Energetic O⁺and H⁺ions in the plasma sheet: Implications for the transport of ionospheric ions

Abstract

[1] The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O + ions, and the characteristics of the H + ions are used as references. The following is a summary of the results. (1) (5) The O + -to-H + ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O + ions is transported directly from the ionosphere to the near-Earth region rather than through the distant tail.

Circulation of Heavy Ions and Their Dynamical Effects in the Magnetosphere: Recent Observations and Models

“…Kronberg et al (2012) showed that the O + /H + intensity at energies above 274 keV is between 0.5 and 1 and is much higher than the ratio at ∼10 keV which may result from a more efficient heating of O + ions than of H + ions. Maggiolo and Kistler (2014) and are in agreement with , , Ohtani et al (2011). These trends indicate that the mid tail O + density is more sensitive to geomagnetic activity than to solar EUV flux.…”

“…Lennartsson and Shelley (1986) found no variation of the O + average energy with geomagnetic activity using AE index contrary to Ohtani et al (2011) who reported a positive correlation between the O + energy and the Sym-H index. Both Lennartsson (1989) and Ohtani et al (2011) reported observations indicating a decrease of the O + average energy with increasing solar EUV flux. Lennartsson (1989) estimated that the O + decreases from ∼4-5 keV for low F10.7 to ∼2-3 keV for high F10.7 and showed that this energy decrease is weaker at high geocentric distances than at low geocentric distances.…”

“…Lennartsson and Shelley (1986) showed that the average O + /H + density ratio increases approximately in proportion with the Auroral Electrojet (AE) index. Modulation of the O + density and energy by geomagnetic activity monitored by the Sym-H index was shown by Ohtani et al (2011). The O + density just inward of the magnetopause in the magnetospheric boundary layer also displays a significant exponential increase with geomagnetic activity indicated by the Dst index (Bouhram et al 2005).…”

“…Ohtani et al (2011) provide much higher estimates of the O + energy (up to 10-20 keV) but from the extrapolation of high energy measurements, which as conceded by the authors may be associated with some errors. Lennartsson and Shelley (1986) found no variation of the O + average energy with geomagnetic activity using AE index contrary to Ohtani et al (2011) who reported a positive correlation between the O + energy and the Sym-H index. Both Lennartsson (1989) and Ohtani et al (2011) reported observations indicating a decrease of the O + average energy with increasing solar EUV flux.…”

“…Solar and Geomagnetic Activity Dependence Statistical evidence for the influence of the solar EUV irradiance (F10.7 index) on the O + ion density in the plasma sheet was provided by , Lennartsson and Shelley (1986), Lennartsson (1989), Denton et al (2005), , , Ohtani et al (2011) and Maggiolo and Kistler (2014). The instruments, observation periods, regions, energy ranges and species investigated in these studies and those in Sect.…”