Solar Flare Particles Research Articles

Transient Particle Acceleration Associated with Solar Flares

Understanding how individual charged particles can be accelerated to extreme energies (10(20) electron volts), remains a foremost problem in astrophysics. Within our solar system, the active sun is capable of producing, on a short time scale, ions with energies higher than 25 gigaelectron volts. Satellite and ground-based observation over the past 30 years have greatly increased our knowledge of the properties of transient bursts of energetic particles emitted from the sun in association with solar flares, but a real understanding of the solar flare particle acceleration process requires greatly refined experimental data. On the practical side, it is also imperative that this problem be solved if man is to venture, for long periods of time, beyond the protective umbrella of Earth's magnetic field, which excludes much of the biologically damaging solar energetic particles. It is only through an understanding of the basic acceleration problem that we can expect to be able to predict the occurrence of a solar flare with lethal solar radiations. For our knowledge of these effects to advance, a new space mission dedicated to studying the high-energy aspects of solar flares at high spatial and energy resolution will be required.

Signature of the solar cosmic-ray event on 1982 June 3

view Abstract Citations (13) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Signature of the Solar Cosmic-Ray Event on 1982 June 3 Debrunner, H. ; Flueckiger, E. O. ; Lockwood, J. A. Abstract Observations of the solar H-alpha, radio, and hard X-ray radiation and measurements made with the gamma-ray spectrometer on the Solar Maximum Mission satellite, the Goddard cosmic-ray detector on Helios 1, and the Jungfraujoch neutron monitor during the solar cosmic-ray event on June 3, 1982 were used to determine the onset times of the various electromagnetic emissions, the injection of the flare protons into the interplanetary magnetic field, and the production of solar neutrons. The results of this analysis show that the time to accelerate the first protons up to energies of a few GeV was about 3.5 minutes longer than the time needed to accelerate the first 20 MeV protons. The accelerations process of the high-energy protons in this event is consistent with the conventional picture of solar flare particle acceleration where energy is dissipated from the flare region, heating the coronal plasma and producing a strong shock wave. The shock, as it then moves through the corona, accelerates the higher energy protons. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1990 DOI: 10.1086/191458 Bibcode: 1990ApJS...73..259D Keywords: Particle Acceleration; Solar Cosmic Rays; Solar Radiation; H Alpha Line; Shock Waves; Solar Flares; Solar Magnetic Field; Solar Maximum Mission; Solar Radio Emission; Solar X-Rays; Solar Physics; COSMIC RAYS: GENERAL; PARTICLE ACCELERATION; SUN: FLARES; SUN: PARTICLE EMISSION; SUN: RADIO RADIATION; SUN: X-RAYS full text sources ADS |

Abiotic synthesis of amino acids and imidazole by proton irradiation of simulated primitive earth atmospheres

Proton irradiation of simulated primitive earth atmosphere was performed, and amino acids and imidazole were analyzed. A mixture of carbon monoxide and nitrogen over water was irradiated by high energy protons (3 MeV, 0.6 µA) generated by a Van de Graaff accelerator for 2–5 h. Various kinds of proteinous and non-proteinous amino acids were detected in the irradiation products. Imidazole present in the irradiation products was also detected by high-performance liquid chromatography and mass spectrometry. The present results suggest that compounds of biological importance such as amino acids could be synthesized from primitive earth atmosphere by radiation of cosmic rays and/or solar flare particles.

Abiotic Synthesis of Amino Acids by Proton Irradiation of a Mixture of Carbon Monoxide, Nitrogen, and Water

Abstract We have shown that proton irradiation simulating the action of cosmic rays and solar flare particles formed proteinous and non-proteinous amino acids such as glycine, alanine, aspartic acid and β-alanine from a mixture of carbon monoxide, carbon dioxide, nitrogen and water. The yield of amino acids per unit energy was the highest obtained among various prebiotic energy sources used. This result suggests the possibility of the formation of amino acids from mildly reduced primitive atmospheres on the earth.

