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Author name code: hagino
ADS astronomy entries on 2022-09-14
author:"Hagino, Masaoki"
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Title: 2021 HC3
Authors: Denneau, L.; Tonry, J.; Heinze, A.; Weiland, H.; Fitzsimmons,
A.; Robinson, J.; Erasmus, N.; Pruyne, T. A.; Christensen, E. J.;
Farneth, G. A.; Fuls, D. C.; Gibbs, A. R.; Grauer, A. D.; Groeller,
H.; Kowalski, R. A.; Larson, S. M.; Leonard, G. J.; Rankin, D.;
Seaman, R. L.; Shelly, F. C.; Wierzchos, K. W.; Dupouy, P.; Hidas,
A.; Holmes, R.; Foglia, S.; Buzzi, L.; Linder, T.; Hug, G.; Romanov,
F. D.; Losse, F.; D'Anna, W.; Birtwhistle, P.; Okumura, S.; Hagino,
M.; Flynn, R. L.; Jacques, C.; Pimentel, E.; Barros, J.; Wells, G.;
Leuty, J.
2021MPEC....J...16D Altcode:
No abstract at ADS
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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
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.
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Title: Infrared spectro-polarimeter on the Solar Flare Telescope
at NAOJ/Mitaka
Authors: Sakurai, Takashi; Hanaoka, Yoichiro; Arai, Takehiko; Hagino,
Masaoki; Kawate, Tomoko; Kitagawa, Naomasa; Kobiki, Toshihiko;
Miyashita, Masakuni; Morita, Satoshi; Otsuji, Ken'ichi; Shinoda,
Kazuya; Suzuki, Isao; Yaji, Kentaro; Yamasaki, Takayuki; Fukuda,
Takeo; Noguchi, Motokazu; Takeyama, Norihide; Kanai, Yoshikazu;
Yamamuro, Tomoyasu
2018PASJ...70...58S Altcode: 2018PASJ..tmp...63S; 2018PASJ..tmp...82S
An infrared spectro-polarimeter installed on the Solar Flare Telescope
at the Mitaka headquarters of the National Astronomical Observatory of
Japan is described. The new spectro-polarimeter observes the full Sun
via slit scans performed at two wavelength bands, one near 1565 nm for a
Zeeman-sensitive spectral line of Fe I and the other near 1083 nm for He
I and Si I lines. The full Stokes profiles are recorded; the Fe I and Si
I lines give information on photospheric vector magnetic fields, and the
helium line is suitable for deriving chromospheric magnetic fields. The
infrared detector we are using is an InGaAs camera with 640 × 512
pixels and a read-out speed of 90 frames s<SUP>-1</SUP>. The solar
disk is covered by two swaths (the northern and southern hemispheres)
of 640 pixels each. The final magnetic maps are made of 1200 × 1200
pixels with a pixel size of 1{^”<SUB>.</SUB>}8. We have been carrying
out regular observations since 2010 April, and have provided full-disk,
full-Stokes maps, at the rate of a few maps per day, on the internet.
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Title: Image enhancement for the observation of the solar corona
Authors: Zhao, M. Y.; Liu, Y.; Song, T. F.; Zhang, X. F.; Hagino,
M.; Sakurai, T.
2018SPIE10701E..29Z Altcode:
In this work, we introduce an image enhancement method ideally suited
for the visualization of coronal intensity images. The steep radial
gradient of the coronal brightness is adjusted by normalising the
coronal image with the Fourier approximation of its local average. A
method based on deconvolution and localised normalising of the data
at many different spatial scales is used to further enhance the fine
structures, and a wavelet shrinkage denoising method is used for noise
suppression. The effectiveness of this method is demonstrated on a
series of images observed by various instruments including spacial
and earth-based coronagraphs as well as photos during total solar
eclipse. This method is very helpful for qualitative analysis of solar
coronal structures that are mostly invisible on original images.
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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.
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.
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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.
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.
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Title: Magnetic Helicity of Solar Active Regions as Revealed by
Vector Magnetograms and Coronal X-Ray Images
Authors: Xu, Haiqing; Gao, Yu; Zhang, Hongqi; Sakurai, Takashi;
Hagino, Masaoki; Sokoloff, Dmitry; Pevtsov, Alexei A.
