Simulation of the Galactic Cosmic Ray Shadow of the Sun

The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth-Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.

Ionization of protoplanetary disks by galactic cosmic rays,solar protons,and supernova remnants

Galactic cosmic rays and solar protons ionize the present terrestrial atmosphere,and the air showers are simulated by well-tested Monte-Carlo simulations,such as PHITS code.We use the latest version of PHITS to evaluate the possible ionization of protoplanetary disks by galactic cosmic rays（GCRs）,solar protons,and by supernova remnants.The attenuation length of GCR ionization is updated as 118 g cm^-2,which is approximately 20% larger than the popular value.Hard and soft possible spectra of solar protons give comparable and 20% smaller attenuation lengths compared with those from standard GCR spectra,respectively,while the attenuation length is approximately 10% larger for supernova remnants.Further,all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance,e.g.128 g cm^-2 for GCRs,which can affect the minimum estimate of the size of dead zones in protoplanetary disks when the incident flux is unusually high.

On Cosmic Ray and Geomagnetic Response to Coronal Mass Ejections （CMEs）

A catalogue of type II bursts and the associated coronal mass ejections （CMEs） observed by the solar and heliospheric observatory （SOHO） mission is used to select the twenty three CMEs events with CME speed equal to and less than 450 km/sec （i.e., less than and equal to the average solar wind speed） during 1997-2008. Our observational results clearly indicate that even slow speed CMEs are capable to produce the cosmic ray and geomagnetic disturbances on day to day basis. The depression in cosmic ray intensity is larger three days after the arrival of the CMEs along with the maximum disturbance in geomagnetic activity on the same day （i.e., after three days from the arrival of CMEs）. Fluctuations in cosmic ray intensity and the geomagnetic activity are also observed before the arrival of the CMEs.

An ACE/CRIS-observation-based Galactic Cosmic Rays heavy nuclei spectra model Ⅱ

An observation-based Galactic Cosmic Ray(GCR)spectral model for heavy nuclei is developed.Zhao and Qin[J.Geophys.Res.Space Phys.118,1837(2013)]proposed an empirical elemental GCR spectra model for nuclear charge 5≤z≤28 over the energy range^30 to 500 Me V/nuc,which is proved to be successful in predicting yearly averaged GCR heavy nuclei spectra.Based on the latest highly statistically precise measurements from ACE/CRIS,a further elemental GCR model with monthly averaged spectra is presented.The model can reproduce the past and predict the future GCR intensity monthly by correlating model parameters with the continuous sunspot number(SSN)record.The effects of solar activity on GCR modulation are considered separately for odd and even solar cycles.Compared with other comprehensive GCR models,our modeling results are satisfyingly consistent with the GCR spectral measurements from ACE/SIS and IMP-8,and have comparable prediction accuracy as the Badhwar&O’Neill 2014 model.A detailed error analysis is also provided.Finally,the GCR carbon and iron nuclei fluxes for the subsequent two solar cycles(SC 25 and 26)are predicted and they show a potential trend in reduced flux amplitude,which is suspected to be relevant to possible weak solar cycles.

Galactic cosmic ray propagation: sub-PeV diffuse gamma-ray and neutrino emission

The Tibet ASγexperiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk,with the highest energy up to 957 TeV.These diffuse gamma rays are most likely the hadronic origin by cosmic ray(CR)interaction with interstellar gas in the galaxy.This measurement provides direct evidence to the hypothesis that the Galactic Cosmic Rays(GCRs)can be accelerated beyond PeV energies.In this work,we try to explain the sub-PeV diffuse gamma-ray spectrum with different CR propagation models.We find that there is a tension between the sub-PeV diffuse gamma-ray and the local CR spectrum.To describe the sub-PeV diffuse gamma-ray flux,it generally requires larger local CR flux than measurement in the knee region.We further calculate the PeV neutrino flux from the CR propagation model.Even all of these sub-PeV diffuse gamma rays originate from the propagation,the Galactic Neutrinos(GNs)only account for less than~15%of observed flux,most of which are still from extragalactic sources.

Galactic cosmic ray propagation: sub-PeV diffuse gamma-ray and neutrino emission

The Tibet ASγexperiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk,with the highest energy up to 957 TeV.These diffuse gamma rays are most likely the hadronic origin by cosmic ray(CR)interaction with interstellar gas in the galaxy.This measurement provides direct evidence to the hypothesis that the Galactic Cosmic Rays(GCRs)can be accelerated beyond PeV energies.In this work,we try to explain the sub-PeV diffuse gamma-ray spectrum with different CR propagation models.We find that there is a tension between the sub-PeV diffuse gamma-ray and the local CR spectrum.To describe the sub-PeV diffuse gamma-ray flux,it generally requires larger local CR flux than measurement in the knee region.We further calculate the PeV neutrino flux from the CR propagation model.Even all of these sub-PeV diffuse gamma rays originate from the propagation,the Galactic Neutrinos(GNs)only account for less than∼15%of observed flux,most of which are still from extragalactic sources.