Exposure history of the regolithic chondrite Fayetteville: II. Solar-gas-free light inclusions

Noble gases and cosmic-ray tracks were determined on light, solar-gas-free inclusions of the solar-gas-rich H4 chondrite Fayetteville. 10Be, 26A1, major and trace element concentrations as well as oxygen isotope ratios complete the data set. One exceptional inclusion is an L-chondrite xenolith, identified by its oxygen isotope signature and the concentration of metallic Fe-Ni. Oxidized Fe of this inclusion equilibrated with the host early in the history of Fayetteville's parent body. Track density variations indicate that the majority of Fayetteville's inclusions were irradiated as pebbles in the parent body by solar flare particles for about 10 4-10 6 years. The L-chondritic inclusion contains an unequivocal excess of GCR produced He and Ne relative to the remaining inclusions. This clast, as well as two more solar-gas-free samples suffered a GCR exposure on the parent body lasting some 10 million years or longer. This exposure is comparable in length to the residence times of solar-gas-rich matrix samples in the GCR active zone of the Fayetteville parent regolith. Probably the other inclusions also were irradiated by GCR during at least several million years prior to the separation of the meteoroid from the parent body.

Anisotropy of shock‐accelerated ion distributions in interplanetary space

Recent reports of energetic particles upstream of interplanetary shocks have concentrated upon the ability of the shocks to accelerate a small percentage of the solar wind thermal ion population. In keeping with the diffusive shock acceleration model, Lee (1983) derived a theory which predicts the asymptotic steady state approached by the energetic particle distribution and low‐frequency wave spectra upstream of interplanetary traveling shocks. More recently, Kennel et al. (1986) have performed a detailed test of the Lee theory by applying it to the observations of the November 12, 1978 shock viewed by the ISEE spacecraft. A major point of departure between the theory and observations rests with the spatial dependence of the particle intensity and anisotropy in the upstream region. We argue that this discrepancy is due to the presence of solar flare particles. These particles form an additional seed population which alters the upstream boundary condition of the energetic population. The resulting anisotropy of the energetic particle distribution several scale lengths upstream of the shock is proportional to the ratio of the streaming of the shock‐accelerated population to the density of the solar flare population. Comparison of this theoretical result with the observed upstream anisotropy suggests that the measured upstream anisotropies are due largely to the streaming of the solar flare ion population. We also compare this theory to the measured particle intensities and anisotropies in the April 4–5, 1979 shock event reported by Sanderson et al. (1985b) and conclude that very little of the upstream particle anisotropy measured for this event can be attributed to the shock acceleration process. Since energetic storm particle (ESP) events at 1 AU are frequently observed in association with solar flare particles, it is anticipated that the discussion presented here should describe a commonly observed aspect of ESP events.

Electron Acceleration in Solar Flares

AbstractFor the period September 1978 to December 1982 we have identified 55 solar flare particle events for which our instruments on board the ISEE-3 (ICE) spacecraft detected electrons above 10 MeV. Combining our data with those from the ULEWAT spectrometer (MPI Garching and University of Maryland) electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (< 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (> 1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.

Gamma-ray spectroscopic tests for the anisotropy of accelerated particles in solar flares

The profiles of 0.429 and 0.478 MeV gamma-ray lines from Be-7 and Li-7 (produced by interactions of flare-accelerated alpha particles with ambient He in the solar atmosphere) and of the 4.438 MeV line from C-12 (produced by inelastic scattering of C-12 by accelerated protons) depend on the angular distribution of the interacting accelerated particles. The line profiles resulting from various assumed accelerated-particle angular distributions are calculated and it is shown that it will be possible to distinguish among them using observations of gamma-ray spectra from solar flares obtained with high resolution detectors.

Extra-terrestrial noble gases in deep sea sediments

Magnetic fractions separated from four deep sea sediments from the Pacific Ocean were analysed for elemental abundances and isotopic ratios of noble gases by stepwise heating. A 3He 4He ratio of (1.8 ± 0.4) × 10 −4 was observed in most samples in the high temperature fractions. In all the samples 20Ne 22Ne ratios are constant (11.6 ± 0.6) in most temperature fractions. These ratios are different from He-A, Ne-A and He-B, Ne-B and appear to come from a unique component. The 40Ar 36Ar ratios in high temperature fractions are lower than the atmospheric ratio, indicating the existence of extra-terrestrial Ar, while the 38Ar 36Ar ratios are indistinguishable from atmospheric, planetary, and solar Ar, indicating negligible spallogenic Ar. The isotopic ratios of Kr and Xe are indistinguishable from atmospheric ratios. From the 20Ne 22Ne ratios and from thermal release patterns of He, we conclude that the extra-terrestrial noble gases are implanted solar flare particles. The energy range of the solar flares is estimated from the relation between the grain size of IDPs (Interplanetary Dust Particles) and the penetration depth of particles impinging on to a grain, which gives less than 1 MeV/n. The uniformity of isotopic ratios of He and Ne can be explained by a grain size sieving effect of IDPs during atmospheric entry and by the subsequent diffusion loss of shallowly implanted solar wind noble gases.

