Abstract

Rapid (<1 s) intensity modulation of pulsating auroras is caused by successive chorus elements as a response to wave‐particle interactions in the magnetosphere. Here we found that a pulsating auroral patch responds to the time spacing for successive chorus elements and possibly to chorus subpacket structures with a time scale of tens of milliseconds. These responses were identified from coordinated Arase satellite and ground (Gakona, Alaska) observations with a high‐speed auroral imager (100 Hz). The temporal variations of auroral intensity in a few‐hertz frequency range exhibited a spatial concentration at the lower‐latitude edge of the auroral patch. The spatial evolution of the auroral patch showed repeated expansion/contraction with tens of kilometer scales in the ionosphere, which could be spatial behaviors in the wave‐particle interactions. These observations indicate that chorus elements evolve coherently within the auroral patch, which is approximately 900 km in the radial and longitudinal directions at the magnetic equator.