Ulysses HISCALE Pages
Authors: L. J. Lanzerotti and C. G. Maclennan, AT&T Bell Laboratories, Murray Hill, NJ; R. E. Gold and S. E. Hawkins III, Johns Hopkins University Applied Physics Laboratory, Laurel, MD; S. J. Tappin, Univ. of Birmingham, U.K.; and R. Forsyth, Imperial College, London, U.K.
Presented at: Sept. 1992 COSPAR Meeting, Washington, DC.
Abstract. The time evolution of the very large solar particle event occurring on days 82-90 (March 23-31), 1991, as measured at 2.5 AU by the instrumentation on the Ulysses spacecraft was quite complex. Measurements by the HISCALE instrument of the nuclear composition (emphasizing Z ≥ 6) of the interplanetary particles at a time resolution of two hours provides information on the different interplanetary regions which swept over the spacecraft. The Fe/O abundance ratio is found to differ slightly in the regions before and after two tangential discontinuities. The Fe/O abundance ratio is also found to depend strongly on the energy/nucleon of the particle, with values of ~0.7 for energies of for energies of ~0.5-1.0 MeV/nucl. to values of ~0.2 for energies ~8-16 MeV/nucl.
|Figure 1. The HISCALE experiment: Complete instrument assembly||Figure 2. Schematic outline of detector telescope configurations in the 2 separate mechanical mounts. The composition data are acquired by the CA60 aperture. The detector coincidence conditions are DCB.|
|Figure 3. Instantaneous look
direction of the four LEMS/LEFS telescopes on the 4π steradian sphere. One
spacecraft rotation (~12 sec) takes each telescope through 360°, and thus the
entire sphere is covered each rotation.
||Figure 4. Calibration data. Energy-loss matrix for the composition aperture for various incident ions. The solid lines outline the discrete delement groups detected (Table 1).|
|Figure 5. Time-intensity (2-hour average) counting rates for 3 Fe energy channels and an O and a Ne-Mg-Si (NMS group) energy channel for days 82-90, 1992. Representative error bars are shown.||Figure 6. Ion flux composition matrix measured by the CA detector system during day 82, 1991, at the beginning of the solar event.|
|Figure 7. Ion flux composition matrix measured by the CA detector system during day 83, 1991.||Figure 8. Ion flux composition matrix measured by the CA detector system during day 84, 1991.|
|Figure 9. Iion flux composition matrix measured by the CA detector system during day 85, 1991.||Figure 10. Details of the onsets of the heavy ions on days 82-83, 1991. At the bottom are plotted the half-hour averages of the interplanetary magnetic field strength at Ulysses. The time of the first interplanetary shock (S) and onset of the driver gas (DG) are indicated.|
|Figure 11. Time dependence of the 2-hour average Fe rates on day 84, 1991, during the time of the second interplanetary shock (S) and the 2 tangential discontinuities (TD).||Figure 12. Two-hour average heavy ion spectra and atomic abundances for several species, as well as atomic abundance ratios (Z>6) relative to O for 2 different time intervals in the event. The energy range for the ratios C/O, N/O, S/O, Fe/O is 5-16 MeV/nucl.; for G/O (NMS/O) the range is 1.0-1.0 MeV/nucl.|
|Figure 13. Energy dependence of the Fe/O abundances for three different MeV/nucl. channels. The times of shocks (S), tangential discontinuities (TD), and the driver gas (DG) are noted.||Figure 14. Sketch of the interplanetary regions delineated by examination of the heavy ion composition as a function of time during the March 1991 event.|
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Last modified February 28, 2006