Dynamics of the Substorm Growth Phase– Multi Instrument Observations

P. T. JAYACHANDRAN, J. W. MACDOUGALL, J. P. ST-MAURICEand D. R. MOORCROFT
University of Western Ontario, Canada
P. PRIKRYL
Communication Research Center, Canada
P. T. NEWELL
Johns Hopkins University/Applied Physics Laboratory, USA.
F. CREUTZBERG
Canadian Space Agency, Ottawa, Canada.

The growth phase of two substorm events was studied using the SuperDARN radar, CANOPUS magnetometer, Meridian Scanning Photometer, All Sky Imager and DMSP satellite particle data. The two substorms occurred following a prolonged magnetic quiescent periods. Our study revealed the following: 1. The expansion of the dusk-midnight sector of the auroral oval started after a delay ~ of 40 minutes following the southward turning of the Interplanetary Magnetic Field (IMF). 2. The equatorward edge of the radar backscatter follows the equatorward edge of the ion precipitation boundary (b2i) and Hb emission. 3. The Hb emission and ion precipitation lies equatorward of the convection reversal boundary identified by SuperDARN. 4. The 6300 A^o emission region and 1-5 keV electron precipitation widens during the growth phase of the substorm and the emission 6300 A^o emission layer bifurcate after a pseudo breakup. 5. The electron acceleration events are always poleward of the convection reversal boundary suggesting that the electron acceleration events occur in the Boundary Plasma Sheet (BPS)/Plasma Sheet Boundary Layer (PSBL). 6. The pseudo substorm onset was poleward of the convection reversal boundary (i.e. in the antisunward convection portion of closed field lines) and substorm onset was equatorward of the convection reversal boundary (i.e. in the sunward convecting field lines). These observations suggest that the pseudo substorm onset was at the BPS/PSBL and substorm onset was at plasma sheet region of the magnetosphere.

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