Proton and Electron Injection Path at Geosynchronous Altitude Journal of Geophysical Research: Space Physics

Using tens to hundreds of keV proton and electron flux measurements and simultaneous magnetic field measurements from three Geostationary Operational Environmental Satellites [GOES-13 (75 degrees W), GOES-14 (105 degrees W), and GOES-15 (135 degrees W)], we investigate proton and electron injections and their relationship to the substorm current wedge at geosynchronous altitude. Proton and electron injection processes occur only in the initial formation of the substorm current wedge, the width of which is less than 2 hr in local time in the premidnight region, for moderate substorms. Proton injections are closely related to the formation of a substorm current wedge at geosynchronous altitude, and thus the onset of a substorm, even before local dipolarization in the magnetic field. Proton injections take place only under the western upward field-aligned currents of the current wedge. Electron injections in the energy range of <100 keV are tightly coupled with local dipolarization in the magnetic field, and these take place mostly in the central region of the current wedge, extending in the region under the western upward field-aligned currents.