In this study, daily cosmic ray data obtained with the KACST muon detector for the period 2002-2012 were analyzed for quasiperiodicities. Power-spectrum analysis was carried out and several periodicities were identified. The results reveal several periodicities at different frequency scales: 817 days (similar to 2.19 years), 617 days (similar to 1.7 years), 475 days (similar to 1.3 years), 421 days (1.15 years), 290 days (similar to 0.8 years), 227 days (similar to 0.62 years), 185 days (similar to 0.52 years), 153 days, 135 days, 120 days, 93 days, 84 days, 73 days, 65 days, 53-45 days, 38 days, 31 days, 25-27 days, 21 days and 13 days. The obtained periodicities are in an agreement with those previously reported by several investigators. The identified periodicities have strong relevance to solar activity parameters such as variations in the interplanetary magnetic field. In comparison, the data from two neutron monitors (NMs), Lomnicky stit and Oulu NMs, for the same period were used and their power spectra were correspondingly obtained. Similarities and differences in the position of the cosmic-ray peaks measured by the KACST muon detector and by the two NMs have been presented and discussed. While most of the periodicities reported by the muon detector are also found in the NM data, the similar to 1.7-yr variation is not found. Instead, a shift of 1.6-1.8 years in the NM data is observed which may be due to the limited epoch considered in this study. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved.

In this study downward longwave (LW) atmospheric radiation data for the period of 2014-2020 were used to search for short-term periodicities using fast Fourier transform (FFT). Several local peaks in the power spectrum density were found and established. The time series exhibits a series of significant peaks (exceeding the 95% confidence limit), such as at 273 days, 227 days, 200 days, 178 days, 157 days, 110 days, 120 days, 87 days, 73 days, 53-56 days, 35-30 days, 25-27 days, 21 days, 13 days, and 9-10 days. Moreover, cosmic ray data from KACST muon detector and the Oulu neutron monitor, as well as the data for the solar radio flux at 10.7 cm (F10.7 cm), Dst index, and solar wind speed for the same period as the LW data, were used to look for common cyclic variations and periodicities matching those found in the LW radiation. This was done to investigate the possible effect of the solar activity parameters on LW radiation. Several common periodicities were observed in the spectra of all the variables considered, such as 227 days, 154-157 days, 25-27 days, and 21 days. Some of the periodicities found in the LW radiation spectrum can be attributed to the modulation of the cosmic ray intensity by solar activity. Others are attributed to the disturbances in the interplanetary magnetic field. Based on the spectral results, we suggest that the solar signals may directly or indirectly affect the variations of the downward longwave radiation, which in turn may affect climate change. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved.

After decades of observations of solar energetic particles from space-based observatories, relevant questions on particle injection, transport, and acceleration remain open. To address these scientific topics, accurate measurements of the particle properties in the inner heliosphere are needed. In this paper we describe the Energetic Particle Detector (EPD), an instrument suite that is part of the scientific payload aboard the Solar Orbiter mission. Solar Orbiter will approach the Sun as close as 0.28 au and will provide extra-ecliptic measurements beyond ∼30° heliographic latitude during the later stages of the mission. The EPD will measure electrons, protons, and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of megaelectronvolts/nucleons. For this purpose, EPD is composed of four units: the SupraThermal Electrons and Protons (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) plus the Instrument Control Unit that serves as power and data interface with the spacecraft. The low-energy population of electrons and ions will be covered by STEP and EPT, while the high-energy range will be measured by HET. Elemental and isotopic ion composition measurements will be performed by SIS and HET, allowing full particle identification from a few kiloelectronvolts up to several hundreds of megaelectronvolts/nucleons. Angular information will be provided by the separate look directions from different sensor heads, on the ecliptic plane along the Parker spiral magnetic field both forward and backwards, and out of the ecliptic plane observing both northern and southern hemispheres. The unparalleled observations of EPD will provide key insights into long-open and crucial questions about the processes that govern energetic particles in the inner heliosphere.

After decades of observations of solar energetic particles from space-based observatories, relevant questions on particle injection, transport, and acceleration remain open. To address these scientific topics, accurate measurements of the particle properties in the inner heliosphere are needed. In this paper we describe the Energetic Particle Detector (EPD), an instrument suite that is part of the scientific payload aboard the Solar Orbiter mission. Solar Orbiter will approach the Sun as close as 0.28 au and will provide extra-ecliptic measurements beyond ∼30◦ heliographic latitude during the later stages of the mission. The EPD will measure electrons, protons, and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of megaelectronvolts/nucleons. For this purpose, EPD is composed of four units: the SupraThermal Electrons and Protons (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the HighEnergy Telescope (HET) plus the Instrument Control Unit that serves as power and data interface with the spacecraft. The low-energy population of electrons and ions will be covered by STEP and EPT, while the high-energy range will be measured by HET. Elemental and isotopic ion composition measurements will be performed by SIS and HET, allowing full particle identification from a few kiloelectronvolts up to several hundreds of megaelectronvolts/nucleons. Angular information will be provided by the separate look directions from different sensor heads, on the ecliptic plane along the Parker spiral magnetic field both forward and backwards, and out of the ecliptic plane observing both northern and southern hemispheres. The unparalleled observations of EPD will provide key insights into long-open and crucial questions about the processes that govern energetic particles in the inner heliosphere.

