Files produced by MATLAB script that selects negatve bay onsets corresponding to the onset of a magnespheric substorm expansion.

The three datasets in this collection were produced by code contained in the document NNNN. The code and datasets are described in a manuscript submitted for publication to JGR Space Physics titled "Application of Pattern Recognition to the Creation of a Substorm Onset List from the SM Lindex". The files include the onset times of 314,560 events during the interval 1966 -2025, and various properties of the events. The files should be useful for a variety of studies on solar wind control of geomagnetic activity in Earth's magnetosphere.