Solar flare particle propagation in interplanetary space

A radial solution has been obtained to the transport equation for solar flare particle propagation in interplanetary space that includes the effects of convection, energy change and anisotropic diffusion with Kṙ=Kο Eα · rβ. It is assumed that the particles are injected impulsively at the flare site and that the radial dependence of the solar wind velocity is linear at r ≦ 1 AU.With this model we are able to reproduce the features of the western hemispheric proton events.

A comparison between .LAMBDA.|| obtained by simulations and deduced from quasi-linear theory.

Spatial diffusion coefficients of parallel (K||) to the direction (z) of averaged magnetic field ‹B› are obtained in the simulated interplanetary magnetic field fluctuations (slab model) by directly calculating the displacement (Δz) of particles along ‹B› and also by using the simple relation ofK||=limΔt→∞[‹Δz2›/(2Δt)], where ‹Δz2› is the mean square of the displacement of particles during the time interval Δt. The calculations are performed under the parameters of η=‹ΔB2›1/2/‹B›, where ‹ΔB2›1/2 is the root mean square of one component of fluctuations perpendicular to z, γ, the power exponent of the magnetic field power spectrum for large wave numbers, and L, correlation length, respectively.The deduced parallel mean free path λ|| (in AU) from λ||=3K||/v for η=0.42, L=6×1011cm and ‹B›=5nT, is well expressed asλ||=0.204(R/R0)0.5+0.109(R/R0)2 for γ=1.5, andλ||=0.217(R/R0)0.15+0.0658(R/R0)2 for γ=2.0, in the rigidity regions of 0.09-9GV, where v and R are velocity and rigidity in units of GV, respectively. Here R0 is 9GV corresponding to the resonant wave numbers of 1/L. λ|| for γ=1.5 and 2.0 are shorter than the values expected in the quasi-linear theory (QLT) by 30-40% and 40-60% respectively in 0.09-3GV (0.01<ρ/L<0.33), where ρ is the cyclotron radius of particles around ‹B›. The scaling law concerning L is also confirmed by the simulations. η2 dependence of λ|| at fixed rigidity predicts that QLT is applicable only below η=0.14-0.1. The comparisons of our λ|| with the values from the observations of solar flare particles show that λ|| for γ=2.0 corresponds better with the observed λ|| in the rigidity of -0.1—a few GV than one for γ=1.5.

Nuclear processes and accelerated particles in solar flares

A detailed review of nuclear processes and particle acceleration in solar flares has been completed recently (Ramaty and Murphy, 1987). Included in this review were a comprehensive discussion of the theory of gamma-ray and neutron production, as well as the results of comparisons of calculations with gamma-ray, neutron and charged-particle observations of solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies and electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site were also discussed. In addition, elemental and isotopic abundances of the ambient gas, derived from gamma-ray observations, were compared to abundances obtained from observations of escaping accelerated particles and other sources. The present paper is a synopsis of this review

Nuclear processes and accelerated particles in solar flares

Nuclear processes and particle acceleration in solar flares are reviewed. The theory of gamma-ray and neutron production is discussed and results of calculations are compared to gamma-ray, neutron, and charged-particle observations from solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies, electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site, are presented. The information on elemental and isotopic abundances derived from gamma-ray observations is compared to abundances obtained from escaping accelerated particles and other sources.

High-Energy Particle Production in Solar Flares (SEP, Gamma-Ray and Neutron Emissions)

Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near Earth, consist of electrons and ions that range in energy from 10 keV to ∼ 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while x-ray, γ-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism.We review the physics of γ-ray and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the Earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. The correlation of the SEP flux with the yield of γ-rays at the Sun is briefly discussed. We review, in some detail, energetic particle production in the large flare on 1982 June 3. Discussed also are gamma ray and neutron observational constraints on particle acceleration mechanisms and a summary of some recent work on solar flare particle acceleration mechanisms.