Beam-plasma interaction effects are studied during the active space experiment with electron and Xe-ion beam injections in an ionospheric plasma. Permanent 40-kHz-modulated electron beam injection occurs simultaneously with a xenon-ion beam injected by the Hall-type plasma thruster operating in a square-pulse mode (100/50 s for a job/pause duration). The unusual behavior of the background charged particle fluxes and wave activity stimulated during the beam-plasma interaction have been registered by the scientific instruments onboard Intercosmos-25 station (IK-25) and Magion-3 subsatellite. The longitudinal and electromagnetic wave instabilities and their mutual relationship are considered in order to explain the observed effects. The excitation of electrostatic waves by the electron injection has been considered for different resonance conditions near the linear stability boundary. Beam-driven electromagnetic instability is responsible for the backward-propagating whistler waves excited via cyclotron resonance. Competition of these two beam instabilities is one of the subjects of the present study.

With the goal of understanding the initiations of solar energetic particle (SEP) (MeV) and ground-level enhancement (GLE) (GeV) particles, we have studied relative timings at. approximately. the Sun between temporal evolutions of the particles and some electromagnetic radiation components representing flares and shocks. Results show that GLE onsets appear after flare prompt onsets and m-type II onsets, while the GLE-associated SEP onsets appear before the flare prompt onsets and m-type II onsets, thus specifying that the GLE-associated SEPs originate over the flare initial phases and get accelerated intensively over the flare prompt phases associated with coronal shocks. The flare initial phase is found always earlier than the coronal mass ejection (CME) initial phase, further justifying that the MeV particles are initiated particularly by the flare initial phases and are accelerated to GeV energetic by flare prompt phases associated with the coronal shocks. On the contrary, most of the non-GLE-SEP onsets appear well after the flare prompt onsets and m-type II onsets, demonstrating that the non-GLE-SEPs mostly generate over the most intense part of the flare rise phases associated with the coronal shocks. In another development, the relative timings of flare prompt onset and peak times to the m-and DH-type II onsets show that usually the m-type II bursts commence before the flare peaks and DH-type II bursts commence after the flare peaks, signifying that the coronal shocks manifested in m-type II bursts operate over the flare main acceleration phases, while the coronal shocks manifested in DH-type II bursts operate over the flare decay and/or CME propagation phases, thereby suggesting that the evolution of the particles accelerated at the flare main acceleration phases can be prolonged by the shocks associated with the CME propagation phases.

In this study, aerosol optical depth (AOD870 nm) data, for the period between 1999 to 2015 obtained from the solar village AERONET site (central Saudi Arabia); have been correlated with cosmic ray (CR) data from Oulu neutron monitor. Positive and significant correlation between the two variables has been found. Moreover, power spectral analyses using the Fourier Transform (FT) technique have been carried out to investigate the periodicities in both the CR and AOD time series. Several common periodicities between the two variables have been recognized indicating possible mutual relation between variations of aerosols and of CR intensity observed on the ground.

Non-recurrent short-term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n−1 were observed between 2016 February 18 and 2017 July 3 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 106 km from Earth. The energy dependence of three Forbush decreases is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n−1 shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence are also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration <2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing causes the majority of the depressions.

We present an overview of the ground-level enhancement (GLE 72) of the cosmic-ray intensity associated with the recent powerful solar flare SOL2017-09-10 (X-ray class X8.9) based on the available neutron monitor (NM) network observations and on data from the satellite GOES 13. The maximum increase at high-latitude near-sea-level NMs was ${\approx }\,6\,\mbox{--}\,7\%$ (2-min averages), greater with better time resolution. A scatter plot of the maximum increase of the GLE versus solar energetic-particle (SEP, proton) flux ${>}\,100~\mbox{MeV}$ shows one of the softest spectra among GLEs relative to the SEP fluxes. However, at two high-mountain middle-latitude NMs the increase was ${\approx }\,1\%$ , indicating the possibility of proton acceleration up to 6 GeV. Among the analyzed NM data the Fort Smith (FSMT) NM shows the earliest and the rather high increase between 16:06 – 16:08 UT. This indicates an anisotropy in the first phase of the GLE event. We calculate the acceptance cones of several NM stations at high latitudes and contours of pitch angles corresponding to the interplanetary magnetic field (IMF). When employing the available data we find that pion-decay $\gamma $ -ray emission onset is in accordance with the time of the main flare energy release. The observed time interval of the impulsive burst of ${>}\,100~\mbox{MeV}$ $\gamma $ -ray emission probably corresponds to the time of a turbulent current sheet creation. The observed location of the impulsive burst pion-decay emission source coincides with the active region and the cusp-shaped structure. It seems that models assuming sub-relativistic proton production beginning in a turbulent reconnecting current sheet are consistent with the observations. If these particles were released from the Sun during a type III emission with a pion-decay maximum at $16{:}00{:}30\pm 30~\mbox{UT}$ , we get a plausible path length equal to $1.5\pm 0.3~\mbox{AU}$ of the particles responsible for the onset of the SEP event and GLE. The time lag of GLE 72 corresponds to the most probable interval of the time difference between GLE onset and main flare energy release. Although other scenarios are not excluded we attribute the protons that create the pion-decay emission and the protons responsible for the GLE and SEP event onset to a general population of accelerated particles.

The JEM-EUSO (Joint Experiment Missions for the Extreme Universe Space Observatory) program aims at developing Ultra-Violet (UV) fluorescence telescopes for efficient detections of Extensive Air Showers (EASs) induced by Ultra-High Energy Cosmic Rays (UHECRs) from satellite orbit. In order to demonstrate key technologies for JEM-EUSO, we constructed the EUSO-Balloon instrument that consists of a similar to 1 m(2) refractive telescope with two Fresnel lenses and an array of multi-anode photo-multiplier tubes at the focus. Distinguishing it from the former balloon-borne experiments, EUSO-Balloon has the capabilities of single photon counting with a gate time of 2.3 mu s and of imaging with a total of 2304 pixels. As a pathfinder mission, the instrument was launched for an 8 h stratospheric flight on a moonless night in August 2014 over Timmins, Canada. In this work, we analyze the count rates over similar to 2.5 h intervals. The measurements are of diffuse light, e.g. of airglow emission, back-scattered from the Earth's atmosphere as well as artificial light sources. Count rates from such diffuse light are a background for EAS detections in future missions and relevant factor for the analysis of EAS events. We also obtain the geographical distribution of the count rates over a similar to 780 km(2) area along the balloon trajectory. In developed areas, light sources such as the airport, mines, and factories are clearly identified. This demonstrates the correct location of signals that will be required for the EAS analysis in future missions. Although a precise determination of count rates is relevant for the existing instruments, the absolute intensity of diffuse light is deduced for the limited conditions by assuming spectra models and considering simulations of the instrument response. Based on the study of diffuse light by EUSO-Balloon, we also discuss the implications for coming pathfinders and future space-based UHECR observation missions. (C) 2018 Published by Elsevier B.V.

High energy cosmic ray (CR) particles are capable of ionizing the Earth's atmosphere, which lead to changes in the atmospheric properties that affect its physical and chemical characteristics. One of the most important results of the interactions between the CR particles and the atmospheric molecules is the formation of aerosol and its subsequent condensation processes. In this study, the relationship between the time series of the aerosol optical properties; namely the aerosol optical depth (AOD) and Angstrom exponent (alpha), and the CR muons and neutrons was investigated and established. AOD and alpha monthly mean data were obtained from the AERONET site located in central Saudi Arabia (24.91 degrees N, 46.41 degrees E, 760 m), for the period of 1999-2015 and the corresponding CR data from Oulu neutron monitor were used for these investigations. Cosmic ray data for the period of 2002-2012 obtained from KACST muon detector were also used in this study. Correlation analyses between the time series of CR data (measured by NM and muon detector) and the aerosol optical properties were carried out and showed significant correlations between these variables. While AOD was positively correlated with the CR data, a showed the opposite. Power spectral analyses using Fast Fourier transform (FFT) were applied on the monthly mean time series of the considered variables to search for possible common periodicities between them. The results showed that there is similarity in position of at least one local peak in PSD (near 1.6-1.7 years) in a and in CR. The correlation and power spectral analyses indicate possible mutual relation between variations of aerosols observed at a particular site and CR intensity observed on the ground.

Compilation of papers presented by the JEM-EUSO Collaboration at the 36th International Cosmic Ray Conference (ICRC), held July 24 through August 1, 2019 in Madison, Wisconsin.

