Magnetic Flux Budget in a Decaying Active Region
Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K.
Bibcode: 2009ASPC..415..359K
Altcode:
We investigate the sunspot decay process in terms of the magnetic flux
budget of a decaying sunspot. This article is based on results in Kubo
et al. 2008. Please see this paper for further details.
Title: Is Flux Submergence an Essential Aspect of Flux Emergence?
Authors: Lites, B. W.; Frank, Z.; Shine, R. A.; Title, A. M.;
Ichimoto, K.
Bibcode: 2009ASPC..415..172L
Altcode:
High resolution Hinode Spectro-Polarimeter observations permit one
to examine the detailed structure of the magnetic field vector in
emerging flux regions. We find the field to have a concave-upward
geometry on the smallest scales observed (0.3 arcsec), indicating the
presence of U-loops at the sites of approaching and canceling opposite
polarities. This structure suggests that reconnection is taking place
at or below the surface, allowing the emerging flux to rid itself of
its considerable mass burden. Supersonic down flows are often observed
adjacent to, but not coincident with, the sites of canceling flux. We
propose that these are the sites that drain the mass contained in the
buoyantly-rising flux elements. The observations then suggest a process
of sub-surface reconnection producing O-loops that then are forced to
descend with the intergranular convective down flows, thus making flux
submergence important to the larger scale flux emergence process.
Title: Helical Shape and Twisting Motion as Intrinsic Properties of
Penumbral Filaments
Authors: Shine, R. A.; Ryutova, M.; Berger, T. E.; Title, A. M.;
Tarbell, T. D.; Ichimoto, K.
Bibcode: 2009AGUFMSH23B1541S
Altcode:
A wealth of high resolution data obtained with advanced ground based
telescopes and the SOT instrument on HINODE have led to new findings
in the properties of penumbral filaments and controversies in their
interpretation. Here we address one such issue, namely the question of
whether the apparent twist of filaments is real or is just a viewing
effect. We show that the helical shape and twisting motions of penumbral
filaments follow from first principles and represent an integral part of
penumbra formation and dynamics. As such, these properties link together
other observed features of filaments including their magnetic and
thermal substructure and their impact on the overlying atmosphere. At
all stages of penumbral dynamics, qualitative agreement of theory and
observations is supported by quantitative analysis as well.
Title: Small-scale studies of magnetic fields with the SOT/Hinode
(Invited)
Authors: Ichimoto, K.
Bibcode: 2009AGUFMSH53B..02I
Altcode:
The Solar Optical Telescope (SOT) abord Hinode is a diffraction
limitted telescope with a 50cm appeature. SOT provides high accuracy
measurements of vector magnetic fields under unprecidentedly stable
condition without the atmospheric seeing. The combination of high
angular resolution (~0.32arcsec) with the high polarimetric accuracy
(~0.1%) enable us to explore the new view of the small scale magnetic
fields on the Sun, i.e., their formation, dynamics and influence
on the upper atmosphere. In this paper, we will present the recent
discoveries of the small scale magnetic fields made by SOT/Hinode,
with a focus on the ubiquitous transient magnetic fields in the quiet
sun, formation of the magnetic flux tubes, and dynamics of small scale
magnetic fields in sunspots. Future perspective with a large apperture
telescope will also be discussed.
Title: Characteristic Dependence of Umbral Dots on Their Magnetic
Structure
Authors: Watanabe, H.; Kitai, R.; Ichimoto, K.
Bibcode: 2009ApJ...702.1048W
Altcode: 2009arXiv0907.2750W
Umbral dots (UDs) were observed in a stable sunspot in NOAA 10944 by
the Hinode Solar Optical Telescope on 2007 March 1. The observation
program consisted of blue continuum images and spectropolarimetric
profiles of Fe I 630 nm line. An automatic detection algorithm
for UDs was applied to the 2 hr continuous blue continuum images,
and using the obtained data, the lifetime, size, and proper motion
of UDs were calculated. The magnetic structure of the sunspot was
derived through the inversion of the spectropolarimetric profiles. We
calculated the correlations between UD's parameters (size, lifetime,
occurrence rate, proper motion) and magnetic fields (field strength,
inclination, azimuth), and obtained the following results. (1) Both
the lifetime and size of UDs are almost constant regardless of the
magnetic field strength at their emergence site. (2) The speed of UDs
increases as the field inclination angle at their emergence site gets
larger. (3) The direction of movement of UDs is nearly parallel to
the direction of the horizontal component of magnetic field in the
region with strongly inclined field, while UDs in the region with
weakly inclined field show virtually no proper motion. Our results
describe the basic properties of magnetoconvection in sunspots. We
will discuss our results in comparison to recent magnetohydrodynamic
simulations by Schüssler & Vögler and Rempel et al.
Title: Advances in solar adaptive optics system at the domeless
solar telescope of the Hida Observatory
Authors: Miura, Noriaki; Noto, Yuuki; Kato, Shuusuke; Yokoyama,
Fumihito; Kuwamura, Susumu; Baba, Naoshi; Hanaoka, Yoichiro; Nagata,
Shin'ichi; Ueno, Satoru; Kitai, Reizaburo; Ichimoto, Kiyoshi; Takami,
Hideki
Bibcode: 2009SPIE.7439E..0UM
Altcode: 2009SPIE.7439E..19M
A solar adaptive optics system for the 60 cm domeless solar
telescope of the Hida Observatory in Japan is developed. A high-speed
deformable mirror with 52 electromagnetic actuators is newly used in an
experimental adaptive optics system. The use of the mirror resulted in
the improvement of Strehl ratios in laboratory experiments. In solar
observations, the system worked well when solar granulation was used
as a target for wavefront sensing. An adaptive optics system being
developed for a vertical spectrograph of the domeless solar telescope
is described.
Title: The tandem Fabry-Perot filter imaging spectro-polarimeter
for the Solar Magnetic Activity Research Telescope (SMART)
Authors: Nagata, Shin'ichi; Otsuji, Kenichi; Ishii, Takako T.;
Ichimoto, Kiyoshi; Ueno, Satoru; Kitai, Reizaburo; Kimura, Goichi;
Shibata, Kazunari; Nakatani, Yoshikazu; Morita, Satoshi
Bibcode: 2009SPIE.7438E..0VN
Altcode: 2009SPIE.7438E..22N
In order to perform precise and high time cadence magnetic field
measurement across the solar surface, the Tandem Fabry-Perot filter
imaging spectro-polarimeter for the Solar Magnetic Activity Research
Telescope (SMART) is revised. By using the CCD with moderate frame
rate of 30fps, full Stokes vectors on the field-of-view 320"x240" can
be obtained at 4 wavelengths around FeI6302 line within about 15s. The
optical performance of the Tandem Fabry-Perof filters is investigated
by using the spectrograph at the Domeless Solar Telescope at Hida
Observatory. The test results show the full-width-half-maximum (FWHM)
of the tandem filters is about 0.017nm over the 60mm clear aperture
is achieved. The system is developed to start the regular observations
from 2010.
Title: Magnetic Flux Budget of a Decaying Sunspot
Authors: Kubo, Masahito; Lites, Bruce W.; Shimizu, Toshifumi;
Ichimoto, Kiyoshi
Bibcode: 2009shin.confE...9K
Altcode:
Numerous small magnetic elements called moving magnetic features (MMFs)
are generally observed in the moat region that surrounds a sunspot. We
attempt to address a basic question how much magnetic flux is carried
away from a sunspot by MMFs and is subsequently removed from the
photosphere. This is essential for understanding decay of sunspots
and distribution of magnetic flux on the Sun. We estimate the magnetic
flux budget in a decaying sunspot and its surrounding moat region by
using a time series of the spatial distribution of vector magnetic
fields in the photosphere. Spectropolarimetric measurements with the
Solar Optical Telescope aboard the Hinode satellite allow us, for
the first time, to know an accurate flux change without any effects
of atmospheric seeing. The amount of magnetic flux that decreases
in the sunspot and (inner) moat region is very similar to magnetic
flux transported to the outer boundary of the moat region. The flux
loss rates of magnetic elements with positive and negative polarities
balance each other around the outer boundary of the moat region. These
results suggest that most of the magnetic flux in the sunspot is
transported to the outer boundary of the moat region as MMFs, and
then the transported flux is removed from the photosphere by apparent
collisions of opposite-polarity magnetic elements (called
Title: A New View of Fine Scale Dynamics and Magnetism of Sunspots
Revealed by Hinode/SOT
Authors: Ichimoto, K.; Suematsu, Y.; Katsukawa, Y.; Tsuneta, S.;
Shimojo, M.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Berger, T.;
Title, A. M.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Nagata, S.
Bibcode: 2009ASPC..405..167I
Altcode:
The Solar Optical Telescope on-board Hinode is providing a new view of
the fine scale dynamics in sunspots with its high spatial resolution and
unprecedented image stability. We present three features related to the
Evershed flow each of which raises a new puzzle in sunspot dynamics;
i.e., twisting appearance of penumbral filaments, the source and sink
of individual Evershed flow channels, and the net circular polarization
in penumbrae with its spatial relation to the Evershed flow channels.
Title: Has Hinode Revealed the Missing Turbulent Flux of the
Quiet Sun?
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2009ASPC..405..173L
Altcode:
The Hinode Spectro-Polarimeter has revealed the presence of surprisingly
strong horizontal magnetic fields nearly everywhere in the quiet
solar atmosphere. These horizontal fields, along with measures of the
vertical fields, may be the signature of the ``hidden turbulent flux''
of the quiet Sun. The measured horizontal fields average at least to
55 Gauss: nearly 5 times that of the measured longitudinal apparent
flux density. The nature of these fields are reviewed, and discussed
in the light of recent magneto-convection numerical simulations of
the quiet Sun.
Title: 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: Small-scale oscillations in a quiescent prominence observed
by HINODE/SOT. Prominence oscillations
Authors: Ning, Z.; Cao, W.; Okamoto, T. J.; Ichimoto, K.; Qu, Z. Q.
Bibcode: 2009A&A...499..595N
Altcode:
Context: Investigations of the behavior of small-scale threads can
provide an alternative approach to studying prominence dynamics and
understanding its origin and nature.
Aims: The behavior of
threads are analyzed in a quiescent prominence, including drifting
and both the horizontally and vertically oscillating motions. These
indicate waves in the solar prominence.
Methods: We used the Hα
images at a setting wavelength of +0.076 Å. A quiescent prominence
was observed by HINODE/SOT on 2008 January 15 for about 3 h in
total.
Results: Consistent with previous findings, prominences
show numerous thread-like structures. Some threads clearly exhibit both
vertically and horizontally oscillatory motions, while others are only
drifting. Complicated cases show both drifting and oscillatory motions
simultaneously. In the upper part of the prominence, the threads are
oscillating independently of each other. We find that three threads
oscillate with the same phase for at least two periods. The oscillations
seem to be strongly damped since they disappear after a few periods. The
maximum number of observed periods is 8 in our observations. In the
lower part of the prominence, however, the different threads have a
mixed character with the individual oscillatory motions unstable for
one entire period. Most oscillatory motions will disappear after a half
period or less, while the new oscillatory motions are excited nearby. A
5-min period is predominant, and the oscillating amplitudes show an
average value of ±3.5 km s-1. We find some upflows in the
spicule layer, and they appear to transport the mass from photosphere
(or spicules themselves) to the prominence. These upflows have an
average velocity amplitude of 0.8 km s-1.
Conclusions:
The threads exhibit three distinct behaviors. The first is only
drifting, the second is typically oscillating, and the third shows
both characteristics. There are no substantial differences between
the periods of horizontally and vertically oscillating threads in
this prominence.
Title: Magnetic Flux Budget of a Decaying Sunspot
Authors: Kubo, Masahito; Lites, B. W.; Shimizu, T.; Ichimoto, K.
Bibcode: 2009SPD....40.0905K
Altcode:
We estimate how much magnetic flux is lost in a decaying sunspot
and how much magnetic flux is carried away from the sunspot through
its surrounding moat region. A time series of spectropolarimetric
measurements with the Solar Optical Telescope aboard Hinode allows us,
for the first time, to investigate an accurate flux change without
any effects of atmospheric seeing. The amount of magnetic flux that
decreases in the sunspot and moat region is almost equal to that of
magnetic flux transported to the outer boundary of the moat region. The
flux loss rates of magnetic elements with positive and negative
polarities are balanced each other around the outer boundary of the
moat region. These results suggest that most of the magnetic flux in
the sunspot is transported to the outer boundary of the moat region
as moving magnetic features, and then removed from the photosphere by
flux cancellation around the moat boundary.
Title: 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: Fine scale structures of sunspots and their role on global
sunspot energetics
Authors: Ichimoto, K.
Bibcode: 2008AGUFMSH52A..05I
Altcode:
The sunspot has highly structured atmosphere of strongly magnetized
plasma; In visible light, the umbra contains a number of small
bright patches called as umbral dots in its dark background, the
penumbra consists of numerous bright and dark filaments with a width
of 0.2--0.3 arcsec. The origin of these features has been a topic
under debate for long time in the sunspot physics.The 'brightness'
of sunspots is another topic under debate on sunspot physics, i.e.,
how the energy for maintaining the brightness of umbrae (10- 20%
of normal photosphere) and penumbrae (70-80% of normal photosphere)
are carried to the solar surface. The Solar Optical Telescope (SOT)
aboard Hinode revealed the close relationship between the fine scale
filamentary structures and the plasma motions (Evershed flow) in
sunspot penumbra; The Evershed flow is confined in narrow channels with
nearly horizontal magnetic fields embedded in deep layer of penumbral
atmosphere. It is a dynamic phenomenon with the flow velocity close
to the sound speed in the photosphere, and individual flow channels
are associated with tiny upflow (source) at the inner end and down flow
(sink) at the outer end. The penumbral bright grains are well correlated
with the upflowing gas, thus the Evershed effect can be interpreted
as a consequence of the thermal convection under the strong inclined
magnetic field of sunspot penumbra. We will present the new picture
of the sunspot penumbra, and discuss the role of the fine structures
on the global sunspot energetics.
Title: Formation of Solar Magnetic Flux Tubes and Convective
Instability
Authors: Nagata, S.; Ichimoto, K.
Bibcode: 2008AGUFMSH52A..04N
Altcode:
The observational evidence for the formation of solar magnetic flux
tubes induced by convective instability was obtained by Hinode Solar
Optical Telescope (SOT). Based on the seeing free observation with
SOT, we found 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. Convective instability in the flux tubes
is discussed by comparing the observations with numerical models.
Title: Erratum: "Magnetic Flux Loss and Flux Transport in a Decaying
Active Region" (ApJ, 686, 1447 [2008])
Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K.
Bibcode: 2008ApJ...689.1456K
Altcode:
No abstract at ADS
Title: The Magnetic Landscape of the Sun's Polar Region
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.;
Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo,
M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008ApJ...688.1374T
Altcode: 2008arXiv0807.4631T
We present observations of the magnetic landscape of the polar region
of the Sun that are unprecedented in terms of spatial resolution,
field of view, and polarimetric precision. They were carried out with
the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington
inversion, we find many vertically oriented magnetic flux tubes
with field strengths as strong as 1 kG scattered in latitude between
70° and 90°. They all have the same polarity, consistent with the
global polarity of the polar region. The field vectors are observed to
diverge from the centers of the flux elements, consistent with a view
of magnetic fields that are expanding and fanning out with height. The
polar region is also found to have ubiquitous horizontal fields. The
polar regions are the source of the fast solar wind, which is channeled
along unipolar coronal magnetic fields whose photospheric source is
evidently rooted in the strong-field, vertical patches of flux. We
conjecture that vertical flux tubes with large expansion around the
photospheric-coronal boundary serve as efficient chimneys for Alfvén
waves that accelerate the solar wind.
Title: Cooperative observation of solar atmospheric heating by Hida
observatory and Hinode
Authors: Kitai, R.; Hashimoto, Y.; Anan, T.; Watanabe, H.; Ishii,
T. T.; Kawate, T.; Matsumoto, T.; Otsuji, K.; Nakamura, T.; Morita,
S.; Nishizuka, N.; Nishida, K.; Ueno, S.; Nagata, S.; Ichimoto, K.;
Shibata, K.
Bibcode: 2008AGUFMSH41B1625K
Altcode:
At Hida observatory of Kyoto University, we continue to study solar
activities and fine structures with Domeless Solar Telescope (DST)
and Solar Magnetic Activity Research Telescope (SMART). In this work,
we will report some recent cooperative observational results with
Hinode on the following topics: (1) Plage heating and waves Analysis
of a long time series of CaII K spectrograms at a plage area showed
us a clear co-existence of 3- and 5-min oscillation in Doppler
velocity. We simulated the response of the VAL model atmosphere to
the input of 3-min/5-min acoustic disturbances, in 1-D geometry and
found that plage chromosphere is heated unsteadily by acoustic shock
waves as was proposed by Carlsson and Stein (1997). (2) Disk spicules
in and around plage regions We clearly identified numerous ejecting
features in a plage area. Their morphological shapes of thin tapered
cylinder and their dynamics strongly suggest that they are spicules
in plage area. Plage spicules were observed to move under constant
deceleration, which are driven by acoustic shock waves predicted by
Shibata and Suematsu (1980) and Hansteen et al. (2007). Our results
will be discussed from the view point of Type I, II classification
of limb spicules ( de Pontieu et al. 2007). (3) Umbral dots We have
confirmed that umbral dots are manifestation of magneto-convection in
strong magnetic filed from the analysis of Hinode/SOT/BFI&SP. We
will discuss the plausibility of monolithic umbral model from the
oscillatory brightening of umbral dots. (4) X-ray brightenings in the
supergranular network XRT showed us numerous bright points in solar
quiet regions. Possible relation between these XBPs and supergranular
network pattern in quiet chromosphere was studied. XBPs were found to be
located in the network not in the cell center. Many of network bright
XBPs were consisted of magnetically bipolar loops. (5) Ellerman bombs
By studying the fine structure of Ellerman bomb, we have found core-halo
structure and loop like fine-structures in the chromosphere. Discussions
on the origin of bombs will be given from the viewpoint of magnetic
reconnection theory.
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 Flux Loss and Flux Transport in a Decaying Active
Region
Authors: Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K.
Bibcode: 2008ApJ...686.1447K
Altcode: 2008arXiv0807.4340K
We estimate the temporal change of magnetic flux normal to the solar
surface in a decaying active region by using a time series of the
spatial distribution of vector magnetic fields in the photosphere. The
vector magnetic fields are derived from full spectropolarimetric
measurements with the Solar Optical Telescope aboard Hinode. We compare
a magnetic flux loss rate to a flux transport rate in a decaying sunspot
and its surrounding moat region. The amount of magnetic flux that
decreases in the sunspot and moat region is very similar to magnetic
flux transported to the outer boundary of the moat region. The flux
loss rates [(dF/dt)loss] of magnetic elements with positive
and negative polarities balance each other around the outer boundary of
the moat region. These results suggest that most of the magnetic flux
in the sunspot is transported to the outer boundary of the moat region
as moving magnetic features, and then removed from the photosphere by
flux cancellation around the outer boundary of the moat region.
Title: Magnetic Fields of the Quiet Sun: A New Quantitative
Perspective From Hinode
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..397...17L
Altcode:
This article summarizes results of studies presented in two papers
already published: Lites et al. (2007a); Lites et al. (2007b). Please
see these for further details.
Title: On-orbit Performance of the Solar Optical Telescope aboard
Hinode
Authors: Ichimoto, K.; Katsukawa, Y.; Tarbell, T.; Shine, R. A.;
Hoffmann, C.; Berger, T.; Cruz, T.; Suematsu, Y.; Tsuneta, S.; Shimizu,
T.; Lites, B. W.
Bibcode: 2008ASPC..397....5I
Altcode: 2008arXiv0804.3248I
On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode
is described with some attention to its unpredicted aspects. In general,
SOT reveals an excellent performance and has been providing outstanding
data. Some unexpected features exist, however, in behaviours of the
focus position, throughput and structural stability. Most of them are
recovered by the daily operation i.e., frequent focus adjustment,
careful heater setting and corrections in data analysis. The
tunable filter contains air bubbles which degrade the data quality
significantly. Schemes for tuning the filter without disturbing the
bubbles have been developed and tested, and some useful procedures
to obtain Dopplergrams and magnetograms are now available. October
and March, when the orbit of satellite becomes nearly perpendicular
to the direction towards the Sun, provide a favourable condition for
continuous runs of the narrow-band filter imager.
