Ground based identification of dispersionless electron injections

Using data from an array of ground‐based single beam riometers and the CRRES Medium Energy B (MEB) particle detector we examine the signature of dispersionless electron injections. We find that it is possible to distinguish a dispersionless electron injection by it's integrated (>30 keV) flux signature at in situ satellites with a simple rise time criteria. If the total electron flux >30 keV exhibits a dramatic rise within 3 minutes then the signature is guaranteed to correspond to a dispersionless injection. Since the Kennel‐Petschek limit for strong pitch angle scattering is almost certainly met during substorm injections and riometers respond to the >30 keV energy range, this translates to an equivalent criteria for riometer absorption. We present results obtained using our selection criteria for the ground‐based identification of dispersionless electron injections including MLT dependence and initial spatial extent of the electron injection region.