Verification of Single Event Upset Rate Estimation Methods with On-Orbit Observations

In an experiment aboard the Hughes Corporation Leasat vehicle at geosynchronous orbit, single event upsets (SEU) have been continuously monitored in a memory consisting of 93L422 RAMs. Using simultaneous measurements of the high energy galactic cosmic ray and solar flare particle environment from The University of Chicago experiment aboard the IMP-8 satellite, together with a Leasat mass distribution model and ground test measurements of the SEU susceptibility for the 93L422, accurate estimates of the SEU rate are calculated based on several improvements to the standard methods. These results are discussed and compared to the Leasat flight observations.

Coronal transport of solar flare particles

We reviewed the observational features supporting the view that azimuthal transport of solar flare particles takes place at the level of the solar corona, and not in the interplanetary medium. A brief description is given of models regarding longitudinal particle transport, in terms of their ability to explain the corresponding observational phenomena. Finally, a model with multiple particle emission phases is proposed, in terms of two coronal azimuthal transport steps, on the basis of the dynamical and static features of the coronal magnetic field, respectively.

Time-dependent coronal shock acceleration of energetic solar flare particles

A global time-dependent model is presented for the coronal and interplanetary shock acceleration and propagation of energetic solar flare particles. The calculations are carried out to help prove that coronal shock acceleration of solar flare particles is responsible for energetic solar flare event data gathered in interplanetary space. The model is based on the theory of diffusive shock acceleration, and requires particle speeds to be much greater than bulk velocities. Also, sufficient scattering must occur upstream and downstream of the shock for the particle scattering mean free path to be smaller than the characteristic scale lengths, which causes the same particles to encounter the shock repeatedly. A spherically symmetric shock wave is assumed, which leads to the same emission configuration for impulsively and monoenergetically emitted particles. Consideration is given to acceleration by compression at the shock front, adiabatic deceleration in the divergent downstream flow, the temporal evolution of the shock and the three-dimensional geometry of the corona. The model is used to generate normalized proton omnidirectional distributions at 1 AU and at the shock front. The spectral exhibit trends similar to those in observational data, especially proton acceleration times and the proton distribution profiles at 1 AU.

Gyrosynchrotron emission of solar flares

The current status of our knowledge on the theory of radio emission from mildly relativistic electrons and its application in the interpretation of solar radio bursts are reviewed. The recent high spatial resolution microwave observations have given important information about the geometry of the emitting region and have helped in the computation of better inhomogeneous models that reproduce qualitatively several observational characteristics of the emission. The limitations of the observations and the theory (particularly the effect of mode coupling on the observed polarisation) are pointed out and the potential of the gyrosynchrotron process as a diagnostic of the physical conditions is discussed. This will help us to obtain quantitative information about the changes of the magnetic field and the acceleration of particles in solar flares.

Linear polarizations of 4.43 MeV12C* and 6.13 MeV16O* gamma-rays as indicators of directions of particles in solar flares

The linear polarizations of the 4.43 MeV 12C* and the 6.13 MeV 16O* gamma-ray lines, that are assumed to be produced in (p, p′) processes in solar flares, are projected as functions of θ, the angle between the line-of-sight and the direction of the particle beam. The projected polarization amplitudes are quite large, and it is suggested that their measurement would facilitate to uniquely determine the particle direction without recourse to Doppler shift measurements.

On the role of energetic particles in solar flares

The importance of energetic particles in the generation of solar flares and related phenomena has been underestimated if not completely neglected. A reexamination of their role in the light of recent observations carried out during the last solar maximum by a number of experiments on SMM and Hinotori satellites points out the continuous and violent evolution of the solar atmosphere. Most observed features can be better explained by the old idea that particles are trapped in magnetic loops above active regions where they are first heated and then accelerated by absorbing part of the wave energy flowing upwards continuously from the convection zone. Their catastrophic release into the chromosphere as a consequence of an instability in the region such as chromospheric heating or due to the emergence of new magnetic flux is considered as being the flare proper. Since the trapping of the particles involves the generation of resonant waves, a reassessment of the isotopic overabundance problem as well as a search for these waves in interplanetary space are proposed.