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During the period from January through mid-May, 1997, four large Earth-directed CMEs were observed by the Large Angle Spectroscopic Coronograph (LASCO). These CMEs were associated with long-lasting fluxes of >1.6 MeV protons detected by the Energetic and Relativistic Nuclei and Electron instrument (ERNE). However, the magnitudes of energetic proton events differed dramatically on different occasions. In strong proton events, production of 10-50 MeV protons started during expansion of the coronal Moreton wave in the western hemisphere of the Sun. The new SOHO observations suggest that potentialities of CMEs to produce energetic particles in the interplanetary medium crucially depend on the previous evolution of the explosion below ∼2R⊙. Forecasting of the near-Earth >10 MeV proton intensity requires multiwavelength observations of the early phase of an event particularly the Extreme-ultraviolet Imaging Telescope (EIT) observations.

ERNE is designed to study the composition and energy spectra of particles encountered in interplanetary space in the energy range from 1 MeV/n to well beyond 500 MeV/n. Several innovative ideas had to be incorporated in the design of the instrument in order to fulfill the scientific requirements. Position-sensitive strip detectors are used in the High Energy Detector (HED) for determining particle trajectories. Integrated interstrip capacitances were designed to allow for a very simple read-out technique from the two edges of each detector. The event recognition, signal multiplexing and control of the pulse height analysis are based on a gate array technique. The versatility of the gate array also allowed an elegant realization of a number of other functions and instrument control tasks. By using the gate array a very compact structure of the digital control electronics was achieved.

This paper provides a detailed description of the Energetic Particle Telescope (EPT) accommodated on board the PROBA-V satellite launched on May 7th, 2013 on a LEO, 820 km altitude, 98.7° inclination and a 10:30 – 11:30 Local Time at Descending Node. The EPT is an ionizing particle spectrometer that was designed based on a new concept and the most advanced signal processing technologies: it performs in-flight electron and ion discrimination and classifies each detected particle in its corresponding physical channels from which the incident spectrum can be readily reconstructed. The detector measures electron fluxes in the energy range 0.5 - 20 MeV, proton fluxes in the energy range 9.5 - 300 MeV and He-ion fluxes between 38 and 1200 MeV. The EPT is a modular configurable instrument with customizable maximum energy, field of view angle, geometrical factor and angular resolution. Therefore, the features of the currently flying instrument may slightly differ from those described in past or future configurations. After a description of the instrument along with the data acquisition and analysis procedures, the first particle fluxes measured by the EPT will be shown and discussed. The web-site located at http://web.csr.ucl.ac.be/csr_web/probav/ which daily displays measured fluxes and other related studies will also be briefly described.

The design of the ERNE experiment of the ESA and NASA collaborative SOHO mission is described. ERNE will investigate the sun by measuring energetic particles. Starting from the design objectives, as determined by the scientific goals of the experiment, and from the adopted basic solutions, the design and structure of the instrument are presented in detail. The fundamental technical aspects encountered in building a space instrument are briefly considered. The methods of implementation of scientifically the most important parts of the instrument, the sensors for measuring energetic particles and the associated electronics, are thoroughly explained. Both hardware and software are examined. The pre-flight calibrations of the instrument are described and the performance of the instrument in space is demonstrated.

The observations of the ERNE instrument on-board the SOHO 1 spacecraft are analysed. The main period under study is from the beginning of May till mid-October 1996. Only very small energetic particle events were observed. A comparison of the ERNE measurements with energetic particle observations during the two previous solar minima indicates that the flux levels of protons during the first half of 1996 are exceptionally low. The daily counting rates of quiet-time protons and 4He in the energy range 13–100 MeV/nucleon show statistically significant variations with time. Following two energetic particle events in July and August, anticorrelations were found between enhancements of low energy protons in the range 1.5–8 MeV, possibly accelerated in a corotating interaction region, and the modulation of high energy protons and helium above 13 MeV/nucleon. The period of the observed anticorrelations coincide with the solar rotation period.

