Continuous Characterization of Growth Phase Using Ground Optical and Magnetic Data

The growth phase of substorms is characterized by equatorward motion of the auroral oval as manifested by optical emissions and the electrojet currents detected on the ground through magnetic perturbations. We will demonstrate the use of an inversion procedure for magnetic data that follows the optical borders detected in the CANOPUS Churchill meridian well. Multispectral meridian scanning photometry allows identification of 486 nm H-beta emission with the equatorward edge of the evening sector growth phase electrojet, consistent with downward field-aligned current at this location. The 630 nm and 557 nm emissions due to the precipitation of electrons are identified with the more poleward regions or the poleward border, and upward field-aligned current. While these results are already known, the use of magnetic data is a new way of continuously monitoring growth phase. The identifications are supported by satellite imaging from Image and POLAR in individual cases. Despite separation of the proton and electron emissions as observed from the ground, our results are consistent with the polar cap boundary determined using proton imaging by SI12 on Image. We have also confirmed precipitation region and FAC coincidence using FAST, and corrected the electrojet position when FAST did not fly directly over the ground array, based on imaging from the high altitude satellites.