Cosmic Ray Intensity Research Articles

Revised cross-correlation and time-lag between cosmic ray intensity and solar activity using Chatterjee’s correlation coefficient

This study revisits the cross-correlation between cosmic ray intensity (CRI) and solar activity (SA) by comparing traditional Pearson correlation with Chatterjee’s correlation coefficient. Traditional analyses using Pearson correlation are useful for identifying linear relationships and time lags. However, they may not fully capture more complex interactions in the data. Chatterjee’s correlation coefficient, while sensitive to different types of relationships, including nonlinear ones, provides a complementary perspective on the temporal relationships between CRI and SA. This approach broadens our understanding of potential dependencies, offering additional insights that may not be captured through Pearson correlation alone.The findings reveal that Chatterjee’s correlation complements Pearson’s insights by providing an alternative view of the relationship between cosmic ray intensity (CRI) and solar activity (SA). The results show that Chatterjee’s correlation coefficients are, on average, approximately 45–50% smaller than Pearson’s, which could reflect different sensitivities to the underlying data structure rather than solely indicating a nonlinear component. Additionally, the time lags identified using Chatterjee’s correlation are generally shorter and more consistent across different solar cycles compared to those obtained with Pearson’s correlation, suggesting that CCC may capture temporal patterns in a distinct manner.Further analysis using Dynamic Time Warping (DTW) and Mean Absolute Percentage Error (MAPE) metrics demonstrated that, in more than half of the scenarios considered, alignment based on Chatterjee’s time lags resulted in lower errors and better alignment of the series compared to Pearson’s lags. This indicates that Chatterjee’s method is particularly effective for capturing the immediate and nuanced responses of CRI to SA changes, especially in recent solar cycles.This comprehensive approach provides broader insights into the dynamic interactions between cosmic ray intensity (CRI) and solar activity (SA), highlighting the importance of considering multiple correlation measures, including both linear and nonlinear approaches, in space weather research. The results suggest that Chatterjee’s correlation offers a complementary perspective on these interactions, providing additional details about how SA influences CRI over time, which may not be fully captured by Pearson’s correlation alone.

Heliospheric Effect on Solar Activity Parameters during MaximumPhase of Solar Cycle 24 (2012-2015)

Abstract The time series of daily data of solar activity proxies, namely the sunspot number (SSN), sunspot area (SSA), solar radio flux (F10.7), modified coronal index (MCI), solar flare index (FI), and cosmic ray intensity (CRI), were analyzed to understand the solar activity modulations and short-term periodicities therein. Rieger-type, and other short-term periods, including the solar rotational period that covers the maximum activity phase period (maximum phase of solar cycle 24). The wavelet power spectra and Periodogram of SSN, SSA, F10.7, MCI, FI, and CRI exhibited a significant short-term period. The heliospheric effects exist for a particular period (~27 days) and it is related to the solar activity phenomena. The cross-correlation coefficients and time lags between the cosmic ray intensity and solar activity parameters were estimated to be 200, 46, 281, 39, and 47 days for SSN, SSA, F10.7, MCI, and FI respectively during the time series 2012-2015 (maximum phase of solar cycle 24).

The galactic cosmic ray intensity fluctuations during perturbations of the solar wind in early November 2021

In order to develop methods for predicting negative manifestations of space weather, the dynamics of fluctuations in the intensity of galactic cosmic rays during geophysical disturbances in early November 2021 is studied. The obtained results point to the possibility of real-time short-term space weather forecasting based on the measurement data of the Russian national ground-based network of cosmic ray stations.

Cosmogenic isotopes in the lunar soil: solar activity and nearby Supernova outbreak

The lunar soil is an integral detector of cosmic rays (CRs) of different origin (Solar and Galactic). Analysis of the deep profiles of cosmogenic isotopes (14C, 41Ca, 36Cl, 10Be, 26Al, 53Mn) allows us to restore the intensity of CR on time scales of 3–4 half-lives of the corresponding isotope. To coordinate data on 10Be, it is required (in addition to the average flux of CRs) the presence of an additional source of accelerated particles with hard spectrum. Such a source can be, for example, an outbreak of a nearby SN 2–3 million years ago.

Features of Forbush decreases according to satellite and ground based detectors

Forbush decreases are sudden drops of cosmic ray intensity recorded by ground based and satellite detectors. This effect is strongly connected with coronal mass ejections from the Sun. Those are the massive eruptions of plasma material from the Sun atmosphere into interplanetary space. Coronal mass ejections affect cosmic ray particles while moving through interplanetary space causing Forbush decrease. In this work, we have studied the behavior of temporal profiles of cosmic ray intensity during Forbush decreases using data on cosmic proton fluxes recorded by the AMS-02 spectrometer during 2011 to 2019.

Dynamics Of Solar Wind And Cosmic Ray Interactions At The Edge Of Interstellar Space: Insights From Voyager 1 And IBEX Data Analysis

This research paper investigates the relationship between solar wind intensity and cosmic ray flux in the outer heliosphere, utilizing data from Voyager 1 and the Interstellar Boundary Explorer (IBEX). Voyager 1’s measurements beyond the heliopause, where the solar wind significantly weakens, show a marked increase in cosmic ray intensities, suggesting that solar wind acts as a modulating force. Meanwhile, IBEX's all-sky maps of energetic neutral atoms (ENAs) offer complementary data, demonstrating how the solar wind interacts with the interstellar medium at the boundary of the solar system. By analyzing the inverse correlation between solar wind strength and cosmic ray penetration into the heliosphere, this study provides a comprehensive understanding of the dynamic processes occurring at the solar system’s edge. The combined data from these missions not only enhance our understanding of space weather but also provide valuable insights into the broader interaction between the heliosphere and the interstellar medium. This research underscores the significance of continuous monitoring and multi-mission data integration for advancing our understanding of cosmic ray modulation and solar wind behavior in the outer reaches of the solar system.

Global Analysis of the Extended Decreases in Cosmic Rays Observed with Worldwide Networks of Neutron Monitors and Muon Detectors: Temporal Variation of the Rigidity Spectrum and Its Implication

This paper presents the global analysis of two extended decreases in the galactic cosmic-ray intensity observed by worldwide networks of ground-based detectors in 2012. This analysis is capable of separately deriving the cosmic-ray density (or omnidirectional intensity) and anisotropy, each as a function of time and rigidity. A simple diffusion model along the spiral field line between Earth and a cosmic-ray barrier indicates the long duration of these events, resulting from about 190° eastern extent of a barrier such as an interplanetary shock followed by the sheath region and/or the corotating interaction region (CIR). It is suggested that the coronal mass ejection merging with and compressing the preexisting CIR at its flank can produce such an extended barrier. The derived rigidity spectra of the density and anisotropy both vary in time during each event period. In particular we find that the temporal feature of the “phantom Forbush decrease (FD)” reported in an analyzed period is dependent on rigidity, and looks quite different at different rigidities. From these rigidity spectra of the density and anisotropy, we derive the rigidity spectrum of the average parallel mean free path of pitch angle scattering along the spiral field line and infer the power spectrum of the magnetic fluctuation and its temporal variation. The possible physical cause of the strong rigidity dependence of the phantom FD is also discussed. These results demonstrate the high-energy cosmic rays observed at Earth responding to remote space weather.

Fifty years of studying the GCR intensity during inversion of the heliospheric magnetic fields. II. HMF inversion on the inner heliospheric boundary

