Particle injections with auroral expansions

We compare the onset of dispersionless energetic particle injections, obser ved as a sudden increase of energetic (tens to hundreds of keV) electron an d ion fluxes on a timescale of similar to1 min, with the start of auroral b reakups. A total of 34 dispersionless injections observed by Los Alamos Nat ional Laboratory (LANL) satellites are analyzed, and their corresponding au roral breakups are determined with global amoral images acquired from the P olar ultraviolet imager. An important finding is that dispersionless inject ions can actually be associated with substorm intensification. The injectio n time at LANL relative to the start of amoral breakups varies from -2 to 8 min and can sometimes be more than 10 min. The average lag time for the in jections compared to the auroral breakups is 1.8 min with a standard deviat ion of 2.5 min. It is suggested that particle energization must take place in the magnetotail similar to1 min earlier than the start of the explosive amoral substorm onset, while the delay of the injections at LANL is due to a propagation effect. An implied average earthward injection boundary is es timated to be similar to 6.9 - 9.2 RE Further analysis of the delay time in dicates that the transport of substorm injections is associated with the en hancement of convection electric field by a factor of similar to5, correspo nding to an earthward convection how speed of 5 - 120 km s(-1) Dispersionle ss injections can take place in a fairly wide magnetic local time (MLT) reg ion from 2000 to 0100 MLT with a peak at 2200 MLT, where amoral breakups oc cur most frequently. More importantly, dispersionless injections have ionos pheric footprints clustered around the location of amoral breakup within +/ -1 hour of MLT, further supporting the concept of the close relationship be tween the substorm injections and the amoral breakups.