Skip to main content
Article thumbnail
Location of Repository

Statistical study of high-latitude plasma flow during magnetospheric substorms

By G. P. Provan, M. Lester, S. B. Mende and Steve E. Milan

Abstract

We have utilised the near-global imaging capabilities of the Northern Hemisphere SuperDARN radars, to perform a statistical superposed epoch analysis of high-latitude plasma flows during magnetospheric substorms. The study involved 67 substorms, identified using the IMAGE FUV space-borne auroral imager. A substorm co-ordinate system was developed, centred on the magnetic local time and magnetic latitude of substorm onset determined from the auroral images. The plasma flow vectors from all 67 intervals were combined, creating global statistical plasma flow patterns and backscatter occurrence statistics during the substorm growth and expansion phases. The commencement of the substorm growth phase was clearly observed in the radar data 18-20min before substorm onset, with an increase in the anti-sunward component of the plasma velocity flowing across dawn sector of the polar cap and a peak in the dawn-to-dusk transpolar voltage. Nightside backscatter moved to lower latitudes as the growth phase progressed. At substorm onset a flow suppression region was observed on the nightside, with fast flows surrounding the suppressed flow region. The dawn-to-dusk transpolar voltage increased from ~40kV just before substorm onset to ~75kV 12min after onset. The low-latitude return flow started to increase at substorm onset and continued to increase until 8min after onset. The velocity flowing across the polar-cap peaked 12-14min after onset. This increase in the flux of the polar cap and the excitation of large-scale plasma flow occurred even though the IMF Bz component was increasing (becoming less negative) during most of this time. This study is the first to statistically prove that nightside reconnection creates magnetic flux and excites high-latitude plasma flow in a similar way to dayside reconnection and that dayside and nightside reconnection, are two separate time-dependent processes

Topics: Magnetospheric physics (Storms and Substorms,\ud plasma convection), Ionosphere (plasma convection)
Publisher: European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany)
Year: 2004
DOI identifier: 10.5194/angeo-22-3607-2004
OAI identifier: oai:lra.le.ac.uk:2381/703

Suggested articles

Citations

  1. (2003). A doi
  2. (2002). A multiinstrument approach to mapping the global dayside merging gap, doi
  3. (1999). An interhemispheric study of the ground magnetic and ionospheric electric fields during the substorm growth and expansion phase onset, doi
  4. (1999). Coherent HF radar backscatter characteristics associated with auroral forms identified by incoherent radar techniques: a comparison of doi
  5. Combined CUTLASS, EISCAT and ESR observations of ionospheric plasma flows at the onset of an isolated substorm, doi
  6. (1978). Development of the auroral electrojets on
  7. (1987). Empirical high-latitude electric field models, doi
  8. (2000). et al.:
  9. (1995). et al.: DARN/SUPERDARN A global view of the dynamics of highlatitude convection, doi
  10. (2000). et al.: Far ultraviolet imaging from the IMAGE spacecraft, doi
  11. (1992). Excitation and decay of solar wind-driven flows in the magnetosphere-ionosphere system, doi
  12. (2002). Excitation of twin-vortex flow in the nightside high-latitude ionosphere during an isolated substorm, doi
  13. (2003). FAST and IMAGE-FUV observations of a substorm onset ,J. doi
  14. (1991). Growth phase of magnetospheric substorms, doi
  15. (2000). HF coherent scatter radar observations of ionospheric convection during magnetospheric substorms,
  16. Interhemispheric HF radar observations of nightside ionospheric convection in response to IMF Bz and By changes and substorm pseudobreakup doi
  17. (2001). Ionospheric ion and electron heating at the poleward boundary of a poleward expanding substorm-disturbed region. doi
  18. (1998). Large-scale imaging of highlatitude convection with Super Dual Auroral Radar Network HF radar observations, doi
  19. (1995). Models of high-latitude electric potentials derived with a least error fit of spherical harmonic coefficients, doi
  20. (2002). Multistage substorm expansion: Auroral dynamics in relation to plasma sheet particle injection, precipitation, and plasma convection, doi
  21. (2001). Observations of two complete substorm cycles during the Cassini Earth swing-by: Cassini magnetometer data in a global context, doi
  22. (1991). On flow reversal boundaries and cross-cap potential in average models of the high latitude convection, doi
  23. (2003). On the lifetime and extent of an auroral westward flow channel (AWFC) observed during a magnetospheric substorm, doi
  24. (1985). Polar cap inflation and deflation, doi
  25. (1995). Radar observations of auroral zone flows during multiple onset substorm, doi
  26. (1973). Semi-annual variation of Geomagnetic Activity, doi
  27. (1996). Statistical patterns of high-latitude convection obtained from the Goose Bay HF radar observations.J. doi
  28. (1996). Substorm correlated absorption on a 3200 km HF propagation path, doi
  29. (1972). The configuration of the magnetosphere in Critical Problems of Magnetospheric Physics,
  30. (1988). The effect of magnetospheric erosion on mid- and high-latitude ionospheric flows, doi
  31. (1997). The excitation of plasma convection in the high-latitude ionosphere, doi
  32. (1999). The influence of the IMF By on the location of pulsed flows in the dayside ionosphere observed by the HF radars, doi
  33. (1998). The reaction of the global convection electrojets to the onset and expansion of the susbtorm current edge, doi
  34. (1987). The response of the large-scale ionospheric convection pattern to changes
  35. (1978). The statistical magnetic signature of magnetospheric substorms, doi
  36. (1998). Two spacecraft observations of a reconnection pulse during an auroral breakup, doi
  37. (2003). Variations in polar cap area during two substorm cycles, doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.