宇宙线分布、氢分布和宇宙γ射线

本文利用几种典型的银河系宇宙线分布律和星际氢分布律计算单漏模式和双漏模式中的弥散宇宙γ射线谱。结果表明,几种典型的宇宙线分布中,李惕碚的分布律优于其他作者的分布律;星际氢分子数量的取值应当比Gordon值除以1.7更小;只要适当地选择宇宙线分布和氢分布就可得到与观测γ谱相近的理论谱,宇宙线分布和氢分布均可在一定范围里选取。     

Cosmic Ray Production Rates in Supernova Remnants

Supernova Remnants (SNRs) are the most likely sources of the galactic cosmic rays up to energies of about 10¹⁵ eV/nuc. The large scale shock waves of SNRs are almost ideal sites to accelerate particles up to these highly non-thermal energies by a first order Fermi mechanism which operates through scattering of the particles at magnetic irregularities. In order to get an estimate on the total amount of the explosion energy E _SNconverted into high energy particles the evolution of a SNR has to be followed up to the final merging with the interstellar medium. This can only be done by numerical simulations since the non-linear modifications of the shock wave due to particle acceleration as well as radiative cooling processes at later SNR stages have to be considered in such investigations. Based on a large sample of numerical evolution calculations performed for different ambient densities n _ext, SN explosion energies, magnetic fields etc. we discuss the final ‘yields’ of cosmic rays at the final SNR stage where the Mach number of the shock waves drops below 2. At these times the cosmic rays start to diffuse out of the remnant. In the range of external densities of10^-2 ≤ n _ext/[cm^-3] ≤ 30 we find a the total acceleration efficiency of about 0.15 E _SN with an increase up to 0.24 E _SN at maximum for an external density of n _ext = 10 cm^-3. Since for the larger ambient densities radiative cooling can reduce significantly the total thermal energy content of the remnant dissipation of Alfvén waves can provide an important heating mechanism for the gas at these later stages. From the collisions of the cosmic rays with the thermal plasma neutral pions are generated which decay subsequently into observable γ-rays above 100 MeV. Hence, we calculate these γ-ray luminosities of SNRs and compare them with current upper limits of ground based γ-raytelescopes. The development of dense shells due to cooling of the thermal plasma increases the γ-ray luminosities and e.g. an external density of n _ext = 10 cm^-3 with E _SN = 10⁵¹ erg can lead to a γ-ray flux above 10^-6 ph cm^-2 s^-1 for a remnant located at a distance of 1 kpc. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evidence for Planetary Forcing of the Cosmic Ray Intensity and Solar Activity Throughout the Past 9400 Years

Paleo-cosmic-ray (PCR) records based on cosmogenic ¹⁰Be and ¹⁴C data are used to study the variations in cosmic-ray intensity and solar activity over the past 9400 years. There are four strong correlations with the motion of the Jovian planets; the probability of occurring by chance being <?10^?5. They are i) the PCR periodicities at 87, 350, 510, and 710 years, which closely approximate integer multiples of half the Uranus–Neptune synodic period; ii) eight periodicities in the torques calculated to be exerted by the planets on an asymmetric tachocline that approximate the periods observed in the PCR; iii) the maxima of the long-term PCR variations are coincident with syzygy (alignment) of the four Jovian planets in 5272 and 644 BP; and iv) in the time domain, the PCR intensity decreases during the first 60 years of the ≈?172 year Jose cycle (Jose, Astron. J. 70, 193, 1965) and increases in the remaining ≈?112 years in association with barycentric anomalies in the distance between the Sun and the center of mass of the solar system. Furthermore, sunspot and neutron-monitor data show that three anomalous sunspot cycles (4th, 7th, and 20th) and the long sunspot minimum of 2006 – 2009 CE coincided with the first and second barycentric anomalies of the 58th and 59th Jose cycles. Phase lags between the planetary and heliospheric effects are ≤?five years. The 20 largest Grand Minima during the past 9400 years coincided with the latter half of the Jose cycle in which they occurred. These correlations are not of terrestrial origin, nor are they due to the planets’ contributing directly to the cosmic-ray modulation process in the heliosphere. Low cosmic-ray intensity (higher solar activity) occurred when Uranus and Neptune were in superior conjunction (mutual cancellation), while high intensities occurred when Uranus–Neptune were in inferior conjunction (additive effects). Many of the prominent peaks in the PCR Fourier spectrum can be explained in terms of the Jose cycle, and the occurrence of barycentric anomalies.     

Cosmic Ray Acceleration Inside Molecular Clouds

Acceleration of charged particles by neutral gas turbulence in giant molecular clouds is considered. The gamma-ray emission from these clouds is estimated. It is shown that molecular clouds can be the counterparts of some of unidentified sources.     

