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Start Over Language Czech Subject astrophysics Type model:article

52. On the light pulsation of bright Geminids according to photographic data

Creator:
Babadzhanov, P. B. and Konovalova, N. A.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, bright Geminids, and photometric light curves
Language:
Czech
Description:
The photometric light curves of bright Geminids are investigated. The analysis of the light curves reveals a peculiar nature of meteor luminosity with rapid flickering and small brightness fluctuations. This peculiarity of the luminosity of the bright Geminids points to a certain ablation process of these meteoroids in the Earth’s atmosphere. According to estimates of the energy of ablation a conclusion wae made that the investigated Geminid meteoroids were disrupted in the atmosphere by the melting and cyclic ablation of the surface-layer of meteoric matter.
Rights:
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53. On the origin and early stages of the meteor streams

Creator:
Plavec, Miroslav
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics and meteor streams
Language:
Czech
Description:
1. Cemetary outbursts and the origin of meteor streams Cometary outbursts, pointed out by Richter, are studied on the basis of recent investigations by Whitney. Unlike Whitney´s assumption of a uniformity of dimensions, a wide range of radii is supposed for the ejected particles. Assuming the distribution law N(s) ds ~ s^-4 ds to be valid over the range from 10^-5 cm to 1 cm, we obtain 7 . 10^11 g for the entire mass of particles ejected at an outburst The dynamical effect of such an outburst upon te comet´s morion is negligible. The ejected particles can produce a remarkable meteoric shower as long as they occupy a space of the same order of dimenstions as do the Draconids. A permanent stream cannot be generated by a single ouburst. In order to explain the existence of the Draconids, it is probably necessary to postulate an ejection of 10^11 g of meteors per revolution of the parental comet. This hypothesis seems to be plausible. Internal forces far fainter than those operating at the outburst would suffice to account for such a process. Slow ejections supposed here cannot manifest itselves in the motion of the comet, but they may be detected photometrically and spectroscopically.., 2. Ejection theory of the formation of the meteor streams An analysis of the Draconids and Leonids shows that the ejection velocities are probably very low. In this case, simple formulae derived in 2.2. can be applied to in computing the orbits of the ejected meteors. The newly formed awarm is very thin, but the meteor become rapidly dispersed along the orbit of the ocmet. Four simple models of meteor awarms after ejection are considered and the distribution of meteors along the orbit investigated., 3. Local perturbations of meteor streams An approximate analytical method is derived to account for local perturbations of meteor streams due to a close approach of a major planet. The cases of the Lyrids and Draconids are investigated. The great importance of planetary perturnbations is shown numerically. It is concluded that the Draconids observed in 1933 and 1946 could hardly have originated before the close approach of the parental comet to Jupiter in 1898., 4. Mass and density of meteor streams A method of calcularing the total mass and density of meteor streams is developed and applied to the Draconids of 1933. From the visual and telescopic observations it is found that the probable mass of this awarn is of the order of 10^12 g. Although the spatial density inside the concentrated cloud is considerable, the total mass is far lower than that of the Geminids or Perseids. This, again, may be due to the fact that the stream is still being formed., and Článek je rozdělen do 4 kapitol, z nichž každá má samostatný abstrakt (na str. 5-6)
Rights:
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55. On the origin of HXIS arches

Creator:
Kopp, R. A. and Poletto, G.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, giant coronal arches, and Hard X-ray Spectrometer
Language:
Czech
Description:
During SMM operation in 1980 the HXIS instrument detected a few giant coronal arches, extending to high altitude (-10 km) and with widely separated footpoints, which always appeared after tworibbon (2-R) flares. The origin of these extensive structures is unknown, but their association with 2-R ovents suggests that both phenomena may be attributed to the same mechanism. Tlie continued energy release during the decay phase of 2-R flare is identifled with reconnection which allows an open field configuration to relax back to a lower energy state, lbe growing post-flare loop system is the visible manifestation of this process, tracing the rise with time of the neutral point. In this paper we examine the possibility that HXIS arches form as a result of magnetic rcconnection occurring at high levels. In order to test this hypothesis we develop a model capable of representing the 3-dimensional geometry of a reconnecting magnetic field and compare model predictions with observations of the giant arch imaged by HXIS on May 22, 1980. We conclude tliat the topology of the reconnected magnetic field, as well as the energy released by reconnection, are in good agreement with the observed shape and thermal energy content of tlie arch, supporting, at least in this case, the hypothesis that HXIS arches form through the reconnection mechanism.
Rights:
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58. Oscillations and waves in sunspots

Creator:
Staude, J., Žugžda, V. D., and Locans, V.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, sunspots, and oscillations
Language:
Czech
Description:
We review the basic features of oscillations observed at different height levels in the sunspot atmosphere, moreover, various possibilities for a theoretical interpretation are discussed. In the umbra oscillation power is concentrated in severa] period bands (3 min., 5 min., and ≥ 20 min.) which on their part are composed of closely packed peaks. The observed amplitudes and phases of velocity and of intensity oscillations depend in a characteristic way on the period and on the height. These features are used to look for the most probable physical mechanisms which could produce the different modes: At subphotospheric depths two independent resonators are acting. A resonator for slow, quasi-transveree waves can explain the lifetimes of umbral dots (≥ 20 min.), while a resonator for fast (acoustic), quasi-longitudinal waves could result in the umbral 5-min. oscillations. The acoustic resonator strongly couples with the slow-mode longitudinal resonator at photospheric and chromospheric heights, the latter produces the resonance peaks in the 3-min. band. Running penumbral waves can be explained by the transformation of 5-min, waves from the convective zone in the almost horizontal magnetic field. The interpretation of oscillations provides a new method of probing not only subphotospheric, but also atmospheric layers of sunspots (e.g., of determining temperature gradients), thus completing customary spectroscopic diagnostics.
Rights:
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59. Paralelní numerické simulace plazmových procesů ve slunečních erupcích

Creator:
Karlický, Marian and Bárta, Miroslav
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
astrofyzika, sluneční erupce, modelování a simulace, astrophysics, solar flares, modeling and simulation, 6, and 53
Language:
Czech
Description:
Sluneční erupce spojené s koronálními výrony hmoty jsou nejenergetičtějšími dynamickými procesy ve sluneční soustavě s dopadem na celou heliosféru, včetně Země a jejího blízkého kosmického okolí. Protože k uvolnění energie v erupcích dochází podle současných představ kaskádním procesem na mnoha škálách, je v tomto článku o numerickém modelování procesů ve slunečních erupcích uplatněno mnohoškálové hledisko: bude představen numerický MHD model erupce na globálních škálách (~10(8) m) i částicové modelování máloškálových (~10 m) plazmových procesů, které mají přímý vztah k disipaci magnetické energie v erupci, k formování svazků urychlenýchh částic a jejich následné termalizaci v bezesrážkovém erupčním plazmatu prostřednictvím vlnově-částicových interakcí., Marian Karlický, Miroslav Bárta., and Obsahuje seznam literatury
Rights:
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