2012PASJ...64...54X Altcode:
We have used photospheric vector magnetograms of 15 different
solar active regions to calculate the current helicity parameter,
α<SUB>av</SUB>, and the linear force-free field (LFFF) parameter,
α<SUB>best</SUB>, that fits best the observed transverse field. The
data were obtained with the Solar Magnetic Field Telescope at the
Huairou Solar Observing Station, the National Astronomical Observatories
of China, the Solar Flare Telescope of the National Astronomical
Observatory of Japan, and the Haleakala Stokes Polarimeter at the
Mees Solar Observatory, University of Hawaii, from 1997 to 2000. The
agreement in sign of α<SUB>av</SUB> between three vector magnetographs
is better than 90%. For α<SUB>best</SUB>, the agreement is 80%-90%. The
line-of-sight magnetograms observed with the Michelson-Doppler Imager
(MDI) on SOHO and coronal X-ray images observed with the Soft X-ray
Telescope (SXT) on Yohkoh have been used to determine the constant
α<SUB>c</SUB> of the LFFF in the corona. The value of α<SUB>c</SUB>
corresponds to the extrapolated coronal field whose field lines best
match, by visual inspection, the structure of coronal loops in X-ray
images. It is found that the sign agreement between photospheric
α<SUB>av</SUB> or α<SUB>best</SUB> and coronal α<SUB>c</SUB>
is lower (60%-85%). We consider the differences in measurements,
observing conditions, data reduction methods, and limitation in LFFF
extrapolation, and discuss their contributions to the dispersions in
the hemispheric sign rule of helicity.
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Title: Infrared Stokes Spectro-Polarimeter at the National
Astronomical Observatory of Japan
Authors: Hanaoka, Y.; Sakurai, T.; Shinoda, K.; Noguchi, M.; Miyashita,
M.; Fukuda, T.; Suzuki, I.; Hagino, M.; Arai, T.; Yamasaki, T.;
Takeyama, N.
2011ASPC..437..371H Altcode:
We are now constructing an infrared spectro-polarimeter for the Solar
Flare Telescope of NAOJ. It observes the full Sun in two wavelength
bands, one near 1.56 μm for highly Zeeman-sensitive spectral lines of
Fe I and the other near 10830 Å for He I and Si I lines. The instrument
records full Stokes profiles, and a Stokes inversion process will
give information on the strength and orientation of the magnetic field
vector for both of the photosphere and the chromosphere. The infrared
detector we are using is an InGaAs camera manufactured by a Belgian
company Xenics. Its format is 640×512 pixels and its read-out speed is
90 frames s<SUP>-1</SUP>. The solar disk will be covered by two swaths
(the northern and southern hemispheres) of 640 pixels each. The final
magnetic maps will be made of 1200×1200 pixels with a pixel size of
1.8 arcsec. Now we are operating regular observations and generate
full-disk, full-Stokes maps (a few maps per day). Our ultimate goal is
to derive the distribution of magnetic helicity over the whole surface
of the Sun, not only in sunspots and active regions.
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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.
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.
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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.
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. <P />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. <P />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.
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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
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.
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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
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).
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Title: Comparison of the Vector Magnetograms taken with the SFT/MTK
and the SST/KSW
Authors: Hagino, M.; Nakatani, Y.; Ishii, T. T.; Hanaoka, Y.; Sakurai,
T.; Hiei, E.; Suzuki, D.
2009ASPC..405..393H Altcode:
We carried out a detailed comparison between the vector magnetograms
obtained with the Solar Flare Telescope (SFT/MTK) of the National
Astronomical Observatory of Japan and those obtained with the
Sextuple Solar Telescope (SST/KSW) of the Kawaguchi Science Museum
(the former name is the Kawaguchi Science World). We investigated
various characteristics of the errors in the Stokes parameters for each
instrument. The level of noise due to seeing effects in the SST/KSW
magnetograms is higher than in the SFT/MTK magnetograms. On the other
hand, we found that about 60% of the data pixels have the same sign
of current helicity α in these magnetograms. We will discuss the
possibility and limitations of the magnetic field studies using these
magnetograms.
