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991.
Kyu-Dong Oh Chun-Hwey Kim Woo-Baik Lee Ho-il Kim Young Woon Kang 《Monthly notices of the Royal Astronomical Society》2006,366(4):1243-1252
BVR light curves of ZZ Aurigae were obtained with the 60-cm Cassegrain reflector at the Sobaek Observatory, Korea, between 2000 February and 2001 February. All collected times of minimum light, including our observations, were used for the period study. The period variation could be of quasi-sinusoidal form superposed on an upward parabola. A continuous period increase of d P /d t =+2.3 × 10−8 d yr−1 was determined for ZZ Aur. The period of quasi-sinusoidal variation is about ∼26–31 yr. Photometric solutions were found using the Wilson–Devinney method. The Roche configuration of ZZ Aur is that of an Algol-type semidetached system where the primary star nearly fills its Roche lobe and the secondary star fills its lobe. The spot model was used to explain the asymmetry in the light curve known as the O'Connell effect. 相似文献
992.
Karoly Szego David T. Young Bruce Barraclough Andrew J. Coates Michele K. Dougherty Donald A. Gurnett Andrea Opitz Michelle F. Thomsen 《Planetary and Space Science》2006,54(2):200-211
In this paper we analyze a pre-shock event that we observed in the foot region of the quasi-parallel bow shock (BS) that the Cassini spacecraft crossed on 30 January 2001, at about 1030 UT. Before crossing the BS, the incoming solar wind first decelerated, and then the bulk velocity both of the proton and α components increased, the flow accelerated and decelerated, heated and cooled several times. We characterize the plasma in the foot using the data measured by the magnetometer, the radio and plasma wave science (RPWS) instrument, and the Cassini plasma spectrometer (CAPS) being carried onboard the Cassini spacecraft, and analyze the observations. We argue that the velocity and temperature changes can be caused by firehose instabilities excited by ions reflected from the shock. We investigate another possibility, shocklet formation, to account for the observed features, but conclude that this explanation seems to be less likely. In the foot we also identified both backstreaming electrons and ions and electrostatic waves in the 100-1000 Hz range very likely excited by the backstreaming electrons. 相似文献
993.
The EUV Imaging Spectrometer for Hinode 总被引:1,自引:0,他引:1
J. L. Culhane L. K. Harra A. M. James K. Al-Janabi L. J. Bradley R. A. Chaudry K. Rees J. A. Tandy P. Thomas M. C. R. Whillock B. Winter G. A. Doschek C. M. Korendyke C. M. Brown S. Myers J. Mariska J. Seely J. Lang B. J. Kent B. M. Shaughnessy P. R. Young G. M. Simnett C. M. Castelli S. Mahmoud H. Mapson-Menard B. J. Probyn R. J. Thomas J. Davila K. Dere D. Windt J. Shea R. Hagood R. Moye H. Hara T. Watanabe K. Matsuzaki T. Kosugi V. Hansteen Ø. Wikstol 《Solar physics》2007,243(1):19-61
The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona and upper transition region emission lines in the wavelength ranges 170?–?210 Å and 250?–?290 Å. The line centroid positions and profile widths will allow plasma velocities and turbulent or non-thermal line broadenings to be measured. We will derive local plasma temperatures and densities from the line intensities. The spectra will allow accurate determination of differential emission measure and element abundances within a variety of corona and transition region structures. These powerful spectroscopic diagnostics will allow identification and characterization of magnetic reconnection and wave propagation processes in the upper solar atmosphere. We will also directly study the detailed evolution and heating of coronal loops. The EIS instrument incorporates a unique two element, normal incidence design. The optics are coated with optimized multilayer coatings. We have selected highly efficient, backside-illuminated, thinned CCDs. These design features result in an instrument that has significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2?–?5 s exposure times in the brightest lines. EIS can scan a field of 6×8.5 arc?min with spatial and velocity scales of 1 arc?sec and 25 km?s?1 per pixel. The instrument design, its absolute calibration, and performance are described in detail in this paper. EIS will be used along with the Solar Optical Telescope (SOT) and the X-ray Telescope (XRT) for a wide range of studies of the solar atmosphere. 相似文献
994.
