Transport of ionospheric ions in the magnetosphere: Theory and observations

A Monte Carlo transport code is described that follows the distribution functions of upward flowing ions (UFI) from a source location in the ionosphere into the magnetosphere. Examples of the guiding-center motion and the full gyration motion of ions from the cusp ionosphere are shown to describe the characteristics of the ions expected in the outer magnetosphere, and these characteristics are compared with measurements of ion streams in the lobes and plasma sheet. This comparison indicates that the ionospheric ions observed in the outer magnetosphere originate from the cusp ionosphere. Moreover, a comparison of ISEE-1 measurements of the distribution functions of H + and O + in the ring current during a magnetic storm with the distribution functions of ions from the ionosphere, computed with an earlier version of the Monte Carlo transport code, indicates that the UFI from the cusp ionosphere may fully account for all the H + and O + in the near-earth plasma sheet and ring current during stormtime conditions. It is also shown that if O + ions from the cusp ionosphere cross the center plane of the magnetotail at distances greater than about 9 R E, their magnetic moments are not conserved.