Inspection of the datasets from a large number of orbits showed that it was convenient to locate the Ion Composition Boundary (ICB), which marks the transition between the shocked solar wind and the planetary plasma (e.g. Martinecz et al., 2008), by considering the mass channel number at which the largest number of ions was observed in each 192 s cycle. Data from times at which the mass channel number of the maximum ion count was 15 or less were taken to correspond to altitudes below the ICB. These data were then considered for further analysis. For example, in the data set for 9th August 2008 shown in Fig. 1, the data between 05:28 UT and 05:47 UT were interpreted as being from inside the ICB. These data are shown within the pink box in Fig. 1, and it was these data that were considered for further analysis in this particular example.
cycle
192 s
s
maximum ion count
mass channel number
15 or less
data set
9th August 2008
data
between 05:28 UT and 05:47 UT
UT