Table 3.

Open questions, possible causes, and contributions from future inner heliospheric missions

Open questions	Possibilities/effects	SPP and SolO contributions
What causes event-to-event variations in SEPs?	Seed populations, Twin CMEs, shock properties, flare contributions	Identify variations in seed populations and determine how they affect CME shock acceleration efficiency and SEPs
Do self-excited proton-generated Alfvén waves exist, and how do they affect SEPs?	Q/M-dependence of low-energy spectral flattening; radial and energy dependence of peak intensities	Study properties of events with self-excited waves, and correlate with associated increases in streaming-limited peak intensities and the possible lack of spectral flattening
How does scattering during transport modify SEPs?	Rigidity-dependent scattering and associated variations or direct flare contributions	Identify and quantify the contributions of flares to large SEP events as transport-related time variations diminish
How do coronal and interplanetary magnetic field configurations affect SEPs?	SEP acceleration and transport in the presence of CMEs, shocks, and other large-scale structures in the low corona and interplanetary medium	Determine CME shock formation and propagation, properties of evolving CMEs, shocks, and other large-scale coronal and IP structures and their relationships with ambient turbulence spectra and SEP properties
Where are the highest energy SEP protons accelerated?	CME shocks in the low corona or flares	Use onset-time analyses to reduce uncertainties and identify source regions in individual SEP events