  Experimental investigations of the fine plasma structure of interplanetary
shocks are extremely difficult to conduct due to their small thickness and high
speed relative to the spacecraft. We study the variations in the parameters of
twice-ionized helium ions (4He++ ions or {\alpha}-particles) in the solar wind
plasma during the passage of interplanetary shocks and Earth's bow shock. We
use data with high time resolution gathered by the BMSW (Bright Monitor of
Solar Wind) instrument installed on the SPEKTR-R satellite, which operated
between August 2011 and 2019. The MHD parameters of He++ ions (the bulk
velocity Va, temperature Ta, absolute density Na, and helium abundance Na/Np)
are analyzed for 20 interplanetary shocks and compared with similar parameters
for 25 Earth's bow shock crossings. Measurements from the WIND, Cluster and
THEMIS satellites were also analyzed. The correlations in the changes in helium
abundance Na/Np with the parameters {\beta}_{i}, {\theta}_{Bn} and M_{ms} were
investigated. A correlation between Na/Np and the angle {\theta}_{Bn} was
found: the lower the value of {\theta}_{Bn}, the greater the drop in helium
abundance Na/Np falls behind the IP shock front. For Earth's bow shock
crossings, we found a significant increase in the helium abundance Na/Np in
quasi-perpendicular events.
