Author name code: kitai
ADS astronomy entries on 2022-09-14
=author:"Kitai, R."
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Title: Magnetic field structures associated with chromospheric
heating in a plage region
Authors: Anan, T.; Schad, T.; Kitai, R.; Dima, G.; Jaeggli, S.;
Collados, M.; Dominguez-Tagle, C.; Kleint, L.
Bibcode: 2021AAS...23821222A
Altcode:
The strongest quasi-steady heating in the solar atmosphere occurs in
the active chromosphere and in particular within plage regions. Our
aim is to investigate the relation between magnetic structures and
the signatures of heating in the plage regions so as to clarify what
mechanisms are at work. We observed a plage region in NOAA active
region 12723 in the near infrared He I triplet and Si I 1082.7 nm
on 2018 October 3 using the Integral Field Unit mode of the GREGOR
Infrared Spectrograph (GRIS) installed at the GREGOR telescope. At the
same time, the Interface Region Imaging Spectrograph (IRIS) obtained
spectra in the ultra-violet Mg II h & k doublet emitted from the
same region. We applied the HAnle and ZEeman Light v2.0 inversion
code (HAZEL v2.0) to the GRIS data to infer the photospheric and
chromospheric magnetic field. We find that the radiative flux of the Mg
II was large between patches of strong magnetic field strength in the
photosphere, or at edges of the magnetic patches. On the other hand,
the spatial correspondences between the Mg II flux and the magnetic
field strength in the chromosphere and between the Mg II flux and the
electric current are not so clear. In conclusion, chromospheric heatings
in the plage region can be related to magnetic field perturbations
produced by interactions of magnetic flux tubes.
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: Evolution and Flare Activity of δ -Sunspots in Cycle 23
Authors: Takizawa, K.; Kitai, R.
Bibcode: 2015SoPh..290.2093T
Altcode: 2015arXiv150706453T; 2015SoPh..tmp...96T
The emergence and magnetic evolution of solar active regions (ARs)
of β γ δ -type, which are known to be highly flare-productive,
were studied with SOHO/MDI data in Cycle 23. We selected 31 ARs that
can be observed from their birth phase as unbiased samples for our
study. From the analysis of the magnetic topology (twist and writhe),
we obtained the following results: i) Emerging β γ δ ARs can be
classified into three topological types as quasi-β , writhed, and
top-to-top. ii) Of these, the writhed and top-to-top types tend to show
high flare activity. iii) As the signs of twist and writhe agree with
each other in most cases of the writhed type (12 cases out of 13),
we propose a magnetic model in which the emerging flux regions in a
β γ δ AR are not separated, but are united as a single structure
below the solar surface. iv) Almost all the writhed-type ARs have
downward knotted structures in the middle part of the magnetic flux
tube. This is probably the essential property of β γ δ ARs. v) The
flare activity of β γ δ ARs is highly correlated not only with the
sunspot area, but also with the magnetic complexity. vi) We suggest
that there is a possible scaling-law between the flare index and the
maximum umbral area.
Title: Morphological model for quadrupolar δ sunspots
Authors: Takizawa, K.; Kitai, R.
Bibcode: 2014AGUFMSH41B4136T
Altcode:
Sunspot with umbrae of opposite polarity within a single common
penumbra are called δ-spot group (Kunzel, 1960). It has been well
known that major flares almost always occur in active region with
δ-configuration. Hence, to investigate the formation and evolution
of δ-configuration is a key in understanding the major flare
activities. However, for the case of δ-spot, emerging flux regions
(EFRs) combine intricately to each other. Therefore it is so difficult
to decipher the relations between multiple EFRs. To clearly follow the
development of the ARs, we should select the ARs which can be observed
from the initial emerging stage. Emergence and magnetic evolution
of solar active regions (ARs) of βγδ-type, which are known to be
highly flare active (Sammis 2000), were studied with the SOHO/MDI data
in the solar cycle 23. 31 ARs, which can be seen from the birth phase,
were selected as unbiased samples of our study. From our analysis, we
found that successive birth of two emerging flux regions, spatially
separated to each other in east-west direction as a series, forming
a quadrupolar magnetic configuration, is a typical way of initial
development of βγδ regions. The δ-configuration was formed by
following polarity of western EFR with preceding polarity of eastern
EFR. We found 11ARs of quadrupolar type among the sampled 31 ARs. In
this work, we propose a plausible model for the quadrupolar type
δ-spots as a simple magnetic tube of helical structure, which have
downward knot in the mid portion of the flux tube. In nine cases out
of 11, the characteristics of the magnetic helicity signs, i.e. the
signs of twist and writhe, are consistent with our model.
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: Magnetic helicity transported by flux emergence and shuffling
motions
Authors: Zhang, Y.; Kitai, R.; Takizawa, K.
Bibcode: 2013IAUS..294..319Z
Altcode:
Magnetic helicity can be transported from sub-photosphere into corona by
the emergence of helical magnetic field lines and the shuffling motions
of foot-points of pre-existing coronal field lines. Active region NOAA
10930 was observed by SP and NFI of SOT on board Hinode when it pass
through the solar meridian. Based on these observations, we calculate
magnetic helicity flow of both terms, by regarding Doppler velocity
as normal velocity. The results are compared with which calculated by
method proposed by Zhang et. al. (2012). Our results show that helicity
injection maps calculated by both methods have similar distribution
and the integration values have the same magnitude.
Title: Prominent Photospheric Downflows on Magnetic Neutral Line in
a Delta-Type Sunspot
Authors: Takizawa, K.; Kitai, R.; Zhang, Y.
Bibcode: 2012SoPh..281..599T
Altcode: 2012SoPh..tmp..219T
It is known that δ-type sunspot groups have a high flare productivity
and produce strong flares. In particular, βγδ type sunspots are the
most active type of all. A βγδ active region NOAA 9957 with frequent
flux cancellations but without any marked flare activity during its
decay phase was studied in this work. Using SOHO/MDI Dopplergrams and
magnetograms, we detected continuous prominent downflow motions of 1500
- 1700 m s−1 for several hours on the magnetic neutral
line in this region. In the downflow region, penumbral structures were
observed to decay. We will interpret and discuss the phenomenon as a
case of submergence of the magnetic flux.
Title: Persistent Circulating Motion in a Sunspot Umbra
Authors: Katsukawa, Y.; Kitai, R.; Watanabe, H.
Bibcode: 2012ASPC..454..213K
Altcode:
We studied temporal evolution of flow patterns inside an umbra
using the local correlation tracking algorithm applied to long-term
filtergram data of a matured sunspot taken with the Hinode Solar
Optical Telescope. We found not only inward migration of umbral dots
in a peripheral region of the umbra but also a circulating motion in
a central region of the umbra. The circulating motion was persistently
observed for at least 3 days. The observation suggests that there are
magnetic and flow structures below a sunspot maintaining the motion
of umbral dots.
Title: 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: Magnetic Helicity Transported by Flux Emergence and Shuffling
Motions in Solar Active Region NOAA 10930
Authors: Zhang, Y.; Kitai, R.; Takizawa, K.