Phenomena in the outer layer of the solar atmosphere, the heliosphere, including the supersonic solar wind, the heliospheric magnetic field (HMF) carried by it, and cosmic rays propagating in the heliosphere are important for many processes occurring in this layer. For some of these processes such as geomagnetic activity or propagation of cosmic rays, not only the strength, but also the direction of the field is significant. Nonetheless, if in this regard the situation during periods of low sunspot activity is quite clear — the heliosphere is divided into two hemispheres with opposite polarity (toward the Sun/away from the Sun), — during periods of high sunspot activity when the HMF inversion occurs, there is no simple model of this phenomenon. The paper is a sequel to the study of the HMF inversion phenomenon and associated effects in the intensity of galactic cosmic rays (GCR). Previously, general ideas about the 22-year cyclicity in the characteristics of the Sun, heliosphere, and cosmic rays have been formulated, and the effects observed in the GCR intensity, which we associate with the HMF inversion, have been discussed in detail. This paper deals with a model of HMF inversion, associated only with the evolution of the magnetic field in the layer between the photosphere and the base of the heliosphere due to changes in the distribution of photospheric fields from one solar rotation to the next one, and shows that this is not enough to explain the main effects in the GCR intensity. In this layer, the magnetic field is the main energy factor. A more complete model of HMF inversion, including the transformation of its characteristics due to the interaction of different-speed solar wind streams in the heliosphere itself, where the solar wind is the main energy factor, will be discussed in the next paper.

Пятьдесят лет исследования поведения интенсивности ГКЛ в периоды инверсии гелиосферного магнитного поля. II. Инверсия ГМП на внутренней границе гелиосферы

Phenomena in the outer layer of the solar atmosphere, the heliosphere, including the supersonic solar wind, the heliospheric magnetic field (HMF) carried by it, and cosmic rays propagating in the heliosphere are important for many processes occurring in this layer. For some of these processes such as geomagnetic activity or propagation of cosmic rays, not only the strength, but also the direction of the field is significant. Nonetheless, if in this regard the situation during periods of low sunspot activity is quite clear — the heliosphere is divided into two hemispheres with opposite polarity (toward the Sun/away from the Sun), — during periods of high sunspot activity when the HMF inversion occurs, there is no simple model of this phenomenon. The paper is a sequel to the study of the HMF inversion phenomenon and associated effects in the intensity of galactic cosmic rays (GCR). Previously, general ideas about the 22-year cyclicity in the characteristics of the Sun, heliosphere, and cosmic rays have been formulated, and the effects observed in the GCR intensity, which we associate with the HMF inversion, have been discussed in detail. This paper deals with a model of HMF inversion, associated only with the evolution of the magnetic field in the layer between the photosphere and the base of the heliosphere due to changes in the distribution of photospheric fields from one solar rotation to the next one, and shows that this is not enough to explain the main effects in the GCR intensity. In this layer, the magnetic field is the main energy factor. A more complete model of HMF inversion, including the transformation of its characteristics due to the interaction of different-speed solar wind streams in the heliosphere itself, where the solar wind is the main energy factor, will be discussed in the next paper.

Явления гистерезиса в отклике геомагнитной активности и параметров космических лучей на вариации межпланетной среды во время магнитной бури

The dynamics of the intensity of cosmic rays is known to be different on the ascending and descending branches of the 11-year solar cycle, i.e., hysteresis phenomena are observed. Recently, it has been obtained that at shorter intervals on the scale of magnetic storms there are also signs of hysteresis in dependences of cosmic ray cutoff rigidities R (geomagnetic thresholds) on heliosphere and geosphere parameters. R is the rigidity below which a particle flux is cut off due to geomagnetic shielding. In this paper, we have analyzed the dependence of the geomagnetic storm index Dst and the variation of the ΔR thresholds on interplanetary magnetic field (IMF) and solar wind (SW) parameters during the two-step magnetic storm on September 7–8, 2017. We have found hysteresis phenomena in the following paired series: (1) dependences of Dst on SW and IMF parameters, and (2) dependences of ΔR on SW and IMF parameters. We have established that the dependence curves in the storm descending phase (main phase) and ascending phase (recovery phase) do not coincide — hysteresis loops are formed. A specific feature of the storm under study is the second lowering of Dst in the recovery phase. The hysteresis pattern reflects this specific storm dynamics, forming two hysteresis loops in response to the two Dst drops.

Hysteresis phenomena in the response of geomagnetic activity and cosmic ray parameters to variations in the interplanetary medium during a magnetic storm

The dynamics of the intensity of cosmic rays is known to be different on the ascending and descending branches of the 11-year solar cycle, i.e., hysteresis phenomena are observed. Recently, it has been obtained that at shorter intervals on the scale of magnetic storms there are also signs of hysteresis in dependences of cosmic ray cutoff rigidities R (geomagnetic thresholds) on heliosphere and geosphere parameters. R is the rigidity below which a particle flux is cut off due to geomagnetic shielding. In this paper, we have analyzed the dependence of the geomagnetic storm index Dst and the variation of the ΔR thresholds on interplanetary magnetic field (IMF) and solar wind (SW) parameters during the two-step magnetic storm on September 7–8, 2017. We have found hysteresis phenomena in the following paired series: (1) dependences of Dst on SW and IMF parameters, and (2) dependences of ΔR on SW and IMF parameters. We have established that the dependence curves in the storm descending phase (main phase) and ascending phase (recovery phase) do not coincide — hysteresis loops are formed. A specific feature of the storm under study is the second lowering of Dst in the recovery phase. The hysteresis pattern reflects this specific storm dynamics, forming two hysteresis loops in response to the two Dst drops.

Implications of Solar Wind Disturbances on Forbush Decrease

This study investigated the role of solar wind disturbances on variations in cosmic ray intensity. To conduct the study, use was made of the data on cosmic rays from the SOPO, CLMX, and MOSC neutron stations, as well as solar wind speed data from 2000 to 2005. The source Forbush decrease (FD) dates were generated from onset journal publications, specifically the FD list of Dumbovi ́c et al., (2011). The manual method of FD selection was used to identify FDs. The FD dates, computed magnitudes, and solar wind speed data were recorded and presented. From the study, FDs were generated, some of which were of the same date as those in the source table, while others were not observed in the source table. FDs not observed in the source table were generated and catalogued by this research. It was also observed that the magnitude of FDs generally depends on the coordinates of the observing neutron stations. A strong correlation with a value of cc = 0.93 was observed between FDs of SOPO and MOSC stations, followed by FDs of CLMX and MOSC stations of value cc = 0.89, and lastly, FDs of SOPO and CLMX stations of value cc = 0.74. This implies that observed FDs from neutron stations are coordinate-dependent. The correlation between FD magnitudes and solar activities shows that solar wind had a high and significant correlation with FD magnitude to the tune of cc = 0.54. Based on the findings, the study concludes that solar wind disturbances play a crucial role in causing a sharp decrease in the intensity of cosmic rays known as Forbush decrease.

Unusual Forbush Decreases and Geomagnetic Storms on 24 March, 2024 and 11 May, 2024

As the current solar cycle 25 progresses and moves towards solar maxima, solar activity is increasing and extreme space weather events are taking place. Two severe geomagnetic storms accompanied by two large Forbush decreases in galactic cosmic ray intensity were recorded in March and May, 2024. More precisely, on 24 March 2024, a G4 (according to the NOAA Space Weather Scale for Geomagnetic Storms) geomagnetic storm was registered, with the corresponding geomagnetic indices Kp and Dst equal to 8 and −130 nT, respectively. On the same day, the majority of ground-based neutron monitor stations recorded an unusual Forbush decrease. This event stands out from a typical Forbush decrease because of its high amplitude decrease phase and rapid recovery phase, i.e., 15% decrease and an extremely rapid recovery of 10% within 1.5 h, as recorded at the Oulu neutron monitor station. Furthermore, on 10–13 May 2024, an unusual G5 geomagnetic storm (geomagnetic indices Kp = 9 and Dst = −412 nT) was registered (the last G5 storm had been observed in 2003). In addition, the polar neutron monitor stations recorded a Ground Level Enhancement (GLE74) during the recovery phase of a large Forbush decrease of 15%, which started on 10 May 2024. In this study, a detailed analysis of these two severe events in regard to the accompanying solar activity, interplanetary conditions and solar energetic particle events is provided. Moreover, the results of the NKUA “GLE Alert++ system”, the NKUA/IZMIRAN “FD Precursory Signals” method and the NKUA “ap Prediction tool” concerning these events are presented.

