It is well known that electrons, protons, and heavier ions can be accelerated to
high energies (≳1 MeV) throughout the solar system by a variety of mechanisms.
We review several of the sources of energetic ions and electrons that can produce
enhanced fluxes of particles near the Earth's orbit. Solar energetic particles and
particles accelerated at interplanetary shock waves are considered. We also review
the properties and potential terrestrial influence of Jovian electrons. Recent measurements
from the SAMPEX spacecraft in low-Earth orbit are examined to look for
extraterrestrial sources of electrons and ions. We find clear evidence of both solar
and Jovian electrons at high latitudes and at high altitudes around the Earth, but
the durably trapped outer zone electron population seems best and most completely
explained by an internal acceleration mechanism