The energy spectra of the anomalous components of helium, nitrogen and oxygen have been measured by the ERNE experiment on board the SOHO spacecraft. During February 28–April 30, 1996, the maximum intensity of anomalous helium was found to be 3.8 × 10-5 cm-2 sr-1 s-1 (MeV nucl-1)-1 in the energy range 10–15 MeV nucl-1. During the period January 26–April 30, 1996, the maximum oxygen intensity was 1.2 × 10-5 cm-2 sr-1 s-1 (MeV nucl-1)-1 at 4–7 MeV nucl-1, and the maximum nitrogen intensity 1.7 × 10-6 cm-2 sr-1 s-1 (MeV nucl-1)-1 at 4–9 MeV nucl-1. These peak intensities are at the same level as two solar cycles ago in 1977, but significantly higher than in 1986. This gives observational evidence for a 22-year solar modulation cycle. A noteworthy point is that the spectra of anomalous nitrogen and oxygen appear to be somewhat broader than in 1977.

The HED particle detector of the ERNE experiment to be flown on the SOHO spacecraft is unique compared to the earlier space-born detectors in its high directional resolution (better than 2°, depending on the track inclination). Despite the fixed view cone due to the three-axis stabilization of the spacecraft, the good angular and temporal resolution of the detector provides a new kind of opportunity for monitoring in detail the development of the anisotropies pertaining, for example, to the onset of SEP events, or passage of shock fronts related to gradual events. In order to optimize the measurement parameters, we have made a preflight simulation study of the HED anisotropy measurement capabilities. The purpose was to prove the feasibility of the selected measurement method and find the physical limits for the HED anisotropy detection. The results show HED to be capable of detecting both strong anisotropies related to impulsive events, and smoother anisotropies associated with gradual events.

SEPServer is a three-year collaborative project funded by the seventh framework programme (FP7-SPACE) of the European Union. The objective of the project is to provide access to state-of-the-art observations and analysis tools for the scientific community on solar energetic particle (SEP) events and related electromagnetic (EM) emissions. The project will eventually lead to better understanding of the particle acceleration and transport processes at the Sun and in the inner heliosphere. These processes lead to SEP events that form one of the key elements of space weather. In this paper we present the first results from the systematic analysis work performed on the following datasets: SOHO/ERNE, SOHO/EPHIN, ACE/EPAM, Wind/WAVES and GOES X-rays. A catalogue of SEP events at 1 AU, with complete coverage over solar cycle 23, based on high-energy (~68-MeV) protons from SOHO/ERNE and electron recordings of the events by SOHO/EPHIN and ACE/EPAM are presented. A total of 115 energetic particle events have been identified and analysed using velocity dispersion analysis (VDA) for protons and time-shifting analysis (TSA) for electrons and protons in order to infer the SEP release times at the Sun. EM observations during the times of the SEP event onset have been gathered and compared to the release time estimates of particles. Data from those events that occurred during the European day-time, i.e., those that also have observations from ground-based observatories included in SEPServer, are listed and a preliminary analysis of their associations is presented. We find that VDA results for protons can be a useful tool for the analysis of proton release times, but if the derived proton path length is out of a range of 1 AU

