The X-ray jets of active galaxies     

D. M. Worrall 《Astronomy and Astrophysics Review》2009,17(1):1-46

Jet physics is again flourishing as a result of Chandra’s ability to resolve high-energy emission from the radio-emitting structures of active galaxies and separate it from the X-ray-emitting thermal environments of the jets. These enhanced capabilities have coincided with an increasing interest in the link between the growth of super-massive black holes and galaxies, and an appreciation of the likely importance of jets in feedback processes. I review the progress that has been made using Chandra and XMM-Newton observations of jets and the medium in which they propagate, addressing several important questions, including: Are the radio structures in a state of minimum energy? Do powerful large-scale jets have fast spinal speeds? What keeps jets collimated? Where and how does particle acceleration occur? What is jet plasma made of? What does X-ray emission tell us about the dynamics and energetics of radio plasma/gas interactions? Is a jet’s fate determined by the central engine?  相似文献   

祁连山海北高寒湿地微气象日变化特征   总被引：2，自引：1，他引：1  

李英年  王勤学  杜明远  赵新全  赵亮  徐世晓  古松 《高原气象》2008,27(1):193-201

利用2004年的观测资料分析了青海海北高寒湿地微气象要素的日变化特征,结果表明,辐射、热量平衡各分量日平均变化中,瞬时最高值出现在中午,最低在早晨。地面长波有效辐射日最高出现在中午,日最低出现在下午。地面反射率表现出早晚高白天低的"U"型分布状况,1月日最低达0.68,而7月日最低仅为0.12。动量通量、垂直风速、水平风速、摩擦速度等均在下午大,夜间到清晨小。垂直风速除10月全天为上升运动外,其他月份夜间还出现下沉运动,而且冬季明显。海北高寒湿地夏季热强明显,冷季热强减弱。因湿地长久积水,地温日变化平稳,40 cm地温<0℃的维持时间不到2个月,60 cm地温全年均>0℃,即季节冻结层浅薄。  相似文献   

云闪辐射脉冲序列的丛集特征     

苟学强  张义军  董万胜  陈明理 《高原气象》2008,27(3):644-647

根据2002年夏季那曲地区野外观测的宽带干涉仪资料, 应用变异系数CV、 Allan因子分析(AFA)和Fano因子分析(FFA)等统计方法, 对33个云闪辐射脉冲事件序列的时间丛集特征进行了分析.结果显示, 放电过程呈现强的分形丛集性, 变异系数平均为5.2, AFA和FFA标度指数αAF及αFF平均分别为1.42和0.81; 同时发现, 初始强K脉冲前CV增加到明显>1.  相似文献   

0.1~40 MHz地闪、 云闪及NBE事件的辐射场频谱特征分析          下载免费PDF全文

蓝渝  张义军  吕伟涛  郑栋  陈绍东 《高原气象》2009,28(5):1025-1033

利用宽带傅立叶分析法对2008年7月30日和8月4日两次雷暴过程中, 距离观测点5~20 km范围内的55次负地闪回击过程, 33次云内闪电过程以及20次双极性窄脉冲事件（NBE）的电磁辐射信号进行了观测分析, 得到地闪回击、 云闪放电初始阶段以及双极性窄脉冲事件在0.1~40 MHz频带宽度下的电磁辐射能量谱密度。结果表明, 这三类闪电放电过程的辐射频谱波形均呈现出随频率增加、 幅值减小的趋势, 但在辐射强度和衰减速率上存在一定的差异。负地闪回击幅频波形在6~28 MHz频段上衰减速率相对缓慢; 云闪初始阶段在全频带上始终遵循f-1.2~f-1.4之间的衰减率递减, 且其频谱幅值与地闪回击的辐射能量谱幅值相差不大; NBE事件在0.1~40 MHz频带中辐射能量谱幅值基本都明显大于其他两类闪电放电过程, 特别是在10 MHz以上的HF、 VHF频带上其差异可达到20 dB。  相似文献   

Galactic X-ray binary jets     

Elena Gallo 《Astrophysics and Space Science》2007,311(1-3):161-165

With their relatively fast variability time-scales, Galactic X-ray binaries provide an excellent laboratory to explore the physics of accretion and related phenomena, most notably outflows, over different regimes. After comparing the phenomenology of jets in black hole systems to that of neutron stars, here I discuss the role of the jet at very low Eddington ratios, and present preliminary results obtained by fitting the broadband spectral energy distribution of a quiescent black hole binary with a ‘maximally jet-dominated’ model. Chandra Fellow  相似文献   

论辐射加热问题的时间积分          下载免费PDF全文

廖洞贤 《应用气象学报》2001,12(2):242-245

在满足有界条件的数值解是计算稳定的定义下, 讨论了辐射加热问题的时间积分, 并证明:如辐射加热和其对时间的一阶微商均连续时, 用向前差分格式计算的数值解是计算稳定的。还用一个例子证明:问题的数值解可以收敛到其解析解。  相似文献   

氮氧化物(NOX)在对流层中的收支与循环的研究   总被引：2，自引：0，他引：2  

罗超  周秀骥 《应用气象学报》1993,4(1):92-99

对氮氧化物（NOx）在对流层中的收支与循环问题，及其在对流层中的各种源汇过程进行了综述与讨论。其中包括NOx的人为排放与自然排放，干、湿沉降的清除及其相对重要性等。并对我国NOx的人为排放与自然排放进行了估算。  相似文献   

On spectral extinction of solar radiation within a tropical atmospheric boundary layer     

C. O. Oluwafemi 《Pure and Applied Geophysics》1980,119(4):831-840

Helicopter measurements of solar irradiance and meteorological data within the atmospheric boundary-layer were made in Lagos during February 1979. Filter samples of aerosols were collected both during flight in February 1979 and at ground level in December 1978. Profile data on spectral aerosol optical depth were obtained and, from these, the aerosol extinction coefficient at two wavelengths (0.5 and 0.88 m) were calculated. Precipitable water was low and was contained mainly within the 750 m layer above ground, suggesting the establishment of a deep unstable boundary layer. Calculated channel energy depletions by aerosols show that, within the first 750 m of the surface, the 0·88 m might be more efficient at attenuating solar energy than 0·5 m. The lagoon (maritime) aerosol sample indicated a more monodisperse size-distribution than the dusty harmattan aerosol sample.  相似文献   

Speculations on the budget of particulate and vapor phase non-methane organic carbon in the global troposphere     

Robert A. Duce 《Pure and Applied Geophysics》1978,116(2-3):244-273

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Approximation of the infra-red radiation flux in an atmosphere with cloud     

M. J. Manton 《Pure and Applied Geophysics》1978,116(6):1049-1062

Summary A three-stream infra-red radiation scheme for use particularly in boundary layer models is described. Local uniformity of the atmosphere (i.e. a generalization of the cooling to space approximation in clear air) is assumed, and the radiation equation is solved by simple collocation rather than by the full discrete ordinate method. In clear air the scheme corresponds to the usual approximation, which incorporates the Elsasser factor in the transmission function to account for diffuse radiation. The band models of Goody for water vapour and Elsasser for carbon dioxide are used for the band averaging of the transmission functions. Consistent with this, the band averaging of the radiation flux in cloud is undertaken by replacing the rapidly varying absorption coefficients for the gases by the actual band-averaged values of those coefficients. The band averaging is precise in the limits of strong and weak gaseous absorption.  相似文献