Solar Cosmic Ray Events Research Articles

Observations of solar cosmic rays using cubesat nanosatellites

We discussed the possibilities of using cubesat nanosatellites for studying solar cosmic rays. SCR electron fluxes in the polar caps at an altitude of ~550 km were detected. The measurements were carried out with DeCoR scintillation detectors operated at several cubesats of Moscow State University during the solar cosmic ray event on September 6–21, 2022.

Isolated Solar Cosmic Ray Events Caused by Energetic Storm Particles (ESPs)

Isolated Solar Cosmic Ray Events Caused by Energetic Storm Particles (ESPs)

Isolated Solar Cosmic Ray Events Caused by Energetic Storm Particles (ESPs)

Based on the catalogs of solar proton events for the 23rd and 24th solar cycles, events were chosenthat lacked a reliable source of particles but were accompanied by interplanetary and geomagnetic disturbances.As a rule, these events involve small proton fluxes that are detected near the Earth. All of the selectedevents occurred during the arrival of shock waves to the Earth, suggesting that they were likely caused by thearrival of energetic storm particles. It has been shown that flares accompanied by coronal mass ejections,which occurred tens of hours before the onset of the increase in particle fluxes in Earth’s orbit, could be thesource of these events. The selected events exhibited several specific features. Only one of them was accompaniedby a single shock front, while the others had two or three shock waves. The time profile of the eventsresembled a structure bounded by two shock fronts, suggesting that the shock waves likely accelerated andconfined the particles within a limited region of space.

Solar Cosmic Ray Acceleration by a Shock Wave in the Lower Solar Corona on May 7, 1978

Based on the theory of diffusive shock acceleration of charged particles, we have theoretically studied the spectra of protons produced by a shock wave driven by a coronal mass ejection (CME) in the lower solar corona with known solar plasma parameters for the solar cosmic ray (SCR) event recorded near the Earth’s orbit on May 7, 1978 (ground level enhancement no. 31, GLE31) using numerical methods. The proton flux data from the CPME instrument installed on the IMP-8 spacecraft and the worldwide network of ground-based neutron monitors combined with the particle measurements by the telescopes on the IMP-7 and IMP-8 satellites have been used to analyze the event. In our calculations, to satisfactorily reproduce the proton spectrum measured at the Earth’s orbit, the CME velocity was assumed to be constant and equal to 600 km s–1. The shock acceleration of SCRs proceeded up to 1.4 R⊙ solar radii for 256 s.

Characteristic Features of Solar Cosmic Rays in the 21st–24th Solar-Activity Cycles According to Data from Catalogs of Solar Proton Events

Homogeneous series of solar cosmic-ray events for four solar-activity cycles against the background of decreased activity in cycles 23 and 24 are considered. The number of solar cosmic-ray events with energies above 10 MeV decreased insignificantly, while the number of ground-level enhancements in comparison between cycles 23 and 24 decreased by eight times. It is shown that the average contribution of flares to the generation of ground-level enhancements decreased from cycle 23 to cycle 24 by three times, and the average contribution of coronal mass ejections decreased by five times; the average contribution of flares to the generation of solar cosmic rays with energy >10 MeV decreased by 1.3 times, and the average contribution of coronal mass ejections increased by 1.4 times.

Is it possible to organize automatic forecasting of expected radiation hazard level from Solar Cosmic Ray (SCR) events for spacecraft in the heliosphere and magnetosphere and for aircraft in the low Atmosphere?