We study the differences in the heavy ion composition of solar energetic particle (SEP) events between solar cycles 23 and 24. We have surveyed the SOHO/ERNE heavy ion data from the beginning of solar cycle 23 until the end of June 2015, that is, well into the declining phase of cycle 24. We used this long observation period to study the properties of heavy ions (from C to Fe) and to compare the two solar cycles in this respect. We surveyed the data for SEP events with enhancements in the Fe/C and Fe/O intensity ratios in the energy range 5-15 MeV per nucleon, and associated the events with solar flare and coronal mass ejections (CME) when possible. We studied the properties of heavy ions in these events and compared the average relative abundances of heavy ions between the two solar cycles. We found that fewer days had C and O intensities higher than ~10$^{-3}$ cm$^{-2}$sr$^{-1}$s$^{-1}$(MeVn$^{-1}$)$^{-1}$ during solar cycle 24 than during cycle 23. For Fe this difference was clear even at lower intensities. We also found that fewer days had Fe/(C+O) > 0.183 during cycle 24. We identified 86 SEP events with at least one Fe-rich day, 65 of which occurred during cycle 23 and only 21 during cycle 24. We found that impulsive events have been almost completely absent during cycle 24. Mean abundances of heavy ions in the events were found to be significantly lower during cycle 24 than in cycle 23. Our results reflect the reduced solar activity in cycle 24 and indicate lower efficiency of particle acceleration processes for both gradual and impulsive SEP events in cycle 24., 14 pages, 9 figures and 3 tables. To be published in A&A

Solar energetic particle (SEP) events are a key ingredient of solar-terrestrial physics both for fundamental research and space weather applications. Multi-satellite observations are an important and incompletely exploited tool for studying the acceleration and the coronal and interplanetary propagation of the particles. While STEREO uses for this diagnostic two identical sets of instrumentation, there are many earlier observations carried out with different spacecraft. It is the aim of the SEPServer project to make these data and analysis tools available to a broad user community. The consortium will carry out data-driven analysis and simulation-based data analysis capable of deconvolving the effects of interplanetary transport and solar injection from SEP observations, and will compare the results with the electromagnetic signatures. The tools and results will be provided on the web server of the project in order to facilitate further analysis by the research community. This paper describes the data products and analysis strategies with one specific event, the case study of 13 July 2005. The release time of protons and electrons are derived using data-driven and simulation-based analyses, and compared with hard X-ray and radio signatures. The interconnection of the experimental and the simulation-based results are discussed in detail.

Models of energetic electrons and protons at low altitudes in space display significant discrepancies. In this paper the possible causes of the observed differences between the most frequently used models are discussed, including instrument-induced data inaccuracy. In parallel, on the basis of simulations and in-beam experimental results, solutions to the instrumentation issues are described focusing on the implementation of these into the Energetic Particle Telescope.

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper, we present measurements of the isotopic ratios [superscript 2]H/[superscript 4]He, [superscript 3]He/[superscript 4]He, [superscript 6]Li/[superscript 7]Li, [superscript 7]Be/([superscript 9]Be+[superscript 10]Be), and [superscript 10]B/[superscript 11]B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June., United States. Dept. of Energy, Massachusetts Institute of Technology

Some observational aspects of solar energetic particles (SEPs) are briefly discussed. The shift from the flare paradigm of SEP origin through the two-class paradigm of impulsive and gradual SEP events to hybrid events is described. Comprehensive investigations of coronal mass ejections (CMEs) and solar energetic particles during the SOHO era have shown that there is a good correlation between the occurrence of large SEP events and fast and wide CMEs. Shocks driven by these CMEs in the solar corona and interplanetary space accelerate the solar wind suprathermal particles. Observations of ionic charge states and elemental composition of high-energy solar particles indicate that also flare material is present in the seed populations of large gradual SEP events. Whether this material is remnant from previous flares and accelerated by CME-driven shocks or is directly accelerated in the flare processes, is still under vigorous research. Significant progress is expected from future solar missions reaching close to the sun and leading to better understanding of the processes in the inner heliosphere.

The new SIXS prototype ASIC has been designed for detecting and measuring solar X-rays in a Mercury orbit onboard BepiColombo. The SIXS detector consists of a CsI(Tl) core detector and 5 Silicon surface detectors. This new ASIC has undergone major modifications and has a new differential charge preamplifier without any pole zero cancellation and has a large dynamic range of 2,000e- to 1,500,000e-. The ASIC has 8 channels, each of which consists of a preamplifier, a CR-RC shaper, a peak detect hold, a comparator, a buffer, and a new 8 bit resistor string DAC which sets the programmable threshold for the comparator There are 6 channels for Si detectors with a shaping time of 1μs and 2 channels for CsI detector with a shaping time of 3μs, one of which has twice the gain to accommodate for low output efficiency of the detector. The channels are multiplexed to a single 10/11 bit SAR ADC which runs at a 10MHz clock and additional on chip programmable phase shifted clocks and programmable Upper and Lower threshold voltages. This ASIC has been manufactured in a 0.35μm CMOS process using enclosed geometry transistors. All digital logic in the ASIC including control and ADC logic use voting logic flipflops for SEU prevention.

