Cosmic Ray Intensity Research Articles

The Southern African neutron monitor program: A regional network to study global cosmic ray modulation

Neutron monitor (NM) observations provide a unique, long-term record of galactic cosmic ray intensities, from which many valuable insights have been drawn as to the transport and modulation of these particles. In this paper, the African Neutron Monitor Network, which provides NM observations for broad range of cutoff rigidities, and spanning an exceptional period of time, is introduced. Aspects of these NM observations from this network are discussed, followed by a demonstration of time-dependent numerical cosmic ray modulation modelling done at the North-West University in South Africa, which hosts this network.

Solar and interplanetary causes of x-class, x-ray solar flare related forbush decreases of higher magnitude in cosmic ray intensity during the period of solar cycle 23 and rising phase of solar cycle 24

Solar and interplanetary causes of x-class, x-ray solar flare related forbush decreases of higher magnitude in cosmic ray intensity during the period of solar cycle 23 and rising phase of solar cycle 24

Cosmic ray intensity variation with solar flare index, solar coronal index and sunspot numbers solar indices during the period of 1986- 2007

Cosmic ray intensity variation with solar flare index, solar coronal index and sunspot numbers solar indices during the period of 1986- 2007

A proposal to extend the spectrographic global survey method

We present a modified spectrographic global survey method to split the cosmic ray variations into components of the interplanetary, geomagnetospheric, and atmospheric origin from ground-based observations of the cosmic ray intensity. We show a possibility to use all the available suite of ground-based instrumentation recording cosmic rays (global network of the neutron monitors located at different locations and altitudes, ground- and underground-based muon telescopes, etc.) for such studies without involving the data from aerologic atmospheric sounding. As a demonstration of the method functionality, we provide the calculation results for the variations in the isotropic flux, pitch angle anisotropy of primary cosmic rays in the interplanetary space, changes in the planetary system of geomagnetic cutoff rigidities for every observational hour, as well as the atmosphere temperature above the point of observation of cosmic ray charged components for selected time intervals.

The impact of various instances of solar wind speed on the fluctuations of cosmic radiation in the solar minima (23, 24, and 25)

Its key role in space weather determines the importance of solar wind study. The solar wind is made up of various plasma streams with varying hydrodynamic and magnetic properties, which has been known for a long time. Because the distinction between the sorts of flows is conditional rather than absolute, there is still no widely agreed terminology, which varies according to the author. The number of these kinds as well as how they are classified is varied. We investigated data on solar wind speed and cosmic ray intensity for four stations, Apatity, Fort Smith, Hermanus, and Moscow, collected from the National Oceanic and Atmospheric Administration and neutron monitors, from 1998 to 2020 for three solar cycles (23, 24, and 25). Slow and rapid wind, as well as disturped streams, are the three basic forms of solar wind. The sluggish solar wind has a typical speed of 300–500 km per second. At speeds of 700–800 km/s, rapid solar wind is emitted. In all cases of solar wind speed, the amplitude and phase of daily variability on selected sites were investigated. The presence of the solar wind was recorded every day during the study time, with low solar wind events occurring more frequently than the rapid and disturped streams.

A new method of nowcasting extreme cosmic ray events

ABSTRACT The daily observations of the cosmic ray intensity carried out by the Athens Neutron Monitoring Station in Greece during the period 1 January 2010 to 14 January 2022 are analysed for the study of the observed extreme events. The high values of this parameter were found to obey the Gutenberg-Richter scaling, which has already been identified in several meteorological parameters. Based on this finding a new nowcasting method has been developed herewith for extreme cosmic rays’ events that may cause interference to telecommunications and problems with transportation and water supply, as well as several disasters. For the development of this nowcasting model, the innovative domain of ‘natural time’ has been employed. Moreover, using the data provided by the Cosmic Rays Database, a power–law relation was found that connects the cosmic ray flux and the particle total energy corresponding to a future cosmic ray event with high intensity. This model will make a major contribution to the further development of ways to prevent, prepare for and deal with potential damages following extreme cosmic rays’ events.

Extra-terrestrial influence on climate variability

Abstract This study is focused on the analysis of signatures of extra-terrestrial influence on the centennial variability of some climatic variables, during the period 1900-2010. The applied lagged cross-correlation analysis shows evidence for a synchronisation between intensity of galactic cosmic rays (GCR) and two climate variables – the air surface temperature and the sea level pressure. The time delay of climatic response is not more than 5 years in the regions of stronger correlations. Moreover, the centennial variability of GCR is imprinted on the ozone mixing ratio at 70 hPa, suggesting its role of a mediator of GCR influence on climate. Having in mind the ozone’s capability to control the near tropopause temperature and humidity, we have suggested a mechanism describing the transmission of GCR signal from lower stratosphere, down to the Earth’s surface.

