Einstein-Gleichungen mit Zusatztermen 4. Ordnung und Raum-Zeit-Modelle vom Bianchi-Typ I

In the vacuum case, Einstein's equations generalized by additive terms containing derivatives of the metric up to the 4th order are applied to cosmological Bianchi-type I model space-times.     

Evidence for downflow following a coronal transient?

On 11 September 1973 a peculiar prominence was observed. The prominence displayed strong ( 50km s^–1) systematic motions toward and away from the observer. The unusual spectrographic appearance of the prominence might have been due to downflowing material lifted into the corona during an earlier coronal transient.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

General relativistic analysis of structure and stability of charged fluid disks around compact objects

In this paper we give a detailed general relativistic formulation of the study of structure and stability of charged fluid disks around compact objects like black holes neglecting the self-gravitation of the disk itself. Having presented the general equations for equilibrium as well as for perturbations we solve explicitly the cases of rigidly and differentially rotating thin disks, with constant charge density and zero pressure, confined to the equatorial plane of the black hole. By using normal mode analysis we have analysed the stability of such disks under purely radial perturbations and find that the disks are generally stable. On leave of absence from Government College, Jagadalpur 494005     

User's guide to REDUCE subroutines for algebraic computations in general relativity

We describe the use of a package of subroutines for general-relativistic algebraic computations written in the LISP-based algebraic programming system REDUCE developed by Anthony Hearn. The first group of routines calculates concomitants of the metric tensor such as the Riemann tensor, Ricci tensor, Ricci scalar, Einstein tensor and Weyl tensor from given covariant or covariant and contravariant metric tensor components. One of these procedures includes the evaluation of the Maxwell equations and invariants as well as the Maxwell energy momentum tensor. A second group of routines takes the components of a null tetrad as input and evaluates the null frame projections of the Riemann tensor, the Einstein tensor as well as – if required – the 14 local invariants of the Riemann tensor. It also includes a determination of the Petrov type. Perturbation calculations may be performed and run effectively. The output can be presented in a flexible format chosen according to the needs of the user. A number of further special-purpose programs are available on request. The article should enable a reader familar with General Relativity but unfamilar with formula manipulating system, to employ the package.     

Using Strong Solar Coronal Emission Lines as Coronal Flux Proxies

We investigate the possibility that strong EUV lines observed with the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) provide good proxies for estimating the total coronal flux over shorter wavelength ranges. We use coordinated SERTS and Yohkoh observations to obtain both polynomial and power-law fits relating the broad-band soft X-ray fluxes to the intensities of Fexvi 335 Ú and 361 Ú, Fexv 284 Ú and 417 Ú, and Mgix 368 Ú measured with SERTS. We found that the power-law fits best cover the full range of solar conditions from quiet Sun through active region, though not surprisingly the cooler Mgix 368 Ú line proves to be a poor proxy. The quadratic polynomial fits yield fair agreement over a large range for all but the Mgix line. However, the linear fits fail conspicuously when extrapolated into the quiet-Sun regime. The implications of this work for the Heii 304 Ú line formation problem are also briefly considered.     

深反射地震揭示喜马拉雅地区地壳上地幔的复杂结构

报告了中、美两国在喜马拉雅山区进行的第一次深反射地震试验的结果．试验剖面南起喜马拉雅山山脊南亚东县的帕里镇,向北穿过喜马拉雅山脊的荡拉,到达康马南的萨马达．剖面长约１００ｋｍ．共中心点（ＣＭＰ）叠加剖面上显示出：１．在地壳中部有一强反射带,向北缓倾斜下去,延长达１００ｋｍ以上．它可能代表了一个活动的逆冲断裂或是一条巨大的拆离带,印度地壳整体或下地壳沿此拆离层俯冲到藏南之下．２．上部地壳的反射很丰富,显示了上地壳存在着大规模的叠瓦状结构．３．下地壳的反射同相轴呈现短而有规律的分布,显示了塑性流变特征．４．在测线南部莫霍反射明显,深度达７２－７５ｋｍ．发现南部有双莫霍层的存在．５．试验中还取得莫霍层下面３２,３８,４８ｓ等双程走时的多条反射,向北倾斜,反射同相轴延续较长,信息丰富,反映了上地幔的成层结构和变形特征．这些结果对印度大陆地壳整体或其下地壳俯冲到藏南特提斯喜马拉雅地壳之下,并导致西藏南端地壳增厚的观点,给予了实质性的支持．     

Primary production in a turbid estuary, the Ems-Dollard: field and model studies

The Ems-Dollard Estuary has a steep axial gradient in turbidity which strongly regulates primary production of phytoplankton and microphytobenthos. A combination of the turbidity and nutrient gradients causes a high pelagic primary production in the outer, seaward part of the estuary, and a high benthic production on high-level mudflats (with long effective photoperiods) in the inner part. Model simulations were used to study phytoplankton succession and the factors influencing this succession. Light limitation was evaluated in a sensitivity run which used a lower compensation light intensity.     

Sunspot intensities and their correction for scattered light

Photoelectric measurements of monochromatic spot intensities obtained with the domeless Coudé refractor in Anacapri are given. The scattered light superimposed on the spot, as deduced from measurements outside the sun's limb, amounts on the average to about 4% of the photospheric intensity. The accuracy of the derived spot intensities is better than 10%. Two of four investigated spots yielded temperatures below 3900K (ΔΘ > 0.5).