Bibcode: 2012ApJ...751...85Z
Altcode: 2012arXiv1203.2096Z
We present a new methodology which can determine magnetic helicity
transport by the passage of helical magnetic field lines from the
sub-photosphere and the shuffling motions of footpoints of preexisting
coronal field lines separately. It is well known that only the
velocity component, which is perpendicular to the magnetic field (υ
B ), has contributed to the helicity accumulation. Here,
we demonstrate that υ B can be deduced from a horizontal
motion and vector magnetograms under a simple relation of υ t
= μ t + (υ n /Bn ) B
t , as suggested by Démoulin & Berger. Then after dividing
υ B into two components, as one is tangential and the
other is normal to the solar surface, we can determine both terms of
helicity transport. Active region (AR) NOAA 10930 is analyzed as an
example during its solar disk center passage by using data obtained
by the Spectropolarimeter and the Narrowband Filter Imager of Solar
Optical Telescope on board Hinode. We find that in our calculation
the helicity injection by flux emergence and shuffling motions have
the same sign. During the period we studied, the main contribution
of helicity accumulation comes from the flux emergence effect, while
the dynamic transient evolution comes from the shuffling motions
effect. Our observational results further indicate that for this AR
the apparent rotational motion in the following sunspot is the real
shuffling motions on the solar surface.
Title: Ellerman Bomb as a Manifestation of Chromospheric Fine Scale
Activity
Authors: Kitai, R.
Bibcode: 2012ASPC..456...81K
Altcode:
Observational and theoretical studies on Ellerman bombs are briefly
reviewed. Including the recent results by high spatial resolution
observation done with Hinode/SOT and so on, we will summarize our
present understanding of Ellerman bomb phenomenon as a chromospheric
fine scale activity driven by successive and intermittent magnetic
reconnection in deeply seated locations of lower chromospheres or in
the upper photosphere.
Title: Properties of Umbral Dots as Measured from the New Solar
Telescope Data and MHD Simulations
Authors: Kilcik, A.; Yurchyshyn, V. B.; Rempel, M.; Abramenko, V.;
Kitai, R.; Goode, P. R.; Cao, W.; Watanabe, H.
Bibcode: 2012ApJ...745..163K
Altcode: 2011arXiv1111.3997K
We studied bright umbral dots (UDs) detected in a moderate size sunspot
and compared their statistical properties to recent MHD models. The
study is based on high-resolution data recorded by the New Solar
Telescope at the Big Bear Solar Observatory and three-dimensional (3D)
MHD simulations of sunspots. Observed UDs, living longer than 150 s,
were detected and tracked in a 46 minute long data set, using an
automatic detection code. A total of 1553 (620) UDs were detected
in the photospheric (low chromospheric) data. Our main findings
are (1) none of the analyzed UDs is precisely circular, (2) the
diameter-intensity relationship only holds in bright umbral areas, and
(3) UD velocities are inversely related to their lifetime. While nearly
all photospheric UDs can be identified in the low chromospheric images,
some small closely spaced UDs appear in the low chromosphere as a single
cluster. Slow-moving and long-living UDs seem to exist in both the low
chromosphere and photosphere, while fast-moving and short-living UDs
are mainly detected in the photospheric images. Comparison to the 3D
MHD simulations showed that both types of UDs display, on average, very
similar statistical characteristics. However, (1) the average number
of observed UDs per unit area is smaller than that of the model UDs,
and (2) on average, the diameter of model UDs is slightly larger than
that of observed ones.
Title: Properties of Umbral Dots as Measured from the New Solar
Telescope Data and MHD Simulations
Authors: Yurchyshyn, V.; Kilcik, A.; Rempel, M.; Abramenko, V.; Kitai,
R.; Goode, P. R.; Cao, W.; Watanabe, H.
Bibcode: 2011sdmi.confE..86Y
Altcode:
We studied bright umbral dots (UDs) detected in the main sunspot
of AR NOAA 11108 and compare their statistical properties to a
state-of-the-art MHD model of a sunspot. The study is based on
high resolution data recorded on September 20, 2010 by the New Solar
Telescope (NST) at Big Bear Solar Observatory and 3D MHD simulations of
sunspots. The 46 min data set included photospheric (0.3nm TiO filter
centered at 705.7 nm) and chromospheric (0.025nm Hα Lyot filter)
adaptive optics corrected and speckle reconstructed images. Bright
UDs, living longer than 150 s, were detected and tracked using an
automatic UD detection code. Total 1553 (620) UDs were detected
in the photospheric (chromospheric) data. Our main findings are:
i) none of the analyzed UDs is of an exact circular shape, ii) the
diameter-intensity relationship only works for bright umbral areas, and
iii) UD velocities inversely related to their life time. Comparison of
photospheric and chromospheric data showed that nearly all photospheric
UDs can be identified in the chromospheric images. However, it appears
that some small closely spaced UDs appear in the chromospheric images
as a single cluster, which may lead to the underestimation of the total
number of detected chromospheric UDs. Also, while slow moving and long
living UDs seem to exist in both chromosphere and photosphere, fast
moving and short living ones are detected mainly in the photospheric
images. Comparison of model and observed data shows that both types
of UDs display very similar statistical characteristics. The main
difference between parameters of model and observed UDs is that i)
the average number of observed UDs per unit area is smaller than that
of the model UDs, and ii) on average, the diameter of model UDs is
slightly larger than that of observed ones.
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: Solar Plages: Observational Study of Their Chromospheric
Heating and Spicular Mass Ejections
Authors: Kitai, R.; Hashimoto, Y.; Anan, T.; Matsumoto, T.; Kawate,
T.; Watanabe, H.; Otsuji, K.; Nakamura, T.; Nishizuka, N.; Nishida,
K.; Ueno, S.; Nagata, S.; Shibata, K.
Bibcode: 2009ASPC..415...19K
Altcode:
We investigated the chromospheric dynamics of plage area. From our
spectroscopic analysis of the CaII K line, we have found that their
periodic variations are due to the propagation of acoustic waves from
the lower layers. Another observational work on Hinode CaII H images,
gave us a new result that there are numerous spicular jets in plage
area, thanks to the stable observing condition of Hinode. The present
paper is an extended abstract of our works which will be published
fully in our future papers.
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: The tandem Fabry Perot Full-Disk Solar Vector Magnetogram
system for the Solar Magnetic Activity Research Telescope (SMART)
Authors: Otsuji, K.; Nagata, S.; Ueno, S.; Kitai, R.; Kimura, G.;
Nakatani, Y.; Ishii, T.; Morita, S.; Shibata, K.
Bibcode: 2009AGUFMSH33B1498O
Altcode:
For solar and heliospheric physics, energy release mechanism of
solar flares and onset of CMEs are one of the most the most important
issues. Solar Magnetic Activity Research Telescope (SMART) in Hida
observatory Kyoto University aims to investigate the relation between
the solar flares and photospheric vector magnetic field. Full disk high
resolution H-alpha images as well as and photospheric vector magnetic
field using Fe I 6302 line have been taken regularly since 2005. In
order to improve the vector magnetic field measurement accuracy,
a tandem Fabry Perot Stokes polarimeter is newly constructed for
the SMART. The system consist of a tandem FP with FWHM of ~0.01nm,
polarization beam splitter and two CCD cameras taking orthogonally
polarized images simultaneously. In this poster we present the
system design and laboratory test results, and expected observational
capabilities. We also present the flux emergence activities observed
with SMART and Hinode satellite.
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: 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: 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.
Bibcode: 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.
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.
Bibcode: 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−1) 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−1. During
the hour before the eruption (26 August around 09:00 UT) the velocity
reached 5 km s−1. 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.
