Session 2: Solar, Planetary and Space Physics

Title:Energetic (50-220 keV)ion distribution upstream from and at the bow shock.
Author(s): G Anagnostopoulos, I. Karanikola (Poster)
Contact: G. Anagnostopoulos, Demokritos University of Thrace, Greece

In a previous study we presented statistical results on the energy extend of the ion spectrum, the presence of relativistic electrons and the status of the magnetosphere during times of 2034 upstream energetic (50-220 keV) ion events observed by IMP-8 between 1982 - 1988 (Anagnostopoulos et al., 1999). Here we extend our previous analysis of the 2034 ion events by studing the distribution of events / intensities in the upstream region and at the bow shock (the distribution at the shock was studied by evaluating the possible connection point of the detecting spacecraft with the bow shock). The most important results of the present analysis are: (1) A dawn-dusk asymmetry in upstream ion intensities (with higher intensities related with the afternoon side of the bow shock front), and (2) A common local time distribution of upstream ion intensities with the distribution of ion intensities detected in the presence of relativistic magnetospheric electrons. The dependence of upstream phenomena on geomagnetic activity, the direction of the interplanetary magnetic field (IMF) and the angle čBn between the IMF and the normal to the bow shock are also considered and discussed. The results of this study further support our previous results (Anagnostopoulos et al., 1999) that the vast majority of the 2034 upstream ion events observed by IMP-8 were generated by leakage of energetic ions from the (dusk) magnetosphere during times of intense magnetospheric activity.