航天员受银河宇宙线辐射的剂量计算

在近地空间（LEO）和深空探测中,航天员遭受的辐射风险主要来自于银河宇宙线（GCR）照射.银河宇宙线的辐射剂量是航天员辐射风险评价的基础.国际放射防护委员会（ICRP）于2013年提出了新的航天员空间辐射剂量估算方法,以更准确给出空间重离子辐射的剂量.基于此方法,开发了宇宙线粒子在物质中输运的蒙特卡罗程序,并在程序中实现用中国成年男性人体数字模型来仿真航天员.采用该程序计算了粒子（Z=1~92）各向同性照射航天员时器官的通量-器官剂量转换因数,并估算出航天员在近地轨道空间受银河宇宙线辐射的剂量.

太阳活动与全球气候变化

太阳不断向地球辐射电磁波和粒子,太阳辐射是地球气候系统最主要的能量来源.地球气候系统对太阳活动的响应是一个复杂的过程,包括辐射过程、动力学过程以及微观物理过程等.根据太阳辐射的卫星观测结果和重建结果,例举了古气候、温度、大气环流和云量等方面太阳影响气候的观测证据,论述了太阳影响气候的三种可能机制,即太阳总辐射变化可以影响地表温度,并通过海气耦合改变大气环流;太阳紫外辐射通过调制平流层的温度和风场影响下面的对流层;太阳通过行星际磁场调制银河宇宙线,而银河宇宙线通过电离大气影响云量,进而改变地球的能量收支.

火星表面辐射环境分析

火星表面没有全球性磁场保护,存在较强的辐射环境。文章基于Mars-GRAM模型和MCD模型的火星大气数据、“海盗号”(Viking Lander 1/2)及“探路者号”(Pathfinder)等测量得到的火星土壤数据、银河宇宙射线环境(CREME 96模型)以及太阳宇宙射线环境(1989年10月太阳事件),采用基于GEANT4的粒子输运方法,分析得到了火星表面辐射环境;并与“好奇号”火星车辐射评价探测器(Radiation Assessment Detector,RAD)实测值进行了比较。结果显示:次级伽马光子和中子通量分析值与实测值偏差不超过50%,辐射剂量分析值与实测值偏差不超过5%。火星表面辐射环境可用于分析航天员在不同位置处遭遇的人体剂量,作为载人火星任务着陆点数据参考。

Studies of the radiation environment on the Mars surface using the Geant4 toolkit

The radiation environment on the surface of Mars is a potential threat for future manned exploration missions to this planet.In this study,a simple geometrical model was built for simulating the radiation environment on the Mars surface caused by galactic cosmic rays;the model was built and studied using the Geant4 toolkit.The simulation results were compared with the data reported by a radiation assessment detector(RAD).The simulated spectra of neutrons,photons,protons,α particles,and particle groups Z=3-5,Z=6-8,Z=9-13,and Z=14-24 were in a reasonable agreement with the RAD data.However,for deuterons,tritons,and 3He,the simulations yielded much smaller values than for the corresponding RAD data.In addition,the particles’spectra within the 90 zenith angle were also obtained.Based on these spectra,we calculated the radiation dose that would have been received by an average human body on Mars.The distribution of the dose throughout the human body was not uniform.The absorbed and equivalent doses for the brain were the highest among all of the organs,reaching 62.0±1.7 mGy/y and 234.1±8.0 mSv/y,respectively.The average absorbed and equivalent doses for the entire body were approximately 44 mGy/y and 153 mSv/y,respectively.Further analysis revealed that most of the radiation dose was owing to a particles,protons,and heavy ions.We then studied the shielding effect of the Mars soil with respect to the radiation.The body dose decreased significantly with increasing soil depth.At the depth of 1.5 m,the effective dose for the entire body was 17.9±2.4 mSv/y,lower than the dose limit for occupational exposure.At the depth of 3 m,the effective dose to the body was 2.7±1.0 mSv/y,still higher than the accepted dose limit.

Single planet formation regime in the high-ionization environment:Possible origin of hot Jupiters and super-Earths

We studied the particle growth in a protoplanetary disk in a high-ionization environment and found that icy planet formation is inactive for a disk with an ionization rate 100 times higher than that of the present Solar System. In particular, in the case of M 〈 10^（-7.4）M_☉yr^（-1）, only rocky planet formation occurs. In such a case, all the solid materials in the disk drift inward, eventually reach the inner MRI front,and accumulate there. They form a dense, thin sub-disk of solid particles, which undergoes gravitational instability to form rocky planetesimals. The planetesimals rapidly grow into a planet through pebble accretion. Consequently, rocky planets tend to be much larger than planets formed through other regimes（tandem planet formation regime and dispersed planet formation regime）, in which icy planet formation actively takes place. These rocky planets may evolve into hot Jupiters if they grow fast enough to the critical core mass of the runaway gas accretion before the dispersal of the disk gas, or they may evolve into super-Earths if the gas dispersed sufficiently early.

