Nowcasting convection velocity in the high-latitude ionosphere using statistical models

The Weimer and IZMEM statistical convection models are driven with a time s eries of interplanetary magnetic field (IMF) measurements made onboard the Wind spacecraft. The model outputs are used to infer the ionospheric convec tion velocity at Casey, Antarctica (80.8 degrees S geomagnetic latitude), a nd then compared with measurements of Doppler velocity made using a Digison de, and measurements of F-region convection implied by a collocated magneto meter. During a single, representative campaign interval, 13-17 February 19 96, the Weimer model explained 19% (42%) of the variation in Doppler speed (direction) observed by the Digisonde, and 21% (14%) of the equivalent conv ection components observed by the magnetometer,This compares with IZMEM whi ch explained 16% (46%) of the variation in Doppler speed (direction) observ ed by the Digisonde, and 34% (32%) of the equivalent convection components observed by the magnetometer. In general, there was better agreement betwee n convection direction than convection speed. Some of the disagreement was probably due to differences between the IMF measured by Wind located simila r to 170 R-E upstream in the solar wind and the IMF actually arriving at th e magnetopause. However, the results of this study do show that measurement s of ionospheric velocity using different experimental techniques need heav y averaging to identify a common component of velocity controlled by the IM F vector. The present time series approach was also used to estimate 16 +/- 5 min as the time required for the ionospheric convection to reconfigure i n response to IMF changes occurring at the magnetopause. (C) 1999 Elsevier Science Ltd. All rights reserved.