Title: Magnetic Field Configuration and Evolution of a Highly
Flare-producitve Region NOAA 10808 (2005-Sep)
Authors: Ishii, T. T.; Nagashima, K.; Kurokawa, H.; Kitai, R.; Ueno,
S.; Nagata, S.; Shibata, K.
Bibcode: 2006IAUJD...3E..59I
Altcode:
Active regions on the Sun have different flare productivities with each
other. Some regions produce many large flares, while others produce no
flares. The key factor of a high flare productivity is the complexity
of magnetic field configuration of the region. In our previous studies,
we found that the twisted structure of emerging magnetic flux bundles
is the essential feature of flare-productive active regions. Vector
magnetic field data sets are necessary to examine the twisted
magnetic field structures (e.g., shear and helicity). Recently we
have constructed our new telescope, Solar Magnetic Activity Research
Telescope (SMART) at Hida Observatory, Kyoto University. We can obtain
high resolution full disk H-alpha images (with Lyot filter; H-alpha
center, blue and reg wing) and full disk vector magnetograms with
SMART. The active region NOAA 10808 showed the highest flare activity
during the current solar cycle (cycle 23) in September 2005. We
studied the formation process of delta-type magnetic configuration
using SOHO/MDI magnetograms and flares using TRACE data. We also
studied the evolution of magnetic shear and H-alpha filaments using
H-alpha full disk images and full disk vector magnetograms obtained
with SMART. In this paper, we summarize the characteristics of magnetic
field configuration of this region and discuss the relation between
the configuration and the high flare activity.
Title: SMART Observation of Magnetic Helicity in Solar Filaments
Authors: Hagino, M.; Kitai, R.; Shibata, K.
Bibcode: 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.
Title: Close causal relation between emergence of twisted flux rope
and strong flares
Authors: Kurokawa, H.; Ishii, T.; Ueno, S.; Nagata, S.; Kitai, R. .;
Shibata, K.
Bibcode: 2006cosp...36.2230K
Altcode: 2006cosp.meet.2230K
Solar flares are considered to occur in the solar corona by magnetic
field reconnection Shibata 1995 The flare energy which is stored in the
twisted magnetic field is supplied to the corona through the photosphere
from the convection zone For this reason observations of evolutional
changes in the magnetic field configuration of flare-productive regions
are fundamentally important for the flare energy build-up study and
the forecast of strong flares Hagyard 1984 showed that flares occurred
along the neutral line of strong magnetic shear The magnetic shear is
however not a sufficient condition for strong flare occurrence and it
is important to study the active region evolutions and examine which
type of magnetic shear development produces strong flares Until now
several works made detailed studies of magnetic shear developments in
flare-productive sunspot regions and suggested that the emergence of a
twisted magnetic flux rope which is originally formed in the convection
zone must be the source of the strong magnetic shear development in a
sunspot region to produce a strong flare activity Kurokawa 1987 Tanaka
1991 Ishii et al 1998 Kurokawa 2002 In this paper we present our recent
studies of energy build-up processes of flare-productive active regions
We studied the evolutional changes of 11 super active regions which
produced more than three X-class flares observed from 1998 through 2005
during the 23 solar sunspot cycle in details We found all these regions
show some common magnetic evolutional features in the course of the
Title: Transition Region Downflows in the Impulsive Phase of Solar
Flares
Authors: Kamio, S.; Kurokawa, H.; Brooks, D. H.; Kitai, R.; UeNo, S.
Bibcode: 2005ApJ...625.1027K
Altcode:
We present observations of four flares that occurred during
coordinated observations between the Coronal Diagnostic Spectrometer
(CDS) on board SOHO and the Domeless Solar Telescope (DST) at Hida
Observatory. We studied the evolution of relative Doppler velocities
in the flare kernels by using He I (3.5×104 K), O V
(2.2×105 K), and Mg IX (1.0×106 K) spectra
obtained with high time cadence (42 s) SOHO CDS observations and the
Hα monochromatic images obtained with the DST. We found that the
transition region plasma of O V showed strong downward velocities
up to 87 km s-1 simultaneously with the downflows in the
lower temperature chromospheric emissions in He I and Hα during the
impulsive phase of all four flares. From these results we suggest
that the downflows in the transition region and the chromosphere are a
common feature in the impulsive phase of flares. For the Mg IX line we
did not detect any significant change in velocity, which suggests that
the 106 K plasma was close to the intermediate temperature
between the upflowing plasma (107 K) and the downflowing
plasma (104-105 K). These are important for
understanding the dynamics of the solar atmosphere in response to the
sudden energy deposition of a flare.
Title: A Study On Surges: I. Automatic Detection Of Dynamic Hα Dark
Features From High-Cadence Full-Disk Observations
Authors: Liu, Y.; Kurokawa, H.; Kitai, R.; Ueno, S.; Su, J. T.
Bibcode: 2005SoPh..228..149L
Altcode:
We present a new method for the automatic identification and
classification of dynamic Hα dark features found in time series of
full-disk solar images at three Hα wavelengths (center, and ± 0.8
Å). The simultaneous Hα observations are obtained by the multi-channel
Flare Monitoring Telescope (FMT) at Hida Observatory. The program
was developed in order to replace the present visual detection and
classification of the phenomena. Usually, an obvious dark feature
found in the Hα −0.8 Å observations probably corresponds to some
phenomenon such as a surge or chromospheric network enhancement,
or filament activity. Thus, one of our aims in this program
is to distinguish each phenomenon by its own properties and key
parameters. We optimized the threshold values of the key parameters
such as the area and darkness of the transiently darkening features in
Hα −0.8 Å so that the computer can reasonably identify surges and
filament activations. In comparison, for a 7-day observation period,
the number of dark events detected by the program contains 89% of the
events recognized visually. However, 10 times more events are detected
automatically. The missing events are mainly caused by the deletion
of data with poor visibility. It is found that the dark events can be
identified with more precise starting and ending times by a machine
than by a human. Some statistical studies of surges or other activities
can be carried out based on the computer-produced database. With some
modifications the program can be applied to monitor real-time dynamic
features on disk, including flare ribbons.
Title: Studies on the Flare Energy Build-Up Process Using SolarB/Solar
Optical Telescope (SOT) and Solar Magnetic Activity Research Telescope
(SMART) at Hida Observatory
Authors: Ishii, T. T.; Nagata, S.; Ueno, S.; Kitai, R.; Kurokawa,
H.; SMART Team
Bibcode: 2004ASPC..325..331I
Altcode:
Evolution of active regions is one of the key topics for understanding
the energy storage and triggering mechanisms of flares. In our previous
studies, we found that the twisted structure of emerging magnetic
flux bundles is the essential feature of flare-productive active
regions. Vector magnetic field data sets are necessary to examine
the twisted magnetic field structures (e.g. shear and helicity). The
SolarB/Solar Optical Telescope (SOT) enables us to study the detailed
magnetic field configuration with a high spatial resolution. Recently
we have constructed our new telescope, Solar Magnetic Activity Research
Telescope (SMART) at Hida Observatory. Vector magnetic field telescope
of SMART has a much wider field of view (FOV) than that of SOT. In
this paper, we propose an observational plan of the active region
evolution and flare energy build-up process with SOT and SMART.
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: Features of Solar Telescopes at the Hida Observatory and the
Possibilities of Coordinated Observations with SolarB
Authors: Ueno, S.; Nagata, S.; Kitai, R.; Kurokawa, H.
