Opacity effects in soft X-ray spectral lines of the solar corona

Current literature suggests that several lines in the soft X-ray portion of the coronal spectrum may not be optically thin. Here, we confirm the results of Schmelz et al. (1996) who find no significant opacity effects for three of the brightest non-iron resonance lines in this part of the spectrum — O VIII at 18.97Å, Ne IX at 13.45Å, and Mg XI at 9.17Å. A comparison is made between each of these lines and an optically thin “reference” line produced by the same element in the same ionization state — O VIII at 15.18Å, Ne IX at 13.55Å, and Mg XI at 9.23Å. In the latter two cases, the comparison line is the intersystem line of the He-like triplet. 33 spectra from the Solar Maximum Mission Flat Crystal Spectrometer are analyzed, all of which were obtained from non-flaring, quasi-stable active regions.     

Initial results from COMPTEL onboard GRO

COMPTEL is the first imaging telescope to explore the MeV gamma-ray range (0.7 to 30 MeV). At present, it is performing a complete sky survey. In later phases of the mission selected celestial objects will be studied in more detail. The data from the first year of the mission have demonstrated that COMPTEL performs very well. First sky maps of the inner part of the Galaxy clearly identify the plane as a bright MeV-source (probably due to discrete sources as well as diffuse radiation). The Crab and Vela pulsar lightcurves have been measured with unprecedented accuracy. The quasars 3C273 and 3C279 have been seen for the first time at MeV energies. Both quasars show a break in their energy spectra in the COMPTEL energy range. The 1.8 MeV line from radioactive ²⁶A1 has been detected from the central region of the Galaxy and a first sky map of the inner part of the Galaxy has been obtained in the light of this line. Upper limits to gamma-ray line emission at 847 keV and 1.238 MeV from SN 1991T have been derived. Upper limits to the interstellar gamma-ray emissivity have been determined at MeV-energies. Several cosmic gamma-ray bursts within the field-of-view have been located with an accuracy of about 1°. On 1991 June 9, 11 and 15, COMPTEL observed gamma-ray emission (continuum and line) from three solar flares. Also neutrons were detected from the June 9 and June 15 flares.     

Experimental study of morphological and convective instabilities: The MEPHISTO space program

It is now well established that the morphological instability, i.e. the transition during solidification from a planar L/S interface to a cellular one, is strongly influenced by convection. The most recent theories on this topic, which are very advanced, suffer from the lack of experimental tests because uncontrolled convective effects cannot be avoid on the ground. Moreover the check of all the pertinent solidification parameters are not controlled in the same time or measured in real time. After a review of the main 1g experiments and their own limitations, we describe a new apparatus (MEPHISTO) which allows :

• •in-situ measurements of the main solidification parameters and in particular the undercooling at the solidification front in real time by a non perturbative method.
• •real time supervision of convective motions influence on crystal growth. First results obtained under 1g condition are presented :
  • ◦hydrodynamic scaling laws testing,
  • ◦instabilities detection,
  • ◦transient phenomena.

Main space results are then anticipated including the role of g-jitters.     

1980年7月14日耀斑和磁流浮现模型

本文利用云南天文台耀斑H_α巡视观测、活动区白光照相及速度场资料,结合SMM的X射线资料和北京天文台的射电观测资料,对1980年7月14日日面3B级大耀斑进行了综合研究。对照耀斑过程的磁流浮现(EMF)模型,我们分析了活动区的形态变化特征,估算了耀斑释放的磁能、耀斑过程的特征时间及耀斑爆发时加速的电子总数和加速电子的平均能量。结果表明:(1)耀斑过程的EMF模型与观测结果基本符合,可以认为EMF模型能够较好地说明耀斑的物理过程。(2)根据对速度场资料及耀斑产生位置的分析,初步认为电流片可能位于速度中性线与磁中性线的交点处及其附近,或速度中性线与暗条的交点处及其附近[3]。(3)观测和计算表明,硬x射线爆是由电流片中加速的高能非热电子所产生,而软X射线爆则由耀斑区的高温等离子体的热轫致辐射所产生。      

Forces acting on a foreign particle near a solidification front

The interaction of inert foreign particles and a solid-liquid interface during solidification is considered. The viscous drag on the particle which produces a force on the interface is calculated under general assumptions as well as the disjoining force for small particles and the buoyancy force for large ones.     

