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173.
O.A. Maltseva G.A. ZhbankovT. Trinh Quang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
One of the methods to adapt the International Reference Ionosphere model to real time conditions is to use instantaneous values of the critical frequency of the ionosphere foF2. It is shown that there can be large discrepancies between model and experimental values of the total electron content TEC after this adaptation. Improvement can be provided by the use of an empirical model of the ionospheric slab thickness τ. This conclusion is based on analysis of contributions of various correction factors connected with foF2 and τ into discrepancies between model and experimental values of TEC. 相似文献
174.
R.G. Ezquer L.A. Scidá Y. Migoya Orué B. Nava M.A. Cabrera C. Brunini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1803-1818
Using vertical total electron content (VTEC) measurements obtained from GPS satellite signals the capability of the NeQuick 2 and IRI Plas models to predict VTEC over the low latitude and South American sector is analyzed. In the present work both models were used to calculate VTEC up to the height of GPS satellites. Also, comparisons between the performance of IRI Plas and IRI 2007 have been done. The data correspond to June solstice and September equinox 1999 (high solar activity) and they were obtained at nine stations. The considered latitude range extends from 18.4°N to ?64.7°N and the longitude ranges from 281.3°E to 295.9°E in the South American sector. The greatest discrepancies among model predictions and the measured VTEC are obtained at low latitudes stations placed in the equatorial anomaly region. Underestimations as strong as 40?TECU [1?TECU?=?1016?m?2] can be observed at BOGT station for September equinox, when NeQuick2 model is used. The obtained results also show that: (a) for June solstice, in general the performance of IRI Plas for low latitude stations is better than that of NeQuick2 and, vice versa, for highest latitudes the performance of NeQuick2 is better than that of IRI Plas. For the stations TUCU and SANT both models have good performance; (b) for September equinox the performances of the models do not follow a clearly defined pattern as in the other season. However, it can be seen that for the region placed between the Northern peak and the valley of the equatorial anomaly, in general, the performance of IRI Plas is better than that of NeQuick2 for hours of maximum ionization. From TUCU to the South, the best TEC predictions are given by NeQuick2.The source of the observed deviations of the models has been explored in terms of CCIR foF2 determination in the available ionosonde stations in the region. Discrepancies can be also related to an unrealistic shape of the vertical electron density profile and or an erroneous prediction of the plasmaspheric contribution to the vertical total electron content. Moreover, the results of this study could be suggesting that in the case of NeQuick, the underestimation trend could be due to the lack of a proper plasmaspheric model in its topside representation. In contrast, the plasmaspheric model included in IRI, leads to clear overestimations of GPS derived TEC. 相似文献
175.
N.K. Sethi R.S. DabasA.K. Upadhayaya 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Bottomside electron density (Ne-h) profiles during midday (10–14 h) are analyzed using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6N, 77.2E, dip 42.4N), for the period from January 2003 to December 2003, pertaining to moderate solar activity (MSA). Each individual profile is normalized with respect to the peak height and density (hmF2, NmF2) of the F2-region. These profiles are compared with those obtained from the International Reference Ionosphere (IRI-2001) model. Bilitza [Bilitza, D. International Reference Ionosphere 2000. Radio Sci. 36 (2), 261–275, 2001] using both the options namely: Gulyaeva’s model [Gulyaeva, T.L. Progress in ionospheric informatics based on electron density profile analysis of ionograms. Adv. Space Res. 7 (6) 39–48, 1987] and B0 Tab. option [Bilitza, D., Radicella, S.M., Reinisch, B.W., Adeniyi, J.O., Mosert Gonzalez, M.E., Zhang, S.R., Obrou, O. New B0 and B1 models for IRI. Adv. Space Res. 25 (1), 89–95, 2000]. The study reveals that during summer and equinox, the IRI model with B0 Tab. option in general, produces better agreement with the observed median profiles, while the IRI predictions using Gulyaeva’s option, overestimate the electron density distribution at all the heights below the F2-peak. However, during winter, in general, the IRI model, using both the options, reveals shows fairly good agreement with the observations. 相似文献
176.
