一种部分森林覆盖环境电波传播特性预测方法

针对部分森林覆盖环境中传播媒介的非均匀性,提出一种基于动态网格的抛物方程(PE)预测方法,该方法采用宽角PE法进行大区域电波传播特性预测。为平衡PE求解的准确性与时效性,引入动态网格技术。通过仿真算例,探讨了基于动态网格的PE法在部分森林覆盖环境电波传播特性预测中的有效性。结果表明:在计算精度相似的情况下,相对于均匀细网格,动态网格会大大减少PE所需的计算时间;而相比均匀粗网格,动态网格具有更高的计算精度。     

极区中层惯性重力波的VHF雷达观测

本文采用ＳＯＵＳＹＶＨＦ雷达１９８７年６月在挪威Ａｎｄｏｐｖａ（６９°Ｎ，１０°Ｅ）的观测数据，研究中层惯性重力波的传播特征．几个周期为数小时的准单色波例子，在垂直方向上有确定的相位移动，表明它们是惯性内重力波．通过分析波相关的流体速度东向和北向分量的变化，获得水平传播矢量的大小和方向，它们与中层高度上典型的观测值一致．同时还观察到三个等相面上行的惯性重力波，其速度偏振椭圆是逆时针旋转的．波相关的扰动速度为１５－４０ｍ／ｓ，说明在中层存在强烈的向下的能量传输．估算出它的运动学参量，周期为数小时，垂直相速度在０．ｌ—０．６ｍ／ｓ之间，垂直波长约为６．０ｋｍ．     

极区中层惯性重力波VHF雷达观测的统计特征

本文采用ＳＯＵＳＹＶＨＦ雷达１９８７年６月２２日至６月２９日在挪威Ａｎｄφｙａ（６９°Ｎ，１０°Ｅ）的观测数据，研究中层惯性重力波传播的统计特征．２１个周期为数小时的准单色波例子，在垂直方向上有确定的相位移动，表明它们是惯性内重力波．通过分析波相关水平扰动速度的矢端曲线，获得了水平传播矢量的大小和方向的分布，大多数（７６％）波具有西向传播的波矢分量，似乎与中层顶具有强的西向背景风有关；水平传播速度的大小与中层高度上典型的观测值一致．本文分析结果还表明在极区中不仅存在向上的能量传输，也存在强烈的向下的能量传输．     

地磁暴前地面宇宙线强度变化Morlet小波特征分析

用Morlet小波变换对Oulu台站和Apatity台站(主要是Apatity台站)1998-2002年间宇宙线静日和地磁暴前的地面宇宙线强度变化特征进行分析，得到：在宇宙线静日期间普遍存在准24h周期变化特征，并且在当地时间0200，1400左右分别出现最小值和最大值；对12个例子的分析可以看到地面宇宙线强度在地磁暴之前l-2天均出现了不同于宇宙线静日期间变化特征，或有小尺度周期出现，或周期变化完全消失，或有异常24h周期变化，这种变化特征在一定程度上可作为地磁预报的先兆特征之一。     

A 3NM-64_He added to LARC for Solar Extreme Event studies during solar cycle 24

The Antarctic Laboratory for Cosmic Rays (LARC, acronym for Laboratorio Antartico per i Raggi Cosmici or Laboratorio Antártico para Rayos Cósmicos) operates on King George Island (South Shetlands). Since January 1991 a standard 6NM-64 detector has been recording continuous cosmic ray measurements and several Ground-Level Enhancements have been registered. Here we describe the different phases performed in Italy for the realization of a 3NM-64_³He detector, which started its measurements during the Italian XXII Antarctic Summer Campaign. Data recorded during solar activity cycle 24 will furnish an useful research tool for the next Solar Extreme Events.     