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Title: Local Twist and Current Helicity Distributions of Active
Region NOAA 10930
Authors: Su, J. T.; Sakurai, T.; Suematsu, Y.; Hagino, M.; Liu, Yu
2009ApJ...697L.103S Altcode:
Hinode high-quality vector magnetograms and G-band data are utilized
to study the distributions of local twist α<SUB> z </SUB> and current
helicity h<SUB>c</SUB> on the active region of NOAA 10930. The new
findings are as follows. (1) The patches of positive and negative
helicities were intermixed showing a mesh pattern in the umbra and
a thread pattern in the penumbra. (2) For its main stable sunspot
(MSS), there was a positive-helicity patch accounting for ~43% of the
umbra area surrounding the inner umbra, which had a predominantly
negative helicity. For its minor rotating sunspot (MRS), there
was a negative-helicity patch appearing in the umbra. (3) The fine
distributions of α<SUB> z </SUB> and h<SUB>c</SUB> on a penumbral
filament indicated that it may be possible for the two opposite
helicities to coexist in a filament and their magnitudes were nearly
equivalent.
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Title: Spectropolarimetric Observation of an Emerging Flux Region:
Triggering Mechanisms of Ellerman Bombs
Authors: Watanabe, H.; Kitai, R.; Okamoto, K.; Nishida, K.; Kiyohara,
J.; Ueno, S.; Hagino, M.; Ishii, T. T.; Shibata, K.
2008ApJ...684..736W Altcode: 2008arXiv0805.4266W
A high spatial resolution observation of an emerging flux region
(EFR) was made using a vector magnetograph and a Hα Lyot filtergraph
with the Domeless Solar Telescope at Hida Observatory on 2006 October
22. In Hα wing images, we could see many Ellerman bombs (EBs) in the
EFR. Observations in two modes, slit scan and slit fixed, were performed
with the vector magnetograph, along with the Hα filtergraph. Using the
Hα wing images, we detected 12 EBs during the slit scan observation
period and 9 EBs during the slit fixed observation period. With the
slit scan observation, we found that all the EBs were distributed in
the area where the spatial gradient of vertical field intensity was
large, which indicates the possibility of rapid topological change in
the magnetic field in the area of EBs. With the slit fixed observation,
we found that EBs were distributed in the areas of undulatory magnetic
fields, in both the vertical and horizontal components. This paper is
the first to report the undulatory pattern in the horizontal components
of the magnetic field, which is also evidence for emerging magnetic flux
triggered by the Parker instability. These results allow us to confirm
the association between EBs and emerging flux tubes. Three triggering
mechanisms for EBs are discussed with respect to emerging flux tubes:
9 out of 21 EBs occurred at the footpoints of emerging flux tubes,
8 occurred at the top of emerging flux tubes, and 4 occurred in the
unipolar region. Each case can be explained by magnetic reconnection
in the low chromosphere.
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Title: On the Solar Cycle Variation of the Hemispheric Helicity Rule
Authors: Pevtsov, A. A.; Canfield, Richard C.; Sakurai, T.; Hagino, M.
2008ApJ...677..719P Altcode:
We study the statistical significance of observed temporal variations
of the solar active-region hemispheric helicity rule, as measured by the
latitudinal gradient of the best-fit linear force-free-field parameter,
dα/dvarphi . Using data from four different vector magnetographs,
we compute and compare average annual dα/dvarphi values for these
instruments for 19 years from solar cycles 21, 22, and 23. We find that
although every instrument shows the "wrong" sign for the hemispheric
rule in some years, there is no agreement among the instruments on
which years are abnormal. None of the four data sets shows annual
values of dα/dvarphi departing from the hemispheric helicity rule
by more than 3 σ. We conclude that because the hemispheric helicity
rule is a weak tendency with significant scatter, an annual subset of
active regions is likely to produce statistically unreliable results.
