High Energy Solar Particle Events Research Articles

Intense solar activity reduces urinary 6-sulfatoxymelatonin in patients with COPD

BackgroundLittle is known about the link between solar activity and variations in melatonin. In this study, we investigated if melatonin's major urinary metabolite, urinary 6-sulfatoxymelatonin (aMT6s), is lowest under periods of intense solar activity.MethodsWe investigated associations between high-energy solar particle events [Coronal Mass Ejection (CME) mass, speed and energy] on creatinine-adjusted aMT6s (aMT6sr) concentrations in 140 patients with chronic obstructive pulmonary disease (COPD) using up to four seasonal urine samples (n = 440). Mixed effect models with a random intercept for each subject were used to estimate associations, including effect modification attributable to diabetes, obesity, and reduced pulmonary function.ResultsHigher values of CME were associated with reduced aMT6sr concentrations, with stronger associations in patients with diabetes. An interquartile range (IQR) increase in natural log CMEspeed averaged through two days before urine collection was associated with a reduction of 9.3% aMT6sr (95%CI: − 17.1%, − 0.8%) in aMT6sr. There was a greater reduction in aMT6sr in patients with diabetes (− 24.5%; 95%CI: − 35.9%, − 11.6%). In patients without diabetes there was no meaningful association (− 2.2%; 95%CI: − 12%, 8.4%). There were similar associations with CMEenergy and CMEmass. There was no effect modification attributable to reduced pulmonary function or obesity.ConclusionsThis is the first study in patients with COPD to demonstrate strong detrimental impact of high-energy solar particle events on aMT6sr, with greater associations in patients with diabetes. Since melatonin is an anti-oxidant, it is possible that adverse effects of intense solar activity may be attributable to a reduction in circulating melatonin and that patients with both COPD and diabetes may be more susceptible.

High Energy Solar Particle Events and Their Relationship to Associated Flare, CME and GLE Parameters

AbstractLarge solar eruptive events, including solar flares and coronal mass ejections (CMEs), can lead to solar energetic particle (SEP) events. During these events, protons are accelerated up to several GeV and pose numerous space weather risks. These risks include, but are not limited to, radiation hazards to astronauts and disruption to satellites and electronics. The highest energy SEPs are capable of reaching Earth on timescales of minutes and can be detected in ground level enhancements (GLEs). Understanding and analyzing these events is critical to future forecasting models. However, the availability of high energy SEP data sets is limited, especially that which covers multiple solar cycles. The majority of analysis of SEP events considers data at energies <100 MeV. In this work, we use a newly calibrated data set using data from Geostationary Operational Environmental Satellite‐high energy proton and alpha detector between 1984 and 2017. Analysis of the SEP events in this time period over three high energy channels is performed, and SEP properties are compared to flare and CME parameters. In addition, neutron monitor (NM) observations are examined for the relevant GLE events. We find that correlations between SEP peak intensity and the CME speed are much weaker than for lower SEP energies. Correlations with flare intensity are broadly similar or weaker. Strong correlations are seen between >300 MeV data and GLE properties from NM data. The results of our work can be utilized in future forecasting models for both high energy SEP and GLE events.

Modeling the Transport of Relativistic Solar Protons along a Heliospheric Current Sheet during Historic GLE Events

There are many difficulties associated with forecasting high-energy solar particle events at Earth. One issue is understanding why some large solar eruptive events trigger ground-level enhancement (GLE) events and others do not. In this work we perform 3D test particle simulations of a set of historic GLEs to understand more about what causes these powerful events. Particular focus is given to studying how the heliospheric current sheet (HCS) affects high-energy proton transport through the heliosphere following an event. Analysis of ≥M7.0 flares between 1976 and 2020 shows that active regions located closer to the HCS (<10°) are more likely to be associated with a GLE event. We found that modeled GLE events where the source region was close to the HCS also led to increased heliospheric transport in longitude and higher count rates (when the Earth was located in the drift direction). In a model that does not include perpendicular diffusion associated with turbulence, the HCS is the dominant mechanism affecting heliospheric particle transport for GLE 42 and 69, and varying other parameters (e.g., a narrow, 10°, or wider, 60°, injection width) causes little change. Overall in our model, the HCS is relevant in 71% of our analyzed GLEs, and including it more accurately reproduces observed intensities near Earth. Our simulations enable us to produce model profiles at Earth that can be compared to existing observations by the GOES satellites and neutron monitors, as well as for use in developing future forecasting models.

Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions

We have analysed 58 high-energy proton events and 36 temporally related near-relativistic electron events from the years 1997 – 2015 for which the velocity dispersion analysis of the first-arriving particles gave the apparent path lengths between 1 and 3 AU. We investigated the dependence of the characteristics of the proton events on the associations of type II, III, and IV radio bursts. We also examined the properties of the soft X-ray flares and coronal mass ejections associated with these events. All proton events were associated with decametric type III radio bursts, while type IV emission was observed only in the meter wavelengths in some of the events (32/58). Almost all proton events (56/58) were associated with radio type II bursts: 11 with metric (m) type II only, 11 with decametric–hectometric (DH) only, and 34 with type II radio bursts at both wavelength ranges. By examining several characteristics of the proton events, we discovered that the proton events can be divided into two categories. The characteristics of events belonging to the same category were similar, while they significantly differed between events in different categories. The distinctive factors between the categories were the wavelength range of the associated type II radio emission and the temporal relation of the proton release with respect to the type II onset. In Category 1 are the events which were associated with only metric type II emission or both m and DH type II and the release time of protons was before the DH type II onset (18/56 events). Category 2 consists of the events which were associated with only DH type II emission or both m and DH type II and the protons were released at or after the DH type II onset (31/56 events). For seven of the 56 events we were not able to determine a definite category due to timing uncertainties. The events in Category 1 had significantly higher intensity rise rates, shorter rise times, lower release heights, and harder energy spectra than Category 2 events. Category 1 events also originated from magnetically well-connected regions and had only small time differences between the proton release times and the type III onsets. The soft X-ray flares for these events had significantly shorter rise times and durations than for Category 2 events. We found 36 electron events temporally related to the proton events, which fulfilled the same path length criterion as the proton events. We compared the release times of protons and electrons at the Sun, and discovered that in 19 of the 36 events protons were released almost simultaneously (within {pm},7 minutes) with the electrons, in 16 events protons were released later than the electrons, and in one event electrons were released after the protons. The simultaneous proton and electron events and the delayed proton events did not unambiguously fall in the two categories of proton events, although most of the events in which the protons were released after the electrons belonged to Category 2. We conclude that acceleration of protons in Category 1 events occurred low in the corona, either by CME-driven shocks or below the CMEs in solar flares or in CME initiation related processes. It seems plausible that protons in Category 2 events were accelerated by CME-driven shocks high in the solar corona. Large delays of protons with respect to type III onsets in the events where protons were released after the electrons suggest late acceleration or release of protons close to the Sun, but the exact mechanism causing the delay remained unclear.

The HESPERIA HORIZON 2020 Project and Book on Solar Particle Radiation Storms Forecasting and Analysis

AbstractThis article presents the High Energy Solar Particle Events forecasting and Analysis (HESPERIA) project, supported by the HORIZON 2020 programme of the European Union (Project 637324) as well as the resultant recently published book entitled Solar Particle Radiation Storms Forecasting and Analysis, The HESPERIA HORIZON 2020 Project and Beyond, edited by Malandraki and Crosby, Springer, Astrophysics and Space Sciences Library, 2018, ISBN 978‐3‐319‐60051‐2. The book reviews the results of the HESPERIA project as well as our current understanding of solar energetic particle physics.

The MAVEN Solar Energetic Particle Investigation

The MAVEN Solar Energetic Particle (SEP) instrument is designed to measure the energetic charged particle input to the Martian atmosphere. SEP consists of two sensors mounted on corners of the spacecraft deck, each utilizing a dual, double-ended solid-state detector telescope architecture to separately measure fluxes of electrons from 20 to 1000 keV and ions from 20–6000 keV, in four orthogonal look directions, each with a field of view of \(42^{\circ}\) by \(31^{\circ}\). SEP, along with the rest of the MAVEN instrument suite, allows the effects of high energy solar particle events on Mars’ upper atmospheric structure, temperatures, dynamics and atmospheric escape rates, to be quantified and understood. Given that solar activity was likely substantially higher in the early solar system, understanding the relationship between energetic particle input and atmospheric loss today will enable more confident estimates of total atmospheric loss over Mars’ history.

High-energy solar particle events in cycle 24

The Sun is already in the declining phase of cycle 24, but the paucity of high-energy solar energetic particle (SEP) events continues with only two ground level enhancement (GLE) events as of March 31, 2015. In an attempt to understand this, we considered all the large SEP events of cycle 24 that occurred until the end of 2014. We compared the properties of the associated CMEs with those in cycle 23. We found that the CME speeds in the sky plane were similar, but almost all those cycle-24 CMEs were halos. A significant fraction of (16%) of the frontside SEP events were associated with eruptive prominence events. CMEs associated with filament eruption events accelerate slowly and attain peak speeds beyond the typical GLE release heights. When we considered only western hemispheric events that had good connectivity to the CME nose, there were only 8 events that could be considered as GLE candidates. One turned out to be the first GLE event of cycle 24 (2012 May 17). In two events, the CMEs were very fast (>2000 km/s) but they were launched into a tenuous medium (high Alfven speed). In the remaining five events, the speeds were well below the typical GLE CME speed (∼2000 km/s). Furthermore, the CMEs attained their peak speeds beyond the typical heights where GLE particles are released. We conclude that several factors contribute to the low rate of high-energy SEP events in cycle 24: (i) reduced efficiency of shock acceleration (weak heliospheric magnetic field), (ii) poor latitudinal and longitudinal connectivity), and (iii) variation in local ambient conditions (e.g., high Alfven speed).