Bibcode: 2004ASPC..325..319U
Altcode:
At the Hida observatory, two solar telescopes, Domeless Solar Telescope
(DST) and Flare Monitoring Telescope (FMT), have been operated for
studying solar fundamental structures and active phenomena which affect
interplanetary environment. In addition, a new telescope named Solar
Magnetic Activity Research Telescope (SMART) was built from 2002 through
2003 to obtain simultaneously Hα image and the vector magnetogram
of the full solar disk with high spatial and temporal resolution. In
this paper, we give an outline and scientific purposes of these three
telescopes, with emphasis on the SMART, and discuss about possibilities
of coordinated observations with SolarB.
Title: Short-Duration Active Region Brightenings Observed in the
Extreme Ultraviolet and Hα by the Solar and Heliospheric Observatory
Coronal Diagnostic Spectrometer and Hida Domeless Solar Telescope
Authors: Brooks, D. H.; Kurokawa, H.; Kamio, S.; Fludra, A.; Ishii,
T. T.; Kitai, R.; Kozu, H.; Ueno, S.; Yoshimura, K.
Bibcode: 2004ApJ...602.1051B
Altcode:
We present the first detection of an Hα counterpart to the EUV
blinker. The observations come from a coordinated campaign between
the Hida Observatory Domeless Solar Telescope (DST) and the Solar
and Heliospheric Observatory Coronal Diagnostic Spectrometer (CDS)
conducted in 2002 July and August. Utilizing studies designed for
high-cadence observations, many short-duration brightenings (<3
minutes) were identified in the He I λ584.334 and O V λ629.732
spectral lines in CDS data of active region NOAA 10039/10044. These
brightenings show similar characteristics (increases in intensity,
size) to longer duration EUV blinkers previously reported in active
regions and the quiet Sun. Focusing on two events that show pronounced
emission in the upper chromosphere (He I), we have been able to identify
cospatial bright points in the lower chromosphere (Hα center, +/-0.5
Å) that show enhanced emission during the EUV blinker. These bright
features have lifetimes similar to those of their EUV counterparts,
and their peak intensities occur nearly simultaneously with the peak
blinker intensities in the He I and O V lines. In both cases the He
I and O V lines show excess line broadening at the peak of the event
(>15 km s-1). Our high-cadence observations also enabled
us to examine the dimensions and lifetimes of short-duration active
region blinkers in detail. We find that the instrumental spatial and
temporal resolution can combine to distort their characteristics:
even short-duration blinkers appear to be composed of elementary
brightening events. The optical brightenings also appear to closely
follow the behavior of the elementary brightenings. The spatial and
temporal relationships between the brightenings indicate a causal link
between the EUV and Hα blinkers.
Title: Short Duration Active Region Brightenings Observed in the
EUV and Ha by SOHO/CDS and HIDA/DST
Authors: Brooks, D. H.; Kurokawa, H.; Kamio, S.; Fludra, A.; Ishii,
T. T.; Kitai, R.; Kosu, H.; Ueno, S.; Yoshimura, K.
Bibcode: 2004ESASP.547..273B
Altcode: 2004soho...13..273B
We present the 1st detection of an H counterpart to the EUV blinker,
using observations from a coordinated campaign between the SOHO Coronal
Diagnostic Spectrometer and the Kyoto University Hida Observatory,
Domeless Solar Telescope (DST). The observations were performed during
July and August 2002. By designing the CDS observing sequences for
high cadence and long duration observations, we were able to identify
many short duration (<3 mins.) brightenings simultaneously in the
He I 584.334A and O V 629.732A spectral lines. These brightenings
show similar characteristics (intensity increases, sizes) to longer
duration EUV blinkers previously reported in active regions and the
'quiet' Sun. Focusing on two events which show pronounced emission
in the upper chromosphere (He I), we have been able to identify
cospatial bright points in the lower chromosphere (H line centre,
60.5A) which show enhanced emission during the EUV blinkers. These
bright features have similar lifetimes to their EUV counterparts and
their peak intensities occur close to simultaneously with the peak
blinker intensities in the He I and O V lines. In both cases the He
I and O V lines show excess line broadening at the peak of the event
(>15 km s01) and in one event evidence of downward (red-shifted)
motion is observed. A statistical study is being performed to provide
a complete picture of the line width and velocity characteristics of
these events and to determine whether the H counterparts are common, or
confined to specific blinkers with pronounced He I emission. The high
cadence of our observations also allowed us to examine the eects of
spatial and temporal averaging on the determination of the properties
of blinkers. We find that both short and long duration blinkers are
composed of elementary brightening events and that such events can
be undetectable in observations with low temporal cadence. Finally,
the H brightenings appear to correlate well with the elementary EUV
brightening events.
Title: Evidence for a Flux Rope driven EUV wave and CME: Comparison
with the Piston Shock Model
Authors: Foley, C. R.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.;
Kitai, R.
Bibcode: 2003A&A...399..749F
Altcode:
This paper examines the relationship between a coronal wave, filament
eruption, flare and Coronal Mass Ejection (CME) which occurred on
2001, April 10th. We study the pre-flare activity which includes the
eruption of a filament and a coronal wave. A large X-ray flare and
a CME follow. We discuss how these phenomena are related and compare
our results to recent models. These are found to be largely consistent
with the numerical simulations of a flux rope driven CME as presented
recently in Chen et al. (2002).
Title: Simultaneous Observation of a Moreton Wave on 1997 November
3 in Hα and Soft X-Rays
Authors: Narukage, N.; Hudson, H. S.; Morimoto, T.; Akiyama, S.;
Kitai, R.; Kurokawa, H.; Shibata, K.
Bibcode: 2002ApJ...572L.109N
Altcode:
We report the observation of a Moreton wave in Hα (line center and
+/-0.8 Å) with the Flare Monitoring Telescope at the Hida Observatory
of Kyoto University at 4:36-4:41 UT on 1997 November 3. The same
region (NOAA Active Region 8100) was simultaneously observed in soft
X-rays with the soft X-ray telescope on board Yohkoh, and a wavelike
disturbance (``X-ray wave'') was also found. The position of the wave
front as well as the direction of propagation of the X-ray wave roughly
agree with those of the Moreton wave. The propagation speeds of the
Moreton wave and the X-ray wave are about 490+/-40 and 630+/-100 km
s-1, respectively. Assuming that the X-ray wave is an MHD
fast-mode shock, we can estimate the propagation speed of the shock, on
the basis of MHD shock theory and the observed soft X-ray intensities
ahead of and behind the X-ray wave front. The estimated fast shock
speed is 400-760 km s-1, which is in rough agreement with
the observed propagation speed of the X-ray wave. The fast-mode Mach
number of the X-ray wave is also estimated to be about 1.15-1.25. These
results suggest that the X-ray wave is a weak MHD fast-mode shock
propagating through the corona and hence is the coronal counterpart
of the Moreton wave.
Title: Multi-wavelength Observations of a Moreton Wave on 2000 March 3
Authors: Narukage, N.; Morimoto, T.; Kitai, R.; Kurokawa, H.;
Shibata, K.
Bibcode: 2002aprm.conf..449N
Altcode:
Moreton waves are flare-associated waves observed to propagate across
the solar disk in Hα (Moreton, 1960). Such waves have been identified
as the intersections of a coronal fast-mode shock fronts and the
chromosphere (Uchida, 1968). We report the observation of a Moreton
wave in Hα (line center and ± 0.8 Å) with the Flare Monitoring
Telescope (FMT) at the Hida Observatory of Kyoto University on 2000
March 3. The same region (NOAA 8882) was simultaneously observed in
soft X-rays with the soft X-ray Telescope (SXT) on board Yohkoh, and
a coronal wave-like disturbance (``X-ray wave") was also found. The
region (NOAA 8882) is near the solar limb. Hence the chromospheric
Moreton wave propagated on the solar disk at a speed of 1050 km/s,
whereas the coronal X-ray wave propagated towards the outer corona
at 1300 km/s. We identified the X-ray wave as an MHD fast-mode shock,
i.e. a coronal counterpart of the Moreton wave, using MHD shock theory
and the observed soft X-ray intensities (Narukage et al., 2002). On the
basis of this result, the propagation of these two waves indicates the
3-dimensional structure of the flare-associated shock wave. This event
is the first observation of the 3-d structure of the shock. Moreover, a
type II radio burst and a coronal mass ejection (CME) were also observed
simultaneously. The shock speed given by the type II radio burst is 1150
km/s. The CME propagated at a speed of 800 km/s. A basic component of
CME is a density enhancement, and the shock preceding the CME propagates
roughly 1.5 times faster than the CME, in this case at 1200 km/s.
Title: Convective Structure in an Emerging Flux Region
Authors: Kozu, H.; Kitai, R.
Bibcode: 2002mwoc.conf...83K
Altcode:
The magnetic field in the Sun is created near the bottom of convective
layer and some of them emerges through convective zone as emerging flux
loops. Flares, surges and other active phenomena can be triggered by
the emerging flux which is affected by surrounding convective motion
and convective structure can play an important role in basic mechanism
of such active events. We observed emerging flux region NOAA 8582 in the
G-band wavelength from 21:00UT to 23:30UT on 1999 June 11 with Real-time
Frame Selector2 (RTFS2) installed in Domeless Solar Telescope in Hida
Observatory, Kyoto University. We observed simultaneously H alpha
center and its wing wavelength with Lyot filter system. We can see many
emerging flux loops and surge activities during the observation period
in H alpha data set. We applied Local Correlation Tracking Method (LCTM)
to the G-band data set and derived horizontal convective structure in
the upper convective zone from it. The resulting convective structure
changed temporary and it can be interpreted as meso-scale convective
structure. In addition to the varying convective structure we found a
temporary continuous up-flow structure under emerging flux loops. The
structure existed continually during the whole observation period and
fixed to the position of middle of foot points of each flux loops. It
means that the up-flow structure is characteristic of the emerging
flux region.
Title: Multi-Wavelength Observation of A Moreton Wave on November
3, 1997
Authors: Narukage, N.; Shibata, K.; Hudson, H. S.; Eto, S.; Isobe,
H.; Asai, A.; Morimoto, T.; Kozu, H.; Ishii, T. T.; Akiyama, S.;
Kitai, R.; Kurokawa, H.
Bibcode: 2002mwoc.conf..295N
Altcode:
No abstract at ADS
Title: Fine Structure inside Flare Ribbons and Temporal Evolution
Authors: Asai, A.; Masuda, S.; Yokoyama, T.; Shimojo, M.; Kurokawa,
H.; Shibata, K.; Ishii, T. T.; Kitai, R.; Isobe, H.; Yaji, K.
Bibcode: 2002mwoc.conf..221A
Altcode:
Non-thermal particles generated in the impulsive phase of
solar flares are observed mainly in microwave, hard X-rays, and
gamma-rays. Observations in Hα can also give important informations
about non-thermal particles precipitating into the chromosphere with
a higher spatial resolution than in other wavelengths. We observed an
X2.3 flare which occurred in the active region NOAA 9415 on 10 April
2001, in Hα with Sartorius Telescope at Kwasan Observatory, Kyoto
University. Thanks to the short exposure time given for the flare, the
Hα images show fine structures inside the flare ribbons. In addition
to Hα, we analyze microwave, hard X-ray, and EUV data obtained with
Nobeyama Radioheliograph, Yohkoh/HXT, and TRACE, respectively. In Hα,
several bright kernels are observed in the flare ribbons. On the other
hand, the hard X-ray images show only a single pair of bright sources
which correspond to one of several pairs of Hα kernels. Examining
the difference in the magnetic field strength and in the time profiles
of Hα emission for these kernels, we discuss the reason why only one
pair kernels are bright in the hard X-ray among the other bright Hα
kernels. Comparing the Hα images with EUV images, we also examine
the three-dimensional structure of solar flares. While broad and
network-like ribbons are observed in Hα, the width of EUV ribbons is
relatively narrow, and EUV ribbons are located at the outer edges of
the corresponding Hα ribbon.
Title: Simultaneous observations of Moreton waves in Hα and Soft
X-ray
Authors: Narukage, N.; Hudson, H.; Morimoto, T.; Kitai, R.; Kurokawa,
H.; Shibata, K.
Bibcode: 2002cosp...34E1337N
Altcode: 2002cosp.meetE1337N
Moreton waves are flare-associated waves observed to propagate
across the solar disk in H (Moreton, 1960). Such waves have been
identified as the intersections of a coronal fast-mode shock fronts
and the chromosphere (Uchida, 1967). We report the two observations of
Moreton waves in H (line center and +/- 0.8 A) with the Flare Monitoring
Telescope (FMT) at the Hida Observatory of Kyoto University. The both
events were simultaneously observed in soft X-rays with the Soft X-ray
Telescope (SXT) on board Yohkoh, and wave-like disturbances ("X-ray
wave") were also found. One event occurred in solar-disk on November 3,
1997, the other near solar limb on March 3, 2000. Assuming that the
X-ray waves are the MHD fast shocks, we can estimate the propagation
speeds of the shocks, based on the MHD shock theory and the observed
soft X-ray intensities ahead and behind the X-ray wave fronts. It is
found that the estimated fast shock speeds are in rough agreement with
the observed propagation speeds of the X-ray waves. The fast mode Mach
numbers of the X-ray waves are also estimated. These results suggest
that the X-ray waves are MHD fast shocks propagating through the corona
and hence are the coronal counterparts of the Moreton waves.
Title: Observations of Moreton Waves and EIT Waves
Authors: Shibata, K.; Eto, S.; Narukage, N.; Isobe, H.; Morimoto,
T.; Kozu, H.; Asai, A.; Ishii, T.; Akiyama, S.; Ueno, S.; Kitai, R.;
Kurokawa, H.; Yashiro, S.; Thompson, B. J.; Wang, T.; Hudson, H. S.
Bibcode: 2002mwoc.conf..279S
Altcode:
The Moreton wave is a flare-associated wave observed in H alpha, and
is now established to be a fast mode MHD shock emitted from the flare,
but the physical mechanism to create the wave is still puzzling. On
the other hand, the EIT wave is a newly discovered flare-associated
wave observed in EUV with the Extreme ultraviolet Imaging Telescope
(EIT) aboard SOHO, and in this case, not only its origin but also
its physical property are both puzzling. We study the relationship
of these two flare-associated waves, Moreton waves and EIT waves, by
analyzing 4 events observed on Nov. 3 and 4, 1997, Aug. 8, 1998, and
Mar. 3, 2000 (Narukage et al. 2001). The Moreton waves were observed
in Ha, Ha+0.8A and Ha-0.8A with the Flare Monitoring Telescope (FMT)
at the Hida Observatory of Kyoto University, while the EIT waves were
observed with SOHO/EIT. In the typical case associated with an X-class
flare in AR 8100 on 4 November 1997 (Eto et al. 2001) the propagation
speeds of the Moreton wave and the EIT wave were approximately 780
km/s and 200 km/s respectively. The data on speed and location show
clearly that the Moreton wave differs physically from the EIT wave in
this case. The detailed analyses of the other events (Nov. 3, 1997,
Aug. 8, 1998, and Mar. 3, 2000) will also be presented, with Yohkoh/SXT
data in the lucky case.