The acceleration of Anomalous Cosmic Rays by stochastic acceleration in the heliosheath

Stochastic acceleration in the heliosheath appears to be a likely mechanism by which Anomalous Cosmic Rays (ACRs) are accelerated. However, most stochastic acceleration mechanisms are not appropriate. The energy density in the ACRs and in the interstellar pickup ions out of which the ACRs are accelerated greatly exceeds the energy density in the turbulence in the heliosheath. Thus, a traditional stochastic acceleration mechanism in which particles are accelerated by damping the turbulence will not work. A stochastic acceleration mechanism has been developed in which the total energy of the pickup ions and the ACRs is conserved. Energy is redistributed from the core pickup ions into a suprathermal tail to create the ACRs. A model for the acceleration of the ACRs in the heliosheath, based on this stochastic acceleration mechanism, is presented. The model provides reasonable fits to the spectra of suprathermal particles and ACRs observed by Voyager.     

Zr-Al-(Ni-Cu)合金的非晶形成能力及热学性能

采用喷射铜模铸造法研究了Ni和Cu含量对Zr-Al-(Ni-Cu)四元合金的非晶形成能力的影响.利用X射线衍射仪分析了铸态合金的相结构,利用差示扫描量热仪研究了非晶合金的热学性能.结果表明:Zr-Al-(Ni-Cu)四元合金的非晶形成能力远大于Zr-Al-Ni和Zr-Al-Cu三元合金的非晶形成能力.Zr65Al7.5Ni10Cu17.5合金显示最高的非晶形成能力,其非晶形成临界直径可以达到7 mm.相似元素Ni和Cu在一定比例下共存,使液态合金的熵值增加,自由能降低,从而有效提高了合金的非晶形成能力.     

The radiation environment in the ISS-USLab measured by ALTEA: Spectra and relative nuclear abundances in the polar,equatorial and SAA regions

We present here the energy spectra relative to different geomagnetic regions as measured by the ALTEA (Anomalous Long Term Effects on Astronauts) detector in the International Space Station – USLab from August 2006 to July 2007.     

Modelling of galactic Carbon in an asymmetrical heliosphere: Effects of asymmetrical modulation conditions

Observations of galactic cosmic rays (GCRs) from the two Voyager spacecraft inside the heliosheath indicate significant differences between them, suggesting that in addition to a possible global asymmetry in the north–south dimensions (meridional plane) of the heliosphere, it is also possible that different modulation (turbulence) conditions could exist between the two hemispheres of the heliosphere. We focus on illustrating the effects on GCR Carbon of asymmetrical modulation conditions combined with a heliosheath thickness that has a significant dependence on heliolatitude. To reflect different modulation conditions between the two heliospheric hemispheres in our numerical model, the enhancement of both polar and radial perpendicular diffusion off the ecliptic plane is assumed to differ from heliographic pole to pole. The computed radial GCR intensities at polar angles of 55° (approximating the Voyager 1 direction) and 125° (approximating the Voyager 2 direction) are compared at different energies and for both particle drift cycles. This is done in the context of illustrating how different values of the enhancement of both polar and radial perpendicular diffusion between the two hemispheres contribute to causing differences in radial intensities during solar minimum and moderate maximum conditions. We find that in the A > 0 cycle these differences between 55° and 125° change both quantitatively and qualitatively for the assumed asymmetrical modulation condition as reflected by polar diffusion, while in the A < 0 cycle, minute quantitative differences are obtained. However, when both polar and radial perpendicular diffusion have significant latitude dependences, major differences in radial intensities between the two polar angles are obtained in both polarity cycles. Furthermore, significant differences in radial intensity gradients obtained in the heliosheath at lower energies may suggest that the solar wind turbulence at and beyond the solar wind termination shock must have a larger latitudinal dependence.     

Modelling and observing Jovian electron propagation times in the inner heliosphere

The propagation of Jovian electrons in interplanetary space was modelled by solving the relevant transport equation numerically through the use of stochastic differential equations. This approach allows us to calculate, for the first time, the propagation time of Jovian electrons from the Jovian magnetosphere to Earth. Using observed quiet-time increases of electron intensities at Earth, we also derive values for this quantity. Comparing the modelled and observed propagation times we can gauge the magnitude of the transport parameters sufficiently to place a limit on the 6 MeV Jovian electron flux reaching Earth. We also investigate how the modelled propagation time, and corresponding Jovian electron flux, varies with the well-known ∼13 month periodicity in the magnetic connectivity of Earth and Jupiter. The results show that the Jovian electron intensity varies by a factor of ∼10 during this cycle of magnetic connectivity.