The Energetic and Relativistic Nuclei and Electron experiment of the SOHO mission contains two sensors LED and HED. The energy ranges of the sensors are of the order of 1–10 MeV/n and 13–540 MeV/n, respectively. One of the design goals was good charge resolution of nuclei in the charge range 1–30. The isotopic resolution of light elements (LED) and all nuclei (HED) were also important objectives. Up to now, first models of the sensors have been built, and their performance has been tested in accelerator runs and by using an alpha particle source. First results of the test measurements are given.

Response of BGO and CSI(Tl) scintillators to ions heavier than helium has been studied at energies below 30 MeV/n. An argon beam was scattered from gold target. The reaction products, covering ions from lithium to argon, were identified by using the conventional ΔE - E method. A thin silicon surface barrier detector was used as an energy loss detector and a scintillator as a residual energy detector. The energies of incident nuclei were determined by using the signals from the calibrated ΔE detector, and the light yield of the scintillators was obtained from the observed pulse heights. Telescope consisting of a silicon transmission detector and either BGO of CsI(Tl) scintillators as a residual energy detector were found to have similar identification capabilities of heavy ions. The light output of BGO was found to be linear at all energies observed, except for the lightest nuclei, where some nonlinearity was apparent below about 6–7 MeV/n. The response of CsI(Tl) was linear for all ions above 6 MeV/n.

The SIXS instrument is designed for detecting and measuring solar X-rays and solar energetic particles in a Mercury orbit onboard BepiColombo. The particle detector consists of a CsI(Tl) core detector and 5 GaAs surface detectors. The front-end electronics of the particle detector is implemented as an ASIC which requires a large dynamic range of 2,000e- to 1,500,000e- and an integral non-linearity (INL) < 3% for a temperature range of -30deg C to +55deg C. The SIXS ASIC test structure has been manufactured to determine performance of differential vs. single-ended designs for noise, power supply rejection and current consumption. The ASIC has 8 channels, each of which consists of a preamplifier, a CR-RC shaper, a peak hold, a comparator and a buffer, all designed using enclosed geometry transistors. There are 6 channels for GaAs detectors with 3 different preamplifier types consisting of a single-ended with pole zero compensation; single-ended without pole zero compensation and a differential configuration. There are 2 channels for Csl detectors with single- ended and differential preamplifier designs. This ASIC has been manufactured in a 0.35 mum CMOS process. The ASIC architecture and design flow are described including simulated and measured results.

Time profiles of the 0.25–10 MeV electrons and the ~(0.1–1) GeV nucleon−1 protons and helium associated with two solar coronal mass ejections (CMEs) are analyzed with a newly formulated method based on modeling of the particle transport in the interplanetary medium. With the modeling, we fit the observed angular distribution of solar particles and infer, for a particular particle instrument and magnetic field orientation, the time delay of the particle registration at 1 AU in respect to the solar source. Then, after the time offset removal, intensity re-normalization and background equalization, the time–intensity profiles of high-energy protons, helium and electrons in different energy channels are superposed and compared. The comparison reveals episodes of remarkable coincidence of different profiles, as well as episodes of essentially different behavior. It implies at least three sources of solar high-energy particles operating in a single event. The first, short-duration source emits electrons next to the flare's impulsive phase and CME liftoff. The second source gradually rises and continues for more than an hour, emitting electrons and lower energy protons, which is consistent with shock acceleration on open magnetic field lines extending to solar wind. An another, third source is the main source of relativistic ions in space. It is retarded in respect to the flare's impulsive phase and may be associated with a structure encountered by the shock within a few solar radii from the Sun.

