We present multipoint Time History of Events and Macroscale Interactions during
Substorms (THEMIS) observations of transient dynamic pressure pulses in the
magnetosheath 3–10 times the background in amplitude, due to enhancements in both the
ion density and velocity. Their spatial dimensions are of the order of 1 RE parallel to
the flow and 0.2–0.5 RE perpendicular to it, inferred from the difference in the
amplitudes observed by the different spacecraft. For the first time, simultaneous
observations of the solar wind and foreshock are also shown, proving no similar dynamic
pressure enhancements exist upstream of the bow shock and that the majority of pulses
are downstream of the quasi-parallel shock. By considering previously suggested
mechanisms for their generation, we show that the pressure pulses cannot be caused by
reconnection, hot flow anomalies, or short, large-amplitude magnetic structures and
that at least some of the pressure pulses appear to be consistent with previous
simulations of solar wind discontinuities interacting with the bow shock. These
simulations predict large-amplitude pulses when the local geometry of the shock changes
from quasi-perpendicular to quasi-parallel, while the opposite case should also produce
notable pulses but typically of lower amplitude. Therefore, in a given region of the
magnetosheath, some of the discontinuities in the solar wind should generate pressure
pulses, whereas others are expected not to. There is also evidence that the pulses can
impinge upon the magnetopause, causing its motion.