Variation in Cosmic-Ray Intensity Lags Sunspot Number: Implications of Late Opening of Solar Magnetic Field

Abstract Galactic cosmic rays (GCRs), the highly energetic particles that may raise critical health issues for astronauts in space, are modulated by solar activity, with their intensity lagging behind the variation in sunspot number (SSN) by about one year. Previously, this lag has been attributed to the combined effect of outward convecting solar wind and inward propagating GCRs. However, the lag’s amplitude and its solar-cycle dependence are still not fully understood. By investigating the solar surface magnetic field, we find that the source of heliospheric magnetic field—the open magnetic flux on the Sun—already lags behind SSN before it convects into the heliosphere along with the solar wind. The delay during odd cycles is longer than that during sequential even cycles. Thus, we propose that the GCR lag is primarily due to the very late opening of the solar magnetic field with respect to SSN, though solar wind convection and particle transport in the heliosphere also matter. We further investigate the origin of the open flux from different latitudes of the Sun and find that the total open flux is significantly contributed by that from low latitudes, where coronal mass ejections frequently occur and also show an odd–even cyclic pattern. Our findings challenge existing theories, and may serve as the physical basis of long-term forecasts of radiation dose estimates for manned deep-space exploration missions.

Voyager's observations in the vicinity of the heliopause

This work analyzes Voyager 2 observations on November 2018 and compares them with Voyager 1 data at the vicinity of the heliopause in July-August 2012. We describe the plasma and cosmic-ray variations at the radial distance of $\approx$ 1 astronomical unit (AU) from the heliopause. We use a simple convection-diffusion cosmic-ray modulation model to qualitatively explain the particle observations. We found a thin layer, with a thickness of $\approx$ 0.04 AU where the radial component of the solar wind speed vanished, the galactic cosmic ray intensity rapidly increased to reach its heliosphere boundary level, and low-energy heliospheric ion intensity drooped. We called this layer the "skin of the heliosphere". Plasma data suggest that Voyager 2 crossed the heliopause on November 5, 2018, at the radial distance of 119.03 AU. We apply our analysis to Voyager 1 observations and conclude that similar behavior in solar wind speed could qualitatively explain the GCR counting rate and that the "skin of the heliosphere" maybe a global characteristic along the heliopause.

Observation of variations in cosmic ray single count rates during thunderstorms and implications for large-scale electric field changes

We present the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of cosmic ray single count rate intensity over a 700 km2 area. Observations of variations in the secondary low-energy cosmic ray counting rate, using the TASD, allow us to study the electric field inside thunderstorms, on a large scale, as it progresses on top of the 700 km2 detector, without dealing with the limitation of narrow exposure in time and space using balloons and aircraft detectors. In this work, variations in the cosmic ray intensity (single count rate) using the TASD, were studied and found to be on average at the ∼(0.5–1)% and up to 2% level. These observations were found to be both in excess and in deficit. They were also found to be correlated with lightning in addition to thunderstorms. These variations lasted for tens of minutes; their footprint on the ground ranged from 6 km to 24 km in diameter and moved in the same direction as the thunderstorm. With the use of simple electric field models inside the cloud and between cloud to ground, the observed variations in the cosmic ray single count rate were recreated using CORSIKA simulations. Depending on the electric field model used and the direction of the electric field in that model, the electric field magnitude that reproduces the observed low-energy cosmic ray single count rate variations was found to be approximately between 0.2 GV–0.4 GV. This in turn allows us to get a reasonable insight on the electric field and its effect on cosmic ray air showers inside thunderstorms.2 MoreReceived 19 November 2021Accepted 3 January 2022DOI:https://doi.org/10.1103/PhysRevD.105.062002© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAtmospheric scienceCosmic rays & astroparticlesInterdisciplinary PhysicsParticles & Fields

Seasonal trends of the cosmic ray intensity observed by 16 neutron monitors for 1964–2020

The intensity of neutrons as secondary cosmic rays has typical modulations, such as diurnal and solar cyclic variation or transient events. Jeong and Oh (2020) examined the seasonal variation using data of the Oulu neutron monitor, but the seasonal variations and their origins were difficult to determine. In this study, the daily data of 16 neutron monitors from 1964 to 2020 were used to examine the seasonal variation and its origin. The solar cyclic variations were eliminated by normalizing to the yearly mean or median and selecting the representative value of each day from the mean or median for 57 years. Sixteen neutron monitors showed a clear seasonal trend for four ways of data transformation based on the Cox and Stuart trend test. Furthermore, the seasonal trend remained steadfast, excluding the outliers of each year to remove the variations by sporadic effects. The seasonal trend showed the maximum in January and the minimum in June. Out of 16 neutron monitors, an attempt was made to find the groups with a homogeneous seasonal trend. The statistical clustering method using the K-means idea provides two types of groups: Thule-type and Newark-type. The difference between the two groups showed the different recovery period from the minimum value and the combination of semiannual wave. This difference may result from a combination of terrestrial and extraterrestrial effects depending on the neutron monitor’s latitude and altitude. We considered the various origins of the seasonal trends including terrestrial and extraterrestrial factors. The seasonal trends may originate from the combination of various sources, including terrestrial and extraterrestrial factors rather than from one independent factor.

Association of Infradian Rhythms of Motor Activity, Concentration of Glucocorticoid Hormones, and One-Minute-Step Oscillations of Body Temperature with Intensity of Fluctuations of Secondary Cosmic Rays.

The study compared the daily mean intensity of one-minute-step fluctuations in intensity of the secondary cosmic rays reflected by neutron count rate and dynamics of body temperature, motor activity, as well as concentration of glucocorticoid hormones in birds and rodents. A positive correlation was established between body temperature oscillations and neutron count rate fluctuations. A similar correlation was observed between physical parameter (neutron count rate), on the one hand, and daily mean motor activity and concentration of glucocorticoid hormones in the animals. The periods and phases of these processes presented in synchronous time series coincided. The facts of simultaneous variations or disturbances of the periods in dynamics of biological and physical parameters attest to their relationships. The study concluded that the infradian rhythms with the periods of 3-5 days depend on some external environmental factor related to fluctuations in intensity of secondary cosmic rays.

The Frequency‐Domain Characterization of Cosmic Ray Intensity Variations Before Forbush Decreases Associated With Geomagnetic Storms

AbstractNonrecurrent geomagnetic storms caused by Coronal Mass Ejection (CME) can induce serious impacts on space‐ and ground‐based equipment. However, these nonrecurrent geomagnetic storms are hard to predict since CMEs are not periodic. Previous studies have shown that the variations of Cosmic Ray Intensity (CRI) before nonrecurrent storms may forebode the coming geomagnetic storm. But it is difficult to extract the variations since the cosmic ray flux is a complex signal. In order to identify the precursory signal in CRI variations triggered by CME, an ensemble self‐adaptive time‐frequency analysis method was proposed and applied to 65 nonrecurrent geomagnetic storms occurred between 1998 and 2019. The results indicate that the precursory signals are successfully identified in 43 of 45 storms, after excluding 20 storms accompanied by ground level enhancement. In addition, it is also found that the spectral density of the precursory signal could reflect the active level of geomagnetic condition, which is lower during geomagnetic quiet period.

On the Accuracy of Underground Muon Intensity Calculations

Abstract Cosmic-ray muons detected by deep underground and underwater detectors have served as an information source on the high-energy cosmic-ray spectrum and hadronic interactions in air showers for almost a century. The theoretical interest in underground muons has nearly faded away because space-borne experiments probe the cosmic-ray spectrum more directly, and accelerators provide precise measurements of hadron yields. However, underground muons probe unique hadron interaction energies and phase space, which are still inaccessible to present accelerator experiments. The cosmic-ray nucleon energies reach the hundred-TeV and PeV ranges, which are barely accessible with space-borne experiments. Our new calculation combines two modern computational tools: mceq for surface muon fluxes and proposal for underground transport. We demonstrate excellent agreement with measurements of cosmic-ray muon intensities underground within estimated errors. Beyond that, the precision of historical data turns out to be significantly smaller than our error estimates. This result shows that the sources of high-energy atmospheric lepton flux uncertainties at the surface or underground can be significantly constrained without taking more data or building new detectors. The reduction of uncertainties can be expected to impact data analyses at large-volume neutrino telescopes and be used for the design of future ton-scale direct dark matter detectors.

Time Lag Between Cosmic-Ray and Solar Variability: Sunspot Numbers and Open Solar Magnetic Flux

Solar magnetic activity drives the dominant 11-year cyclic variability of different space environmental indices, but they can be delayed with respect to the original variations due to the different physical processes involved. Here, we analyzed the pairwise time lags between three global solar and heliospheric indices: sunspot numbers (SSN), representing the solar surface magnetic activity, the open solar flux (OSF), representing the heliospheric magnetic variability, and the galactic cosmic-ray (GCR) intensity near Earth, using the standard cross-correlation and the more detailed wavelet-coherence methods. All the three indices appear highly coherent at a timescale longer than a few years with persistent high coherence at the timescale of the 11-year solar cycle. The GCR variability is delayed with respect to the inverted SSN by about eight 27-day Bartels rotations on average, but the delay varies greatly with the 22-year cycle, being shorter or longer around positive A+ or negative A- solar polarity epochs, respectively. The 22-year cyclicity of the time lag is determined by the global heliospheric drift effects, in agreement with theoretical models. The OSF lags by about one year behind SSN, and is likely determined by a combination of the short lifetime of active regions and a longer (≈3 years) transport time of the surface magnetic field to the poles. GCRs covary nearly in antiphase with the OSF, also depicting a strong 22-year cycle in the delay, confirming that the OSF is a good index of the heliospheric modulation of GCRs. This provides an important observational constraint for solar and heliospheric physics.

Forecasting of cosmic rays intensities with HelMod Model

HelMod model allows one to describe how solar modulation affects the propagation of galactic cosmic rays (GCR) through the heliosphere with an accuracy of the level of actual experimental uncertainties. The GCRs mainly constitute the high energy population of the so-called space radiation environment. The model treats the physical processes involved in solar modulation, like diffusion, particle drift, convection and adiabatic energy losses, and it embeds a description of both the inner and outer heliosphere. To obtain the modulated intensities, the model requires the knowledge of a few time-dependent heliospheric quantities, i.e., sunspot number, tilt angle of the neutral current sheet, solar wind speed and density, and interplanetary magnetic field. Using historical records, we present a template-based procedure that allows one to predict the heliospheric parameters for coming years, and, in turn, the forecasted modulated spectra. The forecasting templates reconstruct the typical time variation along with solar cycles and may be tuned to the current solar cycle. We estimate that the uncertainty of the forecasted cosmic rays intensity is below 5% (±10% at 68% C.L.) on average for short time predictions (up to 4 years), and below 15% (±(20-25)% at 68% C.L.) for long time predictions (up to 11 years).

Asymmetric cosmic ray intensity decreases with solar flares and interplanetary shocks

Asymmetric cosmic ray intensity decreases with solar flares and interplanetary shocks

First measurements of low-energy cosmic rays on the surface of the lunar farside from Chang'E-4 mission.

Human activities on the lunar surface are severely constrained by the space radiation dominated by cosmic rays (CRs). Here, we report the first measurements of the low-energy (about 10 to 100 MeV/nuc) CR spectra on the lunar surface from China’s Chang’E-4 (CE-4) mission around the solar minimum 24/25. The results show that for the proton, helium, CNO, and heavy-ion groups, the ratios (ratio errors) of the CE-4 fluxes to those from the near-earth spacecraft are 1.05 (0.15), 1.30 (0.18), 1.08 (0.16), and 1.24 (0.21), respectively, and to those predicted by the models [CRÈME96 and CRÈME2009] are instead [1.69 (0.17), 2.25 (0.23)], [1.66 (0.17), 1.76 (0.18)], [1.08 (0.11), 1.07 (0.11)], and [1.33 (0.18), 1.17 (0.15)]. Moreover, a notable enhancement of 3He/4He ratio is observed at ~12 MeV/nuc, and the CR dawn-dusk symmetry is confirmed. These results provide valuable insights into the CRs on the lunar farside surface and will benefit future lunar exploration.

Подавление шума и выделение когерентных структур сигнала на основе алгоритма нелинейной адаптации

An algorithm for noise suppression and extraction of coherent structures of a complex signal is proposed. The algorithm is based on the joint application of packet wavelet decompositions and adaptive stochastic thresholds. Thresholds are estimated with a given confidence level based on the α-quantiles of Student's distribution. The operations of the algorithm are described and a scheme for its implementation is proposed. On the example of data from neutron monitors (recording the intensity of secondary cosmic rays, www.nmdb.eu), the efficiency of the algorithm is shown. The selected coherent structures characterize the occurrence of anomalies in variations in the intensity of cosmic rays. Anomalies in cosmic ray data create a radiation hazard, disrupt radio communications, and cause satellites to malfunction, leading to disorientation and destruction. Therefore, the task of timely diagnosis of such events is relevant. The application of the algorithm made it possible to clearly detect and evaluate the moments of occurrence of anomalies in cosmic rays, which were observed during periods of magnetospheric disturbances.

Linking Cosmic Ray Intensities to Cutoff Rigidity Through Multifractal Detrented Fluctuation Analysis

Linking Cosmic Ray Intensities to Cutoff Rigidity Through Multifractal Detrented Fluctuation Analysis