Cummings that I owe to my familiarity with CRS and many of the data analysis programs. The monotonic Z-dependence of the variation between flares observed in the past was demonstrated to actually be Q/M-monotonic.
Low Energy Telescope (I.Er)
For the same reasons, only HET A-end particles stopping in detectors A2 or Cl were included, since A-end particles stopping deeper in the C stack have energies comparable to B-end events. Among other things, it is used to obtain absolute flux measurements by providing normalization for the PHA event sample.
Tmdow Thicknesses
No particular importance is attached to the trends with Z, or the lack of such trends, in the values of the parameters A;. Histogram of
Energy Interval Selection
The statistics of the resulting data set are much worse both because of the comparative rarity of the elements and because of the limitation to three-parameter data. Because the solar particle energy spectrum falls off steeply with energy, the HEl energy range corresponding to three-parameter events does not contribute significantly to the statistics of the three-parameter LET data.
Time Period Selection
The weighting factors for the different data subsets are listed in Appendix F for each of the time periods used in this study. The parameters used to characterize the distributions were the mean values and widths, in
These parameters are used to scale the width of the reference distribution in the two dimensions and to position it in the correct location on the
This was to test the sensitivity of the method to the selection of appropriate events. The graph includes all Voyager LET 3 parameter data in this region of the payload scale. Results of typical maximum likelihood runs for each of the rare and/or poorly resolved elements.
I 0 -IOeO
Average SEP Elemental Abundance s
- Determining t h e Average Abun dance and its Uncertainty
The quantitative evaluations of flare-to-flare variability described above are also used to estimate the total uncertainty for the very rare elements. This figure was converted into an estimate of the uncertainty of the mean a~ for the rare elements by dividing by --!N;tt. For many rare elements, the estimate of flare-to-flare variability is negligible compared to the statistical uncertainty.
Average ratios between adjacent elements of the more abundant heavy elements, calculated from the data in Table 4.4 using the method of combined statistical and population variance weighting of ftares, described in Section 4.3.1. Cook et al.'s SEP composition measurements are derived from Voyager LET data for a four ftare subset of the current ftare set. The average SEP abundances relative to silicon, obtained for all elements in the charge range 3 ~ Z ~ 30, are shown in Table 4.8 and plotted against the charge ranges 3 ~ Z ~ 30.
34;Total uncertainty' is the squared sum of the uncertainty in the SEP abundance and the abundance standard.
Systematics of Flare-to-Flare Variability
For any ratio showing wide variation, the larger flares (i.e. the best-determined abundance values) tend to be clustered near the center of the distribution, with the smaller flares mostly near the extremes of the distribution. However, the important point is that the variation shown by the large flares is very large compared to the measurement uncertainty of the data points. Therefore, a large component of the observed variation is due to a real systematic effect and not simply statistical fluctuation.
The same property is also apparent in a plot of the population width ratio apop vs. Also shown is the best fit to a power-law function of Q/M, obtained from a weighted least-squares fit of eight points for which the photospheric values are well known (uncertainties quoted). Finally, we note that the Q/M dependence of the mean fractionation (Fig. 4.15) is a relatively weak dependence.
This means that the greater part of the fractionation due to the acceleration process is caused by changes in the dependence of this process on the stiffness and not by changes in the stiffnesses themselves.
The SEP-Derived Photospheric Composition
Abundance or Ca, Ti and Cr relative to Fe in the SEP-derived corona (same as SEP-derived photosphere for these elements), compared to. The result was an improvement of a factor of -:1 in the precision of the mean SEP abundance compared to previous studies. Although the amount of high-FIP elements (N. 0, F. Ne, Cl, Ar) is poorly known in the photosphere.
The uncertainties in the SEP-derived photospheric abundances are generally not smaller than those quoted for the spectroscopic photospheric tabulation. This had the effect of discarding some of the "outliers" present in the initial "box" estimate of the oxygen trace. As with HET, the interaction between terms in the function C(x) (equation 3.2) results in meaningless variation of the individual parameters with Z.
