SIGNATURES OF IMPULSIVE CONVECTION IN THE MAGNETOSPHERIC LOBES

We analyze the injections of tailward flowing O+ ions measured by PROG NOZ-8 in the magnetospheric lobes using three-dimensional single-parti cle codes. These injections are shaped as ''inverted Vs'' and unexpect edly well correlated with AE variations during a time interval of abou t 7 hours. Such a correlation leads us to consider the effect of trans ient intensification of the large-scale magnetospheric convection. Usi ng a simple model of time-varying electric field, we show that the sou rce of the Of lies near the dayside cusp. This source extends over a n arrow (a few degrees) latitudinal interval in the vicinity of the last closed field line, likely involving ions expelled into the magnetosph ere after being transversely accelerated. We demonstrate that, downstr eam of the ejection site, impulsive convection leads to prominent stru cturing of the tailward streaming particles with abrupt energy variati ons on small length scales. A good agreement is obtained between the n umerical results and the observations which supports our impulsive con vection based interpretation framework.