Comparison of the transport codes HZETRN,HETC and FLUKA for galactic cosmic rays

The HZETRN deterministic radiation code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events on mission planning and shielding for astronauts and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC–HEDS and FLUKA and the deterministic transport code, HZETRN. Each code is used to transport an ion from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm² aluminum slab followed by a 30 g/cm² water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton and forward, backward and total neutron flux at various depths in the water slab. Comparisons of the secondary light ion ²H, ³H, ³He and ⁴He fluxes are also examined.     

基于CRT扫描的被动式射击训练模拟器设计

该文通过对一般射击训练模拟器技术特点的分析，详细介绍了一种被动式以阴极射线扫描为定位基准的射击训练模拟器的原理，并具体讨论了根据这种原理设计出的实用射击训练模拟器的控制电路以及其中固件的工作流程。     

The Swift GRB MIDEX mission

Swift is a first-of-its-kind multiwavelength transient observatory for γ-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of γ-ray bursts and their afterglows, as well as for using bursts to probe the early Universe. Swift will also monitor the soft gamma repeaters and perform the first sensitive hard X-ray survey of the sky. The mission is being developed by an international collaboration and consists of three instruments, the Burst Alert Telescope (BAT), the X-ray Telescope (XRT), and the Ultraviolet and Optical Telescope (UVOT). The BAT, a wide-field γ-ray detector, will detect >100 γ-ray bursts per year with a sensitivity 5× that of BATSE. The sensitive narrow-field XRT and UVOT will be autonomously slewed to the burst location within 20–70 s to determine 0.3–5.0″ positions and perform optical, UV, and X-ray spectrophotometry. Strong education/public outreach and follow-up programs will help to engage the public and the astronomical community. Swift launch is planned for late 2004.     

Numerical simulation on antenna temperature field of complex structure satellite in solar simulator

A thermal network model is developed for studying the temperature variation of complicated structure satellite surfaces. The solar incident areas, the infrared and solar radiation transfer coefficients among surfaces are numerically simulated by means of Monte Carlo ray tracing (MCRT) method in model. The non-uniformity and the instability of solar radiation, which plays the important roles in simulating outer-space heat flux designation parameters by solar simulator, are studied for analysis variation of antenna temperature fields in detail. Results showed non-uniformity irradiation effects are greater than those of instability for this kind of geometry sheltering structure.     

Time of flight measurements over a radio link from Uppsala to Bruntingthorpe and their application to testing predictions methods that approximate the ray tracing technique

Time of flight measurements (TOF) over the radio link between Uppsala (Tx: 59.9°N, 17.6°E) and Bruntingthorpe (Rx: 52.5°N, 1.1°W) have been performed every 2 min at six frequencies (4.637, 6.954, 8.008, 10.391, 11.118, and 14.364 MHz) during the period November 2006–January 2008. Such measurements have been compared with the TOF provided by three prediction methods that approximate the ray tracing technique: IRI-95, SIRM&BR_D, and ICEPAC. The root mean square deviation (rms) between TOF monthly median measurements and TOF monthly median predictions and the differences (DP) between the length of the median and predicted ray path have been calculated. The results, which are presented in terms of rms and DP for different seasons and different time periods, have indicated that the approximate methods are inadequate and that for more accurate predictions ray tracing techniques should be applied.     

The variability of the proton cosmic ray flux on the Sun’s way around the galactic center

The discovery of direct evidences for the acceleration of high energetic particles at the shell supernova remnant RXJ1713.7-3946 underlined the need to calculate the cosmic ray (CR) distribution in the Galaxy on a spatial grid fine enough to resolve the changes in the CR density due to these kind of objects. It was shown before by Büsching et al. [Büsching, I., Kopp, A., Pohl, M., Schlickeiser, R., Perrot, C., Grenier, I. Cosmic-ray propagation properties for an origin in supernova remnants. ApJ 619, 314–326, 2005] that the discrete nature (both in space and time) of super novae (SN) as sources of Galactic CR leads to CR spectra changing in space and time, resulting in a range of possible CR spectra at a given location in the Galaxy. As the most frequent SN types Ib and II are found within spiral arms, one can expect a significant difference of the range of possible spectra in and outside spiral arms. We investigate the variability of the local interstellar CR proton spectrum during the motion of the Sun in and out of spiral arms in its journey around the Galactic center. Using the code described by Büsching et al. [Büsching, I., Kopp, A., Pohl, M., Schlickeiser, R., Perrot, C., Grenier, I. Cosmic-ray propagation properties for an origin in supernova remnants. ApJ 619, 314–326, 2005], the proton CR density in the Galaxy is calculated with high spatial and temporal resolution (75 pc in galactocentric radius r and azimuth φ at the position of the Sun and 20 pc in z (perpendicular to the galactic plane), with a time step of 1 kyr), assuming stochastically distributed point sources with a probability distribution that resembles the spiral structure of our Galaxy. We find the averaged CR flux outside the spiral arm to be about 50% of that inside a spiral arm. We further find spatial and temporal variations of the CR flux inside spiral arms.     

Interstellar-Terrestrial Relations: Variable Cosmic Environments, The Dynamic Heliosphere, and Their Imprints on Terrestrial Archives and Climate

In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during its propagation through the heliosphere, up to its interaction with the Earth’s magnetosphere, resulting, finally, in the production of cosmogenic isotopes in the Earth’ atmosphere. The interpretation of the cosmogenic isotopes and the cosmic ray – cloud connection are also intensively discussed. Finally, we discuss some open questions.     

Study on solar sources and polar cap absorption events recorded in Antarctica

Particularly intense events occurred on the Sun in a period around minimum of solar activity during cycle 23. We investigated the characteristics of September 2005 and December 2006 events and the properties of the correlated observations of ionospheric absorption, obtained by a 30 MHz riometer installed at Mario Zucchelli Station (MZS-Antarctica), and of geomagnetic activity recorded at Scott Base (Antarctica). Solar events are studied using the characteristics of CMEs measured with SoHO/LASCO coronagraphs and the temporal evolution of solar energetic protons in different energy ranges measured by GOES 11 spacecraft.     

Cosmic ray anisotropies in the outer heliosphere

The observation of the directional distribution of energetic and cosmic ray particles has been done with the Voyager spacecraft over a long period. Since 2002, when the first flux enhancements of charged particles associated with the approach of Voyager 1 to the solar wind termination shock were observed, these anisotropy measurements have become of special interest. They play an important role to understand the magnetic field and shock structure and the basics of the modulation of cosmic ray and anomalous particles at and beyond the termination shock. They also serve as motivation to study the spatial behavior of galactic and anomalous cosmic ray anisotropies with numerical modulation models in order to illustrate how the radial anisotropy, at different energies, change from upstream to downstream of the termination shock. Observations made by Voyager 1 indicate that the termination shock is a complicated region than previously thought, hence the effects of the latitude dependence of the termination shock’s compression ratio and injection efficiency on the radial anisotropies of galactic and anomalous protons will be illustrated. We find that the magnitude and direction of the radial anisotropy strongly depends on the position in the heliosphere and the energy of particles. The effect of the TS on the radial anisotropy is to abruptly increase its value in the heliosheath especially in the A > 0 cycle for galactic protons and in both polarity cycles for anomalous protons. Furthermore, the global effect of the latitude dependence of the shock’s compression ratio is to increase the radial anisotropy for galactic protons throughout the heliosphere, while when combined with the latitude dependence of the injection efficiency this increase depends on modulation factors for anomalous protons and can even alter the direction of the radial anisotropy.     

Present status of very high energy gamma ray observations

Recent results from observations of the southern sky objects are summarized. The unpulsed, persistent very high energy (VHE) emission from the gamma ray pulsars, the Crab and PSR1706-44, is discussed. A process of energetic electrons ejection may take place from a variety of other objects such as from X-ray binaries, similarly to the pulsars. Such an effect may be seen also in pair halos around extragalactic VHE gamma ray emitters, the observational study of which is still in a preliminary stage in the southern hemisphere.