explanation blue bibcodes open ADS page with paths to full text
Author name code: watanabe-tetsuya
ADS astronomy entries on 2022-09-14
=author:"Watanabe, Tetsuya"
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Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
2020SPIE11444E..0NS Altcode:
Solar-C (EUVST) is the next Japanese solar physics mission to
be developed with significant contributions from US and European
countries. The mission carries an EUV imaging spectrometer with
slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
Telescope) as the mission payload, to take a fundamental step towards
answering how the plasma universe is created and evolves and how the
Sun influences the Earth and other planets in our solar system. In
April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
(Japan Aerospace Exploration Agency) has made the final down-selection
for this mission as the 4th in the series of competitively chosen
M-class mission to be launched with an Epsilon launch vehicle in mid
2020s. NASA (National Aeronautics and Space Administration) has selected
this mission concept for Phase A concept study in September 2019 and
is in the process leading to final selection. For European countries,
the team has (or is in the process of confirming) confirmed endorsement
for hardware contributions to the EUVST from the national agencies. A
recent update to the mission instrumentation is to add a UV spectral
irradiance monitor capability for EUVST calibration and scientific
purpose. This presentation provides the latest status of the mission
with an overall description of the mission concept emphasizing on key
roles of the mission in heliophysics research from mid 2020s.
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Title: Resonant electron impact excitation of highly charged Fe ions
studied with a compact electron beam ion trap
Authors: Monobe, Masashi; Sakaue, Hiroyuki A.; Kato, Daiji; Murakami,
Izumi; Hara, Hirohisa; Watanabe, Tetsuya; Nakamura, Nobuyuki
2020XRS....49..511M Altcode:
No abstract at ADS
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Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
2019PASJ...71R...1H Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.
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Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
2019SPIE11118E..07S Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
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Title: Solar Extreme Ultraviolet Spectroscopy: zur NachEISzeit
Authors: Watanabe, Tetsuya
2018ASSL..449...53W Altcode:
No abstract at ADS
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Title: Resonant Electron Impact Excitation of 3d Levels in
Fe<SUP>14+</SUP> and Fe<SUP>15+</SUP>
Authors: Tsuda, Takashi; Shimizu, Erina; Ali, Safdar; Sakaue, Hiroyuki
A.; Kato, Daiji; Murakami, Izumi; Hara, Hirohisa; Watanabe, Tetsuya;
Nakamura, Nobuyuki
2017ApJ...851...82T Altcode: 2017arXiv171003548T
We present laboratory spectra of the 3p-3d transitions in
Fe<SUP>14+</SUP> and Fe<SUP>15+</SUP> excited with a mono-energetic
electron beam. In the energy-dependent spectra obtained by
sweeping the electron energy, resonant excitation is confirmed
as an intensity enhancement at specific electron energies. The
experimental results are compared with theoretical cross sections
calculated based on fully relativistic wave functions and the
distorted wave approximation. Comparisons between the experimental
and theoretical results show good agreement for the resonance
strength. A significant discrepancy is, however, found for the
non-resonant cross section in Fe<SUP>14+</SUP>. This discrepancy is
considered to be the fundamental cause of the previously reported
inconsistency of the model with the observed intensity ratio between
the {}<SUP>3</SUP>{P}<SUB>2</SUB>{--}{}<SUP>3</SUP>{D}<SUB>3</SUB>
and {}<SUP>1</SUP>{P}<SUB>1</SUB>{--}{}<SUP>1</SUP>{D}<SUB>2</SUB>
transitions.
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Title: Neon-like Iron Ion Lines Measured in NIFS/Large Helical Device
(LHD) and Hinode/EUV Imaging Spectrometer (EIS)
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Murakami, Izumi; Kato,
Daiji; Sakaue, Hiroyuki A.; Morita, Shigeru; Suzuki, Chihiro; Tamura,
Naoki; Yamamoto, Norimasa; Nakamura, Nobuyuki
2017ApJ...842...12W Altcode:
Line intensities emerging from the Ne-sequence iron ion (Fe XVII) are
measured in the laboratory, by the Large Helical Device at the National
Institute for Fusion Science, and in the solar corona by the EUV Imaging
Spectrometer (EIS) on board the Hinode mission. The intensity ratios of
Fe XVII λ 204.6/λ 254.8 are derived in the laboratory by unblending
the contributions of the Fe XIII and XII line intensities. They are
consistent with theoretical predictions and solar observations, the
latter of which endorses the in-flight radiometric calibrations of the
EIS instrument. The still remaining temperature-dependent behavior of
the line ratio suggests the contamination of lower-temperature iron
lines that are blended with the λ 204.6 line.
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Title: Measurements of density dependent intensity ratios of extreme
ultraviolet line emission from Fe X, XI, and XII
Authors: Shimizu, Erina; Ali, Safdar; Tsuda, Takashi; Sakaue, Hiroyuki
A.; Kato, Daiji; Murakami, Izumi; Hara, Hirohisa; Watanabe, Tetsuya;
Nakamura, Nobuyuki
2017A&A...601A.111S Altcode:
We report high-resolution density dependent intensity ratio measurements
for middle charge states of iron in the extreme ultraviolet (EUV)
spectral wavelength range of 160-200 Å. The measurements were
performed at the Tokyo EBIT laboratory by employing a flat-field
grazing incidence spectrometer installed on a low energy compact
electron beam ion trap. The intensity ratios for several line pairs
stemming from Fe X, Fe XI and Fe XII were extracted from spectra
collected at the electron beam energies of 340 and 400 eV by varying
the beam current between 7.5 and 12 mA at each energy. In addition,
the effective electron densities were obtained experimentally by imaging
the electron beam profile and ion cloud size with a pinhole camera and
visible spectrometer, respectively. In this paper, the experimental
results are compared with previous data from the literature and with the
present calculations performed using a collisional-radiative model. Our
experimental results show a rather good agreement with the calculations
and previous reported results.
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Title: Atomic-level Pseudo-degeneracy of Atomic Levels Giving
Transitions Induced by Magnetic Fields, of Importance for Determining
the Field Strengths in the Solar Corona
Authors: Li, Wenxian; Yang, Yang; Tu, Bingsheng; Xiao, Jun; Grumer,
Jon; Brage, Tomas; Watanabe, Tetsuya; Hutton, Roger; Zou, Yaming
2016ApJ...826..219L Altcode:
We present a measured value for the degree of pseudo-degeneracy
between two fine-structure levels in Fe<SUP>9+</SUP> from line
intensity ratios involving a transition induced by an external
magnetic field. The extracted fine-structure energy difference
between the 3{p}<SUP>4</SUP>3d{}<SUP>4</SUP>{D}<SUB>5/2</SUB>
and {}<SUP>4</SUP>{D}<SUB>7/2</SUB> levels, where the
latter is the upper state for the magnetic-field induced
line, is needed in our recently proposed method to measure
magnetic-field strengths in the solar corona. The intensity
of the 3{p}<SUP>4</SUP>3d{}<SUP>4</SUP>{D}<SUB>7/2</SUB>\to
3{p}<SUP>5</SUP>{}<SUP>2</SUP>{P}<SUB>3/2</SUB> line at 257.262 Å is
sensitive to the magnetic field external to the ion. This sensitivity
is in turn strongly dependent on the energy separation in the
pseudo-degeneracy through the mixing induced by the external magnetic
field. Our measurement, which uses an Electron Beam Ion Trap with a
known magnetic-field strength, indicates that this energy difference
is 3.5 cm<SUP>-1</SUP>. The high abundance of Fe<SUP>9+</SUP> and the
sensitivity of the line’s transition probability to field strengths
below 0.1 T opens up the possibility of diagnosing coronal magnetic
fields. We propose a new method to measure the magnetic field in the
solar corona, from similar intensity ratios in Fe<SUP>9+</SUP>. In
addition, the proposed method to use the line ratio of the blended
line 3{p}<SUP>4</SUP>3d{}<SUP>4</SUP>{D}<SUB>7/{2,5</SUB>/2}\to
3{p}<SUP>5</SUP>{}<SUP>2</SUP>{P}<SUB>3/2</SUB> with another line
from Fe x as the density diagnostic should evaluate the effect of the
magnetic-field-induced transition line.
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Title: Observation and numerical modeling of chromospheric evaporation
during the impulsive phase of a solar flare
Authors: Imada, Shinsuke; Murakami, Izumi; Watanabe, Tetsuya
2015PhPl...22j1206I Altcode: 2015arXiv150604674I
We have studied the chromospheric evaporation flow during the impulsive
phase of the flare by using the Hinode/EUV Imaging Spectrometer
observation and 1D hydrodynamic numerical simulation coupled to the
time-dependent ionization. The observation clearly shows that the strong
redshift can be observed at the base of the flaring loop only during the
impulsive phase. We performed two different numerical simulations to
reproduce the strong downflows in FeXII and FeXV during the impulsive
phase. By changing the thermal conduction coefficient, we carried out
the numerical calculation of chromospheric evaporation in the thermal
conduction dominant regime (conductivity coefficient κ<SUB>0</SUB> =
classical value) and the enthalpy flux dominant regime (κ<SUB>0</SUB>
= 0.1 × classical value). The chromospheric evaporation calculation in
the enthalpy flux dominant regime could reproduce the strong redshift
at the base of the flare during the impulsive phase. This result might
indicate that the thermal conduction can be strongly suppressed in some
cases of flare. We also find that time-dependent ionization effect is
important to reproduce the strong downflows in Fe XII and Fe XV.
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Title: A Novel Method to Determine Magnetic Fields in Low-density
Plasma Facilitated through Accidental Degeneracy of Quantum States
in Fe<SUP>9+</SUP>
Authors: Li, Wenxian; Grumer, Jon; Yang, Yang; Brage, Tomas; Yao,
Ke; Chen, Chongyang; Watanabe, Tetsuya; Jönsson, Per; Lundstedt,
Henrik; Hutton, Roger; Zou, Yaming
2015ApJ...807...69L Altcode: 2015arXiv150407052L
We propose a new method to determine magnetic fields, by using the
magnetic-field-induced electric dipole transition 3{{{p}}}<SUP>4</SUP>
3{{d}}{ }<SUP>4</SUP>{D}<SUB>7/2</SUB> \to 3{{{p}}}<SUP>5</SUP>{
}<SUP>2</SUP>{P}<SUB>3/2</SUB> in {{Fe}}<SUP>9+</SUP> ions. This ion
has a high abundance in astrophysical plasma and is therefore well
suited for direct measurements of even rather weak fields in, e.g.,
solar flares. This transition is induced by an external magnetic
field and its rate is proportional to the square of the magnetic
field strength. We present theoretical values for what we will label
the reduced rate and propose that the critical energy difference
between the upper level in this transition and the close-to-degenerate
3{{{p}}}<SUP>4</SUP> 3{{d}}{ }<SUP>4</SUP>{D}<SUB>5/2</SUB> should be
measured experimentally since it is required to determine the relative
intensity of this magnetic line for different magnetic fields.
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Title: The Solar-C Mission
Authors: Watanabe, Tetsuya
2014SPIE.9143E..1OW Altcode:
Solar-C is a mission designed to answer some of the most important
questions in solar physics. Recent progress from missions like Hinode
has revealed that the different parts of the solar atmosphere are
coupled in fundamental ways and has defined the spatial scales and
temperature regimes that need to be observed in order to achieve
a comprehensive physical understanding of this coupling. Solar-C
will deploy a carefully coordinated suite of three complementary
instruments: the Solar Ultra-violet Visible and IR Telescope (SUVIT),
the high-throughput EUV Spectroscopic Telescope (EUVST), and an X-ray
Imaging Telescope (XIT). The science of Solar-C will greatly advance
our understanding of the Sun, of basic physical processes operating
throughout the universe, and of how the Sun influences the Earth and
other planets in our solar system.
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Title: Velocity structure of solar flare plasmas
Authors: Watanabe, Tetsuya; Watanabe, Kyoko; Hara, Hirohisa; Imada,
Shinsuke
2014cosp...40E3606W Altcode:
Thanks to its increased sensitivity and spectral resolution, EIS
enabled emission line profile analysis for the first time in solar
EUV spectroscopy, and it found detailed structures in velocity and
temperature in solar flares. A widely accepted model for solar flares
incorporates magnetic reconnection in the corona which results
in local heating as well as acceleration of nonthermal particle
beams. The standard model of solar flares is called the CSHKP model,
arranging the initials of model proposers. We find loop-top hot source,
fast outflows nearby, inflow structure flowing to the hot source that
appeared in the impulsive phase of long-duration eruptive flares. From
the geometrical relationships of these phenomena, we conclude that
they provide evidence for magnetic reconnection that occurs near the
loop-top region. The reconnection rate is estimated to 0.05 - 0.1,
which supports the Petschek-type magnetic reconnection. The nonthermal
particle beams will travel unimpeded until they reach the cold, dense
chromosphere, where the energy of the beam is predominantly used to
heat the chromosphere at the foot points of flaring loops. Explosive
chromospheric evaporation happens when the beam energy is high enough
that the chromosphere cannot radiate away energy fast enough and
hence expands at high velocities into the corona. Spatially resolved
observations of chromopheric evaporation during the initial phases of
impulsive flares, a few bright points of Fexxiii and Fexxiv emission
lines at the footpoints of flaring loops present dominated blue-shifted
components of 300 - 400 kms (-1) , while Fexv/xvi lines are nearly
stationary, and Feviii and Sivii lines present +50 kms (-1) red
shifts. We will review these new views on dynamical structure in flares.
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Title: A Statistical Study of Coronal Active Events in the North
Polar Region
Authors: Sako, Nobuharu; Shimojo, Masumi; Watanabe, Tetsuya; Sekii,
Takashi
2013ApJ...775...22S Altcode:
In order to study the relationship between characteristics of polar
coronal active events and the magnetic environment in which such events
take place, we analyze 526 X-ray jets and 1256 transient brightenings
in the polar regions and in regions around the equatorial limbs. We
calculate the occurrence rates of these polar coronal active events
as a function of distance from the boundary of coronal holes, and
find that most events in the polar quiet regions occur adjacent to
and equatorward of the coronal hole boundaries, while events in the
polar coronal holes occur uniformly within them. Based primarily on
the background intensity, we define three categories of regions that
produce activity: polar coronal holes, coronal hole boundary regions,
and polar quiet regions. We then investigate the properties of the
events produced in these regions. We find no significant differences
in their characteristics, for example, length and lifetime, but there
are differences in the occurrence rates. The mean occurrence rate of
X-ray jets around the boundaries of coronal holes is higher than that
in the polar quiet regions, equatorial quiet regions, and polar coronal
holes. Furthermore, the mean occurrence rate of transient brightenings
is also higher in these regions. We make comparison with the occurrence
rates of emerging and canceling magnetic fields in the photosphere
reported in previous studies, and find that they do not agree with
the occurrence rates of transient brightenings found in this study.
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Title: Plasma Motions and Heating by Magnetic Reconnection in a 2007
May 19 Flare
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.
2011ApJ...741..107H Altcode:
Based on scanning spectroscopic observations with the Hinode EUV
imaging spectrometer, we have found a loop-top hot source, a fast
jet nearby, and an inflow structure flowing to the hot source that
appeared in the impulsive phase of a long-duration flare at the
disk center on 2007 May 19. The hot source observed in Fe XXIII and
Fe XXIV emission lines has the electron temperature of 12 MK and
density of 1 × 10<SUP>10</SUP> cm<SUP>-3</SUP>. It shows excess
line broadening, which exceeds the thermal Doppler width by ~100 km
s<SUP>-1</SUP>, with a weak redshift of ~30 km s<SUP>-1</SUP>. We have
also observed a blueshifted faint jet whose Doppler velocity exceeds
200 km s<SUP>-1</SUP> with an electron temperature of 9 MK. Coronal
plasmas with electron temperature of 1.2 MK and density of 2.5 ×
10<SUP>9</SUP> cm<SUP>-3</SUP> that flow into the loop-top region
with a Doppler velocity of 20 km s<SUP>-1</SUP> have been identified
in the Fe XII observation. They disappeared near the hot source,
possibly by being heated to the hotter faint jet temperature. From
the geometrical relationships of these phenomena, we conclude that
they provide evidence for magnetic reconnection that occurs near the
loop-top region. The estimated reconnection rate is 0.05-0.1, which
supports the Petschek-type magnetic reconnection. Further supporting
evidence for the presence of the slow-mode and fast-mode MHD shocks
in the reconnection geometry is given based on the observed quantities.
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Title: The SOLAR-C mission: current status
Authors: Shimizu, Toshifumi; Tsuneta, Saku; Hara, Hirohisa; Ichimoto,
Kiyoshi; Kusano, Kanya; Sakao, Taro; Sekii, Takashi; Suematsu,
Yoshinori; Watanabe, Tetsuya
2011SPIE.8148E..0BS Altcode: 2011SPIE.8148E..10S
Two mission concepts (plan A: out-of-ecliptic mission and plan B:
high resolution spectroscopic mission) have been studied for the next
Japanese-led solar mission Solar-C, which will follow the scientific
success of the Hinode mission. The both mission concepts are concluded
as equally important and attractive for the promotion of space solar
physics. In the meantime we also had to make efforts for prioritizing
the two options, in order to proceed to next stage of requesting the
launch of Solar-C mission at the earliest opportunity. This paper
briefly describes the two mission concepts and the current status
on our efforts for prioritizing the two options. More details are
also described for the plan B option as the first-priority Solar-C
mission. The latest report from the Solar-C mission concept studies
was documented as "Interim Report on the Solar-C Mission Concept."
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Title: Intensity Ratio of Density-sensitive Lines in Fe Ions Observed
with a Well-defined Laboratory Plasma
Authors: Nakamura, Nobuyuki; Watanabe, Etsushi; Sakaue, Hiroyuki A.;
Kato, Daiji; Murakami, Izumi; Yamamoto, Norimasa; Hara, Hirohisa;
Watanabe, Tetsuya
2011ApJ...739...17N Altcode:
We present spectra of highly charged Fe ions in the extreme ultraviolet
range observed using an electron beam ion trap equipped with a
flat-field grazing incidence spectrometer. The density dependence of
line intensity ratios is investigated for several density-sensitive
lines of Fe XIII, XIV, and XV. Unlike previous studies where the
electron density was estimated from theoretical considerations, here
it is derived from electron beam profile measurements. The experimental
data are compared with model calculations.
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Title: Production of High-temperature Plasmas During the Early Phases
of a C9.7 Flare
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Sterling, Alphonse C.;
Harra, Louise K.
2010ApJ...719..213W Altcode:
Explosive chromospheric evaporation is predicted from some current
solar flare models. In this paper, we analyze a flare with high time
cadence raster scans with the EUV Imaging Spectrometer (EIS) on board
the Hinode spacecraft. This observation covers an area of 240” ×
240”, with the 1” slit in about 160 s. The early phases of a C9.7
flare that occurred on 2007 June 6 were well observed. The purpose of
our analysis is to study for the first time the spatially resolved
spectra of high-temperature plasma, especially from Fe XXIII and Fe
XXIV, allowing us to explore the explosive chromospheric evaporation
scenario further. Sections of raster images obtained between 17:20:09
and 17:20:29 (UT) show a few bright patches of emission from Fe
XXIII/Fe XXIV lines at the footpoints of the flaring loops; these
footpoints were not clearly seen in the images taken earlier, between
17:17:30 and 17:17:49 (UT). Fe XXIII spectra at these footpoints show
dominating blueshifted components of -(300 to 400) km s<SUP>-1</SUP>,
while Fe XV/XIV lines are nearly stationary; Fe XII lines and/or
lower temperature lines show slightly redshifted features, and Fe
VIII and Si VII to He II lines show ~+50 km s<SUP>-1</SUP> redshifted
components. The density of the 1.5-2 MK plasma at these footpoints is
estimated to be 3 × 10<SUP>10</SUP> cm<SUP>-3</SUP> by the Fe XIII/XIV
line pairs around the maximum of the flare. High-temperature loops
connecting the footpoints appear in the Fe XXIII/XXIV images taken over
17:22:49-17:23:08 (UT) which is near the flare peak. Line profiles of
these high-temperature lines at this flare peak time show only slowly
moving components. The concurrent cooler Fe XVII line at 254.8 Å is
relatively weak, indicating the predominance of high-temperature plasma
(>10<SUP>7</SUP> K) in these loops. The characteristics observed
during the early phases of this flare are consistent with the scenario
of explosive chromospheric evaporation.
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Title: FeXVII Emission Lines Seen in A Solar Active Region and the
Large Helical Device
Authors: Watanabe, Tetsuya; Yamamoto, Norimasa; Kato, Daiji; Sakaue,
Hiroyuki A.; Murakami, Izumi
2010cosp...38.2964W Altcode: 2010cosp.meet.2964W
Ne-sequence iron ions, FeXVII, are formed around the temperature of
log Te ∼ 6.7, which nearly correspond to the maximum temperature
reached in solar active regions. The EIS instrument on board the
Hinode mission has detected several week FeXVII emission lines
appearing in its observing wavelengths (170 -210 A, 250 -290 A),
and they are identified as those from the transitions between 2p5
3s/3p -2p5 3p/3d. The observed line intensity ratios among them are
compared with our theoretical calculations. We found that many of
them are blended by lower-temperature week coronal lines, and that
the photon branching ratio of the 2p5 3p3 S0 level to the 2p5 3s
levels is wrong by a factor of 2, roughly. The intensity ratios of
these lines measured in the Large Helical Device (LHD) at NIFS will
also be reported and compared with the solar observations.
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Title: Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations
of the Temperature Structure of the Quiet Corona
Authors: Brooks, David H.; Warren, Harry P.; Williams, David R.;
Watanabe, Tetsuya
2009ApJ...705.1522B Altcode: 2009arXiv0905.3603B
We present a differential emission measure (DEM) analysis of the quiet
solar corona on disk using data obtained by the Extreme-ultraviolet
Imaging Spectrometer (EIS) on Hinode. We show that the expected
quiet-Sun DEM distribution can be recovered from judiciously selected
lines, and that their average intensities can be reproduced to
within 30%. We present a subset of these selected lines spanning the
temperature range log T = 5.6-6.4 K that can be used to derive the DEM
distribution reliably, including a subset of iron lines that can be used
to derive the DEM distribution free of the possibility of uncertainties
in the elemental abundances. The subset can be used without the need for
extensive measurements, and the observed intensities can be reproduced
to within the estimated uncertainty in the pre-launch calibration
of EIS. Furthermore, using this subset, we also demonstrate that
the quiet coronal DEM distribution can be recovered on size scales
down to the spatial resolution of the instrument (1” pixels). The
subset will therefore be useful for studies of small-scale spatial
inhomogeneities in the coronal temperature structure, for example,
in addition to studies requiring multiple DEM derivations in space or
time. We apply the subset to 45 quiet-Sun data sets taken in the period
2007 January to April, and show that although the absolute magnitude
of the coronal DEM may scale with the amount of released energy, the
shape of the distribution is very similar up to at least log T ~ 6.2 K
in all cases. This result is consistent with the view that the shape of
the quiet-Sun DEM is mainly a function of the radiating and conducting
properties of the plasma and is fairly insensitive to the location and
rate of energy deposition. This universal DEM may be sensitive to other
factors such as loop geometry, flows, and the heating mechanism, but
if so they cannot vary significantly from quiet-Sun region to region.
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Title: Spectroscopy of highly charged ions in Solar and astrophysical
plasmas
Authors: Watanabe, Tetsuya
2009JPhCS.163a2002W Altcode:
Spectroscopic observation of EUV emission lines in the transition-region
and corona provide unique information on physical conditions in these
outer atmospheres of the Sun. The EUV Imaging Spectrometer (the EIS)
on board the Hinode mission is capable of observing, for the first time
in Solar EUV observations, spectra and monochromatic images of possibly
non-ionization-equilibrium plasmas in the solar transition-region and
corona at two-wavelength bands of 170 - 210Å and 250 - 290Å, with
typical time-resolutions of 1 -10 seconds. Dynamic plasma acceleration
and heating are found to take place in the solar atmospheres, and they
are confined in tiny structures. A time-dependent collisional-radiative
model for the iron plasmas is developed to diagnose temperatures and
densities in the outer atmospheres of the Sun; no systematic models
yet exist for iron ions at the ionization stages of L- and M-shells,
which are very important for coronal plasma diagnostics. Adopting the
best available theoretical calculations of atomic parameters of these
iron ions, as well as generating the experimental data by a compact
electron beam ion trap (EBIT), is essential to one of the aims of our
research that the mechanism of coronal heating is explored via accurate
diagnostics information obtained by the EIS instrument.
---------------------------------------------------------
Title: New Sunrise of Solar Physics Galvanized by the Hinode Mission
Authors: Watanabe, Tetsuya; Hinode Science Team
2009aogs...14...33W Altcode:
The Solar-B mission was successfully launched on 22-Sep-2006 (UT), put
into a sun-synchronous polar orbit, and called "Hinode," the sunrise in
Japanese. All three mission telescopes on board, namely, solar optical
telescope (SOT), X-ray telescope (XRT), and extreme ultraviolet imaging
spectrometer (EIS) opened their doors about a month after the launch
and started the initial observations. Thanks to the sun-synchronous
orbit, observations will be possible 24 h a day for about 8 months
of the year. The 50 cm diameter SOT is able to obtain a continuous,
seeing-free series of diffraction-limited images (0.2-0.3″) in the
wavelengths of 388-668 nm, and a wide range of scientific advances are
anticipated through this increased capability. XRT is a high resolution
grazing incidence telescope, a successor to the very successful SXT
instrument on board Yohkoh. The EIS utilizes an off-axis parabolic
primary and a toroidal diffraction grating in a normal incidence optical
layout with multi-layer coating, which enables high reflectance two EUV
wavelength ranges, 170-210 Å and 250-290 Å. The current status of the
Hinode mission and the initial scientific results will be summarized.
---------------------------------------------------------
Title: Strongly Blueshifted Phenomena Observed with Hinode EIS in
the 2006 December 13 Solar Flare
Authors: Asai, Ayumi; Hara, Hirohisa; Watanabe, Tetsuya; Imada,
Shinsuke; Sakao, Taro; Narukage, Noriyuki; Culhane, J. L.; Doschek,
G. A.
2008ApJ...685..622A Altcode: 2008arXiv0805.4468A
We present a detailed examination of strongly blueshifted emission
lines observed with the EUV Imaging Spectrometer on board the Hinode
satellite. We found two kinds of blueshifted phenomenon associated
with the X3.4 flare that occurred on 2006 December 13. One was related
to a plasmoid ejection seen in soft X-rays. It was very bright in all
the lines used for the observations. The other was associated with the
faint arc-shaped ejection seen in soft X-rays. The soft X-ray ejection
is thought to be a magnetohydrodynamic (MHD) fast-mode shock wave. This
is therefore the first spectroscopic observation of an MHD fast-mode
shock wave associated with a flare.
---------------------------------------------------------
Title: Observations of Doppler Shift Oscillations with the EUV
Imaging Spectrometer on Hinode
Authors: Mariska, John T.; Warren, Harry P.; Williams, David R.;
Watanabe, Tetsuya
2008ApJ...681L..41M Altcode: 2008arXiv0806.0265M
Damped Doppler shift oscillations have been observed in emission lines
from ions formed at flare temperatures with the Solar Ultraviolet
Measurements of Emitted Radiation spectrometer on the Solar and
Heliospheric Observatory and with the Bragg Crystal Spectrometer
on Yohkoh. This Letter reports the detection of low-amplitude damped
oscillations in coronal emission lines formed at much lower temperatures
observed with the EUV Imaging Spectrometer on the Hinode satellite. The
oscillations have an amplitude of about 2 km s<SUP>-1</SUP> and a
period of around 35 minutes. The decay times show some evidence for
a temperature dependence with the lowest temperature of formation
emission line (Fe XII 195.12 Å) exhibiting a decay time of about 43
minutes, while the highest temperature of formation emission line (Fe XV
284.16 Å) shows no evidence for decay over more than two periods of the
oscillation. The data appear to be consistent with slow magnetoacoustic
standing waves, but may be inconsistent with conductive damping.
---------------------------------------------------------
Title: Coronal Plasma Motions near Footpoints of Active Region Loops
Revealed from Spectroscopic Observations with Hinode EIS
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.; Mariska, John T.; Doschek, George A.
2008ApJ...678L..67H Altcode:
The solar active region 10938 has been observed from the disk center
to the west limb with the Hinode EUV Imaging Spectrometer. In the
disk-center observation, subsonic upflow motions of tens of km
s<SUP>-1</SUP> and enhanced nonthermal velocities have been found
near the footpoints of the active region loops assuming a single
Gaussian approximation for the emission-line profiles. When the same
part of the active region is observed near the limb, both upflows
and enhanced nonthermal velocities essentially decrease. There
is a strong correlation between Doppler velocity and nonthermal
velocity. Significant deviations from a single Gaussian profile are
found in the blue wing of the line profiles for the upflows. These
suggest that there are unresolved high-speed upflows. We discuss the
implications for coronal heating mechanisms.
---------------------------------------------------------
Title: 2006 December 17 Long Duration Flare Observed with the Hinode
EUV Imaging Spectrometer
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Matsuzaki, Keiichi; Harra,
Louise K.; Culhane, J. Leonard; Cargill, Peter; Mariska, John T.;
Doschek, George A.
2008PASJ...60..275H Altcode:
A GOES C-class long-duration flare that occurred near the west limb on
2006 December 17 was observed with the Hinode EUV Imaging Spectrometer
(EIS) in raster-scan observations. Cusp-shaped arcades are prominent in
the spectroheliogram of the CaXVII emission line at 192.86Å. Spatial
relationships between hot flare loops with a cusp apex and cool post
flare loops with various temperatures are clearly shown in the EIS
observations. We find an enhanced line broadening above the bright
loop-top region in the CaXVII observation. The Doppler observations of
cooling post flare loops with coronal temperatures show both downflows
and upflows along the loops, and these are interpreted as a part of
siphon flows. Enhanced nonthermal line broadenings are identified at
the top of the post flare loops.
---------------------------------------------------------
Title: The relation between explosive events and photospheric
magnetic fields
Authors: Kamio, Suguru; Hara, Hirohisa; Watanabe, Tetsuya
2008cosp...37.1434K Altcode: 2008cosp.meet.1434K
The relationship between explosive events and photospheric magnetic
fields in a quiet region is studied by high resolution data obtained
with EIS and SOT on board Hinode. Data from quiet regions near the disk
center were selected and reduced in this paper. He II λ 256.32 (log Te
= 4.7) and other emission lines from the transition region were analyzed
to find a signature of explosive events. Many line-broadening features
are found in the transition region, while they are not found in the
coronal emission lines such as Fe XII λ 195.12. Spectropolarimeter (SP)
allowed us to study photospheric magnetic fields with unprecedentedly
high resolution. In addition, the evolution of magnetic fields was
captured by Narrowband filter imager (NFI). The result indicates that
explosive events occurred around magnetic field patches in the network.
---------------------------------------------------------
Title: Emission Line Imaging Spectroscopy for Diagnosing of Solar
Outer Atmospheres
Authors: Watanabe, Tetsuya; EIS Team
2008PFR.....2S1011W Altcode:
The Extreme Ultraviolet Imaging Spectrometer on board the Japanese Sun
Observing Satellite “Hinode” realizes the highest sensitivity
ever achieved in the two EUV wavelengths of 17-21 nm and 25-29
nm. EIS will be able to provide the detailed diagnostic information
on solar corona and transition region. A new tool of timedependent
collisonal-radiative model will be developed to analyze the data taken
by this EIS instrument, and to diagnose temperatures and densities of
those plasmas in the outer atmospheres of the Sun.
---------------------------------------------------------
Title: FeXIII density diagnostics for solar coronal and flare plasmas
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Yamamoto, Norimasa; Kato,
Takako; Young, Peter R.
2008cosp...37.3434W Altcode: 2008cosp.meet.3434W
Density sensitive FeXIII line ratios were obtained by EUV Imaging
Spectrometer (EUV) on Hinode for quiet-sun, active region, and
flare plasmas. Consistency of density estimates derived from various
density-sensitive line pairs appearing in the EIS observing wavelengths
will be discussed in comparison with theoretical models. The intensity
ratios of FeXIIIλ203.8A/202.0A in flaring active region show its
high-density limit, suggesting that densities at the foot points
of flaring looops exceed 1012 cm-3 , though the value itself is not
exactly consistent with the laboratory data.
---------------------------------------------------------
Title: Coronal Plasma Motions near Footpoints of Active Region Loops
Revealed from Spectroscopic Observations with {it Hinode} EIS
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.; Doschek, G. A.; Mariska, John
2008cosp...37.1175H Altcode: 2008cosp.meet.1175H
We have observed the solar active region 10938 from the disk center
to the west limb with the Hinode EUV Imaging Spectrometer. In the
disk center observation subsonic upflow motions of tens of km s-1 and
enhanced nonthermal velocities have been found near the footpoints of
the active-region loops assuming a single Gaussian approximation for
the emission-line profiles. When the same part of the active region
is observed near the limb, both upflows and enhanced nonthermal
velocities essentially decrease, clearly showing that the enhanced
nonthermal velocities in the disk center observation are mainly due to
line-of-sight motions, which are likely parallel to magnetic field lines
of the coronal loops. There is a strong correlation between Doppler
velocity and nonthermal velocity in the upflow regions. The enhancement
in the blue wing of the line profiles is found for the upflows as a
significant deviation from a single Gaussian profile. These suggest
that there are unresolved high-speed upflows near the footpoints of
active region loops. We discuss the implications for coronal heating
mechanisms.
