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Ann. Geophys., 20, 427-444, 2002
www.ann-geophys.net/20/427/2002/
© European Geosciences Union 2002
Particle transport in 3He-rich events: wave-particle interactions and particle anisotropy measurements
B. T. Tsurutani1, L. D. Zhang1, G. L. Mason2,3, G. S. Lakhina4, T. Hada5, J. K. Arballo1, and R. D. Zwickl6
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
2Department of Physics, University of Maryland, College Park, Maryland, USA
3Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, USA
4Indian Institute of Geomagnetism, Colaba, Mumbai/Bombay, India
5Earth System Science Technology, Kyushu University, Kasuga, Japan
6National Oceanic and Atmospheric Administration, Space Environment Laboratory, Boulder, Colorado, USA
Correspondence to: B. T. Tsurutani
(bruce.tsurutani@jpl.nasa.gov)
Abstract. Energetic particles and
MHD waves are studied using simultaneous ISEE-3 data to investigate particle
propagation and scattering between the source near the Sun and 1 AU. 3 He-rich
events are of particular interest because they are typically low intensity
"scatter-free" events. The largest solar proton events are of
interest because they have been postulated to generate their own waves through
beam instabilities. For 3 He-rich events, simultaneous
interplanetary magnetic spectra are measured. The intensity of the
interplanetary "fossil" turbulence through which the particles have
traversed is found to be at the "quiet" to "intermediate"
level of IMF activity. Pitch angle scattering rates and the corresponding
particle mean free paths lW - P
are calculated using the measured wave intensities, polarizations, and k
directions. The values of lW - P are
found to be ~ 5 times less than the value of lHe
, the latter derived from He intensity and anisotropy time profiles. It
is demonstrated by computer simulation that scattering rates through a 90°
pitch angle are lower than that of other pitch angles, and that this is a
possible explanation for the discrepancy between the lW
- P and lHe
values. At this time the scattering mechanism(s) is unknown. We suggest a means
where a direct comparison between the two l
values could be made. Computer simulations indicate that although scattering
through 90° is lower, it still occurs. Possibilities are either large pitch
angle scattering through resonant interactions, or particle mirroring off of
field compression regions. The largest solar proton events are analyzed to
investigate the possibilities of local wave generation at 1 AU. In accordance
with the results of a previous calculation (Gary et al., 1985) of beam
stability, proton beams at 1 AU are found to be marginally stable. No evidence
for substantial wave amplitude was found. Locally generated waves, if present,
were less than 10-3 nT 2 Hz-1 at the leading
proton event edge, where dispersion effects (beaming) are the greatest, and at
the point of peak proton flux, where the particle energy flux is the greatest.
Key words. Interplanetary physics
(energetic particles; MHD waves and turbulence) – Space plasma physics
(charged particle motion and acceleration; wave-particle interactions)
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