  In situ observations of interplanetary (IP) coronal mass ejections (ICMEs)
and IP shocks are important to study as they are the main components of the
solar activity. Hundreds of IP shocks have been detected by various space
missions at different times and heliocentric distances. Some of these are
followed by clearly identified drivers, while some others are not. In this
study, we carry out a statistical analysis of the distributions of plasma and
magnetic parameters of the IP shocks recorded at various distances to the Sun.
We classify the shocks according to the heliocentric distance, namely from 0.29
to 0.99 AU (Helios-1/2); near 1 AU (Wind, ACE and STEREO-A/B); and from 1.35 to
5.4 AU (Ulysses). We also differentiate the IP shocks into two populations,
those with a detected ICME and those without one. We find, as expected, that
there are no significant differences in the results from spacecraft positioned
at 1 AU. Moreover, the distributions of shock parameters, as well as the shock
normal have no significant variations with the heliocentric distance.
Additionally, we investigate how the number of shocks associated to
stream-interaction regions (SIRs) increases with distance in proportion of
ICME/shocks. From 1 to 5 AU, SIRs/ shock occurrence increases slightly from 21%
to 34%, in contrast ICME/shocks occurrence decreases from 47% to 17%. We find
also indication of an asymmetry induced by the Parker spiral for SIRs and none
for ICMEs.