---------------------------------------------------------
Title: Hot and Cool Loops Composing the Corona of the Quiet Sun
Authors: Matsuzaki, Keiichi; Hara, Hirohisa; Watanabe, Tetsuya; Dere,
Kenneth P.; Brown, Charles M.; Culhane, Len
2007PASJ...59S.683M Altcode:
We performed a raster scan observation of the quiet Sun with the EUV
Imaging Spectrometer (EIS) aboard Hinode and simultaneously analyzed
observed emission lines of Fe VIII to XV. From a combined analysis,
radiance maps from the observed emission lines were deconvolved into
plasma components at five representative temperatures between 0.40MK and
2.63MK. While the lowest temperature component shows network structures
on spatial scales of between 10" and 20", the higher temperature
components show thread-like patterns on larger scales. A comparison of
emission measures at the different temperatures suggests that the lowest
temperature component is mainly composed of bodies of small loops,
rather than a collection of foot points of the higher temperature
loops. The difference in morphologies is interpreted as being due to
different magnetic field configurations, loops within super-granule
cells and fields extending beyond the boundaries of super-granule cells,
with distinct peak temperatures following a loop scaling law.
---------------------------------------------------------
Title: Temperature and Density Structures of Solar Corona, A Test
of Iron Line Diagnostic Capability of EIS Instrument on Board Hinode
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Culhane, Len; Harra,
Louise K.; Doschek, George A.; Mariska, John T.; Young, Peter R.
2007PASJ...59S.669W Altcode:
Increased diagnostic capability of the EUV Imaging Spectrometer
(EIS) aboard Hinode (former Solar-B) has been demonstrated with
a set of iron emission lines emerging in the two EIS observing
wavelength bands (170-210Å and 250-290Å) and their line-intensity
ratios. “Abundance-uncertainty” free relative emission measure
distributions as a function of temperature were deduced using only iron
emission lines of various ionization stages. First-light spectra of a
small active region show iron lines ranging from FeVIII (185.2Å and
186.6Å) through FeXVII (204.7Å, 254.9Å, and 269.4Å). Spectra of a
C-class flare confirms the presence of one of these higher temperature
lines (FeXVII at 254.9Å) more clearly, as well showing FeXXIV (192.0Å
and 255.1Å) and FeXXIII (263.8Å), which are normally only seen at
flare temperatures.
---------------------------------------------------------
Title: The Temperature and Density Structure of an Active Region
Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode
Authors: Doschek, George A.; Mariska, John T.; Warren, Harry P.;
Culhane, Len; Watanabe, Tetsuya; Young, Peter R.; Mason, Helen E.;
Dere, Kenneth P.
2007PASJ...59S.707D Altcode:
The Extreme-Ultraviolet Imaging Spectrometer (EIS) on Hinode
produces high resolution spectra that can be combined via rasters
into monochromatic images of solar structures, such as active
regions. Electron temperature and density maps of the structures can
be obtained by imaging the structures in different spectral lines with
ratios sensitive to either temperature or density. Doppler maps and
ion temperature maps can be made from spectral line wavelengths and
profiles, respectively. In this paper we discuss coronal temperature
and density distributions within an active region, illustrating the
power of EIS for solar plasma diagnostics.
---------------------------------------------------------
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
2007PASJ...59S.699H Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
---------------------------------------------------------
Title: EUV Emission Lines and Diagnostics Observed with Hinode/EIS
Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Dere,
Ken P.; Landi, Enrico; Landini, Massimo; Doschek, George A.; Brown,
Charles M.; Culhane, Len; Harra, Louise K.; Watanabe, Tetsuya; Hara,
Hirohisa
2007PASJ...59S.857Y Altcode: 2007arXiv0706.1857Y
Quiet Sun and active region spectra from the Hinode/EIS instrument are
presented, and the strongest lines from different temperature regions
discussed. A list of emission lines recommended to be included in EIS
observation studies is presented based on analysis of blending and
diagnostic potential using the CHIANTI atomic database. In addition
we identify the most useful density diagnostics from the ions covered
by EIS.
---------------------------------------------------------
Title: Velocity Structure of Jets in a Coronal Hole
Authors: Kamio, Suguru; Hara, Hirohisa; Watanabe, Tetsuya; Matsuzaki,
Keiichi; Shibata, Kazunari; Culhane, Len; Warren, Harry P.
2007PASJ...59S.757K Altcode: 2007arXiv0711.2848K
The velocity structures of jets in a coronal hole have been derived
for the first time. Hinode observations revealed the existence
of many bright points in coronal holes. They are loop-shaped and
sometimes associated with coronal jets. Spectra obtained with the
Extreme-ultraviolet Imaging Spectrometer aboard Hinode were analyzed
to infer the Doppler velocity of bright loops and jets in a coronal
hole of the north polar region. Elongated jets above bright loops are
found to be blue-shifted by 30kms<SUP>-1</SUP> at maximum, while foot
points of bright loops are red-shifted. Blue-shifts detected in coronal
jets are interpreted as being upflows produced by magnetic reconnection
between emerging flux and the ambient field in the coronal hole.
---------------------------------------------------------
Title: Discovery of a Temperature-Dependent Upflow in the Plage
Region During a Gradual Phase of the X-Class Flare
Authors: Imada, Shinsuke; Hara, Hirohisa; Watanabe, Tetsuya; Kamio,
Suguru; Asai, Ayumi; Matsuzaki, Keiichi; Harra, Louise K.; Mariska,
John T.
2007PASJ...59S.793I Altcode:
We present Hinode/EIS raster scan observations of the plage region
taken during the gradual phase of the GOES X3.2 flare that occurred on
2006 December 13. The plage region is located 200" east of the flare
arcade. The plage region has a small transient coronal hole. The
transient coronal hole is strongly affected by an X-class flare,
and upflows are observed at its boundary. Multi-wavelength spectral
observations allow us to determine velocities from the Doppler shifts
at different temperatures. Strong upflows along with stationary plasma
have been observed in the FeXV line 284.2Å (log T / K = 6.3) in the
plage region. The strong upflows reach almost 150kms<SUP>-1</SUP>, which
was estimated by a two-component Gaussian fitting. On the other hand,
at a lower corona/transition region temperature (HeII, 256.3Å, log T /
K = 4.9), very weak upflows, almost stationary, have been observed. We
find that these upflow velocities clearly depend on the temperature
with the hottest line, FeXV, showing the fastest upflow velocity and the
second-highest line, FeXIV, showing the second-highest upflow velocity
(130kms<SUP>-1</SUP>). All velocities are below the sound speed. The
trend of the upflow dependence on temperature dramatically changes
at 1MK. These results suggest that heating may have an important role
for strong upflow.
---------------------------------------------------------
Title: Iron Line Ratio Analysis in an Active Region
Authors: Watanabe, Tetsuya; Hara, H.; Culhane, J. L.; Harra, L. K.;
Doschek, G. A.; Mariska, J. T.; Young, P. R.; Hinode EIS Team
2007AAS...210.7204W Altcode: 2007BAAS...39..179W
Increased diagnostic capability of the EIS instrument on board Hinode
(Solar-B) is demonstrated with a set of iron emission lines appearing
in the two EIS observing wavelengths (170 - 210 A & 250 - 290
A) and their line intensity ratios. First-light spectra of a small
active region show iron lines at the ionization stages of FeVIII
(185.2 A & 186.6 A) through FeXVII (204.7 A, 254.9 A, & 269.4
A). Decay phase spectra of a C-class flare confirms the presence of
this higher temperature line; FeXVII at 254.9 A more clearly, as well
as those lines of flare temperatures; FeXXIV (192.0 A & 255.1 A)
and FeXXIII (263.8 A).
---------------------------------------------------------
Title: Complex Variations in Line-Intensity Ratio of Coronal Emission
Lines with Height Above the Limb
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Watanabe,
Tetsuya
2005BASI...33..362S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Electron Densities of High-Temperature Coronal Loops
Authors: Watanabe, Tetsuya
2004ASPC..325..227W Altcode:
Yohkoh has revealed the existence of persistent high temperature plasmas
in solar active regions where major flare activity takes place. Density
at the energy release site for coronal heating determines the efficiency
of magnetic heating, and hence the heating energy flux. Temperatures
and densities of solar (and stellar) flares at the pre-flare states
are compiled. Preflare conditions are basically derived from the
data taken with the same instruments several tens of minutes before
the onset of the impulsive phase of subsequent flares. It is found
that the temperature increase from the preflare to flare states is
only Δ log T ∼ 0.2, and that density and flux increases are roughly
independent of the flare thermal energy. Namely large flares take place
at the coronal loops where both temperatures and densities are already
high. Several line pairs exist in the EIS observing wavelengths,
which are suitable for plasma density diagnostics, covering wider
temperature ranges. Combining with the emission measure information,
“differential” filling factors will reveal the fundamental structures
of coronal loops proceeding to abrupt magnetic activity.
---------------------------------------------------------
Title: Complex Variations in the Line-Intensity Ratio of Coronal
Emission Lines with Height above the Limb
Authors: Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Watanabe,
Tetsuya
2004ApJ...617L..81S Altcode:
We obtained spectroscopic observations simultaneously in pairs of
coronal emission lines, one line being [Fe X] λ6374 and the other
line being [Fe XI] λ7892, [Fe XIII] λ10747, or [Fe XIV] λ5303, and
we studied the variations in the intensity and FWHM ratios of these
lines with respect to those of 6374 Å as a function of height above
the limb. We find that the intensity ratio of the 7892 and 10747 Å
line with respect to the 6374 Å line increases with height and that
the intensity ratio of 5303 Å to 6374 Å decreases with height above
the limb. This implies that the temperature in coronal loops will
appear to increase with height if we consider the intensity ratio
of 7892 Å to 6374 Å a negligible variation in temperature in the
case of the 10747 and 6374 Å line pair, while the temperature will
appear to decrease with height if we consider the intensity ratio of
5303 Å to 6374 Å. The normalized FWHM (with respect to wavelength)
ratio of 6374 Å to all the other coronal lines observed increases
with height. The FWHM ratio at the limb depends on the pair of emission
lines chosen; it is about 1 in the case of the 6374 and 7892 Å emission
lines, indicating a common temperature and nonthermal velocity in the
coronal loops near the limb, and it is about 0.7 at the limb in the
case of the 6374 and 5303 Å lines and becomes about 1 at a height
of 120". The varying FWHM ratios with height indicate that hotter
and colder plasmas in coronal loops mix with each other. Therefore,
the observed increase in the FWHM of coronal emission lines, which
are associated with plasma at about 1 MK with height, may not be due
to an increase in nonthermal motions caused by coronal waves but may
be due to an interaction with relatively hotter plasma.
---------------------------------------------------------
Title: Development of the Solar-B spacecraft
Authors: Tsuneta, Saku; Ichimoto, Kiyoshi; Suematsu, Yoshinori;
Shimizu, Toshifumi; Hara, Hirohisa; Kano, Ryohei; Nagata, Shin'ichi;
Tamura, Tomonori; Nakagiri, Masao; Noguchi, Motokazu; Kato, Yoshihiro;
Watanabe, Tetsuya; Hanaoka, Yoichiro; Sawa, Masaki; Otsubo, Masashi;
Kosugi, Takeo; Yamada, Takahiro; Sakao, Taro; Matsuzaki, Keiichi;
Minesugi, Kenji; Onishi, Akira; Katsukawa, Yukio; Kobayashi, Ken;
Kubo, Masahito
2003naoj.book....3T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Energetics of an Active Region Observed from Helium-Like
Sulphur Lines
Authors: Watanabe, Tetsuya; Sterling, Alphonse C.; Hudson, Hugh S.;
Harra, Louise K.
2001SoPh..201...71W Altcode:
We report temperature diagnostics derived from helium-like ions of
sulphur for an active region NOAA 7978 obtained with Bragg Crystal
Spectrometer (BCS) on board the Yohkoh satellite. For the same
region we estimate conductive flux downward to the chromosphere by
the Coronal Diagnostic Spectrometer (CDS) on board the Solar and
Heliospheric Observatory (SOHO) satellite. This region appeared as a
region of soft X-ray enhancement in May 1996, underwent a period of
enhanced activity coinciding with flux emergence between 6 July and
12 July, and then continued to exist in a nearly flareless state for
several solar rotations until November 1996. Energy balance of the
non-flaring active region is basically consistent with a model of
an arcade of coronal loops having an average loop-top temperature of
4×10<SUP>6</SUP> K. Energy from flare activity during a period of flux
emergence is comparable to the energy requirements of the non-flaring
active region. However, the non-flaring energy is roughly constant
for the subsequent solar rotations following the birth of the active
region even after the flare activity essentially subsided. Energy
partition between flare activity and steady active-region heating
thus varies significantly over the lifetime of the active region,
and active-region emission cannot always be identified with flaring.
---------------------------------------------------------
Title: Extreme-ultraviolet imaging spectrometer designed for the
Japanese Solar-B satellite
Authors: Culhane, J. L.; Korendyke, Clarence M.; Watanabe, Tetsuya;
Doschek, George A.
2000SPIE.4139..294C Altcode:
The Extreme-ultraviolet Imaging Spectrometer combines, for the first
time, high spectral, spatial and temporal resolution in a satellite
based, solar extreme ultraviolet instrument. The instrument optical
design consists of a multilayer-coated off- axis paraboloid mirror
telescope followed by a toroidal grating spectrometer. The instrument
includes thin film aluminum filters to reject longer wavelength solar
radiation and employs CCD detectors at the focal plane. The telescope
mirror is articulated to allow sampling of a large fraction of the
solar surface from a single spacecraft pointing position. Monochromatic
images are obtained either by rastering the solar image across the
narrow entrance slit or by using a wide slit or slot in place of
the slit. Monochromatic images of the region centered on the slot are
obtained in a single exposure. Half of each optic is coated to maximize
reflectance at 195 angstrom; the other half is coated to maximize
reflectance at 270 angstrom. The two EUV wavelength bands were selected
to optimize spectroscopic plasma diagnostic capabilities. Particular
care was taken to choose wavelength ranges with relatively bright
emission lines to obtain precision line of sight and turbulent bulk
plasma velocity measurements from observed line profiles. The EIS
spectral range contains emission lines formed over a temperature
range from approximately 10<SUP>5</SUP> - 10<SUP>7</SUP> K. The
wavelength coverage also includes several density sensitive emission
line pairs. These line pairs provide spatial resolution independent
density diagnostics at nominal coronal temperatures and densities. Each
wavelength band is imaged onto a separate CCD detector. The main EIS
instrument characteristics are: wavelength bands -- 180 - 204 angstrom
and 250 - 290 angstrom; spectral resolution -- 0.0223 angstrom/pixel
(23 - 34 km/second-pixel); slit dimensions -- 4 slits: 1 X 1024 arc-
seconds and 50 X 1024 arc-seconds with two positions unspecified as
of this writing; fine raster range -- >6 arc-minutes on the sun;
coarse raster range -- > 1600 arc- seconds on the sun; largest
spatial field of view in a single exposure -- 50 X 1024 arc-seconds;
nominal time resolution for active region velocity studies -- 3.4s. The
Solar-B satellite is scheduled for launch in August 2005 into a nominal
600 km sun-synchronous orbit.
---------------------------------------------------------
Title: Preface
Authors: Watanabe, Tetsuya
2000AdSpR..25.1711W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variation of Thermal Structure with Height of a Solar Active
Region Derived from SOHO CDS and YOHKOH BCS Observations
Authors: Sterling, Alphonse C.; Pike, C. D.; Mason, Helen E.; Watanabe,
Tetsuya; Antiochos, Spiro K.
1999ApJ...524.1096S Altcode:
We present observations of NOAA solar Active Region 7999 when it was
near the west solar limb on 1996 December 2 and 3, using data from
the Coronal Diagnostic Spectrometer (CDS) experiment on the SOHO
satellite. Ratios of intensities of 2 MK material (as observed in
CDS Fe XVI images) to 1 MK material (from CDS Mg IX images) indicate
that there is a drop in the ratio of the hotter to the cooler material
with height in the region, up to an altitude of about 10<SUP>5</SUP>
km. At low altitudes the relative amount of 2 MK emission measure to
1 MK emission measure ranges from 8 to 10, while the ratio is minimum
near 10<SUP>5</SUP> km, ranging from 1.3 to 3.5. The decrease with
height of the CDS ratio qualitatively resembles the decrease in S
XV election temperature with height (measurable up to ~85,000 km) in
the same active region obtained from the Bragg crystal spectrometer
instrument on Yohkoh. The CDS images indicate that the highest S
XV temperatures and largest CDS ratios correspond to regions of
microflares, and somewhat lower S XV temperatures and CDS ratios
correspond to diffuse regions. Above 10<SUP>5</SUP> km, the trend of
the CDS ratios changes, either increasing or remaining approximately
constant with height. At these altitudes the CDS images show faint,
large-scale diffuse structures.
---------------------------------------------------------
Title: Design of a High-Resolution Extreme-Ultraviolet Imaging
Spectrometer with Aberration-Corrected Concave Gratings
Authors: Harada, Tatsuo; Sakuma, Hideo; Takahashi, Kaoru; Watanabe,
Tetsuya; Hara, Hirohisa; Kita, Toshiaki
1998ApOpt..37.6803H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational plasma astrophysics : five years of YOHKOH
and beyond
Authors: Watanabe, Tetsuya; Kosugi, Takeo
1998ASSL..229.....W Altcode: 1998opaf.conf.....W
No abstract at ADS
---------------------------------------------------------
Title: Electron Temperatures of the Corona Above a Solar Active
Region Determined from S XV Spectra
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Watanabe, Tetsuya
1997SPD....28.0136S Altcode: 1997BAAS...29..885S
We present high resolution soft X-ray spectral observations of the
corona above an active region, using data from the Bragg crystal
spectrometer (BCS) on board the Yohkoh satellite. We observed NOAA AR
7978 as it rotated beyond the solar limb so that the lower portions of
the region were occulted. Long integrations from times after the region
had totally disappeared some days later show a substantial background
in S xv. Since the background spectrum is featureless, spectral lines
obtained from the time of occultation must originate from the upper
corona of the active region. Our results support previous findings that
the corona consists of two components: a cooler, steady component with
T_e ~ 3 MK, and a hotter, transient component in excess of 5 MK. This
hotter component is due to microflares; outside the time of microflares
there is relatively little or no active region upper coronal plasma
with T_e gtrsim 3.5 MK. There is evidence for a decrease in T_e with
height for the cool component.
---------------------------------------------------------
Title: Electron Temperatures of the Corona Above a Solar Active
Region Determined from S XV Spectra
Authors: Sterling, Alphonse C.; Hudson, Hugh S.; Watanabe, Tetsuya
1997ApJ...479L.149S Altcode:
We present the first high-resolution soft X-ray spectral observations of
the corona above an active region, using the Bragg crystal spectrometer
(BCS) on board the Yohkoh satellite. We observed NOAA AR 7978 as it
rotated beyond the solar limb so that the lower portions of the region
were occulted. Long integrations from times after the region had totally
disappeared some days later show a substantial, variable background
in S XV. Since the background spectrum is featureless, spectral lines
obtained from the time of occultation must originate from the upper
corona of the active region. Our results support previous findings that
the active region corona consists of two components: a cooler, steady
component with T<SUB>e</SUB> ~ 3 MK and a hotter, transient component
in excess of 5 MK. This hotter component is due to microflares; outside
the time of microflares there is relatively little or no active region
upper coronal plasma with T<SUB>e</SUB> >~ 3.5 MK. There is evidence
for a decrease in T<SUB>e</SUB> with height for the cool component.
---------------------------------------------------------
Title: Electron Temperature of Solar Flares Derived from Helium-Like
Sulphur Lines
Authors: Yuda, Sayuri; Hiei, Eijiro; Takahashi, Masaaki; Watanabe,
Tetsuya
1997PASJ...49..115Y Altcode:
The maximum temperatures and emission measures reached in solar flares
were obtained from helium-like sulphur lines, which were observed by
the Bragg Crystal Spectrometer on board Yohkoh. A very weak dependence
of the maximum temperature against the soft X-ray intensity was
found. Similar multi-thermal characteristics prevailed in flares
irrespective of the flare intensity, suggesting that the solar flare
is a homogeneous phenomenon in the solar atmospheres.
---------------------------------------------------------
Title: Results from the YOHKOH Satellite
Authors: Watanabe, Tetsuya
1996JKASS..29..291W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Solar Flare of 1992 August 17 23:58 UT} %
Authors: Takahashi, Masaaki; Watanabe, Tetsuya; Sakai, Jun-Ichi;
Sakao, Taro; Kosugi, Takeo; Sakurai, Takashi; Enome, Shinzo; Hudson,
Hugh S.; Hashimoto, Shizuyo; Nitta, Nariaki
1996PASJ...48..857T Altcode:
A small flare (C4.3 in the GOES X-ray class) was well observed by
all of the instruments on board Yohkoh. The X-ray light curves have
double peaks which are about 5 min apart. Until the first peak from
flare onset, four compact areas brighten up in the soft X-ray region,
which are aligned almost on one straight line. We regard them as being
footpoints of two sets of loops, which are identifiable in soft X-ray
images, since their locations match those of hard X-ray sources. Indeed,
after the second peak, the temporal behavior of the temperature and
emission measure at each point is consistent with the existence of
two such loops. Comparing our results with recent MHD simulations,
we propose a possible scenario for this flare that is based on the
coalescence of two loops.
---------------------------------------------------------
Title: Spatial Relations between Preflares and Flares
Authors: Fárník, František; Hudson, Hugh; Watanabe, Tetsuya
1996SoPh..165..169F Altcode:
We have conducted an initial search for discrete preflare brightenings
as observed in soft X-radiation by Yohkoh. The Yohkoh images allow us
to identify, to within a few arc seconds, the location of a preflare
event relative to the succeeding flare. Our initial motivation in
this study was to search for early coronal brightenings leading
to flare effects, as had been suggested by earlier studies; thus we
concentrated on Yohkoh limb events. We find no evidence for such early
coronal brightenings. Between 15% and 41% of the 131 suitable events
matched our criteria for preflare brightening: the same active region;
brightening within one hour of the flare peak; preflare brightness
less than 30% of the flare peak. In the great majority of the preflare
cases, we found that physically separate nearby structures brightened
initially. Often these structures appeared to share a common footpoint
location with the flare brightening itself. In a few cases the preflare
could have occurred in exactly the same structure as the flare.
---------------------------------------------------------
Title: Temperature Structure of Active Regions Deduced from the
Helium-Like Sulphur Lines
Authors: Watanabe, Tetsuya; Haka, Hirohisa; Shimizu, Toshifumi; Hiei,
Eijiro; Bentley, Robert D.; Lang, James; Phillips, Kenneth J. H.; David
Pike, C.; Fludra, Andrzej; Bromage, Barbara J. I.; Mariska, John T.
1995SoPh..157..169W Altcode:
Solar active-region temperatures have been determined from the full-Sun
spectra of helium-like sulphur (SXV) observed by the Bragg Crystal
Spectrometer on board theYohkoh satellite. The average temperature
deduced from SXV is demonstrated to vary with the solar activity level:
A temperature of 2.5 × 10<SUP>6</SUP> K is derived from the spectra
taken during low solar activity, similar to the general corona, while
4 × 10<SUP>6</SUP> K is obtained during a higher activity phase. For
the latter, the high-temperature tail of the differential emission
measure of active regions is found most likely due to the superposition
of numerous flare-like events (micro/nano-flares).
---------------------------------------------------------
Title: X-ray solar physics from YOHKOH
Authors: Uchida, Yutaka; Watanabe, Tetsuya; Shibata, Kazunari; Hudson,
Hugh S.
1994xspy.conf.....U Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Helium-Like Sulphur Emission Lines in Solar Active Regions
and Their Sub-C Class Variability
Authors: Watanabe, Tetsuya; Hiei, Eijiro; Lang, James; Culhane,
J. Leonard; Bentley, Robert D.; Doschek, George A.; Bromage, Barbara
J. I.; Brown, Charles M.; Feldman, Uri; Fludra, Andrzej; Kato, Takako;
Payne, Jeffrey
1992PASJ...44L.141W Altcode:
Helium-like sulphur spectra (formation temperature, T_m ~ 18times
10(6) K) from coronal active regions are being obtained by the Bragg
Crystal Spectrometer onboard the Yohkoh mission. The average electron
temperatures of the quiescent active regions deduced from the full-disk
integrated sulphur spectra are 3.5--4 times 10(6) K. The temporal
behavior of the emission lines in the sub-C level events shows that
hot plasmas (T > 10(7) K) can be produced in these weak events.
---------------------------------------------------------
Title: Observations of Several Small Flares with the Bragg Crystal
Spectrometer on YOHKOH
Authors: Culhane, J. Leonard; Fludra, Andrzej; Bentley, Robert D.;
Doschek, George A.; Watanabe, Tetsuya; Hiei, Eijiro; Lang, James;
Carter, Martin K.; Mariska, John T.; Phillips, Andrew T.; Phillips,
Kenneth J. H.; Pike, C. David; Sterling, Alphonse C.
1992PASJ...44L.101C Altcode:
We have analysed data from two flares of GOES class C7.1 and C8.5
observed by the Yohkoh Bragg Crystal Spectrometer. The high sensitivity
of the Yohkoh instrument allows us to observe the very early stages of
flare development and to study small events with a high signal-to-noise
ratio. Spectral fitting programs have been used to derive plasma
temperatures, emission measures and velocities from spectra of S XV,
Ca XIX and Fe XXV. Large plasma motions indicative of chromospheric
evaporation have been found. A more detailed analysis of a flare which
occurred on 1991 October 30 is presented.
