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. 3He-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 3He-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 λW-P are calculated using the measured wave intensities, polarizations, and k directions. The values of λW-P are found to be ∼ 5 times less than the value of λHe, 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 λW-P and λHe values. At this time the scattering mechanism(s) is unknown. We suggest a means where a direct comparison between the two λ 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 10-3nT2Hz-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.
|Number of pages||18|
|Publication status||Published - 2002|
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Atmospheric Science
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science