Cooling rate of thermal electrons by electron impact excitation of fine structure levels of atomic oxygen     

A. V. Pavlov  K. A. Berrington 《Annales Geophysicae》1999,17(7):919-924

The atomic oxygen fine structure cooling rate of thermal electrons based on new effective collision strengths for electron impact excitation of the ground-state ³P fine-structure levels in atomic oxygen have been fitted to an analytical expression which is available to the researcher for quick reference and accurate computer modeling with a minimum of calculations. We found that at the F region altitudes of the ionosphere the new cooling rate is much less than the currently used fine structure cooling rates (up to a factor of 2–4), and this cooling rate is not the dominant electron cooling process in the F region of the ionosphere at middle latitudes.  相似文献   

Use of coupled ozone fields in a 3-D circulation model of the middle atmosphere     

T. Reddmann  R. Ruhnke  W. Kouker 《Annales Geophysicae》1999,17(3):415-429

With a detailed chemistry scheme for the middle atmosphere up to 70 km which has been added to the 3-D Karlsruhe simulation model of the middle atmosphere (KASIMA), the effects of coupling chemistry and dynamics through ozone are studied for the middle atmosphere. An uncoupled version using an ozone climatology for determining heating rates and a coupled version using on-line ozone are compared in a 10-month integration with meteorological analyses for the winter 1992/93 as the lower boundary condition. Both versions simulate the meteorological situation satisfactorily, but exhibit a too cold lower stratosphere. The on-line ozone differs from the climatological data between 20 and 40 km by exhibiting too high ozone values, whereas in the lower mesosphere the ozone values are too low. The coupled model version is stable and differs only above 40 km significantly from the uncoupled version. Direct heating effects are identified to cause most of the differences. The well-known negative correlation between temperature and ozone is reproduced in the model. As a result, the coupled version slightly approaches the climatological ozone field. Further feedback effects are studied by using the on-line ozone field as a basis for an artificial climatology. For non-disturbed ozone conditions realistic monthly and zonally averaged ozone data are sufficient to determine the heating rates for modelling the middle atmosphere.  相似文献   

1995—1996年云南地区三次强震前地震活动的短期异常     

杨继登  王世芹 《华南地震》1999,19(2):32-38

在地震学参量年度异常的背景＾（３）,阐述了１９９５￣１９９６年云南地区发生的孟连、武定、丽江三次强震前的地震活动短期异常,包括地震平静、小震群、窗口地震、调制地震、地震波参数以及４级左右地震向震中迁移等。结果表明,这些异常特征表现突出,其演化进程显示了强震孕育的阶段性。  相似文献   

Tides and short-term variabilities in the Kuroshio west of Yonakuni-jima   总被引：1，自引：0，他引：1  

Yuan Yaochu  Arata Kaneko  Wang Huiqun  Zhu Xiaohu  Su Jilan  Noriaki Goh  Chen Hong  Fang Tongde 《海洋学报(英文版)》1999,18(3):311-324

INTRODUCFIONTheKuroshioeastofTaiwanIslandflowsnorthwardandenterstheEastChinaalgathroughapaSSagebetweenTaiwanIslandandlriomote-shima.TOstudyfurthertheKuroshiothereandestimateitstransPOrt,itisnecessarytoobservetheKuroshioCurrentdirectly.Therehavebeen*ThisstudywassupportedbytheNationalNaturalaudienceFoundationofChinaundercontractNo.49476278.severaldirectobservationsoftheKuroshionearTaiwanIsland.Forexample,thedirectcurrentmeasurementat(24'24'N1123'35'E)byinabaetal.(1981)showedtheapp…  相似文献   

黑洞吸积盘内区温度的分布特征和演化特征     

汪定雄 《中国天文和天体物理学报》1999,(4)