Title: Distribution of the Green- and Red-Line Coronal Emissions
and Their Contribution to the K-Corona
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.
Bibcode: 2001AGUSM..SH41B06T
Altcode:
We have made a detailed analysis of the high-resolution images of
the corona obtained during the total solar eclipse on 1991, July
11. The purpose of the analysis is to derive the temperature and
density structure of the observed corona as reliable as possible
by using the absolute intensities of the the green (530.3 nm) and
red (637.4 nm) coronal emission lines and then contrasted to the
continuum intensity. First, we focus our attention to the loops
appeared distinctly in emission-line images. With the help of a
structure-enhancement algorithm, we show the following results in a
quantitative way. (1) The green- and red-line loops are quite separately
distributed in space. (2) In the innermost corona, structures in the
red-line tend to contribute more to the total column density than
the green-line structures. Second, we study individual emission-line
loops and find that, (1) The electron densities are almost the same
between the two wavelengths. (2) Density-falls with height are nearly
hydrostatic in most loops, while some red-line loops significantly
deflected from the hydrostatic curve. (3) Column density of the analysed
loops only explains 0.1 to 0.2 of the total column density derived from
the continuum intensity at the same point. Then, we propose a method to
determine the contribution of the non-loop component of these emission
lines to the total column density. It is found that the total column
density in the analyzed region can be reasonably explained by a mixture
of the 530.3 nm component with a line-of-sight length comparable to the
size of the active region, and the 637.4 nm component, which tends to
concentrate in loop structures. We thereby conclude that the observed
corona is well explained by plasma of temperatures ranging from 1 MK
to 2 MK.
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: Density Structure of the Coronal Loops Derived from the 1991
Total Eclipse Observation
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.
Bibcode: 2000ASPC..205..113T
Altcode: 2000ltse.conf..113T
High-resolution images of the corona obtained during the total solar
eclipse on 11th July, 1991 were carefully analyzed to derive the
electron densities along the loops of the green(530.3 nm) and red(637.4
nm) emission lines. We found no difference more than a factor of 2
between the averaged densities of the green and the red line loops
at corresponding heights. Most of the analyzed loops were found to be
approximately in hydrostatic equilibrium.
Title: An observational search for giant cells in the sun
Authors: Kitai, R.; Kurokawa, H.; Funakoshi, Y.; Ishiura, K.; Kimura,
G.; Shinkawa, T.
Bibcode: 1999AdSpR..24..237K
Altcode:
With the supergranular network pattern seen in Hα wing image of the
Sun as tracers, we derived large-scale horizontal flow field over the
solar surface by a local-correlation-tracking method. We have found
some evidences of the existence of large scale flow cells on the Sun.
Title: Observational relationship between meso-sized convection and
5-min oscillation in the solar atmosphere
Authors: Ueno, S.; Kitai, R.
Bibcode: 1998IAUS..185..457U
Altcode:
In order to understand 3-dimensional structures of upper
solar convection zone, we performed two different kinds of
observation simultaneously with the Domeless Solar Telescope of
Hida Observatory. One is the 2D imaging observation of solar quiet
photosphere in wavelengths around lambda4308 AA. Another is the slit
1D spectroscopy of the neutral iron line lambda6302.5 AA; at the
central region of the field-of-view of the imaging observation. Thus
the horizontal velocity field is obtained from the former observation,
while the radial velocity field is obtained from the latter one at
the same region. In both velocity fields, we found the meso-sized
structures and confirmed convective nature of the flow. And we observed
that amplitudes of 5-min oscillations were increased soon after large
downward motions of convection, similar to the other observations'
results (T.R. Rimmele, P.R. Goode, E. Harold, and R.T. Stebbins 1995;
O. Espagnet, R. Muller, Th. Roudier, P. Mein, N. Mein, and J.M. Malherbe
1996). Moreover, we report the possible relationship between horizontal
velocity gradient distributions and oscillation excitations.
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: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion
of Hot and Cool Loops
Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell,
T.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1997SoPh..174..151V
Altcode:
Observations of the post-flare loops after the X3.9 flare which occurred
on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as
in Hα obtained at 5 different observatories, have provided a unique,
longest ever, set of data for a study of the relationship between the
hot and cool post-flare loops as they evolve. At any given time, the
altitude difference between the hot X-ray loops of 6-7× 106
K and the cool Hα loops of 1.5× 104 K is related to the
expansion rate of the loop systems and their cooling time. Therefore,
measurements of the expansion rate and relative height of hot and
cool loops can provide direct observational values for their cooling
times. We measured the altitude of hot and cool loops for 15 and 19
hours, respectively, and found that the cooling time increased as the
density of the loops decreased. We found a reasonably good agreement
between the observed cooling times and those obtained from model
calculations, although the observed values were always somewhat longer
than the theoretical ones. Taking into account evolutionary effects,
we also found similar shapes and configurations of hot and cool loops
during the entire observing period and confirmed that, at any time,
hot loops are at higher altitude than cool loops, suggesting that cool
loops indeed evolve from hot loops. These results were used to check
the validity of the reconnection model.
Title: Global and Fine Scale Distribution of the Innermost Coronal
Temperature
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.
Bibcode: 1997IAUJD..19E..50T
Altcode:
The observations of the solar corona at the total eclipses continue to
provide us with valuable data, which enables us to study the thermo
dynamic structures. Because of the extremely low scattered lights,
coronal emission intensities measured during the eclipse time are still
higher in accuracy and resolution than the observation from space. It
is rare chance to study temperature and density structure of the very
innermost part of the corona at visible wavelengths. In this paper,
we present the spatial variations of the absolute intensities of the
active region corona from 1.05 to 1.5 Rodot observed at the
total eclipse of 11th July, 1991, in three wavelengths of 2 coronal
emission lines (Fe XIV 530.3 nm and Fe X 637.4 nm) and the continuum
around 610.0nm. Global temperature estimation by taking the intensity
ratio, Fe XIV/Fe X, indicates that average temperature is not always the
highest in the prominent active region corona, since there exists large
amount of the cooler plasma together with the hotter component. Next,
we examine spatial correlation among the fine structures at above
three wavelengths, and show semi-quantitatively that most 1.0 times
10^6K (Fe X) and 2.0 times 10^6K (Fe XIV) plasma are isolated with
each other, and that, if they combined, they explain about 70% of the
continuum structures.
Title: Relative Altitude of Hot and Cool Post-Flare Loops
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell,
T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1996ASPC..111..359V
Altcode: 1997ASPC..111..359V
The authors collected a unique set of data obtained simultaneously at
4 different ground based observatories and with the Yohkoh satellite
to study the relationship between hot X-ray and cool Hα post-flare
loops as they evolved during the long gradual phase of the X3.9 flare
which occurred on 25 June 1992. They found reasonably good agreement
between the computed 'theoretical' cooling times and the 'observed'
cooling times derived from the relative altitudes of hot and cool
loops. Taking into account evolutionary effects, the authors also found
similar shape and configuration of hot and cool loops during the entire
observing period and confirmed that at any time hot loops are at higher
altitude than cool loops, suggesting that cool loops indeed descend
from hot loops. The results provide support for the reconnection model.
