Author name code: watanabe-tetsuya ADS astronomy entries on 2022-09-14 =author:"Watanabe, Tetsuya" ------------------------------------------------------------------------ Title: The Solar-C (EUVST) mission: the latest status Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu, Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto, Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki; Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren, Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca, Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William; Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic; Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise Bibcode: 2020SPIE11444E..0NS Altcode: Solar-C (EUVST) is the next Japanese solar physics mission to be developed with significant contributions from US and European countries. The mission carries an EUV imaging spectrometer with slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic Telescope) as the mission payload, to take a fundamental step towards answering how the plasma universe is created and evolves and how the Sun influences the Earth and other planets in our solar system. In April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA (Japan Aerospace Exploration Agency) has made the final down-selection for this mission as the 4th in the series of competitively chosen M-class mission to be launched with an Epsilon launch vehicle in mid 2020s. NASA (National Aeronautics and Space Administration) has selected this mission concept for Phase A concept study in September 2019 and is in the process leading to final selection. For European countries, the team has (or is in the process of confirming) confirmed endorsement for hardware contributions to the EUVST from the national agencies. A recent update to the mission instrumentation is to add a UV spectral irradiance monitor capability for EUVST calibration and scientific purpose. This presentation provides the latest status of the mission with an overall description of the mission concept emphasizing on key roles of the mission in heliophysics research from mid 2020s. Title: 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 Bibcode: 2020XRS....49..511M Altcode: No abstract at ADS 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. Bibcode: 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. Title: The Solar-C_EUVST mission Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa, Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama, Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra, Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.; Naletto, G.; Zhukov, A. Bibcode: 2019SPIE11118E..07S Altcode: Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a solar physics mission concept that was selected as a candidate for JAXA competitive M-class missions in July 2018. The onboard science instrument, EUVST, is an EUV spectrometer with slit-jaw imaging system that will simultaneously observe the solar atmosphere from the photosphere/chromosphere up to the corona with seamless temperature coverage, high spatial resolution, and high throughput for the first time. The mission is designed to provide a conclusive answer to the most fundamental questions in solar physics: how fundamental processes lead to the formation of the solar atmosphere and the solar wind, and how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. The entire instrument structure and the primary mirror assembly with scanning and tip-tilt fine pointing capability for the EUVST are being developed in Japan, with spectrograph and slit-jaw imaging hardware and science contributions from US and European countries. The mission will be launched and installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in 2025. ISAS/JAXA coordinates the conceptual study activities during the current mission definition phase in collaboration with NAOJ and other universities. The team is currently working towards the JAXA final down-selection expected at the end of 2019, with strong support from US and European colleagues. The paper provides an overall description of the mission concept, key technologies, and the latest status. Title: Solar Extreme Ultraviolet Spectroscopy: zur NachEISzeit Authors: Watanabe, Tetsuya Bibcode: 2018ASSL..449...53W Altcode: No abstract at ADS Title: Resonant Electron Impact Excitation of 3d Levels in Fe14+ and Fe15+ Authors: Tsuda, Takashi; Shimizu, Erina; Ali, Safdar; Sakaue, Hiroyuki A.; Kato, Daiji; Murakami, Izumi; Hara, Hirohisa; Watanabe, Tetsuya; Nakamura, Nobuyuki Bibcode: 2017ApJ...851...82T Altcode: 2017arXiv171003548T We present laboratory spectra of the 3p-3d transitions in Fe14+ and Fe15+ 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 Fe14+. This discrepancy is considered to be the fundamental cause of the previously reported inconsistency of the model with the observed intensity ratio between the {}3{P}2{--}{}3{D}3 and {}1{P}1{--}{}1{D}2 transitions. 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 Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 2016ApJ...826..219L Altcode: We present a measured value for the degree of pseudo-degeneracy between two fine-structure levels in Fe9+ from line intensity ratios involving a transition induced by an external magnetic field. The extracted fine-structure energy difference between the 3{p}43d{}4{D}5/2 and {}4{D}7/2 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}43d{}4{D}7/2\to 3{p}5{}2{P}3/2 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-1. The high abundance of Fe9+ 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 Fe9+. In addition, the proposed method to use the line ratio of the blended line 3{p}43d{}4{D}7/{2,5/2}\to 3{p}5{}2{P}3/2 with another line from Fe x as the density diagnostic should evaluate the effect of the magnetic-field-induced transition line. Title: Observation and numerical modeling of chromospheric evaporation during the impulsive phase of a solar flare Authors: Imada, Shinsuke; Murakami, Izumi; Watanabe, Tetsuya Bibcode: 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 κ0 = classical value) and the enthalpy flux dominant regime (κ0 = 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. Title: A Novel Method to Determine Magnetic Fields in Low-density Plasma Facilitated through Accidental Degeneracy of Quantum States in Fe9+ Authors: Li, Wenxian; Grumer, Jon; Yang, Yang; Brage, Tomas; Yao, Ke; Chen, Chongyang; Watanabe, Tetsuya; Jönsson, Per; Lundstedt, Henrik; Hutton, Roger; Zou, Yaming Bibcode: 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}}}4 3{{d}}{ }4{D}7/2 \to 3{{{p}}}5{ }2{P}3/2 in {{Fe}}9+ 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}}}4 3{{d}}{ }4{D}5/2 should be measured experimentally since it is required to determine the relative intensity of this magnetic line for different magnetic fields. Title: The Solar-C Mission Authors: Watanabe, Tetsuya Bibcode: 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. Title: Velocity structure of solar flare plasmas Authors: Watanabe, Tetsuya; Watanabe, Kyoko; Hara, Hirohisa; Imada, Shinsuke Bibcode: 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. Title: A Statistical Study of Coronal Active Events in the North Polar Region Authors: Sako, Nobuharu; Shimojo, Masumi; Watanabe, Tetsuya; Sekii, Takashi Bibcode: 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. 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. Bibcode: 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 × 1010 cm-3. It shows excess line broadening, which exceeds the thermal Doppler width by ~100 km s-1, with a weak redshift of ~30 km s-1. We have also observed a blueshifted faint jet whose Doppler velocity exceeds 200 km s-1 with an electron temperature of 9 MK. Coronal plasmas with electron temperature of 1.2 MK and density of 2.5 × 109 cm-3 that flow into the loop-top region with a Doppler velocity of 20 km s-1 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. Title: The SOLAR-C mission: current status Authors: Shimizu, Toshifumi; Tsuneta, Saku; Hara, Hirohisa; Ichimoto, Kiyoshi; Kusano, Kanya; Sakao, Taro; Sekii, Takashi; Suematsu, Yoshinori; Watanabe, Tetsuya Bibcode: 2011SPIE.8148E..0BS Altcode: 2011SPIE.8148E..10S Two mission concepts (plan A: out-of-ecliptic mission and plan B: high resolution spectroscopic mission) have been studied for the next Japanese-led solar mission Solar-C, which will follow the scientific success of the Hinode mission. The both mission concepts are concluded as equally important and attractive for the promotion of space solar physics. In the meantime we also had to make efforts for prioritizing the two options, in order to proceed to next stage of requesting the launch of Solar-C mission at the earliest opportunity. This paper briefly describes the two mission concepts and the current status on our efforts for prioritizing the two options. More details are also described for the plan B option as the first-priority Solar-C mission. The latest report from the Solar-C mission concept studies was documented as "Interim Report on the Solar-C Mission Concept." Title: 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 Bibcode: 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. 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. Bibcode: 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-1, 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-1 redshifted components. The density of the 1.5-2 MK plasma at these footpoints is estimated to be 3 × 1010 cm-3 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 (>107 K) in these loops. The characteristics observed during the early phases of this flare are consistent with the scenario of explosive chromospheric evaporation. 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 Bibcode: 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. 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 Bibcode: 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. Title: Spectroscopy of highly charged ions in Solar and astrophysical plasmas Authors: Watanabe, Tetsuya Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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-1 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. Bibcode: 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-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. 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 2007PASJ...59S.699H Altcode: 2007arXiv0711.0487H We use coordinated Hinode SOT/EIS observations that include high-resolution magnetograms, chromospheric, and transition region (TR) imaging, and TR/coronal spectra in a first test to study how the dynamics of the TR are driven by the highly dynamic photospheric magnetic fields and the ubiquitous chromospheric waves. Initial analysis shows that these connections are quite subtle and require a combination of techniques including magnetic field extrapolations, frequency-filtered time-series, and comparisons with synthetic chromospheric and TR images from advanced 3D numerical simulations. As a first result, we find signatures of magnetic flux emergence as well as 3 and 5mHz wave power above regions of enhanced photospheric magnetic field in both chromospheric, transition region, and coronal emission. Title: 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 Bibcode: 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. Bibcode: 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-1 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. Bibcode: 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-1, 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-1). 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 Bibcode: 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 Bibcode: 2005BASI...33..362S Altcode: No abstract at ADS Title: Electron Densities of High-Temperature Coronal Loops Authors: Watanabe, Tetsuya Bibcode: 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 Bibcode: 2004ApJ...617L..81S Altcode: We obtained spectroscopic observations simultaneously in pairs of coronal emission lines, one line being [Fe X] λ6374 and the other line being [Fe XI] λ7892, [Fe XIII] λ10747, or [Fe XIV] λ5303, and we studied the variations in the intensity and FWHM ratios of these lines with respect to those of 6374 Å as a function of height above the limb. We find that the intensity ratio of the 7892 and 10747 Å line with respect to the 6374 Å line increases with height and that the intensity ratio of 5303 Å to 6374 Å decreases with height above the limb. This implies that the temperature in coronal loops will appear to increase with height if we consider the intensity ratio of 7892 Å to 6374 Å a negligible variation in temperature in the case of the 10747 and 6374 Å line pair, while the temperature will appear to decrease with height if we consider the intensity ratio of 5303 Å to 6374 Å. The normalized FWHM (with respect to wavelength) ratio of 6374 Å to all the other coronal lines observed increases with height. The FWHM ratio at the limb depends on the pair of emission lines chosen; it is about 1 in the case of the 6374 and 7892 Å emission lines, indicating a common temperature and nonthermal velocity in the coronal loops near the limb, and it is about 0.7 at the limb in the case of the 6374 and 5303 Å lines and becomes about 1 at a height of 120". The varying FWHM ratios with height indicate that hotter and colder plasmas in coronal loops mix with each other. Therefore, the observed increase in the FWHM of coronal emission lines, which are associated with plasma at about 1 MK with height, may not be due to an increase in nonthermal motions caused by coronal waves but may be due to an interaction with relatively hotter plasma. Title: Development of the Solar-B spacecraft Authors: Tsuneta, Saku; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi; Hara, Hirohisa; Kano, Ryohei; Nagata, Shin'ichi; Tamura, Tomonori; Nakagiri, Masao; Noguchi, Motokazu; Kato, Yoshihiro; Watanabe, Tetsuya; Hanaoka, Yoichiro; Sawa, Masaki; Otsubo, Masashi; Kosugi, Takeo; Yamada, Takahiro; Sakao, Taro; Matsuzaki, Keiichi; Minesugi, Kenji; Onishi, Akira; Katsukawa, Yukio; Kobayashi, Ken; Kubo, Masahito Bibcode: 2003naoj.book....3T Altcode: No abstract at ADS Title: Energetics of an Active Region Observed from Helium-Like Sulphur Lines Authors: Watanabe, Tetsuya; Sterling, Alphonse C.; Hudson, Hugh S.; Harra, Louise K. Bibcode: 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 4×106 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. Bibcode: 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 105 - 107 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 Bibcode: 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. Bibcode: 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 105 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 105 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 105 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 Bibcode: 1998ApOpt..37.6803H Altcode: No abstract at ADS Title: Observational plasma astrophysics : five years of YOHKOH and beyond Authors: Watanabe, Tetsuya; Kosugi, Takeo Bibcode: 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 Bibcode: 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 Bibcode: 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 Te ~ 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 Te >~ 3.5 MK. There is evidence for a decrease in Te 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 × 106 K is derived from the spectra taken during low solar activity, similar to the general corona, while 4 × 106 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 1980PhDT.......140W Altcode: No abstract at ADS