Simultaneous satellite and radar observations of the polar ion outflow and the flux variation with the geomagnetic condition

In the first part of this paper, we present observations of thermal H + and O + ion outflow in the middle to high altitude polar ionosphere from the Suprathermal ion Mass Spectrometer on Akebono satellite. Variations of H + and O + ion flux are given as a function of the geomagnetic activity or the interplanetary magnetic field for different magnetic local time or invariant latitude regions. It is shown that the normalized H + polar wind flux (to 2000 km altitude) varies from 10 7 to 10 8 cm −2 s −1. At both magnetically quiet and active times, the integrated H + ion flux is largest in the noon sector (09∼15 MLT) and smallest in the midnight sector (21∼03 MLT). The O + ion flux was found to correlate positively with the Kp index. In the second part, simultaneous observations of the polar ion outflow is presented by using two instruments for thermal ions and electrons on the Akebono satellite and Sondrestrom radar in the polar ionosphere, with focussing on the dynamics of the ion outflow and its causal relationship to the plasma pressure profile. The drift velocity in the spin plane, plasma temperatures and number density are estimated from the satellite observation at high altitudes (≥ 1500 km), while at low altitudes (≤ 900 km), these parameters are obtained from the radar observation. In the pass of 14h UT on Oct. 15, 1992 (Kp=4 +), high electron temperatures and low number density obtained from the satellite observations are in good agreement with the radar observation. In this event, the high velocity (∼8 km/s at 2500 km) of the H + outflow was significant, while lower velocity of the H + was accompanied by low electron temperature and high density in the pass on Oct. 22, 1992 (Kp=3). Also, it should be noted that characteristic feature of the polar wind (T e , T i < 1 eV) was successively observed as low as 70° invariant latitude.