Title: Evolution of Magnetic 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: 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: Evershed Flow Revealed by the Solar Optical Telescope aboard
Hinode
Authors: Ichimoto, Kiyoshi; Hinode Team
Bibcode: 2008AstHe.101..378I
Altcode:
The Evershed flow, which was discovered about 100 years ago, is
still a mystery on its origin. The Solar Optical Telescope (SOT)
aboard Hinode revealed the fine scale structure of the Evershed
flow and its relation to the filamentary structures of the sunspot
penumbra. The Evershed flow is confined in narrow channels embedded
in deep penumbra that have nearly horizontal magnetic fields. It is
a dynamic phenomenon with the flow velocity close to the sound speed
of the photosphere, and individual flow channels are associated with
tiny upflow of hot gas (source) at the inner end and down flow (sink)
at the outer end. SOT/Hinode also discovered the enigmatic twisting
motions of penumbral filaments and numerous tiny jets in the penumbral
chromosphere. The SOT opened a new step towards the understanding of
the sunspots, though further studies with magnetohydrodynamic modeling
are necessary.
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: Image Stabilization System for Hinode (Solar-B) Solar Optical
Telescope
Authors: Shimizu, T.; Nagata, S.; Tsuneta, S.; Tarbell, T.; Edwards,
C.; Shine, R.; Hoffmann, C.; Thomas, E.; Sour, S.; Rehse, R.; Ito,
O.; Kashiwagi, Y.; Tabata, M.; Kodeki, K.; Nagase, M.; Matsuzaki,
K.; Kobayashi, K.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2008SoPh..249..221S
Altcode:
The Hinode Solar Optical Telescope (SOT) is the first space-borne
visible-light telescope that enables us to observe magnetic-field
dynamics in the solar lower atmosphere with 0.2 - 0.3 arcsec spatial
resolution under extremely stable (seeing-free) conditions. To achieve
precise measurements of the polarization with diffraction-limited
images, stable pointing of the telescope (<0.09 arcsec, 3σ) is
required for solar images exposed on the focal plane CCD detectors. SOT
has an image stabilization system that uses image displacements
calculated from correlation tracking of solar granules to control
a piezo-driven tip-tilt mirror. The system minimizes the motions
of images for frequencies lower than 14 Hz while the satellite and
telescope structural design damps microvibration in higher frequency
ranges. It has been confirmed from the data taken on orbit that
the remaining jitter is less than 0.03 arcsec (3σ) on the Sun. This
excellent performance makes a major contribution to successful precise
polarimetric measurements with 0.2 - 0.3 arcsec resolution.
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: 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: Chromospheric Flows in the Vicinity of Magnetic Features in
the Quiet Sun Observed with Hinode SOT
Authors: Tarbell, T.; de Pontieu, B.; Carlsson, M.; Hansteen, V.;
McIntosh, S.; Ichimoto, K.
Bibcode: 2008AGUSMSP41B..02T
Altcode:
The Narrowband Filter Imager of the Solar Optical Telescope on Hinode
can measure Doppler shifts and line-of- sight magnetic fields in two
lines with contributions from the low chromosphere: Na D 589.6 nm and
Mg b 517.3 nm. The SOT Spectro-Polarimeter also measures very accurate
vector magnetic fields and Doppler velocities in the photosphere. These
observations have diffraction-limited spatial resolution and superb
stability. We present examples of these measurements in quiet sun
at various disk positions. In addition to the expected granulation
and f- and p-modes, conspicuous longer-lived downflows are seen near
strong network flux elements. Transient upflows are also detected,
presumably the base of flows seen in spicules at the limb and H-alpha
mottles on the disk. Velocity features associated with emerging and
cancelling magnetic features are also described. The observations are
compared with synthesized images made from line profiles computed from
the University of Oslo 3-D MHD simulations. This work was supported by
NASA contract NNM07AA01C. The Hinode mission is operated by ISAS/JAXA,
NAOJ, NASA, STFC, ESA and NSC.
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: Sources and Sinks of the Evershed Flow
Authors: Shine, R. A.; Title, A. M.; Ichimoto, K.; Lites, B.
Bibcode: 2008AGUSMSP31A..01S
Altcode:
Extending the work of Ichimoto et al (2007), we investigate the sources
and sinks of the Evershed flow in sunspot penumbra using data from the
Solar Optical Telescope (SOT) instruments on the Hinode satellite. We
use spectral maps taken with the Spectro-Polarimeter (SP) that provide
detailed snapshots of the large sunspot in AR 10930 over a range
of viewing angles as it rotated across the solar disk in December
2006. These are supplemented by images taken with the Filtergraph
(FG) instrument that show the dynamics of the structures. AR 10930 has
some large sunspots showing sources and sinks within the penumbra as
well as near the inner and outer boundaries. There are also regions
of contact between penumbra of two sunspots (of opposite magnetic
polarity) that show stronger horizontal flows and downdrafts than seen
elsewhere in the penumbras. The relationship between Evershed "clouds"
showing quasi-periodic variations in the spatially averaged Evershed
flow and the penumbral fine structures is also investigated. This work
was supported by NASA contract NNM07AA01C.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode/SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008AGUSMSP31B..01K
Altcode:
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features having fields that are stronger and more vertical
than their surroundings). These granules that appear in the outer
penumbra often merge with bright features inside the penumbra that move
with spines as they elongate toward the moat region. This suggests that
convective motions around the penumbral outer boundary are related to
disintegration of magnetic flux in the sunspot. We also find that dark
penumbral filaments frequently elongate into the moat region in the
vicinity of MMFs that detach from penumbral spines. Such elongating
dark penumbral filaments correspond to nearly horizontal fields
extending from the penumbra. Pairs of MMFs with positive and negative
polarities are sometimes observed along the elongating dark penumbral
filaments. This strongly supports the notion that such elongating dark
penumbral filaments have magnetic fields with a "sea serpent"-like
structure. Evershed flows, which are associated with the penumbral
horizontal fields, may be related to detachment of the MMFs from the
penumbral spines, as well as to the formation of the MMFs along the
dark penumbral filaments that elongate into the moat region.
Title: 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: Solar Optical Telescope onboard Hinode for Diagnosing the
Solar Magnetic Fields
Authors: Ichimoto, Kiyoshi; Hinode/SOT Team
Bibcode: 2008PFR.....2S1009I
Altcode:
The Solar Optical Telescope (SOT) onboard Hinode is a 50 cm aperture
telescope to observe the sun in visible lights (388-668 nm) for
the first time with high and extremely stable spatial resolution
from space. The focal plane package of SOT consists of Broad-band
Filter Imager which provides the highest spatial resolution images
of the solar photosphere, the Narrow-band Filter Imager which
takes 2-dimentional Dopplergram and Magnetogram of photosphere and
chromosphere in high cadence and with wide field of view, and the
Spectro-Polarimeter which takes full Stokes line profiles to provide
the highest precision magnetic field maps of the photosphere. The
most outstanding characteristics of SOT is its continuous and uniform
data quality with the unprecedentedly high precision and high spatial
resolution of 0.2-0.3 arcsec. The door of the telescope was deployed on
25th Oct. followed by a successful SOT first light. Initial check-outs
of the instrument were conducted and superior performance of SOT was
confirmed. SOT is starting the regular observation of the daily target
region on the sun and producing excellent scientific data. Overview of
the SOT instrument is summarized and initial results are demonstrated.
Title: Hinode Observations of Flux Emergence in Quiet and Active
Regions
Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger,
T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.;
Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..383...71L
Altcode:
We review briefly the observational understanding of emergence of
flux in both the quiet Sun and active regions in the light of first
results from the joint Japan/US/UK Hinode mission. That spacecraft
is now providing us with our first continuous, high resolution
measurements of the photospheric vector magnetic field, along with
high resolution observations of the thermal and dynamic properties
of the chromosphere and corona. This review is intended to present a
few very early results and to highlight the potential for discovery
offered by this extraordinary new mission. The discovery of ubiquitous
horizontal magnetic flux in the quiet internetwork regions is presented.
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
Bibcode: 2007AGUFMSH52C..06S
Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
Title: Small-Scale Jetlike Features in Penumbral Chromospheres
Authors: Katsukawa, Y.; Berger, T. E.; Ichimoto, K.; Lites, B. W.;
Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.;
Title, A. M.; Tsuneta, S.
Bibcode: 2007Sci...318.1594K
Altcode:
We observed fine-scale jetlike features, referred to as penumbral
microjets, in chromospheres of sunspot penumbrae. The microjets
were identified in image sequences of a sunspot taken through a Ca II
H-line filter on the Solar Optical Telescope on board the Japanese solar
physics satellite Hinode. The microjets’ small width of 400 kilometers
and short duration of less than 1 minute make them difficult to identify
in existing observations. The microjets are possibly caused by magnetic
reconnection in the complex magnetic configuration in penumbrae and
have the potential to heat the corona above a sunspot.
Title: 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: Magnetic and Doppler Observations of the Photosphere and Low
Chromosphere with the Solar Optical Telescope on Hinode
Authors: Tarbell, T. D.; Lites, B. W.; Shine, R. A.; Ichimoto, K.
Bibcode: 2007AGUFMSH53A1064T
Altcode:
We present magnetic field and Doppler shift measurements in the Mg
I b line at 517.3 nm obtained with the Solar Optical Telescope's
Narrowband Filter Imager on Hinode. The line core forms in the low
chromosphere, and the wings where the measurements are made probably
form around the temperature minimum. Stokes IQUV images in the red and
blue wings are combined to make movies of longitudinal magnetograms
and Dopplergrams. The direction of the transverse field component is
also measurable in strong field concentrations. These are compared
with very accurate photospheric magnetic measurements in Fe I 630.2 nm
from the Spectro-Polarimeter. This comparison calibrates the filter
longitudinal magnetograms in flux density and shows changes in field
geometry with height. The Doppler measurements are calibrated using
wavelength scans through the Mg line profile. A number of emerging and
canceling magnetic features were observed in AR 10961 during its disk
passage in late June and early July. Since these were made during the
Hinode eclipse season, the observations have somewhat lower spatial
resolution than usual (0.32 arcsecond pixels), but the uniformity
and sensitivity are excellent. Intermittent upflows seen between
canceling magnetic features are interpreted in terms of reconnection
outflows. Strong, persistent downflows are seen adjacent to but not
on flux concentrations outside of sunspots and pores. In the sunspot,
running penumbral waves are clearly visible, and steady downflows are
observed over the light bridges. Hinode is a Japanese mission developed
and launched by ISAS/ JAXA, with NAOJ as domestic partner and NASA and
STFC (UK) as international partners. It is operated by these agencies
in cooperation with ESA and NSC (Norway).
Title: Chromospheric Anemone Jets as Evidence of Ubiquitous
Reconnection
Authors: Shibata, Kazunari; Nakamura, Tahei; Matsumoto, Takuma; Otsuji,
Kenichi; Okamoto, Takenori J.; Nishizuka, Naoto; Kawate, Tomoko;
Watanabe, Hiroko; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo;
Nozawa, Satoshi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi;
Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Berger,
Thomas E.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M.
Bibcode: 2007Sci...318.1591S
Altcode: 2008arXiv0810.3974S
The heating of the solar chromosphere and corona is a long-standing
puzzle in solar physics. Hinode observations show the ubiquitous
presence of chromospheric anemone jets outside sunspots in active
regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers
long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their
velocity is 10 to 20 kilometers per second. These small jets have an
inverted Y-shape, similar to the shape of x-ray anemone jets in the
corona. These features imply that magnetic reconnection similar to that
in the corona is occurring at a much smaller spatial scale throughout
the chromosphere and suggest that the heating of the solar chromosphere
and corona may be related to small-scale ubiquitous reconnection.
Title: Magnetic nature of coronal loops
Authors: Singh, Jagdev; Muneer, S.; Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2007BASI...35..437S
Altcode:
It is generally believed that the magnetic pressure is much higher than
the gas pressure in the coronal loops and these loops are isothermal
in nature. We made systematic observations of four strong coronal
emission lines in the visible and near infrared part of the spectrum
for about 8 years. Two emission lines were observed at a time, making
raster scans of a steady coronal region. We studied the variation
of line widths of these lines and intensity ratios as a function
of height. The relationship between the widths of these lines and
intensity ratios indicates that the steady coronal loops are not
magnetically isolated. These findings put restrictions on coronal loop
models and indicate that the magnetic pressure in coronal loops may be
much less than assumed. These results strongly suggest that magnetic
field strength in the corona needs to be measured accurately.
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: Fe XIV green/Fe XIII infrared line ratio diagnostics
Authors: Srivastava, A. K.; Singh, Jagdev; Dwivedi, B. N.; Muneer,
S.; Sakurai, T.; Ichimoto, K.
Bibcode: 2007BASI...35..457S
Altcode:
We consider the first 27-level atomic model of Fe XIII (5.9 K <
log T_{e} < 6.4 K) to estimate its ground level populations,
taking account of electron as well as proton collisional excitations
and de-excitations, radiative cascades, radiative excitations and
de-excitations. Radiative cascade is important but the effect of
dilution factor is negligible at higher electron densities. The
^{3}P_{1}-^{3}P_{0} and ^{3}P_{2}-^{3}P_{1} transitions in the
ground configuration 3s^{2} 3p^{2} of Fe XIII result in two forbidden
coronal emission lines in the infrared region, namely 10747 and 10798
Å. While the 5303 Å green line is formed in the 3s^{2} 3p ground
configuration of Fe XIV as a ^2P_{3/2}-^{2}P_{1/2} magnetic dipole
transition. The line-widths of simultaneously observed Fe XIV green
and Fe XIII infrared forbidden coronal emission lines can be a useful
diagnostic tool to deduce temperature and nonthermal velocity in the
largescale coronal structures using intensity ratios of the lines as
the temperature signature, instead of assuming ion temperature to be
equal to the electron temperature. Since the line intensity ratios
I_{G5303}/I_{IR10747} and I_{G5303}/I_{IR10798} have very weak density
dependence, they are ideal monitors of temperature mapping in the
solar corona. The computed ratios will be compared with the recently
obtained observations in our next paper.
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: Initial Helioseismic Observations by Hinode/SOT
Authors: Sekii, Takashi; Kosovichev, Alexander G.; Zhao, Junwei;
Tsuneta, Saku; Shibahashi, Hiromoto; Berger, Thomas E.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2007PASJ...59S.637S
Altcode: 2007arXiv0709.1806S
Results from initial helioseismic observations by the Solar Optical
Telescope on-board Hinode are reported. It has been demonstrated
that intensity oscillation data from the Broadband Filter Imager
can be used for various helioseismic analyses. The k - ω power
spectra, as well as the corresponding time-distance cross-correlation
function, which promise high-resolution time-distance analysis below
the 6-Mm travelling distance, were obtained for G-band and CaII-H
data. Subsurface supergranular patterns were observed from our first
time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and
the time-distance diagram is extended to much shorter travel distances
and times than were observed before, thus revealing great potential
for high-resolution helioseismic observations from Hinode.
Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux
and the ``Hidden Turbulent Magnetic Flux''
Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger,
Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title,
Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu,
Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.571L
Altcode:
We present observations of magnetic fields of the very quiet Sun
near disk center using the Spectro-Polarimeter of the Solar Optical
Telescope aboard the Hinode satellite. These observations reveal for
the first time the ubiquitous presence of horizontal magnetic fields in
the internetwork regions. The horizontal fields are spatially distinct
from the vertical fields, demonstrating that they are not arising mainly
from buffeting of vertical flux tubes by the granular convection. The
horizontal component has an average ``apparent flux density'' of
55Mxcm-2 (assuming the horizontal field structures are
spatially resolved), in contrast to the average apparent vertical flux
density of 11Mxcm-2. The vertical fields reside mainly in
the intergranular lanes, whereas the horizontal fields occur mainly
over the bright granules, with a preference to be near the outside
edge of the bright granules. The large apparent imbalance of vertical
and horizontal flux densities is discussed, and several scenarios are
presented to explain this imbalance.
Title: Strategy for the Inversion of Hinode Spectropolarimetric
Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.837O
Altcode: 2007arXiv0709.2033O
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by Hinode in the quiet Sun. The
Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We
discuss the need to consider a local stray-light contamination to
account for the effects of telescope diffraction. The strategy is
applied to observations of a wide quiet Sun area at disk center. Using
these data we examine the influence of noise and initial guess models
in the inversion results. Our analysis yields the distributions of
magnetic field strengths and stray-light factors. They show that quiet
Sun internetwork regions consist mainly of hG fields with stray-light
contamination of about 0.8.
Title: Hinode 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: Observation of a Coronal Mass Ejection and its Source Region
with NOrikura Green-line Imaging System (NOGIS)
Authors: Suzuki, I.; Sakurai, T.; Ichimoto, K.
Bibcode: 2007ASPC..369..543S
Altcode:
NOrikura Green-line Imaging System (NOGIS), with its unique capability
of Doppler imaging, was used to study a CME and its source region on
1999 May 7. The source region at the north-east limb consisted of two
loop systems. Prior to the CME, one of the two loops moved toward
the neighboring other loop in the plane of the sky. Then, the loop
apparently touched and destabilized the other loop, resulting in the
CME with a red-shifted motion. In the NOGIS field-of-view, the CME
propagated non-radially in the plane of the sky. These observations
indicate that the direction of mass ejection was determined by the
magnetic field configuration around the source region and the location
of the initial energy release in the magnetic field structure.
Title: Estimate on SOT Light Level in Flight with Throughput
Measurements in SOT Sun Tests
Authors: Shimizu, T.; Kubo, M.; Tarbell, T. D.; Berger, T. E.;
Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Miyashita, M.; Noguchi,
M.; Nakagiri, M.; Tsuneta, S.; Elmore, D. F.; Lites, B. W.
Bibcode: 2007ASPC..369...51S
Altcode:
The SOT (Solar Optical Telescope, e.g., Shimizu 2004) optical
system consists of 50cm-aperture optical telescope (OTA) and focal
plane instrument (FPP). The solar light into the telescope penetrates
through many optical elements located in OTA and FPP before illuminating
CCDs. Natural solar light was fed to the integrated SOT in sun tests for
verifying various optical aspects including the confirmation of photon
throughput. CCD exposures provide the number of photons accumulated
in an exposure duration with a clean-room test condition. To estimate
the absolute intensity of the solar light at the telescope entrance
in the clean-room test condition, we developed a pinhole-PSD sensor
for simultaneous monitoring the solar light outside the clean room
and measured the transmission of light through two flat mirrors of
the heliostat and clean-room entrance window glass as a function of
wavelength. The PSD sensor was pre-calibrated with continuous monitoring
the solar light in a day long under a clear constant sky condition,
determining the earth atmospheric attenuation and the PSD output for
the solar light on orbit. These throughput measurements have provided
an estimate on photon throughput for the SOT flight model. The results
confirm suitable number of photons without saturation for proper CCD
exposures in flight.
Title: Performance Characteristics of the Solar-B Spectro-Polarimeter
Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.; Hoffmann,
C. M.; Tarbell, T. D.; Title, A. M.; Shine, R. A.; Ichimoto, K.;
Tsuneta, S.; Shimizu, T.; Suematsu, Y.
Bibcode: 2007ASPC..369...55L
Altcode:
The Focal Plane Package (FPP) of the Solar Optical Telescope (SOT)
includes the first precision Spectro-Polarimeter (SP) for solar space
observations. The FPP/SP will provide high precision measures of
the vector magnetic field in the solar photosphere. Here we present
some as-built performance specifications for the entire system of
telescope + polarimeter. The FPP-SP system represents significant
gains in several aspects over existing spectro-polarimetric systems;
notably, angular resolution, polarimetric accuracy, spectral purity,
and most importantly, temporal continuity of stable, high angular
resolution. In this short summary of the poster, a few of the
performance characteristics of the SP are presented.
Title: Flare-Associated Oscillations in Coronal Multiple-Loops
Observed with the Norikura Green-Line Imaging System
Authors: Hori, K.; Ichimoto, K.; Sakurai, T.
Bibcode: 2007ASPC..369..213H
Altcode:
We report the first detection of a magnetohydrodynamic kink
oscillation in the coronal green line emission (Fe XIV 5303A,
2MK) by the two-dimensional Doppler coronagraph NOGIS (Norikura
Green-Line Imaging System) at the Norikura Solar Observatory, National
Astronomical Observatory of Japan. It was an impulsively triggered
damping oscillation in Doppler shift in a bundle of face-on coronal
loops on the west limb. In the individual loops, both transverse
(fast kink) and longitudinal modes were observed simultaneously. The
longitudinal mode can be slow wave reflecting at both ends of the
loop. The kink mode had larger amplitude than the longitudinal mode,
and lasted up to ∼7 wave periods (> 100 min). Oscillations in
different loops were not synchronized in phase; the phase velocity
increased smoothly with the loop length. Our preliminary results
support the resonant mode conversion as a possible damping mechanism
of the kink oscillations in a certain part of the observed loops.
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: 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: The Hinode (Solar-B) Mission: An Overview
Authors: Kosugi, T.; Matsuzaki, K.; Sakao, T.; Shimizu, T.; Sone,
Y.; Tachikawa, S.; Hashimoto, T.; Minesugi, K.; Ohnishi, A.; Yamada,
T.; Tsuneta, S.; Hara, H.; Ichimoto, K.; Suematsu, Y.; Shimojo, M.;
Watanabe, T.; Shimada, S.; Davis, J. M.; Hill, L. D.; Owens, J. K.;
Title, A. M.; Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Golub, L.
Bibcode: 2007SoPh..243....3K
Altcode:
The Hinode satellite (formerly Solar-B) of the Japan Aerospace
Exploration Agency's Institute of Space and Astronautical Science
(ISAS/JAXA) was successfully launched in September 2006. As the
successor to the Yohkoh mission, it aims to understand how magnetic
energy gets transferred from the photosphere to the upper atmosphere
and results in explosive energy releases. Hinode is an observatory
style mission, with all the instruments being designed and built to
work together to address the science aims. There are three instruments
onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer
(EIS), and the X-Ray Telescope (XRT). This paper provides an overview
of the mission, detailing the satellite, the scientific payload, and
operations. It will conclude with discussions on how the international
science community can participate in the analysis of the mission data.
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: 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: 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: Hinode Observations of Umbral Dots
Authors: Hurlburt, Neal E.; Berger, T.; Ichimoto, K.; SOT Team
Bibcode: 2007AAS...210.9409H
Altcode: 2007BAAS...39..218H
We analyze observations of sunspot umbra taken by the Solar Optical
Telescope (SOT) on Hinode to ascertain the properties of umbral
dots. The observations consist of coordinated, multi-wavelength
observing sequences spanning several hours for each spot
considered. Typically these multi-wavelength observations include
longitudinal magnetograms in 6302, and filtergrams in Calcium II H,
G-band and blue continuum. We report on the spatial and temporal
properties of the umbral dots and their relation to the umbral field
and overlying chromosphere. This work was supported in part by
NASA in part under the Hinode/SOT contract NNM07AA01C.
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: Hinode/SOT Observations of Sunspot Penumbral Dynamics and
Evolution
Authors: Shine, Richard A.; Hagenaar, M.; Tarbell, T.; Title, A.;
Lites, B.; Ichimoto, K.; Tsuneta, S.; Katsakawa, Y.; Suematsu, Y.;
Nagata, S.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9407S
Altcode: 2007BAAS...39..218S
The Solar Optical Telescope (SOT) on the Hinode satellite (launched
October 2006) has obtained long and nearly continuous time series of
several large sunspots including those in NOAA AR's 10923, 10925,
and 10930. Here we use high resolution movies taken primarily with
the broad band Ca II (396.8nm) and G band (430.5nm) channels and
magnetograms taken with the 630.2nm narrow band channel to study
the details and short term evolution of penumbral fine structures
as well as the long term evolution of the sunspots. We compute flow
maps and use space/time slices to track motions of Evershed clouds,
penumbral grains, and visualize oscillations. The data contain examples
of penumbral formation and disintegration including "orphan" penumbra
(i.e., penumbra without an obvious umbra). There is also an interesting
instance of "colliding" penumbra in AR 10930 as two sunspots of opposite
polarity converged. The zone of apparent shear was associated with
several flares. This work was supported by NASA contract NNM07AA01C
Title: 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: Development of a Correlation Tracker and a Tip-Tilt Mirror
System for SOLAR-B
Authors: Kodeki, Kazuhide; Kashiwagi, Yasuhiro; Miki, Shiro; Endoh,
Makoto; Itoh, Osamu; Shimizu, Toshihumi; Matsuzaki, Keiichi; Nagata,
Shinichi; Ichimoto, Kiyoshi; Tsuneta, Saku
Bibcode: 2007JSASS..55...57K
Altcode:
The solar observation satellite “SOLAR-B,” which is being developed
under the joint cooperation of JAXA and NAOJ with the U.S.A. (NASA)
and the U.K. (PPARC), will be launched in summer 2006. SOLAR-B requires
very high pointing stability for its three telescopes. In particular,
the Solar Optical Telescope (SOT), which has the highest resolution
and narrowest field of view among these telescopes, requires 0.06
[arcsec]<SUB>3σ</SUB> of short-term (10[s]) stability to
meet the observation demands. However, it is very difficult to achieve
such levels of stability by only using the satellite attitude control
system due to disturbance from the observation equipment. Therefore,
we propose using the Correlation Tracker and tip-tilt Mirror package
(CTM), which stabilizes the sun observation image. CTM consists of
a correlation tracker and a piezo-based tip-tilt mirror with servo
control electronics. This paper describes the mechanism and the control
and determination methods of the control gain of CTM as well as the
results of experiments conducted to clarify its capability.
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: Observation of CME Source Regions by Coronal Emission-Line
Dopplergrams
Authors: Sakurai, T.; Hori, K.; Suzuki, I.; Ichimoto, K.
Bibcode: 2006ihy..workE..35S
Altcode:
Although observations with SOHO/LASCO show the behavior of CMEs beyond
2.5 solar radii, connection between LASCO CMEs and their source
regions in the lower corona observed with SOHO/EIT or Yohkoh/SXT
is not trivial. One way to fill the gap would be to supplement the
Doppler shift information of the moving CME mass. Such an instrument
was built and has been operated since 1997 July at the Norikura Solar
Observatory (2876 m above sea level) of NAOJ. The instrument we call
NOGIS (NOrikura Green-line Imaging System) is made of a 10 cm-aperture
coronagraph and a tunable birefringent filter. NOGIS can provide both
intensity and Doppler velocity images of 2 MK plasmas using the coronal
green-line emission at 5303 Angstrom of Fe XIV. An intensity image is
made by subtracting the sky background (taken at far wings) from the
line-center image. A Doppler image is constructed by subtracting a
blue-wing image from a red-wing image. The line-of-sight velocity up
to 25 km/s can be obtained with an accuracy of about 0.6 km/s. NOGIS
covers a field of view of 1.03 - 1.33 solar radii in a full frame mode,
or a local small area in a partial frame mode with higher cadence of
about 1 minute. So far we have analyzed two CME events which showed
favorable orientations of the regions against the plane of the sky
(1999 May 7 and 2003 June 2). In both events, interaction between two
magnetic flux systems (loops in the case of 1999 May 7 and arcades in
the case of 2003 June 2) was observed.
Title: A Spectroscopic Observation of a Magnetic Reconnection Site
in a Small Flaring Event
Authors: Hara, Hirohisa; Nishino, Yohei; Ichimoto, Kiyoshi;
Delaboudinière, Jean-Pierre
Bibcode: 2006ApJ...648..712H
Altcode:
We have observed two types of coronal bidirectional flows in a flare
with a small energy release through a spectroscopic observation of
the Fe X emission line at 6374 Å with a ground-based coronagraph
at the Norikura Solar Observatory. We find a bidirectional flow of
+/-3 km s-1 above the top of a flare loop. Remarkable
increases of the line intensity and line width are not observed in
the flow. From the loop geometry and sign of the Fe X Doppler velocity
we conclude that the bidirectional flow is reconnection inflow above
the flare loop. We estimate the reconnection rate to be ~0.003 for
this event. The other bidirectional flow is observed along postflare
loops with significant increases of the line intensity and Doppler
velocity. This flow is interpreted as a cooling upflow having a velocity
of ~10 km s-1 along a postflare loop from its lower part. We
also find that the increase of the nonthermal line width in the loop-top
region starts when the line intensity reaches its peak. This supports
the presence of a mechanism to enhance turbulent plasma motions in
the loop-top region.
Title: Spectroscopic Studies of Solar Corona VI: Trend in Line-width
Variation of Coronal Emission Lines with Height Independent of the
Structure of Coronal Loops
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Muneer, S.
Bibcode: 2006JApA...27..115S
Altcode:
We have obtained spectroscopic observations in coronal emission lines
by choosing two lines simultaneously, one [Fe x] 6374Å and the other
[Fe xi] 7892Å or [Fe xiii] 10747Å or [Fe xiv] 5303 Å. We found that
in 95 per cent of the coronal loops observed in 6374 Å, the FWHM of
the emission line increases with height above the limb irrespective
of the size, shape and orientation of the loop and that in case of
5303Å line decreases with height in about 89 per cent of the coronal
loops. TheFWHMof 7892Å and 10747Å emission lines show intermediate
behavior. The increase in the FWHM of 6374Å line with height is the
steepest among these four lines.We have also studied the intensity ratio
and ratio of FWHM of these lines with respect to those of 6374Å as a
function height above the limb. We found that the intensity ratio of
7892Å and 10747Å lines with respect to 6374Åline increases with
height and that of 5303Å to 6374Å decreases with height above the
limb. This implies that temperature in coronal loops will appear
to increase with height in the intensity ratio plots of 7892Å and
6374 Å; and 10747Å and 6374Å whereas it will appear to decrease
with height in intensity ratio of 5303Å to 6374Å line versus height
plot. These findings are up to a height of about 200 arcsec above the
limb. The varying ratios with height indicate that relatively hotter
and colder plasma in coronal loops interact with each other. Therefore,
the observed increase in FWHM with height above the limb of coronal
emission lines associated with plasma at about 1MK may not be due to
increase in non-thermal motions caused by coronal waves but due to
interaction with the relatively hotter plasma. These findings also do
not support the existing coronal loop models, which predict an increase
in temperature of the loop with height above the limb.
Title: Spectroscopic Studies of Solar Corona VIII. Temperature and
Non-Thermal Variations in Steady Coronal Structures
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Muneer,
S.; Raveendran, A. V.
Bibcode: 2006SoPh..236..245S
Altcode:
With a view to investigate variations in parameters of coronal emission
lines over a large range of radial distance from the limb, raster
scans were made with sufficiently long exposure times on several days
during September - October 2003. An analysis of the data shows that (i)
in most of the coronal structures, the FWHM of the Fe XIV 5303 Å line
decreases up to 300″±50″, (ii) the FWHM of the Fe X 6374 Å line
increases up to about 200″ and then remains unchanged up to about
500″, and (iii) the FWHMs of the Fe XI 7892 Å and Fe XIII 10747 Å
lines show an intermediate behaviour with height. The analysis of the
data also shows that the ratio of FWHM of 6374 Å to that of 5303 Å
increases from 0.93 at the limb to 1.18 at 200″ above the limb. From
this and the ratio of intensities of the two lines we infer that the
plasma in steady coronal structures at a height of about 200″ has
a temperature of about 1.5 MK and a non-thermal velocity around 17
km s−1. The observations also show that non-homogeneous
temperatures and non-thermal velocities largely exist in the lower
corona up to about 300″±100″ above the limb. Amplitudes of
variations in FWHM of different emission lines with height in the
coronal loops are similar to those in the diffuse plasma around the
coronal loops.
Title: Do the Line Widths of Coronal Emission Lines Increase with
Height above the Limb?
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2006ApJ...639..475S
Altcode:
In our earlier studies we obtained off-the-limb spectroscopic
observations in a number of forbidden emission lines ([Fe X-XIV]) to
study the physical properties and their temporal variations in steady
coronal structures. Short exposure times adopted in those observations
permitted us to study the variation in line widths up to about 150"
above the limb. With a view to investigating the variations in the
parameters of coronal emission lines up to about 500", we made raster
scans with exposure times that are longer than the earlier exposure
times by a factor of about 10. We find that the FWHM of the [Fe XIV]
5303 Å line decreases up to 300''+/-50'' and
then remains more or less the same up to 500", while that of the [Fe
X] 6374 Å line increases up to about 250" and subsequently remains
unchanged. The FWHMs of the [Fe XI] 7892 Å and [Fe XIII] 10747 Å
lines show an intermediate behavior. Furthermore, the ratio of the
FWHM of 6374 to 5303 Å increases from 0.93 at the limb to 1.18 at 200"
above the limb. The nonvariability in the FWHM of emission lines after
about 300" above the limb in steady coronal structures does not support
the prevailing view that the nonthermal velocity increases with height
due to either the coronal waves or the high-velocity solar wind. The
present results indicate the inadequacy of the earlier coronal loop
models. The observed variations in FWHM of the coronal emission lines
with height above the limb can be explained by assuming the recent
model of coronal loops proposed by Akiyama et al.
Title: Three-Dimensional Motion of Plasmas Associated with a Coronal
Mass Ejection Observed with NOrikura Green-Line Imaging System (NOGIS)
Authors: Suzuki, Isao; Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2006PASJ...58..165S
Altcode:
In order to investigate the structure and the driving mechanism of
Coronal Mass Ejections (CMEs), it is important to examine in detail
the magnetic field structure in the low corona. NOrikura Green-line
Imaging System, with its unique capability of Doppler imaging, was
used to study a CME and its source region on 1999 May 7. Prior to the
CME, a small loop at the north-east limb moved toward a neighboring
larger loop in the plane of the sky. Then, the small loop apparently
destabilized the large loop, resulting in the CME with a red-shifted
motion. The CME propagated non-radially in the plane of the sky. These
observations indicate that two loop systems were involved in this CME,
and the direction of mass ejection was determined by the magnetic field
configuration around the source region and the location of the initial
energy release in the magnetic field structure. A brief discussion is
given on the loop oscillation phenomenon observed during this event.
Title: Photopolarimetric measurement system of Mueller matrix with
dual rotating waveplates
Authors: Ichimoto, Kiyoshi; Shinoda, Kazuya; Yamamoto, Tetsuya;
Kiyohara, Junko
Bibcode: 2006PNAOJ...9...11I
Altcode:
A new photopolarimetric measurement system of Mueller matrix of optical
elements is developed using dual rotating waveplates. The waveplates in
polarization generator and analyzer rotate continuously with a constant
ratio of revolution speed, and the Mueller matrix of a sample can be
obtained in a few seconds. General principle of such measurement and the
optimization of operation parameters are discussed, followed by detailed
descriptions of the constructed system. Some examples of its application
are also demonstrated. The system is sensitive to <10-3
for each Mueller matrix element for weak polarization elements.
Title: The Solar Optical Telescope Onboard the Solar-B Capability
of the Magnetic Field Diagnostic
Authors: Ichimoto, K.; Sot Team
Bibcode: 2005ESASP.596E..81I
Altcode: 2005ccmf.confE..81I
No abstract at ADS
Title: Complex Variations in Line-Intensity Ratio of Coronal Emission
Lines with Height Above the Limb
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Watanabe,
Tetsuya
Bibcode: 2005BASI...33..362S
Altcode:
No abstract at ADS
Title: The Solar-B Mission
Authors: Ichimoto, Kiyoshi; Solar-B Team
Bibcode: 2005JKAS...38..307I
Altcode:
No abstract at ADS
Title: Contamination evaluation and thermal vacuum bakeout for
SOLAR-B visible-light and X-ray telescope
Authors: Tamura, Tomonori; Hara, Hirohisa; Tsuneta, Saku; Ichimoto,
Kiyoshi; Kumagai, Kazuyoshi; Nakagiri, Masao; Shimizu, Toshifumi;
Sakao, Taro; Kano, Ryouhei
Bibcode: 2005RNAOJ...8...21T
Altcode:
In the development of space telescopes, we are concerned about molecular
outgassing materials from telescope components. In particular, for
solar telescopes in space, the deposition of the outgassing materials
may lead to the increase of solar absorptance at a mirror surface
and it causes the thermal distortion due to the resultant temperature
increase. The mirror reflectivity at vacuum ultraviolet wavelengths
is very sensitive to molecular contamination. We have extensively
evaluated reflectance at 121.6nm (Lyman-alpha) of the contamination
witness mirrors exposed to the telescope testing environments in the
SOLAR-B visible-light telescope program. Thermal vacuum bakeout of
flight components is very effective process to reduce the outgassing
rate. We have severe contamination control program during the assembly
and testing of the SOLAR-B telescope up to launch of the satellite.
Title: Spectroscopic Studies of Solar Corona VII. Formation of a
Coronal Loop by Evaporation
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Suzuki,
Isao; Hagino, Masaoki
Bibcode: 2005SoPh..226..201S
Altcode:
We obtained time-sequence spectroscopic observations in (Fe X) 6374 Å
and (Fe XIV) 5303 Å lines successively with the 25-cm coronagraph,
and narrow-band and Doppler images in 5303 Å line by the 2-D 10-cm
Doppler coronagraph "NOGIS" at the Norikura Solar Observatory, of
a coronal region for about 7 h on 9 19-20, 2001. The raster scans
were obtained with a quasi-periodicity of about 14 min and "NOGIS"
obtained the images with an interval of about 1 min. The coronal region
observed showed the formation of a coronal loop by a high-speed surge
in the 6374 Å line rising from one of the footpoints of the loop. Off
the limb spectroscopic observations in the 6374 Å line showed large
velocities along the line of sight and vertical to the solar limb
at the time of formation of the loop. The 5303 Å line observations
showed negligible line-of-sight velocities and low vertical velocities
when compared to those in the 6374 Å line. A hump in the intensity
plots in 5303 Å with height appears to move up with respect to the
solar limb with an average velocity of 4km s−1. The FWHM
of the 6374 Å showed a much smaller value of about 0.7 Å near the
foot point as compared to a value of 1.2 Å at larger heights at the
beginning of observations. Later as the loop developed, the FWHM of
6374 Å line showed a gradual decrease along the loop up to 70″ from
the limb, reached a minimum value of about 0.5 Å and then increased
with height during the formation of the loop; this trend lasted for
about 2 h. About 3 h after the beginning of the formation of the loop,
the FWHM of 6374 Å emission line showed normal values and normal rate
of increase with height with some fluctuations. The FWHM of the 5303
Å line did not show such variations along the loop and showed normal
decrease in FWHM with height found earlier (Singh et al., 2003a). These
observations suggest that a relatively cooler plasma at a temperature
of about 0.7 MK or less (corresponding to minimum value of FWHM of 0.5
Å) was ejected from the transition region with a large velocity of
about 48km s−1, heated up in the corona by some process
and formed a coronal loop with a height of about 200″ above the limb
that had lifetime greater than 4 h. It appears that the plasma moved
from one of the footpoints and the loop was formed by evaporation of
chromospheric plasma. No large-scale brightening and Hα flare were
observed in this region during the observational period of 7 h.
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: Flare-induced coronal disturbances observed with Norikura
"NOGIS" coronagraph
Authors: Hori, K.; Ichimoto, K.; Sakurai, T.; Sano, I.; Nishino, Y.
Bibcode: 2005IAUS..226...36H
Altcode:
A 2-dimensional Doppler coronagraph "NOGIS" (NOrikura Green-line
Imaging System) at the Norikura Solar Observatory, NAOJ, is a unique
imaging system that can provide both intensity and Doppler velocity
of 2 MK plasma from the green coronal line emission λ5303 Å of
Fe xiv. We present the first detection of a CME onset by NOGIS. The
event was originally induced by a C9.1 confined flare that occurred
on 2003 June 1 at an active region NOAA #10365 near the limb. This
flare triggered a filament eruption in AR 10365, which later evolved
into a partial halo CME as well as an M6.5 flare at the same AR 10365
on 2003 June 2. The CME originated in a complex of two neighboring
magnetic flux systems across the solar equator: AR 10365 and a bundle
of face-on tall coronal loops. NOGIS observed i) a density enhancement
in between the two flux systems in the early phase, ii) a blue-shifted
bubble and jet that later appeared as (a part of) the CME, and iii)
a red-shifted wave that triggered a periodic fluctuations in Doppler
shifts in the face-on loops. These features are crucial to understand
unsolved problems on a CME initiation (e.g., mass supply, magnetic
configuration, and trigger mechanism) and on coronal loop oscillations
(e.g., trigger and damping mechanisms). We stress a possibility that
interaction between separatrices of the two flux systems played a key
role on our event.
Title: Flare-associated Coronal Disturbances Observed with the
Norikura Green-Line Imaging System. I. A Coronal Mass Ejection Onset
Authors: Hori, K.; Ichimoto, K.; Sakurai, T.; Sano, I.; Nishino, Y.
Bibcode: 2005ApJ...618.1001H
Altcode:
We present the first detection of an onset of a coronal mass ejection
(CME) in the coronal green-line emission (Fe XIV λ5303, 2 MK) by
the two-dimensional Doppler coronagraph NOGIS (Norikura Green-Line
Imaging System) at the Norikura Solar Observatory, National Astronomical
Observatory of Japan. On 2003 June 1-2, NOGIS continuously observed the
birthplace of a CME that originated in a complex of two neighboring
magnetic flux systems across the solar equator: a flare-productive
NOAA Active Region 10365, and a bundle of face-on coronal loops
overlaying a quiescent filament. An early precursor of the event
was a density enhancement of a 2 MK plasma in between the two flux
systems. Following a filament eruption from NOAA AR 10365 that was
observed by the Transition Region and Coronal Explorer (TRACE) in the
195 Å passband (1.6 MK), NOGIS observed a blueshifted bubble and a
redshifted wave that almost simultaneously expanded from the boundary
of NOAA AR 10365 and the overlying dense region. The redshifted wave
propagated toward the face-on loop system and triggered a damping
oscillation in Doppler shifts among the adjacent loops within the
system. The blueshifted bubble propagated both inward and upward. The
inward motion triggered an M6.5 flare in AR 10365, while the upward
motion evolved into a partial halo CME that had an angular extent
covering the latitudinal range of the two flux systems. Differing from
typical CME disturbances that evolve within a single flux system with
a bipolar arcade on its center, our event proceeded via interaction,
which was a presumably magnetic reconnection between separatrices
of the two flux systems. These observational properties may suggest
the existence of ``CME corridors'' in multiple complex flux systems,
from which huge CMEs can be launched.
Title: Oscillations in the coronal green-line intensity observed at
Lomnický Stít and Norikura nearly simultaneously
Authors: Minarovjech, Milan; Rušin, Vojtech; Rybanský, Milan;
Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2005naoj.book...36M
Altcode:
No abstract at ADS
Title: A CME onset observed with Norikura NOGIS coronagraph
Authors: Hori, Kuniko; Ichimoto, Kiyoshi; Sakurai, Takashi; Sano,
Issei; Nishino, Yohei
Bibcode: 2005ARAOJ...7...51H
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: Some coronal loops have cooler loop-tops
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2005ARAOJ...7...50S
Altcode:
No abstract at ADS
Title: Spectroscopic Studies of Steady Coronal Structures -- Line
Width Variations with Height of Ion{Fe{X-XIV}} Emission Lines
Authors: Singh, J.; Sakurai, T.; Ichimoto, K.; Watanabe, T.
Bibcode: 2004ASPC..325..235S
Altcode:
We have obtained spectrographic observations of several steady coronal
structures at the limb overlying the sunspot regions on several
days in ion{Fe{x-xiv}} emission lines. The line-width measurements
indicate that in steady coronal structures the FWHM of the 6374 AA line
increases with height above the limb with an average value of 1.02
mAA per arcsec. Whereas the FWHM of the 5303 AA line decreases with
an average value of -0.66 mAA per arcsec. The FWHM of the 7892 AA and
10747 AA lines increases with values of 0.55 and 0.29 mAA per arcsec,
respectively. We find that FWHM of emission lines in coronal structures
increases with height if the associated ionization temperature is less
than 1.6 MK, with gradient depending upon the ionization temperature
of the line, while the FWHM decreases with height for lines whose
ionization temperature is greater than 1.6 MK. It implies that it
may not always be possible to interpret the observed increase in FWHM
with height in terms of an increase in the non-thermal velocity. To
investigate further, we propose simultaneous observations in number of
EUV lines with EIS onboard SolarB and in ion{Fe{x-xiv}} in the visible
wavelengths with the 25-cm coronagraph at Norikura.
Title: Complex Variations in the Line-Intensity Ratio of Coronal
Emission Lines with Height above the Limb
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Watanabe,
Tetsuya
Bibcode: 2004ApJ...617L..81S
Altcode:
We obtained spectroscopic observations simultaneously in pairs of
coronal emission lines, one line being [Fe X] λ6374 and the other
line being [Fe XI] λ7892, [Fe XIII] λ10747, or [Fe XIV] λ5303, and
we studied the variations in the intensity and FWHM ratios of these
lines with respect to those of 6374 Å as a function of height above
the limb. We find that the intensity ratio of the 7892 and 10747 Å
line with respect to the 6374 Å line increases with height and that
the intensity ratio of 5303 Å to 6374 Å decreases with height above
the limb. This implies that the temperature in coronal loops will
appear to increase with height if we consider the intensity ratio
of 7892 Å to 6374 Å a negligible variation in temperature in the
case of the 10747 and 6374 Å line pair, while the temperature will
appear to decrease with height if we consider the intensity ratio of
5303 Å to 6374 Å. The normalized FWHM (with respect to wavelength)
ratio of 6374 Å to all the other coronal lines observed increases
with height. The FWHM ratio at the limb depends on the pair of emission
lines chosen; it is about 1 in the case of the 6374 and 7892 Å emission
lines, indicating a common temperature and nonthermal velocity in the
coronal loops near the limb, and it is about 0.7 at the limb in the
case of the 6374 and 5303 Å lines and becomes about 1 at a height
of 120". The varying FWHM ratios with height indicate that hotter
and colder plasmas in coronal loops mix with each other. Therefore,
the observed increase in the FWHM of coronal emission lines, which
are associated with plasma at about 1 MK with height, may not be due
to an increase in nonthermal motions caused by coronal waves but may
be due to an interaction with relatively hotter plasma.
Title: The Red-Asymmetry Distribution at Hα Flare Kernels Observed
in the 2001 April 10 Solar Flare
Authors: Asai, A.; Ichimoto, K.; Shibata, K.; Kitai, R.; Kurokawa, H.
Bibcode: 2004AGUFMSH13A1134A
Altcode:
We report a detailed examination about the evolution of the Hα flare
kernels during an X2.3 solar flare which occurred on 2001 April 10. The
Hα red-asymmetry, that is, the red-shifted Hα emission, is observed
at almost all Hα flare kernels, during the impulsive phase of the
flare. At Hα kernels nonthermal particles and/or thermal conduction
precipitate into the chromospheric plasma, and this is thought to lead
the downward compression of the chromospheric plasma, which is observed
as the reddening of Hα emission (e.g. Ichimoto & Kurokawa 1984). We
examined the evolution of the flare kernels inside the flare ribbons
by using the Hα images obtained with the Domeless Solar Telescope
at Hida Observatory, Kyoto University. We also examined the spatial
distribution of the Hα kernels which show the red-asymmetry and their
relationship with the intensity of the Hα kernels. We found that the
stronger the red-asymmetry is, the brighter the Hα kernel is. Then, we
compared the strengthes of the Hα red-asymmetry at hard X-ray emitting
sources with those at the Hα kernels without the hard X-ray emissions.
Title: Flare-Induced Coronal Disturbances Observed with Norikura
"NOGIS" Coronagraph: A CME Onset
Authors: Hori, K.; Ichimoto, K.; Sakurai, T.; Nishino, Y.; Nogis Team
Bibcode: 2004ASPC..325..415H
Altcode:
We present the first detection of a CME onset in the coronal green
line emission (ion{Fe{xiv}} 5303 AA, 2 MK) by a 2D Doppler coronagraph
``NOGIS'' at the Norikura Solar Observatory, NAOJ. Different from a
typical CME that evolves within a single magnetic flux system with a
single magnetic neutral line, NOGIS observed a CME that evolved across
two neighboring magnetic flux systems; a flare-productive active region
and an aggregate of face-on coronal loops with a streamer on its top. An
early precursor of the event was a density enhancement of 2 MK plasma in
the space between the two magnetic flux systems. In association with an
M6.5 flare that occurred at the active region, a blue-shifted upward jet
and expansion appeared from a site where the legs of the two systems
apparently connected each other. This expansion later evolved into
a partial halo CME with an angular extent covering the latitudinal
range of the two systems. These observational properties suggest
the existence of sl a CME corridor that is consisted of neighboring
multiple magnetic-flux systems through which a huge CME launches off.
Title: Image stabilization system on SOLAR-B Solar Optical Telescope
Authors: Shimizu, Toshifumi; Nagata, Shin'ichi; Edwards, Chris;
Tarbell, Theodore; Kashiwagi, Yasuhiro; Kodeki, Kazuhide; Ito,
Osamu; Miyagawa, Hiroyuki; Nagase, Masayuki; Inoue, Syunsaku; Kaneko,
Kazumasa; Sakamoto, Yasushi; Ichimoto, Kiyoshi; Tsuneta, Saku; Miki,
Shiro; Endo, Makoto; Tabata, Masaki; Nakaoji, Toshitaka; Matsuzaki,
Keiichi; Kobayashi, Ken; Otsubo, Masashi; Suematsu, Yoshinori; Kumagai,
Kazuyoshi; Noguchi, Motokazu; Tamura, Tomonori; Nakagiri, Masao
Bibcode: 2004SPIE.5487.1199S
Altcode:
Extremely stable pointing of the telescope is required for images on the
CCD cameras to accurately measure the nature of magnetic field on the
sun. An image stabilization system is installed to the Solar Optical
Telescope onboard SOLAR-B, which stabilizes images on the focal plane
CCD detectors in the frequency range lower than about 20Hz. The system
consists of a correlation tracker and a piezo-based tip-tilt mirror with
servo control electronics. The correlation tracker is a high speed CCD
camera with a correlation algorithm on the flight computer, producing
a pointing error from series of solar granule images. Servo control
electronics drives three piezo actuators in the tip-tilt mirror. A
unique function in the servo control electronics can put sine wave
form signals in the servo loop, allowing us to diagnose the transfer
function of the servo loop even on orbit. The image stabilization
system has been jointly developed by collaboration of National
Astronomical Observatory of Japan/Mitsubishi Electronic Corp. and
Lockheed Martin Advanced Technology Center Solar and Astrophysics
Laboratory. Flight model was fabricated in summer 2003, and we measured
the system performance of the flight model on a laboratory environment
in September 2003, confirming that the servo stability within 0-20 Hz
bandwidth is 0.001-0.002 arcsec rms level on the sun.
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: Calibration of the instrumental polarization of the Domeless
Solar Telescope at the Hida Observatory
Authors: Kiyohara, Junko; Ueno, Satoru; Kitai, Reizaburo; Kurokawa,
Hiroki; Makita, Mitsugu; Ichimoto, Kiyoshi
Bibcode: 2004SPIE.5492.1778K
Altcode:
A new spectropolarimeter is developed at the Domeless Solar Telescope
(DST) in Hida Observatory. It consists of a rotating waveplate,
Wollaston prisms, and a high-dispersion spectrograph which is
vertically installed at the focus of the DST. In order to realize
a high-precision measurement, it is inevitable to compensate the
instrumental polarization due to the DST. We observed the quiet
region of the Sun, which is considered to be highly unpolarized,
with and without a sheet linear polarizer or circular polarizer
set at the entrance window of the telescope. The theoretical model
which represents the total instrumental polarization of the DST with
some characteristic parameters was calculated and compared with the
observation. The model that two flat mirrors have different properties
can explain the observation in 0.5% accuracy for the unpolarized light,
and in 7% for the polarized light.
Title: The development of filter vector magnetographs for the Solar
Magnetic Activity Research Telescope (SMART)
Authors: UeNo, Satoru; Nagata, Shin-ichi; Kitai, Reizaburo; Kurokawa,
Hiroki; Ichimoto, Kiyoshi
Bibcode: 2004SPIE.5492..958U
Altcode:
In recent years, it is beginning to be shown observationally and
theoretically that the existence of the magnetic field is indispensable
for active phenomena on the solar surface. In particular, the rotation
or helicity of the magnetic field and their temporal variation are
considered to be important factors which influence solar activity. In
order to confirm this, it is necessary to compute vector components
of the magnetic field with a higher accuracy than before. Therefore,
we developed two kinds of filter-type magnetographs for the Solar
Magnetic Activity Research Telescope (SMART) at Hida observatory, which
allow us to observe the polarization components in sunlight with high
accuracy. We use a Lyot filter in one of two sets of magnetographs. On
the other hand, a tandem-typed Fabry-Perot filter is used in one
more set. For these two instruments, we made the following concrete
advances. 1. The method of coating of the pre-filters. 2. Special
fine-anneal on the main lenses. 3. Highly accurate rotating
wave-plate. 4. Simultaneous observation of two kinds of filtergrams
which have orthogonally polarized light mutually by using Fabry-Perot
channel. 5. Observation in four wavelengths which can suppress various
errors. 6. Low apparent Doppler shift in the FOV due to the oblique
incidence of the rays to the filters. 7. Large format CCD (large-sized
chip, large full-well). 8. High speed data transfer interface between
the CCD and PC. In this paper, we report the details of these points,
the expected effect of them, and the results of initial measurements.
Title: Existence of Nanoparticle Dust Grains in the Inner Solar
Corona?
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Hagino,
Masaoki; Yamamoto, Tetsuya T.
Bibcode: 2004ApJ...608L..69S
Altcode:
Motivated by the recent paper by Habbal et al., we have made
spectroscopic observations in the wavelength range of 1072.8-1079.0
nm of the solar corona above the coronal hole region on several days
using a coronagraph. We made raster scans above the coronal hole
region as well as other coronal regions for comparison. The exposure
time of 200 s at a single location permitted us to detect signals of
the order of 10-7 of the solar disk brightness. We did not
find any indication of emission around 1074.7 nm due to fluorescence
from silicon nanoparticle dust grains in the coronal hole region in the
inner corona proposed by Habbal et al. This may be due to the absence
of silicon nanoparticle dust grains in the coronal hole region or to
our detection limit.
Title: High-cadence Hα imaging of solar flares
Authors: Hanaoka, Y.; Sakurai, T.; Noguchi, M.; Ichimoto, K.
Bibcode: 2004AdSpR..34.2753H
Altcode:
The Hα observation is a powerful tool to study the high-energy
aspect of solar flares. Spiky brightenings of flare kernels at the
Hα center reflect the rapid fluctuation in particle acceleration;
linear polarization of Hα emission might be evidence of accelerated
protons; red-shifts of the Hα line are caused by the chromospheric
evaporation. To study the spiky brightenings of flare kernels with
high-cadence imaging at the Hα center, a high-speed Hα camera for the
Solar Flare Telescope at Mitaka, NAOJ, had been developed and it started
the regular observation in 2001 July. However, the polarimetry and the
Dopplermetry are also important and they are required to be carried
out in parallel with the high-cadence imaging at the Hα center. Then,
we upgraded the original high-speed Hα camera to a new Hα camera
system for the multi-aspect Hα observations, which performs all
of the high-cadence imaging, the linear polarization measurements,
and the off-band imaging for velocity measurements. The new system
started the observation in 2002 July. In this paper, the multi-aspect
Hα imaging system is described and sample Hα images are presented.
Title: Spectroscopic studies of the solar corona using Fe X, XIII,
XIV lines
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Suematsu,
Yoshinori; Takeda, Aki
Bibcode: 2004naoj.book...46S
Altcode:
No abstract at ADS
Title: Spectroscopic observation of coronal waves
Authors: Sakurai, Takashi; Ichimoto, Kiyoshi; Raju, K. P.; Singh,
Jagdev
Bibcode: 2004naoj.book...45S
Altcode:
No abstract at ADS
Title: Flare-induced mhd kink oscillation in coronal multiple loops
Authors: Hori, K.; Ichimoto, K.; Sakurai, T.
Bibcode: 2004cosp...35.1302H
Altcode: 2004cosp.meet.1302H
We provide the first detection of an MHD kink oscillation in the coronal
green line emission (Fe XIV 5303A, 2MK) by a 2D Doppler coronagraph
"NOGIS" at the Norikura Solar Observatory, NAOJ. It was a damping
oscillation in Doppler shifts among an aggregate of face-on coronal
loops that was standing at the solar limb with a streamer on its
top. The oscillation was induced by a mass expansion, which started in
association with an M6.5 flare and later evolved into a partial halo
CME. The oscillation had a period of about 10 min in the inner loops
while about 14 min in the outer loops, and lasted over 100 minutes. We
discuss the trigger and the damping mechanisms of the oscillation. An
application to the Solar-B and STEREO observation will be proposed
for the similar coronal disturbances.
Title: Observation of CMEs with NOrikura Green-line Imaging System
(NOGIS)
Authors: Suzuki, I.; Sakurai, T.; Ichimoto, K.
Bibcode: 2004cosp...35.1948S
Altcode: 2004cosp.meet.1948S
Since 1980s, it has been discussed that CMEs are either planar
loop-like (two-dimensional) or bubble-like (three-dimensional)
structures. Although loop-like configurations were sometimes mentioned,
the majority of opinion is in favor of bubble-like geometry. However,
our view is that this issue has not yet been settled. For investigating
the three-dimensional structure of CMEs, it is important to examine
their driving mechanism and the magnetic field structure around their
associated active regions near the solar surface. NOGIS (NOrikura
Green-line Imaging System) at the Norikura Solar Observatory (NAOJ)
consists of a 10-cm coronagraph and a tunable birefringent filter,
and observes the coronal green-line emission (Fe XIV 5303Å), which
is also one of the lines observed by LASCO C1. This coronagraph has
a field of view of 1.05 -- 1.5R⊙, and can investigate
the appearance of CME onset. Additionally, it can obtain the Doppler
shift images of the green-line corona. We examined all data from 1997,
which is the beginning of observation, to 2003 and found some events
associated with CMEs. And from the Doppler shift images, we found the
loop oscillations by the flare associated with CMEs. We show these
events observed by NOGIS.
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: Fabrication of a bandpass filter for the solar optical
telescope of Solar-B using the IBS
Authors: Waseda, Kouichi; Ichimoto, Kiyoshi
Bibcode: 2004naoj.book...43W
Altcode:
No abstract at ADS
Title: Oscillations in the Coronal Green-Line Intensity Observed at
Lominický Štít and Norikura Nearly Simultaneously.
Authors: Minarovjech, Milan; Rušin, Vojtech; Rybanský, Milan;
Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 2003SoPh..213..269M
Altcode:
We studied intensity oscillations of the coronal green line ([Fe xiv]
530.3 nm) observed with two coronagraphs at Lomnický Štít and
Norikura nearly simultaneously. In the spectroscopic data obtained
at Norikura, we have detected and confirmed the earlier detection
of 5-minute oscillations in photoelectric photometer observations
made at Lomnický Štít. Quasi-periodic structures in the green-line
intensity with a tangential speed up to 400 km s−1 have
been detected for the first time. We briefly discuss the implications
of these oscillations on the coronal heating mechanisms.
Title: Spectroscopic Studies of the Solar Corona. IV. Physical
Properties of Coronal Structure
Authors: Singh, Jagdev; Ichimoto, Kiyoshi; Sakurai, Takashi; Muneer, S.
Bibcode: 2003ApJ...585..516S
Altcode:
We obtained spectrographic observations of several coronal structures
at the limb overlying the sunspot regions, simultaneously in the Fe
XIV (5303 Å) and Fe X (6374 Å) emission lines on several days, and
simultaneously in three coronal emission lines 6374 Å (Fe X), 10747 Å
(Fe XIII), and 10798 Å (Fe XIII) on some other days. The slit width of
160 μm provided a spatial resolution of 4" and a spectral resolution
of 77 mÅ (Fe XIV), 128 mÅ (Fe X), and 291 mÅ (Fe XIII). The width
and intensity of all these lines were computed using Gaussian fits to
the observed line profiles. The FWHM of the emission lines increases
at an average rate of 1.24 mÅ arcsec-1 for Fe X, 0.29 mÅ
arcsec-1 for Fe XIII, and -0.66 mÅ arcsec-1 for
Fe XIV. These values are inversely correlated with the corresponding
ionization temperature for these emission lines. We speculate that the
FWHM of emission lines in coronal structures increases with height if
the associated ionization temperature is less than 1.6×106
K, with the gradient depending upon the ionization temperature of
the line, while it decreases with height for lines whose ionization
temperature is greater than 1.6×106 K. It implies that it
may not always be possible to interpret the observed increase in FWHM
with height in terms of an increase in nonthermal velocity.
Title: High-Speed Hα Camera and the Real-Time Image Processing
System for Solar Observations
Authors: Hanaoka, Yoichiro; Noguchi, Motokazu; Sakurai, Takashi;
Ichimoto, Kiyoshi
Bibcode: 2003SPIE.4853..576H
Altcode:
We have developed a new digital imaging system for the Hα imager
of the Solar Flare Telescope at Mitaka, NAOJ, for high-cadence
observations of solar flares. To resolve individual spikes elementary
bursts) of impulsive solar flares requires a time resolution within
1 s and a spatial resolution of about 1", and the high-speed Hα
camera realized them. Such high-resolution observations produce huge
amount of data, and it has been the major difficulty to construct
a high-cadence system. Generally the amount of data from solar
optical observations is huge, because they are multi-dimensional
(in space/time/wavelength/polarization status). Efficient real-time
processing of observational data is essentially important to extract
meaningful information from the raw data. Recent advances in computer
technology have made possible to handle vast data with a small
computer. Therefore, firstly we have developed a PC-based flexible
real-time image processing system, which is applicable to various
real-time data processings required for solar optical observations. The
high-speed Hα camera is developed based on this system. In this paper,
the real-time image processing system and the high-speed Hα camera
system are described as well as the actual operation of the Hα camera.
Title: Spectroscopic Studies of the Solar Corona - V. Physical
Properties of Coronal Structures
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Muneer, S.
Bibcode: 2003SoPh..212..343S
Altcode:
Spectra around the 6374 Å [Fe x] and 7892 Å [Fe xi] emission lines
were obtained simultaneously with the 25-cm coronagraph at Norikura
Observatory covering an area of 200' '×500' '
of the solar corona. The line width, peak intensity and line-of-sight
velocity for both the lines were computed using Gaussian fits to the
observed line profiles at each location (4' '×4'
') of the observed coronal region. The line-width measurements
show that in steady coronal structures the FWHM of the 6374 Å emission
line increases with height above the limb with an average value of
1.02 mÅ arc sec−1. The FWHM of the 7892 Å line also
increases with height but at a smaller average value of 0.55 mÅ arc
sec−1. These observations agree well with our earlier
results obtained from observations of the red, green, and infrared
emission lines that variation of the FWHM of the coronal emission lines
with height in steady coronal structures depends on plasma temperatures
they represent. The FWHM gradient is negative for high-temperature
emission lines, positive for relatively low-temperature lines and
smaller for emission lines in the intermediate temperature range. Such
a behaviour in the variation of the FWHM of coronal emission lines with
height above the limb suggests that it may not always be possible to
interpret an increase in the FWHM of emission line with height as an
increase in the nonthermal velocity, and hence rules out the existence
of waves in steady coronal structures.
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: High-speed Hα camera for solar flare observations
Authors: Hanaoka, Yoichiro; Noguchi, Motokazu; Ichimoto, Kiyoshi;
Sakurai, Takashi
Bibcode: 2003naoj.book...19H
Altcode:
No abstract at ADS
Title: Development of image stabilization system for solar optical
telescope onboard Solar-B satellite
Authors: Nagata, Shinichi; Shimizu, Toshifumi; Ichimoto, Kiyoshi;
Tsuneta, Saku; Matsuzaki, Keiichi; Kobayashi, Ken
Bibcode: 2003naoj.book....8N
Altcode:
No abstract at ADS
Title: Spectroscopic Studies of the Solar Corona III. Density
Diagnostics Using the Infrared Lines of Fe XIII
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Takeda,
Aki
Bibcode: 2002PASJ...54..807S
Altcode:
We have obtained spectrographic observations of several coronal
regions in three emission lines (6374Å [Fe <FONT SIZE="-2">X
], 10747Å [Fe <FONT SIZE="-2">XIII ], and 10798Å [Fe <FONT
SIZE="-2">XIII ]) simultaneously. The 25-cm coronagraph at Norikura
Observatory and two large-format CCD cameras were used. The peak
intensity, velocity, and line-width values were derived from Gaussian
fits to the observed line profile at each location of the observed
region. The ratio of the intensities of the 10747Å and 10798Å emission
lines in the individual coronal structures range between 1.0 and 2.5
at 10" above the limb, which corresponds to a density range of 9.8 ×
109 - 2.4 × 108 cm-3. The scale-height
temperature values, derived from the variations of the intensity ratio
with height above the limb for all individual coronal structures,
range between 0.6 × 106K and 8.3 × 106K with
a most frequent value around 1.8 × 106K. The large values
of the scale-height temperature for 70% of the structures indicate
that these structures may not be in hydrostatic equilibrium nor be
isothermal in nature.
Title: Spectroscopic Observation of Coronal Waves
Authors: Sakurai, T.; Ichimoto, K.; Raju, K. P.; Singh, J.
Bibcode: 2002SoPh..209..265S
Altcode:
A time sequence over 80 min of coronal green-line spectra was obtained
with a corona- graph at the Norikura Solar Observatory. Doppler
velocities, line intensities, and line widths were derived through
fitting a single Gaussian to the observed line profiles. Coronal waves
have been clearly detected in the Doppler velocity data. The Fourier
analysis shows powers in a 1-3 mHz range, and in higher frequencies
(5-7 mHz) at localized regions. The propagation speed of the waves
was estimated by correlation analysis. The line intensity and line
width did not show clear oscillations, but their phase relationship
with the Doppler velocity indicates propagating waves rather than
standing waves. The existence of Alfvén waves whose speed is 500 km
s−1 or faster is possible but inconclusive, while the
existence of slower waves (of the order of 100 km s−1,
possibly sound waves) is evident. The energy carried by the detected
sound waves is far smaller than the required heat input rate to the
quiet corona.
Title: Observational Study of the Three-Dimensional Magnetic Field
Structure and Mass Motion in Active Regions
Authors: Choudhary, Debi Prasad; Suematsu, Yoshinori; Ichimoto, Kiyoshi
Bibcode: 2002SoPh..209..349C
Altcode:
Spectro-polarimetric observations of active regions were carried
out in the spectral lines of Si i 10827.1 Å and He i 10830 Å to
study the three-dimensional magnetic field structure and associated
plasma flow properties. Comparison of Si i and He i magnetograms
with the potential field model shows that a large fraction of the
magnetic field is consistent with the potential field structure,
by assuming that the height difference between the origin of the two
lines is about 1200 km. The slope of the scatter plot between Si i
and He i magnetograms is 0.5, 0.76 in an emerging flux and a larger
active region, respectively. These values are lower than the scatter
plot slopes obtained from Kitt Peak photospheric and chromospheric
magnetograms, in which case the corresponding values are 0.83 and 0.9,
respectively. Considering the height difference between these two sets
of chromospheric magnetograms, this implies that the magnetic field
spreads out faster near the transition region heights. Dopplergrams
obtained by determining the centroid of the asymmetric line profiles
show that, in case of emerging flux region, the chromospheric upflow
regions are located in the magnetic neutral line areas.
Title: Spectroscopic Studies of the Solar Corona II. Properties of
Green and Red Emission Lines in Open and Closed Coronal Structures
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Suematsu,
Yoshinori; Takeda, Aki
Bibcode: 2002PASJ...54..793S
Altcode:
We obtained profiles of the green (Fe <FONT SIZE="-2">XIV
5303Å) and red (Fe <FONT SIZE="-2">X 6374Å) emission lines
simultaneously on 1998 July18-19 for about 4hours with a cadence
of 10minutes, covering an area of about 200'' × 500'' in the
solar corona. The line width (FWHM), intensity, and Doppler shift
for both lines were computed using Gaussian fits to the observed
line profiles. We then studied any systematic differences in these
parameters between closed and open field structures, and their time
variations. The derived line widths indicate that the FWHM of the red
line increases with height above the limb at a rate of 0.5 - 2.6 mÅ
arcsec-1 and the green-line width decreases with height
at a rate of 1.2 - 3.4 mÅ arcsec-1. The difference in
the time-averaged values of the widths of the green line in open and
closed coronal structures at a given height above the limb is small,
whereas the width of the red line in open structures is substantially
larger than that in the closed loop-like coronal structures.
Title: Contamination evaluation and control for SOLAR-B optical
telescope
Authors: Tamura, Tomonori; Hara, Hirohisa; Tsuneta, Saku; Ichimoto,
Kiyoshi; Kumagai, Kazuyoshi
Bibcode: 2002RNAOJ...6...49T
Altcode:
In space telescopes, the deposition of molecular outgassing from its
component parts may degrade the mirror reflectivity. In the case of the
SOLAR-B visible light telescope, the molecular contamination is even
more threatening since the deposited contaminants, when illuminated by
the ultraviolet light from the sun, not only blacken but also promote
further deposition. We thus started an extensive program to measure
outgassing from all the non-metal material candidates to be used
of the SOLAR-B telescope and to evaluate various chemical-cleaning
(de-oil) procedures for the metal parts. The evaluation is based on
NASA-MSFC-SPEC-1238 specification, and Thermoelectric Quartz Crystal
Microbalance is the primary apparatus for the measurement. We are
able to select the best possible adhesives and de-oil procedures for
the flight model, whenever there are multiple choices. Conditions
for the flight-model vacuum bakeout will also be established based on
the measurements. The program significantly mitigates the risk due to
molecular contamination the SOLAR-B program.
Title: Observation of the total solar eclipse on 21 June 2001
in Zambia
Authors: Takahashi, Noritsugu; Yumoto, Kiyohumi; Ichimoto, Kiyoshi
Bibcode: 2002AstHe..95..179T
Altcode:
On 21 June 2001, path of totality in Angola, Zambia, Zimbabwe,
Mozambique, and Madagascar in Africa. The Japan Scientific Observation
Team, consisting primarily of the members of the Solar Eclipse
Subcommittee of the Committee for International Collaboration in
Astronomy of the Science Council of JAPAN, visited Lusaka in Zambia
to observe the total solar eclipse. Blessed with fine weather, the
observation was successful. The outline of the influence of solar
eclipse on the terrestrial magnetism, polarization of the flash
spectrum, and other observation data, as well as the way educational
activities were carried out, are reported.
Title: High-cadence H-alpha imaging of solar flares
Authors: Hanaoka, Y.; Sakurai, T.; Noguchi, M.; Ichimoto, K.
Bibcode: 2002cosp...34E2277H
Altcode: 2002cosp.meetE2277H
The H-alpha observation is a powerful tool to study the high-energy
aspects of the solar flares. Spiky brightenings of flare kernels at
H-alpha center reflect a rapid fluctuation in particle accelerations;
redshifts of the H-alpha line are caused by chromospheric evaporation;
polarization of H-alpha emission might be evidence of accelerated
protons. Due to the impulsive, rapidly changing nature of the
flares, highcadence image acquisition is required for the H-alpha
observations. We are developing a new digital imaging system for the
H-alpha imager of the Flare Telescope at Mitaka, NAOJ, to carry out
high-cadence observation of solar flares in the H-alpha line. The
problem in the high-cadence observations has been the handling of
huge amount of data produced by such a type of observations, but
the recent advance of the computer technology enables us to handle
vast data with a small computer. We have already started the regular
observation of high-cadence imaging at the H-alpha center with a time
resolution of 1 sec in July 2001 (now it is 0.5 sec), and since then,
we have collaborated with the Yohkoh satellite and RHESSI. Now, the
development of a polarimeter/Dopplermeter system, which will work
in parallel with the H-alpha center imagings, is under way. In the
conference, we will present the system and some observational results.
Title: A High-Speed Hα Camera for Solar Flare Observations
Authors: Hanaoka, Y.; Noguchi, M.; Ichimoto, K.; Sakurai, T.
Bibcode: 2002mwoc.conf..427H
Altcode:
A single 11-year solar activity cycle is going to be covered by the
Yohkoh observations that have started since 1991. In this paper
the changes of coronal structures over the solar activity cycle,
based upon the Yohkoh SXT observations, are reviewed, referring to
previous observations which lead to important concepts for the origin
of the solar activity and comparing with recent observations of the
photosphere and corona by the other satellites.
Title: Plasma Polarization Spectroscopy 5.Measurement of Solar
Magnetic Fields by Means of the Spectro-Polarimetory
Authors: Ichimoto, Kiyoshi
Bibcode: 2002JPFR...78..752I
Altcode:
Magnetic fields play a fundamental role in driving various dynamical
phenomena of the solar atmosphere, and the precise measurement of
photospheric magnetic fields is of vital importance in solar physics
research. A measurement of the spectral line polarizations produced by
the Zeeman effect provides the most powerful means for investigating
solar magnetic fields. The principle of measurements and some aspects
of recent observational results are presented.
Title: Spectroscopic Observation of Coronal Oscillations
Authors: Sakurai, T.; Ichimoto, K.; Raju, K. P.; Singh, J.
Bibcode: 2002mwoc.conf...25S
Altcode:
No abstract at ADS
Title: On the disappearance of H-alpha filaments and soft X-ray
enhancements as seen from Yohkoh SXT
Authors: Singh, Jagdev; Sakurai, T.; Ichimoto, K.
Bibcode: 2001BASI...29..193S
Altcode:
We have studied H-alpha images of the sun taken at Kodaikanal and
Mitaka observatories and soft X-ray images obtained by SXT onboard
Yohkoh for the years 1993 and 94. From events of disappearing quiescent
H-alpha filaments and associated soft X-ray brightenings we find that
in some cases H-alpha filament appears broken and diffused about a day
earlier than beginning of the soft X-ray transient brightening which
lasted for 7 - 10 hours. Further, enhancements began along filament
channels and then moved along arches which were inclined to the
filament direction. From these observations we postulate that heating
of plasma in the filament begins when it appears broken and less dark
and continues till it triggers some physical process, responsible to
begin soft X-ray enhancement. It is not possible to say that if the
H-alpha filament disappears earlier than the beginning of soft X-ray
enhancement or vice versa as there is time difference between H-alpha
and soft X-ray observations.
Title: A universal polarimeter using liquid crystal variable retarders
at the Norikura Solar Observatory
Authors: Shinoda, Kazuya; Ichimoto, Kiyoshi; Fukuda, Takeo; Shin, Junho
Bibcode: 2001RNAOJ...5...97S
Altcode:
A universal Stokes polarimeter was developed for the 25-cm coronagraph
of the Norikura Solar Observatory. The polarimeter utilizes two liquid
crystal variable retarders (LCVR) as the polarization modulator and a
Savart plate as the polarization analyser. By controlling the voltages
applied to LCVRs, modulations of the polarization states are achieved
more flexibly and efficiently in a wavelength range of 450-1,600 nm. The
polarimeter is installed at the primary focus of the coronagraph to
minimize the instrumental polarization caused by optics. Two orthogonal
polarization states are measured simultaneously to minimize the effect
of guiding errors and seeing effects. Combined with the coronagraph and
the high resolution spectrograph at the coude focus, the polarimeter
enables us not only observations of photospheric Zeeman effect but also
various types of diagnostics of the solar atmosphere, including coronal
Zeeman effect, Hanle effect, impact polarization, and Stark effect.
Title: A Spectroscopic Study of the Solar Corona from Norikura and
SOHO data
Authors: Raju, K. P.; Sakurai, T.; Ichimoto, K.
Bibcode: 2001IAUS..203..488R
Altcode:
We report the results from a spectroscopic study of the solar corona,
wherein, we examine some of the current problems in the corona, such
as the plume-interplume differences in coronal holes, coronal loops in
active regions and wave propagation in the corona. The distribution of
emission line intensities, Doppler velocities and line widths in the
corona were obtained from the spectroscopic observations made in the
coronal emission lines from Norikura Coronagraph. The coronal images
in Fe IX,X 171 Å and Fe XII 195 Å from SOHO EIT were used to get
the temperature map of the corona. Combining both, the nonthermal
velocities in the coronal region are obtained without the usual
assumption of a uniform ion temperature. Following results are obtained
from the study. (1) The Doppler velocities show excess blue-shifts
over red-shifts in coronal holes with differences in plume-interplume
regions. (2) The nonthermal velocities show a pronounced difference
between the coronal hole and closed-field regions which points to the
important role of nonthermal broadening mechanism in the acceleration
of fast solar wind. (3) The nonthermal velocities are larger by about
20% at the interplume regions as compared to plumes. This supports
the view that the interplume regions are the source regions of the
fast solar wind. (4) The preliminary analysis of the time sequence
data shows signatures of wave propagation in the corona.
Title: Preliminary study of the evolution of solar magnetic structures
and photospheric horizontal velocity fields
Authors: UeNo, S.; Kitai, R.; Ichimoto, K.; Sakurai, T.; Soltau, D.;
Brandt, P. N.
Bibcode: 2001AdSpR..26.1793U
Altcode:
In October 1997, we made a coordinated observation of the solar
photosphere and chromosphere at Hida observatory (Kyoto university,
Japan) and at Teide observatory (Tenerife) over a 10 day. We obtained
imaging data series continuously during 6 hr 45 min in G-band (4308 Å)
observed with the Domeless Solar Telescope (DST) at Hida on 24th October
(effective FOV; 96″×99″). Additionally, in this observation,
we simultaneously observed image series of the chromosphere during
the latter 4 hr 10 min in H α line center and H α ±0.6 Å. From
these data set, we could detect that emerging flux tubes crossed
the photosphere to the chromosphere and that 'convective collapse'
phenomena appeared at the stage of the spot formation. Moreover,
we confirmed that the lifetime of mesogranulation was about 4000 sec
(70 min) from the temporal evolution of velocity patterns. We show
here only a summary of these observations.
Title: The Physical Conditions in a Polar Coronal Hole and Nearby
Regions from Norikura and SOHO Observations
Authors: Raju, K. P.; Sakurai, T.; Ichimoto, K.; Singh, Jagdev
Bibcode: 2000ApJ...543.1044R
Altcode:
The distribution of emission-line intensities, Doppler velocities, and
line widths in a polar coronal hole and nearby regions are obtained
from the spectroscopic observations carried out on 1998 November 3
at the Norikura Solar Observatory, Japan. The coronal red line [Fe X]
λ6374 that is prominent at coronal hole temperatures is used for the
study. The coronal images in Fe IX and Fe X 171 Å and Fe XII 195 Å
from the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and
Heliospheric Observatory (SOHO) are used to get the temperature map of
the corona at the time of observation. Combining both, we have obtained
the nonthermal velocities in the region without the usual assumption
of a uniform ion temperature. Several plume structures are identified
within the coronal hole, and it is found that line widths are smaller
in plumes than in the interplume regions, which is also reported from
recent SOHO observations. The line-of-sight Doppler velocities in
the coronal hole are larger than those in the quiet region, probably
because of the excess outflow in the coronal hole. A rough negative
correlation between intensity and Doppler velocity, similar to that
between intensity and line width, is observed in the coronal hole. The
typical nonthermal velocity in coronal holes is 24 km s-1
while that in quiet regions is 15 km s-1. The enhanced
nonthermal velocity in the coronal hole is suggestive of the important
role of the nonthermal broadening mechanism in the acceleration of fast
solar wind. Also, the nonthermal velocities are larger (up to 27%) at
the interplume regions as compared to plumes. The findings generally
support the prevailing view that the interplume regions are the source
regions of the fast solar wind.
Title: Magnetic Field Evolution Leading to Solar Flares II. Cases
with High Magnetic Shear and Flare-Related Shear Change
Authors: Li, Hui; Sakurai, Takashi; Ichimoto, Kiyoshi; UeNo, Satoru
Bibcode: 2000PASJ...52..483L
Altcode:
Following Paper I in which we considered five solar flares, we have
selected another three solar flares greater than GOES X-ray class
M/Hα importance 1. The three active regions discussed here are
characterized by high magnetic shear. We investigated the spatial
relationships among Hα flare ribbons, soft X-ray (SXR) flare
loops, and magnetic configurations for the three flares produced
in these active regions. Our results show that only one of these
three flares satisfies the sufficient conditions for a flare to
occur proposed by Hagyard (1990, AAA 052.075.047). We also discuss
the magnetic shear changes around the flaring time only along the
neutral lines associated with the studied flares and over the whole
flaring area. The flare-related changes on the neutral line are small
(2deg-4deg) and the association of these changes
with the flares is not conclusive. The average shear in the flaring
areas of the flares associated with high shear decreases significantly
after the flares and it may be a better parameter to characterize the
flare-related shear changes in such cases.
Title: Magnetic Field Evolution Leading to Solar Flares I. Cases
with Low Magnetic Shear and Flux Emergence
Authors: Li, Hui; Sakurai, Takashi; Ichimoto, Kiyoshi; UeNo, Satoru
Bibcode: 2000PASJ...52..465L
Altcode:
We picked up five solar flares larger than GOES X-ray class M/Hα
importance 1, and studied the magnetic evolution of the corresponding
active regions. In particular, we investigated the spatial relationships
among Hα flare ribbons, soft X-ray (SXR) flare loops, and magnetic
configurations. Our results show that all of these flares are not
associated with high magnetic shear, but with emerging flux, indicating
that flux emergence is a common phenomenon in this kind of solar
flare with low magnetic shear. The maximum values of the transverse
magnetic fields on the neutral lines responsible for these flares are
300-800 G. All of these flares but one have multiple (more than two) Hα
ribbons, and almost all of these ribbons are located at the footpoints
of SXR flare loops. The flare-related shear changes, which can be both
positive and negative, may be determined by the balance of the energy
carried by the emerging flux and that required to power the flare.
Title: Observations of Coronal Oscillations and Waves
Authors: Ichimoto, K.; Singh, J.
Bibcode: 2000ASPC..205...11I
Altcode: 2000ltse.conf...11I
Spectroscopic observations of coronal active regions were performed
with coronagraphs at the Norikura Solar Observatory, and time
variations of intensity and Doppler shift of coronal emission lines
were investigated to study coronal oscillations and waves. It is found
in most observational data that the Doppler signal shows definite
time variabilities compared with the intensity. Periodic variations
were found in Doppler signal with periods ranging from a few minutes
to 40 minutes and amplitudes of 1km/s or less. Recent filter-based
observations give a hint of transient disturbances of Doppler signal
propagating upward in the corona.
Title: On the formation of a helmet streamer on January 24, 1992 at
the south-west limb
Authors: Singh, Jagdev; Sakurai, T.; Ichimoto, K.; Hiei, E.
Bibcode: 2000BASI...28...33S
Altcode:
We have analysed the soft X-ray images of the sun obtained with
the YOHKOH satellite, white light coronal images observed at Mauna
Loa and H-alpha pictures of the sun taken at Mitaka and Kodaikanal
to study helmet streamers. We find that heating of a filament and
subsequent brightening in X-rays, and eruption in the region lead to
the formation of the helmet streamer on January 24, 1992. In another
event of February 24, 1993, only the brightening and eruption-like
expansion of the brightening in soft X-rays lead to the formation of
the streamer. No H-alpha filament was seen in this region before and
after the event of brightening in soft X-rays and formation of streamer
on February 24, 1993. We, therefore, postulate that the plasma in the
streamer comes from the solar surface during the X-ray eruption, and
magnetic field of the region perhaps helps in containing the plasma
and the formation of the streamer.
Title: Active region dynamics
Authors: Harra, L. K.; Matthews, S. A.; Hara, H.; Ichimoto, K.
Bibcode: 2000ssls.work..109H
Altcode:
It has been frequently observed that in solar active regions the
measured line widths are larger than those based on thermal equilibrium
widths. This excess width (characterised as non-thermal velocity,
Vnt) has been proposed as a signature of the heating
mechanism. The behaviour of the Vnt at coronal temperatures
has not produced consistent results with values ranging from 0 to
100 km/s. We investigate this problem by using joint observations
from Norikura Solar Observatory, Japan and the Coronal Diagnostic
Spectrometer (CDS) on SOHO. We find that values of Vnt range
between 10-20 km/s. We analyse the dynamical bahaviour of different
temperature loops and find that for loops with log Te <
5.8, the variability ∝Te0.39. This is comparable
to the dependence of non-thermal velocity on temperature which we have
determined to be Vnt ∝ Te0.35. This
suggests that the excess line broadening is caused by highly dynamical
behaviour in the transition region for active regions. These results
have significant implications for potential heating mechanisms and
these are discussed.
Title: Multi-Wavelength Observations of a Large-Scale Jet and an
Eruptive- Prominence on 28 August 1992
Authors: Watanabe, Ta.; Ashizawa, K.; Nakagawa, Y.; Miyazaki, H.;
Irie, M.; Ichimoto, K.; Kurokawa, H.; Hudson, H.; Yatagai, H.
Bibcode: 1999spro.proc..171W
Altcode:
An eruption of a large (15o) north-south aligned quiescent
prominence and associated coronal disturbance, which took place above
the eastern solar limb near the equator on 28 August 1992, were observed
at a wide range of wavelengths ranging from soft X-rays (Yohkoh) to
microwaves (Nobeyama). The eruption was preceded by the formation of
a large-scale jet which was apparently ejected near the root of the
southern leg of the prominence. The characteristic outward speed of the
jet was 450 km s-1. A potential-field presentation of the
coronal magnetic field suggests that the jet was formed along the open
field which was located immediately to the west of the magnetic arcade,
originally surrounding the eruptive prominence. The temperature of the
jet is suggested to be comparable to that of the nearby quiet corona
(2 × 106 K). In the course of the prominence eruption,
helically twisted loops surrounding the prominence were observed. This
suggests that magnetic reconnection of the sheared arcade took place
underneath the erupting prominence.
Title: An imaging system of coronal green-line with a Lyot filter.
Authors: Imai, H.; Nishino, Y.; Shinoda, K.; Ichimoto, K.
Bibcode: 1999RNAOJ...4..157I
Altcode:
An experimental observation system for taking coronal images in the
green line (Fe XIV 5303 Å) was constructed on the 25 cm coronagraph
of the Norikura Solar Observatory. By re-arranging the birefringent
elements and equipping rotating waveplates on a Lyot filter, the
authors were able to obtain images in coronal green-line and sky
continuum with a high time cadence. It is shown that this system
can provide a powerful tool for diagnosing the physical processes in
coronal transient phenomena.
Title: Shift-and-add reconstruction of solar granulation images
Authors: Baba, N.; Miura, N.; Sakurai, T.; Ichimoto, K.; Soltau, D.;
Brandt, P.
Bibcode: 1999SoPh..188...41B
Altcode:
To restore an atmospherically degraded image of solar granulation the
shift-and-add (SAA) method is applied to its specklegrams. It is the
first time, to the best of our knowledge, that such a technique has
been used for image reconstruction of solar granulation, a largely
extended target. SAA, therefore, enables us to monitor restored images
of solar granulation in a simple and fast way.
Title: Resolution Improvement of Solar Images
Authors: Miura, Noriaki; Baba, Naoshi; Sakurai, Takashi; Ichimoto,
Kiyoshi; Soltau, Dirk; Brandt, Peter
Bibcode: 1999SoPh..187..347M
Altcode:
A method for the improvement of resolution in an observed solar image
is proposed. A blind deconvolution method is used for restoration of an
atmospherically-degraded solar image, and a super-resolution method is
applied to its restored image to improve the resolution. It is confirmed
that a blind deconvolution process can restore fine structures that are
blurred in an observed image, and that the super-resolution process
can make a cutoff frequency in a blind-deconvolved image higher. A
time series of super-resolved images of a sunspot observed with the
70-cm Vacuum Tower Telescope at Teide Observatory is presented.
Title: A New Imaging System of the Corona at Norikura
Authors: Ichimoto, Kiyoshi; Noguchi, Motokazu; Tanaka, Nobuyuki;
Kumagai, Kazuyoshi; Shinoda, Kazuya; Nishino, Tetsuo; Fukuda, Takeo;
Sakurai, Takashi; Takeyama, Norihide
Bibcode: 1999PASJ...51..383I
Altcode:
A new imaging system of the coronal green line (Fe XIV 5303
Angstroms) was constructed at the Norikura Solar Observatory. The
system consists of a 10-cm coronagraph, a tunable Lyot filter, and
a cooled CCD camera. The transmission curve of the Lyot filter can
be modulated by two liquid-crystal variable retarders. This scheme
provides quick wavelength tuning and efficient subtraction of sky
background. Two-dimensional distributions of the intensity and
Doppler shift of the coronal green line can be obtained within 30
seconds with accuracies of better than 10-6I_Solar and 1 km
s-1. Regular operation was started in 1997 September. The
aim of the new system is to investigate plasma motions associated with
the magnetic field reconnection and waves in the solar corona.
Title: Dynamics of solar active region loops
Authors: Harra-Murnion, L. K.; Matthews, S. A.; Hara, H.; Ichimoto, K.
Bibcode: 1999A&A...345.1011H
Altcode:
It has been frequently observed that in solar active regions the
measured line widths are larger than those based on thermal equilibrium
widths. This excess width (characterised as non-thermal velocity,
Vnt) has been proposed as a signature of the heating
mechanism. The behaviour of the Vnt at coronal temperatures
has not produced consistent results with values ranging from 0 to 100
km s(-1) . We investigate this problem by using joint observations
from Norikura Solar Observatory, Japan and the Coronal Diagnostic
Spectrometer (CDS) on SOHO. With CDS we determine temperatures, and
with Norikura we obtain accurate line widths for Fe XIV (~2 MK). We
find that values of Vnt range between 10-20 km s(-1) . We
analyse the dynamical behaviour of different temperature loops and
find that for loops with Log T_e < 5.8, the variability ~ T_e(0.39)
. This is comparable to the dependence of non-thermal velocity on
temperature which we have determined to be Vnt ~ T_e(0.35)
. This suggests that the excess line broadening is caused by highly
dynamical behaviour in the transition region for active regions. These
results have significant implications for potential heating mechanisms
and these are discussed.
Title: Spectroscopic Studies of the Solar Corona I. Spatial Variations
in Line Parameters of Green and Red Coronal Lines
Authors: Singh, Jagdev; Ichimoto, Kiyoshi; Imai, Hideki; Sakurai,
Takashi; Takeda, Aki
Bibcode: 1999PASJ...51..269S
Altcode:
We obtained simultaneously profiles of the coronal green line (Fe
XIV 5303 { Angstroms}) and red line ([Fe X] 6374 { Angstroms}) on a
number of days at several regions covering an area of about 200''times
500'' in the solar corona. The intensity, velocity, and width for
both of these lines were computed by making a Gaussian fit to the
observed line profile. We find that in coronal structures the spatial
variations in the red and green line intensities are correlated. The
ratio of green- to red-line intensities varies between 0.6--9.2 for
different coronal structures. The value of the intensity ratio in an
individual coronal structure also varies with height above the solar
limb along the structure. The range of values of the intensity ratio
observed implies that most of the structures under investigation had
a temperature in the range of 1.2--1.6times 106 K. Also,
we find that in coronal structures the width of the red line increases
with height above the limb, whereas the green-line width in the same
region decreases with height. This behavior of the line widths can be
explained if we assume the mixing of plasma in the middle and higher
portions of the coronal structures by microturbulence or traveling
waves, which have been detected recently. No Hα loops and activity
were seen in these regions during the observation periods.
Title: Microscopic Nonthermal Plasma Motions of Coronal Loops in a
Solar Active Region
Authors: Hara, H.; Ichimoto, K.
Bibcode: 1999ApJ...513..969H
Altcode:
We present a spectroscopic observation of a solar active region NOAA
7590 with a coronagraph at the Norikura Solar Observatory, which
provides high-resolution spectra of the visible coronal emission lines
(Fe X λ6374, Fe XIV λ5303, Ca XV λ5694) with a spatial sampling
of 2.0"×2.3". Nonthermal velocities (ξ) estimated from Fe X λ6374,
Fe XIV λ5303, and Ca XV λ5694 in this observation are 14-20, 10-18,
and 16-26 km s-1, respectively. The first two results are
consistent with the results obtained by Cheng et al. and others. Even
in the Ca XV structures the present observation does not confirm the
large nonthermal velocity of 40-60 km s-1 to be typical
value. The hypothesis that the nonthermal width in coronal emission
lines is due to coronal Alfvén waves is tested by carefully examining
the relationship between the width of coronal emission lines and
orientation of coronal loops to the line-of-sight direction. From the
comparison between edge-on loops in which the direction of magnetic
field is nearly parallel to the line-of-sight direction and face-on
loops in which the magnetic field is almost perpendicular to the
line-of-sight direction, the full width at half-maximum (FWHM) of
coronal emission lines for the edge-on loop appears to become smaller
near the loop top than that for the face-on loops. The obvious decrease
of FWHM of 0.04-0.07 Å (Δξ=3-5 km s-1) is found in the
Fe XIV edge-on loops. Although this may be evidence for the Alfvén
waves in coronal loops, the velocity amplitude seems to be too small
to explain all the nonthermal velocity reported so far.
Title: Stray-Light Effect on Magnetograph Observations
Authors: Chae, Jongchul; Yun, Hong Sik; Sakurai, Takashi; Ichimoto,
Kiyoshi
Bibcode: 1998SoPh..183..229C
Altcode:
To examine the stray-light effect in magnetograph observations, we
have determined the point spread functions of the vector magnetograph
mounted on the Japanese Solar Flare Telescope based on two indirect
methods, one analyzing the solar limb intensity profile, and the
other using the Fourier power spectra of photospheric intensity
distributions. Point spread functions consist of two parts: a blurring
part which describes seeing and small-spread-angle stray light, and
a scattering part which describes large-spread-angle stray light. The
FWHM spatial resolution is typically 3.0'', and the amount of scattered
light is about 15% on clear days. We find that the blurring part is
well described by a Moffat function whose Fourier transform is given
by an exponential function. Our results indicate that polarization
measurements of low-intensity magnetic elements like sunspots may be
significantly underestimated due to the large-spread-angle stray light,
and polarization measurements of magnetic elements which are smaller
than 5-7'' appear to be disturbed by small-spread-angle stray light.
Title: Stray-light correction in magnetograph observations using
the maximum entropy method
Authors: Chae, Jongchul; Yun, Hong Sik; Sakurai, Takashi; Ichimoto,
Kiyoshi
Bibcode: 1998SoPh..183..245C
Altcode:
We have developed a method of stray-light correction which is applicable
to filter-based magnetograph observations. Stray-light-corrected Stokes
images are obtained by performing the deconvolution of observed Stokes
images by the point spread function which is determined from the Stokes
I image. For image deconvolution, the maximum entropy principle is
used to guarantee that intensity should be positive and polarization
degrees should be less than unity. We present an iterative algorithm
for the maximum entropy method, which seeks the solution in Fourier
space and thus accomplishes fast convergence. We find that our method
is effective in correcting stray light which has a spread angle greater
than the full width at half maximum of the point spread function. We
also discuss the effect of stray light on magnetograph calibration.
Title: Multi-wavelength observations of POST flare loops in two long
duration solar flares
Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi,
L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.;
Sakao, T.; Ichimoto, K.
Bibcode: 1998A&A...337..911H
Altcode:
We have analysed two Long Duration solar Events (LDEs) which produced
large systems of Post Flare Loops (PFLs) and which have been observed by
Yohkoh and ground-based observatories. Using the Maximum Entropy Method
(MEM) image synthesis technique with new modulation patterns we were
able to make hard X-ray (HXR) images of the post flare loops recorded
in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We
obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6)
K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray
(SXR) loops lie higher than the Hα loops and the former are overlaid
by HXR emission. This is suggestive of the magnetic reconnection
process. However some details are not consistent with the standard
models. Firstly the separation between the HXR source and the SXR
loop increases with time, with the HXR source being approximately
a factor of five larger than the equivalent source in impulsive
flares. Secondly the cooling times deduced from observations are longer
than the theoretically expected ones and the discrepancy increases
with time. We review the current models in view of these results.
Title: Radiation testing of optical glasses and crystals for Solar-B
optical instruments.
Authors: Nishino, Y.; Suematsu, Y.; Tsuneta, S.; Ichimoto, K.; Kobiki,
T.; Takeyama, N.
Bibcode: 1998RNAOJ...3..145N
Altcode: 1998RNOAJ...3..145N
This report gives some results of γ-ray irradiation (Co60
source) testing on optical glasses and crystals which may be used
in the next Japanese solar space mission Solar-B. Ordinary optical
glasses darken when exposed to high-energy radiation which is present
in natural space environment. In case of Solar-B, whose orbit will be
polar-sun-synchronous, the satellite will undergo the total dose of
more than 1000 krad in five years. Hence it is very crucial for the
success of the mission to know the feasibility of transmitting optical
elements in space. The authors tested two kinds of fused silica, a
fluorite, and ten kinds of UV transmitting glasses. Calcite was also
tested. It was found that the fused silica is radiation-resistant but
the other glasses and the fluorite are nonresistant and become quite
opaque in UV and visible wavelength regions after the irradiation.
Title: Solar Active Region: Heating and Dynamics
Authors: Harra-Murnion, L. K.; Matthews, S. A.; Hara, H.; Ichimoto, K.
Bibcode: 1998sxmm.confE..85H
Altcode:
No abstract at ADS
Title: An Interdisciplinary Study of the Eruptive Prominence of 28
August 1992
Authors: Watanabe, Ta.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto,
K.; Kurokawa, H.; Yatagai, H.
Bibcode: 1998ASSL..229..101W
Altcode: 1998opaf.conf..101W
No abstract at ADS
Title: Horizontal Flow Field in the Solar Photosphere
Authors: Kitai, R.; Funakoshi, Y.; Ueno, S.; Sano, S.; Ichimoto, K.
Bibcode: 1998ASSL..229..319K
Altcode: 1998opaf.conf..319K
No abstract at ADS
Title: Spectroscopic Study of a Quiescent Prominence
Authors: Park, Y. D.; Yun, H. S.; Ichimoto, K.; Sim, K. J.; Moon,
Y. -J.
Bibcode: 1998ASPC..150..217P
Altcode: 1998IAUCo.167..217P; 1998npsp.conf..217P
No abstract at ADS
Title: HeI 10830 Intensity Oscillation in Quiescent Prominences
Authors: Park, Y. D.; Yun, H. S.; Ichimoto, K.
Bibcode: 1998asct.conf...95P
Altcode:
No abstract at ADS
Title: Joint Observations of an Active Region with Norikura and CDS
Authors: Harra-Murnion, L. K.; Matthews, S. A.; Hara, H.; Ichimoto, K.
Bibcode: 1998ASPC..155..346H
Altcode: 1998sasp.conf..346H
No abstract at ADS
Title: Soft X-ray Observations of Eruptive Prominences
Authors: Watanabe, T.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto,
K.; Kurokawa, H.; Yatagai, H.
Bibcode: 1998ASPC..150..376W
Altcode: 1998IAUCo.167..376W; 1998npsp.conf..376W
No abstract at ADS
Title: Coronal and Interplanetary Disturbances Associated with an
Eruptive Prominence of 28 August 1992
Authors: Watanabe, T.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto,
K.; Kurokawa, H.; Yatagai, H.
Bibcode: 1998asct.conf..313W
Altcode:
No abstract at ADS
Title: On the correlation between line width and line depth of the
solar HeI 1083 NM line
Authors: Venkatakrishnan, P.; Sakurai, T.; Suematsu, Y.; Ichimoto, K.
Bibcode: 1997BASI...25..527V
Altcode:
No abstract at ADS
Title: Measurement of the coronal electron temperature at the total
solar eclipse on 1994 November 3.
Authors: Ichimoto, K.; Kumagai, K.; Sano, I.; Kobiki, T.; Sakurai,
T.; Munoz, A.
Bibcode: 1997ASIC..494...31I
Altcode: 1997topr.conf...31I
The coronal electron temperature was determined for the first time from
the shape of weak depressions at 3900 Å and 4300 Å in the continuous
coronal spectra. It was found that the coronal streamer has overall
temperatures of about 1.5 - 1.7 MK, while the coronal hole has evidently
lower temperature of 0.9 - 1.1 MK. No significant height variation of
the temperature was found in the streamer, while the coronal hole shows
evidence of increasing temperature with height. An acceleration of the
expanding motion between 1.1 Rsun and 2.0 Rsun
by ≡80 km s-1 was found in the streamer.
Title: Measurement of the Coronal Electron Temperature at the Total
Solar Eclipse on 1994 November 3
Authors: Ichimoto, Kiyoshi; Kumagai, Kazuyoshi; Sano, Issei; Kobiki,
Toshihiko; Munoz, Alberto; Sakurai, Takashi
Bibcode: 1996PASJ...48..545I
Altcode:
A spectroscopic observation was carried out at the total solar eclipse
on 1994 November 3 in Putre, Chile, in order to investigate the electron
temperature and the expanding motion of the corona. The shape of weak
depressions at 3900 Angstroms and 4300 Angstroms in the continuous
coronal spectra was compared with the theoretical electron-scattered
coronal spectra; thus, the magnitude of the electron thermal motion was
determined directly. It was found that a coronal streamer on the eastern
limb and a coronal hole on the south-pole have overall temperatures of
about 1.5--1.7 MK and 0.9--1.1 MK, respectively. No significant height
variation in the temperature was found in the streamer, while the
coronal hole shows evidence of increasing temperature with height. An
acceleration of the expanding motion between 1.1 RO and 2.0 RO by ~
80 km s(-1) was found in the streamer.
Title: Enhanced He{I} Absorption at the Feet of Solar X-Ray Loops
Authors: Venkatakrishnan, P.; Sakurai, Takashi; Suematsu, Yoshinori;
Ichimoto, Kiyoshi
Bibcode: 1996PASJ...48L...1V
Altcode:
A comparison of He{I} spectroheliograms and Yohkoh soft X-ray images
of active regions indicates that He{I} absorption is enhanced at
the feet of hot X-ray loops. It is suggested that the conduction of
heat from the loops into the transition region at their feet would
produce enhanced transition-region emission around 50 eV that would
in turn cause enhanced excitation of He{I} leading to the excess He{I}
absorption that is observed.
Title: A Coronal Velocity Field around a Long-Duration Event: Search
for Reconnection Inflow
Authors: Hara, H.; Ichimoto, K.
Bibcode: 1996ASPC..111..183H
Altcode: 1997ASPC..111..183H
A coronal Doppler velocity field around an LDE-type solar flare at
the peak phase is presented from observations with a ground-based
coronagraph in a visible coronal emission line (Fe XIV 5303 Å). The
flare loop was in an edge-on configuration to the line-of-sight
direction. At the peak phase, the authors could not find any high-speed
flow around the flare loop, corresponding to the reconnection inflow
whose speed is 0.01 - 0.1 of the Alfvén speed. On the other hand,
high-velocity components exceeding 10 km s-1 and large line
broadening in the emission line were observed near the brightest part
of the flare loop in the decay phase.
Title: X-ray and Magnetic Features of H alpha Surges
Authors: Okubo, A.; Matsumoto, R.; Miyaji, S.; Akioka, M.; Zhang,
H.; Shimojo, M.; Nishino, Y.; Ichimoto, K.; Shibata, K.; Sakurai, T.
Bibcode: 1996mpsa.conf..437O
Altcode: 1996IAUCo.153..437O
No abstract at ADS
Title: Measurement of the Coronal Electron Temperature at the Total
Solar Eclipse on 3rd Nov. 1994
Authors: Ichimoto, K.; Kumagai, K.; Sano, I.; Kobiki, T.; Sakurai,
T.; Munoz, A.
Bibcode: 1996mpsa.conf..413I
Altcode: 1996IAUCo.153..413I
No abstract at ADS
Title: Spectroscopic Analysis of Prominence Hα CAII H and K and
Hei 10830
Authors: Park, Y. D.; Yun, H. S.; Ichimoto, K.
Bibcode: 1995JApAS..16..384P
Altcode:
No abstract at ADS
Title: Coordinated Observation of the Solar Corona Using the Norikura
Coronagraph and the YOHKOH Soft X-Ray Telescope
Authors: Ichimoto, K.; Hara, H.; Takeda, A.; Kumagai, K.; Sakurai,
T.; Shimizu, T.; Hudson, H. S.
Bibcode: 1995ApJ...445..978I
Altcode:
Spectroscopic observations of coronal emission lines were carried
out at the Norikura Solar Observatory in cooperation with the soft
X-ray telescope on board the Yohkoh satellite to study the plasma
distributions at different temperatures. Intensity and velocity
distributions in Fe XIV wavelength 5303 (green), Fe X wavelength
6374 (red), and Ca XV wavelength 5694 (yellow) lines are compared
with the soft X-ray images. It is found that the soft X-ray images
closely resemble those of the yellow line that represents a rather
high temperature component of the corona. On the other hand the
low-temperature component seen in the green and the red lines shows
quite a different distribution from that of the high-temperature
component; the low-temperature component consists of many thin loops
or streaks, while the high-temperature component is more diffuse. We
find that the active elements of the cool component, i.e., complex
loop systems, rapid changes of small structures, and localized large
plasma motions, all tend to be cospatial with the hot component.
Title: An Imaging Observation of the Solar Corona in the Green Line
with a Fabry-Perot Interferometer on a Coronagraph
Authors: Ichimoto, Kiyoshi; Ohtani, Hiroshi; Ishigaki, Tsuyoshi;
Maemura, Hiroyuki; Noguchi, Motokazu
Bibcode: 1995PASJ...47..383I
Altcode:
By using a scanning Fabry-Perot interferometer on a coronagraph, an
imaging observation of the solar corona in the emission line (Fe XIV
5303 Angstroms) was carried out. Subtraction of the scattered light
was performed by changing the central wavelength of the transmission
of the etalon, and thus a two-dimensional distribution of the
emission line intensity was obtained with both high accuracy and high
time resolution. The observed active region (NOAA 7576) was fairly
stationary, showing no distinct active phenomena; the green line image
showed more or less a similar distribution with the soft X-ray images
obtained by the Yohkoh satellite. The observed characteristics can
be attributed to the absence of a hot (3--5 MK) coronal component in
this active region. The superiority of Fabry-Perot interferometry for
imaging observations in the coronal emission lines is also discussed.
Title: Simultaneous Multifrequency Observations of an Eruptive
Prominence at Millimeter Wavelengths
Authors: Irimajiri, Yoshihisa; Takano, Toshiaki; Nakajima, Hiroshi;
Shibasaki, Kiyoto; Hanaoka, Yoichiro; Ichimoto, Kiyoshi
Bibcode: 1995SoPh..156..363I
Altcode:
Radio images and spectra of an eruptive prominence were obtained
from simultaneous multifrequency observations at 36 GHz, 89 GHz,
and 110 GHz on May 28, 1991 with the 45-m radio telescope at Nobeyama
Radio Observatory (NRO), the National Astronomical Observatory, Japan
(NAOJ). The radio spectra indicated that the optical depth is rather
thick at 36 GHz whereas it is thin at 89 and 110 GHz. The Hα data,
taken at Norikura Solar Observatory, NAOJ, suggest that the eruption of
an active region filament was triggered by an Hα flare. The shape and
position of the radio prominence generally coincided with those of Hα
images. The radio emission is explained with an isothermal cool thread
model. A lower limit for the electron temperature of the cool threads
is estimated to be 6100 K. The range of the surface filling factors
of the cool threads is 0.3-1.0 after the Hα flare, and 0.2-0.5 in the
descending phase of the eruptive prominence. The column emission measure
and the electron number density are estimated to be of the order of
1028 cm−5 and 1010 cm−3,
respectively. The physical parameters of a quiescent prominence are also
estimated from the observations. The filling factors of the eruptive
prominence are smaller than those of the quiescent prominence, whereas
the emission measures and the electron densities are similar. These
facts imply that each cool thread of the prominence did not expand
after the eruption, while the total volume of the prominence increased.
Title: Solar Flare Telescope at Mitaka
Authors: Sakurai, Takashi; Ichimoto, Kiyoshi; Nishino, Yohei; Shinoda,
Kazuya; Noguchi, Motokazu; Hiei, Eijiro; Li, Ting; He, Fengbao; Mao,
Weijun; Lu, Haitian; Ai, Guoxiang; Zhao, Zhaowang; Kawakami, Singo;
Chae, Jong-Chul
Bibcode: 1995PASJ...47...81S
Altcode:
A new solar telescope constructed recently at Mitaka, Tokyo, is
described. This instrument, called the Solar Flare Telescope, comprises
four telescopes which respectively perform: (1) magnetic-field vector
measurements, (2) Doppler-velocity measurements, (3) Hα observations,
and (4) continuum observations. The instrument has been operated as
a ground-based support for the X-ray satellite Yohkoh launched in
1991 August.
Title: Measurement of the Coronal Electron Temperature at the Total
Solar Eclipse on November 3, 1994
Authors: Ichimoto, K.; Kumagai, K.; Sano, Y.; Kobiki, T.; Sakurai,
T.; Munos, A.
Bibcode: 1995pist.conf...72I
Altcode:
No abstract at ADS
Title: He I λ1083nm Observations and Chromospheric and Coronal
Activities
Authors: Suematsu, Y.; Ichimoto, K.; Sakurai, T.
Bibcode: 1995itsa.conf..413S
Altcode:
No abstract at ADS
Title: The Magnetic Evolution of the Activity Complex AR:7260 -
a Roadmap
Authors: Leka, K. D.; Canfield, R. C.; Mickey, D. L.; van
Driel-Gesztelyi, L.; Nitta, N.; Sakurai, T.; Ichimoto, K.
Bibcode: 1994SoPh..155..301L
Altcode:
The active region NOAA 7260 rotated onto the north solar hemisphere
as a mature bipole: a dominant negative-polarity sunspot with trailing
plage and scattered small spots in attendance. The dominantp spot itself
had strong magnetic fields and covered almost 400 × 10−6
of a solar hemisphere. For a period of seven days beginning 14 August,
1992 this active region displayed rapid and drastic evolution: no fewer
than 50 magnetic bipoles emerged in the area trailing the large sunspot,
increasing the region's magnetic flux by more than 1022
Mx. This new group of sunspots formed a complexβγδ configuration
with twoδ spots and a high degree of magnetic shear.
Title: Peculiar magnetic field evolution of active region NOAA 7562
in August 1993 - results from campaign observation with Yohkoh
Authors: Sakurai, T.; Suematsu, Y.; Ichimoto, K.; Kurokawa, H.; Kitai,
R.; Akioka, M.; Tohmura, I.; Soltau, D.; Mickey, D. L.; Zhang, H.;
Li, W.; Zirin, H.; Tang, F.
Bibcode: 1994ESASP.373..337S
Altcode: 1994soho....3..337S
No abstract at ADS
Title: Spectroscopic Observations of Coronal Emission Lines and
their Relation to Soft X-ray Images
Authors: Ichimoto, K.; Kumagai, K.; Sakurai, T.; Hara, H.; Takeda,
A.; YOHKOH SXT Team
Bibcode: 1994kofu.symp..113I
Altcode:
Spectroscopic observations of coronal emission lines were carried out
to obtain the plasma distribution at different temperatures. Images
in FeXIV5303A(green), FeX6374A(red) and CaXV5694A(yellow) are compared
with the soft X-ray images taken with the Soft X-ray Telescope on board
Yohkoh. It is found that the distributions of green and red lines are
quit different from that of the soft X-rays, while the yellow line
shows quite similar distribution.
Title: A Morphological Study of Magnetic Shear Development in a
Flare-Productive Region NOAA 7270
Authors: Kurokawa, H.; Kitai, R.; Kawai, G.; Shibata, K.; Yaji, K.;
Ichimoto, K.; Nitta, N.; Zhang, H.
Bibcode: 1994kofu.symp..283K
Altcode:
The evolutional changes of a flare-productive region NOAA 7270 were
examined in details with high resolution H_alpha images, magnetograms
and soft X-ray images to study the process of the magnetic shear
development and its relation to the strong flare activity of the
region. This study led us to the following results and a conclusion:(1)
Several new bipolar pairs simultaneously and or successively emerged in
NOAA 7270 from 5 through 7 September. (2) Magnetic shear configurations
developed at three locations, where most of flares occurred from 5
through 7 , September. (3)These magnetic shear configurations were
formed by successive emergences of twisted magnetic ropes from below
the photosphere.
Title: Flares in Active Region NOAA 7260 - Role of Emerging Flux
Authors: Nitta, N.; Driel-Gesztelyi, L. V.; Leka, K. D.; Mickey, D. L.;
Metcalf, T. R.; Wuelser, J. -P.; Ichimoto, K.; Sakurai, T.; Shibata, K.
Bibcode: 1994kofu.symp..385N
Altcode:
Active region NOAA 7260 exhibited remarkable flare activity as an
emerging flux region appeared in the following part and evolved into
the delta configuration. While it is difficult to associate an emerging
bipole with a flare both temporally and spatially, there is an overall
correlation of the total darkness integrated over of the sunspot area,
as measured in the Yohkoh/SXT white-light images, with the soft X-ray
flux and flare occurrence. It appears that the flares in the emerging
flux region occurred preferentially at locations close to the spot of
preceding polarity that emerged in the earliest evolution of the region.
Title: Electron precipitation and mass motion in the 1991 June 9
white-light flare
Authors: de La Beaujardiere, J. -F.; Canfield, R. C.; Metcalf, T. R.;
Hiei, E.; Sakurai, T.; Ichimoto, K.
Bibcode: 1994SoPh..151..389D
Altcode:
We use Hα line profiles as a diagnostic of mass motion and
nonthermal electron precipitation in the white-light flare (WLF) of
1991 June 9 01:34 UT. We find only weak downflow velocities (≈10 km
s−1) at the site of white-light emission, and comparable
velocities elsewhere.We also find that electron precipitation is
strongest at the WLF site. We conclude that continuum emission in this
flare was probably caused by nonthermal electrons and not by dynamical
energy transport via a chromospheric condensation.
Title: Behavior of Accelerated Electrons in a Small Impulsive Solar
Flare on 1992 August 12
Authors: Takano, Toshiaki; Enome, Shinzo; Nakajima, Hiroshi; Shibasaki,
Kiyoto; Nishio, Masanori; Hanaoka, Yoichiro; Torii, Chikayoshi;
Sekiguchi, Hideaki; Bushimata, Takeshi; Kawashima, Susumu; Shinohara,
Noriyuki; Irimajiri, Yoshihisa; Koshiishi, Hideki; Kosugi, Takeo;
Shiomi, Yasuhiko; Sakurai, Takashi; Ichimoto, Kiyoshi
Bibcode: 1994PASJ...46L..21T
Altcode:
A GOES C1.0-class impulsive flare was observed by the new Nobeyama
Radioheliograph on 1992 August 12 with 1 s temporal and 10('') spatial
resolutions at 17 GHz. The radio flare consisted of an impulsive phase
of ~ 20 s and a decay phase of ~ 90 s. Radio images showed double
sources in the impulsive phase, whereas in the decay phase a single
elongated source appeared which connected the double sources. Soft
X-ray images with Yohkoh/SXT show that the radio double sources
correspond to foot points of newly appearing coronal loops and the
single source was located at the top of one of the loops. The radio
emission for both phases can be explained by gyrosynchrotron radiation
from accelerated electrons. These loops began to brighten at their
intersecting point ~ 1 min before the radio flare. All of these facts
suggest that the reconnection of magnetic fields heated up the coronal
loops and produced accelerated electrons, which ran through the loops,
precipitated onto the foot points, and caused the radio flare. Less
than 1% of the electrons were mirrored at the foot points and trapped
at the top of the loop. The lack of radio emission in the loop top area
during the impulsive phase implies that the accelerated electrons were
highly beamed.
Title: Optical and SXT Observations of the x9 Flare of Nov. 1992
Authors: Ichimoto, K.; Sakurai, T.; Nishino, Y.; Noguchi, M.; Shinoda,
K.; Yamaguchi, A.; Kumagai, K.; Hirayama, T.; Tsuneta, S.; Acton, L.
Bibcode: 1994xspy.conf..259I
Altcode:
No abstract at ADS
Title: Some Compact Flares Take Place in the Intersection of
Magnetic Loops
Authors: Ai, G.; Li, W.; Hirayama, T.; Ichimoto, K.
Bibcode: 1994xspy.conf...79A
Altcode:
No abstract at ADS
Title: Flares in Active Region NOAA 7260
Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Sakurai,
T.; Shibata, K.; Ichimoto, K.; Canfield, R. C.; Wülser, J. -P.;
Metcalf, T. R.; Mickey, D. L.
Bibcode: 1994xspy.conf..111N
Altcode:
No abstract at ADS
Title: X-Ray Activity in Coronal Loops and its
Photospheric/chromospheric Signatures
Authors: Sakurai, T.; Shibata, K.; Ichimoto, K.; Takata, M.
Bibcode: 1994xspy.conf...37S
Altcode:
No abstract at ADS
Title: Observation of a Large Eruptive Hα Prominence with Soft
X-Rays on 30-31 July 1992
Authors: Miyazaki, H.; Miyasita, M.; Yamaguchi, A.; Ichimoto, K.;
Kumagai, K.; Hirayama, T.; Tsuneta, S.
Bibcode: 1994xspy.conf..277M
Altcode:
No abstract at ADS
Title: Construction of magneto-otical filters and their application
to solar observations.
Authors: Miyazaki, H.; Sakurai, T.; Okamoto, T.; Ichimoto, K.;
Miyashita, M.; Koyama, K.; Sakata, A.; Wada, S.
Bibcode: 1993RNAOJ...2..417M
Altcode: 1993RNOAJ...2..417M
The magneto-optical filter (MOF) is made of a transparent cell placed in
a strong magnetic field. The cell contains the vapor of material like
sodium. By utilizing the magneto-optical effect near the wavelength
of a spectral line, MOF provides a very narrow and stable passband,
which is particularly suitable for helioseimological observations. The
cell becomes less transparent as it ages, and can only be used in
observations for several months. The authors' aim was to construct a
filter that can be continuously used for several years without losing
the sodium vapor at the cell wall. This was achieved by heating the
whole cell to about 200°C.
Title: Flares in Active Region NOAA 7260 - Role of Emerging Flux
and Reconnection
Authors: Nitta, N.; Drel-Gesztelyi, L. V.; Leka, K. D.; Mickey, D. L.;
Metcalf, T. R.; Wuelser, J. -P.; Ichimoto, K.; Sakurai, T.; Shibata, K.
Bibcode: 1993BAAS...25.1223N
Altcode:
No abstract at ADS
Title: Solar Flare Telescope project.
Authors: Ichimoto, K.; Sakurai, T.; Hiei, E.; Nishino, Y.; Shinoda, K.;
Noguchi, M.; Imai, H.; Irie, M.; Miyashita, M.; Tanaka, N.; Kumagai,
K.; Sano, I.; Suematsu, Y.; Okamoto, T.; Miyazaki, H.; Fukushima,
H.; Yose, Y.; Zhao, Z. W.
Bibcode: 1993RNAOJ...1..375I
Altcode: 1993RNOAJ...1..375I
The Solar Flare Telescope was built at Mitaka in 1989. This instrument
comprises four telescopes which observe (1) Hα images, (2) continuum
images, (3) vector magnetic fields, and (4) Doppler velocities,
respectively. The instrument aims at the study of energy build-up
and energy release in solar flares, in cooperation with the Solar-A
satellite (Yohkoh). The Solar Flare Telescope has been in operation
since 1990 December.
Title: Magnetic Field Observation with the Solar Flare Telescope
Authors: Ichimoto, K.; Sakurai, T.; Nishino, Y.; Shinoda, K.; Noguchi,
M.; Kumagai, K.; Imai, H.; Irie, M.; Miyashita, M.; Tanaka, N.; Sano,
I.; Suematsu, Y.; Hiei, E.
Bibcode: 1993ASPC...46..166I
Altcode: 1993IAUCo.141..166I; 1993mvfs.conf..166I
No abstract at ADS
Title: Observations of X-ray Jets Using YOHKOH Soft X-Ray Telescope
Authors: Shibata, K.; Ishido, Y.; Acton, L.; Strong, K.; Hirayama,
T.; Uchida, Y.; McAllister, A.; Matsumoto, R.; Tsuneta, S.; Shimizu,
T.; Hara, H.; Sakurai, T.; Ichimoto, K.; Nishino, Y.; Ogawara, Y.
