Numerical simulations of three-dimensional magnetic swirls in a solar flux-tube     

Piotr Chmielewski  Krzysztof Murawski  Alexandr A.Solov’ev 《中国天文和天体物理学报》2014,(7):855-863

We aim to numerically study evolution of Alfv′en waves that accompany short-lasting swirl events in a solar magnetic flux-tube that can be a simple model of a magnetic pore or a sunspot. With the use of the FLASH code we numerically solve three-dimensional ideal magnetohydrodynamic equations to simulate twists which are implemented at the top of the photosphere in magnetic field lines of the flux-tube. Our numerical results exhibit swirl events and Alfv′en waves with associated clockwise and counterclockwise rotation of magnetic lines, with the largest values of vorticity at the bottom of the chromosphere, and a certain amount of energy flux.  相似文献   

The estimation of the mean density in the Universe     

Piotr Flin 《Astrophysics and Space Science》1982,83(1-2):437-439

The mean density of matter, as estimated from deep optical samples of galaxies, is too low to close the Universe. However, some additional considerations do not exclude such a possibility.  相似文献   

The Electrostatic Blow-Off of Cometary Grains and Variations and Outbursts of Brightness of Comets at Large Heliocentric Distances     

Piotr Gronkowski 《Astrophysics and Space Science》2004,294(3-4):135-150

Interaction between the strong solar wind and the dark side of a cometary nucleus was considered. It was calculated that the potential of the dark side of the cometary nucleus could be numerically large and negative. Assuming that the nucleus of the comet has surface mantle which consists of loose, fine dust-ice particles, it was shown that cometary particles could electrostatically levitate over the nucleus. It was examined how this phenomenon affected the changes in the cometary brightness. Calculations were carried out for realistically assumed values of a large range of cometary parameters. It was shown that the considered mechanism could lead to the variations of cometary brightness, sometimes even to the outbursts of brightness.  相似文献   

Directional Distribution of Observable Comets Induced by A Star Passage Through the Oort Cloud     

Piotr A. Dybczyński 《Earth, Moon, and Planets》2002,90(1-4):483-488

We simulated the passage of a star through the Oort cometary cloud andanalyzed the resulting sample of observable long period comets, noting strong asymmetries in the directional distribution of the perihelion points of thosecomets. We discuss the results previously published byWeissman (1996) for the same case. An explanation is suggestedwhy the isotropic output can be obtained only for a very peculiar case. The``cometary shower' density variation with time is also presented and thetime-dependence of the directional distribution is discussed.  相似文献   

Interfacing the DIGICO flux-gate spinner magnetometer to an APPLE IIe microcomputer     

Piotr Tucholka  Jerôme Tessier 《Geophysical Journal International》1987,89(2):705-712

Summary. A hardware configuration and program are described for interfacing a DIGICO spinner rock magnetometer to an APPLE microcomputer. This configuration provides full control of measurements and permits storage of the results on floppy or hard discs. A similar configuration can be used to operate the anisotropy unit.  相似文献   

Period Change of CU Pegasi     

Elena Panko  Piotr Flin  Alexander Pikhun 《Astrophysics and Space Science》2006,305(4):385-388

On the basis of the published times of minima and our own observations, we analysed the period change of the Algol-type eclipsing binary CU Pegasi. Over almost seventy years of observations, the parabolic period change has been clearly seen as dP/dt = 1.38 × 10⁻⁶ d/year. The estimated mass transfer in the system is about 1 × 10⁻⁷ M_M⊙/year.  相似文献   

Origin and evolution of the Bezedna lake–mire complex in the Lublin area (East Poland): a case study for permafrost lakes in karstic regions     

Radosław Dobrowolski  Piotr Kulesza  Jacek Łojek  Irena Agnieszka Pidek 《Journal of Paleolimnology》2015,53(2):191-213

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Periglacial structures within fluvio‐aeolian successions of the end of the Last Glaciation – examples from SE Poland and NW Ukraine     

Paweł Zieliński  Robert J. Sokołowski  Stanisław Fedorowicz  Iwan Zaleski 《Boreas: An International Journal of Quaternary Research》2014,43(3):712-721

The nature of permafrost and related environmental conditions in the Weichselian Late Pleniglacial and Lateglacial are reconstructed based on the assessment of frost structures that are best documented in the Loess Belt and in plateau areas composed of glacial till. Investigations were conducted in the central‐eastern part of the European Sand Belt (SE Poland and NW Ukraine) on a fluvio‐aeolian sedimentary succession and took into account its chronological context given by luminescence dating. Various generations of periglacial structures found in these deposits indicate not only the development of permafrost (ice‐wedge pseudomorphs) and decreased humidity (composite wedge casts) but also the degradation of permafrost (large‐scale involutions) and, finally, the establishment of deep seasonal frost (frost cracks). The diversity of structures in the study region appears to result from local conditions rather than increasing continentality of climate towards the east.  相似文献   

SphinX: The Solar Photometer in X-Rays     

Szymon Gburek  Janusz Sylwester  Miroslaw Kowalinski  Jaroslaw Bakala  Zbigniew Kordylewski  Piotr Podgorski  Stefan Plocieniak  Marek Siarkowski  Barbara Sylwester  Witold Trzebinski  Sergey V. Kuzin  Andrey A. Pertsov  Yurij D. Kotov  Frantisek Farnik  Fabio Reale  Kenneth J. H. Phillips 《Solar physics》2013,283(2):631-649

Solar Photometer in X-rays (SphinX) was a spectrophotometer developed to observe the Sun in soft X-rays. The instrument observed in the energy range ≈?1?–?15 keV with resolution ≈?0.4 keV. SphinX was flown on the Russian CORONAS–PHOTON satellite placed inside the TESIS EUV and X telescope assembly. The spacecraft launch took place on 30 January 2009 at 13:30 UT at the Plesetsk Cosmodrome in Russia. The SphinX experiment mission began a couple of weeks later on 20 February 2009 when the first telemetry dumps were received. The mission ended nine months later on 29 November 2009 when data transmission was terminated. SphinX provided an excellent set of observations during very low solar activity. This was indeed the period in which solar activity dropped to the lowest level observed in X-rays ever. The SphinX instrument design, construction, and operation principle are described. Information on SphinX data repositories, dissemination methods, format, and calibration is given together with general recommendations for data users. Scientific research areas in which SphinX data find application are reviewed.  相似文献   

An empirical test of household identification risk in geomasked maps     

Dara E. Seidl  Piotr Jankowski  Atsushi Nara 《制图学和地理信息科学》2013,40(6):475-488

ABSTRACT

Geomasking techniques displace point data to new locations in order to protect privacy while maintaining overall spatial distributions. If the end users of geomasked data are unaware that the data are masked, there is a risk that they will incorrectly associate individuals at the new locations with the masked data attributes. The probability of correct and false household identification depends on human understanding of whether maps contain masked coordinates and the spatial relationships of the points to contextual geographic data. Using a map-based experiment, this study finds that confidence in performing a household identification is substantially lowered when masked points are situated equidistantly between residential parcels. Despite initial notifications that data are masked, map users often report confidence in assigning masked points to specific households. Only map users who receive frequent notifications that the points are masked have reduced confidence in associating them with particular households, thereby lowering identification risk.  相似文献