Longitudinal distribution of PCA sources on the sun     

L. Fritzová-Svestková  Z. Švestka 《Solar physics》1971,17(1):212-217

For 181 PCA's recorded during the years 1956–1969 the association with flares is studied. Both the number of events which cannot be associated with any flare on the visible hemisphere, as well as the longitude distribution of identified proton flares, lead to the conclusion that 25–30% of PCA's are caused by flares behind the western solar limb. PCA's of this kind are mostly small. During the investigated years no PCA > 13 dB and possibly no PCA > 8.5 dB were caused by flares behind the limb, while hardly 60% of PCA's < l dB had their origin on the visible hemisphere. While the sources of GLE's and of PCA's in general, are centered around 50°W which corresponds to the average curvature of the magnetic field lines in interplanetary space, the strongest PCA's (> 8.5 dB) show an anomalous longitude distribution centered around ∼ 20°W. It is suggested that this anomaly may be a consequence of the fact that in strong PCA events the kinetic energy density of protons below 100 MeV becomes comparable to the magnetic energy density in space, thus leading to a ‘straightening’ of the magnetic field lines.  相似文献   

On the flux of neutrons from flares     

Z. Švestka 《Solar physics》1971,19(1):202-206

Under the assumption that white-light flares are caused by energetic particles penetrating into the photosphere (vestka, 1970a; Najita and Orrall, 1970) the known number of protons needed for the white-light emission is used to obtain an estimate of the production of neutrons occurring at the same time. In the case of the white-light flare of 23 May, 1967, the peak flux of neutrons at the Earth distance had to exceed 3 neutrons/cm²s, thus being detectable in space. This maximum neutron flux reached the Earth as early as the time of the maximum phase of the flare in the H light. However, reasonable estimates show that flares associated with a detectable neutron flux should be fairly rare phenomena, maybe as rare as the white-light flares.On leave from the Astronomical Institute of the Czechoslovak Academy of Sciences, Ondejov.  相似文献   

Polarization properties of silicate-like grains in circumstellar envelopes of late-type stars due to temperature variations     

J. Svatoš  M. Šolc  V. Vanýsek 《Astrophysics and Space Science》1975,34(1):149-154

The influence of temperature changes in circumstellar silicate-like envelopes upon the polarization effects is investigated. It is shown that under the assumption that ΔT _g>50° and conductivity of silicate grains is indirectly proportional toT _g this mechanism can be responsible for the observed dependence of intensity vs polarization in some late-type stars, e.g. V CVn. The same effects can be produced by dirty ices and graphite grains. It is suggested that irradiation by electrons and/or protons can affect the circumstellar envelopes in a similar way, especially those of early-type stars, and irradiation by neutrons can exert an influence on the envelopes of supernovae.  相似文献   

Introduction     

Cornelis De Jager  Zdeněk Švestka 《Solar physics》1981,72(1-2):vii-vii

  相似文献   

On the behaviour of the hydrogen Lyman series in flares     

L. D. De Feiter  Z. Švestka 《Solar physics》1975,41(2):415-424

The Lyman spectrum of hydrogen has been computed for a number of flare models, characterized by the column density of hydrogen atoms in the ground state (N ₁), the electron density (n _e) and the electron temperature (T _e). Broadening by the thermal Doppler effect and by Stark effect has been accounted for. The source functions for the individual lines of the series have been derived from non-LTE calculations of the excitation in hydrogen flares. The aim of the investigation is to evaluate the use of the intensities in between two successive Lyman lines for a determination of the value for N ₁, which is a physical parameter of the flare for which only indirect determinations are available. Whilst in principle this method could give reliable results, its practical application meets with difficulties which hardly can be overcome. Therefore, one probably has to base the N ₁ determination on the highest line resolvable in the spectrum.  相似文献   

Highlights of the Flare Build-up Study     

V. Gaizauskas  Z. Švestka 《Solar physics》1987,114(2):389-398

Years of preparation within the framework of the Flare Build-up Study culminated with intensive observations of solar flares during the Solar Maximum Year (1979–1981). Scientists operating several spacecraft and roughly 70 ground-based observatories participated in an internationally coordinated effort to observe flares with higher spatial, spectral, and temporal resolution over a wider range of wavelengths than heretofore. The FBS stimulated important advances in theories of magnetic reconnection and the growth of plasma instabilities under preflare circumstances. A series of international FBS workshops facilitated data exchanges and collaborative studies for interpreting and synthesizing the wealth of new information about flares. The FBS ended officially at the Symposium on Synopsis of the Solar Maximum Analysis held 2–5 July, 1986 at the COSPAR meeting in Toulouse, France. Here we summarize highlights of its progress towards an understanding of the storage and release of preflare energy.  相似文献   

