Cosmic Ray Flux Research Articles

Generic profile of a long-lived corotating interaction region and associated recurrent Forbush decrease

Context.Corotating interaction regions (CIRs), formed by the interaction of slow solar wind and fast streams that originate from coronal holes (CHs), produce recurrent Forbush decreases, which are short-term depressions in the galactic cosmic ray (GCR) flux.Aims.Our aim is to prepare a reliable set of CIR measurements to be used as a textbook for modeling efforts. For that purpose, we observe and analyse a long-lived CIR, originating from a single CH, recurring in 27 consecutive Carrington rotations 2057–2083 in the time period from June 2007–May 2009.Methods.We studied the in situ measurements of this long-lived CIR as well as the corresponding depression in the cosmic ray (CR) count observed by SOHO/EPHIN throughout different rotations. We performed a statistical analysis, as well as the superposed epoch analysis, using relative values of the key parameters: the total magnetic field strength,B, the magnetic field fluctuations,dBrms, plasma flow speed,v, plasma density,n, plasma temperature,T, and the SOHO/EPHIN F-detector particle count, and CR count.Results.We find that the mirrored CR count-time profile is correlated with that of the flow speed, ranging from moderate to strong correlation, depending on the rotation. In addition, we find that the CR count dip amplitude is correlated to the peak in the magnetic field and flow speed of the CIR. These results are in agreement with previous statistical studies. Finally, using the superposed epoch analysis, we obtain a generic CIR example, which reflects the in situ properties of a typical CIR well.Conclusions.Our results are better explained based on the combined convection-diffusion approach of the CIR-related GCR modulation. Furthermore, qualitatively, our results do not differ from those based on different CHs samples. This indicates that the change of the physical properties of the recurring CIR from one rotation to another is not qualitatively different from the change of the physical properties of CIRs originating from different CHs. Finally, the obtained generic CIR example, analyzed on the basis of superposed epoch analysis, can be used as a reference for testing future models.

Production and attenuation of cosmic-ray boosted dark matter

Light sub-GeV halo dark matter (DM) particles up-scattered by high-energy cosmic-rays (CRs) (referred to as CRDM) can be energetic and become detectable by conventional DM direct detection experiments. We perform a refined analysis on the exclusion bounds of the spin-independent DM-nucleon scattering cross section σχ p in this approach. For the exclusion lower bounds, we determine the parameter of the effective distance Deff for CRDM production using spatial-dependent CR fluxes and including the contributions from the major heavy CR nuclear species. We obtain Deff≃ 9 kpc for CRDM particles with kinetic energy above ∼ 1 GeV, which pushes the corresponding exclusion lower bounds down to σχ p∼ 4× 10-32 cm2 for DM particle mass at MeV scale and below. For the exclusion upper bounds from Earth attenuation, previous estimations neglecting the nuclear form factor leaded to typical exclusion upper bounds of σχ p∼\U0001d4aa(10-28) cm2 from the XENON1T data. Using both the analytic and numerical approaches, we show that for CRDM particles, the presence of the nuclear form factor strongly suppresses the effect of Earth attenuation. Consequently, the cross section that can be excluded by the XENON1T data can be a few orders of magnitude higher, which closes the gap in the cross sections excluded by the XENON1T experiment and that by the astrophysical measurements such that for the cosmic microwave background (CMB), galactic gas cloud cooling, and structure formation, etc..

Global planetary ionization maps in Regener-Pfotzer cosmic ray maximum for GLE 66 during magnetic superstorm of 29–31 October 2003

High-energy particles of cosmic origin e.g. cosmic ray protons and heavier nuclei of galactic and/or solar origin induce complicated nuclear-electromagnetic-meson cascades in the Earth’s atmosphere, eventually leading to an ionization of the ambient air. The induced by cosmic rays atmospheric ionization is related to possible effect of precipitating particles on atmospheric physics and chemistry. These effects can be considerably enhanced during strong and moderately strong solar proton events. While the contribution of galactic cosmic ray particles to ion production in the atmosphere is slightly variable throughout a solar cycle, relativistic solar particles could produce a significant excess on ion pair production, particularly over polar caps. This effect is strong on a short time scales. On the other hand, depressions of the galactic cosmic ray flux, that is, Forbush decreases, can significantly impact the galactic cosmic ray induced ionization. The sequence of three ground level enhancements observed in October-November 2003, specifically the second: GLE 66 which occurred during a giant Forbush decrease, provides unique opportunity to study impact ionization on extended time scale, explicitly considering the reduced galactic cosmic ray flux. Using Monte Carlo simulations we computed the ion production rate and the corresponding ionization effect in the Earth atmosphere during GLE 66 occurred on 29 October 2003, explicitly considering the Forbush decrease and the complex geomagnetospheric conditions.

