Potential for Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy Cosmic-radiation Detection Facility on Board China's Space Station

Precise measurements of the spectra of secondary and primary cosmic rays are crucial for understanding the origin and propagation of those energetic particles.The High Energy Cosmic-radiation Detection(HERD)facility on board China's Space Station,which is expected to operate in 2027,will push the direct and precise measurements of cosmic-ray fluxes up to PeV energies.In this work,we investigate the potential of HERD for studying the propagation of cosmic rays using measurements of boron,carbon,and oxygen spectra.We find that,compared with the current results,the new HERD measurements can improve the accuracy of the propagation parameters by 8%–40%.The constraints on the injection spectra at high energies will also be improved.

Injection Spectra of Different Species of Cosmic Rays from AMS-02, ACE-CRIS and Voyager-1

Precise measurements of energy spectra of different cosmic ray(CR) species have been obtained in recent years, by particularly the AMS-02 experiment on the International Space Station. It has been shown that apparent differences exist in different groups of the primary CRs. However, it is not straightforward to conclude that the source spectra of different particle groups are different since they will experience different propagation processes(e.g., energy losses and fragmentations) either. In this work, we study the injection spectra of different nuclear species using the measurements from Voyager-1 outside the solar system, and ACR-CRIS and AMS-02 on the top of atmosphere, in a physical framework of CR transportation. Two types of injection spectra are assumed, the broken power-law(BPL) form and the non-parametric spline interpolation form. The non-parametric form fits the data better than the BPL form, implying that potential structures beyond the constrained spectral shape of BPL may exist. For different nuclei the injection spectra are overall similar in shape but do show some differences among each other. For the non-parametric spectral form, the helium injection spectrum is the softest at low energies and the hardest at high energies. For both spectral shapes, the low-energy injection spectrum of neon is the hardest among all these species, and the carbon and oxygen spectra have more prominent bumps in 1–10 GV in the R2 d N dRpresentation.Such differences suggest the existence of differences in the sources or acceleration processes of various nuclei of CRs.

Spectral Index Distribution of Various Scale Components in Supernova Remnant Cassiopeia A

Cassiopeia A(Cas A) is a well-known candidate for studying cosmic-ray acceleration, in which compact features of various scales have attracted much attention. Based on observations by the Very Large Array of Cas A at 6 cm and 21 cm, we measure the spectral index distribution of various scale components using the observation of the 1998 epoch. We decompose its total density image into nine scale components, and map the temperature spectral index distribution of each component, which ranges from-2.48 ± 0.01 to-2.91 ± 0.05. We find that the spectral indices increase from the small scale to large scale components. A damped post-shock magnetic field model with a strength larger than ~200 μG and a damping length scale less than ~10% of the remnant radius can account for the spectral index variation naturally.

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

How to Coadd Images.Ⅱ.Anti-aliasing and PSF Deconvolution

We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms.Our approach not only allows for the anti-aliasing of the images but also enables Point-Spread Function(PSF)deconvolution,resulting in enhanced restoration of extended sources,the highest peak signal-to-noise ratio,and reduced ringing artefacts.To test our method,we conducted numerical simulations that replicated observation runs of the China Space Station Telescope/the VLT Survey Telescope(VST)and compared our results to those obtained using previous algorithms.The simulation showed that our method outperforms previous approaches in several ways,such as restoring the profile of extended sources and minimizing ringing artefacts.Additionally,because our method relies on the inherent advantages of least squares fitting,it is more versatile and does not depend on the local uniformity hypothesis for the PSF.However,the new method consumes much more computation than the other approaches.

Revisit of GeV Gamma-Ray Emission from Orion B with the Fermi Large Area Telescope

We revisit the γ-ray emission above 300 Me V towards the massive star-forming region of Orion B by adopting14 yr observations with the Fermi Large Area Telescope and utilizing the updated software tools.The extended γ-ray emission region around Orion B is resolved into two components(region Ⅰ and region Ⅱ).The γ-ray spectrum of region I agrees with the predicted γ-ray spectrum assuming the cosmic ray(CR)density is the same as that of Alpha Magnetic Spectrometer(AMS-02)measured locally.Theγ-ray emissivity of region II appears to be deficit at low energy band(E<3 GeV).Through modeling we find that CR densities exhibit a significant deficit below 20 Ge V,which may be caused by a slow diffusion inside the dense region.This is probably caused by an increased magnetic field whose strength increases with the gas density.

基于低频射电偏振特征的极高能宇宙线背景剔除

自触发射电阵列的设计是宇宙线大气簇射的射电探测所面临的机遇和难题之一,例如由背景源产生高振幅的瞬时噪声会导致射电阵列的误触发,而阵列设计需要避免由噪声导致的误触发.大气簇射射电信号独有的偏振特征为解决阵列的误触发问题提供了解决方案,而利用信号偏振特征解决阵列误触发的方法的前提是射电信号的电场重建.由于背景噪声也会通过天线响应耦合到最终的观测数据中,这对正确重建射电信号的电场构成不可忽视的挑战.基于GRAND(Giant Radio Array for Neutrino Detection)验证阵列GP300(GRAND-Proto 300)的样机,结合模拟软件ZHAireS(ZHS AIR-shower Extended Simulations)模拟大气簇射产生的射电信号,耦合三极化天线的真实响应并使用最小二乘法重建电场,研究了射电信号的偏振特性,最终统计了以偏振为基础的天线的触发效率.

Testing the effect of solar wind parameters and geomagnetic storm indices on Galactic cosmic ray flux variation with automatically-selected Forbush decreases

Forbush decrease(FD),discovered by Scott E.Forbush about 80 years ago,is referred to as the non-repetitive short-term depression in Galactic cosmic ray(GCR)flux,presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field(IMF).It is the most spectacular variability in the GCR intensity which appears to be the compass for investigators seeking solar-terrestrial relationships.The method of selection and validation of FD events is very important to cosmic ray(CR)scientists.We have deployed new computer software to determine the amplitude and timing of FDs from daily-averaged CR data at Oulu Neutron Monitor station.The code selected 230 FDs between 1998 and 2002.In an attempt to validate the new FD automated catalog,the relationship between the amplitude of FDs,and IMF,solar wind speed(SWS)and geomagnetic storm indices(Dst,kp,ap)is tested here.A two-dimensional regression analysis indicates significant linear relationship between large FDs(CR(%)≤-3)and solar wind data and geomagnetic storm indices in the present sample.The implications of the relationship among these parameters are discussed.

Testing the Empirical Relationship between Forbush Decreases and Cosmic Ray Diurnal Anisotropy

The abrupt aperiodic modulation of cosmic ray(CR)flux intensity,often referred to as Forbush decrease(FD),plays a significant role in our understanding of the Sun-Earth electrodynamics.Accurate and precise determinations of FD magnitude and timing are among the intractable problems in FD-based analysis.FD identification is complicated by CR diurnal anisotropy.CR anisotropy can increase or reduce the number and amplitude of FDs.It is therefore important to remove its contributions from CR raw data before FD identification.Recently,an attempt was made,using a combination of the Fourier transform technique and FD-location machine,to address this.Thus,two FD catalogs and amplitude diurnal variation(ADV)were calculated from filtered(FD1 and ADV)and raw(FD2)CR data.In the current work,we test the empirical relationship between FD1,FD2,ADV and solar-geophysical characteristics.Our analysis shows that two types of magnetic fields-interplanetary and geomagnetic(Dst)-govern the evolution of CR flux intensity reductions.

Possible Contribution of Mature γ-ray Pulsars to Cosmic-ray Positrons

We restudy the possible contribution of mature gamma-ray pulsars to cosmic ray positrons based on the new version of outer gap model. In this model, the inclination angle and average properties of the outer gap are taken into account, and more mature pulsars can have the outer gap and emit high energy photons. Half of the primary particles in the outer gaps will flow back toward the star surface and emit synchrotron photons, which can produce electron/positron pairs by the cascade of pair production. Some of these pairs will escape from the light cylinder and be accelerated to relativistic energies in the pulsar wind driven by low-frequency electromagnetic waves. Using a Monte Carlo method, we obtain a sample of mature gamma-ray pulsars and then calculate the production of the positrons from these pulsars. The observed excess of cosmic positrons can be well explained by this model.

The low cosmic-ray density in the Polaris Flare

We reported theγ-ray observation towards the giant molecular cloud Polaris Flare.Together with the dust column density map,we derived the cosmic ray(CR)density and spectrum in this cloud.Compared with the CR measured locally,the CR density in the Polaris Flare is significantly lower and the spectrum is softer.Such a different CR spectrum reveals either a rather large gradient of CR distribution in the direction perpendicular to the Galactic plane or a suppression of CR inside molecular clouds.

Method of Separating Cosmic-Ray Positrons from Electrons in the DAMPE Experiment

A method of identifying positron/electron species from the cosmic rays was studied in the DArk Matter Particle Explorer(DAMPE)experiment.As there is no onboard magnet on the satellite,the different features imposed by the geomagnetic field on these two species were exploited for the particle identification.Application of this method to the simulation of on-orbit electrons/positrons/protons and the real flight data proves that separately measuring the CR positrons/electrons with DAMPE is feasible,though limited by the field of view for the present observation data.Further analysis on the positron flux with this method can be expected in the future.

Investigation of the relation between space-weather parameters and Forbush decreases automatically selected from Moscow and Apatity cosmic ray stations during solar cycle 23

We present the results of an investigation of the relation between space-weather parameters and cosmic ray(CR)intensity modulation using algorithm-selected Forbush decreases(FDs)from Moscow(MOSC)and Apatity(APTY)neutron monitor(NM)stations during solar cycle 23.Our FD location program detected 408 and 383 FDs from MOSC and APTY NM stations respectively.A coincident computer code employed in this work detected 229 FDs that were observed at the same Universal Time(UT)at the two stations.Out of the 229 simultaneous FDs,we formed a subset of 139 large FDs(%)≤-4 at the MOSC station.We performed a two-dimensional regression analysis between the FD magnitudes and the space-weather data on the two samples.We find that there were significant space-weather disturbances at the time of the CR flux depressions.The correlation between the space-weather parameters and decreases in galactic cosmic ray(GCR)intensity at the two NM stations is statistically significant.The implications of the present space-weather data on CR intensity depressions are highlighted.

New Continuum Observations of the Andromeda galaxy M31 with FAST

We present a new total intensity image of M31 at 1.248 GHz,observed with the Five-hundred-meter Aperture Spherical radio telescope(FAST)with an angular resolution of 4'and a sensitivity of about 16 mK.The new FAST image clearly reveals weak emission outside the ring due to its high sensitivity on large-scale structures.We derive a scale length of 2.7 kpc for the cosmic ray electrons and find that the cosmic ray electrons propagate mainly through diffusion by comparing the scale length at 4.8 GHz.The spectral index of the total intensity varies along the ring,which can be attributed to the variation of the spectra of synchrotron emission.This variation is likely caused by the change of star formation rates along the ring.We find that the azimuthal profile of the non-thermal emission can be interpreted by an axisymmetric large-scale magnetic field with varying pitch angle along the ring,indicating a complicated magnetic field configuration in M31.

Correction of the Temperature Effect of Muon Counts Observed at the Guangzhou Station

Muons are the main component of secondary cosmic rays,and the variation in muon intensity indicates the variation in primary cosmic ray intensity.However,before using muons to study the variation in the intensity of cosmic rays,it is necessary to eliminate the atmospheric effects,such as pressure and temperature effects.In this work,the temperature effect of the muons is corrected in terms of empirical method by using ground temperature.The temperature correction is applied to the muon data observed at the Guangzhou station during the period2010–2021 after a barometric correction.It is found that the effect of seasonal variations in temperature on muon counts is greatly eliminated in the corrected data.Furthermore,the muon data are well correlated with the neutron data in comparison,which verifies the reliability of the corrected muon data.Our results show that the correction of muon data by using ground temperature is an effective method.

Cosmic Ray-driven Bioenergetics for Life in Molecular Clouds

According to models such as panspermia or the Nebula-Relay hypothesis,the ancestors of life on Earth once lived in molecular clouds.Then what are the energy source and bioenergetics for such lifeforms?A new bioenergetic mechanism powered by cosmic ray ionization of hydrogen molecules is proposed and its relation with the origin of chemiosmosis is also discussed in this paper.Based on this mechanism,the Last Universal Common Ancestor may be a type of lifeform that utilizes hydrogen molecules as donors of electron transport chains.

对高能粒子扩散理论NLGC-E的系数研究

带电粒子的扩散机制一直被认为是天体物理学的一个很重要的问题.最近,Matthaeus等人在2003年得出了带电粒子垂直扩散的非线性引导中心理论(NLGC),该理论采用平行扩散系数作为一个输入,这个NLGC理论与数值模拟结果符合得比较好.另外,Qin在2007年得到了非线性的平行扩散理论(NLPA),这个理论如果与NLGC理论联立可以得到扩展的非线性引导中心理论(NLGC-E),该理论是两个积分方程的形式并且可以用来同时求出平行和垂直扩散系数.NLGC理论中有一个系数a^2,通过与数值模拟结果比较选定最佳值为1/3.尝试改变NLGC-E中的系数a^2,确定与模拟结果吻合最好的系数值.

宇宙射线源TeV J2032+4130的毫米波观测研究

为了对HEGRA新发现的宇宙射线源TeV J2032+4130进行证认,使用紫金山天文台青海观测站的13.7m毫米波望远镜对源区进行了CO(J=1-0)成图观测.此次观测将源区分为30*30的网格点,对每个网格点积分1min.每个网格点相距2′,亦即成图范围60′*60′.观测中心对应TeV源J2032+4130所在位置,观测所得数据的处理平台是IRAM和de Grenoble联合开发的GILDAS/CLASS软件.在源的方向上,观测到许多地方都有分子谱线发射.速度范围为-80～20km/s,可能与TeV源直接相关的速度成分是-23～18km/s,和-9～3km/s.虽然一般认为宇宙高能射线起源于超新星遗迹,但是观测表明该TeV源没有表现出与周围分子云发生相互作用的直接证据.

Synchrotron X-ray diagnostics of cutoff shape of nonthermal electron spectrum at young supernova remnants

Synchrotron X-rays can be a useful tool to investigate electron accelera- tion at young supemova remnants （SNRs）. At present, since the magnetic field con- figuration around the shocks of SNRs is uncertain, it is not clear whether electron acceleration is limited by SNR age, synchrotron cooling, or even escape from the ac- celeration region. We study whether the acceleration mechanism can be constrained by the cutoff shape of the electron spectrum around the maximum energy. We derive analytical formulae of the cutoff shape in each case where the maximum electron en- ergy is determined by SNR age, synchrotron cooling and escape from the shock. They are related to the energy dependence of the electron diffusion coefficient. Next, we discuss whether information on the cutoff shape can be provided by observations in the near future which will simply give the photon indices and the flux ratios in the soft and hard X-ray bands. We find that if the power-law index of the electron spectrum is independently determined by other observations, then we can constrain the cutoff shape by comparing theoretical predictions of the photon indices and/or the flux ratios with observed data which will be measured by NuSTAR and/or ASTRO-H. Such study is helpful in understanding the acceleration mechanism. In particular, it will supply another independent constraint on the magnetic field strength around the shocks of SNRs.

Testing Lorentz violation using propagating UHECRs

Lorentz invariant violation （LIV） test is important for studying modem physics. All the known astrophysical constraints either have a very small examinable parameter space or are only suitable for some special theoretical models. Here, we suggest that it is possible to directly detect the time-delay of ultra-high-energy cosmic-rays （UHECRs）. We discuss some difficulties in our method, including the intergalactic magnetic fields. It seems that none of them are crucial, hence this method could give a larger examinable parameter space and a stronger constraint on LIV.