Volodymyr Kryvdyk 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Formation of relativistic jets in the magnetosphere of collapsing stars is considered. These jets will be formed in the polar caps of magnetosphere of collapsing star, where the stellar magnetic field increases during the collapse and the charged particles are accelerated. The jets will generate non-thermal radiation. The analysis of dynamics and emission of particles in the stellar magnetosphere under collapse shows that collapsing stars can be powerful sources of relativistic jets. 相似文献
177.
G.N. Kichigin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The paper discusses the possibility of particle acceleration up to high energies in relativistic waves generated by various explosive processes in the interstellar medium. We propose to use the surfatron mechanism of acceleration (surfing) of charged particles trapped in the front of relativistic waves as a generator of high-energy cosmic rays (CRs). Conditions under which surfing in the waves under consideration can be made are studied thoroughly. Ultra-high-energy CRs (up to 1020 eV) are shown to be obtained due to the surfing in relativistic plane and spherical waves. Surfing is supposed to take place in nonlinear Langmuir waves excited by powerful electromagnetic radiation or relativistic beams of charged particles, as well as in strong shock waves generated by relativistic jets or spherical formations that expand fast (fireballs). 相似文献
178.
从高动态星敏感器动态性能需求出发,分析了电子倍增型电荷耦合器件(EMCCD,electron multiplying CCD)噪声来源,推导恒星探测中EMCCD的信噪比公式.针对EMCCD总体参数设计优化问题,提出了EMCCD中电子倍增电压和致冷温度的设计方法,并应用该方法进行高动态星敏感器中EMCCD总体参数设计及仿真.仿真结果表明,角速度为10(°)/s时姿态测量精度优于30″.提出的EMCCD参数确定方法可以为高动态星敏感器设计提供参考. 相似文献
179.
半球谐振子金属化是半球谐振陀螺研制过程中的重要环节,针对半球表面薄膜制备均匀性难以实现的问题,提出了一种将薄膜沉积实验和光学模拟相结合的方法。本文采用电子束蒸发技术在半球上沉积Au薄膜,利用台阶仪测量球面上不同位点的薄膜厚度,将平面上的膜厚等效为半球曲面上的膜厚,研究球面薄膜的均匀性,得出了在半球内外表面上薄膜的膜厚分布;同时对薄膜沉积均匀性进行光学模拟,将半球探测器上辐照度等效为实验中沉积所得到的薄膜厚度,计算得出的半球探测器上辐照度分布与实验测量结果一致性较好,可为半球谐振子纳米薄膜的均匀性制备提供理论基础。 相似文献
180.
Chin-Chun Wu K. Liou Shao-Ju Shan C.-L. Tseng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):611-616
The ionospheric total electron content (TEC) in the northern hemispheric equatorial ionospheric anomaly (EIA) region is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a chain of nine observational sites clustered around Taiwan (21.9–26.2°N, 118.4–112.6°E). In this study, we present results from a statistical study of seasonal and geomagnetic effects on the EIA during solar cycle 23: 1994–2003. It is found that TEC at equatorial anomaly crests yield their maximum values during the vernal and autumnal months and their minimum values during the summer (except 1998). Using monthly averaged Ic (magnitude of TEC at the northern anomaly crest), semi-annual variations is seen clearly with two maxima occurring in both spring and autumn. In addition, Ic is found to be greater in winter than in summer. Statistically monthly values of Ic were poorly correlated with the monthly Dst index (r = −0.22) but were well correlated with the solar emission F10.7 index (r = 0.87) for the entire database for the period during 1994–2003. In contrast, monthly values of Ic were correlated better with Dst (r ? 0.72) than with F10.7 (r ? 0.56) in every year during the low solar activity period (1994–1997). It suggests that the effect of solar activity on Ic is a longer term (years), whereas the effect of geomagnetic activity on Ic is a shorter term (months). 相似文献