Cyclotron features in X-ray spectra of accreting pulsars

The hard X-ray spectra of small subset of accreting pulsars show absorption-like line features in the range 10–100 keV. These lines, referred to as cyclotron lines or cyclotron resonance scattering features, are due to photons scattered out of the line of sight by electrons trapped in the 10¹² G pulsar polar cap magnetic field. In this paper we present a review of observations, from the discovery of a cyclotron line in Hercules X-1 to recent results with RXTE and INTEGRAL.     

Physical parameters affecting living cells in space

The question is posed: Why does a living cell react to the absence of gravity? What sensors may it have? Does it note pressure, sedimentation, convection, or other parameters?

If somewhere in a liquid volume sodium ions are replaced by potassium ions, the density of the liquid changes locally: the heavier regions sink, the lighter regions rise. This may contribute to species transport, to the metabolism. Under microgravity this mechanism is strongly reduced. On the other hand, other reasons for convection like thermal and solutal interface convection are left. Do they affect species transport?

Another important effect of gravity is the hydrostatic pressure. On the macroscopic side, the pressure between our head and feet changes by 0.35 atmospheres. On the microscopic level the hydrostatic pressure on the upper half of a cell membrane is lower than on the lower half. This, by affecting the ion transport through the membrane, may change the surrounding electric potential. It has been suggested to be one of the reasons for graviperception.

Following the discussion of these and other effects possibly important in life sciences in space, an order of magnitude analysis of the residual accelerations tolerable during experiments in materials sciences is outlined. In the field of life sciences only rough estimates are available at present.     

ROSAT PSPC spectra of six Seyfert 1 galaxies

We present six ROSAT PSPC observations of Seyfert 1 galaxies chosen to have low Galactic line-of-sight absorption (N_H 10²⁰ cm⁻²). As expected, it is found that all of these sources possess significantly steeper spectra below 1 keV, than that observed at higher X-ray energies. In addition we find evidence for soft X-ray spectral features, which are best parameterized as line emission at 0.63 keV in NGC7469 and 0.75 keV in ESO198-G24. We examine these results in the light of the accuracy of the PSPC spectral calibration.     

泡沫铜/低熔点合金复合相变材料凝固放热分析

为研究泡沫铜/低熔点合金(LMPA)复合相变材料在间歇放热工作环境下恢复至初始状态的能力及不同孔隙率泡沫铜的添加对其凝固放热过程的影响，通过数值模拟对比分析了47合金、正二十三烷与泡沫铜复合前后的凝固放热过程，并调节泡沫铜/47合金复合材料孔隙率计算模拟芯片温度在凝固放热过程中温度随时间变化曲线。结果表明:泡沫铜的添加对2类材料凝固过程均有促进作用，模拟芯片恢复至目标温度所需时间分别被缩短6.6%和47.7%。因体积潜热值的差距，泡沫铜/47合金凝固时需放出更多热量，恢复至目标温度的时间较长，是正二十三烷复合相变材料的1.52倍。随着孔隙率的增大，复合相变材料恢复至室温状态所用时长变化不大，考虑到孔隙率对相变热控过程中的影响，实际使用时应综合考虑。      

The interstellar heliopause probe technology reference study

The interstellar heliopause probe (IHP) is one of ESA’s technology reference studies (TRS). The TRS aim to focus the development of strategically important technologies of relevance to future science missions by studying technologically demanding and scientifically interesting missions that are currently not part of the science mission programme.

Equipped with a highly integrated payload suite (HIPS), the IHP will perform in situ exploration of the heliopause and the heliospheric interface. The HIPS, which is a standard element in all TRSs, miniaturize payloads through resource reduction by using miniaturized components and sensors, and by sharing common structures and payload functionality.

To achieve the scientific requirements of the mission, the spacecraft is to leave the heliosphere as close to the heliosphere nose as possible and reach a distance of 200 AU from the Sun within 25 years. This is possible by using a trajectory with two solar flybys and a solar sail with characteristic acceleration of 1.1 mm/s², which corresponds to a 245 × 245 m² solar sail and a sail thickness of 1–2 μm. The trajectory facilitates a modest sail design that could potentially be developed in a reasonable timeframe.

In this paper, an update to the results of studies being performed on this mission will be given and the current mission baseline and spacecraft design will be described. Furthermore, alternative solar sail systems and enabling technologies will be discussed.     

