High Energy Cosmic Rays Research Articles

Efficient charged particle propagation methods

In astrophysics, the search for sources of the highest-energy cosmic rays continues. For further progress, not only ever better observatories but also ever more realistic numerical simulations are needed. We compare different approaches for numerical test simulations of ultra-high-energy cosmic rays in the intergalactic magnetic field and show that all methods provide correct statistical propagation characteristics of the particles in means of their diffusive behaviour. Through convergence tests, we show that the necessary requirements for the methods differ and ultimately reveal significant differences in the required simulation time.

Effect of cosmic rays irradiation on the phase change characteristics of an on-orbit fixed point

Using the phase change characteristics of fixed points to trace the temperature of a spaceborne calibration blackbody is an important technical means to carry out the high-precision on-orbit calibration of thermal infrared remote sensors. In contrast to an experimental environment on the ground, a fixed point will produce radiation damage in the high-energy cosmic rays environment and may affect the phase change characteristics. This study investigates the effect of radiation damage caused by cosmic rays irradiation on the phase change characteristics of fixed points in a spaceborne calibration blackbody. In this research, the simulation method of molecular dynamics was used to simulate the irradiation damage effect of a strong cosmic rays environment on fixed-point indium (In). The experimental system was established to measure the phase change curves of samples with different irradiation doses, and then, the influence of irradiation on the phase change characteristics of the samples was analyzed. The results showed that most of the energy of irradiation was deposited on the In fixed point, resulting in the migration of 0.3% of the displacement atoms inside the In to the gap position to form the Frenkel pairs (FPs). The overcooling of the irradiated In fixed point was reduced by 0.3 ^circ hbox {C}, the phase change temperature was increased by 30 mK, and the phase change plateau was more stable.

Locating sources of a high energy cosmic ray extensive air shower using HiSPARC data

In the physics community, there is continued interest in high energy cosmic rays and their co-location to stellar sources, including to supernovae. Observational history and corresponding theories link the high energies associated with these types of cosmic rays to those produced in various latter evolution stages of stellar bodies. We hypothesize that high-energy cosmic ray air showers have a source region associated with specific stellar bodies. Here, we present our analysis of the locations of possible high-energy cosmic ray sources by using data from University of Twente cosmic ray detectors that are part of the High School Project on Astrophysics Research with Cosmics (HiSPARC) network. As an example of the potential of the HiSPARC network to aid cosmic ray source location, we analyzed event count data from a high-energy air shower recorded during the first week of January 2014. The data was then processed such that the direction of the air shower could be ascertained to provide the likely area of air shower origin. Angle and time data were then inputted in to Stellarium™, a free open-source planetarium application from which sources could be located. Our results suggest two sources are candidates for the origins of the high-energy air shower: the Cepheid variable Polaris and the binary system, Iota Ursae Majoris A. In sum, we have shown the potential of the HiSPARC network to aid location of stellar sources that may be responsible for detected cosmic air showers.

Model-independent Evidence for an Increase in the Mean Mass of Cosmic Rays above 3 EeV

Measurements of the Elongation Rate of the depth of shower maximum above 1 EeV are reviewed. There is evidence, from four independent estimates of this rate, made in the two hemispheres using three different techniques, for a decrease in the Elongation Rate above ~3 EeV, as first discovered by the Pierre Auger Collaboration over 15 year ago. Unless there is a dramatic change in the hadronic physics above this energy, the mean mass of the primary cosmic rays must increase as a function of energy, well into the decade beyond 10 EeV. To estimate the mass, the use of hadronic models is required, the accuracy of which remains uncertain. However, the possibility of a dramatic change in the hadronic physics appears unlikely, and would be inconsistent with data from the Auger Collaboration on the mass composition in the range 3 to 10 EeV, and on the anisotropy of arrival directions above 8 EeV. Both of these conclusions are insensitive to uncertainties in the shower models. Some remarks are made about the belief, still firmly held by some, that the highest-energy cosmic rays are dominantly protons.

Starburst Nuclei and Cosmic-Rays Transport Mechanisms: Future Opportunities for Neutrino Astronomy and Beyond Standard Model Studies

Experimental observations have demonstrated a strong correlation between star-forming processes and gamma-ray luminosities, giving strong hints about the nature of the Cosmic-Rays (CRs) transport mechanisms inside Starburst Nuclei. In this contribution, we discuss the imprints on nearby Starburst galaxies (SBGs) gamma-ray spectra left by different CR transport models, quantifying the potentiality of future telescopes to distinguish between them. We also investigate the possibility of constraining the properties of light Dark Matter (DM) particles exploiting the peculiar nature of CR transport inside SBNs. We show that the property of scattering between high-energy CRs and DM particles leads to observable features, thereby posing stringent constraints on the DM parameter space.

Hadronic Interactions Studies at the LHC

The deficit of muons in the simulation of extensive air showers is a long-standing problem and the origin of large uncertainties in the reconstruction of the mass of the high-energy primary cosmic rays. Hadronic interaction models re-tuned after early LHC data have a more consistent description of the muon content among them but still disagree with the data. Furthermore, some inconsistencies are also visible in the electromagnetic component. Ten years after the first LHC-tuned model release, much more detailed data are available both from LHC, SPS and hybrid air shower measurements, allowing for the understanding of some deficiencies in the model which could lead to a change in both Xmax and the muon production by air showers. A better treatment of the core-corona approach according to LHC data has important consequences on the muon production while an update of diffraction and nuclear fragmentation is changing the Xmax distribution. An updated version of EPOS LHC will be presented addressing the main issues of this model.

AugerPrime status and prospects

The Pierre Auger Collaboration started a few years ago the AugerPrime project to increase the Surface Detector (SD) performance of the Pierre Auger Observatory. It aims to address the still open questions on the origin and composition of the highest energy cosmic rays by allowing a better identification of the nature of the primaries. The key element of this major upgrade is the capability of measuring the different components of extensive air showers, which will be significantly improved by the addition of a Surface Scintillator Detector (SSD) on each water-Cherenkov detector (WCD) constituting the SD. Moreover, the dynamic range of measurement is extended through an additional small photomultiplier tube inside the WCD. New electronics is processing the signals from the WCD and the SSD with higher sampling frequency and enhanced resolution. The scintillator module deployment started in 2019, and the new electronics in December 2020. The collected data allow for the evaluation of the first performances of the upgraded array and to adapt the whole data acquisition chain necessary for an efficient and sustainable operation of the Observatory. After the recall of the motivations for the upgrade, the main characteristics of the new detection setup are reviewed, as well as the status of its deployment and commissioning. The expected prospects are also discussed.

Ultra High Energy Cosmic Ray Source Models: Successes, Challenges and General Predictions

Understanding the acceleration of Ultra High Energy Cosmic Rays is one of the great challenges of contemporary astrophysics. In this short review, we summarize the general observational constraints on their composition, spectrum and isotropy which indicate that nuclei heavier than single protons dominate their spectra above ˜ 5 EeV, that they are strongly suppressed above energies ˜ 50 EeV, and that the only significant departure from isotropy is a dipole. Constraints based upon photopion and photodisintegration losses allow their ranges and luminosity density to be estimated. Three general classes of source model are discussed - magnetospheric models (including neutron stars and black holes), jet models (including Gamma Ray Bursts, Active Galactic Nuclei and Tidal Disruption Events) and Diffusive Shock Acceleration models (involving large accretion shocks around rich clusters of galaxies). The value of constructing larger and more capable arrays to measure individual masses at the highest energies and probably identifying their sources is emphasized.

A Brief History of the Study of High Energy Cosmic Rays using Arrays of Surface Detectors

A brief history of the development of surface detectors for the study of the high-energy cosmic rays is presented. The paper is based on an invited talk given at UHECR2022 held in L’Aquila, 3 – 7 October 2022. In a complementary talk, P Sokolsky discussed the development of the fluorescence technique for air-shower detection.

Influence of cosmic rays on environmental ecosystems

AbstractIt is presented a model to consider the effect of high energy cosmic rays on three types of terrestrial ecosystem: coastal macroalgae, lakes, and forests. The model includes insights into muon dosimetry based in the stopping power of muons while traveling in water and soft biological tissues. It is shown that a muon from secondary cosmic rays could deposit in cells an energy much higher than that deposited by ultraviolet photons coming from the Sun. Consequently, drastic short‐term reductions of photosynthesis are obtained if energetic astrophysical phenomena such as gamma ray bursts and neutron star mergers happen in our astronomical neighborhood, while radiational solar storms also cause considerable inhibition of photosynthesis.

Terzina on board NUSES: A pathfinder for EAS Cherenkov Light Detection from space

In this paper we introduce the Terzina telescope as a part of the NUSES space mission. This telescope aims to detect Ultra High Energy Cosmic Rays (UHECRs) through the Cherenkov light emission from the extensive air showers (EAS) that they create in the Earth’s atmosphere. The Cherenkov photons are aligned along the shower axis inside about ∼ 0.2 − 1°, so that they become detectable by Terzina when it points towards the Earth’s limb. A sun-synchronous orbit will allow the telescope to observe only the night side of the Earth’s atmosphere. In this contribution, we focus on the description of the telescope detection goals, geometry, optical design and its photon detection camera composed of Silicon Photo-Multipliers (SiPMs). Moreover, we describe the full Monte Carlo simulation chain developed to estimate Terzina’s performance for UHECR detection. The estimate of the radiation damage and light background rates, the readout electronics and trigger logic are briefly described. Terzina will be able to study the potential for future physics missions devoted to UHECR detection and to UHE neutrino astronomy. It is a pathfinder for missions like POEMMA or future constellations of similar satellites to NUSES.

Results from high energy direct measurements and future prospects

In this contribution a review of the recent results from high energy cosmic ray measurements, in the ’above TeV’ energy regions, will be presented. The future experiments that will be realised to significantly improve the current measurements, aiming to explore the PeV region with direct measurements, will also be described.

A detailed presentation of the highest-energy cosmic rays recorded at the Pierre Auger Observatory

A catalog that contains details of the highest-energy cosmic rays, recorded by the Pierre Auger Collaboration between 1 January 2004 and 31 December 2020, is presented. Data from 100 air showers, generated by particles having energies in the range 78 EeV to 166 EeV, are described, together with nine other very energetic events used in the energy calibration. The catalog has been created to demonstrate the quality of the data that underlie measurements reported by the Collaboration, and to make the details of these events available for scrutiny. After a brief description of the techniques used for data acquisition and reconstruction, the contents of the catalog will be described. Some events within the catalog will be discussed in detail.

Probing Hadronic Interactions with Cosmic Rays

High-energy cosmic rays interact in the Earth’s atmosphere and produce extensive air showers (EASs) which can be measured with large detector arrays at the ground. The interpretation of these measurements relies on models of the EAS development which represents a challenge as well as an opportunity to test quantum chromodynamics (QCD) under extreme conditions. The EAS development is driven by hadron-ion collisions under low momentum transfer in the non-perturbative regime of QCD. Under these conditions, hadron production cannot be described using first principles and these interactions cannot be probed with existing collider experiments. Thus, accurate measurements of the EAS development provide a unique probe of multi-particle production in hadronic interactions.

Measurements of Cosmic Ray Mass Composition with the IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a multi-component detector at the South Pole. Besides studying high-energy neutrinos, it is capable of measuring high-energy cosmic rays from PeV to EeV. This energy region is thought to cover the transition from galactic to extragalactic sources of cosmic rays. The observatory consists of the deep in-ice IceCube array, which measures the high-energy (≥500 GeV) muonic component, and the IceTop surface array, which is sensitive to the electromagnetic and low-energy muonic part of an air shower. The primary energy and the mass composition can be measured simultaneously by applying statistical methods including modern machine-learning techniques to reconstruct cosmic ray air showers. In this contribution, we will discuss recent improvements to the reconstruction techniques, the mass composition sensitivity, and an outlook on future improved measurements with the full surface scintillator/radio array to mitigate snow accumulation and measure the air shower maximum Xmax using imaging air-Cherenkov telescopes IceAct.

Dark dimension, the swampland, and the origin of cosmic rays beyond the Greisen-Zatsepin-Kuzmin barrier

Very recently, it was pointed out that when basic ideas of the Swampland program are combined with the cosmological hierarchy problem (i.e. the smallness of the dark energy in Planck units) and together are confronted to experiment lead to the prediction of the existence of a single extra-dimension (dubbed the dark dimension) with characteristic length-scale in the micron range. We propose a feasible test procedure to probe the dark dimension using the highest energy cosmic rays.

Performance of the RF Detectors of the Astroneu Array

Since 2014, the university campus of Hellenic Open University (HOU) has hosted the Astroneu array, which is dedicated to the detection of extensive air showers (EAS) induced by high-energy cosmic rays (CR). The Astroneu array incorporates 9 large particle scintillation detectors and 6 antennas sensitive to the radio frequency (RF) range 1–200 MHz. The detectors are adjusted in three autonomous stations operating in an environment with a strong electromagnetic background. As shown by previous studies, EAS radio detection in such environments is possible using innovative noise rejection methods, as well as advanced analysis techniques. In this work, we present the analysis of the collected radio data corresponding to an operational period of approximately four years. We present the performance of the Astroneu radio array in reconstructing the EAS axis direction using different RF detector geometrical layouts and a technique for the estimation of the shower core by comparing simulation and experimental data. Moreover, we measure the relative amplitudes of the two mechanisms that give rise to RF emission (the Askaryan effect and geomagnetic emission) and show that they are in good agreement with previous studies as well as with the simulation predictions.

Shell‐type supernova remnants and very high energy cosmic rays

AbstractThe investigation of very high energy (VHE) γ‐ray sources by any methods, including mirror Cherenkov telescopes, touches on the problem of the cosmic‐ray origin and, accordingly, the role of the Galaxy in their generation. The SHALON observations have yielded the results on Galactic supernova remnants (SNR) of different ages. Among them are: the shell‐type SNRs Tycho's SNR, Cas A, IC 443, γCygni SNR, G166.0+4.3. For each of SNRs, the observation results are presented with spectral energy distribution by SHALON in comparison with other experiment data and images by SHALON in together with data from X‐ray by Chandra and radio‐data by CGPS. The experimental data presented here have confirmed the prediction of the theory about the hadronic generation mechanism of VHE 800 GeV–100 TeV γ‐rays in Tycho's SNR, Cas A and IC 443, and also the collected experimental data help to make clear the origin of TeV γ‐ray emission in the older SNRs like γCygni SNR and G166.0+4.3.

Lightning Initiation as a Consequence of Natural Thundercloud Evolution. Part 1. The Role of Detachment in Reducing the Critical Air Breakdown Field

Direct measurements show that the maximum values of electric fields measured in thunderclouds are approximately an order of magnitude lower than the air breakdown (ionization threshold) field. At first glance, this means the impossibility of electron avalanches to form and, as a consequence, the impossibility of a lightning discharge to occur. This circumstance puts the question about the lightning origin physical mechanism on a par with the most amazing mysteries of the nature. For more than half a century of research, several mechanisms have been proposed to solve this problem, among which two main lines can be distinguished. The first group of approaches focuses on the possibility of a streamer or a system of streamers to initiate from the surface of one or several hydrometeors, while the second one interprets lightning initiation as a consequence of the runaway electrons breakdown emerging from the interaction between high-energy cosmic rays and the atmosphere. There are also hybrid scenarios that combine both the ideas. However, in view of certain limitations, none of the proposed approaches has been recognized as the final solution to the problem. The article describes a fundamentally new lightning initiation mechanism that develops sequentially on several spatiotemporal scales. The scenario proposed shows how a series of corona discharges occurring during collisions of hydrometeors seeds the cloud with decimeter-scale elevated ionic conductivity regions, the electric field at the poles of which increases to the level necessary for positive streamers to appear. At the next stage, multiple streamer discharges oriented by the direction of a large-scale electric field are combined into a single plasma network, within which a hot leader channel is formed. The mechanism discussed effectively utilizes small-scale and mesoscale electric field fluctuations arising in a thundercloud and can be implemented if the spatiotemporal frequency of corona discharges, accompanying collisions and near collisions of hydrometeors, and the potential difference between the strong intracloud field zone boundaries exceed 0.1 m-3s-1 and 3 MV, respectively. In contrast to alternative approaches, the proposed lightning initiation scenario can be implemented under the conditions of a typical thundercloud without the need to involve any external auxiliary factors. The study results are presented in three parts. This article gives an introductory part, which sets the general context of the narrative and determines the study aims, and describes the role the detachment of electrons from negative ions plays in the air breakdown field reduction. The authors' lightning initiation scenario based on the results described in the present paper is given in two subsequent publications.

Terrestrial Gamma-Ray Flashes at the Pierre Auger Observatory

The Pierre Auger Observatory is designed to measure the highest energy cosmic rays. However, the surface detector, covering 3000 km2, is also sensitive to events associated with atmospheric electricity. These events can be distinguished from normal cosmic-ray events in both temporal and spatial structure. With signals lasting around 10 μs, they are about an order of magnitude longer than cosmic-ray events. Their circular footprints on the ground are also different and larger than those of typical cosmic-ray showers. Due to their association with thunderstorms and topology, these events are candidates for downward-going terrestrial gamma-ray flashes (TGFs). We show a detailed analysis of the effects that the data-taking system has on recording of TGF candidate events. Furthermore, we present a recently implemented special trigger algorithm aimed at increasing the data-taking efficiency for TGF candidates.