We study selected properties of Solar Energetic Particle (SEP) events as inferred from their associated radio emissions. We used a catalogue of 115 SEP events that consists of entries of proton intensity enhancements at one AU, with complete coverage over solar cycle 23, based on high-energy (~68 MeV) protons from SOHO/ERNE and we calculated the proton release time at the Sun using velocity dispersion analysis (VDA). After an initial rejection of cases with unrealistic VDA path lengths, we assembled composite radio spectra for the remaining events using data from ground-based and space-borne radio-spectrographs. For every event we registered the associated radio emissions and we divided the events in groups according to their associated radio emissions. The proton release was found to be most often accompanied by both type III and II radio bursts, but a good association percentage was also registered in cases accompanied by type IIIs only. The worst association was found for the cases with type II only association. These radio association percentages support the idea that both flare- and shock-resident particle release processes are observed in high-energy proton events. In cases of type III-associated events we extended our study to the timings between the type III radio emission, the proton release, and the electron release as inferred from VDA based on Wind/3DP 20-646 keV data. Typically, the protons are released after the start of the associated type III bursts and simultaneously or before the release of energetic electrons. For the cases with type II radio association we found that the distribution of the proton release heights had a maximum at ~2.5 Rs. Most (69%) of the flares associated to our SEP events were located at the western hemisphere, with a peak within the well-connected region of 50-60 deg western longitude., 17 pages, 11 figures, accepted for publication in A&A

Space weather effects on technology are discussed. After a brief general overview of the consequences of space weather on various technologies and a of the space environment, the effects of plasmas and particle radiation on systems in space are considered in more detail. The processes responsible for spacecraft surface charging and internal charging and the consequences of subsequent discharges are examined. The concepts of total ionising dose, displacement damage, and single event effects are introduced. The principles how they affect semiconductor devices are discussed and the basic ideas for calculating these quantities are presented. Finally, plasma and particle-induced interference and background in scientific sensors are considered. Examples of various types of space weather effects on space systems are given.

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 (June 1998) in a 51.7 deg orbit at altitudes between 320 and 390 km. A search for antihelium nuclei in the rigidity range 1–140 GV was performed. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of < 1.1×10^−6 was obtained. The high energy proton, electron, positron, helium, antiproton and deuterium spectra were accurately measured. For each particle and nuclei two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum. Positrons in the second spectrum were found to be much more abundant than electrons. Tracing particles from the second spectra shows that most of them travel for an extended period of time in the geomagnetic field, and that the positive particles (p and e+) and negative ones (e−) originate from two complementary geographic regions. The second helium spectrum flux over the energy range 0.1–1.2 GeV/nucleon was measured to be (6.3 ± 0.9) × 10^−3(m^2 s sr)^−1. Over 90 percent of the helium flux was determined to be 3He at the 90% confidence level

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 in a 51.7 degree orbit at altitudes between 320 and 390 km. A total of 2.86 * 10^6 helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of < 1.1 * 10^-6 is obtained., 18 pages, Latex, 9 .eps figures

The lepton spectra in the kinetic energy ranges 0.2 to 40 GeV for e − and 0.2 to 3 GeV for e + were measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS–91 at altitudes near 380 km. From the origin of the leptons two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum with positrons much more abundant than electrons. Tracing leptons from the second spectra shows that most of these leptons travel for an extended period of time in the geomagnetic field and that the e + and e − originate from two complementary geographic regions.

The helium spectrum from 0.1 to 100 GeV/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV/nucleon the flux was measured to be (6.3±0.9)×10 −3 ( m 2 sec sr ) −1 and more than ninety percent of the helium was determined to be 3He (at the 90% CL). Tracing helium from the second spectrum shows that about half of the 3He travel for an extended period of time in the geomagnetic field and that they originate from restricted geographic regions similar to protons and positrons.

