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941.
P. Hartogh G.R. Sonnemann M. Grygalashvyly Ch. Jarchow 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We compared 8 years of ozone measurements taken at Lindau (51.66° N, 10.13° E) at altitudes between 40 and 60 km using the microwave technique with the CIRA ozone reference model that was established 20 years ago (Keating et al., 1990). We observed a remarkable decrease in ozone density in the stratopause region (i.e., an altitude of 50 km), but the decrease in ozone density in the middle mesosphere (i.e., up to 60 km in altitude) is slight. Likewise, we observed only a moderate decrease in the atmospheric region below the stratopause. Other studies have found the strongest ozone decrease at 40 km and a more moderate decrease at 50 km, which is somewhat in contradiction to our results. This decrease in ozone density also strongly depends on the season. Similar results showed model calculations using the GCM COMMA-IAP when considering the increase in methane. In the lower mesosphere/stratopause region, the strongest impact on the concentration of odd oxygen (i.e., O3 and O) was observed due to a catalytic cycle that destroys odd oxygen, including atomic oxygen and hydrogen radicals. The hydrogen radicals mainly result from an increase in water vapor with the growing anthropogenic release of methane. The finding suggesting that the stratopause region is apparently attacked more strongly by the water vapor increase has been interpreted in terms of the action of this catalytic cycle, which is most effective near the stratopause and amplified by a positive feedback between the ozone column density and the ozone dissociation rate, thereby chemically influencing the ozone density. However, the rising carbon dioxide concentration cools the middle atmosphere, thereby damping the ozone decline by hydrogen radicals. 相似文献
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944.
Sabiha Tunçel Güçtekin Selçuk Bilir Salih Karaali Olcay Plevne Serap Ak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1360-1373
We used the ugr magnitudes of 1437467 F-G type main-sequence stars with metal abundance dex and estimated radial and vertical metallicity gradients for high Galactic-latitude fields, and , of the Milky Way Galaxy. The radial metallicity gradient dex kpc?1 estimated for the stars with kpc is attributed to the thin-disc population. While, the radial gradients evaluated for stars at higher vertical distances are close to zero indicating that the thick disc and halo have not undergone a radial collapse phase at least at high Galactic latitudes. The vertical metallicity gradients estimated for stars with three different Galactic latitudes, and do not show a strong indication for Galactic latitude dependence of our gradients. The thin disc, kpc, with a vertical metallicity gradient dex kpc?1, is dominant only in galactocentric distance interval kpc, while the thick disc ( kpc) could be observed in the intervals and kpc with compatible vertical metallicity gradients, i.e. dex kpc?1 and dex kpc?1. Five vertical metallicity gradients are estimated for the halo ( kpc) in three galactocentric distance intervals, and kpc. The first one corresponding to the interval kpc is equal to dex kpc?1, while the others at larger galactocentric distances are close to zero. We derived synthetic vertical metallicity gradients for 2,230,167 stars and compared them with the observed ones. There is a good agreement between the two sets of vertical metallicity gradients for the thin disc, while they are different for the thick disc. For the halo, the conspicuous difference corresponds to the galactocentric distance interval kpc, while they are compatible at higher galactocentric distance intervals. 相似文献
945.
E. Amata G. Bellucci V. Formisano 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(12):263-266
Observations of comet Halley through CCD and Schmidt plates have been performed at Catania Observatory (Italy) from October 1985 through April 1986. Preliminary results are presented concerning the spatial structures for different spectral ranges of cometary light. 相似文献
946.
G.G. Pavlov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
A review is given of recent developments in the theory of emission from a magnetized plasma for accreting neutron star conditions. Some observational data on X-ray pulsars are discussed, and present problems are indicated. 相似文献
947.
A. G. Sattarov 《Russian Aeronautics (Iz VUZ)》2008,51(4):452-456
A method and the results of calculating the temperature field distribution for a three-focus plasma formation are presented; the calculation is made by the numerical method with the use of the theoretical Glumb and Krier model. It is proposed that multi-phase plasma formations consisting of solid laser sparks should be used in the absorption chamber of a laser rocket engine (LRE). 相似文献
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949.
Specific features of propagation of a wideband rectangular pulse along the route spacecraft-Martian surface-spacecraft caused by the influence of the planetary ionosphere are considered as applied to the problem of radio pulse sounding of the subsurface Martian soil from the Mars-Express satellite. The night Martian ionosphere considerably reduces the energy of the pulse, but does not lead to degradation of its envelope or uncertainty function. When sounding a two-layer surface, the influence of the ionosphere is also manifested in limitation from below of the thickness of the upper layer accessible for measurement, which is more essential than when sounding with the use of a wideband Gaussian pulse. It is demonstrated that the surface sounding is possible through the dayside planet ionosphere at the parameters of operating pulse of the MARSIS radar. 相似文献
950.
This paper describes an approach to the realization of a VLF loop-type antenna system. The theoretical analysis is applied to a four-loop system for Loran-C reception. 相似文献