Serbian Astronomical Journal最新文献_第8页

Solar flares and variation of local geomagnetic field: Measurements by the Huancayo Observatory over 2001-2010 太阳耀斑与局部地磁场的变化:2001-2010年万卡约天文台的测量

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2017-01-01 DOI: 10.2298/SAJ160424002C

R. C. Reyes, Gabriel A.Gárate Ayesta, F. Navarro

{"title":"Solar flares and variation of local geomagnetic field: Measurements by the Huancayo Observatory over 2001-2010","authors":"R. C. Reyes, Gabriel A.Gárate Ayesta, F. Navarro","doi":"10.2298/SAJ160424002C","DOIUrl":"https://doi.org/10.2298/SAJ160424002C","url":null,"abstract":"We study the local variation of the geomagnetic field measured by the Huancayo Geomagnetic Observatory, Peru, during 2001-2010. Initially, we sought to relate the SFI values, stored daily in the NOAA’s National Geophysical Data Center, with the corresponding geomagnetic index; however, no relation was observed. Nonetheless, subsequently, a comparison between the monthly geomagnetic-activity index and the monthly SFI average allowed observing a temporal correlation between these average indices. This correlation shows that the effect of the solar flares does not simultaneously appear on the corresponding magnetic indices. To investigate this, we selected the most intense X-class flares; then, we checked the magnetic field disturbances observed in the Huancayo Geomagnetic Observatory magnetograms. We found some disturbances of the local geomagnetic field in the second and third day after the corresponding solar flare; however, the disturbance strength of the local geomagnetic field is not correlated with the X-class of the solar flare. Finally, there are some disturbances of the local geomagnetic field that are simultaneous with the X-class solar flares and they show a correlation with the total flux of the solar flare.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

OBSERVATIONS AND LIGHT CURVE SOLUTIONS OF THE ECLIPSING BINARIES USNO-B1.0 1395-0370184 AND USNO-B1.0 1395-0370731 食双星usno-b1.0 1395-0370184和usno-b1.0 1395-0370731的观测及光曲线解

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-12-01 DOI: 10.2298/SAJ160328005K

D. Kjurkchieva, V. Popov, D. Vasileva, N. Petrov

引用次数: 1

On the Galactic Distributions of Radio Pulsars and Plasma Density 射电脉冲星的星系分布与等离子体密度

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-12-01 DOI: 10.2298/SAJ1693001A

A. Ankay, E. Yazgan, P. Kutukcu

{"title":"On the Galactic Distributions of Radio Pulsars and Plasma Density","authors":"A. Ankay, E. Yazgan, P. Kutukcu","doi":"10.2298/SAJ1693001A","DOIUrl":"https://doi.org/10.2298/SAJ1693001A","url":null,"abstract":"Astronomical observations are fundamentally different as compared to laboratory experiments. In the former case, it is not possible to change the physical conditions of the objects under examination nor to fix their physical parameters, whereas in the latter case, controlled experiments can be done. Even the whole set-up can be changed or the object under examination can be replaced with another, more suitable one and the measurements can be repeated under more or less desired conditions. On the other hand, the maximum values of physical variables that can be attained and maintained for long time intervals are highly limited in laboratory conditions. This fact is especially important in checking and finding the limitations and the boundaries of applicability of some fundamental theories in physics. Checking the limit of Einstein’s theory of gravitation for strong gravitational fields is not possible in laboratory experiments done on Earth. The only hope to have some progress in this area of exploration is related to indirect observations of black holes. Neutron stars are next to black holes in having extremely high values of some physical quantities, especially the density and the magnetic field, and they give the advantage of direct observations. The main difficulty in determining some of their intrinsic and extrinsic properties is due to the fact that determining the distances to astronomical objects is a complicated problem in many cases. The neutron star distances need to be known accurately throughout the Galaxy for example to calculate their radiative power.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2016-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Interaction between Yarkovsky Force and Mean-Motion Resonances: Some Specific Properties 亚尔科夫斯基力与平均运动共振的相互作用:一些特殊性质

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-12-01 DOI: 10.2298/SAJ160613007Z

I. Milic-Zitnik

引用次数: 4

Behaviour of electron content in the ionospheric d-region during solar x-ray flares 太阳x射线耀斑期间电离层d区电子含量的行为

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-12-01 DOI: 10.2298/SAJ160404006T

M. Drakul, V. M. vCadevz, J. Bajvceti'c, L. Popovi'c, D. Blagojevi'c, A. Nina

{"title":"Behaviour of electron content in the ionospheric d-region during solar x-ray flares","authors":"M. Drakul, V. M. vCadevz, J. Bajvceti'c, L. Popovi'c, D. Blagojevi'c, A. Nina","doi":"10.2298/SAJ160404006T","DOIUrl":"https://doi.org/10.2298/SAJ160404006T","url":null,"abstract":"One of the most important parameters in ionospheric plasma research also having a wide practical application in wireless satellite telecommunications is the total electron content (TEC) representing the columnal electron number density. The F region with high electron density provides the biggest contribution to TEC while the relatively weakly ionized plasma of the D region (60 km - 90 km above Earths surface) is often considered as a negligible cause of satellite signal disturbances. However, sudden intensive ionization processes like those induced by solar X ray flares can cause relative increases of electron density that are significantly larger in the D-region than in regions at higher altitudes. Therefore, one cannot exclude a priori the D region from investigations of ionospheric influences on propagation of electromagnetic signals emitted by satellites. We discuss here this problem which has not been sufficiently treated in literature so far. The obtained results are based on data collected from the D region monitoring by very low frequency radio waves and on vertical TEC calculations from the Global Navigation Satellite System (GNSS) signal analyses, and they show noticeable variations in the D region electron content (TECD) during activity of a solar X ray flare (it rises by a factor of 136 in the considered case) when TECD contribution to TEC can reach several percent and which cannot be neglected in practical applications like global positioning procedures by satellites.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2016-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 17

Observations and light curve solutions of four ultrashort-period binaries 四个超短周期双星的观测及光曲线解

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-06-01 DOI: 10.2298/SAJ150914001K

D. Kjurkchieva, V. Popov, D. Vasileva, N. Petrov

引用次数: 5

DYNAMICS OF TACHYON FIELDS AND INFLATION - COMPARISON OF ANALYTICAL AND NUMERICAL RESULTS WITH OBSERVATION 速子场和膨胀的动力学——分析和数值结果与观测的比较

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-01-01 DOI: 10.2298/SAJ160312003M

M. Milošević, D. Dimitrijevic, G. Djordjevic, Marko Stojanovic

引用次数: 5

The Newtonian and MOND dynamical models of NGC 5128: Investigation of the dark matter contribution NGC 5128的牛顿和MOND动力学模型:暗物质贡献的研究

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-01-01 DOI: 10.2298/SAJ160113002S

S. Samurović

{"title":"The Newtonian and MOND dynamical models of NGC 5128: Investigation of the dark matter contribution","authors":"S. Samurović","doi":"10.2298/SAJ160113002S","DOIUrl":"https://doi.org/10.2298/SAJ160113002S","url":null,"abstract":"We study the well-known nearby early-type galaxy NGC 5128 (Centaurus A) and use the sample of its globular clusters to analyze its dynamics. We study both Newtonian and MOND models assuming three cases of orbital anisotropies: isotropic case, mildly tangentially anisotropic case and the radially anisotropic case based on the literature. We find that there are two regions with different values of the velocity dispersion: interior to ~ 3 effective radii the value of the velocity dispersion is approximately 150 km s−1 , whereas beyond ~ 3 effective radii its value increases to approximately 190 km s−1 , thus implying the increase of the total cumulative mass which is indicative of the existence of dark matter there in the Newtonian approach: the mass-to-light increases from M/LB = 7 in the inner regions to M/LB = 26 in the outer regions. We found that the Navarro-Frenk-White (NFW) model with dark halo provides good description of the dynamics of NGC 5128. Using three MOND models (standard, simple and toy), we find that they all provide good fits to the velocity dispersion of NGC 5128 and that no additional dark component is needed in MOND. [Projekat Ministarstva nauke Republike Srbije, br. 176021: Visible and Invisible Matter in Nearby Galaxies: Theory and Observations]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Orbit limited theory in the solar wind - κ distributions 轨道限制理论在太阳风- κ分布

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2016-01-01 DOI: 10.2298/SAJ160220004M

M. Martinović

{"title":"Orbit limited theory in the solar wind - κ distributions","authors":"M. Martinović","doi":"10.2298/SAJ160220004M","DOIUrl":"https://doi.org/10.2298/SAJ160220004M","url":null,"abstract":"When a solid object is immersed into ionized gas it gets brought to a certain value of electrostatic potential and surrounded by a space charge region called ‘plasma sheath’. Through this region, particles are attracted or repelled from the surface of the charge collecting object. For collisionless plasma, this process is described by the so-called orbit limited theory, which explains how the collection of particles is determined by the collector geometry and plasma velocity distribution function (VDF). In this article, we provide explicit expressions for orbit-limited currents for generalized Lorentzian (κ) distributions. This work is useful to describe the charging processes of objects in non-collisional plasmas like the solar wind, where the electrons VDF is often observed to exhibit quasi power-law populations of suprathermal particles. It is found that these ‘suprathermals’ considerably increase the charge collection. Since the surface charging process that determines the value of electrostatic potential is also affected by the plasma VDF, calculation of the collector potential in the solar wind is described along with some quantitative predictions. [Projekat Ministarstva nauke Republike Srbije, br. 176002]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Contribution of solar hydrogen Lyα line emission in total ionization rate in ionospheric D-region during the maximum of solar X-flare 太阳x耀斑极大期太阳氢Lyα线发射对电离层d区总电离率的贡献

IF 0.5 4区物理与天体物理

Serbian Astronomical Journal Pub Date : 2015-12-01 DOI: 10.2298/SAJ150828003N

A. Nina, V. M. vCadevz, J. Bajvceti'c

引用次数: 2