Can mirage phenomena be traced on the sun?     

Yngve Öhman 《Solar physics》1985,96(1):209-212

It is suggested, that effects of total reflection and refraction may appear sometimes in various objects on the Sun in connection with grazing incidence towards layers formed by magnetic fields and perhaps also by electrostatic double layers or shock waves. It seems possible that such effects may influence sometimes the contrast of bright structures as well as dark structures at selective wavelengths as well as in white light.  相似文献   

A comparison of the near-ultraviolet continuum and chromospheric emission line fluxes of the late-type giant stars     

Kâmuran Avcioglu  M. Türker Özkan  H. Hüseyin Mentese 《Astrophysics and Space Science》1990,164(2):263-276

We investigate the near-ultraviolet high-resolution LWR spectra of the stars Cas, And, Tau, Gem, Cru, Boo, and Peg, obtained with the aid of the International Ultraviolet Explorer Satellite. We have given here a list of the strongest and most prevalent emission lines in the near-ultraviolet spectra of Boo, KlIIIp, and Peg, M2.5II-III which have the same luminosity class and different spectral type. The near-ultraviolet continuum flux measurements and integrated emission line fluxes of these stars for the 2500–3200 Å region are presented in order to compare the variations in the appearance of the near-ultraviolet flux distribution with the temperature structure of their chromospheres for K and M giant stars. We also discuss differences between observed and calculated fluxes found from the Planck function.  相似文献   

Co-ordinated traffic in a transponder based co-operative system. presentation of the NADAKOS- project     

Reinhard Müller  Thoralf Weißflog  Anke ZÖlder 《Ocean Dynamics》1997,49(4):499-510

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North-South asymmetry in the solar flare index     

Tamer Ataç  Atila Özgüç 《Solar physics》1996,166(1):201-208

This paper reports the results of a study of the N-S asymmetry in the flare index using the results of Knoka (1985) combined with our results for the solar cycles 17 to the current cycle 22. By comparing the time-variation of the asymmetry curve with the solar activity variation of the 11-year cycle, we have found that the flare index asymmetry curve is not in phase with the solar cycle and that the asymmetry peaks during solar minimum. A periodic behaviour in the N-S asymmetry appears: the activity in one hemisphere is more important during the ascending part of the cycle whereas during the descending part the activity becomes more important in the other hemisphere. The dominance of flare activity in the southern hemisphere continues during cycle 22 and, according to our findings, this dominance will increase gradually during the following cycle 23.  相似文献   

COMMENTS ON THE PAPER: RECALCULATION OF H-Lα SKY SURVEYS: NO NEED FOR ANISOTROPIC SOLAR WIND MASS OUTFLOWS?     

Bertaux  Jean-Loup  QuÉmerais  Eric  Lallement  Rosine  KyrÖlÄ  Erkki  Summanen  Tuula 《Solar physics》1997,170(2):365-370

In a recently published paper, Scherer and Fahr (1995) claimed that the departures of sky L emission measured by Prognoz 5 and 6 from an optically thin model can be attributed entirely to deficiencies of the optically thin approximation, and are not due to variations of solar wind ionization rate with latitude, as advocated since many years by our research group. They base their claim on the result of their new sophisticated model of L radiation transport.It is shown here that their new model, in the simple case of isotropic solar wind, predicts a distribution of intensity in a simple geometry which is completely contradicted by the observations: they find a minimum of intensity near the upwind direction, where a maximum has been observed consistently by all L instruments. Therefore, their conclusion based on an erroneous model must be rejected.  相似文献   

Chemical fractionation,mobility and environmental impacts of heavy metals in greenhouse soils from Çanakkale,Turkey     

Ali Sungur  Mustafa Soylak  Hasan Özcan 《Environmental Earth Sciences》2016,75(4):334

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Rock fall hazard assessment in Asar Hill,ancient Mabolla City,Mugla—SW Turkey     

Murat Gül  Ahmet Özbek  Ergun Karacan 《Environmental Earth Sciences》2016,75(19):1310

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Palaeoseismology of the Havran-Balıkesir Fault Zone: evidence for past earthquakes in the strike-slip-dominated contractional deformation along the southern branches of the North Anatolian fault in northwest Turkey     

Hasan Sözbilir  Çağlar Özkaymak  Bora Uzel  Ökmen Sümer  Semih Eski  Çiğdem Tepe 《Geodinamica Acta》2016,28(4):254-272

The Havran-Bal?kesir Fault Zone (HBFZ) is one of the major active structures of the Southern Marmara Region, which has been shaped by the southern branch of North Anatolian fault since the Pliocene. HBFZ is a 10–12 km wide, 120 km long, right-lateral strike-slip fault zone that consists of two ENE-striking main faults, namely, the Havran-Balya and Bal?kesir faults. The 90-km-long Havran-Balya fault exhibits right-stepping en echelon geometry and is made up of (1) Havran, (2) Osmanlar, (3) Turplu and (4) Ovac?k fault segments. On the eastern part, the 70-km-long Bal?kesir fault is divided into two fault segments; (1) Gökçeyaz? and (2) Kepsut. We estimated the long-term slip rate between 3.59 and 3.78 mm/yr using river offset. The Kepsut, Gökçeyaz? and Ovac?k fault segments are capable of generating an earthquake with a moment magnitude of up to 7.2. Detailed palaeoseismological studies show that the HBFZ is responsible for some surface faulting earthquakes with an average recurrence interval of 1000–2000 years during the late Holocene. Considering the fact that there was no evidence of a surface-ruptured earthquake for 2000 years, it can be stated that there is a seismic gap on the Gökçeyaz? fault segment.  相似文献   

Assessing the influence of climate change characteristics on the rainfall duration of Turkey     

Nihal Ata Tutkun  Gamze Özel 《Natural Hazards》2016,84(3):2265-2277

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Reference and current Trophic Level Index of New Zealand lakes: benchmarks to inform lake management and assessment     

Jonathan M. Abell  Paul van Dam-Bates  Deniz Özkundakci  David P. Hamilton 《新西兰海洋与淡水研究杂志》2020,54(4):636-657

ABSTRACT

Knowledge of trophic status is fundamental to understanding the condition and function of lake ecosystems. We developed regression models to predict chlorophyll a concentrations (chl a) in New Zealand lakes for reference and current states, based on an existing dataset of total nitrogen (TN) and total phosphorus (TP) concentrations for 1031 lakes. Models were then developed to predict Secchi depth based on chl a and a sediment resuspension term applicable to shallow lakes. Estimates of all four Trophic Level Index (TLI) variables (chl a, TN, TP and Secchi depth) were analysed to estimate reference and current state TLI for the nationally representative sample of 1031 lakes. There was a trend of eutrophication between reference and current states, with systematic differences among lake geomorphic types. Mean chl a increased 3.5-fold (2.42?mg?m^?3 vs. 8.32?mg?m^?3) and mean Secchi depth decreased (indicating lower clarity) by approximately one-third (9.62?m vs. 6.48?m) between reference and current states. On average, TLI increased by 0.67, with the TLI increase >1 in approximately one-third (31%) of lakes. This study informs the status of lake ecosystems in NZ and provides benchmarks to guide management and assessment.  相似文献