Whistler Waves in the Foot of Quasi‐Perpendicular Supercritical Shocks

Abstract Whistler waves are thought to play an essential role in the dynamics of collisionless shocks. We use magnetospheric multiscale spacecraft study whistler around lower hybrid frequency, upstream 11 quasi‐perpendicular supercritical apply 4‐spacecraft timing method unambiguously determine wave vector k waves. find that oblique background magnetic field with a wave‐normal angle between 20° and 42°, wavelength 100 km, which is close ion inertial length. also predominantly same plane as normal shock. By combining this precise knowledge high‐resolution measurements 3D velocity distribution, we show reflected beam resonance waves, opening up possibility for wave‐particle interaction ions observed whistlers. The linear stability analysis system mimicking distribution suggests such can produce