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Title: Magnetic Causes of the Eruption of a Quiescent Filament
Authors: Schmieder, B.; Bommier, V.; Kitai, R.; Matsumoto, T.; Ishii,
T. T.; Hagino, M.; Li, H.; Golub, L.
2008SoPh..247..321S Altcode: 2007SoPh..tmp..213S
During the JOP178 campaign in August 2006, we observed the
disappearance of our target, a large quiescent filament located at
S25°, after an observation time of three days (24 August to 26
August). Multi-wavelength instruments were operating: THEMIS/MTR
("MulTi-Raies") vector magnetograph, TRACE ("Transition Region and
Coronal Explorer") at 171 Å and 1600 Å and Hida Domeless Solar
telescope. Counter-streaming flows (+/−10 km s<SUP>−1</SUP>) in the
filament were detected more than 24 hours before its eruption. A slow
rise of the global structure started during this time period with a
velocity estimated to be of the order of 1 km s<SUP>−1</SUP>. During
the hour before the eruption (26 August around 09:00 UT) the velocity
reached 5 km s<SUP>−1</SUP>. The filament eruption is suspected to
be responsible for a slow CME observed by LASCO around 21:00 UT on 26
August. No brightening in Hα or in coronal lines, no new emerging
polarities in the filament channel, even with the high polarimetry
sensitivity of THEMIS, were detected. We measured a relatively large
decrease of the photospheric magnetic field strength of the network
(from 400 G to 100 G), whose downward magnetic tension provides
stability to the underlying stressed filament magnetic fields. According
to some MHD models based on turbulent photospheric diffusion, this
gentle decrease of magnetic strength (the tension) could act as the
destabilizing mechanism which first leads to the slow filament rise
and its fast eruption.
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Title: Skew Angle and Magnetic Helicity in Solar Active Regions
Authors: Hagino, M.; Moon, Y. -J.; Sakurai, T.
2007ASPC..369..163H Altcode:
The skew angle and magnetic helicity are important quantities in
understanding the magnetic structures in solar active regions. Using
Yohkoh/SXT images and vector magnetograms from the Solar Flare
Telescope at Mitaka for 106 active regions, we have made the first
attempt to examine the relationship between the skew angle and magnetic
helicity. The skew angle is defined as the angle between the coronal
loop and the line perpendicular to the polarity inversion line. We
found that an active region having a large skew angle tends to have a
large helicity value. This result implies that while a coronal loop with
strong twist is nearly parallel to the axis of the polarity inversion
line, a coronal loop with weak twist is perpendicular to the polarity
inversion line, like a potential field structure.
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Title: SMART Observation of Magnetic Helicity in Solar Filaments
Authors: Hagino, M.; Kitai, R.; Shibata, K.
2006IAUJD...3E..60H Altcode:
We examined the magnetic helicity of solar filaments from their
structure in the chromosphere and corona. The H-alpha telescope of
the Solar Magnetic Activity Research Telescope (SMART) observed 239
intermediate filaments from 2005 July 1 to 2006 May 15. The intermediate
filament usually locates between two active regions. Using these images,
we identified the filament spine and its barbs, and determined the
chromospheric filament helicity from the mean angle between each barbs
and a spine. We found that 71% (78 of 110) of intermediate filaments
in the northern hemisphere are negative helicity and 67% (87 of 129) of
filaments in the southern hemisphere are positive, which agreed with the
well-known hemispheric tendency of the magnetic helicity. Additionally,
we studied the coronal helicity of intermediate filaments. The coronal
filament helicity is defined as the crossing angle of threads formed
a filament. The helicity pattern of coronal filaments obtained with
EIT/SOHO 171A also shows the helicity hemispheric tendency. Namely, 65%
(71 of 110) of coronal filaments in the northern hemisphere exhibit
negative helicity and the 65% (84 of 129) of filaments in the southern
hemisphere show negative helicity. These data were observed in the
same day with the SMART H-alpha data. Moreover, we found 12 filament
eruptions in our data. The 7 of 12 filaments show the clear opposite
sign of the hemispheric tendency of the magnetic helicity. The helicity
seems to be change during temporal evolution. This results suggest
that filament instability may be driven by the opposite sign helicity
injection from the foot point of the barb.
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Title: Solar-Cycle Variation of Magnetic Helicity in Active Regions
Authors: Hagino, Masaoki; Sakurai, Takashi
2005PASJ...57..481H Altcode:
The hemispheric sign rule of helicity and its long-term variation
were studied. The data were obtained from the Solar Flare Telescope
at Mitaka and the 65-cm solar telescope at Okayama. The data covered
the period of 1983-2001, from the declining phase of solar cycle 21 to
the rising phase of cycle 23. Although the hemispheric sign rule of
helicity generally holds, we also found significant time variations
in the yearly values of helicity during the observation period. The
hemispheric sign rule of helicity is satisfied in the solar maximum
phase, but may not be so in the solar minimum phase.
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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
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<SUP>−1</SUP>. 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<SUP>−1</SUP>, 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.
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Title: Hemispheric sign rule of magnetic helicity on the Sun
Authors: Hagino, Masaoki; Sakurai, Takashi
2005ARAOJ...7...49H Altcode:
No abstract at ADS
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Title: On a Cyclic Variation of the Hemispheric Helicity Rule
Authors: Pevtsov, A. A.; Hagyard, M. J.; Blehm, Z.; Smith, J. E.;
Canfield, R. C.; Sakurai, T.; Hagino, M.
2005HiA....13..140P Altcode:
We report the result of a study of magnetic helicity in solar active
regions during 1980-2000 (cycles 21-23). Using the vector magnetograms
from four different instruments (Haleakala Stokes Polarimeter Marshall
Space Flight Center Mitaka Solar Flare Telescope and Okayama Observatory
Solar Telescope) we calculated the force-free parameter alpha as
in Pevtsov et al. (1995). We use alpha as the proxy for current
helicity. For each instrument we computed a gradient dalpha/dL as
the linear fit of alpha versus latitude L using annual subsets of
data. The hemispheric helicity rule (negative/positive helicity in
northern/southern hemisphere) can be expressed in terms of this gradient
as dalpha/dL < 0. We find that each instrument exhibits change in
sign of this gradient for some years which implies that the hemispheric
helicity rule may not hold in some phases of a solar cycle (see Hagino
and Sakurai 2002). However we do not see consistency between different
instruments in regards to years disobeying the rule. The disagreement
may be due to difference in observations and/or insufficient number of
magnetograms in some years. We conclude that the present data sets do
not allow to make statistically significant inference about possible
cyclic variation of the hemispheric helicity rule.
---------------------------------------------------------
Title: Phase Relationship between the Activity Cycles of Sunspots
and Polar Faculae
Authors: Hagino, M.; Sakurai, T.; Miyazawa, A.
2004ASPC..325..157H Altcode:
The eleven-year activity cycles of polar faculae and sunspots are out
of phase by half a cycle. We studied the phase relationship between
the cycles of sunspots and polar faculae, by using the data of sunspot
and facular numbers obtained at Mitaka in the period of 1952--1998 (47
years, four sunspot cycles). We applied the cross-correlation analysis
and wavelet phase differences, and found that the phase relationship
was not persistent. The polar faculae were better correlated with the
sunspots of the previous cycle over two sunspot cycles of 1964--1987,
while the reverse was the case if the data of the whole four cycles
were used.
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Title: Latitude Variation of Helicity in Solar Active Regions
Authors: Hagino, Masaoki; Sakurai, Takashi
2004PASJ...56..831H Altcode:
We studied the current helicity of 230 active regions on the Sun
during the period of 1992-2001. Vector magnetograms used were obtained
with the Solar Flare Telescope, located at the Mitaka campus of
the National Astronomical Observatory. The latitude distribution of
helicity shows a negative slope; namely, the regions in the northern
(southern) hemisphere tend to show a negative (positive) helicity,
respectively, in agreement with previous studies. The scatter seen in
the helicity is significantly larger than expected from the measurement
errors, implying that the process generating the helicity is of random,
turbulent nature. Therefore, convective motion must play an essential
role in generating the helicity of active regions.
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Title: Existence of Nanoparticle Dust Grains in the Inner Solar
Corona?
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Hagino,
Masaoki; Yamamoto, Tetsuya T.
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<SUP>-7</SUP> 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: Loading of magnetic helicity and flare activity
Authors: Hagino, M.; Yamamoto, T.; Sakurai, T.
2004cosp...35.1955H Altcode: 2004cosp.meet.1955H
Studies of twisted flux tubes are important in understanding the
mechanisms of solar flares and coronal mass ejection. In this study,
we have made a comparison between the helicity injection rate
H<SUB>in</SUB> and the force-free parameter α. The latter is an
indicator of accumulated helicity. The magnetograms we used were
obtained with SOHO/MDI and with the Solar Flare Telescope (SFT)
of NAOJ in Mitaka, Tokyo. SFT can take vector magnetograms every
3 minutes. To measure the helicity injection, we have employed
Kusano's method (Kusano et al. 2002) which can derive the helicity
injection due to both shearing motion and emerging motion. We studied
several active regions which produced major flares (for instance, NOAA
9661). We estimated the values of H<SUB>in</SUB> and α in two ways;
(1) by averaging over the whole region and (2) by isolating the flare
area. In the case of NOAA 9661, a GOES X1.7 class flare was observed
on 2001 October 19. The value of α averaged over the whole region was
negative, which agreed with the hemispheric helicity sign rule because
this region appeared in the northern hemisphere. If the area of 100” ×
50” near the flare neutral line was selected, we found the following
results. (1) The temporal changes in α were consistent with the
variations in H<SUB>in</SUB>. (2) No emerging flux activity was seen,
and the contributions to H<SUB>in</SUB> from the emerging motion were
small. (3) The pixel to pixel correlation between H<SUB>in</SUB> and
α in the area showed a positive correlation before the flare. After
the flare the correlation weakened. Property (3) may imply that the
magnetic helicity is being loaded prior to the flare. Therefore, the
correlation between H<SUB>in</SUB> and α can be used as an indicator
of energy build-up process.
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Title: The flare of 1991 June 4 (importance 3B) and the associated
Moreton wave
Authors: Yamaguchi, Kisuke; Sakurai, Takashi; Irie, Makoto; Kumagai,
Kazuyoshi; Hagino, Masaoki; Miyashita, Masakuni; Shiomi, Yasuhiko;
Hiei, Eijiro
2003RNAOJ...6..101Y Altcode:
We observed a Moreton wave associated with a flare of importance 3B
in the NOAA region 6659 on 1991 June 4. The Moreton wave was emitted
from a flare bright point and initially showed the form of a loop. The
speed of the Moreton wave was initially 1500 km s<SUP>-1</SUP> and
was later accelerated to 1800 km s<SUP>-1</SUP>. This acceleration
may be due to the propagation of the wave into a coronal hole (with
low density and high Alfvén velocity.
---------------------------------------------------------
Title: Magnetic Helicity of Solar Active Regions and its Implications
Authors: Sakurai, T.; Hagino, M.
2003JKAS...36S...7S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On a Cyclic Variation of the Hemispheric Helicity Rule.
Authors: Pevtsov, Alexei A.; Hagyard, Mona J.; Blehm, Zachary; Smith,
James E.; Canfield, Richard C.; Sakurai, Takashi; Hagino, Masaoki
2003IAUJD...3E..35P Altcode:
We report the result of a study of magnetic helicity in solar active
regions during 1980-2000 (cycles 21-23). Using the vector magnetograms
from four different instruments (Haleakala Stokes Polarimeter Marshall
Space Flight Center Mitaka Solar Flare Telescope and Okayama Observatory
Solar Telescope) we calculated the force-free parameter alpha as
in Pevtsov et al. (1995). We use alpha as the proxy for current
helicity. For each instrument we computed a gradient dalpha/dL as
the linear fit of alpha versus latitude L using annual subsets of
data. The hemispheric helicity rule (negative/positive helicity in
northern/southern hemisphere) can be expressed in terms of this gradient
as dalpha/dL < 0. We find that each instrument exhibits change in
sign of this gradient for some years which implies that the hemispheric
helicity rule may not hold in some phases of a solar cycle (see Hagino
and Sakurai 2002). However we do not see consistency between different
instruments in regards to years disobeying the rule. The disagreement
may be due to difference in observations and/or insufficient number of
magnetograms in some years. We conclude that the present data sets do
not allow to make statistically significant inference about possible
cyclic variation of the hemispheric helicity rule.
---------------------------------------------------------
Title: Magnetic helicity and flare activity
Authors: Sakurai, T.; Hagino, M.
