New index of long-term variations of galactic cosmic ray intensity

We find that the soft rigidity spectrum of the Galactic Cosmic Ray (GCR) intensity variations for the maximum epoch and the hard rigidity spectrum for the minimum epoch calculated based on the neutron monitors experimental data (1960–2002) are related with the various dependence of the diffusion coefficient on the GCR particle’s rigidity for different epoch of solar activity. This dependence is stronger in the maximum epoch than in the minimum epoch of solar activity, and is provided by the essential temporal rearrangements of the structure of the Interplanetary Magnetic Field (IMF) turbulence from the maxima to minima epoch of solar activity. We also show that the rigidity spectrum of GCR intensity variations is harder for the effective rigidities ∼(10–15) GV (by neutron monitors data), than for the effective rigidities ∼(25–30) GV (by neutron monitors and muon telescopes data). A general scenario of GCR modulation versus solar activity is settled on the essential temporal rearrangements of the structure of the IMF turbulence. Therefore, the temporal changes of the power law rigidity spectrum exponent can be considered as a vital (new) index to explain the 11-year variations of the GCR intensity. We assume that ∼(70–80)% of the changes of the amplitudes of the 11-year variations of GCR intensity is related with the changes of the IMF turbulence versus solar activity.     

Energy dependence of the rigidity spectrum of Forbush decrease of galactic cosmic ray intensity

We show that rigidity spectrum of Forbush decrease (Fd) of galactic cosmic ray (GCR) intensity in September 9–23, 2005 clearly depends on energy. We calculated rigidity spectrum of the Fd based on the neutron monitors and Nagoya muon telescope channels’ data divided in three groups according to their cut off rigidities. We found that temporal changes of rigidity spectrum exponent γ are approximately similar for all cut off rigidity groups, but γ values are the larger the higher are cut off rigidities. We conclude that rigidity spectrum of Fd is hard for lower energy range and is soft for the higher energy range. We believe that an energy dependence of the power law rigidity spectrum of Fd is observed owing to the preferential convection–diffusion mechanism during Fd in September 9–23, 2005. It is a reflection of an influence of the temporal changes of the structure of the interplanetary magnetic field (IMF) turbulence in different range of frequency f during Fd. Particularly, a decisive role in formation of the character of the rigidity spectrum belongs to the changes of the exponent ν of the power spectral density (PSD) of the IMF turbulence (PSD ∝ f^−ν). The exponent ν is greater for high frequency region of the IMF turbulence (responsible for scattering of low rigidity particles of GCR), than for low frequency region of the IMF turbulence (being responsible for scattering of higher rigidity particles). Also, we challenge to estimate an existence of slab/2D structure of solar wind turbulence during the Fd in September 9–23, 2005 based on the distribution of average turbulence energy among the IMF’s components.     

Sharp boundaries of solar wind plasma structures and their relationship to solar wind turbulence

Sharp (<10 min) and large (>20%) solar wind ion flux changes are common phenomena in turbulent solar wind plasma. These changes are the boundaries of small- and middle-scale solar wind plasma structures which can have a significant influence on Earth’s magnetosphere. These solar wind ion flux changes are typically accompanied by only a small change in the bulk solar wind velocity, hence, the flux changes are driven mainly by plasma density variations. We show that these events occur more frequently in high-density solar wind. A characteristic of solar wind turbulence, intermittency, is determined for time periods with and without these flux changes. The probability distribution functions (PDF) of solar wind ion flux variations for different time scales are calculated for each of these periods and compared. For large time scales, the PDFs are Gaussian for both data sets. For small time scales, the PDFs from both data set are more flat than Gaussian, but the degree of flatness is much larger for the data near the sharp flux change boundaries.     

Photon counting detector for space debris laser tracking and lunar laser ranging

We are reporting on a design, construction and performance of solid state photon counting detector package which has been designed for laser tracking of space debris. The detector has been optimized for top photon detection efficiency and detection delay stability. The active area of the commercially available avalanche photodiode manufactured on Si (SAP500 supplied by Laser Components, Inc.) is circular with a diameter of 500 μm. The newly designed control circuit enables to operate the detection sensor at a broad range of biases 5–50 V above its breakdown voltage of 125 V. This permits to select a right trade-off between photon detection efficiency, timing resolution and dark count rate. The photon detection efficiency exceeds 70% at the wavelength of 532 nm. This is the highest photon detection efficiency ever reported for such a device. The timing properties of the detector have been investigated in detail. The timing resolution is better than 80 ps r.m.s, the detection delay is stable within units of picoseconds over several hours of operation. The detection delay stability in a sense of time deviation of 800 fs has been achieved. The temperature change of the detection delay is 0.5 ps/K. The detector has been tested as an echo signal detector in laser tracking of space debris at the satellite laser station in Graz, Austria. Its application in lunar laser ranging is under consideration by several laser stations.     

