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HINOTORI - a Japanese satellite for solar flare studies
2O1-202. 1983 Adv. S~c~~ Vol.2, No.11, pp. PrinLed in Great Britain. All rights reserved.
0273_1l]7/83/110201-02$3,0010 Copyright
©
COSPAR
HINOTORI A JAPANESE SATELLITE FOR SOLAR FLARE STUDIES -
Shinzo Enome Toyokawa Observatory, Research Ins!itute of Atmospherics, Nagoya University, Toyokawa 442, Japan
ABSTRACT
A brief description of an astronomy satellite for solar flares, HINOTORI, is given on observations, data handling, data acquisition, SOX and SXT. INTRODUCTION A Japanese satellite ASTRO—A for observations of high—energy solar flare phenomena was launched on February 21, 1981 from Kagoshima Space Center (KSC) of the Institute of Space and Astronautical Science (ISAS). This satellite, nicknamed as HINOTORI, which means sunbird or phoenix, is the first multi—mission satellite for solar flare studies. It was designed by the ASTRO—A teams, managed by Prof. Y. Tanaka of ISAS, and was fabricated at ISAS. Operations and observations on board the HINOTORI have been coordinated and directed by Prof. Y. Tanaka and Dr. K. Tanaka of Tokyo Astronomical Observatory, the University of Tokyo. The instruments on board the HINOTORI for solar studies, which are Solar X—ray Telescope (SXT), Solar X—ray Aspect Sensor (SXA), High Energy X—ray Monitor (HXM), Solar Gamma Ray Detector (SGR), Flare Monitor (FLM), and Soft X—ray Spectrometers (SOX), are summarized in the table with a brief description of specifications. TABLE HINOTORI INSTRUMENTS FOR SOLAR OBSERVATIONS DETECTOR
ENERGY RANGE
SXT 113 cm2 Nal 113 cm2 Nal
17 17
— —
40/10 40/10
— —
RESOLUTION 27 key 27 keV
SXA Fine Solar Aspect Sensor ~J~14 ~ ~2
NaI Sci.
38”*/ 7 ~
30”*/ 7 ~ 5”
17 40
— —
40 keV 340 keV
SGR 62 cm2 Cal
0.21
FLM 0.5 cm2 Xe
2 — 25 keV Counts in LIE bands
128 ch/4 $ 125 ms
1.72 1.83
2 mA 0.15 mA
Gas Sci. Prop.
—
6.7 Hey
7.8 ms(HXN—1) 125 ms(HXM—2—7) 128 ch/2 s
SOX Sb 2 Nal Sd. S1O2 Nat Sd.
— —
1.95 A 1.89 A
*These values are FWHM’s of the triangular beam pattern, which have a sharp edge of 7”, which means the SXT has a response as fine as 7”, as explained later. In January 1982 a symposium, titled HINOTORI Symposium on Solar Flares, was held at ISAS in Tokyo. Since the proceedings of this symposium are not ready at this time, a very short introduction of the results is given for SOX and SXT. SOFT X—RAY SPECTROMETER (SOX) The soft X—ray rotating crystal spectrometers (SOX) onboard HINOTORI consist of two flat Si02 crystals (2d — 6.69 A for SOX1 and 2d 2.36 A for SOX2) and Nal (Tl) scintillation counters. The wavelength scanning is made according to the spinning of the satellite. Wavelength ranges are 1.72 — 1.95 A and 1.83 — 1.89 A with spectral resolutions of about 2 mA and 0.15 mA for SOX1 and SOX2 respectively. Since wavelength scanning is completed in half a spinperbod, time resolution is about 7 s. An X—class flare has been analysed
201
202
S. Enome
by K. Tanaka et al. (1) and general results are reported by Tanaka et al. in the proceedings, which are derived from the analysis of seven X—class flares~~rvedduring 1981 by SOX. They discuss line identifications and ionization equilibrium, and a comparison Is made for Fe XXVI spectra between observational results and theoretical calculations, The hard X—ray component (> 30 keV) of impulsive bursts in many cases has a few spikes of short duration of 5 s or so, which correspond to the elementary flare bursts, and a gradual part, which is more clearly seen the in 10 — 30 keV energy range, and starts to appear near the maximum phase of the impulsive component. They distinguish these two components as phase I and phase 2. In phase I Fe XXVI lines are not visible but lines from Fe XXV or lower stages do appear and these lines show rapid Intensity variation with time and a polarized component associated with impulsive spikes. Electron beams are suggested to be responsible for the production of the thermal plasma of Te 10 — 20 x 106 K, and thick target electron power input is shown to be consistent with the 3. increase of the In thermal content for an electron 1011 — 1012 Another feature phase energy 1 is strong turbulence, which is density seen in of soft X—rays and cm in H— alpha. Turbulent velocities are 150 — 250 km/s in soft X—rays and 100 km/s, in H—alpha, and bulk motions are upward in soft X—rays and downward In H—alpha with bulk velocities of 400 km/s, equal to the sound speed at 1O7 K, and 100 km/s, respectively. In phase 2 a gradual hard X—ray component appears, with a typical duration of 5 mm, simultaneously with the enhancement of Fe XXVI lines. In some flares (e.g. April 2, 1981) the phase 2 component is detached from the impulsive phase I component. This detached appearance indicates that emission in phase 2 is not related to the power input in phase 1. The temperature and the density of the plasma in phase 2 are 30 — 40 x 106 K and 1011 — 1011 cm3, which is consistent with the observed cooling time of 150 s, assuming radiation cooling. It is inferred that this component is emitted at the loop top as observed by SXT, and a two—step heating mechanism is proposed in the flare loop. SOLAR X—RAY TELESCOPE (SXT) Solar X—Ray Telescope (SXT) is a rotational modulation collimator developed by the SXT team of ASTRO—A. It consists of two orthogonal bigrid modulation collimators for hard X—rays (nominally 17 — 40 key), and of two small lenses for optical collimation. Two Nal X—ray scintillators and two solar—cell optical sensors are installed for both energy bands, respectively. When we look at the Sun through one of SXT collimators, in other words from HINOTORI coordinates, the Sun rotates around the spin axis with an angular radius of 1.2°±0.5°and with an angular speed of 4.3 rpm. Whereas the modulation pattern of SXT is fixed onto the sky with cyclic separation of 2.16’ of beams with nominal FWHM of about 35”. With these geometrical configurations in mind, we can imagine how the image of a flare is scanned by SXT. There will be such a situation that the Sun is scanned almost perpendicular to the modulation pattern, and as the Sun rotates around the spin axis, by e.g., 10°, the scan angle will also change by about 10°. In half of the spin period, therefore, is obtained a 180° scan of the flare image, which is necessary and sufficient for reconstruction of the image.. If data of both modulation collimators are employed for image synthesis, a quarter of the spinning period will be the time resolution. This method of angular scanning of the flare image is very similar to the computer tomography of human bodies, though scanning is not homogeneous in angular space, see Herman (2). There is no universal method which is effective for reconstruction of images in all cases. In the case of SXT, arithmetic reconstruction techniques (ART) and maximum entropy methods (HEM) have been used so far. They found a great variety of X—ray source stuctures such as compact single source as small as 10”, multi—component structures, and large loop—like structures as shown in Takakura etal. (3). Instrumental performance of the SXT collimators is estimated from observed images. The instrumental beam pattern is approximated by a triangular shape with a round edge of a Gaussian shape, and the X—ray flare source is modelled by a core and a halo. These free parameters are adjusted so as to give best chi—square fit. Thus estimated values of instrumental FWHM’s are 38” ±1” and 30” ±1” for the two collimators and instrumental beam roundness or sharp edge is ( 7” for both. The material for this paper Is mostly based on the papers in the proceedings of the HINOTORI Symposium on Solar Flares. The author is very grateful to each member of HINOTORI teams for the preparation of this introductory talk. His sincere thanks are also due to chair persons of Drs. P. Simon and Z. Svestka for giving him an opportunity to give a talk. References (1) K.
Tanaka,
(2) C.T. Herman,
T.
Watanabe,
K.
Nishi,
and K.
Akita,
Astrophys. J., 254, L59,
1982.
Image Reconstruction from Projections, Academic Press, New York, 1980.
(3) T. Takakura, K. Ohki, S. Tsuneta, N. Nitta, K. Makishima, T. Murakami, Y. Ogawara, and M. Oda, submitted to Space Science Rev.
0273_1l]7/83/110201-02$3,0010 Copyright
©
COSPAR
HINOTORI A JAPANESE SATELLITE FOR SOLAR FLARE STUDIES -
Shinzo Enome Toyokawa Observatory, Research Ins!itute of Atmospherics, Nagoya University, Toyokawa 442, Japan
ABSTRACT
A brief description of an astronomy satellite for solar flares, HINOTORI, is given on observations, data handling, data acquisition, SOX and SXT. INTRODUCTION A Japanese satellite ASTRO—A for observations of high—energy solar flare phenomena was launched on February 21, 1981 from Kagoshima Space Center (KSC) of the Institute of Space and Astronautical Science (ISAS). This satellite, nicknamed as HINOTORI, which means sunbird or phoenix, is the first multi—mission satellite for solar flare studies. It was designed by the ASTRO—A teams, managed by Prof. Y. Tanaka of ISAS, and was fabricated at ISAS. Operations and observations on board the HINOTORI have been coordinated and directed by Prof. Y. Tanaka and Dr. K. Tanaka of Tokyo Astronomical Observatory, the University of Tokyo. The instruments on board the HINOTORI for solar studies, which are Solar X—ray Telescope (SXT), Solar X—ray Aspect Sensor (SXA), High Energy X—ray Monitor (HXM), Solar Gamma Ray Detector (SGR), Flare Monitor (FLM), and Soft X—ray Spectrometers (SOX), are summarized in the table with a brief description of specifications. TABLE HINOTORI INSTRUMENTS FOR SOLAR OBSERVATIONS DETECTOR
ENERGY RANGE
SXT 113 cm2 Nal 113 cm2 Nal
17 17
— —
40/10 40/10
— —
RESOLUTION 27 key 27 keV
SXA Fine Solar Aspect Sensor ~J~14 ~ ~2
NaI Sci.
38”*/ 7 ~
30”*/ 7 ~ 5”
17 40
— —
40 keV 340 keV
SGR 62 cm2 Cal
0.21
FLM 0.5 cm2 Xe
2 — 25 keV Counts in LIE bands
128 ch/4 $ 125 ms
1.72 1.83
2 mA 0.15 mA
Gas Sci. Prop.
—
6.7 Hey
7.8 ms(HXN—1) 125 ms(HXM—2—7) 128 ch/2 s
SOX Sb 2 Nal Sd. S1O2 Nat Sd.
— —
1.95 A 1.89 A
*These values are FWHM’s of the triangular beam pattern, which have a sharp edge of 7”, which means the SXT has a response as fine as 7”, as explained later. In January 1982 a symposium, titled HINOTORI Symposium on Solar Flares, was held at ISAS in Tokyo. Since the proceedings of this symposium are not ready at this time, a very short introduction of the results is given for SOX and SXT. SOFT X—RAY SPECTROMETER (SOX) The soft X—ray rotating crystal spectrometers (SOX) onboard HINOTORI consist of two flat Si02 crystals (2d — 6.69 A for SOX1 and 2d 2.36 A for SOX2) and Nal (Tl) scintillation counters. The wavelength scanning is made according to the spinning of the satellite. Wavelength ranges are 1.72 — 1.95 A and 1.83 — 1.89 A with spectral resolutions of about 2 mA and 0.15 mA for SOX1 and SOX2 respectively. Since wavelength scanning is completed in half a spinperbod, time resolution is about 7 s. An X—class flare has been analysed
201
202
S. Enome
by K. Tanaka et al. (1) and general results are reported by Tanaka et al. in the proceedings, which are derived from the analysis of seven X—class flares~~rvedduring 1981 by SOX. They discuss line identifications and ionization equilibrium, and a comparison Is made for Fe XXVI spectra between observational results and theoretical calculations, The hard X—ray component (> 30 keV) of impulsive bursts in many cases has a few spikes of short duration of 5 s or so, which correspond to the elementary flare bursts, and a gradual part, which is more clearly seen the in 10 — 30 keV energy range, and starts to appear near the maximum phase of the impulsive component. They distinguish these two components as phase I and phase 2. In phase I Fe XXVI lines are not visible but lines from Fe XXV or lower stages do appear and these lines show rapid Intensity variation with time and a polarized component associated with impulsive spikes. Electron beams are suggested to be responsible for the production of the thermal plasma of Te 10 — 20 x 106 K, and thick target electron power input is shown to be consistent with the 3. increase of the In thermal content for an electron 1011 — 1012 Another