Title: He I 10830 Angstroms in Solar Active Regions and its
Correlation with Chromospheric Lines
Authors: Kitai, R.; Tohmura, I.; Suematsu, Y.; Akioka, M.; Soltau, D.
Bibcode: 1996mpsa.conf..435K
Altcode: 1996IAUCo.153..435K
No abstract at ADS
Title: Comparison of High Resolution Optical and Soft X-ray Images
of Solar Corona
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.; Golub, L.
Bibcode: 1996mpsa.conf..483T
Altcode: 1996IAUCo.153..483T
No abstract at ADS
Title: Electron Acceleration Site of the 1992 Sep. 6 Flare
Authors: Fujiki, K.; Nakajima, H.; Hanaoka, Y.; Yaji, K.; Kitai, R.
Bibcode: 1996mpsa.conf..547F
Altcode: 1996IAUCo.153..547F
No abstract at ADS
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: 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: Thermal and Density Structure of the Inner Corona Observed
at the 1991 Total Solar Eclipse
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.
Bibcode: 1994kofu.symp..381T
Altcode:
We observed the total solar eclipse on 11 July, 1991 with the
multi-channel telescope at Lapaz,Mexico, and successfully obtained
high-resolution pictures of the innermost corona at the wavelength
shown in Table 1. This is a brief summary of preliminary results
obtained from the photometric mesurement of the photographic pictures
and their image processing.
Title: Flares on September 6, 1992
Authors: Kitai, R.; Kurokawa, H.; Funakoshi, Y.; Nakai, Y.; Shibata,
K.; Yaji, K.; Nitta, N.; YOHKOH Team; NAOJ Flare Telescope Team
Bibcode: 1994kofu.symp..147K
Altcode:
We present some preliminary results of our observational
study of typical eruptive flares in NOAA7270 on September 6,
1992. (1)Magnetic shear and flux emergence are strongly related to
flare production. (2)Observed flares showed a common temporal relation
between cool plasma dynamics seen in H_alpha and coronal energy releases
seen in YOHKOH data. (3)At the pre-heating stage of flares, there were
some indications of slow reconnection of adjacent magnetic loops.
Title: Fine Structures of the Inner Corona Observed at the 1991
Total Solar Eclipse
Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.
Bibcode: 1994scs..conf..565T
Altcode: 1994IAUCo.144..565T
No abstract at ADS
Title: A Prominenece Eruption Followed by a Coronal Arcade Formation
on July 30-31, 1992
Authors: Hanaoka, Y.; Kurokawa, H.; Enome, S.; Nakajima, H.; Shibasaki,
K.; Nishio, M.; Takano, T.; Torii, C.; Sekiguchi, H.; Kawashima, S.;
Bushimata, T.; Shinohara, N.; Irimajiri, Y.; Koshiishi, H.; Shiomi,
Y.; Nakai, Y.; Funakoshi, Y.; Kitai, R.; Ishiura, K.; Kimura, G.
Bibcode: 1994xspy.conf..193H
Altcode:
No abstract at ADS
Title: Prominence Eruption in NOAA7125 on April 6, 1992
Authors: Kitai, R.; Kawai, G.; Anwar, B.; Kurokawa, H.; Funakoshi,
Y.; Nakai, Y.; Tsuneta, S.
Bibcode: 1994xspy.conf..287K
Altcode:
No abstract at ADS
Title: Flares on 1992 September 6
Authors: Shibata, K.; Nitta, N.; Kitai, R.; Kurokawa, H.; Yaji, K.;
Kato, T.; Zarro, D. M.
Bibcode: 1993BAAS...25R1187S
Altcode:
No abstract at ADS
Title: High resolution observations of active phenomena obtained at
Hida Observatory
Authors: Kurokawa, H.; Nakai, Y.; Funakoshi, Y.; Kitai, R.
Bibcode: 1991AdSpR..11e.233K
Altcode: 1991AdSpR..11..233K
Samples of high-resolution observations of solar active regions and
flares obtained with the 60-cm Domeless Solar Telescope (DST) at
Hida Observatory, Kyoto University are presented. What gives rise to
the twist and shear in the magnetic loop structures is the essential
question for the study of solar active phenomena. Several examples
showing the development of twisted or sheared magnetic structures
are demonstrated and morphologically studied. Two examples of
high-resolution spectra of a flare and spicules are also demonstrated.
Title: Photospheric and Chromospheric Umbral Dots in a Decaying
Sunspot
Authors: Kitai, R.
Bibcode: 1986SoPh..104..287K
Altcode:
Time-sequenced Hα filtergrams and narrow-band blue filtergrams
(λ0 = 4308 Å, Δλ = 10 Å) of umbral dots in a decaying
sunspot were studied. The results are: (a) Photospheric umbral dots
have lifetimes of about 40 min. (b) Two types of proper motion were
found for photospheric umbral dots. Umbral dots born in the umbra or
in the light bridge show virtually no proper motion. On the other hand,
umbral dots of penumbral origin move inward to the umbra with speeds of
about 0.4 km s −1. (c) Chromospheric umbral dots, which
have dimensions of 0″.6 × 1″.2 in the mean, were more numerously
found than photospheric umbral dots. (d) Photospheric umbral dots were
observed to be associated with chromospheric umbral dots. Thus umbral
dots are not phenomena confined to photospheric levels but also extend
to chromospheric levels. (e) Some of the chromospheric umbral dots are
unrelated to the photospheric umbral dots. They may be excited by the
infalling matter from the umbral corona.
Title: The Kwasan Image Processing System.
Authors: Nakai, Y.; Kitai, R.; Asada, T.; Iwasaki, K.
Bibcode: 1986MmKyo..37...59N
Altcode:
The Kwasan Image Processing System is a general purpose interactive
image processing and analyzing system designed to process a large
amount of photographic and photoelectric data. The hardware of
the system mainly consists of a PDS MICRO-10 microdensitometer,
a VAX-11/750 minicomputer, a 456 M bytes Winchester disk and a VS11
color-graphic terminal. The application programs "PDS, KIPS, STII"
enable users to analyze spectrographic plates and two-dimensional
images without site-special knowledge of programming.
Title: On the Relation Between Chromospheric and Photospheric Fine
Structure in an Active Region
Authors: Kitai, R.; Muller, R.
Bibcode: 1984SoPh...90..303K
Altcode:
A comparative study was done on the bright fine structure in the upper
photosphere and in the lower chromosphere of an active region. The
results are shown in the following: (a) The bright points in the Hα
wing are cospatial to the facular points, which confirms the result of
Wilson (1981). (b) Some points bright in the Hα wing are associated
with the facular granules which have larger sizes than the facular
points, (c) The brightness enhancement in the Ha wing is positively
correlated to the enhancement in the blue continuum. However, the
correlation is not so strong. (d) The moustache points are also
cospatial to the facular features. (e) The geometrical shape of a
moustache point is like a funnel and diverging upward in the upper
photospheric and the lower chromospheric levels.
Title: On the mass motions and the atmospheric states of moustaches.
Authors: Kitai, R.
