Calculations of heavy ion charge state distributions for nonequilibrium conditions

Numerical calculations of the charge state distributions of test ions in a hot plasma under nonequilibrium conditions are presented. The mean ionic charges of heavy ions for finite residence times in an instantaneously heated plasma and for a non-Maxwellian electron distribution function are derived. The results are compared with measurements of the charge states of solar energetic particles, and it is found that neither of the two simple cases considered can explain the observations

Survey of He(+)/He(2+) abundance ratios in energetic particle events

The helium charge distribution in the energy range 0.4 to 0.62 MeV/nucleon in energetic particle events was studied. An average He+/He2+ ratio of 0.12 + or - 0.04 with ratios exceeding 0.3 for 41 out of 420 days events richest in He+ and no significant differences of the proton energy spectra, and the abundance of helium relative to protons and heavy ions for He+ rich events (He+/He2+ 0.3) and for events with He+/He2+ 0.3, respectively. It is also found that He+ rich events are predominantly low in energetic particle intensity

Carbon-poor solar flare events

Energetic particle flux enhancements over the period October 1973 - December 1977 were surveyed using ULET sensor on the IMP-8 spacecraft. During the four year period the most extreme periods of Fe enrichment compared to oxygen were during solar flare events in February 1974 and May 1974. In these same events, the carbon abundance with respect to oxygen was significantly depleted when compared with a value C:0 is approximately 0.45:1 for typical solar flares. These observations, taken together with previously reported He-3 enrichment in these events, give strong evidence for the importance of a wave-particle interaction in the pre-injection heating of the ambient matter

The composition of heavy ions in solar energetic particle events

Recent advances in determining the elemental, charge state, and isotopic composition of or approximate to 1 to or approximate to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations. Average values of relative abundances measured in a large number of SEP events were found to be roughly energy independent in the approx. 1 to approx. 20 MeV per nucleon range, and showed a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs revealed the surprisingly common presence of energetic He(+) along with heavy ion with typically coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events showed these to be consistent with the universal composition except for the puzzling overabundance of the SEP(22)Ne/(20)Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of (3)He rich, heavy ion rich and carbon poor SEP events, along with direct measurements of the ionization states of SEPs provided essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production

The energy spectra of solar flare electrons

A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares

Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams: Implications for interplanetary acceleration and propagation

Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of approximately 0.15 to approximately 8 MeV/nucleon particles in three corotating streams observed near earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, v sub o, is typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundances of energetic particles in these events resemble most closely the solar coronal composition and, thus, presumably that of the solar wind. These results may imply that the acceleration of these particles, which occurs in corotating interaction regions at several AU from the sun, is by a statistical process

The heavy ion composition in 3HE-rich solar flares

The 3He-rich flares show a tendency to be enriched in heavy ions, and that this enrichment covers the charge range through Fe. The discovery of this association was responsible, in part, for the discarding of 3He enrichment models which involved spallation or thermonuclear reactions, since such models were unable to produce heavy nuclei enhancement. Results of a survey of heavy nucleus abundances observed in 66 3He-rich flares which occurred over the period October 1978 to June 1982 are presented

Unusual emission of iron nuclei from the sun

Sustained emission of low energy solar particles with a composition richer in iron than oxygen is observed in the time period 1974 May 7 to 17. Between 0.7 and 4 MeV/nucleon the relative abundances of C:O:Fe are 0.24:1:1.35. It was suggested that these observations provide indication for effects of heavy ion enrichment in the lower corona of the sun

Differential energy spectra of low energy (less than 8.5 MeV per nucleon) heavy cosmic rays during solar quiet times

Explorer 47 satellite observations of carbon, oxygen, and heavier nuclei differential energy spectra below 8.5 MeV/nucleon are presented for solar quiet time periods. A dE/dx vs E method for particle identification and energy determination was used. The instrumentation telescope included an isobutane proportional counter, a surface barrier Si detector, and a cylindrical plastic scintillator anticoincidence shield. The observations were performed outside the bow-shock and in the ecliptic plane. Results show an anisotropy of about 25% at 22 degrees west of the sun with a C/O ratio of 0.5 supporting a solar origin. The low energy portions of the C and O spectra have steep negative slopes, and the corresponding power law is given. Peculiarities in the O spectrum are discussed

Post-shock spikes: A new feature of proton and alpha enhancements associated with an interplanetary shock wave

Abrupt and prolonged enhancements in the intensities of 100 to approximately 2000 keV nucleon protons and alpha particles observed in interplanetary space are interpreted as particle populations confined between an interplanetary shock front and a magnetic field discontinuity. Prominent intensity spikes observed only below approximately 400 keV per charge for both protons and alpha particles several hours behind the shock front suggest that some fraction of the confined particles is accelerated by an energy per charge dependent process