对黑洞吸积盘内区温度的径向分布特征和演化特征作了详细的讨论．结果表明：（１）盘内区的温度并非随径向坐标ｒ单调减少,在接近盘的内边缘处有一个盘温的峰值环．在盘温的峰值环和盘的内边缘之间形成一个温度梯度很大的冷却区;（２）在盘吸积的过程中,盘内区温度的峰值和冷却区的平均温度梯度均随中心黑洞的无量纲角动量ａ的增加而单调增加,而金温峰值环半径和冷却区的径向宽度均随ａ的增加而单调减小;（３）盘的热辐射光度随ａ的增加而单调增加．  相似文献   

Seyfert 2 星系光谱偏振的汤姆逊散射机制     

朱青峰  林宣滨  程福臻 《中国天文和天体物理学报》1999,(4)

利用简单的ｔｏｒｎｓ束流模型定量计算Ｓｅｙｆｅｒｔ２型星系的偏振度和散射流量的角分布,在“一次电子散射”的假定下,得到偏振度约为１０％～８０％．而偏振流量的角分布与ｔｏｒｎｓ半张角θｃ和观测角φｏ都有关．特别是当φｏ　５５°时,观测方向的流量和总的散射流量的比值为一定值（０．１６）．用这种纯电子散射模型来解释ＮＧＣ１０６８的光谱偏振更为合适．对于其它一些具有低的偏振度的Ｓｅｙｆｅｒｔ２星系,尘埃的作用则不能忽略．  相似文献   

海尔-波普彗星的球状喷出物     

钱伯辰  陶隽  顾敏峰  汤源 《中国天文和天体物理学报》1999,(1)

１９９６年９月观测到海尔－波普彗星的一次喷发,这次喷发持续了几天,在９月１０日和１１日分别观测到彗星的二个球状喷出物,并测得其投影喷出速度约为１００ｍ／ｓ,其后喷出物演变为巨大的喷流．  相似文献   

用ASM/RXTE数据对Crab天区的直接解调成像     

《中国天文和天体物理学报》1999,(1)

  相似文献   

Cyg X-1高态和转换态的X射线短时标爆发     

冯育新  李惕碚  陈黎  陈黎 《中国天文和天体物理学报》1999,(3)

分析ＲＸＴＥ卫星ＰＣＡ探测器对ＣｙｇＸ－１的观测数据,得到了其处于高态及高低态转换时的Ｘ射线短时标爆发（Ｓｈｏｔ）结构．在所观测到的三种态中是不对称的,并且不同的状态中Ｓｈｏｔ的结构有明显差异．Ｓｈｏｔ前后沿可分别由双指数函数近似拟合．Ｓｈｏｔ中的快时变过程是由慢的上升前沿和快的下降后沿构成．在所观测态中Ｓｈｏｔ平均宽度约为０．１１秒（ＦＷＨＭ）,比低态时的宽度窄．同一状态中高能段的Ｓｈｏｔ宽度较低能段窄,且更加不对称．转换态的硬度在Ｓｈｏｔ峰前有明显下降,之后迅速上升,Ｓｈｏｔ期间的平均硬度低于非Ｓｈｏｔ期平均值;而高态时峰前硬度没有明显下降,Ｓｈｏｔ期间的平均硬度高于非Ｓｈｏｔ期间的平均值．本文还就Ｓｈｏｔ的产生机制进行了讨论．  相似文献   

MK标准星的CCD光谱及光谱分类判据向黄红区的扩展     

石火明  石火明  胡景耀  胡景耀 《中国天文和天体物理学报》1999,(2)

本文提供了１２５颗ＭＫ标准星的ＣＣＤ光谱,光谱型从Ｏ到Ｍ,光度级从Ｖ到Ⅰ,构成较完整的二元分类框架,光谱覆盖范围由传统蓝紫区延伸到黄红区．初步考察和归纳了黄红区适于恒星分类的主要光谱特征和判据．这些结果对于采用相似分辨率的恒星光谱分类工作是非常有用的．  相似文献