A solar energetic particle event was observed on 9 July 1996, by the ERNE sensors LED and HED on board the SOHO spacecraft. The arrival of the first protons in the energy range >20 MeV took place at 09:55 UT, 43 min after the maximum in the X-ray and Hα radiation of a flare located at S10 W30. The rise phase of the particle intensities at all energies was exceptionally rapid, At 12:50 UT, the intensities dropped in all energy channels. Simultaneously, the magnetic ield instrument MFI on board WIND, not far from SOHO, detected a sharp and large change in the magnetic ield direction. The analysis of the directional measurements of ERNE in the energy range 14–17 MeV shows the presence of a strong flux anisotropy during the whole period 10:10– 12:50 UT. From 12:50 UT until about 16:00 UT, the directional analysis of the proton fluxes gives only a weak anisotropy at the limit of the sensor resolution, Later on, the flux anisotropy was found to recur, indicating a continuous injection of particles into the flux tubes connected to the SOHO spacecraft. These experimental results lead to strict limits on particle injection and transport models. The first period of the anisotropy and its recurrent phase cover 24 hours. This suggests an extended injection of particles. The strength and stability of the anisotropy indicate that, during these periods, SOHO was in an interplanetary sector where the particle transport was almost scatter-free. On the other hand, during the intermediate 3-hr period, we observed particles which traveled in a sector of diffusive transport or which were retarded by magnetic field disturbances not far from the observation site.

The energetic particle instrument ERNE on-board SOHO started its observations on December 15, 1995. The low-energy sensor of ERNE, LED, is capable of measuring particles in the energy range from 1 to 10 MeV nucl-1. From the beginning of the year 1996 until May 22, 1996, LED-observations included four energetic particle events above threshold intensities.

Context. Different types of interplanetary (IP) type II bursts have been observed, where the more usual ones show narrow-band and patchy emissions, sometimes with harmonics, and which at intervals may disappear completely from the dynamic spectrum. The more unusual bursts are wide-band and diffuse, show no patches or breaks or harmonic emission, and often have long durations. Type II bursts are thought to be plasma emission, caused by propagating shock waves, but a synchrotron-emitting source has also been proposed as the origin for the wide-band type IIs.Aims. Our aim is to find out where the wide-band IP type II bursts originate and what is their connection to particle acceleration.Methods. We analyzed in detail 25 solar events that produced well-separated, wide-band IP type II bursts in 2001–2011. Their associations to flares, coronal mass ejections (CMEs), and solar energetic particle events (SEPs) were investigated.Results. Of the 25 bursts, 18 were estimated to have heights corresponding to the CME leading fronts, suggesting that they were created by bow shocks ahead of the CMEs. However, seven events were found in which the burst heights were significantly lower and which showed a different type of height-time evolution. Almost all the analyzed wide-band type II bursts were associated with very high-speed CMEs, originating from different parts of the solar hemisphere. In terms of SEP associations, many of the SEP events were weak, had poor connectivity due to the eastern limb source location, or were masked by previous events. Some of the events had precursors in specific energy ranges. These properties and conditions affected the intensity-time profiles and made the injection-time-based associations with the type II bursts difficult to interpret. In several cases where the SEP injection times could be determined, the radio dynamic spectra showed other features (in addition to the wide-band type II bursts) that could be signatures of shock fronts.Conclusions. We conclude that in most cases (in 18 out of 25 events) the wide-band IP type II bursts can be plasma emission, formed at or just above the CME leading edge. The results for the remaining seven events might suggest the possibility of a synchrotron source. These events, however, occurred during periods of high solar activity, and coronal conditions affecting the results of the burst height calculations cannot be ruled out. The observed wide and diffuse emission bands may also indicate specific CME leading edge structures and special shock conditions.