Fe XVII X-ray lines in solar coronal plasmas

Calculated intensities of the Fe X-ray lines due to transitions 2p⁶ − 2p⁵3d lines (near 15 Å) and 2p⁶ − 2p⁵3s lines (near 17 Å) are compared with measured line intensities in solar and tokamak spectra. For the solar spectra, temperature T_e is obtained from the ratio of the Fe 16.776 Å line to a nearby Fe line. We find excellent agreement for all the major Fe line features in the 15–17 Å region except the Fe 15.015 Å line, the observed flux of which is less than the theoretical by a factor f. We find that f strongly depends on the heliocentric angle θ of the emitting region, being smallest (0.2) when the region is nearest Sun centre, but nearly 1 near the limb. Attributing this to resonance scattering, we are able to deduce the path length and electron density from the observations. Possible application to stellar active regions is given.     

The influence of microgravity on the growth of metals and alloys—The project of Czechoslovak experiment

The crystal growth under near-zero gravity conditions may lead to materials of better crystalline and compositional perfection [1]. Unidirectional solidification of metals is a part of Czechoslovak programme on space research within the framework of Interkosmos [2]. On the model-like systems of metals grown in the space we want to study the effect of foreign atoms on the surface tension and the lattice defects density. The objectives of our ground-based and space experiments are discussed.     

LaBr3(Ce)元件破损在线监测关键核素确定及效率校准

常用的元件破损在线监测方法受外在因素影响较大,以γ能谱中关键裂变产物核素比活度进行在线定量分析是一种可靠的元件破损监测方法。针对新型LaBr₃(Ce)元件破损监测仪,设计了元件破损模拟实验,对逸出的裂变产物采用HPGe和LaBr₃(Ce)探测器进行了对比测量。通过不同冷却时间γ能谱的核素分析,确定了¹³⁵Xe,⁸⁸Kr,¹³⁸Xe,⁸⁸Rb,¹³⁸Cs等可作为LaBr₃(Ce)元件破损γ能谱监测的关键核素。同时,制备了覆盖能量范围(250～2 400)keV,含⁶⁰Co,¹³⁷Cs,¹³³Ba;²⁴¹Am,¹⁵²Eu;¹⁰⁹Cd,⁸⁸Y,⁵⁷Co及²⁴Na的4组放射性标准溶液,在建立的效率校准系统上,校准了LaBr₃(Ce)在线监测仪的效率。在反应堆一次异常情况分析中,已校准的LaBr₃(Ce)元件破损监测仪对关键核素的现场分析结果与HPGe的取样分析结果一致,表明效率校准结果准确,校准方法可靠。     

金属材料快速凝固激光加工与成形

报道近年来在先进金属材料快速凝固激光表面改性、金属间化合物高温耐磨耐蚀涂层新材料快速凝固激光熔覆制备技术、钛合金及高温合金等高性能金属零件快速凝固激光成形技术等领域的研究进展, 主要内容包括:钛合金激光表面合金化及激光熔覆表面改性、激光熔覆高温耐磨耐蚀多功能金属间化合物涂层、小面相非平衡凝固液固界面结构及生长机制、钛合金及高温合金高性能零部件激光快速成形、难熔高活性金属材料及定向生长柱状晶钛合金激光约束熔铸成形技术.      

L'interaction entre le flot d'helium neutre d'origine interstellaire et l'heliosphere

Elastic collisions between neutral helium atoms from interstellar origin and protons from both the interstellar plasma in the heliospheric interface and the solar wind inside the heliosphere modify parameters of the helium gas. Upstream the heliopause, the helium atoms release momentum to the plasma, which results in a decrease of their bulk velocity, and remove energy from the plasma, which results in an increase of their temperature. Inside the heliosphere, the major part of the energy communicated by solar wind protons to helium atoms is transferred through scarce frontal collisions, which results in the creation of a hot tenuous He component in the downstream (with respect to the sun) region. The modification of the spatial He distribution function near the sun due to slightly deflected atoms is negligible in first approximation. Lastly, we emphasize that the collisional effect is probably insufficient to explain the high temperature of helium derived from photometric measurements of the interplanetary medium at 58.4 nm (16 000 K). By taking into account two other effects which are the light transfer in the He resonance line inside the focusing cone and a possible latitudinal anisotropy of the solar ionizing EUV flux, leading both to a lowering of the contrast of the cone, we show that the temperature discrepancy between H (8 000 K : spectral measurements : line width, Doppler shift) and He (16 000 K : photometric measurements) can be reasonably explained by the combined actions of these three effects : elastic collisions, light transfer at 58.4 nm inside the focusing cone, solar EUV flux latitudinal anisotropy.     