Possible influence of cosmic rays on climate through thunderstorm clouds

With decreasing of cosmic ray (CR) intensity caused by increasing of solar activity (SA) or in some short periods of Forbush-decreases, the intensity of secondary CR relativistic electrons decreases and the probability of formation of thunderstorm clouds and discharges between clouds or between clouds and ground is also expected to decrease. This will influence on weather and climate. In this case is very important to have more detail information on the atmospheric electric field distribution in the atmosphere, additional to information what gave now electric field sensors (EFS) only in about one point near the ground. We show that CR not only influenced on atmospheric electric field phenomenon, but can give practically continuous information on the atmospheric electric field distribution in the atmosphere. We extend our theory of CR atmospheric electric field effect on electron–photon, muon and neutron component including different multiplicities. We take into account that about 0.07 of neutron monitor counting rate caused by negative soft muons captured by lead nucleons and formed mesoatoms with generation of several MeV energy neutrons from lead. In this case the neutron monitor or neutron super-monitor works as analyzer that detects muons of only one, negative sign. It is very important because the atmospheric electric field effect have opposite signs for positive and negative muons that main part of this effect in the muon telescope or in ionization chamber is compensated and we can observe only small part of total effect of one sign muons. On the basis of our general theory of CR atmospheric electric field effects with taking into account of negative soft muon acceleration and deceleration in the Earth atmosphere (in dependence of direction and intensity of electric field) we discuss the possibility of existing this effect in CR neutron monitor counting rate and in different multiplicities and calculate the expected effects in dependence of atmospheric electric field distribution in the atmosphere. We show that the comparison of observed effects with theoretically expected will give important information on the value of atmospheric electric field and its distribution in the atmosphere. We consider also the possible influence of secondary relativistic electrons of CR and relativistic electrons precipitated from the Earth’s radiation belts on thunderstorms and lightnings, and through this – on climate change.     

Study on dependence of hydrodynamic characteristics on gravity in a vertical upward channel bubbly flow

Since the bubbly flow has extensive applications in the space field, it is very necessary to comprehend the dependence of hydrodynamic characteristics on gravity. In this paper, the dependence of the microbubble distribution and the liquid turbulence modulation by the microbubbles on gravity was investigated in detail with the Euler–Lagrange method. The liquid Navier–Stokes equation was solved using direct numerical simulations (DNS), and the microbubble motion was tracked with Newtonian motion equation considering drag force, shear lift force, added mass force, pressure gradient force, and wall lift force. The coupling between the gas and the liquid phases regarded the interphase force as a momentum source term in the momentum equation of the liquid. The results showed that the phase profile and the turbulence modulation by the microbubbles strongly depend on the magnitude of gravity. When the influence of gravity is relatively weak, the microbubbles approximately uniformly disperse in the wide central region of the channel, and the average statistics of the liquid turbulence are almost not influenced due to the addition of the microbubbles. However, when the influence of gravity is comparatively important, the majority of the microbubbles accumulate near the wall of the channel, and the injection of the microbubbles modifies the profiles of the liquid average statistics.     

基于低温辐射计的探测器绝对光谱响应率测量

探测器的绝对光谱响应率是衡量光电探测器性能优劣的重要参数,直接反映其光电转化的能力。通过对低温辐射计,功率稳定系统光路调整的介绍,基于低温辐射计,对探测器可见光范围的7个波长的绝对光谱响应率进行了高精度测量,分析了测量结果。     

宽光谱可调谐纠缠光子源设计

为研制宽光谱可调谐纠缠光子源，提出利用532nm激光抽运周期极化铌酸锂（PPLN）晶体，辅以晶体周期切换和温度调谐的方法。基于PPLN晶体准相位匹配方式，完成对晶体周期、长度和温控精度等特性参数的理论研究。在此基础上计算得到晶体的周期，信号光相关光子带宽分布以及信号光温控精度曲线。研究表明，在50℃~200℃温控范围内，利用9块晶体可实现676nm~2500nm宽光谱可调谐相关光子输出。研究结果为高通量宽光谱可调谐纠缠光子源的研制奠定了基础。     

