Oscar Toshiaki Matsuura

Museum of Astronomy and Related Sciences - MAST, Rio de Janeiro, Brazil

This is a biographical note on the life of Dr. Alexander Postoyev, a victim of Stalin's purge of Soviet astronomers in 1936 - 1937. Together with his family, he left the Soviet Union in 1943 and lived in Germany as a refugee and a "displaced person" until 1952, when he moved to Brazil. There, he started the second part of his professional career. T...

An analysis of the coronal structure for several eclipses, including the eclipse of November 3, 1994, shows that coronal streamers and helmets can be described as folds and pleats produced when the B_r = 0 plane is projected onto the plane of the sky (Vial and Molodensky 1993; Molodensky et al. 1996). We consider equilibrium conditions for plasma i...

Analyses of the orientation of the plane of polarization for the solar corona are presented, based on polarization isophotes of the solar eclipses of June 30, 1973 (Africa), November 3, 1994 (Brazil), and March 9, 1997 (Eastern Siberia). Deviations of the polarization plane from the radial direction, indeed, exist at distances from the solar limb g...

This is a biographical note on the life of Dr Alexander I. Postoiev, a victim of Stalin's purge of Soviet astronomers in 1936-1937 (McCutcheon, 1985). Along with his family, he left the Soviet Union in 1943, and lived in Germany as a refugee and “displaced person” until 1952, when he moved to Brazil. Then he started the second part of his professio...

A polarization analysis of E–limb prominences on November 3, 1994 is presented. Photometry and data reduction of 24 prominence pictures based on IDL software and Stokes–vector presentation and applied to H α emission resulted in an accuracy of 1–1.5% in determination of the polarization degree and of 1.5–2.0° in the polarization direction. Distribu...

The brightness of the solar corona due to Thomson scattering depends linearly on the electron density, while the brightness due to the Balmer continuum is proportional to its square. As a consequence, information on the distribution of the electron density in the corona can be obtained by comparing the radial profiles of the surface brightness in b...

Preliminary data reduction of the color index polarization wave experiment carried out in Brazil (Chapeco town) is described. Distributions of polarization degree (polarization images) in the range 1.1 - 1.6 Rsun are obtained by an algorithm developed on the basis of the Stokes vector presentation and IDL software. The polarization image of the "qu...

Distribution on halfwidths for Fe XIV (5303 Å) coronal line is analyzed. The Fabry-Perot interferogram obtained during the total solar eclipse of November 3, 1994 is used. The profiles not distorted by the white light corona contributions as well as by ghost images were selected. A multimodality with probability of 87% is found in the histogram. Av...

The problems of searching for the solar corona reddening effect are analyzed. A new method is proposed for quantitative color photometry using a color film with significantly reduced sensitivity in the green spectral region. The results of the photometry of the solar corona slides obtained during the total solar eclipse of November 3, 1994 are pres...

An algorithm for polarization imaging of the white light corona has been devised on the basis of the Stokes vector presentation and the IDL software applied to statistical data. The use of the algorithm for a 24-frame color negative polarization film of the corona of November 3, 1994, digitized in the green light allowed new data to be obtained on...

We carried out a morphological analysis on fine structures recorded in large-scale color photographs of white-light corona obtained in the eclipse of July 11, 1991, in Hawaii, Mexico and Brasil by MICE (see Zirker et al, 1992). Images taken through a standard V filter were digitized with a pixel size corresponding to 21, 000 km on the Sun. The MadM...

Raios cometários são estruturas finas e longas da cauda de cometas do Tipo I (ou de plasma). Como eles apresentam simetria cilíndrica, admitem modelos MHD simples. Este trabalho explora essa possibilidade, apresentando um estudo sistemático da estabilidade e das oscilações de raios cometários na aproximação de plasma homogêneo. O critério de estabi...

Using the Sedov’s (1959) method of self-similarity, non-steady solutions were obtained for a plane, one-dimensional and isothermal flow in presence of gravity. Although simple, such a flow seems to be suitable for describing, in a first approximation, the transient plasma ejections along the coronal rays . The topology of the solutions shows that t...

The MHD spectrum of discrete kink modes is derived for a cylindrical, static and isothermal plasma with spatial variations in radial direction only. Such a configuration models, in first approximation, the long and almost radially oriented fine structures of the solar corona denominated coronal rays , whenever cylindrical symmetry holds. Since here...

Morphological properties of the corona and coronal structures, and modifications occurring in a time span greater than 3 hours were investigated through image analysis of three successive color pictures obtained by the Multi-station International Coronal Experiment (MICE). The model of Saito and Akasofu (1987) for the general magnetic field of the...

This paper reports on broad band near-IR photometric observations of 630 objects found in the Valinhos 2.2 μm survey of the southern galactic plane. Ninety percent of them are identified with IRAS Point Sources. The near-IR and Infra Red Astronomical Satelllte (IRAS) fluxes, although not measured simultaneously, are combined to study the overall en...