Li Be B Energetics and Cosmic Ray Origin

Three different models have been proposed for LiBeB production bycosmic rays: the CRI model in which the cosmic rays areaccelerated out of an ISM of solar composition scaled withmetallicity; the CRS model in which cosmic rays with compositionsimilar to that of the current epoch cosmic rays are acceleratedout of fresh supernova ejecta; and the LECR model in which adistinct low energy component coexists with the postulated cosmicrays of the CRI model. These models are usually distinguished bytheir predictions concerning the evolution of the Be and Babundances. Here we emphasize the energetics which favor the CRSmodel. This model is also favored by observations showing that thebulk (80 to 90%) of all supernovae occur in hot, low densitysuperbubbles, where supernova shocks can accelerate the cosmicrays from supernova ejecta enriched matter. This revised version was published online in July 2006 with corrections to the Cover Date.     

The HEAO-3 Cosmic Ray Isotope spectrometer

This paper describes the Cosmic Ray Isotope instrument launched aboard the HEAO-3 satellite on September 20, 1979. The primary purpose of the experiment is to measure the isotopic composition of cosmic ray nuclei from Be-7 to Fe-58 over the energy range 0.5 to 7 GeV/nucleon. In addition charge spectra will be measured between beryllium and tin over the energy range 0.5 to 25 GeV/nucleon. The charge and isotope abundances measured by the experiment provide essential information needed to further our understanding of the origin and propagation of high energy cosmic rays. The instrument consists of 5 Cerenkov counters, a 4 element neon flash tube hodoscope and a time-of-flight system. The determination of charge and energy for each particle is based on the multiple Cerenkov technique and the mass determination will be based upon a statistical analysis of particle trajectories in the geomagnetic field.Representing the Saclay-Copenhagen CollaborationOriginally submitted to the journalSpace Science Instrumentation.The Saclay-Copenhangen Collaboration consists of the authors and the following members.     

Strange Quark Matter in Cosmic Ray Flux and Exotic Events

There have been several reports of exotic nuclear fragments, with highly unusual charge to mass ratio, in cosmic ray experiments. Although there exist experimental uncertainties which make them, at best, only candidate `exotic' events, it is important to understand what they could be, if they are eventually confirmed. Among other possible explanations, some authors have interpreted them to be lumps of strange quark matter (strangelets).A major problem with such an interpretation is that to reach the earth's surface, they must possess an unusually high penetrability through the terrestrial atmosphere. We show that a recently proposed mechanism for the propagation of strangelets through the earth's atmosphere, together with a proper account of charge capture and ionisation loss, would solve this problem. We also argue that this could lead to viable strategies for definitive detection of strange quark matter in cosmic ray flux using aground based large area array of passive detectors. This revised version was published online in July 2006 with corrections to the Cover Date.     

Galactic Cosmic Ray Modulation and the Last Solar Minimum

In this work the galactic cosmic ray modulation in relation to solar activity indices and heliospheric parameters during the years 1996??C?2010 covering solar cycle 23 and the solar minimum between cycles 23 and 24 is studied. A new perspective of this contribution is that cosmic ray data with a rigidity of 10 GV at the top of the atmosphere obtained from many ground-based neutron monitors were used. The proposed empirical relation gave much better results than those in previous works concerning the hysteresis effect. The proposed models obtained from a combination of solar activity indices and heliospheric parameters give a standard deviation <?10?% for all the cases. The correlation coefficient between the cosmic ray variations of 10?GV and the sunspot number reached a value of r=?0.89 with a time lag of 13.6±0.4 months. The best reproduction of the cosmic ray intensity is obtained by taking into account solar and interplanetary indices such as sunspot number, interplanetary magnetic field, CME index, and heliospheric current sheet tilt. The standard deviation between the observed and calculated values is about 7.15?% for all of solar cycle 23; it also works very well during the different phases of the cycle. Moreover, the use of the cosmic ray intensity of 10?GV during the long minimum period between cycles 23 and 24 is of special interest and is discussed in terms of cosmic ray intensity modulation.     

我国4300 m高度上的高能宇宙线研究

随着γ射线天文学的兴起，10年前在西藏高原海拔4300m的羊八井谷地，出现并成长着一个国际知名的宇宙线实验站。其中日合作的ASγ阵列在国际同类实验中，首先观测到了蟹状星云的Multi-TeV稳定γ射线发射及活动星系核Mrk 501在1997年、Mrk 421在2000年的Multi-TeVγ射线强爆发，独家测出了反映太阳和行星际磁场状态的宇宙线太阳阴影的偏移并将之用于太阳活动变化的监测，利用高海拔优势及乳胶室和Burst，探测器与阵列的联合实验进行了超高能宇宙线能谱和成分的研究。以高阻板探测器(RPC)地毯式阵列迈入≈100GeV空白能区的中意合作ARGO(Astroparticle physics Researchat Ground-based Observatory)计划，已进入大规模安装调试阶段。欲牢固占领Multi-GeV-TeV能区和满足对高可变、大峰流、短时标河外γ源的观测所需的高海拔巨型大气契仑可夫光成像望远镜计划5@YorG，也正在酝酿之中。     

Ineffectiveness of Narrow CMEs for Cosmic Ray Modulation

Monthly coronal mass ejection (CME) counts, – for all CMEs and CMEs with widths >?30^°, – and monthly averaged speeds for the events in these two groups were compared with both the monthly averaged cosmic ray intensity and the monthly sunspot number. The monthly P _i-index, which is a linear combination of monthly CME count rate and average speed, was also compared with the cosmic ray intensity and sunspot number. The main finding is that narrow CMEs, which were numerous during 2007?–?2009, are ineffective for modulation. A cross-correlation analysis, calculating both the Pearson (r) product–moment correlation coefficient and the Spearman (ρ) rank correlation coefficient, has been used. Between all CMEs and cosmic ray intensity we found correlation coefficients r=??0.49 and ρ=??0.46, while between CMEs with widths >?30^° and cosmic ray intensity we found r=??0.75 and ρ=??0.77, which implies a significant increase. Finally, the best expression for the P _i-index for the examined period was analyzed. The highly anticorrelated behavior among this CME index, the cosmic ray intensity (r=??0.84 and ρ=??0.83), and the sunspot number (r=+?0.82 and ρ=+?0.89) suggests that the first one is a very useful solar–heliospheric parameter for heliospheric and space weather models in general.     

Cosmic Ray RF detection with the Astroneu array

Results will be shown from the Astroneu array developed and operated in the outskirts of Patras, Greece. An array of 9 scintillator detectors and 3 antennas were deployed to study Extensive Air Showers (EAS) as a tool for calibrating an underwater neutrino telescope, possible other applications in muon tomography, education purposes, and last but not least, for the detection of air showers via their electromagnetic signature. In this work we concentrate to the electromagnetic detection of air showers presenting the operation of the RF system, as well as the analysis of the radio signals captured in coincidence with the scintillator detectors. We demonstrate the adequacy of the method to detect cosmic events even in the presence of high urban electromagnetic background, using noise filters, timing and signal polarization. The results are compared with well understood event reconstruction using the scintillator detectors and are indicating that cosmic showers were detected, proving that such small scale hybrid arrays can operate in strong background noise environments.     

Modulation Cycles of Galactic Cosmic Ray Diurnal Anisotropy Variation

The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the ‘pile-up’ method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle.     

Cosmic Ray Effects on the ISOCAM Long Wave Detector

The ISOCAM detector is subjected to transient effects induced bycosmic rays, the so-called glitches. This paper is focused onthe ISOCAM long wave detector. The predicted glitch rates havebeen re-evaluated by taking into account secondary particlesproduction in the materials surrounding the LW detector. We showin this preliminary study that the difference between thepreviously predicted glitch rate and the observed rate may beexplained by secondary particles.     

Galactic Cosmic Ray Modulation near the Heliospheric Current Sheet

Galactic cosmic rays (GCRs) are modulated by the heliospheric magnetic field (HMF) both over decadal time scales (due to long-term, global HMF variations), and over time scales of a few hours (associated with solar wind structures such as coronal mass ejections or the heliospheric current sheet, HCS). Due to the close association between the HCS, the streamer belt, and the band of slow solar wind, HCS crossings are often associated with corotating interaction regions where fast solar wind catches up and compresses slow solar wind ahead of it. However, not all HCS crossings are associated with strong compressions. In this study we categorize HCS crossings in two ways: Firstly, using the change in magnetic polarity, as either away-to-toward (AT) or toward-to-away (TA) magnetic field directions relative to the Sun and, secondly, using the strength of the associated solar wind compression, determined from the observed plasma density enhancement. For each category, we use superposed epoch analyses to show differences in both solar wind parameters and GCR flux inferred from neutron monitors. For strong-compression HCS crossings, we observe a peak in neutron counts preceding the HCS crossing, followed by a large drop after the crossing, attributable to the so-called ‘snow-plough’ effect. For weak-compression HCS crossings, where magnetic field polarity effects are more readily observable, we instead observe that the neutron counts have a tendency to peak in the away magnetic field sector. By splitting the data by the dominant polarity at each solar polar region, we find that the increase in GCR flux prior to the HCS crossing is primarily from strong compressions in cycles with negative north polar fields due to GCR drift effects. Finally, we report on unexpected differences in GCR behavior between TA weak compressions during opposing polarity cycles.     