Evidence From Galactic Cosmic Rays That the Sun Has Likely Entered a Secular Minimum in Solar Activity

AbstractSince the beginning of the space age, the Sun has been in a multi‐cycle period of elevated activity (secular maximum). This secular maximum is the longest in the last 9300 years. Since the end of solar cycle 21 (SC21), however, the Sun has shown a decline in overall activity, which has remarkably increased the fluxes of galactic cosmic rays (GCRs). Here, we investigate the correlation between the modulation of GCRs, the heliospheric magnetic field, and solar wind speed for the last 24 solar cycles to find trends that can potentially be used to predict future solar activity. Specifically, we develop a tool for predicting future magnetic field intensity, based on the hysteresis in the GCR variation, during the last phases of the current cycle. This method estimates that SC25 will be as weak as or weaker than SC24. This would mean that the Sun has likely entered a secular minimum, which, according to historical records, should last for another two cycles (SC25 and SC26).

Testing the simultaneity of Forbush decreases with algorithm-selected Forbush event catalogue

Accurate detection and precise timing of transient events such as X-ray photons, $$\gamma $$ -ray burst, coronal mass ejections (CMEs), ground-level enhancements (GLEs) and Forbush decreases (FDs) frequently raise issues that remain on the cutting edge of research in astrophysics. In an attempt to automate FD event selection, a combination of Fast Fourier transform as well as FD detection algorithms implemented in the statistical computing software R was developed and recently used to calculate the magnitude and FD event timing. The R-FD code implemented in the present study includes several different calculations. Some subroutines detect both small and large transient intensity reductions (minima/pits) as well as increases (maxima/peaks) in cosmic ray (CR) data. Others calculate event amplitude, timing and cataloguing of the events identified. As the current work focuses on reductions in CR flux (FDs), the subroutine that identifies increases was disabled. Totals of 229 FDs at Magadan neutron monitor (NM), 230 (Oulu NM) and 224 (Inuvick NM) were identified with daily averaged data, while 4032 (Magadan), 4144 (Oulu) and 4055 (Inuvick) were detected with hourly averages. FDs identified as simultaneous at the three stations totaled 99 for the daily and 261 for the hourly CR averages respectively.

Chapter 7 Solar and Heliospheric Physics and Interdisciplinary Research with LHAASO * *Supported in China by National Natural Science Foundation (NSFC) (12047576, U2031101, 11475141), and the National Key R&D Program of China (2018YFA0404201, 2018YFA0404202), and in Thailand by the Thailand Science Research and Innovation (RTA6280002)

In the following sub-sections, studies of solar-heliospheric effects on cosmic rays, investigating a possible link between cosmic ray flux and Earth’s climate, and detection of MeV-range γ-rays from thunderstorms with the data from LHAASO will be discussed; geophysical research with environmental neutrons will be introduced, and some Monte Carlo simulation results about effects of thunderstorm electric fields on LHAASO observations of cosmic rays will be given.

Particle acceleration and multimessenger emission from starburst-driven galactic winds

ABSTRACT The enhanced star-forming activity, typical of starburst galaxies, powers strong galactic winds expanding on kiloparsec (kpc) scales and characterized by bubble structures. Here we discuss the possibility that particle acceleration may take place at the termination shock of such winds. We calculate the spectrum of accelerated particles and their maximum energy, which turns out to range up to a few hundred petaelectronvolt (PeV) for typical values of the parameters. Cosmic rays accelerated at the termination shock are advected towards the edge of the bubble excavated by the wind and eventually escape into extragalactic space. We also calculate the flux of gamma-rays and neutrinos produced by hadronic interactions in the bubble, as well as the diffuse flux resulting from the superposition of the contribution of starburst galaxies on cosmological scales. Finally, we compute the diffuse flux of cosmic rays from starburst bubbles and compare it with existing data.

Analysis of the solar cosmic-ray spectrum during ground-level enhancements

In this work, we analyze the spectrum of solar cosmic rays flux during ground-level enhancements using the pair of lead-free and standard neutron monitors in the South Pole station. Using both monitor data, effects due to anisotropy are considerably reduced. We assume a power-law form for the solar particle spectrum at the top of the atmosphere. The spectral index was computed during all events for which data were available, regardless of the duration or the intensity of the GLE. Seventeen events were analyzed. In this paper, we show the efficiency of the method used, as well as a clear tendency of the spectral index behavior to the ratio between the observed increases in both monitors. It is also shown that the method can be used to calculate the solar cosmic ray spectrum at any required stage of the event. Our results show that the spectral index estimation depends on the choice of the yield function. For the three yield functions used in the analysis, the spectral index changes by about 10%.

Effective Energy of Cosmogenic Isotope (10Be, 14C and 36Cl) Production by Solar Energetic Particles and Galactic Cosmic Rays

AbstractCosmogenic isotopes 14C, 10Be and 36Cl measured in datable natural archives provide the only known quantitative proxy for cosmic‐ray (CR) and solar‐activity variability before the era of direct measurements. Studies of relations between the measured isotope concentrations and CR variability require complicated modeling including the isotope production and transport in the terrestrial system. Here we propose a rough “effective energy” method to make quick estimates of the CR variability directly from the cosmogenic data using an approximate linear scaling between the measured isotope concentrations and the energy‐integrated flux of CR above the effective energy. The method is based on the thoroughly computed effective yield function presented here. A simple way to account for the variable geomagnetic field is also provided. The method was developed for both solar energetic particles (SEPs) and galactic cosmic ray (GCR) variability and is shown to provide a robust result within 20% and 1% accuracy, respectively, without an assumption of the specific spectral shape. Applications of the effective‐energy method to the known extreme SEP events and the secular GCR variability are discussed. The new method provides a simple and quick tool to assess the CR variability in the past. On the other hand, it does not supersede the full detailed modeling required for precise results.

Research on the structure of cosmic-ray electron and positron fluxes in GeV–TeV energy range

The positron–electron fluxes detected by AMS02, CALET, DAMPE and Fermi-LAT have shown their complex structure which deviated from a single power-law, and the results of DAMPE and Fermi-LAT are obviously higher than those of AMS02 and CALET in 100[Formula: see text]GeV–1[Formula: see text]TeV range. We point out that the complex positron–electron flux structures can be attributed to two sources with a natural background, and the difference between the two groups of data can be explained in an anomalous bremsstrahlung theory.

Perspectives for anti deuteron search in cosmic rays with an helium calorimeter

The observation of sub-GeV antideuteron in the cosmic ray flux could be a very strong signature of dark matter annihilation in our galaxy. The goal of the Anti Deuteron Helium Detector (ADHD) project is to study the signatures offered by an high pressure Helium calorimeter for the identification of antideuterons in space. The performance of an high pressure (200 bar) Helium scintillator prototype, capable of fast timing, will be shown.

Cosmic-ray flux predictions and observations for and with Metis on board Solar Orbiter

Context.The Metis coronagraph is one of the remote sensing instruments hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted to carry out the first simultaneous imaging of the solar corona in both visible light (VL) and ultraviolet (UV). High-energy particles can penetrate spacecraft materials and may limit the performance of the on-board instruments. A study of the galactic cosmic-ray (GCR) tracks observed in the first VL images gathered by Metis during the commissioning phase is presented here. A similar analysis is planned for the UV channel.Aims.We aim to formulate a prediction of the GCR flux up to hundreds of GeV for the first part of the Solar Orbiter mission to study the performance of the Metis coronagraph.Methods.The GCR model predictions are compared to observations gathered on board Solar Orbiter by the High-Energy Telescope in the range between 10 MeV and 100 MeV in the summer of 2020 as well as with the previous measurements. Estimated cosmic-ray fluxes above 70 MeV n−1have been also parameterized and used for Monte Carlo simulations aimed at reproducing the cosmic-ray track observations in the Metis coronagraph VL images. The same parameterizations can also be used to study the performance of other detectors.Results.By comparing observations of cosmic-ray tracks in the Metis VL images with FLUKA Monte Carlo simulations of cosmic-ray interactions in the VL detector, we find that cosmic rays fire only a fraction, on the order of 10−4, of the whole image pixel sample. We also find that the overall efficiency for cosmic-ray identification in the Metis VL images is approximately equal to the contribution ofZ ≥ 2 GCR particles. A similar study will be carried out during the whole of the Solar Orbiter’s mission duration for the purposes of instrument diagnostics and to verify whether the Metis data and Monte Carlo simulations would allow for a long-term monitoring of the GCR proton flux.

Constraining positron emission from pulsar populations with AMS-02 data

The cosmic-ray flux of positrons is measured with high precision by the space-borne particle spectrometer AMS-02. The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron (e+) cosmic-ray flux has been consolidated after the observation of a γ-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe.In this work we undertake massive simulations of galactic pulsars populations, adopting different distributions for their position in the Galaxy, intrinsic physical properties, pair emission models, in order to overcome theincompleteness of the ATNF catalog. We fit the e+ AMS-02 data together with a secondary component due to collisions of primary cosmic rays with the interstellar medium.We find that several mock galaxies have a pulsar population able to explain the observed e+ flux, typically by few, bright sources. We determine the physical parameters of the pulsars dominating the e+ flux, and assess the impact of different assumptions on radial distributions, spin-down properties, Galactic propagation scenarios and e+ emission time.

Constraining positron emission from pulsar populations with AMS-02 data

The cosmic-ray flux of positrons is measured with high precision by the space-borne particle spectrometer AMS-02. The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron (e+) cosmic-ray flux has been consolidated after the observation of a γ-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe. In this work we undertake massive simulations of galactic pulsars populations, adopting different distributions for their position in the Galaxy, intrinsic physical properties, pair emission models, in order to overcome the incompleteness of the ATNF catalogue. We fit the e + AMS-02 data together with a secondary component due to collisions of primary cosmic rays with the interstellar medium. We find that several mock galaxies have a pulsar population able to explain the observed e+ flux, typically by few, bright sources. We determine the physical parameters of the pulsars dominating the e + flux, and assess the impact of different assumptions on radial distributions, spin-down properties, Galactic propagation scenarios and e + emission time.

Tunka-Grande scintillation array: resent results

Objectives of the TAIGA Astrophysical complex include the study of the flux of charged cosmic rays and diffuse gamma rays with energies above 100 TeV. This complex is located in the Tunka Valley about 50 km from Lake Baikal at the site of the Tunka-133 Cherenkov facility. TAIGA includes the TAIGA-HiSCORE wide-angle Cherenkov array, the network of Imaging Atmospheric Cherenkov Telescopes (TAIGA-IACT), the Tunka-Grande and TAIGA-Muon scintillation arrays. In this work, we present the results of an analysis of the joint events of the Tunka-Grande scintillation array and TAIGA-HiSCORE and Tunka-133 Cherenkov facilities. The results verify sufficient accuracy of the scintillation experiment for the hybrid study of mass composition of cosmic rays and gamma-hadron separation.

New Properties of Secondary Cosmic Rays observed by the Alpha Magnetic Spectrometer on the International Space Station

Precise measurements of the secondary cosmic ray fluxes and of secondary-over-primary flux ratios as functions of rigidity are essential for cosmic ray propagation study. We report the properties of heavy secondary cosmic ray fluorine (F) nuclei in the rigidity R range 2GV to 3 TV observed by the Alpha Magnetic Spectrometer experiment (AMS-02) on the International Space Station. The secondary-over-primary ratios fluorine-to-silicon and boron-to-oxygen (or boron-to-carbon) will be discussed, showing that the heavy cosmic rays, from fluorine to silicon, have different propagation properties compared to those of light cosmic rays, from helium to oxygen. The properties of cosmic-ray sodium and aluminum nuclei, which are partly secondary and partly primary, will also be presented.

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.

PeV Emission of the Crab Nebula: Constraints on the Proton Content in Pulsar Wind and Implications

Abstract Recently, two photons from the Crab Nebula with energy of approximately 1 PeV were detected by the Large High Altitude Air Shower Observatory (LHAASO), opening an ultrahigh-energy window for studying pulsar wind nebulae (PWNe). Remarkably, the LHAASO spectrum at the highest-energy end shows a possible hardening, which could indicate the presence of a new component. A two-component scenario with a main electron component and a secondary proton component has been proposed to explain the whole spectrum of the Crab Nebula, requiring a proton energy of 1046–1047 erg remaining in the present Crab Nebula. In this paper, we study the energy content of relativistic protons in pulsar winds using the LHAASO data of the Crab Nebula, considering the effect of diffusive escape of relativistic protons. Depending on the extent of the escape of relativistic protons, the total energy of protons lost in the pulsar wind could be 10–100 times larger than that remaining in the nebula presently. We find that the current LHAASO data allow up to (10–50)% of the spindown energy of pulsars being converted into relativistic protons. The escaping protons from PWNe could make a considerable contribution to the cosmic-ray flux of 10–100 PeV. We also discuss the leptonic scenario for the possible spectral hardening at PeV energies.

The cosmogenic production of phosphorus in the atmosphere of Venus

A model of the Venusian atmosphere examines the production of phosphorus via interactions of cosmic rays and solar particles with sulfur and argon. It is estimated that the stable isotope Phosphorus-31 has been generated between 23.7 and 67.7 micrograms per day given the present atmosphere of Venus and the variability in the flux of cosmic rays. If the maximum amount of phosphorus were converted into phosphine, the corresponding cosmogenic upper limit for phosphine production would be 74.3 +/− 0.8 micrograms per day. Assuming the maximum phosphorus is converted into phosphine with no losses over time, our simulations show that the cosmogenic production of phosphine cannot account for the 20 ppb concentrations reported by Greaves et al. (2020). Gamma rays and neutrons resulting from cosmic ray interactions are also examined just after they leave the planet.

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.