1. Are SEP Spectral Breaks due to Acceleration at the Sun or Transport in Interplanetary Space?
Organizers: Mihir Desai, Joe Giacalone, Eric Christian
Large, gradual, SEP events are associated with CMEs.
At energies below a few MeV, the peak SEP intensity is at the ICME-driven interplanetary shock.
Above a few MeV, the peak intensity is before the shock.
The event-integrated spectrum has a spectral break.
The causes of this are not clear, and will be explored in this session.
Does the spectral break provide information about
Particle transport in the turbulent interplanetary magnetic field
Or the nature of particle acceleration at near-sun CME shocks
When: Tuesday, AM
Scene-setting Talks:
Dick Mewaldt, Caltech
Ming Zhang, FIT

5. Formation of spectral break (J. HU)
iPATH simulation of an SEP event with CME going directly towards the observer at 1AU
(Spectral break forms before shock arrives in most head-on and western events)
Poster P122

6. Spectrum unfolds at low energies; same above break
Lulu Zhao
Spectrum unfolds at low energies; same above break

7. Multi-point or multi-time observations Propagation Acceleration
Summary (Zhang)
Multi-point or multi-time observations
Propagation Acceleration
Log F
Log F
Normalized at low E
vs.
Normalized at high E
Log E
Log E

8. Are SEP Spectral Breaks due to Acceleration at the Sun or Transport in Interplanetary Space?
Organizers: Mihir Desai, Joe Giacalone, Eric Christian
Transport processes affect time-intensity profiles and composition ratios throughout the event; especially during SEP onsets
GLE events often have two spectral breaks between ~1-50 MeV and above 200 MeV; studies that combine the full available energy range in individual SEP events are underway
In events with local shocks, transport effects can dominate causing the lower energy spectra to steepen over time while maintaining the same spectral index above the break energy
In western hemisphere events, low-energy spectral indices are independent of species, and the Q/M-dependent spectral breaks are likely due to acceleration at near sun-CME shocks, but transport effects could also play a role and need to be investigated
PSP/ Solar Orbiter will untangle the transport effects from near-Sun acceleration effects