When air passes through a shockwave
its velocity decreases but because of compression its temperature increases, the
temp increase means that the LSS is now higher, and as the air velocity is
down, M of the local flow decreases.
Contrary wise, as applies to your
problem, in an expansion wave the air velocity increases but because of the
expansion the temperature falls. The fall in temp reduces LSS, and as the air
is faster as well, M goes up
These changes occur inside the waves,
but remain behind them. Air that has passed through a shockwave has a higher
pressure, is going slower and is hotter. After an expansion wave the air is
colder and faster and at a lower pressure