The Energetic and Relativistic Nuclei and Electron (ERNE) experiment will investigate the solar atmosphere and the heliosphere by detecting particles produced in various kinds of energy release processes. ERNE is at the upper end in energy among the SOHO particle instruments. The instrument will measure the energy spectra of elements in the range Z=1−30. The energy coverage varies dependent on the particle species from a few MeV/n up to a few hundred MeV/n and electrons from 2 to 50 MeV. At high energies, ERNE records also the direction of the incident particles for accurate measurements of the pitch angle distribution of the ambient flux within the viewing cone. Especially the isotope identification capability has been one of the instrument design goals, thus providing new data regarding various fundamental questions in solar physics.

We consider a numerical model for the shock acceleration of energetic ions in the magnetic environment of the solar corona. The model is motivated by observations of the deka-to-hecto-MeV proton energy spectra, ion and electron timing, and abundances in the beginning of major solar energetic particle (SEP) events, prior to the event's main phase associated with coronal mass ejection (CME) driven shock in the solar wind. Inasmuch as the obliquity of the CME-liftoff-associated shocks in solar corona and hence the seed-particle supply for the shock acceleration are essentially time dependent, a steady state energy spectrum of accelerated protons near the shock could not be attained. Energy spectrum of the SEP emission depends on the spatial and energy distribution of seed particles for the coronal shock acceleration, on the shock wave history, and on the location and scenario of the energetic particle escape into the interplanetary medium. We use a numerical model of the shock acceleration on a semicircular magnetic field line to learn a significance of different effects. If the shock geometry in a particular magnetic tube changes from nearly parallel to perpendicular, the resulting SEP spectrum in most distant sections of the tube, e.g., at the top of a transequatorial loop, resembles a wide beam, which is very different from the standard power-law spectrum that would be expected in a steady state. Possible escape of the shock-accelerated particles from more than one coronal location, stochastic re-acceleration, and the magnetic tube expansion can make the SEP spectra even more complicated.

Neutron monitor measurements using 10-second recording intervals were started at Oulu in September 1987. A special analysis method based on the power spectra was adopted to compensate for the relative low statistics associated with short recording intervals. The preliminary result based on the analysis of 6274 one-hour length data records strongly indicates the existence of periodic scintillations in the whole frequency range 2–50 mHz.

A double neutron monitor consisting of two neutron monitors, one on top of the other, has been constructed. A thick layer of moderating material between the monitors enables two independent measurements of multiplicity. The total thickness of the target layer in the double monitor amounts to about 3 inelastic mean free paths of high-energy hadrons in lead. The construction and functional characteristics of the monitor are discussed. The data collection and recording is based on a microprocessor system. The average efficiency for detecting evaporation neutrons was found to be e = (12.5 ± 0.5)% in both monitors. The contribution of cosmic-ray muons to the counting rates of different multiplicities and the barometric coefficients were determined.

The energy spectra of cosmic-ray neutrons, protons, and pions were determined at sea level in the range 0.1 – 1000 GeV. The results are based on the measurements of the neutron-multiplicity distributions produced by cosmic hadrons in the Turku spectrometer. Below 0.5 GeV, the values γ = 1.47 ± 0.04 and 0.8 ± 0.1 were obtained for the slopes of the neutron and proton spectra. At 1000 GeV, the nucleon spectra are much steeper with γ = 2.79 ± 0.06. The pion spectrum was found to obey the power law with γ = 1.41 ± 0.05 in the low-energy region up to 30 GeV. Above 500 GeV, the spectrum of pions, containing an admixture of accompanied particles, was found to reach the high energy limit with γ = 2.92 ± 0.06.

The time structure of the ground-level event on February 16, 1984 was studied by using 30 s data of the Turku double neutron monitor. The onset time of the event was found to be (09:06:00±1) min U.T. The time between the injection of protons from the flare site and release of relativistic particles into interplanetary space was (6÷7) min. The linear rise rate of the event at Turku was 5.4%/min and the rise time (5±1) min. The event was complicated in structure consisting of at least two separate pulses of particles, the first lasting for about 14 min and the second about 8 min.

