Statistical and Temporal Characteristics of Sawtooth Events

Abstract. Magnetospheric sawtooth events are characterized by periodic particle injections and magnetic dipolarizations spread quasi-simultaneously across a wide range of magnetic local times. We present a comprehensive statistical study of magnetospheric sawtooth events (STEs) during solar cycle 24 (2008–2016), extending previous catalogs and enabling solar cycle comparisons. Our results confirm that STEs predominantly occur during the declining phase of the solar cycle and are strongly associated with geomagnetic storms. Superposed epoch analysis reveals near-simultaneous particle injections across all magnetic local time sectors but magnetic field dipolarization confined to the midnight region, supporting a scenario in which nightside tail reconnection and enhanced convection are the primary drivers. The localization of magnetic dipolarizations during STEs challenges global instability interpretations and suggest that STEs represent a stormtime substorm mode triggered under specific magnetotail conditions.