LaBr3(Ce)元件破损在线监测关键核素确定及效率校准

常用的元件破损在线监测方法受外在因素影响较大，以γ能谱中关键裂变产物核素比活度进行在线定量分析是一种可靠的元件破损监测方法。针对新型LaBr₃(Ce)元件破损监测仪，设计了元件破损模拟实验，对逸出的裂变产物采用HPGe和LaBr₃(Ce)探测器进行了对比测量。通过不同冷却时间γ能谱的核素分析，确定了¹³⁵Xe，⁸⁸Kr，¹³⁸Xe，⁸⁸Rb，¹³⁸Cs等可作为LaBr₃(Ce)元件破损γ能谱监测的关键核素。同时，制备了覆盖能量范围(250～2 400)keV，含⁶⁰Co，¹³⁷Cs，¹³³Ba；²⁴¹Am，¹⁵²Eu；¹⁰⁹Cd，⁸⁸Y，⁵⁷Co及²⁴Na的4组放射性标准溶液，在建立的效率校准系统上，校准了LaBr₃(Ce)在线监测仪的效率。在反应堆一次异常情况分析中，已校准的LaBr₃(Ce)元件破损监测仪对关键核素的现场分析结果与HPGe的取样分析结果一致，表明效率校准结果准确，校准方法可靠。     

The ion energy spectra in the ring current during the geomagnetic storm of February, 1986

Using data from the CHEM instrument on the AMPTE/CCE spacecraft, we follow the development of the ring current energy spectra (1–300 keV/e) of the ion species H⁺, O⁺, He⁺, and He⁺⁺ in the post-noon and pre-noon local time sectors during the geomagnetic storm of February 1986. By comparing displays of phase space density, f, vs. magnetic moment, μ, we can distinguish between enhancements due to newly injected ions and those due to adiabatic energization of a pre-existing population. In both the local time sectors, the initial drop in Dst is associated with enhanced phase space densities of all species. The spectra observed during the pass when the Dst dropped to a minimem of −312 nT show a strong local time asymmetry. In the post-noon sector, the spectra showed the influx of a new population of ions, rich in O⁺ and He⁺⁺. In the pre-noon sector, the flux increase was consistent with adiabatic energization of the ion population injected earlier in the storm. This local time difference is consistent with a greatly enhanced convection electric field which brings a new population from the magnetotail to the post-noon, but not the pre-noon local time sector.     

电离层H2O释放扰动效应的数值模拟研究

为充分研究化学物质在电离层释放的扰动效应和后期发展效果,基于化学物质在电离层的扩散模型、化学反应和电离层扩展F的控制模型,通过电离层H₂O的释放,研究电子e,H₂O,O+和H₂O+共4种粒子的分布状态,分析点源、多源和线源释放对电离层的扰动效果,比较不同高度、不同量和不同时间释放的影响结果,模拟夜间释放后期所激发的扩展F发展差异.结果表明,H₂O在电离层释放后,能有效耗散背景电子形成空洞,O+和H₂O+数密度呈椭圆形分布;点源、多源和运动目标线源等不同释放方式对电离层的扰动效果不同,证实了人工影响一定形态和区域电离层的可能性;H₂O释放扰动幅度,低层大于高层,白天强于夜晚,释放量越多扰动越突出;夜间化学释放能激发扩展F,并且释放量越多,激发效果越好.      

Contribution of solar UV radiation to the observed ozone variations during the 21st and 22nd solar cycles

A two-dimensional dynamical radiative-photochemical model of the ozonosphere including aerosol physics is used to examine the changes of the Earth's ozone layer occurred during the 21st and 22nd solar cycles. The calculated global total ozone changes in the latitude range 60°S—60°N caused by 11-year variation of solar UV radiation, volcanic eruptions, and anthropogenic atmospheric pollution containing CO₂, CH₄, N₂O and chlorine and bromine species are in a rather good agreement with the observed global ozone trend. The calculations show that the anthropogenic pollution of the atmosphere is a main reason of the ozone depletion observed during the last two solar cycles. However, the 11-year solar UV variation as well as volcanic eruptions of El Chichon and Mt. Pinatubo also gave a significant contribution to the observed global ozone changes.     

Her X-1 as seen in the ROSAT all-sky survey

ROSAT performed the first, spectrally resolved, soft X-ray observations of Her X-1 in the SHORT-ON state of the 35^d cycle. The data were taken during the All-Sky survey covering the range 0.1–2.4 keV. The mean luminosity in the ROSAT bandpass is 1.5 × 10³⁶ ergs sec⁻¹. Timing analysis of the data revealed a highly significant signal at a period of 1.237749(1) sec. Finally, we present evidence to support the hypothesis that the resuction in intensity during the SHORT-ON state is caused by hot matter absorption in the disk.