Long‐range transport of anthropogenic and biogenic CO2 to a remote site in the Arctic is studied. A limited area, off‐line, Eulerian atmospheric transport model is used, and the results are compared to the observed CO2 concentration at the "Ny‐Alesund International Arctic Research and Monitoring Facility". Inventories of anthropogenic CO2 emissions and estimates of biogenic CO2 emissions are used to investigate the respective impact of these emissions on Arctic CO2 variations during 4 winter months. A direct comparison of the modelled and observed concentrations reveals remarkably good timing in the modelled variations as compared to the observed variations for most of the time. The correlation of observed versus modelled CO2 concentration is significant at the 95% confidence level. The biogenic and the anthropogenic CO2 emissions are shown to have approximately equal influence on Arctic CO2 variations during winter. Europe is found to be the dominant source of anthropogenic CO2 at the monitoring station, while Siberia and Northern America have little influence on Arctic CO2 , during the months studied. These results contradict Engardt and Holmén whose results indicate that the lower‐Ob region in western Siberia has a large impact on Arctic CO2 . 相似文献
995.
Guzik Joyce A. Neuforge-Verheecke Corinne Young A. Cody Epstein Richard I. Poulin Francis M. Schissel Jason R. 《Solar physics》2001,200(1-2):305-321
We summarize the physical input and assumptions commonly adopted in modern standard solar models that also produce good agreement with solar oscillation frequencies. We discuss two motivations for considering non-standard models: the solar neutrino problem and surface lithium abundance problem. We begin to explore the potential for mixed core models to solve the neutrino problem, and compare the structure, neutrino flux, and oscillation frequency predictions for several models in which the inner 25% of the radius is homogenized, taking into account the effects of non-local equilibrium abundances of 3He. The results for the neutrino flux and helioseismic predictions are far from satisfactory, but such models have the potential to reduce the predicted 7Be/8B neutrino flux ratio, and further studies are warranted. Finally, we discuss how much the neutrino problem can be alleviated in the framework of the standard solar model by using reaction rates, abundances and neutrino capture cross-sections at the limits of their uncertainties, while still satisfying the constraints of helioseismology. 相似文献
996.
997.
998.
Distributions of H2O and CO2 ices on Ariel, Umbriel, Titania, and Oberon from IRTF/SpeX observations
We present 0.8-2.4 μm spectral observations of uranian satellites, obtained at IRTF/SpeX on 17 nights during 2001-2005. The spectra reveal for the first time the presence of CO2 ice on the surfaces of Umbriel and Titania, by means of 3 narrow absorption bands near 2 μm. Several additional, weaker CO2 ice absorptions have also been detected. No CO2 absorption is seen in Oberon spectra, and the strengths of the CO2 ice bands decline with planetocentric distance from Ariel through Titania. We use the CO2 absorptions to map the longitudinal distribution of CO2 ice on Ariel, Umbriel, and Titania, showing that it is most abundant on their trailing hemispheres. We also examine H2O ice absorptions in the spectra, finding deeper H2O bands on the leading hemispheres of Ariel, Umbriel, and Titania, but the opposite pattern on Oberon. Potential mechanisms to produce the observed longitudinal and planetocentric distributions of the two ices are considered. 相似文献
999.
正1.Overview SPARC(Stratosphere-Troposphere Processes and their Role in Climate)is one of the core projects of the World Climate Research Program(WCRP),coordinating international efforts to address relevant issues in climate and climate prediction via better understanding of the stratosphere-troposphere system.SPARC is a broad umbrella body that 相似文献
1000.
Robert Roth Stephen Young Chelsea Nestel Carl Sack Brian Davidson Julia Janicki 《The Professional geographer》2018,70(3):395-411
This article reports on the design and evaluation of Global Madison, a mobile map designed to support teaching and learning about globalization using Madison, Wisconsin, as a situated classroom. Our experience of place increasingly is mediated by mobile devices, opening new opportunities and challenges for research, industry, and education. Despite this rising popularity, few guidelines exist for creating and using mobile maps. Following tenets of user-centered design studies, we conducted two mixed-method evaluations of Global Madison to improve the tool and generate design insights that are potentially transferable to similar mobile mapping contexts: 244 students participated in an online survey after completing the tour and eighteen students were observed in the field. The evaluations generated new design considerations for mobile maps supporting situated learning, include: focus on critical issues that might leave students stranded, append location-based services with traditional mapping, enforce cognitive association between map and landscape, supply a consistent feed of information for new learners, encourage collaborative learning in the landscape, and promote student safety above all else. 相似文献