Rapid Cosmic Ray Fluctuations: Evidence for Cyclic Behaviour

We study rapid cosmic-ray fluctuations using 5-min resolution data from eight neutron monitors with different cutoff rigidities as well as from the ACE satellite. We define a proxy index of rapid cosmic-ray fluctuations as the mean power of the cosmic-ray power spectrum in the frequency range 10⁻⁴ −1.67 × 10⁻³ Hz (10 min to about 3 h). A dominant 11-year periodicity in the index is found in all neutron monitors. We also report on intermittent, short-term periodicities in the power of rapid cosmic-ray fluctuations. A strong mid-term periodicity of about 1.6 – 1.8 years, possibly related to a recently found similar periodicity in IMF, appears in CR fluctuation power since the 1980s. Another strong periodicity is found at 1 year, which is likely related to the relative position of the Earth in the heliosphere. These results also provide new challenge to test the cosmic-ray modulation theory.     

The Role of Extragalactic Antimatter in Cosmic Ray Observations Near Earth

Quest for antimatter in cosmic rays has revealed no compelling evidence of primary, extragalactic antiparticles up to the present time. Recent positron and antiproton observations have been found to be consistent with a pure galactic origin up to energies of 50 GeV and 20 GeV respectively. In this paper it is discussed which role might be played by Ultra High Energy (UHE) extragalactic particles and antiparticles in cosmic-ray observations near Earth. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Global Survey Method Applied to Ground-level Cosmic Ray Measurements

The global survey method (GSM) technique unites simultaneous ground-level observations of cosmic rays in different locations and allows us to obtain the main characteristics of cosmic-ray variations outside of the atmosphere and magnetosphere of Earth. This technique has been developed and applied in numerous studies over many years by the Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN). We here describe the IZMIRAN version of the GSM in detail. With this technique, the hourly data of the world-wide neutron-monitor network from July 1957 until December 2016 were processed, and further processing is enabled upon the receipt of new data. The result is a database of homogeneous and continuous hourly characteristics of the density variations (an isotropic part of the intensity) and the 3D vector of the cosmic-ray anisotropy. It includes all of the effects that could be identified in galactic cosmic-ray variations that were caused by large-scale disturbances of the interplanetary medium in more than 50 years. These results in turn became the basis for a database on Forbush effects and interplanetary disturbances. This database allows correlating various space-environment parameters (the characteristics of the Sun, the solar wind, et cetera) with cosmic-ray parameters and studying their interrelations. We also present features of the coupling coefficients for different neutron monitors that enable us to make a connection from ground-level measurements to primary cosmic-ray variations outside the atmosphere and the magnetosphere. We discuss the strengths and weaknesses of the current version of the GSM as well as further possible developments and improvements. The method developed allows us to minimize the problems of the neutron-monitor network, which are typical for experimental physics, and to considerably enhance its advantages.     

Cosmic Ray Intensity Variations in Relation with Solar Flare Index and Sunspot Numbers

From the monthly data of cosmic ray intensity (CRI), sunspot numbers (SSN) and solar flare index (SFI), an attempt has been made to study the relationship between CRI and solar activity (SA) parameters SSN and SFI. The correlation between SA parameters and CRI for different neutron monitoring stations having low, middle and high cut-off rigidity has been investigated. The anti-correlation between SA and CRI is found to exist with some time lag. Based on the method of minimizing correlation coefficient and time-delayed component method, the observed time-lag between SA parameters (SSN and SFI) and CRI has been found to be large for odd solar cycles in comparison to even solar cycles. The results of time-lag analysis between CRI and SSN and between CRI-SFI have also been compared. The findings of correlative study between CRI and SSN are in agreement with earlier results, while the CRI-SFI relationship provides new insights to understand the solar modulation of cosmic rays.     

Artificial Neural Network Approach of Cosmic Ray Primary Data Processing

One of the most critical points in the detection of cosmic rays by neutron monitors is the correction of the raw data. The data that a detector measures may be distorted by a variety of reasons and the subtraction of these distortions is a prerequisite for processing them further. The final aim of these corrections is to keep only the fluctuations related to the real cosmic-ray intensity. To achieve this, we analyze data from identical neutron monitor detectors which provide a configuration with the ability to exclude the distortions by comparing the counting rate of each detector. Based on this method, a number of effective algorithms have been developed: Median Editor, Median Editor Plus, and Super Editor are some of the algorithms that are being used in the neutron monitor data processing with satisfactory results. In this work, a new approach for the correction of the neutron monitor primary data with a completely different method, based on the use of artificial neural networks, is proposed. A comparison of this method with the algorithms mentioned previously is also presented.