2003AdSpR..32.1943S Altcode:
We studied two active regions appeared in 2001 (NOAA 9415 and 9661),
both of which have produced X-class flares. The time evolutions of
magnetic flux and magnetic helicity were derived based on vector
magnetograph observations. These regions satisfied the so-called
hemispheric rule of magnetic helicity, namely regions in the northern
(southern) hemisphere tend to have negative (positive) helicity. The
magnetic helicity integrated over the regions evolved slowly and
did not show abrupt changes at the time of the flares, although the
distributions of magnetic helicity changed significantly over a few
days in the regions. The appearance of localized regions whose helicity
was opposite to that expected from the hemispheric rule was seen in
both cases.
---------------------------------------------------------
Title: Hemispheric Helicity Asymmetry in Active Regions for Solar
Cycle 21-23
Authors: Hagino, M.; Sakurai, T.
2002mwoc.conf..147H Altcode:
Magnetic helicity observed at the surface carries information on the
invisible, sub-surface processes such as internal rotation and the
behavior of magnetic flux tubes in the convection zone. It has been
recognized that magnetic helicity shows a hemispheric rule; the northern
(southern) hemisphere tends to show negative (positive) helicity. It
is also known that this rule does not change with solar cycle. The
determination of the helicity, requiring vector magnetograms, is
sensitive to various noises and instrumental effects, and is therefore
not an easy task. Considering the importance of magnetic helicity,
here we present the results based on our data set and compare them with
results from other observatories. We analyzed vector magnetograms in
the period of 1992-2000 obtained with the Solar Flare Telescope at the
National Astronomical Observatory of Japan. The current helicity was
determined by two methods for 180 active regions. The first method
calculates the electric currents over active regions by a direct
differentiation and then evaluates the average helicity, alpha = frac
sum (abla times vec {B})<SUB>z</SUB>cdot {m sign} (B<SUB>z</SUB>)
+ B<SUB>z</SUB>. The second method is the fitting of the linear
force-free field vec{B}<SUB>m cal</SUB> (alpha) to the observed
transverse field vec{B}<SUB>m obs</SUB> and finds the best-fit alpha
which minimizes frac sum [vec{B}<SUB>m cal</SUB>(alpha) - vec{B}<SUB>m
obs</SUB>]<SUP>2</SUP> sum B<SUB>m obs</SUB><SUP>2</SUP>. The data
points with transverse fields larger than 150 G (noise level) and with
longitudinal fields weaker than 500 G were used. The latter condition
was to minimize the effect of Faraday rotation that may change the
azimuth of the transverse field. We plotted the helicity against solar
latitude and calculated a linear fit to the data. The slopes of the
fit obtained from the first and the second methods are (-1.08 ± 0.51)
times 10<SUP>-10</SUP> mm<SUP>-1</SUP> m deg<SUP>-1</SUP> and (-3.30
± 1.14) times 10<SUP>-10</SUP> mm<SUP>-1</SUP> m deg}<SUP>-1</SUP>,
respectively. Our results agree with the previous studies and confirm
the hemispheric rule.
---------------------------------------------------------
Title: A Flexible Prism used as an Image Stabilizer
Authors: Sakurai, T.; Noguchi, M.; Shinoda, K.; Tanaka, N.; Aoki,
K.; Hagino, M.; Mochizuki, H.
2002SoPh..205..201S Altcode:
An image stabilizer was constructed by making use of a flexible prism,
which is widely used as an anti-vibration mechanism in handheld video
cameras. The prism responds to frequencies up to 20 Hz, and can be
simply inserted into existing optics. The performance of the prism
has been confirmed by observing the Sun through it.
---------------------------------------------------------
Title: Magnetic helicity and flare activity
Authors: Sakurai, T.; Hagino, M.
2002cosp...34E2093S Altcode: 2002cosp.meetE2093S
We studied two active regions appeared in 2001 (NOAA 9415 and 9661),
both of which have produced X-class flares. Time evolutions of magnetic
flux and magnetic helicity were derived based on vector magnetograph
observations. These regions obey the so-called hemispheric rule
of magnetic helicity, namely regions in the northern (southern)
hemisphere tend to have negative (positive) helicity. The magnetic
helicity showed slow evolution but did not show abrupt changes at
the time of flares. Flare activity was correlated with changes in the
distributions of magnetic helicity that were driven by horizontal flows.