Bibcode: 1983SoPh...87..135K
Altcode:
Analyses of broad moustache profiles of Balmer lines and Ca II H and K
lines are performed based upon our spectroscopic observation under good
seeing conditions. Hα emission profiles are found to consist of three
components, i.e., a central absorption, a Gaussian core and a power-law
wing. Each of them has a different Doppler shift from others. From
the data of Doppler shifts, mass motions with velocity of about 6 km
s−1 are found to be present in chromospheric levels of
moustache atmospheres. Computations of Hα emission profiles radiated
from a variety of model atmospheres are made. Comparison of computed
profiles with the observed ones leads us to the conclusion that a broad
Hα profile is due to a formation of heated (ΔT = 1500 K) and condensed
(ϱ/ϱ0 = 5) chromospheric layers relative to the normal.
Title: Numerical Hydrodynamics of the Jet Phenomena in the Solar
Atmosphere - Part Two - Surges
Authors: Shibata, K.; Nishikawa, T.; Kitai, R.; Suematsu, Y.
Bibcode: 1982SoPh...77..121S
Altcode:
One-dimensional hydrodynamic simulations of surges are performed in
order to make clear their origin and structure. Surges are regarded as
the jets resulting from a sudden pressure increase at the base of the
model atmosphere. The height of the explosion (h0), which
is measured from the level of τ5000 = 1, is regarded as a
free parameter. Another free parameter is the strength of the sudden
pressure increase (p/p0) at h0. Simulations
are performed for values in the ranges of 540 km ≤ h0
≤ 1920 km and 3 ≤ p/p0 ≤ 30. It was found that for a
fixed p/p0 there exists a critical height (hc)
in h0, which separates the jet (surge) models into two
types. For h0 > hc, jets are produced directly
by the pressure gradient force near h0, and made of the
matter ejected from the explosion itself. The essential hydrodynamic
structure of this type is the same as that in a shock tube (this type
is called `shock tube' type). For h0 < hc,
jets are not the direct results of the pressure enhancement, but
are produced by the shock wave which are generated by the pressure
enhancement and which has propagated through the chromosphere (this type
is called the `crest shock' type). It is shown that the critical height
(hc) ranges from 1000 km to 1500 km for 3 ≤ p/p0
≤ 30. General properties of both types are investigated in detail. The
results are compared with observations and it is concluded that small
surges associated with Ellerman bombsbelong to the `crest shock' type,
i.e. they are produced by the shock wave.
Title: Numerical Hydrodynamics of the Jet Phenomena in the Solar
Atmosphere - Part One - Spicules
Authors: Suematsu, Y.; Shibata, K.; Neshikawa, T.; Kitai, R.
Bibcode: 1982SoPh...75...99S
Altcode:
We present a spicule model whose eruption occurs as a result of the
sudden pressure enhancement at the bright point located at the root of
the spicule. To show this, one dimensional (constant cross sectional)
and time dependent hydrodynamic equations are solved numerically in
the realistic solar atmosphere extending from the photosphere to
the corona. Adiabatic motion is assumed. The pressure enhancement
by a bright point at the base of the model atmosphere generates a
shock wave. The shock gets stronger as it passes upward through the
chromosphere and eventually collides with the chromosphere-corona
interface which is a kind of a contact discontinuity. As the result,
the interface begins to move upward. We identify the matter following
behind this interface as the solar spicule. The model explains many
observed features, such as the height and the density of the spicules,
although such features have been hitherto considered not to be explained
easily by shock theories.
Title: On the Emission Spectra of Moustasches
Authors: Kitai, R.
Bibcode: 1980jfss.conf..202K
Altcode:
No abstract at ADS
Title: Morphological Study of the Solar Granulation - Part One -
Dark Dot Formation in the Cell
Authors: Kitai, R.; Kawaguchi, I.
Bibcode: 1979SoPh...64....3K
Altcode:
High resolution images of the solar granulation show the presence of
the small dot-like dark regions in the granulation cells. From the
study of the characteristics of these dark regions, it is found that
the dark regions are formed without any relations to the presence of
the magnetic field. Moreover, it is observed that a granulation cell
splits in a few minutes after the formation of the dark regions in the
cell. Similarities and differences between the granules with the dark
regions and the so-called exploding granules are discussed.
Title: An Interpretation of Hydrogen and Helium Line Spectra of the
Loop Prominence Observed on November 3, 1973
Authors: Kureizumi, T.; Kubota, J.; Tamenaga, T.; Maeda, K.; Kawaguchi,
I.; Kitai, R.
Bibcode: 1977PASJ...29..129K
Altcode:
The H I, He I, and He ii emission lines of the loop prominence observed
on November 3, 1973 in the rapidly developing phase are analyzed. The
difference in widths of these lines suggests they do not originate
in the same volume. The estimated Te (8000-9000 K) and e ( 2x 1012
cm-3) in the loop from the Balmer lines do not change appreciably with
time everywhere in the loop during our observation ( UT). The degree
of ionization of hydrogen is estimated to be in the range of 0.8 to
1.0. The ionizing mechanism may be attributed to the UV radiation (
912A) from the underlying flare region. Local thermodynamic equilibrium
(LTE) is approximately established in the excited levels of He I,
but the singlet levels are somewhat overpopulated. The UV radiation
field ( ) from the surrounding coronal condensation is estimated from
microwave and X-ray flux measurements of SOLRAD 9. The ionization of
He I (ionization degree 0.1-0.2) is mainly controlled by UV radiation
from the coronal condensation. An adequate thread structure model of
the loop prominence is suggested. Key words: Coronal condensation;
Loop prominence; Spectra.
Title: The velocity field associated with the birth of sunspots.
Authors: Kawaguchi, I.; Kitai, R.
Bibcode: 1976SoPh...46..125K
Altcode:
A velocity field is found to occur prior to the birth of sunspots or
during the rapidly developing phase of new spots. Fraunhofer lines
are always shifted redwards in the observed active regions which are
situated at various distances from the disk center. The velocity
amplitude derived from Na I D1-line, λ 5895.940, amounts to, at
maximum, 1.5 km s−1 which is always a little larger than
that derived from the weaker line, NI I λ 5892.883. The velocity field
disappears when the spot ceases to grow. The lifetime of the velocity
is, at least, 1 hr. The velocity field is interpreted in terms of the
continuous downward flow in the process of formation of sunspots.
Title: Photospheric Velocity Field Associated with Moustaches
Authors: Kitai, R.; Kawaguchi, I.
Bibcode: 1975SoPh...44..403K
Altcode:
The photospheric velocity field was observed in an active region which
was prolific in moustaches. It is shown that the moustaches occur at
the locations where the sign of the line-of-sight velocity changes,
and that the extension of the velocity field is large (≈104
km) compared with the dimension of moustaches.
Title: The Brightening of Sunspot Umbra Observed on 29 October, 1972
Authors: Kubota, J.; Tamenaga, T.; Kawaguchi, I.; Kitai, R.
Bibcode: 1974SoPh...38..389K
Altcode:
Brief descriptions are given of the spectroscopic and the monochromatic
observations of the umbral brightening on 29 October, 1972. The source
of the brightening is attributed to the kinetic energy of the infalling
coronal matter with a final velocity of 200 km s−1,
into the umbral gas. The spectra of this brightening reveal many
hydrogen and metallic emission lines. The variety of the widths of
these lines indicates the existence of complex nonthermal velocity
field and of the stratification of various emitting conditions in the
umbral brightening. The kinetic energy of the falling matter would be
expended not only for producing the emissions, but also for exciting
the complex velocity field of nonthermal motion.