HR: 1340h
AN: SM43B-1328    [Abstracts]
TI: Relation of Substorm Onset to Local AL index
AU: Springborn, J
EM: purplewhoppie@yahoo.com
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles 3845 Slichter Hall P.O. Box 951567 Los Angeles, California, Los Angeles, CA 90059-1567, United States
AU: * Weygand, J M
EM: jweygand@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles 3845 Slichter Hall P.O. Box 951567 Los Angeles, California, Los Angeles, CA 90059-1567, United States
AU: McPherron, R L
EM: rmcpherron@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles 3845 Slichter Hall P.O. Box 951567 Los Angeles, California, Los Angeles, CA 90059-1567, United States
AU: Kauristie, K
EM: Kirsti.Kauristie@fmi.fi
AF: Finnish Meteorological Institute, P.O.B. 503, Helsinki, FIN-00101, Finland
AU: Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA 94720-7450, United States
AU: Henderson, M G
EM: mghenderson@lanl.gov
AF: Los Alamos National Laboratory, ISR-1 MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States
AU: Hsu, T
EM: thsu@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles 3845 Slichter Hall P.O. Box 951567 Los Angeles, California, Los Angeles, CA 90059-1567, United States
AB: In this study we investigate the relation of auroral substorm onset to the sharp decrease in the local AL (IL) index during substorms. With a database of over 4200 onsets determined from auroral images we have statistically examined the timing between the auroral substorm onset and the sharp decrease in the IL index, as determined with data from the IMAGE magnetometer network. From the database of onsets, 58 substorms were determined to be within 6° of the central meridian of the IMAGE ground array. Our superposed epoch median curve shows that IL index begins to sharply decrease 4 minutes before the auroral onset, which is twice the 2 minute resolution of the auroral imager. An analysis of the superposed epoch median curves of the SOPA particle data for the LANL spacecraft closest to the auroral onset meridian indicates that both the electron and ion injections begin about 3 to 4 minutes before the auroral onset. The location of the electron injection seems to be in the 01 to 04 MLT sector while the proton injection appears to be in the 22 to 01 MLT sector. These statistical results support the idea that dispersionless particle injection and field aligned and ionospheric currents of the substorm current wedge begin to flow before the auroral onset.
UR: http://www.igpp.ucla.edu/jweygand
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting