explanation blue bibcodes open ADS page with paths to full text
Author name code: sakao
ADS astronomy entries on 2022-09-14
author:"Sakao, Taro"
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Title: Quiet Sun Center to Limb Variation of the Linear Polarization
Observed by CLASP2 Across the Mg II h and k Lines
Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.;
Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto,
T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi,
L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu,
T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De;
Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán,
J.; Carlsson, M.; Leenaarts, J.
2022ApJ...936...67R Altcode: 2022arXiv220701788R
The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket
mission was launched on 2019 April 11. CLASP2 measured the four Stokes
parameters of the Mg II h and k spectral region around 2800 Å along a
200″ slit at three locations on the solar disk, achieving the first
spatially and spectrally resolved observations of the solar polarization
in this near-ultraviolet region. The focus of the work presented here
is the center-to-limb variation of the linear polarization across these
resonance lines, which is produced by the scattering of anisotropic
radiation in the solar atmosphere. The linear polarization signals of
the Mg II h and k lines are sensitive to the magnetic field from the
low to the upper chromosphere through the Hanle and magneto-optical
effects. We compare the observations to theoretical predictions
from radiative transfer calculations in unmagnetized semiempirical
models, arguing that magnetic fields and horizontal inhomogeneities
are needed to explain the observed polarization signals and spatial
variations. This comparison is an important step in both validating and
refining our understanding of the physical origin of these polarization
signatures, and also in paving the way toward future space telescopes
for probing the magnetic fields of the solar upper atmosphere via
ultraviolet spectropolarimetry.
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Title: Temperature and differential emission measure evolution of
a limb flare on 13 January 2015
Authors: Bröse, M.; Warmuth, A.; Sakao, T.; Su, Y.
2022A&A...663A..18B Altcode:
Context. Spatially unresolved observations show that the cooling
phase in solar flares can be much longer than theoretical models
predict. It has not yet been determined whether this is also the case
for different subregions within the flare structure. <BR /> Aims:
We aim to investigate whether or not the cooling times, which are
observed separately in coronal loops and the supra-arcade fan (SAF),
are in accordance with the existing cooling models, and whether the
temperature and emission measure of supra-arcade downflows (SADs)
are different from their surroundings. <BR /> Methods: We analysed
the M5.6 limb flare on 13 January 2015 using SDO/AIA observations. We
applied a differential emission measure (DEM) reconstruction code
to derive spatially resolved temperature and emission measure maps,
and used the output to investigate the thermal evolution of coronal
loops, the SAF, and the SADs. <BR /> Results: In the event of 13
January 2015, the observed cooling times of the loop arcade and the
SAF are significantly longer than predicted by the Cargill model,
even with suppressed plasma heat conduction. The observed SADs show
different temperature characteristics, and in all cases a lower density
than their surroundings. <BR /> Conclusions: In the limb flare event
studied here, continuous heating likely occurs in both loops and SAF
during the gradual flare phase and leads to an extended cooling phase.
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Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1
Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier;
Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song,
Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil,
Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman,
Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri
2021AGUFMSH52A..06M Altcode:
Probing the magnetic nature of the Suns atmosphere requires measurement
of the Stokes I, Q, U and V profiles of relevant spectral lines (of
which Q, U and V encode the magnetic field information). Many of the
magnetically sensitive lines formed in the chromosphere and transition
region are in the ultraviolet spectrum, necessitating observations
above the absorbing terrestrial atmosphere. The Chromospheric
Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown
successfully in April 2019, as a follow-on to the successful flight in
September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP). Both projects were funded by NASAs Heliophysics Technology
and Instrument Development for Science (H-TIDeS) program to develop
and test a technique for observing the Sun in ultraviolet light,
and for quantifying the polarization of that light. By demonstrating
successful measurement and interpretation of the polarization in
hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP
and CLASP2 missions are vital first steps towards routine quantitative
characterization of the local thermal and magnetic conditions in the
solar chromosphere. In October of 2021, we re-flew the CLASP2 payload
with a modified observing program to further demonstrate the maturity
of the UV spectropolarimetry techniques, and readiness for development
into a satellite observatory. During the reflight, called CLASP2.1,
the spectrograph slit was scanned across an active region plage to
acquire a two-dimensional map of Stokes V/I, to demonstrate the ability
of UV spectropolarimetry to yield chromospheric magnetic fields over
a large area. This presentation will display preliminary results from
the flight of CLASP2.1.
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Title: Mapping of Solar Magnetic Fields from the Photosphere to the
Top of the Chromosphere with CLASP2
Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.;
del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.;
Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.;
Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil,
G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.;
Asensio Ramos, A.; Carlsson, M.; Leenaarts, J.
2021AAS...23810603M Altcode:
Coronal heating, chromospheric heating, and the heating &
acceleration of the solar wind, are well-known problems in solar
physics. Additionally, knowledge of the magnetic energy that
powers solar flares and coronal mass ejections, important drivers
of space weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of photospheric
magnetic measurements into the corona is fraught with difficulties and
uncertainties, partly due to the vastly different plasma beta between
the photosphere and the corona. Better results in understanding
the coronal magnetic field should be derived from measurements of
the magnetic field in the chromosphere. To that end, we are pursuing
quantitative determination of the magnetic field in the chromosphere,
where plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown
on a sounding rocket in April 2019, succeeded in measuring all four
Stokes polarization parameters in UV spectral lines formed by singly
ionized Magnesium and neutral Manganese. Because these ions produce
spectral lines under different conditions, CLASP2 thus was able to
quantify the magnetic field properties at multiple heights in the
chromosphere simultaneously, as shown in the recent paper by Ishikawa
et al. In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the chromosphere;
and we will illustrate what is next for the CLASP missions and the
demonstration of UV spectropolarimetry in the solar chromosphere.
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Title: Mapping solar magnetic fields from the photosphere to the
base of the corona
Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán,
Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère,
Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler,
Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage,
Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge,
Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.;
Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán,
Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit
2021SciA....7.8406I Altcode: 2021arXiv210301583I
Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind to
its main driver, the magnetic field. Here we report unprecedented
spectropolarimetric observations of an active region plage and
its surrounding enhanced network, showing circular polarization in
ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We
infer the longitudinal magnetic field from the photosphere to the
very upper chromosphere. At the top of the plage chromosphere the
field strengths reach more than 300 gauss, strongly correlated with
the Mg II $k$ line core intensity and the electron pressure. This
unique mapping shows how the magnetic field couples the different
atmospheric layers and reveals the magnetic origin of the heating in
the plage chromosphere.
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Title: Estimating the Temperature and Density of a Spicule from 100
GHz Data Obtained with ALMA
Authors: Shimojo, Masumi; Kawate, Tomoko; Okamoto, Takenori J.;
Yokoyama, Takaaki; Narukage, Noriyuki; Sakao, Taro; Iwai, Kazumasa;
Fleishman, Gregory D.; Shibata, Kazunari
2020ApJ...888L..28S Altcode: 2019arXiv191205714S
We succeeded in observing two large spicules simultaneously with the
Atacama Large Millimeter/submillimeter Array (ALMA), the Interface
Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly
(AIA) on board the Solar Dynamics Observatory. One is a spicule seen
in the IRIS Mg II slit-jaw images and AIA 304 Å images (Mg II/304 Å
spicule). The other one is a spicule seen in the 100 GHz images obtained
with ALMA (100 GHz spicule). Although the 100 GHz spicule overlapped
with the Mg II/304 Å spicule in the early phase, it did not show any
corresponding structures in the IRIS Mg II and AIA 304 Å images after
the early phase. It suggests that the spicules are individual events and
do not have a physical relationship. To obtain the physical parameters
of the 100 GHz spicule, we estimate the optical depths as a function
of temperature and density using two different methods. One is using
the observed brightness temperature by assuming a filling factor,
and the other is using an emission model for the optical depth. As a
result of comparing them, the kinetic temperature of the plasma and
the number density of ionized hydrogen in the 100 GHz spicule are
∼6800 K and 2.2 × 10<SUP>10</SUP> cm<SUP>-3</SUP>. The estimated
values can explain the absorbing structure in the 193 Å image, which
appear as a counterpart of the 100 GHz spicule. These results suggest
that the 100 GHz spicule presented in this Letter is classified to a
macrospicule without a hot sheath in former terminology.
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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: Comparison of Scattering Polarization Signals Observed by
CLASP: Possible Indication of the Hanle Effect
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pomtieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
2019ASPC..526..305I Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP; Kano et
al. 2012; Kobayashi et al. 2012; Kubo et al. 2014) observed, for the
first time, the linear polarization produced by scattering processes
in the hydrogen Lyman-α (121.57 nm) and Si III (120.56 nm) lines of
the solar disk radiation. The complexity of the observed scattering
polarization (i.e., conspicuous spatial variations in Q/I and U/I
at spatial scales of 10″-20″ and the absence of center-to- limb
variation at the Lyman-α center; see Kano et al. 2017) motivated us
to search for possible hints of the operation of the Hanle effect by
comparing: (a) the Lyman-α line center signal, for which the critical
field strength (B<SUB>H</SUB>) for the onset of the Hanle effect is
53 G, (b) the Lyman-α wing, which is insensitive to the Hanle effect,
and (c) the Si III line, whose B<SUB>H</SUB> = 290 G. We focus on four
regions with different total unsigned photospheric magnetic fluxes
(estimated from SDO/HMI observations), and compare the corresponding
U/I spatial variations in the Lyman-α wing, Lyman-α center, and Si III
line. The U/I signal in the Lyman-α wing shows an antisymmetric spatial
distribution, which is caused by the presence of a bright structure in
all the selected regions, regardless of the total unsigned photospheric
magnetic flux. In an internetwork region, the Lyman-α center shows an
antisymmetric spatial variation across the selected bright structure,
but it does not show it in other more magnetized regions. In the Si III
line, the spatial variation of U/I deviates from the above-mentioned
antisymmetric shape as the total unsigned photospheric magnetic flux
increases. We argue that a plausible explanation of this differential
behavior is the operation of the Hanle effect. <P />This work, presented
in an oral contribution at this Workshop, has been published on The
Astrophysical Journal (Ishikawa et al. 2017).
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Title: CLASP Constraints on the Magnetization and Geometrical
Complexity of the Chromosphere-Corona Transition Region
Authors: Trujillo Bueno, J.; Štěpán, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Ishikawa,
R.; Kano, R.; Winebarger, A.; Auchère, F.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
2018ApJ...866L..15T Altcode: 2018arXiv180908865T
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
suborbital rocket experiment that on 2015 September 3 measured
the linear polarization produced by scattering processes in the
hydrogen Lyα line of the solar disk radiation. The line-center
photons of this spectral line radiation mostly stem from the
chromosphere-corona transition region (TR). These unprecedented
spectropolarimetric observations revealed an interesting surprise,
namely that there is practically no center-to-limb variation (CLV) in
the Q/I line-center signals. Using an analytical model, we first show
that the geometric complexity of the corrugated surface that delineates
the TR has a crucial impact on the CLV of the Q/I and U/I line-center
signals. Second, we introduce a statistical description of the solar
atmosphere based on a 3D model derived from a state-of-the-art radiation
magnetohydrodynamic simulation. Each realization of the statistical
ensemble is a 3D model characterized by a given degree of magnetization
and corrugation of the TR, and for each such realization we solve the
full 3D radiative transfer problem taking into account the impact
of the CLASP instrument degradation on the calculated polarization
signals. Finally, we apply the statistical inference method presented
in a previous paper to show that the TR of the 3D model that produces
the best agreement with the CLASP observations has a relatively weak
magnetic field and a relatively high degree of corrugation. We emphasize
that a suitable way to validate or refute numerical models of the upper
solar chromosphere is by confronting calculations and observations
of the scattering polarization in ultraviolet lines sensitive to the
Hanle effect.
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Title: A Statistical Inference Method for Interpreting the CLASP
Observations
Authors: Štěpán, J.; Trujillo Bueno, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Kano, R.;
Winebarger, A.; Auchère, F.; Ishikawa, R.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
2018ApJ...865...48S Altcode: 2018arXiv180802725S
On 2015 September 3, the Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) successfully measured the linear polarization produced by
scattering processes in the hydrogen Lyα line of the solar disk
radiation, revealing conspicuous spatial variations in the Q/I and U/I
signals. Via the Hanle effect, the line-center Q/I and U/I amplitudes
encode information on the magnetic field of the chromosphere-corona
transition region, but they are also sensitive to the three-dimensional
structure of this corrugated interface region. With the help of a simple
line-formation model, here we propose a statistical inference method
for interpreting the Lyα line-center polarization observed by CLASP.
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Title: Current State of UV Spectro-Polarimetry and its Future
Direction
Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara,
Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito;
Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi,
. Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier;
Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts,
Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke;
Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel;
Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan,
Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey,
Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David;
Rachmeler, Laurel; Bethge, Christian
2018cosp...42E1564I Altcode:
To obtain quantitative information on the magnetic field in low beta
regions (i.e., upper chromosphere and above) has been increasingly
important to understand the energetic phenomena of the outer
solar atmosphere such as flare, coronal heating, and the solar wind
acceleration. In the UV range, there are abundant spectral lines that
originate in the upper chromosphere and transition region. However,
the Zeeman effect in these spectral lines does not give rise to easily
measurable polarization signals because of the weak magnetic field
strength and the larger Doppler broadening compared with the Zeeman
effect. Instead, the Hanle effect in UV lines is expected to be a
suitable diagnostic tool of the magnetic field in the upper atmospheric
layers. To investigate the validity of UV spectro-polarimetry and
the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP), which is a NASA sounding- rocket experiment, was launched at
White Sands in US on September 3, 2015. During its 5 minutes ballistic
flight, it successfully performed spectro-polarimetric observations
of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly
high polarization sensitivity of 0.1% in this wavelength range. CLASP
observed the linear polarization produced by scattering process in VUV
lines for the first time and detected the polarization signals which
indicate the operation of the Hanle effect. Following the success
of CLASP, we are confident that UV spectro-polarimetry is the way
to proceed, and we are planning the second flight of CLASP (CLASP2:
Chromospheric LAyer SpectroPolarimeter 2). For this second flight we
will carry out spectro-polarimetry in the Mg II h and k lines around
280 nm, with minimum modifications of the CLASP1 instrument. The linear
polarization in the Mg II k line is induced by scattering processes and
the Hanle effect, being sensitive to magnetic field strengths of 5 to 50
G. In addition, the circular polarizations in the Mg II h and k lines
induced by the Zeeman effect can be measurable in at least plage and
active regions. The combination of the Hanle and Zeeman effects could
help us to more reliably infer the magnetic fields of the upper solar
chromosphere. CLASP2 was selected for flight and is being developed for
launch in the spring of 2019.Based on these sounding rocket experiments
(CLASP1 and 2), we aim at establishing the strategy and refining the
instrument concept for future space missions to explore the enigmatic
atmospheric layers via UV spectro-polarimetry.
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Title: X-Ray Telescope (XRT) Aboard Hinode: Key Instrumental Features
and Scientific Highlights
Authors: Sakao, Taro
2018ASSL..449...43S Altcode:
No abstract at ADS
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Title: White paper of the "soft X-ray imaging spectroscopy"
Authors: Narukage, Noriyuki; Ishikawa, Shin-nosuke; Kawate, Tomoko;
Imada, Shinsuke; Sakao, Taro
2017arXiv170604536N Altcode:
The solar corona is full of dynamic phenomena, e.g., solar flares,
micro flares in active regions, jets in coronal holes and in the polar
regions, X-ray bright points in quiet regions, etc. They are accompanied
by interesting physical processes, namely, magnetic reconnection,
particle acceleration, shocks, waves, flows, evaporation, heating,
cooling, and so on. The understandings of these phenomena and processes
have been progressing step-by-step with the evolution of the observation
technology in EUV and X-rays from the space. But, there are fundamental
questions remain unanswered, or haven't even addressed so far. Our
scientific objective is to understand underlying physics of dynamic
phenomena in the solar corona, covering some of the long-standing
questions in solar physics such as particle acceleration in flares
and coronal heating. In order to achieve these science objectives,
we identify the imaging spectroscopy (the observations with spatial,
temporal and energy resolutions) in the soft X-ray range (from ~0.5
keV to ~10 keV) is a powerful approach for the detection and analysis
of energetic events.
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Title: Indication of the Hanle Effect by Comparing the Scattering
Polarization Observed by CLASP in the Lyα and Si III 120.65 nm Lines
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
2017ApJ...841...31I Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding
rocket experiment that has provided the first successful measurement
of the linear polarization produced by scattering processes in
the hydrogen Lyα line (121.57 nm) radiation of the solar disk. In
this paper, we report that the Si III line at 120.65 nm also shows
scattering polarization and we compare the scattering polarization
signals observed in the Lyα and Si III lines in order to search for
observational signatures of the Hanle effect. We focus on four selected
bright structures and investigate how the U/I spatial variations vary
between the Lyα wing, the Lyα core, and the Si III line as a function
of the total unsigned photospheric magnetic flux estimated from Solar
Dynamics Observatory/Helioseismic and Magnetic Imager observations. In
an internetwork region, the Lyα core shows an antisymmetric spatial
variation across the selected bright structure, but it does not show
it in other more magnetized regions. In the Si III line, the spatial
variation of U/I deviates from the above-mentioned antisymmetric
shape as the total unsigned photospheric magnetic flux increases. A
plausible explanation of this difference is the operation of the Hanle
effect. We argue that diagnostic techniques based on the scattering
polarization observed simultaneously in two spectral lines with very
different sensitivities to the Hanle effect, like Lyα and Si III,
are of great potential interest for exploring the magnetism of the
upper solar chromosphere and transition region.
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Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV
Range. Part II: In-Flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.;
Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
2017SoPh..292...57G Altcode:
The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding
rocket instrument designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm). The instrument
was successfully launched on 3 September 2015 and observations were
conducted at the solar disc center and close to the limb during the
five-minutes flight. In this article, the disc center observations are
used to provide an in-flight calibration of the instrument spurious
polarization. The derived in-flight spurious polarization is consistent
with the spurious polarization levels determined during the pre-flight
calibration and a statistical analysis of the polarization fluctuations
from solar origin is conducted to ensure a 0.014% precision on the
spurious polarization. The combination of the pre-flight and the
in-flight polarization calibrations provides a complete picture of
the instrument response matrix, and a proper error transfer method
is used to confirm the achieved polarization accuracy. As a result,
the unprecedented 0.1% polarization accuracy of the instrument in the
vacuum ultraviolet is ensured by the polarization calibration.
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Title: Discovery of Scattering Polarization in the Hydrogen Lyα
Line of the Solar Disk Radiation
Authors: Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchère, F.;
Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.;
Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu,
T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.;
Štěpán, J.; Asensio Ramos, A.; Manso Sainz, R.; Champey, P.;
Cirtain, J.; De Pontieu, B.; Casini, R.; Carlsson, M.
2017ApJ...839L..10K Altcode: 2017arXiv170403228K
There is a thin transition region (TR) in the solar atmosphere where
the temperature rises from 10,000 K in the chromosphere to millions
of degrees in the corona. Little is known about the mechanisms that
dominate this enigmatic region other than the magnetic field plays a
key role. The magnetism of the TR can only be detected by polarimetric
measurements of a few ultraviolet (UV) spectral lines, the Lyα line
of neutral hydrogen at 121.6 nm (the strongest line of the solar UV
spectrum) being of particular interest given its sensitivity to the
Hanle effect (the magnetic-field-induced modification of the scattering
line polarization). We report the discovery of linear polarization
produced by scattering processes in the Lyα line, obtained with
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) rocket
experiment. The Stokes profiles observed by CLASP in quiet regions of
the solar disk show that the Q/I and U/I linear polarization signals are
of the order of 0.1% in the line core and up to a few percent in the
nearby wings, and that both have conspicuous spatial variations with
scales of ∼10 arcsec. These observations help constrain theoretical
models of the chromosphere-corona TR and extrapolations of the
magnetic field from photospheric magnetograms. In fact, the observed
spatial variation from disk to limb of polarization at the line core
and wings already challenge the predictions from three-dimensional
magnetohydrodynamical models of the upper solar chromosphere.
---------------------------------------------------------
Title: Creation of Super-Hot Plasmas in a Flux Eruption Event as
seen in Soft X-rays with Hinode/XRT
Authors: Sakao, T.; Shimojo, M.; Narukage, N.
2016AGUFMSH11D..04S Altcode:
The X-Ray Telescope (XRT) aboard Hinode observes soft X-ray emission
from the solar corona with its energy range 0.06 - 2 keV and is capable
of imaging, and diagnosing, a wide range of coronal temperatures
from below 1 MK to beyond 20 MK, without gaps in the temperature
coverage. In particular, the grazing-incidence nature of the XRT
optics is suited for imaging high-temperature plasmas (>20 MK)
created during the course of flares that are not necessarily well
accessible with coronal imagers utilizing EUV emission lines. We
report XRT observations of an eruptive flare (GOES M1.1) that took
place behind the east limb at 18:30 UT on 14 October 2014. X-ray
images traced a flux eruption which corresponds to the early stage of
a CME observed with SoHO/LASCO, with a flux-rope-like feature ejected
as the flare progressed. Filter-ratio temperatures of the soft X-ray
flaring structure derived from multiple-filter observation of the flare
suggest possible creation of super-hot (reaching as high as 30 MK)
plasmas that distributed from near the apex of the erupting structure
(where the flux rope was present), downwards along the sides of the
structure. The observation may be the first identification in images of
super-hot plasmas in the soft X-ray range, covering up to 2 keV. XRT
observations on the creation of super-hot plasmas during the course
of the flux eruption will be reported and its implication discussed.
---------------------------------------------------------
Title: Discovery of Ubiquitous Fast-Propagating Intensity Disturbances
by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP)
Authors: Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Kano, R.; Bando,
T.; Narukage, N.; Ishikawa, R.; Hara, H.; Giono, G.; Tsuneta, S.;
Ishikawa, S.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.;
Cirtain, J.; Champey, P.; Auchère, F.; Trujillo Bueno, J.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
2016ApJ...832..141K Altcode:
High-cadence observations by the slit-jaw (SJ) optics system of the
sounding rocket experiment known as the Chromospheric Lyman Alpha
Spectropolarimeter (CLASP) reveal ubiquitous intensity disturbances
that recurrently propagate in either the chromosphere or the transition
region or both at a speed much higher than the speed of sound. The
CLASP/SJ instrument provides a time series of two-dimensional images
taken with broadband filters centered on the Lyα line at a 0.6 s
cadence. The multiple fast-propagating intensity disturbances appear in
the quiet Sun and in an active region, and they are clearly detected in
at least 20 areas in a field of view of 527″ × 527″ during the 5
minute observing time. The apparent speeds of the intensity disturbances
range from 150 to 350 km s<SUP>-1</SUP>, and they are comparable
to the local Alfvén speed in the transition region. The intensity
disturbances tend to propagate along bright elongated structures away
from areas with strong photospheric magnetic fields. This suggests
that the observed fast-propagating intensity disturbances are related
to the magnetic canopy structures. The maximum distance traveled by
the intensity disturbances is about 10″, and the widths are a few
arcseconds, which are almost determined by a pixel size of 1.″03. The
timescale of each intensity pulse is shorter than 30 s. One possible
explanation for the fast-propagating intensity disturbances observed
by CLASP is magnetohydrodynamic fast-mode waves.
---------------------------------------------------------
Title: Evidence of Electron Acceleration around the Reconnection
X-point in a Solar Flare
Authors: Narukage, Noriyuki; Shimojo, Masumi; Sakao, Taro
2016SPD....4730202N Altcode:
Particle acceleration is one of the most significant features that
are ubiquitous among space and cosmic plasmas. It is most prominent
during flares in the case of the Sun, with which huge amounts of
electromagnetic radiation and high-energy particles are expelled into
the interplanetary space through acceleration of plasma particles
in the corona. Though it has been well understood that energies of
flares are supplied by the mechanism called magnetic reconnection
based on the observations in X-rays and EUV with space telescopes,
where and how in the flaring magnetic field plasmas are accelerated
has remained unknown due to the low plasma density in the flaring
corona. We here report the first observational identification of the
energetic non-thermal electrons around the point of the ongoing magnetic
reconnection (X-point), with the location of the X-point identified
by soft X-ray imagery and the localized presence of non-thermal
electrons identified from imaging-spectroscopic data at two microwave
frequencies. Considering the existence of the reconnection outflows
that carries both plasma particles and magnetic fields out from
the X-point, our identified non-thermal microwave emissions around
the X-point indicate that the electrons are accelerated around the
reconnection X-point.
---------------------------------------------------------
Title: Spectro-polarimetric observation in UV with CLASP to probe
the chromosphere and transition region
Authors: Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère,
Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi,
Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori;
Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi;
Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto;
Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi,
Luca; Carlsson, Mats
2016SPD....4710107K Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA
sounding-rocket experiment that was performed in White Sands in
the US on September 3, 2015. During its 5-minute ballistic flight,
CLASP successfully made the first spectro-polarimetric observation in
the Lyman-alpha line (121.57 nm) originating in the chromosphere and
transition region. Since the Lyman-alpha polarization is sensitive
to magnetic field of 10-100 G by the Hanle effect, we aim to infer
the magnetic field information in such upper solar atmosphere with
this experiment.The obtained CLASP data showed that the Lyman-alpha
scattering polarization is about a few percent in the wings and
the order of 0.1% in the core near the solar limb, as it had been
theoretically predicted, and that both polarization signals have a
conspicuous spatio-temporal variability. CLASP also observed another
upper-chromospheric line, Si III (120.65 nm), whose critical field
strength for the Hanle effect is 290 G, and showed a measurable
scattering polarization of a few % in this line. The polarization
properties of the Si III line could facilitate the interpretation of
the scattering polarization observed in the Lyman-alpha line.In this
presentation, we would like to show how the upper chromosphere and
transition region are seen in the polarization of these UV lines and
discuss the possible source of these complicated polarization signals.
---------------------------------------------------------
Title: Development of precision Wolter mirrors for future solar
x-ray observations
Authors: Sakao, Taro; Matsuyama, Satoshi; Kime, Ayumi; Goto, Takumi;
Nishihara, Akihiko; Nakamori, Hiroki; Yamauchi, Kazuto; Kohmura,
Yoshiki; Miyake, Akira; Hashizume, Hirokazu; Maezawa, Tadakazu;
Suematsu, Yoshinori; Narukage, Noriyuki
2015SPIE.9603E..0US Altcode:
High resolution imagery of the solar X-ray corona provides a
crucial key to understand dynamics and heating processes of plasma
particles there. However, X-ray imagery of the Sun with sub-arcsecond
resolution has yet to be conducted due to severe technical difficulty in
fabricating precision Wolter mirrors. For future X-ray observations of
the Sun's corona, we are attempting to realize precision Wolter mirrors
with sub-arcsecond resolution by adopting advanced surface polish and
metrology methods based on nano-technology to sector mirrors which
consist of a portion of an entire annulus. Following fabrication
of the first engineering mirror and subsequent evaluation on the
X-ray focusing performance in 2013, the second engineering mirror
was made with improvements in both precision polish and metrology
introduced. Measurement of focusing performance on the second mirror
at SPring-8 synchrotron facility with 8 keV X-rays has demonstrated
that the FWHM size of the PSF core reached down to 0.2" while its HPD
(Half Power Diameter) size remained at ~3" due to the presence of
small-angle scatter just outside of the core. Also, there was notable
difference in the focal length between sagittal and meridional focusing
which could have been caused by an error in the sag in the meridional
direction of <10 nm in the mirror area. Further improvements to
overcome these issues have been planned for the next engineering mirror.
---------------------------------------------------------
Title: CLASP: A UV Spectropolarimeter on a Sounding Rocket for
Probing theChromosphere-Corona Transition Regio
Authors: Ishikawa, Ryohko; Kano, Ryouhei; Winebarger, Amy; Auchere,
Frederic; Trujillo Bueno, Javier; Bando, Takamasa; Narukage,
Noriyuki; Kobayashi, Ken; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Giono, Gabriel; Tsuneta, Saku; Hara, Hirohisa; Suematsu,
Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Ichimoto, Kiyoshi;
Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Manso Sainz,
Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca
2015IAUGA..2254536I Altcode:
The wish to understand the energetic phenomena of the outer solar
atmosphere makes it increasingly important to achieve quantitative
information on the magnetic field in the chromosphere-corona
transition region. To this end, we need to measure and model the
linear polarization produced by scattering processes and the Hanle
effect in strong UV resonance lines, such as the hydrogen Lyman-alpha
line. A team consisting of Japan, USA, Spain, France, and Norway has
been developing a sounding rocket experiment called the Chromospheric
Lyman-alpha Spectro-Polarimeter (CLASP). The aim is to detect the
scattering polarization produced by anisotropic radiation pumping in
the hydrogen Lyman-alpha line (121.6 nm), and via the Hanle effect to
try to constrain the magnetic field vector in the upper chromosphere
and transition region. In this talk, we will present an overview
of our CLASP mission, its scientific objectives, ground tests made,
and the latest information on the launch planned for the Summer of 2015.
---------------------------------------------------------
Title: A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP)
Authors: Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.;
Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.;
Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway,
T.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchère,
F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; Asensio Ramos,
A.; Štěpán, J.; Carlsson, M.
2014ASPC..489..307K Altcode:
A sounding-rocket experiment called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is presently under development to measure
the linear polarization profiles in the hydrogen Lyman-alpha (Lyα)
line at 121.567 nm. CLASP is a vacuum-UV (VUV) spectropolarimeter to aim
for first detection of the linear polarizations caused by scattering
processes and the Hanle effect in the Lyα line with high accuracy
(0.1%). This is a fist step for exploration of magnetic fields in
the upper chromosphere and transition region of the Sun. Accurate
measurements of the linear polarization signals caused by scattering
processes and the Hanle effect in strong UV lines like Lyα are
essential to explore with future solar telescopes the strength
and structures of the magnetic field in the upper chromosphere and
transition region of the Sun. The CLASP proposal has been accepted by
NASA in 2012, and the flight is planned in 2015.
---------------------------------------------------------
Title: Current progress of optical alignment procedure of CLASP's
Lyman-alpha polarimetry instrument
Authors: Giono, G.; Ishikawa, R.; Katsukawa, Y.; Bando, T.; Kano, R.;
Suematsu, Y.; Narukage, N.; Sakao, Taro; Kobayashi, K.; Auchère, F.
2014SPIE.9144E..3EG Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
sounding-rocket instrument currently under development at the
National Astronomical Observatory of Japan (NAOJ) as a part of an
international collaboration. CLASP's optics are composed of a Cassegrain
telescope and a spectro-polarimeter which are designed to achieve an
unprecedentedly accurate polarization measurement of the Ly-α line
at 121.6nm emitted from the solar upper-chromosphere and transition
region. CLASP's first flight is scheduled for August 2015. Reaching
such accuracy requires a careful alignment of the optical elements
to optimize the image quality at 121.6 nm. However Ly-α is absorbed
by air and therefore the optics alignment has to be done under vacuum
condition which makes any experiment difficult. To bypass this issue,
we proposed to align the telescope and the spectrograph separately
in visible light. Hence we present our alignment procedure for both
telescope and spectro-polarimeter. We will explain details about the
telescope preliminary alignment before mirrors coating, which was done
in April 2014, present the telescope combined optical performance
and compare them to CLASP tolerance. Then we will present details
about an experiment designed to confirm our alignment procedure for
the CLASP spectro-polarimeter. We will discuss the resulting image
quality achieved during this experiment and the lessons learned.
---------------------------------------------------------
Title: The soft x-ray photon-counting telescope for solar observations
Authors: Sakao, Taro; Narukage, Noriyuki; Suematsu, Yoshinori;
Watanabe, Kyoko; Shimojo, Masumi; Imada, Shinsuke; Ishikawa,
Shin-nosuke; DeLuca, Edward E.
2014SPIE.9144E..3DS Altcode:
We present overview and development activities of a soft X-ray
photon-counting spectroscopic imager for the solar corona that
we conceive as a possible scientific payload for future space
solar missions including Japanese Solar-C. The soft X-ray imager
will employ a Wolter I grazing-incidence sector mirror with which
images of the corona (1 MK to beyond 10 MK) will be taken with
the highest-ever angular resolution (0.5"/pixel for a focal length
of 4 m) as a solar Xray telescope. In addition to high-resolution
imagery, we attempt to implement photon-counting capability for the
imager by employing a backside-illuminated CMOS image sensor as the
focal-plane device. Imaging-spectroscopy of the X-ray corona will be
performed for the first time in the energy range from ~0.5 keV up to
10 keV. The imaging-spectroscopic observations with the soft X-ray
imager will provide a noble probe for investigating mechanism(s) of
magnetic reconnection and generation of supra-thermal (non-thermal)
electrons associated with flares. Ongoing development activities in
Japan towards the photon-counting imager is described with emphasis
on that for sub-arcsecond-resolution grazing-incidence mirrors.
---------------------------------------------------------
Title: Evidence of Electron Acceleration around the Reconnection
X-point in a Solar Flare
Authors: Narukage, Noriyuki; Shimojo, Masumi; Sakao, Taro
2014ApJ...787..125N Altcode: 2014arXiv1404.3288N
Particle acceleration is one of the most significant features that
are ubiquitous among space and cosmic plasmas. It is most prominent
during flares in the case of the Sun, with which huge amounts of
electromagnetic radiation and high-energy particles are expelled into
the interplanetary space through acceleration of plasma particles
in the corona. Though it has been well understood that energies of
flares are supplied by the mechanism called magnetic reconnection
based on the observations in X-rays and EUV with space telescopes,
where and how in the flaring magnetic field plasmas are accelerated
has remained unknown due to the low plasma density in the flaring
corona. We here report the first observational identification of the
energetic non-thermal electrons around the point of the ongoing magnetic
reconnection (X-point), with the location of the X-point identified
by soft X-ray imagery and the localized presence of non-thermal
electrons identified from imaging-spectroscopic data at two microwave
frequencies. Considering the existence of the reconnection outflows
that carries both plasma particles and magnetic fields out from
the X-point, our identified non-thermal microwave emissions around
the X-point indicate that the electrons are accelerated around the
reconnection X-point. Additionally, the plasma around the X-point was
also thermally heated up to 10 MK. The estimated reconnection rate of
this event is ~0.017.
---------------------------------------------------------
Title: Coronal-Temperature-Diagnostic Capability of the Hinode/ X-Ray
Telescope Based on Self-consistent Calibration. II. Calibration with
On-Orbit Data
Authors: Narukage, N.; Sakao, T.; Kano, R.; Shimojo, M.; Winebarger,
A.; Weber, M.; Reeves, K. K.
2014SoPh..289.1029N Altcode: 2013arXiv1307.4489N
The X-Ray Telescope (XRT) onboard the Hinode satellite is an
X-ray imager that observes the solar corona with the capability of
diagnosing coronal temperatures from less than 1 MK to more than
10 MK. To make full use of this capability, Narukage et al. (Solar
Phys.269, 169, 2011) determined the thickness of each of the X-ray
focal-plane analysis filters based on calibration measurements
from the ground-based end-to-end test. However, in their paper,
the calibration of the thicker filters for observations of active
regions and flares, namely the med-Be, med-Al, thick-Al and thick-Be
filters, was insufficient due to the insufficient X-ray flux used in
the measurements. In this work, we recalibrate those thicker filters
using quiescent active region data taken with multiple filters of
XRT. On the basis of our updated calibration results, we present the
revised coronal-temperature-diagnostic capability of XRT.
---------------------------------------------------------
Title: Chromospheric Lyman Alpha SpectroPolarimeter: CLASP
Authors: Kobayashi, Ken; Kano, R.; Trujillo Bueno, J.; Winebarger,
A. R.; Cirtain, J. W.; Bando, T.; De Pontieu, B.; Ishikawa, R.;
Katsukawa, Y.; Kubo, M.; Narukage, N.; Sakao, T.; Tsuneta, S.;
Auchère, F.; Asensio Ramos, A.; Belluzzi, L.; Carlsson, M.; Casini,
R.; Hara, H.; Ichimoto, K.; Manso Sainz, R.; Shimizu, T.; Stepan,
J.; Suematsu, Y.; Holloway, T.
2013SPD....44..142K Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV
spectropolarimeter optimized for measuring the linear polarization of
the Lyman-alpha line (121.6 nm). The Lyman-alpha line is predicted to
show linear polarization caused by atomic scattering in the chromosphere
and modified by the magnetic field through the Hanle effect. The
Hanle effect is sensitive to weaker magnetic fields than Zeeman
effect, and is not canceled by opposing fields, making it sensitive
to tangled or unresolved magnetic field structures. These factors make
the Hanle effect a valuable tool for probing the magnetic field in the
chromosphere above the quiet sun. To meet this goal, CLASP is designed
to measure linear polarization with 0.1% polarization sensitivity
at 0.01 nm spectral resolution and 10" spatial resolution. CLASP is
scheduled to be launched in 2015.
---------------------------------------------------------
Title: Next space solar observatory SOLAR-C: mission instruments
and science objectives
Authors: Katsukawa, Y.; Watanabe, T.; Hara, H.; Ichimoto, K.; Kubo,
M.; Kusano, K.; Sakao, T.; Shimizu, T.; Suematsu, Y.; Tsuneta, S.
2012IAUSS...6E.207K Altcode:
SOLAR-C, the fourth space solar mission in Japan, is under study with a
launch target of fiscal year 2018. A key concept of the mission is to
view the photosphere, chromosphere, and corona as one system coupled
by magnetic fields along with resolving the size scale of fundamental
physical processes connecting these atmospheric layers. It is especially
important to study magnetic structure in the chromosphere as an
interface layer between the photosphere and the corona. The SOLAR-C
satellite is equipped with three telescopes, the Solar UV-Visible-IR
Telescope (SUVIT), the EUV/FUV High Throughput Spectroscopic Telescope
(EUVS/LEMUR), and the X-ray Imaging Telescope (XIT). Observations
with SUVIT of photospheric and chromospheric magnetic fields make it
possible to infer three dimensional magnetic structure extending from
the photosphere to the chromosphere and corona.This helps to identify
magnetic structures causing magnetic reconnection, and clarify how
waves are propagated, reflected, and dissipated. Phenomena indicative
of or byproducts of magnetic reconnection, such as flows and shocks,
are to be captured by SUVIT and by spectroscopic observations using
EUVS/LEMUR, while XIT observes rapid changes in temperature distribution
of plasma heated by shock waves.
---------------------------------------------------------
Title: Hinode observations of the Venus corona during the 2012
transit of Venus
Authors: Kanao, M.; Yamazaki, A.; Imada, S.; Shimizu, T.; Sakao, T.;
Kasaba, Y.; Sakanoi, T.; Kagitani, M.; Nakamura, M.
2012AGUFM.P11D1851K Altcode:
The Hinode satellite successfully observed the transit of Venus on
5th June 2012 with the highest spatial resolution. This presentation
will focus on UV and soft X-ray data acquired with the EUV Imaging
Spectrometer (EIS) and the X-ray Telescope (XRT) onboard Hinode. We
expected the EUV and X-ray emissions from the charge exchange reaction
by the solar wind impacting on the neutral particles in Venus upper
atmosphere. The neutral particles escape through the photoreaction, the
solar wind pick-up process, and so on, in connection with the solar wind
and the solar radiation. However, there are few precedent observations
of the escaping hydrogen and oxygen, ranging from a few eV to a few keV
because of difficulty in the groundbased observations. The atmosphere
loss can be estimated based on the two-dimensional image of the neutral
particle density. Our estimation was made for 18.4nm (OVI), 19.3nm (OV)
and 25.6nm (HII), which intensity and line profiles can be recorded with
EIS, and 1.72-2.18nm (OVII), 1.60-1.90nm(OVIII), 2.85-3.37nm (CVI),
3.50-4.03 nm (CV), which are located in XRT's broadband range. Multi
wavelength observation could clarify the collision velocities between
the solar wind and Venus neutral particles. Before the transit of Venus,
for science planning purpose, we estimated the EUV and X-ray emission
intensities by using typical solar wind parameters (the proton density
10/cc and the solar wind velocity 400 km/sec) with a Venus atmosphere
model. The photon production rate of the X-ray emission is estimated
to be 1.1 x 10^25 photons/s, and that of the OVI emission line (18.4nm)
is 6.9 x 10^23 photons/s. These values are much lower than the emissions
from the solar corona, but unexpected signals may be observed dureing
the transit. In this presentation, we will present the calculation
results on intensity distribution of the Venus corona and some X-ray
and EUV data acquired during the transit. Also we briefly compare
the observed intensities in dark Venus feature with the calculation
results and discuss the signification of the difference.
---------------------------------------------------------
Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP)
Authors: Kano, Ryouhei; Bando, Takamasa; Narukage, Noriyuki; Ishikawa,
Ryoko; Tsuneta, Saku; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Hara, Hirohisa; Shimizu, Toshifumi; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Sakao, Taro; Goto, Motoshi; Kato, Yoshiaki; Imada,
Shinsuke; Kobayashi, Ken; Holloway, Todd; Winebarger, Amy; Cirtain,
Jonathan; De Pontieu, Bart; Casini, Roberto; Trujillo Bueno, Javier;
Štepán, Jiří; Manso Sainz, Rafael; Belluzzi, Luca; Asensio Ramos,
Andres; Auchère, Frédéric; Carlsson, Mats
2012SPIE.8443E..4FK Altcode:
One of the biggest challenges in heliophysics is to decipher the
magnetic structure of the solar chromosphere. The importance of
measuring the chromospheric magnetic field is due to both the key role
the chromosphere plays in energizing and structuring the outer solar
atmosphere and the inability of extrapolation of photospheric fields to
adequately describe this key boundary region. Over the last few years,
significant progress has been made in the spectral line formation
of UV lines as well as the MHD modeling of the solar atmosphere. It
is found that the Hanle effect in the Lyman-alpha line (121.567 nm)
is a most promising diagnostic tool for weaker magnetic fields in
the chromosphere and transition region. Based on this groundbreaking
research, we propose the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP) to NASA as a sounding rocket experiment, for making the first
measurement of the linear polarization produced by scattering processes
and the Hanle effect in the Lyman-alpha line (121.567 nm), and making
the first exploration of the magnetic field in the upper chromosphere
and transition region of the Sun. The CLASP instrument consists
of a Cassegrain telescope, a rotating 1/2-wave plate, a dual-beam
spectrograph assembly with a grating working as a beam splitter, and
an identical pair of reflective polarization analyzers each equipped
with a CCD camera. We propose to launch CLASP in December 2014.
---------------------------------------------------------
Title: The x-ray/EUV telescope for the Solar-C mission: science and
development activities
Authors: Sakao, Taro; Narukage, Noriyuki; Imada, Shinsuke; Suematsu,
Yoshinori; Shimojo, Masumi; Tsuneta, Saku; DeLuca, Edward E.; Watanabe,
Kyoko; Ishikawa, Shin-nosuke
2012SPIE.8443E..0AS Altcode:
We report science and development activities of the X-ray/EUV telescope
for the Japanese Solar-C mission whose projected launch around 2019. The
telescope consists of a package of (a) a normal-incidence (NI) EUV
telescope and (b) a grazing-incidence (GI) soft X-ray telescope. The NI
telescope chiefly provides images of low corona (whose temperature 1
MK or even lower) with ultra-high angular resolution (0.2-0.3"/pixel)
in 3 wavelength bands (304, 171, and 94 angstroms). On the other
hand, the GI telescope provides images of the corona with a wide
temperature coverage (1 MK to beyond 10 MK) with the highest-ever
angular resolution (~0.5"/pixel) as a soft X-ray coronal imager. The
set of NI and GI telescopes should provide crucial information for
establishing magnetic and gas-dynamic connection between the corona and
the lower atmosphere of the Sun which is essential for understanding
heating of, and plasma activities in, the corona. Moreover, we attempt
to implement photon-counting capability for the GI telescope with
which imaging-spectroscopy of the X-ray corona will be performed for
the first time, in the energy range from ~0.5 keV up to 10 keV. The
imaging-spectroscopic observations will provide totally-new information
on mechanism(s) for the generation of hot coronal plasmas (heated
beyond a few MK), those for magnetic reconnection, and even generation
of supra-thermal electrons associated with flares. An overview of
instrument outline and science for the X-ray photoncounting telescope
are presented, together with ongoing development activities in Japan
towards soft X-ray photoncounting observations, focusing on high-speed
X-ray CMOS detector and sub-arcsecond-resolution GI mirror.
---------------------------------------------------------
Title: The SOLAR-C Mission: Plan B Payload Concept
Authors: Shimizu, T.; Sakao, T.; Katsukawa, Y.; Group, J. S. W.
2012ASPC..454..449S Altcode:
The telescope concepts for the SOLAR-C Plan B mission as of the time of
the Hinode-3 meeting were briefly presented for having comments from
the international solar physics community. The telescope candidates
are 1) near IR-visible-UV telescope with 1.5m aperture and enhanced
spectro-polarimetric capability, 2) UV/EUV high throughput spectrometer,
and 3) next generation X-ray telescope.
---------------------------------------------------------
Title: X-ray performance of 0.18 µm CMOS APS test arrays for solar
observation
Authors: Dryer, B. J.; Holland, A. D.; Jerram, P.; Sakao, Taro
2012SPIE.8453E..2JD Altcode:
Solar-C is the third generation solar observatory led by JAXA. The
accepted ‘Plan-B’ payload calls for a radiation-hard solar-staring
photon-counting x-ray spectrometer. CMOS APS technology offers
advantages over CCDs for such an application such as increased radiation
hardness and high frame rate (instrument target of 1000 fps). Looking
towards the solution of a bespoke CMOS APS, this paper reports the
x-ray spectroscopy performance, concentrating on charge collection
efficiency and split event analysis, of two baseline e2v CMOS APSs
not designed for x-ray performance, the EV76C454 and the Ocean Colour
Imager (OCI) test array. The EV76C454 is an industrial 5T APS designed
for machine vision, available back and front illuminated. The OCI test
arrays have varying pixel design across the chips, but are 4T, back
illuminated and have thin low-resistivity and thick high-resistivity
variants. The OCI test arrays’ pixel variants allow understanding
of how pixel design can affect x-ray performance.
---------------------------------------------------------
Title: The Chromospheric Lyman-Alpha SpectroPolarimeter: CLASP
Authors: Kobayashi, K.; Kano, R.; Trujillo-Bueno, J.; Asensio Ramos,
A.; Bando, T.; Belluzzi, L.; Carlsson, M.; De Pontieu, R. C. B.; Hara,
H.; Ichimoto, K.; Ishikawa, R.; Katsukawa, Y.; Kubo, M.; Manso Sainz,
R.; Narukage, N.; Sakao, T.; Stepan, J.; Suematsu, Y.; Tsuneta, S.;
Watanabe, H.; Winebarger, A.
2012ASPC..456..233K Altcode:
The magnetic field plays a crucial role in the chromosphere and the
transition region, and our poor empirical knowledge of the magnetic
field in the upper chromosphere and transition region is a major
impediment to advancing the understanding of the solar atmosphere. The
Hanle effect promises to be a valuable alternative to Zeeman effect
as a method of measuring the magnetic field in the chromosphere and
transition region; it is sensitive to weaker magnetic fields, and
also sensitive to tangled, unresolved field structures. <P />CLASP
is a sounding rocket experiment that aims to observe the Hanle effect
polarization of the Lyman α (1215.67Å) line in the solar chromosphere
and transition region, and prove the usefulness of this technique in
placing constraints on the magnetic field strength and orientation
in the low plasma-β region of the solar atmosphere. The Ly-α line
has been chosen because it is a chromospheric/transition-region line,
and because the Hanle effect polarization of this line is predicted to
be sensitive to 10-250 Gauss, encompassing the range of interest. The
CLASP instrument is designed to measure linear polarization in the
Ly-α line with a polarization sensitivity of 0.1%. The instrument is
currently funded for development. The optical design of the instrument
has been finalized, and an extensive series of component-level tests
are underway to validate the design.
---------------------------------------------------------
Title: The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP)j
Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Bando, T.;
Belluzzi, L.; Casini, R.; Carlsson, M.; Cirtain, J. W.; De Pontieu,
B.; Hara, H.; Ichimoto, K.; Ishikawa, R.; Kano, R.; Katsukawa, Y.;
Kim, T.; Kubo, M.; Manso Sainz, R.; Narukage, N.; Asensio Ramos,
A.; Robinson, B.; Sakao, T.; Shimizu, T.; Stepan, J.; Suematsu, Y.;
Watanabe, H.; West, E.; Winebarger, A. R.
2011AGUFM.P14C..05K Altcode:
We present an overview of the Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP) program. CLASP is a proposed sounding rocket
experiment currently under development as collaboration between Japan,
USA and Spain. The aim is to achieve the first measurement of magnetic
field in the upper chromosphere and transition region of the Sun
through the detection and measurement of Hanle effect polarization
of the Lyman alpha line. The Hanle effect (i.e. the magnetic field
induced modification of the linear polarization due to scattering
processes in spectral lines) is believed to be a powerful tool for
measuring the magnetic field in the upper chromosphere, as it is more
sensitive to weaker magnetic fields than the Zeeman effect, and also
sensitive to magnetic fields tangled at spatial scales too small to be
resolved. The Lyman-alpha (121.567 nm) line has been chosen because
it is a chromospheric/transition-region line, and because the Hanle
effect polarization of the Lyman-alpha line is predicted to be sensitive
to 10-250 Gauss, encompassing the range of interest. Hanle effect is
predicted to be observable as linear polarization or depolarization,
depending on the geometry, with a fractional polarization amplitude
varying between 0.1% and 1% depending on the strength and orientation of
the magnetic field. This quantification of the chromospheric magnetic
field requires a highly sensitive polarization measurement. The
CLASP instrument consists of a large aperture (287 mm) Cassegrain
telescope mated to a polarizing beamsplitter and a matched pair
of grating spectrographs. The polarizing beamsplitter consists
of a continuously rotating waveplate and a linear beamsplitter,
allowing simultaneous measurement of orthogonal polarizations and
in-flight self-calibration. Development of the instrument is underway,
and prototypes of all optical components have been tested using a
synchrotron beamline. The experiment is proposed for flight in 2014.
---------------------------------------------------------
Title: Photon-counting soft x-ray telescope for the Solar-C mission
Authors: Sakao, Taro; Narukage, Noriyuki; Shimojo, Masumi; Tsuneta,
Saku; Suematsu, Yoshinori; Miyazaki, Satoshi; Imada, Shinsuke;
Nishizuka, Naoto; Watanabe, Kyoko; Dotani, Tadayasu; DeLuca, Edward
E.; Ishikawa, Shin-nosuke
2011SPIE.8148E..0CS Altcode: 2011SPIE.8148E..11S
We report instrument outline as well as science of the photon-counting
soft X-ray telescope that we have been studying as a possible scientific
payload for the Japanese Solar-C mission whose projected launch around
2019. Soft X-rays (~1- 10 keV) from the solar corona include rich
information on (1) possible mechanism(s) for heating the bright core of
active regions seen in soft X-rays (namely, the hottest portion in the
non-flaring corona), (2) dynamics and magnetohydrodynamic structures
associated with magnetic reconnection processes ongoing in flares,
and even (3) generation of supra-thermal distributions of coronal
plasmas associated with flares. Nevertheless, imaging-spectroscopic
investigation of the soft X-ray corona has so far remained unexplored
due to difficulty in the instrumentation for achieving this aim. With
the advent of recent remarkable progress in CMOS-APS detector
technology, the photon-counting X-ray telescope will be capable
of, in addition to conventional photon-integration type exposures,
performing imaging-spectroscopic investigation on active regions and
flares, thus providing, for example, detailed temperature information
(beyond the sofar- utilized filter-ratio temperature) at each spatial
point of the observing target. The photon-counting X-ray telescope will
emply a Wolter type I optics with a piece of a segmented mirror whose
focal length 4 meters, combined with a focal-plane CMOS-APS detector
(0.4-0.5"/pixel) whose frame read-out rate required to be as high as
1000 fps.
---------------------------------------------------------
Title: Overview of Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP)
Authors: Narukage, Noriyuki; Tsuneta, Saku; Bando, Takamasa; Kano,
Ryouhei; Kubo, Masahito; Ishikawa, Ryoko; Hara, Hirohisa; Suematsu,
Yoshinori; Katsukawa, Yukio; Watanabe, Hiroko; Ichimoto, Kiyoshi;
Sakao, Taro; Shimizu, Toshifumi; Kobayashi, Ken; Robinson, Brian; Kim,
Tony; Winebarger, Amy; West, Edward; Cirtain, Jonathan; De Pontieu,
Bart; Casini, Roberto; Trujillo Bueno, Javier; Stepan, Jiri; Manso
Sainz, Rafael; Belluzzi, Luca; Asensio Ramos, Andres; Carlsson, Mats
2011SPIE.8148E..0HN Altcode: 2011SPIE.8148E..16N
The solar chromosphere is an important boundary, through which all of
the plasma, magnetic fields and energy in the corona and solar wind
are supplied. Since the Zeeman splitting is typically smaller than
the Doppler line broadening in the chromosphere and transition region,
it is not effective to explore weak magnetic fields. However, this is
not the case for the Hanle effect, when we have an instrument with
high polarization sensitivity (~ 0.1%). "Chromospheric Lyman- Alpha
SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect
linear polarization produced by the Hanle effect in Lyman-alpha line
(121.567 nm) and to make the first direct measurement of magnetic
fields in the upper chromosphere and lower transition region. To
achieve the high sensitivity of ~ 0.1% within a rocket flight (5
minutes) in Lyman-alpha line, which is easily absorbed by materials,
we design the optical system mainly with reflections. The CLASP
consists of a classical Cassegrain telescope, a polarimeter and a
spectrometer. The polarimeter consists of a rotating 1/2-wave plate
and two reflecting polarization analyzers. One of the analyzer also
works as a polarization beam splitter to give us two orthogonal linear
polarizations simultaneously. The CLASP is planned to be launched in
2014 summer.
---------------------------------------------------------
Title: The SOLAR-C mission: current status
Authors: Shimizu, Toshifumi; Tsuneta, Saku; Hara, Hirohisa; Ichimoto,
Kiyoshi; Kusano, Kanya; Sakao, Taro; Sekii, Takashi; Suematsu,
Yoshinori; Watanabe, Tetsuya
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: Coronal-Temperature-Diagnostic Capability of the Hinode/
X-Ray Telescope Based on Self-Consistent Calibration
Authors: Narukage, N.; Sakao, T.; Kano, R.; Hara, H.; Shimojo, M.;
Bando, T.; Urayama, F.; DeLuca, E.; Golub, L.; Weber, M.; Grigis,
P.; Cirtain, J.; Tsuneta, S.
2011SoPh..269..169N Altcode: 2010arXiv1011.2867N; 2011SoPh..tmp....1N
The X-Ray Telescope (XRT) onboard the Hinode satellite is an X-ray
imager that observes the solar corona with unprecedentedly high angular
resolution (consistent with its 1″ pixel size). XRT has nine X-ray
analysis filters with different temperature responses. One of the most
significant scientific features of this telescope is its capability
of diagnosing coronal temperatures from less than 1 MK to more than
10 MK, which has never been accomplished before. To make full use
of this capability, accurate calibration of the coronal temperature
response of XRT is indispensable and is presented in this article. The
effect of on-orbit contamination is also taken into account in the
calibration. On the basis of our calibration results, we review the
coronal-temperature-diagnostic capability of XRT.
---------------------------------------------------------
Title: The Chromospheric Lyman Alpha SpectroPolarimeter (CLASP)
Authors: Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Cirtain,
J. W.; Bando, T.; Kano, R.; Hara, H.; Fujimura, D.; Ueda, K.; Ishikawa,
R.; Watanabe, H.; Ichimoto, K.; Sakao, T.; de Pontieu, B.; Carlsson,
M.; Casini, R.
2010AGUFMSH11B1632K Altcode:
Magnetic fields in the solar chromosphere play a key role in the
energy transfer and dynamics of the solar atmosphere. Yet a direct
observation of the chromospheric magnetic field remains one of the
greatest challenges in solar physics. While some advances have been
made for observing the Zeeman effect in strong chromospheric lines,
the effect is small and difficult to detect outside sunspots. The
Hanle effect offers a promising alternative; it is sensitive to weaker
magnetic fields (e.g., 5-500 G for Ly-Alpha), and while its magnitude
saturates at stronger magnetic fields, the linear polarization signals
remain sensitive to the magnetic field orientation. The Hanle effect
is not only limited to off-limb observations. Because the chromosphere
is illuminated by an anisotropic radiation field, the Ly-Alpha line is
predicted to show linear polarization for on-disk, near-limb regions,
and magnetic field is predicted to cause a measurable depolarization. At
disk center, the Ly-Alpha radiation is predicted to be negligible
in the absence of magnetic field, and linearly polarized to an order
of 0.3% in the presence of an inclined magnetic field. The proposed
CLASP sounding rocket instrument is designed to detect 0.3% linear
polarization of the Ly-Alpha line at 1.5 arcsecond spatial resolution
(0.7’’ pixel size) and 10 pm spectral resolution. The instrument
consists of a 30 cm aperture Cassegrain telescope and a dual-beam
spectropolarimeter. The telescope employs a “cold mirror’’ design
that uses multilayer coatings to reflect only the target wavelength
range into the spectropolarimeter. The polarization analyzer consists of
a rotating waveplate and a polarizing beamsplitter that comprises MgF2
plates placed at Brewster’s Angle. Each output beam of the polarizing
beamsplitter, representing two orthogonal linear polarizations, is
dispersed and focused using a separate spherical varied-line-space
grating, and imaged with a separate 512x512 CCD camera. Prototypes
of key optical components have been fabricated and tested. Instrument
design is being finalized, and the experiment will be proposed for a
2014 flight aboard a NASA sounding rocket.
---------------------------------------------------------
Title: A New View of the Sun with Hinode Mission
Authors: Sakao, Taro; Tsuneta, Saku; Shimojo, Masumi; Narukage,
Noriyuki; Kano, Ryouhei; Obara, Takahiro; Watari, Shinichi; Hinode Team
2009TrSpT...7Tr215S Altcode:
We present highlights of observations of the Sun with Japanese Hinode
mission launched by JAXA in September 2006. The scientific objective
of Hinode mission is to observe, in an unprecedented detail, a wide
variety of plasma activities in the Sun's corona together with magnetic
activities on the photosphere and in the chromosphere, utilizing a suite
of three state-of-the-art telescopes; Solar Optical Telescope (SOT),
X-Ray Telescope (XRT), and EUV Imaging Spectrometer (EIS). Since the
beginning of the observations late in October 2006, Hinode has been
providing ample information on activities of magnetized plasmas in the
solar atmosphere some of which are totally new to us. In this article,
we present an overview of the Hinode mission as well as some highlights
of the observations.
---------------------------------------------------------
Title: Plasma Outflows in the Corona as Observed With Hinode XRT
Authors: Sakao, T.; Kano, R.; Narukage, N.; Deluca, E. E.; Grigis, P.
2008AGUFMSH41B1624S Altcode:
We present imaging observations of plasma outflows in the solar corona
made with X-Ray Telescope (XRT) aboard Hinode satellite. The XRT employs
a back-illuminated CCD as the focal-plane imaging device which enables
us, together with an optimized set of analysis filters, to investigate,
for the first time, dynamic behavior of relatively cool (1-2 MK, say)
plasmas in the corona. The XRT revealed a clear pattern of continuous
outflow of plasmas from the edge of an active region NOAA AR 10942 right
adjacent to a coronal hole. Plasmas of temperature ~1 MK flowed out
with a sub-sonic velocity of typically ~140 km/s along magnetic field
lines that are most likely open towards the interplanetary space. These
outflowing plasmas may constitute a fraction of the (slow) solar
wind. In addition to this discovery, the XRT has so far identified
rich patterns of continuous outflows including those from coronal
hole boundaries and along fan-like field lines rooted inside coronal
holes. XRT observations of such plasma outflows in the corona are
presented and their possible implications to the solar wind discussed.
---------------------------------------------------------
Title: The Thermal Structures of Solar Corona Revealed with Hinode/XRT
Authors: Narukage, N.; Sakao, T.; Kano, R.
2008AGUFMSH52A..03N Altcode:
The solar corona has a wide temperature range from less than 1MK
(1,000,000K) to more than 10MK. The X-ray telescope (XRT) on board
the Hinode satellite has 9 X-ray analysis filters with different
temperature responses making it possible to detect both cool and
hot coronal plasmas. Using the data observed with this telescope,
we successfully derived the coronal temperature and emission measure
around the whole sun, i.e., for not only active regions but also quiet
regions and coronal holes. We also found that coronal structures are
nicely classified using the temperature and emission measure. And the
coronal structures were found to depend on the length of structure
and the heating flux. Furthermore, we calculated the coronal potential
magnetic field using the photospheric magnetic field. To compare the
heating flux estimated with coronal temperature and the calculated
coronal magnetic field might be the great clue to solving the big
coronal heating question: why does the hot 1MK corona stably exist
above the cool 6,000K solar surface? In this talk, we will show some
results of our latest studies about the coronal thermal structures.
---------------------------------------------------------
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: Source Region of the Solar Wind Identified with Hinode X-Ray
Telescope
Authors: Sakao, Taro
2008AstHe.101..491S Altcode:
A possible source region for the slow solar wind was identified with
the X-Ray Telescope aboard Hinode satellite. Continuous outflow of
hot (~ 1 MK) plasmas was found to emanate from the edge of a solar
active region adjacent to a coronal hole. Magnetic field lines along
which outflowing plasmas propagate are most likely opened toward the
interplanetary space. Hence the observed outflow would constitute a
part of the solar wind.
---------------------------------------------------------
Title: Hinode/XRT Diagnostics of Loop Thermal Structure
Authors: Reale, F.; Parenti, S.; Reeves, K. K.; Weber, M.; Bobra,
M. G.; Barbera, M.; Kano, R.; Narukage, N.; Shimojo, M.; Sakao, T.;
Peres, G.; Golub, L.
2008ASPC..397...50R Altcode:
We investigate possible diagnostics of the thermal structure of coronal
loops from Hinode/XRT observations made with several filters. We
consider the observation of an active region with five filters. We
study various possible combinations of filter data to optimize for
sensitivity to thermal structure and for signal enhancement.
---------------------------------------------------------
Title: Japanese Next Solar Mission: SOLAR-C
Authors: Sakao, T.; Solar-C, W. G.
2008ESPM...12..6.5S Altcode:
We present introductory overview on the next Japanese solar mission,
SOLAR-C, which has been envisaged following the success of Hinode
(SOLAR-B) mission. Two plans, Plan A and Plan B, are under extensive
study from science objectives as well as engineering point of view. Plan
A aims to perform out-of-ecliptic observations for investigating,
with helioseismic approach, internal structure and dynamo mechanisms
of the Sun. It also explores polar regions where fast solar wind is
believed to be originated. The baseline orbit for Plan A is a circular
orbit of 1 AU distance from the Sun, with its inclination at around,
or greater than, 40 degrees. Plan B pursues small-scale plasma processes
and structures in the solar atmosphere which attract growing interest,
following Hinode discoveries, for understanding fully dynamism and
magnetic nature of the atmosphere. With Plan B, high-angular-resolution
investigation of the entire solar atmosphere (from the photosphere
to the corona, including their interface layers, i.e., chromosphere
and transition region) is to be performed with enhanced spectroscopic
and spectro-polarimetric capability as compared with Hinode, together
with enhanced sensitivity towards ultra-violet wavelengths. There
has been wide and evolving support for the SOLAR-C mission not only
from solar physics community but also from related research areas in
Japan. We request SOLAR-C to be launched in mid. 2010s. <P />Following
the highly-successful achievements of international collaboration for
Yohkoh and Hinode, we strongly hope the SOLAR-C mission be realized
under extensive collaboration with European and U.S. partners. Japanese
SOLAR-C working group was officially approved by ISAS/JAXA in December
2007 for mission studies and promoting international collaboration. It
is expected that a single mission plan is to be proposed after one
year of investigation on Plan A and Plan B.
---------------------------------------------------------
Title: Vertical Temperature Structures of the Solar Corona Derived
with the Hinode X-Ray Telescope
Authors: Kano, Ryouhei; Sakao, Taro; Narukage, Noriyuki; Tsuneta,
Saku; Kotoku, Jun'ichi; Bando, Takamasa; Deluca, Edward; Lundquist,
Loraine; Golub, Leon; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo,
Masumi; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro
2008PASJ...60..827K Altcode:
We obtained temperature structures in faint coronal features
above and near the solar limb with the X-Ray Telescope aboard the
Hinode satellite by accurately correcting the scattered X-rays
from surrounding bright regions with occulted images during
the solar eclipses. Our analysis yields a polar coronal hole
temperature of about 1.0MK and an emission measure in the range of
10<SUP>25.5</SUP>-10<SUP>26.0</SUP>cm<SUP>-5</SUP>. In addition,
our methods allow us to measure the temperature and emission
measure of two distinct quiet-Sun structures: radial (plume-like)
structures near the boundary of the coronal-hole and diffuse quiet
Sun regions at mid-latitudes. The radial structures appear to have
increasing temperature with height during the first 100Mm, and
constant temperatures above 100Mm. For the diffuse quiet-Sun region
the temperatures are the highest just above the limb, and appear
to decrease with height. These differences may be due to different
magnetic configurations.
---------------------------------------------------------
Title: The Hinode X-Ray Telescope (XRT): Camera Design, Performance
and Operations
Authors: Kano, R.; Sakao, T.; Hara, H.; Tsuneta, S.; Matsuzaki, K.;
Kumagai, K.; Shimojo, M.; Minesugi, K.; Shibasaki, K.; DeLuca, E. E.;
Golub, L.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.;
Dennis, E.; Kent, T.; Weber, M.
2008SoPh..249..263K Altcode:
The X-ray Telescope (XRT) aboard the Hinode satellite is a grazing
incidence X-ray imager equipped with a 2048×2048 CCD. The XRT has
1 arcsec pixels with a wide field of view of 34×34 arcmin. It is
sensitive to plasmas with a wide temperature range from < 1 to 30
MK, allowing us to obtain TRACE-like low-temperature images as well as
Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data
Processor (MDP) controls the XRT through sequence tables with versatile
autonomous functions such as exposure control, region-of-interest
tracking, flare detection, and flare location identification. Data are
compressed either with DPCM or JPEG, depending on the purpose. This
results in higher cadence and/or wider field of view for a given
telemetry bandwidth. With a focus adjust mechanism, a higher resolution
of Gaussian focus may be available on-axis. This paper follows the
first instrument paper for the XRT (Golub et al., Solar Phys.243, 63,
2007) and discusses the design and measured performance of the X-ray
CCD camera for the XRT and its control system with the MDP.
---------------------------------------------------------
Title: The Analysis of Hinode/XRT Observations
Authors: Deluca, E. E.; Weber, M.; Savcheva, A.; Saar, S.; Testa,
P.; Cirtain, J. W.; Sakao, T.; Noriyuki, N.; Kano, R.; Shimizu, T.
2008AGUSMSP51B..02D Altcode:
This poster will present the current state of Hinode/XRT analysis
software. We will give an overview of the XRT Analysis Guide. We will
include a detailed discussion of the following topics: <P />Co-alignment
with SOT and EIS Spot removal for dynamics studies Filter calibration
for thermal studies Dark calibrations <P />Sample data sets will be
discussed and links to the data products will be provided.
---------------------------------------------------------
Title: Outflows at the Edges of Active Regions: Contribution to
Solar Wind Formation?
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
2008ApJ...676L.147H Altcode:
The formation of the slow solar wind has been debated for many years. In
this Letter we show evidence of persistent outflow at the edges of
an active region as measured by the EUV Imaging Spectrometer on board
Hinode. The Doppler velocity ranged between 20 and 50 km s<SUP>-1</SUP>
and was consistent with a steady flow seen in the X-Ray Telescope. The
latter showed steady, pulsing outflowing material and some transverse
motions of the loops. We analyze the magnetic field around the active
region and produce a coronal magnetic field model. We determine from
the latter that the outflow speeds adjusted for line-of-sight effects
can reach over 100 km s<SUP>-1</SUP>. We can interpret this outflow as
expansion of loops that lie over the active region, which may either
reconnect with neighboring large-scale loops or are likely to open to
the interplanetary space. This material constitutes at least part of
the slow solar wind.
---------------------------------------------------------
Title: Erratum: "Outflows at the Edges of Active Regions: Contribution
to Solar Wind Formation?" (ApJ, 676, L147 [2008])
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
2008ApJ...677L.159H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Activities in the X-Ray Corona as seen by Hinode X-Ray
Telescope
Authors: Sakao, Taro
2008cosp...37.2712S Altcode: 2008cosp.meet.2712S
We present observations on the solar corona with the X-Ray Telescope
(XRT) aboard Hinode. XRT is a grazing-incidence imager with a Walter
Type-I-like mirror of 34 cm diameter, with a back-illuminated CCD device
located at its focus position. In addition to its imaging capability for
the X-ray corona with the highest angular resolution (consistent with 1
arcsec CCD pixel size) as a solar X-ray telescope, enhanced sensitivity
of the CCD towards longer X-ray wavelengths (particularly longer than
50 angstroms) enables XRT to image, and perform temperature diagnostics
on, coronal plasmas in a wide temperature range (1-10 MK). This adds a
notable advantage to XRT that it can observe most, if not all, active
phenomena in the corona throughout their entire thermal evolution. XRT
has so far revealed various new aspects of coronal activities. These
include (1) plasma flows in the corona, (2) frequent X-ray jets in the
polar regions, (3) eruptive events even with small or moderate X-ray
activities, (4) fine structure and evolution of flaring loops, (5)
detailed observations on transient brightenings (microflares) in quiet
as well as active regions. Some highlights of Hinode XRT observations,
centered on those on plasma flows, will be presented and discussed.
---------------------------------------------------------
Title: Molecular Contamination Assessments on
<i>Hinode</i> X-Ray Telescope
Authors: Urayama, Fumitaka; Bando, Takamasa; Kano, Ryouhei; Hara,
Hirohisa; Narukage, Noriyuki; Sakao, Taro
2008JSASS..56..536U Altcode:
The <i>Hinode</i> (Solar-B) was launched by M-V rocket on 22
September 2006 UT. The telemetry data of the <i>Hinode</i>
X-ray Telescope (XRT) showed that the X-ray count rate detected with
the XRT had decreased rapidly since the operational heaters on the
XRT telescope tube were turned on. This is attributed to the fact that
molecular contaminants accumulated onto the CCD with the temperature
of -60ºC resulting in the degradation of the XRT sensitivity. We baked
the CCD at the temperature of 35ºC in order to remove the contaminants
from the CCD surface. However many contaminant spots appeared on the
surface. We found that major contaminant source existed in the telescope
tube, and identified the contaminants as diethylhexyl phthalate (DEHP)
or DEHP-like organics. The mechanisms to yield the contaminant spots
were discussed.
---------------------------------------------------------
Title: Relation between coronal temperature and magnetic field
Authors: Narukage, Noriyuki; Kano, Ryouhei; Shiota, Daiko; Sakao, Taro
2008cosp...37.2184N Altcode: 2008cosp.meet.2184N
The solar corona has a wide temperature range from less than 1MK to
more than 10MK. The X-ray telescope (XRT) on board Hinode satellite
has 9 X-ray analysis filters to observe the almost of whole coronal
plasma. Using the data observed with this telescope, we successfully
derived the coronal temperature around the whole sun. We found that
coronal structures are nicely classified using the temperature and
emission measure. The coronal structures were found to depend on the
length of structure and the heating flux. Furthermore, we calculated
the coronal potential magnetic field in high spatial resolution using
the photospheric magnetic field observed with SOHO/MDI. To compare the
heating flux estimated with coronal temperature and the calculated
coronal magnetic field might be the great clue to solving the big
coronal heating question.
---------------------------------------------------------
Title: Dynamics of active regions observed with Hinode XRT
Authors: Sakao, Taro
2008cosp...37.2711S Altcode: 2008cosp.meet.2711S
We present dynamics of active regions observed with the X-Ray Telescope
(XRT) aboard Hinode. XRT is a grazing-incidence imager with a Walter
Type-I-like mirror of 34 cm diameter with a back-illuminated CCD
device. The XRT can image the X-ray corona of the Sun with angular
resolution consistent with 1 arcsec CCD pixel size. In addition to
this unprecedentedly-high angular resolution ever achieved as a solar
X-ray telescope, enhanced sensitivity of the CCD towards longer X-ray
wavelengths (particularly beyond 50 Angstroms) enables XRT to image,
and perform temperature diagnostics on, a wide range of coronal plasmas
from those as low as 1 MK to high-temperature plasmas even exceeding 10
MK. This adds a notable advantage to the XRT such that it can observe
most, if not all, active phenomena taking place in and around active
regions. Since the beginning of observations with XRT on 23 October
2006, the XRT has so far made various interesting observations regarding
active regions. These include (1) continuous outflow of plasmas from
the edge of a solar active region that is likely to be a source of
(slow) solar wind, (2) clear signature of eruptions for activities even
down to GOES B-level, (3) detailed structure and evolution of flaring
loops, (4) formation of large-scale hot loops around active regions,
and so on. Dynamic phenomena in and around active regions observed
with Hinode XRT will be presented and their possible implications to
the Sun-Earth connection investigation will be discussed.
---------------------------------------------------------
Title: Cross calibration of soft X-ray telescopes between Hinode/XRT
and GOES13/SXI
Authors: Narukage, N.; Sakao, T.; Kano, R.; Shimojo, M.; Cirtain,
J.; Deluca, E.; Nitta, N.; Lemen, J.
2007AGUFMSH53A1050N Altcode:
The X-Ray Telescope (XRT) aboard Hinode satellite is a grazing
incidence telescope to observe all the coronal features with a wide
temperature range from less than 1MK to more than 10MK. And the XRT
has 9 X-ray analysis filters which are optimized to observed the
almost whole coronal plasma and to derived the coronal temperature
distribution. Meanwhile, the GOES13 satellite carries a Solar X-ray
Imager (SXI) to monitor the solar X-rays. The SXI is also a grazing
incidence telescope and has 7 X-ray filters. The XRT and SXI are
similar telescopes to observe the dynamic solar corona. On 24 Nov 2006,
the XRT and SXI-team performed the simultaneous observation for the
cross calibration between XRT and SXI. In this study, we analyzed
this data set and checked the actual characteristics of each X-ray
analysis filter.
---------------------------------------------------------
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
2007AGUFMSH52C..06S Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
---------------------------------------------------------
Title: Slipping Magnetic Reconnection in Coronal Loops
Authors: Aulanier, Guillaume; Golub, Leon; DeLuca, Edward E.; Cirtain,
Jonathan W.; Kano, Ryouhei; Lundquist, Loraine L.; Narukage, Noriyuki;
Sakao, Taro; Weber, Mark A.
2007Sci...318.1588A Altcode:
Magnetic reconnection of solar coronal loops is the main process that
causes solar flares and possibly coronal heating. In the standard
model, magnetic field lines break and reconnect instantaneously at
places where the field mapping is discontinuous. However, another mode
may operate where the magnetic field mapping is continuous but shows
steep gradients: The field lines may slip across each other. Soft
x-ray observations of fast bidirectional motions of coronal loops,
observed by the Hinode spacecraft, support the existence of this
slipping magnetic reconnection regime in the Sun’s corona. This
basic process should be considered when interpreting reconnection,
both on the Sun and in laboratory-based plasma experiments.
---------------------------------------------------------
Title: Evidence for Alfvén Waves in Solar X-ray Jets
Authors: Cirtain, J. W.; Golub, L.; Lundquist, L.; van Ballegooijen,
A.; Savcheva, A.; Shimojo, M.; DeLuca, E.; Tsuneta, S.; Sakao, T.;
Reeves, K.; Weber, M.; Kano, R.; Narukage, N.; Shibasaki, K.
2007Sci...318.1580C Altcode:
Coronal magnetic fields are dynamic, and field lines may misalign,
reassemble, and release energy by means of magnetic reconnection. Giant
releases may generate solar flares and coronal mass ejections and,
on a smaller scale, produce x-ray jets. Hinode observations of polar
coronal holes reveal that x-ray jets have two distinct velocities:
one near the Alfvén speed (~800 kilometers per second) and another
near the sound speed (200 kilometers per second). Many more jets were
seen than have been reported previously; we detected an average of
10 events per hour up to these speeds, whereas previous observations
documented only a handful per day with lower average speeds of 200
kilometers per second. The x-ray jets are about 2 × 10<SUP>3</SUP> to
2 × 10<SUP>4</SUP> kilometers wide and 1 × 10<SUP>5</SUP> kilometers
long and last from 100 to 2500 seconds. The large number of events,
coupled with the high velocities of the apparent outflows, indicates
that the jets may contribute to the high-speed solar wind.
---------------------------------------------------------
Title: Continuous Plasma Outflows from the Edge of a Solar Active
Region as a Possible Source of Solar Wind
Authors: Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku,
Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.;
Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito;
Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay
A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto;
Shimizu, Toshifumi; Nakatani, Ichiro
2007Sci...318.1585S Altcode:
The Sun continuously expels a huge amount of ionized material into
interplanetary space as the solar wind. Despite its influence on the
heliospheric environment, the origin of the solar wind has yet to
be well identified. In this paper, we report Hinode X-ray Telescope
observations of a solar active region. At the edge of the active region,
located adjacent to a coronal hole, a pattern of continuous outflow of
soft-x-ray emitting plasmas was identified emanating along apparently
open magnetic field lines and into the upper corona. Estimates of
temperature and density for the outflowing plasmas suggest a mass
loss rate that amounts to ~1/4 of the total mass loss rate of the
solar wind. These outflows may be indicative of one of the solar wind
sources at the Sun.
---------------------------------------------------------
Title: Fine Thermal Structure of a Coronal Active Region
Authors: Reale, Fabio; Parenti, Susanna; Reeves, Kathy K.; Weber,
Mark; Bobra, Monica G.; Barbera, Marco; Kano, Ryouhei; Narukage,
Noriyuki; Shimojo, Masumi; Sakao, Taro; Peres, Giovanni; Golub, Leon
2007Sci...318.1582R Altcode:
The determination of the fine thermal structure of the solar corona is
fundamental to constraining the coronal heating mechanisms. The Hinode
X-ray Telescope collected images of the solar corona in different
passbands, thus providing temperature diagnostics through energy
ratios. By combining different filters to optimize the signal-to-noise
ratio, we observed a coronal active region in five filters, revealing
a highly thermally structured corona: very fine structures in the
core of the region and on a larger scale further away. We observed
continuous thermal distribution along the coronal loops, as well as
entangled structures, and variations of thermal structuring along the
line of sight.
---------------------------------------------------------
Title: Magnetic Feature and Morphological Study of X-Ray Bright
Points with Hinode
Authors: Kotoku, Jun'ichi; Kano, Ryouhei; Tsuneta, Saku; Katsukawa,
Yukio; Shimizu, Toshifumi; Sakao, Taro; Shibazaki, Kiyoto; Deluca,
Edward E.; Korreck, Kelly E.; Golub, Leon; Bobra, Monica
2007PASJ...59S.735K Altcode:
We observed X-ray bright points (XBPs) in a quiet region of the Sun
with the X-Ray Telescope (XRT) aboard the Hinode satellite on 2006
December 19. XRT's high-resolution X-ray images revealed many XBPs with
complicated structure and evolving dramatically with time. Almost all
of the dynamic eruptions in the quiet region were composed of XBPs,
and they had either loop or multiloop shapes, as is observed in larger
flares. Brightening XBPs had strong magnetic fields with opposite
polarities near their footpoints. While we have found a possible
example of associated magnetic cancellation, other XBPs brighten and
fade without any associated movement of the photospheric magnetic field.
---------------------------------------------------------
Title: A Study of Polar Jet Parameters Based on Hinode XRT
Observations
Authors: Savcheva, Antonia; Cirtain, Jonathan; Deluca, Edward E.;
Lundquist, Loraine L.; Golub, Leon; Weber, Mark; Shimojo, Masumi;
Shibasaki, Kiyoto; Sakao, Taro; Narukage, Noriyuki; Tsuneta, Saku;
Kano, Ryouhei
2007PASJ...59S.771S Altcode:
Hinode/SOHO campaign 7197 is the most extensive study of polar jet
formation and evolution from within both the north and south polar
coronal holes so far. For the first time, this study showed that the
appearance of X-ray jets in the solar coronal holes occurs at very high
frequency - about 60 jets d<SUP>-1</SUP> on average. Using observations
collected by the X-Ray Telescope on Hinode, a number of physical
parameters from a large sample of jets were statistically studied. We
measured the apparent outward velocity, the height, the width and
the lifetime of the jets. In our sample, all of these parameters show
peaked distributions with maxima at 160kms<SUP>-1</SUP> for the outward
velocity, 5 × 10<SUP>4</SUP> km for the height, 8 × 10<SUP>3</SUP>
km for the width, and about 10min for the lifetime of the jets. We
also present the first statistical study of jet transverse motions,
which obtained transverse velocities of 0-35kms<SUP>-1</SUP>. These
values were obtained on the basis of a larger (in terms of frequency)
and better sampled set of events than what was previously statistically
studied (Shimojo et al. 1996, PASJ, 48, 123). The results were made
possible by the unique characteristics of XRT. We describe the methods
used to determine the characteristics and set some future goals. We
also show that despite some possible selection effects, jets preferably
occur inside the polar coronal holes.
---------------------------------------------------------
Title: Hinode Calibration for Precise Image Co-Alignment between
SOT and XRT (2006 November-2007 April)
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Matsuzaki, Keiichi;
Ichimoto, Kiyoshi; Kano, Ryohei; Deluca, Edward E.; Lundquist,
Loraine L.; Weber, Mark; Tarbell, Theodore D.; Shine, Richard A.;
Sôma, Mitsuru; Tsuneta, Saku; Sakao, Taro; Minesugi, Kenji
2007PASJ...59S.845S Altcode: 2007arXiv0709.4098S
To understand the physical mechanisms for activity and heating in
the solar atmosphere, the magnetic coupling from the photosphere
to the corona is an important piece of information from the Hinode
observations, and therefore precise positional alignment is required
among the data acquired by different telescopes. The Hinode spacecraft
and its onboard telescopes were developed to allow us to investigate
magnetic coupling with co-alignment accuracy better than 1". Using
the Mercury transit observed on 2006 November 8 and co-alignment
measurements regularly performed on a weekly basis, we have determined
the information necessary for precise image co-alignment, and have
confirmed that co-alignment better than 1" can be realized between
Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our
baseline co-alignment method. This paper presents results from the
calibration for precise co-alignment of CCD images from SOT and XRT.
---------------------------------------------------------
Title: Hinode Observations of the Onset Stage of a Solar Filament
Eruption
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Berger, Thomas
E.; Bobra, Monica; Davis, John M.; Jibben, Patricia; Kano, Ryohei;
Lundquist, Loraine L.; Myers, D.; Narukage, Noriyuki; Sakao, Taro;
Shibasaki, Kiyoto; Shine, Richard A.; Tarbell, Theodore D.; Weber, Mark
2007PASJ...59S.823S Altcode:
We used Hinode X-Ray Telescope (XRT) and Solar Optical Telescope (SOT)
filtergraph (FG) Stokes-V magnetogram observations, to study the
early onset of a solar eruption that includes an erupting filament
that we observe in TRACE EUV images. The filament undergoes a slow
rise for at least 20min prior to its fast eruption and strong soft
X-ray (SXR) flaring; such slow rises have been previously reported,
and the new Hinode data elucidate the physical processes occurring
during this period. XRT images show that during the slow-rise phase,
an SXR sigmoid forms from apparent reconnection low in the sheared core
field traced by the filament, and there is a low-level intensity peak
in both EUV and SXRs during the slow rise. MDI and SOT FG Stokes-V
magnetograms show that the pre-eruption filament is along a neutral
line between opposing-polarity enhanced network cells, and the SOT
magnetograms show that these opposing fields are flowing together
and canceling for at least six hours prior to eruption. From the MDI
data we measured the canceling network fields to be ∼ 40G, and we
estimated that ∼ 10<SUP>19</SUP> Mx of flux canceled during the
five hours prior to eruption; this is only ∼ 5% of the total flux
spanned by the eruption and flare, but apparently its tether-cutting
cancellation was enough to destabilize the sigmoid field holding the
filament and resulted in that field's eruption.
---------------------------------------------------------
Title: Fine Structures of Solar X-Ray Jets Observed with the X-Ray
Telescope aboard Hinode
Authors: Shimojo, Masumi; Narukage, Noriyuki; Kano, Ryohei; Sakao,
Taro; Tsuneta, Saku; Shibasaki, Kiyoto; Cirtain, Jonathan W.;
Lundquist, Loraine L.; Reeves, Katherine K.; Savcheva, Antonia
2007PASJ...59S.745S Altcode:
The X-Ray Telescope (XRT) aboard Hinode has revealed the fine structure
of solar X-ray jets. One of the fine structures observed by XRT is an
expanding loop. The loop appeared near the footpoint of the jet when
footpoint brightening was observed. Additionally, we have found that the
X-ray jets began just after the expanding loop “breaks”. Other fine
structures discovered by XRT are thread-like features along the axis
of the jets. XRT has shown that these thread structures compose the
cross-section of jets. The fine structures and their motions strongly
support an X-ray jet model based on magnetic reconnection, and also
suggest that we must consider the three-dimensional configuration of the
magnetic field to understand the jet phenomenon. We also investigated
the reverse jet associated with the X-ray jet in the quiet Sun, and
propose that the reverse jet is produced by heat conduction, or a MHD
wave subsequent to the main jet.
---------------------------------------------------------
Title: Evolution of the Sheared Magnetic Fields of Two X-Class Flares
Observed by Hinode/XRT
Authors: Su, Yingna; Golub, Leon; van Ballegooijen, Adriaan; Deluca,
Edward E.; Reeves, Kathy K.; Sakao, Taro; Kano, Ryouhei; Narukage,
Noriyuki; Shibasaki Kiyoto
2007PASJ...59S.785S Altcode:
We present multi-wavelength observations of the evolution of the sheared
magnetic fields in NOAA Active Region 10930, where two X-class flares
occurred on 2006 December 13 and December 14, respectively. Observations
made with the X-ray Telescope (XRT) and the Solar Optical Telescope
(SOT) aboard Hinode suggest that the gradual formation of the sheared
magnetic fields in this active region is caused by the rotation and
west-to-east motion of an emerging sunspot. In the pre-flare phase
of the two flares, XRT shows several highly sheared X-ray loops in
the core field region, corresponding to a filament seen in the TRACE
EUV observations. XRT observations also show that part of the sheared
core field erupted, and another part of the sheared core field stayed
behind during the flares, which may explain why a large part of the
filament is still seen by TRACE after the flare. About 2-3 hours after
the peak of each flare, the core field becomes visible in XRT again,
and shows a highly sheared inner and less-sheared outer structure. We
also find that the post-flare core field is clearly less sheared than
the pre-flare core field, which is consistent with the idea that the
energy released during the flares is stored in the highly sheared
fields prior to the flare.
---------------------------------------------------------
Title: An On-Orbit Determination of the On-Axis Point Spread Function
of the Hinode X-Ray Telescope
Authors: Weber, Mark; Deluca, Edward E.; Golub, Leon; Cirtain,
Jonathan; Kano, Ryouhei; Sakao, Taro; Shibasaki, Kiyoto; Narukage,
Noriyuki
2007PASJ...59S.853W Altcode:
The Hinode X-ray Telescope provides unprecedented observations of
the solar corona in X-rays, due in part to its fine resolution. The
X-ray point spread function (PSF) was measured before launch at the
NASA X-ray Calibration Facility to have a FWHM of 0.8”. This paper
describes the work to verify the PSF measurements using on-orbit
observations of planetary transits and solar eclipses. Analysis of a
Mercury transit gives a PSF FWHM = 1.0" ± 0.12".
---------------------------------------------------------
Title: The Hinode (Solar-B) Mission: An Overview
Authors: Kosugi, T.; Matsuzaki, K.; Sakao, T.; Shimizu, T.; Sone,
Y.; Tachikawa, S.; Hashimoto, T.; Minesugi, K.; Ohnishi, A.; Yamada,
T.; Tsuneta, S.; Hara, H.; Ichimoto, K.; Suematsu, Y.; Shimojo, M.;
Watanabe, T.; Shimada, S.; Davis, J. M.; Hill, L. D.; Owens, J. K.;
Title, A. M.; Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Golub, L.
2007SoPh..243....3K Altcode:
The Hinode satellite (formerly Solar-B) of the Japan Aerospace
Exploration Agency's Institute of Space and Astronautical Science
(ISAS/JAXA) was successfully launched in September 2006. As the
successor to the Yohkoh mission, it aims to understand how magnetic
energy gets transferred from the photosphere to the upper atmosphere
and results in explosive energy releases. Hinode is an observatory
style mission, with all the instruments being designed and built to
work together to address the science aims. There are three instruments
onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer
(EIS), and the X-Ray Telescope (XRT). This paper provides an overview
of the mission, detailing the satellite, the scientific payload, and
operations. It will conclude with discussions on how the international
science community can participate in the analysis of the mission data.
---------------------------------------------------------
Title: The X-Ray Telescope (XRT) for the Hinode Mission
Authors: Golub, L.; DeLuca, E.; Austin, G.; Bookbinder, J.; Caldwell,
D.; Cheimets, P.; Cirtain, J.; Cosmo, M.; Reid, P.; Sette, A.; Weber,
M.; Sakao, T.; Kano, R.; Shibasaki, K.; Hara, H.; Tsuneta, S.; Kumagai,
K.; Tamura, T.; Shimojo, M.; McCracken, J.; Carpenter, J.; Haight,
H.; Siler, R.; Wright, E.; Tucker, J.; Rutledge, H.; Barbera, M.;
Peres, G.; Varisco, S.
2007SoPh..243...63G Altcode:
The X-ray Telescope (XRT) of the Hinode mission provides an
unprecedented combination of spatial and temporal resolution in solar
coronal studies. The high sensitivity and broad dynamic range of XRT,
coupled with the spacecraft's onboard memory capacity and the planned
downlink capability will permit a broad range of coronal studies over
an extended period of time, for targets ranging from quiet Sun to
X-flares. This paper discusses in detail the design, calibration, and
measured performance of the XRT instrument up to the focal plane. The
CCD camera and data handling are discussed separately in a companion
paper.
---------------------------------------------------------
Title: The Dynamics Of Fine Structures In Solar X-ray Jets
Authors: Shimojo, Masumi; Narukage, N.; Kano, R.; Sakao, T.; Tsuneta,
T.; Cirtain, J. W.; Lundquist, L. L.; Deluca, E. E.; Golub, L.
2007AAS...210.9422S Altcode: 2007BAAS...39Q.221S
The X-ray telescope(XRT) aboard HINODE satellite has the great
spatial/time resolution in X-ray range. And, the observations using
XRT have revealed the fine structures of solar corona. From the
observations, we found the fine thread structures in the X-ray jets
and the structures move dynamically like wave. We also found that some
X-ray jets start just after small loop expansion in the footpoint
brightening. The observation results suggest that the reconnection
process X-ray jets is very similar to that in large flares.
---------------------------------------------------------
Title: Hinode Data Calibration For Precise Image Co-alignment:
XRT vs. SOT
Authors: Shimizu, Toshifumi; DeLuca, E. E.; Lundquist, L.; Sakao,
T.; Kubo, M.; Narukage, N.; Kano, R.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T.; Shine, D.; Hinode Team
2007AAS...210.9417S Altcode: 2007BAAS...39Q.220S
From late October in 2006, Hinode solar optical telescope (SOT) has
started to produce series of 0.2-0.3 arcsec visible-light images,
revealing dynamical behaviors of solar magnetic fields on the
solar surface. Simultaneously, Hinode X-ray telescope (XRT) has been
providing 1 arcsec resolution X-ray images of the solar corona, giving
the location of heating and dynamics occuring in the corona. Precise
image co-alignment of SOT data on XRT data with sub-arcsec accuracy is
required to provide new information regarding connecting the corona to
the photosphere. This presentation will give an introduction of Hinode
between-telescopes' image co-alignment to SPD participants. For active
region observations with sunspots, sunspots can be used as fiducial to
co-align the data from the two telescopes each other. Satellite jitter
in order of 1 arcsec or less is included in the series of XRT data,
whereas image stabilization system (correlation tracker) removes the
satellite jitter from the series of SOT images. Telescope pointings show
orbital variation in order of a few arcsec, which can be well predicted
from Hinode orbit information. Modeling co-alignment is under study
and it is the only precise method for quiet Sun and limb observations.
---------------------------------------------------------
Title: Coronal Temperature Diagnostics With Hinode X-ray Telescope
Authors: Narukage, Noriyuki; Sakao, T.; Kano, R.; Shimojo, M.; Tsuneta,
S.; Kosugi, T.; Deluca, E. E.; Golub, L.; Weber, M.; Cirtain, J.;
Japan-US X-Ray Telescope Team
2007AAS...210.6304N Altcode: 2007BAAS...39..172N
An X-ray telescope (XRT) on board HINODE satellite observes the Sun
in X-rays with high special resolution (1arcsec 730km on solar the
disk). This telescope has 9 X-ray filters with different temperature
responses. Using these filters, the XRT can detect the coronal
plasma with a wide temperature range from less than 1MK to more
than 10MK. Moreover, based on observations with more than 2 filters,
we can estimate the coronal temperature. In this paper, we use the
filter ratio method for coronal temperature diagnostics. Using this
method, we can easily estimate the averaged temperature of the coronal
plasma along the line-of-sight. This method has been used frequently
in the past, but the high quality XRT data give us temperature maps
with unprecedented accuracy and resolution. The XRT usually takes
the full Sun images with 2 kinds of filters 4 times a day. Using this
data and filter ratio method, we can obtain full Sun temperature maps
with high special resolution. In our analysis, we can derive reliable
temperatures not only in active regions but also in quiet regions and
coronal holes. This map can be created with the data set of one synoptic
observation. This means that we can obtain 4 maps a day. The result is
a full Sun temperature movie that gives us an unprecedented view of the
time evolution of solar temperature. In this meeting, we will show the
full Sun temperature movie and our coronal temperature analysis results.
---------------------------------------------------------
Title: Continuous Upflow of Plasmas at the Edge of an Active Region
as Revealed by the X-ray Telescope (XRT) aboard Hinode
Authors: Sakao, Taro; Kano, R.; Narukage, N.; Kotoku, J.; Bando, T.;
DeLuca, E. E.; Lundquist, L. L.; Golub, L.; Kubo, M.; Katsukawa, Y.;
Tsuneta, S.; Hara, H.; Matsuzaki, K.; Shimojo, M.; Shibasaki, K.;
Shimizu, T.; Nakatani, I.
2007AAS...210.7205S Altcode: 2007BAAS...39Q.179S
We present X-ray imaging observations with Hinode X-Ray Telescope (XRT)
of an active region NOAA AR 10942 made in the period of 20-22 February
2007. A prominent feature that drew our particular attention is that
there revealed continuous upflow of soft-X-ray-emitting plasmas along
apparently-open field lines towards the outer corona emanating from the
edge of the active region. <P />The field lines are originated from
an ensamble of small spots of following polarity, and are located at
a border between the active region and an adjacent equatorial coronal
hole(s) located to the east. The upflow was observed to be continuous
throughout the three days of observation intervals with projected
velocity of 140 km/s, accompanied with undulating motion of the field
lines. <P />We assert that these upflowing plasmas would be a possible
source of slow solar wind material, which supports a foresighted
notion which grew out of interplanetary scintillation observations
that slow solar wind most likely has its origin in the vicinity of
active regions with large flux expansion (Kojima et al. 1999). <P />A
preliminaty analysis indicates that the temperature of the upflowing
material near the base of the field lines is 1.3 MK with number density
of 2 × 10<SUP>9 </SUP>/cm<SUP>3</SUP>. Assuming that all the material
is to escape to the interplanetary space, this leads to a mass loss
rate of 2 × 10<SUP>11</SUP> g/s which amounts to a good fraction of
the total mass loss rate for solar wind. It is noteworthy that, even
apart from this unique upflow, we see continuous (up)flows of plasmas
anywhere around (surrounding) the active region. <P />Details of the
upflow will be presented and their possible implication to slow solar
wind discussed.
---------------------------------------------------------
Title: Structure and Coronal Activity around Filament Channels
Observed with Hinode XRT And TRACE
Authors: Lundquist, Loraine L.; van Ballegooijen, A. A.; Reeves,
K. K.; Sakao, T.; DeLuca, E. E.; Narukage, N.; Kano, R.
2007AAS...210.9427L Altcode: 2007BAAS...39..221L
The combination of multi-wavelength, high resolution, high cadence
data from the Hinode X-Ray Telescope (XRT) and the Transition Region
And Coronal Explorer (TRACE) give an unprecedented view of solar
active region dynamics and coronal topology. We focus on examples of
filament structures observed by TRACE and XRT in December 2006 and
February 2007. Co-alignment of observations in these two instruments
yields a striking picture of the coronal structures, with loops lying
both along and above the filament. Overlying loops exhibit remarkable
dynamics while the filament lies dormant, and numerous x-point and
triple-leg structures undergo repeated brightenings. We also employ
magnetic field data from SOT and from SOLIS to compare a non-linear
force-free model of the coronal magnetic field with the observed loops.
---------------------------------------------------------
Title: Temperature Structures Above Coronal Hole and Quiet Sun
Authors: Kano, Ryouhei; Sakao, T.; Narukage, N.; Kotoku, J.; Bando,
T.; DeLuca, E. E.; Lundquist, L.; Golub, L.; Tsuneta, S.; Hara, H.;
Shibasaki, K.; Shimojo, M.
2007AAS...210.9436K Altcode: 2007BAAS...39..223K
The X-ray Telescope (XRT) on board Hinode satelite has the capability
to derive the temperature structure in the solar corona. We present
the hieght dependence of the temperature above the limb. Because X-ray
intensity above the limb is so faint, it is important to estimate the
scattered light from disk corona. The eclipses happened on February 17
and March 19 in 2007 at Hinode orbit. On February 17, we took X-ray
images above the south polar coronal hole, while Moon passed it. On
March 19, we took the data for quiet Sun in the same way. <P />We
can estimated the scattered light from the eclipse data, and derived
the scatter-free X-ray images above the solar limb. In this meeting,
we will present the temperatures above coronal hole and quiet Sun,
based on the eclipse data.
---------------------------------------------------------
Title: Particle Acceleration in the X3 Event on Dec. 13, 2007
Authors: Shibasaki, Kiyoto; Koshiishi, H.; Shimojo, M.; Minoshima,
T.; Imada, S.; Sakao, T.; Hinode Team
2007AAS...210.9435S Altcode: 2007BAAS...39..223S
Even during the solar minimum period, the active region NOAA 10930 had
a complex magnetic configuration especially around the main sunspot
and produced a couple of X-class events. The one on Dec. 13, 2007 was
well observed by Nobeyama Radioheliograph (NoRH) and Polarimeters
(NoRP). Microwave emission associated with this event has several
interesting characteristics: <P />1. Long lasting non-thermal phase <P
/>2. Very large decimetric flux (several thousand times of the quiet
sun flux) and quite different time development of decimetric emission
compared to shorter wavelengths <P />3. Very high turn-over frequency
(around 35 GHz) <P />This event was also well observed by HINODE
satellite and partially by RHESSI satellite. Optical telescope (SOT) and
Soft X-ray telescope (XRT) onboard HINODE showed that the flare started
around the polarity reversal line which divides the main sunspot and
the closely associated small sunspot with opposite polarity. This line
is the interface of the penumbrae of both sunspots. The flare ribbons
started in the penumbrae and entered into umbrae of both sunspots. <P
/>Microwave images of the event at 17 and 34 GHz are synthesized
and compared with optical and soft X-ray images taken by SOT and XRT
respectively. Based on these overlays, frequency spectral information
(NoRP) and RHESSI images in the later phase of the event, we try to
locate particle acceleration site and discuss possible mechanisms of
acceleration. <P />Hinode is an international project supported by JAXA,
NASA, PPARC and ESA. We are grateful to the Hinode team for all their
efforts in the design, development and operation of the mission. NoRH
and NoRP are operated by Nobeyama Solar Radio Observatory, NAOJ. RHESSI
is a NASA project.
---------------------------------------------------------
Title: Magnetic activity and the solar corona: first results from
the Hinode satellite .
Authors: Reale, Fabio; Parenti, Susanna; Reeves, Kathy K.; Weber,
Mark; Bobra, Monica G.; Barbera, Marco; Kano, Ryohei; Narukage,
Noriyuki; Shimojo, Masumi; Sakao, Taro; Peres, Giovanni; Golub, Leon
2007MmSAI..78..591R Altcode:
The structure, dynamics and evolution of the solar corona are governed
by the magnetic field. In spite of significant progresses in our insight
of the physics of the solar corona, several problems are still under
debate, e.g. the role of impulsive events and waves in coronal heating,
and the origin of eruptions, flares and CMEs. The Hinode mission has
started on 22 september 2006 and aims at giving new answers to these
questions. The satellite contains three main instruments, two high
resolution telescopes, one in the optical and one in the X-ray band,
and an EUV imaging spectrometer. On the Italian side, INAF/Osservatorio
Astronomico di Palermo has contributed with the ground-calibration
of the filters of the X-ray telescope. We present some preliminary
mission results, with particular attention to the X-ray telescope data.
---------------------------------------------------------
Title: Energetics and Dynamics of an Impulsive Flare on March 10, 2001
Authors: Chandra, Ramesh; Jain, Rajmal; Uddin, Wahab; Yoshimura,
Keiji; Kosugi, Takeo; Sakao, Taro; Joshi, Anita; Deshpande, M. R.
2006SoPh..239..239C Altcode: 2006astro.ph..2611C; 2006SoPh..tmp...96C
We present Hα observations from ARIES (Nainital) of a compact and
impulsive solar flare that occurred on March 10, 2001 and which
was associated with a CME. We have also analyzed HXT, SXT/Yohkoh
observations as well as radio observations from the Nobeyama Radio
Observatory to derive the energetics and dynamics of this impulsive
flare. We coalign the Hα, SXR, HXR, MW, and magnetogram images within
the instrumental spatial-resolution limit. We detect a single HXR
source in this flare, which is found spatially associated with one of
the Hα bright kernels. The unusual feature of HXR and Hα sources,
observed for the first time, is the rotation during the impulsive phase
in a clockwise direction. We propose that the rotation may be due to
asymmetric progress of the magnetic reconnection site or may be due
to the change of the peak point of the electric field. In MW emission
we found two sources. The main source is at the main flare site and
another is in the southwest direction. It appears that the remote
source is formed by the impact of accelerated energetic electrons from
the main flare site. From the spatial correlation of multiwavelength
images of the different sources, we conclude that this flare has a
three-legged structure.
---------------------------------------------------------
Title: The Motions of the Hard X-Ray Sources in Solar Flares: Images
and Statistics
Authors: Bogachev, Sergey A.; Somov, Boris V.; Kosugi, Takeo;
Sakao, Taro
2005ApJ...630..561B Altcode:
On the basis of the Yohkoh Hard X-Ray Telescope (HXT) data, we
present a statistical study of different types of the hard X-ray
(HXR) source motions during solar flares. A total of 72 flares that
occurred from 1991 September to 2001 December have been analyzed. In
these flares, we have found 198 intense HXR sources that are presumably
the chromospheric footpoints of flare loops. The average velocity V and
its uncertainty σ were determined for these sources. For 80% of them,
the ratio of V to 3 σ is larger than 1, strongly suggesting that (1)
the moving sources are usually observed rather than stationary ones and
(2) the regular displacements of HXR sources dominate their chaotic
motions. After co-alignment of the HXT images with the photospheric
magnetograms, we have conducted an additional analysis of 31 flares
out of 72 and distinguished between three main types of the footpoint
motions. Type I consists of the motions preferentially away from and
nearly perpendicular to the neutral line (NL). About 13% of flares
(4 out of 31) show this pattern. In type II, the sources move mainly
along the NL in antiparallel directions. Such motions have been found
in 26% of flares (8 out of 31). Type III involves a similar pattern
as type II, but all the HXR sources move in the same direction along
the NL. Flares of this type constitute 35% (11 out of 31). In 26%
of flares (8 out of 31) we observed more complicated motions that can
be described as a combination of the basic types or some modification
of them. For the most interesting flares, the results of analysis are
illustrated and interpretation is suggested.
---------------------------------------------------------
Title: Contamination evaluation and thermal vacuum bakeout for
SOLAR-B visible-light and X-ray telescope
Authors: Tamura, Tomonori; Hara, Hirohisa; Tsuneta, Saku; Ichimoto,
Kiyoshi; Kumagai, Kazuyoshi; Nakagiri, Masao; Shimizu, Toshifumi;
Sakao, Taro; Kano, Ryouhei
2005RNAOJ...8...21T Altcode:
In the development of space telescopes, we are concerned about molecular
outgassing materials from telescope components. In particular, for
solar telescopes in space, the deposition of the outgassing materials
may lead to the increase of solar absorptance at a mirror surface
and it causes the thermal distortion due to the resultant temperature
increase. The mirror reflectivity at vacuum ultraviolet wavelengths
is very sensitive to molecular contamination. We have extensively
evaluated reflectance at 121.6nm (Lyman-alpha) of the contamination
witness mirrors exposed to the telescope testing environments in the
SOLAR-B visible-light telescope program. Thermal vacuum bakeout of
flight components is very effective process to reduce the outgassing
rate. We have severe contamination control program during the assembly
and testing of the SOLAR-B telescope up to launch of the satellite.
---------------------------------------------------------
Title: Development of Heater control equipment for the Solar-B XRT
thermal vacuum test
Authors: Kumagai, Kazuyoshi; Kano, Ryohei; Hara, Hirohisa; Tamura,
Tomonori; Sawa, Masaki; Tsuneta, Saku; Sakao, Taro; Matsuzaki, Keiichi
2005RNAOJ...8...29K Altcode:
The thermal vacuum test of the X-ray Telescope (XRT) aboard the
Solar-B satellite was carried out at NASA/Goddard Space Flight Center
(GSFC) since January 2004. For this thermal test, we developed the
Heater Sensor GSE (HS-GSE). It is an equipment to record flight
temperature sensors in the X-ray camera and to control flight camera
heaters. During the GSFC thermal test, the HS-GSE successfully recorded
the camera temperatures every 10 seconds, and controlled the heaters
automatically. We report the system of the HS-GSE successfully recorded
the camera temperatures every 10 seconds, and controlled the heaters
automatically. We report the system of the HS-GSE with the results in
the thermal test.
---------------------------------------------------------
Title: On upward motions of coronal hard X-ray sources in solar flares
Authors: Somov, B. V.; Kosugi, T.; Bogachev, S. A.; Masuda, S.;
Sakao, T.
2005AdSpR..35.1690S Altcode:
Coronal hard X-ray (HXR) sources were discovered by the Yohkoh
HXT telescope in about two dozen limb flares: Impulsive and gradual
ones. On the basis of HXT data, we investigated the spatial evolution of
coronal sources. Slow ascending motions of sources are seen in several
flares. In five events, it was possible to estimate the velocity
of the upward motion with values between 10 and 30 km/s. We present
these observational results and conclude that coronal source motions
should be studied statistically using the RHESSI high-resolution HXR
imaging data. We discuss the possibility that coronal HXR emission
is generated as bremsstrahlung of the fast electrons accelerated
in collapsing magnetic traps due to joint action of the Fermi-type
first-order mechanism and betatron acceleration.
---------------------------------------------------------
Title: Motion of the HXR sources in solar flares: Yohkoh images
and statistics
Authors: Somov, B. V.; Kosugi, T.; Bogachev, S. A.; Sakao, T.;
Masuda, S.
2005AdSpR..35.1700S Altcode:
Using the Yohkoh Hard X-Ray Telescope (HXT) data, we have examined
motions of the hard X-ray (HXR) sources during 72 solar flares occurred
from 1991 September to 2001 December. In these flares, we have found
198 intense sources that are presumably the chromospheric footpoints
(FPs) of flare loops. The average velocity V and the velocity dispersion
σ were determined by a linear regression for these sources. For 80%
of them, the ratio of V to 3 σ is larger than 1, strongly suggesting
that the regular motions of the HXR sources dominate their chaotic
motions. For 43 of 72 flares, coalignment of the HXT images with
the photospheric magnetograms allows us to consider the HXR sources
located on the both sides of the photospheric neutral line (NL) as
the FP sources, and to distinguish between three main types of the FP
motions. The type I is the motions of the HXR sources preferentially
away from and nearly perpendicular to the NL. Less than 5% of the flares
show this pattern of motion. In the type II, the sources move mainly
along the NL in anti-parallel directions. Such motions have been found
in 26% of flares. The type III involves a similar pattern of motions as
the type II but all the HXR sources move in the same direction along
the NL. Flares of this type constitute 30% of the flares. About 19%
of flares can be described as a combination of these basic types. The
remaining 20% of flares seem to be more complicated or less regular
in the motion scale under consideration. An interpretation of results
is suggested.
---------------------------------------------------------
Title: The first build-up of the Solar-B flight models
Authors: Hara, Hirohisa; Ichimoto, Kiyoshi; Otsubo, Masashi; Katsukawa,
Yukio; Kato, Yoshihiro; Kano, Ryohei; Kumagai, Kazuyoshi; Shibasaki,
Kiyoto; Shimizu, Toshifumi; Shimojo, Masumi; Suematsu, Yoshinori;
Tamura, Tomonori; Tsuneta, Saku; Noguchi, Motokazu; Nakagiri, Masao;
Miyashita, Masakuni; Watanabe, Tesuya; Kosuchi, Takeo; Sakao, Taro;
Matsuzaki, Keiichi; Kitakoshi, Yasunori; Kubo, Masahito; Sakamoto,
Yasushi
2005ARAOJ...7...46H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Science of the X-ray Sun: The X-ray telescope on Solar-B
Authors: DeLuca, E. E.; Weber, M. A.; Sette, A. L.; Golub, L.;
Shibasaki, K.; Sakao, T.; Kano, R.
2005AdSpR..36.1489D Altcode:
The X-Ray Telescope (XRT) on Solar-B is designed to provide high
resolution, high cadence observations of the X-ray corona through
a wide range of filters. The XRT science team has identified four
general problems in coronal physics as the primary science goals for our
instrument. Each of these goals will require collaborative observations
from the other Solar-B instruments: EUV Imaging Spectrograph (EIS)
and Solar Optical Telescope Focal Plane Package (SOT). We will discuss
the science goals and observations needed to address those goals.
---------------------------------------------------------
Title: SolarB X-Ray Telescope (XRT)
Authors: Kano, R.; Hara, H.; Shimojo, M.; Tsuneta, S.; Sakao, T.;
Matsuzaki, K.; Kosugi, T.; Golub, L.; Deluca, E. E.; Bookbinder,
J. A.; Cheimets, P.; Owens, J. K.; Hill, L. D.
2004ASPC..325...15K Altcode:
The Soft X-ray Telescope (XRT) aboard SolarB is a grazing incidence
X-ray telescope equipped with 2k × 2k CCD. XRT has 1 arcsec resolution
with wide field-of-view of 34 × 34 arcmin. It is sensitive to
<1 MK to 30 MK, allowing us to obtain TRACE-like low temperature
images as well. Co-alignment with SOT and EIS is realized through
the XRT visible light telescope and with temperature overlap with
EIS. Spacecraft mission data processor (MDP) controls XRT through
the sequence tables with versatile autonomous functions such as
exposure control, region-of-interest tracking, flare detection and
flare location identification. Data are compressed either with DPCM or
JPEG, depending on the purpose. This results in higher cadence and/or
wider field-of-view for given telemetry bandwidth. With focus adjust
mechanism, higher resolution of Gaussian focus may be available on-axis.
---------------------------------------------------------
Title: Multi-Wavelength Observations of an Unusual Impulsive Flare
Associated with Cme
Authors: Uddin, Wahab; Jain, Rajmal; Yoshimura, Keiji; Chandra,
Ramesh; Sakao, T.; Kosugi, T.; Joshi, Anita; Despande, M. R.
2004SoPh..225..325U Altcode: 2004astro.ph.10177U
We present the results of a detailed analysis of multi-wavelength
observations of a very impulsive solar flare 1B/M6.7, which occurred on
10 March, 2001 in NOAA AR 9368 (N27 W42). The observations show that the
flare is very impulsive with a very hard spectrum in HXR that reveal
that non-thermal emission was most dominant. On the other hand, this
flare also produced a type II radio burst and coronal mass ejections
(CME), which are not general characteristics for impulsive flares. In
Hα we observed bright mass ejecta (BME) followed by dark mass ejecta
(DME). Based on the consistency of the onset times and directions
of BME and CME, we conclude that these two phenomena are closely
associated. It is inferred that the energy build-up took place due to
photospheric reconnection between emerging positive parasitic polarity
and predominant negative polarity, which resulted as a consequence
of flux cancellation. The shear increased to >80° due to further
emergence of positive parasitic polarity causing strongly enhanced
cancellation of flux. It appears that such enhanced magnetic flux
cancellation in a strongly sheared region triggered the impulsive flare.
---------------------------------------------------------
Title: Focal plane CCD camera for the X-Ray Telescope (XRT) aboard
SOLAR-B
Authors: Sakao, Taro; Kano, Ryouhei; Hara, Hirohisa; Matsuzaki,
Keiichi; Shimojo, Masumi; Tsuneta, Saku; Kosugi, Takeo; Shibasaki,
Kiyoto; Kumagai, Kazuyoshi; Sawa, Masaki; Tamura, Tomonori; Iwamura,
Satoru; Nakano, Mitsuhiko; Du, Zhangong; Hiyoshi, Kenji; Horii,
Michihiro; Golub, Leon; Bookbinder, Jay A.; Cheimets, Peter C.; Hill,
Lawrence D.; Owens, Jerry K.
2004SPIE.5487.1189S Altcode:
We present scientific as well as engineering overview of the X-Ray
Telescope (XRT) aboard the Japanese Solar-B mission to be launched in
2006, with emphasis on the focal plane CCD camera that employs a 2k
x 2k back-thinned CCD. Characterization activities for the flight CCD
camera made at the National Astronomical Observatory of Japan (NAOJ)
are discussed in detail with some of the results presented.
---------------------------------------------------------
Title: Design and Performance of Tip-Tilt Mirror System for Solar
Telescope
Authors: Kodeki, Kazuhide; Fukushima, Kazuhiko; Hara, Hirohisa; Inoue,
Masao; Kano, Ryouhei; Kashiwase, Toshio; Nagata, Shin'ichi; Sakao,
Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida, Tsuyoshi
2004JSpRo..41..868K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Impulsive Solar Flares associated with Coronal Mass Ejections
Authors: Jain, R.; Uddin, W.; Kosugi, T.; Kumar, S.; Chandra, R.;
Sakao, T.; Masuda, S.
2004cosp...35..939J Altcode: 2004cosp.meet..939J
We present the multi-wavelength observations of a few impulsive
solar flares, which are associated with Coronal Mass Ejections (CMEs)
during Solar Cycle 23. The optical and radio waveband observations
of the solar flares considered for this investigation were made in
India and Japan, while SOHO, CGRO, YOHKOH and SOXS missions made the
other wavelength observations. We present the optical, radio and X-ray
emission characteristics of impulsive flares associated with CMEs in
view of their energy release and particle acceleration. We conjecture
a qualitative model to interpret our multi-spectral observations
of these impulsive solar flares. It is proposed that a CME of some
magnitude precede the impulsive solar flares to cause strong particle
acceleration as observed in them. In support of our this concept
we present the magnetograms of the active regions that reveal the
cancellation of magnetic flux in all such impulsive events, which in
turn results in generating a CME as seen in different wavelengths.
---------------------------------------------------------
Title: Development of the Solar-B X-ray telescope focal plane camera
Authors: Kano, Ryouhei; Hara, Hirohisa; Kumagai, Kazuyoshi; Sawa,
Masaki; Tsuneta, Saku; Sakao, Taro; Matsuzaki, Keiichi
2004naoj.book....5K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Motion of the HXR Sources in Solar Flares: Yohkoh Images
and Statistics
Authors: Somov, B.; Kosugi, T.; Bogachev, S. A.; Sakao, T.; Masuda, S.
2004cosp...35...13S Altcode: 2004cosp.meet...13S
Using Yohkoh Hard X-ray Telescope (HXT) data of seventy solar flares,
we have synthesized about 20000 images and compared them with the
SOHO MDI and Kit Peak magnetograms. This allowed us to study apparent
motions of the HXR sources in flares. More than 90 % of sources show
well-defined motions in some directions during the impulsive phase
of flares. The apparent displacement, i.e. the distance between the
source positions at the start and at the end of a flare, can reach more
than 10”. We present here some examples and statistical results. A
relationship between the direction of a motion and the magnetic field
configuration in an active region is considered in terms of the rainbow
reconnection model. The possibility of similar research based on the
RHESSI data is discussed.
---------------------------------------------------------
Title: On the Upward Motion of the Coronal HXR Sources in Solar
Flares: Observational and Interpretation Problems
Authors: Somov, B.; Kosugi, T.; Masuda, S.; Sakao, T.; Bogachev, S. A.
2004cosp...35...14S Altcode: 2004cosp.meet...14S
The coronal hard X-ray (HXR) sources were discovered by the Yohkoh
HXT telescope in about a dozen of impulsive flares as well as in
some gradual flares called Long Decay Events (LDEs). On the basis of
the HXT data we have studied the spatial evolution of the coronal
HXR source in these flares. The ascent motions are seen in several
flares. However, in a few of them, we could estimate with a good
accuracy the upward component of velocity of about 10-30 km/sec. We
present these observational results, consider implications of them for
the magnetic reconnection flare models and discuss some difficulties of
interpretation. We conclude that the problem should be studied better
by using the RHESSI high-resolution HXR imaging data.
---------------------------------------------------------
Title: Spatial and Temporal Properties of Hot and Cool Coronal Loops
Authors: Nagata, Shin'ichi; Hara, Hirohisa; Kano, Ryouhei; Kobayashi,
Ken; Sakao, Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida, Tsuyoshi;
Gurman, Joseph B.
2003ApJ...590.1095N Altcode:
A suite of images from the XUV Doppler Telescope (XDT), the Yohkoh Soft
X-ray Telescope (SXT), and the Extreme-Ultraviolet Imaging Telescope
(EIT) on the Solar and Heliospheric Observatory (SOHO) allow us to
see the whole (T>1 MK) temperature evolution of coronal loops. The
detailed morphological comparison of an active region shows that hot
loops seen in SXT (T>3 MK) and cool loops seen in the the EIT 195
Å band (T~1.5 MK) are located in almost alternating manner. The
anticoincidence of the hot and the cool loops is conserved for a
duration much longer than the estimated cooling timescale. However, both
hot and cool loops have counterparts in the intermediate-temperature
images. The cross-correlation coefficients are higher for neighboring
temperature pairs and lower for pairs with larger temperature
differences. These results suggest that loops are not isothermal but
rather have a differential emission measure distribution of modest but
finite width that peaks at different temperatures for different loops.
---------------------------------------------------------
Title: Basic Principles and Examples of Solar-type Flare Modelling
Authors: Somov, B. V.; Kosugi, T.; Sakao, T.
2003ASPC..289..393S Altcode: 2003aprm.conf..393S
We review the fundamental ideas which are under current use
to model flares and other non-stationary phenomena in the solar
atmosphere. Recent multi-wavelength observations of solar flares allow
us to improve a theory of solar-type flares, which can be applied
to many astrophysical phenomena accompanied by fast plasma ejection,
powerful fluxes of radiation, and the acceleration of electrons and
ions to high energies.
---------------------------------------------------------
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: Modeling large solar flares
Authors: Somov, B. V.; Kosugi, T.; Hudson, H. S.; Sakao, T.; Masuda, S.
2003AdSpR..32.2439S Altcode:
The basic ideas to model the large solar flares are reviewed and
illustrated. Some fundamental properties of potential and non-potential
fields in the solar atmosphere are recalled. In particular, we consider
a classification of the non-potential fields or, more exactly, related
electric currents, including reconnecting current layers. The so-called
'rainbow reconnection' model is presented with its properties and
predictions. This model allows us to understand main features of large
flares in terms of reconnection. We assume that in the two-ribbon
flares, like the Bastille-day flare, the magnetic separatrices are
involved in a large-scale shear photospheric flow in the presence of
reconnecting current layers generated by a converging flow.
---------------------------------------------------------
Title: On the Impulsive Solar Flare of 10 March 2001
Authors: Jain, Rajmal; Uddin, Wahab; Kosugi, Takeo; Chandra, Ramesh;
Keiji, Yoshimura; Sakao, Taro; Joshi, Anita; Deshpande, Mohan R.
2003IAUJD...7E...5J Altcode:
We present the observations of an impulsive solar flare of 10 March
2001. The flare was observed with Solar Tower Telescope at State
Observatory Nainital India and space-borne missions viz. YOHKOH
and SOHO and many other ground-based observatories. The flare was
associated with intense and impulsive hard X-ray emission. Our analysis
show that the energy build up took place as a result of photospheric
reconnection which in turn however was going on with increasing shear
in the active region from 60 to almost 90 deg. on 10 March 2001. In
context to multiwavelength radio polarization data from Nobeyama
and magnetograms from MDI/SOHO it further appears that emerging flux
region was the source for triggering the impulsive flare as well as
coronal mass ejection. The alignment of H-alpha images with soft and
hard X-ray images as well as MW radio images enable us to identify
the flare sources in different wavelengths. We propose a model to
interpret our observations and results of this flare event.
---------------------------------------------------------
Title: Magnetic Reconnection Scenario of the Bastille Day 2000 Flare
Authors: Somov, Boris V.; Kosugi, Takeo; Hudson, Hugh S.; Sakao,
Taro; Masuda, Satoshi
2002ApJ...579..863S Altcode:
On the basis of Yohkoh Hard X-Ray Telescope data and the magnetograms
taken by the SOHO Michelson Doppler Imager and the Solar Magnetic
Field Telescope at Huairou Solar Observing Station, we suggest an
interpretation of the well-observed “Bastille Day 2000” flare. The
large-scale structure and dynamics of the flare, as seen in hard X-rays,
can be explained in terms of the three-dimensional reconnection at
a separator in the corona. More specifically, we suggest that before
occurrence of two-ribbon flares with significant decrease of a distance
between the hard X-ray (HXR) footpoints, like the Bastille Day flare,
the bases of magnetic field separatrices are moved by the large-scale
photospheric flows of two types. First, the shear flows, which are
parallel to the photospheric neutral line, increase the length of field
lines in the corona and produce an excess of magnetic energy. Second,
the converging flows, i.e., the flows directed to the neutral line,
create the preflare current layers in the corona and provide an excess
of energy sufficient to produce a large flare. During the flare, both
excesses of magnetic energy are released completely or partially. In
the Bastille Day flare, the model describes two kinds of apparent
motions of the HXR kernels. One is an increase of a distance between
the flare ribbons in which the HXR kernels appear. The effect results
from fast reconnection in a coronal current layer. The second effect is
a decrease of the distance between the kernels moving to each other as a
result of relaxation of magnetic tensions generated by the photospheric
shear flows.
---------------------------------------------------------
Title: Three-dimensional reconnection at the sun: space observations
and collisionless models
Authors: Somov, B. V.; Kosugi, T.; Litvinenko, Y. E.; Sakao, T.;
Masuda, S.; Oreshina, A. V.; Merenkova, E. Y.
2002AdSpR..29.1035S Altcode:
The Yohkoh data on the site and mechanism of magnetic energy
transformation into kinetic and thermal energies of a superhot plasma
at the Sun require new models of reconnection under conditions of
highlyanomalous resistivity, which are similar to that one observed in
toroidal devices performed to study turbulent heating of a collisionless
plasma, and its anomalous heat-conductive cooling. The models
make intelligible the observed properties of the three-dimensional
reconnection in solar flares.
---------------------------------------------------------
Title: Modeling big flares: Principles and practice
Authors: Somov, B.; Kosugi, T.; Hudson, H.; Sakao, T.; Masuda, S.
2002cosp...34E..43S Altcode: 2002cosp.meetE..43S
The basic ideas, which are under current use to model the large-scale
solar flares, are reviewed and illustrated. The so-called `rainbow
reconnection' model is applied to the observations of flares with
the HXT on board Yohkoh, the MDI instrument on the SOHO, the TRACE
satellite, and the Solar Magnetic Field Telescope (SMFT) of the
Beijing Astronomical Observatory. This allows us to improve a theory of
large solar flare (Somov, B., Cosmic Plasma Physics, 2000, Dordrect:
Kluwer). In particular, the famous Bastille day 2000 flare is studied
and interpreted. It is shown that the main large-scale structure and
dynamics of this flare can be explained in terms of the collisionless
3D reconnection.
---------------------------------------------------------
Title: Collisionless Reconnection in the Structure and Dynamics of
Active Regions
Authors: Somov, B. V.; Kosugi, T.; Litvinenko, Y. E.; Sakao, T.;
Masuda, S.; Bogachev, S. A.; Oreshina, A. V.; Merenkova, E. Y.
2001IAUS..203..558S Altcode:
New theoretical interpretations are discussed of the Yohkoh data on
the site and mechanism of magnetic energy transformation into thermal
and kinetic energies of superhot plasmas and accelerated particles. We
develop a model that explains observed properties of reconnection in
active regions and in flares. The transition from slow reconnection to
fast one is demonstrated by numerical solutions of the problem taking
into account anomalous resistivity and anomalous heat conduction. The
model also makes intelligible the observed decrease (increase) of the
separation between the double-footpoint hard X-ray sources in the more
impulsive (less impulsive) flares. An accumulation of the reconnected
magnetic flux can explain the observed ascent motion of the coronal
source of hard X rays in flares. We demonstrate some features of
electron and ion acceleration in collapsing magnetic traps.
---------------------------------------------------------
Title: On the Detection of Solar Coronal High-Velocity Fields Using
the XUV Doppler Telescope
Authors: Kobayashi, Ken; Hara, Hirohisa; Kano, Ryohei; Nagata,
Shin'ichi; Sakao, Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida,
Tsuyoshi; Harrison, Richard
2000PASJ...52.1165K Altcode:
The XUV Doppler Telescope (XDT) is a sounding rocket experiment
designed to detect flows in the solar corona using filter ratios. The
XDT, successfully launched on 1998 January 31, is a normal incidence
telescope composed of narrow-bandpass multilayer mirrors and capable
of obtaining images 2 Å\ above and 2 Å\ below the Fe XIV 211 Å\
(T = 1.7 MK) emission line. It has the potential to make a velocity map
of the entire solar disk with just a few minutes of observation. The
image ratio maps show features that translate to Doppler shifts of
200 km s<SUP>-1</SUP> or more, including several `redshift' features
located near footpoints of coronal loops. However, no corresponding
velocity features were seen by the Solar and Heliospheric Observatory
(SOHO) Coronal Diagnostic Spectrometer (CDS) in the Mg IX 368 Å (T =
1 MK) line, suggesting that the features are not caused by Doppler
shift. Instead, the features seem to be related to contamination
of lower temperature (T < 1 MK) emission lines and the nearby
density-sensitive Fe XIII lines. We conclude that while no flows were
positively identified by the XDT, this observing technique is capable
of detecting flows of 1000 km s^{-1} independently, and 200 km s^{-1}$
when combined with simultaneous plasma diagnostic observation.
---------------------------------------------------------
Title: High-resolution grazing incidence telescope for the Solar-B
observatory
Authors: Golub, Leon; DeLuca, Edward E.; Bookbinder, Jay A.; Cheimets,
Peter; Shibasaki, Kiyoto; Sakao, Taro; Kano, Ryouhei
2000SPIE.4139..313G Altcode:
The X-ray observations from the Yohkoh SXT provided the greatest
step forward in our understanding of the solar corona in nearly two
decades. We believe that the scientific objectives of the Solar-B
mission can best be achieved with an X-ray telescope (XRT) similar to
the SXT, but with significant improvements in spatial resolution and
in temperature response that take into account the knowledge gained
from Yohkoh. We present the scientific justification for this view,
discuss the instrumental requirements that flow from the scientific
objectives, and describe the instrumentation that will meet these
requirements. XRT is a grazing-incidence (GI) modified Wolter I X-ray
telescope, of 35 cm inner diameter and 2.7 m focal length. The 2048 X
2048 back-illuminated CCD has 13.5 (mu) pixels, corresponding to 1.0
arcsec and giving full Sun field of view. This will be the highest
resolution GI X-ray telescope ever flown for Solar coronal studies,
and it has been designed specifically to observe both the high and
low temperature coronal plasma.
---------------------------------------------------------
Title: The X-ray telescope on Solar B.
Authors: Deluca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.;
Shibasaki, K.; Sakao, T.; Kano, R.
2000BAAS...32..827D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Electron Trapping and Precipitation in Asymmetric Solar
Flare Loops
Authors: Aschwanden, M. J.; Fletcher, L.; Sakao, T.; Kosugi, T.;
Hudson, H.
2000IAUS..195..375A Altcode:
Acceleration, propagation, and energy loss of particles energized in
solar flares cannot be studied separately because their radiative
signatures observed in the form of hard X-ray bremsstrahlung or
radio gyrosynchrotron emission represent a convolution of all these
processes. We analyze hard X-ray emission from solar flares using
a kinematic model that includes free-streaming electrons (having an
energy-dependent time-of-flight delay) as well as temporarily trapped
electrons (which are pitch-angle scattered by Coulomb collisional
scattering) to determine various physical parameters (trapping times,
flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare
loops with asymmetric magnetic fields.
---------------------------------------------------------
Title: The X-Ray Telescope on Solar B
Authors: DeLuca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.;
Shibasaki, K.; Sakao, T.; Kano, R.
2000SPD....31Q0293D Altcode:
The X-ray observations from the Yohkoh SXT provided the greatest
step forward in our understanding of the solar corona in nearly two
decades. We believe that the scientific objectives of the Solar-B
mission can best be achieved with an X-ray telescope (XRT) similar to
the SXT, but with significant improvements in spatial resolution and in
temperature response that take into account the knowledge gained from
Yohkoh. We present the scientific justification for this view, discuss
the instrumental requirements that flow from the scientific objectives,
and describe the instrumentation to meet these requirements. XRT is
a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35cm
inner diameter and 2.7m focal length. The 2048x2048 back-illuminated
CCD has 13.5&mu pixels, corresponding to 1.0 arcsec and giving
full Sun field of view. This will be the highest resolution GI X-ray
telescope ever flown for Solar coronal studies, and it has been designed
specifically to observe both the high and low temperature coronal
plasma. A small optical telescope provide visibles light images for
coalignment with the Solar-B optical and EUV instruments. The US XRT
team is support by a NASA Contract from MSFC.
---------------------------------------------------------
Title: Spectral Characteristics of Above-the-Looptop Hard X-Ray Source
Authors: Masuda, S.; Sato, J.; Kosugi, T.; Sakao, T.
2000AdSpR..26..493M Altcode:
It is observed in impulsive flares with the Hard X-ray Telescope (HXT)
onboard Yohkoh that a hard X- ray source is located above the apex
of a soft X-ray flaring loop in addition to double footpoint sources
(Masuda et al. 1994, 1995). This observation suggests that the flare
energy-release, probably magnetic reconnection, takes place not in
the soft X-ray loop, but above the loop. It is important to derive the
hard X-ray spectrum of this source accurately in order to understand
how electrons are energized there. Using an improved image-synthesis
technique with new modulation patterns (Sato 1997), we obtained hard
X-ray images of the 13 January 1992 flare in the four HXT energy
bands with a common photon-accumulation time. The spectrum of the
above-the-looptop source in the energy range of 14-93 keV seems to
be well fit by emission from an isothermal plasma whose temperature
is about 100 MK, rather than by a non-thermal, single power-law
spectrum. Although this is consistent with the observational result
that the density of the ambient plasma is not high enough to stop high
energy electrons, we need to study other events, especially intense
events from which more accurate spectra can be derived, in order to
confirm this result
---------------------------------------------------------
Title: Evolution of Magnetic Field Structure and Particle Acceleration
in Solar Flares
Authors: Sakao, T.; Kosugi, T.; Masuda, S.; Sato, J.
2000AdSpR..26..497S Altcode:
We present hard X-ray imaging observations of impulsive solar flares
with Yohkoh HXT, focusing on the evolution of hard X-ray double
footpoint sources seen in the energy range above 30 keV. In 7 out
of the 14 events studied, the separation between the double sources
increases (at the 3σ confidence level) as the flare progresses,
with the double sources moving nearly anti-parallel to each other
in most cases. Implications of these results to the global magnetic
field structure responsible for solar flare energy release / particle
acceleration are discussed
---------------------------------------------------------
Title: Improvement of Yohkoh HXT Imaging and an Analysis of the 1997
November 6, X9 Flare
Authors: Sato, J.; Masuda, S.; Kosugi, T.; Sakao, T.
2000AdSpR..26..501S Altcode:
The imaging capability of the Hard X-ray Telescope (HXT) on board
Yohkoh has been drastically improved by (1) adopting new instrumental
response functions (modulation patterns) derived from a self-calibration
procedure that makes use of solar flares themselves as calibration
sources, (2) revising the Maximum Entropy (MEM) image synthesis
procedure for better total flux estimation, and (3) incorporating in
MEM properly estimated observation errors. One of the most intense
flares so far observed with HXT, the 1997 November 6, X9 flare, has
been analyzed with the new HXT imaging program. Two footpoint sources
are clearly seen and show systematic motions during the impulsive
phase. This may provide a new clue to understand the coronal magnetic
field structure involved in the energy release process of flares
---------------------------------------------------------
Title: Basic Physics of Collisionless Three-Dimensional Reconnection
in the Solar Corona Related to Yohkoh Observations
Authors: Somov, B. V.; Kosugi, T.; Masuda, S.; Sakao, T.
2000AdSpR..25.1821S Altcode:
New results concerning magnetic reconnection in the solar corona
are reviewed. We apply the collisionless 3D reconnection theory -
more exactly, the model of a high-temperature turbulent-current
non-neutral current sheet - to the coronal conditions derived from the
observations with the HXT and SXT onboard Yohkoh. New interpretations
are discussed of the Yohkoh data on the site and mechanism of magnetic
energy transformation into kinetic and thermal energies of superhot
plasmas and accelerated high-energy particles. Open issues are the
focus of our attention
---------------------------------------------------------
Title: Initial Results from the XUV Doppler Telescope
Authors: Kano, R.; Hara, H.; Kobayashi, K.; Kumagai, K.; Nagata, S.;
Sakao, T.; Shimizu, T.; Tsuneta, S.; Yoshida, T.
2000AdSpR..25.1739K Altcode:
We developed a unique telescope to obtain simultaneous XUV images and
the velocity maps by measuring the line-of-sight Doppler shifts of the
Fe XIV 211A&ring line (T = 1.8 MK): the Solar XUV Doppler Telescope
(hereafter XDT). The telescope was launched by the Institute of Space
and Astronautical Science with the 22nd S520 rocket on January 31,
1998, and took 14 XUV whole sun images during 5 minutes. Simultaneous
observations of XDT with Yohkoh (SXT), SOHO (EIT, CDS, LASCO and MDI)
were successfully carried out. The images taken with EIT, XDT and SXT
are able to cover the wide temperature ranging from 1 to 10 MK, and
clearly show the multi-temperature nature of the solar corona. Indeed,
we notice that both the cool (1-2 MK) loops observed with EIT and
XDT, and the hot (>3 MK) loops observed with SXT exist in the same
active regions but in a spatially exclusive way. The XDT red-blue ratio
between longer- and shorter-wavelength bands of Fe XIV 211A&ring
line indicates a possible down-flow of 1.8 MK plasma near the footpoints
of multiple cool loops
---------------------------------------------------------
Title: Three-dimensional Reconnection in the Solar Corona Related
to Yohkoh Observations
Authors: Somov, B. V.; Merenkova, E. Yu.; Kosugi, T.; Sakao, T.;
Masuda, S.; Oreshina, A. V.
1999ESASP.448..883S Altcode: 1999mfsp.conf..883S; 1999ESPM....9..883S
No abstract at ADS
---------------------------------------------------------
Title: HXT Observations of Solar Flares - A Review and Perspective -
Authors: Sakao, T.
1999spro.proc..321S Altcode:
We present hard X-ray imaging observations of impulsive solar flares
made with the Hard X-ray Telescope (HXT) aboard the Yohkoh satellite,
and emphasise the magnetic field structure and its evolution during
flares. The HXT has revealed that the bulk of hard X-rays above
30 keV is emitted from the footpoints of a flaring magnetic loop
by electrons accelerated near the loop top. This implies that the
evolution of hard X-ray footpoints reflects that of magnetic field
structure responsible for the energy release, through which we can
infer the magnetic field structure itself. We review progress so far
made along these lines, including the relationship between magnetic
field structure and thermal/non-thermal aspects of impulsive flares,
followed by discussion of the (three-dimensional) magnetic field
structure inferred from motions of individual footpoints. We also
discuss, from a viewpoint of magnetic field structure, near-future
perspective of hard X-ray solar physics.
---------------------------------------------------------
Title: Coronal Hard X-rays in Solar Flares: Yohkoh Observations
and Interpretation
Authors: Somov, B. V.; Litvinenko, Y. E.; Kosugi, T.; Sakao, T.;
Masuda, S.; Bogachev, S. A.
1999ESASP.448..701S Altcode: 1999ESPM....9..701S; 1999mfsp.conf..701S
No abstract at ADS
---------------------------------------------------------
Title: Narrow-Bandpass Multilayer Mirrors for an Extreme-Ultraviolet
Doppler Telescope
Authors: Hara, Hirohisa; Nagata, Shin'ichi; Kano, Ryouhei; Kumagai,
Kazuyoshi; Sakao, Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida,
Tsuyoshi; Ishiyama, Wakana; Oshino, Tetsuya; Murakami, Katsuhiko
1999ApOpt..38.6617H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The XUV Doppler Telescope (XDT)
Authors: Sakao, T.; Tsuneta, S.; Hara, H.; Shimizu, T.; Kano, R.;
Kumagai, K.; Yoshida, T.; Nagata, S.; Kobayashi, K.
1999SoPh..187..303S Altcode:
We present an overview and instrumental details of the solar XUV Doppler
Telescope (XDT) launched in January 1998 with the S520CN-22 sounding
rocket of the Institute of Space and Astronautical Science. The XDT
observes nearly single-temperature solar corona at 1.8 MK with angular
resolution of ≈ 5” pixel size, together with the ability to detect
the coronal velocity field with a full-Sun field of view. By use of
normal incidence optics whose primary and secondary mirrors are coated
with multilayer materials in two sectors, the XDT takes images of the
Sun in a set of shorter and longer wavelength bands around the Fe xiv
211.3 Å emission line. Summation of a pair of images in the two bands
provides an image of the 1.8 MK-corona while the difference between
the two provides velocity images of the Fe xiv-emitting plasma. A brief
description on the observation sequence together with the flight result
is also given.
---------------------------------------------------------
Title: Deconvolution of Directly Precipitating and Trap-precipitating
Electrons in Solar Flare Hard X-Rays. III.Yohkoh Hard X-Ray Telescope
Data Analysis
Authors: Aschwanden, Markus J.; Fletcher, Lyndsay; Sakao, Taro;
Kosugi, Takeo; Hudson, Hugh
1999ApJ...517..977A Altcode:
We analyze the footpoint separation d and flux asymmetry A of
magnetically conjugate double footpoint sources in hard X-ray images
from the Yohkoh Hard X-Ray Telescope (HXT). The data set of 54 solar
flares includes all events simultaneously observed with the Compton
Gamma Ray Observatory (CGRO) in high time resolution mode. From the CGRO
data we deconvolved the direct-precipitation and trap-precipitation
components previously (in Paper II). Using the combined measurements
from CGRO and HXT, we develop an asymmetric trap model that allows
us to quantify the relative fractions of four different electron
components, i.e., the ratios of direct-precipitating (q<SUB>P1</SUB>,
q<SUB>P2</SUB>) and trap-precipitating electrons (q<SUB>T1</SUB>,
q<SUB>T2</SUB>) at both magnetically conjugate footpoints. We find mean
ratios of q<SUB>P1</SUB>=0.14+/-0.06, q<SUB>P2</SUB>=0.26+/-0.10,
and q<SUB>T</SUB>=q<SUB>T1</SUB>+q<SUB>T2</SUB>=0.60+/-0.13. We
assume an isotropic pitch-angle distribution at the
acceleration site and double-sided trap precipitation
(q<SUB>T2</SUB>/q<SUB>T1</SUB>=q<SUB>P2</SUB>/q<SUB>P1</SUB>)
to determine the conjugate loss-cone angles
(α<SUB>1</SUB>=42<SUP>deg</SUP>+/-11<SUP>deg</SUP> and
α<SUB>2</SUB>=52<SUP>deg</SUP>+/-10<SUP>deg</SUP>) and magnetic
mirror ratiosat both footpoints (R<SUB>1</SUB>=1.6,...,4.0 and
R<SUB>2</SUB>=1.3,...,2.5). From the relative displacement of
footpoint sources we also measure altitude differences of hard
X-ray emission at different energies, which are found to decrease
systematically with higher energies, with a statistical height
difference of h<SUB>Lo</SUB>-h<SUB>M1</SUB>=980+/-250 km and
h<SUB>M1</SUB>-h<SUB>M2</SUB>=310+/-300 km between the three lower
HXT energy channels (Lo, M1, M2).
---------------------------------------------------------
Title: Development and flight performance of tip-tilt mirror system
for a sounding rocket observation of the Sun.
Authors: Shimizu, T.; Yoshida, T.; Tsuneta, S.; Sakao, T.; Kano,
R.; Hara, H.; Nagata, S.; Kodeki, K.; Inoue, M.; Fukushima, K.;
Kashiwase, T.
1999RNAOJ...4...43S Altcode: 1999RNOAJ...4...43S
A tip-tilt mirror (TTM) system was developed for the XUV Doppler
telescope (XDT) on board an ISAS sounding rocket. The spatial resolution
of the telescope is about 5″ whereas the pointing stability is
only ±0.3° with the rocket pointing control system. To achieve
better than 5″stability on the focal plane of the telescope, the
TTM system controls the tilt of the secondary mirror with fixed-coil
magnetic actuators. The control signal to stabilize focal-plane images
is supplied by the position-sensitive detector (PSD) of a pin-hole
telescope equipped inside XDT. Closed-loop controls are made with
the on-board software on the DSP processor. The sounding rocket was
successfully launched on 31 January 1998 from the Kagoshima Space
Center of ISAS. TTM worked perfectly during the flight, and achieved
better than 5″stability on the focal plane during CCD exposures.
---------------------------------------------------------
Title: Multi-wavelength observations of POST flare loops in two long
duration solar flares
Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi,
L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.;
Sakao, T.; Ichimoto, K.
1998A&A...337..911H Altcode:
We have analysed two Long Duration solar Events (LDEs) which produced
large systems of Post Flare Loops (PFLs) and which have been observed by
Yohkoh and ground-based observatories. Using the Maximum Entropy Method
(MEM) image synthesis technique with new modulation patterns we were
able to make hard X-ray (HXR) images of the post flare loops recorded
in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We
obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6)
K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray
(SXR) loops lie higher than the Hα loops and the former are overlaid
by HXR emission. This is suggestive of the magnetic reconnection
process. However some details are not consistent with the standard
models. Firstly the separation between the HXR source and the SXR
loop increases with time, with the HXR source being approximately
a factor of five larger than the equivalent source in impulsive
flares. Secondly the cooling times deduced from observations are longer
than the theoretically expected ones and the discrepancy increases
with time. We review the current models in view of these results.
---------------------------------------------------------
Title: Development of the tip-tilt mirror system for the solar
XUV telescope
Authors: Kodeki, Kazuhide; Fukushima, Kazuhiko; Kashiwase, Toshio;
Inoue, Masao; Shimizu, Toshifumi; Yoshida, Tsuyoshi; Sakao, Taro;
Hara, Hirohisa; Nagata, Shin'ichi; Kano, Ryouhei; Tsuneta, Saku
1998SPIE.3356..922K Altcode:
This paper describes the design and prelaunch performance of the
tip-tilt mirror (TTM) system developed for the XUV Cassegrain telescope
aboard the ISAS sounding rocket experiment. The spatial resolution
of the telescope is about 5 arcsec, whereas the rocket pointing is
only controlled to be within +/- 0.5 degree around the target without
stability control. The TTM is utilized to stabilize the XUV image
on the focal planes by tilting the secondary mirror with two-axes
fixed-coil type actuators. The two position- sensitive detectors in
the telescope optics and in the TTM mechanical structure from the
normal and local closed-loop modes. The TTM has four grain modes with
automatic transition among the modes. The low gain mode is used in
the initial acquisition, and in case the TTM loses the tracking. The
high gain mode is used in the normal tracking mode. This arrangement
provides us with the wide initial acquisition angle with single TTM
system as well as the high pointing accuracy once the tracking is
established. The TTM has a launch-lock mechanism against the launch
vibration of 16G. The closed-loop control with command and telemetry
interface is done by the flight software against the launch vibration
of 16G. The closed-loop control with command and telemetry interface
is done by the flight software on the DSP processor. The use of the
fast processor brings in the significant reduction in the weight and
size of the control- electronics, more flexible control system, and
shorter design and testing period.
---------------------------------------------------------
Title: Collisionless Three-dimensional Reconnection In Impulsive
Solar Flares
Authors: Somov, Boris V.; Kosugi, Takeo; Sakao, Taro
1998ApJ...497..943S Altcode:
Two subclasses of impulsive solar flares, observed with the Hard X-Ray
Telescope (HXT) onboard Yohkoh, have been discovered by Sakao et al. The
two subclasses can be characterized as more impulsive (MI) and less
impulsive (LI) flares, the former having a shorter total duration of
the impulsive phase in the hard X-ray emission than the latter. We
assume that in both subclasses, the collisionless three-dimensional
reconnection process occurs at the separator with a longitudinal
magnetic field. The high-temperature turbulent-current sheet (HTTCS),
located along the separator, generates accelerated particles and fast
outflows of “superhot” (T >= 30 MK) plasma. Powerful anomalous
heat-conductive fluxes along the reconnected field lines maintain a high
temperature in the superhot plasma. <P />The difference between the LI
and MI flares presumably appears because the footpoint separation (the
distance between two brightest hard X-ray sources) increases in time in
the LI flares, but decreases in the MI flares. According to our model,
in the LI flares the three-dimensional reconnection process accompanies
an increase in the longitudinal magnetic field at the separator. In
contrast, in the MI flares the reconnection proceeds with a decrease
of the longitudinal field; hence, the reconnection rate is higher
in the MI flares. <P />Since reconnection in the MI flares proceeds
with a decrease of the longitudinal field, the reconnected field lines
become shorter in this process. As the reconnected lines become shorter,
accelerated electron beams arrive at the upper chromosphere faster. So,
in the MI flares chromospheric evaporation begins earlier than in the
LI flares. The evaporation process driven by accelerated electron beams
generates upflows of “warm” (T <= 10 MK) plasma that interacts
with downflows of superhot plasma and can switch off the accumulation of
superhot plasma in the MI flares during the impulsive phase. In the LI
flares, however, an observable amount of superhot plasma is accumulated
even during the impulsive phase. Moreover, since the cooling timescales
increase with the length of the reconnected field lines, our argument
for the association of superhot plasma with longer lines may remain
valid to a reasonable extent even if the chromospheric evaporated
plasma mixes with the reconnected outflow and superhot temperatures are
reached in this mixture. Further analysis of the Yohkoh data obtained
simultaneously with the Hard and Soft X-Ray Telescopes and the bent
crystal spectrometer (BCS) is necessary to distinguish the superhot
components of chromospheric and coronal origins in different classes
of flares as well as at different phases of their development.
---------------------------------------------------------
Title: XUV Doppler Telescope Aboard Sounding Rocket
Authors: Yoshida, T.; Kano, R.; Nagata, S.; Hara, H.; Sakao, T.;
Shimizu, T.; Tsuneta, S.
1998ASSL..229..383Y Altcode: 1998opaf.conf..383Y
No abstract at ADS
---------------------------------------------------------
Title: Energy Release and Particle Acceleration in Solar Flares with
Respect to Flaring Magnetic Loops
Authors: Sakao, T.; Kosugi, T.; Masuda, S.
1998ASSL..229..273S Altcode: 1998opaf.conf..273S
No abstract at ADS
---------------------------------------------------------
Title: Summary of Coronal Hard X-Ray Sources Observed with Yohkoh/hxt
Authors: Masuda, S.; Kosugi, T.; Sakao, T.; Sato, J.
1998ASSL..229..259M Altcode: 1998opaf.conf..259M
No abstract at ADS
---------------------------------------------------------
Title: XUV Doppler telescope with multilayer optics
Authors: Hara, Hirohisa; Kano, Ryouhei; Nagata, Shin'ichi; Sakao, Taro;
Shimizu, Toshifumi; Tsuneta, Saku; Yoshida, Tsuyoshi; Kosugi, Takeo
1997SPIE.3113..420H Altcode:
We present an overview of a sounding-rocket experiment, which is
scheduled to be launched by the Institute of Space and Astronautical
Science (ISAS) in January 1998, the rising phase of the 11-year activity
cycle of the sun. The purpose of this experiment is (1) to obtain
whole-sun images taken in an XUV emission line, Fe XIV 211 angstrom,
using the normal incidence multilayer optics with a high spectral
resolution of (lambda) /(Delta) (lambda) approximately equals 40, and
(2) to carry out the velocity-field measurement with detection limit
as high as 100 km/s.
---------------------------------------------------------
Title: Development of multilayer mirrors for the XUV Doppler telescope
Authors: Nagata, Shin'ichi; Hara, Hirohisa; Sakao, Taro; Shimizu,
Toshifumi; Tsuneta, Saku; Yoshida, Tsuyoshi; Ishiyama, Wakana;
Murakami, Katsuhiko; Oshino, Tetsuya
1997SPIE.3113..193N Altcode:
We present the development status of the normal incidence XUV multilayer
mirrors for XUV Doppler telescope, which observes coronal velocity
fields of the whole sun. The telescope has two narrow band-pass
multilayer mirrors tuned to slightly longer and shorter wavelengths
around the Fe XIV line at 211.3 Angstrom. From the intensity difference
of the images taken with these two bands, we can obtain Dopplergram of
1.8 MK plasma of the whole sun. It is required that the multilayer has
high wavelength-resolution ((lambda) /(Delta) (lambda) approximately
30 per mirror), anti-reflection coating for intense He II 304 angstrom
emission line and high d-spacing uniformity of approximately 1%.
---------------------------------------------------------
Title: Hard X-ray Footpoints and Soft X-ray Loops in Solar Flares
Authors: Masuda, S.; Sakao, T.; Kosugi, T.; Sato, J.
1997SPD....28.0170M Altcode: 1997BAAS...29..892M
Yohkoh Hard X-ray Telescope (HXT) found, in the impulsive phase of
solar flares, a compact hard X-ray (HXR) source located above the
corresponding soft X-ray (SXR) loop apex observed with Yohkoh Soft
X-ray Telescope (SXT). This observation suggests that the flare primary
energy release takes place above (outside of) the bright SXR loop, and
that magnetic reconnection is responsible for the energy release. One
possible interpretation is that electrons are energized in or near the
“above-the-loop-top” HXR source where reconnection outflow impinges
the underlying loop and forms a fast MHD shock. The energized electrons
stream down along magnetic field lines to the footpoints (“double
footpoint HXR sources”) of a newly reconnected loop. This implies
that the footpoint HXR sources must be located further from the loop
center than the two ends of the loop found via SXR because reconnection
starts from innermost magnetic fields reaching the outermost ones later
and also because it takes a few minutes for the newly reconnected
loop to be filled with hot plasma and become bright in SXRs. Under
such a motivation, we have compared HXR images in the HXT M1-band a
(23-33 keV) with SXR images taken simultaneously with the SXT Be
filter. In this analysis, the center of each HXR footpoint source
represents the position of that source. For each SXR loop, first we
remove the low-intensity part (< 1/10 of the maximum brightness)
then the two ends of the remaining loop emission are taken to represent
the positions of the SXR footpoints. In seven out of the eleven cases
analyzed, we find that the footpoint HXR sources are located outside
the corresponding SXR loop footpoints. The distance between the HXR
sources is a little longer than that between the SXR loop footpoints,
on average, by ~ 0.9 +/- 1.5 arcsec. Although this result seems to be
consistent with the scenario mentioned above, this difference is not
significantly large. A further study is in progress.
---------------------------------------------------------
Title: Principles, Practical Problems, and the Performance of MEM
Imaging for the YOHKOH Hard X-ray Telescope
Authors: Kosugi, Takeo; Sato, Jun; Sakao, Taro; Masuda, Satoshi
1997SPD....28.1301K Altcode: 1997BAAS...29R.916K
The Hard X-ray Telescope (HXT) on-board Yohkoh is a Fourier-synthesis
telescope with 64 modulation collimators. Solar flare images have been
synthesized using the Maximum Entropy Method (MEM) or some other imaging
techniques from sets of the 64 photon counts. This paper reports our
recent success in improving the MEM imaging for HXT. The key factors
that led us to this success are as follows. First, modulation patterns
for the 64 individual collimators were precisely re-calibrated in orbit
using solar flares themselves as calibration sources. Note that the
patterns we had used before were based on the pre-launch calibrations
using artificial sources. Also the formulae that represent the patterns
are renewed. Second, we re-formulated the MEM principle; now the total
flux is a free parameter to be determined by the MEM principle. This new
formulation was successfully incorporated into an iterative code. Third,
the observation error terms were estimated and incorporated properly in
the MEM imaging. With these improvements, we have confirmed (i) that the
so-called over-resolution problem, sometimes misunderstood as resulting
from the MEM principle itself, disappears so that the stability of
images improves drastically, (ii) that the image quality improves
proportionally with increasing photon counts as naturally expected,
(iii) that the number of events for which MEM imaging fails decreases
(with a small number of exceptions, maybe due to large intrinsic source
size), and (iv) that the similarity between HXT L-band images and SXT
images becomes much clearer than before.
---------------------------------------------------------
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: Japanese sounding rocket experiment with the solar XUV
Doppler telescope
Authors: Sakao, Taro; Tsuneta, Saku; Hara, Hirohisa; Kano, Ryouhei;
Yoshida, Tsuyoshi; Nagata, Shin'ichi; Shimizu, Toshifumi; Kosugi,
Takeo; Murakami, Katsuhiko; Wasa, Wakuna; Inoue, Masao; Miura,
Katsuhiro; Taguchi, Koji; Tanimoto, Kazuo
1996SPIE.2804..153S Altcode:
We present an overview of an ongoing Japanese sounding rocket project
with the Solar XUV Doppler telescope. The telescope employs a pair
of normal incidence multilayer mirrors and a back-thinned CCD, and is
designed to observe coronal velocity field of the whole sun by measuring
line- of-sight Doppler shifts of the Fe XIV 211 angstroms line. The
velocity detection limit is estimated to be better than 100 km/s. The
telescope will be launched by the Institute of Space and Astronautical
Science in 1998, when the solar activity is going to be increasing
towards the cycle 23 activity maximum. Together with the overview of
the telescope, the current status of the development of each telescope
components including multilayer mirrors, telescope structure, image
stabilization mechanism, and focal plane assembly, are reviewed. The
observation sequence during the flight is also briefly described.
---------------------------------------------------------
Title: Hard and Soft X-Ray Observations of Solar Limb Flares
Authors: Mariska, John T.; Sakao, T.; Bentley, R. D.
1996ApJ...459..815M Altcode:
Using observations from the Yohkoh Bragg Crystal Spectrometer, hard
X-ray telescope, and soft X-ray telescope, we have examined eight limb
flares. Four of the flares have the footpoints occulted by the solar
limb. We find that the occulted flares generally have softer hard
X-ray spectra and smaller peak values of the nonthermal broadening
velocity than nonocculted flares. All other physical parameters show
no differences between occulted flares and nonocculted flares. The
hard X-ray spectra support a model in which the footpoint emission
is due to thick-target sources, while the looptop emission is due to
thin-target sources. High spectral resolution hard X-ray observations
should thus show a break in the hard X-ray spectrum of the looptop
source. We can find no obvious explanation for the differences in
nonthermal broadening velocity.
---------------------------------------------------------
Title: Soft X-Ray Flare Dynamics
Authors: Doschek, G. A.; Mariska, John T.; Sakao, T.
1996ApJ...459..823D Altcode:
We discuss the dynamics of four soft X-ray flares as revealed by the
X-ray resonance line profiles of the He-like ions, Fe xxv, Ca xix,
and S xv. The flares chosen for analysis belong to a subclass of
events that have intense Doppler blueshifted spectral signatures
during the rise phase. The spectra were obtained froin the Bragg
crystal spectrometer (BC S) experiment flown on the Japanese Yohkoh
spacecraft. We deconvolve the line profiles into a flare decay phase
component (stationary component) produced by nonmoving plasma with
little or no turbulent motions, and a flare rise phase component
(dynamic component) produced by bulk plasma motion and turbulence. The
dynamic component is further deconvolved into a high-speed component
(greater than 400 km s <SUP>1</SUP>) and a lower speed, more turbulent
component. We find that the dynamic and stationary components have
approximately the same electron temperature. The dynamic and stationary
component fluxes are compared with hard X-ray fluxes obtained from the
hard X-ray telescope (HXT) on Yohkoh We find that the onset time of
the high-speed dynamic component corresponds closely to the onset of
hard X-rays. We discuss the X-ray morphology of the flares as revealed
by the soft X-ray telescope (SXT) and hard X-ray telescope (HXT) on
Yohkoh. From analysis of the X-ray light curves of individual pixels in
the SXT images, we believe we have been able to determine at least some
of the locations of the dynamic component in the images. Although the
observations support many aspects of chromospheric evaporation models,
there are significant problems. No obvious rising fronts of plasma
are observed for any of the flares. There are apparent footpoint hard
X-ray sources that cannot be physically related in an obvious manner
with the main sources of soft X-ray emission. The flares are complex,
and therefore there are some ambiguities in interpretation of the
morphology.
---------------------------------------------------------
Title: Characteristics of hard X-ray double sources in impulsive
solar flares
Authors: Sakao, T.; Kosugi, T.; Masuda, S.; Yaji, K.; Inda-Koide,
M.; Makishima, K.
1996AdSpR..17d..67S Altcode: 1996AdSpR..17...67S
Imaging observations of solar flare hard X-ray sources with the Hard
X-ray Telescope aboard theYohkoh satellite have revealed that hard
X-ray emissions (> 30 keV) originate most frequently from double
sources. The double sources are located on both sides of the magnetic
neutral line, suggesting that the bulk of hard X-rays is emitted
from footpoints of flaring magnetic loops. We also found that hard
X-rays from the double sources are emitted simultaneously within a
fraction of second and that the weaker source tends to be located in
the stronger magnetic field region, showing a softer spectrum. Physical
implications on the observed characteristics of the hard X-ray double
sources are discussed.
---------------------------------------------------------
Title: YOHKOH observations of solar limb flares
Authors: Bentley, R. D.; Mariska, J. T.; Sakao, T.
1996ASPC..109..107B Altcode: 1996csss....9..107B
No abstract at ADS
---------------------------------------------------------
Title: Hard and Soft X-ray Images of an LDE Flare
Authors: Sato, J.; Kosugi, T.; Sakao, T.
1996mpsa.conf..545S Altcode: 1996IAUCo.153..545S
No abstract at ADS
---------------------------------------------------------
Title: Loop-Top Hard X-ray Source in Solar Flares
Authors: Masuda, S.; Kosugi, T.; Shibata, K.; Hara, H.; Sakao, T.
1996mpsa.conf..203M Altcode: 1996IAUCo.153..203M
No abstract at ADS
---------------------------------------------------------
Title: Imaging Spectra of Hard X-ray from the Footpoints of Solar
Impulsive Loop Flares
Authors: Takakura, T.; Kosugi, T.; Sakao, T.; Makishima, K.;
Inda-Koide, M.; Masuda, S.
1996mpsa.conf..541T Altcode: 1996IAUCo.153..541T
No abstract at ADS
---------------------------------------------------------
Title: The Weak Blue Bump of H2106-099 and Active Galactic Nuclei
Dereddening
Authors: Grossan, B.; Remillard, R. A.; Bradt, H. V.; Brissenden,
R. J.; Ohashi, T.; Sakao, T.
1996ApJ...457..199G Altcode: 1996astro.ph.11173G
We present multifrequency spectra of the Seyfert 1 galaxy H2106-099,
from radio to hard X-rays, spanning over a decade of observations. The
hard X-ray (2-20 keV) spectrum measured with Ginga was not unusual,
with a log slope (F<SUB>υ</SUB> ∝ E<SUP>α</SUP>), of -0.80±0.02
on 1988 May 18 and -1.02±0.10 on 1988 May 22/23 UT, and with no
significant observed variations in total flux. Other measurements
showed variability and unusual spectral features: The V band flux
was observed to change by a factor of 1.8 (>10 σ)in 6 weeks. Only
moderate optical Fe II emission is present, but strong [Fe VII] and [Fe
X] epochs. The Balmer lines show greater than 25% variations in flux
relative to the mean, and He I changed by more than 100% relative to
the mean in 6 yr. The most surprising finds came from the composite UV
through near-IR spectrum: If the spectrum is dereddened by the galactic
extinction value derived from 21 cm observations, a residual 2175 Å
absorption feature is present. Additional dereddening to correct the
feature yields E(B - V) = 0.07 mag due to material outside our Galaxy,
most probably associated with the active galactic nucleus (AGN) or its
host galaxy. No other clear indications of reddening are observed in
this object, suggesting that blue bump strength measurements in low
and intermediate redshift AGNs could be incorrect if derived without
UV observations of the region near 2175 A in the AGN frame. After
all reddening corrections are performed, the log slope of H2106 -099
from the near-IR (∼12500 Å) to the UV (∼1400 Å), -0.94±0.05,
is steep compared to other AGNs, suggesting that the blue bump in
this object is intrinsically weak. Weak blue bumps are, therefore,
not always an artifact caused by reddening. The spectral indices of
this object in the optical-UV region are steeper than those predicted
by optically thin free-free emission models; therefore, some other
mechanism must dominate the continuum in this region.
---------------------------------------------------------
Title: Hard and Soft X-ray Observations of Solar Limb Flares
Authors: Mariska, J. T.; Sakao, T.; Bentley, R. D.
1996mpsa.conf..523M Altcode: 1996IAUCo.153..523M
No abstract at ADS
---------------------------------------------------------
Title: Non-Thermal Processes and Superhot Plasma Creation in Solar
Flares
Authors: Sakao, T.; Kosugi, T.
1996mpsa.conf..169S Altcode: 1996IAUCo.153..169S
No abstract at ADS
---------------------------------------------------------
Title: Coordinated OVRO, BATSE, Yohkoh, and BBSO Observations of
the 1992 June 25 M1.4 Flare
Authors: Wang, H.; Gary, D. E.; Zirin, H.; Schwartz, R. A.; Sakao,
T.; Kosugi, T.; Shibata, K.
1995ApJ...453..505W Altcode:
We compare 1-14 GHz microwave images observed at the Owens Valley Radio
Observatory (OVRO), 16- and 256-channel hard X-ray spectra obtained by
the Burst and Transient Source Experiment (BATSE) onboard the Compton
Gamma Ray Observatory (CGRO), soft and and hard X-ray images obtained
by Yohkoh, and Hα images and magnetograms observed at the Big Bear
Solar Observatory (BBSO) for the 1992 June 25 M1.4 flare. We find the
following unique properties for this flare: (1) Soft X-ray emissions
connect two foot- points, the primary microwave source is located at
one footpoint, and hard X-ray emissions are concentrated in the other
footpoint The radio footpoint is associated with an umbra and may
have stronger magnetic field. (2) During the period that 256-channel
BATSE data are available, the hard X-ray photon spectrum consists
of two components: a superhot component with a temperature of 8.4
× 10<SUP>7</SUP> K and emission measure of 2.5 × 10<SUP>46</SUP>
cm<SUP>-3</SUP> and a power-law component with a photon index of
4.2. This is the first time that such a high temperature is reported
for the hard X-ray thermal components. It is even more interesting
that such a superhot component is identified before the peak of the
flare. The microwave brightness temperature spectra during the same
period also demonstrate two components: a thermal component near the
loop top and a nonthermal component at the footpoint of the loop. The
microwave thermal component has the similar temperature as that of
the hard X-ray superhot component. These measurements are consistent
with the theory that the microwaves and hard X-rays are due to the
same group of electrons, despite the fact that they are separated by
35,000 km. (3) The soft X-ray emissions brighten the existing loops and
co-align with Hα emissions throughout the entire duration of the flare.
---------------------------------------------------------
Title: Microwave and Hard X-Ray Observations of Footpoint Emission
from Solar Flares
Authors: Kundu, M. R.; Nitta, N.; White, S. M.; Shibasaki, K.; Enome,
S.; Sakao, T.; Kosugi, T.; Sakurai, T.
1995ApJ...454..522K Altcode:
We investigate radio and X-ray imaging data for two solar flares in
order to test the idea that asymmetric precipitation of nonthermal
electrons at the two ends of a magnetic loop is consistent with the
magnetic mirroring explanation. The events we present were observed in
1993 May by the HXT and SXT X-ray telescopes on the Yohkoh spacecraft
and by the Nobeyama 17 GHz radioheliograph. The hard X-ray images in
one case show two well-separated sources; the radio images indicate
circularly polarized, nonthermal radio emission with opposite polarities
from these two sources, indicating oppositely directed fields and
consistent with a single-loop model. In the second event there are
several sources in the HXT images which appear to be connected by
soft X-ray loops. The strongest hard X-ray source has unpolarized
radio emission, whereas the strongest radio emission lies over strong
magnetic fields and is polarized. In both events the strongest radio
emission is highly polarized and not coincident with the strongest
hard X-ray emission. This is consistent with asymmetric loops in
which the bulk of the precipitation (and hence the X-ray emission)
occurs at the weaker field footpoint.
---------------------------------------------------------
Title: Hard X-Ray Sources and the Primary Energy-Release Site in
Solar Flares
Authors: Masuda, Satoshi; Kosugi, Takeo; Hara, Hirohisa; Sakao, Taro;
Shibata, Kazunari; Tsuneta, Saku
1995PASJ...47..677M Altcode:
Accurately coaligned hard and soft X-ray images, taken simultaneously
with the Hard X-ray Telescope (HXT) and the Soft X-ray Telescope
(SXT) aboard Yohkoh, of impulsive solar flares on 1992 January 13
(17:29 UT), 1992 October 4 (22:21 UT), and 1993 February 17 (10:35
UT), occurring near the limb, clearly reveal that, in addition to
double-footpoint sources, a hard X-ray source exists well above the
corresponding soft X-ray loop structure around the peak time of the
impulsive phase. This hard X-ray source shows an intensity variation
similar to double-footpoint sources and a spectrum that is relatively
hard compared with that of loop-top gradual source which appeared later
in the flare. We believe that this is the first clear evidence that
magnetic reconnection, which is responsible for the primary flare energy
release, is under progress above the soft X-ray flaring loop. Maybe
this “loop-top” hard X-ray source represents the reconnection site
itself or the site where the downward plasma stream, ejected from
the reconnection point far above the hard X-ray source, collides with
the underlying closed magnetic loop. The characteristics of this hard
X-ray source are quantitatively discussed in the schemes of thermal
(T >~ 10(8) K) and nonthermal interpretations of hard X-ray emission.
---------------------------------------------------------
Title: YOHKOH SXT/HXT Observations of a Two-Loop Interaction Solar
Flare on 1992 December 9
Authors: Inda-Koide, Mika; Sakai, Jun-Ichi; Koide, Shinji; Kosugi,
Takeo; Sakao, Taro; Shimizu, Toshifumi
1995PASJ...47..323I Altcode:
Observations with the Soft X-ray and Hard X-ray Telescopes aboard Yohkoh
of a simple solar flare on 1992 December 9 are discussed. The soft X-ray
morphology suggests evidence of a loop-loop interaction mechanism:
the images reveal two parallel magnetic loops prior to the flare,
and their merging just before onset of the hard X-ray burst. This
flare therefore provides a chance to examine the two-loop interaction
model for solar flares. It is found (1) that the observed soft X-ray
behavior of the two loops in the preflare phase well matches to the
two-loop interaction model between strong and weak current loops and
(2) that the observed time scale of the two-loop coalescence is almost
equal to that estimated from explosive-reconnection theory. In the
impulsive phase, it is found (3) that the loop-top portion near to the
interaction region first brightens in the 14--23 keV hard X-rays and (4)
that the 23--33 keV hard X-ray emission around the peak time originates
dominantly from two compact sources at the two ends of the merging
loops. These hard X-ray observations are explained by high-energy
electrons that are produced in the two current loop interaction.
---------------------------------------------------------
Title: Imaging Spectra of Hard X-Rays from the Footpoints of Solar
Impulsive Loop Flares
Authors: Takakura, Tatsuo; Kosugi, Takeo; Sakao, Taro; Makishima,
Kazuo; Inda-Koide, Mika; Masuda, Satoshi
1995PASJ...47..355T Altcode:
The imaging spectra of hard X-rays emitted from one or both footpoints
of solar impulsive loop flares seem to frequently show a better fit
to an extremely hot thermal spectrum, on the order of 10(8) K, than to
a power-law spectrum, in the main phase of the bursts. In the present
study this tendency has been verified by the spectra of nine impulsive
bursts having a sufficient flux for reliable imaging in the H-band
(52.7--92.8 keV) of the hard X-ray telescope (HXT) aboard the Yohkoh
spacecraft. The spectral indexes at the footpoints were derived from the
hard X-ray images in four energy bands of the HXT; their reliability was
verified by mapping simulations. Since the X-ray spectrum depends on the
location in the X-ray loop, the spectrum of the total flux is generally
different from the spatially resolved spectra. The imaging spectrum is
thus crucial for studying the nature of the electrons emitting hard
X-rays. The heat conduction of an extremely hot quasi-thermal plasma
seems to play an essential role in impulsive loop flares.
---------------------------------------------------------
Title: Hard and Soft X-Ray Observations of Solar Limb Flares
Authors: Mariska, J. T.; Sakao, T.; Bentley, R. D.
1995SPD....26.1312M Altcode: 1995BAAS...27..989M
No abstract at ADS
---------------------------------------------------------
Title: Coordinated X-ray and Hα Observations of Eruptive Flares
Authors: Wülser, J. -P.; Canfield, R. C.; Sakao, T.; Acton, L. W.
1995SPD....26.1315W Altcode: 1995BAAS...27..990W
No abstract at ADS
---------------------------------------------------------
Title: Evolution of a Flare Source Inferred from Hard X-Ray and
Radio Observations: Solar Burst on 1992 October 27
Authors: Takakura, Tatsuo; Nishio, Masanori; Nakajima, Hiroshi; Enome,
Shinzo; Shibasaki, Kiyoto; Takano, Toshiaki; Hanaoka, Yoichiro; Kosugi,
Takeo; Sakao, Taro; Masuda, Satoshi; Makishima, Kazuo; Inda-Koide, Mika
1994PASJ...46..653T Altcode:
An impulsive burst which occurred on 1992 October 27 was observed
simultaneously with the hard X-ray telescope on board the Yohkoh
satellite and the Nobeyama Radioheliograph at 17 GHz. The hard X-ray
images show a double-source structure during the main phase. One
footpoint, A, shows a nonthermal spectrum, while another, B, shows
a better fit to the X-rays from extremely hot thermal electrons
with about 80 million degrees, flowing into the chromosphere. The
loop top also shows a better fit to a quasi-thermal spectrum of 75
million degrees at the main peak. On the other hand, the radio images
are a larger single source covering the X-ray source, and are highly
polarized in the L-sense. The larger single image is mainly ascribed
to the beamwidth, and the single polarization may be due to “limiting
polarization". Consequently, the radio source at 17 GHz may be cospatial
with the X-ray source around the loop top. The radio emission at 17 GHz
and a part of the emission at 9.4 GHz are attributed to the thermal
gyro emissions from the extremely hot thermal electrons emitting the
X-rays. The rest of the radio emission at 9.4 GHz and the emission at
3.75 GHz are ascribed to thermal gyro emission at the outer layers
with smaller magnetic fields and lower electron temperatures. The
intense radio emission at 35 GHz at the main peak is ascribed to
gyro-synchrotron emission from the nonthermal electrons in footpoint A.
---------------------------------------------------------
Title: Yohkoh observations of the creation of high-temperature plasma
in the flare of 16 December 1991
Authors: Culhane, J. L.; Phillips, A. T.; Inda-Koide, M.; Kosugi,
T.; Fludra, A.; Kurokawa, H.; Makishima, K.; Pike, C. D.; Sakao, T.;
Sakurai, T.; Doschek, G. A.; Bentley, R. D.
1994SoPh..153..307C Altcode:
Yohkoh observations of an impulsive solar flare which occurred on 16
December, 1991 are presented. This flare was a GOES M2.7 class event
with a simple morphology indicative of a single flaring loop. X-ray
images were taken with the Hard X-ray Telescope (HXT) and soft X-ray
spectra were obtained with the Bragg Crystal Spectrometer (BCS)
on board the satellite. The spectrometer observations were made at
high sensivity from the earliest stages of the flare, are continued
throughout the rise and decay phases, and indicate extremely strong
blueshifts, which account for the majority of emission in CaXIX during
the initial phase of the flare. The data are compared with observations
from other space and ground-based instruments. A balance calculation
is performed which indicates that the energy contained in non-thermal
electrons is sufficient to explain the high temperature plasma which
fills the loop. The cooling of this plasma by thermal conduction
is independently verified in a manner which indicates that the loop
filling factor is close to 100%. The production of `superhot' plasma
in impulsive events is shown to differ in detail from the morphology
and mechanisms appropriate for more gradual events.
---------------------------------------------------------
Title: Particle Acceleration in Flares
Authors: Benz, A. O.; Kosugi, T.; Aschwanden, M. J.; Benka, S. G.;
Chupp, E. L.; Enome, S.; Garcia, H.; Holman, G. D.; Kurt, V. G.;
Sakao, T.; Stepanov, A. V.; Volwerk, M.
1994SoPh..153...33B Altcode:
Particle acceleration is intrinsic to the primary energy release in
the impulsive phase of solar flares, and we cannot understand flares
without understanding acceleration. New observations in soft and hard
X-rays, γ-rays and coherent radio emissions are presented, suggesting
flare fragmentation in time and space. X-ray and radio measurements
exhibit at least five different time scales in flares. In addition,
some new observations of delayed acceleration signatures are also
presented. The theory of acceleration by parallel electric fields is
used to model the spectral shape and evolution of hard X-rays. The
possibility of the appearance of double layers is further investigated.
---------------------------------------------------------
Title: Hard and Soft X-ray Observations of a Super-Hot Thermal Flare
of 6 February, 1992
Authors: Kosugi, T.; Sakao, T.; Masuda, S.; Hara, H.; Shimizu, T.;
Hudson, H. S.
1994kofu.symp..127K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Comparison of Hard X-ray, Soft X-ray, and Microwave Sources
in Solar Flares
Authors: Yaji, K.; Kosugi, T.; Sakao, T.; Masuda, S.; Inda-Koide,
M.; Hanaoka, Y.
1994kofu.symp..143Y Altcode:
Hard X-ray, soft X-ray, and microwave images of about 20 solar flares
that occurred in NOAA 7270 are compared for investigating where
electrons are energized and emit hard X-rays. We find the following:
(i) Usually hard X-ray sources appear inside a soft X-ray flaring
loop or loops. The hard X-ray emission tends to originate from the two
ends of the soft X-ray loop in the impulsive phase (double footpoint
sources), and later the double sources evolve into a single source
located near the loop top (loop-top gradual source). (ii) In a few
cases, another impulsive hard X-ray source with comparable intensity
with the double footpoint sources appears at a site remote from the
footpoint sources. This source shows only weak brightening in soft
X-rays but is bright in microwaves.
---------------------------------------------------------
Title: Hard X-ray Imaging Observations of Footpoint Sources in
Impulsive Solar Flares
Authors: Sakao, T.; Kosugi, T.; Masuda, S.; Yaji, K.; Inda-Koide,
M.; Makishima, K.
1994kofu.symp..169S Altcode:
Hard X-ray imaging observations of intense impulsive flares with the
Yohkoh Hard X-ray Telescope have revealed that the hard X-ray emission
in an energy range above 30 keV originates most frequently from double
sources, suggesting that bulk of hard X-rays is emitted from footpoints
of flaring magnetic loops. Temporal and spectral behaviors of the
double sources are described and their physical implications discussed.
---------------------------------------------------------
Title: Evolution of an Active Region and Flare Productivity
Authors: Kundu, M. R.; Shibasaki, K.; Enome, S.; Nitta, N.; Bruner,
M.; Sakao, T.; Kosugi, T.
1994kofu.symp..353K Altcode:
We have studied the evolution of an active region (AR 7515) in terms
of flare productivity. This region appears at the east limb on May 23,
1993 and then continues its onward march across the disk. We follow
its evolution until June 2. This region produces many small flares. We
study the topology, both magnetic and structural of the neighboring
regions as observed at 17 GHz by the Nobeyama Radio Heliograph (NRH)
and the Yohkoh/SXT to find their effects on the flare-producing AR. We
investigate the spatial structure of the flaring region from 17 GHz
and SXT maps during various times of the impulsive and decay phase,
to understand the difference in the flaring region spatial structure
during the preflare, impulsive and decay phases. In general, the maps
made during these phases show several loops. We try to relate these
flaring loops with the preflare active region structure.
---------------------------------------------------------
Title: H_alpha and X-ray Signatures of Chromospheric Heating Observed
in Solar Flares
Authors: Wuelser, J. -P.; Canfield, R. C.; Sakao, T.; Masuda, S.;
Kosugi, T.; Tsuneta, S.
1994kofu.symp..195W Altcode:
We have studied the spatial and temporal relationship between
thermal and non-thermal energy transport, and the chromospheric
response in solar flares. H_alpha imaging spectra from Mees Solar
Observatory provided the information on the heating and dynamics in the
chromosphere, soft X-ray images from Yohkoh provided the conditions
of the thermal plasma in the corona, and hard X-ray data from Yohkoh
provided the diagnostics of the non-thermal particles. We present
some preliminary results for several large flares, and discuss their
implications for the chromospheric flare heating mechanism.
---------------------------------------------------------
Title: Alignment of Radio, Soft X-ray, Hard X-ray Images of Sources
in Impulsive and Gradual Phases of the Flare of 1992 August 17-18
Authors: Enome, S.; Nakajima, H.; Shibasaki, K.; Nishio, M.; Takano,
T.; Hanaoka, Y.; Torii, C.; Shiomi, Y.; Sekiguchi, H.; Bushimata,
T.; Kawashima, S.; Shinohara, N.; Irimajiri, Y.; Koshiishi, H.; Choi,
Y. -S.; Sakai, J.; Takahashi, M.; Takakura, T.; Sakao, T.; Kosugi, T.
1994kofu.symp..141E Altcode:
This is a preliminary report concerning an impulsive flare, which
occurred on 1992 August 17-18, and was observed with the Nobeyama
Radioheliograph, Yohkoh, and ground-based instruments. Emphasis is put
on the alignment of radio images as well as soft X-ray and hard X-ray
maps, which are compared in both impulsive and gradual phases. In the
impulsive phase, which continued for about 30 s, nonthermal emission
was most remarkable at 17 GHz, and was also seen in hard X-rays at the
southern part of the SXT source, which was about 14" width and 80"
long, extending in the north-east to south-west direction. Thermal
emission was detected in soft X-rays and possibly in hard X-rays at the
northern part. During the gradual phase, about 80 s after the onset of
the impulsive phase, thermal emission dominated and was located at the
northern part of the source over the entire energy range. Difficulties
are discussed concerning a possible simple topology of the magnetic
fields. Note:This is the abstract of the Letter published PASJ 46,
L27-31(1994)
---------------------------------------------------------
Title: Characteristics of solar flare hard X-ray sources as revealed
with the Hard X-ray Telescope aboard the Yohkoh satellite
Authors: Sakao, T.
1994PhDT.......335S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Alignment of Radio, Soft X-Ray, Hard X-Ray Images of Sources
in Impulsive and Gradual Phases of the Flare of 1992 August 17--18
Authors: Enome, Shinzo; Nakajima, Hiroshi; Shibasaki, Kiyoto; Nishio,
Masanori; Takano, Toshiaki; Hanaoka, Yoichiro; Torii, Chikayoshi;
Shiomi, Yasuhiko; Sekiguchi, Hideaki; Bushimata, Takeshi; Kawashima,
Susumu; Shinohara, Noriyuki; Irimajiri, Yoshihisa; Koshiishi, Hideki;
Choi, Yong-Seok; Sakai, Jun-Ichi; Takahashi, Masaaki; Takakura,
Tatsuo; Sakao, Taro; Kosugi, Takeo
1994PASJ...46L..27E Altcode:
This is a preliminary report concerning an impulsive flare, which
occurred on 1992 August 17--18, and was observed with the Nobeyama
Radioheliograph, Yohkoh, and ground-based instruments. Emphasis is put
on the alignment of radio images as well as soft X-ray and hard X-ray
maps, which are compared in both impulsive and gradual phases. In the
impulsive phase, which continued for about 30 s, nonthermal emission
was most remarkable at 17 GHz, and was also seen in hard X-rays at the
southern part of the SXT source, which was about 14” width and 80”
long, extending in the north-east to south-west direction. Thermal
emission was detected in soft X-rays and possibly in hard X-rays at the
northern part. During the gradual phase, about 80 s after the onset of
the impulsive phase, thermal emission dominated and was located at the
northern part of the source over the entire energy range. Difficulties
are discussed concerning a possible simple topology of the magnetic
fields.
---------------------------------------------------------
Title: Multispectral Observations of Chromospheric Evaporation in
the 1991 November 15 X-Class Solar Flare
Authors: Wuelser, Jean-Pierre; Canfield, Richard C.; Acton, Loren W.;
Culhane, J. Leonard; Phillips, Andrew; Fludra, Andrzej; Sakao, Taro;
Masuda, Satoshi; Kosugi, Takeo; Tsuneta, Saku
1994ApJ...424..459W Altcode:
We analyze simultaneous H(alpha) images and spectra (from Mees
Solar Observatory), and soft and hard X-ray images and spectra (from
YOHKOH) during the early phase of an X1.5/3B flare. We investigate
the morphological relationship between chromospheric downflows,
coronal upflows, and particle precipitation sites, and the energetic
relationship between conductive heating, nonthermal particle heating,
and the chromospheric response. We find that the observations
consistently fit the chromospheric evaporation model. In particular,
we demonstrate that the observed upflowing coronal and downflowing
chromospheric plasma components originate in the same locations,
and we show that our unique set of optical and X-ray observations
can clearly distinguish between conductively driven and electron beam
driven evaporation.
---------------------------------------------------------
Title: Impulsive Behavior in Solar Soft X-Radiation
Authors: Hudson, H. S.; Strong, K. T.; Dennis, B. R.; Zarro, D.;
Inda, M.; Kosugi, T.; Sakao, T.
1994ApJ...422L..25H Altcode:
The Yohkoh soft X-ray telescope has observed impulsive, thermal,
soft X-ray emission at the footpoints of magnetic loops during solar
flares. The soft X-ray (thermal) time profiles at the footpoints closely
match the hard X-ray (nonthermal) time profiles, directly demonstrating
the heating of the lower solar atmosphere on short timescales during
the interval of nonthermal energy release. This phenomenon is the rule,
rather than the exception, occurring in the majority of flares that
we have examined with the Yohkoh data. We illustrate the impulsive
behavior with data from the major flare of 1992 January 26. For this
flare, the soft X-ray peak times matched the hard X-ray peak times
within the time resolution of the soft X-ray measurements (about 10 s),
and the soft and hard X-ray locations match within the resolution of
the hard X-ray imager. The impulsive soft X-ray emission clearly has
a thermal spectral signature, but not at the high temperature of a
'superhot' source. We conclude that the impulsive soft X-ray emission
comes from material heated by precipitating electrons at loop footpoints
and evaporating from the deeper atmosphere into the flaring flux tube.
---------------------------------------------------------
Title: Time Variation of Hard X-Ray Image in the Early Phase of
Solar Impulsive Bursts
Authors: Takakura, T.; Inda, M.; Makishima, K.; Masuda, S.; Kosugi,
T.; Sakao, T.; Sakurai, T.; Ogawara, Y.
1994xspy.conf...71T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Particle Acceleration in the 15 November, 1991 Solar Flare
Observed with HXT
Authors: Sakao, T.; Kosugi, T.; Masuda, S.; Yaji, K.; Inda-Koide,
M.; Makishima, K.
1994xspy.conf...91S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HXT observations of non-thermal hard X-ray sources in solar
flares.
Authors: Sakao, T.; HXT Team
1994clis.conf..107S Altcode:
The author describes the HXT experiment, from its historical background
of hard X-ray flare observations, through the instrumentation, to
newly acquired scientific results.
---------------------------------------------------------
Title: HXT Observations of the 24 October, 1991, M9.8 Flare
Authors: Masuda, S.; Kosugi, T.; Sakao, T.
1994xspy.conf..123M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Flare of 16 December 1991
Authors: Culhane, J. L.; Phillips, A.; Pike, D.; Inda, M.; Kosugi,
T.; Sakao, T.
1994xspy.conf...95C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Initial Fifteen Months of Flare Observation with the
YOHKOH Hard X-Ray Telescope (hxt)
Authors: Kosugi, T.; Sakao, T.; Makishima, K.; Murakami, T.; Masuda,
S.; Inda-Koide, M.; Yaji, K.; Sawa, M.; Ogawara, Y.
1994xspy.conf....5K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hα and X-Ray Signatures of Chromospheric Evaporation Observed
during the Early Phase of the 15 November 1991 Flare
Authors: Wülser, J. -P.; Canfield, R. C.; Acton, L. W.; Culhane,
J. L.; Phillips, A.; Fludra, A.; Sakao, T.; Masuda, S.; Kosugi, T.
1994xspy.conf...75W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: YOHKOH HXT Observations of a Solar Flare on 16 December, 1991
Authors: Inda-Koide, M.; Makishima, K.; Kosugi, T.; Sakao, T.
1994xspy.conf...99I Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time Variation of the Hard X-Ray Image during the Early Phase
of Solar Impulsive Bursts
Authors: Takakura, Tatsuo; Inda, Mika; Makishima, Kazuo; Kosugi, Takeo;
Sakao, Taro; Masuda, Satoshi; Sakurai, Takashi; Ogawara, Yoshiaki
1993PASJ...45..737T Altcode:
The time variations of hard X-ray images of four impulsive bursts with
simple source structures were investigated in a comparison with the
magnetic structure. Two of them are limb bursts. Common variations
during the early phase are as follows: i) The hard X-ray brightening
seems to start at the top of a single coronal loop. ii) The X-ray
source spreads during the increasing phase of the burst in both
directions along the loop, and both ends become brighter, especially
at higher energies with generally unequal brightness. The loop top is
still bright, especially at lower energies, to show three peaks. The
speed of the expansion of the X-ray source amounts to about 10(4) km
s(-1) in three cases. iii) At and after the peak of the X-ray flux,
the source tends to be a single source at the loop top, especially
at lower energies. iv) The effective temperature for quasi-thermal
electrons and their number density during the early phase in the
vicinity of the loop top are (4--6)times 10(7) K and (5--2)times 10(9)
cm(-3) , respectively, so that the electron mean free path is greater
than three-times the local temperature scale height. These observations
are consistent with the idea that anomalous resistivity, which triggers
impulsive bursts, is caused by electron plasma waves generated in the
process of heat conduction.
---------------------------------------------------------
Title: Survey of Loop-Footpoint Brightenings During the Impulsive
Phase of Flares
Authors: Strong, K.; Dennis, B.; Hudson, H.; Kosugi, T.; Sakao, T.
1993BAAS...25Q1187S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Impulsive Soft X-Ray Emission in Solar Flares
Authors: Hudson, H. S.; Strong, K. T.; Dennis, B. R.; Zarro, D.;
Inda, M.; Kosugi, T.; Sakao, T.
1993BAAS...25.1177H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: OVRO Microwave and Yohkoh HXT and SXT Observations of a
Solar Flare
Authors: Gary, D. E.; Hurford, G. J.; Sakao, T.
1993BAAS...25.1180G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Yohkoh-SXT Observations from the Spartan and Nixt Max91
Campaign
Authors: Morrison, M.; Bruner, M.; Freeland, S.; Lemen, J.; Linford,
G.; Nitta, N.; Slater, G.; Strong, K.; Hara, H.; Kano, R.; Shimizu,
T.; Tsuneta, S.; Hudson, H.; Ogawara, Y.; Kosugi, T.; Sakao, T.;
Watanabe, T.; Takeda, A.; Acton, L.
1993BAAS...25.1213M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hard X-Ray Imaging Observations by YOHKOH of the 15 November
1991 Flare (Invited)
Authors: Sakao, Taro
1993ASPC...46..258S Altcode: 1993mvfs.conf..258S; 1993IAUCo.141..258S
No abstract at ADS
---------------------------------------------------------
Title: Correlation between X-ray Temporal Variability and Magnetic
Environment in Solar Flares
Authors: Nitta, N.; Harvey, K.; Hudson, H.; Ichimoto, K.; Metcalf,
T.; Mickey, D.; Sakai, J. -I.; Sakao, T.; Sakurai, T.; Takahashi, M.
1992AAS...181.5503N Altcode: 1992BAAS...24.1211N
The X-ray time history of a solar flare can reflect basic processes of
heating and/or acceleration, which in turn may depend on the magnetic
environment of the site. Some flares show a simple rise and fall
temporal behavior, whereas others show more than one peak. Comparisons
of images taken by the Soft X-ray Telescope (SXT) aboard the Yohkoh
spacecraft with ground-based magnetic data (Hawaii, Kitt Peak and
Mitaka) reveal that, at least for a flare-productive active region
(NOAA 7260), flares with double-peaked and single-peaked time profiles
occurred at systematically different locations within the region. We
discuss this result in terms of theoretical models, especially those
of coalescence of two current loops.
---------------------------------------------------------
Title: The Hard X-Ray Telescope (HXT) Onboard Yohkoh: Its Performance
and Some Initial Results
Authors: Kosugi, Takeo; Sakao, Taro; Masuda, Satoshi; Makishima,
Kazuo; Inda, Mika; Murakami, Toshio; Ogawara, Yoshiaki; Yaji, Kentaro;
Matsushita, Kyoko
1992PASJ...44L..45K Altcode:
More than two hundred solar flares, including several GOES X-class
events, were successfully observed with the Hard X-ray Telescope (HXT)
on board Yohkoh during the initial six months of observations since 1991
October. Hard X-ray images taken simultaneously in four X-ray energy
bands (14--23--33--53--93 keV), with angular and temporal resolutions
of ~ 5 ” and 0.5 s, respectively, have been revealing how and where
hard X-rays are emitted in flaring magnetic loops, and further how and
where electrons are accelerated and confined. These HXT observations
are briefly reviewed from the viewpoint of the instrument capability
and performance, with some new scientific results.
---------------------------------------------------------
Title: The X Flare of 1991 November 15: Coordinated Mees/Yohkoh
Observations
Authors: Canfield, Richard C.; Hudson, Hugh S.; Leka, K. D.; Mickey,
Donald L.; Metcalf, Thomas R.; Wuelser, Jean-Pierre; Acton, Loren W.;
Strong, Keith T.; Kosugi, Takeo; Sakao, Taro; Tsuneta, Saku; Culhane,
J. Leonard; Phillips, Andrew; Fludra, Andrzej
1992PASJ...44L.111C Altcode:
This is a preliminary report on two unique new results from coordinated
observations at Mees Solar Observatory and Yohkoh of the X1.5 flare
of 1991 November 15, using vector magnetograms, Hα imaging spectra,
X-ray images, and X-ray spectra. First, we find a close spatial
relationship between Hα redshifts and X-rays from a flare loop and
its footpoints at a time of large X-ray blueshifts. Second, we find
that impulsive-phase hard X-rays originate in regions that are near,
but not coincident with, the peaks of the vertical electrical current
density distribution in AR 6919.
---------------------------------------------------------
Title: Hard X-Ray Imaging Observations by YOHKOH of the 1991 November
15 Solar Flare
Authors: Sakao, Taro; Kosugi, Takeo; Masuda, Satoshi; Inda, Mika;
Makishima, Kazuo; Canfield, Richard C.; Hudson, Hugh S.; Metcalf,
Thomas R.; Wuelser, Jean-P.; Acton, Loren W.; Ogawara, Yoshiaki
1992PASJ...44L..83S Altcode:
We report on hard X-ray imaging observations of the 1991 November 15
flare with the HXT instrument aboard {Yohkoh}. Distributions of the hard
X-ray sources at various stages of the flare, together with an overlay
of the white-light flare, are presented. Attention is concentrated on
the behavior of hard X-ray sources during the impulsive phase. The
hard X-ray source appeared initially as a single source near the
magnetic neutral line, then evolved into a double-source shape with the
separation increasing with time. We believe that this is evidence for a
multiple loop system flaring successively with a rising energy-release
site. At the minima between the individual spikes of the time profile,
the hard X-rays at 20--30 keV were concentrated near the apex of the
flaring loop, whereas the hard X-rays above 30 keV originated from the
footpoints. These observations are compared with the existing models.
---------------------------------------------------------
Title: November 15, 1991 X Flare -- The Movie: Hα , Soft X-rays,
and Hard X-rays and Magnetic Fields
Authors: Wulser, J. -P.; Acton, L.; Sakao, T.; Canfield, R.; Kosugi,
T.; Slater, G.; Strong, K.; Tsuneta, S.
1992AAS...180.3003W Altcode: 1992BAAS...24..775W
The X1.5/3B flare on 1991 November 15, 22:33 UT was well observed
by the Hα Imaging Spectrograph and the Vector Magnetograph
(Stokes Polarimeter) at Mees Solar Observatory, and by the Soft-
and Hard X-ray Telescopes (SXT and HXT) aboard YOHKOH. We have
combined this multispectral dataset into a series of temporally and
spatially co-aligned video movies and analyzed the morphological
and temporal relationships of the various flare emissions. The
earliest manifestations of this flare include unresolved preflare SXR
brightenings very close to the magnetic neutral line and preflare
motions of filaments seen in Hα . In the flare core, SXR and Hα
emission show moving and rotating coronal structures which we interpret
as a successive brightening of adjacent loops during the main phase
of the flare. The HXR source shows much more dramatic variability
than the SXR source, and they are clearly not cospatial. On the other
hand, there is a close spatial relationship between the HXR and Hα
blue wing emission sites. The Hα , HXR, and SXR images all point to
acceleration and heating in a region that starts close to the neutral
line and moves outward during each HXR burst and during the gradual
phase. Spectacular mass ejections are seen in both SXR and Hα , with
clear unwinding of tightly coiled structures, acceleration of X-ray
and Hα material to velocities of order 1000 km/s, and a striking
thermal bifurcation between hot and cold plasma.
---------------------------------------------------------
Title: Preliminary Results from HXT Aboard YOHKOH
Authors: Kosugi, T.; Sakao, T.; Masuda, S.; Makishima, K.; Inda, M.;
Yaji, K.; Matsushita, K.; Ogawara, Y.
1992AAS...180.2302K Altcode: 1992BAAS...24..759K
Several hundred solar flares, including several X-class flares, have
been observed successfully with the Hard X-ray Telescope (HXT) aboard
YOHKOH during the initial six-month observation period. The hard X-ray
images taken simultaneously in four energy bands covering from 15 to
100 keV with angular and temporal resolution of about 5 arcsec and 0.5
s, respectively, reveal the acceleration and confinement mechanisms of
energetic electrons in solar flares, with the aid of soft X-ray images
also taken by YOHKOH and ground-based observations. This paper provides
the following: (i), a summary of the instrumental performance of HXT
from the point of view of its science capability, i.e., sensitivity,
imaging quality, etc.; (ii), a statistical derivation of the average
height of hard X-ray sources (dependent on the observing photon
energies) and a comparison with existing theories; (iii), case studies
of source characteristics of several well-observed flares.
---------------------------------------------------------
Title: Soft X-ray Blueshifts and Hα Redshifts in the November 15,
1991 X-Class Flare
Authors: Wulser, J. -P.; Acton, L.; Canfield, R.; Culhane, L.; Fludra,
A.; Masuda, S.; Phillips, A.; Sakao, T.
1992AAS...180.1805W Altcode: 1992BAAS...24..755W
We analyzed simultaneous Hα line profile observations (from Mees Solar
Observatory), CaXIX line profile observations (from the Bragg Crystal
Spectrometer aboard YOHKOH), and soft- and hard X-ray images (from SXT
and HXT on YOHKOH) of the November 15, 1991 X-class flare. The observed
CaXIX emission shows strong blueshifts very early in the flare. The soft
X-ray images suggest that this blueshifted emission originates from
one or more of three localized soft X-ray bright points. At the same
time, the Hα line profile shows redshifted and blueshifted emission
in several locations. Two Hα redshift kernels are associated with the
two brightest soft X-ray sources. On the basis of their relationship
to the magnetic neutral line and their subsequent development, we
conclude that these Hα redshift kernels are the footpoints of a
single loop, which initially exhibits two soft X-ray bright points
in the loop legs. The results suggest that chromospheric evaporation
is the responsible mechanism for the observed Hα redshifts and CaXIX
blueshifts in the early stage of the flare. The independent hard X-ray
(HXT) and Hα observations both indicate that this chromospheric
evaporation is not associated with strong non-thermal electron
precipitation. The third soft X-ray bright point, the faintest of the
three, is not associated with redshifted Hα emission. This bright spot
develops into a connection between the second Hα redshift kernel,
and another Hα kernel with strong blueshifts. The Hα blueshift is
associated with a mass ejection phenomenon.
---------------------------------------------------------
Title: Electric Currents and Hard X-ray Images in the X Class Flare
of November 15, 1991
Authors: Metcalf, T. R.; Sakao, T.; Acton, L. W.; Canfield, R. C.;
Hudson, H. S.; Inda, M.; Kosugi, T.; Wulser, J. P.
1992AAS...180.3005M Altcode: 1992BAAS...24..776M
We present co-aligned observations of hard x-rays observed with the
Hard X-ray Telescope (HXT) on board the YOHKOH spacecraft and vertical
electric currents derived from a vector magnetogram obtained at the
Mees Solar Observatory, Haleakala, Hawaii. Previous work comparing
the wings of the Hα line to vertical electric currents has suggested
that electron precipitation in flares occurs at the edges of these
currents. The Stark wings of Hα were interpreted as a signature of
non-thermal electrons penetrating the relatively dense chromosphere and
used as a proxy for direct observation of the non-thermal electrons. The
hard X-rays used in this study provide a direct determination of
the locations of the electron energy losses. In the X class flare
of November 15, 1991, we find the same relation between hard X-ray
emission and vertical electric currents as was found between Hα Stark
wing emission and vertical currents: the hard x-ray emission occurs
predominantly at the edges of the vertical current sites, and not
spatially on top of these currents. Canfield, R. C., de La Beaujardiere,
J., and Leka, K. D., in “The Physics of Solar Flares", ed. Culhane and
Jordan, The Royal Society, London, 1991 Canfield, R. C., Leka, K. D.,
and Wulser,J. P., in “Flare Physics in Solar Activity Maximum 22",
ed. Uchida, Canfield, Watanabe, and Hiei, Springer-Verlag, Berlin, 1991
---------------------------------------------------------
Title: Hard X-rays from the contact binary VW Cephei.
Authors: Tsuru, T.; Makishima, K.; Ohashi, T.; Sakao, T.; Pye, J. P.;
Williams, O. R.; Barstow, M. A.; Takano, S.
1992MNRAS.255..192T Altcode:
Ginga observations of the contact binary VW Cep are presented. The
observed X-ray luminosity is 1.1 x 10 exp 30 erg/s in the energy range
of 2-10 keV, assuming a distance of 31 pc. No evidence for X-ray
orbital modulation or for flare events was detected. The observed
X-ray spectrum is very hard, and can be represented well either by a
thermal bremsstrahlung model with a temperature of 11.2 +40/-2.3 keV
or a power-law model with a photon index of 1.90 +0.24/-0.20. These
observational results are interpreted in terms of the thermal emission
from a hot coronal plasma extending beyond the stellar size. The
observed upper limit on the iron K-line intensity is considerably
lower than the theoretical prediction.
---------------------------------------------------------
Title: GINGA observations of the old nova GK Persei in quiescence
and outburst.
Authors: Ishida, M.; Sakao, T.; Makishima, K.; Ohashi, T.; Watson,
M. G.; Norton, A. J.; Kawada, M.; Koyama, K.
1992MNRAS.254..647I Altcode:
Ginga observations of the old nova GK Persei in quiescence, as well
as a brief scanning observation during an outburst are reported. The
X-ray spectrum in quiescence is well fitted by thermal bremsstrahlung
emission of very high temperature (approximately 30 keV), plus an
iron emission line. The outburst spectrum is complex and comprises two
continua with different column densities (about 10 exp 23 and about 10
exp 24/sq cm). The 351-s spin modulation of GH Per was clearly detected
in the quiescence observation, which confirms the results of previous
Exosat observations. The folded light curve shows two peaks that are
not separated by 180 deg in phase, which is quite different from the
Exosat outburst data. It is similar to the Exosat observation at a
similar flux level.
---------------------------------------------------------
Title: The Hard X-ray Telescope (HXT) for the SOLAR-A mission
Authors: Kosugi, T.; Makishima, K.; Murakami, T.; Sakao, T.; Dotani,
T.; Inda, M.; Kai, K.; Masuda, S.; Nakajima, H.; Ogawara, Y.; Sawa,
M.; Shibasaki, K.
1991SoPh..136...17K Altcode:
The Hard X-ray Telescope (HXT) is a Fourier-synthesis imager; a set of
spatially-modulated photon count data are taken from 64 independent
subcollimators and are Fourier-transformed into an image by using
procedures such as the maximum entropy method (MEM) or CLEAN. The
HXT takes images of solar flares simultaneously in four energy bands,
nominally 15 (or 19)-24, 24-35, 35-57, and 57-100 keV, with an ultimate
angular resolution as fine as ∼ 5 arc sec and a time resolution 0.5
s. Each subcollimator has a field of view wider than the solar disk. The
total effective area of the collimator/detector system reaches ∼ 70
cm<SUP>2</SUP>, about one order of magnitude larger than that of the
HINOTORI hard X-ray imager. Thanks to these improvements, HXT will for
the first time enable us to take images of flares at photon energies
above ∼ 30 keV. These higher-energy images will be compared with
lower-energy ones, giving clues to the understanding of nonthermal
processes in solar flares, i.e., the acceleration and confinement of
energetic electrons. It is of particular importance to specify the
acceleration site with regard to the magnetic field figuration in a
flaring region, which will be achieved by collaborative observations
between HXT and the Soft X-ray Telescope on board the same mission.
---------------------------------------------------------
Title: Non-periodic intensity variations in the X-ray pulsar GX301-2.
Authors: Tashiro, M.; Makishima, K.; Ohashi, T.; Sakao, T.; Sansom,
A. E.
1991MNRAS.252..156T Altcode:
Results of Ginga observations of the X-ray binary pulsar GX301 -
1 are analyzed for their temporal and spectral properties in order
to determine whether 'self-similar variation' (SSV) is a common
phenomenon among X-ray pulsars. The unambiguous detection of aperiodic
intensity variations of 7-10 percent rms relative amplitude over
time-scales covering about 16 to 0.1 s is reported. These variations
are self-similar, being well fitted by a power law in power spectral
density versus frequency space. The pulse period measured is 689.80
s, the shortest measured for this source to date. The fraction of
X-rays which is pulsed is energy dependent, being greater at higher
energies. The fractional aperiodic variability shows no such energy
dependence, nor do they appear to be significantly dependent on the
source intensity, pulse phase, or absorbing column measured. It is
inferred that the aperiodic variations are not caused by absorption
variations, but are intrinsic to the source.
---------------------------------------------------------
Title: Cyclotron Line Features in the Spectrum of the Transient
X-Ray Pulsar X0115+634
Authors: Nagase, F.; Dotani, T.; Tanaka, Y.; Makishima, K.; Mihara,
T.; Sakao, T.; Tsunemi, H.; Kitamoto, S.; Tamura, K.; Yoshida, A.;
Nakamura, H.
1991ApJ...375L..49N Altcode:
An outburst of the transient X-ray pulsar X0115 + 634 was detected with
the All Sky Monitor (ASM) on board Ginga on February 5, 1990. Follow-up
observations with the large-area proportional counters (LACs) revealed
complex changes in the energy spectrum which depend on the phase of
the 3.6 s pulsation. Characteristic structures in the spectra above 10
keV can be best interpreted as two dips at about 12 and about 23 keV,
although not at all phases. The results strongly suggest that the
structures in the spectra are due to cyclotron resonant scattering
and the two apparent absorption lines are ascribed to the fundamental
and second harmonics. This indicates a magnetic field strength on the
neutron star surface of about 1 x 10 to the 12th G. Equivalent widths
of the second harmonic line are about 2 times larger than those of
the first harmonic line, depending on the pulse phase.
---------------------------------------------------------
Title: Multi-Frequency Observations of H2106-099: A Weak Blue Bump,
Variable Seyfert 1 with Strong UV Fe II
Authors: Grossan, B.; Remillard, R.; Bradt, H.; Brissenden, R.; Sakao,
T.; Ohashi, T.
1991BAAS...23..921G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The SOLAR-A Hard X-ray Telescope (HXT)
Authors: Kosugi, T.; Makishima, K.; Inda, M.; Murakami, T.; Dotani,
T.; Inda, M.; Kai, K.; Masuda, S.; Nakajima, H.; Ogawara, Y.; Sakao,
T.; Sawa, M.; Shibasaki, K.
1991AdSpR..11e..81K Altcode: 1991AdSpR..11...81K
The Hard X-ray Telescope (HXT), now under fabrication for the SOLAR-A
mission (scheduled for launch in August 1991), is an advanced
Fourier-synthesis imager. An overview of the HXT instrument is
given together with its scientific objectives, that is, the electron
acceleration and confinement mechanisms in solar flares. Scientific
return from HXT will be greatly increased if worldwide collaboration
with other space and ground-based observations is well organized.
---------------------------------------------------------
Title: The Hard X-ray Telescope (HXT) on Board SOLAR-A (Extended
Abstract)
Authors: Sakao, Taro; HXT Group
1991LNP...387...20S Altcode: 1991fpsa.conf...20S
No abstract at ADS
---------------------------------------------------------
Title: Discovery of a Prominent Cyclotron Absorption Feature from
the Transient X-Ray Pulsar X0331+53
Authors: Makishima, K.; Mihara, T.; Ishida, M.; Ohashi, T.; Sakao,
T.; Tashiro, M.; Tsuru, T.; Kii, T.; Makino, F.; Murakami, T.; Nagase,
F.; Tanaka, Y.; Kunieda, H.; Tawara, Y.; Kitamoto, S.; Miyamoto, S.;
Yoshida, A.; Turner, M. J. L.
1990ApJ...365L..59M Altcode:
A remarkable absorption feature at 28.5 keV, attributable to electron
cyclotron resonance, has been discovered in the 1.9-60-keV X-ray
spectrum of the recurrent transient X-ray pulsar X0331 + 53. The
observed resonance energy implies a neutron star surface magnetic
field of 2.5(1 + z) x 10 to the 12th G, where z is the gravitational
redshift. The detection was made with the Ginga observatory in October
1989, during an outburst of this transient with a flux level of about
0.3 Crab. The feature is very deep and has been resolved with excellent
statistics. This is the fourth unambiguous detection of cyclotron
resonant scattering features from X-ray pulsars, suggesting that these
features are a common phenomenon among these objects. An empirical
relation found between the cyclotron resonance energy and the spectral
cutoff energy suggests that the magnetic field strengths of the known
X-ray pulsars are clustered in a range (1-4) x 10 to the 12th G.
---------------------------------------------------------
Title: When will the peculiar X-ray pulsar GX 1+4 resume the fast
spin-up?
Authors: Sakao, T.; Makishima, K.; Ohashi, T.; Dotani, T.; Kani, T.;
Makino, T. K. F.; Nagase, F.; Takeshima, T.
1990MNRAS.246P..11S Altcode:
Results from observations of the ∼110-s X-ray pulsar GX 1+4
(4U 1728-24), made with the GINGA satellite in 1989 August, are
reported. The absorption- corrected 2-20-keV luminosity of the source
was 1.2 × 10<SUP>37</SUP> erg s<SUP>-1</SUP> at an assumed distance
of 10 kpc, which is ∼10 and ∼2 times larger than in 1987 March
and 1988 March, respectively. This implies that GX 1+4 is emerging
from the extended low state which lasted over the middle 1 980s. The
observed pulse period, P = 113.626±0.002 s, indicates that GX 1+4
has been spinning down monotonically at least since 1987 March, in
contrast to the fast spin-up observed through the 1970s. A remarkable
discovery is that the intensity increase since 1987 has hardly
affected the spin-down rate, P<SUP>ṡ</SUP>=4.5 × 10<SUP>-8</SUP>
s s<SUP>-1</SUP>. The 2-30-keV source spectrum is little different in
shape from those observed in the 1970s.
---------------------------------------------------------
Title: New observations of the cyclotron absorption feature in
Hercules X-1
Authors: Mihara, T.; Makishima, K.; Ohashi, T.; Sakao, T.; Tashiro, M.
1990Natur.346..250M Altcode:
ALTHOUGH neutron stars are generally believed to be born with intense
(10<SUP>11</SUP>-10<SUP>13</SUP> G) magnetic fields<SUP>1,2</SUP>,
which then gradually decay<SUP>3</SUP>, measurements of their field
strengths remain uncertain. In the special case of X-ray-emitting
binary pulsars, a direct estimate of the field strength can be
obtained by measuring the energy of spectral features that are due to
electron cyclotron resonance<SUP>4-13</SUP>. With the Ginga satellite
observatory<SUP>14,15</SUP>, we have measured a cyclotron feature in
the hard X-ray spectrum of the 1.24-s binary pulsar Hercules X-1 with
a much greater energy resolution than in previous observations4-9. The
spectrum from 10-60 keV can be described with a simple analytical
formula<SUP>12,16,17</SUP>, which indicates an absorption feature at ~34
keV rather than an emission feature at ~50keV. From this we estimate
the surface magnetic field strength of Her X-1 to be (2.9+/-0.3)
× 10<SUP>12</SUP> G.
---------------------------------------------------------
Title: Discovery of a Cyclotron Absorption Line in the Spectrum of
the Binary X-Ray Pulsar 4U 1538-52 Observed by GINGA
Authors: Clark, George W.; Woo, Jonathan W.; Nagase, Fumiaki;
Makishima, Kazuo; Sakao, Taro
1990ApJ...353..274C Altcode:
A cyclotron absorption line near 20 keV has been found in the
spectrum of the massive eclipsing binary X-ray pulsar 4U 1538 - 52 in
observations with the Ginga observatory. The line is detected throughout
the 529 s pulse cycle with a variable equivalent width that has its
maximum value during the smaller peak of the two-peak pulse profile. It
is found that the profile of the pulse and the phase-dependence of the
cyclotron line can be explained qualitatively by a pulsar model based on
recent theoretical results on the properties of pencil beams emitted by
accretion-heated slabs of magnetized plasma at the magnetic poles of a
neutron star. The indicated field at the surface of the neutron star is
1.7 (1 + z) x 10 to the 12th G, where z is the gravitational redshift.
---------------------------------------------------------
Title: Peculiar pulse profile of GX 1+4 observed in the spin-down
phase.
Authors: Dotani, T.; Kii, T.; Nagase, F.; Makishima, K.; Ohashi, T.;
Sakao, T.; Koyama, K.; Tuohy, I. R.
1989PASJ...41..427D Altcode:
Observations of GX 1+4 made with Ginga in March 1987 and March 1988 have
revealed the following drastic changes in the system: (1) spin-down at
an average rate of 1.2 x 10 to the-2nd/yr, (2) an extended low state
with a luminosity of 1.2 x 10 to the 36th erg/s in 1987 and 5.7 x 10
to the 36th erg/s in 1988, and (3) a peculiar pulse profile witha sharp
dip associated with a narrow maximum. One possible interpretation of the
rapid spin-down rate requires a magnetic dipole moment of 5 x 10 to the
31st G cu cm. However, this interpretation seems implausible. Instead,
a retrograde rotating accretion disk is proposed to explain the present
spin-down of GX 1+4 and its rate of change. The dip structure with a
narrow maximum seems to result from resonance scattering of photons
at the accretion column above the magnetic pole.
---------------------------------------------------------
Title: Spin-down of the X-ray pulsar GX1 +4 during an extended
low state
Authors: Makishima, K.; Ohashi, T.; Sakao, T.; Dotani, T.; Inoue,
H.; Koyama, K.; Makino, F.; Mitsuda, K.; Nagase, F.; Thomas, H. D.;
Turner, M. J. L.; Kii, T.; Tawara, Y.
1988Natur.333..746M Altcode:
X-ray pulsars<SUP>1,2</SUP> are magnetized, spinning neutron stars
accreting matter from their binary companions. Their pulse periods
P, ranging over four orders of magnitude, increase and decrease in
complex ways<SUP>1,3,4</SUP>. The more luminous ones tend to show faster
spin-up<SUP>1,5</SUP>. A puzzle is that the spin-up timescales of many
X-ray pulsars are much shorter than their binary-evolution timescales,
thus apparently violating the steady-state condition. It has there-fore
been suspected<SUP>6</SUP> that there exist many 'turned-off X-ray
pulsars currently spinning down undetected. An excellent test for this
hypothesis became available using the X-ray pulsar GX1 +4, which used
to show the fastest spin-up over a decade<SUP>1,7-10 </SUP>and then
faded away<SUP>11</SUP>. Using the X-ray satellite Ginga<SUP>12</SUP>,
we detected GX1+4 at ~1/40 the previous intensity, and found that it
now has an average spin-down trend. This discovery apparently supports
the above hypothesis.