PC-index fluctuations and intermittency of the magnetospheric dynamics

One minute resolution Polar Cap (PC) index was used for the analysis of magnetospheric dynamics. The 1995–2000 time series analysis revealed that the power spectrum of the PC-index fluctuations is a power law in a wide range of frequencies. However, the obtained exponents differ for low and high frequency regions. The probability distribution functions of the PC-index fluctuations show a strong non-gaussian shape, depending on the time of increment. This indicates that the PC-index exhibits intermittency, previously detected in solar wind and auroral electrojet index fluctuations. The PC-index probability distribution functions were fitted by the functional form proposed by Castaing et al. [Velocity probability density functions of high Reynolds number turbulence. Physica D. 46, 177–200, 1990] to describe intermittency phenomena in ordinary turbulent fluid flows. The agreement between the fitting parameters obtained for the PC index and those reported before for solar wind magnetic field fluctuations is within 30%; which is noticeably less than the difference between the same parameters of solar wind and the AE-index fluctuations. This fact indicates that the PC index reflects the solar wind influence on the high-latitude magnetosphere, especially during the summer.     

微重力量值对气液两相流相分布及液相湍流统计量影响的数值研究

气液两相流在空间领域具有广阔的应用前景, 深入理解微重力量值(微重力大小)对相分布和液相湍流的影响十分必要. 采用欧拉elax-elax拉格朗日双向耦合模型深入研究了不同微重力量值对相分布和液相湍流的影响. 液相速度场通过直接数值模拟求解, 气泡的运动轨迹由牛顿运动方程跟踪. 研究表明, 气泡分布和液相湍流与微重力量值均具有直接联系. 在低微重力量值下, 气泡近似均匀分布在槽道内, 且对液相湍流统计量几乎没有影响; 然而当微重力量值较高时, 大量气泡聚集在壁面附近, 液相湍流由于气泡的注入受到极大调制.      

后向台阶层流分离剪切层特性研究

应用激光测速仪对生向台阶层流边界层分离产生的剪切层在再附前的发展进行了测量，得到了时均速度、湍流强度及剪切层厚度等的分布特性，并研究了来流湍流度对台阶后流场湍强度分布及剪切层发展的影响，实验中发现台阶后有一个流速降低的区域，对此从涡动力学的角度作了解释。     

Perpendicular transport of charged particles: Results for the unified nonlinear transport theory derived from the Newton–Lorentz equation

The perpendicular diffusion coefficient is calculated by combining a recently developed Unified Nonlinear Transport (UNLT) theory with the Newton–Lorentz equation. The total perpendicular mean free path can be described as a combination of a guiding center contribution and a microscopic contribution. It is shown that the total mean free path depends strongly on the energy range of the turbulence power spectrum and on particle energy. Further, a slab/2D composite model is used to investigate the influence of each contribution to the total mean free path for a quasi-3D turbulence model. For pure 2D turbulence the UNLT reduces to the NLGC-theory. For pure slab turbulence the guiding center contribution is subdiffusive in accordance with simulations and the theorem on reduced dimensionality. Conversely, the microscopic contribution is non-zero, which has to be interpreted as normal diffusion.     

阻尼网特性数值模拟

依靠经验公式和工程估算等传统方法,无法对阻尼网性能进行精确评估.为确定阻尼网压力损失系数和降湍性能,采用计算流体力学方法,结合适当的边界条件,对阻尼网进行了模拟.使用数值模拟能够得到不同开孔率阻尼网在不同雷诺数、不同入射方向、不同目数的损失系数,与试验结果更为接近,在30°~45°大角度入射时得到的损失系数更为精确;在入射气流与阻尼网平面呈一定夹角时,阻尼网后的气流压力和速度呈现脉动趋势,传播距离大约为100d;在雷诺数小于40时流动保持层流状态,扰动传播距离为50d,此时降湍效果最好,随雷诺数增加,扰动传播距离增加至400d;在流动未失稳时,开孔率越低,降湍效果越明显,开孔率低于0.5时流动容易失稳;开孔率保持不变,随目数增加阻尼网损失系数增加明显,降湍能力提升.因此可以根据数值模拟结果选择阻尼网的最优参数.     

Dependence of E-sporadic layer response on solar and geomagnetic activity variations from its ion composition

The aim of this paper is to consider an influence of solar and geomagnetic activity level variations on frequency and stochastic parameters of mid-latitude ionosphere sporadic-E layer. Critical frequency of sporadic-E layer, foEs, relative excess of sporadic ionization over monthly median values, foEs − foEm/foEm, and probability of Es layer appearance, PEs, are considered. It has been found that sporadic-E layer parameters response to solar and geomagnetic activity level variations can be both positive (foEs and PEs values are increase) and negative (foEs and PEs values are decrease). In particular, sporadic-E layers response to solar and geomagnetic activity variations are different depending upon layer intensity. It is suggested that revealed differences may be associated with dissimilarity of the layers ion composition (high-intensive layers are composed from metallic ions and low intensive composed from molecular ions).     

