Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...439..482v&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 439, no. 1, p. 482-493
Other
4
Comparison, Interplanetary Magnetic Fields, Mean Free Path, Propagation, Scattering Coefficients, Solar Protons, Solar Wind, Angular Distribution, Nonlinearity, Particle Trajectories, Power Spectra, Sunspots
Scientific paper
In this work we analyze solar particle and interplanetary magnetic field (IMF) data recorded during three solar particle events observed on board Helios 1 on 1978 April 11 and on 1980 June 7. The fluctuating component of the IMF is markedly different in the three cases, the field being very turbulent in the first and very quiet in the second period comprising the other two events. Energetic particle intensities and angular distributions also show different characteristics. Particles propagate in a regime of strong scattering on 1978 April 11, while for 1980 June 7 conditions of weak scattering dominate. Pitch angle coefficients and mean free paths for energetic protons are determined by three different methods: (1) power spectra of IMF fluctuations following quasi-linear theory (QLT), (2) numerical simulations of test particle trajectories using IMF data, and (3) particle time intensity and time anisotropy profiles and angular distributions. Recent investigations (Wanner & Wibberenz 1991b, 1993; Wanner et al. 1993a, b; Droge et al. 1991, 1993) have only compared QLT and particle observations. In this work, we add to these the results of particle trajectory simulations, which are obtained using assumptions different than the QLT calculations. Resulting mean free paths are very similar for the three different approaches, being about 0.015 AU for the event of 1978 April 11 and about 1 AU for the events of 1980 June 7 at 100 MeV particle energy. The agreement found between the mean free path results from the different approaches shows that QLT with the slab wave model leads to a level of scattering coincident with energetic particle determinations for some cases with widely differing scattering conditions. We also find that the shapes of the pitch angle diffusion coefficients do not agree. A discussion of the implications of these findings on the often cited discrepancy between mean free paths determined via QLT and those found by analysis of particle time intensity and anisotropy profiles is given.
Kallenrode May-Britt
Valdés-Galicia Francisco J.
Wanner Wolfgang
Wibberenz Gerd
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