We present the method of automatic forecasting of the impacts of Solar Cosmic Ray (SCR)/Solar Energetic Particle (SEP) and estimation of radiation hazard level. We use the model of SCR/SEP diffusion in general form and coupling functions for neutron monitors of worldwide network with different altitudes and cutoff rigidities, including space detectors such as GOES-11,12. Another observational data for the estimation of energy spectra of SCR/SEP are measurements of different neutron multiplicities by some neutron monitors (e.g., for great SCR/SEP event held in September 29, 1989). A 1-min data of muon telescopes and ionization chambers shielded by 10-cm PB are used for the detection of the highest-energy SCR/SEP components (e.g., for SCR/SEP events held on February 23, 1956; Dorman, 1957). We demonstrate algorithms to automatically estimate event starting times, determine the time evolution of SCR/SEP in space using coupling functions in the frame of spectrographic method, solve inverse problems associated with SCR/SEP generation in solar corona and propagation in the interplanetary space, automatically determine escaping into solar wind and propagation in space based on the CR observation data parameters of SCR/SEP generation and propagation in solar corona. Based on these parameters, we show that it is possible to automatically forecast the first 0.5 h data on expected level of radiation hazards from a full-time event (up to about 48 h) for objects in space on different distances from the Sun, in magnetosphere at different orbits, and in atmosphere at different altitudes and cutoff rigidities. It is important, before the start of the automatic forecasting procedure, to calculate the expected level of radiation hazards for full time of event by determining every 5–10 min recalculated forecasting fluxes of SCR/SEP in space, out of magnetosphere, back to the CR ground detectors, and detectors on satellites using the same coupling functions. If the difference between the obtained results and observed data is smaller or no statistical errors, it is possible to provide effective forecasting automatically and subsequently calculate the expected level of radiation hazards. If the expected level of radiation hazards is high in certain objects, after about 0.5 h from the event starting time, it will be formatted and a corresponding alert is sent. The same alerts will be repeated with time for different objects in space, in magnetosphere, and in atmosphere. Based on the first 0.5 h data from event beginning, the radiation hazard level from high-energy particles such as SCR/SEP is considered to be low (with very small flux). If with increasing time the radiation hazard level rises with energy ≤1 GeV, it is formatted. Also, at the beginning of some SCR/SEP events when the Earth is on or near the force line of IMF connected with the source of SCR/SEP, several CR stations with direct arriving along the magnetic force line with about no scattering SCR/SEP particles on magnetic inhomogeneities will show strong narrow pulse with no information on SCR/SEP diffusion during the propagation from the source to the detector. These CR stations at the beginning of the SCR/SEP event can be used only for estimating SCR/SEP energy spectrum in the source and at the time of injection into solar wind but not on diffusion. Hence, it is necessary to automatically separate the CR stations with strong narrow pulses and exclude them from diffusion analysis. We strive to make this automatic using a program of image identification in the frame of MATLAB.

Solar Cosmic Ray Acceleration by a Shock Wave in the Lower Solar Corona on November 22, 1977

Based on the theory of diffusive shock acceleration of charged particles, we have investigated the spectra of protons recorded in the solar cosmic ray event near the Earth’s orbit on November 22, 1977 (ground level enhancement no. 30, GLE30). The proton flux data from the CPME instrument installed on the IMP-8 spacecraft and the worldwide network of neutron monitors have been used to analyze the event. Using GLE30 as an example, we have shown for the first time that solar cosmic rays of relativistic energies can be produced by a shock wave with a relatively low speed of 560 km s–1 in the lower solar corona at a distance up to 1.6 $${{R}_{ \odot }}$$ ( $${{R}_{ \odot }}$$ is the solar radius) within 615 s. The calculated proton spectra satisfactorily reproduce the measurements in the Earth’s orbit.

New Parameter in the Description of Solar Cosmic Ray Events—Energy of Balance between Solar and Galactic Protons

Solar proton events possess a wide variety of features that reflect the conditions of solar proton acceleration and propagation. Relevant investigations rely on statistical methods that make it possible to classify events with the aim of obtaining deeper insight into physical processes leading to the generation of solar cosmic rays. In classifying events in power, the intensity of particles with energy above 10MeV at the maximum of the event time profile or the fluence of particles throughout the event time is usually used. A new parameter, Eqm, that characterizes the proton event power and which is some kind of approximation of the maximum energy of accelerated particles is analyzed in the present study. Correlations of Eqm with properties of x-ray flares on the Sun and with the velocity of coronal mass ejections are examined.

Spectra of Fe ions in powerful SCR events

Large solar cosmic ray (SCR) events are registered by PLATAN equipment in September–October 1989 aboard the MIR orbital station and in October–November 2003 aboard the International Space Station (ISS). The energy spectra of Fe ions in the energy intervals of 5–200 MeV/nucleon (1989) and 25–90 MeV/nucleon (2003) are measured. Spectra for SCR events of 1989 and 2003 are approximated with high accuracy by the power law function of energy. The SCR events of 1989 greatly exceed those of 2003 in the fluence of Fe particles. High enrichment of the elemental composition of the SCR events 2003 with Fe ions is observed.

Variations in the Fe/O value resulting from changes in the ion energy in flows of accelerated solar particles

Qualitative estimates of the relative iron and oxygen ions (Fe/O) in flows of solar cosmic rays from impulsive and long-duration solar flares are obtained for different ion energy ranges. The Fe/O value serves as a measuring unit for the known FIP effect in the solar atmosphere. It is shown that the FIP effect is most evident (maximum Fe/O values) in impulsive events for ions at energies <2 MeV/n. In long-duration events, the Fe/O value gradually decreases in parallel with ion energy and its maximum values are observable in the area of relatively low energies. The comparison of some flare models provided grounds for a qualitative explanation of the Fe/O behavior in response to changes in ion energies for both classes of solar cosmic ray (SCR) events.