Debates on the Causes of Global Warming

The controversy between the IPCC and Non-governmental IPCC(NIPCC) on the attribution of global warming are reviewed.IPCC holds that today's global warming is mainly due to anthropogenic activities rather than natural variability,which is emphasized by NIPCC.The surface temperature observations since the mid-20th century support the hypothesis of anthropogenic impact,but for the last one hundred years or so,natural forcings such as solar activity, volcanic eruptions and thermohaline circulation variations also have had great influences on the Earth's climate,especially on inter-decadal timescales.In addition,evidence suggests that the Medieval Warm Period(MWP) and Little Ice Age (LIA) are closely associated with the solar activity over the past 1 thousand years.Over the past 10 thousand years, the North Atlantic cold events and solar activity are closely correlated.Nevertheless,the physical mechanisms of the solar-climate variability and interrelation are not well understood,yet.Notably,a prevailing view recently indicates that galactic cosmic rays may result in climatic cooling through modulating global low cloud cover.However,its process and mechanism need to be further investigated.

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks

The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants(SNRs). In this model, the injected particles with energies below the spectral "knee" are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.

基于ACE飞船观测的银河宇宙线与太阳风变化的统计研究

基于ACE飞船的资料,通过时序迭加方法统计分析了最近两个太阳活动极小年时期(2007.0-2009.0和2016.5-2019.0年)的宇宙线计数与太阳风参数的关系.结果表明,宇宙线的计数受太阳风共转流相互作用区的强烈影响,宇宙线计数变化与快慢太阳风流界面的位置密切相关,例如流界面的穿越通常伴随着宇宙线计数的下降.分析表明,第一时段的具有“雪犁”效应的宇宙线计数下降对应于流界面附近的扩散系数急剧下降,而第二时段的非“雪犁”效应的计数下降可能是由穿越流界面后的扩散系数增大引起的.日球层电流片也与宇宙线计数变化存在一定的相关性,宇宙线粒子在日球层电流片附近存在一定程度的堆积.太阳风对宇宙线的作用机制表明,宇宙线的漂移和扩散效应决定了其在1AU附近的分布变化.

The Giant Radio Array for Neutrino Detection(GRAND):Science and design

The Giant Radio Array for Neutrino Detection(GRAND)is a planned large-scale observatory of ultra-high-energy(UHE)cosmic particles,with energies exceeding 10~8 Ge V.Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays.To do this,GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity.GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere.Its design is modular:20 separate,independent sub-arrays,each of 10000 radio antennas deployed over 10000 km^2.A staged construction plan will validate key detection techniques while achieving important science goals early.Here we present the science goals,detection strategy,preliminary design,performance goals,and construction plans for GRAND.

Electron and positron spectra in three-dimensional spatial-dependent propagation model

The spatial-dependent propagation(SDP)model has been demonstrated to account for the spectral hardening of both primary and secondary Cosmic Rays(CRs)nuclei above about 200 GV.In this work,we further apply this model to the latest AMS-02 observations of electrons and positrons.To investigate the effect of different propagation models,both homogeneous diffusion and SDP are compared.In contrast to the homogeneous diffusion,SDP brings about harder spectra of background CRs and thus enhances background electron and positron fluxes above tens of GeV.Thereby,the SDP model could better reproduce both electron and positron energy spectra when introducing a local pulsar.The influence of the background source distribution is also investigated,where both axisymmetric and spiral distributions are compared.We find that considering the spiral distribution leads to a larger contribution of positrons for energies above multi-GeV than the axisymmetric distribution.In the SDP model,when including a spiral distribution of sources,the all-electron spectrum above TeV energies is thus naturally described.In the meantime,the estimated anisotropies in the all-electrons spectrum show that in contrary to the homogeneous diffusion model,the anisotropy under SDP is well below the observational limits set by the Fermi-LAT experiment,even when considering a local source.

Modelling the interaction of the Astro Bio Cube Sat with the Van Allen's Belt radiative field using Monte Carlo transport codes

Purpose The AstroBio Cube Satellite(ABCS)will deploy within the inner Van Allen belt on the Vega C Maiden Flight launch opportunity of the European Space Agency.At this altitude,ABCS will experience radiation doses orders of magnitude greater than in low earth orbit,where CubeSats usually operate.The paper aims to estimate the irradiation effect on the ABCS payload in the orbital condition,their possible mitigation designing shielding solutions and performs a preliminary representativity simulation study on the ABCS irradiation with fission neutron at the TAPIRO(TAratura Pila Rapida Potenza 0)nuclear research reactor facility at ENEA.Methods We quantify the contributions of geomagnetically trapped particles(electron and proton),Galactic Cosmic Rays(GCR ions),Solar energetic particle within the ABCS orbit using the ESA's SPace ENVironment information system.FLUKA(Fluktuierende Kaskade-Fluctuating Cascade)code models the ABCS interaction with the orbital source.Results We found a shielding solution of the weight of 300 g constituted by subsequent layers of tungsten,resins,and aluminium that decreases on average the 20%overall dose rate relative to the shielding offered by the only satellite's structure.Finally,simulations of neutron irradiation of the whole ABCS structure within the TAPIRO's thermal column cavity show that a relatively short irradiation time is requested to reach the same level of 1 MeV neutron Silicon equivalent damage of the orbital source.Conclusions The finding deserves the planning of a future experimental approach to confirm the TAPIRO's performance and establish an irradiation protocol for testing aerospatial electronic components.