간행물

천문학회지 KCI 등재 SCOPUS Journal of The Korean Astronomical Society

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제29권 제S호 (1996년 12월) 178

121.
1996.12 구독 인증기관 무료, 개인회원 유료
It is analysed the discrepancy about the coronal magnetic field between solar optic and solar radio using magnetic fibril concept with filling factor and fractal structure model. The magnetic field of ~ 100 G considered in solar optics is mean value in a large scale, and that of ~1000 G in solar should be the value of fine structures inside 'macro' loop.
3,000원
122.
1996.12 구독 인증기관·개인회원 무료
Assuming that the solar activity and the solar cycle phenomena may be manifestations of global torsional MHD oscillations, we compute the Alfven wave travel times along the field lines in the five models of magnetic field described in the following text. For all these models, we compute standard deviation and it's ratio to mean Alfvenic wave travel times. The last two models yield the smallest relative bandwidth for the frequencies of the MHD oscillations. However, the last model is the only admissible one which can sustain global Alfvenic oscillations with well defined frequency for the fundamental mode
123.
1996.12 구독 인증기관·개인회원 무료
Based on X-ray (1-8 Å) flux data for 1972-1995 the integral spectra of solar flare energy were computed. It has been shown that the spectral index β of the integral energy spectrum (IES) vanes systematically with the 11-year cycle phase. The interval of $\beta$ 수식 이미지-variations (0.47 <β<1) is characteristic of UV-Cet stars. The maximum energy of the X-ray flares does not exceed 10 32 erg.
124.
1996.12 구독 인증기관 무료, 개인회원 유료
Utilizing a Calcium filter, a large two ribbon flare of an importance 2.5Xj31? was recorded at. King Abdul-Aziz University Solar Observatory (KAAUSO) at the 30th of October 1991. This chromosphenc flare observation, which is of special importance since it is rarely reported, was for a flare that occurred near the south west of the equator at the vicinity of a large sunspot group on an active region known as AR 6891. The observed foot points of this flare had a strange behavior in which the separating motion of the ribbons were not typical of most flares, rather were nearly orthogonal. In this article we present the characteristics of the main sunspot group of this active region and try to investigate its evolution and fragmentation with time. Information regarding magnetic fields and velocity fields are necessary to understand the restructuring of the magnetic field pattern and plasma motion, and hence the changes that could lead to the occurrence of such an interesting flare.
3,000원
125.
1996.12 구독 인증기관·개인회원 무료
Using the data on the occurrences of the Ho: and soft X-ray flares for the time interval of January 1, 1986-May :31, 1994, we have studied the middle term(30-300days) pericities of the solar flare production during the activity cycle 22. Power analysis of the time seies of daily Hα flare index in the northern hemisphere shows prominent periodicities at 220, 120, 109, and 92 days(see Figures l(a) and l(b)), while in the southern hemisphere, those at 267, 213, 183, 167, and 107 days are apparent, though their peaks are not so distint as those in the northern hemisphere. Periodogram of daily soft X-ray flare index also reveal the periodicities at 279, 205, 164, 117, and 91 days in the northern hemisphere, and at 266, 220, 199, 162, 120, and 100 days in the southern hemisphere. Howeer, the 155-day periodicity reported for the earlier cycles, 19, 20, and 21, could not be confirmed in our analysis. to be submitted to Solar Physics; an extended abstract.
126.
1996.12 구독 인증기관·개인회원 무료
In the present work we introduce a new flare activity indicator, MAD and examine its characteristics by analyzing a set of successive three days' observations of a typical active region, AR2372. The computed MAD is compared with conventional activity indicator such as separator. It is found that. (1) MAD traces very well the separator, (2) it. singles out. local discontinuity of magnetic field lines and (3) it. is a good measure of describing the evolutionary status of active region.
127.
1996.12 구독 인증기관·개인회원 무료
We present the Programme of Monitoring of Flare Stars in the Orion aggregate by. CCD based. Photometer mounted at the Newtonian focus of 70/98/210-cm meniscus telescope through glass imaging quality C1 filter (3900Å/800Å) with a time resolution of 0.5-1.0 min.
128.
1996.12 구독 인증기관·개인회원 무료
130.
1996.12 구독 인증기관·개인회원 무료
We present 3 rare subtypes of the FFSs observed with high temporal resolution at 4-frequency (1.42, 2.13, 2.84 and 4.2G GHz). The various FFSs occurred during the main and post-flare phase can demonstrate that coronal nonthermal electron acceleration/injection may go through the whole development process of flares, and deduce that there may exist the re-forming of loop-like structures in the post-flare phase, and the complex multi-type magnetic structures in corona.
131.
1996.12 구독 인증기관 무료, 개인회원 유료
Here we report the results from spectroscopic observations of soloar active regions in the HeI 10830 Å line at the German Vacuum Tower Telescope(VTT) in Tenerife during the August 199:3 International EFR(Emerging Flux Region) Campaign. Four active regions in various stages of their evolution, i.e., NOAA7558, 7560, 7561, and 7562, were ovserved on 10 August 1993. From the observed HeI 10830 Å spectra in these active regions, spectroscopic quantities such as equivalent width(EW), doppler shift, doppler width, etc., were derived(see Figure l(a)) and the correlation between them were studied(see Figure l(b)). Our main results are as follows: (I)In NOAA7562, which is a young and evolving EFR, the EW is large, while it is small around a simple and roundish spot of NOAA7558. (2)In these active regions, redshift in the 10830 line is dominant when the EW is larger. (3)As the doppler width increases, the line tends to shift redward. (4)When the EW is smaller, it seems to exist another component which have dynamic characteristics different from the redshifting component. In NOAA7560 and NOAA7561, regions which have several small spots, the values of the EW are intermediate. Results (2) and (3) may suggest the possible existence of downflow above active regions, if the HeI 10830 Å line is formed in the upper chromopshere, and it is consistent with the earlyer result from the SMM extreme-ultraviolet observation by Klimchuk(1987, Astrophys. J., 323, 368) (to be submitted. to Astronomy and Astrophysics; an extended abstract)
3,000원
132.
1996.12 구독 인증기관·개인회원 무료
The long quasi-periodic (several tens of seconds) pulsations were observed at. short decimetric wavelength (1.42 and 2.00 GHz). Here, we introduce the features (about bandwidth, periodicity, amplitude and relative amplitude) of these pulsations, then give the discussion about them.
133.
1996.12 구독 인증기관·개인회원 무료
In the present study we examine physical characteristics of a thin and rigid magnetic flux tube with a steady flow inside, which is embedded vertically upward in the solar atmosphere. We found from this study that (1) The downward material flow gives rise to a dominant heating in the flux tube which works with the conductive heating in the same direction. However, the upflow flow creates a dominant cooling which works against the conductive heating, resulting in a steeper temperature gradient with a shallower transition region. (2) Since the thickness of the transition region determines the material content in the transition region, a broader transition region of the downflow tube produces a larger differential measure.
134.
1996.12 구독 인증기관·개인회원 무료
We present here the solar LOG GF values obtained using the Liege solar at las and the standard solar photospheric models for the spectral lines in the wavelength range ⋋⋋ 6209 - 6273 Å. These log gf values shall be used to interpret a high resolution spectra of the star ɤ Draconics.
135.
1996.12 구독 인증기관·개인회원 무료
Solar IR spectra have been utilised by us to derive log gf values for atomic lines due to 17 chemical elements. in the J and H bands, i.e. in the wavelength ranges 1.00 - 1.34 μm and 1.49 - 1.80 μm respectively. The observed central line depths were based on the FTS atlases published at. Liege and KPNO. We also reprot new log gf values for 51 lines for which neither theoretical nor experimental values are available till date.
136.
1996.12 구독 인증기관·개인회원 무료
The contrasting values of the oscillator strengths for the (0,0) band of SiH+ molecules for the A 1II-X 1∑+ transition reported in literature, motivated us to reinvestigate the same with the help of a new set of well accepted solar photospheric models, elemental abundances and dissociation energy.
137.
1996.12 구독 인증기관 무료, 개인회원 유료
Spectroscopic data between 7 and 15 microns obtained in 1979 by Voyager 1 and 2 Infrared Interferometer Spectrometer (IRIS) have been revisited. Using the spectral data, Jupit.er images have been constructed at the emission bands of hydrocarbons, such as methane, ethane, and acetylene. The resultant. images show differences in emission intensities in the polar regions, suggesting inhomogeneous distributions of the hydrocarbons over the auroral regions of Jupiter.
3,000원
138.
1996.12 구독 인증기관 무료, 개인회원 유료
In this paper it is explained how most of asteroids can avoid very close approach to Jupiter, to the earth for earth orbit crossing asteroids, and to Neptune for Kuiper-belt asteroids by mechanisms which work also for Neptune-Pluto system. In fact the mutual distance of the planets cannot become very small as the critical argument librates around 180° because of 2:3 mean motion resonance and the argument of perihelion of Pluto librates around 90°. And it is found that among nearly 40 Kuiper-belt asteroids discovered in recent years 40% have orbits similar to Pluto. For main-belt asteroids the distribution with respect to the semi-major axes has peculiar characteristics and the author tries to explain how their peaks and gaps are created. It is also found that 30% of 80 earth orbit crossing asteroids which have minimum perihelion distances less than 1.04AU have no chance to collide with the earth. Still 30% of them have a few probability to collide with the earth as they have dynamical characteristics of short-periodic comets.
3,000원
139.
1996.12 구독 인증기관·개인회원 무료
140.
1996.12 구독 인증기관·개인회원 무료
Reanalysis of the observations of Mars made at the Hida Observatory in 1975 with a new image processing method is reported. Red filter images taken in the period before vernal equinox (areocentric longitude of the sun Ls=0°) revealed dark surface features at the northern high latitudes, while blue filter images taken at the same time showed the extensive polar hood. The latitude of the northernmost feature observed was about 67°N. An extensive north polar cap, which is predicted by most of the existing models and observed with Viking, did not exist in our reanalyzed images obtained at the Hida Observatory in 1975.
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