The Study of the Association between the Solar Wind Parameter and Cosmic Ray Intensity to a Severe Geomagnetic Storm (-350 < Dst ≤ -200 nT) during Solar Cycles 24 and 25

The Study of the Association between the Solar Wind Parameter and Cosmic Ray Intensity to a Severe Geomagnetic Storm (-350 < Dst ≤ -200 nT) during Solar Cycles 24 and 25

The Algorithm of the Two Neutron Monitors for the Analysis of the Rigidity Spectrum Variations of Galactic Cosmic Ray Intensity Flux in Solar Cycle 24

The method of the two neutron monitors was used to analyze the parameters of the rigidity spectrum variations (RSV) of galactic cosmic ray intensity (GCR) flux in solar cycle 24 based on the data from the global network of neutron monitors. This method is an alternative to the least squares method when there are few monitors working stably in a given period, and their use in the least squares method is impossible. Analyses of the changes in exponent γ in the RSV of GCR flux from 2009 to 2019 were studied. The soft RSV (γ = 1.2–1.3) of the GCR flux around the maximum epoch and the hard RSV (γ = 0.6–0.9) around the minimum epoch of solar activity (SA) is the general feature of GCR modulation in the GeV energy scale (5, 50), to which neutron monitors were found to correspond. Therefore, various values of the RSV γ in the considered period show that during the decrease and increase period of SA, the essential changes in the large-scale structure of the heliospheric magnetic field (HMF) fluctuations/turbulence take place. The exponent γ of the RSV of the GCR flux can be considered a significant parameter to investigate the long-period changes in the GCR flux.

Extracting the True Cosmic-ray Relative Intensity Sky Map from Normalized Relative Intensity Data Measured by Air Shower Experiments

We use data from the Tibet AS γ experiment for 4 teraelectronvolt (TeV) cosmic rays as an example to perform a nonlinear interstellar distribution model regression according to the way the observed anisotropy is typically presented, from which we extract normalization factors that allow us to obtain a true relative intensity sky map from the measurements. By using various test statistics, we show that the nonlinear fit significantly outperforms the direct linear fit in its ability to model cosmic-ray anisotropy. The procedure also allows us to produce normalization constants that can trace minute latitudinal variations of experimental response to cosmic-ray intensity. Applying the correction of the latitudinal response function to the Tibet ASγ data, we generate a sky map of true relative intensity. As a result, we observe that the measured and corrected sky maps show significant differences in intensity and angular spectral power. Our full anisotropy sky map of true relative intensity contradicts the assumption that the latitudinal variation in longitudinally averaged flux is negligible. The result further confirms that TeV cosmic-ray anisotropy is dominated by a dipole (ℓ = 1) aligned with the interstellar magnetic field’s direction. Our results also confirm the existence of much weaker middle-scale interstellar anisotropy between ℓ = 2 and ℓ = 13.

Investigating the influence of cosmic ray and solar activities on atmospheric weather dynamics within the equatorial electrojet region (Nigeria)

The association between atmospheric weather conditions along the equatorial electrojets and complexity in emergence flux in solar magnetic activity involved in the weather fluctuation processes may be substantial such that it affect the weather conditions particularly in the earth’s equatorial regions. In this study, we have analysed relevant parameters influencing the atmospheric weather conditions across the major cities and zones in Nigeria with solar magnetic activity and cosmic ray intensity covering five solar cycles from 19 to 24. Our investigation was principally based on solar magnetic activity which include solar parameters; flare index, cosmic ray, and atmospheric weather parameters including temperature, relative humidity, and precipitation. We utilized the cross-correlation and wavelet coherence techniques. The study found that the Northern region (Guinea and Sahel Savannah) located along 8.92 to 13.70 degrees latitudes and the Southern regions (Coastal and Derived) located within latitudes 4.5 and 8.9 degree latitudes responded differently to various atmospheric and solar parameters. The temperature and relative humidity in the northern parts is comparatively higher than in the southern region, while the southern region experienced higher precipitation. The flare index and cosmic ray exhibit different patterns as well negatively correlated. The relationships between the precipitations and relative humidity across Nigeria show a distinct behaviour which could be attributed to concentrations of ions influencing cloud properties across the country. There are strong and positive correlations between the two indices, with high coefficients specifically during the examined solar cycles. The difference in responses between Southern and Northern Nigeria could be attributed to mechanism driving the atmospheric weather through the Earth latitudinal couplings.