Bibcode: 1993ASPC...46..343S
Altcode: 1993IAUCo.141..343S; 1993mvfs.conf..343S
No abstract at ADS
Title: Correlation between X-ray Temporal Variability and Magnetic
Environment in Solar Flares
Authors: Nitta, N.; Harvey, K.; Hudson, H.; Ichimoto, K.; Metcalf,
T.; Mickey, D.; Sakai, J. -I.; Sakao, T.; Sakurai, T.; Takahashi, M.
Bibcode: 1992AAS...181.5503N
Altcode: 1992BAAS...24.1211N
The X-ray time history of a solar flare can reflect basic processes of
heating and/or acceleration, which in turn may depend on the magnetic
environment of the site. Some flares show a simple rise and fall
temporal behavior, whereas others show more than one peak. Comparisons
of images taken by the Soft X-ray Telescope (SXT) aboard the Yohkoh
spacecraft with ground-based magnetic data (Hawaii, Kitt Peak and
Mitaka) reveal that, at least for a flare-productive active region
(NOAA 7260), flares with double-peaked and single-peaked time profiles
occurred at systematically different locations within the region. We
discuss this result in terms of theoretical models, especially those
of coalescence of two current loops.
Title: Flare-Related Relaxation of Magnetic Shear as Observed with
the Soft X-Ray Telescope of YOHKOH and with Vector Magnetographs
Authors: Sakurai, Takashi; Shibata, Kazunari; Ichimoto, Kiyoshi;
Tsuneta, Saku; Acton, Loren W.
Bibcode: 1992PASJ...44L.123S
Altcode:
The soft X-ray Telescope of Yohkoh observed an M-class flare on 1992
February 6. As the flare progressed, an initially sheared coronal loop
structure was seen to evolve toward a relaxed magnetic configuration. In
association with this evolution, the vector magnetograph observations
detected a decrease in the electric currents.
Title: Effective Geometrical Thickness and Electron Density of a
Flare of 1991 December 2 Observed with the Soft X-Ray Telescope of
YOHKOH and Coronagraph
Authors: Ichimoto, Kiyoshi; Hirayama, Tadashi; Yamaguchi, Asami;
Kumagai, Kazuyoshi; Tsuneta, Saku; Hara, Hirohisa; Acton, Loren W.;
Bruner, Marilyn E.
Bibcode: 1992PASJ...44L.117I
Altcode:
A very small geometrical thickness of 1000 km was found for an M3.7
flare of 1991 December 2, which occurred beyond the limb. While
the Yohkoh soft X-ray telescope gives the emission measure, a new
coronagraph which can observe continuum images at 6630- Angstroms gives
the electron column density originating from electron scattering of a
10(7) K flare plasma. The reasoning for the latter is because [Fe XIV]
5303 Angstroms images show a much different shape compared with X-ray
and the 6630- Angstroms continuum, and there was no Hα emission. From
these we obtained an electron density of 4times 10(10) cm(-3) and the
above-mentioned small length in the line of sight. Since the apparent
width of a flaring plasma both in soft X-ray and continuum images
measured parallel to the limb is ~ 4 times 10(4) km at a height of 7
times 10(4) km, the smallness of the effective length of 1000 km is
striking, and may have significant bearing on the energy conversion
of the flare. A brief discussion concerning the origin of the mass
and magnetic morphology is given.
Title: Observations of X-Ray Jets with the YOHKOH Soft X-Ray Telescope
Authors: Shibata, Kazunari; Ishido, Yoshinori; Acton, Loren W.; Strong,
Keith T.; Hirayama, Tadashi; Uchida, Yutaka; McAllister, Alan H.;
Matsumoto, Ryoji; Tsuneta, Saku; Shimizu, Toshifumi; Hara, Hirohisa;
Sakurai, Takashi; Ichimoto, Kiyoshi; Nishino, Yohei; Ogawara, Yoshiaki
Bibcode: 1992PASJ...44L.173S
Altcode:
Time series of Soft X-ray Telescope images have revealed many X-ray
jets in the solar corona. The typical size of a jet is 5 times 10(3)
--4 times 10(5) km, the translational velocity is 30--300 km s(-1) ,
and the corresponding kinetic energy is estimated to be 10(25) --10(28)
erg. Many of the jets are associated with flares in X-ray bright points,
emerging flux regions, or active regions. They sometimes occur several
times from the same X-ray feature. In some cases, a dark void appears
after ejection at the footpoint of the jet. The void seems to be
the result of a change in the topology of the X-ray emitting plasma,
perhaps due to magnetic reconnection. Some jets show a structure which
suggests a helical magnetic field configuration along the jet. One
of the jets associated with a flaring bright point was identified as
being an Hα surge. In this case, the X-ray bright point is situated
just on the Hα bright point at the footpoint of the surge. The top
of the surge is not bright in X-rays. We briefly discuss the origin
of these newly discovered X-ray jets.
Title: The X10 Flare of 1991 June 9: White Light, H-alpha, Magnetic
Fields, and Electric Currents
Authors: de La Beaujardiere, J. -F.; Canfield, R. C.; Metcalf, T. R.;
Hiei, E.; Sakurai, T.; Ichimoto, K.
Bibcode: 1992AAS...180.4108D
Altcode: 1992BAAS...24..795D
We present observations by several instruments of the white-light
flare (WLF) of 1991 June 9 01:34 UT. A white-light image from the
National Astronomical Observatory of Japan indicates the location
of the WLF within the active region (NOAA 6659). Stokes polarimetry
from Mees Solar Observatory (University of Hawai`i) yields a vector
magnetogram and a map of the vertical electric currents. Also from
Mees comes Hα imaging spectroscopy, which is an indicator of such
specific chromospheric processes as nonthermal electron precipitation,
high coronal pressure, and mass motion. Both Mees instruments provide
continuum images, allowing coregistration of the various datasets. The
white-light emission arises from an extended area including both
sunspot umbra and penumbra. The active region magnetic field is strongly
nonpotential and has numerous vertical electric current channels. The
WLF is situated in an area of relatively low current density at the
edge of the strongest current in the active region, and the nearby
magnetic neutral line is highly sheared. The WLF site shows electron
precipitation, but only in its penumbral portion; stronger magnetic
mirroring in the umbra may inhibit precipitation there. Also, the
precipitation is not especially strong (relative to that observed
elsewhere in this flare), suggesting that the electron-beam model
for WLFs is not appropriate in this case. Also, the lack of strong
redshifts argues against a dynamical energy transport model.
Title: White-Light Flares of 1991 June in the NOAA Region 6659
Authors: Sakurai, Takashi; Ichimoto, Kiyoshi; Hiei, Eijiro; Irie,
Makoto; Kumagai, Kazuyoshi; Miyashita, Masakuni; Nishino, Yohei;
Yamaguchi, Kisuke; Fang, Geng; Kambry, Maspul Aini; Zhao, Zhaowang;
Shinoda, Kazuya
Bibcode: 1992PASJ...44L...7S
Altcode:
We report on observations of flare activities in an active region NOAA
6659, which appeared on the sun in 1991 June. Among six X-class flares
in this region, we observed three flares (June 4, 9, and 11), all of
which were white-light flares. A detailed discussion is given concerning
a particularly interesting white-light flare which occurred on June 11.
Title: Solar Meriodional Motions Derived from Sunspot Observations
Authors: Kambry, M. A.; Nishikawa, J.; Sakurai, T.; Ichimoto, K.;
Hiei, E.
Bibcode: 1991SoPh..132...41K
Altcode:
Sunspot drawings obtained at the National Astronomical Observatory of
Japan during the years 1954-1986 were used to determine meridional
motions of the Sun. A meridional flow of a few ms−1
was found, which is equatorward in the latitude range from -20°
to +15° and is poleward at higher latitudes in both hemispheres. A
northward flow of 0.01° day−1 or 1.4 ms−1
at mid-latitudes (between 10° and 20°) was also detected. From our
limited data-set of three solar cycles, an indication of solar-cycle
dependence of meridional motions was found.
Title: HeI 10830 Å Observations of Active Regions
Authors: Hiei, E.; Ichimoto, K.; Fang, G.
Bibcode: 1991LNP...387...67H
Altcode: 1991fpsa.conf...67H
A number of HeI 10830Å spectroheliograms were obtained with a 25-cm
aperture coronagraph at the Norikura Solar Observatory. From these
data we found; 1) a close relationship between the steady features
in HeI 108301Å intensity, velocity fields, and the magnetic fields,
2) darkenings of points in active regions with a time scale of 10-20
minutes, and 3) various manifestations of flares in HeI 10830Å . The
HeI 10830 Å line will give us sensitive diagnostics of chromospheric
and coronal active phenomena.
Title: Construction and experimentation of the new 10 cm coronagraph
at the Norikura Solar Observatory.
Authors: Kumagai, K.; Yamaguchi, A.; Ichimoto, K.; Nishino, Y.;
Hirayama, T.
Bibcode: 1991RNAOJ...1..139K
Altcode: 1991RNOAJ...1..139K
A new 10 cm-aperture coronagraph was constructed and installed at the
Norikura Solar Observatory of the National Astronomical Observatory. The
basic optical design follows the original Lyot's one. The coronal
images taken with a 2/3-inch commercial CCD camera are digitized
and integrated with an image processing unit in order to increase the
accuracy of the measurement. The primary purpose of this coronagraph is
to observe the flare images beyond the limb in the electron scattering
continuum, so that if combined with the X-ray observation from Solar-A,
the distribution and its temporal changes of the electron density and
effective line-of-sight length will be obtained for the 107K
plasma. Other objective of this coronagraph-imaging system is to
acquire faint coronal images particularly in the IR region and to
determine the prominence magnetic field.
Title: Solar Flare Telescope and 10-cm New Coronagraph
Authors: Ichimoto, K.; Sakurai, T.; Yamaguchi, A.; Kumagai, K.;
Nishino, Y.; Suematsu, Y.; Hiei, E.; Hirayama, T.
Bibcode: 1991LNP...387..320I
Altcode: 1991fpsa.conf..320I
Two new telescopes were built at the National Astronomical
Observatory of Japan, i.e. the Solar Flare Telescope and the 10-cm New
Coronagraph. The Solar Flare Telescope was constructed at Mitaka to make
observations of photospheric velocity fields, vector magnetic fields,
and H and continuum images of active regions simultaneously. The whole
system will be completed in 1991. The 10-cm new coronagraph, which
was developed to make precise measurements of the coronal intensity in
several wavelengths, has already been in operation for one year at the
Norikura Solar Observatory. At present the accuracy of about 10-6 of
the solar disk intensity is achieved in continuum light, but further
improvement in the photometric accuracy remains to be done.
Title: Advances in solar observations.
Authors: Nishio, M.; Ichimoto, K.
Bibcode: 1991AstHe..84..152N
Altcode:
No abstract at ADS
Title: Construction of Long-Life Magneto-optical Filters for
Helioseismology Observations
Authors: Sakurai, T.; Tanaka, K.; Miyazaki, H.; Ichimoto, K.; Sakata,
A.; Wada, S.
Bibcode: 1990LNP...367..277S
Altcode: 1990psss.conf..277S
A design of magneto-optical filters we are developing is described. By
heating the cell to about 200°C, a lifetime more than a year has
been achieved.
Title: CCD data acquisition system installed on the spectrograph at
the Norikura Solar Observatory.
Authors: Hamana, S.; Kumagai, K.; Ichimoto, K.; Sakurai, T.; Hiei, E.
Bibcode: 1990RNAOJ...1...13H
Altcode: 1990RNOAJ...1...13H
A new data acquisition system is installed on the 25-cm coudé-type
coronagraph at the Norikura Solar Observatory. Three CCD cameras (2/3
inch, 512×480 pixels) are mounted on the spectrograph; one at the short
focal length exit window and the other two at the long focal length exit
window. Fields of view along the entrance slit of the spectrograph are
9'15″ 2'22″and 3'00″ respectively. Spectral images are digitized
and integrated on the image processing unit. The new system has made
possible (1) the observations in the near-infrared wavelength, (2)
high accuracy in data compared to photographic observations, and (3)
the analyses of large amounts of spectral data.
Title: Phase Relation between Velocities and Temperature Fluctuations
of the Solar 5-Minute Oscillation
Authors: Ichimoto, K.; Hamana, S.; Kumagai, K.; Sakurai, T.; Hiei, E.
Bibcode: 1990LNP...367..205I
Altcode: 1990psss.conf..205I
Phase relations between the velocities and temperature oscillations in
the solar photosphere are investigated on the - diagram. Distributions
of the phase differences on the - plane are roughly reproduced
by a simple analytical model, but the detailed fitting is not
satisfactory. In the 5-minute band, temperature reaches its peak when
the atmosphere is moving downward. The amount of the phase difference
between temperature and velocity suggests the radiative damping time
of 1-40 s. Identification of the g-mode oscillation is not clear.
Title: Spectral manifestations of the granular velocity field near
the solar limb
Authors: Ichimoto, Kiyoshi; Hiei, Eijiro; Nakagomi, Yoshiteru
Bibcode: 1989PASJ...41..333I
Altcode:
It is found that high-resolution spectra taken near the solar limb show
very different wiggly line patterns of photospheric lines compared
with those taken near the disk center. (1) The absorption line look
like twisted threads. As the line of sight moves towards the limb,
the lines first show a gradual redshift and then it is followed by a
quick change to a blueshift. (2) The velocity distribution measured
in the line core is displaced toward the limb relative to that in the
line wing. These characteristics are well reproduced by an atmospheric
model with a two-dimensional grandular velocity field. It is shown that
the horizontal component of the grandular velocity plays an important
role for producing a line wiggle near the solar limb.
Title: Evershed effect observed in various solar photospheric lines
Authors: Ichimoto, K.
Bibcode: 1988VA.....31..113I
Altcode:
Observational data of the Evershed effect are used to examine the
validity of the models to account for the origin of the filamentary
structure of the penumbra. The rolling convection model of Danielson
(1961) and the elevated dark filament model of Moore (1981) and Cram
et al. (1981) are considered. The dependence of the Evershed velocity
on the equivalent width at the outer edge of the penumbra is compared
with that in the inner penumbra. Also, the dependence of the Evershed
velocity on the lower level excitation potential of spectral lines
is studied. The results show that the elevated dark filament model
produces a better agreement with the observational data than to rolling
convection model.
Title: Evershed effect observed in various solar photospheric
lines. II - Dependence on the excitation potential
Authors: Ichimoto, Kiyoshi
Bibcode: 1988PASJ...40..103I
Altcode:
A total of 85 photospheric lines are investigated in order to clarify
the dependence of the Evershed velocity on the excitation potential
of spectral lines. After removing the variation with the equivalent
width and the Landé factor of the spectral lines, it is found that
the shift of the line wing shows a variation with the excitation
potential: the higher the excitation potential, the larger the line
shift. The dependence on the excitation potential gives the author
a clue for understanding the temperature-velocity structure in
the sunspot penumbrae. Using two-component penumbral models with a
prescribed velocity field, the author performs an LTE calculation of
line profiles. The observed variation of the Evershed velocity with
the excitation potential can be naturally explained by the penumbral
model in which the penumbral dark regions carrying the Evershed motion
are dense filaments elevated in the photosphere, where the temperature
in the filaments is not much lower than that in the bright regions.
Title: The 17-MONTH Periodicity of Sunspot Activity
Authors: Akioka, M.; Kubota, J.; Suzuki, M.; Ichimoto, K.; Tohmura, I.
Bibcode: 1987SoPh..112..313A
Altcode:
A statistical study of sunspot activity during 1969 to 1986 was carried
out by using the number of sunspot groups and their areas. We found a
17-month periodicity, which is consistent with the 500-day periodicity
of flare occurrence (Ichimoto et al., 1985).
Title: Evershed effect observed in various solar photospheric lines. I
- Dependence of the velocity distribution across the penumbra on
the equivalent width
Authors: Ichimoto, Kiyoshi
Bibcode: 1987PASJ...39..329I
Altcode:
The spatial variations of the Evershed effect across a sunspot
penumbra is investigated using 88 photospheric lines. It is found
that the position where the Evershed velocity reaches a maximum varies
systematically with the equivalent width of the absorption line; the
stronger lines show the maximum velocity at a more outward position
of the penumbra. As a result, the dependence of the Evershed velocity
on the equivalent width gets weak at the outer edge of the penumbra,
where the degree of the line asymmetry is also reduced. To interpret the
variations of the Evershed effect across the penumbra, LTE calculations
of line profiles are performed based on some inhomogeneous penumbral
models. The observed change of the dependence of velocities on the
equivalent widths can be well explained by assuming that the material
flow occurs in dense filaments elevated in the photo sphere, while the
density, therefore the opacity, of the flow channel decreases towards
the outer edge of the penumbra. On the other hand, it is difficult to
explain the observed characteristics by the model that the Evershed
flow is confined in the deep layer and sinks down under the photo
sphere at the outer border of the penumbra.
Title: High resolution observation of Hα solar flares and temporal
relation between Hα and X-ray, microwave emission
Authors: Kurokawa, H.; Kitahara, T.; Nakai, Y.; Funakoshi, Y.;
Ichimoto, K.
Bibcode: 1986Ap&SS.118..149K
Altcode:
We studied the evolutional characteristics of fine structures in
Hα flare emitting regions and their relation to X-ray and microwave
emissions for selected events observed with the 60 cm Domeless Solar
Telescope at Hida Observatory, University of Kyoto. The principal
conclusions of this investigation are: (1) Hα kernel consists of some
finer bright points or Hαflare points whose individual size is less
than 1 arc sec. (2) Impulsive brightnenings of Hα flare points occurred
simultaneously with the spikes of the hard X-ray and microwave bursts
within the time resolution of our Hα observations which varied from
1 to 10 s. (3) It is concluded that fast electron beams must be the
principal mechanism of heating Hα flares during the impulsive phase
of a flare.
Title: Periodic behaviour of solar flare activity
Authors: Ichimoto, K.; Kubota, J.; Suzuki, M.; Tohmura, I.; Kurokawa,
H.
Bibcode: 1985Natur.316..422I
Altcode:
The periodic nature of solar activity has been studied using parameters
such as the sunspot Wolf numbers, calcium plage areas and flare
indices. The magnitude of the solar activity based on these parameters
reveals periodicities other than the most pronounced 11-yr one. Any
absolute detection of periodicity in active phenomena would have
fundamental significance for our understanding of solar activity. Here
we investigate the temporal variation of the flare activity of the Sun
using the data of 8,821 Hα flares which occurred during the period
January 1965 to February 1984, and show new evidence for 155-day and
17-month periodicities of the flare activity. The 155-day periodicity
is examined by taking into account the location of the flare on the
Sun. It is suggested that the 155-day period may be related to the
timescale for the storage and/or the escape of the magnetic field.
Title: Hα Red Asymmetry of Solar Flares
Authors: Ichimoto, K.; Kurokawa, H.
Bibcode: 1984SoPh...93..105I
Altcode:
The evolutional characteristics of the red asymmetry of Hα flare
line profiles were studied by means of a quantitative analysis of
Hα flare spectra obtained with the Domeless Solar Telescope at Hida
Observatory. Red-shifted emission streaks of Hα line are found at the
initial phase of almost all flares which occur near the disk center,
and are considered to be substantial features of the red asymmetry. It
is found that a downward motion in the flare chromospheric region is the
cause of the red-shifted emission streak. The downward motion abruptly
increases at the onset of a flare, attains its maximum velocity of
about 40 to 100 km s-1 shortly before the impulsive peak of
the microwave burst, and rapidly decreases before the intensity of Hα
line reaches its maximum. Referring to the numerical simulations made
by Livshits et al. (1981) and Somov et al. (1982), we conclude that
the conspicuous red-asymmetry or the red-shifted emission streak of
Hα line is due to the downward motion of the compressed chromospheric
flare region produced by the impulsive heating by energetic electron
beam or thermal conduction.
Title: Anomalous V/R Variation in EW Lac
Authors: Kogure, T.; Asada, Y.; Ichimoto, K.; Suzuki, M.
Bibcode: 1981IBVS.1952....1K
Altcode:
No abstract at ADS