Particle fluxes and pitch angle distributions of relativistic solar protons at Earth's orbit have been determined by Monte Carlo calculations. The analysis covers two hours after the release of the particles from the Sun and total of 8 × 106 particle trajectories were simulated. The pitch angle scattering was assumed to be isotropic and the scattering mean free path was varied from 0.1 to 4 AU. The intensity-time profiles after a delta-like injection from the Sun show that the interplanetary propagation is clearly non-diffusive at scattering mean-free paths above 0.5 AU. All pitch angle distributions have a steady minimum at 90 °, and they become similar about 20 min after the arrival of first particles. As an application, the solar injection profile and the interplanetary scattering mean-free path of particles that gave rise to the GLE on 7 May, 1978 were determined. In contrast to the values of 3–5 AU published by other authors, the average scattering mean-free path was found to be about 1 AU.

We have recently started a systematic study of short-period (periods less than 60 min) variations in the cosmic-ray intensity. By making use of the MEM, we have found intensity oscillations with periods varying from 16 to 27 minutes during the GLE on February 16, 1984.

During solar flares and coronal mass ejections, nuclei and electrons accelerated to high energies are injected into interplanetary space. These accelerated particles can be detected at the SOHO satellite by the ERNE instrument. From the data produced by the instrument, it is possible to identify the particles and to calculate their energy and direction of propagation. Depending on variable coronal/interplanetary conditions, different kinds of effects on the energetic particle transport can be predicted. The problems of interest include, for example, the effects of particle properties (mass, charge, energy, and propagation direction) on the particle transport, the particle energy changes in the transport process, and the effects the energetic particles have on the solar-wind plasma. The evolution of the distribution function of the energetic particles can be measured with ERNE to a better accuracy than ever before. This gives us the opportunity to contribute significantly to the modeling of interplanetary transport and acceleration. Once the acceleration/transport bias has been removed, the acceleration-site abundance of elements and their isotopes can be studied in detail and compared with spectroscopic observations.

Based on energetic particle observations made at $\approx$1 AU, we present a catalogue of 46 wide-longitude (>45{\deg}) solar energetic particle (SEP) events detected at multiple locations during 2009-2016. The particle kinetic energies of interest were chosen as >55 MeV for protons and 0.18-0.31 MeV for electrons. We make use of proton data from the Solar and Heliospheric Observatory/Energetic and Relativistic Nuclei and Electron experiment (SOHO/ERNE) and the Solar Terrestrial Relations Observatory/High Energy Telescopes (STEREO/HET), together with electron data from the Advanced Composition Explorer/Electron, Proton, and Alpha Monitor (ACE/EPAM) and the STEREO/Solar Electron and Proton Telescopes (SEPT). We consider soft X-ray data from the Geostationary Operational Environmental Satellites (GOES) and coronal mass ejection (CME) observations made with the SOHO/Large Angle and Spectrometric Coronagraph (LASCO) and STEREO/Coronagraphs 1 and 2 (COR1, COR2) to establish the probable associations between SEP events and the related solar phenomena. Event onset times and peak intensities are determined; velocity dispersion analysis (VDA) and time-shifting analysis (TSA) are performed for protons; TSA is performed for electrons. In our event sample, there is a tendency for the highest peak intensities to occur when the observer is magnetically connected to solar regions west of the flare. Our estimates for the mean event width, derived as the standard deviation of a Gaussian curve modelling the SEP intensities (protons $\approx$44{\deg}, electrons $\approx$50{\deg}), largely agree with previous results for lower-energy SEPs. SEP release times with respect to event flares, as well as the event rise times, show no simple dependence on the observer's connection angle, suggesting that..., Comment: This is a pre-print of an article to be published in Solar Physics. The final authenticated version will be available online at: https://doi.org/10.1007/s11207-018-1284-7