Hinotori Satellite Research Articles

Occurrence characteristics of low latitude ionosphere irregularities observed by impedance probe on board the Hinotori satellite.

The statistical analyses of occurrence characteristics of the plasma bubbles and blobs are made by using more than 1000 cases of observation data from the swept frequency impedance probe aboard the Hinotori satellite. The results show that formations of the plasma bubbles have the following characteristics. 1) The spatial distribution of the occurrence of the plasma bubbles is in the equatorial region within ±30° of the magnetic dip latitude centered around the magnetic equator, 2) the occurrence of the plasma bubbles is limited in the nighttime; favorable periods of the plasma bubble formation depend on the type of the plasma bubbles; multiple plasma bubbles (MPB) have tendency to be generated in pre-midnight, while quasi periodic plasma bubbles (QPB) show their maximum occurrence in the post-midnight period. Solitary plasma bubbles (SPB) occur, however, rather independently to the local time in so far as in the night period, 3) the magnetic activity also controls the occurrence of the plasma bubbles; the occurrence of MPB phenomena shifts the peak period to the midnight side with increasing magnetic activity and the occurrence of QPB phenomena which covers the period from midnight to the morning side shows the expansion of their occurrence into late morning period with increasing magnetic activity, 4) correlation of the occurrence of the plasma bubbles to the solar radiation flux represented by F10.7 solar radio flux is evident for MPB and QPB while there is no relation between F10.7 and the occurrence of SPB. Occurrence of the plasma blobs has a complementary nature with that of the plasma bubbles. The occurrence region of the plasma blobs is limited in the edge parts of the plasma bubble occurrence region being limited in the nighttime. The occurrence of the plasma blobs decreases with increasing magnetic activity, while there is a strong anti-correlation of the occurrence of the plasma blobs to the solar radiation (F10.7). The relation of occurrence of the plasma bubbles and blobs to the development of the equatorial anomaly and the asymmetrical distributions of the background electron density suggests the importance of the generalized Rayleigh-Taylor instability including the effects of the electric field and the neutral wind in addition to the gravitational force for the generation of the plasma bubbles and blobs.

Observation of low latitude ionosphere by the impedance probe on board the Hinotori satellite.

By the impedance probe (IMP) on board the Hinotori satellite, that was launched on February 21, 1981, into the semi-equatorial orbit with inclination of 31° and nearly constant altitude of 650km, data of electron density profiles along more than 1500 orbits have been obtained with an error less than ±3%. The detected profiles of electron density contain the data of the equatorial plasma bubbles. Preliminary statistic studies on the occurrence frequency indicate that there are at least three types of the plasma bubbles. The plasma bubbles that belong to the first type grow mainly from the evening to the midnight period with large depletion rates of electron density; since the depletion regions are sequencially aligned those are called here multiple plasma bubbles (MPB). The second type plasma bubbles are enhanced mainly after midnight, even in sunlit condition, with periodic features and are called here quasi periodic plasma bubbles (QPB). There is a third type of plasma bubble characterized by its solitary features called here solitary plasma bubble (SPB). The SPB phenomena takes place in all of the night time period. In the topside region of the ionosphere near the edge of the occurrence region of the plasma bubble, there frequently appear electron density enhancements with deviation of a few percent to the background electron density. These newly discovered phenomena are called here plasma blob. Occurrence characteristics of the plasma blob are also discussed.

Observations of Solar Flare Photon Spectra from 20 keV to 7 MeV

Solar flare photon energy spectra in the 20 keV to 7 MeV range are derived from the 1981 Apr. 1, Apr. 4, Apr. 27 and May 13 flares. The flares were observed with a hard X-ray and a gamma-ray spectrometers on board the Hinotori satellite. The results reveal that the shape of hard X-ray spectrum for the gamma-ray flares does not much vary from flare to flare, and the spectra harden apparently at energy about 400 keV. Effects of nuclear line emission on the continuum and of higher energy electron bremsstrahlung are considered to explain the spectral hardening.

A comprehensive analysis of the loop prominence of 1981 April 27

We make comprehensive analysis of morphological tracings and positional measurements of Hα images, white-light sunspot photographs and chromosphere velocity field, obtained at Yunnan Observatory, and hard X-ray images obtained by the Hinotori satellite, of the loop prominence of 1981 April 27. It seems likely that the observed loop is the projection of a post-flare loop system, and the associated flare occurred on the rear side of the solar disk. A two-ribbon flare such as in the Kopp-Pneuman model can satisfactorily explain all the observed features. The occurrence of such a flare seems likely from the evidence given by the data.

Longitudinal distribution of the hard X-ray bursts on the Sun

The analysis of 315 hard X-ray bursts (HXR) producing solar flares observed by Hinotori satellite shows that the HXR bursts occur most prominently at 110°, 140°, 290°, and 320° longitude, respectively. These longitudes are not only prolific in producing flares in number but also in producing flares with large photon counts.

On the role of energetic particles in solar flares

The importance of energetic particles in the generation of solar flares and related phenomena has been underestimated if not completely neglected. A reexamination of their role in the light of recent observations carried out during the last solar maximum by a number of experiments on SMM and Hinotori satellites points out the continuous and violent evolution of the solar atmosphere. Most observed features can be better explained by the old idea that particles are trapped in magnetic loops above active regions where they are first heated and then accelerated by absorbing part of the wave energy flowing upwards continuously from the convection zone. Their catastrophic release into the chromosphere as a consequence of an instability in the region such as chromospheric heating or due to the emergence of new magnetic flux is considered as being the flare proper. Since the trapping of the particles involves the generation of resonant waves, a reassessment of the isotopic overabundance problem as well as a search for these waves in interplanetary space are proposed.

Solar Gamma-Ray Lines and Interplanetary Solar Protons

Solar gamma-ray lines and protons were simultaneously observed for six flares on 1 April, 4 April, 27 April, 13 May 1981, 1 Feb., and 6 June, 1982 by Hinotori and Himawari satellites. The flare list is presented in Table I and the time histories of gamma-rays and protons are shown in Figs. 1 to 6. The relation-ship between the gamma-ray line fluences and peak proton fluxes for these flares is shown in Fig. 7. It does not reveal an apparent correlation between them. The present results imply that the protons producing gamma-ray lines in the flare region and protons observed near the Earth do not always belong to the same population, and favor the downward streaming model for the gamma-ray line production.

Heating and acceleration processes in hot thermal and impulsive solar flares

A simple model to describe the unusual characteristics of hot thermal flares as observed with the Hinotori satellite and the overall hard X-ray time evolution of impulsive flare is presented. Unver the assumption of a steady electric field applied by an external driver during the course of flare evolution, it is shown that the plasma density in the energy release site plays an essential role in the mode of energy release. In the impulsive phase, more than 10/sup 35/ electrons s/sup -1/ can run away because of the large ratio (approx.0.3) of the applied electric field to the Dreicer field due to the relatively low background plasma density (n or =10/sup 11/ cm/sup -3/) due to the chromospheric evaporation, and Joule heating becomes energetically predominant as compared with particle acceleration. The plasma in the energy-release site is in the classical state throughout the flare, with the possible occurrence of ion-cyclotron turbulence only at the onset of themore » impulsive phase. For hot thermal flares, a high plasma density probably due to the low-altitude of the flaring loop makes epsilon< or =0.1, resulting in intense Joule heating from the start of the flare without an evident impulsive (acceleration) phase.« less

Ratios of the Fluence of 2.22 MeV Gamma-Ray Line to the Fluence of 4.44 MeV Gamma-Ray Line in Solar Flares

The Hinotori satellite observed eight solar gamma-ray line flares between April, 1981 and June, 1982. Ratios of the fluence of 2.22 MeV gamma-ray line restulting from neutron capture on proton to the fluence of 4.44 MeV gamma-ray line resulting from the nuclear deexcitation of C are shown as a function of the heliolongitude of flare. The ratios are roughly constant for disk flares, but decreased for limb flares. The present result suggests that the particle acceleration produces energy spectra that do not vary much from flare to flare. The limb darkening of the ratios can be interpreted in terms of the attenuation of the 2.22 MeV gamma-ray line by Compton scattering in the photosphere.

Hard X-ray imaging of a solar gradual hard X-ray burst on April 1, 1981

An intense solar X-ray burst occurred on April 1, 1981. X-ray images of this gradual hard X-ray burst were observed with the hard X-ray telescope aboard the Hinotori satellite for the initial ten minutes of rise and maximum phases of the burst. The hard X-ray images (13–29 keV) look like a large loop without considerable time variation of an elongated main source during the whole observation period. The main X-ray source seems to lie along a ridge of a long coronal arcade 2 × 104 km above a neutral line, while a tangue-like sub-source may be another large coronal loop although the whole structure of the X-ray source looks like a large semi-circular loop. Both nonthermal and hot thermal (3–4 × 107 K) electrons are contributing to the source image. The ratio of these components changed in a wide range from 2.3 to 0.4 during the observation, while the image was rather steady. It suggests that both heating and accelerations of electrons are occurring simultaneously in a common source. Energetic electrons of 15–30 keV would be collisionally trapped in the coronal magnetic loops with density of the order of 1011 cm−3.

Organisation of a unified system of energetic calibration of X-ray experiments

X-ray data obtained by the Prognoz 5,6,7 and 8 hard X-ray photometers are compared with the measurements carried out by similar instruments aboard the Solrad 11, ISEE 3, SMM and Hinotori satellites. Using the method of relative amplitude analysis, the apparent disagreement in the energy discrimination level calibration between the instruments is pointed out. The results of the comparison and the possible sources of disagreement are given. We suggest an international effort be made to develop a system of uniform pre-launch calibration of photometers based on a reference calibration source.

Gamma-ray bursts observed from the Hinotori satellite

During February, 1981 and June, 1982 the gamma-ray and the hard X-ray spectrometers on the Hinotori satellite observed four gamma-ray bursts on 28 February, 21 July, 1981, 26 February and 13 March, 1982. These gamma-ray bursts were simultaneously observed by other satellites. The time histories and energy spectra are shown for these gamma-ray bursts, and the burst sizes (erg cm−2) are estimated. Two possible source locations for the burst of 21 July, 1981 are roughly determined from arrival time delays between two pairs of satellites, PVO-Hinotori and ISEE-3-Hinotori. The weak gamma-ray line peak structure around 1.8 MeV was observed for the burst of 13 March, 1982. The line could be interpreted in terms of gravitationally redshifted neutron capture line at 2.22 MeV.

Energetic electrons as an energy transport mechanism in solar flares

We review the observations and theory relating to the role of energetic electrons in the solar flare, with particular emphasis on discriminating between “thermal” and “nonthermal” origins of these electrons. We discuss diagnostics in hard X-rays, especially those relating to the recent observations of the SMM and HINOTORI satellites. We also briefly address the response of the atmosphere to energy input in the form of high energy electrons, in particular through the diagnostics of both the Fe Kα feature and optically thin transition region lines such as 0V. Finally, we discuss the relative roles of electron and proton heating in γ-ray flare events.

Imaging of impulsive solar flare phenomena

We review some recent advances in our understanding of impulsive solar flare phenomena obtained through new hard X-ray and radio imaging instruments (the Solar Maximum Mission and Hinotori satellites, the VLA and VLBI).

