The pump acceleration mechanism

Starting in the early 2000s, Fisk and Gloeckler developed a theory for a pump acceleration mechanism to account in detail for the ubiquitously observed, so-called, -5 spectra, a distribution function that is a power law in particle speed with spectral index of -5. To date, this theory has seen no general use in explaining data and relatively little constructive discussion. In this paper, we will make another attempt to interest experimentalists and theorists in using and expanding on the pump acceleration mechanism. The inevitability of the pump acceleration occurring in conditions that are common in space plasmas will be discussed, along with supporting numerical studies and observations. (paper)