High-latitude Ulysses Observations of the H/He Intensity Ratio Under Solar Minimum and Solar Maximum Conditions

We analyze measurements of the 0.5-1.0 MeV/nucleon H/He intensity ratio from the Ulysses spacecraft during its first (1992-94) and second (1999-2000) ascent to southern high latitude regions of the heliosphere. These cover a broad range of heliocentric distances (from 5.2 to 2.7 AU) and out-of-ecliptic latitudes (from 18 S to 70 S). 

During Ulysses' first southern pas, the HI-SCALE instrument measured a series of enhanced particle fluxes associated with the passage of a recurrent corotating interaction region (CIR). Low values (~6) of the H/He ratio were observed in these recurrent CIR events, with a clear minimum following the passage of the corotating reverse shock.