Hard X-ray imaging of a solar limb flare with the X-ray telescope aboard the HINOTORI satellite

view Abstract Citations (44) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hard X-ray imaging of a solar limb flare with the X-ray telescope aboard the HINOTORI satellite Takakura, T. ; Tsuneta, S. ; Nitta, N. ; Makishima, K. ; Murakami, T. ; Ogawara, Y. ; Oda, M. ; Ohki, K. ; Miyamoto, S. Abstract X-ray images of the intense solar X-ray burst of Apr. 27, 1981 which were made aboard the satellite Hinotori are discussed. The hard X-ray telescope aboard the satellite is described, and the mapping spectrometric functions are considered. The hard X-ray images are shown along with time profiles of the flare. The images reveal the height structure of a strong hard X-ray source located in the corona. The source contains two sources, a steady main one of about 20 arcsec and a subordinate one exhibiting variable intensity relative to the main source. Both sources were located in the corona without any evidence of an appreciable chromospheric source throughout the observation. The obtained photon spectra fit better to power laws than to isothermal spectra. Publication: The Astrophysical Journal Pub Date: July 1983 DOI: 10.1086/184075 Bibcode: 1983ApJ...270L..83T Keywords: Solar Flares; Solar X-Rays; X Ray Imagery; Japanese Spacecraft; Solar Corona; Solar Limb; Solar Physics full text sources ADS |

Hard X-ray dynamic spectrum of flares observed by Hinotori

Time variations of the hard X-ray spectrum in solar flares are observed by the hard X-ray spectrometer (HXM) aboard the Hinotori satellite. With a new presentation of the dynamic spectrum we have studied the differences between impulsive and gradual hard X-ray bursts. In the impulsive events a “bent” spectrum up to some hundred keV persists at least until the main peak. In the gradual events, on the other hand, a power-law spectrum augmented by a low-energy excess is dominant.

Sub-second pulsations simultaneously observed at microwaves and hard X rays in a solar burst

Sub-second time structures have been found in millimetre waves1,2 and, independently, in hard X rays3,4 emitted during solar bursts. However, because simultaneous observations of such fast time structures in millimetre radio and X-ray ranges had not been available, we planned coordinated observations of the solar burst in November 1981 with a high time resolution of a few milliseconds. The hard X rays (30–40 keV) were observed by the hard X-ray monitor, HXM5, aboard the Hinotori Satellite with a time resolution of 7.81 ms and the radio emissions were observed on the ground by the 45-ft dish at Itapetinga Radio Observatory with a high time resolution (1 ms) and high sensitivities at 22 GHz and 44 GHz (ref. 6), supplemented by patrol observations at 7 GHz with a time resolution of 100 ms. Absolute timing at Itapetinga and Hinotori is better than 10 ms. Correlated sub-second time structures at hard X-ray and at millimetre wavelengths were found for the first time.

High-resolution solar flare X-ray spectra obtained with rotating spectrometers on the HINOTORI satellite

view Abstract Citations (115) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-resolution solar flare X-ray spectra obtained with rotating spectrometers on the HINOTORI satellite Tanaka, K. ; Watanabe, T. ; Nishi, K. ; Akita, K. Abstract Rotating crystal spectrometer observations of an impulsive flare are reported. The resolved spectrum of Fe XXVI and its time variations are presented and various plasma parameters are derived from the spectra of Fe XXIV, Fe XXV, and Fe XXVI. For an impulsive X2.2 flare that occurred on April 2, 1981, time profiles of various line intensities, line widths, and plasma parameters are derived. Increases of electron temperatures and a decrease of the line width are found to occur with steady increases of the line fluxes and the smooth hard X-ray burst. A large emission measure and high density was found for the Fe XXVI emitting plasma. Publication: The Astrophysical Journal Pub Date: March 1982 DOI: 10.1086/183756 Bibcode: 1982ApJ...254L..59T Keywords: Solar Flares; Solar Spectrometers; Solar X-Rays; X Ray Spectroscopy; High Resolution; Ionization; Iron; Japanese Space Program; Solar Physics full text sources ADS |