---------------------------------------------------------
Title: The Status of YOHKOH in Orbit: an Introduction to the Initial
Scientific Results
Authors: Ogawara, Yoshiaki; Acton, Loren W.; Bentley, Robert D.;
Bruner, Marilyn E.; Culhane, J. Leonard; Hiei, Eijiro; Hirayama,
Tadashi; Hudson, Hugh S.; Kosugi, Takeo; Lemen, James R.; Strong, Keith
T.; Tsuneta, Saku; Uchida, Yutaka; Watanabe, Tetsuya; Yoshimori, Masato
1992PASJ...44L..41O Altcode:
In this introductory article accompanying the initial scientific
papers from the Yohkoh mission, we briefly summarize the design
and in-orbit function of the spacecraft and its four scientific
instruments. Although these initial results include mainly studies
based upon individual Yohkoh experiments at this early stage, there
are also analyses of combined data sets provided by several on-board
and ground-based instruments in progress. The results presented here,
and anticipated future results, suggest that the Yohkoh observations
with their comprehensive coverage of solar high-energy phenomena will
come to represent a significant milestone in the progress of solar
physics. This will be true not only regarding flares, but also for
fainter coronal structures and even coronal holes.
---------------------------------------------------------
Title: YOHKOH Bragg Crystal Spectrometer Observations of the Dynamics
and Temperature Behavior of a Soft X-Ray Flare
Authors: Doschek, George A.; Mariska, John T.; Watanabe, Tetsuya;
Hiei, Eijiro; Lang, James; Culhane, J. Leonard; Bentley, Robert D.;
Brown, Charles M.; Feldman, Uri; Phillips, Andrew T.; Phillips,
Kenneth J. H.; Sterling, Alphonse C.
1992PASJ...44L..95D Altcode:
We describe X-ray spectra of an M1.5 flare that occurred on 1991
November 9, starting at about 0313 UT. This flare is unusual in that
very intense blueshifted components are observed in the resonance
lines of Fe XXV, Ca XIX, and S XV. During the onset of the flare,
the resonance lines of Ca XIX and Fe XXV are primarily due to
this blueshifted component, which from the Doppler effect indicates
line-of-sight speeds and turbulent motions that in combination extend
up to 800 km s(-1) .
---------------------------------------------------------
Title: The YOHKOH Wide-Band Spectrometer: Performance and Initial
Results
Authors: Yoshimori, Masato; Takai, Yukio; Morimoto, Kouji; Suga,
Kazuharu; Ohki, Kenichiro; Watanabe, Tetsuya; Yamagami, Takamasa;
Kondo, Ichiro; Nishimura, Jun
1992PASJ...44L..51Y Altcode:
Descriptions of the in-flight performance of the Wide-Band Spectrometer
(WBS) and the initial results of both gamma-ray and hard X-ray
observations are presented. The gamma-ray observations indicate that
there are two types of gamma-ray flares. The 1991 October 27 flare
emitted strong gamma-ray lines, while the 1991 December 3 flare emitted
a strong bremsstrahlung continuum spectrum extending to 10 MeV. The
hard X-ray observation of the 1991 November 10 flare shows that the
spectrum shape significantly varies with the time and spectral index,
since the high-energy band (80--600 keV) varies largely with time,
compared with that for the low-energy band (20--80 keV).
---------------------------------------------------------
Title: The Performance of the YOHKOH Bragg Crystal Spectrometer
Authors: Lang, James; Bentley, Robert D.; Brown, Charles M.; Culhane,
J. Leonard; Doschek, George A.; Watanabe, Tetsuya; Hiei, Eijiro;
Deslattes, Richard D.; Fludra, Andrzej; Guttridge, Philip R.; Magraw,
John E.; Payne, Jeffrey; Pike, C. David; Trow, Matthew W.
1992PASJ...44L..55L Altcode:
An overview of the Yohkoh Bragg Crystal Spectrometer is given,
complemented by details of the laboratory testing prior to launch. The
in-orbit performance of the instrument is described.
---------------------------------------------------------
Title: The SOLAR-A related scientific programs
Authors: Watanabe, Tetsuya
1991AdSpR..11e..33W Altcode: 1991AdSpR..11Q..33W
Scientific implications of SOLAR-A mission flown in this solar activity
maximum are briefly reviewed. A coordinated set of instruments will
be able to observe high energy phenomena on the solar surface in X-ray
and gamma-ray energy ranges. Organized observations among the onboard
instruments can be achieved by softwares of the data processor. A
qualitative increase of data volume obtained by SOLAR-A will be
accomplished by extra downlinks other than at Kagoshima. Collaborations
with other facilities will be indispensable for understanding of
solar flares.
---------------------------------------------------------
Title: Flare Physics in Solar Activity Maximum 22
Authors: Uchida, Yutaka; Canfield, Richard C.; Watanabe, Tetsuya;
Hiei, Eijiro
1991LNP...387.....U Altcode: 1991fpsa.conf.....U
No abstract at ADS
---------------------------------------------------------
Title: Plasma motions in the flare of 1982 June 6 (X12)
Authors: Watanabe, Tetsuya
1990SoPh..126..351W Altcode:
This paper analyzes soft X-ray spectra obtained from the Hinotori
spacecraft for the investigation of plasma motions during the initial
phase of the great flare, 1982 June 6. The wavelength calibration
of the scanning spectrometers is determined from information on the
spacecraft attitude and from the position of the FeXXV resonance line
during the decay phase. Hard X-ray bursts, nonthermal line broadenings
and blueshifted components in X-ray lines are temporally correlated
with time differences of 0-30 s. The possible contribution of the
blueshifted component to the line width decreases more rapidly than
the nonthermal broadening, which suggests dominant plasma motions are
taking place at higher and higher altitude in the corona, because of
the increase of electron density in flaring loops. The evolution of
the input kinetic energy content to the thermal plasma inferred from
line broadenings in the impulsive phase resembles that of the thermal
energy content in the source of the FeXXVI emission, which is different
from that deduced for FeXXV source. This suggests that the origins of
the nonthermal line broadening and FeXXVI source are closely coupled.
---------------------------------------------------------
Title: The wide band spectrometer for the solar flare satellite
SOLAR-A
Authors: Yoshimori, Masato; Okudaira, Kiyoaki; Hirasima, Yo;
Yanagimachi, Tomoki; Kondo, Ichiro; Ohki, Ken-Ichiro; Watanabe,
Tetsuya; Nishimura, Jun; Yamagami, Takamasa; Murakami, Toshio; Ito,
Masayuki; Yoshida, Atsumasa
1988NIMPA.264..436Y Altcode:
The Wide Band Spectrometer (WBS) for the solar flare satellite SOLAR-A
scheduled for launch in 1991 consists of three kinds of detectors to
observe the wide band spectrum from soft X-rays to gamma-rays. The
soft X-ray spectrometer (gas proportional counter), hard X-ray
spectrometer (NaI scintillation counter and gamma-ray spectrometer
(two BGO scintillation counters) cover the 2-30 keV, 20-400 keV and
0.2-100 MeV bands, respectively. Further, the WBS contains a radiation
belt monitor consisting of a NaI scintillation counter which is capable
of detecting cosmic gamma-ray bursts. The details of these detectors,
electronics systems and data collection are described.
---------------------------------------------------------
Title: An indication of extended chromospheres in Line
Width-Luminosity Relations.
Authors: Watanabe, Tetsuya
1988PASJ...40..475W Altcode:
Measurements of Mg II k, Ca II K, and H-alpha line widths in late-type
stars are compiled together with stellar basic parameters and the
net radiative losses of their chromospheres (estimated from the Mg II
emission line intensities). It is found that in giants and supergiants
the Mg II kl width corrected for activity and abundance difference
shows a different power dependence on the stellar surface gravity
from that in dwarfs. The widths of Mg II k and Ca II K lines are
linearly correlated even in these giants and supergiants. These facts
indicate that the extended chromosphere is a universal phenomenon in
the low-gravity late-type stars.
---------------------------------------------------------
Title: Optical properties of soft X-ray telescope aboard SOLAR-A.
Authors: Watanabe, Tetsuya
1987TokAB.277.3213W Altcode: 1987BTok..277.3213W
The optical properties of soft X-ray telescope (SXT) aboard Solar-A
are analyzed and the characteristics of the SXT Wolter type-I mirror
are described. The effects of defocusing, decentering, and tilting the
mirrors, and of the paraboloid length at the optimal image plane on the
diameter of rms blur circle were determined. The tolerance limits for
the focusing, the centering of the mirrors, and the angle between the
mirrors were estimated to be 50 microns, 10 microns, and 0.7 arcsec,
respectively. Using the SXT, the whole sun can be observed with the
resolution better than 3 arcsec.
---------------------------------------------------------
Title: On the thermally-driven stellar winds for late-type stars
Authors: Watanabe, Tetsuya
1980PhDT.......140W Altcode:
No abstract at ADS
