ICS-13 Abstract View


Injection Propagation: A View from Space and the Ground
Gabrielse, C., cgabrielse@ucla.edu (1)
Spanswick, E., emma@phys.ucalgary.ca (2)
Nishimura, Y., toshi@atmos.ucla.edu (1), (3)
Angelopoulos, V., vassilis@ucla.edu (1)
Lyons, L., larry@atmos.ucla.edu, (1)
Donovan, E., edonovan@ucalgary.ca, (2)
The injection region's propagation has been heavily studied at geosynchronous orbit, where substorms were initially studied in-depth. With the launch of new missions providing more data points throughout the tail, observations of particle energization could be extended beyond geosynchronous orbit. We explore the injection region's propagation using the injection database from THEMIS [Gabrielse et al., 2014], which collected data from GEO out to ~20 RE. We compare multi-point observations in space with all-sky-imagers and riometers on the ground, the latter of which provide a 2D picture to supplement the satellite measurements. Although the separated satellites observe dipolarization, fast flows, electric fields, and particle injection almost simultaneously-which could indicate a wide injection region-ground observations make it clear that azimuthal (westward) and poleward (tailward) propagation occurs after initiating in a localized region. The picture supports a paradigm in which a very localized injection region forms in space and expands azimuthally and radially along with the substorm current wedge, magnetic flux pile-up, and azimuthal and poleward expansion of the aurora and particle precipitation (as seen by the riometer chain). The azimuthal expansion occurs quickly in space, which is seen by the spacecraft as they are engulfed by the dipolarization and injection region almost simultaneously. The earthward flows consistently seen at the beginning of dipolarization and injection indicate their continued presence and contribution throughout the expansion.
(1) University of California, Los Angeles; Los Angeles, CA 90025
(2) University of Calgary; Calgary, AB, Canada
(3) Boston University; Boston, MA 02215