Articles | Volume 24, issue 3
Ann. Geophys., 24, 861–872, 2006
Ann. Geophys., 24, 861–872, 2006

  19 May 2006

19 May 2006

Precipitation and total power consumption in the ionosphere: Global MHD simulation results compared with Polar and SNOE observations

M. Palmroth1, P. Janhunen2,1, G. Germany3, D. Lummerzheim4, K. Liou5, D. N. Baker6, C. Barth6, A. T. Weatherwax7, and J. Watermann8 M. Palmroth et al.
  • 1Space Research Division, Finnish Meteorological Institute, Helsinki, Finland
  • 2Department of Physical Sciences, University of Helsinki, Helsinki, Finland
  • 3University of Alabama in Huntsville, Huntsville, AL, USA
  • 4Geophysical Institute, University of Alaska, Fairbanks, AK, USA
  • 5Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD, USA
  • 6Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO, USA
  • 7Siena College, Department of Physics, Loudonville, NY, USA
  • 8Danish Meteorological Institute, Atmosphere Space Research Division, Farum, Denmark

Abstract. We compare the ionospheric electron precipitation morphology and power from a global MHD simulation (GUMICS-4) with direct measurements of auroral energy flux during a pair of substorms on 28-29 March 1998. The electron precipitation power is computed directly from global images of auroral light observed by the Polar satellite ultraviolet imager (UVI). Independent of the Polar UVI measurements, the electron precipitation energy is determined from SNOE satellite observations on the thermospheric nitric oxide (NO) density. We find that the GUMICS-4 simulation reproduces the spatial variation of the global aurora rather reliably in the sense that the onset of the substorm is shown in GUMICS-4 simulation as enhanced precipitation in the right location at the right time. The total integrated precipitation power in the GUMICS-4 simulation is in quantitative agreement with the observations during quiet times, i.e., before the two substorm intensifications. We find that during active times the GUMICS-4 integrated precipitation is a factor of 5 lower than the observations indicate. However, we also find factor of 2-3 differences in the precipitation power among the three different UVI processing methods tested here. The findings of this paper are used to complete an earlier objective, in which the total ionospheric power deposition in the simulation is forecasted from a mathematical expression, which is a function of solar wind density, velocity and magnetic field. We find that during this event, the correlation coefficient between the outcome of the forecasting expression and the simulation results is 0.83. During the event, the simulation result on the total ionospheric power deposition agrees with observations (correlation coefficient 0.8) and the AE index (0.85).