Steady magnetospheric convection selection criteria: Implications of global SuperDARN convection measurements

Abstract

Quantitative definitions have been developed to detect intervals of steady magnetospheric convection (SMC), but these methods are based only on proxies of convection, such as the Auroral Electrojet (AE) indices. For the first time, observations of ionospheric convection on a global scale are studied during intervals identified as steady magnetospheric convection events. The SMC occurrence and SuperDARN transpolar voltage exhibit a strong seasonal bias, which is believed to be due to the seasonal variation of ionospheric conductivity. Equivalent AE values in winter and summer correspond to similar electrojet current strengths but to different levels of convection. Events selected using a constant AE threshold correspond to enhanced convection but above a variable threshold. This SuperDARN study is the first step in improving the reliability of SMC event selection by using convection observations. We present a new variable AE cutoff function to reduce the seasonal dependence of SMC selection on ionospheric conductivity. Copyright 2008 by the American Geophysical Union.