康普顿化的计算——推广的Kompaneets方程与Monte Carlo方法比较

在X射线天文学以及辐射物理学中,当硬X射线穿过“冷”的等离子体时所发生的Compton软化是一种重要的辐射转移过程。简要介绍推广的Kompaneets方程,该方程在hv《m_ec^2及kT_e《m_ec^2较宽松的条件下广泛成立,因此不仅能处理Compton硬化过程,而且也适用于Compton软化过程,后者在目前快速发展的X射线和γ射线天文学中十分重要。基于此方程,我们对天体物理中4种常见辐射谱(Gauss型发射谱线、黑体辐射谱、幂律辐射谱和热轫致辐射谱)在Compton软化情况下的港演化进行了数值求解,并同 Monte Carlo模拟结果做比较,证实了推广的 Kompaneets方程的正确性和有效性。最后指出此方程在X射线天文学和γ射线天文学中的重要意义和潜在应用。

A Study of Air/Space-borne Dual-Wavelength Radar for Estimation of Rain Profiles

In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Measurement （GPM） precipitation radar, a dual-wavelength radar that will operate in the Ku （13.6 GHz） and Ka （35 GHz） bands. A key aspect of the retrievals is the relationship between the differential frequency ratio （DFR） and the median volume diameter, Do, and its dependence on the phase state of the hydrometeors. It is shown that parametric plots of Do and particle concentration in the plane of the DFR and the radar reflectivity factor in the Ku band can be used to reduce the ambiguities in deriving Do from DFR. A self-consistent iterative algorithm, which does not require the use of an independent pathattenuation constraint, is examined by applying it to the apparent radar reflectivity profiles simulated from a drop size distribution （DSD） model. For light to moderate rain, the self-consistent rain profiling approach converges to the correct solution only if the same shape factor of the Gamma distributions is used both to generate and retrieve the rain profiles. On the other hand, if the shape factors differ, the iteration generally converges but not to the correct solution. To further examine the dual-wavelength techniques, the selfconsistent iterative algorithm, along with forward and backward rain profiling algorithms, are applied to measurements taken from the 2nd generation Precipitation Radar （PR-2） built by the Jet Propulsion Laboratory. Consistent with the model results, it is found that the estimated rain profiles are sensitive to the shape factor of the size distribution when the iterative, self-consistent approach is used but relatively insensitive to this parameter when the forward- and backward-constrained approaches are used.

“Trends” and variations of global oceanic evaporation data sets from remote sensing

The variability in global oceanic evaporation data sets was examined for the period 1988-2000. These data sets are satellite estimates based on bulk aerodynamic formulations and include the NASA/Goddard Space Flight Center Satellite-based Surface Turbulent Flux version 2 （ GSSTF2）, the Japanese-ocean flux using remote sensing observations （J-OFURO）, and the Hamburg Ocean-Atmosphere Parameters and Fluxes from Satellite version 2 （HOAPS2）. The National Center for Environmental Prediction （NCEP） reanalysis is also included for comparison. An increase in global average surface latent heat flux （SLHF） can be observed in all the data sets. Empirical mode decomposition （EMD） shows long-term increases that started around 1990 for all remote sensing data sets. The effect of Mt. Pinatubo eruption in 1991 is clearly evident in HOAPS2 but is independent of the longterm increase. Linear regression analyses show increases of 9.4%, 13.0%, 7. 3%, and 3.9% for GSSTF2, J-OFURO, HOAPS2 and NCEP, for the periods of the data sets. Empirical orthogonal function （EOF） analyses show that the pattern of the first EOF of all data sets is consistent with a decadal variation associated with the enhancement of the tropical Hadley circulation, which is supported by other satellite observations. The second EOF of all four data sets is an ENSO mode, and the correlations between their time series and an SO1 are 0.74, 0.71,0.59, and 0.61 for GSSTF2, J-OFURO, HOAPS2, and NCEP in that order. When the Hadley modes are removed from the remote sensing data, the residue global increases are reduced to 2.2% , 7. 3%, and 〈 1% for GSSTF2, J-OFURO and HOAPS, respectively. If the ENSO mode is used as a calibration standard for the data sets, the Hadley mode is at least comparable to, if not larger than, the ENSO mode during our study period.

