共查询到20条相似文献，搜索用时 562 毫秒
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Abstract— We discuss possible evidence for a dilution of 14C caused by the Tunguska impact event, proposed by Rasmussen et al. (1999). The results presented in that paper and other available information do not support this hypothesis. 相似文献
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Martin Harwit 《Icarus》1977,30(2):435-436
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Joachim Müller Sven Simon Yung-Ching Wang Uwe Motschmann Daniel Heyner Josef Schüle Wing-Huen Ip Gero Kleindienst Gavin J. Pringle 《Icarus》2012,218(1):666-687
During the first and second Mercury flyby the MESSENGER spacecraft detected a dawn side double-current sheet inside the Hermean magnetosphere that was labeled the “double magnetopause” (Slavin, J.A. et al. [2008]. Science 321, 85). This double current sheet confines a region of decreased magnetic field that is referred to as Mercury’s “dayside boundary layer” (Anderson, M., Slavin, J., Horth, H. [2011]. Planet. Space Sci.). Up to the present day the double current sheet, the boundary layer and the key processes leading to their formation are not well understood. In order to advance the understanding of this region we have carried out self-consistent plasma simulations of the Hermean magnetosphere by means of the hybrid simulation code A.I.K.E.F. (Müller, J., Simon, S., Motschmann, U., Schüle, J., Glassmeier, K., Pringle, G.J. [2011]. Comput. Phys. Commun. 182, 946–966). Magnetic field and plasma results are in excellent agreement with the MESSENGER observations. In contrast to former speculations our results prove this double current sheet may exist in a pure solar wind hydrogen plasma, i.e. in the absence of any exospheric ions like sodium. Both currents are similar in orientation but the outer is stronger in intensity. While the outer current sheet can be considered the “classical” magnetopause, the inner current sheet between the magnetopause and Mercury’s surface reveals to be sustained by a diamagnetic current that originates from proton pressure gradients at Mercury’s inner magnetosphere. The pressure gradients in turn exist due to protons that are trapped on closed magnetic field lines and mirrored between north and south pole. Both, the dayside and nightside diamagnetic decreases that have been observed during the MESSENGER mission show to be direct consequences of this diamagnetic current that we label Mercury’s “boundary-layer-current“. 相似文献
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Earth, Moon, and Planets - 相似文献
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《天文和天体物理学研究(英文版)》2015,(8)
We present chromospheric activity index SHK measurements for 119 995 F, G and K stars with high signal-to-noise ratio(S/N 80) spectra, extracted from LAMOST DR1 in SDSS g band. The index δS for each of these stars is calculated by the difference between its SHK value and the baseline determined from very inactive stars. The effect of metallicity on measurement of δS varies with stellar Teff. No evident Vaughan-Preston gap appears in our sample. The relation between δS and vertical distance from the Galactic plane is determined for stars with Teff 5500 K. Stars with higher δS tend to be closer to the Galactic plane. Two open clusters in the DR1 sample, M45 and M67, exhibit the expected general trend that δS decays with age.For stars with Teff 5500 K, similar δS levels appear in both young and old cluster stars, which supports Pace's suggestion that caution should be exercised when deriving the age of a single star by using its chromospheric activity. Finally, we investigate the relation between δS and the kinematics of our sample. 相似文献
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Srinivas N. Mohan 《Icarus》1979,40(2):317-330
The global distribution of existing lunar topography suffers from a lack of measurements of far-side radii because of the sparsity of data types in the nonequatorial regions. This paper presents determinations of far-side lunar radii based on the reduction of photogrammetric measurements derived from selected Apollo 16 trans-Earth phase photographs. The regions covered in this analysis lie west of Mare Moscoviense between longitudes 90 and 130°E and latitudes 10 and 60°N. The determinations are made using control points appearing on both NASA topographic orthophoto maps and the Apollo 16 photographs. The estimated lunar radii are referred to these control points and determined with a relative accuracy of 500 m. The new lunar radii are used to generate a topographic map covering the area investigated. The map shows that, with the given spatial density of surface festures measured, basin-sized features can be resolved. In particular, the far-side craters Fabry, Riemann, and Szilard comprise a topographically depressed region about 500 km in diameter centered at 120°E and 38.5°N. The floor of this basin is 2.4 to 3.4 km below the reference sphere of 1738.0 km and 4.8 to 5.8 km below the northern rim of the basin. A comparison of the depth of the unfilled basin with the depths of maria-filled front-side basins leads to the conclusion that basalt fill of the near-side maria may be 2 km deep. The topographic map shows good correlation with geologic provinces of young plains and cratered terra in the far-side highland region investigated. Lack of correlation between sampled values of the state-of-the-art 16th-order and 16th-degree harmonic gravity field model and corresponding topographical values leads to the conclusion that the far-side region investigated is isostatically compensated. 相似文献
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《时间频率公报》1995,(9)
UTC(CSAO)一Signal时刻(UTC)1995年9月MJDBPL/6000 100 kHz 8h (拌s)LC/9970 100 kH名 护 (卢) BPMe2。5,5,10,15 MH名 护 (刃几s) BPMI2.5,5,10,15 MHz 护 (ms)号频呼载一一一一一4996149962499634996449965一0。06一0。06一O。07一0。05一0。05一19。99一19.99一20。00一19.99一19.99151。5153.6155.7157.7159.8,么20口41匕4996649967499684996949970一0。05一0。03一0。05一0。08一0。10一19.98一19.97一19.98一19.99一19.98161.9164.0165.9168.1170。1一一一一一哆自O自乃白寸白内」 ..…O‘连.月叮n己印廿厅分厅‘,了..… 相似文献
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《时间频率公报》1995,(11)
UTC(CSAO)一Signal粤频呼载时刻(UTC)1995年11月MJDBPL/6000 100 kH名08:00:00 (料s)LC/9970 100 kH:00:00:00 (料s) BPMe2.5,5,10,15 MH名 00:00:00 (ms) BPM-2。5,5,10,15 MHz 00:00:00 (ms)一一一5002250023500245002550026一0。08一0。09一0。07一0。06一O。05一20.01一20.01一20。00一20。01一20。01299。1301。3303。7306。0308。31几,目,必奋,.之.舀006曰.勺自O ..…06曰﹄勺月了O甘口.二..二自.几,且..几,曰,曰,叨,叨,口5002750028500295003050031eeo。03一0。03一0。04一0。03一0。04一20.01一20。00一20。01一19.99… 相似文献
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《时间频率公报》2005,(11)
呼号BPL/6000LC/8930BPMc BPM1载频1001002.5,5,10,152.5,5,10,15kHz kHz MHz MHz时刻(UTC)08:00:0000:00:0000:00:0000:00:002005年11月MJD(μs)(μs)(ms)(ms)1536750.28--20.01626.172536760.26--20.01627.163536770.27--20.01627.904536780.27--20.01628.435536790.24--20.01628.736536800.19--20.01628.967536810.30--20.01629.188536820.30--20.01629.499536830.30--20.01630.2610536840.18--20.01631.2711536850.22--20.00632.4812536860.33--20.00633.8313536870.23--20.00635.1714536880.18--20.00636.3815536890.18--20.… 相似文献
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《时间频率公报》1995,(3)
T,TC(CSAO)一Signal时刻(UTC)1995年3月MJDBPL/6000 100 kHz 8七 (拜s)LC/9970 100 kHz 0、 (邵) BPMe2.5,5,10,15 MHz 0b (幻以s) BPMI2.5,5,10,15 MHz 0h (ms)号频呼载一一一一一O曰n甘﹄U,.山,占连.哎J工﹄Jl匕一﹄︺ ..…0 0 OC甘04977749778497794978049781一20。01一20。01一20。00一20。01一20。01一244.8一242.0一239.3一236。4一233。6,.占均白丹j连﹄4978249783497844978549786一20。01一20.00一20。01一20。00一20.00一230.8一228.0一225.2一222.4一219.6一一一一一,曰OU内b作1 11口连﹃连.连﹄连‘j任 ..…00… 相似文献
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