Search Results (94)

The Forbush effects (FEs) in cosmic rays associated with interplanetary disturbances caused by the disappearance of solar filaments (DSFs) outside active regions (ARs) are considered. In total, 481 FEs were detected for 1995–2023 using the database of Forbush Effects and Interplanetary Disturbances (FEID). The behavior of the cosmic ray density was calculated using the Global Survey Method (GSM). The distributions of the FE numbers depending on their duration and magnitude, as well as on the characteristics of the interplanetary and near-Earth medium, were obtained. It is found that the average duration of such FEs (33.4 ± 0.5 h) is almost the same as for events associated with CMEs from ARs, but the average magnitude is much smaller (0.83 ± 0.03%). It is also shown that coronal mass ejections (CMEs) caused by DSFs are often low-speed interplanetary disturbances (with an average maximum SW speed of 423.2 ± 3.5 km/s), the velocities of which are close to the speed of the background solar wind (SW). During FEs associated with CMEs after DSFs outside ARs, on average, unsettled geomagnetic activity is observed. Magnetic storms were recorded only in 19% of events. Lower values of FE magnitude and geomagnetic activity are associated with weakened magnetic fields and low speeds of such interplanetary disturbances. Full article

The investigation of the two phenomena of Space Weather, i.e., Forbush decreases in the cosmic ray intensity and geomagnetic storms, is a highly developing field of modern scientific research, since these two phenomena can affect not only technological activities, e.g., electronics, telecommunications, navigations, etc., but also, as evidenced by recent studies, human life as well. This study analyses data of heart rate of volunteers of the Polyclinico Tor Vergata, Rome, Italy, with regard to geomagnetic field’s variations (i.e., geomagnetic storms) and cosmic ray intensity’s fluctuations (i.e., Forbush decreases). Data concerning geomagnetic (Dst- and Ap-index values) and cosmic ray activity derived from the Rome Cosmic Ray Station (Studio Variazioni Intensità Raggi Cosmici: S.V.I.R.CO.) were analyzed. The analysis expands from 24 April 2003 to 12 May 2004 and includes October–November 2003, which was a period of severe activity, when extreme events were recorded (i.e., the Great Halloween Solar Storms and the super storm on November 2003). The variations in heart rate were studied using the ANalysis Of Variance—ANOVA (for various levels of activity of the geophysical environment) and the superimposed epochs methods (during an event’s temporal evolution). Results revealed that high geomagnetic (defined by Dst-index values) and cosmic rays activity is related to heart rate increase. Moreover, the most significant heart rate variations are observed two days before until two days after the development of an event (either geomagnetic storm or a variation in the cosmic ray intensity). The results are in agreement with conclusions presented in the international scientific literature. Full article

Millimeter-waveband spectra of Venus from both the James Clerk Maxwell Telescope (JCMT) and the Atacama Large Millimeter/submillimeter Array (ALMA) seem to indicate there may be evidence (signal-to-noise ratio of about 15σ) of a phosphine absorption-line profile against the thermal background from deeper, hotter layers of the atmosphere. Phosphine is an important biomarker; e.g., the trace of phosphine in the Earth’s atmosphere is unequivocally associated with anthropogenic activity and microbial life (which produces this highly reducing gas even in an overall oxidizing environment). Motivated by the JCMT and ALMA tantalizing observations, we reexamine whether Venus could accommodate Earthly life. More concretely, we hypothesize that the microorganisms populating the Venusian atmosphere are not free floating but confined to the liquid environment inside cloud aerosols or droplets. Armed with this hypothesis, we generalize a study of airborne germ transmission to constrain the maximum size of droplets that could be floating in the Venusian atmosphere by demanding that their Stokes fallout times to reach moderately high temperatures are pronouncedly larger than the microbe’s replication time. We also comment on the effect of cosmic ray showers on the evolution of aerial microbial life. Full article

The origin and acceleration of high-energy particles, constituting cosmic rays, is likely to remain an important topic in modern astrophysics. Among the two categories galactic and solar cosmic rays, the latter are much less investigated. The primary source of solar cosmic ray particles are impulsive explosions of the magnetized plasma, known as solar flares and coronal mass ejections. These particles, however, are characterized by relatively low energies compared to their galactic counterparts. In this work, we explore the resonance wave–wave (RWW) interaction between the polarized electromagnetic radiation emitted by the solar active regions and the quantum waves associated with high-energy, relativistic electrons generated during solar flares. Mathematically, the RWW interaction problem boils down to analyzing a Klein–Gordon Equation (spinless electrons) embedded in the electromagnetic field. We find that RWW could accelerate the relativistic electrons to enormous energies even comparable to energies in the galactic cosmic rays. Full article

