SSLUC

Berkeley 2010 June ACE/SOHO/STEREO/Wind Workshop

Interplanetary Propagation of Solar Impulsive Energetic

Electrons

Linghua Wang, Bob Lin and Säm Krucker

Space Sciences Lab, UC Berkeley

Summary for the five events

*Two different PAD behaviors at low and high energies:

At low energies (~0.3keV to E0), the PAHM remains roughly constant below 30° (corresponding to an actual PAHM of <~15°, limited by the instrumental response) from onset through the peak.

At high energies (E0 to ~300 keV), the PAHM increases with energy, e.g., from ~30° at E0 up to 85° at 300 keV at the peak; it also increases with time.

The energy transition E0 varies from ~10 to 30 keV, from event to event.

ρe = ρTp

* Although the energy transition E0 varies from ~10 to 30 keV and the Tp varies from ~7 to 33 eV, the E0 always corresponds to a ρe0 ~ 0.7-1.2 ρTp.

The ratio Λ of the peak flux of outward-traveling scattered electrons to field-aligned scatter-free electrons

Summary for the five events

The ratio Λ of the peak flux of outward-traveling scattered electrons to field-aligned scatter-free electrons

Summary for the five events

At energies with ρe > ρTp, electrons would scatter more due to stronger power densities for fluctuations/waves at scale λ > ρTp (the inertial range), and the power-law increase of Λ with ρe may be associated with the power-law increase of turbulence power density with λ (P λβ) .

At energies with ρe < ρTp, electrons would be weakly scattered because of weak power densities for resonant fluctuations/waves at scale λ < ρTp (the dissipation range).

* For high-energy electrons, the observed flux-time profiles retain a rapid-rise, rapid-decay peak and the estimated path length is only ~4-18% longer than the smooth spiral field length, indicating that strong scattering, if it existed within 1 AU, only occurred near 1 AU since strong scattering (mean free path <~ 0.4 AU) throughout the inner solar system would produce a fast-rise, very slow-decay (with the e-folding decay time of > 4hours for mean free path <~ 0.4 AU) peak [Lin, 1974] and a much larger path length.

Such propagation cannot explain the previously reported delay of ~10-30 min for high-energy electrons [Krucker et al., 1999; Haggerty & Roelof, 2002; Wang et al., 2006]. Thus, this delay must reflect the actual delay in the solar injection of high-energy electrons.

Summary for the five events