Wind/EPACT Observations of Temporal Evolution in Elemental Composition during Large Solar Energetic Particle Events
Abstract
With a collecting power of 51 cm2-sr, the Low-Energy Matrix Telescope (LEMT) in the Wind satellite's Energetic Particle Acceleration, Composition, and Transport (EPACT) experiment (von Rosenvinge et al. 1995; Reames et al. 1997) provides unprecedented high-precision studies of the temporal evolution in elemental abundances during solar energetic particle (SEP) events at approximately 2-10 MeV/nuc. We briefly review recently published studies of the 20 April 1998 SEP event (Tylka, Reames, & Ng 1999), which showed dramatic systematic compositional variation that can be largely understood in terms of transport through a time-dependent Alfven wavefield generated by the streaming energetic protons (Ng, Reames, & Tylka 1999). We compare those results to the 24 April 1999 SEP event, which was caused by a similar fast western coronal mass ejection (CME) but had a much softer proton spectrum, thereby leading to much weaker compositional variation. We also briefly comment on other events with different patterns of compositional evolution, which may also be significantly influenced by proton-generated waves.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1999
- Accession Number
- ADA636073
Entities
People
- Allan J. Tylka
- Chee K. Ng
- D. V. Reames
Organizations
- National Aeronautics and Space Administration