A Note on Reviving the Goddard Satellite-Based Surface Turbulent Fluxes (GSSTF) Dataset

Accurate sea surface flux measurements are crucial for understanding the global water and energy cycles. The oceanic evaporation, which is a major component of the global oceanic fresh water flux, is useful for predicting oceanic circulation and transport. The global Goddard Satellite-based Surface Turbulent Fluxes Version-2 （GSSTF2; July 1987–December 2000） dateset that was o？cially released in 2001 has been widely used by scientific community for global energy and water cycle research, and regional and short period data analyses. We have recently been funded by NASA to resume processing the GSSTF dataset with an objective of continually producing a uniform dataset of sea surface turbulent fluxes, derived from remote sensing data. The dataset is to be reprocessed and brought up-to-date （GSSTF2b） using improved input datasets such as a recently upgraded NCEP/DOE sea surface temperature reanalysis, and an upgraded surface wind and microwave brightness temperature V6 dataset （Version 6） from the Special Sensor Microwave Imager （SSM/I） produced by Remote Sensing Systems （RSS）. A second new product （GSSTF3） is further proposed with a finer temporal （12-h） and spatial （0.25° × 0.25°） resolution. GSSTF2b （July 1987–December 2008） and GSSTF3 （July 1999–December 2009） will be released for the research community to use by late 2009 and early 2011, respectively.

The Influence of Changes in Vegetation Type on the Surface Energy Budget

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A striking confluence between theory and observations of high-mass X-ray binary pulsars

We analyze the most powerful X-ray outbursts from neutron stars in eleven Magellanic high-mass X-ray binaries and three pulsating ultraluminous X-ray sources. Most of the outbursts rise to Lmax which is about the level of the Eddington luminosity, while the remaining more powerful outbursts also appear to recognize that limit when their emissions are assumed to be anisotropic and beamed toward our direction. We use the measurements of pulsar spin periods Ps and their derivatives Ps to calculate the X-ray luminosities Lp in their faintest accreting （＂propeller-line＂） states. In five cases with unknown Ps, we use the lowest observed X-ray luminosities, which only adds to the heterogeneity of the sample. Then we calculate the ratios Lp/Lmax and we obtain an outstanding confluence of theory and observations from which we conclude that work done on both fronts is accurate and the results are trustworthy： sources known to reside on the lowest Magellanic propeller line are all located on/near that line, whereas other sources jump higher and reach higher-lying propeller lines. These jumps can be interpreted in only one way, higher-lying pulsars have stronger surface magnetic fields in agreement with previous empirical results in which Ps and Lp values were not used.

Flaring activity from quiescent states in neutron-star X-ray binaries

We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curves of seven pulsars: four HMXBPs, two MSBPs and the ultraluminous X-ray pulsar M82 X-2. We discuss the physics of their flaring activities or lack thereof, paying special attention to their emission properties when they are found on the propeller line, inside the Corbet gap or near the light-cylinder barrier. We provide guiding principles for future interpretations of faint X-ray observations, as well as a method of constraining the propeller lines and the dipolar surface magnetic fields of pulsars using a variety of quiescent states. In the process, we clarify some disturbing inaccuracies that have made their way into the published literature.

A Physical Origin for Quantum Entanglement and Probabilistic Behaviors

Quantum Mechanics’ entanglement and probabilistic behaviors are viewed in the light of Quantum Field Theory’s (QFT’s) advances made during the last century. In particular, Bohm’s version (B-EPR) of the Einstein, Podolsky, Rosen (EPR) experiment is now viewed with the aid of QFT’s modern description of electrons. In QFT, free electrons possess a bare core surrounded by a “dressing”. The dressing consists of one or more virtual particles/fields pulled from the vacuum during the bound electron’s parturition. In QFT, a bound electron’s freedom is aided by eliminating its energy losses from bremsstrahlung. The paper develops a “Shimony” numerical model using QFT’s free electron structure with the aid of a “random vector paradigm” (RVP). The RVP simply expresses QFT’s free electron as a bare core surrounded by an EM dressing. Using this RVP, we imbue newly freed electrons with a vector-like EM spin property of 1/2. From this, the Shimony Monte Carlo computer analysis provides a detailed comparison of the B-EPR experiment as described by Bell. The entanglement property can serve to provide a way to transport shared encoded information. Overall, the electron dressing can convey random elements that may provide QM with its entanglement and probabilistic behaviors.

THEMIS星座对2008年2月26日磁层亚暴的观测--磁尾重联触发的亚暴分析研究

本文利用THEMIS卫星结合地面极光和地磁的观测,研究了2008年2月26日04:05和04:55UT的两次亚暴事件.Angelopoulos已经对发生在04:55UT的第二个亚暴事件做了分析.本文对两次亚暴的相关活动进行了详细研究,特别对第一次做了深入讨论,并着重分析了磁重联与亚暴活动的关系.在两次亚暴的初始阶段,第一次极光增亮发生在中磁尾磁重联后2～3min,但是持续时间较短,极向膨胀缓慢,与伪暴的特征相似,标志了亚暴的初突发(initial onset).两次亚暴都存在第二次极光增亮和极光的极向膨胀,且时间与近地磁尾观测的地向流和磁场偶极化同时发生,并与亚暴膨胀相的其他活动的发生同步,标志了亚暴的主突发(major onset).在两次亚暴的增长相期间,极盖区开放磁通量持续增加;在亚暴膨胀相和恢复相中,极盖区磁通量迅速减少.表明两次亚暴膨胀相的演化分别与两次尾瓣开放磁力线重联过程相联系的.从亚暴活动的参数分析,这两次亚暴都属于小亚暴范围;从重联率分析,两次磁重联都属于弱重联.本文的观测结果表明,中磁尾磁尾重联首先触发伪暴;高速流将磁通量和能量传输到近地磁尾;高速流减速最终导致亚暴电流楔(substorm current wedge,简称SCW)的形成和电流中断,产生近地偶极化和极光膨胀,引起亚暴膨胀相突发.本文的观测结果是对近地中性线模型(near earth neutral line,简称NENL)和重联-电流中断协同模型(synthesis scenario of MR and CD,简称RCS)模型及亚暴膨胀相两步突发观点的有力支持.

THEMIS observations of two substorms on February 26,2008

Two substorms occurred at ～04:05 and ～04:55 UT on February 26,2008 are studied with the in-situ observations of THEMIS satellites and ground-based aurora and magnetic field measurements.Angelopoulos et al.have made a comprehensive study of the 04:55 UT event.We showed detailed features of the two substorms with much attention to the first event and to the rela-tionship between mid-tail magnetic reconnection(MR) and substorm activities.It was found that in the earlier stage of each substorm,a first auroral intensification occurred 2-3 min soon after the start of mid-tail MR,followed by a slow and very lim-ited expansion.The auroral arcs were weak,short-lived,and localized,characterizing all features of a pseudobreakup.We re-garded the first auroral brightening as the initial onset of the substorms.A few minutes later,a second stronger auroral intensification appeared,followed by quick and extensive expansions.It was interesting to note that the second brightening and related poleward expansion happened almost simultaneously(within a couple of minutes) with the onset of earthward flow and dipolarization in the near-Earth tail and other phenomenon of the substorm expansion phase.We thus regarded the second auroral brightening as the major onset of the substorms.Furthermore,it was seen that during the growth phase of the two substorms,the polar cap open flux Ψ kept increasing,while it quickly reduced during the substorm expansion and recovery phase.These variations of Ψ implied that the evolution of the two substorm expansion phases were closely related to MR of tail lobe open field lines.Analysis of substorm activities revealed that the two events studied were small substorms;while estimate of MR rate indicated that the MR processes in the two substorms were weak.The aforementioned observations suggested that mid-tail MR initiated the pseudobreakup first;the earthward flow generated by MR transported magnetic flux and energy to the near-Earth tail to cause the formation of SCW and CD,which induced near-Earth dipolarization and major auroral brightening,and eventually led to the onset of the substorm expansion phase.These results were clearly consistent with the picture of NENL and RCS models and supported the two step initiation scenario of substorms.

Metadata requirements analysis for the emerging Sensor Web

The Sensor Web has emerged from Earth Science research with the development of Web technology,to achieve process automation,sensor interoperation,and service synergy.These promises require the discovery of the right sensor at the right time and the right location with the right quality.Metadata,for sensor,platform,and data,are crucial for achieving such goals.However,analysis and practical use of these metadata reveals that the metadata and their associations are not applicable or suitable for the Sensor Web.The shortfalls are(1)the nonstandard metadata expression language;(2)the missing link between sensor and domain knowledge;(3)the insufficiency in the information for geographic locating and sensor tasking;and(4)the enhanced requirements on the quality,security,and ownership of both sensors and their sensed data.This paper reviews the current standards that have metadata components for the sensor and its platform,especially those from ISO TC211,Open Geospatial Consortium Inc.,and The National Aeronautics and Space Administration Global Change Master Directory.A recommendation on metadata that meets the requirement of crossmission sensor discovery in a pervasive Web environment is derived from them.The recommendation addresses issues on language formalization,sensor geolocation,semantics,quality,and accessibility.Roles of the emerging semantic Web technology for enabling robust discovery of sensor are discussed.

Development of an operational land water mask for MODIS Collection 6,and influence on downstream data products

Data from the Moderate Resolution Imaging Spectro-radiometer(MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to be run or when an algorithm needs to follow a different pathway.Entering the fourth reprocessing(Collection 6(C6))the MODIS team replaced the 1 km water mask with a 500 m water mask for improved representation of the continental surfaces.The new water mask represents more small water bodies for an overall increase in water surface from 1%to 2%of the continental surface.While this is still a small fraction of the overall global surface area the increase is more dramatic in certain areas such as the Arctic and Boreal regions where there are dramatic increases in water surface area in the new mask.MODIS products generated by the on-going C6 reprocessing using the new land water mask show significant impact in areas with high concentrations of change in the land water mask.Here differences between the Collection 5(C5)and C6 water masks and the impact of these differences on the MOD04 aerosol product and the MOD11 land surface temperature product are shown.