Arsenic Speciation in Lichens and in Coarse and Fine Airborne Particulate Matter by HPLC–UV–HG–AFS     

M. M. Farinha  Z. Šlejkovec  J. T. van Elteren  H. Th. Wolterbeek  M. C. Freitas 《Journal of Atmospheric Chemistry》2004,49(1-3):343-353

A three-step sequential extraction procedure with Milli-Q, CaCl₂ and H₃PO₄ was applied for extraction of arsenic species in lichen transplants and airborne particulate matter (fine and coarse fractions). The samples used in this work were collected in 1994–1995 near coal-fired power plants. Both transplant lichens and airborne particulate matter were submitted to the same environment simultaneously. Arsenic species identification and quantification was performed by HPLC–UV–HG–AFS. Inorganic forms of arsenic (arsenite and arsenate) were present in significant amounts in most of the samples. Only in lichens also organic forms of arsenic (monomethyl arsonic acid and dimethyl arsinic acid) were identified which may indicate biotransformation of inorganic arsenic.  相似文献   

Large-scale horizontal flows in the solar photosphere IV. On the vertical structure of large-scale horizontal flows     

M. Švanda  M. Klvaňa  M. Sobotka  A.G. Kosovichev  T.L. Duvall 《New Astronomy》2009,14(4):429-434

In the recent papers, we introduced a method utilised to measure the flow field. The method is based on the tracking of supergranular structures. We did not precisely know, whether its results represent the flow field in the photosphere or in some subphotospheric layers. In this paper, in combination with helioseismic data, we are able to estimate the depths in the solar convection envelope, where the detected large-scale flow field is well represented by the surface measurements. We got a clear answer to question what kind of structures we track in full-disc Dopplergrams. It seems that in the quiet Sun regions the supergranular structures are tracked, while in the regions with the magnetic field the structures of the magnetic field are dominant. This observation seems obvious, because the nature of Doppler structures is different in the magnetic regions and in the quiet Sun. We show that the large-scale flow detected by our method represents the motion of plasma in layers down to ～10 Mm. The supergranules may therefore be treated as the objects carried by the underlying large-scale velocity field.  相似文献   

The importance of symbols in the region formation process     

Miroslav Šifta  Pavel Chromý 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(2):98-113

The aim in the article is to conceptualize the general foundations of research on the importance of regional symbolism in the process of region and regional identity formation. The article is founded on a critical analysis of works pertaining not only to the field of the new regional geography, but also to the field of regional marketing and/or branding, sociology, and semiology. The authors focus on meanings attributed to symbols and symbolism in literature, and observe which elements are viewed as regional symbols and how these symbols contribute to the process of regional development and institutionalization, especially in the formation of its symbolic shape. They examine the thematic and theoretical grounds, looking at identity, regional identity, and regional institutionalization. Next, regional symbols are defined and classified according to their types and forms, and their importance in the process of regional formation and institutionalization is discussed. The results show that symbols of any type can play an important role in a region’s marketing, and become the key image associated with a region. The authors conclude that regional symbols are a significant feature of the formation of a region and its identity, both outwardly (the external image of a region) and inwardly (concerning the inhabitants’ relationships with their region).  相似文献   

PROJECTIONS OF CLIMATE CHANGE FOR THE CZECH REPUBLIC     

Jaroslava KALVOVÁ  Ivana NEMEŠOVÁ 《Climatic change》1997,36(1-2):41-64

The paper deals with a selection of the climatological baseline, GCM validity and construction of the climate change scenarios for an impact assessment in the Czech territory. The period of 1961–1990 has been selected as the climatological baseline. The corresponding database includes more than 50 monthly mean temperature and precipitation series, and 16 time series of daily meteorological data that contain also the solar radiation data. The 1× CO₂ outputs produced by four GCMs, provided by the CSMT (GISS, GFD30, GFD01, and CCCM), were compared with observed temperature and precipitation conditions in western and central Europe with a particular attention devoted to the Czech territory. The GCM ability to simulate annual cycles of temperature, precipitation and radiation was thoroughly examined. The GISS and CCCM were selected as a basis for constructing climate change scenarios as they simulated reasonably the observed patterns. According to the GISS variant, 2× CO₂ climate assumes a higher winter and lower summer warming, and an increase in annual precipitation amounts. A dangerous combination of the summer temperature increase and declining precipitation amounts is a specific feature of the CCCM scenario. An incremental scenario for temperature and precipitation is based on the combination of prescribed changes in both annual means and annual courses.  相似文献