Diffusive shock acceleration at interplanetary perpendicular shock waves: Influence of the large scale structure of turbulence on the maximum particle energy

We calculate the maximum energy that a particle can obtain at perpendicular interplanetary shock waves by the mechanism of diffusive shock acceleration. The influence of the energy range spectral index of the two-dimensional modes of the interplanetary turbulence is explored. We show that changes in this parameter lead to energies that differ in at least one order of magnitude. Therefore, the large scale structure of the turbulence is a key input if the maximum particle energy is calculated.     

Estimation of long-term cosmic ray intensity variation in near future and prediction of their contribution in expected global climate change

On the basis of results obtained in our paper [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], we determine: the dimension of the Heliosphere (modulation region), radial diffusion coefficient and other parameters of convection–diffusion; drift mechanisms of long-term variations of cosmic ray (CR) dependence on particle energy; level of solar activity (SA); and generally, the solar magnetic field. We obtain this important information on the basis of CR and SA data in the past, taking into account the theory of convection–diffusion and global drift modulation of galactic CR in the Heliosphere. By using these results and other regularly published predictions of expected SA variation in the near future, as well as predictions of the next SA cycle, we may make predictions of long-term cosmic ray intensity variation expected in the near future (up to 10–12 years). In [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], properties of connections between long-term variation in CR intensity and some part of a global climate change were estimated, controlled by solar activity through CR. We show that in this way we may make predictions of some part of a global climate change expected in the near future (up to 10–12 years and maybe more, depending upon the period during which definite predictions of SA can be made), controlled by solar activity through CR. In this case, estimations of expected long-term changes in the planetary distribution of cutoff rigidities, which also influence CR intensity, as well as CR-influenced effects on global climate variation, become important.     

Orbital debris–debris collision avoidance

We focus on preventing collisions between debris and debris, for which there is no current, effective mitigation strategy. We investigate the feasibility of using a medium-powered (5 kW) ground-based laser combined with a ground-based telescope to prevent collisions between debris objects in low-Earth orbit (LEO). The scheme utilizes photon pressure alone as a means to perturb the orbit of a debris object. Applied over multiple engagements, this alters the debris orbit sufficiently to reduce the risk of an upcoming conjunction. We employ standard assumptions for atmospheric conditions and the resulting beam propagation. Using case studies designed to represent the properties (e.g. area and mass) of the current debris population, we show that one could significantly reduce the risk of nearly half of all catastrophic collisions involving debris using only one such laser/telescope facility. We speculate on whether this could mitigate the debris fragmentation rate such that it falls below the natural debris re-entry rate due to atmospheric drag, and thus whether continuous long-term operation could entirely mitigate the Kessler syndrome in LEO, without need for relatively expensive active debris removal.     

沟槽面湍流边界层湍流度分布

应用激光测速(LDV)技术对沟槽面湍流边界层湍流度分布进行了精细的测量,实验结果表明,在湍流边界层区域沟槽面湍流度最大值比光滑面要小,但出现的位置比光滑面要远.此外,紧靠沟槽面,即y++<4内,沟槽面有较大的湍流度,说明沟槽面有使近壁区流动紊动增加的趋势.对于y/δ≥0.06的区域,湍流度可用u′\u=2.3 exp (-0.9y/δ)描述,而在y/δ<0.06内,则有u′/u =36.4y/δ.     

Comparative study of the dust emission of 19P/Borrelly (Deep space 1) and 1P/Halley

Images obtained by the Miniature Integrated Camera and Imaging Spectrometer (MICAS) experiment onboard the Deep Space 1 spacecraft which encountered comet 19P/Borrelly on September 22nd 2001 show a dust coma dominated by jets. In particular a major collimated dust jet on the sunward side of the nucleus was observed. Our approach to analyse these features is to integrate the observed intensity in concentric envelopes around the nucleus. The same procedures has been used on the Halley Multicolour Camera images of comet 1P/Halley acquired on March 14th 1986. We are able to show that at Borrelly the dust brightness dependence as a function of radial distance is different to that of Halley. At large distances both comets show constant values as the size of the concentric envelopes increases (as one would expect for force free radial outflow). For Halley the integral decreases as one gets closer to the nucleus. Borrelly shows opposite behaviour. The main cause for Halley's intensity distribution is either high optical thickness or particle fragmentation. For Borrelly, we have constructed a simple model of the brightness distribution near the nucleus. This indicates that the influence of deviations from point source geometry is insufficient to explain the observed steepening of the intensity profile close to the nucleus. Dust acceleration or fragmentation into submicron particles appear to be required. We also estimate the dust production rate of Borrelly with respect to Halley and compare their dust to gas ratios.