feature phase energy 1 is strong turbulence, which is density seen in of soft X—rays and cm in H— alpha. Turbulent velocities are 150 — 250 km/s in soft X—rays and 100 km/s, in H—alpha, and bulk motions are upward in soft X—rays and downward In H—alpha with bulk velocities of 400 km/s, equal to the sound speed at 1O7 K, and 100 km/s, respectively. In phase 2 a gradual hard X—ray component appears, with a typical duration of 5 mm, simultaneously with the enhancement of Fe XXVI lines. In some flares (e.g. April 2, 1981) the phase 2 component is detached from the impulsive phase I component. This detached appearance indicates that emission in phase 2 is not related to the power input in phase 1. The temperature and the density of the plasma in phase 2 are 30 — 40 x 106 K and 1011 — 1011 cm3, which is consistent with the observed cooling time of 150 s, assuming radiation cooling. It is inferred that this component is emitted at the loop top as observed by SXT, and a two—step heating mechanism is proposed in the flare loop. SOLAR X—RAY TELESCOPE (SXT) Solar X—Ray Telescope (SXT) is a rotational modulation collimator developed by the SXT team of ASTRO—A. It consists of two orthogonal bigrid modulation collimators for hard X—rays (nominally 17 — 40 key), and of two small lenses for optical collimation. Two Nal X—ray scintillators and two solar—cell optical sensors are installed for both energy bands, respectively. When we look at the Sun through one of SXT collimators, in other words from HINOTORI coordinates, the Sun rotates around the spin axis with an angular radius of 1.2°±0.5°and with an angular speed of 4.3 rpm. Whereas the modulation pattern of SXT is fixed onto the sky with cyclic separation of 2.16’ of beams with nominal FWHM of about 35”. With these geometrical configurations in mind, we can imagine how the image of a flare is scanned by SXT. There will be such a situation that the Sun is scanned almost perpendicular to the modulation pattern, and as the Sun rotates around the spin axis, by e.g., 10°, the scan angle will also change by about 10°. In half of the spin period, therefore, is obtained a 180° scan of the flare image, which is necessary and sufficient for reconstruction of the image.. If data of both modulation collimators are employed for image synthesis, a quarter of the spinning period will be the time resolution. This method of angular scanning of the flare image is very similar to the computer tomography of human bodies, though scanning is not homogeneous in angular space, see Herman (2). There is no universal method which is effective for reconstruction of images in all cases. In the case of SXT, arithmetic reconstruction techniques (ART) and maximum entropy methods (HEM) have been used so far. They found a great variety of X—ray source stuctures such as compact single source as small as 10”, multi—component structures, and large loop—like structures as shown in Takakura etal. (3). Instrumental performance of the SXT collimators is estimated from observed images. The instrumental beam pattern is approximated by a triangular shape with a round edge of a Gaussian shape, and the X—ray flare source is modelled by a core and a halo. These free parameters are adjusted so as to give best chi—square fit. Thus estimated values of instrumental FWHM’s are 38” ±1” and 30” ±1” for the two collimators and instrumental beam roundness or sharp edge is ( 7” for both. The material for this paper Is mostly based on the papers in the proceedings of the HINOTORI Symposium on Solar Flares. The author is very grateful to each member of HINOTORI teams for the preparation of this introductory talk. His sincere thanks are also due to chair persons of Drs. P. Simon and Z. Svestka for giving him an opportunity to give a talk. References (1) K.
Tanaka,
(2) C.T. Herman,
T.
Watanabe,
K.
Nishi,
and K.
Akita,
Astrophys. J., 254, L59,
1982.
Image Reconstruction from Projections, Academic Press, New York, 1980.
(3) T. Takakura, K. Ohki, S. Tsuneta, N. Nitta, K. Makishima, T. Murakami, Y. Ogawara, and M. Oda, submitted to Space Science Rev.