EUSO-TA is a ground-based telescope, installed at the Telescope Array (TA) site in Black Rock Mesa, Utah, USA. This is the first detector to successfully use a Fresnel lens based optical system and multi-anode photomultipliers (64 channels per tube, 2304 channels encompassing a 10.6 degrees x 10.6 degrees field of view) for detection of Ultra High Energy Cosmic Rays (UHECR). The telescope is located in front of one of the fluorescence detectors of the TA experiment. Since its installation in 2013, the detector has observed several ultra-high energy cosmic ray events and, in addition, meteors. The limiting magnitude of 5.5 on summed frames (similar to 3 ms) has been established. Measurements of the UV night sky emission in different conditions and moon phases and positions have been completed. The performed observations serve as a proof of concept for the future application of this detector technology. (C) 2018 Elsevier B.V. All rights reserved.

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We present a short overview of the event associated with the recent strong solar flare on 10 September 2017 (X 8.2) based on the available data both from satellite GOES-13 and from selected neutron monitors. The onset time of SPE/GLE at 1 AU was found between 16:06 and 16:08 UT. The GLE effect was anisotropic with a maximum increase of 6 %. The maximum energy of accelerated protons was about 6 GeV. We estimated the release time of sub-relativistic protons into open field lines as 15:53 to 15:55 UT.

EUSO-Balloon is a pathfinder mission for the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). It was launched on the moonless night of the 25th of August 2014 from Timmins, Canada. The flight ended successfully after maintaining the target altitude of 38 km for five hours. One part of the mission was a 2.5 hour underflight using a helicopter equipped with three UV light sources (LED, xenon flasher and laser) to perform an inflight calibration and examine the detectors capability to measure tracks moving at the speed of light. We describe the helicopter laser system and details of the underflight as well as how the laser tracks were recorded and found in the data. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. Finally, we present a first reconstruction of the direction of the laser tracks relative to the detector.

Oscillations of energetic ion fluxes with periods 10-100s are often present in the Earth's foreshock. Detailed analysis of wave properties with Time History of Events and Macroscale Interactions during Substorms data and comparisons with other data sets confirm that these oscillations are the previously unnoticed part of well-known 30s waves but are observed mainly for higher-speed solar wind. Simultaneous magnetic oscillations have similar periods, large amplitudes, and nonharmonic unstable waveforms or shocklet-type appearance, suggesting their nonlinearity, also typical for high solar wind speed. Analysis of the general foreshock data set of Interball project shows that the average flux of the backstreaming energetic ions increases more than 1 order of magnitude, when solar wind speed increases from 400 to 500km/s.

JEM-EUSO is a space mission designed to investigate Ultra-High Energy Cosmic Rays and Neutrinos (E>5⋅1019eV) from the International Space Station (ISS). Looking down from above its wide angle telescope is able to observe their air showers and collect such data from a very wide area. Highly specific trigger algorithms are needed to drastically reduce the data load in the presence of both atmospheric and human activity related background light, yet retain the rare cosmic ray events recorded in the telescope. We report the performance in offline testing of the first level trigger algorithm on data from JEM-EUSO prototypes and laboratory measurements observing different light sources: data taken during a high altitude balloon flight over Canada, laser pulses observed from the ground traversing the real atmosphere, and model landscapes reproducing realistic aspect ratios and light conditions as would be seen from the ISS itself. The first level trigger logic successfully kept the trigger rate within the permissible bounds when challenged with artificially produced as well as naturally encountered night sky background fluctuations and while retaining events with general air-shower characteristics.

Anomalous wave effects and stimulated charged particle fluxes were registered during 40kHz-modulated electron beam injection in active space experiment carried out in a double satellite system. To explain these effects, the beam-plasma instability for a two-wave longitudinal interaction has been considered. The growth of instability depends on the frequency and wavenumber detunings between these longitudinal waves one of them is a slow beam mode with negative or zero wave energy defined near the linear stability boundary.

Since March 2014, there is a continuous measurement of secondary cosmic rays by the detector system SEVAN (Space Environmental Viewing and Analysis Network) at Lomnický štít, altitude 2,634 m above sea level. Starting from June 2016, the count rates (1 s resolution) obtained from the three SEVAN detectors and from their coincidences are available, along with selected meteorological characteristics. Since 30 May 2016 the electric field measurements have been installed at the same site. Several events with clear increase of the count rate in the upper detector of SEVAN were observed during the thunderstorms until 17 September 2016. Examples of these measurements are presented and discussed. Barometric pressure correction and elimination of low‐frequency variability from the signal allow to extract 2 min averaged increases from the data. It is shown that the 2 min averaged increases of count rates measured by SEVAN correspond with periods of high electric field (with higher probability during negative polarity) rather than with the individual discharges (lightning).