HR: 1340h
AN: SH33A-1082    [Abstracts]
TI: Do Large Solar Energetic Particle Events Observed at 1 AU Include Particles Accelerated by the Associated Solar Flare?
AU: * von Rosenvinge, T T
EM: tycho@milkyway.gsfc.nasa.gov
AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, United States
AU: Cane, H V
EM: hilary.cane@utas.edu.au
AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, United States
AU: Richardson, I G
EM: richardson@lheavx.gsfc.nasa.gov
AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, United States
AU: Cohen, C M
EM: cohen@srl.caltech.edu
AF: California Institute of Technology, 220-47 Downs Laboratory, Pasadena, CA 91125, United States
AU: Mewaldt, R A
EM: rmewaldt@srl.caltech.edu
AF: California Institute of Technology, 220-47 Downs Laboratory, Pasadena, CA 91125, United States
AB: Many large solar energetic particle (SEP) events observed at 1 AU start with a high Fe/O ratio (measured at a fixed MeV/nucleon) that then decays to a lower value. One possible explanation is that particles in these events are a combination of flare particles, with high Fe/O, and shock accelerated particles with a lower ratio. In this scenario, one would expect that when there is good magnetic connection to the flaring region, flare particles would be detected at the start of the event. The Fe/O ratio would decrease with time to an extent dependent on the strength of the associated shock and the energy of the observations. A second possible explanation is that only shock-accelerated particles are observed, and that the time-varying Fe/O ratio is a result of escape from the shock: at a fixed MeV/nucleon, Fe particles, with their higher rigidity, escape more readily than O and therefore arrive earlier at 1 AU. Yet a third suggestion is that Fe and O have similar injection profiles near the Sun and then undergo rigidity-dependent interplanetary scattering. We will present data from the ACE Solar Ion Spectrometer (SIS) from a variety of SEP events and consider the implications for these three scenarios. We will also consider the possibility that, by combining observations from the two STEREO spacecraft and near-earth spacecraft (ACE and WIND), we may be able to rule out one or even two of these scenarios.
DE: 2139 Interplanetary shocks
DE: 7513 Coronal mass ejections (2101)
DE: 7514 Energetic particles (2114)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting