Z-rich solar particle event characteristics 1972--1976
A systematic analysis of the hourly average Z> or =3 rate date (1972) September--1976 December) measured with the JHU/APL IMP 7 and IMP 8 detectors has revealed 13 short-lived events that have greatly enhanced Z> or = 3 fluxes. In addition to confirming the results of earlier studies that all /sup 3/He-rich events are Fe-rich but not vice versa, we find that these 13 enriched events have several remarkable characteristics: (1) they are generally not associated with major solar flares but appear to be associated with low levels of activity (subflares) in western-hemisphere solar active regions that are located very close to the spacecraft's high coronal interplanetary magnetic field connection longitude; (2) they have very large and prolonged outward streaming anisotropies, sometimes persisting approx.1 day; (3) the spectra indices measured for p, ..cap alpha.., and Z> or =3 particles during the times of maximum flux for the Z-rioch events are identical within errors to those measured in large flare events, while small impulsive and corotating events generally show a softer spectrum; and (4) Z-rich events appear to be associated with the low-speed wind that precedes the onset of solar wind streams. We conclude from this study that the same type of acceleration process that is responsible for the large proton events is responsible for the small Z-rich events, and therefore that the Z+ or =3 and /sup 3/He enrichments are more likely due to enhanced abundances in the preaccelerated plasma than to preferential enrichment during the acceleration process. This interpretation is complementary to recent findings concerning abundances and coronal emission structure of low-speed solar wind. We conclude that compositional studies of low-energy solar particle events offer a good diagnostic of the flare acceleration process and possible inhomogeneities in the solar atmosphere, but are poor indicators of solar composition on a global scale.
- Research Organization:
- Applied Physics Laboratory, The Johns Hopkins University
- OSTI ID:
- 6583993
- Journal Information:
- Astrophys. J.; (United States), Vol. 225:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
SOLAR FLARES
SOLAR PARTICLES
MASS SPECTRA
NUCLEONS
SOLAR ALPHA PARTICLES
SOLAR PROTONS
SOLAR WIND
ULTRAVIOLET SPECTRA
ALPHA PARTICLES
BARYONS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
HADRONS
PROTONS
RADIATIONS
SOLAR ACTIVITY
SOLAR RADIATION
SPECTRA
STELLAR RADIATION
640104* - Astrophysics & Cosmology- Solar Phenomena