2011 SuperDARN Workshop
SAPS intensification during substorm recovery: A multi-instrument case study
R.A. Makarevich (1), A.C. Kellerman (2), J.C. Devlin (2), H. Ye (2), L.R. Lyons (3) and Y. Nishimura (3)
(1) Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
(2) School of Engineering and Mathematical Sciences, La Trobe University, Melbourne, Victoria, Australia
(3) Department of Oceanic and Atmospheric Sciences, University of California Los Angeles, Los Angeles, CA, USA
abstract. A case of the major intensification of the subauroral polarization stream (SAPS) during the substorm recovery phase is presented. The continuous high-time-resolution Doppler velocity measurements in the subauroral and auroral regions were conducted with the Unwin HF radar, and these are analyzed in the context of the simultaneous and coincident measurements of the auroral luminosity and the total electron content by the IMAGE and GPS satellites. Additional information was provided by other SuperDARN radars, DMSP F15 satellite crossing the fully-developed SAPS region, ground-based measurements near the location of the substorm onset, and GOES and LANL satellites in the inner magnetosphere. The strong association between the SAPS region and the electron density trough is further substantiated at relatively short time scales and in two horizontal dimensions, with some evidence of the relationship breaking during substorm recovery. It is also demonstrated that the positive feedback processes between the electric fields and electron densities were probably not responsible for the observed strong SAPS intensification. Moreover, it is proposed that the strong and steady plasma acceleration within SAPS may be triggered by a burst of auroral activity, rather than accompanied by a similarly steady variation in other observed parameters either in the ionosphere or in the inner magnetosphere. It is argued that the SAPS major intensification occurring during the recovery phase is not necessarily expected from the current models of the SAPS formation and evolution, but is consistent with the observationally-based view of a fully-developed SAPS as a substorm recovery phenomenon.