The Annual Cosmic-Radiation Intensities 1391 – 2014; The Annual Heliospheric Magnetic Field Strengths 1391 – 1983, and Identification of Solar Cosmic-Ray Events in the Cosmogenic Record 1800 – 1983

The annual cosmogenic $^{10}\mathrm{Be}$ ice-core data from Dye 3 and the North Greenland Ice-core Project (NGRIP), and neutron-monitor data, 1951 – 2014, are combined to yield a record of the annual cosmic-ray intensity, 1391 – 2014. These data were then used to estimate the intensity of the heliospheric magnetic field (HMF), 1391 – 1983. All of these annual data are provided in the Electronic Supplementary Material. Analysis of these annual data shows that there were significant impulsive increases in $^{10}\mathrm{Be}$ production in the year following the very large solar cosmic-ray events of 1942, 1949, and 1956. There was an additional enhancement that we attribute to six high-altitude nuclear explosions in 1962. All of these enhancements result in underestimates of the strength of the HMF. An identification process is defined, resulting in a total of seven impulsive $^{10}\mathrm{Be}$ events in the interval 1800 – 1942 prior to the first detection of a solar cosmic-ray event using ionization chambers. Excision of the $^{10}\mathrm{Be}$ impulsive enhancements yields a new estimate of the HMF, designated B(PCR-2). Five of the seven $^{10}\mathrm{Be}$ enhancements prior to 1941 are well correlated with the occurrence of very great geomagnetic storms. It is shown that a solar cosmic-ray event similar to that of 25 July 1946, and occurring in the middle of the second or third year of the solar cycle, may merge with the initial decreasing phase of the 11-year cycle in cosmic-ray intensity and be unlikely to be detected in the $^{10}\mathrm{Be}$ data. It is concluded that the occurrence rate for solar energetic-particle (SEP) events such as that on 23 February 1956 is about seven per century, and that there is an upper limit to the size of solar cosmic-ray events.

Effects of extraordinary solar cosmic ray events on variations in the atmospheric electric field at high latitudes

Studies of variations in the atmospheric electric field vertical component (Ez) are illustrated based on data from the Apatity high-latitude observatory (geomagnetic latitude Φ' = 63.8°) for three solar cosmic ray (SCR) events that occurred on April 15, April 18, and November 4, 2001. For the SCR event of April 15, 2001, the observed Ez variations have been compared with the corresponding data from the Voeykovo midlatitude observatory and the Vostok observatory on the polar cap. It has been indicated that solar coronal mass ejections and some powerful SCR events can result in variations in the global electric circuit. Disturbances in the atmospheric electric field can be used to diagnose the development of intense processes on the Sun.

The low energy magnetic spectrometer onUlyssesand ACE response to near relativistic protons

Aims. We show that the Heliosphere Instrument for Spectra Composition and Anisotropy at Low Energies (HISCALE) on board the Ulysses spacecraft and the Electron Proton Alpha Monitor (EPAM) on board the Advance Composition Explorer (ACE) spacecraft can be used to measure properties for ion populations with kinetic energies in excess of 1 GeV. This previously unexplored source of information is valuable for understanding the origin of near relativistic ions of solar origin.Methods. We model the instrumental response from the low energy magnetic spectrometers from EPAM and HISCALE using a Monte Carlo approach implemented in the Geant4 toolkit to determine the response of different energy channels to energies up to 5 GeV. We compare model results with EPAM observations for 2012 May 17 ground level solar cosmic ray event, including directional fluxes.Results. For the 2012 May event, all the ion channels in EPAM show an onset more than one hour before ions with the highest nominal energy range (1.8 to 4.8 MeV) were expected to arrive. We show from Monte Carlo simulations that the timing at different channels, the ratio between counts at the different channels, and the directional fluxes within a given channel, are consistent with and can be explained by the arrival of particles with energies from 35 MeV to more than 1 GeV. Onset times for the EPAM penetrating protons are consistent with the rise seen in neutron monitor data, implying that EPAM and ground neutron monitors are seeing overlapping energy ranges and that both are consistent with GeV ions being released from the Sun at 10:38 UT.

Differences in published characteristics of GLE60 and their consequences on computed radiation dose rates along selected flight paths

The radiation dose rates at flight altitudes can increase by orders of magnitude for a short time during energetic solar cosmic ray events, so called ground level enhancements (GLEs). Especially at high latitudes and flight altitudes, solar energetic particles superposed on galactic cosmic rays may cause radiation that exceeds the maximum allowed dosage limit for the general public. Therefore the determination of the radiation dose rate during GLEs should be as reliable as possible. Radiation dose rates along flight paths are typically determined by computer models that are based on cosmic ray flux and anisotropy parameters derived from neutron monitor and/or satellite measurements. The characteristics of the GLE on 15 April 2001 (GLE60) were determined and published by various authors. In this work we compare these results and investigate the consequences on the computed radiation dose rates along selected flight paths. In addition, we compare the computed radiation dose rates with measurements that were made during GLE60 on board two transatlantic flights.

Radiation doses along selected flight profiles during two extreme solar cosmic ray events

The radiation dose rates at flight altitudes may be hazardously increased during solar cosmic ray events. Within the scope of this paper we investigate the total accumulated radiation doses, i.e. the contribution of galactic and solar cosmic rays, during the two extreme solar cosmic ray events on 29 September 1989 and on 20 January 2005 along selected flight profiles. In addition, the paper discusses the consequences of possible solar cosmic ray flux approximations on the results of the radiation dose computations.

Interhemispheric observations of impulsive nitrate enhancements associated with the four large ground-level solar cosmic ray events (1940–1950)

We present a compelling similarity of impulsive nitrate enhancements observed in polar ice from the northern and southern hemispheres. This analysis concentrates on the period 1940–1950, during which time the first four recorded solar cosmic ray ground-level enhancements (GLEs) occurred. GLEs are strong solar proton events. We show that large and sudden enhancements in the nitrate records from both hemispheres were observed within weeks following the recorded solar cosmic ray ground-level event. The observation of impulsive nitrate enhancements simultaneously in both hemispheres shortly after a large fluence solar proton event is strong evidence in support of a causal connection and argues strongly for rapid transport of atmospheric nitrates generated through the polar atmosphere by energetic solar proton events.

The brief history of experimental research of cosmic ray variations in Yakutia

Some unknown historical facts of cosmic ray studies in the north-east of the former Soviet Union related to the Yakutsk scientific group are reported for the benefit of the international scientific community. It focuses on the founders of Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Branch of Russian Academy of Sciences. A chronology of measurements of cosmic ray intensity variations since 1949 in Yakutia (Sakha Republic; NE Siberia) is given. In particular, for the first time the data of the first solar cosmic ray event registered at Yakutsk (GLE04), with a small ionization chamber S-2 (volume: 20 L) are presented. Moreover, the data of the large ionization chamber ASK-1 (volume: 950 L) for the 1953–2003 period useful for specialists in the field of cosmic ray variations are also shown.

Research by the Tasmanian cosmic ray group during the International Geophysical Year

Systematic recording of the cosmic radiation commenced in Hobart in 1946 and at Mawson in Antarctica in 1955, making these two of the longest running cosmic ray observatories in the world. For the IGY, observations were also made at a sub-Antarctic island and near the equator, and an airborne survey of the nucleonic component was made from Geomagnetic Latitude −60°, south of Australia, to Japan and back. At Hobart there were neutron monitors, vertical and inclined muon telescopes, an ionization chamber, and two muon telescopes at ∼40 m of water equivalent underground. The research based on these and other observations determined the energy dependence of the Forbush and 11-year variations and concentrated, in particular, on understanding the anisotropic nature of galactic cosmic rays up to 150 GeV; the anisotropies in the onset phase of Forbush decreases; and the anisotropies in solar cosmic ray events. An investigation was initiated to calculate the trajectories and cutoff rigidities of cosmic rays in a high order simulation of the geomagnetic field. This was completed in 1959–60.

Decay phase of energetic electrons and protons in solar cosmic ray events

The decay phase of solar energetic particle (proton and electron) events is considered. The propagation mechanisms for particles of different kind may differ in the same events, which should manifest itself in the pecularities of their decay phases. To compare the propagation parameters of protons and electrons, we used the data of simultaneous measurements of few-MeV proton and few-hundred-keV electron fluxes from IMP-8 CPME and SOHO COSTEP. Nearly half of clear-shaped simultaneously measured electron and proton decays have similar character (exponential or power-law), suggesting that at least in a part of events electrons can be subjected to the same propagation mechanisms as protons.

The solar cosmic ray ground-level enhancements on 20 January 2005 and 13 December 2006

Close to the current solar activity minimum, two large solar cosmic ray ground-level enhancements (GLE) were recorded by the worldwide network of neutron monitors (NM). The enormous GLE on 20 January 2005 is the largest increase observed since the famous GLE in 1956, and the solar cosmic-ray event recorded on 13 December 2006 is among the largest in solar cycle 23. From the recordings of the NMs during the two GLEs, we determined the characteristics of the solar particle flux near Earth.