Shock-associated low-energy ion enhancements observed by Voyagers 1 and 2
Observations of shock-associated > or =30 keV ion enhancements are presented using data from the Low Energy Charged Particle (LECP) experiment on Voyagers 1 and 2, launched on days 248 and 232, 1977, respectively. The observations include examples of energetic storm particle (ESP) events associated with flare-produced shocks and examples of corotating particle events (CPE) associated with forward and reverse shocks that bound corotating interaction regions in the outer heliosphere. The first well-defined CPE are not seen at Voyagers 1 and 2 until late 1978 when each spacecraft was at a heliocentric radial distance of approx.4 AU. Thus far, seven CPE have been identified in the Voyager 1 LECP data from launch through day 170, 1979. Most of these CPE show features similar to many of those observed at Pioneers 10 and 11, e.g., they have recurrent double-packed intensity enhancements showing little or no velocity dispersion at peak intensities, time durations of several days, soft (..gamma..> or approx. =4 for protons approx.1 MeV) energy spectra extending up to approx.5 MeV/nucleon and p/..cap alpha.. ratios that are lowest at the reverse peaks. The new LECP measurements also show for the first time that the CPE ion spectra extend, with no sign of a low-energy turnover, to energies as low as 30 keV/ion. If the CPE are produced by shock acceleration of an ambient particle source, the fact that the observed CPE exhibit well-formed high intensity peaks at 30 keV/ion means that the pre-acceleration energy of the source particle was <30 keV/ion. In several of the shock events, the lowest energy ion enhancements are confined mainly downstream of the CIR shocks, with the magnitude and duration of the upstream enhancements increasing with increasing ion energy. The similarities in the low energy ion morphologies observed near the shock during an ESP event and a CPE suggest that the same shock acceleration mechanism and propagation processes were operative in each case.
- Research Organization:
- Applied Physics Laboratory, The John Hopkins University, Laurel, Maryland 20810
- OSTI ID:
- 5566889
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 86:A10
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
JUPITER PLANET
PLANETARY MAGNETOSPHERES
IONS
PLASMA WAVES
SHOCK WAVES
SOLAR FLARES
SOLAR WIND
VOYAGER SPACE PROBES
ATMOSPHERES
CHARGED PARTICLES
PLANETARY ATMOSPHERES
PLANETS
SOLAR ACTIVITY
SPACE VEHICLES
VEHICLES
640107* - Astrophysics & Cosmology- Planetary Phenomena