Abstract Collisionless shocks can exhibit non‐stationary behavior even under steady upstream conditions, forming a complex transition region. Ion phase‐space holes, linked to shock self‐reformation and surface ripples, are a signature of this non‐stationarity. We statistically analyze their occurrence using 521 crossings of Earth’s quasi‐perpendicular bow shock. Phase‐space holes appear in 65% of cases, though the actual rate may be higher as the holes may not be resolved during fast shock crossings. The occurrence rate peaks at 70% for shocks with Alfvén Mach numbers MA>7 ${M}_{A} > 7$. These findings suggest that Earth’s quasi‐perpendicular bow shock is predominantly non‐stationary.

Read original article

Read original article