The Forbush decrease observed by the SEVAN particle detector network in the 25th solar activity cycle

The temporal variations of cosmic-ray intensity, measured by ground-based detectors at various latitudes, longitudes, and altitudes, are related to the geophysical and solar phenomena. The latter are interplanetary coronal mass ejections and fast solar wind from coronal holes, which cause interplanetary magnetic field (IMF) abrupt variations near Earth. Interacting with the magnetosphere, they cause worldwide sudden decreases (Forbush decreases, FDs) of intensity followed by gradual recovery. The amplitude of the flux depletion depends on the type and energy of the registered particle, which in turn depends on geographical coordinates and the detector's energy threshold and selective power. SEVAN particle detector network with nodes in Europe and Armenia selects three types of particles that demonstrate coherent depletion and recovery and correspond to different energy galactic protons interacting with disturbed magnetospheric plasmas.On November 3–4, 2021, an interplanetary coronal mass injection (ICME) hit the magnetosphere, sparking a strong G3-class geomagnetic storm and auroras as far south as California and New Mexico. All detectors of the SEVAN network have registered an (FD) of ≈5% depletion in a 1-min time series of count rates. Approaching the maximum solar activity cycle, large variations of the particle flux intensity were registered on February 27, March 23, 2023, and March 24, 2024.In this work, we present measurements of these FDs performed on mountain altitudes on Aragats (Armenia), Lomnicky Stit (Slovakia), Mileshovka (Czechia), and at sea level DESY (Hamburg, Germany). We compared FD measurements made by SEVAN detectors and neutron monitors located on Aragats and Lomnicky Stit and made a correlation analysis of FD registration at different locations.

Cosmic ray intensity for minimum phase of 24 solar cycle

Cosmic ray intensity for minimum phase of 24 solar cycle

Dynamics of the energy spectrum of solar-diural variations in the intensity of cosmic rays in 22–25 cycles of solar activity

Periodic 24-hour variations in the intensity of galactic cosmic rays, continuously observed by ground-based detectors, are called solar diurnal variations. The nature of these variations lies in the existence in the interplanetary medium of an anisotropic spatial distribution of galactic cosmic rays, which arises during the interaction of these particles with the heliosphere. It is believed that the physical factors responsible for the observed anisotropy of galactic cosmic rays are the processes of convection, diffusion and their drift. The combination of these factors determines the main parameters of solar diurnal variations, such as amplitude, phase and energy spectrum. To study the energy spectrum of solar-diurnal variations, we used measurement data from muon telescopes of the Yakutsk Cosmic Ray Spectrograph after A.I. Kuzmin and Nagoya stations (Japan). The research approach is based on the idea of the crossed telescope method, originally designed to take into account the temperature effect. Due to the difference in the receiving characteristics of the crossed northern and southern directions of the above muon telescopes, the intensity variations recorded by them are sensitive to changes in the energy spectrum of solar-diurnal variations. This property was used to assess the dynamics of the energy spectrum of solar-diurnal variations for 22–25 cycles of solar activity. Analysis of the data obtained showed that in the last minimum of solar activity in 2018-2021. An anomalously early phase of solar-diurnal variations was observed. To study this phenomenon, we simulated the ratio and phase difference of a pair of northern and southern crossed directions for both muon telescopes for different types and values of the energy spectrum of solar-diurnal variations. A comparison of model calculations and observational data has made it possible to establish that during periods of minimum solar activity in the positive polarity of the general magnetic field of the Sun, a significant softening of the energy spectrum of solar-diurnal variations is observed. The reasons for the discovered phenomenon are discussed.