Its occurrence at Fe, as a percentage of the total Fe event sample, is generally much larger than in the LETs (~40% for Voyager 1 HET 2); this is clearly seen for elements as low on the charge scale as Mg in some telescopes (Voyager 1 HET 2 and Voyager 2 HET 2); and for 3-parameter events it can sometimes be seen in one (or both) 6E detectors, rather than just the last one, resulting in several displaced groups of events in those telescopes (Voyager 1 HAS 1 and Voyager 2 HAS 2) .
LET Ll Detec tor .Jupiter Encounter Radiation Damage and Post-Enc ounter Annealing
Later laboratory work using spare CRS and pulse generators (Martin 1983) was able to reproduce the effect with greatly improved statistics and to verify the magnitude of the time constant (~6.us) implied by the flight data while extending the coverage to event rates. more than an order of magnitude above the highest seen m flight data. For 3-way data. the preselected charge consistency requirement is restrictive enough to easily exclude misidentified events; the amount of data lost is an insignificant 0.2% of the total. and the rest of the data set is as "clean" .. as those from other telescopes. The problem is more serious for two-parameter data, since there is no other determination of Z that allows normal and abnormal events to be separated; is a non-removable background source of data.
The front detectors of HETs are much thicker than those of LETs and protected by a thicker window. The effect of radiation damage on the post-Jupiter data is evident as a shift in the location of trace elements at flE compared to. The Ll thickness adjustment was then incorporated into an iterative cycle to calculate Z.
The radiation damage did not have a noticeable effect on the intrinsic charge resolution of the telescopes, so with the above modifications the post-Jupiter flare data could be treated in the same way as the pre-Jupiter data.
Voyager 2 LET C Temporary Gain Shift
6.t is the time since the Jupiter encounter in days, and ~4>(Z) is the linear or quadratic function of Z that closely fits the required thickness changes for the first post-Jupiter flares. This anomaly was noted previously (Cook 1981), and the telescope was rejected for analysis because of the problem. Since the energy calibration used in the analyzers is easily adjusted to compensate for the problem, since the payload resolution and background of the telescope does not seem to be affected by the problem and since the three 7 flares account for a large part of all the SEP data, it was decided to include Voyager 2 LET C in the analysis with the special treatment described above.
At e:ertain ttmes during the Voyager mission, the configuration of the CRS instruments was changed in ways that affect data analysis. At the beginning of each flight, the LETs were configured to require triggering of the L3 detector for pulse height analysis; that is, only 3-parameter events were analyzed. Normally, the instrument cycles between high- and low-gain modes, but after the Jupiter encounter, HET 1 on Voyager 2 was switched to a high-gain mode, so no post-Jupiter SEP heavy ion data were obtained from this telescope.
This required changes in the particle weighting factors for HET relative to LET for Voyager 2 for all post-Jupiter tlars.
Voyager 1 Block I PHA Problem
Differences in the peak particle flux between Voyager 1 and 2 and its dependence on Z for each burst, and the associated differences in the spatial location of the two spacecraft at the time of the burst. The slope and offset are best-fit values derived from a least-squares fit to the line of Vl/V2 ratios for the various elements. 1984, "Anomalies and Other Problems Encountered in the Analysis of Voyager LET and HET Data", Space Radiation Laboratory Internal Report No. 89,.
1982, "Elemental and Nuclide Abundances in the Solar System." in Essays in Nuclear Astrophysics, ed. 1976, "MJS CRS Science Requirements Document," Space Radiation Laboratory Technical Report 76-1, California Institute of Technology. 1984, "Ion composition in the solar wind in relation to solar abundance," International Conference on Isotopic Conditions in the Solar System.
1977, "Realistic Uncertainties on Galactic Abundances and the Significance of Cosmic Ray Source Composition", Proc.