630 sources detected by the Valinhos 2 μm survey were observed in the JHKLM bands with the ESO 1-m telescope. The objects were also identified with entries of the IRAS point source catalogue. Based on a statistical investigation of their infrared energy distribution, the authors propose a classification of the sources.

Near IR photometric observations of Comet Halley obtained at the Cerro Tololo Inter-American Observatory in 1985 are presented and examined. It is observed that (K-L) is affected by thermal emission; for heliocentric distances greater than about 2 AU; (J-H) and (H-K) are significantly redder than normally found in comets; and as the heliocentric di...

This paper reports on the observational data from the photographic monitoring program of comet Halley run at the Brazilian National Laboratory for Astrophysics, from September 25, 1985 to July 10, 1986. For a resolution of ≡4arcsec, the set of 280 pictures is suitable for image processing of structures of dust, neutral gas and ionized gas. The full...

Horizontal parts of long distance coronal loops are studied. Under currently verifiable hypotheses, the conclusion is drawn that the matter is in isothermal and static state. Therefore the heating has only to balance the radiative loss. Applying this result to different types of steady state loops, the heating can be related to the loops' sizes a...

A survey of infrared sources with declination < 35 is being carried out on a belt j50 wide along the Galactic Plane since mid 1982 in the K band with a 60 cm telescope at A. de Moraes Observatory in Valinhos, State of Sao Paulo. The limiting magnitude is K- 4.5 and the beam width is 3.5. Most of the results obtained before 1984 were reported to the...

This paper reports on JHKLM photometric measurements of 338 bright infrared stars found in a 2.2 micron survey of a 10°×100° lane of the southern galactic plane. More than 2/3 of the objects are not identified with catalogued stars and are likely to be long-period variable or reddened giant or supergiant stars.

A stationary state of production of solid material in the coma of a comet is sought by assuming a production and dynamics of solid grains liberated during the vaporization of cometary nuclei under the action of solar radiation.

Statistical analysis of the quantity of dust in the cometary atmosphere in relation to the direction of motion of the comet about the Sun suggests an excess of dust for the retrograde comets. This excess is analyzed in the light of Harwit's theory of the cloud of “boulders” and of Öpik's impact theory. A comparison is also made between these excess...

By considering alternative explanations in order to account for the time evolutive features of the spectrum of impulsive bursts, a suitable model for these events and accompanying phenomena is presented. Established on the grounds of a few cases, the model looks suitable for all the impulsive class, bringing information on plasma phenomena like Raz...

A plasmoid may be ejected during a flare and condensed by a radiative instability. The spectral shape of the mean fluxes of Simple 3 (or long-enduring) solar events is interpreted in terms of a thermal emission from this transient condensation in the higher levels of the solar atmosphere. This condensation is thick enough to block the radiation fro...

A statistical analysis on 220 impulsive microwave bursts showed a marked preference to occur in sunspots of type D, E and F (after Zrich classification). Assuming a shock mechanism for accelerating electrons, this tendency seems to be related to the size of the magnetic loops.

The more impulsive 7 GHz bursts seem to prefer the solar limb regions, while the degree of polarization decreases with increasing impulsivity.

The evolution with time of circular polarization (t) from solar bursts at 7 GHz presents, in the majority of cases, a polarization degree peak before the maximum flux time. The subsequent evolution of (t) is continuous and usually increasing. The changes could be caused by superimposed polarization effects, due to the fast emissive electrons (domin...

A magnetohydrodynamic (MHD) approach is presented that appears to be comprehensive for the interpretation of the recently discovered microwave solar events, in which only the degree of circular polarization changes, without any increase in the output of the total solar flux. On the basis of this explanation experimental evidence is suggested for Al...

It has been studied statistically the incidence of solar radio flux fluctuations in nearly 1000 hr of continuous observations at 7 GHz, and shown that some tropospheric phenomena can be analysed by this method. Of the fluctuations 93 per cent were coincident with the presence of CL clouds whose borders seem to be the major factors responsible for r...

There are microwave bursts not observable in the total flux from the Sun, but only in circular polarization. The production of these events in the Sun requires equivalent changes of the magnetic field imposed on the emission regions during the bursts.

DETAILED spectral information on the Sun in the range of wavelengths from near 3 cm to 21 cm was obtained on November 12, 1966, when total solar eclipse measurements were being made. Several observers, using accurate equipment, reported the residual solar emission during totality, and these data were used in a discussion of the cm–wavelength solar...

Radio observations of the Sun with a 4.28-cm radio polarimeter were performed during the 12 November 1966 total solar eclipse at a site located near the city of Bagé, in the extreme south of Brazil. The solar activity during that period is discussed, giving additional data for the eclipse measurements themselves. The difference between radio and op...