High Energy Particle Generation in Cosmic Rays and Solar Particle Events

It is assumed that cosmic rays and other high-energy particles of extraterrestrial origin can be produced by first-order Fermi diffusive shock acceleration in plasma up to 5x1019 eV, the point where they interact with the cosmic microwave background (CMB). First-order Fermi shock acceleration is due to a supersonic shock with a Mach number dependent on the index (or logarithmic slope) of the shock-induced power-law spectrum. The local all-particle interstellar cosmic-ray spectrum can be obtained from the solution of a Fredholm integral equation in rigidity, yielding both the “knee” and the “ankle” of the primary spectrum. The effect of the maximum galactic acceleration mechanism at high energies near the ankle is to increase the relative number of heavy nuclei relative to protons. Multiple cutoffs of heavier nuclei due to interactions with the CMB have the opposite effect just below the Greisen-Zatsepin-Kuz’min (GZK) cutoff, resulting in fluxes enriched in protons. Earthward-directed supersonic coronal mass ejections are responsible for the great bulk of high-energy solarparticle events because of diffusive shock acceleration in the heliosphere. Keywords: Air shower data, cosmic rays, GZK cutoff, Monte Carlo solution to integral equations, plasma, Shock acceleration, solar modulation, the local interstellar spectrum.

Study of magnetic field expansion using a plasma generator for space radiation active protection

There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth's radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.

The L5 mission for space weather forecasting

We have studied a number of interplanetary space mission scenarios for space weather research and operational forecasting experiments and concluded that a spacecraft should be deployed at the L5 point of the Sun–Earth system to enable remote sensing of the Sun and interplanetary space and in situ measurements of solar wind plasma and high energy solar particle events. The L5 point is an appropriate position for making side-view observations of geo-effective coronal mass ejections and interplanetary plasma clouds. Here, we describe briefly the mission plan and the ongoing BBM development of important subsystems such as the wide field coronal imager (WCI) and the mission processor. The WCI will have a large CCD array with 16-bit sampling, to achieve a dynamic range of several thousand in order to detect very small deviations due to plasma clouds under zodiacal light contaminations a hundred times brighter than the clouds. The L5 mission we propose will surely contribute to the construction of an international space weather observation network.

The JPL proton fluence model: an update

The development of new technologies and the miniaturization of sensors bring new requirements for our ability to predict and forecast hazardous space weather conditions. Of particular importance are protons in the energy range from 10s to 100s of MeV which cause electronic part and solar cell degradation, and pose a hazard to biological systems in space and to personnel in polar orbit. Sporadic high-energy solar particle events are a main contributor to the fluences and fluxes of such protons. A statistical model, JPL 1991 (J. Geophys. Res. 98 (1991) 13,281), was developed to specify fluences for spacecraft design and is now widely used. Several major solar proton events have occurred since that model was developed and one objective of this paper is to see if changes need to be made in the model due to these recent events. Another objective is to review the methods used in JPL 1991 in the light of new understandings and to compare the JPL methods with those used in other models. We conclude that the method used in developing JPL 1991 model is valid and that the solar events occurring since then are completely consistent with the 1991 model. Since no changes are needed we suggest that the name of the model be changed to “the JPL fluence model”.

Comment on the use of GOES solar proton data and spectra in solar proton dose calculations

There is a need to understand the calibration and response of the GOES solar particle detectors since the GOES data are being used to evaluate high energy solar particle events. We share some of our experience in utilizing these data in the analysis of solar particle ground-level events (GLEs). For the 29 September 1989 event, we have evaluated the solar proton and alpha particle spectral characteristics throughout the event. The results show that the solar cosmic ray spectrum is extremely hard at low energies with the magnitude of the slope increasing with increasing energy and with time.

SEE relative probability maps for space operations

Normalized flux and dose data for protons with energies >50 MeV are used to produce contour maps of relative probabilities of experiencing Single Event Effects (SEEs) in the Earth's inner radiation belt. The data were taken on the APEX and CRRES satellites. To make the maps, the data are averaged in 3/spl deg/ by 3/spl deg/ bins in geographic latitude and longitude, and in 50 km steps in altitude. All geographic longitudes, and latitudes between /spl les/70/spl deg/ are covered. The altitude range extends from 350 km to 14,000 km. This geographic range includes the complete region of inner belt >50 MeV protons, except in the area of the South Atlantic Anomaly below 350 km. The maps easily locate regions of high risk for SEEs and are designed primarily for use in space mission planning and operations. The data base includes the added proton peak following the March 1991 magnetic storm, but does not include SEE probabilities in the polar cap regions associated with high energy solar particle events.

High-energy solar-particle events

Recent high-energy solar-particle events have been illustrated and described individually. The manner in which the observations have been used to develop and test concepts of the hydromagnetic behaviour of the solar plasma in space has been outlined. Some of the events have been analyzed in more detail than hitherto. The results seem to support the concept that the magnetic field of a sunspot tends to erupt, or to balloon, into space in the form of a great tongue or sack attached to the sun near the sunspot. Supersonic shock processes also must be involved in the propagation of disturbances in planetary space, and the fluxes of galactic and of solar particles may change in the vicinity of such shocks, but alone shocks do not appear to be capable of explaining all the observed effects.