This paper shows statistical results of the ring current ion composition and its variability as a function of solar cycle and magnetospheric activity for 3 < L < 8. Spin-averaged energetic particle (1-200 keV) measurements from Polar are combined with geomagnetic indices as well as solar wind and interplanetary observations from the Wind spacecraft during a period from September 1996 to March 1999. The statistics are performed both for time-averaged values for all periods as well as for peak flux values during geomagnetic storms (defined as Dst < -50 nT) that occurred during this period. The average O+ energy density increases by about a factor of 5 during the rising phase of the solar cycle from the minimum values in 1996, while the average values of H+ and He show variability but no consistently increasing trend. The O+ flux is small (below 10%) compared with the hydrogen flux, and the average energy density ranges from a few percent at solar minimum to ∼10% at high solar activity time in early 1999. The O+ flux is typically smaller than the He+ flux, reaching comparable values only during the latter part of the period when the solar activity increased. Analogously, the energy densities of O+ and He+ are about equal during 1996 and 1997, whereas the O+ energy density is about twice the He+ energy density during the higher solar activity period in 1998 and early 1999.
Document Object Identifier (DOI)
Pulkkinen, T.I., Ganushkina, N.Y., Baker, D.N., Turner, N.E., Fennell, J.F., Roeder, J., Fritz, T.A., ... & Kettmann, G. (2001). Ring current ion composition during solar minimum and rising solar activity: Polar/CAMMICE/MICS results. Journal of Geophysical Research: Space Physics, 106(A9), 19131-19147. doi: 10.1029/2000JA003036.
Journal of Geophysical Research: Space Physics