Radio emissions reveal Alfvenic activity and electron acceleration prior to substorm onset.

ABSTRACT: Magnetospheric substorms are among the most dynamic phenomena in the Earth's magnetosphere, yet their triggering mechanisms remain unclear. Ground-based observations have identified wave-like aurora as precursors to substorms. Here, we report a new precursor feature in space-based observations of auroral kilometric radiation (AKR), marked by the appearance of emissions with slowly frequency-drifting tones (<2 kHz/s) above 100 kHz. Simultaneous multi-instrument observations and statistical analysis suggest that these AKR precursors occur concurrently with wave-like aurora, either manifesting as pseudo-breakup features (with about 5 min duration) or as pre-onset activity (about 2 min prior to substorm expansion), indicating a common driving mechanism. Analysis of the emissions with frequency

SUBMITTER: Wu SY 

PROVIDER: S-EPMC12657864 | biostudies-literature | 2025 Nov

REPOSITORIES: biostudies-literature