The Cusp as a VLF Saucer Source: First Rocket Observations of Long‐Duration VLF Saucers on the Dayside

Abstract Auroral whistler‐mode radio emissions called saucers are of fundamental interest because they require an unusually stationary emission process in the dynamic auroral environment, and it is a mystery how that can happen this or similar conditions elsewhere geospace. The Cusp Alfvén Plasma Electrodynamics Rocket (CAPER‐2), launched into cusp, obtained first rocket measurements large‐scale, multiple‐armed dayside saucer, to those observed by DEMETER satellite, with addition particle ground‐based measurements. Analysis saucer shapes, directional using waveforms, data show that, accounting for estimated uncertainties, these originate at altitudes ∼4,000 km within eastern side which penetrated ∼100 s after encountered. On‐board instruments dispersed electron bursts Alfvénically accelerated above sources.