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Based upon recent evidence from abundance patterns of chemical elements insolar energetic particles (SEPs), and, ironically, the belated inclusion of Hand He, we can distinguish four basic SEP populations: (1) SEP1 - pure"impulsive" SEPs are produced by magnetic reconnection in solar jets showingsteep power-law enhancements of 1<= Z <= 56 ions versus charge-to-mass ratioA/Q from a ~3 MK plasma. (2) SEP2 - ambient ions, mostly protons, plus SEP1ions reaccelerated by the shock wave driven by the narrow coronal mass ejection(CME) from the same jet. (3) SEP3 - a "gradual" SEP event is produced when amoderately fast, wide CME-driven shock wave barely accelerates ambient protonswhile preferentially accelerating accumulated remnant SEP1 ions from an activeregion fed by multiple jets. (4) SEP4 - a gradual SEP event is produced when avery fast, wide CME-driven shock wave is completely dominated by ambientcoronal seed population of 0.8 - 1.8 MK plasma usually producing a full powerlaw vs. A/Q for 1<= Z <= 56 ions. We begin with element abundances in thephotosphere that are fractionated during transport up to the corona based upontheir first ionization potential (FIP); this important "FIP effect" for SEPsprovides our reference abundances and is different for SEPs from that for thesolar wind. We then show evidence for each of the processes of acceleration,reacceleration, and transport that conspire to produce the four abundancespatterns we distinguish.

Four Distinct Pathways to the Element Abundances in Solar Energetic Particles