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WIND Observations of Energetic Solar Proton Events Down to keV Energies
The 3-D Plasma and Energetic Particles experiment on the WIND spacecraft
was designed to provide high sensitivity measurements of both suprathermal
ions and electrons down to solar wind energies. A statistical survey of
52 solar proton events has been investigated. For all proton events, a
temporally related electron event is observed. The presented results focus
on the properties of protons released near the Sun which show a velocity
dispersion when detected at 1 AU. The analysis of the spectral, temporal,
and spatial observations reveal the following main results: 1) Dispersive
protons show a low energy cut off between 0.1 and 1 MeV.2) There are two
classes of proton events: For one class (70% of the events), the first
arriving protons are traveling almost scatterfree as indicated by the derived
path lengths between 1.1 and 1.3 AU, whereas the events of the second class
show significantly larger path lengths around 2 AU.3) Relative to
the electron release time at the Sun, the almost scatterfree traveling
protons of the first class of events are release delayed by 0.5 to 2 hours.
For the events of the second class, protons and electrons seemed to be
released simultaneously within the accuracy of 20 minutes.
Authors: Sa"m Krucker, Robert P. Lin
Organization: Space Sciences Laboratory
Telephone: 510 643 3101
Address: University of California,
Berkeley, CA 94720-7450
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