Jets emanating from active galactic nuclei (AGNs) represent some of the most formidable particle accelerators in the universe, thereby emerging as viable candidates responsible for the detection of ultra-high-energy cosmic rays (UHECRs). If AGN jets indeed serve as origins of UHECRs, then the diffuse flux of these cosmic rays would be dependent on the power and duty cycle of these jets, which are inherently connected to the nature of black hole accretion flows. In this article, we present our cosmological semi-analytic framework, JET (Jets from Early Times), designed to trace the evolution of jetted AGN populations. This framework serves as a valuable tool for predictive analyses of cosmic ray energy density and, potentially, neutrino energy density. By using JET, we model the formation and evolution of galaxies and supermassive black holes (SMBHs) from $z=20$ to $z=1$, incorporating jet formation and feedback mechanisms and distinguishing between various accretion states determined by the SMBH Eddington ratios. The implications of different SMBH growth models on predicting cosmic ray flux are investigated. We provide illustrative examples demonstrating how the associated diffuse UHECR fluxes at the source may vary in relation to the jet production efficiencies and the selected SMBH growth model, linking cosmological models of SMBH growth with astroparticle backgrounds. Full article

Particle radiation on the Moon is influenced by a combination of galactic cosmic rays, high-energy solar particles, and secondary particles interacting on the lunar surface. When China’s Chang’e-7 lander lands at the Moon’s South Pole, it will encounter this complex radiation environment. Therefore, a payload detection technology was developed to comprehensively measure the energy spectrum, direction, and radiation effects of medium- and high-energy charged particles on the lunar surface. During the ground development phase, the payload performance was tested against the design specifications. The verification results indicate that the energy measurement ranges are 30 keV to 300 MeV for protons, 30 keV to 12 MeV for electrons, and 8 to 400 MeV/n for heavy ions. The energy resolution is 10.81% for 200 keV electrons of the system facing the lunar surface; the dose rate measurement sensitivity is 7.48 µrad(Si)/h; and the LET spectrum measurement range extends from 0.001 to 37.014 MeV/(mg/cm²). These comprehensive measurements are instrumental in establishing a lunar surface particle radiation model, enhancing the understanding of the lunar radiation environment, and supporting human lunar activities. Full article

A novel tool utilizing machine learning techniques was designed to forecast ap index values for the next three consecutive days (24 values). The tool employs time series data from the 3 h ap index of solar cycles 23 and 24 to train the Long Short-Term Memory (LSTM) model, predicting ap index values for the next 72 h at three-hour intervals. During periods of quiet geomagnetic activity, the LSTM model’s performance is sufficient to yield favorable outcomes. Nevertheless, during geomagnetically disturbed conditions, such as geomagnetic storms of different levels, the model needs to be adapted in order to provide accurate ap index results. In particular, when coronal mass ejections occur, the ap Prediction tool is modulated by inserting predominant features of coronal mass ejections such as the date of the event, the estimated time of arrival and the linear speed. In the present work, this tool is described thoroughly; moreover, results for G2 and G3 geomagnetic storms are presented. Full article

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. Full article

Ultra-high-energy cosmic rays (UHECRs) are extremely rare energetic particles of ordinary matter in the Universe, traveling astronomical distances before reaching the Earth’s atmosphere. When primary cosmic rays interact with atmospheric nuclei, cascading extensive air showers (EASs) of secondary elementary particles are developed. Radio detectors have proven to be a reliable method for reconstructing the properties of EASs, such as the shower’s axis, its energy, and its maximum (${\mathrm{X}}_{\max }$). This aids in understanding fundamental astrophysical phenomena, like active galactic nuclei and gamma-ray bursts. Concurrently, data science has become indispensable in UHECR research. By applying statistical, computational, and deep learning methods to both real-world and simulated radio data, researchers can extract insights and make predictions. We introduce a convolutional neural network (CNN) architecture designed to classify simulated air shower events as either being generated by protons or by iron nuclei. The classification achieved a stable test error of 10%, with Accuracy and ${\mathrm{F}}_1$ scores of 0.9 and an MCC of 0.8. These metrics indicate strong prediction capability for UHECR’s nuclear composition, based on data that can be gathered by detectors at the world’s largest cosmic rays experiment on Earth, the Pierre Auger Observatory, which includes radio antennas, water Cherenkov detectors, and fluorescence telescopes. Full article

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. Full article

Any Geiger counter can be used as an effective cosmic ray detector on its own. In fact, it is known that even in the absence of a radioactive source, the instrument detects what is known as background radiation, which consists of various types of ionizing particles present in the environment. Remarkably, it is estimated that up to 15% of this background radiation is attributable to cosmic rays, high-energy particles originating from outer space. The remaining radiation detected by the Geiger counter originates from terrestrial sources, such as natural radioactivity in the ground and in the air. The main goal of this project is to build a muon detector for scientific and educational purposes using two commercial DIY Geiger counter kits and just a few additional components. To identify cosmic radiation from terrestrial radiation and improve the accuracy of cosmic ray measurements, the use of a coincident circuit is essential. This coincident circuit was introduced in cosmic ray physics by Walther Bothe and Bruno Rossi in the early 1930s and allows for the detection of a subatomic particle passing through two or more sensors, thereby reducing false positives and enhancing the reliability of cosmic ray detection. The following idea is an alternative replica of our AMD5 detectors, instruments that we have been using for years to teach and perform scientific experiments in the cosmic ray field under the umbrella of the ADA project (2023 Particles, Arcani et al.). The resulting device, named AMD5ALI, offers a reliable and inexpensive solution for the same goal, making it a valuable tool for both educational purposes and scientific surveys. Practical applications range from cosmic ray physics to radioactivity, including the relationship between cosmic ray flux and meteorology, the zenithal effect, the Regener–Pfotzer curve in the atmosphere, and the anti-correlation of cosmic particle intensity with solar activity. Full article

This article covers the overall design hardware choices for the prototyping activities for the DUCK (Detector system of Unusual Cosmic ray casKades). The primary goal of the DUCK system is to verify the existence of the unusual cosmic events reported by other collaborations and to look at the possibilities of adding innovations to the EAS (Extensive Atmospheric Shower) analysis methods of the EAS disk measurements at the observation level. Additionally, design and construction of the system provide educational experience to the students involved in the project and are developing the research capabilities of the university campus. The prototyping process has helped to choose between various design solutions in the process of optimizing of the individual detector components. Full article

Large-scale cosmic filaments connect galaxies, clusters, and voids. They are permeated by magnetic fields with a variety of topologies. Cosmic rays with energies up to ${10}^{20}\mathrm{eV}$ can be produced in astrophysical environments associated with star-formation and AGN activities. The fate of these cosmic rays in filaments, which cannot be directly observed on Earth, are rarely studied. We investigate the high-energy processes associated with energetic particles (cosmic rays) in filaments, adopting an ecological approach that includes galaxies, clusters/superclusters, and voids as key cosmological structures in the filament ecosystem. We derive the phenomenology for modelling interfaces between filaments and these structures, and investigate how the transfer and fate of energetic cosmic ray protons are affected by the magnetism of the interfaces. We consider different magnetic field configurations in filaments and assess the implications for cosmic ray confinement and survival against hadronic pion-producing and photo-pair interactions. Our analysis shows that the fate of the particles depends on the location of their origin within a filament ecosystem, and that filaments act as ‘highways’, channelling cosmic rays between galaxies, galaxy clusters, and superclusters. Filaments can also operate as cosmic ‘fly paper’, capturing cosmic ray protons with energies up to ${10}^{18}\mathrm{eV}$ from cosmic voids. Our analysis predicts the presence of a population of ∼${10}^{12}$–${10}^{16}\mathrm{eV}$ cosmic ray protons in filaments and voids accumulated continually over cosmic time. These protons do not suffer significant energy losses through photo-pair or pion production, nor can they be cooled efficiently. Instead, they form a cosmic ray fossil record of the power generation history of the Universe. Full article

In orbital and ground-based experiments, it has been demonstrated that ionizing radiation (IR) can stimulate the locomotor and exploratory activity of rodents, but the underlying mechanism of this phenomenon remains undisclosed. Here, we studied the effect of combined IR (0.4 Gy γ-rays and 0.14 Gy carbon-12 nuclei) on the locomotor and exploratory activity of rats, and assessed the sensorimotor cortex volume by magnetic resonance imaging-based morphometry at 1 week and 7 months post-irradiation. The sensorimotor cortex tissues were processed to determine whether the behavioral and morphologic effects were associated with changes in neurotrophin content. The irradiated rats were characterized by increased locomotor and exploratory activity, as well as novelty-seeking behavior, at 3 days post-irradiation. At the same time, only unirradiated rats experienced a significant decrease in the sensorimotor cortex volume at 7 months. While there were no significant differences at 1 week, at 7 months, the irradiated rats were characterized by higher neurotrophin-3 and neurotrophin-4 content in the sensorimotor cortex. Thus, IR prevents the age-associated decrease in the sensorimotor cortex volume, which is associated with neurotrophic and neurogenic changes. Meanwhile, IR-induced increases in locomotor activity may be the cause of the observed changes. Full article

The effects of solar activity and the accompanying space weather events on human pathological conditions, physiological parameters and other psycho-physiological disturbances have been analyzed in numerous recent investigations. Moreover, many of these studies have particularly focused on the different physical reactions humans have, according to their sex, during variations in the physical environment. In the framework of the above, this work analyses heart rate data obtained from volunteers (687 men and 534 women) from three different regions (Athens, Piraeus and Heraklion) of Greece in relation to the geophysical activity and variations of environmental factors. Dst index and Ap index data, along with cosmic ray intensity data derived from the Athens Neutron Monitor Station (A.Ne.Mo.S.), were used. The study expands from April 2011 to January 2018, covering solar cycle 24. The ANalysis Of Variance (ANOVA) and the superimposed epochs methods were used in order to examine heart rate variations depending on sex. Results revealed that women tend to be more sensitive to physical environmental changes. Statistically significant results are related to the geomagnetic activity but were not obtained for cosmic ray variations. Full article